COMBINING TIME-BASED CHO AND RACH-LESS ACCESS WITH RESTRICTED PRECONFIGURED UL GRANTS

TECHNICAL FIELD

[001] This disclosure relates to combining time-based conditional handover (CHO) and RACH-less access with restricted preconfigured uplink (UL) grants.

BACKGROUND

[002] In 3 GPP release 8, the Evolved Packet System (EPS) was specified. EPS is based on the Long-Term Evolution (LTE) radio network and the Evolved Packet Core (EPC). It was originally intended to provide voice and mobile broadband (MBB) services but has continuously evolved to broaden its functionality. Since 3GPP release 13, Narrow Band Internet-of-Things (NB-IoT) and LTE-M are part of the LTE specifications and provide connectivity to massive machine type communications (mMTC) services.

[003] In 3GPP release 15, the first release of the 5G system (5GS) was specified. This is a next generation (NG) radio access technology intended to serve use cases such as enhanced mobile broadband (eMBB), ultra-reliable and low latency communication (URLLC) and mMTC. 5G includes the New Radio (NR) access stratum interface and the 5G Core Network (5GC). The NR physical and higher layers reuse parts of the LTE specification, and to that add needed components when motivated by the new use cases. One such component is the introduction of a sophisticated framework for beam forming and beam management to extend the support of the 3 GPP technologies to a frequency range going beyond 6 GHz.

[004] Random access in NR

[005] This disclosure is related to the random access (RA) procedure in NR, including the two random access types: 1) 4-step RA and 2) 2-step RA. Background information on these procedures and how they are configured is provided below.

[006] In NR, the RA procedure is described in the NR MAC specifications and parameters are configured by the Radio Resource Control (RRC) protocol (e.g. in system information or handover (RRCReconfiguration with reconfigurationWithSync)). RA is triggered in many different scenarios, for example, when the UE is in RRC IDLE or RRC INACTIVE and the UE wants to access a cell that it is camping on (i.e. transition to RRC CONNECTED). In NR, Random Access Channel (RACH) configuration is broadcast in SIB1, as part of the servingCellConfigCommon IE. In addition, RACH configuration can be conveyed to the UE in dedicated RRC signaling. This is e.g., the case when contention-free random access is configured in conjunction with handover. Inherited from LTE, a 4-step RA procedure is specified for NR in 3GPP release 15. In release 16, an alternative RA procedure, denoted the 2-step RA has been specified, which can be used in parallel with the 4-step RA procedure. The following RRC information elements (IES) (extracted from 3GPP TS 38.331 version 16.1.0 (hereafter “TS 38.331”)) are relevant for 4-step and 2-step random access configuration.

TABLE 1 - RACH-ConfigGeneric IE

[007] RACH-ConfigGeneric IE field descriptions

[008] msgl-FDM

[009] The number of PRACH transmission occasions FDMed in one time instance..

[0010] msgl -FrequencyStart

[0011] Offset of lowest PRACH transmission occasion in frequency domain with respective to PRB 0. The value is configured so that the corresponding RACH resource is entirely within the bandwidth of the UL BWP.

[0012] powerRampingStep

[0013] Power ramping steps for PRACH.

[0014] prach-ConfigurationFrameOffset-IAB

[0015] Scaling factor for ROs defined in the baseline configuration indicated by prach- Configurationlndex and is used only by the IAB-MT.

[0016] prach-Configurationlndex

[0017] PRACH configuration index. For prach-Configurationlndex configured under beamFailureRecovery-Config, the prach-Configurationlndex can only correspond to the short preamble format, If the field prach-ConfigurationIndex-vl610 is present, the UE shall ignore the value provided in prach-Configurationlndex (without suffix).

[0018] prach-ConfigurationPeriodScaling-IAB

[0019] Scaling factor to extend the periodicity of the baseline configuration indicated by prach-Configurationlndex and is used only by the IAB-MT. Value scfl correponds to scaling factor of 1 and so on.

[0020] prach-ConfigurationSOffset-IAB

[0021] Subframe/Slot offset for ROs defined in the baseline configuration indicated by prach-Configurationlndex and is used only by the IAB-MT.

[0022] preambleReceivedTargetPower

[0023] The target power level at the network receiver side. Only multiples of 2 dBm may be chosen (e.g. -202, -200, -198,...).

[0024] preambleTransMax

[0025] Max number of RA preamble transmission performed before declaring a failure).

[0026] ra-ResponseWindow

[0027] Msg2 (RAR) window length in number of slots. The network configures a value lower than or equal to 10 ms when Msg2 is transmitted in licensed spectrum and 40 ms when Msg2 is transmitted with shared spectrum channel access. UE ignores the field if included in SCellConfig. If ra-ResponseWindow-vl610 is signalled, UE shall ignore the ra- ResponseWindow (without suffix). For operation with shared spectrum channel access and when ra-ResponseWindow value is more than 10 ms, the network always includes the two LSB bits of the SFN corresponding to the PRACH occasion where the preamble is received in the DCI scheduling Msg2.

[0028] zeroCorrelationZoneConfig

[0029] N-CS configuration, see Table 6.3.3.1-5 in 3GPP TS 38.211.

TABLE 2 - RACH-ConfigGenencTwoStepRA IE

[0030] RACH-ConfigGenericTwoStepRA field descriptions

[0031] msgA-PreamblePowerRampingStep

[0032] Power ramping steps for msgA PRACH. If the field is absent, UE shall use the value of powerRampingStep in RACH-ConfigGeneric in the configured BWP (, 5.1.3). This field may only be present if no 4-step type RA is configured in the BWP or in the case of separate ROs with 4-step type RA. The field is absent if RACH-ConfigGenericTwoStepRA is included in CFRA-TwoStep in RACH-ConfigDedicated and then the UE uses the value of msgA-PreamblePowerRampingStep in RACH-ConfigGenericTwoStepRA configured for CBRA.

[0033] msgA-PreambleReceivedTargetPower [0034] The target power level at the network receiver side. Only multiples of 2 dBm may be chosen (e.g -202, -200, -198, ... ). If the field is absent, UE shall use the value of preambleReceivedTargetPower in RACH-ConfigGeneric in the configured BWP. This field may only be present if no 4-step type RA is configured in the BWP. The field is absent if RACH- ConfigGenericTwoStepRA is included in CFRA-TwoStep in RACH-ConfigDedicated and then the UE uses the value of msgA-PreambleReceivedTargetPower in RACH- ConfigGenericTwoStepRA configured for CBRA.

[0035] msgA-PRACH-Configurationlndex

[0036] Cell-specific PRACH configuration index for 2-step RA type. If the field is absent the UE shall use the value of corresponding 4-step random access parameter in the configured BWP. If the value is in the range of 256 to 262, the field prach-ConfigurationIndex-vl610 should be considered configured This field may only be present if no 4-step type RA is configured in the BWP or in the case of separate ROs with 4-step type RA.

[0037] msgA-RO-FDM

[0038] The number of msgA PRACH transmission occasions Frequency-Division

Multiplexed in one time instance. If the field is absent, UE shall use value of msgl-FDM in RACH-ConfigGeneric in the configured BWP This field may only be present if no 4-step type RA is configured in the BWP or in the case of separate ROs with 4-step type RA.

[0039] msgA-RO-FrequencyStart

[0040] Offset of lowest PRACH transmissions occasion in frequency domain with respect to PRB 0. If the field is absent, UE shall use value of msgl -FrequencyStart in RACH- ConfigGeneric in the configured BWP. This field may only be present if no 4-step type RA is configured in the BWP or in the case of separate ROs with 4-step type RA.

[0041] msgA-ZeroCorr elationZoneConfig

[0042] N-CS configuration for msgA preamble. If the field is absent, UE shall use value zeroCorrelationZoneConfig in RACH-ConfigGeneric in the configured BWP. This field may only be present if no 4-step type RA is configured in the BWP or in the case of separate ROs with 4-step type RA.

[0043] msgB-ResponseWindow [0044] MsgB monitoring window length in number of slots. The network configures a value lower than or equal to 40ms. If the field is absent, the UE use the value of msgB- ResponseWindow in RACH-ConfigGenericTwoStepRA configured for CBRA.

[0045] preambleTransMax

[0046] Max number of RA preamble transmission performed before declaring a failure (, clauses 5.1.4, 5.1.5). If the field is absent, UE shall use the value of preambleTransMax in RACH-ConfigGeneric in the configured BWP. The field is absent if RACH- ConfigGenericTwoStepRA is included in CFRA-TwoStep in RACH-ConfigDedicated and then the UE uses the value of preambleTransMax in RACH-ConfigGenericTwoStepRA configured for CBRA.

TABLE S

TABLE 4- RA-Prioritization IE

[0047] RA-Prioritization field descriptions

[0048] powerRampingStepHighPrioritiy

[0049] Power ramping step applied for prioritized random access procedure.

[0050] scalingFactorBI

[0051] Scaling factor for the backoff indicator (BI) for the prioritized random access procedure.. Value zero corresponds to 0, value dot25 corresponds to 0.25 and so on.

TABLE 5 - RACH-ConfigCommon IE

[0052] RACH-ConfigCommon field descriptions

[0053] messagePowerOffsetGroupB

[0054] Threshold for preamble selection. Value is in dB. Value minusinfinity corresponds to -infinity. Value dBO corresponds to 0 dB, dB5 corresponds to 5 dB and so on.

[0055] msgl -SubcarrierSpacing

[0056] Subcarrier spacing of PRACH. Only the values 15 or 30 kHz (FR1), and 60 or 120 kHz (FR2) are applicable. If absent, the UE applies the SCS as derived from the prach- Configurationlndex in RACH-ConfigGeneric (see tables Table 6.3.3.1-1 and Table 6.3.3.2-2, TS 38.211). The value also applies to contention free random access (RACH-ConfigDedicated), to Si-request and to content! on- based beam failure recovery (CB-BFR). But it does not apply for contention free beam failure recovery (CF-BFR) (see BeamFailureRecoveryConfig).

[0057] msg3-transformPrecoder

[0058] Enables the transform precoder for Msg3 transmission according to clause 6.1.3 of TS 38.214. If the field is absent, the UE disables the transformer precoder.

[0059] numberOfRA-PreamblesGroupA

[0060] The number of CB preambles per SSB in group A. This determines implicitly the number of CB preambles per SSB available in group B.. The setting should be consistent with the setting of ssb-perRACH-OccasionAndCB-PreamblesPerSSB. [0061] prach-RootSequencelndex

[0062] PRACH root sequence index. The value range depends on whether L=839 or L=139. The short/long preamble format indicated in this IE should be consistent with the one indicated in prach-Configurationlndex in the RACH-ConfigDedicated (if configured). If prach- RootSequenceIndex-rl6 is signalled, UE shall ignore the prach-RootSequencelndex (without suffix).

[0063] ra-ContentionResolutionTimer

[0064] The initial value for the contention resolution timer. Value sf8 corresponds to 8 subframes, value sfl6 corresponds to 16 subframes, and so on.

[0065] ra-Msg3SizeGroupA

[0066] Transport Blocks size threshold in bits below which the UE shall use a contention-based RA preamble of group A.

[0067] ra-PrioritizationForAI

[0068] Indicates whether the field ra-Prioritization-rl6 applies for Access Identities. The first/leftmost bit corresponds to Access Identity 1, the next bit corresponds to Access Identity 2. Value 1 indicates that the field ra-Prioritization-rl6 applies otherwise the field does not apply.

[0069] ra-Prioritization

[0070] Parameters which apply for prioritized random access procedure on any UL BWP of SpCell for specific Access Identities (, clause 5.1.1a).

[0071] rach-ConfigGeneric

[0072] RACH parameters for both regular random access and beam failure recovery.

[0073] restrictedSetConfig

[0074] Configuration of an unrestricted set or one of two types of restricted sets, , clause 6.3.3.1.

[0075] rsrp-ThresholdSSB

[0076] UE may select the SS block and corresponding PRACH resource for path-loss estimation and (re)transmission based on SS blocks that satisfy the threshold. [0077] rsrp-ThresholdSSB-SUL

[0078] The UE selects SUL carrier to perform random access based on this threshold. The value applies to all the BWPs.

[0079] ssb-perRACH-OccasionAndCB-PreamblesPerSSB

[0080] The meaning of this field is twofold: the CHOICE conveys the information about the number of SSBs per RACH occasion. Value oneEighth corresponds to one SSB associated with 8 RACH occasions, value oneFourth corresponds to one SSB associated with 4 RACH occasions, and so on. The ENUMERATED part indicates the number of Contention Based preambles per SSB. Value n4 corresponds to 4 Contention Based preambles per SSB, value n8 corresponds to 8 Contention Based preambles per SSB, and so on. The total number of CB preambles in a RACH occasion is given by CB-preambles-per-SSB * max(l, SSB-per-rach- occasion)..

[0081] totalNumberOfRA-Preambles

[0082] Total number of preambles used for contention based and contention free 4-step or 2-step random access in the RACH resources defined in RACH-ConfigCommon, excluding preambles used for other purposes (e.g. for SI request). If the field is absent, all 64 preambles are available for RA. The setting should be consistent with the setting of ssb-perRACH- OccasionAndCB-PreamblesPerSSB, i.e. it should be a multiple of the number of SSBs per RACH occasion.

[0083] L139: The field is mandatory present if prach-RootSequencelndex L=139, otherwise the field is absent, Need S.

[0084] SUL: The field is mandatory present in initialUplinkBWP in supplementaryUplink; otherwise, the field is absent.

[0085] InitialBWP-Only: This field is optionally present, Need R, if this BWP is the initial BWP of SpCell. Otherwise the field is absent.

TABLE 6 - RACH-ConfigCommonTwoStepRA IE

[0086] RACH-ConfigCommonTwoStepRA field descriptions

[0087] groupB-ConfiguredTwoStepRA

[0088] Preamble grouping for 2-step random access type. If the field is absent then there is only one preamble group configured and only one msg A PUS CH configuration.

[0089] msgA-CB-PreamblesPerSSB-PerSharedRO

[0090] Number of contention-based preambles used for 2-step RA type from the non- CBRA 4-step type preambles associated with each SSB for RO shared with 4-step type RA. The number of preambles for 2-step RA type shall not exceed the number of preambles per SSB minus the number of contention-based preambles per SSB for 4-step type RA. The possible value range for this parameter needs to be aligned with value range for the configured SSBs per RACH occasion in SSB-perRACH-OccasionAndCB-PreamblesPerSSB in RACH- ConfigCommon. The field is only applicable for the case of shared ROs with 4-step type random access. [0091] msg A-PRACH-RootS equencelndex

[0092] PRACH root sequence index. If the field is not configured, the UE applies the value in field prach-RootS equencelndex in RACH-ConfigCommon in the configured BWP. When both 2-step and 4-step type random access is configured, this field is only configured for the case of separate ROs between 2-step and 4-step type random access.

[0093] msgA-RestrictedSetConfig

[0094] Configuration of an unrestricted set or one of two types of restricted sets for 2- step random access type preamble. If the field is not configured, the UE applies the value in field restrictedSetConfig in RACH-ConfigCommon in the configured BWP. When both 2-step and 4- step type random access is configured, this field is only configured for the case of separate ROs between 2-step and 4-step type random access.

[0095] msg A-RSRP- Threshold

[0096] The UE selects 2-step random access type to perform random access based on this threshold. This field is only present if both 2-step and 4-step RA type are configured for the BWP.

[0097] msgA-RSRP-ThresholdSSB

[0098] UE may select the SS block and corresponding PRACH resource for path-loss estimation and (re)transmission based on SS blocks that satisfy the threshold.

[0099] msgA- S SB-PerRACH-OccasionAndCB-PreamblesPerS SB

[00100] The meaning of this field is twofold: the CHOICE conveys the information about the number of SSBs per RACH occasion. Value oneEight corresponds to one SSB associated with 8 RACH occasions, value oneFourth corresponds to one SSB associated with 4 RACH occasions, and so on. The ENUMERATED part indicates the number of Contention Based preambles per SSB. Value n4 corresponds to 4 Contention Based preambles per SSB, value n8 corresponds to 8 Contention Based preambles per SSB, and so on. The total number of CB preambles in a RACH occasion is given by CB-preambles-per-SSB * max(l, SSB-per-rach- occasion). If the field is not configured and both 2-step and 4-step are configured for the BWP, the UE applies the value in the field ssb-perRACH-OccasionAndCB-PreamblesPerSSB in RACH-ConfigCommon. The field is not present when RACH occasions are shared between 2- step and 4-step type random access in the BWP.

[00101] msgA-SSB-SharedRO-Masklndex

[00102] Indicates the subset of 4-step type ROs shared with 2-step random access type for each SSB. This field is configured when there is more than one RO per SSB. If the field is absent, and 4-step and 2-step has shared ROs, then all ROs are shared.

[00103] msgA-SubcarrierSpacing

[00104] Subcarrier spacing of PRACH. Only the values 15 or 30 kHz (FR1), and 60 or 120 kHz (FR2) are applicable. The field is only present in case of 2-step only BWP, otherwise the UE applies the SCS as derived from the msgl -SubcarrierSpacing in RACH-ConfigCommon. The value also applies to contention free 2-step random access type (RACH-ConfigDedicated).

[00105] msgA-TotalNumberOfRA-Preambles

[00106] Indicates the total number of preambles used for contention-based and contention- free 2-step random access type when ROs for 2-step are not shared with 4-step. If the field is absent, and 2-step and 4-step does not have shared ROs, all 64 preambles are available for 2-step random access type.

[00107] msgA-TransMax

[00108] Max number of MsgA preamble transmissions performed before switching to 4- step random access (, clauses 5.1.1). This field is only applicable when 2-step and 4-step RA type are configured and switching to 4-step type RA is supported. If the field is absent, switching from 2-step RA type to 4-step RA type is not allowed.

[00109] ra-PrioritizationForAI

[00110] Indicates whether the field ra-Prioritization-rl6 applies for Access Identities. The first/leftmost bit corresponds to Access Identity 1, the next bit corresponds to Access Identity 2. Value 1 indicates that the field ra-Prioritization-rl6 applies, otherwise the field does not apply.

[00111] ra-ContentionResolutionTimer

[00112] The initial value for the contention resolution timer for fallback RAR in case no 4-step random access type is configured. Value sf8 corresponds to 8 subframes, value sfl6 corresponds to 16 subframes, and so on. If both 2-step and 4-step random access type resources are configured on the BWP, then this field is absent.

[00113] ra-Prioritization

[00114] Parameters which apply for prioritized random access procedure on any UL BWP of SpCell for specific Access Identities (, clause 5.1.1a).

[00115] rach-ConfigGenericTwoStepRA

[00116] 2-step random access type parameters for both regular random access and beam failure recovery.

[00117] GroupB-ConfiguredTwoStepRA field descriptions

[00118] messagePowerOffsetGroupB

[00119] Threshold for preamble selection. Value is in dB. Value minusinfinity corresponds to -infinity. Value dBO corresponds to 0 dB, dB5 corresponds to 5 dB and so on..

[00120] numberofRA-PreamblesGroupA

[00121] The number of CB preambles per SSB in group A for idle/inactive or connected mode. The setting of the number of preambles for each group should be consistent with ssb- perRACH-OccasionAndCB-PreamblesPerSSB-TwoStepRA or msgA-CB-PreamblesPerSSB if configured.

[00122] ra-MsgA-SizeGroupA

[00123] Transport block size threshold in bits below which the UE shall use a contentionbased RA preamble of group A.

TABLE 7

TABLE 8 - RACH-ConfigDedicated IE

[00124] CFRA-CSIRS-Resource field descriptions

[00125] csi-RS

[00126] The ID of a CSI-RS resource defined in the measurement object associated with this serving cell.

[00127] ra-OccasionList

[00128] RA occasions that the UE shall use when performing CF-RA upon selecting the candidate beam identified by this CSI-RS. The network ensures that the RA occasion indexes provided herein are also configured by prach-Configurationlndex and msgl-FDM. Each RACH occasion is sequentially numbered, first, in increasing order of frequency resource indexes for frequency multiplexed PRACH occasions; second, in increasing order of time resource indexes for time multiplexed PRACH occasions within a PRACH slot and Third, in increasing order of indexes for PRACH slots.

[00129] ra-Preamblelndex

[00130] The RA preamble index to use in the RA occasions associated with this CSI-RS.

[00131] CFRA field descriptions

[00132] occasions

[00133] RA occasions for contention free random access. If the field is absent, the UE uses the RA occasions configured in RACH-ConfigCommon in the first active UL BWP.

[00134] ra-ssb-OccasionMasklndex

[00135] Explicitly signalled PRACH Mask Index for RA Resource selection in 3GPP TS 38.321. The mask is valid for all SSB resources signalled in ssb-ResourceList.

[00136] rach-ConfigGeneric

[00137] Configuration of contention free random access occasions for CFRA. The UE shall ignore preambleReceivedTargetPower, preambleTransMax, powerRampingStep, ra- ResponseWindow signaled within this field and use the corresponding values provided in RACH-ConfigCommon.

[00138] ssb-perRACH-Occasion

[00139] Number of SSBs per RACH occasion.

[00140] totalNumberOfRA-Preambles

[00141] Total number of preambles used for contention free random access in the RACH resources defined in CFRA, excluding preambles used for other purposes (e.g. for SI request). If the field is absent but the field occasions is present, the UE may assume all the 64 preambles are for RA. The setting should be consistent with the setting of ssb-perRACH-Occasion, if present, i.e. it should be a multiple of the number of SSBs per RACH occasion.

[00142] CFRA-SSB-Resource field descriptions

[00143] msg A-PU S CH-r esour ce-Index

[00144] Identifies the index of the PUSCH resource used for MSGA CFRA. The PUSCH resource index indicates a valid PUSCH occasion (as specified in TS 38.213, subclause 8.1 A) and the associated DMRS resources corresponding to a PRACH slot. The PUSCH resource indexes are sequentially numbered and are mapped to valid PUSCH occasions corresponding to a PRACH slot which are ordered, first, in increasing order of frequency resource indexes for frequency multiplexed PUSCH occasions; second, in increasing order of DMRS resource indexes within a PUSCH occasion, where a DMRS resource index DMRS _id is determined first in an ascending order of a DMRS port index and then in an ascending order of a DMRS sequence index, third in increasing order of time resource indexes for time multiplexed PUSCH occasions within a PUSCH slot and fourth, in increasing order of indexes for PUSCH slots. For the case of contention free 2-step random access type, if this field is absent, the UE shall use the value 0.

[00145] ra-Preamblelndex

[00146] The preamble index that the UE shall use when performing CF-RA upon selecting the candidate beams identified by this SSB.

[00147] ssb

[00148] The ID of an SSB transmitted by this serving cell.

[00149] CFRA-TwoStep field descriptions

[00150] msgA-CFRA-PUSCH

[00151] PUSCH resource configuration(s) for msgA CFRA.

[00152] msgA-TransMax

[00153] Max number of MsgA preamble transmissions performed before switching to 4- step type random access (, clauses 5.1.1). This field is only applicable when 2-step and 4-step RA type are configured and switching to 4-step type RA is supported. If the field is absent in RACH-ConfigDedidated, switching from 2-step RA type to 4-step RA type is not allowed.

[00154] occasionsTwoStepRA

[00155] RA occasions for contention free random access. If the field is absent, the UE uses the RA occasions configured in RACH-ConfigCommonTwoStepRA in the first active UL BWP.

[00156] ra-SSB-OccasionMasklndex

[00157] Explicitly signalled PRACH Mask Index for RA Resource selection in TS 38.321. The mask is valid for all SSB resources signalled in ssb-ResourceList.

[00158] rach-ConfigGenericTwoStepRA

[00159] Configuration of contention free random access occasions for CFRA 2-step random access type.

[00160] ssb-PerRACH-OccasionTwoStep

[00161] Number of SSBs per RACH occasion for 2-step random access type.

[00162] RACH-ConfigDedicated field descriptions

[00163] cfra

[00164] Parameters for contention free random access to a given target cell. If this field and cfra-TwoStep are absent, the UE performs contention based random access.

[00165] cfra-TwoStep

[00166] Parameters for contention free 2-step random access type to a given target cell. Network ensures that cfra and cfra-TwoStep are not configured at the same time. If this field and cfra are absent, the UE performs contention based random access. This field may only be present if msgA-ConfigCommon is configured on the BWP.

[00167] ra-prioritization

[00168] Parameters which apply for prioritized random access procedure to a given target cell.

[00169] ra-PrioritizationTwoStep [00170] Parameters which apply for prioritized 2-step random access type procedure to a given target cell.

TABLE 9

TABLE 10 - MsgA-ConfigCommon

[00171] MsgA-ConfigCommon field descriptions

[00172] msgA-PUSCH-Config

[00173] Configuration of cell-specific MsgA PUSCH parameters which the UE uses for contention-based MsgA PUSCH transmission of this BWP. If the field is not configured for the selected UL BWP, the UE shall use the MsgA PUSCH configuration of initial UL BWP.

[00174] rach-ConfigCommonTwoStepRA [00175] Configuration of cell specific random access parameters which the UE uses for contention based and contention free 2-step random access type procedure as well as for 2-step RA type contention based beam failure recovery in this BWP.

TABLE 11

TABLE 12 - MsgA-PUSCH-Config IE

[00176] MsgA-PUSCH-Config field descriptions

[00177] msg A-DataS cramblingindex

[00178] Identifier used to initiate data scrambling (c init) for msgA PUSCH. If the field is absent the UE applies the value Physical cell ID (physCelllD).

[00179] msgA-DeltaPreamble

[00180] Power offset of msgA PUSCH relative to the preamble received target power.

[00181] msg A-PU S CH-ResourceGr oup A

[00182] MsgA PUSCH resources that the UE shall use when performing MsgA transmission using preambles group A. If field is not configured for the selected UL BWP, the UE shall use the MsgA PUSCH configuration for group A of initial UL BWP.

[00183] msg A-PU S CH-ResourceGr oupB

[00184] MsgA PUSCH resources that the UE shall use when performing MsgA transmission using preambles group B.

[00185] msgA-TransformPrecoder

[00186] Enables or disables the transform precoder for MsgA transmission (see clause 6.1.3 of TS 38.214).

[00187] MsgA-PUSCH-Resource field descriptions

[00188] guardBandMsgA-PUSCH

[00189] PRB-level guard band between FDMed PUSCH occasions.

[00190] guardPenodMsgA-PUSCH

[00191] Guard period between PUSCH occasions in the unit of symbols.

[00192] frequency StartMsgA-PUS CH

[00193] Offset of lowest PUSCH occasion in frequency domain with respect to PRB 0.

[00194] inter lacelndexFirstPO-MsgA-PUSCH [00195] Interlace index of the first PUSCH occasion in frequency domain if interlaced PUSCH is configured. For 30kHz SCS only the integers 1, 2, 3, 4, 5 are applicable.

[00196] mappingTypeMsgA-PUSCH

[00197] PUSCH mapping type A or B. If the field is absent, the UE shall use the parameter msgA-PUSCH-TimeDomainAllocation.

[00198] msgA-Alpha

[00199] Dedicated alpha value for MsgA PUSCH. If value is absent, the UE shall use the value of msg3 -Alpha if configured, else UE applies value 1.

[00200] msgA-DMRS- Config

[00201] DMRS configuration for msgA PUSCH.

[00202] msgA-HoppingBits

[00203] Value of hopping bits to indicate which frequency offset to be used for second hop.

[00204] msgA-IntraSlotFrequencyHopping

[00205] Intra-slot frequency hopping per PUSCH occasion.

[00206] msgA-MCS

[00207] Indicates the MCS index for msgA PUSCH from the Table 6.1.4.1-1 for DFT-s-

OFDM and Table 5.1.3.1-1 for CP-OFDM in 38.214.

[00208] msgA-PUSCH-TimeDomainAllocation

[00209] Indicates a combination of start symbol and length and PUSCH mapping type from the TDRA table (PUSCH-TimeDomainResourceAllocationList if provided in PUSCH- ConfigCommon, or else the default Table 6.1.2.1.1-2 in 38.214 is used if pusch- TimeDomainAllocationList is not provided in PUSCH-ConfigCommon). The parameter K2 in the table is not used for msgA PUSCH. The network configures one of msgA-PUSCH- TimeDomainAllocation and startSymbolAndLengthMsgA-PO, but not both. If the field is absent, the UE shall use the value of startSymbolAndLenghtMsgA-PO.

[00210] msg A-PU S CH- T imeDomainOffset [00211] A single time offset with respect to the start of each PRACH slot (with at least one valid RO), counted as the number of slots (based on the numerology of active UL BWP). See 38.213, clause 8.1 A.

[00212] nrofDMRS- Sequences

[00213] Number of DMRS sequences for MsgA PUSCH for CP-OFDM. In case of single PUSCH configuration or if the DMRS symbols of multiple configurations are not overlapped, if the DMRS resources configured in one PUSCH occasion is no larger than 8 (for len2) or 4 (for lenl), then only DMRS port is configured.

[00214] nroflnterlacesPerMsgA-PO

[00215] Number of consecutive interlaces per PUSCH occasion if interlaced PUSCH is configured. For 30kHz SCS only the integers 1, 2, 3, 4, 5 are applicable.

[00216] nrofMsgA-PO-FDM

[00217] The number of msgA PUSCH occasions FDMed in one time instance.

[00218] nrofMsgA-PO-PerSlot

[00219] Number of time domain PUSCH occasions in each slot. PUSCH occasions including guard period are contiguous in time domain within a slot.

[00220] nrofPRBs-PerMsgA-PO

[00221] Number of PRBs per PUSCH occasion.

[00222] nrofSlotsMsgA-PUSCH

[00223] Number of slots (in active UL BWP numerology) containing one or multiple

PUSCH occasions, each slot has the same time domain resource allocation.

[00224] startSymbolAndLengthMsgA-PO

[00225] An index giving valid combinations of start symbol, length and mapping type as start and length indicator (SLIV) for the first msgA PUSCH occasion, for RRC CONNECTED UEs in non- initial BWP as described in TS 38.214 clause 6.1.2. The network configures the field so that the allocation does not cross the slot boundary. The number of occupied symbols excludes the guard period. If the field is absent, the UE shall use the value in msgA-PUSCH- TimeDomainAllocation. The network configures one of msgA-PUSCH-TimeDomainAllocation and startSymbolAndLengthMsgA-PO, but not both. If the field is absent, the UE shall use the value of msgA-PUSCH-TimeDomainAllocation.

[00226] MsgA-DMRS-Config field descriptions

[00227] msgA-DMRS - AdditionalPosition

[00228] Indicates the position for additional DM-RS. If the field is absent, the UE applies value pos2.

[00229] msgA-MaxLength

[00230] indicates single-symbol or double-symbol DMRS. If the field is absent, the UE applies value lenl .

[00231] msgA-PUSCH-DMRS-CDM-group

[00232] 1 -bit indication of indices of CDM group(s). If the field is absent, then both CDM groups are used.

[00233] msgA-PUSCH-NrofPort

[00234] 0 indicates 1 port per CDM group, 1 indicates 2 ports per CDM group. If the field is absent then 4 ports per CDM group are used.

[00235] msgA-ScramblingIDO

[00236] UL DMRS scrambling initialization for CP-OFDM. If the field is absent the UE applies the value Physical cell ID (physCelllD).

[00237] msgA-ScramblingIDl

[00238] UL DMRS scrambling initialization for CP-OFDM. If the field is absent the UE applies the value Physical cell ID (physCelllD).

TABLE 13

[00239] 4-step random access procedure

[00240] A traditional 4-step approach is used for the NR Rel-15 (as well as for the LTE) random access procedure (see FIG. 1). In this approach, the UE detects a synchronization signal (SS) and decodes the broadcast system information before it initiates the actual random access procedure. To initiate the random access procedure, the UE transmits a random access preamble on the PRACH (referred to as message 1 (Msgl)) in the uplink using the transmission resources of a PRACH occasion (also referred to as RACH occasion (RO)) as configured by the system information. The gNB replies with a Random Access Response (RAR) message (referred to as message 2 (Msg2)). The UE then transmits a UE identification (referred to as message 3 (Msg3)) on the PUSCH, wherein the UE identification may be a 5G-S-TMSI in an RRCSetupRequest message (if the UE is in RRC IDLE state) or an I-RNTI in an RRCResumeRequest message (if the UE is in RRC INACTIVE state) or a C-RNTI in a C-RNU MAC CE in a MAC PDU typically containing user plane data (if the UE is in RRC CONNECTED state). This is referred to as message 3 (Msg3) and is transmitted on uplink resources allocated by the RAR message. As a last step, the gNB transmits a contention resolution message (referred to as message 4 (Msg4)), wherein a UE Contention Resolution Identification MAC CE is included, containing the 48 first bits of Msg3, in order to resolve a possible situation where two or more UEs have transmitted the same preamble in the same PRACH occasion.

[00241] The UE transmits PUSCH (message 3) after receiving a timing advance command in the RAR, allowing PUSCH to be received with a timing accuracy within the cyclic prefix. Without this timing advance, a very large cyclic prefix (CP) would be needed in order to be able to detect and demodulate the PUSCH transmission, except in a cell with small distances between cell edge and gNB, where the roundtrip propagation delay between the cell edge and the gNB is less than the CP. Because NR will also support larger cells with a need for providing a timing advance to the UE, the 4-step random access procedure is designed to allow the UE to transmit on the PUSCH with a proper timing advance rather than a very large CP.

[00242] The above description of the 4-step RA procedure applies in its entirety only in the case of contention-based random access (CBRA). In the case of contention-free random access (CFRA), the random access procedure is in principle regarded as completed by the reception of the RAR message (provided that it includes a response to the CFRA preamble the UE transmitted).

[00243] PRACH configuration for 4-step random access

[00244] In NR, the time and frequency resource on which a PRACH preamble is transmitted is defined as a PRACH occasion. The PRACH occasion may also be called RACH occasion, or RA occasion, or in short RO. And sometimes the RO used for the transmission of the preambles in 2-step RA is called 2-step RO, while the RO used for the transmission of the preambles in 4-step RA is called 4-step RO.

[00245] The time resources and preamble format for PRACH transmission are configured by a PRACH configuration index, which indicates a row in a PRACH configuration table specified in 3GPP TS 38.211 rev. 15.6.0 Tables 6.3.3.2-2, 6.3.3.2-3, 6.3.3.2-4 for FR1 paired spectrum, FR1 unpaired spectrum and FR2 with unpaired spectrum, respectively.

[00246] Part of the Table 6.3.3.2-3 for FR1 unpaired spectrum for PRACH preamble format 0 is copied in table 14 below, where the value of x indicates the PRACH configuration period in number of system frames. The value of y indicates the system frame within each PRACH configuration period on which the PRACH occasions are configured. For instance, if y is set to 0, then, it means PRACH occasions only configured in the first frame of each PRACH configuration period. The values in the column “subframe number” indicate which subframes are configured with PRACH occasion. The values in the column “starting symbol” is the symbol index.

[00247] In case of TDD, semi-statically configured DL parts and/or actually transmitted SSBs can override and invalidate some time-domain PRACH occasions defined in the PRACH configuration table. More specifically, PRACH occasions in the UL part are always valid, and a PRACH occasion within the X part is valid as long as it does not precede or collide with an SSB in the PRACH slot and it is at least N symbols after the DL part and the last symbol of an SSB. N is 0 or 2 depending on PRACH format and subcarrier spacing.

TABLE 14 - PRACH configuration for preamble format 0 for FR1 unpaired spectrum.

[00248] In the frequency domain, NR supports multiple frequency-multiplexed (also referred to as FDMed) PRACH occasions on the same time-domain PRACH occasion. This is mainly motivated by the support of analog receive beam sweeping in NR gNBs, such that the PRACH occasions associated with one SSB are configured at the same time instance but different frequency locations. The number of PRACH occasions FDMed in one time domain PRACH occasion, can be 1, 2, 4, or 8. FIG. 2 gives an example of the PRACH occasion configuration in NR.

[00249] In NR Rel-15, there are up to 64 sequences that can be used as random-access preambles per PRACH occasion in each cell. The RRC parameter totalNumberOfRA-Preambles determines how many of these 64 sequences are used as random-access preambles per PRACH occasion in each cell. The 64 sequences are configured by including firstly all the available cyclic shifts of a root Zadoff-Chu sequence, and secondly in the order of increasing root index, until 64 preambles have been generated for the PRACH occasion.

[00250] 2-step random access

[00251] An alternative to the regular 4-step RA procedure is introduced in NR in 3 GPP release 16. This alternative RA type is called 2-step RA (or Type 2 RA).

[00252] 2-step random access procedure

[00253] With the 2-step random access approach, a UE is able to complete a random access procedure in only two steps, as illustrated in FIG. 3.

[00254] Step 1 : The UE sends a message A (msgA) including random access preamble

(transmitted on the PRACH) together with a PUSCH transmission, typically containing higher layer data such as an RRC message (in the case of a UE in RRC IDLE or RRC INACTIVE state) or user plane data (in the case of a UE in RRC CONNECTED state). The part of msgA transmitted on the PRACH, i.e. the random access preamble, is sometimes referred to as msgA preamble or 2-step preamble. The part of msgA transmitted on the PUSCH is herein often referred to as msgA PUSCH.

[00255] Step 2: The gNB sends a response, called message B (msgB). A msgB may contain a response to multiple UEs and it may also contain a backoff indicator, which is an indication to UEs which transmitted 2-step random access preamble in the concerned PRACH occasion, but which did not find any matching response in the received msgB. The response to a UE contained in a msgB may have the form of a successRAR (more strictly denoted successRAR MAC subPDU) or a fallbackRAR (more strictly denoted fallbackRAR MAC subPDU). The response is a successRAR in case the gNB successfully received msgA, including both the preamble and the msgA PUSCH transmission. The fallbackRAR is used in the case where the gNB only received the preamble but failed to receive the msgA PUSCH transmission and chooses to instruct the UE to fallback to 4-step RA for the remainder of the RA procedure, i.e. to conclude the random access procedure with a msg3 (retransmitting the content of msgA PUSCH) and a msg4. A successRAR MAC subPDU includes a UE contention resolution identity, a timing advance command, a C-RNTI assigned to the UE and HARQ feedback configuration consisting of a transmit power control command for the PUCCH, HARQ feedback timing information and a PUCCH resource indicator. The content of a fallbackRAR MAC subPDU is the same as in a MAC RAR, i.e. the response to a UE in the RAR message, that is, a timing advance command, an UL grant and a temporary C-RNTI. MsgB and its content are specified in the MAC specification 3GPP TS 38.321.

[00256] Note that the above description of the 2-step RA procedure applies in its entirety only in the case of contention-based random access (CBRA). In the case of contention-free random access (CFRA), msgB is used only in the case of fallback to 4-step RA (i.e. with a fallbackRAR addressed to the UE) whereas in the successful case, the 2-step random access procedure is concluded by a PDCCH downlink assignment addressed to the UE’s C-RNH, with an Absolute Timing Advance Command MAC CE contained in the associated PUSCH transmission.

[00257] One of the benefits of 2-step RA is the latency gains. Depending on the numerology that is used in NR, the 2-step RA procedure could lead to a reduction of approximately a factor 3 compared to the 4-step RA procedure (see Error! Reference source not found.).

[00258] PRACH configuration for 2-step random access

[00259] The configuration of 2-step RA builds on the configuration means specified for 4- step RA, but extends it with configuration data to cater for the special characteristics of 2-step RA, in particular to configure related to the fact that a MsgA transmission consists of a both PRACH transmission (a preamble) and a PUSCH transmission (data), and configuration data to control the co-existence of 2-step RA and 4-step RA.

[00260] In 2-step RA, a preamble is associated with a so called PUSCH Resource Unit (PUSCH RU), which is used for the MsgA PUSCH transmission. A PUSCH RU consists of a PUSCH occasion (PO), which consists of the time/frequency resource allocation for the transmission, combined with the DMRS configuration (DMRS port and DMRS sequence initialization) to be used for the MsgA PUSCH transmission. In 3GPP release 16, the MsgA PUSCH configuration is specified in the MsgA-PUSCH-Resource-rl6 IE, as follows:

TABLE 15 - MsgA-PUSCH-Resource-rl6 IE

[00261] A set of MsgA PUSCH resources configured as above are associated with each PRACH slot (i.e. a slot containing one or more PRACH occasions), such that for all the PRACH transmissions in the PRACH slot, the associated MsgA PUSCH transmission occurs in a MsgA PUSCH resource following after the PRACH slot (i.e. one of the MsgA PUSCH resources associated with the PRACH slot).

[00262] Regarding the PRACH occasions (or RACH occasions, ROs), the ROs for 2-step RA may be shared with the ROs for 4-step RA or may be separate (used only for 2-step RA). Either shared ROs or separate ROs are configured in a cell - they cannot both be used in parallel. When shared ROs are configured, separate RA preamble ranges are configured for 4-step RA and 2-step RA.

[00263] Hence, there will be a set of preambles that are dedicated for use for 2-step RA in a cell where shared ROs are configured for 2-step RA and 4-step RA. When this configuration option is used, 2-step RA may be configured for all or a subset of the ROs configured for 4-step RA and the ROs which are shared are indicated by a configured mask. This mask can hence be used to achieve a configuration where some ROs are shared while some ROs are used only for 4- step RA. However, the opposite is not possible, i.e. there may be no ROs only for 2-step RA when shared ROs are configured.

[00264] To configure ROs dedicated for 2-step RA, the alternative configuration option, i.e. separate ROs, have to be used, where separate PRACH resources (i.e. time/frequency resources) are provided for 2-step ROs and 4-step ROs respectively. With that configuration option, each RO is configured for either 2-step RA or 4-step RA, but no RO is shared by both 2- step RA and 4-step RA. As an example of configuration of separate ROs, there may for instance be N frequency multiplexed PRACH resources (i.e. occurring simultaneously but on different frequencies, e.g. different subcarriers), where M (M < N) of these PRACH resources are associated with regular 4-step RA, while the remaining N - M PRACH resources are associated with 2-step RA.

[00265] Selection between 2-step and 4-step random access

[00266] When both 4-step RA and 2-step RA are configured in a cell, a UE selects which RA type to use based on the RSRP the UE experiences in the cell (measured on the UE’s configured pathloss reference signal). If the measured RSRP exceeds an RA type selection threshold, the UE selects 2-step RA, otherwise the UE selects 4-step RA. The UE performs the RA type selection only once for an entire RA procedure (where an RA procedure in this context consists of a series of RA attempts (i.e. preamble or MsgA transmissions) ending either in success or failure. The RA type selection threshold is configured by the msgA-RSRP-Threshold- rl6 parameter.

[00267] If the UE selects 2-step RA, and a certain number of attempts fail, then UE may switch to 4-step RA and continue with further RA attempts. The number of failed 2-step RA attempts after which the UE switches to 4-step RA is configured by the msgA-TransMax-rl6 parameter.

[00268] Uplink scheduling in NR

[00269] The gNB schedules a UE for PUSCH transmission by sending a DCI on the PDCCH scrambled with the UE’s C-RNU, wherein the DCI contains an UL grant which provides an uplink transmission resource allocation to the UE through a time domain resource allocation and a frequency domain resource allocation. The time domain resource allocation consists of four bits which indicate a row in a time domain resource allocation table. The applicable time domain resource allocation table is configured in the PUSCH-ConfigCommon IE (in SIB1 in the broadcast system information or in an RRCReconfiguration message) or in the PUSCH-Config IE in an RRCReconfiguration message, or else a default time domain resource allocation table specified in 3 GPP TS 38.214 is used.

[00270] Each row in the time domain resource allocation table contains: i) A slot offset, K2, indicating the number of slots between the UL grant and the slot for the allocated uplink transmission resources, ii) a start symbol, S, indicating the start symbol for the allocated resources within the slot indicated by K2, iii) a length indicator, L, indicating the length in number of symbols of the allocated resources within the slot indicated by K2, iv) a PUSCH mapping type, A or B, which is related to which combinations of S and L that are valid and which symbol(s) of the allocated resources the DMRS may be allocated to.

[00271] The scheduling of downlink transmission resources on the PDSCH works according to similar principles, albeit not without differences. [00272] Mobility in RRC CONNECTED state

[00274] An RRC CONNECTED UE in NR can be configured by the network to perform measurements on neighbor cells as well as on the serving cell, and, upon receiving a measurement report from the UE indicating that it may be preferable to move the UE’s RRC connection to a neighbor cell (e.g. because the measurement report indicates that the radio link in the service cell is deteriorating and/or that the radio channel quality in the neighbor cell has become (significantly) better than the radio channel quality in the serving cell), the network may send a message to the UE to instruct the UE to execute a handover. This message is an RRCReconfiguration message with a reconfigurationWithSync IE. The message is often informally referred to as a “handover command” (although a HandoverCommand is really an inter-gNB RRC message which is transferred in the “Target NG-RAN node To Source NG-RAN node Transparent Container” IE in the Handover Request Acknowledge XnAP message during preparation of an Xn handover and in the “Target to Source Transparent Container” IE in the Handover Request Acknowledge NGAP message and the Handover Command NGAP message during preparation of an NG handover).

[00275] These reconfigurations are actually prepared by the target gNB on a request from the source gNB over the Xn interface (or over the NG interface via an AMF in case of an NG handover) and may take into account the existing RRC configuration the UE has in the source cell (wherein this source cell configuration is provided from the source gNB to the target gNB in the inter-gNB handover preparation procedure, i.e. in the Handover Request XnAP message. Among other parameters, the reconfiguration provided by target gNB contains all information the UE needs to access the target cell, e.g., random access configuration, a new C-RNTI assigned by the target gNB and security parameters enabling the UE to calculate new security keys associated with the target cell so the UE can send a handover complete message (which really is an RRCReconfigurationComplete message) on SRB1, encrypted and integrity protected using new security keys upon accessing the target cell.

[00276] In NR, the following principles exist for handovers (or in more general terms, mobility in RRC CONNECTED state): Mobility in RRC CONNECTED state is network- controlled as the network has the best information regarding the current overall situation, such as load conditions, resources in different nodes, available frequencies, etc. The network can also take into account the situation of many UEs in the network, from a resource allocation perspective. The network prepares a target cell before the UE accesses that cell. The source gNB provides UE with the RRC configuration to be used in the target cell, including SRB1 configuration to send HO complete. The source gNB in turn receives this RRC configuration from the target gNB in the form of a HandoverCommand inter-node RRC message included in the Handover Request Acknowledge XnAP message (where the HandoverCommand is included in the “Target NG-RAN node To Source NG-RAN node Transparent Container” IE).

[00277] In the RRC configuration the target gNB provides to the UE via the source gNB, the target gNB configures the UE with a C-RNTI to be used in the target cell. The target gNB leverages this C-RNH to identify the UE from Msg3 on MAC level for the HO complete message (which is an RRCReconfigurationComplete message transmitted by the UE in the target cell to indicate the successful completion of the handover). Hence, there is no context fetching, unless a failure occurs, because the UE context was already transferred to the UE during the handover preparation (in the Handover Request XnAP message in the case of Xn handover).

[00278] To speed up the handover, the network provides needed information on how to access the target cell, e.g. RACH configuration, so the UE does not have to acquire SI (other than the MIB) prior to the handover. This information is included in the HandoverCommand and thus in the target cell RRC configuration sent to the UE.

[00279] The UE may be provided with contention free random access (CFRA) resources (in the above mentioned RRC configuration forwarded to the UE by the source gNB). The CFRA resources consist of one or more CFRA preamble(s) and may also contain CFRA occasions (i.e. PRACH transmission resources that are not included in the common PRACH configuration). In that case the target gNB identifies the UE from the random access preamble (Msgl). The principle is that the procedure can always be optimized with dedicated resources.

[00280] Security is prepared before the UE accesses the target cell, i.e. security keys must be refreshed before sending the HO complete message (i.e. the RRCReconfigurationComplete message), so that new keys are used to encrypt and integrity protect the HO complete message, enabling verification in the target cell.

[00281] The target cell RRC configuration may be provided to the UE in two different forms: full configuration or delta configuration. In the former case, the provided RRC configuration is complete and self-contained, but a delta configuration only contains the configuration parts that are different in the target cell than in the source cell. The advantage of delta configuration is that the size of the HandoverCommand can be minimized.

[00282] Conditional handover (CHO)

[00283] As previously described, handover typically occurs when the channel quality of the serving cell is degrading. The network is in control and bases the handover decision on measurement reports from the UE. In a typical case the UE is configured to send a measurement report when an A3 event (neighbor cell quality becomes offset better than serving cell quality) is fulfilled. This will then trigger the gNB to decide to pursue a handover for the UE with the target cell being selected based on the reported neighbor cell measurements. If this is an inter-gNB neighbor cell, the serving gNB initiates the handover preparation by sending a Handover Request XnAP message to the neighbor gNB and the neighbor gNB responds with a Handover Request Acknowledge XnAP message containing, in the form of a HandoverCommand the RRC configuration the UE should apply when connecting to the target cell. The serving (source) gNB then forwards the HandoverCommand to the UE as an RRCReconfiguration message. When the UE receives this message, it releases the source cell and starts the procedure of connecting to the target cell (i.e. synchronizing with the target cell and performing random access).

[00284] However, given the typical circumstances for handover, i.e. that the channel quality in the serving (source) cell is deteriorating, the handover operation is quite susceptible to errors. FIG. 8 illustrates two such error cases.

[00285] As FIG. 8 illustrates, one potential error associated with handover is that the measurement report from the UE, which would trigger the gNB to initiate the handover, never reaches the gNB because of too many transmission/reception errors. Another potential error is that all handover preparations are successful, but the gNB fails to reach the UE with the RRCReconfiguration message constituting the Handover Command. Both these errors are typically caused by a serving cell channel quality degrading faster than expected.

[00286] To combat such errors, a special variant of handover called Conditional Handover (CHO) was introduced in 3 GPP release 16. The CHO feature allows the serving gNB to configure a UE to autonomously trigger handover execution, when a handover execution condition (or trigger condition) configured by the serving gNB is fulfilled. To realize this feature, the serving gNB includes a handover execution condition - often referred to as a CHO execution condition (denoted as condExecutionCond-rl6 in the ASN.l code in the RRC specification 3 GPP TS 38.331) - together with the Handover Command forwarded from the candidate target gNB. Release 16 of the 3 GPP standards supports configuration of two triggering events, which in the context of CHO are referred to as conditional events (CondEvents). The supported CondEvents are A3 and A5 which are reused from the RRM framework. When used as CondEvents, A3 is defined as “Conditional reconfiguration candidate becomes amount of offset better than PCell/PSCell” and A5 is defined as “PCell/PSCell becomes worse than absolute threshold 1 AND Conditional reconfiguration candidate becomes better than another absolute threshold2”. Furthermore, the specification also allows the combination of two events, whose conditions both have to be fulfilled for the duration of the configured time-to-trigger period, in order for the CHO execution to be triggered.

[00287] CHO is applicable for both intra-gNB handover and inter-gNB handover. The remainder of this CHO background description looks at the feature in the inter-gNB CHO case, because this is the most comprehensive and challenging case which best illustrates the complete concept.

[00288] When the UE receives the RRCReconfiguration message including configuration of CHO (i.e. including a Handover Command and an associated CHO execution condition, it does not initiate execution of the handover, but instead remains connected to the serving cell, but begins to monitor the configured CHO execution condition (for the indicated candidate target cell (a cell associated with a conditional handover configuration (i.e. a cell which the UE may connect to if the CHO execution condition is fulfilled) may be referred to as a candidate target cell. Similarly, a gNB controlling a cell associated with a conditional handover configuration may be referred to as a candidate target gNB)). The UE may be configured with multiple candidate target cells. For each candidate target cell, the UE is provided with an associated Handover Command (i.e. an RRC configuration to be applied if/when connecting to the candidate target cell) and an associated CHO execution condition.

[00289] If/when the CHO execution condition is fulfilled for a candidate target cell, the UE releases the source cell and starts executing the handover towards the candidate target cell (which then becomes the target cell) for which the associated CHO execution condition was fulfilled. From the UE’s point of view, the rest of the procedure proceeds like a regular handover procedure, except that the UE discards all CHO configurations when it has successfully connected to the target cell.

[00290] On the network side, the serving/source gNB is not aware of if or when a CHO execution condition is fulfilled for the UE, i.e. the UE will silently release the source cell. Therefore, after handover completion, i.e. after successful random access and successful reception of the RRCReconfigurationComplete message (which often is referred to as the Handover Complete message), the target gNB sends a Handover Success XnAP message to the source gNB. This informs the source gNB that the UE has left the source cell and successfully completed a handover to the target cell. If multiple candidate target gNBs were prepared for CHO for the UE, the source gNB can cancel the CHO preparations in the other (non-selected) candidate target gNBs using the Handover Cancel XnAP message, so that these gNBs can release any reserved resources.

[00291] During a regular handover, the source gNB starts to forward user plane data arriving in the source gNB to the target gNB (for further forwarding to the UE) as soon as the Handover Command is sent to the UE. In CHO, however, due to the uncertainty of if and when the UE will actually execute a handover, it may be suboptimal to start forwarding user plane data to a candidate target gNB upon transmission of the Handover Command, because this will cause unnecessary load on the Xn user plane, as well as processing load in the candidate target gNB. Therefore, the source gNB can choose not to initiate user plane forwarding until it receives the Handover Success XnAP message from the target gNB. On the other hand, not initiating user plane forwarding until the Handover Success XnAP message is received delays the availability of buffered downlink data in the target gNB, which increases the handover interruption time. Therefore, both options are available for CHO, referred to as early data forwarding (any time after transmission of the Handover Command and before reception of the Handover Success XnAP message) and late data forwarding (upon reception of the Handover Success XnAP message). The conditional handover procedure is illustrated in FIG. 7.

[00292] Because the Conditional Handover is not executed immediately when its associated Handover Command is delivered to the UE, it can be configured proactively while the radio channel quality in the serving cell is still sufficiently good. Typically, configuration of CHO can be triggered by a measurement report from the UE, but this measurement report can be triggered earlier (e.g. when the serving cell channel quality is better) than a measurement report whose purpose is to trigger the gNB to initiate the handover procedure. Nevertheless, even though Conditional Handover is more robust than regular handover, it is not always successful. If the handover execution fails, e.g. due to random access failure and/or expiry of timer T304, the UE will go to RRC IDLE state and attempt to re-establish the RRC connection through the RRC connection re-establishment procedure. This involves selecting a cell for the re-establishment, wherein the cell is selected according to the cell selection principles. If it turns out that the UE has a stored CHO configuration for the cell selected for re-establishment (i.e. the selected cell is one of the candidate target cells), then the UE proceeds as if it was executing a conditional handover towards the selected cell, i.e. after the random access procedure in the selected cell, the UE transmits the RRCReconfigurationComplete message constituting the Handover Complete message. In this way, the CHO can eventually be completed and neither the target gNB nor the source gNB will know that this involved an initial handover failure followed by an initiated RRC connection re-establishment procedure which was turned into a conditional handover (unless this is visible in a report, e.g. a handover report or an RLF report, that the UE may send to the network for SON purposes).

[00293] In addition to the above described Conditional Handover, there is a special flavor of it called Conditional PSCell Change (CPC). CPC uses the same conditional reconfiguration framework as conditional handover, but instead of a handover, the PSCell change is executed when the execution condition is fulfilled. As a further addition, Conditional PSCell Addition is currently being specified for 3GPP release 17.

[00294] RACH-less handover/SCG change

[00295] RACH-less handover (and RACH-less SCG change) has been specified for LTE, as part of 3GPP Release 14, in order to decrease the interruption time at handover and SCG change, respectively. The RACH-less handover procedure means that the Msgl (i.e. RA preamble) transmission and the Msg2 (i.e. RAR) transmission are skipped in the RA procedure, when the UE accesses the target cell during (RACH-less) handover (or SCG change).

[00296] In the regular RA procedure, the network uses the RA preamble in Msgl to determine the UE’s uplink transmission timing in order to allocate an accurate timing advance (TA) to the UE, wherein the UE will use this TA for subsequent uplink transmissions in order to compensate for the UE-eNB roundtrip time (RTT), so that every uplink transmission arrives at the eNB at the right point in time. In the regular RA procedure, the network uses Msg2 (i.e. the RAR) to allocate the TA to the UE and also includes an UL grant which the UE is expected to use for transmission of more information to the network, in a so called Msg3.

[00297] At a RACH-less handover/SCG change, the UE is instead provided with a TA value in the handover command prior to accessing the target cell. In order for the Msg3 message to reach the target eNB at the right point in time, the correct TA value to use for the UE in the target cell thus needs to be known in advance. The use of RACH-less handover/SCG change is thus restricted to cases where the target cell is known to be served by the same antenna(s) (e.g. collocated with), and thus will have the same TA, as another cell where the UE already has a connection and thus a known TA value (such as a PCell, PSCell or SCell) when the handover is initiated; or the target cell is known to have a TA value = 0, i.e. it is a small cell.

[00298] Furthermore, at RACH-less handover, the UL grant for Msg3 transmission in the target cell is, can be provided to the UE in two different ways: (1) The UL grants are preallocated to the UE in the HO Command message, i.e. within the RRCConnectionReconfiguration message instructing the UE to perform the handover or SCG change, or (2) the target cell schedules the UE with UL grants (PUSCH transmission resources) using the PDCCH, wherein the UE is scheduled through the PDCCH with a DCI addressed to the C-RNTI that the UE (in the handover command) has been configured with for use in the target cell.

[00299] In the alternative to pre-allocate the UL grants the target eNB needs to configure UL grants (PUSCH transmission resources) to the UE in advance, meaning that those resources cannot be allocated to any other UE. This may be problematic at e.g. high load scenarios or if several RACH-less handover/SCG changes are to be performed simultaneously. The alternative to schedule the UE via the PDCCH in the target cell gives more flexibility for the target eNB in its resource allocation, but it requires an additional PDCCH resource in the target cell for each UL grant, and it imposes an additional delay compared to the pre-allocation alternative. The additional delay is due to that there is a delay between the reception of the PDCCH scheduling in the target cell until the presence of the scheduled UL grant (PUSCH resource). [00300] The alternative to pre-allocate UL grants to the UE instead means that the UE can access the target cell at the first UL grant that is available (pre-allocated) for it when it is ready for transmission in the target cell, i.e. after e.g. downlink synchronization and tuning towards the target cell. The typical delay until the first available UL grant then depends on the frequency of the pre-allocated UL grants. Three different periodicities have been specified for the preallocated UL grants, either every 2 ^nd , every 5 ^th or every 10 ^th subframe, where a subframe corresponds to 1 millisecond.

[00301] The UE assumes the RACH-less configuration to be valid until successful completion of the handover or SCG change, or until expiry of timer T304 or T307, which are supervision timers for handover and SCG change respectively. The UE starts timer T304 or T307 when it receives a RRCConnectionReconfiguration message instructing it to perform a handover or SCG change, respectively. This means that the UE that is configured with pre-allocated UL grants will consider itself to have received UL grants for that time. In case the UE receives a RACH-less configuration with the PDCCH scheduling alternative, it will instead monitor the PDCCH for UL grant scheduling during the same time period.

[00302] RACH-less HO/SCG change has not been standardized for NR. The specification work was started in the 3 GPP release 16 work, but was put on ice, as it was seen to provide too little benefits compared to 2-step CFRA, which was anyway being specified for release 16. However, it is not unlikely that RACH-less HO/SCG change will be specified for NR too in coming releases of the 3 GPP standard. A potential development could be that RACH-less HO is specified (at least initially) only for NR in Non-Terrestrial Networks. In any case, RACH-less HO (and RACH-less SCG change) in NR can be expected to use the corresponding LIE mechanism as the baseline.

[00303] Satellite communication and Non-Terrestrial Networks

[00304] There is an ongoing resurgence of satellite communications. Several plans for satellite networks have been announced in the past few years. The target services vary, from backhaul and fixed wireless, to transportation, to outdoor mobile, to loT. Satellite networks could complement mobile networks on the ground by providing connectivity to underserved areas and multi cast/broadcast services.

[00305] To benefit from the strong mobile ecosystem and economy of scale, adapting the terrestrial wireless access technologies including LTE and NR for satellite networks is drawing significant interest, which has been reflected in the 3 GPP standardization work. In 3 GPP release 15, 3GPP started the work to prepare NR for operation in a Non-Terrestrial Network (NTN). The work was performed within the study item “NR to support Non-Terrestrial Networks” and resulted in reference [Error! Reference source not found.]. In 3GPP release 16, the work to prepare NR for operation in an NTN network continued with the study item “Solutions for NR to support Non- Terrestrial Network”, which has been captured in reference [2], In parallel the interest to adapt NB-IoT and LTE-M for operation in NTN is growing. As a consequence, 3GPP release 17 contains both a work item on NR NTN (see reference [3]) and a study item on NB-IoT and LTE-M support for NTN (see reference [4]).

[00306] A satellite radio access network usually includes the following components: A satellite that refers to a space-borne platform; an earth-based gateway that connects the satellite to a base station or a core network, depending on the choice of architecture; a feeder link that refers to the link between a gateway and a satellite; access link, or service link, that refers to the link between a satellite and a UE.

[00307] Depending on the orbit altitude, a satellite may be categorized as low earth orbit (LEO), typical heights ranging from 250 - 1,500 km, with orbital periods ranging from 90 - 120 minutes medium earth orbit (MEO), typical heights ranging from 5,000 - 25,000 km, with orbital periods ranging from 3 - 15 hours or geostationary earth orbit (GEO) height at about 35,786 km, with an orbital period of 24 hours satellite.

[00308] Two basic architectures can be distinguished for satellite communication networks, depending on the functionality of the satellites in the system: (1) Transparent pay load (also referred to as bent pipe architecture). The satellite forwards the received signal between the terminal and the network equipment on the ground with only amplification and a shift from uplink frequency to downlink frequency. When applied to general 3GPP architecture and terminology, the transparent payload architecture means that the gNB is located on the ground and the satellite forwards signals/data between the gNB and the UE; (2) Regenerative payload. The satellite includes on-board processing to demodulate and decode the received signal and regenerate the signal before sending it back to the earth. When applied to general 3 GPP architecture and terminology, the regenerative payload architecture means that the gNB is located in the satellite.

[00309] In the work item for NRNTN in 3 GPP release 17, only the transparent pay load architecture is considered. FIG. 5 illustrates an example architecture of a satellite network with bent pipe transponders (i.e. the transparent payload architecture). The gNB may be integrated in the gateway or connected to the gateway via a terrestrial connection (wire, optic fiber, wireless link).

[00310] A communication satellite typically generates several beams over a given area. The footprint of a beam is usually in an elliptic shape, which has traditionally been considered as a cell, but cells consisting of the coverage footprint of multiple beams are not excluded in the 3 GPP work. The footprint of a beam is also often referred to as a spotbeam. Its size depends on the system design, and may range from tens of kilometers to a few thousand kilometers.

[00311] Two different cell deployment principles are considered in 3GPP: 1) Moving cells; and 2) earth fixed cells (also referred to as pseudo earth fixed cells). In the case of moving cells, each cell (the footprint of its beam(s)) moves across the surface of the earth as its serving satellite moves along its orbit. In the case of earth fixed cells, the cell area (as the name implies) remains fixed to the same geographical area, regardless of satellite movements. To enable this, a serving satellite has to have means for dynamically directing its beam(s), so that the same area of the earth is covered despite the satellite’s movement. However, because the satellites orbit around the earth, the same satellite will only be able to cover the same area on the earth for a limited time, unless the satellite is in a geostationary orbit (and note that LEO satellites have the most traction in the satellite communication industry). This means the different satellites will have the task of covering a certain geographical cell area at different time periods. When this task is switched from one satellite to another, this in principle means that one cell is replaced by another, although covering the same area. As a consequence, all UEs connected in the old cell (i.e. UEs in RRC CONNECTED state) have to be handed over (or otherwise moved, e.g. using RRC connection reestablishment) from the old to the new cell, and all UEs camping on the old cell (i.e. UEs in RRC IDLE or RRC INACTIVE state) have to perform cell reselection to the new cell.

[00312] In terms of such cell switches there are two alternative principles: 1) Hard switch; and 2) soft switch. With hard switch, there is an instantaneous switch from the old to the new cell, i.e. the new cell appears at the same time as the old cell disappears. This makes completely seamless (i.e. interruption free) handover in practice impossible and creates a situation which may lead to overload of the access resources in the new cell, due to potential access attempt peaks when many UEs try to access the new cell right after the cell switch. With soft switch there is a time period during which the new and the old cell coexist (i.e. overlap), covering the same geographical area. This coexistence/overlap period allows some time for connected UEs to be handed over and for camping UEs to reselect to the new cell, which facilitates distribution of the access load in the new cell and thereby also provides better conditions for handovers with shorter interruption time.

[00313] Propagation delay is an important aspect of satellite communications. Its expected impact in NTN is different from the impacts of propagation delay in a terrestrial mobile system. For a bent pipe satellite network, the round-trip delay may, depending on the orbit height, range from tens of ms in the case of LEO satellites to several hundreds of ms for GEO satellites. As a comparison, the round-trip delays in terrestrial cellular networks are typically below 1 ms.

[00314] The distance between the UE and a satellite can vary significantly, depending on the position of the satellite and thus the elevation angle s seen by the UE. Assuming circular orbits, the minimum distance is realized when the satellite is directly above the UE (s = 90°), and the maximum distance when the satellite is at the smallest possible elevation angle. Table 16 shows the distances between satellite and UE for different orbital heights and elevation angles together with the one-way propagation delay and the maximum propagation delay difference (the difference from the propagation delay at s = 90°). Note that this table assumes regenerative payload architecture. For the transparent payload case, the propagation delay between gateway and satellite needs to be considered as well, unless the base station corrects for that.

TABLE 16 - Propagation delay for different orbital heights and elevation angles

[00315] The propagation delay may also be highly variable due to the high velocity of the LEO and MEO satellites and change in the order of 10 - 100 ps every second, depending on the orbit altitude and satellite velocity.

[00316] For Non-Terrestrial Networks using 3GPP technology, in particular 5G/NR, the long propagation delay means that the timing advance (TA) the UE uses for its uplink transmissions is essential and has to be much greater than in terrestrial networks in order for the uplink and downlink to be time aligned at the gNB, as is the case in NR and LTE. One of the purposes of the random access (RA) procedure is to provide the UE with a valid TA (which the network later can adjust based on the reception timing of uplink transmission from the UE). However, even the random access preamble (i.e. the initial message from the UE in the random access procedure) has to be transmitted with a timing advance to allow a reasonable size of the RA preamble reception window in the gNB (and to ensure that the cyclic shift of the preamble’s Zadoff-Chu sequence cannot be so large that it makes the Zadoff-Chu sequence, and thus the preamble, appear as another Zadoff Chu sequence, and thus preamble, based on the same Zadoff- Chu root sequence), but this TA does not have to be as accurate as the TA the UE subsequently uses for other uplink transmissions. The TA the UE uses for the RA preamble transmission in NTN is called “pre-compensation TA”. Various proposals have been considered for how to determine the pre-compensation TA, all of which involves information originating both at the gNB and at the UE. In brief, the remaining discussed alternative proposals include:

[00317] The UE autonomously calculates the propagation delay between the UE and the satellite, based on the UE’s and the satellite’s respective positions, and the network/gNB broadcasts the propagation delay between the satellite and the UL/DL alignment reference point (which typically is located in the gNB, but which in principle also may be located in the satellite or anywhere in between). The pre-compensation TA is then twice the sum of the propagation delay on the feeder link and the propagation delay between the satellite and the UE. (3 GPP has agreed to require support for this mechanism.); and

[00318] The gNB broadcasts a timestamp (in SIB9), which the UE compares with a reference timestamp acquired from GNSS. Based on the difference between these two timestamps, the UE can calculate the propagation delay between the gNB and the UE, and the pre-compensation TA is twice as long as this propagation delay.

[00319] In conjunction with the random access procedure, the gNB provides the UE with an accurate (i.e. fine-adjusted) TA in the Random Access Response message (in 4-step RA) or MsgB (in 2-step RA), based on the time of reception of the random access preamble. The gNB can subsequently adjust the UE’s TA using a Timing Advance Command MAC CE (or an Absolute Timing Advance Command MAC CE), based on the timing of receptions of uplink transmissions from the UE. A goal with such network control of the UE’s timing advance is typically to keep the time error of the UE’s uplink transmissions at the gNB’s receiver within the cyclic prefix (which is required for correct decoding of the uplink transmissions). The timing advance control framework also includes a time alignment timer that the gNB configures the UE with. The time alignment timer is restarted every time the gNB adjusts the UE’s TA and if the time alignment timer expires, the UE is not allowed to transmit in the uplink without a prior random access procedure (which serves the purpose to provide the UE with a valid timing advance). For NTN, 3GPP has also agreed that in addition to the gNB’s control of the UE’s TA, the UE is allowed to autonomously update its TA based on estimation of changes in the UE-gNB RTT using the UE’s location (e.g. obtained from GNSS measurement) and knowledge of the serving satellite’s ephemeris data and feeder link delay information from the gNB. 3GPP is also considering letting the UE signal the TA it used for the preamble transmission in Msg3 or Msg5 in 4-step RA and in MsgA (or a subsequent message) in 2-step RA.

[00320] A second relevant aspect is that not only is the propagation delay between the UE and a satellite, or between the UE and a gNB, very long in NTN, but the due to the large distances, the difference in propagation delay to two different satellites, or two different gNBs, may be significant on the timescales relevant for cellular communication, including signaling procedures, even when the satellites/gNBs serve neighboring cells. This has an impact on all procedures involving reception or transmission in two cells served by different satellites and/or different gNBs.

[00321] A third important aspect related to the long propagation delay/RTT in NonTerrestrial Networks is the introduction of an additional parameter to compensate for the long propagation delay/RTT. In terrestrial cellular networks, the UE-gNB RTT may range from more or less zero to several tens of microseconds in a cell. A major difference in Non-Terrestrial Networks, apart from the shear size of the propagation delay/RTT, is that even at the location in the cell where the propagation delay/RTT is the smallest, it will be large and nowhere close to zero. In fact, the variation of the propagation delay/RTT within a NTN cell is small compared to the propagation delay/RTT. This speaks in favor of introducing an offset which essentially takes care of the RTT between the cell’s footprint on the ground and the satellite, while other mechanisms, including signaling and control loops, take care of the RTT dependent aspects within the smaller range of RTT variation within the cell on top of the offset. To this end, 3 GPP has agreed to introduce such a parameter, which is denoted Koffset (or sometimes K offset).

[00322] The Koffset parameter may potentially be used in various timing related mechanisms, but in the context of this disclosure, the relevant application of Koffset is its use in scheduling of uplink transmissions on the PUSCH. Koffset is used to indicate an additional delay between the UL grant and the PUSCH transmission resources allocated by UL grant to be added to the slot offset parameter K2 in the DCI containing the UL grant. The offset between the UL grant and the slot in which the PUSCH transmission resources are allocated is thus Koffset + K2. When used this way in uplink scheduling, Koffset can be said to serve the purpose to ensure that the UE is never scheduled to transmit at a point in time that, due to the large TA the UE has to apply, would occur before the point in time when the UE receives the UL grant.

[00323] As opposed to K2, Koffset is assumed to neither be included in the UL grant nor in the uplink time domain resource allocation table to be applied. Instead, Koffset is assumed to be signaled by other means, such as RRC signaling or MAC signaling (the details of this signaling are not decided yet in 3 GPP but some form of RRC signaling is the most likely outcome). In 3 GPP, it is also discussed to let the network’s configuration of Koffset take into account the TA the UE has signaled that it has used.

[00324] A fourth important aspect closely related to the timing is a Doppler frequency offset induced by the motion of the satellite. The access link may be exposed to Doppler shift in the order of 10 - 100 kHz in sub-6 GHz frequency band and proportionally higher in higher frequency bands. Also, the Doppler shift is varying, with a rate of up to several hundred Hz per second in the S-band and several kHz per second in the Ka-band.

[00325] In reference [2] it has been captured that ephemeris data should be provided to the UE, for example to assist with pointing a directional antenna (or an antenna beam) towards the satellite, and to calculate a correct Timing Advance (TA) and Doppler shift. Procedures on how to provide and update ephemeris data have not yet been studied in detail, though, but broadcasting of ephemeris data in the system information is one option.

[00326] A satellite orbit can be fully described using 6 parameters. Exactly which set of parameters is chosen can be decided by the user; many different representations are possible. For example, a choice of parameters used often in astronomy is the set (a, s, i, Q, co, t). Here, the semi-major axis a and the eccentricity s describe the shape and size of the orbit ellipse; the inclination i, the right ascension of the ascending node Q, and the argument of periapsis co determine its position in space, and the epoch t determines a reference time (e.g. the time when the satellites moves through periapsis). This set of parameters is illustrated in FIG. 6.

[00327] As an example of a different parametrization, the TLEs use mean motion n and mean anomaly M instead of a and t. A completely different set of parameters is the position and velocity vector (x, y, z, v _x , v _y , v _z ) of a satellite. These are sometimes called orbital state vectors. They can be derived from the orbital elements and vice versa, because the information they contain is equivalent. All these formulations (and many others) are possible choices for the format of ephemeris data to be used in NTN. To enable further progress, the format of the data should be agreed upon.

[00328] The discussion in Section 2.2.1 has shown that it is important that a UE can determine the position of a satellite with accuracy of at least a few meters. However, several studies have shown that this might be hard to achieve when using the de-facto standard of TLEs. On the other hand, LEO satellites often have GNSS receivers and can determine their position with some meter level accuracy. [00329] Another aspect discussed during the study item and captured in reference [2], is the validity time of ephemeris data. Predictions of satellite positions in general degrade with increasing age of the ephemeris data used, due to atmospheric drag, maneuvering of the satellite, imperfections in the orbital models used, etc. Therefore, the publicly available TLE data are updated quite frequently, for example. The update frequency depends on the satellite and its orbit and ranges from weekly to multiple times a day for satellites on very low orbits which are exposed to strong atmospheric drag and need to perform correctional maneuvers often.

[00330] So, while it seems possible to provide the satellite position with the required accuracy, care needs to be taken to meet these requirements, e.g. when choosing the ephemeris data format, or the orbital model to be used for the orbital propagation.

[00331] As the outcome of the study items (see references [1] and [2]) in 3 GPP lay the foundation for the specification work of Non-Terrestrial Networks in 3GPP, it is relevant as background information herein. The following includes some relevant information from the study items and the resulting technical reports.

[00332] The coverage pattern of NTN is described in section 4.6 of reference [1] as follows:

[00333] Satellite or aerial vehicles typically generate several beams over a given area. The foot print of the beams are typically elliptic shape. The beam footprint may be moving over the earth with the satellite or the aerial vehicle motion on its orbit. Alternatively, the beam foot print may be earth fixed, in such case some beam pointing mechanisms (mechanical or electronic steering feature) will compensate for the satellite or the aerial vehicle motion.

TABLE 17 - Typical beam footprint size

[00334] Typical beam patterns of various NTN access are illustrated in FIG. 9.

[00335] The TR of the second study item (see reference [2]) describes scenarios for the NTN work as follows:

[00336] Non-Terrestrial Network typically features the following elements:

[00337] One or several sat-gateways that connect the Non-Terrestrial Network to a public data network

[00338] a GEO satellite is fed by one or several sat-gateways which are deployed across the satellite targeted coverage (e.g. regional or even continental coverage). We assume that UE in a cell are served by only one sat-gateway

[00339] A Non-GEO satellite served successively by one sat-gateway at a time. The system ensures service and feeder link continuity between the successive serving sat-gateways with sufficient time duration to proceed with mobility anchoring and hand-over

[00340] Four scenarios are considered as depicted in table 8 and are detailed in table 19.

TABLE 18 - Reference scenarios

TABLE 19 - Reference scenario parameters

[00341] Each satellite has the capability to steer beams towards fixed points on earth using beamforming techniques. This is applicable for a period of time corresponding to the visibility time of the satellite. Max delay variation within a beam (earth fixed user equipment) is calculated based on Min Elevation angle for both gateway and user equipment. Max differential delay within a beam is calculated based on Max beam foot print diameter at nadir.

[00342] For scenario D, which is LEO with regenerative payload, both earth-fixed and earth moving beams have been listed. So, when we factor in the fixed/non-fixed beams, we have an additional scenario. The complete list of 5 scenarios in reference [2] is then: (1) Scenario A - GEO, transparent satellite, Earth-fixed beams; (2) Scenario B - GEO, regenerative satellite, Earth fixed beams; (3) Scenario C - LEO, transparent satellite, Earth-moving beams; (4) Scenario DI - LEO, regenerative satellite, Earth-fixed beams; (5) Scenario D2 - LEO, regenerative satellite, Earth-moving beams. [00343] GNSS

[00344] A Global Navigation Satellite System comprises a set of satellites orbiting the earth in orbits crossing each other, such that the orbits are distributed around the globe. The satellites transmit signals and data that allows a receiving device on earth to accurately determine time and frequency references and, maybe most importantly, accurately determine its position, provided that signals are received from a sufficient number of satellites (e.g. four). The position accuracy may typically be in the range of a few meters, but using averaging over multiple measurements, a stationary device may achieve much better accuracy.

[00345] A well-known example of a GNSS is the American Global Positioning System (GPS). Other examples are the Russian Global Navigation Satellite System (GLONASS), the Chinese BeiDou Navigation Satellite System and the European Galileo.

[00346] The transmissions from GNSS satellites include signals that a receiving device uses to determine the distance to the satellite. By receiving such signals from multiple satellites, the device can determine its position. However, this requires that the device also knows the positions of the satellites. To enable this, the GNSS satellites also transmit data about their own orbits (from which position at a certain time can be derived). In GPS, such information is referred to as ephemeris data and almanac data (or sometimes lumped together under the term navigation information).

[00347] The time required to perform a GNSS measurement, e.g. GPS measurement, may vary widely, depending on the circumstances, mainly depending on the status of the ephemeris and almanac data the measuring devices has previously acquired (if any). In the worst case, a GPS measurement can take several minutes. GPS is using a bit rate of 50 bps for transmitting its navigation information. The transmission of the GPS date, time and ephemeris information takes 90 seconds. Acquiring the GPS almanac containing orbital information for all satellites in the GPS constellation takes more than 10 minutes. If a UE already possesses this information the synchronization to the GPS signal for acquiring the UE position and Coordinated Universal Time (UTC) is a significantly faster procedure.

[00348] 3 GPP NTN dependence of GNS S

[00349] To handle the timing and frequency synchronization in a NR or LTE based NTN a promising technique is to equip each device with a Global Navigation Satellite System (GNSS) receiver. The GNSS receiver allows a device to estimate its geographical position. In one example, a NTN gNB carried by a satellite broadcasts its ephemeris data (i.e. data that informs the UE about the satellite’s position, velocity and orbit) to a GNSS equipped UE. The UE can then determine the propagation delay, the delay variation rate, the Doppler shift and its variation rate based on its own location (obtained through GNSS measurements) and the satellite location and movement (derived from the ephemeris data).

[00350] The GNSS receiver also allows a device to determine a time reference (e.g. in terms of Coordinated Universal Time (UTC)) and frequency reference. This can also be used to handle the timing and frequency synchronization in a NR or LTE based NTN. In a second example a NTN gNB carried by a satellite broadcasts its timing (e.g. in terms of a Coordinated Universal Time (UTC) timestamp) to a GNSS equipped UE. The UE can then determine the propagation delay, the delay variation rate, the Doppler shift and its variation rate based on its time/frequency reference (obtained through GNSS measurements) and the satellite timing and transmit frequency.

[00351] The UE may use this knowledge to compensate its UL transmissions for the propagation delay and Doppler effect. The 3GPP release 17 SID on NB-IoT and LTE-M for NTN supports this observation: “GNSS capability in the UE is taken as a working assumption in this study for both NB-IoT and eMTC devices. With this assumption, UE can estimate and precompensate timing and frequency offset with sufficient accuracy for UL transmission. Simultaneous GNSS and NTN NB-IoT/eMTC operation is not assumed.”

[00352] Furthermore, in the NTN work item and loT NTN study item for 3 GPP release 17, GNSS capability is assumed, i.e. it is assumed that a NTN capable UE also is GNSS capable and GNSS measurements at the UEs are essential for the operation of the NTN.

[00353]

[00354] Connected mode mobility challenges have been studied in the NTN Release 16 study item phase and are reported in reference [2], Two of the challenges discussed in the Technical Report are frequent and unavoidable handovers (e.g. due to feeder link switch) and handover of a large number of UEs, both of them could result in significant control plane overheads and frequent service interruptions. This issue is perhaps most pronounced in the quasi- earth-fixed cell scenario when a geographic area is covered by a satellite (cell) for a limited time period while being replaced by a new satellite (cell) during the next time period, and so on. When the satellite covering the geographic area is replaced, the cell is also replaced, meaning that all the UEs connected in the old cell have to be handed over to the new cell, which potentially results in a high control signaling peak, because all the handovers have to occur in conjunction with the cell replacement (a.k.a. cell switch). Hard and soft cell switch have been discussed, with preference for the soft switch case, wherein the old and the new cell both (simultaneously) cover the geographic area during a short overlap period, to simplify handovers with low interruptions.

[00355] To mitigate the expected signaling overhead at frequent handovers for a large number of UEs, 3 GPP agreed to introduce support for Conditional Handover (CHO) for NTN in Release 17 with the CHO procedure and the trigger conditions as defined in Release 16 as a baseline.

[00356] In terrestrial networks, a UE can typically determine it is near a cell edge due to a clear difference in received signal strength (e.g. by performing RSRP-based measurements) as compared to the cell center. In NTN deployments on the other hand, it is typically a small difference in signal strength between the cell center and the cell edge. Thus, a UE may experience a small difference in signal strength between two beams (cells) in a region of overlap. This may lead to suboptimal UE behaviors such as repetitive handovers (“ping-pong”) between the two cells.

[00357] To avoid an overall reduction in handover robustness, 3 GPP agreed to introduce the following trigger conditions (apart from the already existing trigger conditions, the A3 and A5 events) for CHO in NTN. A new time-based trigger condition, defining a time period, or a time window, when the UE may execute CHO to a candidate target cell. A new location-based trigger condition, defining a distance threshold from the UE to the source cell and to a candidate target cell, based on which the UE may trigger and execute CHO, reuse of the existing A4 event (Neighbor becomes better than threshold) as defined in 3 GPP TS 38.331.

[00358] The time-based trigger condition is defined by 3 GPP as the time period [tl, t2] associated to each candidate target cell, where Tl is the starting point of the time period represented by a Coordinated Universal Time (UTC), e.g. 00:00:01, and T2 is the end point of the time period represented by a time duration or a timer value, e.g. 10 seconds.

[00359] In the present running Change Request (CR) (as of January 11 , 2022) for NR NTN for 3GPP TS 38.331 in Release 17 (a CR that is still being revised in 3GPP TSGRAN2), the time-based condition (condEventTl-rl7) is defined in ASN.1 in the ReportConfigNR IE as shown below:

TABLE 20

[00360] The duration encoded by the duration-r 17 field should be counted as starting from

Tl, which means that in principle T2 = T1 + duration = tl-Threshold-rl7 + duration-rl7. As can be seen, the definition of the duration-r 17 field (i.e. the different timer/ duration values) is still not concluded in 3GPP TSG RAN2. 3GPP further agreed that the time-based trigger condition can only be configured to the UE in combination with one of the signal strength/quality based events A3, A4 or A5. This implies that the UE may only perform CHO to the candidate target cell in the time window defined by Tl and T2 if the signal strength/quality based event is fulfilled within this time frame.

SUMMARY

[00361] There currently exist certain challenges with combining CHO and RACH-less HO to reap the benefits of both features, i.e. both robustness and reduction of handover interruption. For example, a significant difference between regular handover and CHO is that with regular handover the handover is executed immediately after the handover preparation, whereas the time between preparation and execution of CHO is inherently a priori unknown. The time during which a target node has to reserve PUSCH resources for pre-allocated UL grants or for dynamically scheduled UL grants during a regular RACH-less handover is thus limited with a predictable upper bound (limited by timer T304 plus a possible margin), while the corresponding time when RACH-less access is combined with CHO becomes unlimited and consequently the cost in terms of reserved/wasted PUSCH resources may be significant and potentially prohibitively large.

[00362] Certain aspects of the disclosure and their embodiments may provide solutions to these or other challenges. For example, it is proposed to limit the amount of PUSCH resources that can be wasted in a (candidate) target cell. In some embodiments of the proposed solution, this is achieved by configuring a CHO execution condition based on a time period (e.g., in the form of an absolute time and a duration), during which the CHO may be executed, i.e. indicating the longest the UE can delay the CHO execution as well as the earliest time it can execute the CHO. This time period can provide upper bounds to the time period during which UL grants are pre-allocated or dynamically scheduled via PDCCH transmissions. With the time-bound execution of the CHO, the target base station (e.g., gNB or eNB) may limit the pre-allocated UL grants (or dynamically allocated UL grants) it provides to a (potentially) small set, e.g. 1, 2, 3, 4 or 5.

[00363] This concept of limiting the number of pre-allocated (or dynamically allocated) UL grants for RACH-less access may also be applied without a combination with CHO (or other conditional mobility procedure), wherein the procedure should rather be seen as a handover (or other access) with time-scheduled access execution, e.g. in a target cell. Such a small/limited set of pre-allocated UL grants may be configured using an extension of the parameters specified for configuration of pre-allocated UL grants for RACH-less handover/access in LTE, or may consist completely of new configuration parameters. That is, it is proposed to limit the amount of PUSCH resources that may be wasted (i.e. allocated but not utilized) in conjunction with RACH- less access, in particular when RACH-less access is combined with a conditional mobility procedure, such as CHO. In some embodiments, this is achieved by having a time-bound period for potential execution of RACH-less access attempts, within which pre-allocated or dynamically allocated UL grants are provided. In other embodiments, the pre-allocated UL grants are configured as a specific set of UL grants, which constitute the UE’s only chance(s) to execute the RACH-less access.

[00364] Accordingly, in one aspect there is provided a method performed by a UE. The method includes obtaining a message (a CHO configuration message or a handover command) configuring a time period during which a CHO can be executed. The method also includes obtaining a set of one or more pre-allocated uplink grants to be used with the CHO.

[00365] In another aspect there is provided a method performed by a network node. The method includes providing a user equipment, UE, with a message (a CHO configuration message or a handover command) configuring a time period during which a CHO can be executed, the method also includes providing the UE with a set of one or more pre-allocated uplink grants to be used with the CHO.

[00366] Certain embodiments may provide one or more of the following technical advantage(s). For example, certain embodiments allow conditional handover (CHO) and RACH-less handover/access to be combined without excessive waste of PUSCH transmission resources.

BRIEF DESCRIPTION OF THE DRAWINGS

[00367] FIG. 1 illustrates a 4-step random access procedure.

[00368] FIG. 2 Illustrates of PRACH configuration in NR.

[00369] FIG. 3 illustrates a 2-step random access procedure.

[00370] FIG. 4 illustrates timing and latency differences between 4-step RA and 2-step RA.

[00371] FIG. 5 illustrates an example architecture of a satellite network with bent pipe transponders.

[00372] FIG. 6 illustrates orbital elements.

[00373] FIG. 7 illustrates a conditional handover procedure

[00374] FIG. 8 illustrates two error cases which are addressed by the Conditional

Handover concept.

[00375] FIG. 9 illustrates typical beam patterns of various NTN access

[00376] FIG. 10 is a flowchart illustrating a process according to an embodiment.

[00377] FIG. 11 shows an example of a communication system in accordance with some embodiments. [00378] FIG. 12 shows a UE in accordance with some embodiments.

[00379] FIG. 13 shows a network node in accordance with some embodiments.

[00380] FIG. 14 shows a host in accordance with some embodiments.

[00381] FIG. 15 is a block diagram illustrating a virtualization environment in which functions implemented by some embodiments may be virtualized.

[00382] FIG. 16 shows a communication diagram of a host communicating via a network node with a UE over a partially wireless connection in accordance with some embodiments.

[00383] FIG. 17 is a flowchart illustrating a process according to some embodiments.

[00384] FIG. 18 is a flowchart illustrating a process according to some embodiments.

DETAILED DESCRIPTION

[00385] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art. As an initial matter, reference to a network node will typically be a gNB or eNB, but which may also be another type of network node with the ability to communicate with a UE. Transmission of a random access preamble, or random access preamble transmission, can be considered equivalent to the term PRACH transmission (because the random access preamble is transmitted on the Physical Random Access Channel (PRACH)). In the context of this disclosure, the term “preamble” is used as short for “random access preamble”.

[00386] The term “pre-allocated UL grant” in most cases refers to the PUSCH transmission resources allocated by the pre-allocated UL grant, but in some cases, depending on the context, it may refer to the scheduling information of the UL grant itself. The terms “Handover Command” and “HandoverCommand” are used interchangeably, and when used for a conditional handover, “CHO command” and “conditional handover command” are also used as a equivalent terms. When CHO is configured for a UE, a cell which the UE potentially can connect to (i.e. if the CHO execution condition is fulfilled for the cell) is denoted as “candidate target cell”. Similarly, a RAN node controlling a candidate target cell is denoted as “candidate target node”, “candidate target gNB” or “candidate target eNB”. However, once the UE has detected a fulfilled CHO execution condition for a candidate target cell, this terminology becomes a bit blurred. At this point, during the actual execution of the CHO and when the UE has connected to the new cell, the concerned cell may be referred to as either a “candidate target cell” or a “target cell”. Similarly, a RAN node controlling such a cell, may in this situation be referred to as either a “candidate target node/gNB/eNB” or a “target node/gNB/eNB”.

[00387] To address the problem associated with the combination of CHO and RACH-less handover, a means to limit the amount of PUSCH resources that can be wasted in a (candidate) target cell is needed. To this end, it is proposed herein to configure a CHO execution condition based on a time period (e.g., in the form of an absolute time indication and a duration), during which the CHO may be executed, i.e. indicating the longest the UE can delay the CHO execution as well as the earliest time it can execute the CHO. This time period indication can provide upper bounds to the time period during which UL grants are pre-allocated or scheduled via PDCCH transmissions. As one option, the end of the time period during which UL grants are pre-allocated or scheduled via PDCCH transmissions would be some time after the end of the time period indicated in the CHO execution condition, because the UE may not start its first access attempt in the target cell until the end of the indicated time period is reached, or right before it is reached and may sometimes also need multiple attempts before the access succeeds.

[00388] In some embodiments, the time-based CHO execution condition mandates the UE to successfully access the candidate target cell before the time period indicated in the CHO execution condition expires (i.e. in the context of this disclosure the UE has to successfully utilize an UL grant before the time period expires). With this option, the candidate target node may not pre-allocate any UL grants or dynamically allocate any UL grants via the PDCCH after the end of the time period indicated in the CHO execution condition (although if the UE successfully accesses the target cell, the target node may continue to allocate UL grants to the UE via the PDCCH when appropriate).

[00389] In some embodiments, the end of the time period indicated in the CHO execution condition should be interpreted as the latest point in time when the UE can transmit the Handover Complete message (i.e. the RRCReconfigurationComplete message (in NR) or RRCConnectionReconfigurationComplete message (in LTE) confirming the RRC configuration received in the Handover Command). In some embodiments, the Handover Complete message must be successfully received by the gNB or eNB no later than the end of the time period indicated in the CHO execution condition. In some embodiments, it is enough that the UE sends a first transmission of the Handover Complete message before the end of the indicated time period and then HARQ retransmissions are allowed to continue after the indicated time.

[00390] In 3GPP release 17, the time-based CHO execution condition will always be combined with a signal strength/quality-based CHO condition. However, CHO configurations where the CHO execution condition may consist of only the time period indication (or a single time indication, e.g. indicating the earliest allowed or the latest allowed CHO execution), are conceivable in future releases of the standard, which would mean that the CHO in principle becomes a predictably delayed handover execution. This option may be useful, e.g. in earth fixed cells deployments in NTN, when the time at which a UE needs to handover from an old cell to a new cell covering the same geographical area (but served via another satellite) is predictable, as the time of the cell switch (with or without a time period of coexistence/overlap between the new and the old cell) is known a priori in the network.

[00391] With the time-bound execution of the conditional handover (with or without a signal strength/quality-based CHO execution condition in addition to the time-based CHO execution condition), the target gNB or eNB may limit the pre-allocated UL grants it provides to a time period (e.g. corresponding to the time period indicated in the time-based CHO execution condition), or a (potentially) small set, e.g. 1, 2, 3, 4 or 5 pre-allocated UL grants, where the last UL grant in the set may (as one option) occurs at a time at or close to the latest CHO execution time according to the time-based CHO execution condition. In principle, the set could consist of only a single pre-allocated UL grant, or a set whose combined duration does not fill up the entire time period indicated by the time-based CHO execution condition. In the case where the timebased CHO execution condition is combined with a signal strength/quality-based CHO execution condition, such a single pre-allocated UL grant (or set of pre-allocated UL grants) would preferably be located at the end (or close to the end) of the time period indicated in the timebased CHO execution condition to allow the signal strength/quality-based CHO execution condition to have a maximum chance of being fulfilled when the pre-allocated UL grant occurs (or when the last pre-allocated UL grant in the set of pre-allocated UL grants occurs). On the other hand, in the case where the time-based CHO execution condition is the only CHO execution condition, a single pre-allocated UL grant (or a set of pre-allocated UL grants) could be configured to occur at any time during the time period indicated in the time-based CHO execution condition.

[00392] Even though a single pre-allocated UL grant in principle would suffice in conjunction with a time-based CHO execution condition, a reason for pre-allocating more than one UL grant is that it gives the UE a few chances to (re-)try, in case the first access attempt (i.e. attempt to transmit on the PUSCH resources allocated by a pre-allocated UL grant) fails. If the UE’s UL transmission attempt fails on all the pre-allocated UL grants (or if it skips some, and fails on the rest), the UE may optionally revert to contention-based random access (CBRA) to access the (candidate) target cell, e.g. until the handover supervision timer (timer T304) expires. If that also fails, the UE may determine that the handover has failed and may initiate the RRC connection reestablishment procedure. As an option, after failing to utilize any of the preallocated UL grants, the UE may skip trying to access the target cell using contention based random access and instead go directly to the RRC connection reestablishment procedure. As another option, the network may have configured the UE with contention-free random access (CFRA) resources, e.g. in the form of one or more dedicated CFRA preambles, in addition to the RACH-less configuration. In such a case, the UE may try CFRA after failing the RACH-less access and if that also fails, the UE may try to access the target cell using CBRA, and finally, if this also fails initiate the RRC connection reestablishment procedure. As yet another option, if the UE fails to utilize any of the pre-allocated UL grants, after the time of the last pre-allocated UL grant, the network, e.g. the gNB or eNB, may attempt to schedule the UE using dynamic UL grants on the PDCCH (i.e. in essence reverting to the other type of RACH-less access). If this strategy is used, the network should configure the UE to be prepared for this network behavior beforehand, e.g. by indicating in the conditional handover configuration, the handover configuration, the RACH-less configuration, or in the message carrying any of these configurations to the UE.

[00393] When only a limited set of pre-allocated UL grants are provided, the configuration parameters for the pre-allocated UL grants (i.e. the occasions in the time domain at which PUSCH time/frequency resources are allocated by the pre-allocated UL grants) may be extended with parameters indicating at least two of start, stop and duration of the set, or two out of start (first), stop (last) and number of pre-allocated UL grants in the set. Together with the current parameters, which express the periodicity of the pre-allocated UL grants (i.e. the periodicity of the PUSCH resources allocated by the pre-allocated UL grants) and the transmission resources in the OFDM time/frequency grid, the new parameters would provide the UE with the complete information to determine exactly at what time (or times) and frequency (or frequencies) it is allowed to transmit when it executes the RACH-less CHO. Another option for the configuration could be explicit indication(s) of each of the pre-allocated UL grant(s) (i.e. the PUSCH resources it allocates) in the set.

[00394] The time indications, e.g. for the first and the last pre-allocated UL grant allocation, should be unambiguous. The means required to provide such unambiguity may depend on the time duration/delay between the time of configuration and the point in time the time indication points out. If this duration/delay is less than an SFN cycle (which is 10.24 seconds), then the SFN combined with a slot number and symbol number (where time domain information inherently included in an UL grant - e.g. a slot offset and a start symbol indication - optionally may be included). If the duration/delay between the time of configuration and the indicated timepoint is longer than an SFN cycle, then additional information may be needed to make the time indication unambiguous. Such additional information may for example be an indication of the number of full SFN cycles, e.g. in the form of a Hyper-SFN (HSFN) which is defined for certain scenarios in LTE. Another option could be a UTC timestamp, or a GNSS timestamp, which at least approximately indicates the concerned point in time, wherein the complementing SFN, slot and symbol indication makes the indication precise. Alternatively, the UTC or GNSS timestamp may be more accurate such that it only needs to be combined with slot and symbol number, or only symbol number, or no complementing information at all (i.e. only UTC or GNSS timestamp).

[00395] When a limited set of pre-allocated UL grant is configured, with an unambiguous indication of the occasions at which they occur in the time domain, e.g. indications of the first and the last pre-allocated UL grant (i.e. the occurrences of the PUSCH resources they allocate) and the periodicity of the pre-allocated UL grants in the set (or an indication of the time of the first pre-allocated UL grant, the number of pre-allocated UL grants and the periodicity of the preallocated UL grants in the set) , an observation is that the CHO execution condition may be superfluous if it consists of only a time-based execution condition (i.e. a time period during which the CHO must be executed). One may thus skip the time-based condition and only indicate the small set of pre-allocated UL grants (which in principle becomes a time-based CHO execution condition, because they imply a time period (from the first to the last of the UL grants in the set) during which the RACH-less handover may be executed). In principle, this time period is actually a set of timepoints, or very short subintervals, represented by the PUSCH occasions, i.e. the UL transmission resources allocated by the pre-allocated UL grants.

[00396] In the above embodiments where a CHO execution condition is described as including, or consisting of, a time-based condition, this time-based condition may alternatively be contained in the (conditional) Handover Command instead of the CHO execution condition.

[00397] A similar concept can be applied when dynamically allocated UL grants are used for the RACH-less access, leveraging the time interval configured in the time-based CHO execution condition, within which the RACH-less access must occur. According to one embodiment, within this time interval, the candidate target gNB/eNB may schedule the UE using dynamically allocated UL grants (on the PDCCH) in the candidate target cell. As one option, the number of times the candidate target gNB/eNB schedules the UE in the candidate target gNB/eNB is not configured, and the candidate target gNB/eNB is free to do it any number of times that it chooses, until the configured time interval ends, or the UE successfully utilizes one of the dynamically allocated UL grant(s). As another option, the candidate target gNB/eNB configures the number of times, N, the candidate target gNB/eNB will schedule the UE in the candidate target cell using dynamically allocated UL grant(s) within the configured time interval. If the UE successfully utilizes one of the dynamically allocated UL grants, the target gNB/eNB may skip any remaining of the configured number N of dynamically allocated UL grants. On the UE side, if the UE receives N dynamically allocated UL grant(s) on the PDCCH, but the UE fails to utilize it/them (i.e. the UE fails to utilize any of the N dynamically allocated UL grants despite receiving all of them on the PDCCH), e.g. due to transmission/reception errors, poor channel quality and/or lack of explicit or implicit positive feedback (e.g. HARQ or RLC), the UE may stop monitoring the PDCCH for unsolicited dynamically allocated UL grants and instead conclude that the RACH-less access has failed. (Note that there is a risk in doing this, because it is possible that one (or more) of the reception(s) of a dynamically allocated UL grant on the PDCCH was erroneously perceived as such due to a bit error that the forward error correction mechanisms failed to correct, which would mean that target gNB/eNB may not yet have sent the N dynamically allocated UL grants in the target cell.)

[00398] After the UE has determined that the RACH-less access has failed, it may proceed as previously described for the embodiments involving RACH-less access using pre-allocated UL grants, i.e. the UE may try to access the target cell using CBRA, or using CFRA followed by CBRA in case CFRA fails and/or initiate the RRC connection reestablishment procedure if the RACH-less access fails or if both the RACH-less access and any RA-based access attempts fail.

[00399] A UE can be provided with a set of CHO commands for RACH-less CHO, e.g. for different candidate target cells. Presently, if a UE executes a CHO command towards a selected target cell, the target gNB (or target eNB if CHO is specified for LTE) determines that the UE has executed a handover towards a target cell controlled by the target gNB (or eNB), and the target gNB (or eNB) informs the source gNB using the HANDOVER SUCCESS XnAP message (or informs the source eNB in a corresponding X2AP message). In one embodiment, in response to this, the source gNB (or eNB) indicates to other candidate target gNB(s) (or eNB(s)) (i.e. other gNB(s) (or eNB(s) which also have provided CHO commands to the UE), which were not selected for CHO execution by the UE, that the UE has executed a CHO. Those other gNB(s) (or eNB(s)) may in response to such an indication determine that the allocated RACH-less access resources for the UE (if any) - such as PUSCH resources allocated by pre-allocated UL grants - are obsolete and/or that they will not be used by the UE. Those resource may hence be used to schedule other UEs, etc.

[00400] In all the above embodiments, where CHO is involved, the embodiments may also be applied in scenarios where CHO is replaced by any other conditional mobility procedure or conditional mobility related procedure or conditional RRC reconfiguration (or other conditional reconfiguration) involving or requiring access to a cell, e.g. conditional PSCell change or conditional PSCell addition.

[00401] In case a UE is configured with a CHO, the UE can execute a stored CHO if the UE experiences RLF in the source cell. This ensures that a connection reestablishment procedure is avoided and instead the UE applies the already provided (conditional) handover command if an RLF is triggered. In case the UE has received a CHO configuration with a CHO command with a RACH-less configuration, and if RLF is detected in the source cell, the UE may be configured to ignore the RACH-less component of the CHO command and instead execute the CHO by applying a RA procedure. This ensures that if RLF is experienced and if the UE finds a cell for which it has a CHO command, the UE would execute that CHO command directly (by performing an RA procedure) even though the network has indicated to the UE that the UE shall perform a RACH-less execution of that CHO command e.g. utilizing UL grants pre-allocated that will not occur until after some further delay into the future. That is, this feature would ensure that the UE does not unduly delay the access to the target cell (after RLF in the source cell) by waiting for pre-allocated UL grants to occur. If the UE supports this behavior, the UE may be configured to discard the RACH-less resources that it has been provided with in the CHO command. This UE behavior may be conditioned by the remaining delay to the first or next preallocated UL grant, e.g. such that if this remaining delay exceeds a configured (or specified) threshold, the UE ignores the RACH-less resources and tries to access the cell using random access, while if this remaining delay is below the threshold, the UE waits for the first/next preallocated UL grant and utilizes this pre-allocated UL grant to try to access the cell. Similarly, on the network side: the target gNB/eNB can, upon detection that the UE performs a (RA-based) CHO towards the target cell, realize that the UE has executed the CHO towards the target cell by means of Random Access (rather than by means of a RACH-less procedure). The target gNB/eNB can then consider the RACH-less resources provided for the UE as obsolete and/or can determine that they will not be used by this UE.

[00402] A similar approach as in the above described methods related to RACH-less access could also be applied to CFRA, e.g. in conjunction with a mobility procedure in RRC CONNECTED state (such as handover, reconfigurationWithSync, PSCell addition or PSCell change). To this end, a target gNB/eNB could configure a small set of PRACH occasions for which a CFRA configuration is valid (e.g. configured in the RACH-ConfigDedicated IE), wherein the last of these PRACH occasions occurs before the T304 timer expires, possibly allowing time for one or more CBRA attempts in the target cell between the last PRACH occasion for CFRA and the expiration of timer T304. This approach limits the usage of potentially scarce CFRA resources, while not restricting the time the UE has to execute a handover (governed by the T304 timer), i.e. without configuring an undesirably short T304 timer. It may be applied to both 4-step RA and 2-step RA.

[00403] This principle could also be applied to 2-step RA resources in conjunction with handover, wherein it may be beneficial to limit the configured 2-step RA resources without shortening the time the UE has to execute the handover, having in mind that 2-step RA resources are more costly than 4-step RA resources, because, for 2-step RA, PUSCH resources are configured (and reserved) in addition to PRACH resources. For instance, the network (e.g. a target gNB/eNB) could allocate a limited set of 2-step RA resources (which could be 2-step CFRA resources or 2-step CBRA resources), wherein the last of these 2-step RA resources (in terms of PRACH occasion and associated PUSCH occasion) occurs before the T304 timer expires, possibly allowing time for one or more 4-step RA attempts in the target cell between the last PRACH occasion (and associated PUSCH occasion) for 2-step RA and the expiration of timer T304.

[00404] Combinations of the above RA configuration methods in conjunction with mobility in RRC_CONNECTED state are also conceivable. To this end, a target gNB/eNB may configure multiple limited sets of special resources, e.g. a combination of a limited set of 2-step CFRA resources, a limited set of 2-step CBRA resources, and/or a limited set of 4-step CFRA resources. As one option, the multiple limited sets may be configured such that they will occur in sequence in the time domain. As an example of such a scheme, a target gNB of a mobility procedure in RRC CONNECTED state may configure a limited set of 2-step CFRA resources, followed by a limited set of 2-step CBRA resources, followed by a limited set of 4-step CFRA resources. When provided with such a configuration for target cell access in conjunction with a mobility procedure in RRC CONNECTED state, the UE may first try to access the target cell using the limited set of configured 2-step CFRA resources, and if this fails, the UE may try the limited set of 2-step CBRA resources, and if this also fails, the UE may try the limited set of 4- step CFRA resources, and if this also fails, the UE may try to access the target cell using 4-step CBRA if there are any PRACH occasions for 4-step RA available before the T304 timer expires.

[00405] As another example, the target gNB of a mobility procedure in

RRC CONNECTED state may configure a limited set of 2-step CBRA resources, followed by a limited set of 4-step CFRA resources. When provided with such a configuration for target cell access in conjunction with a mobility procedure in RRC CONNECTED state, the UE may first try to access the target cell using a limited set of configured 2-step CBRA resources, and if this fails, the UE may try another limited set of 4-sep CFRA resources, and if this also fails, the UE may try to access the target cell using 4-step CBRA if there are any PRACH occasions for 4-step RA available before the T304 timer expires.

[00406] As another example, the target gNB/eNB may configure a limited set of 2-step CFRA resources, followed by a limited set of 2-step CBRA resources. When provided with such a configuration for target cell access in conjunction with a mobility procedure in RRC CONNECTED state, the UE may first try to access the target cell using the limited set of configured 2-step CFRA resources, and if this fails, the UE may try the limited set of 2-sep CBRA resources, and if this also fails, the UE may try to access the target cell using 4-step CBRA if there are any PRACH occasions for 4-step RA available before the T304 timer expires.

[00407] As yet another example, the target gNB/eNB may configure limited set of 2-step CFRA resources, followed by a limited set of 4-step CFRA resources. When provided with such a configuration for target cell access in conjunction with a mobility procedure in

RRC CONNECTED state, the UE may first try to access the target cell using the limited set of configured 2-step CFRA resources, and if this fails, the UE may try the limited set of 4-step CFRA resources, and if this also fails, the UE may try to access the target cell using 4-step CBRA if there are any PRACH occasions for 4-step RA available before the T304 timer expires.

[00408] FIG. 17 is a flow chart illustrating a process 1700, according to an embodiment, that is performed by a UE. Process 1700 may begin in step si 702. Step si 702 comprises obtaining a message configuring a time period during which a conditional handover, CHO, can be executed. Step si 704 comprises obtaining a set of one or more pre-allocated uplink grants to be used with the CHO. The message is a conditional handover (CHO) configuration or a handover command.

[00409] FIG. 18 is a flow chart illustrating a process 1800, according to an embodiment, that is performed by a network node. Process 1800 may begin in step si 802. Step si 802 comprises providing a user equipment, UE, with a message configuring a time period during which a conditional handover, CHO, can be executed. Step si 804 comprises providing the UE with a set of one or more pre-allocated uplink grants to be used with the CHO. The message is a conditional handover (CHO) configuration or a handover command.

[00410] FIG. 11 shows an example of a communication system 1100 in accordance with some embodiments.

[00411] In the example, the communication system 1100 includes a telecommunication network 1102 that includes an access network 1104, such as a radio access network (RAN), and a core network 1106, which includes one or more core network nodes 1108. The access network 1104 includes one or more access network nodes, such as network nodes 1110a and 1110b (one or more of which may be generally referred to as network nodes 1110), or any other similar 3 ^rd Generation Partnership Project (3 GPP) access node or non-3GPP access point. The network nodes 1110 facilitate direct or indirect connection of user equipment (UE), such as by connecting UEs 1112a, 1112b, 1112c, and 1112d (one or more of which may be generally referred to as UEs 1112) to the core network 1106 over one or more wireless connections.

[00412] Example wireless communications over a wireless connection include transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system 1100 may include any number of wired or wireless networks, network nodes, UEs, and/or any other components or systems that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections. The communication system 1100 may include and/or interface with any type of communication, telecommunication, data, cellular, radio network, and/or other similar type of system.

[00413] The UEs 1112 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and/or operable to communicate wirelessly with the network nodes 1110 and other communication devices. Similarly, the network nodes 1110 are arranged, capable, configured, and/or operable to communicate directly or indirectly with the UEs 1112 and/or with other network nodes or equipment in the telecommunication network 1102 to enable and/or provide network access, such as wireless network access, and/or to perform other functions, such as administration in the telecommunication network 1102.

[00414] In the depicted example, the core network 1106 connects the network nodes 1110 to one or more hosts, such as host 1116. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network 1106 includes one more core network nodes (e.g., core network node 1108) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and/or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 1108. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and/or a User Plane Function (UPF).

[00415] The host 1116 may be under the ownership or control of a service provider other than an operator or provider of the access network 1104 and/or the telecommunication network 1102, and may be operated by the service provider or on behalf of the service provider. The host 1116 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio/video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

[00416] As a whole, the communication system 1100 of FIG. 11 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LIE), and/or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and/or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z- Wave, Near Field Communication (NFC) ZigBee, LiFi, and/or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.

[00417] In some examples, the telecommunication network 1102 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network 1102 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 1102. For example, the telecommunications network 1102 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and/or Massive Machine Type Communication (mMTC)/Massive loT services to yet further UEs.

[00418] In some examples, the UEs 1112 are configured to transmit and/or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network 1104 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 1104. Additionally, a UE may be configured for operating in single- or multi-RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LIE, i.e. being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved- UMTS Terrestrial Radio Access Network) New Radio - Dual Connectivity (EN-DC).

[00419] In the example, the hub 1114 communicates with the access network 1104 to facilitate indirect communication between one or more UEs (e.g., UE 1112c and/or 1112d) and network nodes (e.g., network node 1110b). In some examples, the hub 1114 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub 1114 may be a broadband router enabling access to the core network 1106 for the UEs. As another example, the hub 1114 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 1110, or by executable code, script, process, or other instructions in the hub 1114. As another example, the hub 1114 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub 1114 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub 1114 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 1114 then provides to the UE either directly, after performing local processing, and/or after adding additional local content. In still another example, the hub 1114 acts as a proxy server or orchestrator for the UEs, in particular in if one or more of the UEs are low energy loT devices.

[00420] The hub 1114 may have a constant/persistent or intermittent connection to the network node 1110b. The hub 1114 may also allow for a different communication scheme and/or schedule between the hub 1114 and UEs (e.g., UE 1112c and/or 1112d), and between the hub 1114 and the core network 1106. In other examples, the hub 1114 is connected to the core network 1106 and/or one or more UEs via a wired connection. Moreover, the hub 1114 may be configured to connect to an M2M service provider over the access network 1104 and/or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes 1110 while still connected via the hub 1114 via a wired or wireless connection. In some embodiments, the hub 1114 may be a dedicated hub - that is, a hub whose primary function is to route communications to/from the UEs from/to the network node 1110b. In other embodiments, the hub 1114 may be a non-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and network node 1110b, but which is additionally capable of operating as a communication start and/or end point for certain data channels.

[00421] FIG. 12 shows a UE 1200 in accordance with some embodiments. As used herein, a UE refers to a device capable, configured, arranged and/or operable to communicate wirelessly with network nodes and/or other UEs. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless cameras, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop- embedded equipment (LEE), laptop-mounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehicle-mounted or vehicle embedded/integrated wireless device, etc. Other examples include any UE identified by the 3rd Generation Partnership Project (3 GPP), including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and/or an enhanced MTC (eMTC) UE.

[00422] A UE may support device-to-device (D2D) communication, for example by implementing a 3 GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle- to-everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and/or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter).

[00423] The UE 1200 includes processing circuitry 1202 that is operatively coupled via a bus 1204 to an input/output interface 1206, a power source 1208, a memory 1210, a communication interface 1212, and/or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in FIG. 12. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

[00424] The processing circuitry 1202 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory 1210. The processing circuitry 1202 may be implemented as one or more hardware- implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry 1202 may include multiple central processing units (CPUs).

[00425] In the example, the input/output interface 1206 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and/or output devices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into the UE 1200. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device.

[00426] In some embodiments, the power source 1208 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. The power source 1208 may further include power circuitry for delivering power from the power source 1208 itself, and/or an external power source, to the various parts of the UE 1200 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source 1208. Power circuitry may perform any formatting, converting, or other modification to the power from the power source 1208 to make the power suitable for the respective components of the UE 1200 to which power is supplied.

[00427] The memory 1210 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable readonly memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory 1210 includes one or more application programs 1214, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 1216. The memory 1210 may store, for use by the UE 1200, any of a variety of various operating systems or combinations of operating systems.

[00428] The memory 1210 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and/or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as ‘ SIM card.’ The memory 1210 may allow the UE 1200 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory 1210, which may be or comprise a device-readable storage medium.

[00429] The processing circuitry 1202 may be configured to communicate with an access network or other network using the communication interface 1212. The communication interface 1212 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 1222. The communication interface 1212 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network). Each transceiver may include a transmitter 1218 and/or a receiver 1220 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter 1218 and receiver 1220 may be coupled to one or more antennas (e.g., antenna 1222) and may share circuit components, software or firmware, or alternatively be implemented separately.

[00430] In the illustrated embodiment, communication functions of the communication interface 1212 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short- range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and/or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol/internet protocol (TCP/IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

[00431] Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 1212, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., when moisture is detected an alert is sent), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

[00432] As another example, a UE comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or to a robotic arm performing a medical procedure according to the received input.

[00433] A UE, when in the form of an Internet of Things (loT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an loT device are a device which is or which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door/window sensor, a flood/moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or Virtual Reality (VR), a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an loT device comprises circuitry and/or software in dependence of the intended application of the loT device in addition to other components as described in relation to the UE 1200 shown in FIG. 12.

[00434] As yet another specific example, in an loT scenario, a UE may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another UE and/or a network node. The UE may in this case be an M2M device, which may in a 3 GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation.

[00435] In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g. by controlling an actuator) to increase or decrease the drone’s speed. The first and/or the second UE can also include more than one of the functionalities described above. For example, a UE might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators.

[00436] FIG. 13 shows a network node 1300 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and/or operable to communicate directly or indirectly with a UE and/or with other network nodes or equipment, in a telecommunication network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs) and NR NodeBs (gNBs)).

[00437] Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units and/or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

[00438] Other examples of network nodes include multiple transmission point (multi- TRP) 5G access nodes, multi- standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell/multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self- Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and/or Minimization of Drive Tests (MDTs).

[00439] The network node 1300 includes a processing circuitry 1302, a memory 1304, a communication interface 1306, and a power source 1308. The network node 1300 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which the network node 1300 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node 1300 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 1304 for different RATs) and some components may be reused (e.g., a same antenna 1310 may be shared by different RATs). The network node 1300 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 1300, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 1300.

[00440] The processing circuitry 1302 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other network node 1300 components, such as the memory 1304, to provide network node 1300 functionality.

[00441] In some embodiments, the processing circuitry 1302 includes a system on a chip (SOC). In some embodiments, the processing circuitry 1302 includes one or more of radio frequency (RF) transceiver circuitry 1312 and baseband processing circuitry 1314. In some embodiments, the radio frequency (RF) transceiver circuitry 1312 and the baseband processing circuitry 1314 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 1312 and baseband processing circuitry 1314 may be on the same chip or set of chips, boards, or units.

[00442] The memory 1304 may comprise any form of volatile or non-volatile computer- readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or any other volatile or non-volatile, non-transitory device-readable and/or computer-executable memory devices that store information, data, and/or instructions that may be used by the processing circuitry 1302. The memory 1304 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and/or other instructions capable of being executed by the processing circuitry 1302 and utilized by the network node 1300. The memory 1304 may be used to store any calculations made by the processing circuitry 1302 and/or any data received via the communication interface 1306. In some embodiments, the processing circuitry 1302 and memory 1304 is integrated.

[00443] The communication interface 1306 is used in wired or wireless communication of signaling and/or data between a network node, access network, and/or UE. As illustrated, the communication interface 1306 comprises port(s)/terminal(s) 1316 to send and receive data, for example to and from a network over a wired connection. The communication interface 1306 also includes radio front-end circuitry 1318 that may be coupled to, or in certain embodiments a part of, the antenna 1310. Radio front-end circuitry 1318 comprises filters 1320 and amplifiers 1322. The radio front-end circuitry 1318 may be connected to an antenna 1310 and processing circuitry 1302. The radio front-end circuitry may be configured to condition signals communicated between antenna 1310 and processing circuitry 1302. The radio front-end circuitry 1318 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry 1318 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 1320 and/or amplifiers 1322. The radio signal may then be transmitted via the antenna 1310. Similarly, when receiving data, the antenna 1310 may collect radio signals which are then converted into digital data by the radio front-end circuitry 1318. The digital data may be passed to the processing circuitry 1302. In other embodiments, the communication interface may comprise different components and/or different combinations of components.

[00444] In certain alternative embodiments, the network node 1300 does not include separate radio front-end circuitry 1318, instead, the processing circuitry 1302 includes radio front-end circuitry and is connected to the antenna 1310. Similarly, in some embodiments, all or some of the RF transceiver circuitry 1312 is part of the communication interface 1306. In still other embodiments, the communication interface 1306 includes one or more ports or terminals 1316, the radio front-end circuitry 1318, and the RF transceiver circuitry 1312, as part of a radio unit (not shown), and the communication interface 1306 communicates with the baseband processing circuitry 1314, which is part of a digital unit (not shown).

[00445] The antenna 1310 may include one or more antennas, or antenna arrays, configured to send and/or receive wireless signals. The antenna 1310 may be coupled to the radio front-end circuitry 1318 and may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly. In certain embodiments, the antenna 1310 is separate from the network node 1300 and connectable to the network node 1300 through an interface or port.

[00446] The antenna 1310, communication interface 1306, and/or the processing circuitry 1302 may be configured to perform any receiving operations and/or certain obtaining operations described herein as being performed by the network node. Any information, data and/or signals may be received from a UE, another network node and/or any other network equipment. Similarly, the antenna 1310, the communication interface 1306, and/or the processing circuitry 1302 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and/or signals may be transmitted to a UE, another network node and/or any other network equipment.

[00447] The power source 1308 provides power to the various components of network node 1300 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source 1308 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 1300 with power for performing the functionality described herein. For example, the network node 1300 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source 1308. As a further example, the power source 1308 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

[00448] Embodiments of the network node 1300 may include additional components beyond those shown in FIG. 13 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and/or any functionality necessary to support the subject matter described herein. For example, the network node 1300 may include user interface equipment to allow input of information into the network node 1300 and to allow output of information from the network node 1300. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node 1300.

[00449] FIG. 14 is a block diagram of a host 1400, which may be an embodiment of the host 1116 of FIG. 11, in accordance with various aspects described herein. As used herein, the host 1400 may be or comprise various combinations hardware and/or software, including a standalone server, a blade server, a cloud-implemented server, a distributed server, a virtual machine, container, or processing resources in a server farm. The host 1400 may provide one or more services to one or more UEs.

[00450] The host 1400 includes processing circuitry 1402 that is operatively coupled via a bus 1404 to an input/output interface 1406, a network interface 1408, a power source 1410, and a memory 1412. Other components may be included in other embodiments. Features of these components may be substantially similar to those described with respect to the devices of previous figures, such as Figures 12 and 13, such that the descriptions thereof are generally applicable to the corresponding components of host 1400.

[00451] The memory 1412 may include one or more computer programs including one or more host application programs 1414 and data 1416, which may include user data, e.g., data generated by a UE for the host 1400 or data generated by the host 1400 for a UE. Embodiments of the host 1400 may utilize only a subset or all of the components shown. The host application programs 1414 may be implemented in a container- based architecture and may provide support for video codecs (e.g., Versatile Video Coding (WC), High Efficiency Video Coding (HEVC), Advanced Video Coding (AVC), MPEG, VP9) and audio codecs (e.g., FLAC, Advanced Audio Coding (AAC), MPEG, G.711), including transcoding for multiple different classes, types, or implementations of UEs (e.g., handsets, desktop computers, wearable display systems, heads-up display systems). The host application programs 1414 may also provide for user authentication and licensing checks and may periodically report health, routes, and content availability to a central node, such as a device in or on the edge of a core network. Accordingly, the host 1400 may select and/or indicate a different host for over-the-top services for a UE. The host application programs 1414 may support various protocols, such as the HTTP Live Streaming (HLS) protocol, Real-Time Messaging Protocol (RTMP), Real-Time Streaming Protocol (RTSP), Dynamic Adaptive Streaming over HTTP (MPEG-DASH), etc.

[00452] FIG. 15 is a block diagram illustrating a virtualization environment 1500 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments 1500 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized.

[00453] Applications 1502 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment Q400 to implement some of the features, functions, and/or benefits of some of the embodiments disclosed herein.

[00454] Hardware 1504 includes processing circuitry, memory that stores software and/or instructions executable by hardware processing circuitry, and/or other hardware devices as described herein, such as a network interface, input/output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 1506 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 1508a and 1508b (one or more of which may be generally referred to as VMs 1508), and/or perform any of the functions, features and/or benefits described in relation with some embodiments described herein. The virtualization layer 1506 may present a virtual operating platform that appears like networking hardware to the VMs 1508.

[00455] The VMs 1508 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 1506. Different embodiments of the instance of a virtual appliance 1502 may be implemented on one or more of VMs 1508, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

[00456] In the context of NFV, a VM 1508 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each of the VMs 1508, and that part of hardware 1504 that executes that VM, be it hardware dedicated to that VM and/or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 1508 on top of the hardware 1504 and corresponds to the application 1502.

[00457] Hardware 1504 may be implemented in a standalone network node with generic or specific components. Hardware 1504 may implement some functions via virtualization. Alternatively, hardware 1504 may be part of a larger cluster of hardware (e.g. such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration 1510, which, among others, oversees lifecycle management of applications 1502. In some embodiments, hardware 1504 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system 1512 which may alternatively be used for communication between hardware nodes and radio units.

[00458] FIG. 16 shows a communication diagram of a host 1602 communicating via a network node 1604 with a UE 1606 over a partially wireless connection in accordance with some embodiments. Example implementations, in accordance with various embodiments, of the UE (such as a UE 1112a of FIG. 11 and/or UE 1200 of FIG. 12), network node (such as network node 1110a of FIG. 11 and/or network node 1300 of FIG. 13), and host (such as host 1116 of FIG. 11 and/or host 1400 of FIG. 14) discussed in the preceding paragraphs will now be described with reference to FIG. 16.

[00459] Like host 1400, embodiments of host 1602 include hardware, such as a communication interface, processing circuitry, and memory. The host 1602 also includes software, which is stored in or accessible by the host 1602 and executable by the processing circuitry. The software includes a host application that may be operable to provide a service to a remote user, such as the UE 1606 connecting via an over-the-top (OTT) connection 1650 extending between the UE 1606 and host 1602. In providing the service to the remote user, a host application may provide user data which is transmitted using the OTT connection 1650.

[00460] The network node 1604 includes hardware enabling it to communicate with the host 1602 and UE 1606. The connection 1660 may be direct or pass through a core network (like core network 1106 of FIG. 11) and/or one or more other intermediate networks, such as one or more public, private, or hosted networks. For example, an intermediate network may be a backbone network or the Internet.

[00461] The UE 1606 includes hardware and software, which is stored in or accessible by UE 1606 and executable by the UE’s processing circuitry. The software includes a client application, such as a web browser or operator-specific “app” that may be operable to provide a service to a human or non- human user via UE 1606 with the support of the host 1602. In the host 1602, an executing host application may communicate with the executing client application via the OTT connection 1650 terminating at the UE 1606 and host 1602. In providing the service to the user, the UE's client application may receive request data from the host's host application and provide user data in response to the request data. The OTT connection 1650 may transfer both the request data and the user data. The UE's client application may interact with the user to generate the user data that it provides to the host application through the OTT connection 1650.

[00462] The OTT connection 1650 may extend via a connection 1660 between the host 1602 and the network node 1604 and via a wireless connection 1670 between the network node 1604 and the UE 1606 to provide the connection between the host 1602 and the UE 1606. The connection 1660 and wireless connection 1670, over which the OTT connection 1650 may be provided, have been drawn abstractly to illustrate the communication between the host 1602 and the UE 1606 via the network node 1604, without explicit reference to any intermediary devices and the precise routing of messages via these devices.

[00463] As an example of transmitting data via the OTT connection 1650, in step 1608, the host 1602 provides user data, which may be performed by executing a host application. In some embodiments, the user data is associated with a particular human user interacting with the UE 1606. In other embodiments, the user data is associated with a UE 1606 that shares data with the host 1602 without explicit human interaction. In step 1610, the host 1602 initiates a transmission carrying the user data towards the UE 1606. The host 1602 may initiate the transmission responsive to a request transmitted by the UE 1606. The request may be caused by human interaction with the UE 1606 or by operation of the client application executing on the UE 1606. The transmission may pass via the network node 1604, in accordance with the teachings of the embodiments described throughout this disclosure. Accordingly, in step 1612, the network node 1604 transmits to the UE 1606 the user data that was carried in the transmission that the host 1602 initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step 1614, the UE 1606 receives the user data carried in the transmission, which may be performed by a client application executed on the UE 1606 associated with the host application executed by the host 1602.

[00464] In some examples, the UE 1606 executes a client application which provides user data to the host 1602. The user data may be provided in reaction or response to the data received from the host 1602. Accordingly, in step 1616, the UE 1606 may provide user data, which may be performed by executing the client application. In providing the user data, the client application may further consider user input received from the user via an input/output interface of the UE 1606. Regardless of the specific manner in which the user data was provided, the UE 1606 initiates, in step 1618, transmission of the user data towards the host 1602 via the network node 1604. In step 1620, in accordance with the teachings of the embodiments described throughout this disclosure, the network node 1604 receives user data from the UE 1606 and initiates transmission of the received user data towards the host 1602. In step 1622, the host 1602 receives the user data carried in the transmission initiated by the UE 1606.

[00465] One or more of the various embodiments improve the performance of OTT services provided to the UE 1606 using the OTT connection 1650, in which the wireless connection 1670 forms the last segment. More precisely, the teachings of these embodiments may improve the power consumption of UE devices during handover and thereby provide benefits such as extended battery life and running time.

[00466] In an example scenario, factory status information may be collected and analyzed by the host 1602. As another example, the host 1602 may process audio and video data which may have been retrieved from a UE for use in creating maps. As another example, the host 1602 may collect and analyze real-time data to assist in controlling vehicle congestion (e.g., controlling traffic lights). As another example, the host 1602 may store surveillance video uploaded by a UE. As another example, the host 1602 may store or control access to media content such as video, audio, VR or AR which it can broadcast, multicast or unicast to UEs. As other examples, the host 1602 may be used for energy pricing, remote control of non-time critical electrical load to balance power generation needs, location services, presentation services (such as compiling diagrams etc. from data collected from remote devices), or any other function of collecting, retrieving, storing, analyzing and/or transmitting data.

[00467] In some examples, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 1650 between the host 1602 and UE 1606, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection may be implemented in software and hardware of the host 1602 and/or UE 1606. In some embodiments, sensors (not shown) may be deployed in or in association with other devices through which the OTT connection 1650 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 1650 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not directly alter the operation of the network node 1604. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling that facilitates measurements of throughput, propagation times, latency and the like, by the host 1602. The measurements may be implemented in that software causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 1650 while monitoring propagation times, errors, etc.

[00468] Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and/or software needed to perform the tasks, features, functions and methods disclosed herein.

Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and/or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and/or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware.

[00469] In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer- readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer- readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and/or by end users and a wireless network generally.

[00470] FIG. 10 depicts a method in accordance with a particular embodiment. For purposes of simplifying the discussion, the steps performed by a user equipment and a network node have been combined in the above flow chart. Neither a user equipment nor a network node will perform all the steps of FIG. 10. The embodiments disclosed herein may be covered by a single device, such as a UE, that performs the UE related steps. Moreover, in some embodiments the NN may be part of an NTN.

[00471] As depicted, the method begins at step 1010 where the NN provides, and the UE obtains, a CHO configuration message. The configuration message configures a time period during which the CHO can be executed. The time period may be an absolute time, a duration of time, a range of times comprising an earliest and latest time (an upper and a lower bound) when the CHO can be executed.

[00472] At step 1015 the NN provides and the UE obtains one or more pre-allocated uplink grants. The uplink grants may be a small set or subset of pre-allocated uplink grants. In some embodiments, the one or more uplink grants are pre-allocated for a time after the end of the time period indicated in the CHO configuration message. This may give the UE time to complete CHO. In some embodiments, no pre-allocated UL grants or dynamically allocated UL grants are available to the UE after the end of the time period. In some embodiments, the UE may be given dynamically allocated UL grants. These may be provided multiple times within the time allowed by the timer period. In some embodiments, the pre-allocated UL grant is limited to a second time period (e.g., corresponding to the time period, or a subset (e.g., 1, 2, 3, 4 or 5) of pre-allocated UL grants.

[00473] At step 1020 the UE attempts to access a candidate target cell. This may be considered a handover. The UE may use the pre-allocated UL grants to attempt to access the candidate target cell. In some embodiments, the UE may be given additional time. This may be done, for example, if initial attempts to access the candidate cell fail.

[00474] At step 1025 the UE sends and the NN receives a handover complete message. For example, the UE may send an RRCReconfigurationComplete message (in NR) or an RRCConnectionReconfigurationComplete message (in LEE)). In some embodiments this may need to be sent before the end of the time period. The message may be sent to the candidate NN and then forwarded or otherwise communicated to the target NN. In some embodiments, an indication of the successful HO may be communicated to other target NN that were not selected for the HO. In some embodiments, once the UE completes the HO, the target NN considers the resources provided for the UE as obsolete and will not be used by the UE.

[00475] Although not illustrated in the above flow chart, in some scenarios the preallocated UL may fail to provide the UE with a connection to the target cell. In such a scenario, the UE may, upon failing to complete handover on all the pre-allocated UL grants, use contention-based random access (CBRA) to access the candidate target cell. If that fails, the UE may then initiate an RRC connection reestablishment procedure.

[00476] At step 1035, the UE provides user data (e.g., a request for data based on user input). At step 1040 the UE forwards the user data to a host computer via the NN. At step 1045 the NN obtains the user data. At step 1050 the NN then forwards the user data to the host computer. User data can also flow in the opposite direction in which the NN obtains user data and then forwards the data to the UE.

[00477] Summary of Various Embodiments

[00478] Group A Embodiments

[00479] 1. A method performed by a user equipment for conditional handover, the method comprising: obtaining a conditional handover (CHO) configuration message, the configuration message configuring a time period during which the CHO can be executed; and obtaining one or more pre-allocated uplink grants to be used with the CHO.

[00480] 2. The method of 1 wherein the timer period comprises one or more of the following: an absolute time; a duration of time; a range of times comprising an earliest and latest time (an upper and a lower bound) when the CHO can be executed; [00481] 2b. The method any of 1-2 wherein small set of pre-allocated UL grants;

[00482] 3. The method of any of 1 -2b wherein the one or more uplink grants are preallocated for a time after the end of the time period indicated in the CHO configuration message.

[00483] 4. The method of any of 1-3 wherein the UE successfully accesses a candidate target cell before the time period indicated in the CHO configuration message expires

[00484] 5. The method of any of 4 wherein the candidate target cell does not pre-allocate any UL grants or dynamically allocate any UL grants via the PDCCH after the end of the time period.

[00485] 6. The method of any of 1-5 further comprising sending a handover complete message (e.g., RRCReconfigurationComplete message (in NR) or RRCConnectionReconfigurationComplete message (in LTE)) before the end of the timer period.

[00486] 7. The method of 6 wherein the handover complete message is received by the target gNB before the end of the timer period.

[00487] 8. The method of any of 1-7 wherein the CHO configuration message comprises only the time period.

[00488] 9. The method of any of 1-8 wherein the UE is being handed over to a candidate cell of a earth fixed cell deployments in NTN (e.g., to a new satellite covering the same geographical area).

[00489] 10. The method of any of 1-9 wherein the CHO configuration message further comprises a signal strength/quality parameter.

[00490] 11. The method of any of 1-10 wherein the pre-allocated UL grant is limited to a second time period (e.g., corresponding to the time period, or a subset (e.g., 1, 2, 3, 4 or 5) of pre-allocated UL grants

[00491] 12. The method of any of 1-11 wherein the UE makes a second handover attempt if the first attempt failed.

[00492] 13. The method of any of 1-12 further comprise, upon failing to complete handover on all the pre-allocated UL grants, using contention-based random access (CBRA) to access the candidate target cell. [00493] 14. The method of 13 further comprising, upon CBRA access failing, initiating an

RRC connection reestablishment procedure.

[00494] 15. The method of any of 1-12 further comprising, upon failing to complete handover on all the pre-allocated UL grants, initiating an RRC connection reestablishment procedure.

[00495] 16. The method of any of 1-15 further comprising obtaining a message providing the UE with contention-free random access (CFRA) resources.

[00496] 17. The method of any of 1-16 further comprising obtaining dynamic UL grants for a network node on the PDCCH.

[00497] 18. The method of any of 1-17 further comprising obtaining a message that extends the timer period.

[00498] 19. The method of 18 wherein the time period is extended via parameters indicating at least two of start, stop and duration of the set, or two out of start (first), stop (last) and number of pre-allocated UL grants in the set.

[00499] 20. The method of any of 1-19 wherein, upon a duration/delay between the time of configuration and the indicated timepoint being less than an SFN cycle, the timer period comprises the SFN combined with a slot number and symbol number.

[00500] 21. The method of any of 1-19 wherein upon a duration/delay between the time of configuration and the indicated timepoint being longer than an SFN cycle, the time period comprises one or more of an indication of the number of full SFN cycles (e.g., in the form of a Hyper-SFN (HSFN) which is defined for certain scenarios in LTE), a UTC timestamp, a GNSS timestamp.

[00501] 22. The method of any of 1-21 wherein the time period is specified in a handover command instead of the CHO configuration message.

[00502] 23. The method of any of 1-22 further comprising obtaining dynamically allocated UL grants (e.g., on the PDCCH) in the candidate target cell, wherein the dynamically alloaced UL grants are provided multiple times until the time period ends or the UE successfully utilizes one of the dynamically allocated UL grant(s). [00503] 24. The method of any of 1-23 wherein the candidate target gNB/eNB configures the number of times, N, the candidate target gNB/eNB will schedule the UE in the candidate target cell using dynamically allocated UL grant(s) within the time period.

[00504] 25. The method of any of 1-24 wherein the UE obtains a set of CHO commands for RACH-less CHO (e.g., for different candidate target cells).

[00505] 26. The method of 25 further comprising: if a remaining delay exceeds a configured (or specified) threshold, the UE ignores the RACH-less resources and tries to access the cell using random access; if the remaining delay is below the threshold, the UE waits for the first/next pre-allocated UL grant and utilizes this pre-allocated UL grant to try to access the cell.

[00506] 27. The method of any of 1-26 wherein steps related to RACH-less access are applied to CFRA (e.g., in conjunction with a mobility procedure in RRC CONNECTED state (such as handover, reconfigurationWithSync, PSCell addition or PSCell change)) or 2-step random access.

[00507] 28. The method of 27 wherein the UE obtains a small set of PRACH occasions for which a CFRA configuration is valid (e.g. configured in the RACH-ConfigDedicated IE), wherein the last of these PRACH occasions occurs before the T304 timer expires.

[00508] 29. The method of 27 wherein the UE obtains a limited set of 2-step RA resources, wherein the last of the 2-step RA resources in the set (in terms of PRACH occasion and associated PUSCH occasion) occurs before the T304 timer expires.

[00509] 30. The method of 29 wherein the UE allows time for one or more 4-step RA attempts in the target cell between the last PRACH occasion (and associated PUSCH occasion) for 2-step RA and the expiration of timer T304.

[00510] 31. The method of any of 1-30 wherein the UE obtains multiple limited sets of special resources, the multiple sets comprising a combination of two or more of a limited set of 2-step CFRA resources, a limited set of 2-step CBRA resources, and a limited set of 4-step CFRA resources.

[00511] 32. The method of 31 wherein the multiple limited sets are configured to occur in sequence in the time domain.

[00512] 33. The method of any of 1-32 wherein the UE executes a CHO upon experiencing radio link failure (RLF) in the source cell.

[00513] 34. The method of any of 1-33, wherein CHO is replaced by any other conditional mobility procedure or conditional mobility related procedure or conditional RRC reconfiguration (or other conditional reconfiguration) involving or requiring access to a cell.

[00514] 35. The method of any of the previous embodiments, further comprising: providing user data; and forwarding the user data to a host via the transmission to the network node.

[00515] Group B Embodiments

[00516] 36. A method performed by a network node for conditional handover, the method comprising: providing a UE with a conditional handover (CHO) configuration message, the configuration message configuring a time period during which the CHO can be executed; and providing the UE with one or more pre-allocated uplink grants to be used with the CHO

[00517] 37. The method of 36 further comprising providing a candidate target gNB(s) (or eNB(s)) which was not selected for CHO execution by the UE, with an indication that the UE has executed a CHO.

[00518] 38. The method of any of 36-37 further comprising, upon detection that the UE performs a (RA-based) CHO towards the target cell, the target gNB/eNB considers the RACH- less resources provided for the UE as obsolete and will not be used by the UE.

[00519] 39. The method of any of 36-38 wherein the time period comprises one or more of the following: an absolute time; a duration of time; a range of times comprising an earliest and latest time (an upper and a lower bound) when the CHO can be executed; small set of preallocated UL grants;

[00520] 40. The method of any of 36-39 wherein the one or more uplink grants are preallocated for a time after the end of the time period indicated in the CHO configuration message.

[00521] 41. The method of any of 36-40 wherein the UE is configured to successfully accesses a candidate target cell before the time period indicated in the CHO configuration message expires

[00522] 42. The method of 41 wherein the candidate target cell does not pre-allocate any UL grants or dynamically allocate any UL grants via the PDCCH after the end of the time period.

[00523] 43. The method of any of 36-42 wherein the CHO configuration message comprises only the time period.

[00524] 44. The method of any of 36-43 wherein the UE is being handed over to a candidate cell of a earth fixed cell deployment in NTN (e.g., to a new satellite covering the same geographical area).

[00525] 45. The method of any of 36-44 wherein the CHO configuration message further comprises a signal strength/quality parameter.

[00526] 46. The method of any of 36-45 wherein the pre-allocated UL grant is limited to a second time period (e.g., corresponding to the time period, or a subset (e.g., 1, 2, 3, 4 or 5) of pre-allocated UL grants

[00527] 47. The method of any of 36-46 wherein the UE is configured to make a second handover attempt if the first attempt fails.

[00528] 48. The method of any of 36-46 wherein the UE is further configured to, upon failing to complete handover on all the pre-allocated UL grants, use contention-based random access (CBRA) to access the candidate target cell.

[00529] 49. The method of 48 further comprising, configuring the UE to, upon CBRA access failing, initiate an RRC connection reestablishment procedure.

[00530] 50. The method of any of 36-46 further comprising configuring the UE to, upon failing to complete handover on all the pre-allocated UL grants, initiate an RRC connection reestablishment procedure.

[00531] 51. The method of any of 36-50 further comprising providing the UE with a message specifying contention- free random access (CFRA) resources for use by the UE.

[00532] 52. The method of any of 36-51 further comprising providing the UE with dynamic UL grants for a network node on the PDCCH.

[00533] 53. The method of any of 36-52 further comprising providing the UE with a message that extends the time period. [00534] 54. The method of 53 wherein the time period is extended via parameters indicating at least two of start, stop and duration of the set, or two out of start (first), stop (last) and number of pre-allocated UL grants in the set.

[00535] 55. The method of any of 36-54 wherein, upon a duration/delay between the time of configuration and the indicated timepoint being less than an SFN cycle, the timer period comprises the SFN combined with a slot number and symbol number.

[00536] 56. The method of any of 36-54 wherein upon a duration/delay between the time of configuration and the indicated timepoint being longer than an SFN cycle, the time period comprises one or more of an indication of the number of full SFN cycles (e.g., in the form of a Hyper-SFN (HSFN) which is defined for certain scenarios in LTE), a UTC timestamp, a GNSS timestamp.

[00537] 57. The method of any of 36-56 wherein the time period is specified in a handover command instead of the CHO configuration message.

[00538] 58. The method of any of 36-57 further comprising providing the UE with dynamically allocated UL grants (e.g., on the PDCCH) in the candidate target cell, wherein the dynamically alloaced UL grants are provided multiple times until the time period ends or the UE successfully utilizes one of the dynamically allocated UL grant(s).

[00539] 59. The method of any of 36-58 wherein the candidate target gNB/eNB configures the number of times, N, the candidate target gNB/eNB will schedule the UE in the candidate target cell using dynamically allocated UL grant(s) within the time period.

[00540] 60. The method of any of 36-59 further comprising providing the UE with a set of

CHO commands for RACH-less CHO (e.g., for different candidate target cells).

[00541] 61. The method of 60 wherein the UE is configured by the network node to: if a remaining delay exceeds a configured (or specified) threshold, the UE ignores the RACH-less resources and tries to access the cell using random access; if the remaining delay is below the threshold, the UE waits for the first/next pre-allocated UL grant and utilizes this pre-allocated UL grant to try to access the cell.

[00542] 62. The method of any of 36-61 wherein steps related to RACH-less access are applied to CFRA (e.g., in conjunction with a mobility procedure in RRC CONNECTED state (such as handover, reconfigurationWithSync, PSCell addition or PSCell change)) or 2-step random access.

[00543] 63. The method of 62 further comprising providing the UE with a small set of

PRACH occasions for which a CFRA configuration is valid (e.g. configured in the RACH- ConfigDedicated IE), wherein the last of these PRACH occasions occurs before the T304 timer expires.

[00544] 64. The method of 63 further comprising providing the UE with a limited set of 2- step RA resources, wherein the last of the 2-step RA resources in the set (in terms of PRACH occasion and associated PUSCH occasion) occurs before the T304 timer expires.

[00545] 65. The method of 64 wherein the UE is configured to allow time for one or more

4-step RA attempts in the target cell between the last PRACH occasion (and associated PUSCH occasion) for 2-step RA and the expiration of timer T304.

[00546] 66. The method of any of 36-66 further comprising providing the UE with multiple limited sets of special resources, the multiple sets comprising a combination of two or more of a limited set of 2-step CFRA resources, a limited set of 2-step CBRA resources, and a limited set of 4-step CFRA resources.

[00547] 67. The method of 66 wherein the multiple limited sets are configured to occur in sequence in the time domain.

[00548] 68. The method of any of 36-67, wherein CHO is replaced by any other conditional mobility procedure or conditional mobility related procedure or conditional RRC reconfiguration (or other conditional reconfiguration) involving or requiring access to a cell.

[00549] 69. The method of any of the previous embodiments, further comprising: obtaining user data; and forwarding the user data to a host or a user equipment.

[00550] Group C Embodiments

[00551] 70. A user equipment for conditional handover, comprising: processing circuitry configured to perform any of the steps of any of the Group A embodiments; and power supply circuitry configured to supply power to the processing circuitry.

[00552] 71. A network node for conditional handover, the network node comprising: processing circuitry configured to perform any of the steps of any of the Group B embodiments; power supply circuitry configured to supply power to the processing circuitry.

[00553] 72. A user equipment (UE) for conditional handover, the UE comprising: an antenna configured to send and receive wireless signals; radio front-end circuitry connected to the antenna and to processing circuitry, and configured to condition signals communicated between the antenna and the processing circuitry; the processing circuitry being configured to perform any of the steps of any of the Group A embodiments; an input interface connected to the processing circuitry and configured to allow input of information into the UE to be processe d by the processing circuitry; an output interface connected to the processing circuitry and configured to output information from the UE that has been processed by the processing circuitry; and a battery connected to the processing circuitry and configured to supply power to the UE.

[00554] 73. A host configured to operate in a communication system to provide an over- the-top (OTT) service, the host comprising: processing circuitry configured to provide user data; and a network interface configured to initiate transmission of the user data to a cellular network for transmission to a user equipment (UE), wherein the UE comprises a communication interface and processing circuitry, the communication interface and processing circuitry of the UE being configured to perform any of the steps of any of the Group A embodiments to receive the user data from the host.

[00555] 74. The host of the previous embodiment, wherein the cellular network further includes a network node configured to communicate with the UE to transmit the user data to the UE from the host.

[00556] 75. The host of the previous 2 embodiments, wherein: the processing circuitry of the host is configured to execute a host application, thereby providing the user data; and the host application is configured to interact with a client application executing on the UE, the client application being associated with the host application.

[00557] 76. A method implemented by a host operating in a communication system that further includes a network node and a user equipment (UE), the method comprising: providing user data for the UE; and initiating a transmission carrying the user data to the UE via a cellular network comprising the network node, wherein the UE performs any of the operations of any of the Group A embodiments to receive the user data from the host. [00558] 77. The method of the previous embodiment, further comprising: at the host, executing a host application associated with a client application executing on the UE to receive the user data from the UE.

[00559] 78. The method of the previous embodiment, further comprising: at the host, transmitting input data to the client application executing on the UE, the input data being provided by executing the host application, wherein the user data is provided by the client application in response to the input data from the host application.

[00560] 79. A host configured to operate in a communication system to provide an over- the-top (OTT) service, the host comprising: processing circuitry configured to provide user data; and a network interface configured to initiate transmission of the user data to a cellular network for transmission to a user equipment (UE), wherein the UE comprises a communication interface and processing circuitry, the communication interface and processing circuitry of the UE being configured to perform any of the steps of any of the Group A embodiments to transmit the user data to the host.

[00561] 80. The host of the previous embodiment, wherein the cellular network further includes a network node configured to communicate with the UE to transmit the user data from the UE to the host.

[00562] 81. The host of the previous 2 embodiments, wherein: the processing circuitry of the host is configured to execute a host application, thereby providing the user data; and the host application is configured to interact with a client application executing on the UE, the client application being associated with the host application.

[00563] 82. A method implemented by a host configured to operate in a communication system that further includes a network node and a user equipment (UE), the method comprising: at the host, receiving user data transmitted to the host via the network node by the UE, wherein the UE performs any of the steps of any of the Group A embodiments to transmit the user data to the host.

[00564] 83. The method of the previous embodiment, further comprising: at the host, executing a host application associated with a client application executing on the UE to receive the user data from the UE. [00565] 84. The method of the previous embodiment, further comprising: at the host, transmitting input data to the client application executing on the UE, the input data being provided by executing the host application, wherein the user data is provided by the client application in response to the input data from the host application.

[00566] 85. A host configured to operate in a communication system to provide an over- the-top (OTT) service, the host comprising: processing circuitry configured to provide user data; and a network interface configured to initiate transmission of the user data to a network node in a cellular network for transmission to a user equipment (UE), the network node having a communication interface and processing circuitry, the processing circuitry of the network node configured to perform any of the operations of any of the Group B embodiments to transmit the user data from the host to the UE.

[00567] 86. The host of the previous embodiment, wherein: the processing circuitry of the host is configured to execute a host application that provides the user data; and the UE comprises processing circuitry configured to execute a client application associated with the host application to receive the transmission of user data from the host.

[00568] 87. A method implemented in a host configured to operate in a communication system that further includes a network node and a user equipment (UE), the method comprising: providing user data for the UE; and initiating a transmission carrying the user data to the UE via a cellular network comprising the network node, wherein the network node performs any of the operations of any of the Group B embodiments to transmit the user data from the host to the UE.

[00569] 88. The method of the previous embodiment, further comprising, at the network node, transmitting the user data provided by the host for the UE.

[00570] 89. The method of any of the previous 2 embodiments, wherein the user data is provided at the host by executing a host application that interacts with a client application executing on the UE, the client application being associated with the host application.

[00571] 90. A communication system configured to provide an over-the-top service, the communication system comprising: a host comprising: processing circuitry configured to provide user data for a user equipment (UE), the user data being associated with the over-the-top service; and a network interface configured to initiate transmission of the user data toward a cellular network node for transmission to the UE, the network node having a communication interface and processing circuitry, the processing circuitry of the network node configured to perform any of the operations of any of the Group B embodiments to transmit the user data from the host to the UE.

[00572] 9 k The communication system of the previous embodiment, further comprising: the network node; and/or the user equipment.

[00573] 92. A host configured to operate in a communication system to provide an over- the-top (OTT) service, the host comprising: processing circuitry configured to initiate receipt of user data; and a network interface configured to receive the user data from a network node in a cellular network, the network node having a communication interface and processing circuitry, the processing circuitry of the network node configured to perform any of the operations of any of the Group B embodiments to receive the user data from a user equipment (UE) for the host.

[00574] 93. The host of the previous 2 embodiments, wherein: the processing circuitry of the host is configured to execute a host application, thereby providing the user data; and the host application is configured to interact with a client application executing on the UE, the client application being associated with the host application.

[00575] 94. The host of the any of the previous 2 embodiments, wherein the initiating receipt of the user data comprises requesting the user data.

[00576] 95. A method implemented by a host configured to operate in a communication system that further includes a network node and a user equipment (UE), the method comprising: at the host, initiating receipt of user data from the UE, the user data originating from a transmission which the network node has received from the UE, wherein the network node performs any of the steps of any of the Group B embodiments to receive the user data from the UE for the host.

[00577] 96. The method of the previous embodiment, further comprising at the network node, transmitting the received user data to the host.

[00578] REFERENCES

[00579] [ 1 ] TR 38.811, Study on New Radio (NR) to support non-terrestrial networks

[00580] [2] TR 38.821, Solutions for NR to support non-terrestrial networks [00581] [3] RP-193234, Solutions for NR to support non-terrestrial networks (NTN),

3 GPP RAN#86

[00582] [4] RP-193235, Study on NB-Iot/eMTC support for Non-Terrestrial Network,

3 GPP RAN#86

[00583] ABBREVIATIONS

[00584] At least some of the following abbreviations may be used in this disclosure. If there is an inconsistency between abbreviations, preference should be given to how it is used above. If listed multiple times below, the first listing should be preferred over any subsequent listing(s).

[00585] 3 GPP 3rd Generation Partnership Project

[00586] 5G 5th Generation

[00587] ARQ Automatic Repeat Request

[00588] BCCH Broadcast Control Channel

[00589] BCH Broadcast Channel

[00590] 5GC 5G Core

[00591] 5GS 5G System

[00592] AMF Access and Mobility management Function

[00593] bps Bits per second

[00594] BS Base Station

[00595] BWP Bandwidth Part

[00596] CA Carrier Aggregation

[00597] CB Contention-Based

[00598] CBRA Contention-Based Random Access

[00599] CC Carrier Component

[00600] CCCH SDU Common Control Channel SDU [00601] CDM Code Division Multiplexing

[00602] CDMA Code Division Multiple Access

[00603] CE Control Element

[00604] CF Contention-Free

[00605] CFRA Contention-Free Random Access

[00606] CGI Cell Global Identifier

[00607] CN Core Network

[00608] CHO Conditional Handover

[00609] CP Cyclic Prefix

[00610] CPC Conditional PSCell Change

[00611] CPICH Common Pilot Channel

[00612] CQI Channel Quality information

[00613] CRM Contention Resolution Message

[00614] C-RNTI Cell RNTI

[00615] CSI Channel State Information

[00616] CSI-RS Channel State Information Reference Signal

[00617] DCCH Dedicated Control Channel

[00618] DCI Downlink Control Information

[00619] DL Downlink

[00620] DMRS Demodulation Reference Signal

[00621] DRX Discontinuous Reception

[00622] DTX Discontinuous Transmission

[00623] E-CID Enhanced Cell-ID (positioning method)

[00624] eMBB Enhanced Mobile Broadband [00625] eMTC Enhanced Machine Type Communication

[00626] eNB E-UTRAN NodeB

[00627] ePDCCH enhanced Physical Downlink Control Channel

[00628] EPC Evolved Packet Core

[00629] EPS Evolved Packet System

[00630] E-UTRA Evolved UTRA

[00631] E-UTRAN Evolved UTRAN

[00632] FDD Frequency Division Duplex

[00633] FDM Frequency Division Multiplexing

[00634] FFS For Further Study

[00635] FR Frequency Range

[00636] gNB Base station in NR

[00637] GEO Geostationary Earth Orbit

[00638] GHz Gigahertz

[00639] GLONASS Global Navigation Satellite System

[00640] GNSS Global Navigation Satellite System

[00641] GPS Global Positioning System

[00642] GSM Global System for Mobile communication

[00643] GW Gateway

[00644] HAPS High Altitude Platform System / High Altitude Platform Station

[00645] HARQ Hybrid Automatic Repeat Request

[00646] HO Handover

[00647] HSFN Hyper System Frame Number

[00648] HSPA High Speed Packet Access [00649] Hz Hertz

[00650] ID Identity /Identifier

[00651] IE Information Element

[00652] loT Internet of Things

[00653] I-RNTI A Radio Network Temporary Identifier for a UE in

RRC INACTIVE state.

[00654] kHz Kilohertz

[00655] LEO Low Earth Orbit

[00656] LOS Line of Sight

[00657] LPP LIE Positioning Protocol

[00658] LSB Least Significant Bit

[00659] LTE Long-Term Evolution

[00660] LTE-M LTE-Machine Type Communication

[00661] MAC Medium Access Control

[00662] MAC CE MAC Control Element

[00663] MBB Mobile Broadband

[00664] MBMS Multimedia Broadcast Multicast Services

[00665] MBSFN Multimedia Broadcast multicast service Single Frequency Network

[00666] MCS Modulation and Coding Scheme

[00667] MEO Medium Earth Orbit

[00668] MIB Master Information Block

[00669] ps Microsecond

[00670] MME Mobility Management Entity

[00671] mMTC Massive Machine Type Communication [00672] ms Millisecond

[00673] MSC Mobile Switching Center

[00674] Msg/msg Message

[00675] Msgl Message 1

[00676] Msg2 Message 2

[00677] Msg3 Message 3

[00678] Msg4 Message 4

[00679] Msg5 Message 5

[00680] MsgA/msgA Message A

[00681] MsgB/msgB Message B

[00682] NB-IoT Narrowband Internet of Things

[00683] NG The interface between the RAN and the core network in 5G/NR.

[00684] NGAP NG Application Protocol

[00685] NPDCCH Narrowband Physical Downlink Control Channel

[00686] NR New Radio

[00687] NTN Non-terrestrial Network

[00688] OCNG OFDMA Channel Noise Generator

[00689] OFDM Orthogonal Frequency Division Multiplexing

[00690] OFDMA Orthogonal Frequency Division Multiple Access

[00691] OSI Other System Information

[00692] OSS Operations Support System

[00693] OTDOA Observed Time Difference of Arrival

[00694] O&M Operation and Maintenance

[00695] PBCH Physical Broadcast Channel [00696] P-CCPCH Primary Common Control Physical Channel

[00697] PCell Primary Cell

[00698] PDCCH Physical Downlink Control Channel

[00699] PDCP Packet Data Convergence Protocol

[00700] PDSCH Physical Downlink Shared Channel

[00701] PDU Packet Data Unit

[00702] PGW Packet Gateway

[00703] PLMN Public Land Mobile Network

[00704] PMI Precoder Matrix Indicator

[00705] PO PUSCH Occasion

[00706] PRACH Physical Random Access Channel

[00707] PRB Physical Resource Block

[00708] PRS Positioning Reference Signal

[00709] PSS Primary Synchronization Signal

[00710] PUCCH Physical Uplink Control Channel

[00711] PUSCH Physical Uplink Shared Channel

[00712] PSCell Primary Secondary Cell

[00713] PSS Primary Synchronization Signal

[00714] RA Random Access

[00715] RACH Random Access Channel

[00716] RAN Radio Access Network

[00717] RAR Random Access Response

[00718] RAT Radio Access Technology

[00719] RLC Radio Link Control [00720] RLF Radio Link Failure

[00721] RLM Radio Link Management

[00722] RMSI Remaining Minimum System Information

[00723] RNC Radio Network Controller

[00724] RNTI Radio Network Temporary Identifier

[00725] RO RACH Occasion (equivalent to PRACH occasion)

[00726] RRC Radio Resource Control

[00727] RRM Radio Resource Management

[00728] RS Reference Signal

[00729] RSCP Received Signal Code Power

[00730] RSRP Reference Symbol Received Power OR

Reference Signal Received Power

[00731] RSRQ Reference Signal Received Quality OR Reference Symbol Received Quality

[00732] RSSI Received Signal Strength Indicator

[00733] RSTD Reference Signal Time Difference

[00734] RTT Roundtrip time

[00735] RU Resource Unit

[00736] SCH Synchronization Channel

[00737] SCell Secondary Cell

[00738] SDAP Service Data Adaptation Protocol

[00739] SDU Service Data Unit

[00740] SFN System Frame Number

[00741] SGW Serving Gateway

[00742] SCG Secondary Cell Group [00743] SFN System Frame Number

[00744] SI Study Item

[00745] SI System Information

[00746] SIB System Information Block

[00747] SID Study Item Description

[00748] SNR Signal to Noise Ratio

[00749] SON Self Optimized Network

[00750] SS Synchronization Signal

[00751] SSB Synchronization Signal Block

[00752] SSS Secondary Synchronization Signal

[00753] TA Timing Advance

[00754] TDD Time Division Duplex

[00755] TLE Two-Line Element set / Two-Line Element

[00756] TMSI Temporary Mobile Subscriber Identity

[00757] TR Technical Report

[00758] TS Technical Specification

[00759] TSS Tertiary Synchronization Signal

[00760] TTI Transmission Time Interval

[00761] UE User Equipment

[00762] UL Uplink

[00763] UMTS Universal Mobile Telecommunication System

[00764] UPF User Plane Function

[00765] URLLC Ultra-Reliable Low-Latency Communication

[00766] USIM Universal Subscriber Identity Module [00767] UTC Coordinated Universal Time

[00768] UTRA Universal Terrestrial Radio Access

[00769] UTRAN Universal Terrestrial Radio Access Network

[00770] Uu The interface between a UE and an eNB or between a UE and a gNB.

[00771] WCDMA Wide CDMA

[00772] WLAN Wide Local Area Network

[00773] X2 The interface between two eNBs.

[00774] X2AP X2 Application Protocol

[00775] Xn The interface between two gNBs

[00776] XnAP Xn Application Protocol