TECHNICAL FIELD

[0001] Embodiments of the present application generally relate to wireless communication technology, especially to technology of supporting physical random access channel (PRACH) transmission, e.g., PRACH transmission in scenarios of multi-downlink control information (DCI) (M-DCI) based multi-transmit-receive point (TRP) (M-TRP) or scenarios of layer 1 (Ll)/layer 2 (L2)-triggered mobility (or L1/L2 triggered mobility or L1/L2 based mobility etc.) (LTM).

BACKGROUND

[0002] A wireless communication system may include one or multiple network communication devices, such as base stations, which may be otherwise known as an eNodeB (eNB), a next-generation NodeB (gNB), or other suitable terminology. Each network communication devices, such as a base station may support wireless communications for one or multiple user communication devices, which may be otherwise known as user equipment (UE), or other suitable terminology. The wireless communications system may support wireless communications with one or multiple user communication devices by utilizing resources of the wireless communication system (e.g., time resources (e.g., symbols, slots, subframes, frames, or the like) or frequency resources (e.g., subcarriers, earners). Additionally, the wireless communications system may support wireless communications across various radio access technologies including third generation (3G) radio access technology, fourth generation (4G) radio access technology, fifth generation (5G) radio access technology, among other suitable radio access technologies beyond 5G (e.g., sixth generation (6G)).

[0003] It is known that timing advance (TA) acquisition is performed by a random access channel (RACH) procedure. For example, a PRACH (or PRACH resource or preamble etc.) will be transmitted to a TRP to obtain a TA for the TRP, or to a candidate cell to obtain a TA for the candidate cell. There are many contributions discussing the PRACH transmission in the topics of two TAs in multiple-input multiple-output (MIMO) work item description (WID) and TA management in L1/L2 triggered mobility WID. However, there is no discussion about the validation of PRACH occasions for the PRACH transmission.

SUMMARY OF THE APPLICATION

[0004] Some embodiments of the present application provide a wireless communication apparatus, e.g., a UE, which includes: a transceiver; and a processor coupled to the transceiver, wherein the processor is configured to: receive, from a serving cell on an active bandwidth part (BWP), a physical downlink control channel (PDCCH) order triggering a PRACH transmission associated with a cell that works on an unpaired spectrum, wherein the cell is same as or different from the serving cell; and determine valid PRACH occasions for the PRACH transmission based on synchronization signal (SS)Zphysical broadcast channel (PBCH) block (SSB) configuration information, wherein, in the case that L1/L2 triggered mobility is configured in the serving cell, the SSB configuration information includes any of: SSB configuration information associated with the serving cell, SSB configuration information for LI beam measurement/reporting, and SSB configuration information associated with a candidate cell; or in the case that a plurality of values of control resource set (CORESET) pool index are configured for CORESETs in the BWP of the serving cell, the SSB configuration information includes any of: the SSB configuration information associated with the serving cell, the SSB configuration information for LI beam measurement/reporting, and SSB configuration information associated with at least one additional PCI.

[0005] Some other embodiments of the present application provide a wireless communication method, e.g., a method performed in a UE, which includes: receiving, from a serving cell on an active BWP, a PDCCH order triggering a PRACH transmission associated with a cell that works on an unpaired spectrum, wherein the cell is same as or different from the serving cell; and determining valid PRACH occasions for the PRACH transmission based on SSB configuration information, wherein, in the case that L1/L2 triggered mobility is configured in the serving cell, the SSB configuration information includes any of: SSB configuration information associated with the serving cell, SSB configuration information for LI beam measurement/reporting, and SSB configuration information associated with a candidate cell; or in the case that a plurality of values of CORESET pool index are configured for CORESETs in the BWP of the serving cell, the SSB configuration information includes any of: the SSB configuration information associated with the serving cell, the SSB configuration information for LI beam measurement/reporting, and SSB configuration information associated with at least one additional PCI.

[0006] In some embodiments of the present application, in the case that the L1/L2 triggered mobility is configured in the serving cell, the cell is the serving cell or the candidate cell and the processor is configured to determine a PRACH occasion associated with the cell in a PRACH slot is valid in the case that: no parameter as tdd-UL-DL-ConfigurationCommon is provided, and the PRACH occasion does not precede an SSB in the PRACH slot and starts at least N _gap symbols after a last SSB symbol, N _gap >=0; or a parameter as tdd-UL-DL-ConfigurationCommon is provided, and: the PRACH occasion is within uplink symbols, or the PRACH occasion does not precede an SSB in the PRACH slot and starts at least N _gap symbols after a last downlink symbol and at least N _gap symbols after a last SSB symbol, N _gap >=0.

[0007] According to some embodiments of the present application, the cell is the candidate cell and the processor is configured to determine whether the PRACH occasion associated with the cell in a PRACH slot is valid based on the following SSB configuration information: SSB indexes of SSBs corresponding to SSB indexes associated with the candidate cell; or indexes of SSBs corresponding to SSB indexes associated with the candidate cell and SSB indexes associated with the serving cell; or SSB indexes of SSBs corresponding to SSB indexes associated with the candidate cell and SSBs configured for LI beam measurement/reporting; or SSB indexes of SSBs corresponding to SSB indexes associated with the candidate cell, SSB indexes associated with the serving cell, and SSBs configured for LI beam measurement/reporting; or SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell and SSBs configured for LI beam measurement/reporting.

[0008] According to some embodiments of the present application, the cell is the serving cell and the processor is configured to determine whether the PRACH occasion associated with the cell in a PRACH slot is valid based on the following SSB configuration information: SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell and SSBs configured for LI beam measurement/reporting.

[0009] According to some embodiments of the present application, the cell is the candidate cell and the processor is configured to determine subcarrier space (SCS) of the PRACH transmission associated with the cell according to PRACH configuration associated with the candidate cell.

[0010] In some embodiments of the present application, in the case that a plurality of values of CORESET pool index are configured for CORESETs in the BWP of the serving cell, the cell is the serving cell or a non-serving cell and the processor is configured to determine a PRACH occasion associated with a PCI of the cell in a PRACH slot is valid in the case that: no parameter as tdd-UL-DL-ConfigurationCommon is provided, and the PRACH occasion does not precede an SSB in the PRACH slot and starts at least N _gap symbols after a last SSB symbol, N _gap >=0; or a parameter as tdd-UL-DL-ConfigurationCommon is provided, and: the PRACH occasion is within uplink symbols, or the PRACH occasion does not precede an SSB in the PRACH slot and starts at least N _gap symbols after a last downlink symbol and at least N _gap symbols after a last SSB symbol, N _gap >=0.

[0011] According to some embodiments of the present application, the cell is the non-serving cell and the processor is configured to determine whether the PRACH occasion associated with the PCI of the cell in a PRACH slot is valid based on the following SSB configuration information: candidate SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell and SSB indexes associated with the at least one additional PCI, wherein the at least one additional PCI is the PCI of the cell, an activated additional PCI which is associated with at least one activated transmission configuration indication (TCI) state of the serving cell, or the PCI of the cell and the activated additional PCI; or SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell and SSBs configured for LI beam measurement/reporting; or SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell, SSBs configured for LI beam measurement/reporting, and SSB indexes associated with the at least one additional PCI, wherein the at least one additional PCI is the PCI of the cell, an activated additional PCI which is associated with at least one activated TCI state of the serving cell, or the PCI of the cell and the activated additional PCI.

[0012] According to some embodiments of the present application, the cell is the serving cell and the processor is configured to determine whether the PRACH occasion associated with the PCI of the cell in a PRACH slot is valid based on the following SSB configuration information: SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell and SSB indexes associated with the at least one additional PCI, wherein the at least one additional PCI is an activated additional PCI which is associated with at least one activated TCI state of the serving cell; or SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell and SSBs configured for LI beam measurement/reporting; or SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell, SSBs configured for LI beam measurement/reporting and SSB indexes associated with the at least one additional PCI, wherein the at least one additional PCI is an activated additional PCI which is associated with at least one activated TCI state of the serving cell.

[0013] In some scenarios of the present application, the SSB indexes associated with the candidate cell are configured by radio resource control (RRC) signaling.

[0014] In some scenarios of the present application, the SSB indexes associated with the serving cell are provided by a parameter as ssb-PositionsInBurst in system information block (SIB) or in ServingCellConfigCommon of the serving cell.

[0015] In some scenarios of the present application, SSB indexes associated with an additional PCI are provided by a parameter as ssb-PositionsInBurst in SSB-MTC-AdditionalPCI of the additional PCI. [0016] In some scenarios of the present application, the PCI of the cell and the activated additional PCI are the same or different.

[0017] In some scenarios of the present application, N _gap is provided in Table 8.1-2 ofTS38.213.

[0018] Some yet other embodiments of the present application also provide another wireless communication apparatus, e.g., a radio access network (RAN) node, which includes: a transceiver; and a processor coupled to the transceiver, wherein the processor is configured to: transmit, from a serving cell on an active BWP, a PDCCH order triggering a PRACH transmission associated with a cell that works on an unpaired spectrum, wherein the cell is same as or different from the serving cell; and determine valid PRACH occasions for the PRACH transmission based on SSB configuration information, wherein, in the case that L1/L2 triggered mobility is configured in the serving cell, the SSB configuration information includes any of: SSB configuration information associated with the serving cell, SSB configuration information for LI beam measurement/reporting, and SSB configuration information associated with a candidate cell; or in the case that a plurality of values of CORESET pool index are configured for CORESETs in the BWP of the serving cell, the SSB configuration information includes any of: the SSB configuration information associated with the serving cell, the SSB configuration information for LI beam measurement/reporting, and SSB configuration information associated with at least one additional PCI.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to describe the manner in which advantages and features of the application can be obtained, a description of the application is rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. These drawings depict only example embodiments of the application and are not therefore to be considered limiting of its scope.

[0020] FIG. 1 is a schematic diagram illustrating an exemplary wireless communication system according to an embodiment of the present application. [0021] FIG. 2 illustrates a flow chart of a method of supporting PRACH transmission according to some embodiments of the present application.

[0022] FIG. 3 illustrates a block diagram of an apparatus of supporting PRACH transmission according to some embodiments of the present application.

[0023] FIG. 4 illustrates a block diagram of an apparatus of supporting PRACH transmission according to some other embodiments of the present application.

DETAILED DESCRIPTION

[0024] To support TA acquisition in new radio (NR), a mass of issues on PRACH transmission needed to be solved, especially considering two TAs in MIMO WID and TA management in LTM WID. For example, issues regarding the validation of PRACH occasions for PRACH transmissions need to be solved in scenarios of M-DCI based M-TRP and scenarios of LTM.

[0025] At least considering the above issues, embodiments of the present application provide technical solutions of supporting PRACH transmission. Although the technical solutions of supporting PRACH transmission are proposed originally considering the TA acquisition in scenarios of M-DCI based M-TRP or scenarios of LTM, they should not be unduly limited to the purpose for TA acquisition.

[0026] For example, some embodiments of the present application provide an exemplary method of supporting PRACH transmission, which may be performed in the remote side, e.g., by a UE and include: receiving, from a serving cell on an active BWP, a PDCCH order triggering (or initiating) a PRACH transmission associated with a cell that works on an unpaired spectrum, e.g., works on time division duplex (TDD) or in TDD operation. In some cases, the cell that works on an unpaired spectrum is the same as the serving cell. In some other cases, the cell that works on an unpaired spectrum is different from the serving cell, e.g., being a candidate cell in scenarios of LTM or a non-serving cell in scenarios of M-DCI based M-TRP. The exemplary method of supporting PRACH transmission may further include: determining valid PRACH occasions for the PRACH transmission based on SSB configuration information. For example, in the scenarios of LTM, determining valid PRACH occasions for the PRACH transmission is based on the SSB configuration information including any of: SSB configuration information associated with the serving cell, SSB configuration information for LI beam measurement/reporting (e.g., measurement, reporting, or both measurement and reporting), and SSB configuration information associated with a candidate cell. In the scenarios of M-DCI based M-TRP, determining valid PRACH occasions for the PRACH transmission is based on the SSB configuration information including any of: the SSB configuration information associated with the serving cell, the SSB configuration information for LI beam measurement/reporting, and SSB configuration information associated with at least one additional PCI. An additional PCI may also be referred to as a non-serving cell PCI or the like. The at least one additional PCI may be the PCI of the cell (in the case of a non-serving cell), an activated additional PCI, or the PCT of the cell and the activated additional PCI. Regarding an activated additional PCI, it is an additional PCI associated with at least one activated TCI state of the serving cell.

[0027] For another example, some embodiments of the present application provide another exemplary method of supporting PRACH transmission, which may be performed in the network side, e.g., by a RAN node (e.g., a gNB) and include: transmitting, from a serving cell on an active BWP, a PDCCH order triggering a PRACH transmission associated with a cell that works on an unpaired spectrum. The cell that works on an unpaired spectrum is the same as or different from the serving cell. The exemplary method of supporting PRACH transmission may further include: determining valid PRACH occasions for the PRACH transmission based on SSB configuration information. For example, in the scenarios of LTM, determining valid PRACH occasions for the PRACH transmission is based on the SSB configuration information including any of: SSB configuration information associated with the serving cell, SSB configuration information for LI beam measurement/reporting, and SSB configuration information associated with a candidate cell. In the scenarios of M-DCI based M-TRP, determining valid PRACH occasions for the PRACH transmission is based on the SSB configuration information including any of: the SSB configuration information associated with the serving cell, the SSB configuration information for LI beam measurement/reporting, and SSB configuration information associated with at least one additional PCI. [0028] Generally, embodiments of the present application provide a technical solution of supporting PRACH transmission, solving issues on validation of PRACH occasions for PRACH transmissions in multi-DCI based multi-TRP scenarios and LTM scenarios, and thus can facilitate and improve the implementation of NR.

[0029] Reference will now be made in detail to some embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings.

[0030] FIG. 1 illustrates a schematic diagram of an exemplary wireless communication system 100 according to some embodiments of the present application.

[0031] As shown in FIG. 1 , the wireless communication system 100 includes a UE 103 and a base station (BS) 101. Although merely one BS is illustrated in FIG. 1 for simplicity, it is contemplated that the wireless communication system 100 may include more BSs in some other embodiments of the present application. Similarly, although merely one UE is illustrated in FIG. 1 for simplicity, it is contemplated that the wireless communication system 100 may include more UEs in some other embodiments of the present application.

[0032] The wireless communication system 100 is compatible with any type of network that is capable of sending and receiving wireless communication signals. For example, the wireless communication system 100 is compatible with a wireless communication network, a cellular telephone network, a time division multiple access (TDMA)-based network, a code division multiple access (CDMA) -based network, an orthogonal frequency division multiple access (OFDMA)-based network, an LTE network, a 3 GPP-based network, a 3 GPP 5G network, a satellite communications network, a high altitude platform network, and/or other communications networks.

[0033] The BS 101 may also be referred to as an access point, an access terminal, a base, a macro cell, a node-B, an enhanced node B (eNB), a gNB, a home node-B, a relay node, or a device, or described using other terminology used in the art. The BS 101 is generally part of a radio access network that may include a controller communicably coupled to the BS 101. [0034] In addition, a BS 101 may be configured with one TRP (or panel), i.e., in a single-TRP scenario or more TRPs (or panels), i.e., a multi-TRP scenario. That is, one or more TRPs are associated with the BS 101. A TRP can act like a small BS. Two TRPs can have the same cell ID (identity or index) or different cell IDs. Two TRPs can communicate with each other by a backhaul link. Such a backhaul link may be an ideal backhaul link or a non-ideal backhaul link. Latency of the ideal backhaul link may be deemed as zero, and latency of the non-ideal backhaul link may be tens of milliseconds and much larger, e.g. on the order of tens of milliseconds, than that of the ideal backhaul link.

[0035] A single TRP can be used to serve one or more UE 103 under the control of a BS 101. In different scenarios, a TRP may be referred to as different terms, which may be represented by a TCI state index or CORESET pool index (e.g., represented by CORESETPoolIndex) value etc. It should be understood that the TRP(s) (or panel(s)) configured for the BS 101 may be transparent to a UE 103.

[0036] The UE 103 may include computing devices, such as desktop computers, laptop computers, personal digital assistants (PDAs), tablet computers, smart televisions (e.g., televisions connected to the Internet), set-top boxes, game consoles, security systems (including security cameras), vehicle on-board computers, network devices (e.g., routers, switches, and modems), or the like. According to an embodiment of the present application, the UE 103 may include a portable wireless communication device, a smart phone, a cellular telephone, a flip phone, a device having a subscriber identity module, a personal computer, a selective call receiver, or any other device that is capable of sending and receiving communication signals on a wireless network. In some embodiments of the present application, the UE 103 may include wearable devices, such as smart watches, fitness bands, optical head-mounted displays, or the like. Moreover, the UE 103 may be referred to as a subscriber unit, a mobile, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal, or a device, or described using other terminology used in the art. The UE 103 may move among different cells. Conventionally, serving cell change is performed by explicit RRC reconfiguration signaling to trigger the synchronization of target cell based on layer 3 (L3) measurements report. In 3 GPP R18, a new work item on further NR mobility enhancements is approved to enable a serving cell change via lower layer signaling, e.g., LI or L2 signaling, in order to reduce the latency, overhead and interruption time.

[0037] A PRACH transmission triggered (or initiated) by a PDCCH order will be transmitted to the network side, e.g., both gNBs in a serving cell and a candidate cell in different time in scenarios of LTM; or to both a TRP associated with a serving cell PCI and another TRP associated with a non-serving cell PCI in scenarios of M-DCI based M-TRP (e.g., inter-cell M-DCI based M-TRP). The PRACH transmission will be transmitted in a valid PRACH occasion, which can be determined in various manners according to embodiments of the present application.

[0038] FIG. 2 illustrates a flow chart of a method of supporting PRACH transmission according to some embodiments of the present application. Although the method is illustrated in a system level by a UE in a remote side (or UE side) and a RAN node (or BS) in a network side (or BS side), persons skilled in the art can understand that the method implemented in the remote side and that implemented in the network side can be separately implemented and incorporated by other apparatus with similar functions. In addition, no transmission or reception failure is considered in the illustrated embodiments of the present application.

[0039] As shown in FIG. 2, in step 201, the network side, e.g., a gNB may transmit a PDCCH order from the serving cell on an active BWP to the UE. Accordingly, the UE will receive the PDCCH order from the serving cell on the active BWP in step 202. The PDCCH order will trigger a PRACH transmission (or trigger a RACH procedure) associated with a cell that works on an unpaired spectrum (may also be referred to as a cell in TDD operation or the like), e.g., to acquire TA from the cell. The cell is the same as or different from the serving cell. For example, the cell that works on an unpaired spectrum is the serving cell or a candidate cell in scenarios of LTM. For another example, the cell that works on an unpaired spectrum is the serving cell or a non-serving cell in scenarios of M-DCI based M-TRP.

[0040] In response to the received PDCCH order, the UE will transmit a PRACH (PRACH transmission, PRACH resource, or preamble etc.) triggered by the PDCCH order on a valid PRACH occasion. Accordingly, the network side will receive the PRACH transmission triggered by the PDCCH order on a valid PRACH occasion. Both the network side and the remote side will determine valid PRACH occasions for the PRACH transmission. Specifically, the network side will determine valid PRACH occasions for the PRACH transmission based on SSB configuration information in step 203, and the UE will determine valid PRACH occasions for the PRACH transmission based on SSB configuration information in step 204. Regarding which one of the valid PRACH occasions will be used for the PRACH transmission, there are various determination manners. However, that is not related to the issues discussed in the present application, and thus will not be illustrated herein.

[0041] In different scenarios, the SSB configuration information based on which the valid PRACH occasions are determined for the PRACH transmission may be the same or different. The network side and the remote side will determine whether the UE is configured in M-DCI based M-TRP or whether the UE is configured in LTM, or in other scenarios.

[0042] There are various manners for determining whether the UE is configured in M-DCI based M-TRP or whether the UE is configured in LTM. For example, the network side and remote side will determine whether a plurality of values of CORESET pool index (e.g., CORESETPoolIndex values, each corresponding to a TRP) are configured for CORESETs in the BWP of the serving cell, to determine whether the UE is configured in M-DCI based M-TRP. The M-DCI based M-TRP may be inter-cell M-DCI based M-TRP or intra-cell M-DCI based M-TRP. Only a PRACH transmission can be triggered by a PDCCH order to a non-serving cell in inter-cell M-DCI based M-TRP, therefore, only inter-cell M-DCI based M-TRP is considered. The network side and remote side will determine whether LTM is configured in the serving cell, e.g., by RRC signaling or other manners to determine whether the UE is configured in LTM. Since the technical solutions of the present application mainly focus on PRACH transmission in LTM scenarios and inter-cell M-DCI based M-TRP scenarios, herein, it is always assumed that the UE is in M-DCI based M-TRP scenarios or LTM scenarios.

[0043] In the scenarios of inter-cell M-DCI based on M-TRP, e.g., a plurality of values of CORESET pool index (e.g., multiple CORESETpoolindex values) are configured for CORESETs in the BWP of the serving cell, the network side and the remote side will determine valid PRACH occasions for the PRACH transmission based on the SSB configuration information associated with the serving cell, the SSB configuration information for LI beam measurement/reporting, the SSB configuration information associated with at least one additional PCI, or any combination of the aforementioned.

[0044] For example, in the case that the cell is the non-serving cell, the SSB configuration information may be: a) SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell and SSB index(s) associated with the at least one additional PCI; or b) SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell and SSBs (or SSB indexes) configured for LI beam measurement/reporting; or c) SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell, SSBs (or SSB indexes) configured for LI beam measurement/reporting, and SSB index(s) associated with the at least one additional PCI. The at least one additional PCI in a) and c) is the PCI of the non-serving cell, an activated additional PCI, or the PCI of the non-serving cell and the activated additional PCI. The PCI of the non-serving cell and the activated additional PCI are the same or different.

[0045] In the case that the cell is the serving cell, the SSB configuration information may be: a) SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell and SSB indexes associated with the at least one additional PCI; or b) SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell and SSBs (or SSB indexes) configured for LI beam measurement/reporting; or c) SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell, SSBs (or SSB indexes) configured for LI beam measurement/reporting and SSB indexes associated with the at least one additional PCI. The at least one additional PCI in a) and c) is an activated additional PCI.

[0046] In the scenarios of LTM, e.g., L1/L2 triggered mobility is configured in the serving cell, the network side and the remote side will determine valid PRACH occasions for the PRACH transmission based on the SSB configuration information associated with the serving cell, SSB configuration information for LI beam measurement/reporting, SSB configuration information associated with a candidate cell, or any combination of the aforementioned.

[0047] For example, in the case that the cell is the candidate cell, the SSB configuration information may be: a) SSB indexes of SSBs corresponding to SSB indexes associated with the candidate cell; or b) SSB indexes of SSBs corresponding to SSB indexes associated with the candidate cell and SSB indexes associated with the serving cell; or c) SSB indexes of SSBs corresponding to SSB indexes associated with the candidate cell and SSBs (or SSB indexes) configured for LI beam measurement/reporting; or d) SSB indexes of SSBs corresponding to SSB indexes associated with the candidate cell, SSB indexes associated with the serving cell, and SSBs (or SSB indexes) configured for LI beam measurement/reporting; or e) SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell and SSBs (or SSB indexes) configured for LI beam measurement/reporting.

[0048] In the case that the cell is the serving cell, the SSB configuration information may be: SSB indexes of SSBs corresponding to SSB indexes associated with the serving cell and SSBs (or SSB indexes) configured for LI beam measurement/reporting.

[0049] Some embodiments of the present application also propose how to determine a PRACH occasion is valid based on the SSB configuration information. For example, the network side and remote side will determine a PRACH occasion associated with the cell in a PRACH slot is valid in the case that no parameter as tdd-UL-DL-ConfigurationCommon is provided and the PRACH occasion does not precede an SSB in the PRACH slot and starts at least N _gap symbols after a last SSB symbol, N _gap >=0. For another example, the network side and remote side will determine a PRACH occasion associated with the cell in a PRACH slot is valid in the case that a parameter as tdd-UL-DL-ConfigurationCommon is provided and the PRACH occasion is within uplink symbols. For yet another example, the network side and remote side will determine a PRACH occasion associated with the cell in a PRACH slot is valid in the case that a parameter as tdd-UL-DL-ConfigurationCommon is provided and the PRACH occasion does not precede an SSB in the PRACH slot and starts at least N _gap symbols after a last downlink symbol and at least N _gap symbols after a last SSB symbol, N _gap >=0.

[0050] In some embodiments of the present application, N _gap is the N _gap provided in Table 8.1-2 of TS38.213 as shown below, which provide N _gap values for different preamble SCS p. For preamble format B4, N _gap = 0. Persons skilled in the art should well know that as the evolution of 3GPP, the Table 8.1-2 of TS38.213 may develop into another table. Thus, herein, Table 8.1-2 of TS38.213 should not be unduly limited to the current Table 8.1-2 of TS38.213, and should include any evolution or derivation of Table 8.1-2 of TS38.213.

Table 8.1-2 ofTS38.213

[0051] More detailed embodiments of the present application will be illustrated in the following respectively in view of LTM scenarios and M-DCI based M-TRP scenarios.

LTM scenarios

[0052] In exemplary LTM scenarios, a PDCCH order can trigger a PRACH transmission to the serving cell of the UE, e.g., to obtain TA for the serving cell, or to a candidate cell of one or more candidate cells configured for the UE, e.g., to obtain TA for the candidate cell for L1/L2 based cell switch. It has already been agreed that SSB associated with each configured candidate cell will be configured for downlink synchronization with the one or more candidate cells before cell switch and SSBs associated with the one or more candidate cells can be configured for LI beam measurement/reporting.

[0053] In addition, since the validation of a PRACH occasion only needs to be determined for unpaired spectrum, cells that work on unpaired spectrum (or in TDD operation) will be considered. The serving cell and candidate cell can have the same duplex mode or different duplex modes, and the configuration of slot format may be different too even if they both work on unpaired spectrum.

[0054] According to some embodiments of the present application, a PDCCH order triggers a PRACH transmission in a PRACH occasion associated with a candidate cell that works on unpaired spectrum. In the case that a UE is not provided tdd-UL-DL-ConfigurationCommon or the like associated with the candidate cell, a PRACH occasion associated with the candidate cell in a PRACH slot will be valid if the PRACH occasion does not precede an SSB in the PRACH slot and starts at least Ngap symbols after a last SSB symbol, where N _gap is provided in Table 8.1 -2 of TS38.213 or the like. In the case that a UE is provided tdd-UL-DL-ConfigurationCommon or the like associated with the candidate cell (which means slot format configuration of the candidate cell is provided for the UE before cell switch), a PRACH occasion associated with the candidate cell in a PRACH slot will be valid if: a) the PRACH occasion is within uplink symbols, or b) the PRACH occasion does not precede an SSB in the PRACH slot and starts at least Ng _a p symbols after a last downlink symbol and at least N _gap symbols after a last SSB symbol, where N _gap is provided in Table 8.1-2 of TS38.213 or the like.

[0055] Regarding the SSB index(s) (or SSB(s)) for determining validation of a PRACH occasion (also referred to as candidate SSB indexes or candidate SSBs etc.) associated with the candidate cell, it will be determined in various manners.

[0056] For example, the candidate SSB indexes are SSB indexes of the SSBs corresponding to the SSB indexes associated with the candidate cell, e.g., which are configured by RRC signaling.

[0057] For another example, the candidate SSB indexes are SSB indexes of the SSBs corresponding to: a) the SSB indexes associated with the candidate cell, e.g., which are configured by RRC signaling; and b) the SSB indexes associated with the serving cell, e.g., which are provided by ssb-PositionsInBurst in SIB1 or in ServingCellConfigCommon associated with the serving cell. [0058] For yet another example, the candidate SSB indexes are SSB indexes of the SSBs corresponding to the SSB indexes associated with the candidate cell, e.g., configured by RRC signaling and the SSBs (or SSB indexes) configured for LI beam measurement/reporting.

[0059] For yet another example, the candidate SSB indexes are SSB indexes of the SSBs corresponding to: a) the SSB indexes associated with the candidate cell, e.g., configured by RRC signaling; b) the SSB indexes associated with the serving cell, e.g., which are provided by ssb-PositionsInBurst in SIB1 or in ServingCellConfigCommon associated with the serving cell; and c) the SSBs (or SSB indexes) configured for LI beam measurement/reporting.

[0060] For yet another example, the candidate SSB indexes are SSB indexes of the SSBs corresponding to: a) the SSB indexes associated with the serving cell, e.g., which are provided by ssb-PositionsInBurst in SIB 1 or in ServingCellConfigCommon associated with the serving cell; and b) the SSBs (or SSB indexes) configured for LI beam measurement/reporting.

[0061] Some embodiments of the present application also enhance validation determination of a PRACH occasion associated with the serving cell in LTM scenarios.

[0062] According to some embodiments of the present application, a PDCCH order triggers a PRACH transmission in a PRACH occasion associated with a serving cell that works on unpaired spectrum. In the case that a UE is not provided tdd-UL-DL-ConfigurationCommon or the like associated with the serving cell, a PRACH occasion associated with the serving cell in a PRACH slot will be valid if the PRACH occasion does not precede an SSB in the PRACH slot and starts at least N _gap symbols after a last SSB symbol, where N _gap is provided in Table 8.1-2 of TS38.213 or the like. In the case that a UE is provided tdd-UL-DL-ConfigurationCommon or the like associated with the serving cell, a PRACH occasion associated with the serving cell in a PRACH slot is valid if the PRACH occasion is within uplink symbols, or if the PRACH occasion does not precede an SSB in the PRACH slot and starts at least N _gap symbols after a last downlink symbol and at least N _gap symbols after a last SSB symbol, where N _gap is provided in Table 8.1-2 of TS38.213 or the like.

[0063] Regarding the SSB indexes for determination of validation of a PRACH occasion associated with the serving cell, it can be determined as the SSB indexes of the SSBs corresponding to: a) the SSB indexes associated with the serving cell, e.g., which are provided by ssb-PositionsInBurst in SIB1 or in ServingCellConfigCommon associated with the serving cell; and b) the SSBs (or SSB indexes) configured for LI beam measurement/reporting.

[0064] Besides, the SCS configuration of PRACH transmissions associated with a candidate cell may be the same or different from the SCS configuration of PRACH transmissions associated with the serving cell. Therefore, if a random access procedure is initiated by a PDCCH order to the UE according to legacy specification, a PRACH transmission cannot always be with the same SCS as a PRACH transmission initiated by higher layers of the UE. According to some embodiments of the present application, for a PRACH transmission associated with a candidate cell initiated by a PDCCH order, the SCS of the PRACH transmission will be determined according to the PRACH configuration associated with the candidate cell, e.g., which is configured by RRC signaling.

M-DCI based M-TRP scenarios

[0065] In exemplary M-DCI based M-TRP scenarios, e.g., inter-cell M-DCI based M-TRP scenarios, two CORESET pool index values, e.g., two CORESETPoolIndex values will be configured for CORESETs, where one CORESETPoolIndex value is associated with a serving cell PCI (or a serving cell) while the other CORESETPoolIndex value is associated with an additional PCI (or non-serving cell PCI, or a non-serving cell). An exemplary SSB configuration associated with each additional PCI is shown below:

SSB-MTC-AdditionalPCI-rl 7 ::= SEQUENCE { additional! ³ Cllndex-rl 7 Additional PCIIndex-rl 7, additionalP Cl-rl 7 PhysCellld, periodicity-r 17 ENUMERATED { ms5, ms 10, ms20, ms40, ms80, msl60, spare2, sparel }, ssb-PositionsInBurst-rl 7 CHOICE { shortBitmap BIT STRING (SIZE (4)), mediumBitmap BIT STRING (SIZE (8)), longBitmap BIT STRING (SIZE (64)) }, ss-PBCH-BlockPower-rl 7 INTEGER (-60..50) }

Additional? Cllndex-rl 7 ::= INTEGER(l..maxNrofAdditionalPCI-rl 7).

[0066] Only one additional PCI of all configured additional PCIs for a UE will be activated in inter-cell M-DCI based M-TRP, which means all activated TCI states are either associated with the serving cell PCI or the activated additional PCI at the same time. Therefore, the activated additional PCI will be associated with at least one activated TCI state. TRPs in inter-cell M-DCI based M-TRP scenarios will work on the same SCS, BWP, frequency and slot format. Therefore, if the serving cell works on an unpaired spectrum, the non-serving cell will also work on an unpaired spectrum. Besides, the serving cell PCI and the non-serving cell PCI will share the same tdd-UL-DL-ConfigurationCommon.

[0067] In addition, although it is agreed that one additional PRACH configuration is configured for each configured additional PCI (or non-serving cell), it still needs to further determine whether to support a PDCCH order triggering a PRACH towards a non-activated additional PCI.

[0068] According to some embodiments of the present application, a PDCCH order triggers a PRACH transmission in a PRACH occasion associated with a non-serving cell (or an additional PCI) that works on unpaired spectrum (that is, the serving cell also works on unpaired spectrum). In the case that a UE is not provided tdd-UL-DL-ConfigurationCommon or the like associated with the serving cell, a PRACH occasion associated with the non-serving cell in a PRACH slot will be valid if the PRACH occasion does not precede an SSB in the PRACH slot and starts at least N _gap symbols after a last SSB symbol, where N _gap is provided in Table 8.1-2 of TS38.213 or the like. In the case that a UE is provided tdd-UL-DL-ConfigurationCommon or the like associated with the serving cell, a PRACH occasion associated with the non-serving cell or the additional PCI in a PRACH slot will be valid if: a) the PRACH occasion is within uplink symbols, or b) the PRACH occasion does not precede an SSB in the PRACH slot and starts at least N _gap symbols after a last downlink symbol and at least N _gap symbols after a last SSB symbol, where N _gap is provided in Table 8.1-2 of TS38.213 or the like.

[0069] Regarding the SSB index(s) (or SSB(s)) for determining validation of a PRACH occasion associated with the non-serving cell or the additional PCI, it will be determined in various manners.

[0070] For example, the candidate SSB indexes are SSB indexes of the SSBs corresponding to: a) the SSB indexes associated with the serving cell (or serving cell PCI), e.g., which are provided by ssb-PositionsInBurst in SIB1 or in ServingCellConfigCommon associated with the serving cell; and b) the SSB indexes associated with the additional PCI (or the non-serving cell), e.g., which are provided by ssb-PositionsInBurst in SSB-MTC-AdditionalPCI associated with the additional PCI.

[0071] For another example, the candidate SSB indexes are SSB indexes of the SSBs corresponding to: a) the SSB indexes associated with the serving cell, e.g., which are provided by ssb-PositionsInBurst in SIB1 or in ServingCellConfigCommon associated with the serving cell; and b) the SSB indexes associated with the activated additional PCI, e.g., which are provided by ssb-PositionsInBurst in SSB-MTC-AdditionalPCI associated with the activated additional PCI.

[0072] For yet another example, the candidate SSB indexes are SSB indexes of the SSBs corresponding to: a) the SSB indexes associated with the serving cell, e.g., which are provided by ssb-PositionsInBurst in SIB1 or in ServingCellConfigCommon associated with the serving cell; b) the SSB indexes associated with the additional PCI, e.g., which are provided by ssb-PositionsInBurst in SSB-MTC-AdditionalPCI associated with the additional PCI; and c) the SSB indexes associated with an activated additional PCI, e.g., which are provided by ssb-PositionsInBurst in SSB-MTC-AdditionalPCI associated with the activated additional PCI.

[0073] For yet another example, the candidate SSB indexes are SSB indexes of the SSBs corresponding to: a) the SSB indexes associated with the serving cell, e.g., which are provided by ssb-PositionsInBurst in SIB1 or in ServingCellConfigCommon associated with the serving cell; and b) the SSBs (or SSB indexes) configured for LI beam measurement/reporting.

[0074] For yet another example, the candidate SSB indexes are SSB indexes of the SSBs corresponding to: a) the SSB indexes associated with the serving cell, e.g., which are provided by ssb-PositionsInBurst in SIB1 or in ServingCellConfigCommon associated with the serving cell; b) the SSB indexes associated with the additional PCI, e.g., which are provided by ssb-PositionsInBurst in SSB-MTC-AdditionalPCI associated with the additional PCI; and c) the SSBs (or SSB indexes) configured for LI beam measurement/reporting.

[0075] For yet another example, the candidate SSB indexes are SSB indexes of the SSBs corresponding to: a) the SSB indexes associated with the serving cell, e.g., which are provided by ssb-PositionsInBurst in SIB1 or in ServingCellConfigCommon associated with the serving cell; b) the SSB indexes associated with an activated additional PCI, e.g., which are provided by ssb-PositionsInBurst in SSB-MTC-AdditionalPCI associated with the activated additional PCI; and c) the SSBs (or SSB indexes) configured for LI beam measurement/reporting.

[0076] For yet another example, the candidate SSB indexes are SSB indexes of the SSBs corresponding to: a) the SSB indexes associated with the serving cell, e.g., which are provided by ssb-PositionsInBurst in SIB1 or in ServingCellConfigCommon associated with the serving cell; b) the SSB indexes associated with the additional PCI, e.g., which are provided by ssb-PositionsInBurst in SSB-MTC-AdditionalPCI associated with the additional PCI; c) the SSB indexes associated with an activated additional PCI, e.g., which are provided by ssb-PositionsInBurst in SSB-MTC-AdditionalPCI associated with the activated additional PCI; and d) the SSBs (or SSB indexes) configured for LI beam measurement/reporting.

[0077] The activated additional PCI may be the same or different from the additional PCI (the PCI of the non-serving cell) associated with the PRACH occasion. In the case that activated additional PCI is the same as the additional PCI associated with the PRACH occasion, the first three of the aforementioned exemplary schemes will be the same and the last three schemes of the aforementioned exemplary will be the same. [0078] Similarly, some embodiments of the present application also enhance validation determination of a PRACH occasion associated with the serving cell in inter-cell M-DCI based M-TRP scenarios.

[0079] According to some embodiments of the present application, a PDCCH order triggers a PRACH transmission in a PRACH occasion associated with a serving cell (or a serving cell PCI) that works on unpaired spectrum. In the case that a UE is not provided tdd-UL-DL-ConfigurationCommon or the like associated with the serving cell, a PRACH occasion associated with the serving cell or serving cell PCI in a PRACH slot will be valid if the PRACH occasion does not precede an SSB in the PRACH slot and starts at least N _gap symbols after a last SSB symbol, where N _gap is provided in Table 8.1 -2 of TS38.213 or the like. In the case that a UE is provided tdd-UL-DL-ConfigurationCommon or the like associated with the serving cell, a PRACH occasion associated with the serving cell or serving cell PCI in a PRACH slot is valid if the PRACH occasion is within uplink symbols, or if the PRACH occasion does not precede an SSB in the PRACH slot and starts at least N _gap symbols after a last downlink symbol and at least N _gap symbols after a last SSB symbol, where Ngap is provided in Table 8.1-2 of TS38.213 or the like.

[0080] Regarding the SSB indexes for determination of validation of a PRACH occasion associated with the serving cell or serving cell PCI, it will also be determined in various manners.

[0081] For example, the candidate SSB indexes are SSB indexes of the SSBs corresponding to: a) the SSB indexes associated with the serving cell, e.g., which are provided by ssb-PositionsInBurst in SIB1 or in ServingCellConfigCommon associated with the serving cell; and b) the SSB indexes associated with the activated additional PCI, e.g., which are provided by ssb-PositionsInBurst in SSB-MTC-AdditionalPCI associated with the activated additional PCI.

[0082] For another example, the candidate SSB indexes are SSB indexes of the SSBs corresponding to: a) the SSB indexes associated with the serving cell, e.g., which are provided by ssb-PositionsInBurst in SIB1 or in ServingCellConfigCommon associated with the serving cell; and b) the SSBs (or SSB indexes) configured for LI beam measurement/reporting.

[0083] For yet another example, the candidate SSB indexes are SSB indexes of the SSB corresponding to: a) the SSB indexes associated with the serving cell, e.g., which are provided by ssb-PositionsInBurst in SIB1 or in ServingCellConfigCommon associated with the serving cell; b) the SSB indexes associated with the activated additional PCI, e.g., which are provided by ssb-PositionsInBurst in SSB-MTC-AdditionalPCI associated with the activated additional PCI; and c) the SSBs (or SSB indexes) configured for LI beam measurement/reporting.

[0084] Persons skilled in the art should well know that although some configurations and/or parameters, e.g., "tdd-UL-DL-ConfigurationCommon," "ssb-PositionsInBurst" "ServingCellConfigCommon" and "SSB-MTC-AdditionalPCI" etc. are common known in legacy specifications, they may evolve into other terms as the evolution of 3GPPP. Thus, the name of such configurations and/or parameters should not be used to unduly limit the scope of the present application, and should be reasonably interpreted with their technical substance. In addition, although some embodiments are illustrated in view of only one side, e.g., the network side or the remote side, persons skilled in the art would clearly determine how to consistently apply the technical solutions in the other side based on the consistency between the network side and remote side.

[0085] Besides methods, embodiments of the present application also propose an apparatus of supporting PRACH transmission.

[0086] For example, FIG. 3 illustrates a block diagram of an apparatus of supporting PRACH transmission 300 according to some embodiments of the present application.

[0087] As shown in FIG. 3, the apparatus 300 may include at least one non-transitory computer-readable medium 301, at least one receiving circuitry 302, at least one transmitting circuitry 304, and at least one processor 306 coupled to the non-transitory computer-readable medium 301, the receiving circuitry 302 and the transmitting circuitry 304. The at least one processor 306 may be a central processing unit (CPU), a digital signaling processing (DSP), a microprocessor etc. The apparatus 300 may be a RAN node, e.g., a gNB or a remote apparatus, e.g., a UE configured to perform a method illustrated in the above or the like.

[0088] Although in this figure, elements such as the at least one processor 306, transmitting circuitry 304, and receiving circuitry 302 are described in the singular, the plural is contemplated unless a limitation to the singular is explicitly stated. In some embodiments of the present application, the receiving circuitry 302 and the transmitting circuitry 304 can be combined into a single device, such as a transceiver. In certain embodiments of the present application, the apparatus 300 may further include an input device, a memory, and/or other components.

[0089] In some embodiments of the present application, the non-transitory computer-readable medium 301 may have stored thereon computer-executable instructions to cause a processor to implement the method with respect to the RAN node, e.g., the gNB as described above. For example, the computer-executable instructions, when executed, cause the processor 306 interacting with receiving circuitry 302 and transmitting circuitry 304, so as to perform the steps with respect to the RAN node as depicted above.

[0090] In some embodiments of the present application, the non-transitory computer-readable medium 301 may have stored thereon computer-executable instructions to cause a processor to implement the method with respect to the remote apparatus, e.g., the UE as described above. For example, the computer-executable instructions, when executed, cause the processor 306 interacting with receiving circuitry 302 and transmitting circuitry 304, so as to perform the steps with respect to the remote apparatus as illustrated above.

[0091] FIG. 4 is a block diagram of an apparatus of supporting PRACH transmission 400 according to some other embodiments of the present application.

[0092] Referring to FIG. 4, the apparatus 400, for example a RAN node or a UE may include at least one processor 402 and at least one transceiver 404 coupled to the at least one processor 402. The transceiver 404 may include at least one separate receiving circuitry 406 and transmitting circuitry 404, or at least one integrated receiving circuitry 406 and transmitting circuitry 404. The at least one processor 402 may be a CPU, a DSP, a microprocessor etc. [0093] According to some embodiments of the present application, the apparatus 500 is a remote apparatus, e.g., a UE, which includes: a transceiver; and a processor coupled to the transceiver, wherein the processor is configured to: receive, from a serving cell on an active BWP, a PDCCH order triggering a PRACH transmission associated with a cell that works on an unpaired spectrum, wherein the cell is same as or different from the serving cell; and determine valid PRACH occasions for the PRACH transmission based on SSB configuration information, wherein, in the case that L1/L2 triggered mobility is configured in the serving cell, the SSB configuration information includes any of: SSB configuration information associated with the serving cell, SSB configuration information for LI beam measurement/reporting, and SSB configuration information associated with a candidate cell; or in the case that a plurality of values of CORESET pool index are configured for CORESETs in the BWP of the serving cell, the SSB configuration information includes any of: the SSB configuration information associated with the serving cell, the SSB configuration information for LI beam measurement/reporting, and SSB configuration information associated with at least one additional PCI.

[0094] According to some embodiments of the present application, the apparatus 500 is a RAN node, e.g., a gNB, which includes: a transceiver; and a processor coupled to the transceiver, wherein the processor is configured to: transmit, from a serving cell on an active BWP, a PDCCH order triggering a PRACH transmission associated with a cell that works on an unpaired spectrum, wherein the cell is same as or different from the serving cell; and determine valid PRACH occasions for the PRACH transmission based on SSB configuration information, wherein, in the case that L1/L2 triggered mobility is configured in the serving cell, the SSB configuration information includes any of: SSB configuration information associated with the serving cell, SSB configuration information for LI beam measurement/reporting, and SSB configuration information associated with a candidate cell; or in the case that a plurality of values of CORESET pool index are configured for CORESETs in the BWP of the serving cell, the SSB configuration information includes any of: the SSB configuration information associated with the serving cell, the SSB configuration information for LI beam measurement/reporting, and SSB configuration information associated with at least one additional PCI. [0095] The method according to embodiments of the present disclosure can also be implemented on a programmed processor. However, the controllers, flowcharts, and modules may also be implemented on a general purpose or special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, an integrated circuit, a hardware electronic or logic circuit such as a discrete element circuit, a programmable logic device, or the like. In general, any device capable of implementing the flowcharts shown in the figures may be used to implement the processor functions of this application. For example, an embodiment of the present disclosure provides an apparatus, including a processor and a memory. Computer programmable instructions for implementing a method are stored in the memory, and the processor is configured to perform the computer programmable instructions to implement the method. The method may be a method as stated above or other method according to an embodiment of the present disclosure.

[0096] An alternative embodiment preferably implements the methods according to embodiments of the present disclosure in a non-transitory, computer-readable storage medium storing computer programmable instructions. The instructions are preferably executed by computer-executable components preferably integrated with a network security system. The non-transitory, computer-readable storage medium may be stored on any suitable computer readable media such as random access memory (RAMs), read only memory (ROMs), flash memory, electrically erasable programmable read only memory (EEPROMs), optical storage devices (compact disc (CD) or digital video disc (DVD)), hard drives, floppy drives, or any suitable device. The computer-executable component is preferably a processor but the instructions may alternatively or additionally be executed by any suitable dedicated hardware device. For example, an embodiment of the present disclosure provides a non-transitory, computer-readable storage medium having computer programmable instructions stored therein. The computer programmable instructions are configured to implement a method as stated above or other method according to an embodiment of the present disclosure.

[0097] The detailed description of the appended drawings is intended as a description of the currently preferred embodiments of the present disclosure and is not intended to represent the only form in which the present disclosure may be practiced. It is to be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the present disclosure.

[0098] To facilitate understanding, embodiments are provided under specific network architecture and new service scenarios, such as 3GPP 5G, 3GPP long-term evolution (LTE), and so on. It is contemplated that along with the developments of network architectures and new service scenarios, all embodiments in the present disclosure are also applicable to similar technical problems. Moreover, the terminologies recited in the present disclosure may change, which should not affect the principle of the present disclosure.

[0099] In addition, in this disclosure, the terms "includes," "including," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "a," "an," or the like does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that includes the element. Also, the term "another" is defined as at least a second or more. The terms "having," and the like, as used herein, are defined as "including."