METHOD AND USER EQUIPMENT FOR HANDLING AUTONOMOUS GAPS

Technical field

The present disclosure relates generally to a method and a User Equipment, UE, for handling autonomous gaps in communication between the UE and a network node on at least one serving carrier. The autonomous gaps may be used as measurement gaps and are autonomously created by the UE.

Background

In this disclosure, the term“User Equipment, UE” is used to represent any communication entity capable of radio communication with a wireless network by sending and receiving radio signals, such as e.g. mobile telephones, tablets, laptop computers and Machine-to-Machine (M2M) devices, also known as Machine Type Communication (MTC) devices. Another common generic term in this field is“wireless device” which could be used herein as a synonym for UE.

Further, the term“network node”, is used herein to represent any node of a wireless network that is operative to communicate radio signals with wireless devices. For example, the wireless network may be operating according to Long Term Evolution (LTE) or according to 5G, also referred to as“New Radio” NR, both being defined by the third Generation Partnership Project, 3GPP. The radio network node may refer to a base station, eNB, gNB, ng-eNB, depending on the terminology used, although this disclosure is not limited to these examples. The node ng-eNB is defined for 5G in the 3GPP document TS38.300 section 3.

A UE in communication with a serving network node of a serving cell typically operates to use so-called autonomous gaps comprising a time interval during which the UE does not receive or transmit any signals in the serving cell. The gaps provide an opportunity for the UE to perform other tasks such as reading and measuring signals transmitted in other non-serving cells, e.g. to assist handover procedures and read system information to identify the non-serving cells, among other things. Summary

It is an object of embodiments described herein to address at least some of the problems and issues outlined herein. It is possible to achieve this object and others by using a method and a User Equipment, UE, as defined in the attached independent claims.

According to one aspect, a method performed by a UE is provided for handling autonomous gaps in communication between the UE and a serving network node of a wireless network. In this method the UE determines to use a type of

autonomous gaps on at least one serving carrier to enable operation on a non- serving carrier frequency, the type of autonomous gaps being one of UE-specific autonomous gaps and frequency-dependent autonomous gaps. The UE also determines an autonomous gap configuration for the type of autonomous gaps determined to be used. The UE then configures the autonomous gaps based on the type of autonomous gaps determined to be used and on the determined autonomous gap configuration, to meet a UE requirement.

According to another aspect, a UE is arranged to handle autonomous gaps in communication between the UE and a serving network node of a wireless network. The UE is configured or adapted to determine to use a type of autonomous gaps on at least one serving carrier to enable operation on a non-serving carrier frequency, the type of autonomous gaps being one of UE-specific autonomous gaps and frequency-dependent autonomous gaps.

The UE is further configured or adapted to determine an autonomous gap configuration for the type of autonomous gaps determined to be used, and to configure the autonomous gaps based on the type of autonomous gaps

determined to be used and on the determined autonomous gap configuration, to meet a UE requirement.

The above method and UE may be configured and implemented according to different optional embodiments to accomplish further features and benefits, to be described below. A computer program is also provided comprising instructions which, when executed on at least one processor in the above UE, cause the at least one processor to carry out the method described above. A carrier is also provided which contains the above computer program, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium.

Brief description of drawings

The solution will now be described in more detail by means of exemplary embodiments and with reference to the accompanying drawings, in which: Figure 1 is a communication overview illustrating how an architecture for an NR Radio Access network, RAN, denoted NG-RAN, could be structured.

Figures 2A-2D illustrate some examples of how NR could be deployed with respect to core nodes and base stations, BSs.

Figure 3 is a time-frequency diagram illustrating a structure comprising a

Synchronization Signal (SS) and a Physical Broadcast Channel (PBCFI) block, also referred to herein as the SS/PBCFI block.

Figure 4 is a communication overview illustrating how a UE communicates with a network node of a wireless network, where the embodiments described herein may be used. Figure 4A is a flow chart illustrating a procedure in a UE, according to some example embodiments.

Figure 5 illustrates some examples of how different autonomous gap patterns may be used in NR when 100, 50 and 0% puncturing, respectively, is allowed over a certain time of an SS/PBCFI block Measurement Timing Configuration (SMTC). Figure 6 illustrates some examples of autonomous gap patterns at different Signal to Interference and Noise Ratios (SINRs) Z<Y<X of a target carrier when 100% puncturing is allowed of SMTC. Figure 7 illustrates some further examples of autonomous gap patterns at different SINRs Z<Y<X of a target carrier when 50% puncturing is allowed of SMTC.

Figure 8 is a flow chart illustrating a procedure in a network node, according to further example embodiments. Figure 9 is a block diagram illustrating how a UE and a network node may be structured, according to further example embodiments.

Detailed description

The embodiments and examples described herein may be used in a procedure for handling autonomous gaps in communication between a UE and a network node on one or more carriers.

First, some conventional procedures and features related to measurement gaps will be described. Any acronyms and abbreviations occurring in this disclosure are explained at the end of the Detailed Description.

The use of autonomous gaps in LTE and a mechanism for reading a Cell Global Identifier (CGI) will now be described. Reference will also be made to E-UTRAN which means Evolved UMTS Terrestrial Radio Access Network, where UMTS denotes Universal Mobile Telecommunications System.

In E-UTRAN, a cell serving a UE, referred to as the serving cell, can request the UE to acquire the CGI, which uniquely identifies a cell, of a target cell which may be a candidate for handover of the UE. In order to acquire the CGI of the target cell, the UE has to read at least part of the cell’s broadcasted System Information (SI) including Master Information Block (MIB) and the relevant System Information Block (SIB) such as SIB1 , to be described later below. The reading of SI for the acquisition of CGI is carried out during measurement gaps which are

autonomously created by the UE, which are therefore called autonomous gaps. In LTE, the UE reads the MIB and SIB1 of the target cell E-UTRAN cell to acquire its CGI, also known as Evolved CGI (ECGI), when the target cell is E-UTRAN intra- or inter-frequency), which is described in 3GPP TS 36.331 , Section 5.5.3.1.

In LTE the MIB includes a limited number of most essential and most frequently transmitted parameters that are needed to acquire other information from the cell, and is transmitted on a Broadcast Channel (BCH). In particular, the following information is currently included in MIB:

• Downlink (DL) bandwidth,

• Physical HARQ Indication Channel (PHICH) configuration, and · System Frame Number (SFN).

The MIB is transmitted periodically with a periodicity of 40 ms and repetitions made within 40 ms. The first transmission of the MIB is scheduled in subframe #0 of radio frames for which the SFN mod 4 = 0, and repetitions are scheduled in subframe #0 of all other radio frames.

In LTE the SIB1 contains, e.g., the following information:

• Public Land Mobile Network (PLMN) identity,

• Cell identity,

• Closed Subscriber Group (CSG) identity and indication,

· Frequency band indicator,

• Sl-window length,

• Scheduling information for other SIBs.

The LTE SIB1 may also indicate whether a change has occurred in the SI messages. The UE is notified about any forthcoming change in the SI by a paging message, from which the UE will know that the system information will change at the next modification period boundary. The modification period boundaries are defined by SFN values for which SFN mod m= 0, where m is the number of radio frames comprising the modification period. The modification period is configured by system information.

The LTE SIB1 , as well as other SIB messages, is transmitted on a Downlink Shared Channel (DL-SCH). The SIB1 is transmitted with a periodicity of 80 ms and repetitions made within 80 ms. The first transmission of

SystemlnformationBlockTypel is scheduled in subframe #5 of radio frames for which the SFN mod 8 = 0, and repetitions are scheduled in subframe #5 of all other radio frames for which SFN mod 2 = 0.

In the following, the term RAT is used to denote Radio Access Technology. In case of inter-RAT UTRAN, the UE reads the MIB and SIB3 of the target cell UTRAN cell to acquire its CGI.

Some scenarios for reading the CGI will now be described.

The target cell whose CGI can be acquired can be intra-frequency cell, inter- frequency cell or even inter-RAT cell, e.g. UTRAN, GERAN, CDMA2000 or High Rate Packet Data (FIRPD). There are at least few well known scenarios for which the serving cell may request the UE to report the CGI of the target cell.

• Verification of CSG cell

• Establishment of Self-organizing network (SON) Automatic Neighbor

Relations (ANR) · MDT

It will now be described how a CSG cell can be verified for CSG inbound mobility.

In order to support mobility, the UE is required to identified a number of neighbor cells and report their Physical Cell Identity (PCI) to the serving network node, e.g. serving eNode B in E-UTRAN. The UE may also be requested to report the neighbor cell measurements such as Reference Signal Received Power (RSRP) and/or Reference Signal Received Quality (RSRQ) in E-UTRAN or Common Pilot Channel (CPICFI) Received Signal Code Power (RSCP) and/or CPICFI Ec/No in UTRAN or even GERAN carrier Received Signal Strength Indication (RSSI) or even pilot strength for CDMA2000/HRPD. In response to the reported UE measurement, the serving network node sends handover command to the UE.

Due to smaller cell sizes in a dense deployment scenarios (e.g. femto cells, restricted small cells like femto closed subscriber group, pico cells etc), the PCIs are more frequently reused. In order to prevent a Handover (HO) command to a non-allowed home base station, e.g. CSG cell, the serving network node may also request the UE to decode and report the CGI of the target cell. This is also referred to as home inbound mobility. The CGI is unique in the network allowing the network to distinguish between macro BS and home BS or to uniquely identify that the reported cell belongs to CSG.

The procedure and the associated requirements for the target cell’s CGI reporting are specified in E-UTRAN. One key aspect of the CGI decoding is that it is performed by the UE during the autonomous gaps, which are created by the UE itself. The reason of acquiring the target cell CGI during autonomous gaps stems from the fact that the typical UE implementation is not capable to simultaneously receive the data from the serving cell and acquire the target cell’s system information, which contains the CGI. Furthermore the CGI acquisition of inter- frequency or inter-RAT target cell requires the UE to even switch the carrier frequency. Hence the use of autonomous gaps is inevitable for acquiring the target cell’s CGI. The autonomous gaps are created both in uplink and downlink.

It will now be described how cell relations may be created in a Self-Organizing Network (SON).

The SON function in E-UTRAN allows the operators to automatically plan and tune the network parameters and network nodes. The conventional method is based on manual tuning, which consumes enormous amount of time, resources and requires considerable involvement of work force. Due to network complexity, a large number of system parameters, Inter-RAT (IRAT) technologies etc., it would be useful to have reliable schemes to perform the test of self-organization in the network whenever necessary.

An operator can also add or delete a cell or an entire base station that may serve multiple cells. Especially new cells are added more frequently during an early phase of network deployment. In the later stages an operator can still upgrade the network by adding more carriers or more base stations on the same carrier. It can also add cells related to another technology. This is referred to as the Automatic Neighbor cell Relation (ANR) establishment and is part of the SON. In order to ensure correct establishment of the neighbor cell relation, the serving cell requests the UE to report the CGI of the new target cell, whose PCI is identified and reported to the said serving cell. The CGI acquisition requires the UE to read the target cell’s system information and is thus carried out by the UE during the autonomous gaps. As in case of home inbound mobility, the CGI acquisition for ANR purpose, also lead to interruption of the data from the serving cell.

A feature called“minimization of drive tests” which can be used in the field of network planning, will now be described.

The Minimization of Drive Test (MDT) feature has been introduced in LTE and HSPA release 10. The MDT feature provides means for reducing the effort for operators when gathering information for the purpose of network planning and optimization. The MDT feature requires that the UEs log or obtain various types of measurements, events and coverage related information. The logged or collected measurements or relevant information are then sent to the network. This is in contrast to the traditional approach where the operator has to collect similar information by means of the so-called drive tests and manual logging. The MDT is described in TS 37.320.

The UE could collect the measurements during connected as well as in low activity states e.g. idle state in UTRA/E-UTRA, cell PCH states in UTRA etc.

Some examples of potential UE measurements related to MDT are: • Mobility measurements e.g. RSRP, RSRQ etc

• Random access failure

• Paging Channel Failure, also called PCCH Decode Error

• Broadcast Channel failure

· Radio link failure report

The UE could also be configured to report the CGI of the target cells along with other measurements (e.g. RSRP, RSRQ etc). In connected mode the existing procedures are used to acquire the CGI of the target cells for the purpose of the MDT. In idle mode the UE can be configured to log the cell measurements along with the CGI and report the logged measurements to the network at suitable occasion (e.g. when UE goes to connected mode). One key aspect that distinguishes the normal CGI reporting is that in case of MDT, the acquired CGI of the target cells are acquired by the MDT functionality e.g. MDT node which can be a logical or physical node. The MDT node can use the acquired CGI for network planning and optimizing of the network.

The CGI for MDT purpose is also acquired during the autonomous gaps as in case of CSG inbound mobility or SON ANR.

It will now be described how a UE may apply SI acquisition when carrier aggregation is employed.

The UE applies the system information acquisition and change monitoring procedures for the Primary cell (PCell) only. For Secondary cells (SCells), E- UTRAN provides, via dedicated signaling, all system information relevant for operation in RRC_CONNECTED when adding the SCell, where RRC denotes Radio Resource Control. Flence the UE creates autonomous gaps for reading the neighbor cell CGI in the downlink and uplink on the PCell.

Some requirements for reading SI will now be described.

ECGI requirements in E-UTRAN are specified for the following two scenarios: • Intra-frequency ECGI reporting

• Inter-frequency ECGI reporting

• Inter-RAT UTRAN CGI reporting The UE is required to report the intra-frequency ECGI within about 150 ms from a target intra-frequency cell provided its SINR is at least -6 dB or higher. During the acquisition of the target cell’s ECGI on the serving carrier frequency the UE is allowed to create autonomous gaps in the downlink and uplink. When

acknowledged mode is applied, the UE is required to transmit feedback to the serving network node to indicate whether downlink data has been received or not, the feedback comprising either an acknowledgment (ACK) or a non- acknowledgment (NACK), commonly referred to as ACK/NACK for short. Under continuous allocation, the UE is required to transmit certain number of ACK/NACK on the uplink to ensure that the UE does not create excessive gaps. The UE is required to report the inter-frequency ECGI also within about 150 ms from a target inter-frequency cell provided its SINR is at least -4 dB or higher. During the acquisition of the target cell’s ECGI on the serving carrier frequency the UE is allowed to create autonomous gaps in the downlink and uplink. This causes UE to interrupt downlink reception and uplink transmission in the serving cell. In UTRAN, the target cell’s CGI acquisition is much longer e.g. more than 1 second depending upon the periodicity of the SIB3, which contains the CGI.

Furthermore due to the autonomous gaps created by the UE to acquire the target cell’s CGI, the interruption of the data transmission and reception from the serving cell can be 600 ms or longer. A typical useful architecture for NR will now be described.

The first release of the so-called 5G system is being standardized in 3GPP and New Radio (NR) is a common term used for the radio interface. One of the characteristics is the Frequency Range (FR) going to higher frequencies than LTE, e.g., above 6 GFIz, where the propagation conditions are known to be more challenging e.g. due to higher penetration and path losses. To mitigate some of these effects, multi-antenna technologies such as beamforming will be massively used. Yet another NR characteristic is the use of multiple numerologies in DL and UL in a cell or for a UE and/or in different frequency bands. For instance, in frequency range 1 (FR1 ) which ranges up to 6GFIz, a slot comprising 14

Orthogonal Frequency Division Multiplexing (OFDM) symbols is either 1 or 0.5ms, depending on chosen numerology, whereas in frequency range 2 (FR2) which ranges from 24GFIz, the same slot is either 0.25 or 0.125ms long. Yet another characteristic is the possibility to enable shorter latencies. Both standalone and non-standalone NR deployments have been standardized in 3GPP. The standalone deployments may be single or multi-carrier, e.g., NR CA or dual connectivity with NR PCell and NR Primary SCell (PSCell). The non- standalone deployments are currently meant to describe a deployment with LTE PCell and NR PSCell. There may also be one or more LTE SCells and one or more NR SCells.

In NR, Dual Connectivity (DC) can be employed between E-UTRA and NR where the master can be E-UTRA or NR while the secondary serving node can be NR and E-UTRA, respectively, and Dual Connectivity within NR only.

An NG-RAN node or NR radio network node is currently either: - a gNB, providing NR user plane and control plane protocol terminations towards the UE; or

- an ng-eNB, providing E-UTRA user plane and control plane protocol

terminations towards the UE.

The gNBs and ng-eNBs are interconnected with each other by means of the Xn interface. The gNBs and ng-eNBs are also connected by means of the NG interfaces to the 5GC, more specifically to the Access and Mobility Management Function (AMF) by means of the NG-C interface and to the User Plane Function (UPF) by means of the NG-U interface, see 3GPP TS 23.501. The NG-RAN architecture is illustrated in Figure 1 , and some NR deployment examples are illustrated in Figures 2A-2D.

It will now be described how UE measurements and gaps are handled in NR. For NR RRM, the UE can perform intra-frequency, inter-frequency, and inter-RAT measurements, e.g., UE connected to NR serving cell is measuring LTE or UTRA or other-RAT cells. For NR RRM measurements requiring measurement gaps, the network shall decide on and provide the UE with a measurement gap configuration index. No autonomous gaps have been standardized yet for NR RRM. Flowever, autonomous gaps are expected to be introduced in Rel-16, e.g., for SON.

Generally, the NR RRM measurements can be performed based e.g. on

Synchronization Signal Blocks (SSBs) or CSI-RS signals.

For Observed Time Difference Of Arrival (OTDOA) positioning, only inter-RAT measurements are currently supported in NR, e.g., E-UTRA Reference Signal Time Difference (RSTD) based on LTE Positioning Reference Signals (PRS) defined in 3GPP TS 36.211 ; positioning signals for RSTD in NR are not yet standardized. For Enhanced Cell Identity (E-CID) positioning in NR, UE can report intra-frequency, inter-frequency, and inter-RAT measurements.

In LTE, for inter-frequency positioning measurements requiring gaps, the UE indicates to the serving cell an offset to enable alignment of measurement gaps to be configured by the serving cell for RSTD measurements with PRS configuration. Only offset is needed in LTE since measurement gap periodicity for RSTD can only be 40 ms. The PRS configuration as well as an offset between the reference cell PRS and inter-frequency cell PRS are always received from the so-called E- SMLC which is a positioning node.

In NR, the positioning node may not know the timing of inter-RAT cells, hence the UE may need to determine the timing of inter-RAT PRS occasions by itself, before it sends a request to the NR serving cell for measurement gaps for inter-RAT RSTD measurements, otherwise at least the offset for measurement gaps being requested cannot be provided by the UE. To acquire the timing of inter-RAT PRS occasion for positioning purpose, the UE needs autonomous gaps, which are being standardized in NR.

The network transmits the above-mentioned SS/PBCH block at regular intervals with a certain periodicity, which will now be described. Figure 3 illustrates a Time- frequency structure of the SS/PBCH block.

The synchronization signal and PBCH block comprise a Primary Synchronization Signal (PSS) and A secondary Synchronization Signal (SSS), each occupying 1 symbol and 127 subcarriers, and PBCH spanning across 3 OFDM symbols and 240 subcarriers, but on one symbol leaving an unused part in the middle for SSS as show in figure 3. The periodicity of the SS/PBCH block can be configured by the network and the time locations where SS/PBCH block can be sent are determined by sub-carrier spacing. The occasions at which the UE is to perform RRM measurements on the SS/PBCH block are signaled to the UE as the SMTC, and may be sparser than the periodicity by which the SS/PBCH block is actually transmitted. The time duration of each such SMTC occasion is called SMTC window, and is configurable to between 1 to 5 ms.

Polar coding and QPSK modulation is used for PBCH. The UE may assume a band-specific sub-carrier spacing for the SS/PBCH block unless a network has configured the UE to assume a different sub-carrier spacing. PBCH symbols carry its own frequency-multiplexed Demodulation Reference Signal (DMRS). The PBCH physical layer model is described in 3GPP TS 38.202.

Some potential problems with the above-described procedures and features will now be discussed. · Autonomous gaps are being introduced in NR, however, their design and configuration details have not yet been established.

• In LTE, during autonomous gaps the UE cannot receive or transmit in any serving cell, e.g., the gaps are always UE-specific and do not depend on the frequency on which the UE is acquiring CGI. Applying the same approach to NR, i.e. , assuming that autonomous gaps are always UE-specific, is unnecessarily too pessimistic and will have a significant impact on the UE and network performance. This is, for example, because a UE supporting NR measurements in FR2 which is above 6 GHz, and LTE measurements would most typically need to have at least two separate receiver chains which may allow the UE to perform LTE radio measurements without impacting its operation in FR2. On the other hand, the UE may be supporting NR FR1 measurements and LTE measurements, for which different UEs may have different architectures, so that depending on the UE the gaps for LTE measurements may or may not impact its operation in NR FR1.

• If frequency-dependent autonomous gaps are introduced, it is not known how to decide frequencies impacted and frequencies not impacted by the gaps as well as autonomous gaps configuration, the rules for which may impact the UE architecture, UE measurement procedures, and UE serving cells operations.

• If both UE-specific and frequency-dependent autonomous gaps are

supported by the standard, it is not known how to choose the type of the autonomous gaps, neither the impacted/non-impacted frequencies if frequency-dependent autonomous gaps are selected. · The above problems apply not only when autonomous gaps are needed for receiving signals/channels on LTE frequencies while being served by NR but in general, including when the UE is also receiving signals/channels on NR or any other RAT frequencies. For example, in Rel-16 the UE may be allowed to use autonomous gaps for SON on NR frequencies during its operation on NR or other-RAT frequencies; or the other way around - the UE may be allowed to use autonomous gaps for SON on non-NR frequencies during its operation on NR.

• Another specific example: autonomous gaps used for receiving LTE

signals/channels for positioning by a UE served by NR, e.g., to acquire timing of PRS occasions on an LTE frequency or to acquire timing of an LTE cell prior to requesting measurement gaps for E-UTRA RSTD measurements.

The examples and embodiments to be described below may involve the following aspects: · Selecting between usage of autonomous gaps on all (“per-UE”) or on a

subset (e.g.,“per-FR”) of serving carriers, according to UE receiver architecture (receiver capabilities), pre-defined rules and/or signaling provided by the network.

• Selecting puncturing pattern for the autonomous gaps, applied to all or a subset of serving carriers as determined in previous step, based on UE decoder capabilities, pre-defined and/or signaled restrictions on the extent of puncturing allowed e.g. of SMTC windows.

Some advantages that may be achieved when employing the examples and embodiments to be described below, include:

• It may be possible to use frequency-dependent autonomous gaps in NR.

• It may be possible to choose between U E-specific and frequency-dependent autonomous gaps.

• It may be possible to decide autonomous gaps configuration. · It may be possible to perform inter-RAT positioning measurements when the network cannot provide the inter-RAT cell timing.

It may be possible to use autonomous gaps for SON in NR.

A solution will now be described which can be used to overcome at least some of the above problems. A communication scenario where the solution may be employed is illustrated in Figure 4 involving a UE 10 which is served by a network node 12 of a wireless network 14. The UE 10 and the network node 12 are capable of communicating with each other over a wireless communication link.

The UE 10 operates to configure autonomous gaps on at least one serving carrier which carrier is used by the UE 10 for communication with the serving network node 12. The autonomous gaps are to be used by the UE 10 for operation on a non-serving carrier frequency which may be transmitted by another network node, not shown, that is currently not serving the UE 10. Such an operation may include measuring quality and/or signal strength of the non-serving carrier transmitted by such a non- serving network node. These measurements are reported to the serving network node 12 as a basis for evaluating network nodes for future communication with the UE 10, thus potentially triggering an inter-node handover. The non-serving carrier frequency may alternatively be transmitted by the serving network node 12 so that the measurements may trigger an intra-node handover from the current serving carrier to the target carrier. An example of how the solution may be employed in terms of actions performed by a User Equipment such as the UE 10, is illustrated by the flow chart in Figure 4A which will now be described with further reference to Figure 4. Figure 4A thus illustrates a procedure in the UE 10 for handling autonomous gaps in

communication between the UE 10 and the serving network node 12 of a wireless network 14.

A first action 400 illustrates that the UE 10 may acquire information which may, without limitation, be related to one or more of UE capability, pre-defined rules and signaling received from the network 14 via the network node 12. Examples of the above information have been described above. In another action 402, the UE 10 determines to use a type of autonomous gaps on at least one serving carrier to enable operation on a non-serving carrier frequency. The type of autonomous gaps is one of UE-specific autonomous gaps and frequency-dependent autonomous gaps. The UE-specific autonomous gaps and frequency-dependent autonomous gaps can thus be seen as different types of autonomous gaps. The UE 10 may further signal the determined type(s) of autonomous gaps to the network node 12, as shown in an optional action 404.

In another action 406, the UE 10 further determines an autonomous gap configuration for the type of autonomous gaps determined to be used. Some useful but non-limiting examples of how the autonomous gap configuration might be determined will be described later below.

In another action 408, the UE 10 further configures the autonomous gaps based on the type of autonomous gaps determined to be used and on the determined autonomous gap configuration, to meet a UE requirement. This UE requirement may require a minimum number of ACK/NACKs to be transmitted by the UE on the at least one serving carrier during a time period.

Some terminology that may be employed in this context will now be outlined.

In some embodiments, the general term“network node” may be used and it can correspond to any type of radio network node or any network node, which communicates with a UE directly or via another node, and/or with another network node. Examples of network nodes are radio base station, gNB, ng-eNB, positioning node, and test equipment.

In some embodiments, the non-limiting term User Equipment (UE) or wireless device may be used and it refers to any type of wireless device communicating with a network node and/or with another UE in a cellular or mobile

communication system. Examples of UE are NR-capable UE, target device, Device to Device (D2D) UE, machine type UE or UE capable of Machine to Machine (M2M) communication, Personal Digital Assistant (PDA), PAD, Tablet, mobile terminals, smart phone, Laptop Embedded Equipment (LEE), Laptop Mounted Equipment (LME), Universal Serial Bus (USB) dongles, UE category M1 , UE category M2, Proximity Service (ProSe) UE, Vehicle-to-Vehicle (V2V)

UE, V2X UE, etc.

The embodiments and examples herein are described for NR. However, the embodiments and examples herein are applicable to any RAT or multi-RAT systems, where the UE receives and/or transmit signals (e.g. data) e.g.

standalone NR, non-standalone NR, 5G, LTE Frequency/Time Division Duplex (FDD/TDD), WCDMA/HSPA, GSM/GERAN, Wi Fi, WLAN, CDMA2000, etc.

The term time unit or time resource used herein may correspond to any type of physical resource or radio resource expressed in terms of length of time.

Examples of time resources are: symbol, mini-slot, time slot, subframe, radio frame, Transmission Time Interval (TTI), interleaving time, etc. The term TTI used herein may correspond to any time period over which a physical channel can be encoded and interleaved for transmission. The physical channel is decoded by the receiver over the same time period (TO) over which it was encoded. The TTI may also interchangeably be referred to as short TTI (sTTI), transmission time, slot, sub-slot, mini-slot, short subframe (SSF), mini-subframe etc.

The embodiments and examples described herein may apply to any RRC state, e.g, RRC_CONNECTED, RRCJDLE, or INACTIVE.

The embodiments and examples herein are applicable to single carrier as well as to multicarrier operation of the UE. Examples of multicarrier operation of the UE are Carrier Aggregation (CA) and Multi-Connectivity (MC) where Dual

Connectivity (DC) is a special case. In CA the UE is able to receive and/or transmit data to more than one serving cells. Dual Connectivity (DC) is a special case or example of MC. The DC comprises one main or Master Cell Group (MCG) containing at least PCell and one Secondary Cell Group (SCG) containing at least PSCell. The term Carrier Aggregation (CA) is also called (e.g.

interchangeably called)“multi-carrier system”,“multi-cell operation”,“multi-carrier operation”,“multi-carrier” transmission and/or reception. In CA one of the

Component Carriers (CCs) is the Primary Component Carrier (PCC) or simply primary carrier or even anchor carrier. The remaining ones are called Secondary Component Carrier (SCC) or simply secondary carriers or even supplementary carriers. The serving cell is interchangeably referred to as primary cell Primary Cell (PCell) or Primary Serving Cell (PSC). Similarly the secondary serving cell is interchangeably referred to as Secondary Cell (SCell) or Secondary Serving Cell (SSC). In one example of DC operation involving E-UTRA and NR, the E-UTRA is the master. In another example of the DC operation involving E-UTRA and NR, NR is the master. The DC operation may also involve only NR serving cells, e.g. NR PCell, NR PSCell and NR SCells, or LTE serving cells, e.g. LTE PCell, LTE PSCell and LTE SCells.

The UE may operate using Coverage Enhancement (CE) with respect to a cell e.g. celH or at different coverage levels. The coverage level can be configured by the network or autonomously by the UE. The CE level of the UE is also

interchangeably referred to as coverage level of the UE. The CE level can be expressed in terms of: received signal quality and/or received signal strength at the UE with respect to a cell, and/or received signal quality and/or received signal strength at a cell with respect to the UE.

The CE level of the UE be defined with respect to any cell such as serving cell, a neighbor cell, a reference cell etc. For example it can be expressed in terms of received signal quality and/or received signal strength at the UE with respect to a target cell on which it performs one or more radio measurements. Examples of how signal quality can be specified by various parameters are Signal to Noise Ratio (SNR), SINR, Channel Quality Indicator (CQI), NRSRQ, RSRQ, CRS Es/lot, SCH Es/lot etc. Examples of how signal strength can be specified by various parameters are path loss, RSRP, NRSRP, SCH_RP etc. The notation Es/lot is defined as ratio of

• Es, which is the received energy per RE (power normalized to the subcarrier spacing) during the useful part of the symbol, i.e. excluding the cyclic prefix, at the UE antenna connector, to • lot which is the received power spectral density of the total noise and interference for a certain RE (power integrated over the RE and normalized to the subcarrier spacing) as measured at the UE antenna connector

The CE level can be expressed in at least two different levels. Consider an example of two different CE levels defined with respect to signal quality (e.g. SNR) at the UE comprising of:

Coverage enhancement level 1 (CE1 ) comprising of SNR > -6 dB at UE with respect to its serving cell; and - Coverage enhancement level 2 (CE2) comprising of -15 dB < SNR < -6 dB at

UE with respect to its serving cell.

In the above example the CE1 may also be interchangeably referred to as Normal Coverage Level (NCL), baseline coverage level, reference coverage level, basic coverage level, legacy coverage level etc. On the other hand, CE2 may be termed as enhanced coverage level or extended coverage level (ECL).

A parameter defining coverage level of the UE with respect to a cell may also be signalled to the UE by the network node. Examples of such parameters are CE Mode A and CE Mode B signalled to UE category M1 , UE category M2 etc. The UE configured with CE Mode A and CE Mode B are also said to operate in normal coverage and enhanced coverage respectively.

The UE may also be configured with different activity levels, e.g., Discontinuous Reception (DRX) or non-DRX, or different DRX cycle lengths and/or DRX ON duration periods, measurement cycle lengths (may be used e.g. for measurements on deactivated CCs), etc. The activity level may be configured by the network and/or configured autonomously (for all or at least some of the parameters determining the UE activity-level) by the UE. The UE may operate with DRX, whereby it monitors PDCCH periodically according to a configured DRX cycle or cycles, for a configured DRX on duration. When the UE is scheduled, an inactivity timer is started and the UE monitors each PDCCH continuously until such time as the inactivity timer expires. A short and long DRX cycle may be configured. When DRX is in use, the UE is only required to perform measurements according to requirements which are relaxed compared to the non DRX measurements, allowing it to save power by also not measuring during the time when the UE is not required to monitor PDCCH. When dual connectivity is configured, cells in the so called Master Cell Group (MGC) use a DRX cycle which follows that of the PCell, and cells in the so called Secondary Cell Group (SCG) use a DRX cycle which follows that of the PSCell. The terms frequencies, frequency bands, frequency ranges and carrier

frequencies can be used interchangeably, at least in some embodiments. In other embodiments the terms carrier frequencies and frequencies are comprised in terms frequency ranges, while the terms frequency ranges are comprised in terms frequency ranges. Herein, the terms“frequency-dependent autonomous gaps”,“frequency-range dependent autonomous gaps”,“FR-dependent autonomous gaps”,“frequency- specific autonomous gaps”,“frequency-range specific autonomous gaps”, and “FR-specific autonomous gaps” can be used interchangeably at least in some embodiments. In other embodiments, autonomous gaps can be FR-specific (FR- dependent) but also frequency-specific (frequency-dependent), i.e., the gaps depend on FR but also on a frequency within the FR. In other embodiments, frequency-specific autonomous gaps comprise implicitly also FR-specific autonomous gaps.

Some methods and procedures for supporting frequency-dependent autonomous gaps will now be discussed.

The solution herein may be described in terms of at least one of the following example embodiments. According to a first example embodiment, a UE, which is supporting autonomous UE-specific gaps and autonomous frequency-dependent gaps, is served at least on a carrier frequency fO and needs to perform one or more operations on a non- serving carrier frequency: - Determines whether frequency-dependent autonomous gaps or UE-specific autonomous gaps are to be used to enable the operation on the non-serving carrier frequency,

Determines autonomous gap configuration for the determined type of the autonomous gaps. In some embodiments, the UE may need to first determine at least some configuration parameters needed for autonomous gaps and then based on this decide the type of autonomous gaps, i.e. , the order of said determination steps may be different, and

- Configures autonomous gaps, based on the selected type and autonomous gap configuration.

The autonomous gaps are configured to meet a UE requirement which may e.g. require that a minimum number of ACK/NACKs are to be transmitted by the UE during a certain time period.

According to a second example embodiment, a UE supporting or determined to use autonomous frequency-dependent gaps is served at least on a carrier frequency fO and needs to perform one or more operations on at least one of: non- serving carrier frequency f1 and non-serving carrier frequency f2, for which the UE:

Determines that the UE needs to create autonomous gaps on fO for its operation on f1 , determines autonomous gap configuration for operating on f1 , creates autonomous gap(s) on fO based on the determined configuration, and operates on fO and f1 accordingly (performance on fO can be relaxed, e.g. one or more may apply: the measurement period or evaluation period or response time on fO can be longer compared to that without autonomous gaps, the measurement accuracy on fO can be less accurate, the UE is not expected to receive all messages transmitted by a network node on fO and allowed to not transmit (i.e. , allowed to drop) some limited number of ACK/NACKs in response, etc.), - Determines that the UE shall not create autonomous gaps on fO for its

operation on f2 and operate on fO and f2 accordingly (the performance on fO shall not be relaxed due to its operation on f2 since no autonomous gaps are created).

It should be noted that the second example embodiment above may also be applied for each of the serving cells when the UE is served by multiple serving cells.

To further support the above first and second example embodiments, the UE may also support the following signaling to: - Indicate to a network node that it does not support frequency-dependent autonomous gaps or that it supports UE-specific autonomous gaps only.

Implicitly or explicitly indicate to a network node the type of gaps it selects or prefers: UE-specific or frequency-dependent autonomous gaps.

Indicate to a network node that it supports frequency-dependent autonomous gaps.

Indicate to a network node that it supports frequency-dependent autonomous gaps in a specific frequency range. indicate to a network node that it needs or uses autonomous gaps on fO to operate on f1. - indicate to a network node the supported or preferred or used (or to be used) autonomous gap configuration(s). indicate to a network node that it does not need autonomous gaps on fO to operate on f2. Each of fO and f2 can be individual frequencies, a plurality of frequencies, or one or more frequency ranges.

Indicate to the network that even though it supports it is not able currently to configure a certain type of autonomous gaps, e.g., frequency-dependent autonomous gaps without impacting a certain set of frequencies/cells.

The network may indicate the type of autonomous gaps for one or more UE in a broadcast, multicast, or dedicated signaling or system information; in a further embodiment, this may further apply for a specific purpose, e.g., SON or positioning, or operation type.

The network may also indicate on which serving frequencies or frequency ranges autonomous gaps are not allowed or on which serving frequencies or frequency ranges autonomous gaps are allowed, e.g., whether a frequency, or cells on this frequency, or a frequency range can be impacted by autonomous gaps.

Herein, autonomous gaps may be seen as gaps which are not fully configured or controlled by a network node or uniquely pre-defined, e.g., by the standard. All or at least one of the configuration parameters which are characterizing the autonomous gaps, such as autonomous gap duration or gap length D,

autonomous gap periodicity T, autonomous gap start to and autonomous gap offset Delta, to be described below, are decided by the UE, i.e. , autonomous gaps have at least one autonomously decided or autonomously selected gap

configuration parameter. During the autonomous gaps, the UE cannot transmit and/or receive

signals/channels or perform radio measurements on fO during: time duration D of an autonomous gaps, • time duration D_before which precedes the autonomous gap, e.g., the UE does not transmit x symbols before or y ms before the gap, and

• time duration D_after which follows the autonomous gaps, e.g., the UE does not transmit x symbols after or y ms after the gap. Some possible procedures for determining autonomous gaps parameters will now be described.

The length of D, D_before, and D_after are measured in time units. D>0. In some embodiments, D_before and/or D_after can be zero. In other embodiments, at least one of D_before and/or D_after are greater than zero. One or both of D_before and D_after can be pre-defined, configured by a network node, autonomously decided, or autonomously selected from a pre-defined set of values by the UE.

The autonomous gaps can be aperiodic, e.g., a single gap for a specific purpose or a set of gaps according to a pattern, or periodic, e.g., a gap or a gap pattern occurring with periodicity T.

An autonomous gap starts at time to and ends at time t1 , e.g., t1 -t0=D. The starting point to may also be determined by an offset Delta with respect to a reference time, e.g., SFNO or a function of SFN e.g. mod(SFN, T). The UE may determine an autonomous gaps configuration based on one or more of the following:

• UE complexity, such as high-end or low-complexity: where low-complexity UEs may need longer gaps and/or longer periodicity.

• UE power class or UE type, e.g., fixed wireless device or mobile UE: fixed wireless device may use longer-periodicity gaps since mobility may be less important. • Indicated capability, e.g., UE can indicate autonomous gap configurations or pattern which it can support.

• The UE’s receiver architecture or capability, e.g., smaller number of

available receiver chains implies sharing among many frequencies hence shorter autonomous gaps may be preferred; or enhanced channel, e.g., MIB decoder capability may allow for combining of channel repetitions or redundancy versions in a more flexible way which also impacts how autonomous gaps can be configured.

• A pre-defined rule, or algorithm.

The autonomous gap configuration parameters may further depend on one or more of the following:

• Receiver utilization, e.g., longer periodicity T and/or longer duration D of autonomous gaps when the receiver utilization on fO is below a threshold.

• UE activity level, e.g., no autonomous gaps are allowed when the activity on the serving frequency fO is low, e.g., DRX cycle > 320 ms, since the UE can use inactivity periods instead.

• Coverage enhancement level, e.g., longer and/or more gaps when the

coverage level of the target cell is such that the UE operates in low-signal conditions e.g. enhanced coverage or CE level B or signal quality Es/lot <-6 dB.

• Signal/channel configuration (duration, periodicity, etc.) of the

signal/channel to be received in the non-serving carrier frequency, e.g., autonomous gaps length, periodicity and offset are configured to comprise positioning occasions on the non-serving frequency or PBCH occasions on the non-serving frequency or occasions with channels comprising a certain system information of interest on the non-serving frequency.

• SMTC periodicity on the serving and non-serving carrier frequencies.

• Signaled or pre-defined restriction on to what extent autonomous gaps are allowed to puncture e.g. intra- and/or inter-frequency SMTC reception, e.g. no puncturing allowed on intra- and/or inter-frequency, puncturing allowed on intra and/or inter-frequency, up to X% puncturing allowed where

0<X<100 and where different values may apply for intra- and inter- frequency, and where the restriction may or may not depend on the SMTC periodicities in use on intra- and/or inter-frequency carriers.

• MIB decoder capabilities, e.g. legacy MIB decoder that only can handle repetitions from the same cycle (40 ms period in E-UTRA), or enhanced MIB decoder that can combine repetitions across two or more different cycles (40 ms periods in E-UTRA).

· CA configuration or DC configuration, e.g., a first autonomous gap

configuration is used when the UE is configured with DC of a certain type e.g. NR-NR DC or is configured with up to a number X of serving carriers to be combined, and a second autonomous gap configuration is used when the UE is configured with EN-DC or with more than the number X of serving carriers.

• Radio Access Technology (RAT)(s) currently used by the UE, e.g.,

autonomous gaps are allowed if fO and f1 are of different Radio Access Technologies (RATs) or when fO is NR and f1 is E-UTRA.

• A synchronization level between fO and the non-serving carrier frequency, e.g., longer and/or more autonomous gaps may be needed when the misalignment is above a threshold, etc.

An example of how the autonomous gap pattern may depend on pre-defined rules and/or signaled restrictions is shown in Figure 5. Some examples of autonomous gap patterns for inter-RAT E-UTRA SFN acquisition in NR are shown when 100, 50 and 0% puncturing, respectively, is allowed over a certain time of SMTC with periodicity 20ms. When up to 100% puncturing of intra-frequency SMTC is allowed, the UE uses a first autonomous gap pattern for acquiring SFN on the target cell. Flere the UE does not have to take into account when the SMTC windows occur. When up to 50% puncturing of intra-frequency SMTC is allowed, the UE uses a second autonomous gap pattern since it has to place the autonomous gaps in such manner that only every second SMTC is punctured. The acquisition time of the E-UTRA SFN becomes extended, compared to the case when no restrictions apply.

When no puncturing is allowed (0%), the UE has to place the autonomous gaps such that none of the gaps collide with the SMTC window. The E-UTRA SFN acquisition time becomes even more extended and the UE may have to use a different approach for decoding the MIB in which the SFN is carried. In first two example sequences, the MIB is decoded using a legacy MIB decoder which needs at most 3 blocks from the same 40 ms period to guarantee successful decoding under the applicable side conditions. In the second example, where the UE never can acquire more than 2 repetitions from each 40 ms period due to the restriction on not being allowed to puncture, it is assumed that the UE is using an enhanced MIB decoder which can combine and decode repetitions from different 40 ms periods. Alternatively, a legacy MIB decoder may be employed, and the acquisition time to be extended even more to allow more decoding attempts (“keep trying”) to compensate for lower probability of success for each attempt when only 2 repetitions are used from each 40 ms period.

An example of how the number of autonomous gaps may vary with E-UTRA inter- RAT target carrier SINR is illustrated in Figure 6, where SMTC 20 ms is assumed for the NR carrier and no restrictions on puncturing are imposed. The carrier SINR basically indicates a coverage level of the carrier. Figure 6 shows some examples of autonomous gap patterns for inter-RAT E-UTRA SFN acquisition under different target carrier SINRs Z<Y<X when 100% puncturing is allowed of SMTC with periodicity 20 ms. Some examples of having different SINRs X, Y and Z in Figure 6 will now be described.

For SINR X, say -3dB, the UE needs to acquire 3 repetitions of MIB from the same 40ms period in order to meet the required probability of successful decoding of the same using a legacy MIB decoder. Flence, 5 gaps are needed. For SINR Y, say -7dB, the UE needs to acquire 4 repetitions of MIB from the same 40ms period to reach the required probability of success using a legacy MIB decoder. Hence, 7 gaps are needed.

For SINR Z, say -12dB, the UE needs to acquire 4 repetitions each from two 40ms periods, and combine them using an enhanced MIB decoder that can combine repetitions from different 40ms periods. Alternatively, for SINR Z, a legacy MIB decoder may be used in a“keep trying” manner (see previous example), whereby even more repetitions may be needed for successful decoding of the MIB.

Another example of how number of autonomous gaps may vary with E-UTRA inter-RAT target carrier SINR is illustrated in Figure 7, where SMTC 20ms is assumed for the NR carrier and restrictions on maximum puncturing of 50% of SMTC windows are imposed. Figure 7 shows some examples of autonomous gap patterns for inter-RAT E-UTRA SFN acquisition under different target carrier SINRs Z<Y<X when 50% puncturing is allowed of SMTC with periodicity 20 ms. Some examples of having different SINRs X, Y and Z in Figure 7 will now be described.

For SINR X, say -3dB, the UE needs to acquire 3 repetitions of MIB from the same 40ms period in order to meet the required probability of successful decoding of the same using a legacy MIB decoder. Hence, 5 gaps are needed. For SINR Y, say -7dB, the UE needs to acquire 4 repetitions of MIB from the same

40ms period to reach the required probability of success using a legacy MIB decoder. However, due to restrictions on puncturing of SMTC windows, the UE can only retrieve 3 MIB blocks from the same 40ms period. It therefore uses an enhanced MIB decoder instead, and combines 3 repetitions from two 40ms periods each, to meet the required probability of successful decoding. Hence, 8 autonomous gaps are needed. Alternatively, the UE uses a legacy MIB decoder in a“keep trying” manner, whereby even more gaps may be needed.

For SINR Z, say -12dB, the UE acquires 3 repetitions from three 40ms periods each, and either combines all three periods using an enhanced MIB decoder, or combines repetitions from two periods (period 1 and 2, period 2 and 3, and potentially also period 1 and 3) in the MIB decoding, i.e. a hybrid approach including both enhanced MIB decoder and“keep trying” (if combination of 1 and 2 doesn’t work, try 2 and 3, etc). Hence, 11 gaps are need. Alternatively, the UE uses a legacy MIB decoder in a“keep trying” manner, whereby even more gaps may be needed.

In some examples, SFN acquisition may further include also determining timing with higher granularity than SFN which gives the granularity of 1 radio frame (=10 subframes), e.g., in terms of number of subframes and/or slots and/or symbols. For this the UE may need to also receive synchronization signals, in addition to SFN reading. Primary Synchronization Signal/ Secondary Synchronization Signal (PSS/SSS) reading may also be needed for determining the subframes carrying MIB. Autonomous gaps can therefore be also used for receiving synchronization signals for this purpose and similar rules, e.g., for selecting the type of

autonomous gaps and/or gap configuration, may also apply in this case.

In other examples, SFN may be known (e.g., from network signaling) but more detailed timing resolution on a frequency/cell is not known, so the UE may not need to acquire SFN but may need to read PSS/SSS and still use autonomous gaps. In one example, for PSS/SSS and SFN reading on LTE frequency(s) autonomous gaps with 6 ms measurement gap length may be sufficient, if the offset is properly configured. But the first gap may be longer to allow for Automatic Gain Control, AGC, and frequency correction prior to receiving signal/channel. The periodicity of gaps would need to be adapted to PSS/SSS and MIB periodicity which may also depend on the MIB receiver capability in the latter case, as discussed herein.

Some possible procedures for determining autonomous gap pattern and timing, e.g., SFN and acquisition time, will now be described.

According to some further possible embodiments and examples, the network node may determine the expected time for timing acquisition (e.g., SFN acquisition and/or higher granularity timing in number of subframes/slots/symbols etc. which may be based e.g. on synchronization signals) and the expected maximum number of interrupted slots for the UE based on some or more of the information described above. Some examples of such information are as follows: · Coverage level for the target cell, as e.g. determined from reported RSRP,

RSRQ, and/or SINR.

• Coverage level as determined by the network based on UE location and

knowledge of the network deployment, e.g. acquired coverage maps (e.g. via SON, MDT, ANR) or theoretical deployment maps; UE location may be determined by e.g. finger-printing methods (e.g. relative strength or reported neighbor cells), Global Navigation Satellite System (GNSS)/Assisted GNSS (A- GNSS), etc.

• Coverage level as explicitly reported by the UE, e.g., a coverage index value, a required repetition level, a required coverage enhancement mode, a required SFN acquisition time, etc.

• UE capability with respect to channel decoding (e.g. legacy MIB decoder, enhanced MIB decoder, a UE profile with respect to receiver complexity

(low/high), etc.).

• UE power class, where some power classes, e.g. associated with fixed wireless connection, may have lesser capabilities for mobility-related received

functionality than UEs of other classes, and hence may require longer time.

• Signaled restrictions on puncturing of SMTC windows, configured measurement gaps, etc.

• Signaled SMTC period(s) on the one or more carriers onto which the

autonomous gaps will be applied.

• Pre-defined rules in the standard on the allowed level of puncturing of SMTC windows, measurement gaps, etc, if such rules are defined, and where the rules further may stipulate maximum allowed interruptions and/or maximum allowed SFN acquisition time under various side conditions.

• UE activity level, i.e. , whether UE will get scheduled or not by the network node during one or more DRX cycles, i.e. active time or inactive time, where for the latter, collisions with SMTC can be disregarded as the UE is not required to measure in SMTC windows during inactive time of a DRX cycle.

The network node may take the determined expected acquisition time for the timing, e.g., SFN or higher granularity timing, acquisition by the UE into account e.g. in the scheduling, and may refrain from scheduling non-essential messages on the downlink during the time the SFN acquisition is expected to be ongoing, in order to minimize the loss of system throughput caused by messages not being received by the UE due to the UE being in an autonomous gap, or received messages not being acknowledged by the UE (ACK/NACK) due to the UE being in an autonomous gap at the time when the feedback is to be transmitted to the network node. Essential information may here comprise RRC messages

associated e.g. to RRM, e.g. mobility-related signaling and radio resource re- configurations, but may also comprise time-critical data services such as voice over IP (VoIP) and video calls. Non-essential messages may comprise for instance data transfers associated with services that are not time-critical, e.g. associated with browsing.

A certain autonomous gap pattern or at least some of autonomous gap

configuration parameters and/or the set of impacted frequencies may also be implicitly enforced by UE requirements, e.g., on a minimum number of transmitted ACK/NACKs (or maximum number of not received or not transmitted ACK/NACKs) due to the gaps, the maximum number of and/or the maximum length of interruptions during the time the UE is acquiring the timing, e.g., no interruption means no impact should be caused or X ms interruptions means the gap length cannot be longer, etc., required total time for the timing acquisition which implicitly includes also the number of samples or repetitions to be received within this time since only a finite number of them are available, etc. The network node may further take the determined expected maximum number of interruptions into account in its Outer Loop Link Adaptation (OLLA). OLLA is setting a target for the block error rate of messages received by the UE or the base station, e.g. 10%, and adjusting the Modulation and Coding Scheme (MCS) accordingly to achieve this target. During the sequence of autonomous gap, block errors will arise that are not due to the selection of MCS but due to that the UE is tuning away from the serving cell(s). In order not to impact the selection of MCS - whereby a more robust MCS than needed would be selected and a loss of system throughput would result - the OLLA procedure may e.g. be frozen during the acquisition time of the SFN, or may otherwise account for that there will be additional block errors induced by the autonomous gaps.

Some possible procedures for selecting between UE-specific and frequency- dependent autonomous gaps will now be described.

According to some further possible embodiments and examples, a UE supporting UE-specific and frequency-dependent autonomous gaps can select between UE- specific and frequency-dependent autonomous gaps, e.g., based on one or more pre-defined rules, or a message received from a network node, or both.

In one example, a network node can instruct the UE on which one of the two types of the autonomous gaps to use: UE-specific or frequency-dependent. In another example, a network node can allow or prohibit configuring of a certain type of autonomous gaps by a specific UE (dedicated signaling) or multiple UEs on the carrier (multicast or broadcast or system information), e.g., allow UE- specific autonomous gaps or prohibit UE-specific autonomous gaps. The network control of the type of autonomous gaps may also apply for autonomous gaps for a specific purpose, e.g., for mobility, SON or for positioning (the applicable purpose may be pre-defined or signaled).

The network may also indicate on which serving frequencies or frequency ranges autonomous gaps are not allowed or on which serving frequencies or frequency ranges autonomous gaps are allowed; if autonomous gaps are allowed on all frequencies, the UE may also use UE-specific autonomous gaps. Using UE- specific autonomous gaps may be less restrictive on which receiver/transmitter configuration to use and thus may allow for more flexibility while having more impacts; using frequency-specific autonomous gaps may require the UE to be currently configured in a certain way and may limit using receiver chains to certain frequencies or frequency ranges but has less performance impacts.

In yet another example, the UE’s decision or network node’s instruction may be based on one or more of the following rules, which may be applied alone or in any combination where applicable: · If UE does not support (in general or under specific conditions) frequency- dependent gaps or independent gap patterns for different frequencies or frequency ranges, use UE-specific autonomous gaps.

• If, with the current UE receiver configuration, the UE cannot support frequency- dependent gaps or independent gap patterns for different frequencies or frequency ranges, the UE is allowed to use UE-specific autonomous gaps.

• If, the autonomous gaps are needed for a certain purpose and inter-RAT(e.g., SFN reading for positioning purpose and/or performing positioning

measurement on an inter-RAT carrier such as E-UTRA), the UE shall use frequency-dependent autonomous gaps (if this requires the UE to reconfigure its current receiver configuration or adapt the allocation of its receiver chain(s) to different frequencies, then the UE shall do so to enable using frequency- dependent autonomous gaps).

• Use frequency-dependent autonomous gaps when a specific gap configuration, e.g., gap pattern, gap periodicity, gap length, etc., is needed which is not allowed with UE-specific autonomous gaps.

• Use frequency-dependent autonomous gaps for SFN and frame timing

difference (SFTD) measurements, e.g., between NR and NR; between NR and LTE, etc. • Use frequency-dependent autonomous gaps to enable operations on a carrier frequency above a threshold, e.g., above 6 GHz, or operations based on subcarrier spacing (SCS) above a threshold which could be useful to reduce wasting of radio resources due to different SCS. · Use only frequency-dependent autonomous gaps when the difference in

numerology between the serving carrier frequency and the non-serving carrier frequency is above a threshold, e.g., the non-serving subcarrier spacing is larger by a threshold than the serving subcarrier spacing.

• Use only frequency-dependent autonomous gaps when the smallest difference, e.g., frequency separation, between the UE’s serving frequency and the non- serving frequency is above a threshold.

• Use only frequency-dependent autonomous gaps for positioning (e.g., for SFN reading or RSTD measurements) based on LTE signals when there are at least N (e.g., N=1 , 2, ... ) serving frequencies in FR2, otherwise the UE may use UE- specific autonomous gaps.

• The UE is allowed to use UE-specific autonomous gaps for inter-RAT based positioning (e.g., E-UTRA based positioning with NR serving cell), e.g., for SFN acquisition of E-UTRA RSTD reference cell timing, while the UE may be required to only use frequency-dependent autonomous gaps for SON. · The UE is required to use frequency-dependent autonomous gaps when the needed gap periodicity T is below a threshold (e.g., more frequent than 160 ms) and the serving and measured non-serving frequencies are separated by more than a threshold or comprised in different frequency ranges.

• The UE is required to use frequency-dependent autonomous gaps when the target measured signal or channel on the non-serving frequency (e.g., PRS occasions or PBCH) is to be received with a periodicity which is below a threshold (e.g., more frequent than 160 ms) and the serving and measured non- serving frequencies are separated by more than a threshold or comprised in different frequency ranges. • The UE is required to use frequency-dependent autonomous gaps if otherwise the UE-specific autonomous gaps would result in at least X% collision with certain measurement occasions, e.g., SMTC occasions, Synchronization Signal Block (SSB) occasions, positioning occasions, PBCH occasions, SIB1 occasions, PSS/SSS occasions, etc., on a serving frequency which may be the serving frequency where the at least X% collision occurs should be excluded from the set of impacted by the gaps frequencies.

• The UE is required to use frequency-dependent autonomous gaps, if it does not have enhanced channel decoder or received signal combiner capability and needs to receiver the channel/signal on a serving frequency when the

channel/signal occasions excessively collide (overlap in time) with autonomous gaps, e.g., enhanced MIB or SIB1 decoder or combining reference signal samples over a longer period.

• The UE is required to use frequency-dependent autonomous gaps in first radio environment conditions, e.g., signal quality, propagation characteristics, velocity, indoor/outdoor, etc., and can use UE-specific autonomous gaps in second radio environment conditions.

• The UE is required to use frequency-dependent autonomous gaps if the gaps are colliding (overlapping in time) with at least N number or Y % of received signal/channel occasions on a serving frequency for which the UE is not allowed to extend or extend enough the measurement/reception period for that signal/channel due to the collisions. The serving frequency may therefore be excluded from the set of impacted frequencies by the autonomous gaps.

Note that in the above rules, the UE may be able to choose between the two types of autonomous gaps when the UE architecture supports this, but the UE may or may not be able to configure the required or selected type of autonomous gaps. For example, to configure a required type of autonomous gaps and/or the set of impacted/non-impacted frequencies the UE may need to adapt its configuration (e.g., set of serving cells), receiver allocation to frequencies, set of measured non- serving frequencies, set of measurements, etc. In some cases, during the transition phase from one gap type to another, the UE may be allowed to cause some degradation, e.g., drop or delay a measurement or extend measurement time.

Some possible procedures for determining impacted and not impacted frequencies for frequency-dependent autonomous gaps, will now be described.

According to some further possible embodiments and examples, the UE may determine impacted and not impacted frequencies (or cells on those frequencies) in which the UE needs to create frequency-dependent autonomous gaps to enable operation on a non-serving carrier frequency. For example, when the UE has serving frequencies f0_1 , f0_2, ... , f0_n; to perform measurements on f1 , it may determine that it needs to create autonomous gaps on serving frequencies f0_1 and f0_n (“impacted frequencies”) but not on f0_2 (“not impacted frequency”). For convenience, the impacted frequencies are comprised in set FJmp and not impacted frequencies are comprised in set Fjiotimp. The determining may be based on one or more of the following rules and UE capability (e.g., provided the UE architecture is supporting the rules), which may be used alone or in any combination where applicable

* FJmp comprises frequencies or frequency ranges separated from f1 by less than a threshold. · Fjiotimp comprises frequencies or frequency ranges separated from f1 by more than a threshold.

• If f2 is comprised in FR2 (frequency range 2), then Fjiotimp comprises all frequencies in FR1 or frequencies in the lower part of FR1 (e.g., below 3 GHz). · If f2 is comprised in FR2 (frequency range 2), then Fjiotimp comprises all non-NR (e.g., LTE) frequencies (e.g., in case of EN-DC where PCell is LTE). • If f2 is comprised in FR1 or is a non-NR frequency below 3 GHz, then

Fjiotimp comprises at least NR frequencies of FR2.

• A serving frequency shall be excluded from the set of impacted frequencies if otherwise the autonomous gaps would collide (overlap in time) with one, some, or all measured/received signal/channel occasions (e.g., SMTC occasions, positioning occasions, SSB occasions, PBCH or channels carrying system information occasions, ACK/NACK occasions, control channel occasions, persistent or semi-persistent scheduling occasions, paging occasions, etc.) on the serving frequency resulting in non-acceptable amount of degradation on the serving frequency (e.g., too long measurement or evaluation period, no possibility to complete an operation within a required time, reduced measurement accuracy, increased error rate, excessive number of retransmissions, number of not received and/or not transmitted by the UE ACK/NACK exceeding a threshold, etc.) due to the collisions with gaps.

In another example, if the UE has reported in its UE RF capabilities that it supports a band combination of one or more of the bands associated with active serving cells in combination with the band associated with the target cell for which SFN is to be acquired, then communication can be sustained with the one or more serving cells during the acquisition of the SFN. In case the set of serving cells is in the supported band combination, but only subsets of the serving cells are in supported band combinations that include the band associated with the target carrier for the SFN acquisition, the above rules may define the subset of serving cells for which communication shall be sustained during the SFN acquisition. For instance, if serving carriers are A, B and C, and the carrier for the SFN acquisition is D, then there may hypothetically be supported band combinations: A+B+C, A+B+D, B+C+D, A+C+D. The UE thus can receive A+B, B+C, or A+C while acquiring SFN for carrier in D without interruptions. Carrier C, A, or B, respectively, would be interrupted by autonomous gaps.

The above rules may apply also when autonomous gaps are used for another purpose than or in addition to timing or SFN acquisition and on other than LTE frequencies. A certain autonomous gap pattern or at least some of autonomous gap

configuration parameters and/or the set of impacted frequencies may also be implicitly enforced by UE requirements, e.g., on a minimum number of transmitted ACK/NACKs (or maximum number of not received or not transmitted ACK/NACKs) due to the gaps, the maximum number of and/or the maximum length of interruptions during the time the UE is acquiring the timing (e.g., no interruption means no impact should be caused or X ms interruptions means the gap length cannot be longer, etc.), required total time for the timing acquisition which implicitly includes also the number of samples or repetitions to be received within this time since only a finite number of them are available, etc.

Another example of how the solution may be employed in terms of actions performed by a network node such as the network node 12, is further illustrated by the flow chart in Figure 8 which will now be described likewise with further reference to Figure 4. Figure 8 thus illustrates a procedure in the network node 12 for handling autonomous gaps in communication with the UE 10.

A first action 800 illustrates that the network node 12 acquires information e.g. related to one or more of UE capability, pre-defined rules and signaling provided from the network 14, which information may be similar to the information in action 400. A further action 802 illustrates that the network node 12 selects at least one of UE-specific autonomous gaps and frequency-dependent autonomous gaps to be used by the UE 10, based on the acquired information. In another action 804, the network node 12 instructs (e.g. by signalling) the UE 10 to use the selected type(s) of autonomous gaps on one or more carriers.

Any of the above-described examples and embodiments may be used in either of the procedures of Figures 4A and 8, where appropriate.

A block diagram in Figure 9 illustrates a detailed but non-limiting example of how a UE 900 and a network node 902, respectively, may be structured to bring about the above-described solution and embodiments thereof. In this figure, the UE 900 and the network node 902 may be configured to operate according to any of the examples and embodiments of employing the solution as described herein, where appropriate. The UE 900 thus corresponds to the UE 10 and the network node 902 corresponds to the network node 12. Each of the UE 900 and the network node 902 is shown to comprise a processor“P”, a memory“M” and a communication circuit“C” with suitable equipment for transmitting and receiving radio signals in the manner described herein.

The communication circuit C in each of the UE 900 and the network node 902 thus comprises equipment configured for communication with each other using a suitable protocol for the communication depending on the implementation. The solution is however not limited to any specific types of radio signals or protocols.

The UE 900 is, e.g. by means of units, modules or the like, configured or arranged to perform at least some of the actions of the flow chart in Figure 4A and as follows. Further, the network node 902 is, e.g. by means of units, modules or the like, configured or arranged to perform at least some of the actions of the flow chart in Figure 8 and as follows.

The UE 900 is arranged to handle autonomous gaps in communication with the network node 902 of a wireless network such as the network 14 shown in Figure 4. The UE 900 may be configured or adapted to acquire information which may be related to one or more of UE capability, pre-defined rules and signaling received from the network node 902. This operation may be performed by an acquiring module 900A in the UE 900, as also illustrated in action 400. The acquiring module 900A could alternatively be named a receiving or collecting module.

The UE 900 is configured or adapted to determine to use a type of autonomous gaps on at least one serving carrier, to enable operation on a non-serving carrier frequency. The type of autonomous gaps is one of UE-specific autonomous gaps and frequency-dependent autonomous gaps. The UE 900 may be configured to perform this determining based on the above-mentioned information acquired by the acquiring module 900A. This operation to determine to use a type of

autonomous gaps may be performed by a determining module 900B in the UE 900, as also illustrated in action 402. The determining module 900B could alternatively be named a logic module.

The UE 900 is also configured or adapted to determine an autonomous gap configuration for the type of autonomous gaps determined to be used, which operation may be performed by the determining module 900B, as also illustrated in action 406.

The UE 900 is further configured or adapted to configure the autonomous gaps based on the type of autonomous gaps determined to be used and on the determined autonomous gap configuration, to meet a UE requirement, as also illustrated in action 408.

The UE 900 may be further configured or adapted to signal the determined type(s) of autonomous gaps to the network node 902. For example, the type of

autonomous gaps determined to be used may be signalled to the network node 902. This operation may be performed by a signaling module 900C in the UE 900, as also illustrated in action 404.

The network node 902 is arranged to handle autonomous gaps in communication with the UE 900. The network node 902 is configured to acquire information e.g. related to one or more of UE capability, pre-defined rules and signaling provided from the network. This operation may be performed by an acquiring module 902A in the network node 902, as illustrated in action 800. The acquiring module

902A could alternatively be named a receiving or collecting module.

The network node 902 is further configured to select at least one of U E-specific autonomous gaps and frequency-dependent autonomous gaps to be used by the UE 900, based on the acquired information. This operation may be performed by a selecting module 902B in the network node 902, as illustrated in action 802. The selecting module 900B could alternatively be named a logic module.

The network node 902 is further configured to instruct (e.g. by signalling) the UE 900 to use the selected type(s) of autonomous gaps on one or more carriers. This operation may be performed by an instructing module 902C in the network node 902 as illustrated in action 804. The instructing module 900C could alternatively be named a signaling module.

It should be noted that Figure 9 illustrates various functional modules in the UE 900 and the network node 902, respectively, and the skilled person is able to implement these functional modules in practice using suitable software and hardware equipment. Thus, the solution is generally not limited to the shown structures of the UE 900 and the network node 902, and the functional modules therein may be configured to operate according to any of the features, examples and embodiments described in this disclosure, where appropriate.

The functional modules 900A-C and 902A-C described above may be

implemented in the UE 900 and the network node 902, respectively, by means of program modules of a respective computer program comprising code means which, when run by the processor P causes the UE 900 and the network node 902 to perform the above-described actions and procedures. Each processor P may comprise a single Central Processing Unit (CPU), or could comprise two or more processing units. For example, each processor P may include a general purpose microprocessor, an instruction set processor and/or related chips sets and/or a special purpose microprocessor such as an Application Specific Integrated Circuit (ASIC). Each processor P may also comprise a storage for caching purposes.

Each computer program may be carried by a computer program product in each of the UE 900 and the network node 902 in the form of a memory having a computer readable medium and being connected to the processor P. The computer program product or memory M in each of the UE 900 and the network node 902 thus comprises a computer readable medium on which the computer program is stored e.g. in the form of computer program modules or the like. For example, the memory M in each node may be a flash memory, a Random-Access Memory (RAM), a Read-Only Memory (ROM) or an Electrically Erasable Programmable ROM (EEPROM), and the program modules could in alternative embodiments be distributed on different computer program products in the form of memories within the respective UE 900 and network node 902. The solution described herein may be implemented in each of the UE 900 and the network node 902 by a computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the actions according to any of the above embodiments and examples, where appropriate. The solution may also be implemented at each of the UE 900 and the network node 902 in a carrier containing the above computer program, wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

While the solution has been described with reference to specific exemplifying embodiments, the description is generally only intended to illustrate the inventive concept and should not be taken as limiting the scope of the solution. For example, the terms“network node”,“User Equipment, UE”,“autonomous gap”,

“UE capability”,“predefined rules”, and“signaling” have been used in this disclosure, although any other corresponding entities, functions, and/or parameters could also be used having the features and characteristics described here.

Abbreviations

ACK Acknowledged

AGC Automatic Gain Control

ANR Automatic Neighbor Relation

BCH Broadcast Channel

BS Base Station

CA Carrier Aggregation

CC Component Carrier

CG Cell Group

CGI Cell Global Identity

CPICH Common pilot Channel

CQI Channel Quality Indicator CSG Closed Subscriber Group

DC Dual Connectivity

DL Downlink

DL-SCH Downlink Shared Channel

DRX Discontinuous Reception

ECGI Evolved CGI

eNB eNodeB

FDD Frequency Division Duplex

FR Frequency Range

HD-FDD Half Duplex FDD

HO Handover

M2M Machine to Machine

MCG Master Cell Group

MCS Modulation and Coding Scheme

MDT Minimization of Drive Tests

MIB Master Information Block

NACK Not Acknowledged

OFDM Orthogonal Frequency Division Multiplexing

OLLA Outer Loop Link Adaptation

OTDOA Observed Time Difference Of Arrival

SI System Information

SIB System Information Block

PBCH Physical Broadcast Channel

PCC Primary Component Carrier

PCI Physical Cell Identity

PCell Primary Cell PCH Paging Channel

PHICH Physical HARQ Indication Channel

PLMN Public Land Mobile Network

ProSe Proximity Service

PSCell Primary SCell

PSC Primary Serving Cell

PSS Primary Synchronization Signal

RAT Radio Access Technology

RF Radio Frequency

RRC Radio Resource Control

RRM Radio Resource Management

RSCP Received Signal Code Power

RSRP Reference Signal Received Power

RSRQ Reference Signal Received Quality

RSSI Received Signal Strength Indication

RSTD Reference Signal Time Difference

SCC Secondary Component Carrier

SCell Secondary Cell

SCG Secondary Cell Group

SFN System Frame Number

SINR Signal to Interference and Noise Ratio, sometimes denoted Es/lot SMTC SS/PBCH block Measurement Timing Configuration

SON Self-Organizing Network

SS Synchronization Signal

SSC Secondary Serving Cell

SSS Secondary Synchronization Signal TDD Time Division Duplex

Tx Transmitter

UE User Equipment

UL Uplink

V2X Vehicle-to-X

V2I Vehicle-to-lnfrastructure

VoIP Voice over IP