A method, network entity and computer software for configuring a user equipment to measure one or more synchronisation signals and receiving synchronisation signal measurements

Abstract

A method of configuring a user equipment, UE, to measure one or more synchronisation signals from one or more potential target base stations is provided. A serving base station of the UE is configured to periodically transmit a first synchronisation signal and a second synchronisation signal. Each of the one or more potential target base stations is configured to periodically transmit a first synchronisation signal. The method comprises communicating, from each of the one or more potential target base stations to the serving base station, an indication of whether the respective base station is periodically transmitting a second synchronisation signal. The method further comprises communicating, from the serving base station to the UE, configuration data that causes the UE to measure one or more synchronisation signals from the one or more potential target base stations. If at least a threshold number of the one or more potential target base stations are periodically transmitting a second synchronisation signal, the configuration data causes the UE to measure the second synchronisation signal of each of the one or more potential target base stations. If a number of the one or more potential target base stations lower than the threshold number are periodically transmitting a second synchronisation signal, the configuration data causes the UE to measure the first synchronisation signal of each of the one or more potential target base stations.

Description

A method, network entity and computer software for configuring a user equipment to measure one or more synchronisation signals and receiving synchronisation signal measurementsField

[0001] The present invention relates to configuring devices in a telecommunications network to measure synchronisation signals. In particular, the invention relates to configuring devices in scenarios where base stations are configured to transmit a plurality of separate synchronisation signals. The present invention also relates to receiving synchronisation signal measurements from the devices.Glossary eMBB - Enhanced Mobile BroadbandURLLC - Ultra-Reliable Low Latency Communications loT - Internet of ThingsI loT - Industrial Internet of Things mMTC - Massive Machine-Type CommunicationsLPWA - Low-Power Wide AreaLTE-M - Long Term Evolution for MachinesNB-loT - Narrowband loTMIMO - Multiple-Input Multiple-OutputSISO - Single-Input Single-OutputFR1 - Frequency Range 1FR2 - Frequency Range 2HD-FDD - Half-Duplex Frequency Division DuplexFD-FDD - Full-Duplex Frequency Division DuplexBD - Blind DecodingCCE - Control Channel ElementPDCCH - Physical Downlink Control ChannelSFN - System Frame Number eDRX - Extended Discontinuous Reception RRM - Radio Resource Management IE - Information ElementRACH - Random-Access ChannelSSB - Synchronisation Signal BlockPSS - Primary Synchronization SignalSSS - Secondary Synchronization SignalPBCH - Physical Broadcast ChannelDMRS - DeModulation Reference SignalMIB - Master Information BlockSIB - System Information BlockCD-SSB - Cell Defining SSBNCD-SSB - Non-Cell Defining SSBBWP - Bandwidth PartSMTC - SS / PBCH Block Measurement Timing ConfigurationRMSI - Remaining Minimum System InformationCAM - Operations, Administration, and ManagementMO - Measurement ObjectRAN - Radio Access NetworkUE - User EquipmentBS - Base StationABS - Advanced Base StationBTS - Base Transceiver StationBSS - Basic Service SetESS - Extended Service SetAP - Access PointNB - Node B (Radio Base Station Receiver) eNB - Evolved Node B gNB - Next-Generation Node BTRP - Transmission and Reception PointPS - Processing ServerTE - Terminal EquipmentMS - Mobile StationMT - Mobile TerminalUT - User TerminalSS - Subscriber StationPDA - Personal Digital AssistantCDMA - Code Division Multiple AccessFDMA - Frequency Division Multiple AccessTDMA - Time Division Multiple AccessOFDMA - Orthogonal Frequency Division Multiple AccessSC-FDMA - Single Carrier Frequency Division Multiple AccessMC-FDMA - Multicarrier Frequency Division Multiple AccessUTRA - Universal Terrestrial Radio AccessGSM - Global System for Mobile CommunicationsGPRS - General Packet Radio ServiceEDGE - Enhanced Data Rates for GSM EvolutionIEEE - Institute of Electrical and Electronics EngineersE-UTRA - Evolved UTRAUMTS - Universal Mobile Telecommunications SystemE-UMTS - Evolved UMTS3GPP - 3rd Generation Partnership ProjectDL - DownlinkUL - UplinkLTE - Long Term Evolution (4G)LTE-A - LTE-AdvancedNR - New Radio (5G)FDD - Frequency Division DuplexTDD - Time Division DuplexCRS - Cell-specific Reference SignalCSI-RS - Channel State Information Reference SignalFPGA - Field-Programmable-Gate-ArrayASIC - Application-Specific-lntegrated-CircuitDSP - Digital-Signal-ProcessorCD-ROM - Compact Disc Read-Only MemoryDVD-ROM - Digital Versatile Disc Read-Only MemoryROM - Read-Only MemoryRAM - Random-Access MemoryEEPROM - Electrically Erasable Programmable Read-Only MemoryEPROM - Erasable Programmable Read-Only MemoryBackground

[0002] Releases 15 and 16 of the 3GPP (5G) standard provide enhanced mobile broadband (eMBB) services for high speed and capacity data connections with reliable coverage and mobility tolerance. An alternative service requirement is defined for devices / that require high reliability and the lowest possible latency: Ultra-Reliable Low Latency Communications (URLLC). However, not every UE requires such an elevated level of service. For example, loT devices (sometimes referred to as I loT in 5G) may only need to send small volumes of data and may be tolerant to high latency. These devices may be connected in large numbers in a particular area. A third service requirement for such devices is defined as Massive Machine-Type Communications (mMTC) in 5G. There may also be some devices that require a level of service between these extremes, such as sensor devices, surveillance devices, and wearable devices.

[0003] Release 17 of the 3GPP (5G) standard adds a definition of a new UE type requiring performance characteristics (e.g., data throughput and speed) that are reduced compared to eMBB and URLLC but enhanced compared to LPWA (i.e., LTE-M / NB-loT) or mMTC. This UE type is referred to as a “reduced capability” or RedCap UE.

[0004] 3GPP technical report (TR) 38.875 (which is incorporated by reference) specifies three potential use cases for RedCap devices, including industrial sensors, surveillance devices, and health wearables.

[0005] Some RedCap devices implement strategies to reduce complexity, cost, and power consumption. One strategy is to use fewer antennas in the device, which also reduces the maximum number of MIMO layers. Some RedCap devices only support 2x2 MIMO for the downlink and SISO for the uplink.

[0006] RedCap devices may also support lower bandwidths than other devices. For example, some RedCap devices may only support bandwidths of 20 MHz for FR1 and 100 MHz for FR2. Lower bandwidths reduce power amplifier complexity and may enable efficient operation of the device.

[0007] In addition, some RedCap devices use half-duplex FDD (HD-FDD) transmission instead of full-duplex FDD (FD-FDD). This prevents the device from transmitting andreceiving data on different frequencies at the same time and therefore reduces complexity.Isolation of the transmit path from the receive path may not be required in such devices. RedCap devices may therefore use switches instead of duplexers.

[0008] Additional strategies may be employed to reduce power consumption in RedCap devices. In some examples, RedCap UEs have reduced blind decoding (BD) and control channel element (CCE) limits monitored by the device in the physical downlink control channel (PDCCH), which may reduce power consumption.

[0009] RedCap devices may use the system frame number (SEN) technique to increase extended discontinuous reception (eDRX) cycles when the device disconnects from the network or becomes idle, which can reduce power consumption. Longer eDRX cycles may also be beneficial in specific use cases such as industrial sensors. Release 17 also allows RedCap devices to transmit data without connecting to the network.

[0010] In addition, radio resource management (RRM) requirements may be reduced to accommodate RedCap devices, which can enable devices to reduce their power consumption.

[0011] Modifications to a device’s capabilities also have implications for the network. For example, lower bandwidth support may require corresponding changes in bandwidth part (BWP) configurations. New information elements (IE) may also enable dynamic adaptation of the bandwidth.

[0012] Lower bandwidths may also impact the RACH procedure used by the devices to access the network. The network may specify a specific BWP for RedCap devices or may reduce the size of the BWP for these devices.

[0013] In 5G(NR), a gNB periodically transmits an SSB, which is used by UEs for synchronisation, cell search and initial beamforming. The SSB is comprised of synchronisation signals (PSS and SSS) and PBCH. The PBCH is comprised of PBCH DMRS, which functions as a reference signal for decoding the PBCH, and payload data, which is used for transmitting the MIB.

[0014] For reduced capability devices, an alternative version of the SSB may be used, which is the NCD-SSB.

[0015] Release 18 of the 3GPP (5G) standard introduces a definition of another new UE type allowing performance characteristics (e.g., data throughput and speed) that are even further reduced compared to Redcap UEs. This UE type is referred to as an “enhanced RedCap” or eRedCap UE. For example, RedCap UEs may be limited to 20 MHz bandwidth, whilst eRedCap UEs may be limited to 5MHz bandwidth. Release 18 also extends support of the NCD-SSB to all UEs, rather than just RedCap UEs.Summary

[0016] Some prior art devices use a separate NCD-SSB for reduced capability devices. However, they do not consider whether there are sufficient devices in the network that would use the NCD-SSB to justify the resources used by transmitting a separate NCD- SSB. Against this background, a method of selectively enabling NCD-SSB is provided.

[0017] A method of a base station facilitating synchronisation of a plurality of user equipments, UEs, is provided. The plurality of UEs comprises at least one UE of a first capability type. The method comprises: periodically transmitting a first synchronisation signal; determining a level of network traffic communicated via the base station and associated with the at least one UE of the first capability type; and selectively periodically transmitting a second synchronisation signal, based on the level of network traffic communicated via the base station and associated with the at least one UE of the first capability type.

[0018] Network traffic may be a measure of data communicated between the UE and the base station.

[0019] Where we refer to a UE “of a first capability type,” this could equally be written as a UE “having a first capability type.” The first capability type may be used to define a group of UEs having similar capabilities (e.g., reduced capability UEs). Alternatively, the first capability type may be used to define a group of UEs all having at least a minimum set of required capabilities. UEs having additional / enhanced capabilities may be permitted to bedefined as belonging to the first capability type, provided they meet the minimum requirements. One example of a minimum capability requirement for the first capability type is that the UE is capable of synchronisation using the second synchronisation signal.

[0020] Selectively periodically transmitting the second synchronisation signal based on the level of traffic communicated via the base station and associated with the at least one UE of the first capability type may comprise: if the level of network traffic communicated via the base station and associated with the at least one user equipment of the first capability type exceeds a first threshold, periodically transmitting the second synchronisation signal; and if the level of network traffic communicated via the base station and associated with the at least one user equipment of the first capability type falls below a second threshold, disabling periodic transmission of the second synchronisation signal.

[0021] The first and second threshold may be the same or may be different. Having two separate thresholds for enabling and disabling of NCD-SSB may provide some flexibility to the network.

[0022] In a first example, the UE measures on the NCD-SSB, if the NCD-SSB can be found. Otherwise, the UE falls back to the CD-SSB. In a second example, the network informs the UE whether to measure on the NCD-SSB or not, based on the network decision. The second example requires another signal from the network to the UE, to inform the UE of the network decision.

[0023] With flexibility introduced of having two separate thresholds, and based on the behaviour described above, the network can inform the UEs of a change to the NCD-SSB in a manner that is tolerant to delay. In other words, the network does not need to inform the UE immediately when the network decision is made.

[0024] The threshold may be an absolute threshold or may be a relative threshold. The “level” of network traffic may be measured as an absolute value or may be measured as a proportion of the overall network traffic communicated via the base station (associated with a UE of any capability type).

[0025] The method may further comprise:receiving, from one or more base stations corresponding to one or more neighbouring cells, a level of network traffic communicated via the respective base station and associated with one or more UEs of the first capability type, wherein selectively periodically transmitting the second synchronisation signal is further based on the level of network traffic communicated via the one or more base stations corresponding to the one or more neighbouring cells and associated with UEs of the first capability type.

[0026] Selectively periodically transmitting the second synchronisation signal based on the level of network traffic communicated via the base station and associated with the at least one UE of the first capability type and further based on the level of network traffic communicated via the one or more base stations corresponding to the one or more neighbouring cells and associated with UEs of the first capability type may comprise: determining, for the base station and the one or more base stations corresponding to the one or more neighbouring cells, an overall level of network traffic associated with UEs of the first capability type by combining the level of network traffic communicated via the base station and associated with the at least one UE of the first capability type with the level of network traffic communicated via the one or more base stations corresponding to the one or more neighbouring cells and associated with UEs of the first capability type; if the overall level of network traffic associated with UEs of the first capability type exceeds a first threshold, periodically transmitting the second synchronisation signal; if the overall level of network traffic associated with UEs of the first capability type falls below a second threshold, disabling periodic transmission of the second synchronisation signal.

[0027] Combining the level of network traffic communicated via the base station and associated with the at least one UE of the first capability type with the level of network traffic communicated via the one or more base stations corresponding to the one or more neighbouring cells and associated with UEs of the first capability type may comprise one or more of: summing the level of network traffic communicated via the base station and associated with the at least one UE of the first capability type and each of the levels of network traffic communicated via the one or more base stations corresponding to the one or more neighbouring cells and associated with UEs of the first capability type; andcalculating a weighted average of the level of network traffic communicated via the base station and associated with the at least one UE of the first capability type and each of the levels of network traffic communicated via the one or more base stations corresponding to the one or more neighbouring cells and associated with UEs of the first capability type.

[0028] The method may further comprise sending, to one or more base stations corresponding to one or more neighbouring cells, the level of network traffic communicated via the base station and associated with the at least one UE of the first capability type.

[0029] The plurality of UEs may further comprise at least one UE of a second capability type, wherein: the first capability type corresponds with a reduced capability compared to the second capability type; the first capability type is not reduced compared to the second capability type and corresponds with UEs that are compatible with the second synchronisation signal; or the first capability type corresponds with UEs that are compatible with the second synchronisation signal and wherein the at least one UE of the first capability type includes at least one UE having a reduced capability compared to the second capability type and at least one UE not having reduced capability compared to the second capability type.

[0030] The first capability type may correspond with a reduced capability “RedCap” capability type and / or an enhanced RedCap “eRedCap” capability type.

[0031] Alternatively, the first capability type may correspond with one or more non-RedCap UEs supporting synchronisation based on the second synchronisation signal (support for NCD-SSB measurements by non-RedCap UEs is planned for Release 18 of the 3GPP standards).

[0032] Alternatively, UEs of the first capability type may include a combination of zero or more RedCap UEs (optionally including zero or more eRedCap UEs) and zero or more non-RedCap UEs supporting measurements of the second synchronisation signal (NCB- SSB).

[0033] The second synchronisation signal may be for facilitating synchronisation of the at least one UE of the first capability type.

[0034] A UE of the first capability type (e.g., a RedCap UE) may be capable of synchronising using the second synchronisation signal (e.g., NCD-SSB). Redcap UEs are compatible with the new synchronisation information. From Release 18, other (non- RedCap) UEs may also be capable of synchronising using the second synchronisation signal (e.g., NCD-SSB).

[0035] The first synchronisation signal (e.g., CD-SSB) may be used for facilitating synchronisation of the at least one UE of the second capability type in some examples. A non-RedCap UE may require a CD-SSB (e.g., if the UE is not compatible with the NCD- SSB).

[0036] The first synchronisation signal may be used for facilitating synchronisation of the at least one UE of the first capability type when periodic transmission of the second synchronisation signal is disabled.

[0037] The CD-SSB may be used to synchronise the non-RedCap UEs. The NCD-SSB may be used to facilitate synchronisation of the RedCap UEs (and optionally eRedCap UEs and / or Release 18+ UEs), when it is being transmitted. The CD-SSB may be used to synchronise the RedCap UEs (and optionally eRedCap UEs and / or Release 18+ UEs) when the NCD-SSB is switched off. In other words, if the NCD-SSB is not available (i.e., switched off), the UEs that would otherwise use the NCD-SSB (i.e., are compatible with the NCD-SSB, such as RedCap UEs, eRedCap UEs and compatible Release 18+ UEs) may fall back to using the CD-SSB.

[0038] If NCD-SSB is configured (i.e., switched on), UEs operating in the corresponding BWP (e.g., RedCap UEs, eRedCap UEs and / or Release 18+ UEs) may use NCD-SSB for the purposes for which it would otherwise have used the CD-SSB of the serving cell (e.g., obtaining sync, measurements, RLM, and the like).

[0039] Each of the first synchronisation signal and the second synchronisation signal may be a synchronisation signal block comprising: a primary synchronisation signal, PSS; a secondary synchronisation signal, SSS; a physical broadcast channel, PBCH; anda physical broadcast channel demodulation reference signal, PBCH DMRS.

[0040] For each of the first synchronisation signal and the second synchronisation signal, the PBCH may comprise a master information block, MIB.

[0041] The MIB of the first synchronisation signal may comprise information about reference subcarrier spacing, control channel for SIB PDSCH, DMRS position, and the like. SIB1 may carry all the basic information for UE to perform the initial attachment procedure (at least up to RrcSetup). SIB1 may also carry scheduling information for other SIBs.

[0042] The MIB of the second synchronisation signal may lack information relating to SIBs, because the second synchronisation signal may not be associated with any SIBs.

[0043] The first synchronisation signal may comprise data to enable a UE to obtain a first system information block, SIB1. In contrast, the second synchronisation signal may not be used to obtain SIB1.

[0044] In other words, as defined in the 3GPP physical layer specification, a NCD-SSB may be a SSB which not used to obtain SIB1 .

[0045] Alternatively, the first synchronisation signal may be associated with a system information block, SIB, whereas the second synchronisation signal may not be associated with a SIB.

[0046] The first synchronisation signal may be associated with a Remaining Minimum System Information, RMSI, block. The second synchronisation signal may not be associated with a RMSI block.

[0047] The first synchronisation signal may be a cell-defining synchronisation signal block, CD-SSB. The second synchronisation signal may be a non-cell-defining synchronisation signal block, NCD-SSB.

[0048] Each of the first synchronisation signal and the second synchronisation signal may comprise a plurality of parameters.

[0049] The second synchronisation signal may comprise parameters that are different to the parameters of the first synchronisation signal.

[0050] The second synchronisation signal may comprise a greater number of parameters than the first synchronisation signal.

[0051] A subset of the parameters of the second synchronisation signal may have different values compared to the first synchronisation signal (and the rest may be the same).

[0052] Each of the first synchronisation signal and the second synchronisation signal may comprise a plurality of information elements, wherein each plurality of information elements comprises the respective plurality of parameters.

[0053] An information element of the second synchronisation signal may comprise one or more of the following parameters: an absolute frequency of the synchronisation signal; a periodicity of the synchronisation signal; and a time offset of the second synchronisation signal relative to the first synchronisation signal.

[0054] An information element of the first synchronisation signal may comprise one or more of the following parameters: an absolute frequency of the synchronisation signal; a periodicity of the synchronisation signal; and a time offset.

[0055] A periodicity of the second synchronisation signal may be different to a periodicity of the first synchronisation signal.

[0056] Since the second synchronisation signal may be used for devices having reduced capabilities, the signal may be transmitted with a greater periodicity (i.e., less frequently). As a result, radio resources may be conserved.

[0057] Determining a level of network traffic communicated via the base station and associated with the at least one user equipment of the first capability type may comprisedetermining whether a UE communicating via the base station is a UE of the first capability type, based on UE device type information and / or UE capability information reported to the base station by the UE.

[0058] The UE may report its radio access capabilities to the base station.

[0059] Determining whether a UE is a UE of the first capability type may comprise: determining that the UE is a RedCap UE or an eRedCap UE; determining that the UE is a UE (e.g., a non-RedCap UE) capable of using the second synchronisation signal (e.g., NCD-SSB); or determining that the UE is either a RedCap UE, an eRedCap UE or a UE capable of using the second synchronisation signal.

[0060] RedCap UEs from 3GPP Release 17 onwards may be compatible with the second synchronisation signal. From 3GPP Release 18 onwards, non-RedCap UEs may be compatible with the second synchronisation signal (as well as RedCap UEs and eRedCap UEs).

[0061] The method may further comprise requesting UE device type information and / or UE capability information from each of the plurality of UEs and receiving the UE device type information and / or UE capability information in response.

[0062] UE device type information and / or UE capability information may be provided in an information element relating specifically to the first capability type. Determining whether a UE communicating via the base station is a UE of the first capability type may be based on the presence of the information element relating specifically to the first capability type in signalling from the UE.

[0063] The information element may be RedCapParameters or UE-NR-Capability, for example.

[0064] As discussed above, determining whether a UE is a UE of the first capability type may comprise: determining that the UE is a RedCap UE or eRedCap UE; determining that the UE is a Rel 18 UE capable of using NCD-SSB; ordetermining that the UE is either a RedCap UE, an eRedCap UE or a 3GPP Release 18+ UE capable of using NCD-SSB.

[0065] A network entity configured to perform a method as described above is also provided.

[0066] Computer software comprising instructions that, when executed on a processor, cause the processor to perform a method described above is also provided.

[0067] As described above, a base station may transmit two separate synchronisation signals (e.g., synchronisation signal blocks, SSBs) where a first synchronisation signal is suitable for all devices and a second synchronisation signal is provided for devices that support measurements of the second synchronisation signal (e.g., RedCap devices, eRedCap devices and / or devices complying with Release 18 of the 3GPP standards). The second synchronisation may be simplified compared to the first synchronisation (and may be a non-cell defining synchronisation signal block, NCD-SSB, while the primary synchronisation signal may be a cell defining synchronisation signal block, CD-SSB).

[0068] As described above, the base station may selectively enable a secondary synchronisation signal based on levels of network traffic associated with devices that are able to use the secondary synchronisation signals. Moreover, during times of high traffic, the base station may selectively enable additional synchronisation signals (e.g., third and fourth synchronisation signals).

[0069] Synchronisation signals may be selectively enabled and disabled based on network traffic levels. Therefore, a region may include a mix of base stations, some of which have a secondary synchronisation signal enabled and some of which have a secondary synchronisation signal disabled.

[0070] In order for a UE to handover to a different cell when appropriate (e.g., because network conditions change or because the UE has moved), the UE periodically measures signal strengths of synchronisation signals from potential target bases stations. In order to do so, the UE is configured to measure synchronisation signals on one or more frequencies.

[0071] Prior art methods configure UEs to measure primary synchronisation signals (e.g., CD-SSB) and also to measure secondary synchronisation signals (e.g., NCD-SSB), where available.

[0072] In contrast to the prior art, the proposed methods communicate, for each neighbouring base station, an indication to the adjacent base station (which may be a serving base station if UEs are attached, although the indication may be received shortly after the base station powers up, before any UEs are connected) of whether the neighbouring base station is transmitting a second synchronisation signal. Based on this indication, a serving base station can send configuration data to the UE that causes the UE to measure the second synchronisation signal of the neighbouring base station (if available). If enough of the neighbouring base stations are transmitting a second synchronisation signal, the UE may not need to measure the first synchronisation signal of any of the base stations.

[0073] A method of configuring a user equipment, UE, to measure one or more synchronisation signals from one or more potential target base stations is provided. A serving base station of the UE is configured to periodically transmit a first synchronisation signal and a second synchronisation signal. Each of the one or more potential target base stations is configured to periodically transmit a first synchronisation signal. The method comprises communicating, from each of the one or more potential target base stations to the serving base station, an indication of whether the respective base station is periodically transmitting a second synchronisation signal. The method further comprises communicating, from the serving base station to the UE, configuration data that causes the UE to measure one or more synchronisation signals from the one or more potential target base stations. If at least a threshold number of the one or more potential target base stations are periodically transmitting a second synchronisation signal, the configuration data causes the UE to measure the second synchronisation signal of each of the one or more potential target base stations. If a number of the one or more potential target base stations lower than the threshold number are periodically transmitting a second synchronisation signal, the configuration data causes the UE to measure the first synchronisation signal of each of the one or more potential target base stations.

[0074] So that the serving base station can correctly configure the UE to measure synchronisation signals from neighbouring base stations, the serving base station needs toknow whether the neighbouring base stations are transmitting a second synchronisation signal. Therefore, the proposed methods communicate this information between neighbouring base stations (e.g., from the potential target base stations to the serving base station of the UE).

[0075] Where the method comprises communicating the indication of whether the respective base station is periodically transmitting a second synchronisation signal, from each of the one or more potential target base stations to the serving base station, it should be noted that the serving base station may not be a serving base station of the UE at the time the indication is received. The indication may be received in advance, before the UE attaches to the base station. Therefore, the communication may be alternatively written as a communication of the indication between neighbouring base stations. In some examples, the indication may be communicated between base stations shortly after one of the base stations is switched on.

[0076] If every neighbouring base station is transmitting the second synchronisation signal, the UE may only need to measure the second synchronisation signal of each of the neighbouring base stations (i.e., the UE may not need to measure the first synchronisation signal of any of the base stations). Moreover, if each of the neighbouring base stations is transmitting the second synchronisation signal on the same frequency, then the UE may only need to measure synchronisation signals on one frequency.

[0077] If most (but not all) of the neighbouring base stations are transmitting the second synchronisation signal, the UE may measure the second synchronisation signal of each of the neighbouring base stations that is transmitting a second synchronisation signal but may not need to measure the first synchronisation of any of the base stations, including those that are not transmitting a second synchronisation signal. In this case, the UE would not consider the minority of neighbouring base stations that are not transmitting the second synchronisation signal as candidates for handover.

[0078] The first and / or second synchronisation signal of each of the one or more potential target bases stations may be used for determining whether to perform handover from the serving base station of the UE to the respective potential target base station.

[0079] Each of the one or more potential target base stations may be associated with one or more neighbouring cells. The indication may be an indication of whether each of the one or more neighbouring cells are periodically transmitting a second synchronisation signal. A base station (e.g., gNB) may have multiple cells. For example, each sector and frequency band may be a different cell. Each cell may have a different number of NCD-SSBs enabled. For example, a base station with 100 MHz bandwidth on 3.5GHz cells and 10 MHz bandwidth on 900 MHz cells may not have an NCD-SSB enabled on the 900 MHz cells, as their total bandwidth may be less than 20 MHz.

[0080] A base station that is said to be periodically transmitting a second synchronisation signal may be understood to be actively periodically transmitting the synchronisation signal at the time the indication is communicated to the serving base station.

[0081] The configuration data may cause the UE to measure the second synchronisation signal of the serving base station.

[0082] If at least the threshold number of potential target base stations are periodically transmitting a second synchronisation signal, the configuration data may cause the UE to measure only the second synchronisation signal of each of the one or more potential target base stations that is periodically transmitting a second synchronisation signal. The configuration data may cause the UE to not measure a first synchronisation signal (e.g., CD-SSB) of any of the potential target base stations (and the serving base station), whether they are periodically transmitting a second synchronisation signal or not.

[0083] The one or more potential target base stations may all transmit a second synchronisation signal on the same predetermined frequency. Therefore, the configuration data may cause the UE to measure the second synchronisation signal of each of the one or more potential target base stations that is periodically transmitting a second synchronisation signal on the predetermined frequency.

[0084] If at least the threshold number of potential target base stations are periodically transmitting a second synchronisation signal, the configuration data may cause the UE to measure only on the predetermined frequency.

[0085] If a number of potential target base stations lower than the threshold number are periodically transmitting a second synchronisation signal, the configuration data may cause the UE to measure the first synchronisation signal of each of the one or more potential target base stations that is not periodically transmitting a second synchronisation signal.

[0086] The configuration data may cause the UE to measure the first synchronisation signal of each of the one or more potential target base stations as well as measuring the second synchronisation signal of each of the one or more potential target base stations that is periodically transmitting a second synchronisation signal.

[0087] The second synchronisation signal may be transmitted on a different frequency to the first synchronisation signal. Therefore, the configuration data may cause the UE to measure the second synchronisation signal of each of the one or more potential target base stations that is periodically transmitting a second synchronisation signal on the predetermined frequency and to measure the first synchronisation signal of each of the one or more potential target base stations on a different frequency.

[0088] The configuration data may cause the UE to measure on multiple different frequencies.

[0089] The one or more potential target base stations may all transmit a first synchronisation signal on the same predetermined frequency as each other (but different to the predetermined frequency of the second synchronisation signal).

[0090] If a number of potential target base stations lower than the threshold number are periodically transmitting a second synchronisation signal (so that the UE needs to measure the first synchronisation signal of some of the potential target base stations), the configuration data may cause the UE to measure the first synchronisation signal and the second synchronisation signal of the potential target base stations that are periodically transmitting both first and second synchronisation signals.

[0091] In some examples, the configuration data causes the UE to measure at least one synchronisation signal from each of the one or more potential target base stations, in other examples, the UE might not measure a signal from some potential target base stations.

[0092] For example, if there is only one potential target base station that is not transmitting a NCD-SSB, the UE may ignore this one and only measure signals from base stations that are transmitting NCD-SSB. In other words, since measuring on two different frequencies may increase scheduling complexity in the base station and reduce the data rate of the UE, it might be preferable to measure only the NCD-SSB, rather than measuring the NCD-SSB on one frequency and the CD-SSB on a different frequency, just so that at least one synchronisation from the one potential target base station that is not transmitting a NCD- SSB is measured.

[0093] The neighbouring base stations may be configured to communicate with each other via a X2 or Xn interface. In particular, the serving base station may be configured to communicate with each of the one or more potential target base stations via a X2 or Xn interface.

[0094] For example, the neighbouring base stations communicate via the X2 or Xn interface, the indication of whether they are periodically transmitting a second synchronisation signal. Base stations may also communicate via the X2 or Xn interface, information relating to the number of RedCap UEs being served by the base station and the traffic load, and may receive corresponding information back. Base stations may also communicate via the X2 or Xn interface, instructions or requests to enable / disable periodic transmission of a second synchronisation signal.

[0095] Communicating an indication of whether the respective base station is periodically transmitting a second synchronisation signal may comprise communicating one or more of the following messages from the respective base station to the serving base station: a change modification message, an Xn Setup Response message, an Xn Setup Request message, and an NG-RAN node Configuration Update message.

[0096] If the respective base station is periodically transmitting a second synchronisation signal, communicating an indication of whether the respective base station is periodically transmitting a second synchronisation signal may comprise communicating an indication of one or more of: an absolute frequency of the second synchronisation signal,a periodicity of the second synchronisation signal, a time offset of the second synchronisation signal relative to the first synchronisation signal, and a frequency offset of the second synchronisation signal relative to the first synchronisation signal.

[0097] Communicating configuration data that causes the UE to measure the second synchronisation signal of a potential target base stations may comprise communicating an indication of a frequency of the second synchronisation signal.

[0098] Communicating configuration data that causes the UE to measure the first synchronisation signal of a potential target base stations may comprise communicating an indication that the UE should measure a frequency of the first synchronisation signal. The absolute frequency of the CD-SSB may already be known to the UE and so may not need to be communicated to the UE.

[0099] The base station may be configured to facilitate synchronisation of a plurality of UEs. The plurality of UEs may comprise at least one UE of a first capability type. The method may further comprise periodically transmitting the first synchronisation signal. The method may further comprise determining a level of network traffic communicated via the base station and associated with the at least one UE of the first capability type. The method may further comprise selectively periodically transmitting one or more additional synchronisation signals, based on the level of network traffic communicated via the base station and associated with the at least one UE of the first capability type. The one or more additional synchronisation signals may comprise the second synchronisation signal.

[0100] As described above, a base station may selectively enable the second synchronisation signal (e.g., NCD-SSB) if there is sufficient demand. Additionally, a base station may selectively enable further additional synchronisation signals if there is sufficient demand. For example, the base station may activate a third synchronisation signal, forth synchronisation signal, and so on. The first synchronisation signal may be a CD-SSB and the second and subsequent synchronisation signals maybe NCD-SSBs.

[0101] Each of the one or more potential target base stations may be configured to selectively periodically transmit one or more additional synchronisation signals, based on alevel of network traffic communicated via the respective base station. The one or more additional synchronisation signals may comprise the second synchronisation signal.

[0102] Optionally, the level of network traffic communicated via the respective base station may be a level of network traffic associated with one or more UEs of a first capability type (e.g., UEs that are capable of measuring NCD-SSB).

[0103] The threshold number may be expressed as a threshold proportion of a total number of potential target base stations.

[0104] The threshold proportion may be 100%.

[0105] In other words, if all of the one or more potential target base stations are periodically transmitting a second synchronisation signal, the configuration data may cause the UE to measure the second synchronisation signal of each of the one or more potential target base stations, and if any of the one or more potential target base stations are not periodically transmitting a second synchronisation signal, the configuration data may cause the UE to measure the first synchronisation signal of each of the one or more potential target base stations that is not periodically transmitting a second synchronisation signal.

[0106] The method may further comprise communicating, from the serving base station to at least one potential target base station that is not periodically transmitting a second synchronisation signal, an instruction to enable periodic transmission of a second synchronisation signal.

[0107] The instruction may further comprise a frequency of the second synchronisation signal.

[0108] The serving base station may instruct (or request) neighbouring base stations to enable the second synchronisation signal and may stipulate a required frequency. The required frequency may be the same as a frequency of the second synchronisation signal of the serving base station and / or may be the same as a frequency of the second synchronisation signal of one or more other potential target base stations.

[0109] The base station may be configured to facilitate synchronisation of a plurality of UEs. The plurality of UEs may comprise at least one UE of a first capability type. The first capability type may comprise one or more of: reduced capability, RedCap, UEs; enhanced reduced capability, eRedCap, UEs; and non-RedCap UEs supporting measurements of the second synchronisation signal.

[0110] A frequency of the first synchronisation signal may be predetermined and fixed (e.g., defined by standards). A frequency of the second synchronisation signal may be configurable. In one example, the second synchronisation signal may be provided at one end of the available spectrum. In another example, a frequency of the second synchronisation signal may be allocated using an algorithm. The base stations may all use common logic for allocating the frequency of the second synchronisation signal, so that the frequencies of the second synchronisation signals on neighbouring base stations are likely to be aligned.

[0111] The method may further comprise enabling periodic transmission of the second synchronisation signal and allocating a frequency of the second synchronisation signal based on a frequency of a second synchronisation signal of a base station associated with a neighbouring cell.

[0112] When a base station is first powered on, there will be no initial load so the second synchronisation signal is unlikely to be enabled. After the base station is powered on, it may acquire information relating to the second synchronisation signals of neighbouring base stations (including the frequency on which the second synchronisation signal is transmitted by the neighbouring base stations). When the second synchronisation signal of the base station is unilaterally enabled (e.g., based on levels of network traffic), a frequency of the second synchronisation signal may be set to match a frequency of the second synchronisation signal of one or more neighbouring base stations. Alternatively, when the second synchronisation signal of a base station is enabled as a result of instructions received from an instructing base station (e.g., a neighbouring base station), a frequency of the second synchronisation signal may be set by the instructing base station to match a frequency of the second synchronisation signal of the instructing base station and / or one or more neighbouring base stations of the instructing base station.

[0113] Alternatively, each of the base stations may be configured with a preselected frequency for the second synchronisation signal.

[0114] Advantageously, if neighbouring base stations are each configured to transmit a second synchronisation signal on the same frequency, a UE measuring the second synchronisation signals of each of the base stations may only need to measure one frequency. This may improve efficiency.

[0115] The measurements of the synchronisation signals from the one or more potential target base stations taken by the UE may be radio resource management, RRM, measurements.

[0116] Each of the first synchronisation signal and the second synchronisation signal may be a synchronisation signal block, SSB. A SSB may comprise one or more of: a primary synchronisation signal, PSS; a secondary synchronisation signal, SSS; a physical broadcast channel, PBCH; and a physical broadcast channel demodulation reference signal, PBCH DMRS.

[0117] For each of the first synchronisation signal and the second synchronisation signal, the PBCH may comprise a master information block, MIB.

[0118] The first synchronisation signal may comprise data to enable a UE to obtain a first system information block, SIB1. The second synchronisation signal may not be used to obtain SIB1.

[0119] The first synchronisation signal may be associated with a Remaining Minimum System Information, RMSI, block. The second synchronisation signal may not be associated with a RMSI block.

[0120] The first synchronisation signal may be a cell-defining synchronisation signal block, CD-SSB. The second synchronisation signal may be a non-cell-defining synchronisation signal block, NCD-SSB.

[0121] Each of the first synchronisation signal and the second synchronisation signal may comprise a plurality of parameters.

[0122] The second synchronisation signal may comprise parameters that are different to the parameters of the first synchronisation signal.

[0123] Each of the first synchronisation signal and the second synchronisation signal may comprise a plurality of information elements. Each plurality of information elements may comprise the respective plurality of parameters.

[0124] An information element of the second synchronisation signal may comprise one or more of the following parameters: an absolute frequency of the second synchronisation signal; a periodicity of the second synchronisation signal; and a time offset of the second synchronisation signal relative to the first synchronisation signal.

[0125] A periodicity of the second synchronisation signal may be different to a periodicity of the first synchronisation signal.

[0126] The configuration data may comprise SS / PBCH Block Measurement Timing Configuration, SMTC.

[0127] The configuration data may comprise one or more of the following parameters: an absolute frequency of the first synchronisation signal; a periodicity of the first synchronisation signal; an absolute frequency of the second synchronisation signal; a periodicity of the second synchronisation signal; and a time offset of the second synchronisation signal relative to the first synchronisation signal.

[0128] The configuration data may comprise SS / PBCH Block Measurement Timing Configuration, SMTC.

[0129] A network entity configured to perform a method as described above is also provided.

[0130] A computer program comprising instructions that, when executed on a processor, cause the processor to perform a method described above is also provided.

[0131] As described above, a potential target base station may be configured to transmit two separate synchronisation signals (e.g., synchronisation signal blocks, SSBs). However, there may be some potential target base stations that are only transmitting a first synchronisation signal. As a result, a UE may be provided with configuration data that causes the UE to measure the first synchronisation signal of some of the potential target base stations (e.g., those that are not transmitting a second synchronisation signal), and to measure the second synchronisation signal of some others of the potential target base stations (e.g., those that are transmitting a second synchronisation signal).

[0132] Measuring the first synchronisation signal of some of the potential target base stations may comprise measuring signals on a particular frequency. If all of the potential target base stations are transmitting a first synchronisation signal on the same frequency then the UE may measure the first synchronisation signal from every potential target base station, including those that are transmitting a second synchronisation signal. As a result, the UE may measure both the first synchronisation signal and the second synchronisation signal of the potential target base stations that are periodically transmitting both first and second synchronisation signals.

[0133] Each base station may be associated with a cell. Each cell may have an identifier. The synchronisation signals may include the identifier of the associated potential target cell. A UE may receive a plurality of synchronisation signals from a plurality of potential target cells and send one or more measurement report messages to its serving cell. The one or more measurement report messages may include, for each synchronisation signal received, a measurement report entry comprising signal strength data and the identifier of the potential target cell associated with the synchronisation signal. The cell identifiers may be locally unique, so that the UE and / or serving cell can uniquely identify the potential target cell to which each synchronisation signal relates.

[0134] If a measurement report message includes more than one measurement report entry with the same cell identifier, prior art methods would assume that the UE had received the signals from two different cells and that two cells simultaneously visible to the UE have been assigned the same cell identifier. This could cause problems if the signal strength of one of these cells met a handover condition, as the serving cell may not be able to uniquely identify which cell had met the handover condition and may be unable to perform the handover, or, may attempt to handover the UE to the wrong cell, potentially leading to communication failure. Therefore, prior art methods may raise an alarm in such a situation. Alternatively or additionally, prior art methods may increase a counter, such as an OAM counter, to document that an unusual condition has been detected.

[0135] In contrast to the prior art, the proposed methods recognise that two different synchronisation signals may be received that are associated the same cell (whereas previously, each cell may have only been associated with one synchronisation signal).

[0136] A method of receiving synchronisation signal measurements in a cellular network is provided. The method comprises receiving, from a user equipment, UE, one or more measurement report messages comprising a first measurement report entry relating to a first synchronisation signal of a first potential target cell. The first measurement report entry comprises a cell identifier of the first potential target cell. The one or more measurement report messages further comprise a second measurement report entry relating to a second synchronisation signal of the first potential target cell. The second measurement report entry comprises the cell identifier of the first potential target cell. The method further comprises identifying that the one or more measurement report messages comprise two measurement report entries that each comprise the same cell identifier, and determining whether to raise an alarm and / or increase a counter in response. The method further comprises determining that the two measurement report entries relate to the same cell and suppressing the alarm.

[0137] In other words, the proposed methods may supress the alarm if the two measurement report entries relate to the same cell.

[0138] The first measurement report entry and the second measurement report entry may be in the same measurement report message. In other words, a single measurement report message may comprise two measurement report entries that each comprise the same cellidentifier. Whether the measurement report entries are sent by the UE in a single measurement report message or separate measurement report messages may depend on the reporting configuration. The UE may consolidate multiple measurements report entries in the same measurement report message at the same time, or may send different measurement report messages at different times.

[0139] Each measurement report entry may correspond to a synchronisation signal received by the UE. The UE may send the measurement report entries corresponding to the first synchronisation signal of each potential target base station together in one measurement report message (these entries may correspond to a first measurement object configured on the UE that causes the UE to measure synchronisation signals on a frequency on which each of the first synchronisation signals is transmitted). The UE may send the measurement report entries corresponding to the second synchronisation signal of each potential target base station (each potential target base station that is transmitting a second synchronisation signal) together in another measurement report message (these may correspond to a second measurement object configured on the UE that causes the UE to measure synchronisation signals on a frequency on which each of the second synchronisation signals is transmitted).

[0140] The configuration data may define one or more measurement objects. Each measurement object may relate to a specific frequency. A measurement report message may comprise measurement quantities (e.g., RSRP, RSRQ) of the synchronisation signals (which may also be referred to as “reference signals”) associated with each measurement object. The UE may send a measurement report message to the serving base station that comprises a plurality of measurement report entries, each entry may correspond to a particular synchronisation signal of a particular potential target base station.

[0141] Determining that the two measurement report entries relate to the same cell may comprise determining that the two measurement report entries relate to different synchronisation signals of the same cell (i.e. a first synchronisation signal and a second synchronisation signal transmitted by a base station associated with the cell).

[0142] Determining that the two measurement report entries relate to the same cell may be based on information from the cell (such as information communicated from a base station associated with the potential target cell to a base station associated with a serving cell ofthe UE). For example, the base station associated with the potential target cell may provide an indication that it is periodically transmitting a first synchronisation signal and a second synchronisation signal.

[0143] The indication may further comprise an indication of the respective frequencies of each of the synchronisation signals.

[0144] The information may be communicated via an X2 and / or Xn interface.

[0145] The method may be performed by a base station associated with a serving cell of the UE.

[0146] The two measurement report entries that relate to the same cell may be the first measurement report entry and the second measurement report entry.

[0147] Identifying that the one or more measurement report messages comprise two measurement report entries that each relate to the same cell may comprise determining that two measurement report entries comprise the same cell identifier.

[0148] The method may further comprise receiving one or more further measurement report messages (e.g., from a different UE). The method may further comprise identifying that the one or more further measurement report messages comprise two measurement report entries that each comprise the same cell identifier, and determining whether to raise an alarm and / or increase a counter in response. The method may further comprise determining that the two measurement report entries of the one or more further measurement report messages relate to different cells and raising an alarm and / or increasing a counter.

[0149] In other words, the method may suppress the alarm (and / or the counter increase) if the measurement report entries relate to different synchronisation signals associated with the same cell but may raise the alarm (and / or increase the counter) if the measurement report entries relate to different cells that have been mistakenly assigned the same identifier.

[0150] If the potential target cell is only transmitting one synchronisation signal then the measurement report entries may relate to different cells and an alarm may be raised (and / or a counter may be increased).

[0151] Determining that the two measurement report entries relate to different cells may comprise receiving an indication from the cell that it is not transmitting a second synchronisation signal (e.g., NCD-SSB).

[0152] The method may further comprise communicating, to the UE, configuration data that causes the UE to measure the first synchronisation signal of the first potential target cell and the second synchronisation signal of the first potential target cell.

[0153] The first synchronisation signal of the first potential target cell may be transmitted on a first frequency and the second synchronisation signal of the first potential target cell may be transmitted on a second frequency. The configuration data may cause the UE to measure signals on the first frequency and the second frequency.

[0154] The UE may be configured to measure a frequency on which the synchronisation signal is transmitted, rather than being configured to read a specific synchronisation signal. As a result, the UE may receive all synchronisation signals that are transmitted on the same frequency from cells that are within range of the UE.

[0155] The configuration data may comprise SS / PBCH Block Measurement Timing Configuration, SMTC.

[0156] The configuration data may comprise one or more of the following parameters: an absolute frequency of the first synchronisation signal; a periodicity of the first synchronisation signal; an absolute frequency of the second synchronisation signal (or a frequency offset of the second synchronisation signal relative to the first synchronisation signal); a periodicity of the second synchronisation signal; and a time offset of the second synchronisation signal relative to the first synchronisation signal.

[0157] The method may further comprise communicating, from the first potential target cell to a serving cell of the UE, an indication that the first potential target cell is periodically transmitting the second synchronisation signal.

[0158] The indication may be communicated via the X2 or Xn interface.

[0159] Each of the two measurement report entries may further comprise a signal strength measurement relating to the respective synchronisation signal.

[0160] The measurement report entries may comprise radio resource management, RRM, measurements.

[0161] Each of the first synchronisation signal and the second synchronisation signal may be a synchronisation signal block comprising: a primary synchronisation signal, PSS; a secondary synchronisation signal, SSS; a physical broadcast channel, PBCH; and a physical broadcast channel demodulation reference signal, PBCH DMRS.

[0162] For each of the first synchronisation signal and the second synchronisation signal, the PBCH may comprise a master information block, MIB.

[0163] The first synchronisation signal may comprise data to enable a UE to obtain a first system information block, SIB1. The second synchronisation signal may not be used to obtain SIB1.

[0164] The first synchronisation signal may be associated with a Remaining Minimum System Information, RMSI, block. The second synchronisation signal may not be associated with an independent RMSI block.

[0165] The first synchronisation signal may be a cell-defining synchronisation signal block, CD-SSB. The second synchronisation signal may be a non-cell-defining synchronisation signal block, NCD-SSB.

[0166] Each of the first synchronisation signal and the second synchronisation signal may comprise a plurality of parameters.

[0167] The second synchronisation signal may comprise parameters that are different to the parameters of the first synchronisation signal.

[0168] Each of the first synchronisation signal and the second synchronisation signal may comprise a plurality of information elements. Each plurality of information elements may comprise the respective plurality of parameters.

[0169] An information element of the second synchronisation signal may comprise one or more of the following parameters: an absolute frequency of the second synchronisation signal; a periodicity of the second synchronisation signal; and a time offset of the second synchronisation signal relative to the first synchronisation signal.

[0170] A periodicity of the second synchronisation signal may be different to a periodicity of the first synchronisation signal.

[0171] A network entity configured to perform a method as described above is also provided.

[0172] A computer program comprising instructions that, when executed on a processor, cause the processor to perform a method described above is also provided.

[0173] A method of a base station facilitating handover of a user equipment, UE, is also provided. The base station is configured to periodically transmit a first synchronisation signal and selectively periodically transmit a second synchronisation signal. The method comprises: determining that a procedure to disable periodic transmission of the second synchronisation signal should be initiated, based on network traffic levels; determining that a handover procedure has been initiated in respect of a UE, based on measurements of the second synchronisation signal taken by the UE, wherein the base station is a target base station of the handover procedure; andmodifying one or more procedures and completing the handover procedure, so that the base station becomes a serving base station of the UE.

[0174] The base station may be configured to selectively periodically transmit the second synchronisation signal based on a level of network traffic associated with one or more UEs of a first capability type.

[0175] The level of network traffic associated with one or more UEs of the first capability type may comprise: a level of network traffic communicated via the base station and associated with one or more UEs of the first capability type; and a level of network traffic communicated via one or more base stations corresponding to one or more neighbouring cells and associated with UEs of the first capability type.

[0176] The base station may be configured to communicate with a plurality of UEs, wherein the plurality of UEs comprises at least one UE of a first capability type and at least one UE of a second capability type, wherein: the first capability type corresponds with a reduced capability compared to the second capability type; the first capability type is not reduced compared to the second capability type and corresponds with UEs that are compatible with the second synchronisation signal; or the first capability type corresponds with UEs that are compatible with the second synchronisation signal and wherein the at least one UE of the first capability type includes at least one UE having a reduced capability compared to the second capability type and at least one UE not having reduced capability compared to the second capability type.

[0177] The UE in respect of which the handover procedure has been initiated may be a UE of the first capability type.

[0178] The measurements of the second synchronisation signal taken by the UE may be radio resource management, RRM, measurements.

[0179] In some alternative examples, the measurements of the second synchronisation signal taken by the UE may be radio resource control, RRC, measurements.

[0180] Each of the first synchronisation signal and the second synchronisation signal may be a synchronisation signal block comprising: a primary synchronisation signal, PSS; a secondary synchronisation signal, SSS; a physical broadcast channel, PBCH; and a physical broadcast channel demodulation reference signal, PBCH DMRS.

[0181] For each of the first synchronisation signal and the second synchronisation signal, the PBCH may comprise a master information block, MIB.

[0182] The first synchronisation signal may comprise data to enable a UE to obtain a first system information block, SIB1. The second synchronisation signal may not be used to obtain SIB1.

[0183] The first synchronisation signal may be associated with a Remaining Minimum System Information, RMSI, block. The second synchronisation signal may not be associated with a RMSI block.

[0184] The first synchronisation signal may be a cell-defining synchronisation signal block, CD-SSB. The second synchronisation signal may be a non-cell-defining synchronisation signal block, NCD-SSB.

[0185] Each of the first synchronisation signal and the second synchronisation signal may comprise a plurality of parameters.

[0186] The second synchronisation signal may comprise parameters that are different to the parameters of the first synchronisation signal.

[0187] Each of the first synchronisation signal and the second synchronisation signal may comprise a plurality of information elements, wherein each plurality of information elements comprises the respective plurality of parameters.

[0188] An information element of the second synchronisation signal may comprise one or more of the following parameters:an absolute frequency of the synchronisation signal; a periodicity of the synchronisation signal; and a time offset of the second synchronisation signal relative to the first synchronisation signal.

[0189] A periodicity of the second synchronisation signal may be different to a periodicity of the first synchronisation signal.

[0190] In some examples, a periodicity of the second synchronisation signal may be greater than a periodicity of the first synchronisation signal. In other examples, A periodicity of the second synchronisation signal may be less than a periodicity of the first synchronisation signal.

[0191] Determining that a handover procedure has been initiated may comprise receiving, from a neighbouring base station (e.g., via a network interface Xn or X2), carrier resource information identifying a portion of carrier bandwidth (BWP) associated with the second synchronisation signal.

[0192] The bandwidth part (BWP) may comprise the second synchronisation signal in some examples. In other words, the NCD-SSB may be within the BWP. In other examples, the second synchronisation signal may be separate from the BWP.

[0193] Modifying one or more procedures may comprise modifying the procedure to disable periodic transmission of the second synchronisation signal.

[0194] Modifying the procedure to disable periodic transmission of the second synchronisation signal may comprise delaying (or “suppressing,” or “temporarily suppressing”) the procedure to disable periodic transmission of the second synchronisation signal, so that periodic transmission of the second synchronisation signal continues while the handover procedure is ongoing.

[0195] In the example described above, periodic transmission of the second synchronisation signal may continue while the handover procedure is ongoing, despite the determination by the base station that periodic transmission of the second synchronisation signal should be disabled, based on network traffic levels.

[0196] The method may further comprise disabling periodic transmission of the second synchronisation signal after the handover procedure has been completed.

[0197] Completing the handover procedure may comprise completing the handover procedure based on the second synchronisation signal.

[0198] Modifying one or more procedures may comprise modifying the handover procedure.

[0199] Modifying the handover procedure may comprise providing configuration to the UE to cause the UE to measure the first synchronisation signal (instead of the second synchronisation signal).

[0200] The configuration may comprise SS / PBCH Block Measurement Timing Configuration, SMTC.

[0201] The configuration may comprise one or more of the following parameters: an absolute frequency of the first synchronisation signal; a periodicity of the first synchronisation signal; and a time offset of the first synchronisation signal.

[0202] The time offset of the first synchronisation signal may be relative to an overall resource block grid. The time offset may be provided in terms of a number of subcarriers.

[0203] The method may further comprise disabling periodic transmission of the second synchronisation signal while the handover procedure is ongoing (before the handover procedure has been completed).

[0204] Completing the handover procedure may comprise completing the handover procedure based on the first synchronisation signal.

[0205] A network entity configured to perform a method described above is also provided.

[0206] Computer software comprising instructions that, when executed on a processor, cause the processor to perform a method as described above is also provided.Brief description of the drawings

[0207] The invention will be described with reference to the non-limiting examples illustrated in the following Figures.

[0208] Fig. 1 illustrates a telecommunications network according to a specific example.

[0209] Fig. 2 illustrates a flow diagram of an example method.Detailed description

[0210] To serve use cases in between eMBB and loT, a new device capability type is defined. In some scenarios, the new device capability type represents reduced capabilities compared to other devices in the network that are designed to use eMBB. Therefore, devices having the new device capability type are sometimes referred to as “RedCap” devices. The new device capability type may be suitable for use cases including sensor devices, wearable devices, and surveillance cameras. By defining specific capabilities for the new device capability type (which may be reduced compared to eMBB) lower complexity devices may be designed to use the new device capability type. By designing devices with such capabilities in mind, the complexity and overall cost of such devices may be reduced.

[0211] As described above, a device operating in accordance with the new device type has reduced capabilities, when compared to a device operating in accordance with a eMBB use case. The new device capability type may impose some restrictions and limitations, in order to implement these reduced capabilities. In some examples, the new device capability type has the following limitations:• up to 20 MHz of UL / DL bandwidth,• a reduced number of MIMO layers and RX / branches of up to 2,• reduced modulation order, and• no support for carrier aggregation or dual connectivity.

[0212] UE capability information may be communicated to the network via an information element. In some examples, a RedCapParameters information element may be used. In other examples, a different information element may be used to communicate UE capabilities.

[0213] The RedCapParameters information element definition according to a specific example is reproduced below.- ASN1 START- TAG-REDCAPPARAMETERS-STARTRedCapParameters-r17::= SEQUENCE {- R1 28-1 : RedCap UE supportOfRedCap-r17 ENUMERATED {supported} OPTIONAL, supportOf16DRB-RedCap-r17 ENUMERATED {supported} OPTIONAL }RedCapParameters-v1740::= SEQUENCE { ncd-SSB-ForRedCaplnitialBWP-SDT-r17 ENUMERATED {supported} OPTIONAL}- TAG-REDCAPPARAMETERS-STOP- ASN1STOP

[0214] The IE RedCapParameters is used to indicate the UE capabilities supported by RedCap UEs. This IE may be used to provide RedCap capability information to the network.

[0215] Given the nature of the devices that are likely to be designated as RedCap devices (sensors, surveillance, wearables, and the like), it is expected that large numbers of RedCap devices may be present in the network after support for these devices is implemented. Efforts in standardization have been undertaken to achieve coexistence with legacy devices, and to provide mechanisms to offload and to leverage the resources of a network for these devices. A specific enhancement in Release 17 for RedCap UEs is the introduction of an additional non-cell defining synchronization block (NCD-SSB). In someexamples, the NCD-SSB differs from the legacy cell-defining synchronization block (CD- SSB) by not being associated with SIB. The NCD-SSB is configured by the network in a bandwidth part (BWP), allowing RedCap UEs operating in this BWP to use this SSB for the purposes for which it would otherwise have used the CD-SSB of the serving cell (e.g., obtaining sync, measurements, radio link monitoring). This extra synchronization block provides advantages. For example, it provides flexibility for the network to offload part or all the RedCap traffic in a cell.

[0216] In some examples, the NCD-SSB differs from the CD-SSB by the parameters defined in the nonCellDefiningSSB Information Element.

[0217] The NonCellDefiningSSB information element definition according to a specific example is reproduced below.- ASN1 START- TAG-NONCELLDEFININGSSB-STARTNonCellDefiningSSB-r17 ::= SEQUENCE { absoluteFrequencySSB-r17 ARFCN-ValueNR, ssb-Periodicity-r17 ENUMERATED { ms5, ms10, ms20, ms40, ms80, ms160, spare2, spare 1 } OPTIONAL, - Need S ssb-TimeOffset-r17 ENUMERATED { ms5, ms10, ms15, ms20, ms40, ms80, spare2, spare 1 } OPTIONAL, - Need S}- TAG-NONCELLDEFININGSSB-STOP- ASN1STOP

[0218] The IE NonCellDefiningSSB is used to configure a NCD-SSB to be used while the UE operates in a RedCap-specific initial BWP or dedicated BWP.

[0219] Field descriptions for the NonCellDefiningSSB IE are provided in the table below.

[0220] This enhancement was extended in Release 18 to cover both non-RedCap UEs and eRedCap UEs (enhanced RedCap).

[0221] The ERedCapParameters Information Element may be used to indicate the UE capabilities supported by eRedCap UEs. The ERedCapParameters Information Element definition according to a specific example is reproduced below.- ASN1 START - TAG-EREDCAPPARAMETERS-STARTERedCapParameters-r18::= SEQUENCE {- R1 48-1 : eRedCap UE with reduced peak data rate and reduced baseband bandwidth in FR1 supportOfERedCap-r18 ENUMERATED {supported},- R1 48-2: eRedCap UE with reduced peak data rate without reduced baseband bandwidth in FR1 eRedCapNotReducedBB-BW-r18 ENUMERATED {supported} OPTIONAL, eRedCaplgnoreCapabilityFiltering-r18 ENUMERATED {supported} OPTIONAL }- TAG-EREDCAPPARAMETERS-STOP- ASN1STOP

[0222] The RF-Parameters Information Element may be used to convey RF-related capabilities for NR operation (e.g., for non-RedCap UEs). In Release 18, this IE is extended to include NCD-SSB capability (e.g., via the ncd-SSB-BWP-Wor-r18 field).

[0223] Transmitting an extra synchronization block, with similar characteristics as the legacy one, will increase the overall network signalling overhead, increase the network energy consumption, and reduce the number of resources that the network has available to schedule for data transmission. Therefore, a mechanism is proposed to selectively control the NCD-SSB transmission. The mechanism may enable the network operator to benefit from the advantages associated with using NCD-SSB and to balance these benefits against the drawbacks.

[0224] To control the NCD-SSB transmission, a method is proposed that takes into account the number of RedCap UEs camped in a cell, the traffic load they represent in the overall cell, and similar information from the neighbour cells. In some examples, NCD-SSB is transmitted after a particular threshold is met in terms of the factors mentioned above, and not transmitted whenever there is little or no RedCap traffic.

[0225] Fig. 1 illustrates a telecommunications network according to a specific example. Three neighbouring cells are illustrated, each having a respective base station 100A, 100B and 100C. In each cell, there are one or more UEs. Each UE may be a UE of a first capability type (e.g., a RedCap UE) 120AA, 120AB, 120CA, 120CB and 120CC or a UE of a second capability type (e.g., a mobile phone configured for enhanced mobile broadband) 110AA, 110AB, 110BA and 110CA. The base stations 100A, 100B and 100C may communicate via an X2 or Xn interface 150.

[0226] The purpose of including neighbour cells as one of the criteria for the transmission, is whilst there may not be traffic in a cell, its neighbour cells may have RedCap traffic and these UEs can be performing neighbour cell measurements for handover purposes. For example, as illustrated in Fig. 1 , base station 100B is not currently serving any RedCap UEs. However, there are RedCap UEs in the neighbouring cells, many of which could handover to base station 100B. In particular, RedCap UEs 120AB, 120CB and 120CC may handover to base station 100B. Therefore, despite RedCap UE traffic being low for base station 100B, it may nevertheless be advantageous for the base station 100B to transmit a NCD-SSB.

[0227] A flow diagram illustrating an example method is shown in Fig. 2. The procedural behaviour is as follows:

[0228] At step 201 , the network measures the number of RedCap UEs through their early identification during initial access. This value is stored as one important parameter. A traffic load attributed to RedCap UEs in the cell is also measured and updated as another (or alternative) important parameter.

[0229] The RedCapParameters information element is used to indicate the UE capabilities supported by RedCap UEs. This can be used to identify the UEs supporting RedCap in the cell. UE capabilities may be communicated to the base station in one or more other information elements. For example, the UE-NR-Capabilities information element may include this information.

[0230] The traffic load related to RedCap UEs may be monitored separately form the rest of the network traffic.

[0231] At step 202, the base station exchanges information relating to the number of RedCap UEs and the traffic load with its neighbour cells through the X2 (or Xn) interface, and receives corresponding information back. A new signalling parameter (or parameters) may be introduced over the X2 or Xn signalling interface for communication of this information.

[0232] At step 203, the network decides whether to transmit the NCD-SSB or not. This decision is based on a number of RedCap UEs connected to the base station, traffic loadattributable to the RedCap UEs, and / or information from neighbour cells. These values may be compared to one or more thresholds defined at the base station.

[0233] The values of the thresholds can be set by the network, by implementation, or set from a value in the standards.

[0234] The decision to transmit NCD-SSB or not, based on the traffic load and / or number of connected RedCap UEs can either be left to gNB implementation (each individual gNB may make a decision based on thresholds configured individually) or controlled by OAM (gNBs that belong to the same OAM centre may follow the same decision / policy and use the same thresholds).

[0235] The decision of whether to enable one (or more) Non-Cell-Defining SSBs in a cell may depend upon the number of connected UEs that can use the NCD-SSB and / or a level of the network traffic attributable to those UEs. Likewise, the decision may be further based on the number of UEs that cannot use the NCD-SSB (UEs that need to use a Bandwidth Part containing the Cell Defining SSB, such as “non-RedCap” UEs) and / or a level of the network traffic attributable to those UEs. The numbers of UEs and levels of network traffic are likely to be different in different cells. Therefore, the number of NCD SSBs in a cell may be varied dynamically, based on one or more of these factors. In other words, as load increases, the base station may activate a second synchronisation signal (a first NCD-SSB) (e.g. at one end of the spectrum). If load increases further, the base station may activate a third synchronisation signal (e.g., second NCD-SSB). If load increases further, additional synchronisation signals (e.g., NCD-SSBs) may be enabled.

[0236] In order to cause the UE to measure one or more synchronisation signals (which may be CD-SSB and / or NCD-SSB), the serving base station may send configuration data to the UE. The configuration data may define one or more measurement objects (MO), each of which comprises a frequency on which the UE should measure synchronisation signals. For each measurement object, the UE may report the results of the measurements of one or more synchronisation signals received on that frequency to the serving base station in a measurement report message.

[0237] The network may configure a measurement object on a frequency corresponding to the NCD-SSB of the serving cell if it wants the UE to use the NCD-SSB for serving cell measurements.

[0238] For neighbour cell measurements, it is up to network to configure one or more MOs on frequencies corresponding to the CD-SSB and / or one or more NCD-SSBs of the neighbour cells.

[0239] If all of the neighbour cells are transmitting NCD-SSB on the same frequency, the UE may make all measurements on using one MO.

[0240] If one or more neighbour cells are not transmitting NCD-SSB then the UE may need to measure CD-SSB for those cells. To do so, the network may configure a separate measurement object on a frequency corresponding to the CD-SSB.

[0241] If one or more neighbour cells are transmitting NCD-SSB but on a different frequency to the serving cell, the network may configure a separate measurement object on a frequency corresponding to the NCD-SSB of the one or more neighbour cells.

[0242] If a UE is using a BWP containing an NCD-SSB, then any measurements on the CD-SSB are “intER frequency” measurements. Some form of “measurement gaps” may need to be used if a UE (with a BWP containing NCD-SSB) has to measure the CD-SSB (e.g. to perform neighbour cell measurements).

[0243] Likewise, “measurement gaps” may need to be used if a UE with a BWP containing a first NCD-SSB on a first frequency has to also measure a second NCD-SSB on a second (different) frequency, to perform neighbour cell measurements.

[0244] Measurement gaps may increase the complexity of the scheduling and degrade UE performance and throughput (and practical network capacity). Therefore, efficiency may be improved by avoiding measurement gaps. Hence it will be useful if a serving base station knows whether or not all neighbour cells (on the UE’s frequency band) are transmitting an NCD-SSB on the same frequency as the NCD-SSB that the UE is using (the NCD-SSB of the serving cell). In this case, the UE may not need to measure the CD-SSB, or any NCD-SSBs on different frequencies. Therefore, measurement gaps may not be required (and the MO corresponding to the CD-SSB may be dispensed with).

[0245] TS 38.423 (which is incorporated by reference), describes that the Xn Setup Request / Response (and NG-RAN NODE CONFIGURATION UPDATE) signalling does not carry any information about the presence / absence of NCD-SSBs (nor their carrier frequency). The Redcap information in these messages is only about the sending cell’s (e)Redcap UE barring settings.

[0246] In a first aspect, the proposed methods improve on the current state of the art by communicating to the serving base station an indication of whether each of the neighbouring base stations is periodically transmitting a second synchronisation signal (and optionally, the frequency of the second synchronisation signal). The indication may be added to the Xn Setup Request / Response and NG-RAN NODE CONFIGURATION UPDATE messages.

[0247] The proposed methods may facilitate dynamic exchange of this information, which the serving base station may use to configure the UEs to make measurements more efficiently. In order to do so, the serving base station may configure one or more measurement objects on the UE at one or more predetermined frequencies.

[0248] The base stations may also use the information to coordinate their second synchronisation signals so that each base station is transmitting a second synchronisation signal on the same frequency. Advantageously, this may reduce the number of different frequencies on which a UE is required to measure synchronisation signals and may therefore improve the efficiency of the UE.

[0249] As noted above, there are situations where a UE is using an NCD-SSB of the serving base cell but one or more neighbour cells are not transmitting NCD-SSB (or at least are not doing so on the same frequency). Therefore, the UE may be configured to measure the CD-SSB of such neighbouring cells. In order to do so, the network may configure the UE with separate MOs for CD-SSB and NCD-SSB (on separate frequencies).

[0250] In this situation, there may nevertheless be one or more neighbouring cells that are transmitting both CD-SSB and NCD-SSB. In this scenario, the UE may report the signalstrength of both the CD-SSB and NCD-SSB of the neighbour cell. The NCD SSB(s) in a cell use the same Physical Cell ID (PCI) as the Cell defining SSB. Therefore, each measurement report entry will carry the same PCI.

[0251] Before the introduction of NCD-SSB, a serving gNB would detect two measurement report entries having the same PCI and determine that this is an unusual situation indicative of an error. For example, if two neighbour cells are erroneously allocated the same PCI, the gNB may receive a measurement report message from a UE with two measurement report entries for the same PCI. In this case, the gNB may inform O&M and / or trigger Automatic neighbour Cell Reporting to diagnose the issue.

[0252] In a second aspect, the proposed methods improve on the current state of the art by detecting that a measurement report message from a UE includes two measurement report entries having the same PCI and suppressing the alarm (and / or counter increase) if this is a normal situation (e.g., because the reports relate to the CD-SSB and NCD-SSB of the same cell).

[0253] If the UE (e.g., Redcap UE or Release 18+ Bandwith Part Without Restiction type [C] UE) is using a BWP with an NCD-SSB and the gNB has configured MOs for both CD- SSB and NCD-SSB, then the gNB may accept this situation as a normal situation and not trigger alarms, increase an CAM counter or trigger updates to Automatic Neighbour Relations (e.g., via an automatic neighbour cell reporting function).

[0254] As described in TS 38.331 (which is incorporated by reference), the NCD-SSB allows a RedCap UE operating in the corresponding BWP to use the NCD-SSB for the purposes for which it would otherwise have used the CD-SSB of the serving cell (e.g. obtaining sync, measurements, radio link monitoring). All these operations are in RRC_Connected mode as there is no standards support for idle / inactive.

[0255] These types of measurements can be the basis of a handover decision and, depending on the state of the NCD-SSB transmission at the serving and target cells, the following example scenario can occur:• A UE performs RRM measurements on the NCD-SSB,• the network makes the decision for handover based on the measurements based on the NCD-SSB of the neighbouring cell,in the meantime, the neighbouring cell decides to switch off NCD-SSB.

[0256] Due to a number of factors, this scenario will hopefully be rare in most cases. One reason is that hysteresis is preferably configured in the switching-on and switching-off of the NCD-SSB, so that switching happens only infrequently. The time period between the UE making the measurements and the neighbouring cell deciding to switch off the NCD- SSB should therefore be small, compared to the time during which the NCD-SSB is on and uninterrupted. Therefore, the probability of this scenario should be low. Moreover, the decision to switch off the NCD-SSB is based on information from neighbouring cells so should only be taken if there are relatively few connected RedCap devices in neighbouring cells. Therefore, the probability of a RedCap device attempting handover to the cell after the decision has been taken to switch off the NCD-SSB should be low.

[0257] Nevertheless, this scenario can happen, and the network should be able to manage the scenario when it does occur. The following two solutions are proposed to address the scenario.

[0258] In a first solution, the target cell is not allowed to shut down the NCD-SSB transmission before the handover is finalized.

[0259] After the handover decision has been taken (e.g. by a base station in the network), the frequency information of the BWP corresponding to the NCD-SSB (i.e., an indication of the NCD-SSB that should not be shut down) is communicated by the source cell to the target cell over the network interface (e.g., X2 or Xn).

[0260] In a second solution, the target cell provides changes measurement configuration upon handover. The target cell may send configuration so that handover is performed using the initial BWP of the target cell or a different BWP not corresponding to the NCD-SSB. SS / PBCH Block Measurement Timing Configuration (SMTC) may be configured for the UE to cover the CD-SSB absolute frequency. Remaining configuration (such as periodicity and offset) may be provided to enable the UE to perform measurements on another SSB (e.g., the CD-SSB), rather than on the NCD-SSB. Once the configuration has been provided, the base station may proceed to shutdown NCD-SSB transmission, based on the criteria discussed above (traffic, thresholds, and the like).

[0261] The NCD-SSB has the same values for many properties of the corresponding CD- SSB (e.g., ssb-PositionsInBurst, PCI, ssb-PBCH-BlockPower). However, the values of the properties configured in the NonCellDefiningSSB-r17 IE may be different for the NCD-SSB. These properties include (as discussed above):• absoluteFrequencySSB,• ssb-Periodicity, and• ssb-TimeOffset.

[0262] Given that the UE is measuring on NCD-SSB and the attributes for NCD-SSB are different from CD-SSB, it is not accurate to compare the measurements on NCD-SSB to CD-SSB. Whatever measurements are used for the handover decision (measurements prior to the handover) should be consistent during the handover. Otherwise, the handover was made based on arbitrary measurements or measurements which are no longer valid, resulting in ambiguity of the handover decision.

[0263] In some examples, a RedCap UE may comprise simplified components compared to other UEs that are not designated as RedCap (which may communicate via eMBB). While a “RedCap” UE may be referred to as a “reduced capability” UE, the UE itself may nevertheless be capable of communication via eMBB (at higher data rates). A UE may be designated as a RedCap UE for a number of reasons, including power saving, reducing network load, and the like. In some examples, a RedCap UE may comprise simplified components and require reduced power consumption.

[0264] Moreover, devices that are not designated as “RedCap” UE but are nevertheless capable of synchronising using the second synchronisation signal may use the second synchronisation signal. This may conserve network resources and / or enable the device to implement power-saving techniques.

[0265] Any of the methods described herein may be implemented as a computer program. The computer program may be configured to control a RAN entity (e.g., a network node) and / or UE to perform any method according to the disclosure. A RAN entity (e.g., a network node) of a cellular network and / or a UE may also be provided, configured to operate in accordance with certain methods disclosed herein. For example, the RAN entity may include a processor and at least one communication interface, particularly comprising one or both of a transmitter and receiver. A UE may also be provided, configured tooperate in accordance with certain methods disclosed herein. The UE may likewise include a processor and at least one communication interface, particularly comprising one or both of a transmitter and receiver.

[0266] Although specific embodiments have now been described, the skilled person will understand that various modifications and variations are possible. For example, whilst the disclosure is described in relation to existing network architecture, it will be understood that changes to the architecture (and / or nomenclature) are possible, but the present disclosure may still be applicable in this case. Also, combinations of any specific features shown with reference to one embodiment or with reference to multiple embodiments are also provided, even if that combination has not been explicitly detailed herein.

[0267] A base station (BS) generally refers to a fixed station that performs communication with a UE and / or another BS, and exchanges various kinds of data and control information with the UE and another BS. The BS may be referred to as an advanced base station (ABS), a base transceiver station (BTS), a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), an access point (AP), a Node B (NB), an eNode B (eNB), a gNode B (gNB), a transmission and reception point (TRP), a processing server (PS), or some other suitable terminology, depending on the protocol, standard, context or technology. In some examples, a base station may include two or more transceivers that may or may not be collocated. Each transceiver may communicate on the same or different carrier frequency within the same or different frequency band.

[0268] Where this application refers to a server or network entity, for instance, this may actually be a pair of servers, or network entities (primary and failover), for redundancy.

[0269] In the present invention, a node refers to a fixed point capable of transmitting / receiving a radio signal through communication with a UE. Various types of base stations (such as those described above) may be used as nodes, irrespective of the terms used. In other examples, a node may be a relay, a repeater, and the like.

[0270] In the present invention, a UE may be a fixed or mobile device. Examples of the UE include various devices that transmit and receive user data and / or various kinds of control information to and from a base station. The UE may be referred to as a terminal equipment(TE), a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, a personal digital assistant (PDA), a wireless modem, a handheld device, etc.

[0271] Whilst the above methods are described in relation to a 5G / NR network, these methods, techniques, apparatuses, and systems may be applied to a variety of wireless multiple access systems. Examples of the multiple access systems include CDMA, FDMA, TDMA, OFDMA, SC-FDMA, and MC-FDMA. CDMA may be embodied through radio technology such as UTRA or CDMA2000. TDMA may be embodied through radio technology such as GSM, GPRS, or EDGE. OFDMA may be embodied through radio technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or E-UTRA. UTRA is a part of a UMTS. 3GPP LTE is a part of E-UMTS using E-UTRA. 3GPP LTE employs OFDMA in DL and SC-FDMA in UL. LTE-A is an evolved version of 3GPP LTE. 3GPP NR employs OFDMA for both downlink and uplink and can operate in both FDD and TDD. For convenience of description, it is assumed that the present invention is applied to 3GPP NR. However, the technical features of the present invention are not limited thereto. For example, although the following detailed description is given based on a mobile communication system corresponding to a 3GPP NR system, aspects of the present invention that are not specific to 3GPP NR are applicable to other mobile communication systems.

[0272] In the present invention, a cell refers to a geographical area to which one or more nodes provide a communication service. Accordingly, in the present invention, communicating with a specific cell may mean communicating with an gNB or a node which provides a communication service to the specific cell. Furthermore, channel status / quality of a specific cell refers to channel status / quality of a channel or communication link formed between an gNB or node which provides a communication service to the specific cell and a UE. The UE may measure DL channel state received from a specific node using cellspecific reference signal(s) (CRS(s)) transmitted on a CRS resource and / or channel state information reference signal(s) (CSI-RS(s)) transmitted on a CSI-RS resource, allocated by antenna port(s) of the specific node to the specific node. Meanwhile, a 3GPP system uses the concept of a cell in order to manage radio resources and a cell associated with the radio resources is distinguished from a cell of a geographic region.

[0273] The examples may be carried out on any suitable data processing device, such as a personal computer, laptop, mobile telephone, server, virtual machine, and the like. The above description of the systems and methods has been simplified for purposes of discussion, and is intended to provide a specific example to illustrate the invention. Different types of systems and methods may be used, as will be appreciated by the skilled person. It will be appreciated that the boundaries between logic blocks are merely illustrative and that alternative embodiments may merge logic blocks or elements, or may impose an alternate decomposition of functionality upon various logic blocks or elements.

[0274] It will be appreciated that the above-mentioned functionality may be implemented as one or more corresponding modules as hardware and / or software. For example, the above-mentioned functionality may be implemented as one or more software components for execution by a processor of the system. Alternatively, the above-mentioned functionality may be implemented as hardware, such as on one or more FPGAs, and / or one or more ASICs, and / or one or more DSPs, and / or other hardware arrangements. Method steps implemented in flowcharts contained herein, or as described above, may each be implemented by corresponding respective modules. Moreover, multiple method steps implemented in flowcharts contained herein, or as described above, may be implemented together by a single module.

[0275] Examples may be implemented by computer software or a “computer program.” A storage medium and a transmission medium carrying the computer software are also provided. The computer software may comprise one or more instructions, or code, that, when executed by a computer, causes the methods described to be performed. Computer software may be a sequence of instructions designed for execution on a computer system, and may include a subroutine, a function, a procedure, a module, an object method, an object implementation, an executable application, an applet, a servlet, source code, object code, a shared library, a dynamic linked library, and / or other sequences of instructions designed for execution on a computer system. The storage medium may be a magnetic disc (such as a hard drive or a floppy disc), an optical disc (such as a CD-ROM, a DVD- ROM, or a Blu-ray disc), or a memory (such as a ROM, a RAM, EEPROM, EPROM, Flash memory or a portable / removable memory device), etc. The transmission medium may be a communications signal, a data broadcast, a communications link between two or more computers, etc.

[0276] Each feature disclosed in this specification, unless stated otherwise, may be replaced by alternative features serving the same, equivalent, or similar purpose. Thus, unless stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0277] As used herein, including in the claims, unless the context indicates otherwise, singular forms of the terms herein are to be construed as including the plural form and vice versa. For instance, unless the context indicates otherwise, a singular reference herein including in the claims, such as "a" or "an" (such as a UE, a node, a network entity, a RAN entity, or a cell) means "one or more” (for instance one or more UE, one or more nodes, one or more network entities, one or more RAN entities, or one or more cells). Throughout the description and claims of this disclosure, the words "comprise", "including", "having" and "contain" and variations of the words, for example "comprising" and "comprises" or similar, mean "including", and are not intended to (and do not) exclude other components.

[0278] The use of any and all examples, or exemplary language ("for instance", "such as", "for example" and like language) provided herein, is intended merely to better illustrate the invention, and does not indicate a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any nonclaimed element as essential to the practice of the invention.

[0279] Any steps described in this specification may be performed in any order or simultaneously unless stated or the context requires otherwise. Moreover, where a step is described as being performed after a step, this does not preclude intervening steps being performed.

[0280] All of the aspects and / or features disclosed in this specification may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. As described herein, there may be particular combinations of aspects that are of further benefit, such the aspects of determining a set of compensation parameters and applying a set of compensation parameters to measurements. In particular, the preferred features of the invention are applicable to all aspects of the invention and may be used in any combination. Likewise, features described in non- essential combinations may be used separately (not in combination).

[0281] A method of manufacturing and / or operating any of the devices disclosed herein is also provided. The method may comprise steps of providing each of the features disclosed and / or configuring or using the respective feature for its stated function.

Claims

CLAIMS:1 . A method of receiving synchronisation signal measurements in a cellular network, the method comprising: receiving, from a user equipment, UE, one or more measurement report messages comprising a first measurement report entry relating to a first synchronisation signal of a first potential target cell, wherein the first measurement report entry comprises a cell identifier of the first potential target cell, wherein the one or more measurement report messages further comprise a second measurement report entry relating to a second synchronisation signal of the first potential target cell, wherein the second measurement report entry comprises the cell identifier of the first potential target cell; identifying that the one or more measurement report messages comprises two measurement report entries that each comprise the same cell identifier, and determining whether to raise an alarm and / or increase a counter in response; and determining that the two measurement report entries relate to the same cell and suppressing the alarm and / or counter increase.

2. The method of claim 1 , further comprising: receiving one or more further measurement report messages; identifying that the one or more further measurement report messages comprise two measurement report entries that each comprise the same cell identifier, and determining whether to raise an alarm and / or increase a counter in response; and determining that the two measurement report entries of the one or more further measurement report messages relate to different cells and raising an alarm and / or increasing a counter.

3. The method of claim 1 or claim 2, further comprising: communicating, to the UE, configuration data that causes the UE to measure the first synchronisation signal of the first potential target cell and the second synchronisation signal of the first potential target cell.

4. The method of claim 3, wherein the configuration data comprises SS / PBCH Block Measurement Timing Configuration, SMTC.

5. The method of claim 3 or claim 4, wherein the configuration data comprises one or more of the following parameters: an absolute frequency of the first synchronisation signal; and a periodicity of the first synchronisation signal.

6. The method of any preceding claim, further comprising: communicating, from the first potential target cell to a serving cell of the UE, an indication that the first potential target cell is periodically transmitting the second synchronisation signal.

7. The method of any preceding claim, wherein each of the two measurement report entries further comprise a signal strength measurement relating to the respective synchronisation signal.

8. The method of any preceding claim, wherein the measurement report entries comprise radio resource management, RRM, measurements.

9. The method of any preceding claim, wherein each of the first synchronisation signal and the second synchronisation signal is a synchronisation signal block, SSB, comprising one or more of: a primary synchronisation signal, PSS; a secondary synchronisation signal, SSS; a physical broadcast channel, PBCH; and a physical broadcast channel demodulation reference signal, PBCH DMRS.

10. The method of claim 9, wherein for each of the first synchronisation signal and the second synchronisation signal, the PBCH comprises a master information block, MIB.11 . The method of any preceding claim, wherein: the first synchronisation signal comprises data to enable a UE to obtain a first system information block, SIB1 ; and the second synchronisation signal is not used to obtain SIB1.

12. The method of any preceding claim, wherein:the first synchronisation signal is associated with a Remaining Minimum System Information, RMSI, block; and the second synchronisation signal is not associated with an independent RMSI block.

13. The method of any preceding claim, wherein: the first synchronisation signal is a cell-defining synchronisation signal block, CD-SSB; and the second synchronisation signal is a non-cell-defining synchronisation signal block, NCD- SSB.

14. The method of any preceding claim, wherein each of the first synchronisation signal and the second synchronisation signal comprise a plurality of parameters.

15. The method of claim 14, wherein the second synchronisation signal comprises parameters that are different to the parameters of the first synchronisation signal.

16. The method of claim 14 or claim 15, wherein each of the first synchronisation signal and the second synchronisation signal comprise a plurality of information elements, wherein each plurality of information elements comprises the respective plurality of parameters.

17. The method of claim 16, wherein an information element of the second synchronisation signal comprises one or more of the following parameters: an absolute frequency of the second synchronisation signal; a periodicity of the second synchronisation signal; and a time offset of the second synchronisation signal relative to the first synchronisation signal.

18. The method of any preceding claim, wherein a periodicity of the second synchronisation signal is different to a periodicity of the first synchronisation signal.

19. A network entity configured to perform the method of any preceding claim.

20. A computer program comprising instructions that, when executed on a processor, cause the processor to perform the method of any of claims 1 to 18.

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