Sidelink communications

Abstract

A method, apparatus and computer program is described comprising: obtaining sidelink information relating to sidelink communications of an LTE sidelink module, said sidelink information including side

Description

Field The present specification relates to sidelink communications. In particular, the specification relates to LTE and New Radio sidelink communications. Background Sidelinks can be provided in mobile communication systems to enable direct communications between user equipment (UEs). For example, sidelink communication can be used in vehicle-to-vehicle (V2V) and vehicle-to-eveiything (V2X) communication systems, and in many other communication systems (such as between smartphones or other user devices). There remains a need for further developments in this field. Summary In a first aspect, this specification describes an apparatus comprising: means for obtaining sidelink information relating to sidelink communications of an LTE sidelink module (such as an LTE sidelink UE or some other user device, such as a smartphone), said sidelink information including sidelink signal strength measurements for monitored LTE subchannels; means for altering, reducing or removing said signal strength measurements for LTE subchannels which do not overlap in the frequency domain with any subchannels of a NR sidelink module; and means for altering, reducing or removing said signal strength measurements from LTE subchannels that are determined to be in use by the NR sidelink module. The said sidelink signal strength measurements may be Received Signal Strength Indicator (RSSI) measurements. The apparatus maybe (or may form part of) said NR sidelink module. Alternatively, the apparatus may include the LTE sidelink module and the NR sidelink module. Some example embodiments further comprise means for determining subchannels that are in use by the NR sidelink module. Some example embodiments further comprise means for mapping NR sidelink slots to LTE sidelink subframes or slots. The means for obtaining sidelink signal strength measurements for monitored LTE subchannels may be configured to receive said sidelink signal strength measurements for monitored LTE subchannels from said LTE sidelink module (e.g. from an LTE sidelink UE). Some example embodiments further comprise means for obtaining said sidelink signal strength measurements for monitored LTE subchannels from NR signal strength measurements. Some example embodiments further comprise means for estimating an LTE signal strength measurement for each of a plurality of NR candidate resources. The means for estimating said LTE signal strength measurement for each of the plurality of NR candidate resources may comprise: means for obtaining, for each of the plurality of candidate NR resources, signal strength measurement estimates for LTE sub-channels that overlap with the respective candidate NR resource based, at least in part, on each of a plurality of periodicity options; and means for combining the signal strength measurement estimates into a single signal strength estimate for each candidate NR resource. The apparatus may further comprise means for selecting a NR resource from the plurality of candidate NR resources based, at least in part, on the single signal strength measurement estimates for the respective candidate NR resources. The said means may comprise at least one processor storing instructions that, when executed by the at least one processor, cause the performance of the apparatus. In a second aspect, this specification describes an apparatus comprising: means for obtaining, for each of a plurality of candidate NR resources, signal strength measurement estimates based, at least in part, on each of a plurality of periodicity options; and means for combining the signal strength measurement estimates into a single signal strength estimate for each candidate NR resource. Some example embodiments further comprise means for selecting a NR resource from the plurality of candidate NR resources based, at least in part, on the single signal strength measurement estimates for the respective candidate NR resources. The apparatus may be (or may form part of) said NR sidelink module. Alternatively, the apparatus may include the LTE sidelink module and the NR sidelink module. The said means may comprise at least one processor storing instructions that, when executed by the at least one processor, cause the performance of the apparatus. In a third aspect, this specification describes a method comprising: obtaining sidelink information relating to sidelink communications of an LTE sidelink module (such as an LTE sidelink UE or some other user device, such as a smartphone), said sidelink information including sidelink signal strength measurements for monitored LTE subchannels; altering, reducing or removing said signal strength measurements for LTE subchannels which do not overlap in the frequency domain with any subchannels of a NR sidelink module; and altering, reducing or removing said signal strength measurements from LTE subchannels that are determined to be in use by the NR sidelink module. The said sidelink signal strength measurements may be Received Signal Strength Indicator (RSSI) measurements. The method may further comprise determining subchannels that are in use by the NR sidelink module. The method may further comprise mapping NR sidelink slots to LTE sidelink subframes. Obtaining sidelink signal strength measurements for monitored LTE subchannels may comprise receiving said sidelink signal strength measurements for monitored LTE subchannels from said LTE sidelink module (e.g. from an LTE sidelink UE). The method may further comprise obtaining said sidelink signal strength measurements for monitored LTE subchannels from NR signal strength measurements. The method may further comprise estimating an LTE signal strength measurement for each of a plurality of NR candidate resources. Estimating said LTE signal strength measurement for each of the plurality of NR candidate resources may comprise: obtaining, for each of the plurality of candidate NR resources, signal strength measurement estimates for LTE sub-channels that overlap with the respective candidate NR resource based, at least in part, on each of a plurality of periodicity options; and combining the signal strength measurement estimates into a single signal strength estimate for each candidate NR resource. The method may further comprise selecting a NR resource from the plurality of candidate NR resources based, at least in part, on the single signal strength measurement estimates for the respective candidate NR resources. In a fourth aspect, this specification describes a method comprising: obtaining, for each of a plurality of candidate NR resources, signal strength measurement estimates based, at least in part, on each of a plurality of periodicity options; and combining the signal strength measurement estimates into a single signal strength estimate for each candidate NR resource. The method may further comprise selecting a NR resource from the plurality of candidate NR resources based, at least in part, on the single signal strength measurement estimates for the respective candidate NR resources. In a fifth aspect, this specification describes computer-readable instructions which, when executed by a computing apparatus, cause the computing apparatus to perform (at least) any method as described herein (including the methods of the third and fourth aspects described above). In a sixth aspect, this specification describes a computer-readable medium (such as a non-transitory computer-readable medium) comprising program instructions stored thereon for performing (at least) any method as described herein (including the methods of the third and fourth aspects described above). In a seventh aspect, this specification describes an apparatus comprising: at least one processor; and at least one memory including computer program code which, when executed by the at least one processor, causes the apparatus to perform (at least) any method as described herein (including the methods of the third and fourth aspects described above). In an eighth aspect, this specification describes a computer program comprising instructions which, when executed by an apparatus, cause the apparatus to: obtain sidelink information relating to sidelink communications of an LTE sidelink module, said sidelink information including sidelink signal strength measurements for monitored LTE subchannels; alter, reduce or remove said signal strength measurements for LTE subchannels which do not overlap in the frequency domain with any subchannels of a NR sidelink module; and alter, reduce or remove said signal strength measurements from LTE subchannels that are determined to be in use by the NR sidelink module. In a ninth aspect, this specification describes a computer program comprising instructions which, when executed by an apparatus, cause the apparatus to: obtain, for each of a plurality of candidate NR resources, signal strength measurement estimates based, at least in part, on each of a plurality of periodicity options; and combine the signal strength measurement estimates into a single signal strength estimate for each candidate NR resource. In a tenth aspect, this specification describes: a receiver (or some other means) for obtaining sidelink information relating to sidelink communications of an LTE sidelink module, said sidelink information including sidelink signal strength measurements for monitored LTE subchannels; a control module (or some other means) for altering, reducing or removing said signal strength measurements for LTE subchannels which do not overlap in the frequency domain with any subchannels of a NR sidelink module; and a / the control module (or some other means) for altering, reducing or removing said signal strength measurements from LTE subchannels that are determined to be in use by the NR sidelink module. In an eleventh aspect, this specification describes: a receiver (or some other means) for obtaining, for each of a plurality of candidate NR resources, signal strength measurement estimates based, at least in part, on each of a plurality of periodicity options; and a processor (or some other means) for combining the signal strength measurement estimates into a single signal strength estimate for each candidate NR resource. Brief description of the drawings Example embodiments will now be described, by way of example only, with reference to the following schematic drawings, in which: FIG. 1 is a block diagram of an example sidelink communication system; FIG. 2 is a block diagram of an example LTE sidelink communication system; FIG. 3 is a block diagram of an example NR sidelink communication system; FIG. 4 shows example NR sidelink slot structures; FIG. 5 is a block diagram of device in accordance with an example embodiment; FIG. 6 is a flow chart showing an algorithm in accordance with an example embodiment; FIG. 7 shows a message flow sequence in accordance with an example embodiment; FIG. 8 is a block diagram of system in accordance with an example embodiment; FIG. 9 is a flow chart showing an algorithm in accordance with an example embodiment; FIG. io is a flow chart showing an algorithm in accordance with an example embodiment; FIG. ii shows a message flow sequence in accordance with an example embodiment; FIG. 12 is a block diagram demonstrating a mapping in accordance with an example embodiment; FIG. 13 is a block diagram demonstrating features of an example embodiment; FIG. 14 is a block diagram demonstrating features of an example embodiment; FIG. 15 is a schematic diagram of components of one or more of the example embodiments described previously; and FIG. 16 shows tangible media for storing computer-readable code which when run by a computer may perform methods according to example embodiments described herein. Detailed description The scope of protection sought for various embodiments of the disclosure is set out by the independent claims. The embodiments and features, if any, described in the specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the disclosure. In the description and drawings, like reference numerals refer to like elements throughout. FIG. 1 is a block diagram of an example sidelink communication system, indicated generally by the reference numeral 10. The system 10 comprises a first user device 12, a second user device 14 and a network node 16 (such as a base station). In addition to being able to communicate with each other via the network node 16, the two user devices may be able communication directly, using sidelink (SL) technology. By way of example, sidelink communication can be used in vehicle-to-vehicle (V2V) and vehicle-to-everything (V2X) communication, although the principles described herein are not restricted to V2X communications.. -J- FIG. 2 is a block diagram of an example LTE (Long-Term Evolution) sidelink communication system, indicated generally by the reference numeral 20. The system 20 comprises a first (transmitting) vehicle 22, a second (receiving) vehicle 24 and a base station 26. The system 20 is an example implementation of the system 10 described above. LTE sidelink technologies (such as LTE-V2X) have been developed during 3GPP Rel-14 and Rel-15 to facilitate direct / sidelink communication between a vehicle (such as the transmitting vehicle 22 in the system 20) and other nearby vehicles (such as the receiving vehicle 24 in the system 20). In LTE-V2X, two resource allocation modes have been specified, denoted as LTE SL mode 3 and LTE SL mode 4. LTE-V2X uses SC-FDMA (Single-Carrier Frequency-Division Multiple Access) and supports 10 MHz and 20 MHz channels. The channel is divided into 180 kHz Resource Blocks (RBs) that correspond to 12 subcarriers of 15 kHz each. In the time domain, the channel is organized into 1 ms subframes. Each subframe has 14 OFDM symbols with normal cyclic prefix. Nine of these symbols are used to transmit data and four of them (3rd, 6th, 9th, and 12th) are used to transmit demodulation reference signals (DMRSs) for channel estimation and combating the Doppler effect at high speeds. The last symbol is used as a guard symbol for timing adjustments and for allowing vehicles to switch between transmission and reception across subframes. In LTE-V2X, resource blocks (RBs) are grouped into sub-channels. A sub-channel can include RBs only within the same subframe. The number of RBs per sub-channel can vary and may be (pre-)configured. Sub-channels are used to transmit data and control information. The data is organized in Transport Blocks (TBs) that are carried in the Physical Sidelink Shared Channel (PSSCH). ATB contains a full message (e.g., a CAM or a BSM). A TB can occupy one or several subchannels depending on the size of the packet, the number of RBs per sub-channel, and the utilized Modulation and Coding Scheme (MCS). TBs can be transmitted, for example, using QPSK, 16-QAM or 64QAM modulations and turbo coding. Each transport block (TB) has an associated Sidelink Control Information (SCI) message that is carried in the Physical Sidelink Control Channel (PSCCH). It is also referred to as Scheduling Assignment (SA). An SCI occupies two resource blocks (RBs) and includes information such as: an indication of the RBs occupied by the associated TB; the MCS used for the TB; the priority of the message that is being transmitted; an indication of whether it is a first transmission or a blind retransmission of the TB; and the resource reservation interval. A blind retransmission refers to a scheduled retransmission or repetition of the TB (i.e., not based on feedback from the receiver). The resource reservation interval specifies when the vehicle will utilize the reserved sub-channel(s) to transmit its next TB. The SCI includes critical information for the correct reception of the TB. A TB cannot be decoded properly if the associated SCI is not received correctly. A TB and its associated SCI must be transmitted always in the same subframe. FIG. 3 is a block diagram of an example NR (New Radio) sidelink communication system, indicated generally by the reference numeral 30. The system 30 comprises a first (transmitting) vehicle 32, a second (receiving) vehicle 34 and a base station 36. The system 30 is an example implementation of the system 10 described above and is similar to the LTE system 20 described above. New Radio (NR) sidelink technologies (such as NR-V2X) have been developed during 3GPP Rel-16 to facilitate direct / sidelink communication between a vehicle (such as the transmitting vehicle 32 in the system 30) vehicles and other nearby vehicles (such as the receiving vehicle 34 in the system 30). In NR-V2X, two resource allocation modes have been specified, and a particular SL transmitter (TX) UE 32 is configured with one of these nodes to perform its NR SL transmissions. In NR SL mode 1, a sidelink transmission resource is assigned (scheduled) by the network (NW) to the SL TX UE (e.g. the transmitting vehicle 32 in the system 30), while a SL TX UE in NR SL mode 2 autonomously selects its SL transmission resources. The configuration of the resources in the sidelink resource pool defines the minimum information required for a RX UE to be able to decode a transmission, which includes the number of sub-channels, the number of PRBs per sub-channels, the number of symbols in the PSCCH, which slots have a PSFCH and other configuration aspects not relevant to the present discussion. However, the details of the actual sidelink transmission (i.e., the payload) is provided in the PSCCH (ist-stage SCI) for each individual transmission, which includes: the time and frequency resources, the DMRS configuration of the PSSCH, the MCS, PSFCH, among other parameters. It should be noted that whilst FIGS. 2 and 3 shows V2X arrangements, the principles described herein are not restricted to V2X applications. For example, the principles described herein may be implemented in systems providing sidelink communications between different entities, such as smartphone or some other user device (such as from one smartphone to another, between a vehicle and a smartphone or between different combinations of smartphones, other user devices, vehicles, and other entities). FIG. 4 shows example NR sidelink slot structures. Specifically, a first slot 42 is shown with PSCCH / PSSCH and a second slot 44 is shown with PSCCH / PSSCH where the last symbols are used for PSFCH. The configuration of the PSCCH (e.g., DMRS, MCS, number of symbols used etc.) is part of resource pool configuration. The configuration of PSFCH, PSCCH and PSSCH is also provided in the resource pool configuration. The configuration of the PSSCH includes the number of symbols used, the DMRS pattern and the MCS list. A PSSCH transmission is accompanied by a PSCCH transmission which includes the ist-stage SCI which is the payload sent within the PSCCH and provides the information needed by the receiver to decode the PSSCH, such as the MCS and the physical time and frequency resources as well as whether HARQ feedback is expected afterwards. Both LTE and NR have a procedure for selecting a candidate resource based on information acquired in the sensing window. These procedures have many similarities, but they are not the same. To better understand the similarities and differences, the resource selection procedure for Mode 2 (NR) and Mode 4 (LTE) is discussed further below. In step 1, an empty candidate resource set is initialised at both NR (Sa) and LTE (Sa and Sb). This step corresponds to the Step 4 in TS 38.214 section 8.1.4. In step 2, possible reservations in non-monitored slots / subframes are excluded. This step is in principle similar for both procedures. At a high level, the step involves any candidate resources which could have been selected with a reservation in a slot or subframe that was not monitored (which includes all feasible transmission periodicities) are removed. This step is only present in NR, where NR can re-add the excluded resources from Step i if there are not sufficient resources left in the candidate resource set. In step 3, all reserved resources that overlaps a candidate resource are excluded, based on any detected Sidelink Control Information (SCI) and its content. This step is similar for both LTE and NR. An RSRP threshold may be used to exclude only if the Reference Signal Received Power (RSRP) from the resource where the SCI was received is above this threshold. Step 4 checks the number of remaining candidate resources and, if necessary, increases the RSRP exclusion threshold in step 3 (and then re-runs step 3). Step 5 is only implemented in LTE. In this step, the LTE module calculates an RSSI value per candidate resource, based on the RSSI measurements in sensed resources that would map to the candidate resource with the desired transmission periodicity. The LTE SL module will then fill a second candidate resource set, from lowest RSSI value, until 20% of the possible candidate resources in the selection window is reached. In this way, the LTE SL module minimizes the interference level with the selected candidate resources to other LTE SL transmissions which has not been detected and taken into account in step 3. FIG. 5 is a block diagram of device 50, in accordance with an example embodiment. The device includes an LTE SL module 52 and a NR SL module 54. Thus, the device 50 is capable of supporting both LTE and NR sidelink communications and may be referred to as a Type-A device. FIG. 6 is a flow chart showing an algorithm, indicated generally by the reference numeral 60, in accordance with an example embodiment. The algorithm 60 may be implemented by the device 50. The algorithm 6o starts at operation 62, where the NR SL module 54 receives LTE sidelink information from the LTE module 52. At operation 64, the NR SL module 54 uses the LTE sidelink information in an enhanced resource selection procedure. The LTE sidelink information may include one or more of: decoded LTE sidelink control information (SCO) filed, non-monitored slots and signal strength (e.g. Received Signal Strength Indicator (RSSI)) measurements. The sidelink information may identify LTE subframes that are not monitored. The operation 64 of the algorithm 60 is not trivial for a number of reasons. For example, as noted above, the are some differences between LTE and NR resource selection procedures, including: • Some existing NR resource selection processes do not use signal strength measurements for candidate resource selection. This contrasts with LTE, which uses RSSI measurements for ranking candidate resources. The underlying assumption is that LTE, by doing this sorting, may identify a transmission pattern for which an associated SCI was not decoded. • NR and LTE sidelink communications can have different subcarrier spacing. These differences mean that there is no straightforward mechanism to use signal strength measurements such as RSSI in NR SL candidate selection. If the LTE module 52 using signal strength measurement during resource selection, but the NR SL module 54 does not, there is a risk that the NR SL module 54, when selecting resources in a RP which overlaps the LTE RP, may select resources that would cause more interference, than an LTE module would. FIG. 7 shows a message flow sequence, indicated generally by the reference numeral 70, in accordance with an example embodiment. The message flow sequence demonstrates an algorithm that may be implemented by the LTE SL module 52 and the NR SL module 54 described above. The message flow sequence 70 starts with message 72, in which LTE sidelink data is sent from the LTE SL module 52 to the NR SL module 54. The receipt of the LTE-SL data is an example of the operation 62 of the algorithm 60 described above. On receipt of the LTE-SL data, the NR SL module 54 performs an RSSI Cleanup procedure (operation 74) and an RSSI calculation procedure (operation 76). The RSSI cleanup and calculation procedures form part of an example implementation of the operation 64 of the algorithm 60 described above. In other words, NR-SL resource(s) may be selected based on RSSI data (or some other signal strength data) that has been processed in operations 74 and 76. FIG. 8 is a block diagram of system 80, in accordance with an example embodiment. The system 80 may be used in an example implementation of the algorithm 70 described above. The system comprises an LTE module 82, a NR module 83, an RSSI Cleanup Module 84 and an RSSI Calculation module 85. The LTE module 82 may be the LTE SL module 52 described above. Similarly, the NR module 83 may be the NR SL module 54 described above. The RSSI Cleanup Module 84 and an RSSI Calculation module 85 maybe separate to the NR module 83. Alternatively, the NR module 83, RSSI Cleanup Module 84 and an RSSI Calculation module 85 may form part of a single NR module, as indicated by the dashed line 86 in FIG. 8. The LTE module 82 provides information to the NR module 83. This information could be delivered in a periodic manner (e.g. every radio frame or every subframe) or triggered by an event (e.g. LTE decoding an SCI or a request from the NR module). The information provided to the NR module 83 includes sidelink information relating to sidelink communications of the LTE sidelink module 82. The sidelink information includes sidelink signal strength measurements (e.g. RSSI) for monitored LTE subchannels. The RSSI Cleanup module 84 is provided to alter, reduce or remove some signal strength measurements from the sidelink signal strength measurements for the monitored LTE subchannels. As discussed in further detail below, the RSSI Cleanup module 84 may provide signal strength measurements (e.g. RRSI) per LTE subchannel to the RSSI Calculation module 85. The RSSI Calculation module 85 seeks to generate signal strength estimates per candidate NR resource. These estimates can then be used by the NR module 83 when selecting a NR resource from the candidate resource set. FIG. 9 is a flow chart showing an algorithm, indicated generally by the reference numeral 90, in accordance with an example embodiment. The algorithm 90 maybe implemented by the RSSI Cleanup module 84 described above (and may implement the operation 74 of the message flow sequence 70). The algorithm 90 starts at operation 92, where sidelink information is obtained relating to sidelink communications of an LTE sidelink module. The sidelink information may include sidelink signal strength measurements (e.g. RSSI) for monitored LTE subchannels. The sidelink information may be obtained from the LTE module (e.g. the LTE module 82) and may be obtained periodically. The sidelink information may identify LTE subframes that are not monitored. At operation 94, signal strength measurements (e.g. RSSI) are altered, reduced or removed for LTE subchannels which do not overlap in the frequency domain with any subchannels of a NR sidelink module. Implementing the operation 94 may include mapping NR sidelink slots to LTE subframes. At operation 96, signal strength measurements (e.g. RSSI) are altered, reduced or received from LTE subchannels that are determined to be in use by the NR sidelink module. Implementing the operation 96 may require a module for determining subchannels that are in use by the NR sidelink module. Of course, the operations 94 and 96 may be performed at the same time or in a different order. FIG. 10 is a flow chart showing an algorithm, indicated generally by the reference numeral 100, in accordance with an example embodiment. The algorithm 100 may be implemented by the RSSI Calculation module 85 described above (and may implement the operation 76 of the message flow sequence 70). The algorithm 100 starts at operation 102, where for each of a plurality of candidate NR resources, signal strength measurement estimates (e.g. RSSI) are obtained based, at least in part, on each of a plurality of periodicity options. As discussed further below, signal strength measurements may be received at the NR SL module from the LTE sidelink module for monitored LTE subchannels. Alternatively, the sidelink signal strength measurements for monitored LTE subchannels may be based on NR signal strength measurements. At operation 104, the signal strength measurement estimates are combined into a single signal strength estimate for each candidate NR resource. The combination could take many forms, such as a taking an average, or selecting the highest value. At optional operation 106, a NR resource maybe selected from the plurality of candidate NR resources based, at least in part, on the single signal strength measurement estimates for the respective candidate NR resources generated in the operation 104. For example, the NR resource associated with the lowest signal strength measurement estimate may be selected. In the algorithms described above (including the algorithms 90 and 100), RSSI is described by way of example only. Other signal strength measures (such as RSRP) could be used in addition to, or instead of, RSSI. FIG. 11 shows a message flow sequence, indicated generally by the reference numeral 110, in accordance with an example embodiment. The message flow sequence 110 provides further details of an example implementation of the message flow sequence 70 and the algorithms 90 and 100 described above. The message flow sequence may be implemented by the system 80 described above. The message flow sequence 110 shows messages between an LTE sidelink module 112 (which may be the LTE SL module 52 or the LTE module 82 described above) and a NR sidelink module 114 (which may be the NR SL module 54 or the NR module 83 described above). Moreover, the LTE sidelink module 112 may, for example, be one of the UEs 12, 22 or 32 described above and the NR sidelink module 114 may be one of the UEs 14, 25 or 34. One or more of the LTE slidelink module 112 and the NR sidelink module 114 may be implemented by a smartphone. The sequence 110 includes thirteen steps, which are discussed in detail below. In step 1, the LTE module 112 provides information to the NR module 114. This could be periodic (e.g. every radio frame or every subframe) or triggered by an event (e.g. LTE decoding an SCI or a request from the NR module). In step 2, the NR module 114 executes a resource exclusion procedure which takes into account the NR and LTE decoded SCI and non-monitored slots. In step 3, the RSSI measurements (or other signal strength measurements) which may be sent from the LTE module 112 to the NR module 114. Alternatively, measurements may be made by the NR module 114. If signal strength measurements are obtained by the NR module 114, the NR module may measure RSSI (or some other signal strength indicator) over at least the NR RP, but might also restrict measurement to subchannels where the NR and LTE RP overlap. The RSSI cleanup procedure starts at step 4. In step 4, the NR module 114 creates a map of NR slots to LTE subframes. This may take into account the sub-carrier spacing of NR and LTE space respectively as this affects the logical subframes and slot offset. The mapping may also take into account the location of the reserved slots, as these are not a part of the RP, and is used for transmission of synchronization signals. In step 5, the NR module 114 removes signal strength (e.g. RSSI) measurements from subchannels which do not overlap both NR and LTE resource pool (RP), including those that are partially overlapping (in frequency). In one implementation of step 5, the NR module 114 may determine subchannel overlap based on the RP configurations. Note that by “removing” an RSSI measurement from a subchannel, we mean that the subchannel (and measurement) is not used in the RSSI calculation procedure in step 8 onwards. In an alternative implementation, the NR module does not remove an existing NR RSSI from the resource, but either keeps it (if one exists) or sets the RSSI value to a low value such as minDtxRSSI (or otherwise alters or reduces the RSSI measurement). This means that an RSSI value will be associated to this candidate resources that is not overlapping (or partially overlapping) the LTE RP. In step 6, the NR module 114 removes RSSI measurements from subchannels that it estimates were used by NR. The intention is to detect underlying LTE transmission patterns that would be impacted by NR transmission (rather than to detect underlying NR transmission patterns). The detection of whether NR has used resources overlapping the LTE subframes in the RP may be implemented in at least two different ways: • In the event that the NR module 114 has received an SCI which indicates a reservation for a subchannel in the slot (initial or retransmission or periodic transmission), the NR module can remove the signal strength (e.g. RSSI) measurements of the resources indicated. • If the NR module 114 uses a higher SCS than LTE, the NR module may detect if only a part of the slots that overlap the LTE subframe has a subchannel with an RSSI value above a threshold minTxRSSL This will likely mean that an NR transmission had taken place, and if there are “non-used” NR slots in the time duration of the LTE subframe, the subframe was not used by LTE. As the main objective is to calculate an LTE RSSI for each NR resource, the NR module can remove the RSSI value for the sub-channels that overlaps the LTE subframe, if the RSSI is above the threshold minTxRSSI and it is detected that it was only NR using resources overlapping this LTE subframe. In an alternative implementation, the NR module will not remove an existing NR RSSI from the resource, but either keep it (if one exists) or set the RSSI value to a low value such as minDtxRSSI (which may be preferable as it is only introducing a minimum of NR RSSI noise to the LTE related RSSI calculation), or otherwise alters or reduces the RSSI measurement. This can be particularly beneficial in the case where NR module selects the NR candidate resource with an RSSI value, and NR is not always applying candidate resources that does not overlap all of the LTE subframe. Note again that by “removing” an RSSI measurement from a subchannel, we mean that the subchannel (and measurement) is not used in the RSSI calculation procedure in step 8 onwards. In step 7, RSSI values are assigned from NR RSSI measurements if the RSSI measurements are acquired by the NR module. All LTE subchannels that overlap an NR subchannel with an RSSI measurement, will be associated with the same RSSI value. The LTE RSSI calculation procedure discussed in detail above, starts at step 8. In step 8, for each feasible LTE periodicity (e.g. in LTE SL Rel-17 that is X ms (X 6 [1; 10]ioos, 50ms and 20ms)) select all subframes that can map to the candidate set, based on the periodicity and FRIV and TRIV feasible values from LTE SCI format la. In step 9, a periodicityRSSI value is calculated based on a function of all RSSI for subchannels within the selected subframes. For RSSI measurements from NR, an average of RSSI measurements from the subchannels in all slots that overlap the subframe may be determined. The simplest function may be a linear average. Another function is to calculate an average of the highest RSSI in a subchannel per selected subframe. Other functions are not precluded (and will be apparent to the skilled person). In step 10, a combinedRSSI value is calculated with some function with the set of periodicityRSSI as input. The simplest function is a linear average. Another function is to select the highest RSSI of the periodicityRSSI with the rationale that if any of the feasible periodicities shows high RSSI, there could be an undetected LTE transmission pattern that maps to the candidate resource and hence it should be accounted for, and that this pattern might partly vanish for the other periodicities. Once again, other functions are not precluded (and will be apparent to the skilled person). In step 11, a single NR RSSI value is created based on the set of combinedRSSI values calculated from each LTE candidate resource equivalent (if there are more than one). If the RSSI measurements is delivered by the NR module, only one is typically needed. In step 12, a candidate resource set Sb is generated (or the candidate resource set Sa is sorted) using the calculated RSSI. This new / sorted resource set is parsed to higher layers. The usage of a candidate resource set Sb can be similar as doneby the LTE module and is described in TS 36.213 section 14.1.1.6. In an example embodiment, the new / sorted resource set is parsed along with the RSSI values (lower is better). In this case, the NR higher layer can do a biased / weighted selection. In step 13, the NR module 114 selects a resource from the candidate resource set. In an embodiment, the candidate resource set resembles an LTE candidate resource set (with RSSI ranking) and the set Sb (or a subset of Sa) is then used to exclude candidate resources from the NR candidate resource set (generated in a legacy (e.g. Rel-17) manner). This can be done at either the MAC or PHY layer. As noted above, many variants of the message sequence 110 are possible. For example, although references are made to RSSI, other signal strength indications could be used. FIG. 12 is a block diagram, indicated generally by the reference numeral 120, demonstrating a mapping in accordance with an example embodiment. The block diagram 120 demonstrates aspects of the mapping of NR sidelink slots to LTE sidelink slots in an example implementation of the step 4 of the message sequence 110. In step 4, a means for mapping the NR sidelink slots to LTE sidelink slots first creates a timeline of the physical locations of NR slots and LTE subframes in the resource pool (RP) configuration. This is shown in the block diagram 120. Next, the NR module creates a table with the mapping between the NR slots and the LTE subsframes. Based on the mapping shown in FIG. 12, that table may be as follows: NR LTE 0 0 1 0 2 1 3 1 4 2 5 3 6 3 7 4 8 4 9 - 10 - 11 5 12 5 13 6 14 6 Note that NR slots 9 and 10 does not map to an LTE subframe, since the relevant LTE subframe is reserved. FIG. 13 is a block diagram, indicated generally by the reference numeral 130, demonstrating features of an example embodiment. The block diagram 130 demonstrates aspect of an example RSSI cleanup arrangement (showing steps 5-7 of the message sequence 110). In step 5, RSSI measurements for NR subchannels that do not overlap with LTE subchannels are removed (or otherwise altered or reduced). In step 6, an RSSI measurement is removed (or otherwise altered or reduced) as it relates to an NR transmission (and is therefore not relevant to LTE SL transmissions). FIG. 14 is a block diagram, indicated generally by the reference numeral 140, demonstrating features of an example embodiment. The block diagram 140 demonstrates aspects of an example RSSI calculation procedure (showing steps 8-10 of the message sequence 110). In step 8, all subchannels that can be relevant to a candidate resource equivalent are selected. In step 9, RSSI measurements are obtained for all relevant periodicities. In step 10, a combined RSSI measurement is determined. For completeness, FIG. 15 is a schematic diagram of components of one or more of the example embodiments described previously, which hereafter are referred to generically as a processing system 300. The processing system 300 may, for example, be (or may include) the apparatus referred to in the claims below. The processing system 300 may have a processor 302, a memoiy 304 coupled to the processor and comprised of a random access memory (RAM) 314 and a read only memory (ROM) 312, and, optionally, a user input 310 and a display 318. The processing system 300 may comprise one or more network / apparatus interfaces 308 for connection to a network / apparatus, e.g. a modem which maybe wired or wireless. The network / apparatus interface 308 may also operate as a connection to other apparatus such as device / apparatus which is not network side apparatus. Thus, direct connection between devices / apparatus without network participation is possible. The processor 302 is connected to each of the other components in order to control operation thereof. The memory 304 may comprise a non-volatile memory, such as a hard disk drive (HDD) or a solid state drive (SSD). The ROM 312 of the memory 304 stores, amongst other things, an operating system 315 and may store software applications 316. The RAM 314 of the memory 304 is used by the processor 302 for the temporary storage of data. The operating system 315 may contain code which, when executed by the processor implements aspects of the methods, algorithms and sequences 60, 70,90, too and 110 described above. Note that in the case of small device / apparatus the memory can be most suitable for small size usage i.e. not always a hard disk drive (HDD) or a solid state drive (SSD) is used. The processor 302 may take any suitable form. For instance, it may be a microcontroller, a plurality of microcontrollers, a processor, or a plurality of processors. The processing system 300 may be a standalone computer, a server, a console, or a network thereof. The processing system 300 and needed structural parts may be all inside device / apparatus such as loT device / apparatus i.e. embedded to very small size. In some example embodiments, the processing system 300 may also be associated with external software applications. These may be applications stored on a remote server device / apparatus and may run partly or exclusively on the remote server device / apparatus. These applications maybe termed cloud-hosted applications. The processing system 300 maybe in communication with the remote server device / apparatus in order to utilize the software application stored there. FIG. 16 shows tangible media, specifically a removable memory unit 365, storing computer-readable code which when run by a computer may perform methods according to example embodiments described above. The removable memory unit 365 may be a memory stick, e.g. a USB memory stick, having internal memory 366 for storing the computer-readable code. The internal memory 366 may be accessed by a computer system via a connector 367. Other forms of tangible storage media may be used. Tangible media can be any device / apparatus capable of storing data / information which data / information can be exchanged between devices / apparatus / network. Embodiments of the present invention may be implemented in software, hardware, application logic or a combination of software, hardware and application logic. The software, application logic and / or hardware may reside on memory, or any computer media. In an example embodiment, the application logic, software or an instruction set is maintained on any one of various conventional computer-readable media. In the context of this document, a “memory” or “computer-readable medium” maybe any non-transitory media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. Reference to, where relevant, “computer-readable medium”, “computer program product”, “tangibly embodied computer program” etc., or a “processor” or “processing circuitry” etc. should be understood to encompass not only computers having differing architectures such as single / multi-processor architectures and sequencers / parallel architectures, but also specialised circuits such as field programmable gate arrays FPGA, application specify circuits ASIC, signal processing devices / apparatus and other devices / apparatus. References to computer program, instructions, code etc. should be understood to express software for a programmable processor firmware such as the programmable content of a hardware device / apparatus as instructions for a processor or configured or configuration settings for a fixed function device / apparatus, gate array, programmable logic device / apparatus, etc. If desired, the different functions discussed herein may be performed in a different order and / or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or may be combined. Similarly, it will also be appreciated that the flow diagrams and sequences of FIGS. 6, 7, 9,10 and 11 are examples only and that various operations depicted therein may be omitted, reordered and / or combined. It will be appreciated that the above-described example embodiments are purely illustrative and are not limiting on the scope of the invention. Other variations and modifications will be apparent to persons skilled in the art upon reading the present specification. Moreover, the disclosure of the present application should be understood to include any novel features or any novel combination of features either explicitly or implicitly disclosed herein or any generalization thereof and during the prosecution of the present application or of any application derived therefrom, new claims may be formulated to cover any such features and / or combination of such features. Although various aspects of the invention are set out in the independent claims, other aspects of the invention comprise other combinations of features from the described example embodiments and / or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims. It is also noted herein that while the above describes various examples, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims. For example, some embodiments may relate to sidelink communications to, or with, a UE which is a smartphone, or between UEs which are smartphones.

Claims

1. An apparatus comprising:means for obtaining sidelink information relating to sidelink communications of5 a Long Term Evolution (LTE) sidelink module, said sidelink information including sidelink signal strength measurements for monitored LTE subchannels;means for altering, reducing or removing said signal strength measurements for LTE subchannels which do not overlap in the frequency domain with any subchannels of a New Radio (NR) sidelink module; andio means for altering, reducing or removing said signal strength measurementsfrom LTE subchannels that are determined to be in use by the NR sidelink module.

2. An apparatus as claimed in claim 1, wherein said sidelink signal strength measurements are Received Signal Strength Indicator (RSSI) measurements.

153. An apparatus as claimed in claim 1 or claim 2, further comprising: means for determining subchannels that are in use by the NR sidelink module.

4. An apparatus as claimed in any one of the preceding claims, further comprising 20 means for mapping NR sidelink slots to LTE sidelink subframes.

5. An apparatus as claimed in any one of the preceding claims, wherein the means for obtaining sidelink signal strength measurements for monitored LTE subchannels is configured to receive said sidelink signal strength measurements for monitored LTE25 subchannels from said LTE sidelink module.

6. An apparatus as claimed in any one of claims 1 to 4, further comprising means for obtaining said sidelink signal strength measurements for monitored LTE subchannels from NR signal strength measurements.

307. An apparatus as claimed in any one of the preceding claims, further comprising: means for estimating an LTE signal strength measurement for each of aplurality of NR candidate resources.

8. An apparatus as claimed in claim 7, wherein the means for estimating said LTE signal strength measurement for each of the plurality of NR candidate resources comprises:means for obtaining, for each of the plurality of candidate NR resources, signal 5 strength measurement estimates for LTE sub-channels that overlap with the respective candidate NR resource based, at least in part, on each of a plurality of periodicity options; andmeans for combining the signal strength measurement estimates into a single signal strength estimate for each candidate NR resource.

109. An apparatus as claimed in claim 8, further comprising:means for selecting a NR resource from the plurality of candidate NR resources based, at least in part, on the single signal strength measurement estimates for the respective candidate NR resources.001510. An apparatus as claimed in any one of claims 1 to 9, wherein the apparatus is, or forms part of, said NR sidelink module.

11. An apparatus as claimed in any one of claims 1 to 9, wherein the apparatus20 includes the LTE sidelink module and the NR sidelink module.

12. An apparatus as claimed in any one of the preceding claims, in which the means comprise at least one processor storing instructions that, when executed by the at least one processor, cause the performance of the apparatus.2513. A method comprising:obtaining sidelink information relating to sidelink communications of an LTE sidelink module, said sidelink information including sidelink signal strength measurements for monitored LTE subchannels;30 altering, reducing or removing said signal strength measurements for LTEsubchannels which do not overlap in the frequency domain with any subchannels of a NR sidelink module; andaltering, reducing or removing said signal strength measurements from LTE subchannels that are determined to be in use by the NR sidelink module.3514- A method as claimed in claim 13, further comprising estimating an LTE signal strength measurement for each of a plurality of NR candidate resources.

15. A computer program comprising instructions which, when executed by an5 apparatus, cause the apparatus to:obtain sidelink information relating to sidelink communications of an LTE sidelink module, said sidelink information including sidelink signal strength measurements for monitored LTE subchannels;alter, reduce or remove said signal strength measurements for LTE subchannels10 which do not overlap in the frequency domain with any subchannels of a NR sidelink module; andalter, reduce or remove said signal strength measurements from LTE subchannels that are determined to be in use by the NR sidelink module.15co CM

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