Sidelink Positioning

TECHNOLOGICAL FIELD

Examples of the disclosure relate to sidelink positioning. Some relate to sidelink positioning using discontinuous reception (DRX).

BACKGROUND

Sidelink positioning enables terminal devices to perform positioning procedures with other terminal devices without a participation of a base station in the messages. In such procedures some terminal devices will act as anchor devices and some will act as target devices.

BRIEF SUMMARY

According to various, but not necessarily all, examples of the disclosure there may be provided a terminal device comprising means for: detecting a wake-up signal while in a discontinuous reception (DRX) off mode wherein the wake-up signal is transmitted from a further terminal device and comprises an indication of a DRX class of the further terminal device; and supporting positioning of the further terminal device based on the DRX class indicated in the wake-up signal.

The wake-up signal may comprise an indication of a sidelink positioning request

Supporting positioning of the further terminal device may comprise determining if the positioning request from the further terminal device is to be serviced by the terminal device, wherein the positioning request is associated with a sidelink signalling between the terminal device and the further terminal device.

The means may be for determining how a sidelink positioning request can be serviced. The means may be for controlling a DRX mode of the terminal device being on or off based on the determining if the sidelink positioning request can be serviced by the terminal device.

The means may be for switching the terminal device to DRX on mode if it is determined that the sidelink positioning request could be serviced by the terminal device.

The means may be for causing transmission of a message indicating that the sidelink positioning request can be accepted wherein the message comprises an indication of a DRX class of the terminal device.

The means may be for maintaining the terminal device in the DRX off mode if it is determined that the sidelink positioning request cannot be serviced by the terminal device.

The supporting of the positioning may be based on a DRX class hierarchy.

The hierarchy of DRX classes may be configured so that a terminal device can serve as anchor for further terminal devices of higher or equal classes.

The hierarchy of DRX classes may be configured such that higher DRX classes have longer sleep durations than lower DRX classes

The DRX class may have a predefined sleep cycle.

The DRX class may be specific to a type of terminal device.

The DRX class may have at least one of: a specific occasion for a wake-up signal, a specific signature for a wake-up signal.

The means may be for providing anchor capabilities.

According to various, but not necessarily all, examples of the disclosure there may be provided a method comprising: detecting a wake-up signal while in a discontinuous reception (DRX) off mode wherein the wake-up signal is transmitted from a further terminal device and comprises an indication of a DRX class of the further terminal device; and supporting positioning of the further terminal device based on the DRX class indicated in the wake-up signal.

According to various, but not necessarily all, examples of the disclosure there may be provided a computer program comprising instructions which, when executed by processor, cause a terminal device to perform at least: detecting a wake-up signal while in a discontinuous reception (DRX) off mode wherein the wake-up signal is transmitted from a further terminal device and comprises an indication of a DRX class of the further terminal device; and supporting positioning of the further terminal device based on the DRX class indicated in the wake-up signal.

According to various, but not necessarily all, examples of the disclosure there may be provided a terminal device comprising means for: causing transmission of a wake-up signal comprising an indication of a discontinuous reception (DRX) class of the terminal device to one or more candidate terminal devices; and collecting responses from candidate terminal devices having suitable DRX classes wherein the suitability of the DRX class is determined based on a DRX class hierarchy.

The wake-up signal may comprise an indication of a sidelink positioning request

The suitable DRX classes may comprise matching DRX classes.

The wake-up signal may be transmitted following a sidelink positioning request from an application.

The means may be for selecting one or more candidate terminal devices from the candidate terminal devices based, at least in part on DRX classes.

The wake-up signal may comprise a point to multipoint signal. According to various, but not necessarily all, examples of the disclosure there may be provided a method comprising: causing transmission of a wake-up signal comprising an indication of a discontinuous reception (DRX) class of the terminal device to one or more candidate terminal devices; and collecting responses from candidate terminal devices having suitable DRX classes wherein the suitability of the DRX class is determined based on a DRX class hierarchy.

According to various, but not necessarily all, examples of the disclosure there may be provided a computer program comprising instructions which, when executed by processor, cause a terminal device to perform at least: causing transmission of a wake-up signal comprising an indication of a discontinuous reception (DRX) class of the terminal device to one or more candidate terminal devices; and collecting responses from candidate terminal devices having suitable DRX classes wherein the suitability of the DRX class is determined based on a DRX class hierarchy.

While the above examples of the disclosure and optional features are described separately, it is to be understood that their provision in all possible combinations and permutations is contained within the disclosure. It is to be understood that various examples of the disclosure can comprise any or all of the features described in respect of other examples of the disclosure, and vice versa. Also, it is to be appreciated that any one or more or all of the features, in any combination, may be implemented by/comprised in/performable by an apparatus, a method, and/or computer program instructions as desired, and as appropriate.

BRIEF DESCRIPTION

Some examples will now be described with reference to the accompanying drawings in which:

FIG. 1 shows an example network;

FIG. 2 shows sidelink positioning;

FIG. 3 shows sidelink positioning;

FIG. 4 shows an example method;

FIG. 5 shows another example method;

FIG. 6 show an example signal chart;

FIG. 7 shows an example method; FIG. 8 shows another example method; and

FIG. 9 shows an example controller.

The figures are not necessarily to scale. Certain features and views of the figures can be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Corresponding reference numerals are used in the figures to designate corresponding features. For clarity, all reference numerals are not necessarily displayed in all figures.

DEFINITIONS

AMF Access and Mobility Function

AoD Angle of Departure

AS Access stratum

DL Downlink

DRX Discontinuous Reception gNB NR base station

HARQ Hybrid Automatic Repeat Request

ID Identification

HOT Industrial Internet of Things

L2 Layer 2

LDPC Low Density Parity Check

LPHAP Low Power High Accuracy Positioning

NR New Radio

OFDM Orthogonal Frequency-Division Multiplexing

O-RAN Open-Radio Access Network

PSSCH Physical Sidelink Control Channel

QAM Quadrature Amplitude Modulation

QoS Quality of Service

RAN Radio Access Network

RedCap Reduced Capacity

RRC Radio Resource Control

RTT Round Trip Time

SCI Sidelink Control Information SL Sidelink

SL PRS Sidelink Positioning Reference Signal

UE User Equipment

UL Uplink

WUSP Wake-up signal for SL Positioning

DETAILED DESCRIPTION

Fig. 1 illustrates an example of a network 100 comprising a plurality of network entities including terminal devices 110, nodes 120 and one or more network devices 130. The terminal devices 1 10 and nodes 120 communicate with each other. The one or more network devices 130 communicate with the access nodes 120. In some examples the one or more network devices 130 communicate with the terminal devices 110.

The one or more network devices 130 can, in some examples, communicate with each other. The one or more nodes 120 can, in some examples, communicate with each other. The one or more terminal devices 110 can, in some examples, communicate with each other.

The network 100 can be a cellular network comprising a plurality of cells 122 each served by a node 120 or a plurality of nodes. In this example, the interface between the terminal devicel 10 and a node 120 defining a cell 122 is a wireless interface 124.

The node 120 comprises one or more cellular radio transceivers. The terminal device 110 comprises one or more cellular radio transceivers.

In the example illustrated the cellular network 100 is a third generation Partnership Project (3GPP) network in which the terminal device 1 10 are user equipment (UE) and the nodes 120 can be access nodes such as base stations.

The term ‘user equipment’ is used to designate mobile equipment comprising a smart card for authentication/encryption etc such as a Subscriber Identity Module (SIM). In some examples the term ‘user equipment’ is used to designate mobile equipment comprising circuitry embedded as part of the user equipment for authentication/ encryption such as software SIM. Some examples of a user equipment include a mobile station (mobile phone), smartphone, personal digital assistant (PDA), handset, device using a wireless modem (alarm or measurement device, etc.), laptop and/or touch screen computer, tablet, game console, notebook, smart glasses, and multimedia device.

The nodes 120 can be any suitable base station. A base station is an access node. It can be a network element responsible for radio transmission and reception in one or more cells to or from the terminal device 1 10. The node 120 can be a network element in a Radio Access Network (RAN), an Open-Radio Access Network (O-RAN) or any other suitable type of network.

The network device 130 can be part of a core network. The network device 130 can be configured to manage functions relating to connectivity for the terminal devices 1 10. For example, the network device 130 can be configured to manage functions such as connectivity, mobility, authentication, authorization and/or other suitable functions. In some examples the network device 130 can comprise an Access and Mobility management Function (AMF) and/or a User Plane Function (UPF) or any other suitable entities.

In the example of Fig. 1 the network device 130 is shown as a single entity. In some examples the network device 130 could be distributed across a plurality of entities. For example, the network devices 130 could be cloud based or distributed in any other suitable manner.

The network 100 can be a 4G or 5G network, for example. It can for example be a New Radio (NR) network that uses gNB or eNB as access nodes 120. New Radio is the 3GPP name for 5G technology. In such cases the node 120 can comprise gNodeBs (gNBs) 120 configured to provide user plane and control plane protocol terminations towards the UEs 1 10 and/or to perform any other suitable functions. The gNBs 120 are interconnected with each other by means of an X2/Xn interface 126. The gNBs are also connected by means of the N2 interface 128 to the network device 130. The gNBs can be connected to an AMF or any other suitable network device 130. Other types of networks and interfaces could be used in other examples. Other types of network could comprise next generation mobile and communication network, for example, a 6G network.

The network 100 can also support sidelink (SL) communications. The SL communications can comprise direct communication between two UEs 1 10 with or without the participation of a gNB 120 in the transmission and reception of signals. The SL could be used for sidelink positioning.

Fig. 2 shows an example of a SL positioning scenario. Fig, 2 shows a target UE 110 -1 , a first anchor UE 110-A, and a second anchor UE 1 10-A.

In this example the UEs 110 comprise vehicles or devices connected to vehicles. Other types of UEs 1 10 could be used in other examples.

In the SL positioning scenario a target UE 110-T is a UE 1 10 that is to be positioned and an anchor UE 1 10-A, is a UE 1 10 that can support the positioning of a target UE 1 10-T. The anchor UE 110-A can support the positioning of the target UE 1 10-T by transmitting and/or receiving refence signals over an SL interface. In the example of Fig. 2 one target UE 1 10- T and two anchor UEs 110-A, are shown. Other numbers of the respective UEs 1 10 could be used in other scenarios. The SL positioning is similar to Uplink/Downlink (UL/DL) positioning where gNBs 120 serving as anchors transmit/receive reference signals to/from target UEs 1 10 for positioning.

Any suitable procedure can be used to enable the SL positioning. In some examples a Sidelink Positioning Reference Signal (SL PRS) can be transmitted from the respective anchor UEs 110-A, and received by the target UE 1 10-T or there can be SL PRS exchange between the anchor UEs 1 10-A and the target UE 110-T during an SL session. The SL positioning can be enabled with precise latency and accuracy requirements of the corresponding SL session.

In the SL positioning scenario shown in Fig. 2 the target UE 1 10-T is performing an SL positioning session. In the SL positioning session the target UE 110-T exchanges SL-PRS with two anchor UEs 110-A in order to determine the location of the target UE 1 10-T. In this scenario the anchor UEs 1 10-A are said to provide SL-PRS assistance to the target UE 1 10-T.

To reduce power consumption Discontinuous Reception (DRX) can be used for a SL communication session. DRX cycles having DRX ON and DRX OFF configuration can be defined for the SL sessions. A UE 1 10 can turn off their radio components during a DRX OFF duration to save power. SL communication sessions can support timer-based SL DRX for unicast, groupcast and broadcast signals. Parameters such as on-duration, inactivity timer, retransmission-timer, cycle and any other suitable parameter can be defined for SL DRX to determine the SL active time for SL DRX.

During the SL active time for SL DRX, the receiving UE 1 10 performs monitoring of Sidelink Control Information (SCI) for data reception. For example, the receiving UE 1 10 monitors Physical Sidelink Control Channel (PSCCH) and second stage SCI on PSSCH. During the SL inactive time for SL DRX, the receiving UE 1 10 does not perform monitoring of SCI) for data reception. During the inactive time the receiving UE 110 can skip the monitoring of the PSCCH and second stage SCI on PSSCH for data reception.

In this scenario the SL active time of the receiving UE 1 10 comprises time in which any of its applicable on-duration timer(s), inactivity-timer(s) or retransmission timer(s) (for any of unicast, groupcast, or broadcast) are running.

In cases in which unicast is used, the receiving UE 1 10 is configured to maintain a set of SL DRX timers for pairs of source/destination identifications (L2 ID) and directions. The receiving UE 1 10 is configured to start or restart the timers with a value configured for the respective pair of source/destination L2 ID and direction. The DRX configuration between a pair of source/destination L2 IDs and a direction can be negotiated between the transmitting UE 110 and the receiving UE 1 10 in the Access Stratum (AS) layer.

For DRX configuration of the respective directions, where one UE 110 is transmitting UE 1 10 and the other is the receiving UE 1 10, an approach centred around the transmitting UE can be supported whereby:

• receiving UE 1 10 sends assistance information to the transmitting UE using a PC5-Radio Resource Control (RRC) message or any other suitable message

• the transmitting UE 110 sends the SL DRX configuration to be used by the receiving UE 1 10 to the receiving UE 1 10 using RRCReconfigurationSidelink

When the transmitting UE 110 is in-coverage and in RRC_CONNECTED mode, the transmitting UE 1 10 can report the received assistance information to its serving gNB 120 and can obtain the SL DRX configuration to send to the receiving UE 1 10 in dedicated RRC signalling from the network 100. When the receiving UE 110 is in-coverage and in RRC_CONNECTED mode, the receiving UE 110 can report the received SL DRX configuration to its serving gNB 120.

On-duration timer, inactivity-timer, Hybrid Automatic Repeat Request (HARQ) Round Trip Time (RTT) and retransmission timers are supported in unicast scenarios. SL HARQ RTT timer and SL retransmission timer are maintained for respective SL HARQ processes at the receiving UE 110. The transmitting UE 110 maintains a timer corresponding to the SL inactivity timer in the receiving UE 1 10 for respective pairs of source/destination L2 ID, and uses the timer as part of the criterion for determining the allowable transmission time for the receiving UE 1 10.

For groupcast/broadcast, SL DRX can be configured among multiple UEs 1 10 based on Quality of Service (QoS) profile and L2 ID. On-duration timer, inactivity-timer, HARQ RTT and retransmission timers are supported for groupcast scenarios. On-duration timer is supported for broadcast scenarios. SL HARQ RTT timer and SL retransmission timer are maintained for respective SL HARQ processes at the receiving UE 1 10. The transmitting UE 110 maintains a timer corresponding to the SL inactivity timer in the receiving UE 1 10 for respective pairs of source/destination L2 ID, and uses the timer as part of the criterion for determining the allowable time for to the receiving UE 110

An issue with SL DRX definition is that the broadcast SL DRX configuration cannot be dynamically adapted for positioning services. Therefore, when applied for SL positioning at an anchor UE 1 10, SL DRX cannot ensure a fair tradeoff between power saving and SL positioning update rate for all target UEs 1 10-T. As described above SL positioning requirements (such as accuracy, latency, update rate requirements) span a wide range and respective anchor UEs 110-A might need to support target UEs 1 10-T with diverse requirements. The anchor UEs 1 10-A can be configured with shorter DRX sleep cycles in anticipation of target UEs 110-T with stringent SL positioning requirements, however this results in significant power wastage at the anchor UE 1 10-A, if no such target UEs 1 10-T are in the vicinity. Conversely, the anchor UE 110-A can be configured with longer DRX sleep cycles to save power, however this might result in the anchor UE1 10-A not being able to support target UEs 110-T with stringent SL positioning requirements. An example of this issues is shown in Fig. 3. Fig. 3 shows an example sidelink positioning scenario.

In this example a target UE 110-T is to be positioned. The target UE 1 10-T therefore has to select and activate a set of anchor UEs 110-A1 , 1 10-A2, 1 10-A3 with which it should exchange SL PRS.

In the example of Fig. 3 there are three candidate anchor UEs 1 10-A1 , 110-A2, 1 10-A3 in the region around the target UE 110-T. The different candidate anchor UEs 110-A1 , 1 10- A2, 1 10-A3 use different SL DRX configurations. In this case the first candidate anchor UE 1 10-A1 uses a first SL DRX configuration, the second candidate anchor UE 110-A2 uses a second SL DRX configuration, and the third candidate anchor UE 1 10-A3 uses a third SL DRX configuration. The different SL DRX configurations can have different DRX cycle periods, DRX On durations or differ in any other suitable manner.

A first problem that can arise in this scenario is that the target UE 1 10-T might not be able to find enough candidate anchor UEs 110-A1 , 1 10-A2, 110-A3 for the SL positioning session. This problem can arise because the nearby candidate anchor UEs 110-A1 , 1 10- A2, 1 10-A3 might have different DRX configurations so that the SL UEs 110 monitor the SL channel with different time patterns.

A second problem that arises is enabling the SL positioning session to be finalized within a latency target. This problem can arise even if the target UE 1 10-T has found sufficient candidate anchor UEs 1 10-A1 , 1 10-A2, 110-A3 with the same DRX configuration for the SL positioning session because the DRX cycle could be too long.

Examples of the disclosure address these problems.

Fig. 4 shows an example method. The method of Fig. 4 could be implemented by a terminal device such as a candidate anchor UE 110-A or any other suitable type of device or apparatus.

The method comprises, at block 400, detecting a wake-up signal. The wake-up signal can be detected by the terminal device 1 10-A while the terminal device 110-A is in a DRX off mode. The wake-up signal can be transmitted from a further terminal device 1 10 1. The further terminal device 110-T can be a target UE 1 10-T that is to be positioned. The wake-up signal can comprise an indication of a DRX class of the further terminal device 110-T. The wakeup signal can comprise a signature that is specific to the DRX class of the further terminal device 110-T.

The wake-up signal can comprise an indication of a sidelink positioning request. The sidelink positioning request can be for the positioning of the further terminal device 1 10-T that transmitted the wake-up signal. The wake-up signal can comprise a wake-up signal for SL positioning (WUSP) or any other suitable type of signal.

The method comprises, at block 402, supporting positioning of the further terminal device 1 10-T based on the DRX class indicated in the wake-up signal. In some examples the DRX class could be indicated by a signature of the wake-up signal. The signature can comprise a waveform type, bandwidth, carrier frequency, code, modulation scheme, duration of the signal or any other suitable characteristic. In some examples the wake-up signal could comprise a payload and the payload could comprise information indicative of the DRX class.

In some examples information associated with the DRX class can be used to support the positioning of the further terminal device 1 10-T. The information associated with the DRX class can relate to any of the parameters that define the DRX class. In some examples the information associated with the DRX class can comprise sleep cycles or any other suitable information.

Supporting positioning of the further terminal device 110-T can comprise determining if the positioning request from the further terminal device 110-T is to be serviced by the terminal device 1 10-A. The positioning request can be associated with a sidelink communication between the terminal device 110-A and the further terminal device 110-T.

In some examples supporting positioning of the further terminal device 110-T can also comprise determining how a sidelink positioning request can be serviced. For example, it can comprise determining if the positioning request can be delayed or serviced using specific resources. A DRX mode of the terminal device 110-A can be controlled based on the determining if the sidelink positioning request can be serviced by the terminal device. For example, it can be controlled whether the terminal device 110-A is in a DRX ON mode or a DRX OFF mode.

The terminal device 1 10-A can be switched to DRX on mode if it is determined that the sidelink positioning request could be serviced by the terminal device 110-A. Once the terminal device 110-A has been switched to DRX on mode a message indicating that the sidelink positioning request can be accepted can be transmitted from the terminal device 1 10-A to the further terminal device 1 10-T. The message can comprise an indication of a DRX class of the terminal device 110-A.

The terminal device 110-A can be maintained in the DRX off mode if it is determined that the sidelink positioning request cannot be serviced by the terminal device 110-A. In such cases the terminal device 1 10-A does not transmit a response to the wake-up signal.

In some examples the supporting of the positioning by the terminal device 110-A can be based on a DRX class hierarchy. In such cases the DRX class of the further terminal device 1 10-T and the DRX class of the terminal device 1 10-A can be compared using a hierarchy. This means that the DRX classes of the further terminal devices 110-T do not need to be the same as the DRX class of the terminal device 1 10-A because the DRX class hierarchy can be used to determine whether the respective classes are compatible.

The hierarchy of DRX classes can be configured in any suitable arrangement. The hierarchy of DRX classes can be configured so that a terminal device 1 10-A can serve as anchor for further terminal devices 110-T of higher or equal classes within the hierarchy. In some examples the hierarchy of DRX classes can be configured such that higher DRX classes have longer sleep durations than lower DRX classes. This means that a terminal device 110-A can serve as an anchor for further terminal devices 110-T that have longer sleep durations. Other rules or processes could be used to enable terminal devices 1 10-A to server as anchors for further terminal devices 1 10-T that have different DRX configurations. The rules or processes could be based on sleep durations, UE types or any other suitable parameters. The rules or processes need not be based on a hierarchy.

The DRX classes can be determined by any suitable parameters or groups of parameters. In some examples a DRX class can have a predefined sleep cycle. In such cases different DRX classes could have different sleep cycles. In some examples the DRX class can be specific to a type of terminal device 1 10. In such cases an indication of a type of terminal device 110 could therefore serve as an indication of a DRX class.

In some examples a DRX class can have a specific occasion for a wake-up signal, a specific signature for a wake-up signal or any other suitable characteristics associated with a wakeup signal. The signature in the wake-up signal could be a waveform type, a code or any other identifying characteristic. When the terminal device 1 10-A is listening for a wake-up signal the terminal device 110-A can listen for wake-up signals having specific signatures or characteristics.

Fig. 5 shows another example method. The method of Fig. 5 could be implemented by a terminal device such as a target UE 1 10 -1 or any other suitable type of device or apparatus.

The method comprises, at block 500, causing transmission of a wake-up signal. The wakeup signal comprises an indication of a DRX class of the terminal device 1 10 -1. The wakeup signal can comprise a signature that is specific to a DRX class. The signature could comprise a waveform type, a code or any other identifying characteristic. In some examples the wake-up signal can comprise a payload. In such cases the payload can comprise information indicative of the DRX class.

The wake-up signal can also comprise an indication of a sidelink positioning request. The wake-up signal can comprise a wake-up signal for SL positioning (WUSP) or any other suitable type of signal.

The wake-up signal can be a point to multipoint signal. The wake-up signal can be transmitted to one or more candidate terminal devices 1 10-A. The candidate terminal devices 1 10-A could be candidate anchors. The wake-up signal can comprise a point to multipoint signal.

The wake-up signal can be transmitted following any suitable trigger event. In some examples the wake-up signal can be transmitted following a sidelink positioning request from an application layer. In some examples the sidelink positioning request could be received from an Access and Mobility Management Function (AMF) or any other suitable entity. At block 502 the method comprises collecting responses from candidate terminal devicesl 10-A having suitable DRX classes. The suitability of the DRX class of the candidate terminal device 110-A can be determined based on a DRX class hierarchy, the types of devices or any other suitable factor.

In some examples the suitability of the DRX class can be determined based on whether there is a match between the DRX class of the terminal device 1 10-T and the DRX class of the candidate terminal device 110-A. For example, if the candidate terminal device 1 10-A has the same DRX class as the terminal device 1 10-T that is to be positioned then the candidate terminal 110-A may be able to service the SL positioning request.

In some examples the suitability of the DRX class can be determined based on the DRX class hierarchy. In such cases the DRX class of the terminal device 110-T and the DRX class of the candidate terminal device 1 10-A can be compared using a hierarchy. The hierarchy of DRX classes can be configured in any suitable arrangement. The hierarchy of DRX classes can be configured so that a candidate terminal device 110-A can serve as anchor for terminal devices 1 10-T of higher or equal classes within the hierarchy. In some examples the hierarchy of DRX classes can be configured such that higher DRX classes have longer sleep durations than lower DRX classes. This means that a candidate terminal device 110-A can serve as an anchor for terminal devices 1 10-T that have longer sleep durations.

The terminal device 110-T can be configured to select one or more candidate terminal devices 1 10-A to use as an anchor from the candidate terminal devices 110-A from which responses have been collected. The candidate terminal devices 1 10-A can be selected based, at least in part on DRX classes of the terminal device 110-T and the candidate terminal devices 1 10-A. Once the candidate terminal devices 1 10-A have been selected the SL positioning can be deployed.

Fig. 6 show an example signal chart that could be used in some implementations of the disclosure. The signal chart shows signals that could be transmitted between a candidate anchor UE 1 10-A and a plurality of different target UEs 1 10-T 1 , 110-T2, 110-T3. Different target UEs 1 10 can have different DRX classes. The different DRX classes can be defined by any suitable characteristics. In some examples the DRX classes can be defined by different sleep cycles or ON/OFF durations, a requirement to listen for WUSPs in the same class or in a corresponding class, or any other relevant characteristics. In the example of Fig. 6 a first target UE 110-T 1 has DRX class 1 , a second target UE 110-T2 has DRX class 2, a second target UE 110-T3 has a third DRX class. Other numbers and arrangements of the target UEs 1 10 and the DRX classes could be used in examples of the disclosure.

In the example of Fig. 6 the candidate anchor UE 110-A is monitoring for wake-up signals from target UEs 1 10-T having suitable classes. In this example a class hierarchy is used to determine if the candidate anchor has a suitable DRX class for a target UE 1 10.

The class hierarchy enables interactions between UEs 1 10 having different classes. The class hierarchy is configured so that candidate anchor UE 1 10-A with a DRX class k monitors for WUSPs from target UEs 1 10-T of class j where j>k. the hierarchy of DRX classes can be configured such that higher DRX classes have longer sleep durations than lower DRX classes. This enables a candidate anchor UE 1 10-A to serve as an anchor for target UEs 1 10-T having a DRX equal to their own or higher than their own.

The DRX classes that are defined for the SL positioning can be denoted as DRXP classes.

Examples of different DRXP classes could be:

A Reduced Capacity (RedCap) UE obeys a DRXP cycle with pattern DRXP-type-RedCap A Low Power High Accuracy Positioning (LPHAP) UE obeys a DRXP cycle with pattern DRXP-type-LPHAP

All other type UE obeys a DRXP cycle with pattern DRXP-type-Gen.

In this case the general class would be a lower class and the RedCap class would be a higher class. Using the class hierarchy a candidate anchor UE 110-A having DRXP-type- Gen. would be able to service requests from target UEs 1 10-T having DRXP-type-RedCap or DRXP-type-LPHAP. However, a candidate anchor UE 110-A having DRXP-type-LPHAP would only be able to service requests from target UEs 110-T that also have DRXP-type- LPHAP. Such candidate anchor UEs 1 10-A would not be able to service requests from target UEs 1 10-T having DRXP-type-Gen or DRXP-type-LPHAP.

The respective DRX or DRXP classes can be defined so that a UE 1 10 of class J:

Has an ON duration of on(j) seconds,

Has an OFF duration of off(j) seconds,

- May send a WUSP with signature(j) - if it needs to become a SL target.

- Should listen and attempt to detect all WUSP with signature(k), where k>=j.

Therefore:

1. For DRXP class-1 , a UE 1 10 has: a. a class-1 specific ON and OFF duration b. may perform the transmission of a WUSP with signaturel , where the signature can comprise a waveform type, bandwidth, carrier frequency, code, modulation scheme, duration of the signal or any other suitable characteristic c. should listen and attempt to detect the reception of a WUSP whose signature is from a list L-class-1 = {signaturel , signature 2, signature 3, ..., signature N}.

2. For DRXP class-2, a UE 1 10 has: a. a class-2 specific ON and OFF duration b. may perform the transmission of a WUSP with signature2 where the signature can comprise a waveform type, bandwidth, carrier frequency, code, modulation scheme, duration of the signal or any other suitable characteristic c. should listen and attempt to detect the reception of WUSP whose signature is from a list L-class-2 = {signature 2, signature 3, ..., signature N}.

3. ...

4. For DRXP class DRXP class-N with a class-N specific ON and OFF duration a UE 1 10 has: a. a class-N specific ON and OFF duration b. may perform the transmission of a WUSP with signature where the signature can comprise a waveform type, bandwidth, carrier frequency, code, modulation scheme, duration of the signal or any other suitable characteristic c. should listen and attempt to detect the reception of a WUSP whose signature is from a list L-class-N = {signature N}.

In some examples the DRX or DRXP classes could also be defined with respect to the UE types. In such cases different types of UEs would be associated with different DRX or DRXP classes. In such cases the DRX or DRXP class can have an attribute that specifies the UE type(s) associated with the class.

The use of the DRX or DRXP classes and the class hierarchy can ensure sufficient availability of anchor UEs 110-A to service the SL positioning requests from target UEs 110. The class hierarchy enables candidate anchor UEs 110-A having a different DRX or DRXP class those of the target UE 1 10-T to wake up and serve the target UE 110-T.

In Fig. 6, at block 600, the target UEs 110-T 1 , 1 10-T2, 110-T3 transmit wake-up signals. In this example the wake-up signals can be WUSP signals.

The WUSP signals can be point-to-multipoint (or broadcast) wakeup signal for SL- positioning. The WUSP signals are intended to wake up candidate anchor UEs 1 10-A.

The WUSP signals can be class based so that a WUSP signal can comprise an indication of the DRX class or DRXP class of the target UE 110-T that has transmitted the WUSP signal.

In the example of Fig. 6 the WUSP transmitted by the first target UE 110-T1 comprises an indication of DRX class 1 , the WUSP transmitted by the second target UE 110-T2 comprises an indication of DRX class 2, and the WUSP transmitted by the third target UE 1 10-T3 comprises an indication of DRX class 3.

In some examples the WUSP can comprise an SL positioning request. In some examples the SL positioning request could be transmitted separately. When a candidate anchor UE 1 10-A detects a WUSP of appropriate class the candidate anchor UE 110-A will monitor the next DRX ON duration for SL position requests. If a DRX class hierarchy is used the WUSP of appropriate class would be one of class j where j>k. and k is the class of candidate anchor UE 1 10-A. The use of an indication of the DRX or DRXP class in the WUSP helps to avoid unnecessary wakeups occur during the next ON duration. At block 602 the candidate anchor UE 110-A detects the WUSPS. The candidate anchor UE 1 10-A can asses the respective DRX classes to determine if the candidate anchor UE 1 10-A can service a SL positioning request from the target UE 1 10 that has transmitted the WUSP.

In the example of Fig. 6 the candidate anchor UE 110-A has class 1 and can serve all of the target UEs 110-T 1 , 110-T2, 110-T3 which have classes of 1 or higher. In this example the candidate anchor UE 1 10-A determines an order in which the respective UEs 1 10-T are to be served. In this case the candidate anchor UE 110-A determines to serve first UE 1 10- T 1 first, then the second UE 1 10-T2, then the third UE 110-T3. In a different scenario the candidate anchor UE 1 10-A could determine a different order. For instance, if the candidate anchor UE 110-A determines has assessed that it has already helped the first target UE 1 10-T (for instance, if target UEs 110-T in the same class have recently asked for SL positioning support), then the candidate anchor UE 1 10-A may determine to serve the second target UE 110-T2 first.

Once the candidate anchor UE 110-A has determined the order in which the positioning requests are to be serviced then at block 604 the candidate anchor UE 110-A replies to the first target UE 1 10-T 1 with a positive acknowledgement and replies to the second target UE 1 10-T2 and the third target UE 110-T3 with a conditional acknowledgement.

At block 606 the first target UE 1 10-T1 responds to the positive acknowledgement by deploying the SL positioning session. At block 608 the second target UE 110-T2 responds to the positive acknowledgement by deploying the delayed SL positioning session. At block 610, instead of deploying an SL positioning session the third target UE 110-T3 can cancel the request due to unacceptable delay.

As mentioned above, in some examples a DRX or DRXP class be defined based on a type of UE 1 10. For instance, specific types of target UEs 1 10-T might have specific SL positioning requirements. As an example, if the target UE 1 10-T is an Industrial Internet of Things (lloT) device this could have a first set of requirements while if the target UE 110-T is a vehicle this could have a different set of requirements. The requirements for an I loT device could be 10 ms target latency, positioning accuracy within 1 m while the requirements for a vehicle could be 100ms target latency. In such cases the lloT device could be configured with DRXP-type-lloT where the ON duration of the DRXP-type-lloT ensures that the relevant requirements for the HoT device are met. Similarly, a vehicle could be configured with DRXP-type-V2X where the ON duration of the DRXP-type-V2X ensures that the relevant requirements for the vehicle are met.

Defining a DRX or DRXP class based on a type of UE 1 10 can provide the benefit that it enables candidate anchor UEs 1 10-A having capabilities similar to those of the target UE 1 10-T to wake up. For example, if a target UE 1 10-T is an I loT terminal, it is beneficial that other I loT UEs 1 10-A act as anchors, because they can be configured to perform similar functions. For example, they can process signals of similar bandwidths, implement the same positioning methods (such as RTT, AOD) and extract the same type of measurements (for example, compute Rx-Tx time difference with same granularity.).

Fig. 7 shows an example method. The method of Fig. 7 could be implemented by a device such as a candidate anchor UE 1 10-A. The method of Fig. 7 corresponds to blocks 602 and 604 as shown in Fig. 6.

The candidate anchor UE 110-A has DRX or DRXP class K. At block 700 the candidate anchor UE 1 10-A is configured in a DRX or DRXP OFF mode.

At block 702 the candidate anchor UE 110-A listens for WUSP from one or more target UEs 1 10-T

At block 704 the candidate anchor UE 110-A detects the WUSP signatures. The signatures of the WUSPs comprise the parameter set that describes the generation of the WUSP and the transmission of the WUSP over the air.

In some examples the WUSP can comprise a raw reference signal. This can be referred to as raw-WUSP. The signature of raw-WUSP can comprise:

- a time-frequency duration/allocation: o X consecutive Orthogonal Frequency-Division Multiplexing (OFDM) symbols. o Y frequency comb (that is, every Y-th subcarrier is occupied by a WUSP sample). o A code such as Zadoff-Chu code with root u and length N, Gold code, Quadrature Amplitude Modulation (QAM) modulation order, or any other suitable code.

In some examples the WUSP can comprise a payload signal. This can be referred to as payload-WUSP. The signature of payload- WUSP can comprise:

A set of symbols reserved for reference signal transmission

- A set of symbols for data transmission, where the payload comprises information at least about the class and/or positioning requirements. The payload can be encoded with a known code such as Low Density Parity Check (LDPC), and modulated with a known modulation such as 16QAM.

At block 706 the candidate anchor UE 1 10-A asses the DRX class or DRXP class of the detected WUSP signals. The assessment of the class of the WUSP signals can determine whether or not the target UEs 1 10-T have classes that can be serviced by the candidate anchor UE 1 10-A

As an example, a candidate anchor UE 1 10-A having a DRX cycle of class-K is configured to listen for WUSP from a list L-class-K = {signature-K, signature-K+1 , ..., signature-N}. The signatures can be the signatures of any type of WUSP such as raw-WUSP or payload- WUSP.

In examples where the DRX or DRXP class is specific to the type of UE the list would only comprise one element because the candidate anchor UE 110-A would be listening to WUSPs from the same type of UE 1 10-T.

The candidate anchor UE 1 10-A can detect any of the WUSP of the list L-class-K. If multiple WUSPs are detected then the candidate anchor UE 110-A will asses which of the SL positioning session it should join. Any suitable process can be used to assess which SL positioning session should be joined. For example, the candidate anchor UE 110-A could join the session associated with the WUSP of the closest class, and conditionally join the other sessions (the condition being whether the closest class session is deployed or not).

If a WUSP of an appropriate class is detected then, at block 708, the candidate anchor UE 1 10-A switches the configuration of the DRX or DRXP mode to ON. At block 710 the candidate anchor UE 110-A accepts the SL positioning request and at block 712 the candidate anchor UE 1 10-A informs the target UE 110-T of the DRX or DRXP class of the candidate anchor UE 110-A.

Fig. 8 shows another example method. The method of Fig. 8 could be implemented by a device such as a target UE 110-T. The target UE 1 10-T could be any of the target UEs 1 10-T as shown in Fig. 6 or any other suitable target UE 1 10-T.

At block 800 the target UE 110-T receives an SL positioning request from an application layer of a network 100. The receipt of the SL positioning request triggers the wake up of the target UE 110-T so that, at block 802 the target UE 1 10-T is configured in a DRX or DRXP ON mode. This enables the target UE 110-T to transmit the WUSP.

In this example the target UE 1 10-T has DRX or DRXP class J. Once the target UE 1 10-T has switched to an ON mode the target UE 1 10-T, at block 804, transmits a WUSP. The WUSP comprises the signature for class J.

After the WUSP has been transmitted the target UE 110-T listens for responses from candidate anchor UEs 110-A. The target UE 110-T can collect responses that are received during the listening window. The responses will be received from candidate anchor UEs 1 10-A that have appropriate classes. The responses can be received from candidate anchor UEs 110-A that have class k<j.

At block 808 the target UE 1 10-T selects anchors from a list of candidate anchors 110-A. The anchor that is to be used can be selected using any suitable criteria. For example, it can be selected based on power saving requirements.

At block 810 the target UE 1 10 starts the SL positioning with the selected anchors.

Fig. 9 illustrates an example of a controller 900. The controller 900 could be provided within terminal device such as a UE 110. Implementation of a controller 900 may be as controller circuitry. The controller 900 may be implemented in hardware alone, have certain aspects in software including firmware alone or can be a combination of hardware and software (including firmware). As illustrated in Fig. 9 the controller 900 can be implemented using instructions that enable hardware functionality, for example, by using executable instructions of a computer program in a general-purpose or special-purpose processor 902 that may be stored on a computer readable storage medium (disk, memory etc.) to be executed by such a processor 902.

The processor 902 is configured to read from and write to the memory 904. The processor 902 may also comprise an output interface via which data and/or commands are output by the processor 902 and an input interface via which data and/or commands are input to the processor 902.

The memory 904 stores a computer program comprising computer program instructions 906 (computer program code) that controls the operation of the apparatus when loaded into the processor 902. The computer program instructions 906, of the computer program, provide the logic and routines that enables the apparatus to perform the methods illustrated in the Figs. The processor 902 by reading the memory 904 is able to load and execute the computer program.

In examples where the controller 900 is provided within a device for providing anchor capabilities 110-A the controller 900 comprises: at least one processor 902; and at least one memory 904, the at least one memory 904 storing instructions that, when executed by the at least one processor 902, cause the device at least to perform: detecting 400 a wake-up signal while in a discontinuous reception (DRX) off mode wherein the wake-up signal is transmitted from a further terminal device and comprises an indication of a DRX class of the further terminal device; and supporting 402 positioning of the further terminal device based on the DRX class indicated in the wake-up signal.

In examples where the controller 900 is provided within a device to be positioned 110-T the controller 900 comprises: at least one processor 902; and at least one memory 904, the at least one memory 904 storing instructions that, when executed by the at least one processor 902, cause the device at least to perform: causing transmission 500 of a wake-up signal comprising an indication of a discontinuous reception (DRX) class of the terminal device to one or more candidate terminal devices; and collecting 502 responses from candidate terminal devices having suitable DRX classes wherein the suitability of the DRX class is determined based on a DRX class hierarchy.

The instructions 906 may arrive at the UE 110 via any suitable delivery mechanism 908. The delivery mechanism 908 may be, for example, a machine readable medium, a computer-readable medium, a non-transitory computer-readable storage medium, a computer program product, a memory device, a record medium such as a Compact Disc Read-Only Memory (CD-ROM) or a Digital Versatile Disc (DVD) or a solid-state memory, an article of manufacture that comprises or tangibly embodies the instructions 906. The delivery mechanism may be a signal configured to reliably transfer the instructions 906. The apparatus may propagate or transmit the instructions 906 as a computer data signal. The instructions 906 can comprise computer code or software code.

The computer program can comprise computer program instructions 906 for causing a UE 1 10 to perform at least the following or for performing at least the following: detecting 400 a wake-up signal while in a discontinuous reception (DRX) off mode wherein the wake-up signal is transmitted from a further terminal device and comprises an indication of a DRX class of the further terminal device; and supporting 402 positioning of the further terminal device based on the DRX class indicated in the wake-up signal.

The computer program can comprise computer program instructions 906 for causing a UE 1 10 to perform at least the following or for performing at least the following: causing transmission 500 of a wake-up signal comprising an indication of a discontinuous reception (DRX) class of the terminal device to one or more candidate terminal devices; and collecting 502 responses from candidate terminal devices having suitable DRX classes wherein the suitability of the DRX class is determined based on a DRX class hierarchy.

The computer program instructions may be comprised in a computer program, a non- transitory computer readable medium, a computer program product, a machine readable medium. In some but not necessarily all examples, the computer program instructions may be distributed over more than one computer program. Although the memory 904 is illustrated as a single component/circuitry it may be implemented as one or more separate components/circuitry some or all of which may be integrated/removable and/or may provide permanent/semi-permanent/ dynamic/cached storage.

Although the processor 902 is illustrated as a single component/circuitry it may be implemented as one or more separate components/circuitry some or all of which may be integrated/removable. The processor 902 may be a single core or multi-core processor.

References to ‘computer-readable storage medium’, ‘computer program product’, ‘tangibly embodied computer program’ etc. or a ‘controller’, ‘computer’, ‘processor’ etc. should be understood to encompass not only computers having different architectures such as single /multi- processor architectures and sequential (Von Neumann)/parallel architectures but also specialized circuits such as field-programmable gate arrays (FPGA), application specific circuits (ASIC), signal processing devices and other processing circuitry. References to computer program, instructions, code etc. should be understood to encompass software for a programmable processor or firmware such as, for example, the programmable content of a hardware device whether instructions for a processor, or configuration settings for a fixed-function device, gate array or programmable logic device etc.

As used in this application, the term ‘circuitry’ may refer to one or more or all of the following:

(a) hardware-only circuitry implementations (such as implementations in only analog and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable):

(i) a combination of analog and/or digital hardware circuit(s) with software/fi rmware and

(ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions and

(c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g. firmware) for operation, but the software may not be present when it is not needed for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

The stages illustrated in Figs. 3 to 8 can represent steps in a method and/or sections of code in the computer program. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the block may be varied. Furthermore, it can be possible for some blocks to be omitted.

Where a structural feature has been described, it may be replaced by means for performing one or more of the functions of the structural feature whether that function or those functions are explicitly or implicitly described.

The term ‘comprise’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X may comprise only one Y or may comprise more than one Y. If it is intended to use ‘comprise’ with an exclusive meaning then it will be made clear in the context by referring to “comprising only one...” or by using “consisting”.

In this description, the wording ‘connect’, ‘couple’ and ‘communication’ and their derivatives mean operationally connected/coupled/in communication. It should be appreciated that any number or combination of intervening components can exist (including no intervening components), i.e., so as to provide direct or indirect connection/coupling/communication. Any such intervening components can include hardware and/or software components.

As used herein, the term "determine/determining" (and grammatical variants thereof) can include, not least: calculating, computing, processing, deriving, measuring, investigating, identifying, looking up (for example, looking up in a table, a database or another data structure), ascertaining and the like. Also, "determining" can include receiving (for example, receiving information), accessing (for example, accessing data in a memory), obtaining and the like. Also, " determine/determining" can include resolving, selecting, choosing, establishing, and the like. In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term ‘example’ or ‘for example’ or ‘can’ or ‘may’ in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some of or all other examples. Thus ‘example’, ‘for example’, ‘can’ or ‘may’ refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all of the instances in the class. It is therefore implicitly disclosed that a feature described with reference to one example but not with reference to another example, can where possible be used in that other example as part of a working combination but does not necessarily have to be used in that other example.

Although examples have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the claims.

Features described in the preceding description may be used in combinations other than the combinations explicitly described above.

Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

Although features have been described with reference to certain examples, those features may also be present in other examples whether described or not.

The term ‘a’, ‘an’ or ‘the’ is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising a/an/the Y indicates that X may comprise only one Y or may comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use ‘a’, ‘an’ or ‘the’ with an exclusive meaning then it will be made clear in the context. In some circumstances the use of ‘at least one’ or ‘one or more’ may be used to emphasis an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning. The presence of a feature (or combination of features) in a claim is a reference to that feature or (combination of features) itself and also to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result.

In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described.

The above description describes some examples of the present disclosure however those of ordinary skill in the art will be aware of possible alternative structures and method features which offer equivalent functionality to the specific examples of such structures and features described herein above and which for the sake of brevity and clarity have been omitted from the above description. Nonetheless, the above description should be read as implicitly including reference to such alternative structures and method features which provide equivalent functionality unless such alternative structures or method features are explicitly excluded in the above description of the examples of the present disclosure.

Whilst endeavoring in the foregoing specification to draw attention to those features believed to be of importance it should be understood that the Applicant may seek protection via the claims in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not emphasis has been placed thereon. l/we claim: