Methods, communications devices, and infrastructure equipment

Abstract

A method of performing a relay selection procedure by a remote communications device configured to transmit signals to and / or receive signals from a wireless communications network is provided. The method comprises determining that a plurality of available relay paths exist between the remote communications device and the wireless communications network, each of the available relay paths either being single-hop relay paths comprising one relay communications device or multi-hop relay paths comprising two or more relay communications devices, determining one or more candidate relay paths from among the plurality of available relay paths in accordance with a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multi-hop relay paths, wherein the candidate relay paths are determined based on a quality of a communications link between the remote communications device and a first relay communications device of each of the candidate relay paths being above a first threshold quality, selecting one of the candidate relay paths, and transmitting signals to and / or receiving signals from the wireless communications network via a first relay communications device with which the remote communications device is connected via a sidelink communications interface, the first relay communications device forming part of the selected relay path.

Description

[0001] METHODS, COMMUNICATIONS DEVICES, AND INFRASTRUCTURE EQUIPMENT

[0002] BACKGROUND Field of Disclosure

[0003] The present disclosure relates to communications devices, infrastructure equipment and methods for the more effective and efficient selection and reselection of sidelink relays by remote communications devices.

[0004] The present application claims the Paris Convention priority from European patent application number EP24192184.0, filed on 31 July 2024, the contents of which are hereby incorporated by reference.

[0005] Description of Related Art

[0006] The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.

[0007] Previous generation mobile telecommunication systems, such as those based on the 3GPP defined UMTS and Long Term Evolution (LTE) architecture, are able to support a wider range of services than simple voice and messaging services offered by previous generations of mobile telecommunication systems. For example, with the improved radio interface and enhanced data rates provided by LTE systems, a user is able to enjoy high data rate applications such as mobile video streaming and mobile video conferencing that would previously only have been available via a fixed line data connection. The demand to deploy such networks is therefore strong and the coverage area of these networks, i.e. geographic locations where access to the networks is possible, is expected to continue to increase rapidly.

[0008] Current and future wireless communications networks are expected to routinely and efficiently support communications with an ever-increasing range of devices associated with a wider range of data traffic profiles and types than existing systems are optimised to support. For example, it is expected future wireless communications networks will be expected to efficiently support communications with devices including reduced complexity devices, machine type communication (MTC) devices, high resolution video displays, virtual reality headsets, extended Reality (XR) and so on. Some of these different types of devices may be deployed in very large numbers, for example low complexity devices for supporting the “The Internet of Things”, and may typically be associated with the transmissions of relatively small amounts of data with relatively high latency tolerance. Other types of device, for example supporting high-definition video streaming, may be associated with transmissions of relatively large amounts of data with relatively low latency tolerance. Other types of device, for example used for autonomous vehicle communications and for other critical applications, may be characterised by data that should be transmitted through the network with low latency and high reliability. A single device type might also be associated with different traffic profiles / characteristics depending on the application(s) it is running. For example, different consideration may apply for efficiently supporting data exchange with a smartphone when it is running a video streaming application (high downlink data) as compared to when it is running an Internet browsing application (sporadic uplink and downlink data) or being used for voice communications by an emergency responder in an emergency scenario (data subject to stringent reliability and latency requirements).

[0009] In view of this there is expected to be a desire for current wireless communications networks, for example those which may be referred to as 5G or new radio (NR) systems / new radio access technology (RAT) systems, or indeed future 6G wireless communications, as well as future iterations / releases of existing systems, to efficiently support connectivity for a wide range of devices associated with different applications and different characteristic data traffic profiles and requirements.

[0010] One example of a new service is referred to as Ultra Reliable Low Latency Communications (URLLC) services which, as its name suggests, requires that a data unit or packet be communicated with a high reliability and with a low communications delay. Another example of a new service is enhanced Mobile Broadband (eMBB) services, which are characterised by a high capacity with a requirement to support up to 20 Gb / s. URLLC and eMBB type services therefore represent challenging examples for both LTE type communications systems and 5G / NR communications systems.

[0011] 5G NR has continuously evolved and the current work plan includes 5G-NR-advanced in which some further enhancements are expected, especially to support new use-cases / scenarios with higher requirements. The desire to support these new use-cases and scenarios gives rise to new challenges for efficiently handling communications in wireless communications systems that need to be addressed.

[0012] SUMMARY OF THE DISCLOSURE

[0013] The present disclosure can help address or mitigate at least some of the issues discussed above.

[0014] Embodiments of the present technique can provide a method of performing a relay selection procedure by a remote communications device configured to transmit signals to and / or receive signals from a wireless communications network. The method comprises determining that a plurality of available relay paths exist between the remote communications device and the wireless communications network, each of the available relay paths either being single-hop relay paths comprising one relay communications device or multi-hop relay paths comprising two or more relay communications devices, determining one or more candidate relay paths from among the plurality of available relay paths in accordance with a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multi-hop relay paths, wherein the candidate relay paths are determined based on a quality of a communications link between the remote communications device and a first relay communications device of each of the candidate relay paths being above a first threshold quality, selecting one of the candidate relay paths, and transmitting signals to and / or receiving signals from the wireless communications network via a first relay communications device with which the remote communications device is connected via a sidelink communications interface, the first relay communications device forming part of the selected relay path.

[0015] Embodiments of the present technique, which, in addition to methods of operating remote communications devices, relate to methods of operating infrastructure equipment, to remote communications devices and infrastructure equipment, circuitry for remote communications devices and infrastructure equipment, communications systems, computer programs, and computer-readable storage mediums, can allow for the more effective and efficient selection and reselection of sidelink relays by remote communications devices.

[0016] Respective aspects and features of the present disclosure are defined in the appended claims.

[0017] It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the present technology. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein like reference numerals designate identical or corresponding parts throughout the several views, and wherein:

[0019] Figure 1 schematically represents some aspects of an LTE-type wireless telecommunication system which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0020] Figure 2 schematically represents some aspects of a new radio access technology (NR) wireless telecommunications system which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0021] Figure 3 is a schematic block diagram of an example infrastructure equipment and communications device which may be configured to operate in accordance with certain embodiments of the present disclosure;

[0022] Figure 4 illustrates examples of L2 user equipment to network (U2N) relay paths, including a single-hop path and multi-hop paths including different number of relay UEs;

[0023] Figure 5 shows a part schematic, part message flow diagram representation of a communications system comprising a communications device and an infrastructure equipment in accordance with embodiments of the present technique; and

[0024] Figure 6 shows a flow diagram illustrating an example process of communications in a communications system in accordance with embodiments of the present technique.

[0025] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] Long Term Evolution Advanced Radio Access Technology (4G)

[0027] Figure 1 provides a schematic diagram illustrating some basic functionality of a mobile telecommunications network / system 6 operating generally in accordance with LTE principles, but which may also support other radio access technologies, and which may be adapted to implement embodiments of the disclosure as described herein. Various elements of Figure 1 and certain aspects of their respective modes of operation are well-known and defined in the relevant standards administered by the 3GPP (RTM) body, and also described in many books on the subject, for example, Holma H. and Toskala A [1], It will be appreciated that operational aspects of the telecommunications networks discussed herein which are not specifically described (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be implemented in accordance with any known techniques, for example according to the relevant standards and known proposed modifications and additions to the relevant standards.

[0028] The network 6 includes a plurality of base stations 1 connected to a core network 2. Each base station provides a coverage area 3 (i.e. a cell) within which data can be communicated to and from communications devices 4. Although each base station 1 is shown in Figure 1 as a single entity, the skilled person will appreciate that some of the functions of the base station may be carried out by disparate, inter-connected elements, such as antennas (or antennae), remote radio heads, amplifiers, etc. Collectively, one or more base stations may form a radio access network.

[0029] Data is transmitted from base stations 1 to communications devices 4 within their respective coverage areas 3 via a radio downlink (DL). Data is transmitted from communications devices 4 to the base stations 1 via a radio uplink (UL). The core network 2 routes data to and from the communications devices 4 via the respective base stations 1 and provides functions such as authentication, mobility management, charging and so on. Communications devices may also be referred to as mobile stations, user equipment (UEs), user terminals, mobile radios, terminal devices, wireless transmit and receive units (WTRUs), and so forth. Services provided by the core network 2 may include connectivity to the internet or to external telephony services. The core network 2 may further track the location of the communications devices 4 so that it can efficiently contact (i.e. page) the communications devices 4 for transmitting downlink data towards the communications devices 4.

[0030] Base stations, which are an example of network infrastructure equipment, may also be referred to as transceiver stations, nodeBs, e-nodeBs, eNB, g-nodeBs, gNB and so forth. In this regard different terminology is often associated with different generations of wireless telecommunications systems for elements providing broadly comparable functionality. However, certain embodiments of the disclosure may be equally implemented in different generations of wireless telecommunications systems, and for simplicity certain terminology may be used regardless of the underlying network architecture. That is to say, the use of a specific term in relation to certain example implementations is not intended to indicate these implementations are limited to a certain generation of network that may be most associated with that particular terminology.

[0031] New Radio Access Technology (5G)

[0032] Systems incorporating NR technology are expected to support different services (or types of services), which may be characterised by different requirements for latency, data rate and / or reliability. For example, Enhanced Mobile Broadband (eMBB) services are characterised by high capacity with a requirement to support up to 20 Gb / s. The requirements for Ultra Reliable and Low Latency Communications (URLLC) services are for one transmission of a 32 byte packet to be transmitted from the radio protocol layer 2 / 3 SDU ingress point to the radio protocol layer 2 / 3 SDU egress point of the radio interface within 1 ms with a reliability of 1 - 10'5(99.999 %) or higher (99.9999%) [2],

[0033] Massive Machine Type Communications (mMTC) is another example of a service which may be supported by NR-based communications networks. In addition, systems may be expected to support further enhancements related to Industrial Internet of Things (IIoT) in order to support services with new requirements of high availability, high reliability, low latency, and in some cases, high-accuracy positioning.

[0034] An example configuration of a wireless communications network which uses some of the terminology proposed for and used in NR and 5G is shown in Figure 2. In Figure 2 a plurality of transmission and reception points (TRPs) 10 are connected to distributed control units (DUs) 41, 42 by a connection interface represented as a line 16. Each of the TRPs 10 is arranged to transmit and receive signals via a wireless access interface within a radio frequency bandwidth available to the wireless communications network. Thus, within a range for performing radio communications via the wireless access interface, each of the TRPs 10, forms a cell of the wireless communications network as represented by a circle 12. As such, wireless communications devices 14 which are within a radio communications range provided by the cells 12 can transmit and receive signals to and from the TRPs 10 via the wireless access interface. Each of the distributed units 41, 42 are connected to a central unit (CU) 40 (which may be referred to as a controlling node) via an interface 46. The central unit 40 is then connected to the core network 20 which may contain all other functions required to transmit data for communicating to and from the wireless communications devices and the core network 20 may be connected to other networks 25.

[0035] The elements of the wireless access network shown in Figure 2 may operate in a similar way to corresponding elements of an LTE network as described with regard to the example of Figure 1. It will be appreciated that operational aspects of the telecommunications network represented in Figure 2, and of other networks discussed herein in accordance with embodiments of the disclosure, which are not specifically described (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be implemented in accordance with any known techniques, for example according to currently used approaches for implementing such operational aspects of wireless telecommunications systems, e.g. in accordance with the relevant standards.

[0036] The TRPs 10 of Figure 2 may in part have a corresponding functionality to a base station or eNodeB of an LTE network. Similarly, the communications devices 14 may have a functionality corresponding to the UE devices 4 known for operation with an LTE network. It will be appreciated therefore that operational aspects of a new RAT network (for example in relation to specific communication protocols and physical channels for communicating between different elements) may be different to those known from LTE or other known mobile telecommunications standards. However, it will also be appreciated that each of the core network component, base stations and communications devices of a new RAT network will be functionally similar to, respectively, the core network component, base stations and communications devices of an LTE wireless communications network.

[0037] In terms of broad top-level functionality, the core network 20 connected to the new RAT telecommunications system represented in Figure 2 may be broadly considered to correspond with the core network 2 represented in Figure 1, and the respective central units 40 and their associated distributed units / TRPs 10 may be broadly considered to provide functionality corresponding to the base stations 1 of Figure 1. The term network infrastructure equipment / access node may be used to encompass these elements and more conventional base station type elements of wireless telecommunications systems. Depending on the application at hand the responsibility for scheduling transmissions which are scheduled on the radio interface between the respective distributed units and the communications devices may lie with the controlling node / central unit and / or the distributed units / TRPs. A communications device 14 is represented in Figure 2 within the coverage area of the first communication cell 12. This communications device 14 may thus exchange signalling with the first central unit 40 in the first communication cell 12 via one of the distributed units / TRPs 10 associated with the first communication cell 12.

[0038] It will further be appreciated that Figure 2 represents merely one example of a proposed architecture for a new RAT based telecommunications system in which approaches in accordance with the principles described herein may be adopted, and the functionality disclosed herein may also be applied in respect of wireless telecommunications systems having different architectures.

[0039] Thus, certain embodiments of the disclosure as discussed herein may be implemented in wireless telecommunication systems / networks according to various different architectures, such as the example architectures shown in Figures 1 and 2. It will thus be appreciated the specific wireless telecommunications architecture in any given implementation is not of primary significance to the principles described herein. In this regard, certain embodiments of the disclosure may be described generally in the context of communications between network infrastructure equipment / access nodes and a communications device, wherein the specific nature of the network infrastructure equipment / access node and the communications device will depend on the network infrastructure for the implementation at hand. For example, in some scenarios the network infrastructure equipment / access node may comprise a base station, such as an LTE-type base station 1 as shown in Figure 1 which is adapted to provide functionality in accordance with the principles described herein, and in other examples the network infrastructure equipment may comprise a control unit / controlling node 40 and / or a TRP 10 of the kind shown in Figure 2 which is adapted to provide functionality in accordance with the principles described herein. A more detailed diagram of some of the components of the network shown in Figure 2 is provided by Figure 3. In Figure 3, a TRP 10 as shown in Figure 2 comprises, as a simplified representation, a wireless transmitter 30, a wireless receiver 32 and a controller or controlling processor 34 which may operate to control the transmitter 30 and the wireless receiver 32 to transmit and receive radio signals to one or more UEs 14 within a cell 12 formed by the TRP 10. As shown in Figure 3, an example UE 14 is shown to include a corresponding transmitter 49, a receiver 48 and a controller 44 which is configured to control the transmitter 49 and the receiver 48 to transmit signals representing uplink data to the wireless communications network via the wireless access interface formed by the TRP 10 and to receive downlink data as signals transmitted by the transmitter 30 and received by the receiver 48 in accordance with the conventional operation.

[0040] The transmitters 30, 49 and the receivers 32, 48 (as well as other transmitters, receivers and transceivers described in relation to examples and embodiments of the present disclosure) may include radio frequency filters and amplifiers as well as signal processing components and devices in order to transmit and receive radio signals in accordance for example with the 5G / NR standard. The controllers 34, 44 (as well as other controllers described in relation to examples and embodiments of the present disclosure) may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc., configured to carry out instructions which are stored on a computer readable medium, such as a non-volatile memory. The processing steps described herein may be carried out by, for example, a microprocessor in conjunction with a random access memory, operating according to instructions stored on a computer readable medium. The transmitters, the receivers and the controllers are schematically shown in Figure 3 as separate elements for ease of representation. However, it will be appreciated that the functionality of these elements can be provided in various different ways, for example using one or more suitably programmed programmable computer(s), or one or more suitably configured application-specific integrated circuit(s) / circuitry / chip(s) / chipset(s). As will be appreciated the infrastructure equipment / TRP / base station as well as the UE / communications device will in general comprise various other elements associated with its operating functionality.

[0041] As shown in Figure 3, the TRP 10 also includes a network interface 50 which connects to the DU 42 via a physical interface 16. The network interface 50 therefore provides a communication link for data and signalling traffic from the TRP 10 via the DU 42 and the CU 40 to the core network 20.

[0042] The interface 46 between the DU 42 and the CU 40 is known as the F 1 interface which can be a physical or a logical interface. The Fl interface 46 between CU and DU may operate in accordance with specifications 3GPP TS 38.470 [3] and 3GPP TS 38.473 [4], and may be formed from a fibre optic or other wired or wireless high bandwidth connection. In one example the connection 16 from the TRP 10 to the DU 42 is via fibre optic. The connection between a TRP 10 and the core network 20 can be generally referred to as a backhaul, which comprises the interface 16 from the network interface 50 of the TRP 10 to the DU 42 and the Fl interface 46 from the DU 42 to the CU 40.

[0043] Sidelink Relay

[0044] As mentioned above, the introduction of a wide range of new device types and capabilities in NR creates technical challenges in maintaining device connectivity with a wireless communications network. One aspect of NR currently under development of the 3GPP group is that of the sidelink relay, which is discussed in 3GPP Release-17. For example, 3GPP study item [5] discusses a single-hop NR sidelinkbased relay, which relays signals between two remote UEs to each of which it is connected via a PC5 interface. In particular, [5] targets: • Study mechanism(s) with minimum specification impact to support Service and System Aspect (SA) requirements for sidelink-based UE-to-network (U2N) and UE-to-UE (U2U) relay, focusing on the following aspects (if applicable) for layer-3 (L3) relay and layer-2 (L2) relay [RAN2]; o Relay (re-)selection criterion and procedure; o Relay / Remote UE authorisation; o Quality of service (QoS) for relaying functionality; o Service continuity; o Security of relayed connection after SA3 has provided its conclusions; and o Impact on user plane protocol stack and control plane procedure, e.g., connection management of relayed connection; and

[0045] • Study mechanism(s) to support upper layer operations of discovery model / procedure for sidelink relaying, assuming no new physical layer channel / signal [RAN2] .

[0046] It is noted in [5] that it is expected that U2N relays and U2U relays will use the same relaying solution, and that forward compatibility for multi-hop relay support in future releases of standards should be taken into account. It is also noted in [5] that, for L2 U2N relays, the architecture of end-to-end Packet Data Convergence Protocol (PDCP) and hop-by-hop Radio Link Control (RLC), as recommended in [6], is taken as a starting point.

[0047] NR Multi-Hop Sidelink Relay

[0048] Multi-hop sidelink relaying is, as the term suggests, where the communications path between the remote / end UE and the network involves more than one sidelink relay UE. Examples of various sidelink U2N relay solutions are shown in Figure 4.

[0049] As can be seen in Figure 4, there are three different relay paths available to a remote UE 61 in order to communicate (i.e. transmit and / or receive) with a base station 62 of a radio access network. The first path is a single hop path, comprising just a single sidelink relay UE 63 between the remote UE 61 and the base station 62. The second path is a multi -hop path comprising two UEs - a first relay UE 64 and a last relay UE 65 - between the remote UE 61 and the base station 62. The third path is also a multi-hop path, but with this path comprising three UEs - a first relay UE 66, a second relay UE 67, and a last relay UE 68 - between the remote UE 61 and the base station 62.

[0050] A work item description (WID) is detailed in [7], with objectives relating to multi-hop L2 U2N sidelink relays. The following description of multi-hop L2 U2N sidelink relays is reproduced from section 4.1 of [7].

[0051] The objective of [7] is to specify solutions that are needed to support multi -hop L2 U2N relay for a single indirect path via sidelink relay UEs based on Rel-17 / 18 sidelink relay functionality [RAN2, RAN3],

[0052] Such solutions relate to the specification of mechanisms to support up to two additional hops (i.e. two additional relays in the path) on top of the Rel-17 U2N relay. This starts with one additional hop relay (i.e., remote UE -> first relay UE -> last relay UE -> gNB), before a further check will be made in respect of whether this can be easily extended to two additional hop relays (i.e., remote UE -> first relay UE -> second relay UE -> last relay UE -> gNB). A necessary criterion for the specified mechanisms is easy extensible to support two additional hop relays and to be forward compatible for future extensions for additional relays.

[0053] Such mechanisms for which specification is required include relay discovery and (re)selection [RAN2], signalling support for relay UEs and remote UE authorisation if needed [RAN3], impact on sidelink relay adaptation protocol (SRAP) and QoS handling for multi-hop [RAN2], and control plane procedures [RAN2, RAN3],

[0054] Such solutions relate to the specification of the following intra-gNB service continuity scenarios for multi -hop U2N relays based on Rel-17 / 18 procedures (for remote UEs). At a first priority level, such scenarios include intra-gNB multi-hop indirect to direct path switching using the existing framework and intra-gNB multi-hop indirect to single-hop indirect path switching using the existing framework. At a second priority level (and in order of importance), such scenarios include intra-gNB direct to multi-hop indirect path switching, and intra-gNB single-hop indirect to multi -hop indirect path switching. These scenarios at the second priority level are limited to path switching to a target indirect path consisting of the last relay UE in “direct” RRC Connected mode and all the other intermediate relay(s) in “indirect” RRC Connected mode to the same cell.

[0055] It should be noted here that the current existing measurement framework and existing data forwarding mechanisms should be reused for multi -hop L2 U2N relay implementations.

[0056] When determining a suitable relay (or relay path in the case of multi-hop relays) to select or reselect, a remote UE first considers the quality of the sidelink between the remote UE and the single-hop relay UE or a first relay UE of the multi-hop path. This quality may be measured, for example, based on reference signal received power (RSRP) or reference signal received quality, and these measurements may be performed on sidelink reference signals (i.e. SL-RSRP / SL-RSRQ) or on discovery signals received from the relay UEs (i.e. SD-RSRP / SD-RSRQ). The remote UE may, for example, consider that all relays for which the measured quality exceeds a threshold can be considered as relay candidates. In [8], in section 16. 12.4, it is defined that, if there are multiple suitable U2N relay candidates, it is up to the remote UE’s implementation to select one of these.

[0057] There are therefore various different types of sidelink relays - e.g., L2 U2N relay, U2U relay, multi -hop U2N relay. From the point of view of reliability and latency, reliability will be reduced as the number of hops of the relay path increases, while latency will increase as the number of hops increases. If it is fully up to remote UE implementation to select / reselect a relay from among the relay candidates that have sufficient quality, as is defined in [8], a number of issues can arise. A first of these is that the remote UE may need to reselect a relay path very frequently, as the introduction of multi-hop relays means the number of candidates will be much greater. This consumes time and power, and the remote UE may often select multi-hop relay paths that - though the measured quality was good at the time of measurement - may be far less reliable or have higher latency than other relay candidates. Secondly, the remote UE may perform such path switching very frequently during data transmission, which causes such data transmission to be less efficient, to be less reliable, and to have higher latency.

[0058] It is thus recognised by the present inventors that the introduction of multi-hop relaying will make selection / reselection procedures more complicated, particularly considering there are already separate procedures for U2N and U2U sidelink relays. Embodiments of the present disclosure address those challenges imposed by multi-hop sidelink relays and enable them to co-exist with multiple other types of relay in current and future wireless communications networks.

[0059] Multi-Hop Sidelink Relay Selection and Reselection

[0060] Figure 5 shows a part schematic, part message flow diagram representation of a communications system 100 comprising a remote communications device (e.g. UE) 101 configured to perform a relay selection procedure, one or more relay communications devices (e.g. UE) 102, and an infrastructure equipment (e.g. gNB) in accordance with at least some embodiments of the present technique. The communications system 100 may also comprise one or more further infrastructure equipment (e.g. gNBs) together forming a radio access network (RAN) (i.e. a wireless communications network) with the infrastructure equipment (e.g. gNB) 103, although these are not shown in Figure 5. Likewise, the communications system 100 may also comprise a core network part, though this is also not shown in Figure 5. Those skilled in the art would appreciate that the communications system 100 may comprise a great number more communications devices to those shown, including for example a plurality of further relay communications devices that, together with the relay communications device 102, form a number of different relay paths between the remote communications device 101 and the wireless communications network (e.g. the infrastructure equipment 103 or other infrastructure equipment) though such further communications devices are not shown in Figure 5 for the purposes of simplicity.

[0061] The remote communications device 101 may be configured to transmit signals to and / or receive signals from the relay communications device 102, which may operate as a relay device for the remote communications device 101. Specifically, the remote communications device 101 may be configured to transmit data to and / or receive data from the relay communications device 102 (and / or other relay communications device not shown in Figure 5) via a sidelink (i.e. PC5) interface between the remote communications device 101 and the relay communications device 102 (and / or other the relay communications device not shown in Figure 5). The relay communications device 102 (and / or other relay communications device not shown in Figure 5) may be configured to communicate, additionally, with the wireless communications network (e.g. the infrastructure equipment 103), by transmitting signals to and / or receiving signals from the wireless communications network (e.g. infrastructure equipment 103) via a wireless radio (e.g. Uu) interface provided by the wireless communications network (e.g. infrastructure equipment 103).

[0062] The remote communications device 101 may be capable of communicating directly with the wireless communications network via the Uu interface, but may instead be configured to communication with the wireless communications network (e.g. with the infrastructure equipment 103) via relay (sidelink relay) communications devices such as relay communications device 102 since the remote communications device 101 may be in poor coverage, for example. The remote communications device 101 (as well as relay communications device 102 and infrastructure equipment 103) may also be configured to exchange signalling with the core network as would be well understood by those skilled in the art, although again in the interests of simplicity this is not shown in Figure 5.

[0063] The remote communications device 101, the relay communications device 102, and the infrastructure equipment 103, as shown in Figure 5 (and indeed those communications devices and infrastructure equipment not shown in Figure 5), may each comprise a transceiver (or transceiver circuitry) 101.1, 102.1, 103.1, and a controller (or controller circuitry) 101.2, 102.2, 103.1. Each of the controllers, such as controllers 101.2, 102.2, 103.3 may be, for example, a microprocessor, a CPU, or a dedicated chipset, etc, and may each be coupled with a buffer and / or memory.

[0064] As shown in the example of Figure 5 , the transceiver circuitry 101.1 and the controller circuitry 101.2 of the remote communications device 101 are configured in combination to determine 110 that a plurality of available relay paths (some of which may include relay communications device 102) exist between the remote communications device 101 and the wireless communications network (e.g. infrastructure equipment 103), each of the available relay paths either being single-hop relay paths comprising one relay communications device (such as relay communications device 102) or multi -hop relay paths comprising two or more relay communications devices (which for some paths may include relay communications device 102), to determine 120 one or more candidate relay paths from among the plurality of available relay paths in accordance with a path selection rule specified for the remote communications device 101 that configures the remote communications device 101 to prioritise single-hop relay paths over multi -hop relay paths, wherein the candidate relay paths are determined based on a quality of a communications link between the remote communications device 101 and a first relay communications device (e.g. relay communications device 102) of each of the candidate relay paths being above a first threshold quality (which may be fixed in the specifications or indicated dynamically or semi-statically or broadcast to the remote communications device 101 by the wireless communications network), to select 130 one of the candidate relay paths, and to transmit 140 signals to and / or to receive 140 signals from the wireless communications network (e.g. to / from the infrastructure equipment 103) via a first relay communications device (e.g. relay communications device 102 as shown in the example of Figure 5) with which the remote communications device 101 is connected via a sidelink communications interface, the first relay communications device forming part of the selected relay path.

[0065] Essentially, embodiments of the present technique therefore propose that priorities should be specified for a remote UE in respect of how the remote UE selects a sidelink relay when there is more than one relay candidate; and particularly when those multiple relay candidates include both single-hop relays and multihop relays. Arrangements of embodiments of the present technique propose various ways to implement such a solution.

[0066] In some arrangements of embodiments of the present technique, the order of the L2 U2N relay selection / reselection will be specified. That is, candidate relays are considered in terms of lowest number of hops first, and the remote UE is configured not to consider multi -hop relays unless there are no suitable single-hop relay candidates. In other words, the path selection rule may define that the remote communications device is to determine the candidate relay paths only from among the single-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality. Here, the path selection rule may define that the remote communications device is to determine, only if the quality of the communications link between the remote communications device and the first relay communications device of each of the single-hop relay paths is not above the first threshold quality, the candidate relay paths from among the multi-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality.

[0067] Here, once the remote UE has determined one or more candidate relays, (i.e. among single-hop relay paths only, assuming one or more are available, and among multi-hop relay paths if not), the remote UE can select one of the available candidate relays in accordance with previously defined remote UE operation, e.g. as described in [8]; including (but not exclusively based on) the link quality between the remote UE and relay UE. That is, the remote communications device may select the selected relay path based on one or more parameters of the selected relay path, the one or more parameters including the quality of the communications link between the remote communications device and the first relay communications device of the selected relay path.

[0068] In respect of such arrangements, for the remote UE to select / reselect a L2 U2N relay, multi-hop L2 U2N relay selection will therefore only be triggered if there is no suitable one hop L2 U2N relay available. That is, the selection / reselection of multi-hop L2 U2N relays will be triggered after the selection / reselection of L2 U2N relay has been performed and has failed. In such arrangements therefore, the selection / reselection of single-hop L2 U2N relay and multi-hop L2 U2N relay do not run simultaneously. In some other arrangements of embodiments of the present technique, different priorities to select / reselect the relay among the candidate relays will be specified, while the determination of candidate relays is not limited based on number of hops as defined in other arrangements above. That is, candidate relays may include all relay paths that meet threshold quality requirements, no matter the number of hops. In other words, the path selection rule may define that a priority of the single-hop relay paths is higher than a priority of the multi-hop relay paths, and wherein the remote communications device determines the candidate relay paths from among both the single-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality and the multi-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality.

[0069] This means that the selection / reselection of one hop L2 U2N relay and multi-hop L2 U2N relay run simultaneously and among the one or more candidate relays of various numbers of hops. Here, the priorities of relay paths (based on the number of hops) does not impact the relay path’s determination and selection as a candidate relay path, but does impact the likelihood of selection by the remote UE. That is, rather than selecting one of the available candidate relays in accordance with previously defined remote UE operation, e.g. as described in [8], the remote UE also takes the priority of the relay path into account when performing selection / reselection. In other words, the remote communications device may select the selected relay path based on both of the priority of the selected relay path and one or more other parameters of the selected relay path, the one or more parameters including the quality of the communications link between the remote communications device and the first relay communications device of the selected relay path. This therefore enables the remote UE to select an appropriate relay path based on a trade-off between reliability and (current) quality.

[0070] In at least some such arrangements, the priority may be decreased as the number of hops increases. That is the priority of a one hop L2 U2N relay > the priority of a two hop L2 U2N relay > the priority of a three hop L2 U2N relay, and so on. In other words, the priority of each of the multi-hop relay paths may be dependent on a number of hops of that multi-hop relay path, and wherein the priority decreases as the number of hops increases. This therefore enables a remote UE to select a longer multi-hop relay path when such a path truly is the best relay candidate for the remote UE to communicate with the network, but the remote UE is heavily incentivised to pick a shorter route if possible. This is because the longer a relay path is, the more communications links it has that may suffer from radio link (RLF) or that may decrease in quality based on mobility of the remote / relay UEs, causing such a longer relay path to be more likely to decrease in quality more quickly. Such longer routes are therefore less reliable, but where significantly better (in terms of quality for example) than shorter routes, remote UEs should still have the flexibility to be able to select them.

[0071] In accordance with at least some arrangements of embodiments of the present technique, the number of hops between the remote UE and the network is assumed in most cases to be included in the discovery message of that relay, and so the remote UE will be aware of the number of hops of each available or candidate relay path. However, as an alternative and in accordance with at least some other arrangements of embodiments of the present technique, the relay UE may broadcast this information in a new message format. This is shown in the example of Figure 5, where before performing the relay selection procedure, the remote communications device 101 may receive 220 from each available relay communications device (e.g. relay communications device 102) such a relay discovery message / new message that indicates the number of hops of each relay path that includes that relay communications device as a first (or only) relay on the path. In other words, the remote communications device may be configured to determine, based on a message 220 (e.g. discovery message or other new message format) received from a first relay communications device of each of the available relay paths, whether each of the available relay paths is a single-hop relay path or a multi-hop relay path, wherein the message further indicates, for each of the multi -hop relay paths, a number of hops of that multi-hop relay path.

[0072] In some arrangements of embodiments of the present technique, the remote UE may determine the relay candidates from among all available relay paths based on a consideration of the PC5 link quality between itself and the first relay UE of each path in respect of two different thresholds; one for single-hop relays and one for multi-hop relays. In other words, the path selection rule defines that the communications device is to determine the candidate relay paths from among both the single-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality and the multi-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above a second threshold quality. Here, the second threshold quality can be set higher than the first threshold quality; i.e. the determined quality of a relay link for a remote UE to consider it as a relay candidate can be lower for single-hop relays than multi-hop relays. This takes into consideration the relative reliability and packet survival latency of multi-hop relays (particularly as the number of hops grows) being lower than that of single-hop relays. In some implementations however, the thresholds can be set to be the same. Both the first and second thresholds may be fixed in the specifications or may be indicated dynamically or semi-statically or broadcast to the remote UE by the network.

[0073] In some arrangements of embodiments of the present technique, the remote UE may be configured by the network in respect of whether it is allowed to select multi -hop L2 U2N relays. This may be irrespective of the manner of determination / selection of candidate relays as described above; the network may impose a hard and strict limit on the number of hops the remote UE is able to consider for relay selection / reselection. In other words, and again with reference to Figure 5, the remote communications device 101 may be configured to receive, from the wireless communications network (e.g. from the infrastructure equipment 103 as shown in the example of Figure 5), control signalling 210 indicating whether or not the remote communications device 101 is allowed to select a multi-hop relay path as the selected relay path.

[0074] In some such arrangements, the network may broadcast an indication (for example in the configuration of whether the remote UE is allowed to select a multi-hop L2 U2N relay or not) that only when the Uu link quality (i.e. of the Uu link between the remote UE and the network) is below a threshold (e.g. an RSRP threshold), is the remote UE allowed to select multi-hop L2 U2N relay. This threshold can be included in the broadcast signalling, signalled separately by the network in a dynamic or semi-static manner, or preconfigured and known to the remote UE (e.g. fixed in the specifications). In other words, the control signalling may indicate that the remote communications device is allowed to select a multi-hop relay path as the selected relay path if a quality of a communications link between the remote communications device and the wireless communications network is below a third threshold quality.

[0075] In some such arrangements, the network will indicate (and / or configure) a series of Uu link quality thresholds e.g., RSRP thresholds, where each threshold corresponds to a maximum number of hops a remote UE is allowed to select / reselect if such a threshold quality is not met. Here, the lower the RSRP threshold value is, the greater the number of hops the remote UE is allowed to consider when selecting / reselecting a L2 U2N relay. In other words, the control signalling may indicate that the remote communications device is allowed to select a multi-hop relay path as the selected relay path if a quality of a communications link between the remote communications device and the wireless communications network is below one of a set of third threshold qualities, each of the set of third threshold qualities being associated with a different number of hops of the multi -hop relay path and decreasing as the number of hops increases.

[0076] In the legacy one-hop L2 U2N, the triggers for the remote UE to perform relay reselection include:

[0077] • PC5 link quality (between the remote UE and relay UE) being below a threshold;

[0078] • Relay UE Uu link (between the relay UE and network) failure;

[0079] • PC5 release message being received from the relay UE; and

[0080] • PC5 radio link failure (RLF) or RLF indicated by an upper layer.

[0081] However, with the introduction of multi-hop L2 U2N relaying, further triggers, or expansion on the above-recited triggers, may be required. Accordingly, in some arrangements of embodiments of the present technique, the remote UE may be triggered to perform relay selection / reselection if a PC5 RLF occurs between any two intermediate relays in the multi-hop relay path. In other words, the remote communications device may be configured to perform the relay selection procedure dependent on receiving, from a first relay communications device of a current relay path (i.e. a multi-hop relay path) being used by the remote communications device to transmit signals to and / or receive signals from the wireless communications network, an indication that a radio link failure has occurred on a communications link between (any) two relay communications devices of the current relay path.

[0082] Such a PC5 RLF will be forwarded to the remote UE by the relay UEs. The intermediate relay UE that finds the PC5 RLF with its parent relay should forward the RLF notification to its child relay UE in turn, until notification of the PC5 RLF reaches the remote UE. As those skilled in the art would be aware, such a RLF notification being passed down from parent node to child node has been defined previously in Integrated Access and Backhaul (IAB), and is known as backhaul RLF. The difference here however is that such a PC5 RLF notification should be forwarded to the remote UE specifically in order to trigger relay reselection. The remote UE and the intermediate relay node(s) may need, in accordance with such (and indeed other) arrangements of embodiments of the present technique to maintain a routing table such as that maintained by IAB nodes to keep track of available relay paths and links.

[0083] Figure 6 shows a flow diagram illustrating an example process of communications in a communications system in accordance with embodiments of the present technique. The process shown by Figure 6 is a method of performing a relay selection procedure by a remote communications device configured to transmit signals to and / or receive signals from a wireless communications network.

[0084] The method begins in step SI. The method comprises, in step S2, determining that a plurality of available relay paths exist between the remote communications device and the wireless communications network, each of the available relay paths either being single-hop relay paths comprising one relay communications device or multi -hop relay paths comprising two or more relay communications devices. In step S3, the process comprises determining one or more candidate relay paths from among the plurality of available relay paths in accordance with a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multihop relay paths, wherein the candidate relay paths are determined based on a quality of a communications link between the remote communications device and a first relay communications device of each of the candidate relay paths being above a first threshold quality. The method next comprises, in step S4, selecting one of the candidate relay paths before, in step S5, transmitting signals to and / or receiving signals from the wireless communications network via a first relay communications device with which the remote communications device is connected via a sidelink communications interface, the first relay communications device forming part of the selected relay path. The process ends in step S6. Those skilled in the art would appreciate that the method shown by Figure 6 may be adapted in accordance with embodiments of the present technique. For example, other intermediate steps may be included in such a method, or the steps may be performed in any logical order. Though embodiments of the present technique have been described largely by way of the example communications systems shown in Figure 5, it would be clear to those skilled in the art that they could be equally applied to other systems and scenarios to those described herein.

[0085] Those skilled in the art would further appreciate that such infrastructure equipment and / or communications devices as herein defined may be further defined in accordance with the various arrangements and embodiments discussed in the preceding paragraphs. It would be further appreciated by those skilled in the art that such infrastructure equipment and communications devices as herein defined and described may form part of communications systems other than those defined by the present disclosure.

[0086] The following numbered paragraphs provide further example aspects and features of the present technique:

[0087] Paragraph 1. A method of performing a relay selection procedure by a remote communications device configured to transmit signals to and / or receive signals from a wireless communications network, the method comprising determining that a plurality of available relay paths exist between the remote communications device and the wireless communications network, each of the available relay paths either being single-hop relay paths comprising one relay communications device or multi-hop relay paths comprising two or more relay communications devices, determining one or more candidate relay paths from among the plurality of available relay paths in accordance with a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multi-hop relay paths, wherein the candidate relay paths are determined based on a quality of a communications link between the remote communications device and a first relay communications device of each of the candidate relay paths being above a first threshold quality, selecting one of the candidate relay paths, and transmitting signals to and / or receiving signals from the wireless communications network via a first relay communications device with which the remote communications device is connected via a sidelink communications interface, the first relay communications device forming part of the selected relay path.

[0088] Paragraph 2. A method according to Paragraph 1, wherein the path selection rule defines that the remote communications device is to determine the candidate relay paths only from among the single-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality.

[0089] Paragraph 3. A method according to Paragraph 1 or Paragraph2, wherein the path selection rule defines that the remote communications device is to determine, only if the quality of the communications link between the remote communications device and the first relay communications device of each of the single-hop relay paths is not above the first threshold quality, the candidate relay paths from among the multi-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality. Paragraph 4. A method according to any of Paragraphs 1 to 3, wherein the remote communications device selects the selected relay path based on one or more parameters of the selected relay path, the one or more parameters including the quality of the communications link between the remote communications device and the first relay communications device of the selected relay path.

[0090] Paragraph 5. A method according to any of Paragraphs 1 to 4, wherein the path selection rule defines that a priority of the single-hop relay paths is higher than a priority of the multi -hop relay paths, and wherein the remote communications device determines the candidate relay paths from among both the single-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality and the multi-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality. Paragraph 6. A method according to Paragraph 5, wherein the priority of each of the multi -hop relay paths is dependent on a number of hops of that multi-hop relay path, and wherein the priority decreases as the number of hops increases.

[0091] Paragraph 7. A method according to Paragraph 5 or Paragraph 6, wherein the remote communications device selects the selected relay path based on both of the priority of the selected relay path and one or more other parameters of the selected relay path, the one or more parameters including the quality of the communications link between the remote communications device and the first relay communications device of the selected relay path.

[0092] Paragraph 8. A method according to any of Paragraphs 1 to 7, wherein the path selection rule defines that the communications device is to determine the candidate relay paths from among both the single-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality and the multi-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above a second threshold quality.

[0093] Paragraph 9. A method according to any of Paragraphs 1 to 8, comprising determining, based on a message received from a first relay communications device of each of the available relay paths, whether each of the available relay paths is a single-hop relay path or a multihop relay path, wherein the message further indicates, for each of the multi-hop relay paths, a number of hops of that multi-hop relay path.

[0094] Paragraph 10. A method according to any of Paragraphs 1 to 9, comprising receiving, from the wireless communications network, control signalling indicating whether or not the remote communications device is allowed to select a multi-hop relay path as the selected relay path.

[0095] Paragraph 11. A method according to Paragraph 10, wherein the control signalling indicates that the remote communications device is allowed to select a multi-hop relay path as the selected relay path if a quality of a communications link between the remote communications device and the wireless communications network is below a third threshold quality.

[0096] Paragraph 12. A method according to Paragraph 10 or Paragraph 11, wherein the control signalling indicates that the remote communications device is allowed to select a multi-hop relay path as the selected relay path if a quality of a communications link between the remote communications device and the wireless communications network is below one of a set of third threshold qualities, each of the set of third threshold qualities being associated with a different number of hops of the multi-hop relay path and decreasing as the number of hops increases.

[0097] Paragraph 13. A method according to any of Paragraphs 1 to 12, wherein the remote communications device is configured to perform the relay selection procedure dependent on receiving, from a first relay communications device of a current relay path being used by the remote communications device to transmit signals to and / or receive signals from the wireless communications network, an indication that a radio link failure has occurred on a communications link between two relay communications devices of the current relay path.

[0098] Paragraph 14. A method according to any of Paragraphs 1 to 13, wherein the relay selection procedure is an initial relay selection procedure that is performed by the remote communications device at a time at which the remote communications device is not currently communicating with the wireless communications network via a relay communications device.

[0099] Paragraph 15. A method according to any of Paragraphs 1 to 14, wherein the relay selection procedure is a relay reselection procedure that is performed by the remote communications device at a time at which the remote communications device is currently communicating with the wireless communications network via one or more relay communications devices of a current relay path and the remote communications device determines that it is to reselect a new relay path.

[0100] Paragraph 16. A remote communications device configured to perform a relay selection procedure, the remote communications device comprising transceiver circuitry to transmit signals to and / or receive signals from a wireless communications network, and controller circuitry configured in combination with the transceiver circuitry to determine that a plurality of available relay paths exist between the remote communications device and the wireless communications network, each of the available relay paths either being single-hop relay paths comprising one relay communications device or multi-hop relay paths comprising two or more relay communications devices, to determine one or more candidate relay paths from among the plurality of available relay paths in accordance with a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multi-hop relay paths, wherein the candidate relay paths are determined based on a quality of a communications link between the remote communications device and a first relay communications device of each of the candidate relay paths being above a first threshold quality, to select one of the candidate relay paths, and to transmit signals to and / or to receive signals from the wireless communications network via a first relay communications device with which the remote communications device is connected via a sidelink communications interface, the first relay communications device forming part of the selected relay path.

[0101] Paragraph 17. Circuitry for a remote communications device configured to perform a relay selection procedure, the circuitry comprising transceiver circuitry to transmit signals to and / or receive signals from a wireless communications network, and controller circuitry configured in combination with the transceiver circuitry to determine that a plurality of available relay paths exist between the remote communications device and the wireless communications network, each of the available relay paths either being single-hop relay paths comprising one relay communications device or multi-hop relay paths comprising two or more relay communications devices, to determine one or more candidate relay paths from among the plurality of available relay paths in accordance with a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multi-hop relay paths, wherein the candidate relay paths are determined based on a quality of a communications link between the remote communications device and a first relay communications device of each of the candidate relay paths being above a first threshold quality, to select one of the candidate relay paths, and to transmit signals to and / or to receive signals from the wireless communications network via a first relay communications device with which the remote communications device is connected via a sidelink communications interface, the first relay communications device forming part of the selected relay path.

[0102] Paragraph 18. A method of operating an infrastructure equipment forming part of a communications network and configured to transmit signals to and / or receive signals from a remote communications device, the method comprising transmitting, to the remote communications device, control signalling indicating whether the remote communications device is allowed to select a multi-hop relay path for transmitting signals to and / or receiving signals from the wireless communications network or whether the remote communications is only allowed to select a single-hop relay path for transmitting signals to and / or receiving signals from the wireless communications network, wherein single-hop relay paths comprise one relay communications device between the remote communications device and the infrastructure equipment and multi-hop relay paths comprise two or more relay communications devices between the remote communications device and the infrastructure equipment, and transmitting signals to and / or receiving signals from the remote communications device via a selected relay path selected by the remote communications device in accordance with both of the control signalling and a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multi -hop relay paths. Paragraph 19. A method according to Paragraph 18, wherein the control signalling indicates that the remote communications device is allowed to select a multi-hop relay path as the selected relay path if a quality of a communications link between the remote communications device and the wireless communications network is below a threshold quality.

[0103] Paragraph 20. A method according to Paragraph 18 or Paragraph 19, wherein the control signalling indicates that the remote communications device is allowed to select a multi-hop relay path as the selected relay path if a quality of a communications link between the remote communications device and the wireless communications network is below one of a set of threshold qualities, each of the set of threshold qualities being associated with a different number of hops of the multi-hop relay path and decreasing as the number of hops increases.

[0104] Paragraph 21. An infrastructure equipment forming part of a communications network, the infrastructure equipment comprising transceiver circuitry to transmit signals to and / or receive signals from a remote communications device, and controller circuitry configured in combination with the transceiver circuitry to transmit, to the remote communications device, control signalling indicating whether the remote communications device is allowed to select a multi-hop relay path for transmitting signals to and / or receiving signals from the wireless communications network or whether the remote communications is only allowed to select a single-hop relay path for transmitting signals to and / or receiving signals from the wireless communications network, wherein single-hop relay paths comprise one relay communications device between the remote communications device and the infrastructure equipment and multi-hop relay paths comprise two or more relay communications devices between the remote communications device and the infrastructure equipment, and to transmit signals to and / or to receive signals from the remote communications device via a selected relay path selected by the remote communications device in accordance with both of the control signalling and a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multi -hop relay paths.

[0105] Paragraph 22. Circuitry for an infrastructure equipment forming part of a communications network, the infrastructure equipment comprising transceiver circuitry to transmit signals to and / or receive signals from a remote communications device, and controller circuitry configured in combination with the transceiver circuitry to transmit, to the remote communications device, control signalling indicating whether the remote communications device is allowed to select a multi-hop relay path for transmitting signals to and / or receiving signals from the wireless communications network or whether the remote communications is only allowed to select a single-hop relay path for transmitting signals to and / or receiving signals from the wireless communications network, wherein single-hop relay paths comprise one relay communications device between the remote communications device and the infrastructure equipment and multi-hop relay paths comprise two or more relay communications devices between the remote communications device and the infrastructure equipment, and to transmit signals to and / or to receive signals from the remote communications device via a selected relay path selected by the remote communications device in accordance with both of the control signalling and a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multi -hop relay paths.

[0106] Paragraph 23. A communications system comprising a first communications device according to Paragraph 16 and an infrastructure equipment according to Paragraph 21.

[0107] Paragraph 24. A computer program comprising instructions which, when loaded onto a computer, cause the computer to perform a method according to any of Paragraphs 1 to 15 or Paragraphs 18 to 20. Paragraph 25. A non-transitory computer-readable storage medium storing a computer program according to Paragraph 24.

[0108] It will be appreciated that the above description for clarity has described embodiments with reference to different functional units, circuitry and / or processors. However, it will be apparent that any suitable distribution of functionality between different functional units, circuitry and / or processors may be used without detracting from the embodiments.

[0109] Described embodiments may be implemented in any suitable form including hardware, software, firmware or any combination of these. Described embodiments may optionally be implemented at least partly as computer software running on one or more data processors and / or digital signal processors. The elements and components of any embodiment may be physically, functionally and logically implemented in any suitable way. Indeed, the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the disclosed embodiments may be implemented in a single unit or may be physically and functionally distributed between different units, circuitry and / or processors.

[0110] Although the present disclosure has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognise that various features of the described embodiments may be combined in any manner suitable to implement the technique.

[0111] References

[0112] [1] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based radio access”, John Wiley and Sons, 2009.

[0113] [2] TR 38.913, “3rdGeneration Partnership Project; Technical Specification Group Radio Access Network; Study on Scenarios and Requirements for Next Generation Access Technologies (Release 14)”, 3GPP, V 14.3.0, August 2017.

[0114] [3] TS 38.470, “3rdGeneration Partnership Project; Technical Specification Group Radio Access Network; NG-RAN; Fl general aspects and principles”, (Release 17)”, 3GPP, V17.2.0, September 2022.

[0115] [4] TS 38.473, “3rdGeneration Partnership Project; Technical Specification Group Radio Access Network; NG-RAN; Fl application protocol (F1AP) (Release 17)”, 3GPP, V17.2.0, September 2022.

[0116] [5] RP-193253, “New SID: Study on NR sidelink relay”, (OPPO), December 2019.

[0117] [6] TR 36.746, “3rdGeneration Partnership Project; Technical Specification Group Radio Access Network; Study on further enhancements to LTE Device to Device (D2D), User Equipment (UE) to network relays for Internet of Things (loT) and wearables (Release 15)”, 3GPP, VI 5. 1.1, April 2018.

[0118] [7] RP-241609, “New WID on NR sidelink multi -hop relay”, (LG Electronics, InterDigital, FirstNet), June 2024.

[0119] [8] TS 38.300, “3rdGeneration Partnership Project; Technical Specification Group Radio Access Network; NR; NR and NG-RAN Overall Description; Stage 2 (Release 18)”, 3GPP, V18.2.0, June 2024.

Claims

CLAIMSWhat is claimed is:

1. A method of performing a relay selection procedure by a remote communications device configured to transmit signals to and / or receive signals from a wireless communications network, the method comprising determining that a plurality of available relay paths exist between the remote communications device and the wireless communications network, each of the available relay paths either being single-hop relay paths comprising one relay communications device or multi-hop relay paths comprising two or more relay communications devices, determining one or more candidate relay paths from among the plurality of available relay paths in accordance with a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multi-hop relay paths, wherein the candidate relay paths are determined based on a quality of a communications link between the remote communications device and a first relay communications device of each of the candidate relay paths being above a first threshold quality, selecting one of the candidate relay paths, and transmitting signals to and / or receiving signals from the wireless communications network via a first relay communications device with which the remote communications device is connected via a sidelink communications interface, the first relay communications device forming part of the selected relay path.

2. A method according to Claim 1, wherein the path selection rule defines that the remote communications device is to determine the candidate relay paths only from among the single-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality.

3. A method according to Claim 1, wherein the path selection rule defines that the remote communications device is to determine, only if the quality of the communications link between the remote communications device and the first relay communications device of each of the single-hop relay paths is not above the first threshold quality, the candidate relay paths from among the multi-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality.

4. A method according to Claim 1, wherein the remote communications device selects the selected relay path based on one or more parameters of the selected relay path, the one or more parameters including the quality of the communications link between the remote communications device and the first relay communications device of the selected relay path.

5. A method according to Claim 1, wherein the path selection rule defines that a priority of the single-hop relay paths is higher than a priority of the multi -hop relay paths, and wherein the remote communications device determines the candidate relay paths from among both the single-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality and the multi-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality.

6. A method according to Claim 5, wherein the priority of each of the multi-hop relay paths is dependent on a number of hops of that multi -hop relay path, and wherein the priority decreases as the number of hops increases.

7. A method according to Claim 5, wherein the remote communications device selects the selected relay path based on both of the priority of the selected relay path and one or more other parameters of the selected relay path, the one or more parameters including the quality of the communications link between the remote communications device and the first relay communications device of the selected relay path.

8. A method according to Claim 1, wherein the path selection rule defines that the communications device is to determine the candidate relay paths from among both the single-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above the first threshold quality and the multi-hop relay paths for which the quality of the communications link between the remote communications device and the first relay communications device is above a second threshold quality.

9. A method according to Claim 1, comprising determining, based on a message received from a first relay communications device of each of the available relay paths, whether each of the available relay paths is a single-hop relay path or a multihop relay path, wherein the message further indicates, for each of the multi-hop relay paths, a number of hops of that multi-hop relay path.

10. A method according to Claim 1, comprising receiving, from the wireless communications network, control signalling indicating whether or not the remote communications device is allowed to select a multi-hop relay path as the selected relay path.

11. A method according to Claim 10, wherein the control signalling indicates that the remote communications device is allowed to select a multi-hop relay path as the selected relay path if a quality of a communications link between the remote communications device and the wireless communications network is below a third threshold quality.

12. A method according to Claim 10, wherein the control signalling indicates that the remote communications device is allowed to select a multi-hop relay path as the selected relay path if a quality of a communications link between the remote communications device and the wireless communications network is below one of a set of third threshold qualities, each of the set of third threshold qualities being associated with a different number of hops of the multi -hop relay path and decreasing as the number of hops increases.

13. A method according to Claim 1, wherein the remote communications device is configured to perform the relay selection procedure dependent on receiving, from a first relay communications device of a current relay path being used by the remote communications device to transmit signals to and / or receive signals from the wireless communications network, an indication that a radio link failure has occurred on a communications link between two relay communications devices of the current relay path.

14. A method according to Claim 1, wherein the relay selection procedure is an initial relay selection procedure that is performed by the remote communications device at a time at which the remote communications device is not currently communicating with the wireless communications network via a relay communications device.

15. A method according to Claim 1, wherein the relay selection procedure is a relay reselection procedure that is performed by the remote communications device at a time at which the remote communications device is currently communicating with the wireless communications network via one or more relay communications devices of a current relay path and the remote communications device determines that it is to reselect a new relay path.

16. A remote communications device configured to perform a relay selection procedure, the remote communications device comprising transceiver circuitry to transmit signals to and / or receive signals from a wireless communications network, and controller circuitry configured in combination with the transceiver circuitry to determine that a plurality of available relay paths exist between the remote communications device and the wireless communications network, each of the available relay paths either being single-hop relay paths comprising one relay communications device or multi-hop relay paths comprising two or more relay communications devices, to determine one or more candidate relay paths from among the plurality of available relay paths in accordance with a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multi-hop relay paths, wherein the candidate relay paths are determined based on a quality of a communications link between the remote communications device and a first relay communications device of each of the candidate relay paths being above a first threshold quality, to select one of the candidate relay paths, and to transmit signals to and / or to receive signals from the wireless communications network via a first relay communications device with which the remote communications device is connected via a sidelink communications interface, the first relay communications device forming part of the selected relay path.

17. Circuitry for a remote communications device configured to perform a relay selection procedure, the circuitry comprising transceiver circuitry to transmit signals to and / or receive signals from a wireless communications network, and controller circuitry configured in combination with the transceiver circuitry to determine that a plurality of available relay paths exist between the remote communications device and the wireless communications network, each of the available relay paths either being single-hop relay paths comprising one relay communications device or multi-hop relay paths comprising two or more relay communications devices, to determine one or more candidate relay paths from among the plurality of available relay paths in accordance with a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multi-hop relay paths, wherein the candidate relay paths are determined based on a quality of a communications link between the remote communications device and a first relay communications device of each of the candidate relay paths being above a first threshold quality, to select one of the candidate relay paths, and to transmit signals to and / or to receive signals from the wireless communications network via a first relay communications device with which the remote communications device is connected via a sidelink communications interface, the first relay communications device forming part of the selected relay path.

18. A method of operating an infrastructure equipment forming part of a communications network and configured to transmit signals to and / or receive signals from a remote communications device, the method comprising transmitting, to the remote communications device, control signalling indicating whether the remote communications device is allowed to select a multi-hop relay path for transmitting signals to and / or receiving signals from the wireless communications network or whether the remote communications is only allowed to select a single-hop relay path for transmitting signals to and / or receiving signals from the wireless communications network, wherein single-hop relay paths comprise one relay communications device between the remote communications device and the infrastructure equipment and multi-hop relay paths comprise two or more relay communications devices between the remote communications device and the infrastructure equipment, and transmitting signals to and / or receiving signals from the remote communications device via a selected relay path selected by the remote communications device in accordance with both of the control signalling and a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multi -hop relay paths.

19. A method according to Claim 18, wherein the control signalling indicates that the remote communications device is allowed to select a multi-hop relay path as the selected relay path if a quality of a communications link between the remote communications device and the wireless communications network is below a threshold quality.

20. A method according to Claim 18, wherein the control signalling indicates that the remote communications device is allowed to select a multi-hop relay path as the selected relay path if a quality of a communications link between the remote communications device and the wireless communications network is below one of a set of threshold qualities, each of the set of threshold qualities being associated with a different number of hops of the multi -hop relay path and decreasing as the number of hops increases.

21. An infrastructure equipment forming part of a communications network, the infrastructure equipment comprising transceiver circuitry to transmit signals to and / or receive signals from a remote communications device, and controller circuitry configured in combination with the transceiver circuitry to transmit, to the remote communications device, control signalling indicating whether the remote communications device is allowed to select a multi-hop relay path for transmitting signals to and / or receiving signals from the wireless communications network or whether the remote communications is only allowed to select a single-hop relay path for transmitting signals to and / or receiving signals from the wireless communications network, wherein single-hop relay paths comprise one relay communications device between the remote communications device and the infrastructure equipment and multi-hop relay paths comprise two or more relay communications devices between the remote communications device and the infrastructure equipment, and to transmit signals to and / or to receive signals from the remote communications device via a selected relay path selected by the remote communications device in accordance with both of the control signalling and a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multi -hop relay paths.

22. Circuitry for an infrastructure equipment forming part of a communications network, the infrastructure equipment comprisingtransceiver circuitry to transmit signals to and / or receive signals from a remote communications device, and controller circuitry configured in combination with the transceiver circuitry to transmit, to the remote communications device, control signalling indicating whether the remote communications device is allowed to select a multi-hop relay path for transmitting signals to and / or receiving signals from the wireless communications network or whether the remote communications is only allowed to select a single-hop relay path for transmitting signals to and / or receiving signals from the wireless communications network, wherein single-hop relay paths comprise one relay communications device between the remote communications device and the infrastructure equipment and multi-hop relay paths comprise two or more relay communications devices between the remote communications device and the infrastructure equipment, and to transmit signals to and / or to receive signals from the remote communications device via a selected relay path selected by the remote communications device in accordance with both of the control signalling and a path selection rule specified for the remote communications device that configures the remote communications device to prioritise single-hop relay paths over multi -hop relay paths.

23. A communications system comprising a first communications device according to Claim 16 and an infrastructure equipment according to Claim 21.

24. A computer program comprising instructions which, when loaded onto a computer, cause the computer to perform a method according to Claim 1 or Claim 18.

25. A non-transitory computer-readable storage medium storing a computer program according to Claim 24.

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