Methods and apparatus for managing multi-path communication in multi-path relay

Abstract

Methods and apparatus for use in managing multi-path communication in a wireless communication system supporting relaying between a User Equipment, UE, and a network including a first base station are disclosed. A method performed at a first base station, where a first communication path has been established between the UE and the first base station, comprises sending, to the UE, a configuration message including configuration information for configuring the UE for communication with the network, wherein the configuration message further includes multi-path information for indicating the configuration information is associated with at least one other communication path to be configured between the UE and the network to provide multiple paths between the UE and the network or information indicating multiple paths are to be configured.

Description

[0001] METHODS AND APPARATUS FOR MANAGING MULTI-PATH COMMUNICATION IN MULTI-PATH RELAY

[0002] Field of the Invention

[0003] The present invention generally relates to managing multi-path communication in a wireless communication system supporting relaying (e.g. multi-path or multiple paths relaying) between a user equipment, UE, and a base station. For example, the present invention relates to a multi-path sidelink relay in a communication system supporting sidelink (SL) relaying (e.g., multipath relaying transmission). In particular, the present invention relates to methods for managing a path addition so as a user equipment, UE, and a base station of a communication system supporting multi-path using sidelink relaying are able to communicate with each other through several paths.

[0004] Background

[0005] The 3rd Generation Partnership Project (3GPP) has initiated the development of new radio access technology known as fifth-generation New Radio (5G NR) to respond to requirements related to very high reliability and very low latency. The 5G NR is not referred only to the enhancement of radio access technology but also to address a wide range of new services to be enabled by future mobile communication. Three distinctive categories of use cases are defined in NR from enhanced mobile broadband (eMBB), massive machine typing communication (mMTC) to Ultra-Reliable and Low Latency communication (URLLC).

[0006] A first version of Sidelink for 5G, or New Radio (NR) Sidelink, has been developed in 3GPP Release 16 as part of the 5G V2X Work Item, to support advanced vehicle-to-anything (V2X) scenarios and commercial applications and services in addition to complement former basic safety services. NR V2X addresses advanced driving use cases where vehicles are exchanging large amount of data while respecting a low latency requirement. NR Sidelink is designed to provide three basic transmission scenarios: broadcast, groupcast and unicast communications, while considering both out-of-coverage and in-network coverage deployment scenarios.

[0007] Based on the NR sidelink technology, 3 GPP introduced the sidelink-based relaying functionality as part of the 3GPP Release 17 framework, where a relay UE may provide User Plane (UP) and Control Plane (CP) data relaying between a set of served remote UEs and the network (UE-to-network, or U2N, relay) or between a source remote UE, or source UE, and a target remote UE, or target UE (UE-to-UE, or U2U relay). The purpose of the Release 17 sidelink relaying functionality was to both extend sidelink / network coverage and improve power efficiency, while considering a wider range of applications and services, including V2X, Public Safety and commercial applications and services. Some of these new V2X scenarios require ultra-reliability and low latency (URLLC) performance, in order to meet high-speed and high-density constraints, while requiring some network coverage extension, which may be achieved through sidelink relaying.

[0008] This first version of the sidelink relaying functionality, as defined in the Release 17 specification, mainly aimed at supporting the UE-to-network (U2N) relay with basic functionalities and limited features. For better support of the use cases requiring sidelink relay, further enhancements are necessary in order to introduce the potential solutions identified during the Rel-17 study item. The follow-up 3GPP Release 18 work item “NR Sidelink Relay (SLR) Enhancements” has addressed several solutions considered as enhancement areas needed in NR Sidelink Relay system for the V2X, public safety and commercial use cases.

[0009] The multipath relay has been identified as a solution to specify in the Release 18 NR SLR Enhancements WI, where a remote UE is connected to the network via a direct path (e.g. the path is the link between the UE and a base station (also referred to as a gNB) of the network which link is referred to as a Uu link) and an indirect path (e.g. a path which includes a relay UE between the remote UE and the base station (also referred to as a gNB) of the network, where the link between the remote UE and the relay UE is referred to as a PC5 link and thus the path includes a PC5 link and a Uu link), with a potential to improve the reliability, the robustness and the throughput.

[0010] This multipath relay solution aims to provide applications requiring high Uplink data rates on 5G terminals, to achieve the required UL data rate, especially at the edge of a cell. Furthermore, the multipath relaying can improve the reliability and the stability of the provided services while reducing the latency if one of the paths is suffering from deteriorating channel conditions.

[0011] A remote UE configured for multipath relaying can transmit the data via multiple paths. The transmitted data is associated to a radio bearer configured by the network. In order to improve the reliability and / or the throughput, the data can be transmitted via multiple paths and thus, one radio bearer can be mapped to multiple configured paths. This radio bearer has been considered in RAN2 meetings for Release 18 multipath relaying scenarios and has been named “MP split bearer” or “MP bearer”. A MP bearer can be a Signaling Radio Bearer (SRB) for control data or a Data Radio Bearer (DRB) for user data. Since the data can be transmitted via multiple paths with a MP bearer, the transmitted data volume can be balanced on the multiple paths in order to achieve higher reliability and / or throughput as functions of the channel occupancy or radio conditions on the different paths. For this purpose, the data split can be used and the data packets can be delivered through the direct path or the indirect path or both of the multipath relaying system.

[0012] However, to use this multi-path system to improve the data communication as described above, there is a need to define a new procedure to add a second path to an ongoing single path configuration and so enable the multi-path communication. This path addition can also be seen as a multi-path setup procedure. In addition, when a multi-path is already established and according to environment variations due for example to the mobility of the involved User Equipments (Remote and / or Relay UE) or to the load of the current serving nodes (cells, base stations or relays) or to the appearance of interference that impacts the serving nodes, it could be desirable for the remote UE to adapt its configuration so as to maintain or improve a high quality of service. Besides, it is also an objective to define the behaviour when the system failed adding a new path or to modifying an existing one.

[0013] Therefore, some new mechanisms are required to define the multi-path setup or modification procedure in a communication system supporting sidelink relay and / or multipath relaying which take account of the aforementioned considerations.

[0014] Summary

[0015] In accordance with a first aspect of the present invention, there is provided a method, performed at a first base station, for managing multi-path communication in a wireless communication system supporting relaying between a User Equipment, UE, and a network including at least the first base station as recited in claim 1 of the accompanying claims.

[0016] In accordance with a second aspect of the present invention, there is provided a method, performed at a User Equipment, UE, for managing multi-path communication in a wireless communication system supporting relaying between a User Equipment, UE, and a network including at least the first base station, as recited in claim 23 of the accompanying claims.

[0017] In accordance with a third aspect of the present invention, there is provided a method, performed at a relay node, for managing multi-path communication in a wireless communication system supporting relaying between a User Equipment, UE, and a network including at least the first base station, as recited in claim 70 of the accompanying claims.

[0018] In accordance with a fourth aspect, there is provided a method, performed at a User Equipment, UE, for managing multi-path communication in a wireless communication system supporting relaying between a User Equipment, UE, and a network including a first base station, wherein a first communication path has been established between the UE and the first base station, and wherein a second UE (e.g. in the vicinity of the UE) is capable of establishing a non-3GPP connection with the UE and supporting relaying between the UE and the network. The method comprises sending, to the first base station, a measurement report message, the measurement report message for indicating a non-3GPP connection can be established between the UE and the second UE. By sending the measurement report message indicating that a non- 3GPP connection can be established between the UE and a second UE (e.g. a non-3GPP candidate) in the measurement report message (which measurement report message may also include information about other UE(s) in the vicinity of the UE that could be a candidate relay node(s) using 3GPP connections (e.g. 3GPP relay candidates), the base station receives information about all potential relay candidates (non-3GPP relay candidates and 3 GPP relay candidates if available) in one message and does not need to wait for additional messages to indicate the candidate relays for the UE.

[0019] In accordance with a fifth aspect of the present invention, there is provided apparatus for a base station for a wireless communication system supporting relaying as recited in claim 88 of the accompanying claims.

[0020] In accordance with a sixth aspect of the present invention, there is provided apparatus for a UE for a wireless communication system supporting relaying as recited in claim 89 of the accompanying claims.

[0021] In accordance with another aspect, a method at a User Equipment, UE, operating in a wireless communication system capable of supporting relaying between the UE and a network including a base station is provided. The method comprises receiving information (e.g. capability information) for at least one other UE. For each of the at least one other UE, the capability information indicates at least one of the other UE is capable of operating as a relay node for providing an indirect communication path between the UE and the network; the other UE supports PC5 triggering where the relay node can be triggered to enter a RRC CONNECTED state using a PC5 message. The capability information may be received from one or more neighbouring UEs in a discovery message (e.g. as part of a discovery procedure) and before the UE is configured by the network (e.g. before the UE is configured to set up multiple communication paths). As discussed below, the capability information may be an indication that the UE has release 18 capability.

[0022] The method may further comprise sending, to the base station, the capability information. For example, the capability information may be sent in a measurement report and / or in a SidelinkUEInformationNR message. The capability information may be used by the base station to configure the UE. For example, the base station may use the information about the PC5 triggering support for the at least one candidate relay UE to configure the SRB1 on the indirect path if the relay UE does not support PC5 triggering.

[0023] Further example features of the invention are described in other independent and dependent claims.

[0024] Any feature in one aspect of the invention may be applied to other aspects of the invention, in any appropriate combination. In particular, method aspects may be applied to apparatus / device / unit aspects, and vice versa.

[0025] Furthermore, features implemented in hardware may be implemented in software, and vice versa. Any reference to software and hardware features herein should be construed accordingly. For example, in accordance with other aspects of the invention, there are provided a computer program comprising instructions which, when the program is executed by one or more processing units, cause the one or more processing units to carry out the method of any aspect or example described above and a computer readable storage medium carrying the computer program.

[0026] Brief Description of the Drawings

[0027] Different aspects of the invention will now be described, by way of example only, and with reference to the following drawings in which:

[0028] Figure la is a schematic diagram illustrating an example wireless communication system in which the present invention may be implemented according to one or more embodiments;

[0029] Figure lb is a schematic diagram illustrating a typical 5G Proximity-based Services (ProSe) Relay reference architecture;

[0030] Figure 2 is a schematic diagram illustrating user plane stacks of some protocol layers involved in Sidelink relay operations for UE-to-network (U2N) based relaying;

[0031] Figures 3 to 8 are schematic and simplified diagrams illustrating examples of message flows for managing multi-path communication in a wireless communication system in accordance with one or more embodiments of the invention;

[0032] Figures 9 to 11 are schematic and simplified diagrams illustrating examples of message flows for managing multi-path communication in a wireless communication system in a case of multi-path adaptation failure in accordance with one or more embodiments of the invention; Figure 12 is a schematic and simplified diagram illustrating examples of message flows for managing multi-path communication in a wireless communication system in accordance with one or more embodiments of the invention;

[0033] Figures 13 is a schematic and simplified diagram illustrating examples of message flows for managing multi-path communication in a wireless communication system in a case of multi-path adaptation failure in accordance with one or more embodiments of the invention;

[0034] Figure 14 is a simplified flowchart of a method performed at a base station in accordance with one or more embodiments of the present invention;

[0035] Figure 15 is a simplified flowchart of a method performed at a UE in accordance with one or more embodiments of the present invention;

[0036] Figure 16 is a simplified flowchart of a method performed at a relay node in accordance with one or more embodiments of the present invention;

[0037] Figure 17 is a block schematic diagram of an example wireless communication device in accordance with embodiments of the present invention.

[0038] Detailed Description

[0039] Figure la represents an example of a wireless communication system 100 capable of supporting relaying between a User Equipment (UE) and a base stationand shows a relay arrangement or system (or network) including a plurality of nodes including one or more relay nodes (e.g. relay User Equipment (UE)) serving one or more remote User Equipment (UE).

[0040] In the following description reference is made to a wireless communication system 100 capable of supporting Sidelink Relay where a path between a remote UE and a base station includes a sidelink connection (also known as a PC5 link) between the remote UE and a relay UE and a network connection (also known as a Uu link) between the relay UE and the base station. However, it is not intended that the present invention is limited to a PC5 link between the remote UE and the relay UE and could apply to relaying configurations where the link between the remote UE and the relay UE is via another type of connection (e.g. a non-3GPP connection), such as a WiFi or Bluetooth.

[0041] With reference to Figure la, UE node 110 is served by network node 101 and may operate as a relay UE node relaying data between one of the UE nodes 111, 112 (referred to as remote UE nodes) and the network node 101, hence performing UE-to-network (U2N) relay. In its turn, UE 111 may operate as a relay UE node relaying between the UE node 113 and the network node 101 through the other relay node 110. In the example of the figure la, the UE 112 may act as a remote UE and as a relay UE. In an example where the network node 101 is part of a cellular network, the relay UE 110 is served by a cell controlled by the network node 101.

[0042] UE node 120 is also served by network node 101 and may have some relaying capability, i.e. UE node 120 may act as a UE-to-network (U2N) relay UE at some time (e.g. for UE node 112 via link 112c), even though it is not serving any remote UE at the time represented in Figure la.

[0043] UE node 130 is served by network node 102 and may also operate as a UE-to-network (U2N) relay UE node (for example, relaying data between the remote UE 131 and the network node 102).

[0044] The network nodes 101 and 102 may be base stations of a wireless network or network, such as a fifth-generation (5G) New Radio (NR) network or a Long Term Evolution (LTE) network. Figure la only shows the base stations of the wireless network for clarity. Although not shown in figure la, the base stations are connected to a core network. For a 5GNR network, the network node 101, or 102, is referred to as a gNB and are part of the NG-RAN.

[0045] Even though sidelink relay is most likely to be considered in the context of V2X networks, it is not intended that the invention is limited to UE nodes that are in or part of a vehicle. Each of the UE nodes (relay or remote) may be a wireless communication device located in or part of a vehicle or a Road Side Unit (RSU) or a wireless communication device of a Vulnerable Road User (VRU) (e.g. a mobile or portable communication device (such as a smart phone, PDA, laptop, or similar devices) of a pedestrian or cyclist). In the following, a relay UE node will also be referred to as a relay UE, a remote UE node will also be referred to as a remote UE and a network node will be referred to as a base station or as a gNB. It will however be appreciated that the terms first and second UEs may be used instead of remote UE and relay UE. Although in the following description, embodiments and examples of embodiments of the present invention will be described with respect to a 5G NR network, it will be appreciated that it is not intended that the present invention is limited to 5G NR systems and may be used in any wireless communication systems supporting sidelink (or peer to peer) relay communications.

[0046] In an example shown in Figure la, in a UE-to-Network (or U2N) scenario with the UE 110 (or UE 130) operating as UE-to-Network relay UE, the UE-to-Network relay UE 110 (or relay UE130) connects the UEs 111 and 112 (or UE 131), operating as remote UEs, to the gNB 101 (or gNB 102). The remote UE 111 is connected to the relay UE 110 via or through a sidelink I l la which may be referred to as a PC5 hop or link or connection or interface I l la. Similarly, remote UE 112, remote UE 113 and remote UE 131 have PC5 hops, or links or connections or interfaces 112a, 113a and 131a respectively with the relay UE 110, relay UE 111 and relay UE 130. A Uu hop or link or connection or interface 110a connects the relay UE 110 to the gNB 101, while a Uu hop or link or connection or interface 120a and 130a respectively connect the relay UE 120 to the gNB 101 and the UE 130 to the gNB 102. PC5 connections are used for the relayed traffic of the remote UEs (111, 112, 113 and 131) and the non-relayed traffic specific to the relay UE 110, 111, 130, i.e. for the direct communications between relay UE 110, 111, 130 and the other remote UEs (111, 112, 113 and 131). Therefore, the remote UE I l l is connected to the gNB 101 through the relay UE 110 with a PC5 hop I l la and a Uu hop 110a. For uplink communication, the remote UE 111 is the source node (or transmitter node for transmitting data) and the gNB 101 is the destination or target node (or receiver node for receiving data) for a sidelink relay connection established between the remote UE 111 and the gNB 101 with a PC5 hop I l la and a second Uu hop 110a and for downlink communication, the remote UE I l l is the destination or target node (or receiver node) and the gNB 101 is the source node (or transmitter node). Similarly, the remote UE 131 is connected to the gNB 102 through the relay UE 130 with a PC5 hop 131a and a Uu hop 130a. The remote UE 113 for its part is connected to the gNB 101 through the relay UE 111 with a 1stPC5 hop 113a and then through the relay UE 110 with a 2ndPC5 hop I l la and a Uu hop 110a. It will be appreciated that the terms first and second could be used in place of source and target.

[0047] At some point, the gNB 101 may decide to setup a multi-path to the remote UE 112. For example, to maintain the QoS despite an increase of the applicative traffic to transmit / receive from / to the remote UE 112. Then, based on some information such as measurement information received from the different UEs (relay, remote) in, for example, measurement reports and / or measurements made by the gNB 101 itself, the source gNB 101 may decide to add an additional path either a direct path (link 112b) or a new indirect path through the relay UE 120 (links 112c and 120a) so as to set up a multi-path between the remote UE 112 and the network.

[0048] At some other point, the gNB 101, acting as a source gNB, may decide to hand over the relay UE 110 to the gNB 102, which would then act as a target gNB. For example, in the case where the radio conditions in the serving cell (not shown in Figure la) controlled by the source gNB 101 deteriorate such that the radio conditions in the target cell (not shown in Figure la) controlled by the target gNB 102 are better than the serving cell, the source gNB 101 may decide to handover the relay UE 110 to the target gNB 102. In such a case, the relay UE 110 would detach from the source gNB 101, thereby releasing the Uu link 110a to further connect to the target gNB 102 through Uu link 110b (shown in dotted lines in Figure la) established as part of a re-establishment procedure. In addition to the handover of the relay UE 110, the gNB 101 may further decide to modify the multi-path configuration of the remote UE 112 so as to keep all paths in the same serving cell (i.e. gNB 101) either by replacing the indirect path through the relay UE 110 by a new path attached to the gNB 101, for example, a direct path (link 112b) or a new indirect path through the relay UE 120 (links 112c and 120a) or move the remote UE 112 to the gNB 102. A multi-path to connect the remote UE 112 may be reestablished to the gNB 102. In another variant, the remote UE 112 may keep its multi-path attached to two different gNBs (101 and 102).

[0049] At some other point, where the remote UE 112 and the gNB 101 have an established multi-path with a direct path (link 112b) and an indirect path (links 112a and 110a) through the relay UE1 110, the gNB 101 may decide to modify one of the paths of the multi-path. For example, in the case where the radio conditions in the serving cell controlled by the gNB 101 deteriorate i.e. if the link quality or signal strength of the direct path (link 112b) to the gNB 101 becomes lower to a threshold and meanwhile a relay UE 120 appears to be a good candidate i.e. if the link quality or signal strength of the candidate relay UE 120 served by the gNB 101 is greater than a threshold, the gNB 101 may decide to replace the direct path (link 112b) by an indirect path through the relay UE 120 (links 112c and 120a). In other word, the remote UE 112 is getting to become out-of-coverage (no more direct link connection available whatever the gNB) and the gNB 101 decides to modify the multi-path from one direct and one indirect path to two indirect paths. In such a case, the remote UE 112 may maintain a multi-path enabled even in out-of-coverage case.

[0050] The remote and relay UEs are attached to the core network through their serving gNB. Figure lb represents a typical 5G Proximity-based Services (ProSe) Relay reference architecture and shows the different connections between the core network entities of the 5G core (5GC) such as the Access and Mobility Management Function (AMF) entity, the Session Management Function (SMF) entity and the User Plane Function (UPF) entity, the UEs (5G ProSe Remote and 5G ProSe Relay) and the NG-RAN (i.e. base station or gNB). The 5G ProSe Remote UE and 5G ProSe Relay may be served by the same or different PLMNs (Public Land Mobile Network). If the serving PLMNs of the 5G Remote UE and the 5G ProSe Relay are different then the NG-RAN is shared by the serving PLMNs.

[0051] In order to set up a relayed traffic between a first node (remote UE) and a second node (gNB or remote UE), a Sidelink relay architecture may be used according to the 3 GPP TR 38.836. The user plane architecture or protocol stack is shown in Figure 2 and represents the Sidelink Relay adaptation layer called SRAP that is introduced between the PDCP layer and the RLC layer at the extreme nodes and above the RLC layer in the relay UE. This architecture was first documented in the TR 38.836 and finally refined in 3GPP TS 38.300 while the SRAP layer is defined in 3GPP TS 38.351.

[0052] This architecture shown in Figure 2 shows the Sidelink relay architecture 200 for the UE- to-Network relay scenario. As shown in Figure 2 illustrating a UE-to-Network relay scenario, the remote UE, such as remote UE 112, has a PC5 SRAP layer or entity 201 between its Uu PDCP layer 211 and its PC5 RLC layer 221. Similarly, the gNB, such as gNB 101, has a Uu SRAP layer or entity 204 between its Uu PDCP layer 212 and its Uu RLC layer 224.

[0053] As shown in Figure 2 related to a UE-to-Network relay scenario, at the relay UE, such as relay UE 110, there are two SRAP layers to interface with the PC5 hop 112a and the Uu hop 110a: the PC5 SRAP layer or entity 202 is connected to the PC5 SRAP 201 of the remote UE 112 through the PC5 hop 112a; and the Uu SRAP layer or entity 203 is connected to the Uu SRAP layer 204 at the gNB side 101 through the Uu link 110a. A remote UE 112 establishes End-to-End radio bearers 205 with the gNB 101. These radio bearers could be a Signalling Radio Bearer SRB or Data Radio Bearer DRB. Figure 2 shows an E2E Uu DRB / SRB 205 between the remote UE 112 and the gNB 101 by way of example.

[0054] The PC5 SRAP layer 202 of the UE-to-Network relay UE 110 receives data or packets (traffic data or signalling) over or via ingress PC5 Relay RLC channels 206 through the PC5- RLC layer from remote UE 112 (at PC5 hop 112a) in an uplink direction and transmits the packets to the Uu SRAP entity 203 of the same relay UE 110.

[0055] The Uu SRAP 203 entity will map the corresponding ingress PC5 Relay RLC channels 206 to egress Uu Relay RLC channels 207a and / or 207b at Uu link 110a. Thus, a mapping table is required for uplink and it is configured by gNB 101 at the Uu SRAP entity 203 of the relay UE 110.

[0056] The mapping table takes at its input an identifier of the remote UE 112 (e.g. L2-ID), an identifier of the E2E radio bearer 205 (e.g. the E2E Uu DRB ID) and an identifier of the ingress PC5 Relay RLC channel (or bearer) 206 and identifies the egress Uu Relay RLC bearer ID where the E2E radio bearers are mapped. For example, the UE E2E bearer ID and remote UE ID can be obtained from the header of a data packet received at the Uu SRAP entity 203 via the PC5-SRAP entity 202. An example of an entry for an uplink mapping table with one entry configured at the Uu SRAP entity 203 is shown in Table 1 below. It will be appreciated that the mapping table will be configured so that it has an entry for each remote UE connected to the relay UE.

[0057] Table 1

[0058] At the Uu side or link 110a, different radio bearers of the same remote UE or different remote UEs can be subject to N: 1 mapping and data multiplexing over Uu RLC channels 207a and 207b.

[0059] In the downlink direction, data or packets transmitted from gNB 101 arrive at the relay UE 110 through the Uu link 110a. The Uu SRAP layer 203 of the UE-to-Network relay UE 110 receives data or packets (traffic data or signalling) over or via ingress Uu Relay RLC channels 207a and 207b through the Uu-RLC layer from gNB 101 and transmits the packet to the PC5 SRAP entity 202 of the same relay UE 110. Those ingress Uu Relay RLC channels 207a and 207b will be mapped at the PC5 SRAP entity 202 of the relay UE 110 to the egress PC5 Relay RLC channels 206 at PC5 hop 112a. Thus, a mapping table is required for downlink and it is configured by the gNB 101 at PC5 SRAP entity 202 of the relay UE 110. The mapping table requires at its input the remote UE 112 L2-ID, the End-to-End radio bearer 205 ID and the ingress Uu Relay RLC channel (or bearer) 207a and 207b ID and identifies the egress PC5 Relay RLC channels (or bearer) 206 ID of the PC5 hop 112a. The End-to-End Radio bearer 205 is then mapped at the PC5 hop 112a to the egress PC5 Relay RLC channels 206. For example, the UE E2E bearer ID and remote UE ID can be obtained from the header of a packet received at the PC5 SRAP entity 202 via the Uu SRAP entity 203. An example of a downlink mapping table with one entry configured at the PC5 SRAP entity 202 is shown in Table 2 below. It will be appreciated that the mapping table will be configured so that it has an entry for each remote UE connected to the relay UE.

[0060] Table 2

[0061] As mentioned in 3GPP TS 38.351, each SRAP entity has a transmitting part and a receiving part. Across the PC5 interface 112a, the transmitting part of the PC5 SRAP entity 201 at the remote UE 112 has a corresponding receiving part at PC5 SRAP entity 202 at the UE-to-Network Relay UE 110, and vice-versa. Across the Uu interface 110a, the transmitting part of the Uu SRAP entity 203 at the UE-to-Network Relay UE 110 has a corresponding receiving part at Uu SRAP entity 204 at the gNB 101, and vice-versa. To summarize, the transmitting part of each SRAP entity at the UE-to-Network Relay UE 110 receives the data packet with its SRAP header from its corresponding receiving part (receiving part of the SRAP entity 202 forwards the data to the transmitting part of the SRAP entity 203 and vice-versa). The transmitting part of each SRAP entity owns a mapping table configured by the gNB 101 which allows the identification of the egress RLC channel (at Uu or PC5 link) based on the ingress RLC channel where the data packet is received and the UE and Bearer IDs carried in the SRAP header. Specific mapping rules may be applied for SRB0 and SRB 1 as specified in TS38.351 and TS38.331.

[0062] In the case of the multi-path with one indirect and one direct path, the remote UE 112 and the gNB 101 may communicate with each other through both paths. Thereby, each node has two protocol stacks: one for the indirect path such as described above and one for the direct path. The split between the direct and / or the indirect path is performed at the PDCP layer of each node. For the direct path, in the downlink direction, data or packets transmitted from gNB 101 through the direct path arrive at the remote UE 112 via ingress Uu Direct Path RLC channel 208 of the Uu link 112b. On the other hand, in the uplink direction, data or packets transmitted from the remote UE 112 through the direct path arrive at the gNB 101 via ingress Uu Direct Path RLC channel 208 of the Uu link 112b.

[0063] Referring now to Figure 3 which is a schematic and simplified diagram illustrating an example of message flows for managing multi-path communication (e.g. communication over multiple paths) in a wireless communication system, such as that shown in figure la, supporting relaying and in particular for managing a path addition procedure to enable or establish a multipath or Multi-Path (MP) comprising one direct and one indirect path, in accordance with one or more embodiments of the invention.

[0064] In one example, a remote UE, like remote UE 112, is connected to a base station, such as base station 101 (also referred to as gNB 101). The remote UE 112 and the base station 101 101 (also referred to as first base station 101) communicate with each other, in other words the remote UE 112 transmits some uplink data, or UL User Data 310, to the first base station 101 and / or the first base station 101 transmits some downlink data or DL User Data 310 to the remote UE 112. The communication path between the base station 101 and remote UE 112 could be direct (e.g. there is a direct connection between the base station 101 and UE 112) as shown in figure 3 for the path for the UL / DL User Data 310 or indirect (e.g. there is an indirect connection between the base station 101 and UE 112 via a relay node, such as a relay UE). The remote UE 112 may also send to the first base station some measurement report through respectively the Measurement Report message 311 as defined in 3GPP TS 38.331. The reporting includes at least Relay UE ID, Relay UE' s serving cell ID, and sidelink measurement quantity information. The sidelink measurement quantity information is further described below. The base station 101 may alternatively or additionally receive measurement report information from cells and / or UEs (possible candidate relay nodes) neighbouring or surrounding the remote UE 112.

[0065] In the particular case where the relay and remote UEs can be connected through a non- 3GPP connectivity (e.g. Bluetooth, wifi, or other peer-to-peer technology ...), the remote UE may also indicate a non-3GPP connection can be established between the remote UE and another UE that can support relaying for the remote UE in the measurement report. In that case, the information carried by the measurement report in relation to the relay UE(s) capable of establishing a non-3GPP connection may be all or part of the following: the Relay UE ID, Relay UE’s serving cell ID, the sidelink measurement quantity information and information that the connectivity between the relay UE and the remote UE is a non-3GPP link or connection (e.g., a N3C_Relay flag or bit that is set to true or 1 or which is conditionally present). In that case, the Relay UE ID may be one of the RNTI of the relay UE (e.g., C-RNTI or I-RNTI). In addition, the sidelink measurement quantity information may carry measurement information related to the non-3GPP technology with an indication on the kind of technology e.g., wlan measurement or Bluetooth measurement. The measurement report may also include PLMNs information of the relay which can be received through the non-3GPP link or connection. In a particular example, the PLMNs information is carried in a 3GPP Cellular Network ANQP element (as specified in the TS24.302) received from a WLAN station.

[0066] Thus, in the case where another UE(s) (or another node(s)) in the vicinity of or surrounding or neighbouring the remote UE 112 (such as UE 120) is capable of establishing a non-3GPP connection or link with the remote UE 112 and is capable of supporting relaying between the remote UE and the base station 101 (i.e. such other UE(s) is a potential candidate to operate as a non-3GPP relay node for the remote UE 112), the remote UE 112 may send, to the base station 101, a measurement report message for indicating a non-3GPP connection (e.g. Bluetooth, wifi, or other peer-to-peer technology ...) can be established between the remote UE 112 and the other UE. As discussed above, the measurement report message may include an information element, such as a N3C_Relay flag or bit that is set to true or 1, for indicating a non-3GPP connection can be established between the remote UE 112 and another UE. In another example, the measurement report message may only include an information element indicating a non-3GPP connection can be established when a non-3GPP connection can be established (i.e. if a non-3GPP connection cannot be established no IE is included in the measurement report message). The measurement report message may include at least one of: identification information for identifying the other UE(s) (e.g., C-RNTI or I-RNTI); serving cell identification information for identifying the cell serving of the other UE(s); link measurement quantity information associated with the non-3GPP connection. The link measurement quantity information may include information relating to the QoS, latency, link quality, signal strength of the non-3GPP connection. The measurement report message may include, in addition to the non-3GPP connection measurement report information, measurement report information for one or more 3GPP connections that can be established for relaying between other UEs and the remote UE 112. Such measurement report information is discussed in more detail below but may include at least one of: identification information for identifying the other UE(s) (e.g., C-RNTI or I-RNTI) capable of supporting relaying using a 3 GPP connection; serving cell identification information for identifying the cell serving of the other UE(s) capable of supporting relaying using a 3 GPP connection; link measurement quantity information associated with the 3 GPP connection that can be established.

[0067] In a variant, for a non-3GPP link, the remote UE may use a specific value in the sidelink measurement quantity information to indicate that the link is a non-3GPP link (e.g., the measurement quantity information value may be set to “0” or to its maximum value).

[0068] In one aspect, some information on or related to the non-3GPP relay, e.g., non-3GPP relay ID, may be reported to the base station autonomously by the remote UE when the link quality of this non-3GPP connectivity is satisfying some specific requirement, e.g., the link could be used for relaying data. For example, after the remote UE determines a non-3GPP connection that can be established between another UE and the remote UE meets a certain requirement, the remote UE sends a measurement report message indicating a non-3GPP connection (e.g. Bluetooth, wifi, or other peer-to-peer technology ...) can be established between the remote UE and the other UE. The certain requirement may relate to one or more of QoS, latency, link quality, signal strength (and thresholds associated with such parameters). For example, when the measured latency of the non-3GPP connection is equal to or less than a certain threshold (that can be configured by the network as discussed below), the remote UE 112 can determine that it is to report the non-3GPP connection to the base station 101. As another example, when the measured link quality of the non-3GPP connection is equal to or greater than a certain threshold (that can be configured by the network), the remote UE can determine that it is to report the non-3GPP connection to the gNB. Similarly for thresholds for QoS, signal strength. These thresholds may be configured by the network as mentioned above or determined by the UE in order to meet the requirement of its application. The application layer may then provide those thresholds, or the UE may derive the thresholds from the application requirements. The thresholds may also be based on QoS parameters such as the 5QI (5G QoS index specified in TS23.501) provided by the UE to the network during the PDU session establishment or DSCP (Differentiated Services Code Point) or UP (User Priority).

[0069] In another aspect, the remote UE may report on the potential relevance of the non-3GPP link for performing further data relaying based on some measurement report configuration supplied by the network (gNB). In an example, such measurement report configuration may indicate whether the remote UE is authorized to report some information on non-3GPP relay UE(s) (e.g., non-3GPP relay UE ID) and may also include one or more quality threshold(s) (related to the certain or specific requirement to be met as discussed above) to be used for determining whether some information related to non-3GPP link(s) are to be reported to the network. In one variant, the gNB may also not authorize the remote UE to use non-3GPP relay to avoid interferences (in this case, for example, the gNB may indicate to the remote UE that it is not authorized to use a non-3GPP connection during RRC connection or PDU establishment) and so the non-3GPP link information is not included in the measurement report. In a variant, the remote UE may report the non-3GPP relay only when no other relays are available.

[0070] Based on the information carried by the received Measurement Report messages, the first base station 101 may decide to adapt the connection or connectivity of the remote UE 112 to the network (step 320). In another variant illustrated with reference to the figure 4, the step 320 may be triggered upon the detection of QoS failure (latency, reliability), or a request from the core network (which is described in more detail below with reference to figure 4) or when the resources allocated to the remote UE 112 are insufficient to fulfil the bandwidth need (successive reported BSR indicating increase of the buffer size at the remote UE 112) or when requested by the remote UE 112. Then, in that case, the base station 101 requests the remote UE 112 provides a measurement report so that the base station 101 can obtain information of the environment of the remote UE 112, especially information relating to the surrounding cells and relays.

[0071] According to one aspect, the first base station may decide to setup a multi-path by adding to the existing path (e.g. a communication path established between the base station 101 and the remote UE 112, such as, the direct path as shown in figure 3), that connects the remote UE 112 to the first base station 101, a second path, which may be direct or indirect, that would also connect the remote UE 112 to the first base station 101. In the example of figure 3, the second path is an indirect path. The second path could instead be a direct path. The base station 101 may decide to add more than one communication path to the existing or already established communication path. The first base station 101 may decide to add a second path so as to fulfil the requirement of the remote UE 112 i.e. to increase the available bandwidth (UL or DL or both) for this specific remote UE or to improve the reliability by combining the two paths to obtain spatial diversity or to fulfil some other QoS parameters such as latency.

[0072] According to another aspect, the first base station 101 may decide, in the case where a Multi Path has already been set up (i.e. at least two communication paths or connections have been established between the base station 101 and remote UE 112), to modify the existing Multi-path so as to adapt the connection or connectivity of the remote UE 112 to the network. The modification may involve modifying one or more of the existing at least two communication paths.

[0073] More specifically, in one aspect, the first base station 101 may decide to add a new direct path towards the remote UE 112 if the link quality level, or the signal strength, of a cell served by a base station (101 or 102) is greater than or equal to some predefined threshold or if the link quality level or the signal strength, of the serving relay UE 110 is lower than a second predefined offset threshold and if the link quality level, or the signal strength, of a cell served by a base station (101 or 102) is greater than or equal to a third predefined threshold. It will be appreciated that a new direct path may be added to an existing path which may be an indirect path or a direct path.

[0074] In another aspect, the first base station 101 may decide to modify or change the direct path towards the remote UE 112 if the link quality level, or the signal strength, of a cell served by a second base station 102 reported in the received MEASUREMENT REPORT message 311 is greater than a predefined offset threshold than the link quality level, or the signal strength, of the cell served by the first base station 101 to which the remote UE 112 is connected currently. Thus, in this case the change is from a direct path to a different direct path. Alternatively, the change may be from a direct path to an indirect path.

[0075] In another aspect, the first base station 101 may decide to add a new indirect path towards the remote UE 112 if the link quality level or the signal strength, of a candidate relay UE 110 or 120 served by a base station 101 or 102 reported in the received MEASUREMENT REPORT message 311 is greater than a predefined offset threshold or if the link quality level or the signal strength, of a candidate relay UE 110 or 120 served by a base station 101 or 102 reported in the received MEASUREMENT REPORT message 311 is greater than a second predefined offset threshold and if the link quality level, or the signal strength, of the cell to which the remote UE 112 is connected or of the serving relay UE 110 to which the remote UE 112 is connected becomes worse than a third threshold. It will be appreciated that a new indirect path may be added to an existing path which may be an indirect path or a direct path.

[0076] In another aspect, the first base station 101 may decide to modify or change the indirect path towards the remote UE 112 if the link quality level or the signal strength, of the serving relay UE 110 reported in the received MEASUREMENT REPORT message 311 is lower than a predefined offset threshold or if the link quality or the signal strength, of a candidate relay UE 120 reported in the received MEASUREMENT REPORT message 311 is greater than a predefined offset threshold. The candidate relay UE 120 could be served by the same base station 101 or by another base station for example the base station 102. Thus, in this case the change is from an indirect path to a different indirect path. Alternatively, the change may be from an indirect path to a direct path.

[0077] The base station may also decide to perform remote UE connection adaptation based on any combination of the above listed events. Therefore, the base station may also decide to modify or change an indirect path to a direct path or vice versa or to add a second direct path when a first direct path is already established or add a second indirect path when a first indirect path is already established. The different paths could be served by the same or different base stations.

[0078] The link quality described above may be reported in the received MEASUREMENT REPORT message 311.

[0079] According to one example, link quality level, or the signal strength, measurements considered for connection adaptation decision by the first base station 101 (e.g. at step 320) include all or part of the following metrics: Reference Signal Received Power (RSRP), which provides a measure of the received power of the strongest reference signal from the considered cell; Reference Signal Received Quality (RSRQ), which provides a measure of the quality of the received reference signal from the considered cell, relative to the interference level in the cell; Signal-to-Noise Ratio (SNR), which provides a measure of the signal quality relative to the noise level in the cell and can be used to determine the strength of the signal from the considered cell; Channel Quality Indicator (CQI), which provides a measure of the quality of a received signal; Sidelink Reference Signal Received Power (SL-RSRP) or Sidelink Discovery Reference Signal Received Power (SD-RSRP) which provide a measure of the received power of the strongest reference signal from a relay UE based respectively on data or discovery message. In addition to the aforementioned metrics, other measurements such as cell identity, beamforming quality, and channel state information (for instance sidelink channel busy ratio or interference) may also be considered for link quality level, or signal strength measurement.

[0080] The first base station 101 may notify the remote UE 112 to perform a connection adaptation i.e. setup one or more additional paths or modify an existing path by sending a configuration message, such as the RRC Reconfiguration message 321 as defined in 3GPP TS 38.331.

[0081] In one aspect, the configuration message (e.g. RRC Reconfiguration message 321) includes all or part of the following information elements or information: multi-path information that indicates that the RRC Reconfiguration intends to setup a multi-path by adding a new path to the existing one. In a variant this multi-path information indicates that the RRC Reconfiguration intends to modify the multi-path configuration by updating or changing at least one of the existing indirect or direct paths. For example, the multi-path information included in the configuration message indicates configuration information included in the configuration message is associated with at least one other communication path to be configured between the remote UE 112 and network to provide a multi-path between the remote UE 112 and the network, which multi-path includes a first communication path already established between the remote UE 112 and the first base station 101. In an example, the configuration message includes information (or multi-path information) for indicating at least one other communication path is to be configured between the UE and the network in addition to a first communication path already established between the remote UE 112 and the first base station to provide multiple paths (e.g. communication paths) between the UE and the network. In other words, the configuration message includes information (or multipath information) for indicating multiple paths are to be configured.

[0082] A list of relays: this list contains at least one relay identified by its ID. This list indicates to the remote UE 112 to which relay UE (e.g. relay node) the remote UE should be connected. This list may carry several relay UEs if the RRC Reconfiguration aims to establish several indirect paths. For example, the relay list provides relay identification information for identifying at least one relay node with which the remote UE 112 is to establish a connection for a respective at least one communication path of the multipath. This list of relays is associated with the primary or main relay UE(s) and which is also referred to as a target relay UE(s).

[0083] A list of backup relays: this list includes at least one backup relay identified by its ID. This list indicates to the remote UE 112 to which relay UE the remote UE should be connected in case of deficiency of the principal or main relay UE. If the list includes several relays, priority information may also be provided for indicating a priority order for the relays so that the remote UE can attempt connection to the relays in the order indicated by the priority information. The remote UE can attempt connection in order if no priority information is provided.

[0084] A primary cell which indicates the primary cell to connect. This cell is identified by a cell ID (e.g. physCellld). For example, the configuration message may include primary or main cell information for identifying a primary or main cell with which the UE is to establish a connection (e.g. for a direct path between the UE and the network) to provide the multi-path and this primary cell information may include the cell ID.

[0085] A list of secondary cells: this list includes at least one cell identified by its cell ID (e.g. sCellld). This list may be used as a backup list if the connection with the primary cell failed or maybe used to connect a second direct path. For example, the configuration message may include backup cell information (e.g. list of secondary cells) for identifying at least one secondary cell with which the UE is to establish a connection (e.g. for a direct path between the UE and the network) to provide the multi-path in the case of failure to establish a connection with the primary cell identified by the primary cell information and this backup cell information may include the cell ID of each of the at least one secondary cell. a path ID which identifies each connection / path. If the RRCReconfiguration includes an identifier that is part of the UE’s configuration already, then the UE considers the procedure as path modification otherwise the UE consider the procedure as a path addition.

[0086] The two above list may be concatenate into a single list and an additional element may indicate the number of indirect paths to establish.

[0087] In addition, the RRC Reconfiguration message includes configuration information for the one or more additional paths and / or for the communication path to be updated / changed / modified. The configuration information for an indirect path may include PC5 Relay RLC channel configuration for relay traffic and the associated end-to-end radio bearer(s). The configuration information for an indirect path (e.g. an Information Element for the configuration of an indirect path) may also include information for indicating to the remote UE that the remote UE is to trigger the relay node to enter the RRC-CONNECTED state by using a PC5 message (as further discussed in Figure 8). The information could be a bit or field or flag in the configuration message. In one aspect, the RRCReconfiguration message 321 only includes the configuration related to the new path or the path to modify (and the multi-path information or information indicating multiple paths are to be configured). The remote UE 112 infers that this configuration is for a multi-path setup based on the multi-path information. This multi-path information or information indicating multiple paths are to be configured could be a bit or field (e.g. a multi-path bit or field) set to 1 or enable or true or an Information element including all information related to the Multi-path configuration, or the presence of a SCell configuration or SpCell configuration (in addition to the relay UE(s) identity for a new or a modification of an indirect path) in the CellGroupConfig information element carried in the RRCReconfiguration message. In another aspect, the RRCReconfiguration message may include the configuration of all paths, the existing one(s) and the new (or to modify) one(s). The complete configuration may be included if the fullconfig flag carried in the RRCReconfiguration message is set to true.

[0088] By providing the multi-path information in the configuration message sent to the remote UE, the remote UE 112 is notified that it is to set up a multi-path or change / modify an existing multi-path configuration. This also means only configuration information for the new path or path to be modified needs to be sent to the remote UE.

[0089] In another aspect, an mrdc-SecondaryCellGroup information element could also be included in the configuration message 321 if a new path to be set up involves another or second base station (such as base station 102). This element included in the configuration message 321 includes the RRCReconfiguration message as generated by the second base station and thus, includes configuration information for configuring at least one communication path between the UE and the second base station. This second RRCReconfiguration may also include a configuration for a direct path or an indirect path or both as described above. For example, the remote UE 112 would be connected to base station 101 through the relay UE 110 and to the second base station 102 directly.

[0090] The selection of the relay UE by the base station 101 for the addition of an indirect path is based on the information included in the measurement reports received at the base station 101 from the different UEs (measurement report 311a from remote UE 112, measurement report 311b from relay UE 110 and measurement report 311c from relay UE 120). The base station 101 assesses the different relays included in the measurement report by the remote UE 112, by evaluating the global connection i.e. the different hops in the paths of each of the different relay UEs. The RRC Reconfiguration may include a primary relay UE or main relay UE or target relay UE (or in the case of the addition of a plurality of indirect paths, a plurality of such relays) and one or more backup relays if the available relays reported by the remote UE 112 suffer from unstable link quality and so may be prone to connection failure. In its relay selection, the base station 101 may give precedence to relay UEs already in RRC CONNECTED state when selecting one or more main relay UEs in order to decrease the latency of the new path establishment. If no relay UE(s) reported by the remote UE 112 are in RRC CONNECTED state, the base station 101 may also include a backup relay in the RRC Reconfiguration in case of deficiency of the selected main relay UE. For example, in the case where a main relay UE in RRC INACTIVE or RRC IDLE has performed or is performing a cell reselection to another base station (e.g. the base station 102) when the remote UE attempts to connect the base station 101 through it, the path establishment may fail.

[0091] Upon reception of a RRC Reconfiguration message 321 from the first base station 101 including a multi-path information as described above, the remote UE 112 starts Path Addition Modification failure timer in the step 331 and attempts to establish the additional path(s) to set up a multi-path or modify an existing path of a multi-path between the remote UE 112 and the network. The Path Addition Modification failure timer (not shown in the figures) may be implemented in hardware or software (e.g. by a module of a program that includes instructions for execution by one or more processing units, such as the central processing unit 1711) and is configured to time a certain or predefined time period from start of the timer (i.e. when the path failure timer reaches a certain or predefined value). In the example of figure 3, the remote UE 112 is notified to add an indirect path through the relay UE 110 to set up the multi-path. Then the remote UE 112 tries to establish a PC5 connection with the relay UE 110 identified in the RRC Reconfiguration. The establishment of the PC5 connection is illustrated by the message exchange 322. The PC5 connection establishment procedure 322 is further described with reference to figure 8. In the example of the present figure, the PC5 connection establishment between the remote UE 112 and the relay UE 110 is successfully completed. As a result, the remote UE 112 and the relay UE 110 are able to directly communicate with each other. Meanwhile, the base station 101 sends to the main relay UE 110 a RRC Reconfiguration 341 which includes the Remote UE identifier (Local and L2 ID), the RLC layer configuration (Uu and PC5 RLC channel configuration for relaying) and the SRAP configuration (the bearer mapping configuration as discussed above). The relay UE 110 configures its different layers as indicated by the RRC Reconfiguration message 341 to enable its L2 relaying functionality. Then, it sends as a response to the base station 101 a RRC Reconfiguration Complete message 342. The reception of this RRC Reconfiguration message 342 completes the Relay UE configuration procedure. In the example of figure 3, the Relay UE is already in RRC CONNECTED state, thereby the base station 101 may send the RRC Reconfiguration message 341 at any time between the step 320 and the message 323. The description with reference to figures 4, 5, 6 and 7 describe some examples wherein the selected relay UE is in RRC IDLE or RRC INACTIVE states i.e. not in RRC CONNECTED state.

[0092] In a variant with several relays (backup relay and / or multiple indirect paths), the base station 101 may transmit the configuration to several relays (for example, the RRC Reconfiguration procedure 340 (in addition to the RRC Reconfiguration 341)). Considering the uncertainty of the usage of the configuration by the backup relay, the base station 101 may provide the configuration for relaying as a conditional configuration i.e. the configuration for the relaying should be applied if the remote UE establishes a PC5 connection with the backup relay. Moreover, the configuration could be cancelled after a predefined period of time.

[0093] Back to the remote UE 112 and after the completion of the PC5 connection establishment, the remote UE 112 configures its different layers according to the configuration received from the base station 101 (e.g. configuration information) in the RRC Reconfiguration message 321. At this time for example, the remote UE 112 applies the Signal Radio Bearer (control plane) configuration (if any) for the new indirect path. If a SRB1 is configured for this new path, the remote UE 112 may send a RRC Reconfiguration message 323 to the base station 101 through the relay UE 110 by using this new path. On the one hand, the successful transmission of this RRC Reconfiguration message 323 (e.g. the remote UE 112 may determine the transmission of RRC Reconfiguration message 323 is successful on receipt of an acknowledgement of RRC Reconfiguration message 323 from the base station 101 or from the relay 110) acknowledges the addition of the path and so the setup of the multi-path at the remote UE side 112, then the remote UE 112 stops the Path Addition Modification failure timer in step 332 after successful transmission of the RRC Reconfiguration message 323. On the other hand, upon the reception of this RRC Reconfiguration message at the base station 101, the base station 101 completes the procedure of path addition and the setup of the multi-path (step 350). As a result, the base station 101 and the remote UE 112 may communicate with each other via both paths of the multi-path, the direct one and the indirect one through the relay UE 110. In other words, the remote UE 112 transmits some uplink data, or UL User Data, to the first base station 101 and / or the first base station 101 transmits some downlink data or DL User Data to the remote UE 112 directly via a direct path as shown by UL / DL User Data 360a or through the relay UE via indirect path as shown by UL / DL User Data 360b.

[0094] Referring now to Figure 4 which is a schematic and simplified diagram illustrating an example of message flows for managing multi-path communication in a wireless communication system, such as that shown in figure la, supporting relaying and in particular for managing path addition procedure to enable a Multi-path comprising one direct and one indirect path, in accordance with one or more embodiments of the invention. In this figure 4, the Relay UE 110 is not in RRC CONNECTED when it is selected to act as a relay UE in the Multi-path configuration. This figure illustrates a way to move the relay UE from an RRC IDLE or RRC INACTIVE to RRC CONNECTED state according to one example. In the example of the figure, the trigger to move the relay UE from a non-connected RRC state (e.g. from RRC INACTIVE or RRC IDLE) to the RRC CONNECTED state is sent by the network. The same elements (e.g. steps, messages, frames, entities, nodes, etc.) in figure 4 as those in figure 3 are referenced by the same reference numbers. The description of the same elements as figure 3 will be omitted here for figure 4 to simplify the description but the details of these same elements can be found above in the description of figure 3.

[0095] In one example, a remote UE, like remote UE 112, is connected to a base station, such as base station 101 (also referred to as gNB 101). The remote UE 112 and the base station 101 (also referred to as first base station 101) communicate with each other, in other words the remote UE 112 transmits some uplink data, or UL User Data 310, to the first base station 101 and / or the first base station 101 transmits some downlink data or DL User Data 310 to the remote UE 112.

[0096] The remote UE 112 may also send to the first base station 101 some measurement report through respectively the Measurement Report message 311 as defined in 3 GPP TS 38.331.

[0097] Based on the information carried by the received Measurement Report messages, the first base station 101 may decide to adapt the connection or connectivity of the remote UE 101 to the network (step 320). In another variant illustrated in this figure, the step 320 may be triggered upon the detection of QoS failure (latency, reliability), or a request from the core network or when the resource allocated to the remote UE are insufficient to fulfil the bandwidth need (successive reported BSR with increase of the buffer size) or requested by the remote UE. Then, in that case, the base station 101 requests a measurement report to the remote UE 112 to obtain information of its environment especially the surrounded cells and relays.

[0098] In one aspect, a monitoring of the QoS (QoS Monitoring Request field in QoS Flow Level QoS Parameters subclause 9.3.1.12 in TS 38.413) may be requested by the core network (e.g. core network entity 140, such as AMF entity; SMF entity; UPF entity as shown in figure lb) during the PDU session (end-to-end User plane session) resource setup or PDU session resource modify. During the monitoring, the base station 101 or gNB can detect that the QoS requirement is no longer achieved for some UEs and consequently decide to set a multi-path (step 320). In a variant, the gNB 101 may inform the core network of this QoS issue through some QoS Monitoring Report 315 (specified in TS23.501). Based on this report, the core network may request (message 316) to the base station 101 to setup a multi-path so as, for example, to sustain the specified QoS. This Multi-Path setup may be requested by the core network during the PDU session resource setup or PDU session resource modify. In this variant, the base station 101 may inform the core network that the multi-path has been successfully setup (or modified) by sending the message MP setup ack (MP modify ack) 351.

[0099] The first base station 101 may notify the remote UE 112 to perform a connection adaptation i.e. setup one or more additional paths or modify an existing path by sending a RRC Reconfiguration message 321 as defined in 3GPP TS 38.331.

[0100] In one aspect, the RRC Reconfiguration message 321 includes all or part of the information elements or information described in the aforementioned description of figure 3.

[0101] Upon reception of a RRC Reconfiguration message 321 from the first base station 101 including a multi-path information as described above, the remote UE 112 proceeds with the addition of a new indirect path according to the information element carried in the RRC Reconfiguration 321. The path addition processing at the remote UE begins by starting the Path Addition Modification failure timer in step 331 and then the remote UE attempts to establish the PC5 connection with the main relay UE identified by the identifier (e.g. targetRelayUE-Identity as specified in TS38.331) carried in the RRC Reconfiguration 321.

[0102] The establishment of the PC5 connection is illustrated by the message exchange 322. The PC5 connection establishment procedure 322 is further described with reference to figure 8. In the example of the present figure, the PC5 connection establishment between the remote UE 112 and the relay UE 110 is successfully completed. As a result, the remote UE 112 and the relay UE 110 are able to directly communicate with each other.

[0103] Back to the base station 101, the base station 101 in step 320 notices or determines that the selected relay UE (e.g. relay UE 110) that is or will be included in the RRC Reconfiguration message 321 is not in the RRC CONNECTED state. Then, the base station 101 may decide to send a trigger message to the selected relay UE. This message 400 aims to trigger the L2 U2N Relay UE to enter RRC CONNECTED state.

[0104] In one aspect, this trigger message 400 may be a paging message as defined in TS38.331. This paging message may include the identity of the relay UE 110 and a paging cause indicating that the relay UE should start a connection procedure. In a variant, the paging message may include a paging record indicating that the base station 101 has some data / control to send to the relay UE 110 for the remote UE 112. It is noted that the paging message will normally have to be sent in a specific period of time called paging occasion in which the UEs (even in power saving) have to be awake to monitor in case the network addresses any paging to them.

[0105] In another aspect, the base station 101 may use a System Information Block including a list of UE(s) that needs to enter in RRC CONNECTED. In case of sidelink relay, this SIB could be the SIB 12.

[0106] In a variant, a new message could be used to trigger the relay UE 110 to enter in RRC CONNECTED.

[0107] Then, upon or after reception of the Network triggers relay message 400, the relay UE 110 attempts to establish a RRC connection with the base station 101. To do so, the relay UE 110 follows the RRC Resume or RRC setup procedures as defined in the TS 38.331 respectively clause 5.3.13 and 5.3.3. The RRC Resume / Setup is illustrated by the message or frame exchange 410.

[0108] Then, the base station 101 sends to the main relay UE 110, that has just entered in RRC CONNNECTED state, a RRC Reconfiguration 341 which includes the Remote UE identifier (Local and L2 ID), the RLC layer configuration (Uu and PC5 RLC channel configuration for relaying) and the SRAP configuration (the bearer mapping configuration) as discussed above. The relay UE 110 configures its different layers according to the RRC Reconfiguration message to enable its L2 relaying functionality. Then, the relay UE 110 sends as a response to the base station 101 a RRC Reconfiguration Complete message 342. The reception of this RRC Reconfiguration message 342 completes the Relay UE configuration procedure.

[0109] Back to the remote UE 112 and after the completion of the PC5 connection establishment procedure 322, the remote UE 112 configures its different layers according to the configuration received from the base station 101 in the RRC Reconfiguration message 321. At this time, the remote UE applies (or has applied) the Signal Radio Bearer (control plane) configuration (if any) for the new indirect path. If a SRB1 is configured for this new path, the remote UE 112 may send a RRC Reconfiguration message 323 to the base station 101 through the relay UE 110 by using this new path. On the one hand, the successful transmission of this RRC Reconfiguration message 323 acknowledges the addition of the path and so the setup of the multi-path at the remote UE side, then the remote UE 112 stops the Path Addition Modification failure timer in step 332 as discussed above. On the other hand, upon the reception of this RRC Reconfiguration message 323 at the base station 101, the base station 101 completes the procedure of path addition and the setup of the multi-path (step 350). As a result, the base station 101 and the remote UE 112 may communicate with each other via both paths, the direct one and the indirect one through the relay UE 110 in other words, the remote UE 112 transmits some uplink data, or UL User Data, to the first base station 101 and / or the first base station 101 transmits some downlink data or DL User Data to the remote UE 112 directly 360a or through the relay UE 360b.

[0110] Referring now to Figure 5 which is a schematic and simplified diagram illustrating an example of message flows for managing multi-path communication in a wireless communication system, such as that shown in figure la, supporting relaying and in particular for managing path addition procedure to enable a Multi-path comprising one direct and one indirect path. In this figure, the Relay UE 110 is not in RRC CONNECTED when it is selected to act as a relay UE in the Multi-path configuration. This figure illustrates a way to move the relay UE 110 from a non-connected RRC state (such as an RRC IDLE or RRC INACTIVE state) to RRC CONNECTED state according to one example. In the example of the figure, the network triggers the relay UE 110 to enter in RRC CONNECTED state. When the relay UE 110 effectively enters in RRC CONNECTED and has applied its relay configuration, the relay UE 110 notifies the remote UE 112. The same elements (e.g. steps, messages, frames, entities, nodes, etc.) in figure 5 as those in figures 3 and 4 are referenced by the same reference numbers. The description of the same elements as figures 3 and 4 will be omitted here for figure 5 to simplify the description but the details of these same elements can be found above in the description of figures 3 and 4.

[0111] In one example, a remote UE, like remote UE 112, is connected to a base station, such as base station 101. The remote UE 112 and the base station 101 communicate with each other, in other words the remote UE 112 transmits some uplink data, or UL User Data 310, to the first base station 101 and / or the first base station transmits some downlink data or DL User Data 310 to the remote UE 112.

[0112] The remote UE 112 may also send to the first base station 101 some measurement report through respectively the Measurement Report message 311 as defined in 3 GPP TS 38.331.

[0113] Based on the information carried by the received Measurement Report messages, the first base station 101 may decide to adapt the connection or connectivity of the remote UE 112 to the network (step 320).

[0114] The first base station 101 may notify the remote UE 112 to perform a connection adaptation i.e. setup one or more additional paths or modify an existing path by sending a RRC Reconfiguration message 321 as defined in 3GPP TS 38.331.

[0115] In one aspect, the RRC Reconfiguration message 321 includes all or part of the information elements or information described in the aforementioned description of figure 3. Upon reception of a RRC Reconfiguration message 321 from the first base station 101 including a multi-path information as described above, the remote UE 112 proceeds with the addition of a new indirect path according to the information element carried in the RRC Reconfiguration 321. The path addition processing at the remote UE 112 begins by starting the Path Addition Modification failure timer in step 331 and then the remote UE 112 attempts to establish the PC5 connection with the main relay UE identified by the identifier (e.g. targetRelayUE-Identity as specified in TS38.331) carried in the RRC Reconfiguration 321.

[0116] The establishment of the PC5 connection is illustrated by the message exchange 322. The PC5 connection establishment procedure 322 is further described with reference to figure 8. In the example of the present figure, the PC5 connection establishment between the remote UE 112 and the relay UE 110 is successfully completed. As a result, the remote UE 112 and the relay UE 110 are able to directly communicate with each other.

[0117] Back to the base station 101, the base station in step 320 notices or determines that the selected relay UE (e.g. relay UE 110) that is or will be included in the RRC Reconfiguration message 321 is not in the RRC CONNECTED state. Then, the base station 101 may decide to send a trigger message to the selected relay UE 110. This message 400 aims to trigger the relay UE to enter RRC CONNECTED state.

[0118] Then, upon reception of the Network triggers relay message 400, the relay UE 110 attempts to establish a RRC connection with the base station 101. To do so, the relay UE 110 follows the RRC Resume or RRC setup procedures as defined in the TS 38.331 respectively clause 5.3.13 and 5.3.3. The RRC Resume / Setup is illustrated by the frame or message exchange 410.

[0119] Then, the base station 101 sends to the main relay UE 110, that has just entered in RRC CONNNECTED state, a RRC Reconfiguration message 341 which includes the Remote UE identifier (Local and L2 ID), the RLC layer configuration (Uu and PC5 RLC channel configuration for relaying) and the SRAP configuration (the bearer mapping configuration). The relay UE 110 configures its different layers according to the RRC Reconfiguration message 341 to enable its L2 relaying functionality. Then, the relay UE 110 sends as a response to the base station 101 a RRC Reconfiguration Complete message 342. The reception of this RRC Reconfiguration message 342 completes the Relay UE configuration procedure.

[0120] Once the relay UE 110 has sent the message 342, it sends a notification (Relay feedback 500) to the remote UE 112 to inform this latter that it (the relay UE 110) has entered in the RRC CONNECTED state and has applied the relay configuration and so may act as an active relay for the remote UE 112. The relay feedback message includes a feedback cause which is set to relayUE-RRC CONNECTED.

[0121] In one aspect, this Relay feedback message 500 may be a NotificationMessageSidelink message as defined in TS38.331 clause 6.6.2 with a new input “relayUE-RRC-Connected” in the indicationType.

[0122] In another variant, the Relay feedback message 500 may be a RRCReconfigurationCompleteSidelink message as defined in TS38.331. This message is part of the PC5 Connection establishment procedure or state 322 as further described with reference to figure 8 and is sent in response to the RRCReconfigurationSidelink 811. In this variant, the relay UE 110 may delay the sending of the RRCReconfigurationCompleteSidelink 812 to the remote UE 112 until it enters in RRC CONNECTED state. Thereby, the reception of the RRCReconfigurationCompleteSidelink 812 at the remote UE 112 (e.g. as the Relay feedback message 500) indicates both the Sidelink configuration has succeeded and the relay UE 110 is in RRC CONNECTED state.

[0123] Upon receiving the Relay feedback message 500 indicating that the relay UE 110 is now RRC CONNECTED, the Remote UE 112 stops the Path Addition Modification failure timer in step 332. Indeed, the remote UE 112 considers that the reception of the Relay feedback message 500 completes the addition of the new indirect path. The reception of the Relay feedback message 500 is a stop condition of the Path Addition Modification failure timer.

[0124] At this time, the remote UE 112 applies (or has applied) the Remote UE configuration included in the RRC Reconfiguration message 321 for the new indirect path i.e. the PC5 Relay RLC channel configuration for relay traffic and the associated end-to-end radio bearer(s). Among the end-to-end radio bearer(s), the configuration of the Signal Radio Bearer (SRB dedicated to the control plane) can have an impact on the way the path addition or path modification procedure is completed. Indeed, if a SRB1 is configured for this new path, the remote UE 112 may send a RRC Reconfiguration message 323 to the base station through the relay UE 110 by using this new path (as illustrated in figures 3 and 4). Otherwise the remote UE 112 sends the RRC Reconfiguration Complete message 501 through the formerly existing path for which the SRB1, or more generally the control plane, is configured.

[0125] The reception of this RRC Reconfiguration message 501 at the base station 101 completes the procedure of path addition (modification) and the setup of the multi-path (step 350). As a result, the base station 101 and the remote UE 112 may communicate with each other via both paths, the direct one and the indirect one through the relay. In other words, the remote UE 112 transmits some uplink data, or UL User Data, to the first base station 101 and / or the first base station 101 transmits some downlink data or DL User Data to the remote UE 112 directly via a direct path as indicated by UL / DL User Data 360a or indirectly via an indirect path through the relay UE 110 as indicated by UL / DL User Data 360b.

[0126] Referring now to Figure 6 which is a schematic and simplified diagram illustrating an example of message flows for managing multi-path communication in a wireless communication system, such as that shown in figure la, supporting relaying and in particular for managing path addition procedure to enable a Multi-path comprising one direct and one indirect path, in accordance with one or more embodiments of the invention. In this figure, the Relay UE 110 is not in RRC CONNECTED when it is selected to act as a relay UE in the Multi-path configuration. This figure illustrates how the network triggers the relay UE to enter RRC CONNECTED state according to one example. However, in this figure, the relay UE is triggered by the network once the network has received the RRCReconfigurationComplete message from the Remote UE through the direct path. The same elements (e.g. steps, messages, frames, entities, nodes, etc.) in figure 6 as those in figures 3, 4 and 5 are referenced by the same reference numbers. The description of the same elements as figures 3, 4 and 5 will be omitted here for figure 6 to simplify the description but the details of these same elements can be found above in the description of figures 3, 4 and 5.

[0127] The flows in this figure 6 begins as with the flows of the previous figures. The remote UE 112 and the base station 101 communicate with each other (e.g. UL / DL User Data 310). Upon the modification of its environment e.g. improvement of the link quality or the signal strength with a candidate Relay UE(s) or drop of the link quality or the signal strength with its serving cell and so on, the remote UE 112 sends a Measurement Report 31 la to the base station 101. The Measurement report includes one or multiple candidate Relay UE(s) and Uu (surrounded cells) measurements. Each candidate Relay UE is identified by its Relay UE ID and its serving cell and is accompanied by a sidelink measurement quantity information e.g. SL-RSRP or SD-RSRP as described with reference to figure 3. The base station 101 may also receive measurement report information from UEs that may be candidate relays for the remote UE 112 (e.g. measurement report 31 lb).

[0128] Based for example on the information carried by the received Measurement Report messages (31 la, 31 lb), the base station 101 may decide in the step 320 to adapt the remote UE configuration to setup a Multi-path in order to improve (reliability, bandwidth...) the connection between the Remote UE 112 and the network. Then, the first base station 101 notifies the remote UE 112 to perform a connection adaptation i.e. setup one or more additional paths or modify an existing path by sending a RRC Reconfiguration message 321 as defined in 3GPP TS 38.331. As discussed above, this message 321 may further include a multi-path information, a list of relays and a list of backup relays, a primary cell, a list of secondary cells, a path ID per configuration path (each element being optional and added on purpose by the base station).

[0129] Upon reception of a RRC Reconfiguration message 321 from the first base station 101 including a multi-path information as described above, the remote UE 112 proceeds with the addition of a new indirect path according to the information element carried in the RRC Reconfiguration 321. The path addition processing at the remote UE 112 begins by starting the Path Addition Modification failure timer in step 331 and then the remote UE 112 attempts to establish the PC5 connection with the main relay UE identified by the identifier (e.g. targetRelayUE-Identity as specified in TS38.331) carried in the RRC Reconfiguration 321. In the meanwhile, the remote UE 112 applies the Remote UE configuration included in the RRC Reconfiguration message 321 for the new indirect path i.e. the PC5 Relay RLC channel configuration for relay traffic and the associated end-to-end radio bearer(s).

[0130] In one aspect, the remote UE 112 may send to the base station 101 a UEAssistancelnformation message 610 in response to the RRCReconfiguration 321 or at any other instant previously to the reception of the RRCReconfiguration 321. This message may include all or part of the following information elements or information: the preference of the remote UE concerning the relay UE selection i.e. if the remote UE prefers a relay UE in RRC CONNECTED state or not (preferredRelayUE-RRC-State: connected, idle, inactive, no_preference) and if the relay UE could belong to a cell or gNB different from the remote UE serving cell (preferredRelayUE-cell: intra-cell, inter-cell, inter-gNB). If this element is set to RRC CONNECTED for the relay UE preferred state, the network may select a relay UE in RRC INACTIVE or RRC IDLE but the network is in charge to trigger the selected relay UE to connect to the network and enter the RRC CONNECTED state. This preference may also be referred to as relay state preference information.

[0131] The preference of the remote UE to trigger a relay UE i.e. whether the remote UE prefers to trigger the relay UE to enter in RRC CONNECTED or if the remote UE prefers that the network triggers the relay UE to enter in RRC CONNECTED (preferredRelayUE-trigger: PC5, network). If the preference is set to the network, it means that the network must trigger the relay UE or configure SRB1 on the new path (via the relay UE) to allow to use for example RRCReconfigurationComplete message on the new path as a trigger for the relay UE. This preference may also be referred to as relay trigger preference information.

[0132] In the example of the figure 6, the remote UE 112 informs the base station 101 that the remote UE 112 prefers the network to trigger the relay UE 110.

[0133] The UE Assistanceinformation message 610 may also be sent after PC5 establishment to ask the network to trigger the relay UE 110 to enter in RRC CONNECTED, for example if the relay UE 110 does not support PC5_trigger to enter in RRC CONNECTED and its current state is not RRC CONNECTED. The capability of the remote UE 112 and Relay UE 110 may be shared through the UECapabilitylnformationSidelink as described with reference to figure 8.

[0134] In another aspect, the remote and the relay UEs may inform the base station 101 about their capability to support PC5_trigger (as emitter or receiver). This information could be part of the UECapability Information message.

[0135] In another aspect, this information could be part of the SidelinkUEInformationNR.

[0136] If the capability to support PC5_trigger is received after the sending of the RRCReconfiguration 321 which asks the remote UE to adapt its connectivity and that RRCReconfiguration is not suitable to the actual capabilities of the UEs, the gNB may send a new RRCReconfiguration that allows the triggering of the relay either with a configuration of the SRB1 on the indirect path or by asking the remote UE to trigger the relay by using the PC5 RRC trigger.

[0137] When the establishment of the PC5 connection 322 is successfully completed i.e. the remote UE 112 and the relay UE 110 may communicate directly with each other, the remote UE 112 sends the RRC Reconfiguration Complete message 501 to the base station 101. The sending of message 501 onto the direct path may be dictated by the non-configuration of the control path on the new indirect path or may be decided for any other reasons.

[0138] Upon reception of the RRC Reconfiguration Complete message 501 and in order to complete the Multi-Path setup, the base station 101 checks the actual status of the relay UE 110 in step 600. If the latter is RRC INACTIVE or RRC IDLE, the base station 101 sends a message 400 (e.g. a paging or SIB12) to trigger the relay UE 110 to enter in RRC CONNECTED state. Consequently, the relay UE 110 tries to establish a RRC connection with the base station 101 through the RRC Resume or RRC setup procedures as defined in the TS 38.331 respectively clause 5.3.13 and 5.3.3. The RRC Resume / Setup is illustrated by the frame or message exchange 410. Once in RRC CONNECTED state, the relay UE 110 receives the RRC Reconfiguration message 341 including the Remote UE identifier (Local and L2 ID), the RLC layer configuration (Uu and PC5 RLC channel configuration for relaying) and the SRAP configuration (the bearer mapping configuration). The relay UE 110 configures its different layers according to the RRC Reconfiguration message 341 to enable its L2 relaying functionality. Then, the relay UE 110 sends as a response to the base station 101, such as a RRC Reconfiguration Complete message 342, along with a Relay feedback message 500 to the Remote UE 112.

[0139] When receiving the RRC Reconfiguration message 342, the base station 101 deems the Relay UE configuration procedure and also the Multi Path setup have been completed (step 350).

[0140] Upon receiving the Relay feedback message 500 indicating that the relay UE 110 is now RRC CONNECTED, the Remote UE 112 stops the Path Addition Modification failure timer in step 332. Indeed, the remote UE 112 considers that the reception of the Relay feedback message completes the addition of the new indirect path. The reception of the Relay feedback message 500 is a stop condition of the Path Addition Modification failure timer.

[0141] As a result, the base station 101 and the remote UE 112 may communicate with each other via both paths, the direct one and the indirect one through the relay UE 110. In other words, the remote UE 112 transmits some uplink data, or UL User Data, to the first base station 101 and / or the first base station 101 transmits some downlink data or DL User Data to the remote UE directly via a direct path as shown by UL / DL User Data 360a or through the relay UE via indirect path as shown by UL / DL User Data 360b.

[0142] Referring now to Figure 7 which is a schematic and simplified diagram illustrating an example of message flows for managing multi-path communication in a wireless communication system, such as that shown in figure la, supporting relaying and in particular for managing path addition procedure to enable a Multi-path comprising one direct and one indirect path, in accordance with one or more embodiments of the invention. In this figure, the Relay UE 110 is not in RRC CONNECTED when it is selected to act as a relay UE in the Multi-path configuration. This figure illustrates how the Remote UE triggers the relay UE to enter RRC CONNECTED state according to one example. The same elements (e.g. steps, messages, frames, entities, nodes, etc.) in figure 7 as those in figures 3 to 6 are referenced by the same reference numbers. The description of the same elements as figures 3 to 6 will be omitted here for figure 7 to simplify the description but the details of these same elements can be found above in the description of figures 3 to 6. The remote UE 112 and the base station lOlcommunicate with each other (e.g. UL / DL User Data 310). Upon the modification of its environment e.g. improvement of the link quality or the signal strength with a candidate Relay UE(s) or drop of the link quality or the signal strength with its serving cell and so on, the remote UE 112 sends a Measurement Report 311a to the base station 101. The Measurement report includes one or multiple candidate Relay UE(s) and Uu (surrounded cells) measurements. Each candidate Relay UE is identified by its Relay UE ID and its serving cell and is accompanied by a sidelink measurement quantity information e.g. SL-RSRP or SD-RSRP as described with reference to figure 3. The base station 101 may also receive measurement report information from UEs that may be candidate relays for the remote UE 112 (e.g. measurement report 31 lb).

[0143] Based for example on the information carried by the received Measurement Report messages (31 la, 31 lb), the base station 101 may decide in the step 320 to adapt the remote UE configuration to setup a Multi-path in order to improve (reliability, bandwidth...) the connection between the Remote UE and the network. Then, the first base station 101 notifies the remote UE 112 to perform a connection adaptation i.e. setup one or more additional paths or modify an existing path by sending a RRC Reconfiguration message 321 as defined in 3GPP TS 38.331. As discussed above, this message 321 may further include a multi-path information, a list of relays a list of backup relays, a primary cell, a list of secondary cells and a path ID per configuration path (each element being optional and added on purpose by the base station).

[0144] Upon reception of a RRC Reconfiguration message 321 from the first base station including a multi-path information as described above, the remote UE 112 proceeds with the addition of a new indirect path according to the information element carried in the RRC Reconfiguration 321. The path addition processing at the remote UE 112 begins by starting the Path Addition Modification failure timer in step 331 and then the remote UE 112 attempts to establish the PC5 connection with the main relay UE identified by the identifier (e.g. targetRelayUE-Identity as specified in TS38.331) carried in the RRC Reconfiguration 321. In the meanwhile, the remote UE 112 applies the Remote UE configuration included in the RRC Reconfiguration message 321 for the new indirect path i.e. the PC5 Relay RLC channel configuration for relay traffic and the associated end-to-end radio bearer(s).

[0145] Once the PC5 connection is established after performing PC5 connection establishment 322, the remote UE 112 sends a message 700 to trigger the relay UE 110 to enter in RRC CONNECTED state. This message could be sent whatever the RRC state of the relay UE 110. In another variant, the relay UE 110 may inform the remote UE on its RRC state before the remote UE 112 sends the triggering message 700. According to one aspect, this triggering message 700 could be a RemoteUEInformationSidelink as specified in TS38.331. However, in this new usage, the RemoteUEInformationSidelink message will be sent when the remote UE 112 is in RRC CONNECTED. In this case the RemoteUEInformationSidelink message includes a new IE SI RelayUE RRCConnected Req which if present, requests the relay UE 110 to enter in RRC CONNECTED state.

[0146] Upon the reception of the message 700, the relay UE 110 that is not in RRC CONNECTED state, begins the procedure to connect to the base station 101 through the RRC Resume or RRC setup procedures as defined in the TS 38.331. The RRC Resume / Setup is illustrated by the frame or message exchange 410.

[0147] Once in RRC CONNECTED state, the relay UE 110 sends a Relay feedback message 500 to the Remote UE 112. When receiving the Relay feedback message 500 indicating that the relay UE 110 is now RRC CONNECTED, the Remote UE 112 stops the Path Addition Modification failure timer in step 332.

[0148] The relay UE 110 may receive the RRC Reconfiguration message 341 including the Remote UE identifier (Local and L2 ID), the RLC layer configuration (Uu and PC5 RLC channel configuration for relaying) and the SRAP configuration (the bearer mapping configuration). The relay UE 110 configures its different layers according to the RRC Reconfiguration message 341 to enable its L2 relaying functionality. Then, the relay UE 110 sends, as a response to the base station 101, a RRC Reconfiguration Complete message 342. When receiving the RRC Reconfiguration message 342, the base station 101 deems the Relay UE configuration procedure and also the Multi Path setup have been completed (step 350).

[0149] As a result, the base station 101 and the remote UE 112 may communicate with each other via both paths, the direct one and the indirect one through the relay UE 110. In other words, the remote UE 112 transmits some uplink data, or UL User Data, to the first base station 101 and / or the first base station 101 transmits some downlink data or DL User Data to the remote UE 112 directly via a direct path as shown by UL / DL User Data 360a or through the relay UE via indirect path as shown by UL / DL User Data 360b.

[0150] Referring now to Figure 8 which is a schematic and simplified diagram illustrating an example of message flows for managing multi-path communication in a wireless communication system, such as that shown in figure la, supporting relaying and in particular for managing path addition procedure to enable a Multi-path comprising one direct and one indirect path, in accordance with one or more embodiments of the invention. In this figure, the Relay UE 110 is not in RRC CONNECTED when it is selected to act as a relay UE in the Multi-path configuration. This figure illustrates how the Remote UE 112 triggers the relay UE 110 to enter RRC CONNECTED state according to one example. This figure presents an alternative to the figure 7 when the Remote UE 112 triggers the relay UE 110 to enter RRC CONNECTED. The same elements (e.g. steps, messages, frames, entities, nodes, etc.) in figure 8 as those in figures 3 to 7 are referenced by the same reference numbers. The description of the same elements as figures 3 to 7 will be omitted here for figure 8 to simplify the description but the details of these same elements can be found above in the description of figures 3 to 7.

[0151] The remote UE 112 and the base station 101 communicate with each other (e.g. UL / DL User data 310). Upon the modification of its environment e.g. improvement of the link quality or the signal strength with a candidate Relay UE(s) or drop of the link quality or the signal strength with its serving cell and so on, the remote UE 112 sends a Measurement Report 311a to the base station 101. The Measurement report includes one or multiple candidate Relay UE(s) and Uu (surrounded cells) measurements. Each candidate Relay UE is identified by its Relay UE ID and its serving cell and is accompanied by a sidelink measurement quantity information e.g. SL-RSRP or SD-RSRP as described with reference to figure 3. The base station 101 may also receive measurement report information from UEs that may be candidate relays for the remote UE 112 (e.g. measurement report 31 lb).

[0152] Based for example on the information carried by the received Measurement Report messages (31 la, 31 lb), the base station 101 may decide in the step 320 to adapt the remote UE configuration to setup a Multi-path in order to improve (reliability, bandwidth...) the connection between the Remote UE and the network. Then, the first base station 101 notifies the remote UE 112 to perform a connection adaptation i.e. setup one or more additional paths or modify an existing path by sending a RRC Reconfiguration message 321 as defined in 3GPP TS 38.331. As discussed above, this message 321 may further include a multi-path information, a list of relays, a list of backup relays, a primary cell, a list of secondary cells, a path ID per configuration path (each element being optional and added on purpose by the base station).

[0153] Upon reception of a RRC Reconfiguration message 321 from the first base station 101 including a multi-path information as described above, the remote UE 112 proceeds with the addition of a new indirect path according to the information element carried in the RRC Reconfiguration 321. If the path addition configuration does not include SRB1 configuration, it means that the remote UE 112 won’t be able to send the RRCReconfigurationComplete through the new indirect path and so it won’t be able to trigger a relay UE which is not in RRC CONNECTED state by sending the RRCReconfigurationComplete message. Therefore, in this example, the remote UE 112 has to trigger the relay UE 110 with a PC5_trigger as described below. However, the remote UE 112 may decide to use this PC5_trigger even if SRB1 or more generally the control plane is configured on this new path.

[0154] The path addition processing at the remote UE 112 begins by starting the Path Addition Modification failure timer in step 331 and then the remote UE 112 attempts to establish the PC5 connection with the main relay UE identified by the identifier (e.g. targetRelayUE-Identity as specified in TS38.331) carried in the RRC Reconfiguration 321. In the meanwhile, the remote UE 112 applies the Remote UE configuration included in the RRC Reconfiguration message 321 for the new indirect path i.e. the PC5 Relay RLC channel configuration for relay traffic and the associated end-to-end radio bearer(s).

[0155] The PC5 connection establishment 322 starts with a PC5-S frame exchange. The Remote UE 112 sends a Direct Communication Request 801 to the Relay UE 110 to initiate the PC5 connection establishment. The Direct Communication Request message 801 includes at least one of:

[0156] - Source User Info: the initiating UE's Application Layer ID (i.e. Remote UE's Application Layer ID);

[0157] - Target User Info: the target UE's Application Layer ID (i.e. Relay UE's Application Layer ID). This information may be supplied by upper layer e.g. ProSe application;

[0158] - ProSe Service Info: the information about the ProSe identifier(s) requesting link establishment;

[0159] - Security Information: the information for the establishment of security.

[0160] Two types of link establishment (as specified in TS23.287) may be used either UE oriented link establishment based on the Target User Info if included in the Direct Communication Request or ProSe Service oriented link establishment if the Target User Info is not included in the Direct Communication Request.

[0161] A Direct Communication Accept message is sent to Remote UE 112 by the Relay UE 110 that has successfully established security with the Remote UE 112 (security establishment is voluntarily not shown in the figure for the sake of clarity), if the Target User Info included matches the Relay UE's Application Layer ID or if the Relay UE is interested by the ProSe services announced. The Direct Communication Accept message includes at least one of:

[0162] - Source User Info: Application Layer ID of the UE sending the Direct Communication Accept message (i.e. Relay UE);

[0163] - QoS Info: the information about PC5 QoS Flow(s). For each PC5 QoS Flow, the PC5 QoS Flow Identifier (PFI) and the corresponding PC5 QoS parameters requested by Remote UE (i.e. PC5 5G QoS Identifier (PQI) and conditionally other parameters such as Maximum Flow Bit Rate (MFBR) / Guaranteed Flow Bit Rate (GFBR), etc.) and optionally the associated ProSe identifiers(s).

[0164] - Optional PC5 QoS Rule(s).

[0165] At the end of this Direct Communication Request / Accept exchange, the Remote UE 112 and Relay UE 110 may use the PC5 link to communicate with each other.

[0166] Then, the remote UE 112 may initiate a RRCReconfigurationSidelink procedure. The purpose of this procedure is to modify a PC5-RRC connection, e.g. to establish / modify / release sidelink DRBs or PC5 Relay RLC channels, to (re-)configure NR sidelink measurement and reporting, and so on. The remote UE 112 sends to the Relay UE a RRCReconfigurationSidelink message 811 which includes the parameters or configuration information to configure the Relay UE 110. In one aspect, the RRCReconfigurationSidelink sent by the remote UE 112 may include a new IE SI RelayUE RRCConnected Req which if present, requests the relay UE 110 to enter in RRC CONNECTED state.

[0167] Upon the reception of the RRCReconfigurationSidelink message 811, the Relay UE 110 may apply the received configuration and send as a response a RRCReconfigurationCompleteSidelink 812 to the Remote UE 112 to acknowledge the configuration procedure. In one aspect, the Relay UE 110 may include its RRC state to inform the remote UE 112 if the Relay UE 110 is RRC CONNECTED or not. This information may be used by the remote UE 112 to know if it has to trigger the relay UE 110 to enter in RRC CONNECTED state. If the relay UE 110 is unable to support the configuration notified by the remote UE 112, the relay UE sends a RRCReconfigurationFailureSidelink (not shown in the figure).

[0168] In another aspect, the remote UE 112 may configure the sidelink measurement reporting so as the relay UE 110 sends a MeasurementReportSidelink 831 when it enters in RRC CONNECTED or more generally if its RRC state changes. In this variant, a new event(s) based on the RRC state is defined in addition to the existing ones (the link quality level or the signal strength, of the serving cells of the relay UE 110 is lower than a predefined low threshold or is higher than a predefined high threshold). In other words, a new event is defined to trigger the sending of a Sidelink measurement report including the relay UE RRC state and so inform the remote UE about the relay UE RRC state change. In addition, the MeasurementReportSidelink 831 includes the RRC state as a new Information Element. Thereby, the Relay UE 110 may inform the remote UE 112 about its current RRC state when the measurement report sidelink is configured (after the sending of the RRCReconfigurationCompleteSidelink 812) for example, through the

[0169] MeasurementReportSidelink message 831.

[0170] In one aspect, the remote UE 112 may ask the relay UE 110 about its capability by sending a UECapabilityEnquirySidelink message 821. This message may optionally include the capability of the remote UE 112 in the UECapabilitylnformationSidelink Information Element. This capability can carry information to notice or inform the relay UE 110 that the remote UE 112 supports the sending of or has the capability to send the message that triggers the relay UE to enter in RRC CONNECTED (e.g. message 700). From the remote UE’s standpoint, it means it is able to send this triggering message (e.g. message 700) to the relay UE 110. As a response, the relay UE 110 sends a UECapabilitylnformationSidelink message 822 including the capability of the relay UE 110 and more especially if the relay UE 110 supports to be triggered by the remote UE 112 to enter in RRC CONNECTED: for example, the relay UE 110 sends to the remote UE 112 information indicating the relay UE supports a PC5_trigger to enter in RRC CONNECTED. In a variant, this feature may be mandatory for a release 18 sidelink relay UE and so a relay UE or remote UE with the AccessStratumReleaseSidelink field set to rell8 in the UECapabilitylnformationSidelink should support this functionality (i.e. PC5_trigger). This message 822 may also be sent autonomously by the relay UE 110 to inform the remote UE 112 about its capabilities. The UE Capability may also be exchanged prior to the RRCReconfigurationSidelink procedure (frame exchange 811 / 812) as long as the Direct Communication is established.

[0171] In a variant, the relay UE may 110 inform the remote UE 112 about its preference to be triggered through PC5 RRC trigger or by receiving a RRC message (e.g. RRCReconfigurationComplete message) through the SRB. In an example, the relay UE 110 may use UEAssistancelnformationSidelink message to carry this preference information. The remote UE 112 may use this information to build its own preference sent to the gNB for example with the UEAssistancelnformation message 610. The remote UE 112 may also forward this information to the gNB 101.

[0172] In the following description, a release 18 capability may refer to or indicate the support by the relay UE of PC5 triggering to enter the RRC CONNECTED state. For example, in a case where this feature of supporting PC5 triggering is mandatory for a release 18 UE, when a UE indicates it has release 18 capability such a capability can indicate the UE supports PC5 triggering to enter the RRC CONNECTED state where in the case of a relay UE, the relay UE can be triggered to enter in RRC CONNECTED using a PC5 message (e.g. using a PC5 connection or link). In a variant, the releasel8 capability may be carried in a discovery message shared between the relay and the remote UE. For example, a relay UE can send to a remote UE capability information indicating whether the relay node supports PC5 triggering in a discovery announcement message or in response to a request from the remote UE as part of a discovery procedure (Solicitation and Response frame exchange).

[0173] In another variant, the relay UE may transmit its capability to support PC5 triggering to the gNB, for example in the SidelinkUEInformationNR message, in response to a SIB 12 or autonomously.

[0174] The releasel8 capability may also be forwarded by the remote UE to the gNB (e.g., part of the SidelinkUEInformationNR message). When receiving this capability, and similar to the reception of the preference of the remote UE concerning the triggering of the relay UE to enter the RRC CONNECTED state (see previous description), the gNB may include in a RRCReconfiguration message (such as message 321) an indication to the remote UE to trigger the relay UE. This indication could be implicit, i.e., if the configuration in the RRCReconfiguration message does not include SRB1 configuration for the new indirect path, the remote UE has to trigger the relay UE with PC5 RRC trigger, or explicit. In the explicit case, the configuration message sent by the gNB to the remote UE may include information for indicating to the remote UE that the remote UE is to trigger the relay node to enter the RRCCONNECTED state by using a PC5 message. The information could be a bit or field or flag in the configuration message (RRCReconfiguration message 321). More particularly, this information could be included in the indirect path configuration. On the other hand, if the network knows that the relay UE does not support PC5 RRC triggering (e.g. the network knows that the relay UE is not a release 18 relay UE which supports PC5 RRC triggering), the gNB may decide to configure SRB1 on the new path so that the remote UE can send a RRCReconfigurationComplete message on the new path to trigger the relay UE to enter the RRC CONNECTED state. The acquisition of the UE capability could be explicit i.e. the network may receive information from the UE (relay or remote or both) that states or indicates the relay UE does not support PC5 RRC triggering or implicit where the network may not receive information on the PC5 RRC triggering capability and so infers the relay UE does not support the PC5 RRC triggering. In both cases where PC5 triggering is not supported, the network may decide to trigger the relay UE e.g. by sending SRB1 configuration to the remote UE to allow the remote UE to trigger the relay UE to enter in RRC CONNECTED or direct trigger by sending a paging message to trigger the relay UE to enter in RRC CONNECTED. Once the PC5 connection is established after performing PC5 connection establishment 322, the remote UE 112 sends a message 700 to trigger the relay UE 110 to enter in RRC CONNECTED state. This message could be sent whatever the RRC state of the relay UE 110. In another variant, the relay UE 110 may inform the remote UE 112 on its RRC state before the remote UE 112 sends the triggering message 700 for example as aforementioned through the RRCReconfigurationCompleteSidelink 812 or through the MeasurementReportSidelink 831. The trigger message 700 may be conditioned to the remote UE and relay UE capabilities shared through the messages 821 and 822 i.e. if the relay UE supports or not a PC5_trigger to enter in RRC CONNECTED.

[0175] The triggering message 700 could be a new message RemoteUETriggerSidelink.

[0176] In a variant, this triggering message 700 could be a RemoteUEInformationSidelink as specified in TS38.331. However, in this new usage, the RemoteUEInformationSidelink message will be sent when the remote UE 112 is in RRC CONNECTED. In this case the RemoteUEInformationSidelink message includes a new IE SI RelayUE RRCConnected Req which if present, requests the relay UE 110 to enter in RRC CONNECTED state.

[0177] In another variant, triggering message 700 could be a RRCReconfigurationSidelink including a new IE SI RelayUE RRCConnected Req which if present, requests the relay UE 110 to enter in RRC CONNECTED state.

[0178] In another variant, the triggering message 700 could be a RRCReestablishmentRequest that uses the default configuration for the SL-RLC0 (as specified in TS38.331 clause 9.1.1.4) and for the SRB0 (as specified in TS38.331 clause 9.1.1.2). Similarly, other message(s) belonging to SRB0 or SRB1 may be used by using default configuration even if a dedicated configuration was received in the RRCReconfiguration message 321 to prevent the usage of SRB0 and / or SRB1 on the new path. The dedicated configuration should be applied after the relay UE 110 goes in RRC CONNECTED. In this variant, the relay UE 110 may be triggered by SRB0 or SRB1 message from the remote UE 112 but these messages that are normally forwarded to the base station 101 could be filtered by the relay UE 101 and so not sent on to the base station 101 or the base station 101 may be configured to ignore these messages.

[0179] Upon the reception of the message 700, the relay UE 110 that is not in RRC CONNECTED state, begins the procedure to connect to the base station 101 through the RRC Resume or RRC setup procedures as defined in the TS 38.331. The RRC Resume / Setup is illustrated by the frame or message exchange 410.

[0180] And the relay UE 110 may receive from the base station 101 the RRC Reconfiguration message including the Remote UE identifier (Local and L2 ID), the RLC layer configuration (Uu and PC5 RLC channel configuration for relaying) and the SRAP configuration (the bearer mapping configuration). The relay UE 110 configures its different layers according to the RRC Reconfiguration message to enable its L2 relaying functionality. Then, the relay UE 110 sends as a response to the base station 101 a RRC Reconfiguration Complete message. This procedure is illustrated by the frame exchange 340. This procedure can be executed any time after procedure 410 and is independent of the sending of the relay feedback message 500: in other words this RRC Reconfiguration 340 may occur after the sending of the relay feedback message 500.

[0181] Once in RRC CONNECTED state, the relay UE 110 sends a Relay feedback message 500 to the Remote UE 112. This message could be a MeasurementReportSidelink 831 including the RRC state set as connected or a NotificationMessageSidelink as described above.

[0182] When receiving the Relay feedback message 500 indicating that the relay UE 110 is now RRC CONNECTED, the remote UE sends the RRCReconfigurationComplete message 501 to the base station 101 through the direct path. The successful transmission of this RRCReconfigurationComplete message 501 acknowledges the addition of the path and so the setup of the multi-path at the remote UE side, then the remote UE 112 stops the Path Addition Modification failure timer in step 332.

[0183] In a variant, the Relay feedback message 500 may be optional and the remote UE 112 may send the RRCReconfigurationComplete message 501 to the base station 101 after sending the PC5_trigger message 700.

[0184] When receiving the RRC Reconfiguration message 501, the base station 101 deems the Multi Path setup have been completed (step 350).

[0185] As a result, the base station 101 and the remote UE 112 may communicate with each other via both paths, the direct one and the indirect one through the relay UE 110. In other words, the remote UE transmits some uplink data, or UL User Data, to the first base station and / or the first base station transmits some downlink data or DL User Data to the remote UE directly via a direct path as shown by UL / DL User Data 360a or through the relay UE via indirect path as shown by UL / DL User Data 360b.

[0186] Referring now to Figure 9 which is a schematic and simplified diagram illustrating an example of message flows for managing multi-path communication in a wireless communication system, such as that shown in figure la, supporting relaying and in particular for managing path addition procedure to enable a Multi-path comprising one direct and one indirect path, in accordance with one or more embodiments of the invention. This figure presents a multi path failure management case wherein the new path addition / modification failed and more especially when the remote and the relay UEs fail to establish a PC5 connection together. In the example of this figure, the failure cancels the path addition or modification i.e. the base station 101 and the remote UE 112 go back to the configuration prior to the reconfiguration request. The same elements (e.g. steps, messages, frames, entities, nodes, etc.) in figure 9 as those in figures 3 to 8 are referenced by the same reference numbers. The description of the same elements as figures 3 to 8 will be omitted here for figure 9 to simplify the description but the details of these same elements can be found above in the description of figures 3 to 8.

[0187] In one example, a remote UE, like remote UE 112, is connected to a base station, such as base station 101. The remote UE 112 and the base station 101 communicate with each other: in other words the remote UE 112 transmits some uplink data, or UL User Data 310, to the first base station 101 and / or the first base station 101 transmits some downlink data or DL User Data 310 to the remote UE 112.

[0188] The remote UE 112 may also send to the first base station 101 some measurement report information through respectively the Measurement Report message 311 as defined in 3 GPP TS 38.331.

[0189] Based on the information carried by the received Measurement Report messages, the first base station 101 may decide to adapt the connection or connectivity of the remote UE 112 to the network (step 320). In another variant illustrated in this figure, the step 320 may be triggered upon the detection of QoS failure (latency, reliability), or a request from an entity 140 of the core network (e.g. AMF entity; SMF entity; UPF entity as shown in figure lb) or when the resource allocated to the remote UE 112 are insufficient to fulfil the bandwidth need (successive reported BSR with increase of the buffer size) or when requested by the remote UE 112 (for example by using a dedicated MAC Control Element) or when requested by a second base station in a mobility procedure by including multi-path information for example in the Handover (Handover request / request acknowledge) or Inter-gNB path switch messages (as defined in TS38.423). Then, in that case, the base station 101 requests a measurement report to be sent by the remote UE 112 to obtain information of its environment especially the surrounded cells and relays.

[0190] In one aspect of the invention, a monitoring of the QoS (QoS Monitoring Request field in QoS Flow Level QoS Parameters subclause 9.3.1.12 in TS 38.413) may be requested by the core network during the PDU session (end-to-end User plane session) resource setup or PDU session resource modify. During the monitoring, the base station or gNB 101 can detect that the QoS requirement is no longer achieved for some UEs and consequently decide to set a multi-path (step 320). In a variant, the gNB 101 may inform the core network of this QoS issue through some QoS Monitoring Report 315 (specified in TS23.501). Based on this report, the core network may request (message 316) to the base station 101 to setup a multi-path for example to sustain the specified QoS. This Multi-Path setup may be requested by the core network during the PDU session resource setup or PDU session resource modify. When the MP setup request message 316 is received, the base station 101 may request a measurement report to be sent by its UEs (not shown in the figure) to obtain an up-to-date information of their environment.

[0191] Then, based on the step 320, the base station 101 may notify the remote UE 112 to perform a connection adaptation i.e. setup one or more additional paths or modify an existing path by sending a RRC Reconfiguration message 321 as defined in 3GPP TS 38.331.

[0192] In one aspect of the invention, the RRC Reconfiguration message 321 includes all or part of the information elements or information described in the aforementioned description of figure 3.

[0193] Upon reception of a RRC Reconfiguration message 321 from the base station 101 including a multi-path information as described above, the remote UE 112 proceeds with the addition of a new indirect path according to the information element carried in the RRC Reconfiguration 321. The path addition processing at the remote UE 112 begins by starting the Path Addition Modification failure timer in step 331. Then the remote UE 112 attempts to establish the PC5 connection with the main relay UE identified by the identifier (e.g. targetRelayUE-Identity as specified in TS38.331) carried in the RRC Reconfiguration 321. The establishment of the PC5 connection is illustrated by the message exchange 322. The PC5 connection establishment procedure 322 is further described with reference to figure 8. In the example of the present figure, the PC5 connection establishment between the remote UE 112 and the relay UE 110 fails: for example, the relay UE 110 may not respond positively to the Direct Communication Request 801 (e.g. due to security establishment failure, mismatch with the target User Info or Prose Service Info carried in the Direct Communication Request message) or the remote UE 112 receives a RRCReconfigurationFailureSidelink in response to the RRCReconfigurationSidelink 811 that indicates the failure of a PC5 RRC reconfiguration to the remote UE 112. As a result, the remote UE 112 and the relay UE 110 are unable to communicate with each other or to establish a configuration suitable for the relaying.

[0194] When the Remote UE 112 is unable to establish a PC5 connection with the target relay UE 110 indicated in the RRCReconfiguration message 321 and the Path Addition Modification failure timer expires (e.g. on expiry of a time period measured from the start of the timer) or reaches a predefined or a certain value(step 333), the remote UE 112 enters in a failure management procedure. In this procedure, the remote UE 112 may send a failure report message or failure message 900 to the base station 101. This failure message 900 may include all or part of the following information:

[0195] Cause of the failure (or type of failure) indicates that the multi-path setup (or modification) failed or path addition / modification failed or path failure timer expiry;

[0196] - RelayUE-identity indicates the identity of the relay UE that the remote UE failed to connect (if any);

[0197] Cell ID indicates the identity of the cell that the remote UE failed to connect (if any);

[0198] - New Candidate Relay list includes a list of potential relay UE(s) that may be used for further path addition based on measurements collected up to the moment the UE detected the failure. Each input of the new candidate relay list may include signal quality measured by the remote UE (SD-RSRP or SL-RSRP) and an ID which identifies the relay. For example, the failure message may include candidate relay information (e.g. the new Candidate Relay list) for one or more relay nodes that are or may be considered as candidates for providing one or more new communication paths connecting the UE to the network (e.g. to provide a multi-path). A candidate relay node may be a 3GPP node or a non-3GPP relay node (e.g. a WiFi node). The candidate relay information may include signal quality information for each candidate relay node and / or an identifier for each candidate relay node;

[0199] - Neighbor cell reporting includes the best measured cells, ordered such that the best cell is listed first, and based on measurements collected up to the moment the UE detected the failure. For example, neighbor cell reporting may include neighour cell information for indicating one or more cells neighbouring the remote UE that are or may be considered as candidates for providing one or more new direct path for connecting the UE to the network (e.g. to provide a multi-path). For example, the candidate cells may include suitable cells (e.g. cells with signal quality above a threshold measured up to the moment the UE detected the failure) for establishing a new direct path. The neighbour cell reporting or neighbour cell information may include identified s) of the cell(s) or each base station associated with the cell(s); a path ID which identifies each failed connection / path.

[0200] In one aspect, the failure report message 900 could be a MCGFailurelnformation as specified in TS38.331. In another aspect, the failure report message 900 could be a RRCRestablishmentRequest as specified in the TS38.331 clause 5.3.7. This second option may be particularly useful if the control plane and more specifically the SRBO and SRB1 configurations were released from the existing path and moved to the new path by the RRCReconfiguration message 321. In that case, the RRCReestablishmentRequest will allow to re-establish the control plane based on the previous configuration i.e. on the existing path and so will enable the remote UE 112 to communicate again with the base station 101.

[0201] In the meantime, the remote UE 112 goes back to the previous configuration (prior to the reception of the RRCReconfiguration 321) illustrated by the step 920. This ends the path addition / modification failure management from the remote UE’s standpoint.

[0202] When receiving the failure report 900, the base station 101 also goes back to the previous configuration by cancelling the latest modification (step 910) and optionally may send as a response to the MP setup (or modification) request message 316, a MP setup (or modification) failure message 352 to the core network 140.

[0203] As a result, the base station 101 and the remote UE 112 may communicate with each other via the former existing path.

[0204] Referring now to Figure 10 which is a schematic and simplified diagram illustrating an example of message flows for managing multi-path communication in a wireless communication system, such as that shown in figure la, supporting relaying and in particular for managing path addition procedure to enable a Multi-path comprising one direct and one indirect path. This figure presents a multi path failure management case wherein the new path addition / modification failed and more especially when the remote and the relay UEs fail to establish a PC5 connection together. In this figure, based on a failure report, the base station provides a new configuration to the remote UE to establish a second or another path or to modify the path requested by the base station. The same elements (e.g. steps, messages, frames, entities, nodes, etc.) in figure 10 as those in figures 3 to 9 are referenced by the same reference numbers. The description of the same elements as figures 3 to 9 will be omitted here for figure 10 to simplify the description but the details of these same elements can be found above in the description of figures 3 to 9.

[0205] In one example, a remote UE, like remote UE 112, is connected to a base station, such as base station 101. The remote UE 112 and the base station 101 communicate with each other: in other words the remote UE 112 transmits some uplink data, or UL User Data 310, to the first base station 101 and / or the first base station 101 transmits some downlink data or DL User Data 310 to the remote UE 112. The remote UE 112 may also send to the first base station 101 some measurement report information through respectively the Measurement Report message 311 as defined in 3GPP TS 38.331.

[0206] Based on the information carried by the received Measurement Report messages or other trigger as described in the previous figures, the first base station 101 may decide to adapt the connection or connectivity of the remote UE to the network (step 320).

[0207] Then, based on the step 320, the base station 101 may notify the remote UE 112 to perform a connection adaptation i.e. setup one or more additional paths or modify an existing path by sending a RRC Reconfiguration message 321 as defined in 3GPP TS 38.331.

[0208] Upon reception of a RRC Reconfiguration message 321 from the base station 101 including a multi-path information as described above, the remote UE 112 proceeds with the addition of a new indirect path according to the information element carried in the RRC Reconfiguration 321. The path addition processing at the remote UE 112 begins by starting the Path Addition Modification failure timer in step 331. Then the remote UE 112 attempts to establish the PC5 connection with the main relay UE identified by the identifier (e.g. targetRelayUE-Identity as specified in TS38.331) carried in the RRC Reconfiguration 321. The establishment of the PC5 connection is illustrated by the message exchange 322. The PC5 connection establishment procedure 322 is further described with reference to figure 8. In the example of the present figure, the PC5 connection establishment between the remote UE 112 and the relay UE 110 fails: for example, the relay UE 110 may not respond positively to the Direct Communication Request 801 (e.g. due to security establishment failure, mismatch with the target User Info or Prose Service Info carried in the Direct Communication Request message) or the remote UE 112 receives a RRCReconfigurationFailureSidelink in response to the RRCReconfigurationSidelink 811 that indicates the failure of a PC5 RRC reconfiguration to the remote UE 112. As a result, the remote UE 112 and the relay UE 110 are unable to communicate with each other or to establish a configuration suitable for the relaying.

[0209] When the Remote UE 112 is unable to establish a PC5 connection with the target relay UE 110 indicated in the RRCReconfiguration message 321 and the Path Addition Modification failure timer expires (e.g. on expiry of a time period measured from the start of the timer) or reaches a predefined or a certain value (step 333), the remote UE 112 enters in a failure management procedure.

[0210] As in the previous figure, the remote UE 112 may send a failure report message 900 to the base station 101. This failure message 900 may include all or part of the following information: Cause of the failure (or type of failure) indicates that the multi-path setup (or modification) failed or path addition / modification failed or path failure timer expiry;

[0211] - RelayUE-identity indicates the identity of the relay UE that the remote UE failed to connect (if any);

[0212] Cell ID indicates the identity of the cell that the remote UE failed to connect (if any);

[0213] - New Candidate Relay list includes a list of potential relay UE(s) that may be used for further path addition based on measurements collected up to the moment the UE detected the failure. Each input of the new candidate relay list may include signal quality measured by the remote UE (SD-RSRP or SL-RSRP) and an ID which identifies the relay. For example, the failure message may include candidate relay information (e.g. the new Candidate Relay list) for one or more relay nodes that are or may be considered as candidates for providing one or more new communication paths connecting the UE to the network (e.g. to provide a multi-path). A candidate relay node may be a 3GPP node or a non-3GPP relay node (e.g. a WiFi node). The candidate relay information may include signal quality information for each candidate relay node and / or an identifier for each candidate relay node;

[0214] - Neighbor cell reporting includes the best measured cells, ordered such that the best cell is listed first, and based on measurements collected up to the moment the UE detected the failure. For example, neighbor cell reporting may include neighour cell information for indicating one or more cells neighbouring the remote UE that are or may be considered as candidates for providing one or more new direct path for connecting the UE to the network (e.g. to provide a multi-path). For example, the candidate cells may include suitable cells (e.g. cells with signal quality above a threshold measured up to the moment the UE detected the failure) for establishing a new direct path. The neighbour cell reporting or neighbour cell information may include identified s) of the cell(s) or each base station associated with the cell(s); a path ID which identifies each failed connection / path.

[0215] In one aspect, the failure report message 900 could be a MCGFailurelnformation as specified in TS38.331.

[0216] In another aspect, the failure report message 900 could be a RRCRestablishmentRequest as specified in the TS38.331 clause 5.3.7. This second option may be particularly useful if the control plane and more specifically the SRBO and SRB1 configurations were released from the existing path and moved to the new path by the RRCReconfiguration message 321. In that case, the RRCReestablishmentRequest will allow to re-establish the control plane based on the previous configuration i.e. on the existing path and so will enable the remote UE 112 to communicate again with the base station 101.

[0217] When receiving the failure report 900, the base station 101 tries to setup or modify the multi-path by using a backup relay (new candidate relay) based on the measurement (neighbour cell report or / and candidate relay list) that may be included in the failure report. Then in process or phase 1000, the base station 101 and the remote UE 112 attempt to setup or modify the multi-path with this new relay (or new cell for another direct path). This phase 1000 is similar to any one of the phases or processes 390-890 (i.e. the phase x90 described in the figures 3 to 8, with x being replaced by the number of the figure).

[0218] At the end of this phase 1000, the remote UE 112 and the base station 101 successfully setup or modify the multi-path and thus they may communicate with each other via both paths, the direct one and the indirect one through the backup relay UE. In other words, the remote UE 112 transmits some uplink data, or UL User Data, to the first base station 101 and / or the first base station 101 transmits some downlink data or DL User Data to the remote UE 112 directly via a direct path as shown by UL / DL User Data 360a or through the backup relay UE via indirect path as shown by UL / DL User Data 360c.

[0219] Referring now to Figure 11 which is a schematic and simplified diagram illustrating an example of message flows for managing multi-path communication in a wireless communication system, such as that shown in figure la, supporting relaying and in particular for managing path addition procedure to enable a Multi-path comprising one direct and one indirect path. This figure presents a multi path failure management case wherein the new path addition / modification failed and more especially when the remote and the relay UEs fail to establish a PC5 connection together. In this figure, upon failure detection, the remote UE attempts another configuration to establish a second path or another path or to modify the path requested by the base station. The same elements (e.g. steps, messages, frames, entities, nodes, etc.) in figure 10 as those in figures 3 to 9 are referenced by the same reference numbers. The description of the same elements as figures 3 to 9 will be omitted here for figure 10 to simplify the description but the details of these same elements can be found above in the description of figures 3 to 9.

[0220] In one example, a remote UE, like remote UE 112, is connected to a base station, such as base station 101. The remote UE 112 and the base station 101 communicate with each other: in other words the remote UE 112 transmits some uplink data, or UL User Data 310, to the first base station 101 and / or the first base station 101 transmits some downlink data or DL User Data 310 to the remote UE 112. The remote UE 112 may also send to the first base station 101 some measurement report information through respectively the Measurement Report message 311 as defined in 3 GPP TS 38.331.

[0221] Based on the information carried by the received Measurement Report messages (311a, 31 lb, 311c) or other trigger as described in the previous figures, the first base station 101 may decide to adapt the connection or connectivity of the remote UE to the network (step 320).

[0222] Then, based on the step 320, the base station 101 may notify the remote UE 112 to perform a connection adaptation i.e. setup one or more additional paths or modify an existing path by sending a configuration message such as a RRC Reconfiguration message 321 as defined in 3GPP TS 38.331.

[0223] In one aspect, the configuration message (e.g. RRC Reconfiguration message 321) includes all or part of the following information elements or information: multi-path information that indicates that the RRC Reconfiguration intends to setup a multi-path by adding a new path to the existing one. In a variant this multi-path information indicates that the RRC Reconfiguration intends to modify the multi-path configuration by updating or changing at least one of the existing indirect or direct paths. For example, the multi-path information included in the configuration message indicates configuration information included in the configuration message is associated with at least one other communication path to be configured between the remote UE 112 and network to provide a multi-path between the remote UE 112 and the network, which multi-path includes a first communication path already established between the remote UE 112 and the first base station 101.

[0224] A list of relays: this list contains at least one relay identified by its ID. This list indicates to the remote UE 112 to which relay UE (e.g. relay node) the remote UE should be connected. This least may carry several relay UEs if the RRC Reconfiguration aims to establish several indirect paths. For example, the relay list provides relay identification information for identifying at least one relay node with which the remote UE 112 is to establish a connection for a respective at least one communication path of the multipath. This list of relays is associated with the primary or main relay UE(s) and which is also referred to as a target relay UE(s).

[0225] A list of backup relays: this list includes at least one backup relay identified by its ID. This list indicates to the remote UE 112 to which relay UE the remote UE should be connected in case of deficiency of the principal or main relay UE(s). If the list includes several relays, priority information may also be provided for indicating a priority order for the relays so that the remote UE can attempt connection to the relays in the order indicated by the priority information. The remote UE can attempt connection in order if no priority information is provided.

[0226] A primary cell which indicates the primary cell to connect. This cell is identified by a cell ID (e.g. physCellld). For example, the configuration message may include primary or main cell information for identifying a primary or main cell with which the UE is to establish a connection (e.g. for a direct path between the UE and the network) to provide the multi-path and this primary cell information may include the cell ID.

[0227] A list of secondary cells: this list includes at least one cell identified by its cell ID (e.g. sCellld). This list may be used as a backup list if the connection with the primary cell failed or maybe used to connect a second direct path. For example, the configuration message may include backup cell information (e.g. list of secondary cells) for identifying at least one secondary cell with which the UE is to establish a connection (e.g. for a direct path between the UE and the network) to provide the multi-path in the case of failure to establish a connection with the primary cell identified by the primary cell information and this backup cell information may include the cell ID of each of the at least one secondary cell. a path ID which identifies each connection / path. If the RRCReconfiguration includes an identifier that is part of the UE’s configuration already, then the UE considers the procedure as path modification otherwise the UE consider the procedure as a path addition.

[0228] The two above list may be concatenate into a single list and an additional element may indicate the number of indirect paths to establish.

[0229] In addition, the RRC Reconfiguration message includes configuration information for the one or more additional paths and / or for the communication path to be updated / changed / modified. The configuration information for an indirect path may includePC5 Relay RLC channel configuration for relay traffic and the associated end-to-end radio bearer(s). The configuration information for an indirect path (e.g. an Information Element for the configuration of an indirect path) may also include information for indicating to the remote UE that the remote UE is to trigger the relay node to enter the RRC-CONNECTED state by using a PC5 message (as further discussed in Figure 8). The information could be a bit or field or flag in the configuration message.

[0230] In one aspect, the RRCReconfiguration message 321 only includes the configuration related to the new path or the path to modify (and the multi-path information or information indicating multiple paths are to be configured). The remote UE 112 infers that this configuration is for a multi-path setup based on the multi-path information. This multi-path information or information indicating multiple paths are to be configured could be a bit or field (e.g. a multi-path bit or field) set to 1 or enable or true or an Information element including all information related to the Multi-path configuration, or the presence of a SCell configuration or SpCell configuration (in addition to the relay UE(s) identity for a new or a modification of an indirect path) in the CellGroupConfig information element carried in the RRCReconfiguration message. In another aspect, the RRCReconfiguration message may include the configuration of all paths, the existing one(s) and the new (or to modify) one(s). The complete configuration may be included if the fullconfig flag carried in the RRCReconfiguration message is set to true.

[0231] In another aspect, the RRCReconfiguration may include a conditional configuration to apply in case of failure. This conditional configuration may replace the backup relay list. This conditional configuration may include all the configuration required to connect to a backup relay(s) in case of failure of the primary relay UE connection. This configuration may also include a condition or attempt condition that is to be met in order to apply this configuration. In case where the condition is based on path addition failure (e.g. establishment of a PC5 connection with a remote UE after path additional failure), the conditional configuration could include a new cell (as in a Conditional handover CHO case) and a relay UE attached to this new cell. On applying such a conditional configuration in the event of path addition failure, this reconfiguration could lead to a Multi-path switch.

[0232] In the meantime, the base station 101 may transmit the configuration to several relay UEs (for example, the RRC Reconfiguration procedure 1101 for relay UE1 110 and 1102 for relay UE2 120). For each relay UE, these configurations include the Remote UE identifier (Local and L2 ID), the RLC layer configuration (Uu and PC5 RLC channel configuration for relaying) and the SRAP configuration (the bearer mapping configuration). Considering the uncertainty of the usage of the configuration by the backup relay UE, the base station 101 may provide the configuration for relaying to the backup relay UE as a conditional configuration: i.e. the configuration for the relaying should be applied only if the remote UE establishes a PC5 connection with the backup relay. Moreover, in an example, the configuration could be cancelled after a predefined period of time. The RRCReconfiguration of the relay UEs may occur whenever after they become RRC CONNECTED. The way to trigger a relay UE in RRC IDLE or RRC INACTIVE state to go into RRC CONNECTED state either by the network or by the remote UE has been described above with reference to figures 3 to 8. Upon reception of a RRC Reconfiguration message 321 from the base station 101 including a multi-path information as described above, the remote UE 112 proceeds with the addition of a new indirect path according to the information element carried in the RRC Reconfiguration 321. The path addition processing at the remote UE 112 begins by starting the Path Addition Modification failure timer in step 331. Then the remote UE 112 attempts to establish the PC5 connection with the main relay UE 110 identified by the identifier (e.g. targetRelayUE-Identity as specified in TS38.331) carried in the RRC Reconfiguration 321. The establishment of the PC5 connection is illustrated by the message exchange 322. The PC5 connection establishment procedure 322 is further described with reference to figure 8. In the example of the present figure, the PC5 connection establishment between the remote UE 112 and the relay UE 110 fails: for example, the relay UE 112 may not respond positively to the Direct Communication Request 801 (e.g. due to security establishment failure, mismatch with the target User Info or Prose Service Info carried in the Direct Communication Request message) or the remote UE 112 receives a RRCReconfigurationFailureSidelink in response to the RRCReconfigurationSidelink 811 that indicates the failure of a PC5 RRC reconfiguration to the remote UE 112. As a result, the remote UE 112 and the relay UE 110 are unable to communicate with each other or to establish a configuration suitable for the relaying.

[0233] When the Remote UE is unable to establish a PC5 connection with the target relay UE indicated in the RRCReconfiguration message 321 and the Path Addition Modification failure timer expires (e.g. on expiry of a time period measured from the start of the timer) or reaches a predefined or a certain value (step 333), the remote UE 112 enters in a failure management procedure.

[0234] Upon detection of the path addition / modification failure, the remote UE 112 searches for a backup relay UE 120 to connect to, replacing the relay UE (110) to which it was unable to connect (step 1110). The remote UE may select a backup relay from the information provided in the RRCReconfiguration 321 (for example, from the backup relay list).

[0235] In a variant in which the RRCReconfiguration does not include a list of backup relay, the remote UE 112 may autonomously select a new relay UE based on its own measurement as it may be done in a relay reselection procedure.

[0236] The remote UE 112 may select more than one backup relay UE in the case where more than one additional paths are to be established.

[0237] When the remote UE 112 finds a suitable backup relay UE (e.g. relay UE 120), it starts a Path Addition Modification recovery timer in the step 1131 and attempts to establish the additional path(s). The Path Addition Modification recovery timer (not shown in the figures) may be implemented in hardware or software (e.g. by a module of a program that includes instructions for execution by one or more processing units, such as the central processing unit 1711) and is configured to time a certain or predefined time period from start of the timer (i.e. when the path recovery timer reaches a certain or predefined value). In a variant the timer may be started when the RRCReestablishment message 1112 is sent. Then the remote UE 112 tries to establish a PC5 connection with the backup relay UE (120) identified in the RRC Reconfiguration as a backup relay or relying on the relay reselection procedure. The establishment of the PC5 connection with the backup relay UE 120 is illustrated by the message exchange 1111. The PC5 connection establishment procedure 1111 follows the description of the procedure or phase 322 described with reference to figure 8. Eventually, the remote UE 112 succeeds to establish a PC5 connection establishment with the backup relay UE 120. As a result, the remote UE 112 and the backup relay UE 120 are able to directly communicate with each other.

[0238] Then, the remote UE 112 initiates a re-establishment procedure. The re-establishment procedure aims to continue the RRC connection when a failure condition occurs (path addition / modification failure in the example of the figure). To do so, the remote UE 112 first establishes a SRAP entity, if needed, applies the default configurations (SL-RLCO as defined in TS38.331 clause 9.1.1.4, SDAP and PDCP as defined in TS38.331 clause 9.1.1.2) for SRBO. The SRBO is used to send the RRCReestablishmentRequest message. Then, the remote UE 112 establishes or modifies (e.g. via release and add) PC5 RLC entity 221 (or SL RLC) in figure 2, applies the default configurations (SL-RLC1 as defined in TS38.331 clause 9.2.4, PDCP as defined in TS38.331 clause 9.2.1 and SRAP as defined in TS38.331 clause 9.2.5) for SRB1 (control plane) and resumes the SRB1. The SRB1 is used to receive the RRCReestablishment message 1113 from the base station 101 and transmit the RRCReestablishmentComplete message 1114 to the base station 101. Then, the remote UE 112 sends a RRCReestablishmentRequest message 1112 to the base station 101 through the backup relay UE 120. This message 1112 provides the UE identity (e.g. the PCI and C-RNTI of the remote UE 112 may be included in message 1112) to the gNB 101. In addition, the message 1112 may include all or part of the following information:

[0239] Cause of the failure (or type of failure) indicates that the multi-path setup (or modification) failed or path addition / modification failed or timer expiry;

[0240] - RelayUE-identity indicates the identity of the relay UE that the remote UE failed to connect (if any);

[0241] Cell ID indicates the identity of the cell that the remote UE failed to connect (if any); a path ID which identifies each failed connection / path.

[0242] If the backup relay 120 is not RRC CONNECTED, the reception of the RRCReestablishmentRequest message 1112 may trigger the relay UE 120 to enter in RRC CONNECTED state. Other methods to trigger the relay UE have been described above with reference to figures 3 to 8.

[0243] In a variant, the RRCReestablishmentRequest may also be sent through the direct path if the former configuration received in the message 321 does not include SRBO and SRB1 for the new path.

[0244] When receiving the RRCReestablishmentRequest message 1112, the base station 101 infers that this message is related to a recovery of the path addition / modification based on the cause failure and / or the presence of the RelayUE-identity and / or the path ID, then the base station 101 prepares and sends a RRCReestablishment message 1113. This message 1113 may include information associated with a RRC procedure for use in continuing the RRC connection for the UE, such as, information used for security and partial remote UE configuration (SRAP configuration used for the SRB1 and local UE ID) and RRC-Transactionldentifier which is used for the identification of an RRC procedure. The partial UE configuration part may be ignored if the configuration was already transmitted in the primary RRCReconfiguration message 321. This message 1113 may be sent to the remote UE 112 on the direct or indirect path depending on the configuration wanted by the base station 101.

[0245] Upon reception of this RRCReestablishment message 1113, the remote UE 112 applies, if required, the configuration included in the message and sends as a response a RRCReestablishmentComplete message 1114. This message 1114 may include all or at least some of the following information:

[0246] - RRC-Transactionldentifier which is used for the identification of the RRC procedure and set to the same value as the value received in the RRCReestablishment message 1113;

[0247] - New Candidate Relay list includes a list of potential relay UE(s) that may be used for further path addition based on measurements collected up to the moment the UE detected the failure. Each input of the new candidate relay list may include signal quality measured by the remote UE (SD-RSRP or SL-RSRP) and an ID which identifies the relay. For example, the message 1114 may include candidate relay information (e.g. the new Candidate Relay list) for one or more relay nodes that are or may be considered as candidates for providing one or more new communication paths connecting the UE to the network (e.g. to provide a multi-path). A candidate relay node may be a 3GPP node or a non-3GPP relay node (e.g. a WiFi node). The candidate relay information may include signal quality information for each candidate relay node and / or an identifier for each candidate relay node;

[0248] - Neighbor cell reporting includes the best measured cells, ordered such that the best cell is listed first, and based on measurements collected up to the moment the UE detected the failure. For example, neighbor cell reporting may include neighour cell information for indicating one or more cells neighbouring the remote UE that are or may be considered as candidates for providing one or more new direct path for connecting the UE to the network (e.g. to provide a multi-path). For example, the candidate cells may include suitable cells (e.g. cells with signal quality above a threshold measured up to the moment the UE detected the failure) for establishing a new direct path. The neighbour cell reporting or neighbour cell information may include identified s) of the cell(s) or each base station associated with the cell(s);

[0249] Information relative to or associated with the connection failure with the primary relay UE; for example, this information may include RelayUE-identity information for indicating the identity of the relay UE that the remote UE failed to connect (if any), and / or a path ID which identifies the path in failure.

[0250] This message 1114 may be sent on the direct or indirect path depending on the configuration provided by the base station 101 in the RRCReconfiguration message 321 or based on the partial configuration received in the RRCReestablishment message 1113 or based on a default configuration. This completes the path addition / modification recovery management from the remote UE’s standpoint, so the remote UE 112 stops the Path Addition Modification recovery timer in the step 1132.

[0251] In another aspect, at the end of the recovery procedure, the remote UE 112 may apply the full configuration received in the RRCReconfiguration 321 (or a new configuration received subsequently during the RRCReestablishment procedure) and send as a response a RRCReconfigurationComplete 1115 through the direct or indirect path depending on the configuration for the control plane and more especially for the SRB1.

[0252] When receiving the RRCReestablishmentComplete message 1114 and optionally the RRC Reconfiguration message 1115, the base station 101 deems the Multi Path setup has been completed (step 350).

[0253] As a result, the base station 101 and the remote UE 112 may communicate with each other via both paths, the direct one and the indirect one through the backup relay UE 120. In other words, the remote UE 112 transmits some uplink data, or UL User Data, to the first base station 101 and / or the first base station 101 transmits some downlink data or DL User Data to the remote UE 112 directly via a direct path as shown by UL / DL User Data 360a or through the backup relay UE via indirect path as shown by UL / DL User Data 360c.

[0254] According to the above description, the behavior of the Path Addition Modification failure timer (also referred to as path failure timer) is summarized as follow:

[0255] Start condition: The reception of a configuration message, such as a RRC Reconfiguration message 321, including a Multi-Path configuration to add or modify an indirect path, triggers the remote UE to start the path failure timer.

[0256] Stop condition: The successful sending of a RRC Reconfiguration Complete message to the base station through the relay UE if the control plane is configured on this new path (e.g. a Signalling Radio Bearer such as SRB1 is configured on the new indirect path), or the reception of a Relay feedback message including an indication that the relay is configured or RRC CONNECTED or the successful sending of a RRC Reconfiguration Complete message to the base station through the direct path and an information indicating that the relay UE is RRC CONNECTED triggers the remote UE to stop the path failure timer. Different examples of messages which may trigger the remote UE to stop the path failure timer are described above. These include, for example, feedback message 500, PC5 RRC Reconfiguration complete message, NotificationMessageSidelink message, RRCReconfigurationCompleteSidelink 812, MeasurementReportSidelink 831.

[0257] - Failure condition: At expiry, the remote UE 112 sends a failure report and / or tries a RRCRestablishment procedure through a backup relay UE. The backup relay UE is provided by the base station or autonomously selected by the remote UE (as in relay reselection procedure). In other words, the path addition / modification failure may trigger the remote UE to perform a relay (re) sei ection.

[0258] The above description of the behavior of the Path Addition Modification failure timer (also referred to as path failure timer) has been made with respect to receiving a configuration message including configuration information and multi-path information. It will however be appreciated that the behavior of the Path Addition Modification failure timer (also referred to as path failure timer) as summarized above may also apply in the case where the configuration information does not include the multi-path information and includes configuration information for configuring the UE (e.g. remote UE 112) for communication with the network. In this case, the path failure timer is started by the remote UE 112 on receipt of the configuration information. According to the above description, the behavior of the Path Addition Modification recovery timer (also referred to as path recovery timer) is summarized as follow:

[0259] Start condition: The successful sending of a RRC Reconfiguration of a RRCReestablishmentRequest message (such as message 1112) to the base station in response to the expiration of the path failure timer, triggers the remote UE to start the path recovery timer.

[0260] Stop condition: The successful sending of a RRCReestablishmentComplete message to the base station through the relay UE if the control plane is configured on this new path, or the reception of a Relay feedback message including an indication that the relay is RRC CONNECTED or the successful sending of a RRCReestablishmentComplete message to the base station through the direct path and an information indicating that the relay UE is RRC CONNECTED triggers the remote UE to stop the path recovery timer. Different examples of messages which may trigger the remote UE to stop the path recovery timer are described above. These include, for example, feedback message 500, PC5 RRC Reconfiguration complete message, NotificationMessageSidelink message, RRCReconfigurationCompleteSidelink 812, MeasurementReportSidelink 831.

[0261] Failure condition: At expiry, the remote UE keeps the former configuration before the reception of the RRCReconfiguration that requested a new configuration and may send a failure report.

[0262] The above description of the behavior of Path Addition Modification recovery timer (also referred to as path recovery timer) has been made with respect to receiving a configuration message including configuration information and multi-path information. It will however be appreciated that the behavior of the Path Addition Modification recovery timer (also referred to as path recovery timer) as summarized above may also apply in the case where the configuration information does not include the multi-path information and includes configuration information for configuring the UE (e.g. remote UE 112) for communication with the network.

[0263] The above description (with reference to figures 3-11) that refers to path addition to setup a multi-path may be used also for a path modification: that is, modification of at least one path of multiple paths (multi-path setup) that have been set up and established between the remote UE and the network. In that case, the RRCReconfiguration message 321 from the base station 101 to the remote UE 112 includes the configuration relative to the path to release and the configuration relative to the path to add for example in the RadioBearerConfig (for PDCP) and CellGroupConfig (for MAC and RLC) Information elements. SRAP modifications may be also required for the path modification and especially in the mapping table that associates the bearers to the PC5 RLC channels to be used. Thereby, this mapping table defines which bearer will go through the Uu and which bearer will go through the PC5 links. This release and add information being interpreted as a path modification.

[0264] Similarly, the behaviour for the addition / modification of a direct path (figures 12 and 13) may use the description of the above figures. But for the addition / modification of a direct path, the RRCReconfiguration may not include the relay UE lists, the connection with the base station requires a RACH (Random Access CHannel) procedure for its initial access as specified in TS38.300 clause 9.2.6.

[0265] Figures 12 and 13 illustrate the direct path addition / modification respectively in normal case and in case of failure.

[0266] Referring now to Figure 12 which is a schematic and simplified diagram illustrating an example of message flows for managing multi-path communication in a wireless communication system, such as that shown in figure la, supporting relaying and in particular for managing path addition procedure to enable a Multi-path. In this figure, the remote UE 112 and the base station are connected through the relay UE 110 and attempt to add a new direct or indirect path to setup a multi-path. The same elements (e.g. steps, messages, frames, entities, nodes, etc.) in figure 12 as those in figures 3 to 11 are referenced by the same reference numbers. The description of the same elements as figures 3 to 11 will be omitted here for figure 12 to simplify the description but the details of these same elements can be found above in the description of figures 3 to 11.

[0267] In one example, a remote UE, like remote UE 112, is connected to a base station, such as base station 101, through a relay UE 110. The remote UE 112 and the base station 101 communicate with each other through the relay UE 110, in other words the remote UE 112 transmits some uplink data, or UL User Data 310, to the first base station 101 through the relay UE 110 and / or the first base station transmits some downlink data or DL User Data 310 to the remote UE 112 also through the relay UE 110.

[0268] The remote UE 112 and the relay UE 110 may also send to the first base station some measurement report information through respectively the MEASUREMENT REPORT messages 311a and 31 lb. In the example of the figure, the message 31 la is forwarded by the relay UE 110 (relayed traffic or message is indicated by a circle in the figures). Based on the information carried by the received Measurement Report messages, the first base station 101 may decide to adapt the connection of the remote UE to the network (step 320).

[0269] In other variants, the step 320 may be triggered upon the detection of QoS failure (latency, reliability), or a request 316 from an entity 140 of the core network (e.g. AMF, SMF, UPF entities illustrated in figure lb) or when the resource allocated to the remote UE are insufficient to fulfil the bandwidth need (successive reported BSR with increase of the buffer size) or when requested by the remote UE (for example by using a dedicated MAC Control Element) or when requested by a second base station in a mobility procedure by including multi-path information for example in the Handover (Handover request / request acknowledge) or Inter-gNB path switch messages (as defined in TS38.423). Then, in that case, the base station requests a measurement report is sent by the remote UE 112 to obtain information of its environment especially the surrounded cells and relays.

[0270] Then, based on the step 320, the base station 101 may notify the remote UE 112 to perform a connection adaptation i.e. setup an additional path or modify an existing path by sending configuration message, such as a RRC Reconfiguration message 321 as defined in 3GPP TS 38.331 through the relay UE 110.

[0271] In one aspect of the invention, the configuration message (e.g. RRC Reconfiguration message 321) includes all or part of the following information elements or information: multi-path information that indicates that the RRC Reconfiguration intends to setup a multi-path by adding a new path to the existing one. In a variant this multi-path information indicates that the RRC Reconfiguration intends to modify the multi-path configuration by updating or changing at least one of the existing indirect or direct paths. For example, the multi-path information included in the configuration message indicates configuration information included in the configuration message is associated with at least one other communication path to be configured between the remote UE 112 and network to provide a multi-path between the remote UE 112 and the network, which multi-path includes a first communication path already established between the remote UE 112 and the first base station 101.

[0272] A list of relays: this list contains at least one relay identified by its ID. This list indicates to the remote UE 112 to which relay UE (e.g. relay node) the remote UE should be connected. This least may carry several relay UEs if the RRC Reconfiguration aims to establish several indirect paths. For example, the relay list provides relay identification information for identifying at least one relay node with which the remote UE 112 is to establish a connection for a respective at least one communication path of the multipath. This list of relays is associated with the primary or main relay UE(s) and which is also referred to as a target relay UE(s).

[0273] A list of backup relays: this list includes at least one backup relay identified by its ID. This list indicates to the remote UE 112 to which relay UE the remote UE should be connected in case of deficiency of the principal or main relay UE. If the list includes several relays, priority information may also be provided for indicating a priority order for the relays so that the remote UE can attempt connection to the relays in the order indicated by the priority information.

[0274] A primary cell which indicates the primary cell to connect. This cell is identified by a cell ID (e.g. physCellld). For example, the configuration message may include primary or main cell information for identifying a primary or main cell with which the UE is to establish a connection (e.g. for a direct path between the UE and the network) to provide the multi-path and this primary cell information may include the cell ID.

[0275] A list of secondary cells: this list includes at least one cell identified by its cell ID (e.g. sCellld). This list may be used as a backup list if the connection with the primary cell failed or maybe used to connect a second direct path. For example, the configuration message may include backup cell information (e.g. list of secondary cells) for identifying at least one secondary cell with which the UE is to establish a connection (e.g. for a direct path between the UE and the network) to provide the multi-path in the case of failure to establish a connection with the primary cell identified by the primary cell information and this backup cell information may include the cell ID of each of the at least one secondary cell. a path ID which identifies each connection / path. If the RRCReconfiguration includes an identifier that is part of the UE’s configuration already, then the UE considers the procedure as path modification otherwise the UE consider the procedure as a path addition.

[0276] The two above relay lists may be concatenate into a single list and an additional element may indicate the number of indirect paths to establish.

[0277] Similarly, an additional field may indicate the number of direct paths to set.

[0278] Each path is associated to a configuration that includes RLC, Radio bearer configurations and all the configuration parts required to establish and use the path.

[0279] In one aspect, the RRCReconfiguration message 321 only includes the configuration related to the new path or the path to modify (and the multi-path information). The remote UE 112 infers that this configuration is for a multi-path setup based on the multi-path information. This multi-path information could be a multi-path bit or field set to 1 or enable or true or an Information element including all information related to the Multi-path configuration, or the presence of a SCell configuration or SpCell configuration (in addition to the relay UE(s) identity for a new or a modification of an indirect path) in the CellGroupConfig information element carried in the RRCReconfiguration message. In another aspect, the RRCReconfiguration message may include the configuration of all paths, the existing one(s) and the new (or to modify) one(s). The complete configuration may be included if the fullconfig flag carried in the RRCReconfiguration message is set to true.

[0280] In another aspect, an mrdc-SecondaryCellGroup information element could also be included in the configuration message 321 if a new path to be set up involves another or second base station. This element included in the configuration message 321 includes the RRCReconfiguration message as generated by the second base station. This second RRCReconfiguration may also include a configuration for a direct path or an indirect path or both as described above. For example, the remote UE 112 would be connected to base station 101 through the relay UE 110 and to the second base station 102 directly.

[0281] The selection of one or more cells by the base station 101 for the addition of a direct path may be based on the information included in the measurement report from the different UEs (e.g. from Remote UE 112 in measurement report 31 la and from Relay UE 110 in measurement report 311b). The base station 101 assesses the different cells included in the measurement reports. The RRC Reconfiguration message 321 may include a primary cell and one or more backup cells if the primary cell reported by the remote UE 112 suffers from unstable link quality and so could be prone to connection failure. In its cell selection, the base station 101 may give precedence to the serving cell of the relay UE 110 in order to ease the management of the multi-path. The selected cell may be a cell controlled by the base station 101 or may be a cell controlled by another or second base station (such as gNB 102).

[0282] Upon reception of a RRC Reconfiguration message 321 from the base station 101 including a multi-path information as described above, the remote UE 112 proceeds with the addition of a new direct path (or the modification of an existing one) according to the information element or information carried in the RRC Reconfiguration 321. The path addition processing at the remote UE 112 begins by starting the Path Addition Modification failure timer in step 331. Then the remote UE 112 attempts to establish the connection directly with the base station identified from the information in the RRC Reconfiguration message 321. To do so, the remote UE 112 synchronizes with the base station and performs Random Access procedure as specified in TS38.300 clause 9.2.6. In the example shown in figure 12, this base station is the first base station 101. The establishment of the connection with the base station 101 is illustrated by the message exchange 1210. In the example of the present figure, the RACH procedure succeeds and as a result, the remote UE 112 and the base station 101 may communicate directly with each other.

[0283] Upon successful completion of the Random -Access procedure, the remote UE 112 stops the Path Addition Modification failure timer in step 332. At this time, the remote UE 112 has applied the configuration received in the RRCReconfiguration message 321 and thus the Signal Radio Bearer (control plane) configuration (if any) for the new direct path. If a SRB1 is configured for this new path, the remote UE 112 may send a RRCReconfigurationComplete message 501 to the base station 101 through the new direct path otherwise, the remote UE 112 sends the RRCReconfigurationComplete message 323 to the base station 101 through the existing indirect path. In the example shown in figure 12, the remote UE 112 uses the existing path (indirect via relay UE 110) to transmit the RRCReconfigurationComplete message to the base station 101.

[0284] In a variant, the successful transmission of this RRCReconfigurationComplete message may trigger the remote UE to stop the Path Addition Modification failure timer in step 332.

[0285] When receiving the the RRCReconfigurationComplete message 323 (or RRCReconfigurationComplete message 501), the base station 101 considers the Multi Path setup have been completed (step 350). The base station 101 may inform the core network that the multi-path has been successfully setup (or modify) by sending the message MP setup ack (MP modify ack) 351 in response to the MP setup request 316.

[0286] As a result, the base station 101 and the remote UE 112 may communicate with each other via both paths, the direct one and the indirect one through the relay UE 110. In other words, the remote UE 112 transmits some uplink data, or UL User Data, to the first base station 101 and / or the first base station 101 transmits some downlink data or DL User Data to the remote UE 112 directly via a direct path as shown by UL / DL User Data 360a or through the relay UE via indirect path as shown by UL / DL User Data 360b.

[0287] Referring now to Figure 13 which is a schematic and simplified diagram illustrating an example of message flows for managing multi-path communication in a wireless communication system, such as that shown in figure la, supporting relaying and in particular for managing path addition procedure to enable a Multi-path. In this figure, the remote UE 112 and the base station 101 are connected through the relay UE 110 and attempt to add a new direct or indirect path to setup a multi-path. This figure presents a multi path failure management case wherein the new path addition / modification failed and more especially when the Random-Access procedure fails. The same elements (e.g. steps, messages, frames, entities, nodes, etc.) in figure 13 as those in figures 3 to 12 are referenced by the same reference numbers. The description of the same elements as figures 3 to 12 will be omitted here for figure 13 to simplify the description but the details of these same elements can be found above in the description of figures 3 to 12.

[0288] In one example, a remote UE, like remote UE 112, is connected to a base station, such as base station 101, through a relay UE 110. The remote UE 112 and the base station 101 communicate with each other through the relay UE 110, in other words the remote UE 112 transmits some uplink data, or UL User Data 310, to the first base station 101 through the relay UE 110 and / or the first base station 101 transmits some downlink data or DL User Data 310 to the remote UE 112 also through the relay UE 110.

[0289] The remote UE 112 and the relay UE 110 may also send to the first base station some measurement report information through respectively the MEASUREMENT REPORT messages 311a and 31 lb. In the example of the figure, the message 31 la is forwarded by the relay UE 110 (relayed traffic or message is indicated by a circle in the figures).

[0290] Based on the information carried by the received Measurement Report messages, the first base station 101 may decide to adapt the connection of the remote UE 112 to the network (step 320).

[0291] In other variants, the step 320 may be triggered upon the detection of QoS failure (latency, reliability), or a request 316 from an entity 140 of the core network (e.g. AMF, SMF, UPF entities illustrated in figure lb) or when the resource allocated to the remote UE 112 are insufficient to fulfil the bandwidth need (successive reported BSR with increase of the buffer size) or when requested by the remote UE 112 (for example by using a dedicated MAC Control Element) or when requested by a second base station in a mobility procedure by including multi-path information for example in the Handover (Handover request / request acknowledge) or Inter-gNB path switch messages (as defined in TS38.423). Then, in that case, the base station 101 requests a measurement report is sent by the remote UE 112 to obtain information of its environment especially the surrounded cells and relays.

[0292] Then, based on the step 320, the base station 101 may notify the remote UE 112 to perform a connection adaptation i.e. setup an additional path or modify an existing path by sending a configuration message, such as a RRC Reconfiguration message 321 as defined in 3GPP TS 38.331 through the relay UE 110. In one aspect, the RRC Reconfiguration message 321 includes all or part of the information elements or information in the aforementioned description of the figures 3-12.

[0293] Upon reception of a RRC Reconfiguration message 321 from the base station 101 including a multi-path information as described above, the remote UE 112 proceeds with the addition of a new direct path (or the modification of an existing one) according to the information element or information carried in the RRC Reconfiguration 321. The path addition / modification processing at the remote UE begins by starting the Path Addition Modification failure timer in step 331. Then the remote UE 112 attempts to establish the connection directly with the base station identified from the information in the RRC Reconfiguration message 321. To do so, the remote UE synchronizes with the base station and performs Random Access procedure as specified in TS38.300 clause 9.2.6. In the example shown in figure 13, this base station is the first base station 101. The establishment of the connection with the base station 101 is illustrated by the message exchange 1210. In the example of the present figure, the RACH procedure fails.

[0294] When the Remote UE 112 is unable to establish the connection with the base station 101 indicated in the RRCReconfiguration message 321 and the Path Addition Modification failure timer expires (e.g. on expiry of a time period measured from the start of the timer) or reaches a predefined or a certain value (step 333), the remote UE 112 enters in a failure management procedure. In this procedure, the remote UE 112 may send a failure report message or failure message 900 to the base station 101. In the example of the figure, the failure report message 900 is sent through the indirect path via the relay UE 110 to reach the base station 101. This failure message 900 may include all or part of the following information:

[0295] Cause of the failure (or type of failure) indicates that the multi-path setup (or modification) failed or path addition / modification failed or path failure timer expiry;

[0296] - RelayUE-identity indicates the identity of the relay UE that the remote UE failed to connect (if any);

[0297] Cell ID indicates the identity of the cell that the remote UE failed to connect (if any);

[0298] - New Candidate Relay list includes a list of potential relay UE that may be used for further path addition based on measurements collected up to the moment the UE detected the failure. Each input of the relay list may include signal quality measured by the remote UE (SD-RSRP or SL-RSRP) and an ID which identifies the relay. For example, the failure message may include candidate relay information (e.g. the new Candidate Relay list) for one or more relay nodes that are or may be considered as candidates for providing one or more new communication paths connecting the UE to the network (e.g. to provide a multi-path). A candidate relay node may be a 3GPP node or a non-3GPP relay node (e.g. a WiFi node). The candidate relay information may include signal quality information for each candidate relay node and / or an identifier for each candidate relay node;

[0299] - Neighbor cell reporting includes the best measured cells, ordered such that the best cell is listed first, and based on measurements collected up to the moment the UE detected the failure. For example, neighbor cell reporting may include neighour cell information for indicating one or more cells neighbouring the remote UE that are or may be considered as candidates for providing one or more new direct path for connecting the UE to the network (e.g. to provide a multi-path). For example, the candidate cells may include suitable cells (e.g. cells with signal quality above a threshold measured up to the moment the UE detected the failure) for establishing a new direct path. The neighbour cell reporting or neighbour cell information may include identified s) of the cell(s) or each base station associated with the cell(s); a path ID which identifies each failed connection / path.

[0300] In one aspect, the failure report message 900 could be a MCGFailurelnformation as specified in TS38.331.

[0301] In another aspect, the failure report message 900 could be a RRCRestablishmentRequest as specified in the TS38.331 clause 5.3.7. This second option may be particularly useful if the control plane and more specifically the SRBO and SRB1 configurations were released from the existing path and moved to the new path by the RRCReconfiguration message 321. In that case, the RRCReestablishmentRequest will allow to re-establish the control plane based on the previous configuration i.e. on the existing path and so will enable the remote UE 112 to communicate again with the base station 101.

[0302] In the meantime, the remote UE 112 goes back to the previous configuration (prior to the reception of the RRCReconfiguration 321) illustrated by the step 920. This ends the path addition / modification failure management from the remote UE’s standpoint.

[0303] When receiving the failure report 900, the base station 101 also goes back to the previous configuration by cancelling the latest modification (step 910) and optionally may send as a response to the MP setup (or modification) request message 316, a MP setup (or modification) failure message 352 to the core network.

[0304] As a result, the base station 101 and the remote UE 112 may communicate with each other via the former existing path. In a variant, the reception of a failure report message 900 may trigger the base station 101 to setup or modify the multi-path by using another cell or another relay UE based on the measurement (neighbour cell report or / and candidate relay list) that may be included in the failure report message. Then, the base station 101 and the remote UE 112 may attempt to setup or modify the multi-path with this new configuration. For example, the remote UE 112 and base station 101 may perform the phase or process 1000 as discussed above with respect to figure 10 (i.e. perform any one of the phases or processes 390-890). This new configuration may configure an inter-gNB path switch and then the multi-path setup may occur on the new base station.

[0305] In another variant, upon failure detection, the remote UE 112 may enter in a path addition / modification recovery procedure such as a recovery procedure as discussed above with reference to figure 11. In this procedure, the remote UE 112 searches for a backup cell to connect to, replacing the primary cell to which it was unable to connect. The remote UE 112 may select a backup cell from the list provided in the RRCReconfiguration message 321 : e.g. from the list of secondary cells, or included as a conditional configuration which may include all the configuration information required to connect to a backup cell(s) in case of failure of the primary cell connection. The remote UE 112 may also autonomously perform a cell reselection procedure based on its own measurement. The remote UE 112 may also consider a connection through a second relay to add another indirect path (e.g. based on a relay list provided in the RRCReconfiguration message 321).

[0306] Referring now to figure 14 which is a flow chart showing steps of a method 1400 for managing multi-path communication in a wireless communication system supporting relaying between a UE and a network in accordance with one or more embodiments of the present invention. The wireless communication system supports sidelink relaying and / or other peer-to- peer relaying, such as over WiFi relaying or Bluetooth relaying. In the case where the wireless communication system supports sidelink relaying the UE is referred to as a remote UE and the relay node is referred to as a relay UE (e.g. a UE operating or functioning as a relay). The network of the wireless communication system includes at least a first base station. Method 1400 is performed at the first base station (i.e. is performed at a base station of the network) after a first communication path has been established between the UE and the first base station. The first communication path may be a direct path between the UE and the first base station or an indirect path between the UE and the first base station via at least one relay node. The UE may be configured so that it can communicate with the network via the first base station over at least two separate paths or multiple paths (referred to as multi-path). For example, the UE may be directly connected to the base station via a direct path and also may be indirectly connected to the base station via at least one relay node (e.g. a relay UE) and thus, via an indirect path. Additionally or alternatively, the UE may be connected to the base station via at least two indirect paths and / or at least two direct paths. The UE may also be configured so that it can communicate with the network via a second base station over one or more direct and / or indirect paths. With respect to the example shown in figure 1, the first base station performing method 1400 may be base station 101 (also referred to as gNB 101) and the UE may be remote UE 112. The second base station may be base station 102. The method 1400 as shown in and described with respect to figure 14 may be performed by software elements and / or hardware elements. Thus, for example, the method as shown in and described with respect to figure 14 may be performed by an apparatus for the base station comprising one or more processing units configured to carry out the method. The base station may be implemented in a communication device 1700 as shown in and described with reference to figure 17 with the method as shown in and described with respect to figure 14 being performed by one or more processing units, such as the central processing unit 1711.

[0307] Briefly, at step 1404, the base station 101 sends to the remote UE 112 a configuration message including configuration information for configuring the remote UE 112 for communication with or connection to the network. The configuration information (also referred to as multi-path, MP, configuration information) may include all or part of the information described above with respect to the RRC Reconfiguration message 321. The configuration message may be the RRC Reconfiguration message 321. The configuration message further includes multi-path information for indicating the configuration information is associated with at least one other communication path to be configured between the remote UE 112 and the network to provide, with the first communication path, multiple paths or multi-path between the remote UE 112 and the network or information indicating multiple paths are to be configured. The configuration information may be for a new communication path to be added to provide a multi-path or in the case where multiple paths are already established, the configuration information is for modifying (or changing or updating) at least one of the multiple paths already established. In the latter case, the modification may include replacing one established or existing communication path between the UE and the network with another communication path between the UE and the network: for example, by releasing the established or existing communication path and adding the at least one other communication path.

[0308] As discussed above, the multi-path information (or information indicating multiple paths are to be configured) could be a bit or field (e.g. a multi-path bit or field) set to 1 or enable or true or an Information element including all information related to the Multi-path configuration, or the presence of a SCell configuration or SpCell configuration (in addition to the relay UE(s) identity for a new or a modification of an indirect path) in the CellGroupConfig information element carried in the RRCReconfiguration message.

[0309] By providing the multi-path information in the configuration message sent to the remote UE, the remote UE 112 is notified that it is to set up a multi-path or change / modify an existing multi-path configuration. This also means only configuration information for the new path or path to be modified needs to be sent to the remote UE.

[0310] The first communication path may be a direct or indirect path (e.g. via a relay node, such as relay UE 110). The at least one another communication path may include at least one indirect and / or at least one direct path. The at least one another communication path may be between the UE and a second base station (such as base station 102) of the network (e.g. one or more direct paths to the second base station and / or one or more indirect paths to the second base station).

[0311] In an example, and as shown by step 1402 in dotted lines in figure 14, the first base station 101 may determine connectivity or connection of the remote UE 112 to the network is to be adapted (e.g. changed, modified, updated) and may send the configuration message after determining connectivity of the UE 112 is to be adapted. The determination by the first base station 101 may be based on measurement report information received at the first base station 101. The measurement report information may include information received in one or more measurement reports sent by the remote UE 112 (e.g. measurement report 311a) and / or information received in one or more measurement reports received from other UEs, such as UE 110, in the wireless communication system (e.g. measurement reports 31 lb, 311c). These other UEs which are in the vicinity of or surrounding or neighbouring the remote UE 112 are potential candidates to operate as a relay node for the remote UE 112. In addition, the first base station 101 may receive measurement report information associated with cells controlled by other base stations in the vicinity or neighbouring the remote UE 112. The determination by the first base station 101 may be in response to or after receipt of a request received from a core network entity (such as entity 140), such as a MP setup request 316 as discussed above or after receipt of a request received from the UE or after receipt of a request received from a second base station (e.g. 102), such as in a mobility procedure by including multi-path information for example in the Handover (Handover request / request acknowledge) or Inter- gNB path switch messages (as defined in TS38.423). As discussed above, the MP setup request 316 may be sent after the first base station 101 sends information indicating a QoS requirement is not being met (e.g. in a QoS monitoring report 315).

[0312] The determining by the first base station 101 that the connectivity of the UE 112 to the network is to be adapted includes determining to set up multiple paths between the UE 112 and the network including the first communication path by adding at least one other communication path between the UE 112 and the network or in the case where multiple paths have been established already (or exist) between the UE 112 and the network including the first communication path and a second communication path (between the UE and first base station or between the UE and a second base station), determining to modify the multiple paths or multi-path by changing at least the second communication path to at least one other communication path between the UE 112 and the network. Examples of such determinations by the first base station 101 are described above with respect to the MP setup / modification decision step 320.

[0313] In an example, the first base station 101 may select the at least one other communication path based on measurement report information received at the first base station. For example, the received measurement report information may include information received in one or more measurement reports sent by the remote UE 112 (e.g. measurement report 311a) and / or information received in one or more measurement reports received from other UEs, such as UE 110, in the wireless communication system (e.g. measurement reports 31 lb, 311c) and / or measurement report information associated with cells controlled by other base stations in the vicinity or neighbouring the remote UE 112, as discussed above. Selecting may include selecting at least one relay node, such as relay UE 110, to which the remote UE 112 is to connect based on the measurement report information or selecting at least one cell (e.g. a cell controlled by second base station 102) to which the remote UE 112 is to connect based on the measurement report information. For example, for an indirect other communication path including a second relay node 110, the second relay node 110 may be selected based on measurement report information for the second relay node 110 and for an direct other communication path between the UE and a second base station 102, the second base station 102 may be selected based on measurement report information for a cell served by the second base station 102. In its relay selection, the first base station 101 may give precedence to relay UEs already in a RRC CONNECTED state when selecting one or more main relay UEs in order to decrease the latency of the new path establishment.

[0314] In the case where at least one relay node is selected for at least one indirect path, the first base station 101 sends, to each of the selected at least one relay node (e.g. relay UE 110), configuration information for configuring the selected relay node for the respective indirect path between the UE and the network. The configuration information may be sent in a RRC Reconfiguration message 341 as discussed above. If the selected relay node 110 is in a nonconnected RRC state (e.g. RRC INACTIVE or RRC IDLE), the first base station 101 sends to the selected relay node 110 a trigger message to trigger the selected relay node 110 to enter the RRC connected state (e.g. RRC CONNECTED). The trigger message may be message 400 which is sent after the first base station 101 checks the RRC state of the relay UE as described in step 600 above. The trigger message may be a paging message or a System Information Block (e.g. SIB 12)

[0315] The above description of how the base station 101 can trigger the relay UE to enter a RRC connected state has been made with respect to when the configuration message includes configuration information and multi-path information. It will however be appreciated that the base station 101 can trigger the relay UE to enter a RRC connected state based on the above description in the case where the configuration information does not include the multi-path information and includes configuration information for configuring the UE (e.g. remote UE 112) for communication with the network.

[0316] The first base station 101 may receive a failure message from the remote UE 112 in the event of failure to set up the at least one other communication path. The failure message may be message 900 (e.g. a MCGFailurelnformation message) and may include all or part of the information described above for message 900. After or in response to receiving the failure message, the first base station may cancel the configuration of the at least one communication path (for example, as described above with reference to step 910). The first base station 101 may then send a multi-path failure message, such as message 352, to the core network.

[0317] After receiving the failure message, in an example, the first base station 101 may then select at least one new communication path and send to the remote UE 112 a configuration message including configuration information for configuring the at least one new communication path and multi-path information for indicating the at least one new communication path to be configured is to provide multiple paths or multi-path between the UE and the network. The first base station 101 may select the at least one new communication path based on information provided in the failure message. Phase or process 1000 discussed above provides an example of how the first base station 101 selects a new path and sends configuration information to the remote UE 112 for the new path to provide multi-path.

[0318] Referring now to figure 15 which is a flow chart showing steps of a method 1500 for managing multi-path communication in a wireless communication system supporting relaying between a UE and a network in accordance with one or more embodiments of the present invention. The wireless communication system supports sidelink relaying and / or other peer-to- peer relaying, such as over WiFi relaying or Bluetooth relaying. In the case where the wireless communication system supports sidelink relaying the UE is referred to as a remote UE and the relay node is referred to as a relay UE (e.g. a UE operating or functioning as a relay). The network of the wireless communication system includes at least a first base station. Method 1500 is performed at the UE after a first communication path has been established between the UE and the first base station. The first communication path may be a direct path between the UE and the first base station or an indirect path between the UE and the first base station via at least one relay node. The UE may be configured so that it can communicate with the network via the first base station over at least two separate paths or multiple paths (referred to as multipath). For example, the UE may be directly connected to the base station via a direct path and also may be indirectly connected to the base station via at least one relay node (e.g. a relay UE) and thus, via an indirect path. Additionally or alternatively, the UE may be connected to the base station via at least two indirect paths and / or at least two direct paths. The UE may also be configured so that it can communicate with the network via a second base station over one or more direct and / or indirect paths. With respect to the example shown in figure 1, the UE performing method 1500 may be UE or remote UE 112 and the first base station may be base station 101 (also referred to as gNB 101). The second base station may be base station 102. The method 1500 as shown in and described with respect to figure 15 may be performed by software elements and / or hardware elements. Thus, for example, the method as shown in and described with respect to figure 15 may be performed by an apparatus for the base station comprising one or more processing units configured to carry out the method. The base station may be implemented in a communication device 1700 as shown in and described with reference to figure 17 with the method as shown in and described with respect to figure 15 being performed by one or more processing units, such as the central processing unit 1711.

[0319] Briefly, at step 1502, the remote UE 112 receives from the base station 101 a configuration message including configuration information for configuring the remote UE 112 for communication with or connection to the network. The configuration information (also referred to as multi-path, MP, configuration information) may include all or part of the information described above with respect to the RRC Reconfiguration message 321. The configuration message may be the RRC Reconfiguration message 321. The configuration message further includes multi-path information for indicating the configuration information is associated with at least one other communication path to be configured between the remote UE 112 and the network to provide, with the first communication path, multiple paths or multipath between the remote UE 112 and the network. The configuration information received at the remote UE 112 from the first base station 101 corresponds to the configuration information sent by the first base station as discussed above with respect to figure 14. Thus, for more details of the configuration information and the first communication path, see the above description with respect to figure 14.

[0320] Instead of the first base station 101 making the determination that the connectivity or connection of the remote UE 112 to the network is to be adapted (e.g. changed, modified, updated), the remote UE 112 may make the determination. For example, the remote UE 112 may determine an additional bandwidth need based on the steady increase in data held in its buffer(s) (e.g. when preparing a BSR) or upon reception of many negative acknowledgement messages (e.g. NACKs) from the relay UE to which it is connected. In this case, the remote UE 112 may send, to the first base station 101, a request to establish at least one other communication path between the UE and the network to provide multiple paths or multi-path between the UE and the network.

[0321] In an example, and as shown by step 1504 in dotted lines in figure 15, the remote UE 112 may initiate connection adaptation to adapt (or modify or change or update) connectivity of the UE to the network based on information in the received configuration message.

[0322] Connection adaptation may include setting up multiple paths between the UE 112 and the network by adding at least one other communication path between the UE 112 and the network to provide multiple paths or multi-path between the UE and the network including the first communication path or in the case where multiple paths have been established already (or exist) between the UE 112 and the network including the first communication path and a second communication path (between the UE and first base station or between the UE and a second base station), modifying the multiple paths or multi-path by changing at least the second communication path to at least one other communication path between the UE 112 and the network.

[0323] In response to or after receiving the configuration message, the remote UE 112 may start a path failure timer (e.g. a Path addition / modification / failure timer). The remote UE 112 may stop the path failure timer in response to or after sending, by the remote UE 112, a message indicating setup of the at least one other communication path at the remote UE 112 is completed. The message sent by the remote UE 112 may be the RRC Reconfiguration message 323 or RRCReconfigurationComplete message 501. The remote UE 112 may stop the path failure timer in response to or after successful transmission of the message. In an example, the message 323 or 501 is sent by the remote UE 112 when a Signalling Radio Bearer (e.g. SRB1) is configured on an indirect path between the remote UE 112 and the network. In another example, the remote UE 112 may stop the path failure timer in response to or after receiving a relay message indicating the relay node (e.g. relay UE 110) is configured (e.g. configuration of PC5 RRC AS has been completed) or active. The relay message may also indicate the relay node 110 is connected to the first base station 101. In an example, the relay message is sent when a Signalling Radio Bearer (e.g. SRB1) is not configured on an indirect path between the remote UE 112 and the network. For example, the relay message includes information indicating the relay UE 110 is in a RRC connected state (RRC CONNECTED). The relay message may be the feedback message 500, NotificationMessageSidelink message, RRCReconfigurationCompleteSidelink 812, MeasurementReportSidelink 831, as discussed above.

[0324] When the path failure timer reaches a certain value (e.g. on expiry of the timer), the remote UE 112 sends, to the first base station 101, a failure message for indicating failure to set up the at least one other communication path. The failure message may be message 900 (e.g. a MCGFailurelnformation message) and may include all or part of the information described above for message 900.

[0325] In an example case where the at least one other communication path includes an indirect path including a relay node, the remote UE 112 initiates connection adaptation by sending, to the relay node, configuration information for configuring the relay node for the indirect path. The configuration information may be sent in a RRCReconfigurationSidelink message 811. In response to sending the configuration information, the remote UE 112 may receive an acknowledgement indicating configuration at the relay UE 110 is complete (e.g. in a RRCReconfigurationCompleteSidelink message 812).

[0326] After sending the configuration information, the remote UE 112 may send to the relay UE 110 a message (e.g. RRCReconfigurationSidelink 811 or RemoteUEInformationSidelink 700) to trigger the relay node to enter a RRC connected state. The RRCReconfigurationSidelink sent by the remote UE 112 may include a new IE SI RelayUE RRCConnected Req which if present, requests the relay UE 110 to enter in RRC CONNECTED state.

[0327] The remote UE 112 may receive, from the relay UE 110, information indicating whether the relay UE 110 supports to be triggered by the UE to enter in a RRC connected state. The information may be sent as part of a UECapabilitylnformationSidelink message 822 in response to a request from the UE UECapabilityEnquiry Sidelink message 821 or automatically on its own volition. The capability exchange may occur before the RRCReconfigurationSidelink as long as Direct Communication is established. The remote UE 112 can determine whether the relay UE 110 supports to be triggered by the remote UE 112 based on information received from the relay UE 100 and may then send the trigger message after determining the relay UE 110 supports to be triggered by the remote UE 112.

[0328] The above description of how the remote UE 112 can trigger the relay UE to enter a RRC connected state has been made with respect to receiving a configuration message including configuration information and multi-path information. It will however be appreciated that the remote UE 112 can trigger the relay UE to enter a RRC connected state based on the above description in the case where the configuration information does not include the multi-path information and includes configuration information for configuring the UE (e.g. remote UE 112) for communication with the network.

[0329] In an example, the remote UE 112 sends to the first base station 101 at least one of: information for indicating whether, in a case where an indirect path is to be configured, the UE prefers a relay node in a connected RRC state or in a non-connected RRC state; information for indicating whether, in a case where an indirect path is to be configured and a relay node of the indirect path is in a non-connected RRC state, the UE prefers to trigger the relay node to enter the connected RRC state. Such information may be sent in a UEAssistancelnformation message 610.

[0330] As discussed above, in response to or after receiving the configuration message, the remote UE 112 may start a path failure timer (e.g. a Path addition / modification / failure timer). In an example, after the path failure timer reaches a certain value (e.g. on expiry of the timer) indicating failure to set up the at least one other communication path, the remote UE 112 selects at least one new communication path (e.g. at least one direct path and / or at least one indirect path). After selecting at least one new communication path, the remote UE 112 starts a path recover timer (e.g. Path addition / modification / recovery timer) and after starting this timer, the remote UE 112 attempts to establish at least one connection to set up the at least one communication path.

[0331] The remote UE 112 may start the path recovery timer in response to or after sending a RRCReestablishment message, such as message 1112, or in response to selecting the at least one new communication path. The remote UE 112 may stop the path recovery timer in response to sending, by the remote UE 112, a message indicating setup of the at least one new communication path is completed. The message may be a RRCRestablishmentComplete message 1114 or a RRC Reconfiguration Complete message 323 / 501. The remote UE 112 may stop the path recovery timer in response to or after successful transmission of the message. In an example case where the at least one new communication path includes a new indirect path including a relay node, the remote UE 112 stops the path recovery timer in response to receiving a relay message: such as a message indicating the relay UE 110 is configured or active and which message may also indicate the relay UE 110 is connected to the first base station 101. For example, the relay message includes information indicating the relay UE 110 is in a RRC connected state (RRC CONNECTED). The relay message may be the feedback message 500, NotificationMessageSidelink message, RRCReconfigurationCompleteSidelink 812, MeasurementReportSidelink 831, as discussed above.

[0332] The remote UE 112 may receive from the first base station 101 backup identification information for identifying at least one backup communication path. The backup identification information may include backup relay identification information, such as the backup relay list as discussed above with reference to configuration message 321 and / or backup cell information, such as the cell list as discussed above with reference to configuration message 321. After the path failure timer reaches a certain value, the remote UE 112 may select at least one relay node identified in the backup relay identification information and in this case the at least one new communication path includes at least one new indirect path through the selected one of the at least one relay node and / or the remote UE 112 may select at least one secondary cell identified in the backup cell information, in this case the at least one new communication path includes at least one new direct path to the selected one of the at least one secondary cell.

[0333] In another example, after the path failure timer reaches a certain value, the remote UE 112 may select at least one new communication path based on measurements performed at the UE.

[0334] After the remote UE 112 determines setup of the at least one new communication path is completed, the remote UE 112 may then perform a RRC re-establishment procedure to continue a RRC connection for the remote UE 112. This RRC re-establishment procedure may include sending a RRC re-establishment request message, such as message 1112, receiving a RRC re-establishment message, such as message 1113, and sending a RRC re-establishment complete message, such as message 1114, as discussed above with reference to figure 11.

[0335] The above description of the behavior of the Path Addition Modification failure timer (also referred to as path failure timer) and the behavior of Path Addition Modification recovery timer (also referred to as path recovery timer) has been made with respect to receiving a configuration message including configuration information and multi-path information. It will however be appreciated that the behavior of these timers may also apply in the case where the configuration information does not include the multi-path information and includes configuration information for configuring the UE (e.g. remote UE 112) for communication with the network.

[0336] Referring now to figure 16 which is a flow chart showing steps of a method 1600 for managing multi-path communication in a wireless communication system supporting relaying between a UE and a network in accordance with one or more embodiments of the present invention. The wireless communication system supports sidelink relaying and / or other peer-to- peer relaying, such as over WiFi relaying or Bluetooth relaying. In the case where the wireless communication system supports sidelink relaying the UE is referred to as a remote UE and the relay node is referred to as a relay UE (e.g. a UE operating or functioning as a relay). The network of the wireless communication system includes at least a first base station. Method 1600 is performed at a relay UE after a first communication path has been established between the UE and the first base station. The first communication path may be a direct path between the UE and the first base station or an indirect path between the UE and the first base station via at least one other relay node. The UE may be configured so that it can communicate with the network via the first base station over at least two separate paths or multiple paths (referred to as multi-path). For example, the UE may be directly connected to the base station via a direct path and also may be indirectly connected to the base station via at least one relay node (e.g. a relay UE) and thus, via an indirect path. Additionally or alternatively, the UE may be connected to the base station via at least two indirect paths and / or at least two direct paths. The UE may also be configured so that it can communicate with the network via a second base station over one or more direct and / or indirect paths. With respect to the example shown in figure 1, the relay UE performing method 1600 may be UE 110 operating as a relay UE, the UE may be remote UE 112 and the first base station may be base station 101 (also referred to as gNB 101). The second base station may be base station 102. The method 1600 as shown in and described with respect to figure 16 may be performed by software elements and / or hardware elements. Thus, for example, the method as shown in and described with respect to figure 16 may be performed by an apparatus for the base station comprising one or more processing units configured to carry out the method. The base station may be implemented in a communication device 1700 as shown in and described with reference to figure 17 with the method as shown in and described with respect to figure 16 being performed by one or more processing units, such as the central processing unit 1711.

[0337] Briefly, at step 1602, the relay UE 110 receives (e.g. from the base station 101, such as in a RRC Reconfiguration message 341 or from the remote UE 112, such as in a RRCReconfigurationSidelink message 811) configuration information for configuring the relay node for an indirect communication path between the UE and the network so as to provide with the first communication path multiple paths between the UE and the network.

[0338] At step 1604, the relay UE 110 sends, to the remote UE 112, information indicating a current RRC state of the relay UE 110 (e.g. whether the relay node is in a RRC connected state (e.g. RRC CONNECTED)). The information may be sent in any one of a Feedback message 500, NotificationMessageSidelink message, MeasurementReportSidelink 831, RRCReconfigurationCompleteSidelink 812 as described above or any other PC5 RRC Reconfiguration complete message. For example, the relay UE 110 may send a relay message indicating the relay node is configured or active and which message may also indicate the relay UE 110 is connected to the first base station and may include information indicating the relay UE 110 is in a RRC connected state (RRC CONNECTED). The relay message may be the feedback message 500, NotificationMessageSidelink message, RRCReconfigurationCompleteSidelink 812, MeasurementReportSidelink 831, as discussed above.

[0339] The configuration information may include measurement reporting configuration information for configuring the relay node to send measurement reporting information after a change in RRC state. The relay UE 110 may send, to the remote UE 112, after determining a change in RRC state at the relay UE 110, measurement reporting information including the information indicating the current RRC state of the relay UE. The measurement reporting information may be sent in a MeasurementReportSidelink 831.

[0340] In an example, the relay UE 110 sends to the remote UE 112 information indicating whether the relay node supports to be triggered by the UE to enter in a RRC connected state. The information may be sent as part of a UECapabilitylnformationSidelink message 822 in response to a request from the UE UECapabilityEnquiry Sidelink message 821 or automatically on its own volition. In the example case where the relay UE 110 does support triggering by the remote UE 112 to enter in a RRC connected state and the current RRC state of the relay UE 110 is a non-connected RRC state, the relay UE 110 enters into the RRC connected state in response to receiving a trigger message (e.g. RRCReconfigurationSidelink 811 or RemoteUEInformationSidelink 700) from the remote UE 112.

[0341] In another example, the relay UE 110 may receive a message from the first base station 101 to trigger the relay UE 110 to enter into the RRC connected state. Such a message may be the message 400. Figure 17 shows a schematic representation of an example communication device or station, in accordance with one or more example embodiments of the present disclosure.

[0342] The communication device 1700 may be a device such as a micro-computer, a workstation or a light portable device. The communication device 1700 comprises a communication bus 1713 to which there are preferably connected: a central processing unit 1711, such as a microprocessor, denoted CPU; memory for storing data and computer programs containing instructions for the operation of the communication device 1700. The computer programs may contain a number of different program elements or sub-routines containing instructions for a variety of operations and for implementing the invention. For example, the program elements include at least one element for managing multi-path communication as discussed above. The at least one element when executed by the central processing unit 1711 configure one or more processing units (e.g. functioning as or part of the CPU 1711) to perform the method(s) as described above.

[0343] The communication device 1700 may further comprise at least one communication interface 1702 connected to the radio communication network 1703 over which digital data packets or frames or control frames are transmitted, for example a 5G NR wireless communication network. The frames are written from a FIFO sending memory in RAM 1712 to the communication interface 1702 for transmission or are read from the communication interface 1702 for reception and writing into a FIFO receiving memory in RAM 1712 under the control of a software application running in the CPU 1711.

[0344] Each of a UE and base station may comprise such a communication device 1700.

[0345] The central processing unit 1711 may be a single processing unit or processor or may comprise two or more processing units or processors carrying out the processing required for the operation of the communication device 1700. The number of processing units or processors and the allocation of processing functions to the processing unit(s) is a matter of design choice for a skilled person.

[0346] The memory may include: a read only memory 1707, denoted ROM, for storing computer programs for implementing methods according to embodiments of the invention; a random-access memory 1712, denoted RAM, for storing the executable code of methods according to embodiments of the invention as well as the registers adapted to record variables and parameters necessary for implementing methods according to embodiments of the invention.

[0347] Optionally, the communication device 1700 may also include the following components: a data storage means 1704 such as a hard disk, for storing computer programs for implementing methods according to one or more embodiments of the invention; a disk drive 1705 for a disk 1706, the disk drive being adapted to read data from the disk 1706 or to write data onto said disk; a screen 1709 for displaying decoded data and / or serving as a graphical interface with the user, by means of a keyboard 1710 or any other user input means.

[0348] Preferably the communication bus 1713 provides communication and interoperability between the various elements included in the communication device 1700 or connected to it. The representation of the bus 1713 is not limiting and in particular, the central processing unit is operable to communicate instructions to any element of the communication device 1700 directly or by means of another element of the communication device 1700.

[0349] The disk 1706 may optionally be replaced by any information medium such as for example a compact disk (CD-ROM), rewritable or not, a ZIP disk, a USB key or a memory card and, in general terms, by an information storage means that can be read by a microcomputer or by a microprocessor, integrated or not into the apparatus, possibly removable and adapted to store one or more programs whose execution enables a method according to embodiments of the invention to be implemented.

[0350] The executable code may optionally be stored either in read only memory 1707, on the hard disk 1704 or on a removable digital medium such as for example a disk 1706 as described previously. According to an optional variant, the executable code of the programs can be received by means of the communication network 1703, via the communication interface 1702, in order to be stored in one of the storage means of the communication device 1700, such as the hard disk 1704, before being executed.

[0351] The central processing unit 1711 is preferably adapted to control and direct the execution of the instructions or portions of software code of the program or programs according to the invention, which instructions are stored in one of the aforementioned storage means. On powering up, the program or programs that are stored in a non-volatile memory, for example on the hard disk 1704 or in the read only memory 1707, are transferred into the random-access memory 1712, which then contains the executable code of the program or programs, as well as registers for storing the variables and parameters necessary for implementing the invention.

[0352] In an embodiment, the apparatus is a programmable apparatus which uses software to implement the invention. However, alternatively, the present invention may be implemented in hardware (for example, in the form of an Application Specific Integrated Circuit or ASIC). In such a case, logic units are configured to perform the steps of the method(s) in accordance with the present invention described above.

[0353] While the present invention has been described with reference to embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. It will be appreciated by those skilled in the art that various changes and modification might be made without departing from the scope of the invention, as defined in the appended claims. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0354] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be advantageously used.

[0355] In the preceding embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over, as one or more instructions or code, a computer-readable medium and executed by a hardware-based processing unit.

[0356] Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer-readable media generally may correspond to (1) tangible computer-readable storage media which is non- transitory or (2) a communication medium such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and / or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer- readable medium.

[0357] By way of example, and not limitation, such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It should be understood, however, that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but are instead directed to non-transient, tangible storage media. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

Claims

Claims1. A method for managing multi-path communication in a wireless communication system supporting relaying between a User Equipment, UE, and a network including at least a first base station, wherein a first communication path has been established between the UE and the first base station, the method at the first base station comprising: sending, to the UE, a configuration message including configuration information for configuring the UE for communication with the network, wherein the configuration message includes information for indicating at least one other communication path is to be configured between the UE and the network in addition to the first communication path to provide multiple paths between the UE and the network.

2. The method of claim 1, wherein sending the configuration message includes, sending, to the UE, the configuration message after determining connectivity of the UE to the network is to be adapted such that multiple paths are provided between the UE and the network.

3. The method of claim 2, further comprising determining connectivity of the UE to the network is to be adapted based on measurement report information received at the first base station.

4. The method of claim 2, further comprising determining connectivity of the UE to the network is to be adapted after receipt of a request received from a core network entity or after receipt of a request received from the UE or after receipt of a request received from a second base station.

5. The method of claim 2, further comprising: sending, to the core network entity, information indicating a Quality-Of-Service, QoS, requirement is not being met by the first communication path; receiving, from the core network entity, a multi-path setup request after sending the information indicating a QoS requirement is not being met; determining connectivity of the UE to the network is to be adapted after receipt of the multi-path setup request.

6. The method of any one of claims 2 to 5, wherein determining connectivity of the UE to the network is to be adapted includes determining to set up multiple paths between the UE and the network including the first communication path by adding at least one other communication path between the UE and the network, wherein the configuration message includes path configuration information for configuring the UE for the at least one other communication path.

7. The method of any one of claims 2 to 5, wherein in the case where multiple paths have been established between the UE and the network including the first communication path and a second communication path, determining connectivity of the UE to the network is to be adapted includes determining to modify the multiple paths by changing at least the second communication path to at least one other communication path between the UE and the network, wherein the configuration message includes path configuration information for configuring the UE for the at least one other communication path.

8. The method of any one of the preceding claims, further comprising: selecting the at least one other communication path based on measurement report information received at the first base station.

9. The method of claim 8, wherein selecting the at least one other communication path includes selecting at least one relay node to which the UE is to connect based on the measurement report information, in this case the at least one other communication path includes at least one indirect path through the selected at least one relay node.

10. The method of claim 8, wherein selecting the at least one other communication path includes selecting at least one cell to which the UE is to connect based on the measurement report information, in this case the at least one other communication path includes at least one direct path to the selected at least one cell.

11. The method of claim 9, further comprising: sending, to each of the selected at least one relay node, configuration information for configuring the selected relay node for the respective indirect path between the UE and the network.

12. The method of any one of claims 1 to 9, or claim 11, further comprising: receiving capability information for indicating whether a relay node that is a candidate relay node for providing an indirect communication path between the UE and the network supports PC5 triggering where the relay node can be triggered to enter a RRC CONNECTED state using a PC5 message.

13. The method of any one of claims 1 to 12, wherein sending the configuration message includes: sending, to the UE, a configuration message including configuration information for configuring a Signalling Radio Bearer, SRB, on the at least one other communication path for use by the UE in triggering the relay node to enter the RRC CONNECTED state.

14. The method of claim 12, further comprising: after determining the relay node does not support PC5 triggering based on the received capability information, determining, by the base station, the base station is to send a trigger message for triggering the relay node to enter the RRC CONNECTED state.

15. The method of claim 9 or claim 11 or claim 14, further comprising: after determining that a selected relay node is in a non-connected RRC state, sending to the selected relay node a trigger message to trigger the selected relay node to enter RRC connected state.

16. The method of claim 15, wherein the trigger message is one of: a paging message including an identifier for the selected relay node and paging cause information for indicating the selected relay node is to initiate a connection procedure; a paging message for indicating the first base station has data to send to the relay node for the UE.

17. The method of any one of the preceding claims, further comprising receiving, from the UE, a failure message for indicating failure to set up the at least one other communication path.

18. The method of claim 17, wherein the failure message includes at least one of: failure type information indicating a type of failure to set up the at least one other communication path;identification information for identifying a relay node to which the UE failed to connect in the case of failure to set up an indirect path; cell information for identifying a cell to which the UE failed to connect in the case of failure to set up a direct path; candidate relay information for one or more relay nodes that are candidates for providing one or more new communication paths connecting the UE to the network; neighbour cell information for indicating one or more cells neighbouring the UE that are candidates for providing one or more new communication paths connecting the UE to the network; path identification information for identifying the at least one communication path for which set up has failed or for identifying each connection of the at least one communication path for which set up has failed.

19. The method of claim 17 or claim 18, further comprising: after receiving the failure message, cancelling the configuration of the at least one other communication path.

20. The method of claim 17 or claim 18, further comprising: after receiving the failure message, cancelling the configuration of the at least one other communication path and sending a multi-path failure message to a core network entity.

21. The method of claim 17 or claim 18, further comprising: after receiving the failure message, selecting at least one new communication path; sending, to the UE, a configuration message including configuration information for configuring the at least one new communication path and information for indicating the at least one new communication path to be configured is to provide multiple paths between the UE and the network.

22. The method of any one of the preceding claims, wherein the configuration message further includes at least one of: relay identification information for identifying at least one relay node with which the UE is to establish a connection for the at least one other communication path to provide the multiple paths;backup relay identification information for identifying at least one relay node with which the UE is to establish a connection to provide the multiple paths in the case of failure to establish a connection with a first relay node; primary cell information for identifying a primary cell with which the UE is to establish a connection for the at least one other communication path to provide the multiple paths; backup cell information for identifying at least one secondary cell with which the UE is to establish a connection to provide the multiple paths in the case of failure to establish a connection with a primary cell; path identification information for identifying the at least one other communication path or for identifying each connection of the at least one other communication path; configuration information for configuring at least one communication path between the UE and a second base station to provide the multiple paths.

23. A method for managing multi-path communication in a wireless communication system supporting relaying between a User Equipment, UE, and a network including a first base station, wherein a first communication path has been established between the UE and the first base station, the method at the UE comprising: receiving, from the first base station, a configuration message including configuration information for configuring the UE for communication with the network, wherein the configuration message includes information for indicating at least one other communication path is to be configured between the UE and the network in addition to the first communication path to provide multiple paths between the UE and the network.

24. The method of claim 23, further comprising sending, to the first base station, a request to establish at least one other communication path between the UE and the network to provide multiple paths between the UE and the network.

25. The method of claim 23 or claim 24, further comprising: initiating connection adaptation to adapt connectivity of the UE to the network based on information in the received configuration message.

26. The method of any one of claims 23 to 25, further comprising: after receiving the configuration message, starting a path failure timer.

27. The method of claim 26, wherein initiating connection adaptation includes initiating connection adaptation after starting the path failure timer.

28. The method of claim 26 or claim 27, further comprising: stopping the path failure timer in response to sending, by the UE, a message indicating setup of the at least one other communication path at the UE is completed.

29. The method of claim 26 or claim 27, further comprising: stopping the path failure timer in response to sending, by the UE, a message indicating setup of the at least one other communication path at the UE is completed after a Signalling Radio Bearer, SRB, is configured on the at least one other communication path.

30. The method of claim 26 or claim 27, further comprising: stopping the path failure timer in response to receiving a message indicating setup of the at least one other communication path at the UE is completed when a Signalling Radio Bearer, SRB, is not configured on the at least one other communication path.

31. The method of claim 26 or claim 27, wherein in the case where the at least one other communication path includes an indirect path including a relay node, the method further comprises: stopping the path failure timer in response to receiving a relay message indicating the relay node is configured.

32. The method of claim 26 or claim 27 or claim 30, wherein in the case where the at least one other communication path includes an indirect path including a relay node, the method further comprises: stopping the path failure timer in response to receiving a RRCReconfigurationcompleteSidelink message.

33. The method of claim 31, wherein the relay message includes information indicating the relay node is in a RRC connected state.

34. The method of any one of claims 25 to 33, wherein connection adaptation includes adding the at least one other communication path to provide multiple paths between the UE and thenetwork including the first communication path or in the case where multiple paths have been established between the UE and the network including the first communication path and a second communication path, connection adaptation includes modifying the multiple paths by changing at least the second communication path to at least one other communication path between the UE and the network.

35. The method of any one of claims 25 to 34, wherein in the case where the at least one other communication path includes an indirect path including a relay node, initiating connection adaptation includes: initiating establishment of a PC5 connection with the relay node for the indirect path.

36. The method of claim 35, further comprising after initiating establishment of a PC5 connection, receiving, from the relay node, an acknowledgement indicating establishment of a PC5 connection at the relay node is complete.

37. The method of any one of claims 35 to 36, wherein in the case where the at least one other communication path includes an indirect path including a relay node, the method further comprising after initiating establishment of a PC5 connection, receiving, from the relay node, information indicating whether the relay node is in a RRC connected state.

38. The method of any one of claims 35 to 37, wherein in the case where the at least one other communication path includes an indirect path including a relay node, the method further comprising sending, to the relay node, a message to trigger the relay node to enter a RRC connected state.

39. The method of any one of claims 23 to 37, wherein in the case where the at least one other communication path includes an indirect path including a relay node, the method further comprising sending, to the relay node, a RemoteUEInformationSidelink message to trigger the relay node to enter a RRC connected state.

40. The method of any one of claims 23 to 37, wherein in the case where the at least one other communication path includes an indirect path including a relay node and the UE is in a RRC connected state, the method further comprising sending, to the relay node, a message to trigger the relay node to enter a RRC connected state.

41. The method of any one of claims 38 to 40, wherein the message includes information for triggering the relay node to enter a RRC connected state.

42. The method of any one of claims 23 to 41, wherein in the case where the at least one other communication path includes an indirect path including a relay node, the method further comprising, receiving information indicating whether the relay node supports to be triggered by the UE to enter in a RRC connected state.

43. The method of any one of claims 23 to 41, wherein in the case where the at least one other communication path includes an indirect path including a relay node, further comprising, receiving capability information indicating whether the relay node supports PC5 triggering where the relay node can be triggered by the UE to enter a RRC connected state using a PC5 message.

44. The method of any one of claims 23 to 43, wherein in the case where the at least one other communication path includes an indirect path including a relay node, further comprising, receiving preference information indicating whether the relay node prefers to be triggered through PC5 triggering where the relay node can be triggered by the UE to enter a RRC connected state using a PC5 message or RRC triggering where the relay node can be triggered by the UE to enter a RRC connected state using a RRC message.

45. The method of claim 42 or claim 43 or claim 44, further comprising sending, to the first base station, capability information indicating whether the relay node supports PC5 triggering where the relay node can be triggered by the UE to enter a RRC connected state using a PC5 message and / or preference information indicating whether the relay node prefers to be triggered through PC5 triggering where the relay node can be triggered by the UE to enter a RRC connected state using a PC5 message or RRC triggering where the relay node can be triggered by the UE to enter a RRC connected state using a RRC message.

46. The method of claim 38 or claim 39 or claim 40 and claim 42, or claim 38 or claim 39 or claim 40 and claim 43, wherein sending, to the relay node, a message to trigger the relay node includes sending, to the relay node, a message to trigger the relay node to enter a RRC connected state after determining the relay node supports to be triggered by the UE.

47. The method of any one of claims 23 to 38, in the case where the at least one other communication path includes an indirect path including a relay node, the method further comprising: when the configuration information does not include a Signal Radio Bearer, SRB, configuration for the indirect path, determining, by the UE, the UE is to trigger the relay node to enter a RRC CONNECTED state by using a PC5 message.

48. The method of any one of claims 23 to 38, in the case where the at least one other communication path includes an indirect path including a relay node, the method further comprising: determining, by the UE, the UE is to trigger the relay node to enter a RRC CONNECTED state by using a PC5 message based on the configuration message.

49. The method of any one of claims 23 to 48, further comprising sending, to the first base station, at least one of: information for indicating whether, in a case where an indirect path is to be configured, the UE prefers a relay node in a connected RRC state or in a non-connected RRC state; information for indicating whether, in a case where an indirect path is to be configured and a relay node of the indirect path is in a non-connected RRC state, the UE prefers to trigger the relay node to enter the connected RRC state.

50. The method of any one of claims 23 to 49, further comprising: in response to receiving the configuration message, starting a path failure timer; sending, when the path failure timer reaches a certain value, a failure message for indicating failure to set up the at least one other communication path and / or a RRCReestablishment message.

51. The method of claim 50, wherein the failure message includes at least one of: failure type information indicating a type of failure to set up the at least one other communication path; identification information for identifying a relay node to which the UE failed to connect in the case of failure to set up an indirect path; cell information for identifying a cell to which the UE failed to connect in the case of failure to set up a direct path;candidate relay information for one or more relay nodes that are candidates for providing one or more new communication paths connecting the UE to the network; neighbour cell information for indicating one or more cells neighbouring the UE that are candidates for providing one or more new communication paths connecting the UE to the network; path identification information for identifying the at least one communication path for which set up has failed or for identifying each connection of the at least one communication path for which set up has failed.

52. The method of any one of claims 23 to 51, further comprising after failure to set up the at least one other communication path, starting a path recovery timer after sending a RRCReestablishment message for initiating a RRC re-establishment procedure.

53. The method of any one of claims 23 to 51, in the case where the first communication path is a direct path that has been suspended and after failure to set up an indirect path as the at least one other communication path, the method further comprising: starting a path recovery timer after sending a RRCReestablishment message for initiating a RRC re-establishment procedure to re-establish the direct path; stopping the path recovery timer in response to sending, by the UE, a message indicating re-establishment of the direct path is completed.

54. The method of any one of claims 23 to 51, further comprising: after receiving the configuration message, starting a path failure timer; after the path failure timer reaches a certain value indicating failure to set up the at least one other communication path, selecting at least one new communication path; after selecting the at least one new communication path, starting a path recovery timer; after starting the path recovery timer, attempting to establish at least one connection to set up the at least one new communication path.

55. The method of claim 54, further comprising stopping the path recovery timer in response to sending, by the UE, a message indicating setup of the at least one new communication path is completed.

56. The method of claim 54, further comprising in the case where the at least one new communication path includes a new indirect path including a relay node, stopping the path recovery timer in response to receiving a relay message indicating the relay node is configured.

57. The method of claim 56, wherein the relay message includes information indicating the relay node is in a RRC connected state.

58. The method of any one of claims 54 to 57, further comprising receiving, from the first base station, backup identification information for identifying at least one backup communication path, wherein selecting comprises selecting one of the at least one backup communication path as the at least one new communication path.

59. The method of claim 58, wherein the backup identification information includes backup relay identification information for identifying at least one relay node with which the UE can establish a connection to provide the multiple paths, wherein selecting comprises selecting one of the at least one relay node identified in the backup relay identification information, in this case the at least one new communication path includes at least one new indirect path through the selected one of the at least one relay node.

60. The method of claim 59, wherein attempting to establish at least one connection comprises performing connection establishment to establish a connection with the selected one of the at least one relay node.

61. The method of claim 58, wherein the backup identification information includes backup cell information for identifying at least one secondary cell with which the UE can establish a connection to provide the multiple paths, wherein selecting comprises selecting one of the at least one secondary cell identified in the backup cell information, in this case the at least one new communication path includes at least one new direct path to the selected one of the at least one secondary cell.

62. The method of any one of claims 54 to 57, wherein selecting the at least one new communication path comprises selecting the at least one new communication path based on measurements performed at the UE.

63. The method of claim 55 or claim 56, wherein after determining setup of the at least one new communication path is completed, initiating a RRC re-establishment procedure to continue a RRC connection for the UE.

64. The method of claim 52 or claim 53 or claim 63, wherein initiating a RRC reestablishment procedure includes: sending, to the first base station, a RRC re-establishment request message, the RRC reestablishment request message including identification information for identifying the UE; receiving, from the first base station, a RRC re-establishment message, the RRC reestablishment message including information associated with a RRC procedure for use in continuing the RRC connection for the UE; sending, to the first base station in response to the RRC re-establishment message, a RRC re-establishment complete message indicating a RRC connection associated with the RRC procedure has been completed.

65. The method of claim 64, wherein the RRC re-establishment request message further includes at least one of: cause information indicating a cause of the failure to set up the at least one other communication path; identification information for identifying a relay node to which the UE failed to connect in the case of failure to set up an indirect path; cell information for identifying a cell to which the UE failed to connect in the case of failure to set up a direct path; path identification information for identifying the at least one communication path for which set up has failed or for identifying each connection of the at least one communication path for which set up has failed.

66. The method of claim 64 or claim 65, wherein the information associated with a RRC procedure includes at least one of: security information for the RRC procedure;UE configuration information including SRAP configuration information and identifier for the UE; an identifier for the RRC procedure.

67. The method of any one of claims 64 to 66, wherein the RRC re-establishment complete message includes at least one of: an identifier for the RRC procedure; candidate relay information for one or more relay nodes that are candidates for providing one or more new communication paths connecting the UE to the network; neighbour cell information for indicating one or more cells neighbouring the UE that are candidates for providing one or more new communication paths connecting the UE to the network; information associated with the failure of the UE to connect to a relay node in the case of failure to set up an indirect path.

68. The method of any one of claims 23 to 51, further comprising: in response to receiving the configuration message, starting a path failure timer; after the path failure timer reaches a certain value indicating failure to set up the at least one other communication path, performing relay (re) sei ection.

69. The method of any one of the claims 23 to 68, wherein the configuration message further includes at least one of: relay identification information for identifying at least one relay node with which the UE is to establish a connection for the at least one other communication path to provide the multiple paths; backup relay identification information for identifying at least one relay node with which the UE is to establish a connection to provide the multiple paths in the case of failure to establish a connection with a first relay node; primary cell information for identifying a primary cell with which the UE is to establish a connection for the at least one other communication path to provide the multiple paths; backup cell information for identifying at least one secondary cell with which the UE is to establish a connection to provide the multiple paths in the case of failure to establish a connection with a primary cell; path identification information for identifying the at least one other communication path or for identifying each connection of the at least one other communication path; configuration information for configuring at least one communication path between the UE and a second base station to provide the multiple paths.

70. A method for managing multi-path communication in a wireless communication system supporting relaying between a User Equipment, UE, and a network including a first base station, wherein a first communication path has been established between the UE and the first base station, the method at a relay node comprising: receiving configuration information for configuring the relay node for an indirect communication path between the UE and the network so as to provide with the first communication path multiple paths between the UE and the network.

71. The method of claim 70, further comprising sending, to the UE, information indicating whether the relay node supports to be triggered by the UE to enter in a RRC connected state.

72. The method of claim 70 or claim 71, further comprising, receiving, from the UE, a message to trigger the relay node to enter a RRC connected state.

73. The method of claim 72, further comprising in the case where the relay node does support triggering by the UE to enter in a RRC connected state and the current RRC state of the relay node is a non-connected RRC state, entering into the RRC connected state in response to receiving the trigger message from the UE.

74. The method of any one of claims 70 to 73, further comprising sending, to the UE, information indicating a current RRC state of the relay node.

75. The method of any one of claims 70 to 73, further comprising sending, to the UE, a relay message indicating the relay node is configured.

76. The method of claim 75, wherein the relay message includes information indicating the current RRC state of the relay node.

77. The method of any one of claims 70 to 76, wherein the configuration information includes measurement reporting configuration information for configuring the relay node to send measurement reporting information after a change in RRC state.

78. The method of claim 77, further comprising, sending, to the UE, after determining a change in RRC state at the relay node, measurement reporting information including information indicating the current RRC state of the relay node.

79. A method for managing multi-path communication in a wireless communication system supporting relaying between a User Equipment, UE, and a network including a first base station, wherein a first communication path has been established between the UE and the first base station, and wherein a second UE is capable of establishing a non-3GPP connection with the UE and supporting relaying between the UE and the network, the method at the UE comprising: sending, to the first base station, a measurement report message, the measurement report message for indicating a non-3GPP connection can be established between the UE and the second UE.

80. The method of claim 79, wherein the measurement report message includes an information element for indicating a non-3GPP connection can be established between the UE and the second UE.

81. The method of claim 79 or claim 80, wherein the measurement report message includes at least one of: identification information for identifying the second UE; serving cell identification information for identifying the cell serving of the second UE; link measurement quantity information associated with the non-3GPP connection.

82. The method of claim 79, wherein the measurement report message includes link measurement quantity information associated with the non-3GPP connection and wherein a certain value of the link measurement quantity information identifies the connection that can be established between the UE and the second UE is a non-3GPP connection.

83. The method of any one of claims 79 to 82, wherein the measurement report message includes at least one of: identification information for identifying one or more other UEs capable of supporting relaying between the UE and the network using a 3 GPP connection with the UE;for each of one or more other UEs capable of supporting relaying between the UE and the network using a 3 GPP connection with the UE, serving cell identification information for identifying the cell serving the respective other UE; for each of one or more other UEs capable of supporting relaying between the UE and the network using a 3 GPP connection with the UE, link measurement quantity information associated with the respective 3 GPP connection.

84. The method of any one of the claims 79 to 83, further comprising: receiving, from the first base station, measurement report configuration including information indicating the UE is authorised to report information associated with a non-3GPP connection.

85. The method of any one of the claims 79 to 84, wherein sending comprises: after determining a non-3GPP connection that can be established between the second UE and the UE meets a certain requirement, sending, to the first base station, the measurement report message.

86. The method of claim 85, wherein the measurement report configuration includes information for indicating the certain requirement for use in determining by the UE whether a non-3GPP connection is to be reported to the first base station.

87. The method of any one of claims 79 to 83, further comprising: receiving, from the first base station, configuration indicating the UE is not authorised to establish a non-3GPP connection with another UE.

88. An apparatus for a base station for a wireless communication system supporting relaying, the apparatus comprising: one or more processing units configured to perform the method as recited in any one of claims 1 to 22.

89. An apparatus for a User Equipment, UE, for a wireless communication system supporting relaying, the apparatus comprising: one or more processing units configured to perform the method as recited in any one of claims 23 to 69, 79 to 87.

90. An apparatus for a relay node, for a wireless communication system supporting relaying, the apparatus comprising: one or more processing units configured to perform the method as recited in any one of claims 70 to 78.

91. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the control method according to any one of claims 1 to 87.

92. A computer-readable medium carrying a computer program according to claim 91.

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