Transitioning of a multi-hop connection to a single-hop connection

Abstract

Techniques for transitioning of a multi -hop connection to a single hop connection are described. In one aspect, a first UE transmits a first set of information to a first network node. The first set of information identifies an existing User Equipment to Network (U2N) multi-hop relay connection including the first UE serving as a User Equipment to User Equipment (U2U) relay UE and a second UE serving as a remote UE, and receive a first message from the first network node to reconfigure the first UE as a U2N relay UE for the second UE, where the first message is based on the first set of information.

Description

TRANSITIONING OF A MULTI-HOP CONNECTION TO A SINGLE-HOP CONNECTIONTECHNICAL FIELD

[0001] The present subject matter relates, in general, to transitioning of a multi -hop connection to a single-hop connection.BACKGROUND

[0002] In a multi-hop connection, multiple networking devices communicate with one another through a sidelink connection such as a New Radio Sidelink (NR-SL). For example, a Sidelink (SL) based multi-hop UE to Network (U2N) relay connection may be formed, where a remote networking device is being served by a serving network through multiple networking devices. Communication between two networking devices generally takes place through a sidelink and communication between the networking device and the serving network takes place through an interface that links the networking device and the serving network, such as a Universal Mobile Telecommunications System air interface (Uu) interface.

[0003] In an example multi-hop connection, the remote networking device communicates with the serving network through multiple networking devices, for example, through a first networking device and a second networking device. The first networking device, such as a User Equipment (UE), may be connected in between the remote networking device and the second networking device, and the second networking device may be connected to the serving network. The first networking device connected between two networking devices, such as the remote networking device and the second networking device, may serve as a UE-to-UE relay (U2U relay), and the second networking device connected directly to the serving network may serve as a UE to Network relay (U2N relay). In one example scenario, the second networking device serving as the U2N relay may be in the coverage area of the serving network, while the first networking device serving as the U2U relay may be in an Out of Coverage (OoC) area of the serving network. In such a situation, the remote networking device communicates with the second networking device through the first networking device.

[0004] Generally, in a multi-hop connection, such as the one described earlier, mechanisms of transitioning of the networking device serving as a U2U relay to a U2N relay are not known. For example, when the first networking device serving as the U2U relayenters the coverage area of the serving network, or enters the coverage area of another network, which is currently not serving the remote networking device, transitioning of the first networking device from serving as the U2U relay to a U2N relay, is not known. Therefore, handling the mobility of the networking device serving as the U2U relay moving from an OoC area into an In Coverage (IC) area of a communication network, while serving an existing multi-hop U2N relay connection of the remote networking device through the second networking device serving as the U2N relay, is not enabled.SUMMARY

[0005] Aspects of the present subject matter provide techniques for transitioning of a multi-hop connection into a single-hop connection by facilitating transition of a UE serving as a U2U relay UE in a multi-hop connection, to serving as a U2N relay UE.

[0006] According to an example of the present subject matter, a first UE is described. The first UE includes at least one processor, and a machine-readable storage medium including instructions that, when executed by the at least one processor, cause the first UE to transmit a first set of information to a first network node, where the first set of information identifies an existing User Equipment to Network (U2N) multi-hop relay connection including the first UE serving as a User Equipment to User Equipment (U2U) relay UE and a second UE serving as a remote UE, and receive a first message from the first network node to reconfigure the first UE as a U2N relay UE for the second UE, where the first message is based on the first set of information.

[0007] According to an example of the present subject matter, a first network node is described. The first network node includes at least one processor, a machine-readable storage medium comprising instructions that, when executed by the at least one processor, cause the first network node to receive a first set of information from a first UE, where the first set of information identifies an existing User Equipment to Network (U2N) multi-hop relay connection including the first UE serving as a User Equipment to User Equipment (U2U) relay UE and a second UE serving as a remote UE, and transmit a first message to the first UE to reconfigure the first UE as a U2N relay UE for the second UE, where the first message is based on the first set of information.

[0008] According to an example of the present subject matter, a second UE is described. The second UE includes at least one processor, a machine-readable storage medium comprising instructions that, when executed by the at least one processor, cause thesecond UE to receive a second message from a first UE where the first UE is serving as a User Equipment to User Equipment (U2U) relay UE in an existing User Equipment to Network (U2N) multi-hop relay connection for the second UE serving as a remote UE, the second message contains reconfiguration information from a first network node to reconfigure the second UE for a path switch to the first network node via the first UE serving as a U2N relay UE, send a sidelink connection request to the first UE based on the second message or establishing a new sidelink connection with the first UE, establish the new sidelink connection with the first UE on receiving a sidelink connection accept from the first UE, and send a fourth message to the first UE to be relayed to the first network node in response to the second message.

[0009] According to an example present subject matter, a method implemented by a first UE is described. The method includes establishing a connection with a first network node, transmitting a first set of information to the first network node, where the first set of information is indicative of the at least an existing first connection, where the existing first connection is a User Equipment to Network (U2N) multi-hop relay connection between at least a second network node, a third UE serving as a U2N relay UE, the first UE serving as a User Equipment to User Equipment (U2U) relay UE, and a second UE as the remote UE, and receiving a first message from the first network node to reconfigure the first UE as a U2N relay UE, where the first message is generated based on the first set of information, sending a sidelink connection request to the second UE after receiving the first message from the first network node for establishing a new sidelink connection with the second UE, establishing a new sidelink connection with the second UE on receiving a sidelink connection accept from the first UE, sending the second message to the second UE over the new sidelink connection, receiving a fourth message from the second UE in response to the second message over the new sidelink connection, and sending a third message and the fourth message to the first network node after receiving the fourth message from the second UE.

[0010] According to an example present subject matter, a method implemented by a first network node is described. The method includes receiving a request to establish a connection request from a first UE, obtaining a first set of information from the first UE, where the first set of information is indicative of the at least an existing first connection, where the existing first connection is a User Equipment to Network (U2N) multi-hop relay connection between at least a second network node, a third UE serving as a U2N relay UE,the first UE serving as a User Equipment to User Equipment (U2U) relay UE, and a second UE, and transmitting a first message to reconfigure the first UE as a U2N relay UE for the second UE, where the first message is generated based on the first set of information.

[0011] According to an example present subject matter, a method implemented by a second UE is described. The method includes receiving a second message from a first UE and establishing a new sidelink connection with the first UE and sending a sidelink connection request to the first UE to establish the new sidelink connection. In response to sending the sidelink connection request: receiving a sidelink connection accept from the first UE and establishing the new sidelink connection with the first UE based on the sidelink connection accept message.BRIEF DESCRIPTION OF DRAWINGS

[0012] The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

[0013] Fig. 1 illustrates a multi-hop connection network environment and depicts different U2U relay to U2N relay switch scenarios based on mobility, in accordance with an example implementation of the present subject matter.

[0014] Figs. 2 illustrates a first user equipment communicatively coupled to a second user equipment, in accordance with an example implementation of the present subject matter.

[0015] Fig. 3 illustrates a first network node of the first serving network, in accordance with an example implementation of the present subject matter.

[0016] Fig. 4 illustrates a first call flow when a first user equipment moves into an In Coverage (IC) area of a first serving network that is currently serving the second UE, in accordance with an example implementation of the present subject matter.

[0017] Fig. 5 illustrates a second call flow when the first user equipment moves into an IC area of the first serving network that is currently serving the second UE, in accordance with an example implementation of the present subject matter.

[0018] Fig. 6 illustrates a first call flow when the first user equipment moves into an IC area of a second serving network that is currently not serving the second UE, in accordance with an example implementation of the present subject matter.

[0019] Fig. 7 illustrates a second call flow when the first user equipment moves into an IC area of the second serving network that is currently not serving the second UE, in accordance with an example implementation of the present subject matter.

[0020] Fig. 8 illustrates a method implemented by the first user equipment, in accordance with an example implementation of the present subject matter.

[0021] Fig. 9 illustrates a method implemented by the first network node, in accordance with an example implementation of the present subject matter.

[0022] Fig. 10 illustrates a method implemented by the second user equipment, in accordance with an example implementation of the present subject matter.DETAILED DESCRIPTION

[0023] The present subject matter provides techniques to handle transitioning of a networking device, for example, a first UE, from serving as a U2U relay UE, to serving as a U2N relay UE, when the first UE moves from an OoC area into an In Coverage (IC) area of a communication network.

[0024] In operation, when a first UE serving as a U2U relay UE moves into an In Coverage (IC) area of a first serving network having a first network node, while serving a second UE through an existing multi-hop U2N relay connection, the first UE serving as the U2U relay UE may potentially transition to serving as a U2N relay UE for the second UE. The coverage area into which the first UE may enter may either be a serving network that is currently serving the second UE, such as the first serving network, or may be a serving network which is not currently serving the second UE, such as a new network or any other network except the first serving network.

[0025] When the first UE moves into the coverage area of the first serving network, the first UE may provide a first set of information to the first serving network to indicate that the first UE is willing to serve as a U2N relay UE for the second UE. The first set of information would indicate, amongst other information, at least an existing first connection, where the existing first connection is U2N multi-hop relay connection between at least the second UE acting as the remote UE, the first UE serving as the U2U relay UE and a third UE serving as a U2N relay UE.

[0026] On receiving the first set of information, the first serving network may transmit a first message for reconfiguring the first UE to serving as a U2N relay UE for the second UE. In one example, the first message may be sent to the first UE, where the first messagemay include a second message. The second message may contain reconfiguration information for the second UE to reconfigure the second UE for a path switch to the first network node via the first UE serving as a U2N relay UE, which may be subsequently forwarded to the second UE. Accordingly, a new sidelink connection between the first UE and the second UE is established. On establishment of the new sidelink connection between the first UE and the second UE, the first serving network may release the third UE of the existing multi-hop connection from serving the second UE as the U2N relay UE.

[0027] If the first UE moves into the coverage area of the first serving network, where a second network node is serving the second UE through the existing U2N multi-hop relay connection, the first serving network may transmit a Handover (HO) notification to the second serving network 110 based on at least the first set of information. The second serving network 110 may decide to either acknowledge the HO or choose not to respond. In a scenario where the second serving network 110 acknowledges the HO, the first serving network may transmit the first message and the second message for the first UE and the second UE, respectively, and the transitioning of the first UE from serving as the U2U relay UE to serving as the U2N relay UE for the second UE may occur as discussed above.

[0028] Therefore, techniques of the present subject matter facilitate transitioning of a multi-hop connection to a single-hop connection, thereby shortening the path of communication.

[0029] The above and other features, aspects, and advantages of the subject matter will be better explained with regards to the following description and accompanying figures. It should be noted that the description and figures merely illustrate the principles of the present subject matter along with examples described herein and should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and examples thereof, are intended to encompass equivalents thereof. Further, for the sake of simplicity, and without limitation, the same numbers are used throughout the drawings to reference like features and components.

[0030] Fig. 1 illustrates a multi -hop connection network environment 100, in accordance with an example implementation of the present subject matter. In one example, the multi -hop connection network environment 100 may include multiple networking devices, such as mobile UEs participating in a multi-hop connection. In one example, themulti -hop connection may be a Layer 2 (L2) multi -hop connection. For example, in a situation, a first UE 102 may move into a coverage area of a first serving network 104 having a first network node 106.

[0031] In a scenario where the first network node 106 is serving the multi -hop connection including the first UE 102 and a second UE 108, the first network node 106 may be alternatively referred to as a source network node. Alternatively, in a scenario where the first network node 106, is not serving the multi -hop connection including the first UE 102 and the second UE 108, and the multi hop connection is being served by through a second serving network 110 having a second network node 112, the first network node 106 may be referred to as a target network node. For the ease of understanding, the following description has been described with reference to the first network node 106 as the source network node or the target network node depending on the multi-hop connection involving the first UE 102 and the second UE 108, as applicable, and is not to be construed as a limitation.

[0032] In one example, the multiple UEs participating in the multi-hop connection, among other functions, may facilitate communication with a serving network, for example, a public land mobile networks (PLMNs). In one example, the multiple UEs may utilize one or more universal subscriber identity modules (USIMs) for facilitating communication with the multiple PLMNs.

[0033] The PLMNs may support a variety of cellular network architectures, such as Long-Term Evolution (LTE) cellular network architecture and 5th Generation / New Radio (5G / NR) cellular network architecture. Further, each of the multiple PLMNs may include a node, respectively. The type and functionality of the nodes may vary based on the type of cellular network architecture being supported by the PLMN. For instance, for LTE cellular network architecture, the nodes may be evolved NodeB (eNodeB). Similarly, for 5G / NR cellular network architecture, the nodes may be next generation NodeB (gNodeB), Access and Mobility Management Function (AMF), and User plane function (UPF), reference to which have not been included herein for the sake of brevity.

[0034] Further, the multiple UEs may be connected to the multiple PLMNs, through a communication network. It may be understood that the communication network may be a wireless or a wired network, or a combination thereof. The communication network can be a collection of individual networks, interconnected with each other and functioning as a single large network. Examples of such individual networks include, but are not limited to, Global System for Mobile communication (GSM) network, Universal MobileTelecommunications System (UMTS) network, Long Term Evolution (LTE) network, personal communications service (PCS) network, Time-division multiple access (TDMA) network, Code-Division Multiple Access (CDMA) network, next-generation network (NGN), public switched telephone network (PSTN), and Integrated Services Digital Network (ISDN). Depending on the terminology, the communication network includes various network entities, such as gateways and routers; however, such details have been omitted to maintain the brevity of the description.

[0035] In one example, as depicted in Fig. 1, the multi -hop connection may include an established path 114 between the second UE 108, the first UE 102, a third UE 116, and the first serving network 104, where the second UE 108 serving as a remote UE may communicate with the first serving network 104 through the first UE 102 serving as a U2U relay UE and the third UE 116 serving as a U2N relay UE in a sidelink connection. In one example, the first UE 102 serving as the U2U relay UE may be connected in between the second UE 108 and the third UE 116, where the first UE 102 and the second UE 108 may be connected through a first sidelink 118, and the first UE 102 and the third UE 116 may be connected through a second sidelink 120. Further, the third UE 116 may be further connected to the first network node 106 through a Uu interface 122. It may be understood that although the following description has been described based on a single remote UE connected to a single UE functioning as a U2U relay UE for the ease of understanding, similar principles may be applicable to multiple UEs that may be involved in the multi-hop connection.

[0036] Initially, in the established path 114, the first UE 102 may be in an OoC area of any serving network. However, there may be a possibility for a change in the established path 114, when the first UE 102 moves from its initial position ‘I’ as depicted in Fig. 1, into an IC area of the first serving network 104 represented by ‘I” in Fig.l. The first serving network 104 either being a source serving network or a target serving network.

[0037] In both these examples described above, the first UE 102 may have the potential to transition from serving as a U2U relay UE to serving as a U2N relay UE for the second UE 108. Transitioning of the first UE 102 from serving as the U2U relay UE to serving as the U2N relay UE for the second UE 108 has been discussed with reference to Figs. 2-7. In one example, the second UE 108 may move along with the first UE 102 and remain connected to the first UE 102 when the first UE 102 moves either into the IC area of the source serving network or into the IC area of the target serving network. For example, in vehicular networks, or in applications similar to a smart phone and a smart watch, and thelike, the first UE may be the smart phone and the second UE may be the smart watch. When the smart phone moves from a source serving network to a target serving network, the smart watch which is communicatively coupled to the smart phone may also move from the source serving network to the target serving network.

[0038] Transitioning of the first UE 102 from serving as the U2U relay UE to serving as the U2N relay UE results in transitioning of the multi-hop relay connection into a single hop connection. The multi-hop relay connection with the established path 114 involving the second UE 108, the first UE 102 serving as the U2U relay UE, the third UE 116 serving as the U2N relay UE, and the first serving network 104, transitions to a newly established path 124 of a single-hop connection involving the second UE 108, the first UE 102 serves as a U2N relay UE, and the first serving network 104, thereby resulting in a shorter path of communication.

[0039] Fig. 2 illustrates a first UE 102 communicatively coupled to a second UE 108, in accordance with an example implementation of the present subject matter. As discussed above, in an existing connection between the various entities participating in the multi-hop connection, the first network node 106 of the first serving network 104 may serve the second UE 108 through the third UE 116, where the third UE 116 is in the IC area of the first serving network 104 and the third UE 116 may be serving as the U2N relay UE, and the first UE 102 which is OoC of the first serving network 104 may be serving as the U2U relay UE.

[0040] Although the following description has been described with respect to a multihop connection involving a single second UE 108, alternatively referred to as the remote UE, a single U2U relay UE 102, and a single U2N relay UE 116, it would be understood that similar principles of the present subject matter would be applicable to multiple UEs participating in the multi -hop connection. For example, the connection between the second UE 108 and the third UE 116 may be a number of U2U relay UEs, including the first UE 102 which moves from an OoC area into an IC area of the first serving network 104.

[0041] In one example, the first UE 102 may include a processor 202a and memory 204a coupled to the processor 202a. Similarly, the second UE 108 may include a processor 202b and a memory 204b coupled to the processor 202b. The functions of functional block labelled as “processor(s)”, may be provided through the use of dedicated hardware as well as hardware capable of executing instructions. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use ofthe term “processor” would not be construed to refer exclusively to hardware capable of executing instructions, and may implicitly include, without limitation, digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing instructions, random access memory (RAM), non-volatile storage. Other hardware, standard and / or custom, may also be included.

[0042] Memory 204a and 204b may include any computer-readable medium including, for example, volatile memory (e.g., RAM), and / or non-volatile memory (e.g., EPROM, flash memory, etc.).

[0043] In the present examples, the machine-readable storage medium may store instructions that, when executed by the processing resource, cause the user equipments to perform certain functionalities. In such examples, the UEs may include the machine-readable storage medium storing the instructions and the processing resource to execute the instructions. In other examples of the present subject matter, the machine-readable storage medium may be located at a different location but accessible to the UEs and the processors 202a and 202b.

[0044] Further, the first UE 102 may include interface(s) 206a and the second UE 108 may include interface(s) 206b, where interfaces 206a, 206b may allow the connection or coupling of the first UE 102 and the second UE 108, respectively, with one or more other devices (say devices or systems within the network environment 100), through a wired (e.g., Local Area Network, i.e., LAN) connection or through a wireless connection (e.g., Bluetooth®, Wi-Fi). The interface(s) 206a, 206b may also enable intercommunication between different logical as well as hardware components of the user equipments.

[0045] The first UE 102 and the second UE 108 may further include data 208a and 208b respectively, that serves, amongst other things, as a repository for storing data that may be fetched, processed, received, or generated by the UEs or the serving networks. The data 208a and 208b may include communication data, first set of information, reconfiguration messages, OoC and IC data in correspondence to the serving networks, and the like. In an example, the data 208a and 208b may be stored in the memory 204a and 204b, respectively.

[0046] In one example, because the third UE 116 may be directly connected to the first network node 106, the third UE 116 may be in a RRC connected state (RRC CONNECTED state). Whereas the first UE 102 may be in any one state of the first serving network 104 which is currently serving the second UE 108. For example, the first UE 102 may be in anout-of-coverage (OoC) DETACHED state, an in-coverage (IC) RRC IDLE state, an IC RRC INACTIVE state, or an IC RRC CONNECTED state.

[0047] In the example where the first UE 102 moves into an IC area of the source serving network, the first UE 102 may be configured to transmit a first set of information to the first network node, where the first set of information identifies the existing U2N multihop relay connection including at least the second UE serving as the remote UE, the first UE serving as the U2U relay UE, and the third UE serving as the U2N relay UE.

[0048] In one example, to transmit the first set of information, the first UE 102 may initiate a state transition to an RRC CONNECTED state corresponding to the first serving network 104, at least for a network registration, if the first UE 102 was initially in a DETACHED state.

[0049] When the first UE 102 moves into the IC area of the first serving network 104, a set of predetermined criteria may be checked. For example, the set of predetermined criteria may include, amongst other conditions, whether the first network node 106 selected or reselected by the first UE 102, is the same as the network node serving the second UE 108, or is a neighbouring cell of the network node serving the second UE 108, and from the same serving network (i.e., PLMN) of the second UE 108. Further, whether the first UE 102 is willing to and able to serve as a U2N relay UE for the second UE 108, i.e., not only having the necessary L2 U2N relay capability, but also meeting conditions, such as Uu conditions, and the like, may be checked for.

[0050] However, in a scenario where the first UE 102 moves into IC area which is not from the same serving network (i.e., PLMN) of the second UE 108, i.e., when the first UE 102 moves into the IC area of a new serving network, and transitioning of the first UE 102 from serving as the U2U relay UE to serving as the U2N relay UE cannot take place, the existing U2N multi-hop relay connection may be maintained. Also, in a scenario, where the first UE 102 is unwilling to serve as a U2N relay UE for the second UE 108, or is incapable of serving as the U2N relay UE due to non-presence of required UE capability to serve as the U2N relay UE, for example, when the first UE 102 may not have sufficiently good Uu conditions, and the like, the existing multi -hop path may be maintained and the first UE 102 may continue to serve the second UE 108 as the U2U relay UE.

[0051] Further, in one example, the first UE 102 may connect to the first network node 106 to establish an RRC connection with the first network node 106. In one example, the first UE 102 may transmit the first set of information to the first network node, onestablishing the RRC connection. In one example, the first set of information, amongst other information, may include information associated with at least the existing multi-hop connection, where the existing first connection is aU2N multi-hop relay connection between at least the first network node, the third UE 116 serving as the U2N relay UE, the first UE 102 serving as the U2U relay UE, and the second UE 108 serving as the remote UE. Further, the first set of information may also include identifiers (IDs), such as a UE identifier of the second UE 108, a UE identifier of the third UE 116, and a cell identifier of a serving cell of the second UE 108. Furthermore, the first set of information may include a first ID and a second ID of the first UE 102, where the first ID may correspond to the ID utilized by the first UE 102 while serving as the U2U relay UE and the second ID may correspond to the ID utilized by the first UE 102 while serving as the U2N relay UE. Additionally, the first UE 102 may also indicate information corresponding to a U2U relay traffic associated with the first UE 102.

[0052] In one example, in response to transmitting the first set of information, the first UE 102 may receive a first message from the first network node 106 to reconfigure the first UE 102 as a U2N relay UE for the second UE 108, where the first message is based on the first set of information. In one example, the first message may be a first RRC reconfiguration message. It would be understood that the first RRC reconfiguration message is to reconfigure the first UE 102 from serving as the U2U relay UE for the second UE 108 to serve as a U2N relay UE for the second UE 108. In one example, the first UE 102 may establish a new sidelink connection with the second UE 108 in response to receiving the first message.

[0053] Further, in one example, the first message may be embedded with a second message, where the second message may be targeted to the second UE 108. The second message may contain reconfiguration information for the second UE. In one example, the second message may be a second RRC reconfiguration message. The second message may be transmitted to second UE 108 in the following ways, where in one example, at least one processor of the first UE 102 may cause the first UE 102 to forward the second message to the second UE 108. In another example, the first message and the second message may be received separately, where the first message may be received by the first UE 102 and the second message may be received by the third UE 116. The third UE 116 may then forward the second message to the first UE 102, and the first UE 102 may subsequently forward the second message to the second UE 108.

[0054] Further, in a scenario where the first UE 102 utilizes two different IDs for serving as the U2U relay UE and the U2N relay UE, i.e., the first L2 ID and the second L2 ID, a new SL connection between the first UE 102 and the second UE 108 may be set up. To request the second UE 108 to consider the first UE 102 as the U2N relay UE, upon receiving the first message, in one example, the first UE 102 may send a sidelink connection request with an indication of path switch to the second UE 108 to establish a new sidelink connection between the first UE 102 and the second UE 108, where the first UE 102 may forward the second message to the second UE over the new sidelink connection. In one example, the sidelink connection request may be a Direct Communication Request (DCR) message.

[0055] On receiving the sidelink connection request, the second UE 108 may send a sidelink connection accept, which in one example may be a DCA message to the first UE 102. In one example, based on the sidelink connection accept message received from the second UE 108, the first UE 102 may release the existing sidelink used for communicating with the second UE 108, where the existing sidelink was used for communicating with the second UE 108 when the first UE 102 was serving as the U2U relay UE. In the scenario as discussed above, the first UE 102 may forward the second message to the second UE 108 over the newly established sidelink, where the new sidelink may be used for communicating with the first UE 102 as the new U2N relay for further communications.

[0056] In another example, the first UE 102 may send the second message to the second UE 108 using the existing sidelink between them and indicate the second L2 ID of the first UE 102 that the first UE 102 would be using while serving as the U2N relay UE (in case this has not been indicated before). Subsequently, the second UE 108 may initiate a new sidelink connection request to the first UE 102 in order to establish the new sidelink connection between them, where the first UE 102 would serve as the U2N relay UE. In response to sending the sidelink connection request, the second UE 108 may receive a sidelink connection accept from the first UE 102, and the second UE 108 may establish the new sidelink connection with the first UE 102 based on the sidelink connection accept message. In one example, on receiving the DCR accept message in response to sending the DCR message to the first UE 102, the second UE 108 may release the existing sidelink connection between the first UE 102 and the second UE 108 that was used for communicating with the first UE 102 when the first UE 102 was serving as the U2U relay UE and may utilize the new sidelink with the first UE 102 for communication purposes.

[0057] On establishment of the new sidelink connection between the first UE 102 and the second UE 108, the first UE 102 may send a third message to the first network node 106. In one example, the third message may be an RRC reconfiguration complete message. In one example, the first RRC reconfiguration complete message may be generated in response to the first message. In one example, the first UE 102 may send the third message on receiving a fourth message, where the fourth message may be transmitted in response to the second message, from the second UE 108. In one example, the fourth message may be a second RRC reconfiguration complete message. The second UE 108 may send the fourth message to the first UE 102 over the new sidelink connection. Subsequently, the first UE 102 may forward the fourth message to the first network node.

[0058] In one example, on receiving the third message and the fourth message from the first UE 102, the first network node 106 may release the third UE 116 from serving the second UE 108 as the U2N relay UE.

[0059] Similarly, in a scenario where the first UE 102 moves from an OoC area into an IC area of the target serving network, where the target serving network is a new serving network, which is not currently serving the second UE 108, in one example, the first UE 102 may trigger an RRC connection establishment with the first network node of the target serving network. In one example, to establish an RRC connection with the first network node of the target serving network, similar to the first set of information provided to the first network node of the source serving network as described above, the first UE 102 may inform the first network node about information associated with at least the existing multi-hop connection, where the existing first connection is aU2N multi-hop relay connection between at least a second network node 112, the third UE 116 serving as the U2N relay UE, the first UE 102 serving as the U2U relay UE, and the second UE 108 serving as the remote UE. Further, the first set of information may also include identifiers (IDs), such as a UE identifier of the second UE 108, a UE identifier of the third UE 116, and a cell identifier of the serving cell of the second UE 108, and the like.

[0060] In one example, a Handover (HO) for the second UE 108 from the second network node 112 which is currently serving the second UE 108 may be initiated by the first network node, through the first UE 102. In one example, a HO notification for the second network node 112 may carry both the first L2 ID and the second L2 ID of the first UE 102. In a scenario, where a successful HO takes place, the first UE 102 may receive the first message from the first network node, similar to the first message as discussed above.

[0061] In one example, the first message may be embedded with the second message. In another example, the first message and the second message may be received separately, where the first message may be received by the first UE 102 from the first network node and the second message may be received by the third UE 116 connected to the second network node 112 of the second serving network 110, where the third UE 116 may subsequently forward the second message to the second UE 108 through the first UE 102. In both these examples, when the first UE 102 receives the first message, the establishment of the new sidelink between the second UE 108 and the first UE 102 takes place as described above and has not been repeated for the sake of brevity.

[0062] Furthermore, similar to the intimating the first network node of the source serving network on completion of reconfiguration, the first UE 102 may forward the first RRC reconfiguration complete message and the second reconfiguration complete message to the first network node of the target serving network. In one example, the first UE 102 may receive the second RRC reconfiguration complete message from the second UE 108 on the new sidelink connection established between the second UE 108 and the first UE 102. In response to sending the first and second RRC reconfiguration complete message to the first network node, the third UE 116 connected in the multi -hop connection may be released from serving the second UE 108 as the U2N relay UE.

[0063] Therefore, the present subject matter facilitates efficient transitioning of the first UE 102 from serving as the U2U relay UE to serving as the U2N relay UE, thereby shortening the effective path of communication between the serving network and the second UE 108.

[0064] Fig. 3 illustrates the first network node 106 of the first serving network 104, in accordance with an example implementation of the present subject matter. In one example, the first serving network 104 may either be the source serving network currently serving the second UE or may be the target serving network which is currently not serving the second UE 108. For the ease of understanding, the following description has been described with reference to the first serving network 104 which can either be a serving network that is currently serving the second UE 108 or may be any other network which is not currently serving the second UE 108 and any implementation is not to be construed as a limitation on applicability of the described techniques.

[0065] In one example, the first network node 106 of the first serving network 104 may be a first gNodeB, where the first network node 106 may include a processor 302 anda memory 304, where the memory 304 may be coupled to the processor 302. The functions of functional block labelled as “processor(s)”, may be provided through the use of dedicated hardware as well as hardware capable of executing instructions. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared. Moreover, explicit use of the term “processor” would not be construed to refer exclusively to hardware capable of executing instructions, and may implicitly include, without limitation, digital signal processor (DSP) hardware, network processor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), read only memory (ROM) for storing instructions, random access memory (RAM), non-volatile storage. Other hardware, standard and / or custom, may also be included.

[0066] The memory 304 may include any computer-readable medium including, for example, volatile memory (e.g., RAM), and / or non-volatile memory (e.g., EPROM, flash memory, etc.).

[0067] In the present examples, the machine-readable storage medium may store instructions that, when executed by the processing resource, cause the nodes of the serving network to perform certain functionalities. In such examples, the first gNB may include the machine-readable storage medium storing the instructions and the processing resource to execute the instructions. In other examples of the present subject matter, the machine- readable storage medium may be located at a different location but accessible to the first serving network and the processors 302.

[0068] Further, the first network node 106 may include interface(s) 306, where interfaces 306 may allow the connection or coupling of the first network node 106 with one or more other devices (say devices or systems within the network environment 100), through a wired (e.g., Local Area Network, i.e., LAN) connection or through a wireless connection (e.g., Bluetooth®, Wi-Fi). The interface(s) 306 may also enable intercommunication between different logical as well as hardware components of the user equipments.

[0069] The first network node 106 may further include data 308, that serves, amongst other things, as a repository for storing data that may be fetched, processed, received, or generated by the UEs or other serving networks. The data 308 may include communication data, first set of information, reconfiguration messages, OoC and IC data in correspondence to the serving networks, information associated with multiple UEs, and the like. In an example, the data 308 may be stored in the memory 304.

[0070] In one example, when the first UE 102 willing to serve as a U2N relay UE for the second UE 108 moves from an OoC area of the first gNB into the IC area of the first network node, the first network node may receive a first set of information from the first UE 102, where the first set of information is indicative of the at least an existing first connection, where the existing first connection is a U2N multi-hop relay connection between at least second UE 108 serving as the remote UE, the first UE 102 serving as the U2U relay UE, and the third UE 116 as the serving U2N relay UE.

[0071] The first set of information may also include identifiers (IDs), such as a UE identifier of the second UE 108, a UE identifier of the third UE 116 serving as a U2N relay UE in the existing U2N multi-hop relay connection, and a cell identifier of a serving cell of the second UE 108, and the like. Furthermore, the first set of information may include a first ID and a second ID of the first UE 102, where the first ID of the first UE 102 corresponds to the ID utilized by the first UE 102 while serving as the U2U relay UE and the second ID of the first UE 102 corresponds to the ID utilized by the first UE 102 while serving as the U2N relay UE. Additionally, the first UE 102 may also indicate information corresponding to a U2U relay traffic associated with the first UE 102.

[0072] In one example, based on the first set of information received, the first network node may determine whether the transitioning of the first UE 102 serving as the U2U relay UE to serving as the U2N relay UE needs to be performed. In another example, the first network node 106 may initiate transitioning of the first UE 102 proactively. In such a scenario, the first network node 106 may transmit a first message to reconfigure the first UE 102 to transition from serving as the U2U relay UE to serve as the U2N relay UE for the second UE 108. In one example, the first message may be the first RRC reconfiguration message.

[0073] Furthermore, the first network node 106 may transmit a second message to reconfigure the second UE 108. In one example, the second message may be a second RRC reconfiguration message. Accordingly, based on the first RRC reconfiguration message and the second RRC reconfiguration message generated and transmitted to the first UE 102, a new sidelink connection between the first UE 102 and the second UE 108 may be established as discussed with reference to description of Fig. 2. On establishment of the new sidelink connection, the first network node 106 may receive a third message and a fourth message from the first UE 102, where the third message may be a first RRC reconfiguration complete message and the fourth message may be a second RRC reconfiguration complete message.The first RRC reconfiguration complete message may be received in response to the first RRC reconfiguration message and the second RRC reconfiguration complete message may be received in response to the second RRC reconfiguration message.

[0074] On receiving the third and fourth messages, the first network node 106 may release the third UE 116 from serving the second UE 108 as U2N relay UE as well as any other U2U relay UEs that may be connected in between the third UE 116 and the first UE 102 from serving the second UE 108 as U2U relay UEs, while these relay UEs may serve other remote UEs.

[0075] In a scenario where the first serving network 104 is a serving network which is currently not serving the second UE 108, and the second UE 108 is being served through a second network node 112 that is part of a second serving network 110, the first network node 106 may initiate a handover request of the second UE 108.

[0076] In such an example, the first network node may receive an RRC connection request from the first UE 102 and may also receive the first set of information from the first UE 102, where the first set of information is indicative of at least the existing U2N multihop relay connection between at least the second UE 108 as the remote UE, the first UE 102 serving as the U2U relay UE and the third UE 116 serving as the current U2N relay UE. Additionally, the first set of information may also include a serving cell ID of the second UE 108, and L2 IDs of the second UE 108 and the third UE 116 participating in the multi -hop relay connection, and the like, as discussed above.

[0077] On receiving the first set of information, the first network node 106 may trigger the handover (HO) request for the second UE 108 currently being served by the second network node 112, through the first UE 102. The first network node 106 may inform the second network node 112 about the possible HO or an inter-gNB path switch for the second UE 108 via the first UE 102 and let the second network node 112 initiate the HO request. In one example, the trigger to indicate a possibility of the HO may be initiated through a HO notification message. In one example, the HO notification message may include the first L2 ID and the second L2 ID of the first UE 102.

[0078] On receiving the HO notification, the second network node 112 may decide whether to agree with the HO or not. In a scenario where the second network node 112 disagrees with the HO, in one example, the second network node 112 may send a HO notification Negative Acknowledgement (NACK) to the first network node 106 to indicate the disagreement with the HO. In another example, the second network node 112 may notrespond to the HO notification, i.e., the second network node 112 does not initiate the HO request or send the NACK notification to the first network node 106. In either of the situations, when the NACK notification is sent or when there is no response from the second network node 112, the HO may not take place. Any of these two behaviors will result in maintaining the existing multi-hop relay connection.

[0079] However, in a scenario where the second network node 112 decides to proceed with the HO, the second network node 112 may send a HO request message to the first network node 106 which may contain the information associated with the second UE 108. On receiving the HO request, the first network node 106 may send a HO request acknowledge message to the second network node 112. Subsequently, the first network node 106 may send the first message directly to the first UE 102 to reconfigure the first UE 102 to serve as a U2N relay UE for the second UE 108.

[0080] In one example, the first message for the first UE 102 may be embedded with a second message for the second UE 108. The first UE 102 may further transmit the second message to the second UE 108 by forwarding the message to the second UE 108. In another example, the first network node 106 may transmit the first message for the first UE 102 and the second network node 112 may transmit the second message for the second UE 108. The second network node 112 may send the second message to the third UE 116, and the third UE 116 may further relay the second message to the first UE 102, which in turn forwards the second message to the second UE 108. Accordingly, based on the first and second messages, the new sidelink connection between the first UE 102 and the second UE 108 may be established.

[0081] Further, on establishment of the new sidelink connection between the first UE 102 and the second UE 108, in one example, the second network node 112 may release the third UE 116 from serving the second UE 108 as the U2N relay UE and also may release the other U2U relay UEs in between the third UE 116 and the first UE 102 from serving the second UE 108, while these relay UEs may still serve other remote UEs. Accordingly, techniques of the present subject matter ensure successful transitioning of a multi -hop relay connection to a single-hop connection, thereby resulting in a shorter path for communication between the multiple entities involved.

[0082] Fig. 4 illustrates a first call flow 400 when the first UE 102 moves into an IC area of a first serving network, in accordance with an example implementation of the present subject matter. The first call flow 400 describes a scenario in which the first UE 102 movesinto the IC area of the first serving network, where the first serving network is the serving network that is currently serving the second UE 108.

[0083] At step 402 of the first call flow 400, the first UE 102 moves into the IC area of the first serving network 104 for establishing an RRC connection with the first network node 106, such as a first gNB.

[0084] At step 404, a first UE 102 transmits a first set of information to the first gNB, where the first set of information, amongst other information, includes an identifier of the UEs, such as the L2 IDs of the second UE 108, the third UE 116, and the serving cell ID of the second UE 108 to the first gNB. Additionally, the first UE 102 also indicates a first L2 ID and a second L2 ID of the first UE 102, where the first L2 ID of the first UE 102 corresponds to the ID utilized by the first UE 102 while serving as the U2U relay UE and the second L2 ID of the first UE 102 corresponds to the ID utilized by the first UE 102 while serving as the U2N relay UE.

[0085] At step 406, the first gNB sends a first RRC reconfiguration message to the first UE 102, in response to receiving the first set of information. In one example, the first RRC reconfiguration message contains the configurations for the first UE 102 to undertake the role of a U2N relay UE for the second UE 108. In one example, the first RRC reconfiguration message for the first UE 102 may be embedded with a second RRC reconfiguration message targeted to the second UE 108.

[0086] At step 408, the first UE 102 forwards the second RRC reconfiguration message, which was embedded in the first RRC reconfiguration message, to the second UE 108 in a SL RRC message.

[0087] At step 410 of the first call flow 400, on receiving the second RRC reconfiguration message, the second UE 108 initiates a sidelink connection establishment. The second UE sends a sidelink connection request, such as a DCR message to the first UE 102 to establish a new sidelink connection. In one example, the second UE 108 initiates the sidelink connection request and sends it to the first UE 102 on receiving the second RRC reconfiguration message, as represented in the call flow to establish a new sidelink connection. Alternatively, the first UE 102 may initiate a sidelink connection request instead of the second UE 108 (not represented in the first call flow 400) and send it to second UE 108 to establish the new sidelink connection.

[0088] At step 412, the first UE 102 sends a sidelink connection accept message to the second UE 108. Alternatively, in the example where the first UE 102 initiates establishmentof the new sidelink connection, the second UE 108 may send the sidelink connection accept message to the first UE 102.

[0089] On receiving the sidelink connection accept message, the second UE 108 initiates establishment of the new sidelink connection, and subsequently, the new sidelink connection is established. Furthermore, on establishment of the new sidelink connection, at step 414, the second UE 108 sends a second RRC reconfiguration complete message to the first UE 102 in response to the second RRC reconfiguration message for second UE 108. Alternatively, in the example where the first UE 102 initiates the establishment of the sidelink connection, the new sidelink is established when the first UE 102 receives the sidelink connection accept message from the second UE 108.

[0090] On establishment of the new sidelink connection with the first UE 102, which would now serve as the U2N relay UE, the first UE 102 may receive the second RRC reconfiguration complete message. Receiving the second RRC reconfiguration complete message from the second UE 108 would indicate that the second UE 108 has agreed to use the first UE 102 as the U2N relay UE. Accordingly, at step 416, the first UE 102 sends a first RRC reconfiguration complete message to the first gNB, where the first RRC reconfiguration complete message is sent in response to the first RRC reconfiguration message.

[0091] At step 418, the first UE 102 relays the second RRC reconfiguration complete message to the first gNB. In one example, the second RRC reconfiguration message to the first gNB may be sent using the U2N relay configuration provided in the RRC reconfiguration message for the second UE 108.

[0092] When the first gNB receives both the first and second RRC reconfiguration complete messages, the first gNB may send an RRC message to the third UE 116 in order to release the third UE 116 from serving the second UE 108 as U2N relay UE. Although the third UE 116 may be released from serving the second UE 108, the third UE 116 may maintain the capability to serve other remote UEs that may be connected to it. Further, the third UE 116 may initiate the release of the other U2U relay UEs connected between the third UE 116 and the second UE 108 from serving the second UE 108. While the other U2U relay UEs connected between the third UE 116 and the second UE 108 may be released from serving the second UE 108, the other U2U relay UEs, may maintain the capability to serve other second UEs.

[0093] Fig. 5 illustrates a second call flow 500 when the first UE 102 moves into an IC area of a first serving network, in accordance with an example implementation of the present subject matter. The second call flow 500 describes a scenario in which the first UE 102 moves into the IC area of the first serving network, where the first serving network is the network currently serving the second UE 108.

[0094] At step 502 of the first call flow 500, the first UE 102 moves into the IC area of the first serving network 104 for establishing an RRC connection with the first gNB.

[0095] At step 504 of the call flow 500, the first UE 102 transmits a first set of information to the first gNB, where the first set of information, amongst other information, includes the L2 IDs of the second UE 108, the third UE 116, and the serving cell ID of the second UE 108 to the first gNB. Additionally, the first UE 102 also indicates a first L2 ID and a second L2 ID of the first UE 102, where the first L2 ID of the first UE 102 corresponds to the ID utilized by the first UE 102 while serving as the U2U relay UE and the second L2 ID of the first UE 102 corresponds to the ID utilized by the first UE 102 while serving as the U2N relay UE.

[0096] At step 506 of the call flow 500, the first gNB sends a first RRC reconfiguration message to the first UE 102, in response to receiving the first set of information. The first RRC reconfiguration message contains the configurations for the first UE 102 to undertake the role of a U2N relay UE for the second UE 108.

[0097] At step 508, the first gNB sends a second RRC reconfiguration message for the second UE 108 to the third UE 116, for configuring the second UE 108.

[0098] On receiving the second RRC reconfiguration message for the second UE 108, at step 510 of the call flow 500, the third UE 116 transmits the second RRC reconfiguration message to the first UE 102.

[0099] At step 512 of the call flow 500, the first UE 102 forwards the second RRC reconfiguration message to the second UE 108 in a SL RRC message.

[0100] On receiving the second RRC reconfiguration message, at step 514 of the second call flow 500, the second UE 108 sends a sidelink connection request, such as a DCR message, to the first UE 102 to establish a new L2 link connection.

[0101] In one example, on receiving the second RRC reconfiguration message, the second UE 108 initiates the sidelink connection request message and sends it to the first UE 102 as represented in the call flow 500 to establish a new L2 link connection. Alternatively, the first UE 102 may initiate a sidelink connection request message instead of the secondUE 108 (not represented in the second call flow 500) and send it to second UE 108 to establish the new sidelink connection.

[0102] On receiving the sidelink connection request message, at step 516 of the second call flow 500, the first UE 102 sends a sidelink connection accept message to the second UE 108. Alternatively, in the example where the first UE 102 initiates establishment of the new sidelink connection, the second UE 108 may send the sidelink connection accept message to the first UE 102.

[0103] On receiving the sidelink connection accept message, the second UE 108 initiates an establishment of the new sidelink connection, and subsequently, the new sidelink connection is established. Further, on establishment of the new sidelink connection, at step 518, the second UE 108 sends a second RRC reconfiguration complete message to the first UE 102 in response to the second RRC reconfiguration message for second UE 108. Alternatively, in the example where the first UE 102 initiates the establishment of the sidelink, the new sidelink is established when first UE 102 receives the sidelink connection accept message from the second UE 108.

[0104] On establishment of the new sidelink connection with the first UE 102, which would now serve as the U2N relay UE, the first UE 102 may receive the second RRC reconfiguration complete message. Receiving the second RRC reconfiguration complete message would indicate that the second UE 108 has agreed to use the first UE 102 as the U2N relay UE. Accordingly, at step 520, the first UE 102 sends a first RRC reconfiguration complete message to the first gNB, where the first RRC reconfiguration complete message is sent in response to the first RRC reconfiguration message.

[0105] At step 522, the first UE 102 relays the second RRC reconfiguration complete message to the first gNB. In one example, the second RRC reconfiguration complete message to the first gNB may be sent using the U2N relay configuration provided in the RRC reconfiguration message for the second UE 108.

[0106] When the first gNB receives both the first and second RRC reconfiguration complete messages, the first gNB may release the third UE 116 from serving the second UE 108. Although the third UE 116 may be released from serving the second UE 108, the third UE 116 may maintain the capability to serve other remote UEs that may be connected to it. Further, the third UE 116 may initiate the release of the U2U relay UEs between the third UE 116 and the second UE 108 from serving the second UE 108. While the other U2U relay UEs connected between the third UE 116 and the second UE 108 may be released fromserving the second UE 108, the other U2U relay UEs, may maintain the capability to serve other remote UEs.

[0107] Fig. 6 illustrates a first call flow 600 when the first UE 102 moves into an IC area of a first serving network, in accordance with an example implementation of the present subject matter. The first call flow 600 describes a scenario in which the first UE 102 moves into the IC area of the first serving network, where the first serving network may be any serving network that is currently not serving the second UE 108, while the first UE 102 is serving a multi -hop relay connection involving the second UE 108 and is serving the second UE 108 through a second network node 112 of second serving network 110, such as a second gNB.

[0108] At step 602 of call flow 600, the first UE 102 moves into the IC area of the first serving network 104 for establishing an RRC connection with the first gNB.

[0109] At step 604, the first UE 102 transmits a first set of information to the first gNB, where the first set of information, amongst other information, includes the L2 IDs of the second UE 108, the third UE 116, and the serving cell ID of the second UE 108 to the first gNB. Additionally, the first UE 102 also indicates a first L2 ID and a second L2 ID of the first UE 102, where the first L2 ID of the first UE 102 corresponds to the ID utilized by the first UE 102 while serving as the U2U relay UE and the second L2 ID of the first UE 102 corresponds to the ID utilized by the first UE 102 while serving as the U2N relay UE.

[0110] At step 606, the first gNB sends a Handover HO notification message to the second gNB of the second serving network 110, where the first gNB requests the second gNB to initiate the HO.

[0111] At step 608 of the call flow 600, the second gNB takes a decision on the HO, i.e., the second gNB decides if the HO should be initiated, or not.

[0112] In a scenario, in response to the HO decision, where the second gNB decides to go ahead with the HO, at step 610, the second gNB sends a HO request to the first gNB, where the HO request includes information associated with the second UE 108.

[0113] On receiving the HO request from the second gNB, at step 612, the first gNB sends a HO request acknowledge message to the second gNB.

[0114] At step 614, the first gNB sends a first RRC reconfiguration message to the first UE 102, in response to receiving the first set of information. In one example, the first RRC reconfiguration message contains the configurations for the first UE 102 to undertake the role of a U2N relay UE for the second UE 108. In one example, the first RRCreconfiguration message for the first UE 102 may be embedded with a second RRC reconfiguration message targeted to the second UE 108. Embedding the second RRC reconfiguration message in the first RRC reconfiguration message accelerates the HO process.

[0115] At step 616, the first UE 102 forwards the second RRC reconfiguration message, which was embedded in the first RRC reconfiguration message, to the second UE 108 in a SL RRC message.

[0116] At step 618, on receiving the second RRC reconfiguration message, the second UE 108 initiates a sidelink connection request for example through a DCR message and sends it to the first UE 102 to establish a new sidelink connection. In one example, the second UE 108 initiates the sidelink connection request message and sends it to the first UE 102, on receiving the second RRC reconfiguration message, as represented in the call flow to establish a new sidelink connection. Alternatively, the first UE 102 may initiate a sidelink connection request message instead of the second UE 108 (not represented in the first call flow 600) and send it to second UE 108 to establish the new sidelink connection.

[0117] On receiving the sidelink connection request message, at step 620, the first UE 102 sends a sidelink connection accept message to the second UE 108. Alternatively, in the example where the first UE 102 initiates establishment of the new sidelink connection, the second UE 108 may send the sidelink connection accept message to the first UE 102.

[0118] On receiving the sidelink connection accept message, the second UE 108 initiates establishment of the new sidelink connection, and subsequently, the new sidelink connection is established. Further, on establishment of the new sidelink, connection at step 622, the second UE 108 sends a second RRC reconfiguration complete message to the first UE 102 in response to the second RRC reconfiguration message for second UE 108. Alternatively, in the example where the first UE 102 initiates the establishment of the sidelink connection, the new sidelink connection is established when first UE 102 receives the sidelink connection accept message from the second UE 108.

[0119] On establishing the new sidelink connection with the first UE 102, which would now serve as the U2N relay UE, and on receiving the second RRC reconfiguration complete message, it would indicate that the second UE 108 has agreed to use the first UE 102 as the U2N relay UE. Accordingly, at step 624, the first UE 102 sends a first RRC reconfiguration complete message to the first gNB, where the first RRC reconfiguration complete message is sent in response to the first RRC reconfiguration message.

[0120] At step 626, the first UE 102 relays the second RRC reconfiguration complete message to the first gNB. In one example, the second RRC reconfiguration complete message to the first gNB may be sent using the U2N relay configuration provided in the RRC reconfiguration message for the second UE 108.

[0121] On receiving the first and second RRC reconfiguration complete messages, at step 628, the first gNB releases the resources of the second gNB.

[0122] At step 630, the second gNB releases the third UE 116 from serving the second UE 108. Although the third UE 116 may be released from serving the second UE 108, the third UE 116 may maintain the capability to serve other remote UEs that may be connected to it. Further, the third UE 116 initiates the release of the U2U relay UEs connected between the third UE 116 and the second UE 108 from serving the second UE 108. While the other U2U relay UEs connected between the third UE 116 and the second UE 108 may be released from serving the second UE 108, the other U2U relay UEs, may maintain the capability to serve other remote UEs.

[0123] Fig. 7 illustrates a second call flow 700 when the first UE 102 moves into an IC area of a first serving network 104, in accordance with an example implementation of the present subject matter. The second call flow 700 describes a scenario in which the first UE 102 moves into the IC area of the first serving network 104, where the first serving network 104 may be any serving network that is currently not serving the second UE 108, while the first UE 102 is serving a multi -hop relay connection involving the second UE 108 and is serving the second UE 108 through the second gNB.

[0124] At step 702 of the second call flow 700, the first UE 102 moves into the IC area of the first serving network 104 for establishing an RRC connection with the first gNB.

[0125] At step 704, the first UE 102 transmits a first set of information to the first gNB, where the first set of information, amongst other information, includes the L2 IDs of the second UE 108, the third UE 116, and the serving cell ID of the second UE 108 to the first gNB. Additionally, the first UE 102 also indicates a first L2 ID and a second L2 ID of the first UE 102, where the first L2 ID of the first UE 102 corresponds to the ID utilized by the first UE 102 while serving as the U2U relay UE and the second L2 ID of the first UE 102 corresponds to the ID utilized by the first UE 102 while serving as the U2N relay UE.

[0126] At step 706, the first gNB sends a Handover HO notification message to the second gNB of the second serving network 110, where the first gNB requests the second gNB to initiate the HO.

[0127] At step 708 of the call flow 700, the second gNB takes a decision on the HO, i.e., the second gNB decides if the HO should be initiated, or not.

[0128] In a scenario, in response to the HO decision, where the second gNB decides to go ahead with the HO, at step 710, the second gNB sends a HO request to the first gNB, where the HO request includes information associated with the second UE 108.

[0129] On receiving the HO request from the second gNB, at step 712, the first gNB sends a HO request acknowledge message to the second gNB.

[0130] At step 714, the first gNB sends a first RRC reconfiguration message to the first UE 102, in response to receiving the first set of information. Where, the first RRC reconfiguration message contains the configurations for the first UE 102 to undertake the role of a U2N relay UE for the second UE 108.

[0131] At step 716, the second gNB sends a second RRC Reconfiguration message for the second UE 108 to the third UE 116, for configuring the second UE 108.

[0132] On receiving the second RRC reconfiguration message for the second UE 108, at step 718, the third UE 116 transmits the second RRC reconfiguration message to the first UE 102.

[0133] At step 720, the first UE 102 forwards the second RRC reconfiguration message, to the second UE 108 in a SL RRC message.

[0134] At step 722, on receiving the second RRC reconfiguration message, the second UE 108 initiates a sidelink connection request message and sends it to the first UE 102 to establish a new sidelink connection. In one example, the second UE 108 initiates the sidelink connection request message and sends it to the first UE 102 on receiving the second RRC reconfiguration message, as represented in the call flow to establish a new sidelink connection. Alternatively, the first UE 102 may initiate a sidelink connection request message instead of the second UE 108 (not represented in the second call flow 700) and send it to second UE 108 to establish the new sidelink connection.

[0135] On receiving the sidelink connection request message, at step 724, the first UE 102 sends a sidelink connection accept message to the second UE 108. Alternatively, in the example where the first UE 102 initiates establishment of the new sidelink connection, the second UE 108 may send the sidelink connection accept message to the first UE 102.

[0136] On receiving the sidelink connection accept message, the second UE 108 initiates an establishment of the new sidelink connection, and subsequently, the new sidelink connection is established. Further, on establishment of the new sidelink connection, at step726, the second UE 108 sends a second RRC reconfiguration complete message to the first UE 102 in response to the second RRC reconfiguration message for the second UE 108. Alternatively, in the example where the first UE 102 initiates the establishment of the sidelink, the new sidelink is established when first UE 102 receives the sidelink connection accept message from the second UE 108.

[0137] On establishing the new sidelink connection with the first UE 102, which would now serve as the U2N relay UE, and on receiving the second RRC reconfiguration complete message, it would indicate that the second UE 108 has agreed to use the first UE 102 as the U2N relay UE. Accordingly, at step 728, the first UE 102 sends a first RRC reconfiguration complete message to the first gNB, where the first RRC reconfiguration complete message is sent in response to the first RRC reconfiguration message.

[0138] At step 730, the first UE 102 relays the second RRC reconfiguration complete message to the first gNB. In one example, the second RRC reconfiguration complete message to the first gNB may be sent using the U2N relay configuration provided in the RRC reconfiguration message for the second UE 108.

[0139] On receiving the first and second RRC reconfiguration complete messages, at step 732, the first gNB releases the resources of the second gNB.

[0140] At step 734, the second gNB releases the third UE 116 from serving the second UE 108. Although the third UE 116 may be released from serving the second UE 108, the third UE 116 may maintain the capability to serve other remote UEs that may be connected to it. Further, the third UE 116 initiates the release of the U2U relay UEs connected between the third UE 116 and the second UE 108 from serving the second UE 108. While the other U2U relay UEs connected between the third UE 116 and the second UE 108 may be released from serving the second UE 108, the other U2U relay UEs, may maintain the capability to serve other remote UEs.

[0141] Fig. 8 illustrates a method 800 implemented by a first UE 102, in accordance with an example implementation of the present subject matter. The order in which the method 800 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement method 800 or an alternative method. Additionally, individual blocks may be deleted from method 800 without departing from the scope of the subject matter described herein. Furthermore, the method 800 may be implemented in any suitable hardware, computer readable instructions,firmware, or combination thereof. For discussion, the method 800 is described with reference to the implementations illustrated in Fig(s). 1-7.

[0142] At block 802 of the method 800 includes transmitting a first set of information to a first network node, where the first set of information identifies an existing User Equipment to Network (U2N) multi-hop relay connection including the first UE serving as a User Equipment to User Equipment (U2U) relay UE and a second UE serving as a remote UE. Further, the first set of information further includes a UE identifier of the second UE, a UE identifier of a third UE serving as a U2N relay UE in the existing U2N multi-hop relay connection, a cell identifier of a serving cell of the second UE, an indication that the first UE may act as a U2N relay UE for the second UE, first L2 ID of the first UE which is utilized by the first UE while serving as the U2U relay UE, and the second L2 ID of the first UE while serving as the U2N relay UE.

[0143] In one example, the first network node may be a node that is currently serving the second UE 108. In another example, the first network node may be a new node that is currently not serving the second UE 108.

[0144] At block 804, the method 800 includes receiving a first message from the first network node to reconfigure the first UE as a U2N relay UE for the second UE, where the first message is based on the first set of information. In one example, the first message may be a first RRC reconfiguration message and may be embedded with a second message for the second UE. In one example, the second message may be a second RRC reconfiguration message to reconfigure the second UE. In one example, the second message may be forwarded to the second UE, where the second message may be forwarded to the second UE in a sidelink (SL) RRC message.

[0145] In one example, the method includes sending a sidelink connection request to the second UE after receiving the first message from the first network node for establishing a new sidelink connection with the second UE. In one example, the sidelink connection request may be a DCR message.

[0146] In response to sending the sidelink connection request message, method includes receiving a sidelink connection accept from the second UE. Further, establishing a new sidelink connection with the second UE may be based on sidelink connection accept.

[0147] In one example, the method includes sending the second message to the second UE over the new sidelink connection.

[0148] In one example, on establishment of the new sidelink between the first UE and the second UE, a fourth message from the second UE is received in response to the second message over the new sidelink connection. In one example, the fourth message may be a second RRC reconfiguration complete message obtained from the remote UE on completion of reconfiguration the second UE.

[0149] In one example, a third message and the fourth message may be sent to the first network node after receiving the fourth message from the second UE. Where, the third message is a first RRC reconfiguration complete message generated in response to the first message, on completion of reconfiguration of the first UE.

[0150] Therefore, techniques of the present subject matter facilitate transitioning of the first UE from serving as the U2U relay UE to serving as the U2N relay UE, thereby transitioning a L2 multi-hop connection to a single-hop connection which in turn results in shortening the path of communication.

[0151] Fig. 9 illustrates a method 900 implemented by a first network node, in accordance with an example implementation of the present subject matter. The order in which the method 900 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement method 900 or an alternative method. Additionally, individual blocks may be deleted from method 900 without departing from the scope of the subject matter described herein. Furthermore, the method 900 may be implemented in any suitable hardware, computer readable instructions, firmware, or combination thereof. For discussion, the method 900 is described with reference to the implementations illustrated in Fig(s). 1-7.

[0152] At block 902, the method 900 includes receiving a first set of information from a first UE, the first set of information identifies an existing User Equipment to Network (U2N) multi-hop relay connection including the first UE serving as a User Equipment to User Equipment (U2U) relay UE and a second UE serving as a remote UE. The first set of information also includes a UE identifier of the second UE, a UE identifier of the third UE, a cell identifier of a serving cell of the second UE, an indication that the first UE may act as a U2N relay UE for the second UE,, the first L2 ID of the first UE, which the first UE may utilize while serving as the U2U relay UE, and the second L2 ID of the first UE, which the first UE may utilize while serving as the U2N relay UE.

[0153] At block 904, the method 900 includes transmitting a first message to the first UE to reconfigure the first UE as a U2N relay UE, where the first message is based on the first set of information.

[0154] In one example, method 900 further includes transmitting a second message for the second UE, where the second message is for reconfiguring the second UE. In one example, the first message may be embedded with the second message. In another example, the first message and the second message may be transmitted separately. In one example, the first message may be transmitted to the first UE and the second message may be transmitted to the second UE.

[0155] Fig. 10 illustrates a method 1000 implemented by the second UE, in accordance with an example implementation of the present subject matter. The order in which the method 1000 is described is not intended to be construed as a limitation, and any number of the described method blocks can be combined in any order to implement method 1000 or an alternative method. Additionally, individual blocks may be deleted from the method 1000 without departing from the scope of the subject matter described herein. Furthermore, the method 1000 may be implemented in any suitable hardware, computer readable instructions, firmware, or combination thereof. For discussion, the method 1000 is described with reference to the implementations illustrated in Fig(s). 1-7.

[0156] At block 1002, the method 1000 includes receiving a second message from a first UE where the first UE is serving as a User Equipment to User Equipment (U2U) relay UE in an existing User Equipment to Network (U2N) multi-hop relay connection for the second UE serving as a remote UE, the second message contains reconfiguration information from a first network node to reconfigure the second UE for a path switch to the first network node via the first UE serving as a U2N relay UE.

[0157] At block 1004, the method 1000 includes sending a sidelink connection request to the first UE based on the second message for establishing a new sidelink connection with the first UE. In one example, the sidelink connection request may be a Direct Communication Request (DCR) message.

[0158] In response to sending the sidelink connection request, at block 1006, method 1000 includes receiving a sidelink connection accept from the first UE.

[0159] At block 1008, method 1000 includes establishing the new sidelink connection with the first UE based on the sidelink connection accept message.

[0160] At block 1010, method 1000 includes sending a fourth message to the first UE to be relayed to the first network node in response to the second message.

[0161] Although examples of the present subject matter have been described in language specific to methods and / or structural features, it is to be understood that the present subject matter is not limited to the specific methods or features described. Rather, the methods and specific features are disclosed and explained as examples of the present subject matter.

Claims

We claim:

1. A first user equipment (UE) comprising: at least one processor; a machine-readable storage medium comprising instructions that, when executed by the at least one processor, cause the first UE to: transmit a first set of information to a first network node, wherein the first set of information identifies an existing User Equipment to Network (U2N) multi-hop relay connection including the first UE serving as a User Equipment to User Equipment (U2U) relay UE and a second UE serving as a remote UE; and receive a first message from the first network node to reconfigure the first UE as a U2N relay UE for the second UE, wherein the first message is based on the first set of information.

2. The first UE as claimed in claim 1, wherein the first set of information comprises at least one of: a UE identifier of the second UE; a UE identifier of a third UE serving as a U2N relay UE in the U2N multihop relay connection; and a cell identifier of a serving cell of the second UE.

3. The first UE as claimed in claim 1 or 2, wherein the first set of information further comprises an indication that the first UE may act as a U2N relay UE for the second UE.

4. The first UE as claimed in claim 1, wherein the at least one processor is configured to cause the first UE to establish a sidelink connection with the second UE in response to receiving the first message.

5. The first UE as claimed in claim 1, wherein the at least one processor is configured to receive a second message from the first network node, the second message including reconfiguration information for the second UE.

6. The first UE as claimed in any of claims 1 to 4, wherein the first message includes a second message containing reconfiguration information for the second UE.

7. The first UE as claimed in claim 6, wherein the at least one processor is configured to cause the first UE to forward the second message to the second UE using the existing U2N multi-hop relay connection.

8. The first UE as claimed in claim 6 depending from claim 4, wherein the at least one processor is configured to cause the first UE to forward the second message to the second UE over the sidelink connection.

9. The first UE as claimed in claim 1, wherein the at least one processor is configured to cause the first UE to: send a sidelink connection request with an indication of path switch to the second UE to establish a sidelink connection between the first UE and the second UE.

10. The first UE as claimed in claim 9, wherein the sidelink connection request is a Direct Communication Request (DCR) message.

11. A first network node comprising: at least one processor, a machine-readable storage medium comprising instructions that, when executed by the at least one processor, cause the first network node to: receive a first set of information from a first UE, wherein the first set of information identifies an existing User Equipment to Network (U2N) multi-hop relay connection including the first UE serving as a User Equipment to User Equipment (U2U) relay UE and a second UE serving as a remote UE; and transmit a first message to the first UE to reconfigure the first UE as a U2N relay UE for the second UE, wherein the first message is based on the first set of information.

12. The first network node as claimed in claim 11, wherein the first set of information comprises at least one of a UE identifier of the second UE; a UE identifier of a third UE serving as a U2N relay UE in the existing U2N multi-hop relay connection; and a cell identifier of a serving cell of the second UE.

13. The first network node as claimed in claim 11 or 12, wherein the first set of information further comprises an indication that the first UE may act as a U2N relay UE for the second UE.

14. The first network node as claimed in claim 11, wherein the at least one processor is configured to transmit a second message to the first UE, the second message including reconfiguration information for the second UE.

15. The first network node as claimed in any of claims 11 to 14, wherein the first message includes the second message containing reconfiguration information for the second UE.

16. The first network node as claimed in claim 11, wherein the first network node is the network node serving the second UE through the existing U2N multi-hop relay connection.

17. The first network node as claimed in claim 11, wherein a second network node is serving the second UE through the existing U2N multi-hop relay connection.

18. The first network node as claimed in claim 17, wherein the at least one processor is to cause the first network node to: transmit a handover (HO) notification to the second network node based on at least the first set of information; receive a HO request for the second UE from the second network node; and in response to the HO request, transmit the first message to the first UE.

19. A second UE comprising:at least one processor, a machine-readable storage medium comprising instructions that, when executed by the at least one processor, cause the second UE to: receive a second message from a first UE wherein the first UE is serving as a User Equipment to User Equipment (U2U) relay UE in an existing User Equipment to Network (U2N) multi-hop relay connection for the second UE serving as a remote UE, the second message contains reconfiguration information from a first network node to reconfigure the second UE for a path switch to the first network node via the first UE serving as a U2N relay UE; send a sidelink connection request to the first UE based on the second message for establishing a new sidelink connection with the first UE; receive a sidelink connection accept from the first UE; establish the new sidelink connection with the first UE based on the sidelink connection accept; and send a fourth message to the first UE to be relayed to the first network node in response to the second message.

20. A method implemented by a first User Equipment (UE), the method comprising: transmitting a first set of information to a first network node, wherein the first set of information identifies an existing User Equipment to Network (U2N) multihop relay connection including the first UE serving as a User Equipment to User Equipment (U2U) relay UE and a second UE serving as a remote UE; and receiving a first message from the first network node to reconfigure the first UE as a U2N relay UE for the second UE, wherein the first message is based on the first set of information.

21. A method implemented by a first network node, the method comprising: receiving a first set of information from a first UE, wherein the first set of information identifies an existing User Equipment to Network (U2N) multi-hop relay connection including the first UE serving as a User Equipment to User Equipment (U2U) relay UE and a second UE serving as a remote UE; andtransmitting a first message to the first UE to reconfigure the first UE as a U2N relay UE for the second UE, wherein the first message is based on the first set of information.

22. A method implemented by a second UE, the method comprising: receiving a second message from a first UE wherein the first UE is serving as a User Equipment to User Equipment (U2U) relay UE in an existing User Equipment to Network (U2N) multi-hop relay connection for the second UE serving as a remote UE, the second message contains reconfiguration information from a first network node to reconfigure the second UE for a path switch to the first network node via the first UE serving as a U2N relay UE; sending a sidelink connection request to the first UE based on the second message for establishing a new sidelink connection with the first UE; receiving a sidelink connection accept from the first UE; establishing the new sidelink connection with the first UE based on the sidelink connection accept; and sending a fourth message to the first UE to be relayed to the first network node in response to the second message.

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