WO2025199769A1

WO2025199769A1 - Devices and methods for communication

Info

Publication number: WO2025199769A1
Application number: PCT/CN2024/083924
Authority: WO
Inventors: You Li; Gang Wang
Original assignee: NEC Corp
Current assignee: NEC Corp
Priority date: 2024-03-26
Filing date: 2024-03-26
Publication date: 2025-10-02
Anticipated expiration: 2026-09-26

Abstract

Embodiments of the present disclosure provide a solution for a multi-hop relay for a user equipment (UE) -to-network (U2N) transmission. In a solution, a first relay terminal device determines information about at least one second relay terminal device, wherein each second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device; and transmit the information about at least one second relay terminal device.

Description

DEVICES AND METHODS FOR COMMUNICATION

FIELDS

Example embodiments of the present disclosure generally relate to the field of communication techniques and in particular, to devices and methods for a multi-hop relay for a user equipment (UE) -to-network (U2N) transmission.

BACKGROUND

Release 17 specified mechanisms to support single-hop a user equipment (UE) -to-network (U2N) relay and release 18 specified mechanisms to support single-hop UE-to-UE (U2U) relay. In release 19, a multi-hop U2N relay is expected to be supported. Specifically, taking the single-hop U2N relay as a baseline, specify one or more additional hops for the U2N transmission. In a case of multi-hop U2N relay, how to transmit the uplink packet and the downlink packet is desirable to be further discussed.

SUMMARY

In general, embodiments of the present disclosure provide a solution for handling a multi-hop relay for a U2N transmission.

In a first aspect, there is provided a first relay terminal device. The first relay terminal device comprises: a processor configured to cause the terminal device to: determine information about at least one second relay terminal device, wherein each second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device; and transmit the information about at least one second relay terminal device, wherein, each second relay terminal device is indicated by an indication that the second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, the information about the at least one second relay terminal device is associated with a specific relay service code (RSC) , or the information about the at least one second relay terminal device is comprised in a specific information element or a discovery announcement message specific to a multi-hop U2N transmission.

In a second aspect, there is provided a remote terminal device. The remote terminal device comprises: a processor configured to cause the remote terminal device to: generate a first solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, the first solicitation message comprises an indication that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the first solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission; and transmit the first solicitation message.

In a third aspect, there is provided a first relay terminal device. The first relay terminal device comprises: a processor configured to cause the first relay terminal device to:revive a first solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, the first solicitation message comprises an indication that the remote terminal device aims to discover at least one second relay terminal device, the first solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the first solicitation message is a discovery solicitation message dedicated to a multi-hop U2N transmission; transmit a second solicitation message generated based on the first solicitation message by at least adding an identity of the first relay terminal device to the first solicitation message.

In a fourth aspect, there is provided a second relay terminal device. The second relay terminal device comprises: a processor configured to cause the second relay terminal device to: revive a second solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, the second solicitation message comprises an indication that the remote terminal device aims to discover the at least one second relay terminal device, the second solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the second solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the second solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission; and transmit, a first response to the second solicitation message.

In a fifth aspect, there is provided a remote terminal device. The remote terminal device comprises: a processor configured to cause the remote terminal device to: generate a packet for carrying Uu interface data of a signalling radio bearer (SRB) , wherein, the packet comprising a specific sidelink bearer identity pre-defined for a Uu interface transmission, or the packet is submitted to a specific radio link control (RLC) channel pre-defined for a Uu interface transmission, or the packet comprises an indication that the packet carries the Uu interface data.

In a sixth aspect, there is provided a remote terminal device. The remote terminal device comprises: a processor configured to cause the remote terminal device to: apply a specific configuration for a Uu interface transmission in response to at least one of the following: an initiation a radio resource control (RRC) connection establishment, an RRC connection reestablishment or an RRC connection resuming procedure with a network device, a successful selection of a first relay terminal device, a successful selection of a second relay terminal device, an establishment of a connection with a first relay terminal device, an establishment of a connection with a second relay terminal device, an establishment of a connection between a first relay terminal device and a second relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) remote terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device.

In a seventh aspect, there is provided a first relay terminal device. The first relay terminal device comprises: a processor configured to cause the first relay terminal device to: apply a specific configuration for a Uu interface transmission in response to at least one of the following: an establishment of a connection with a remote terminal device, an establishment of a connection with a second relay terminal device, or performing as a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2U relay terminal device.

In an eighth aspect, there is provided a second relay terminal device. The second relay terminal device comprises: a processor configured to cause the second relay terminal device to: apply a specific configuration for a Uu interface transmission in response to at least one of the following: an establishment of a connection with a remote terminal device, an establishment of a connection with a first relay terminal device, or performing as a multi-hop user equipment (UE) -to-network (U2N) relay terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2U relay terminal device.

In a ninth aspect, there is provided a second relay terminal device. The second relay terminal device comprises: a processor configured to cause the second relay terminal device to: in accordance with a determination that the second relay terminal device is in a radio resource control (RRC) idle state or an RRC inactive state, initiate a transition to an RRC connected state in response to at least one of the following: an establishment of a PC5-RRC connection with a remote terminal device, an establishment of a PC5-RRC connection with a first relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) relay terminal device, receiving a PC5-RRC message or PC5-Signaling message from the remote terminal device, or receiving a message from the first relay terminal device, the message requesting the second relay terminal device to transition to the RRC connected state, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device.

In a tenth aspect, there is provided a first relay terminal device. The first relay terminal device comprises: a processor configured to cause the first relay terminal device to:in accordance with a determination that the first relay terminal device is in a radio resource control (RRC) idle state or an RRC inactive state, initiate a transition to an RRC connected state in response to at least one of the following: a successful selection of a second relay terminal device, an establishment of a PC5-RRC connection with a remote terminal device, an establishment of a PC5-RRC connection with a second relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device, being indicated that the first relay terminal device is selected for a multi-hop U2N transmission by one of the following: the remote terminal device, the second relay terminal device, an upper layer of the first relay terminal device, receiving a message from the second relay terminal device or the remote terminal device, the message requesting the second relay terminal device to transition to the RRC connected state, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device.

In an eleventh aspect, there is provided a communication method performed by a first relay terminal device. The method comprises: determining information about at least one second relay terminal device, wherein each second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device; and transmitting the information about at least one second relay terminal device, wherein, each second relay terminal device is indicated by an indication that the second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, thing information about the at least one second relay terminal device is associated with a specific relay service code (RSC) , or thing information about the at least one second relay terminal device is comprised in a specific information element or a discovery announcement message specific to a multi-hop U2N transmission.

In a twelfth aspect, there is provided a communication method performed by a remote terminal device. The method comprises: generateing a first solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, the first solicitation message comprises an indication that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the first solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission; and transmitting the first solicitation message.

In a thirteenth aspect, there is provided a communication method performed by a first relay terminal device. The method comprises: reviving a first solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, the first solicitation message comprises an indication that the remote terminal device aims to discover at least one second relay terminal device, the first solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the first solicitation message is a discovery solicitation message dedicated to a multi-hop U2N transmission; transmitting a second solicitation message generated based on the first solicitation message by at least adding an identity of the first relay terminal device to the first solicitation message.

In a fourteenth aspect, there is provided a communication method performed by a second relay terminal device. The method comprises: reviving a second solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, the second solicitation message comprises an indication that the remote terminal device aims to discover the at least one second relay terminal device, the second solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the second solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the second solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission; and transmitting, a first response to the second solicitation message.

In a fifteenth aspect, there is provided a communication method performed by a remote terminal device. The method comprises: generateing a packet for carrying Uu interface data of a signalling radio bearer (SRB) , wherein, the packet comprising a specific sidelink bearer identity pre-defined for a Uu interface transmission, or the packet is submitted to a specific radio link control (RLC) channel pre-defined for a Uu interface transmission, or the packet comprises an indication that the packet carries the Uu interface data.

In a sixteenth aspect, there is provided a communication method performed by a remote terminal device. The method comprises: applying a specific configuration for a Uu interface transmission in response to at least one of the following: an initiation a radio resource control (RRC) connection establishment, an RRC connection reestablishment or an RRC connection resuming procedure with a network device, aing successful selection of a first relay terminal device, aing successful selection of a second relay terminal device, an establishment of a connection with a first relay terminal device, an establishment of a connection with a second relay terminal device, an establishment of a connection between a first relay terminal device and a second relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) remote terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device.

In a seventeenth aspect, there is provided a communication method performed by a first relay terminal device. The method comprises: applying a specific configuration for a Uu interface transmission in response to at least one of the following: an establishment of a connection with a remote terminal device, an establishment of a connection with a second relay terminal device, or performing as a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2U relay terminal device.

In an eighteenth aspect, there is provided a communication method performed by a second relay terminal device. The method comprises: applying a specific configuration for a Uu interface transmission in response to at least one of the following: an establishment of a connection with a remote terminal device, an establishment of a connection with a first relay terminal device, or performing as a multi-hop user equipment (UE) -to-network (U2N) relay terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2U relay terminal device.

In a nineteenth aspect, there is provided a communication method performed by a second relay terminal device. The method comprises: in accordance with a determination that the second relay terminal device is in a radio resource control (RRC) idle state or an RRC inactive state, initiating a transition to an RRC connected state in response to at least one of the following: an establishment of a PC5-RRC connection with a remote terminal device, an establishment of a PC5-RRC connection with a first relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) relay terminal device, receiving a PC5-RRC message or PC5-Signaling message from the remote terminal device, or receiving a message from the first relay terminal device, the message requesting the second relay terminal device to transition to the RRC connected state, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device.

In a twentieth aspect, there is provided a communication method performed by a first relay terminal device. The method comprises: in accordance with a determination that the first relay terminal device is in a radio resource control (RRC) idle state or an RRC inactive state, initiating a transition to an RRC connected state in response to at least one of the following: aing successful selection of a second relay terminal device, an establishment of a PC5-RRC connection with a remote terminal device, an establishment of a PC5-RRC connection with a second relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device, being indicated that the first relay terminal device is selected for a multi-hop U2N transmission by one of the following: the remote terminal device, the second relay terminal device, an upper layer of the first relay terminal device, receiving a message from the second relay terminal device or the remote terminal device, the message requesting the second relay terminal device to transition to the RRC connected state, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device.

In a twenty-first aspect, there is provided a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to the eleventh, twelfth, thirteenth, fourteenth, fifteenth, sixteenth, seventeenth, eighteenth, nineteenth, or twentieth aspect.

Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the more detailed description of some example embodiments of the present disclosure in the accompanying drawings, the above and other objects, features and advantages of the present disclosure will become more apparent, wherein:

FIG. 1A illustrates a signaling flow of control plane procedures for layer 2 (L2) U2N relay;

FIG. 1B illustrates a signaling flow of control plane procedures for L2 U2U relay;

FIG. 1C illustrates a signaling flow of discovery for U2U relay;

FIG. 1D illustrates another signaling flow of discovery for U2U relay;

FIG. 2 illustrates an example communication environment in which example embodiments of the present disclosure can be implemented;

FIG. 3 illustrates a signaling flow of communication according to some example embodiments of the present disclosure;

FIG. 4 illustrates a flowchart of a communication method implemented at a first relay terminal device according to some example embodiments of the present disclosure;

FIG. 5 illustrates a flowchart of a communication method implemented at a remote terminal device according to some example embodiments of the present disclosure;

FIG. 6 illustrates a flowchart of a communication method implemented at a first relay terminal device according to some example embodiments of the present disclosure;

FIG. 7 illustrates a flowchart of a communication method implemented at a second relay terminal device according to some example embodiments of the present disclosure;

FIG. 8 illustrates a flowchart of a communication method implemented at a remote terminal device according to some example embodiments of the present disclosure;

FIG. 9 illustrates a flowchart of a communication method implemented at a remote terminal device according to some example embodiments of the present disclosure;

FIG. 10 illustrates a flowchart of a communication method implemented at a first relay terminal device according to some example embodiments of the present disclosure;

FIG. 11 illustrates a flowchart of a communication method implemented at a second relay terminal device according to some example embodiments of the present disclosure;

FIG. 12 illustrates a flowchart of a communication method implemented at a second relay terminal device according to some example embodiments of the present disclosure;

FIG. 13 illustrates a flowchart of a communication method implemented at a first relay terminal device according to some example embodiments of the present disclosure;

FIG. 14 illustrates a simplified block diagram of an apparatus that is suitable for implementing example embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. Embodiments described herein can be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

As used herein, the term ‘terminal device’ refers to any device having wireless or wired communication capabilities. Examples of the terminal device include, but not limited to, user equipment (UE) , personal computers, desktops, mobile phones, cellular phones, smart phones, personal digital assistants (PDAs) , portable computers, tablets, wearable devices, internet of things (IoT) devices, Ultra-reliable and Low Latency Communications (URLLC) devices, Internet of Everything (IoE) devices, machine type communication (MTC) devices, devices on vehicle for V2X communication where X means pedestrian, vehicle, or infrastructure/network, devices for Integrated Access and Backhaul (IAB) , Space borne vehicles or Air borne vehicles in Non-terrestrial networks (NTN) including Satellites and High Altitude Platforms (HAPs) encompassing Unmanned Aircraft Systems (UAS) , eXtended Reality (XR) devices including different types of realities such as Augmented Reality (AR) , Mixed Reality (MR) and Virtual Reality (VR) , the unmanned aerial vehicle (UAV) commonly known as a drone which is an aircraft without any human pilot, devices on high speed train (HST) , or image capture devices such as digital cameras, sensors, gaming devices, music storage and playback appliances, or Internet appliances enabling wireless or wired Internet access and browsing and the like. The ‘terminal device’ can further have ‘multicast/broadcast’ feature, to support public safety and mission critical, V2X applications, transparent IPv4/IPv6 multicast delivery, IPTV, smart TV, radio services, software delivery over wireless, group communications and IoT applications. It may also incorporate one or multiple Subscriber Identity Module (SIM) as known as Multi-SIM. The term “terminal device” can be used interchangeably with a UE, a mobile station, a subscriber station, a mobile terminal, a user terminal or a wireless device.

The term “network device” refers to a device which is capable of providing or hosting a cell or coverage where terminal devices can communicate. Examples of a network device include, but not limited to, a Node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a next generation NodeB (gNB) , a transmission reception point (TRP) , a remote radio unit (RRU) , a radio head (RH) , a remote radio head (RRH) , an IAB node, a low power node such as a femto node, a pico node, a reconfigurable intelligent surface (RIS) , and the like.

The terminal device or the network device may have Artificial intelligence (AI) or Machine learning capability. It generally includes a model which has been trained from numerous collected data for a specific function, and can be used to predict some information.

The terminal or the network device may work on several frequency ranges, e.g., FR1 (e.g., 450 MHz to 6000 MHz) , FR2 (e.g., 24.25GHz to 52.6GHz) , frequency band larger than 100 GHz as well as Tera Hertz (THz) . It can further work on licensed/unlicensed/shared spectrum. The terminal device may have more than one connection with the network devices under Multi- Radio Dual Connectivity (MR-DC) application scenario. The terminal device or the network device can work on full duplex, flexible duplex and cross division duplex modes.

The embodiments of the present disclosure may be performed in test equipment, e.g., signal generator, signal analyzer, spectrum analyzer, network analyzer, test terminal device, test network device, channel emulator. In some embodiments, the terminal device may be connected with a first network device and a second network device. One of the first network device and the second network device may be a master node and the other one may be a secondary node. The first network device and the second network device may use different radio access technologies (RATs) . In some embodiments, the first network device may be a first RAT device and the second network device may be a second RAT device. In some embodiments, the first RAT device is eNB and the second RAT device is gNB. Information related with different RATs may be transmitted to the terminal device from at least one of the first network device or the second network device. In some embodiments, first information may be transmitted to the terminal device from the first network device and second information may be transmitted to the terminal device from the second network device directly or via the first network device. In some embodiments, information related with configuration for the terminal device configured by the second network device may be transmitted from the second network device via the first network device. Information related with reconfiguration for the terminal device configured by the second network device may be transmitted to the terminal device from the second network device directly or via the first network device.

As used herein, the singular forms ‘a’ , ‘an’ and ‘the’ are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term ‘includes’ and its variants are to be read as open terms that mean ‘includes, but is not limited to. ’ The term ‘based on’ is to be read as ‘at least in part based on. ’ The term ‘one embodiment’ and ‘an embodiment’ are to be read as ‘at least one embodiment. ’ The term ‘another embodiment’ is to be read as ‘at least one other embodiment. ’ The terms ‘first, ’ ‘second, ’ and the like may refer to different or same objects. Other definitions, explicit and implicit, may be included below.

In some examples, values, procedures, or apparatus are referred to as ‘best, ’ ‘lowest, ’ ‘highest, ’ ‘minimum, ’ ‘maximum, ’ or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made, and such selections need not be better, smaller, higher, or otherwise preferable to other selections.

As used herein, the term “resource, ” “transmission resource, ” “uplink resource, ” or “downlink resource” may refer to any resource for performing a communication, such as a resource in time domain, a resource in frequency domain, a resource in space domain, a resource in code domain, or any other resource enabling a communication, and the like. In the following, unless explicitly stated, a resource in both frequency domain and time domain will be used as an example of a transmission resource for describing some example embodiments of the present disclosure. It is noted that example embodiments of the present disclosure are equally applicable to other resources in other domains.

It has been agreed that new radio (NR) sidelink (SL) multi-hop Relay work in RAN2 will focus on the following: layer 2 (L2) U2N SL Relay (only single indirect U2N path via SL relay UEs will be supported) ; it will start with specifying one additional hop relay (i.e. on top of Rel-18) and see if it can be easily extended to two additional hops relays; aim to support two additional hops relay and to have a forward compatible solution for future extension for additional relays; and only limited service continuity scenarios will be considered.

Reference is now made to FIG. 1A, which illustrates a signaling flow 100A of control plane procedures for L2 U2N relay.

At Step 1, the L2 U2N Remote and L2 U2N Relay UE perform discovery procedure, and establish a PC5-radio resource control (RRC) connection using the NR sidelink PC5 unicast link establishment procedure. At Step 2, the L2 U2N Remote UE sends the first RRC message (i.e., RRC SetupRequest) for its connection establishment with gNB via the L2 U2N Relay UE, using a specified PC5 Relay RLC channel configuration. The L2 U2N Relay UE sends the SidelinkUEInformationNR message to request for the dedicated configurations required to support the relay operation for the L2 U2N Remote UE. If the L2 U2N Relay UE is not in RRC_CONNECTED, it needs to do its own Uu RRC connection establishment upon reception of a message on the specified PC5 Relay radio link control (RLC) channel. After L2 U2N Relay UE's RRC connection establishment procedure and sending the SidelinkUEInformationNR message, gNB configures Signaling Radio Bearer 0 (SRB 0) relaying Uu Relay RLC channel to the U2N Relay UE. The gNB responds with an RRC Setup message to L2 U2N Remote UE. The RRC Setup message is sent to the L2 U2N Remote UE using SRB0 relaying Uu Relay RLC channel over Uu and a specified PC5 Relay RLC channel over PC5.

At Step 3, the gNB and L2 U2N Relay UE perform relaying channel setup procedure over Uu. According to the configuration from gNB, the L2 U2N Relay/Remote UE establishes a PC5 Relay RLC channel for relaying of SRB1 towards the L2 U2N Remote/Relay UE over PC5. At Step 4, the RRC Setup Complete message is sent by the L2 U2N Remote UE to the gNB via the L2 U2N Relay UE using SRB1 relaying channel over PC5 and SRB1 relaying channel configured to the L2 U2N Relay UE over Uu. Then the L2 U2N Remote UE is as in RRC_CONNECTED with the gNB.

At Step 5, the L2 U2N Remote UE and gNB establish security following the Uu security mode procedure and the security messages are forwarded through the L2 U2N Relay UE. At Step 6. the gNB sends an RRCReconfiguration message to the L2 U2N Remote UE via the L2 U2N Relay UE, to setup the end-to-end SRB2/DRBs of the L2 U2N Remote UE. The L2 U2N Remote UE sends an RRCReconfigurationComplete message to the gNB via the L2 U2N Relay UE as a response. In addition, the gNB may configure additional Uu Relay RLC channels between the gNB and L2 U2N Relay UE, and PC5 Relay RLC channels between L2 U2N Relay UE and L2 U2N Remote UE for the relaying traffic.

For L2 U2N Relay UE in RRC_IDLE, an RRC connection establishment is initiated in the following cases: if any message is received from a L2 U2N Remote UE via SL-RLC0 or SL-RLC1. Further, For L2 U2N Relay UE in RRC_INACTIVE, an RRC connection establishment is resumed in the following cases: if any message is received from the L2 U2N Remote UE via SL-RLC0 or SL-RLC1.

Upon initiation of the procedure, if the UE is acting as L2 U2N Remote UE: establish a SRAP entity, if no SRAP entity has been established; apply the specified configuration of SL-RLC0; and apply the SDAP configuration and PDCP configuration for SRB0.

Reference is now made to FIG. 1B, which illustrates a signaling flow 100B of control plane procedures for L2 U2N relay.

At Step 1, a discovery procedure is performed. At Step 2a, the L2 U2U Remote UE establishes/modifies a PC5-RRC connection with the selected L2 U2U Relay UE.

At Step 2b, the L2 U2U Relay UE establishes/modifies a PC5-RRC connection with the peer L2 U2U Remote UE. At Step 3, the L2 U2U Relay UE allocates two local IDs and it is delivered via RRCReconfigurationSidelink message to each of the L2 U2U Remote UEs: one local ID to identify the L2 U2U Remote UE, the other local ID to identify the peer L2 U2U Remote UE. When the local ID is delivered, an L2 ID of the peer L2 U2U Remote UE is also delivered to the U2U Remote UE for making the association between the local ID and the L2 ID of the peer U2U Remote UE.

At Step 4, the L2 U2U Remote UE establishes end-to-end PC5-RRC connection with the peer L2 U2U Remote UE via the L2 U2U Relay UE. For the end-to-end connection establishment, fixed indexes (i.e., 0/1/2/3) are defined for end-to-end SL-SRB 0/1/2/3 respectively, and specified PC5 Relay RLC Channel configuration is used on each hop. The sidelink UE capability is exchanged between the L2 U2U Remote UEs via PC5-RRC (e.g., SL-SRB3) message.

At Step 5, the L2 U2U Remote UE sends to the L2 U2U Relay UE all the QoS profiles for the end-to-end QoS flows via PC5-RRC. At Step 6, the L2 U2U Relay UE performs QoS split only for PDB. It is up to L2 U2U Relay UE implementation on how to split PDB.

At Step 7, the L2 U2U Relay UE sends the split QoS value (i.e., PDB) via PC5-RRC message to the L2 U2U Remote. At Step 8, the L2 U2U Remote UE or the serving gNB of the L2 U2U Remote UE derives the packet data convergence protocol (PDCP) and SDAP configuration for end-to-end SL-DRB and provides the portion of the configuration related to reception to the peer L2 U2U Remote UE using end-to-end RRCReconfigurationSidelink messages. The end-to-end bearer IDs for SL-SRB and SL-DRB are used as input for the L2 U2U Relay ciphering and deciphering at PDCP.

At Step 9a, the L2 U2U Remote UE or the serving gNB of the L2 U2U Remote UE derives the first hop configuration (e.g. PC5 Relay RLC Channel configuration) for SL-DRB and provides to the L2 U2U Relay UE of the configuration related to receiving on the first hop (i.e., Rx by the relay UE) , using per-hop RRCReconfigurationSidelink message.

At Step 9b, the L2 U2U Relay UE or the serving gNB of the L2 U2U Relay UE derives the second hop configuration (e.g. PC5 Relay RLC Channel configuration) for each SL-DRB and provides to the peer L2 U2U Remote UE of the configuration related to receiving data packets on the second hop (i.e., RX by the peer remote UE) , using per-hop RRCReconfigurationSidelink message.

Reference is now made to FIG. 1C, which illustrates a signaling flow 100C of discovery for U2U relay.

At Step 1, the 5G ProSe UE-to-UE Relay has discovered other UEs in proximity (e.g. via a previous 5G ProSe UE-to-UE Relay Discovery or 5G ProSe UE-to-UE Relay Communication procedures) . The 5G ProSe UE-to-UE Relay obtains the User Info ID of other UEs in proximity per RSC.

At Step 2, the 5G ProSe UE-to-UE Relay sends a UE-to-UE Relay Discovery Announcement message. The UE-to-UE Relay Discovery Announcement message contains the Type of Discovery Message, User Info ID of the 5G ProSe UE-to-UE Relay, RSC and list of User Info ID of the 5G ProSe End UEs supporting the RSC. The UE-to-UE Relay Discovery Announcement message is sent using the Source Layer-2 ID and Destination Layer-2 ID.

Reference is now made to FIG. 1D, which illustrates another signaling flow 100D of discovery for U2U relay.

At Step 1, the discoverer 5G ProSe End UE (UE-1) sends a 5G ProSe UE-to-UE Relay Discovery Solicitation message. The 5G ProSe UE-to-UE Relay Discovery Solicitation message contains the Type of Discovery Message, User Info ID of itself, RSC and User Info ID of the discoveree 5G ProSe End UE (UE-2) and is sent using the Source Layer-2 ID and Destination Layer-2 ID.

At Step 2, if the RSC contained in the solicitation message matches any of the (pre) configured RSC (s) , of a 5G ProSe UE-to-UE Relay, the 5G ProSe UE-to-UE Relay sends a 5G ProSe UE-to-UE Relay Discovery Solicitation message. The 5G ProSe UE-to-UE Relay Discovery Solicitation message contains the Type of Discovery Message, User Info ID of the discoverer 5G ProSe End UE (UE-1) , User Info ID of UE-to-UE Relay, RSC and User Info ID of the discoveree 5G ProSe End UE (UE-2) and is sent using the Source Layer-2 ID and Destination Layer-2 ID.

At Step 3, if the RSC contained in the solicitation message matches any of the (pre) configured RSC (s) , of the discoveree 5G ProSe End UE (UE-2) , and the discoveree 5G ProSe End UE (UE-2) matches the User Info ID of the discoveree 5G ProSe End UE (UE-2) contained in the solicitation message, then the discoveree 5G ProSe End UE (UE-2) responds to the 5G ProSe UE-to-UE Relay with a 5G ProSe UE-to-UE Relay Discovery Response message. The 5G ProSe UE-to-UE Relay Discovery Response message contains the Type of Discovery Message, RSC, User Info ID of the discoverer 5G ProSe End UE (UE-1) and User Info ID of discoveree 5G ProSe End UE (UE-2) and is sent using the Source Layer-2 ID and Destination Layer-2 ID as described in clause 5.8.4. If the discoveree 5G ProSe End UE (UE-2) receives multiple UE-to-UE Relay Discovery Solicitation messages from different 5G ProSe UE-to-UE Relays with the same RSC and the User.

At Step 4, the 5G ProSe UE-to-UE Relay sends a 5G ProSe UE-to-UE Relay Discovery Response message. The 5G ProSe UE-to-UE Relay Discovery Response message contains the Type of Discovery Message, User Info ID of UE-to-UE Relay, RSC, User Info ID of the discoverer 5G ProSe End UE (UE-1) and User Info ID of the discoveree 5G ProSe End UE (UE-2) and is sent using the Source Layer-2 ID and Destination Layer-2 ID.

During the PC5 Relay RLC channel addition/modification, upon PC5-RRC connection establishment between the L2 U2N Relay UE and L2 U2N Remote UE, the L2 U2N Relay UE shall: establish a SRAP entity, if no SRAP entity has been established; apply RLC specified configuration of SL-RLC0: apply RLC default configuration of SL-RLC1 as defined in clause 9.2.4 if the L2 U2N Relay UE is in RRC_IDLE/INACTIVE state.

Further, parameters that are specified for NR sidelink L2 U2U Relay operations, which is used for the PC5 Relay RLC channel for U2U Remote UE's SL-SRB0/1/2/3 message transmission/reception with the peer U2U Remote UE. The PC5 Relay RLC channel using this configuration is named as SL-U2U-RLC. Below table 1 illustrated example parameters.

Table 1

As used herein, an egress RLC channel refers to an RLC channel on which a packet is transmitted by a U2N Relay UE, a U2N Remote UE, a U2U Remote UE, a U2U Relay UE or a network node.

As used herein, an egress link refers to a radio link on which a packet is transmitted by a U2N Relay UE, a U2N Remote UE, a U2U Remote UE, a U2U Relay UE or a network node.

As used herein, an ingress RLC channel refers to an RLC channel on which a packet is received from a U2N Relay UE, a U2N Remote UE, a U2U Remote UE, a U2U Relay UE or a network node.

As used herein, an ingress link refers to a radio link on which a packet is received from a U2N Relay UE, a U2N Remote UE, a U2U Remote UE, a U2U Relay UE or a network node.

As used herein, “Remote UE” also may be referred to as “remote terminal device” , “Relay UE” also may be referred to as “Relay” or “relay terminal device” .

As used herein, an RSC is used for the case of UE-to-Network Relay as well as for the case of UE-to-UE Relay. For the case of UE-to-UE Relay, the Relay Service Code is used to identify a connectivity service the 5G ProSe UE-to-UE Relay provides and the authorized users the 5G ProSe UE-to-UE Relay would offer service to. The definition of values of Relay Service Code for the case of UE-to-UE Relay is out of scope of this specification.

As used herein, the User Info ID is configured for Model A or Model B Group Member Discovery, 5G ProSe UE-to-Network Relay Discovery and 5G ProSe UE-to-UE Relay Discovery, either for public safety or commercial applications based on the policy of the HPLMN or via the ProSe application server that allocates it. The definition of values of User Info ID is out of scope of this specification.

As used herein, RLC channel may refer to PC5 relay RLC channel, an SL relay RLC channel, a PC5 RLC channel or an SL RLC channel.

As used herein, a Link with U2N Relay UE may refer to a PC5-RRC connection or PC5 unicast link.

As used herein, an upper layer may be PC5 signalling (PC5-S) layer, proximity services (ProSe) layer, vehicle-to-everything (V2X) layer, Non-Access Stratum (NAS) layer.

Principles and implementations of the present disclosure will be described in detail below with reference to the figures.

EXAMPLE OF COMMUNICATION ENVIRONMENT

FIG. 2 illustrates a schematic diagram of an example communication environment 200 in which example embodiments of the present disclosure can be implemented.

The communication environment 200 comprises a remote terminal device 210 and a network device 230. In communication environment 200, the remote terminal device 210 and the network device 230 may communicate with each other via a multi-hop relay, i.e., via at least two relay terminal devices. In the example of FIG. 2, the remote terminal device 210 and the network device 230 may communicate with each other via the relay terminal device 220-1 and the relay terminal device 220-2.

In the example of FIG. 2, the relay terminal device 220-2 is closest to the network device 230, and the relay terminal device 220-1 is connected with two terminal devices. In the following, the relay terminal device 220-1 is referred to as the first relay terminal device, a U2U Relay UE or an intermediate Relay UE (which means that a Remote UE may connect with a U2N Relay UE via the intermediate Relay UE) , and the relay terminal device 220-2 is referred to as the second relay terminal device or an U2N Relay UE.

It should be understood that in other embodiments, only two relay terminal devices 220 or more than three relay terminal devices 220 may be comprised, as illustrated in FIG. 2. The present disclosure is not limited in this regard.

In some example embodiments, a link from the network device 230 to the remote terminal device 210 is referred to as a downlink (DL) , while a link from the remote terminal device 210 to the network device 220 is referred to as an uplink (UL) . In DL, the network device 220 is a transmitting (TX) device (or a transmitter) and the terminal device 210 is a receiving (RX) device (or a receiver) . In UL, the terminal device 210 is a TX device (or a transmitter) and the network device 220 is a RX device (or a receiver) .

The communications in the communication environment 200 may conform to any suitable standards including, but not limited to, Global System for Mobile Communications (GSM) , Long Term Evolution (LTE) , LTE-Evolution, LTE-Advanced (LTE-A) , New Radio (NR) , Wideband Code Division Multiple Access (WCDMA) , Code Division Multiple Access (CDMA) , GSM EDGE Radio Access Network (GERAN) , Machine Type Communication (MTC) and the like. The embodiments of the present disclosure may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) communication protocols, 5.5G, 5G-Advanced networks, or the sixth generation (6G) networks.

It is to be understood that the number of devices and their connections shown in FIG. 2 are only for the purpose of illustration without suggesting any limitation. The communication environment 200 may include any suitable number of network devices and/or terminal devices adapted for implementations of example embodiments of the present disclosure. Although not shown, it would be appreciated that one or more additional devices may be located in the cell, and one or more additional cells may be deployed in the communication environment 200.

EXAMPLE PROCESSES

Reference is now made to FIG. 3, which illustrates a signaling flow 300 of communication according to some example embodiments of the present disclosure. In the example of FIG. 3, at Step 1, discovery message including information on multi-hop U2N relay may be exchanged. At Step 2a, a PC5 connection establishment procedure is performed, where the peer Remote UE is U2N Remote UE. At Step 2b, a PC5 connection establishment procedure is performed, where the peer Remote UE is U2N Relay UE. At Step 3 and Step 4, U2U relay procedures are performed.

With Step 5 to Step 12, Uu message is forwarded via specific (U2U) PC5 Relay RLC channel (s) for E2E PC5-RRC connection. With Step 13 and Step 14, the gNB may configure additional PC5 Relay RLC channels between L2 intermediate Relay UE and L2 U2N Relay UE, and PC5 Relay RLC channels between L2 intermediate Relay UE and L2 U2N Remote UE, for the relaying traffic.

It should be understood that FIG. 3 is an example process, which are only for the purpose of illustration without suggesting any limitations.

In in the following, more details will be discussed with reference is FIG. 2, for example, by using the remote terminal device 210, the first relay terminal device 220-1, the second relay terminal device 210-2 and the network device 230.

Further, the remote terminal device 210 may be referred to as a Remote UE, the first relay terminal device 220-1 may be referred to as U2U Reay UE, and the second relay terminal 220-2 may be referred to as U2N Relay UE sometimes.

According to some embodiments of the present discourse, the discovery procedure (Step 1 in FIG. 3) may be improved.

As discussed above, the discovery procedure may be performed with a Mode A manner and Mode B manner. In the following, examples of Mode A and Mode B will be discussed separately.

In a case of Mode A, in operation, the first relay terminal device 210-1 determines information about at least one second relay terminal device 210-2, where each second relay terminal device 220-2 is able to communicate with a network device 230 via a direct connection or able of performing as (or acting as) a user equipment (UE) -to-network (U2N) relay terminal device.

Then, the first relay terminal device 210-1 transmits the information about at least one second relay terminal device 210-2.

According to some embodiments of the present discourse, the first relay terminal device 210-1 needs to indicate the at least one second relay terminal device 210-2.

In one example, each second relay terminal device 210-2 is indicated by an indication that the second relay terminal device 210-2 is able to communicate with a network device 230 via a direct connection or able of performing as a U2N relay terminal device. For example, in a Discovery Announcement message, each second relay terminal device 210-2 is associated with 1-bit indication, which may be set with value 1.

In another example, the information about the at least one second relay terminal device 210-2 is associated with a specific relay service code (RSC) . For example, the Discovery Announcement message comprises a specific RSC, and the at least one second relay terminal device 210-2 is associated with the specific RSC. That is, the at least one second relay terminal device 210-2 is indicated by the specific RSC that the second relay terminal device 210-2 is able to communicate with a network device 230 via a direct connection or able of performing as a U2N relay terminal device.

In a further example, the information about the at least one second relay terminal device 210-2 is comprised in a specific information element or a discovery announcement message specific to a multi-hop U2N transmission. That is, the at least one second relay terminal device 210-2 is indicated by the specific information element or the discovery announcement message specific to a multi-hop U2N transmission that the second relay terminal device 210-2 is able to communicate with a network device 230 via a direct connection or able of performing as a U2N relay terminal device implicitly.

In some embodiments, for a second relay terminal device 210-2 of the at least one second relay terminal device 210-2, the first relay terminal device 210-1 may transmit further information about at least one of the following: a serving cell of the second relay terminal device 210-2, or a radio resource control (RRC) state of the second relay terminal device 210-2.

In a case of Mode B, in operation, the remote terminal device 210 generates a first solicitation message for discovering at least one second relay terminal device 210-2 being able to communicate with a network device 230 via a direct connection or able of performing as a U2N relay terminal device. Then, the remote terminal device 210 transmits the first solicitation message.

According to the present discourse, the remote terminal device 210 may indicate that the remote terminal device 210 aims to find a U2N Relay, such that a U2N transmission may be performed.

In one example, the first solicitation message may comprise an indication that the remote terminal device 210 aims to discover the at least one second relay terminal device 210-2.

In another example, the first solicitation message may comprise a specific relay service code (RSC) implying that the remote terminal device 210 aims to discover the at least one second relay terminal device 210-2.

In a further example, the first solicitation message may comprise a specific user identity, such as User Info ID or layer 2 ID or local ID, implying that the remote terminal device 210 aims to discover the at least one second relay terminal device 210-2.

Alternatively, or in addition, the first solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission.

As for the first relay terminal device 210-1, after receiving the first solicitation message, the first relay terminal device 210-1 may transmit a second solicitation message generated based on the first solicitation message by at least adding an identity of the first relay terminal device 210-1 to the first solicitation message. Alternatively, or in addition, the second solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission.

In some embodiments, the transmission of the second solicitation message may be performed conditionally. Specifically, the first relay terminal device 210-1 may transmit the second solicitation message if at least one of the following:

● the first solicitation message comprises the indication,

● the first solicitation message comprises the specific RSC,

● the first solicitation message comprises the specific user identity,

● the RSC indicated in the first solicitation message matches a pre-configured RSC,

● the first solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission,

● the first relay terminal device 210-1 is not able communicate with a network device 230 via a direct connection or not able of performing as a U2N relay terminal device,

● the first relay terminal device 210-1 is not able communicate with a network device 230 via a direct connection or not able of performing as a multi-hop U2N relay terminal device, or

● the first relay terminal device 210-1 is able communicate with a network device 230 via at least one another relay terminal device or able of performing as (or acting as or capable of) an intermediate relay terminal device for multi-hop transmission.

As for the second relay terminal device 210-2, as the second relay terminal device 210-2 is a U2N Relay UE, the U2N Relay UE may transmit a response accordingly.

Specifically, in operation, after reviving a second solicitation message for discovering at least one second relay terminal device 210-2 being able to communicate with a network device 230 via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, the second relay terminal device 210-2 transmits a first response to the second solicitation message. Alternatively, or in addition, the first response is a discovery response message specific to a multi-hop U2N transmission.

In some embodiments, the second relay terminal device 210-2 may transmit the first response to the second solicitation message if at least one of the following:

● the second solicitation message comprises the indication and the second relay terminal device 210-2 is able communicate with a network device 230 via a direct connection or able of performing as a multi-hop U2N relay terminal device,

● the second solicitation message comprises the specific RSC and the second relay terminal device 210-2 is able communicate with a network device 230 via a direct connection or able of performing as a multi-hop U2N relay terminal device,

● the second solicitation message comprises the specific user identity and the second relay terminal device 210-2 is able communicate with a network device 230 via a direct connection or able of performing as a multi-hop U2N relay terminal device,

● the RSC indicated in the second solicitation message matches a pre-configured RSC,

● the second solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission, or

● the second relay terminal device 210-2 is able communicate with a network device 230 via a direct connection or able of performing as a multi-hop U2N relay terminal device.

In some embodiments, the first response may comprise an identity of the second relay terminal device 210-2. In some other embodiments, the first response may comprise an identity of the second relay terminal device 210-2 and at least one of the following:

● a serving cell of the second relay terminal device 210-2, or

● a radio resource control (RRC) state of the second relay terminal device 210-2.

As for the first relay terminal device 210-1, after receiving the first response from a second relay terminal device 210-2, the first relay terminal device 210-1 may transmit a second response generated based on the first response by at least adding an identity of the first relay terminal device 210-1 to the first response. In some embodiments, the second response is a discovery response message specific to a multi-hop U2N transmission.

As a result, the remote terminal device 210 may receive the second response from a first relay terminal device 210-1.

According to the above processes, a multi-hop Relay discovery procedure is enabled.

In the following, how to transmit the U2N data between the remote terminal device 210 and the network device 230 will be discussed.

In operation, the remote terminal device 210 generates a packet for carrying Uu interface data of a signalling radio bearer (SRB) .

In some embodiments, the packet comprises a specific sidelink bearer (also referred to as Sidelink radio bearer or sidelink SRB) identity pre-defined for a Uu interface transmission. That is, specific SL SRBs are configured to the Uu SRB transmission. In this event, there is no need to configure specific RLC channel (s) for the Uu SRB transmission.

Alternatively, or in addition, in some other embodiments, the packet is submitted to a specific radio link control (RLC) channel pre-defined for a Uu interface transmission. That is, a specific RLC channel (s) are configured to the Uu SRB transmission. In this event, there is no need to configure specific SL SRB (s) for the Uu SRB transmission.

Alternatively, or in addition, in some other embodiments, the packet comprises a specific sidelink bearer identity pre-defined for a Uu interface transmission, and is submitted to a specific RLC channel pre-defined for a Uu interface transmission. In this event, both specific SL SRB (s) and specific RLC channel (s) are introduced.

Alternatively, or in addition, in some other embodiments, the packet comprises an indication that the packet carries the Uu interface data. In this event, there is no need to configure specific SL SRB (s) and specific RLC channel (s) for the Uu SRB transmission.

Further, different Uu interface data of a signalling radio bearer may be submitted to a same RLC channel (such as PC5 Relay RLC channel) or different RLC channels.

Specifically, in some embodiments, a first packet carrying Uu interface data of a signalling radio bearer with a first identity (such as SL-SRB 0) is submitted to a first RLC channel, and a second packet carrying Uu interface data of a signalling radio bearer with a second identity (such as, SRB 1/2) is submitted to a second RLC channel, the second RLC channel being different from or the same as the first RLC channel.

Further, the U2N transmission (or Uu interface transmission over/via Sidelink (connection) or E2E sidelink (connection) ) and the PC5/sidelink transmission (or E2E sidelink transmission, or E2E PC5 transmission) may be associated with different sets of sidelink bearer identities. Specifically, in some embodiments, a first set of sidelink bearer identities (such as, SL-SRB 0 to SL-SRB 3) may be defined for sidelink transmission, and a second set of sidelink bearer identities (such as, SL-SRB 4 to SL-SRB 6) may be defined for Uu interface transmission, the second set of sidelink bearer identities being different from the first set of sidelink bearer identities.

In order to enable such as an initial transmission, the remote terminal device 210, the first/second relay terminal device 220 need to apply a default configuration. These embodiments will be discussed separately.

In operation, the remote terminal device 210 applies a specific configuration for a Uu interface transmission in response to at least one of the following:

● an initiation a radio resource control (RRC) connection establishment, an RRC connection reestablishment or an RRC connection resuming procedure with a network device 230,

● a successful selection of a first relay terminal device 210-1,

● a successful selection of a second relay terminal device 210-2,

● an establishment of a connection with a first relay terminal device 210-1,

● an establishment of a connection with a second relay terminal device 210-2,

● an establishment of a connection between a first relay terminal device 210-1 and a second relay terminal device 210-2, or

● performing as (or acting as or capable of) a multi-hop user equipment (UE) -to-network (U2N) remote terminal device 210.

In operation, the first relay terminal device 210-1 applies a specific configuration for a Uu interface transmission in response to at least one of the following:

● an establishment of a connection with a remote terminal device 210,

● an establishment of a connection with a second relay terminal device 210-2, or

● performing as (or acting as or capable of) a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device.

In operation, the second relay terminal device 210-2 applies a specific configuration for a Uu interface transmission in response to at least one of the following:

● an establishment of a connection with a remote terminal device 210,

● an establishment of a connection with a first relay terminal device 210-1, or

● performing as (or acting as or capable of) a multi-hop user equipment (UE) -to-network (U2N) relay terminal device.

In some cases, the first relay terminal device 210-1/the second relay terminal device 210-2 may be in RRC idle/inactive state. If so, the first relay terminal device 210-1/the second relay terminal device 210-2 may be in RRC idle/inactive state needs to transition to the RRC connected state. In the following, these embodiments will be discussed separately.

In operation, the first relay terminal device 210-1 which is in RRC idle/inactive state initiates a transition to an RRC connected state in response to at least one of the following:

● a successful selection of a second relay terminal device 210-2,

● an establishment of a PC5-RRC connection with a remote terminal device 210,

● an establishment of a PC5-RRC connection with a second relay terminal device 210-2,

● performing as (or acting as or capable of) a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device,

● being indicated that the first relay terminal device 210-1 is selected for a multi-hop U2N transmission by one of the following: the remote terminal device 210, the second relay terminal device 210-2, an upper layer of the first relay terminal device 210-1, or

● receiving a message from the second relay terminal device 210-2 or the remote terminal device 210, the message requesting the second relay terminal device 210-2 to transition to the RRC connected state.

In some embodiments, the first relay terminal device 210-1 may transmit a message to the second relay terminal device 210-2, the message may request the second relay terminal device 210-2 to transition to the RRC connected state.

In operation, the second relay terminal device 210-2 which is in RRC idle/inactive state initiates a transition to an RRC connected state in response to at least one of the following:

● an establishment of a PC5-RRC connection with a remote terminal device 210,

● an establishment of a PC5-RRC connection with a first relay terminal device 210-1,

● performing as (or acting as or capable of a multi-hop user equipment (UE) -to-network (U2N) relay terminal device,

● receiving a PC5-RRC message or PC5-Signaling message from the remote terminal device 210, or

● receiving a message from the first relay terminal device 210-1, the message requesting the second relay terminal device 210-2 to transition to the RRC connected state.

EMBODIMENTS

Example embodiments will be further discussed with reference to FIG. 2 and FIG. 3. In the following discussions, the first relay terminal device 220-1 will be referred to as U2U Relay UE, intermediate Relay UE or U2U relay, the second relay terminal device 220-1 will be referred as U2N Relay UE, U2N relay or End UE or peer End UE, and the remote terminal device 210 will be referred as the Remote UE or end UE or peer End UE, the network device 230 will be referred as gNB.

It should be noted that below example embodiments are only for the purpose of illustration without suggesting any limitations. The present disclosure is not limited in this regard.

Example discovery processes (such as, step 1 in FIG. 3) will be discussed in the following. In a case of Mode A, in operation, the first relay terminal device 220-1 may provide information of U2N Relay UE (s) . In particular, the first relay terminal device 220-1 may connect to or is connecting to gNB via at least one another Relay UE.

In some embodiments, the existing U2U Relay Discovery Announcement message may be reused by suitable enhancements. Specifically, U2U Relay UE may send a U2U Relay Discovery Announcement message comprising the user information ID or layer 2 ID or local ID of at least one (5G ProSe) End UE (such as U2N Relay UE) which is able to connect/is connecting to gNB directly, or is performing/to perform as a U2N relay or not.

Additionally, each End UE is associated with an indication (such as, a 1-bit flag) . In one specific scenario, the U2U Relay Discovery Announcement message may comprise UE#1, UE#2 and UE#3, where the UE#3 is able to connect/is connecting to gNB directly, or is performing/to perform as a U2N relay. The UE#3 may be associated with an indication (such as, a 1-bit flag with value ‘1’ ) . Alternatively, or in addition, the UE#2 and UE#3 may be not associated with the indication or associated with an indication (such as, a 1-bit flag with value ‘0’ ) .

As another example, the U2U Relay Discovery Announcement message may comprise a specific RSC, where the specific RSC may imply the associated UE is a U2N relay. Also refer to the above specific scenario, the UE#3 may be associated with the specific RSC.

As another example, the U2U Relay Discovery Announcement message may comprise a specific information element (IE) , where the specific IE may imply the associated UE is a U2N relay. Also refer to the above specific scenario, the UE#3 may be comprised in this specific IE.

Alternatively, in some embodiment, a new Discovery Announcement message may be introduced for indicating the U2N relay. In this event, the U2U Relay UE may send a multi-hop U2N Relay Discovery Announcement message comprising the user information ID of at least one (5G ProSe) end UE which is able to connect/is connecting to gNB directly, or is performing/to perform as a U2N Relay UE. That is, using the message type to indicate those UEs with User Info ID indicated by this massage are performing/to perform as U2N Relay UE.

Regardless of whether to indicate the user information ID of at least one (5G ProSe) end UE via an existing or new Discovery Announcement message, bellow information may be indicated additionally, the serving cell of this End UE, and/or the RRC state of the End UE.

In this way, the remote UE may determine which relay terminal device (s) is U2N relay terminal device, such as the U2N relay terminal device for multi-hop transmission.

Example discovery processes of Mode B will be discussed in the following. In operation, the remote UE (i.e., the discoverer) may request a U2N Relay UE (s) .

In some embodiments, an existing Discovery Solicitation message may be reused. In this event, the discoverer end UE may send a U2U Relay Discovery Solicitation message #1 which contains at least one of the following:

● an indication indicating the end UE aims to discover a (multi-hop) U2N relay,

● a specific RSC for multi-hop U2N relay, or

● a specific User information ID of peer end UE for multi-hop U2N relay. Alternatively, or in addition, a specific layer2 ID/local ID of peer end UE for multi-hop U2N relay.

As for the U2U Relay, after receiving the U2U Relay Discovery Solicitation message #1, the U2U Relay may send another U2U Relay Discovery Solicitation message (called as U2U Relay Discovery Solicitation message #2) if one of the following:

● the UE-to-UE Relay Discovery Solicitation message #1 includes an indication indicating the end UE aims to discover a (multi-hop) U2N relay;

● the RSC contained in the U2U Relay Discovery Solicitation message #1 is/matches the Specific RSC for multi-hop U2N relay. That is, the RSC contained in the UE-to-UE Relay Discovery Solicitation message #1 matches any of the (pre) configured RSC (s) ,

● user information ID of the discoveree end UE contained in the UE-to-UE Relay Discovery Solicitation message #1 is/matches the specific User information ID for multi-hop U2N relay. As one example, the user information ID contained in the U2U Relay Discovery Solicitation message #1 matches any of the (pre) configured User information ID(s) .

In some embodiments, the U2U Relay Discovery Solicitation message #2 may contain at least one of the following:

● an identify of the U2U relay,

● a specific RSC for multi-hop U2N relay, or

As for the U2N relay (such as, discoveree 5G ProSe end UE/the second relay terminal device 220-2) , after receiving the U2U Relay Discovery Solicitation message #2, the U2N relay may respond (to the U2U Relay) with a 5G ProSe U2U Relay Discovery Response message if one of the following:

● the U2N relay is performing/to perform as a U2N Relay UE;

● the U2N relay is able to connect/is connecting to gNB directly;

● the UE-to-UE Relay Discovery Solicitation message #2 includes an indication indicating the end UE aims to discover a (multi-hop) U2N relay;

● the RSC contained in the U2U Relay Discovery Solicitation message #2 is/matches the Specific RSC for multi-hop U2N relay. That is, the RSC contained in the U2U Relay Discovery Solicitation message #2 matches any of the (pre) configured RSC (s) ;

● user information ID of the discoveree end UE contained in the U2U Relay Discovery Solicitation message #2 is/matches the specific User information ID for multi-hop U2N relay. As one example, the user information ID contained in the UE-to-UE Relay Discovery Solicitation message #2 matches any of the (pre) configured User information ID(s) .

In some embodiments, the U2U Relay Discovery Response may contain the Type of Discovery Message, RSC, User Info ID of the discoverer 5G ProSe End UE (i.e., the remote terminal device 210) and User Info ID of discoveree 5G ProSe End UE (i.e., the U2N relay) .

Additionally, in some embodiments, the U2U Relay Discovery Response may contain the serving cell of the discoveree 5G ProSe End UE ( (i.e., the U2N relay) , or RRC state of the discoveree 5G ProSe End UE (i.e., the U2N relay) .

Additionally, the U2U relay may receive multi-hop U2N Relay Discovery Response message and send another Response message (for example, adding an identity of the U2U relay) to the discoverer End UE (the remote terminal device 210) .

Alternatively, in some embodiment, a new Discovery Announcement message (called as multi-hop U2N Relay Discovery Solicitation message) may be introduced, the new message may indicate that the end UE is requesting a multi-hop U2N Relay UE) .

In operation, the discoverer End UE (remote terminal device 210) may send a multi-hop U2N Relay Discovery Solicitation message. In some embodiment, the multi-hop U2N Relay Discovery Solicitation message #1 may include at least one of the following:

● a specific RSC for multi-hop U2N relay, or

● a specific User information ID of peer end UE for multi-hop U2N relay.

As for the U2U Relay, after receiving the multi-hop U2N Relay Discovery Solicitation message #1, the U2U Relay may send another UE-to-UE Relay Discovery Solicitation message (called as multi-hop U2N Relay Discovery Solicitation message #2) if one of the following:

● determine that the message type is for multi-hop U2N Relay,

● the multi-hop U2N Relay Discovery Solicitation message #1 includes an indication indicating the end UE aims to discover a (multi-hop) U2N relay;

● the RSC contained in the multi-hop U2N Relay Discovery Solicitation message #1 is/matches the Specific RSC for multi-hop U2N relay. That is, the RSC contained in the UE-to-UE Relay Discovery Solicitation message #1 matches any of the (pre) configured RSC(s) ,

● user information ID of the discoveree end UE contained in the U2N Relay Discovery Solicitation message #1 is/matches the specific User information ID for multi-hop U2N relay. As one example, the user information ID contained in the multi-hop U2N Relay Discovery Solicitation message #1 matches any of the (pre) configured User information ID(s) .

As for the U2N relay (such as, discoveree 5G ProSe end UE/the second relay terminal device 220-2) , after receiving the multi-hop U2N Relay Discovery Solicitation message #2, the U2N relay may respond (to the U2U Relay) with a 5G ProSe multi-hop U2N Relay Discovery Response message if one of the following:

● the U2N relay is performing/to perform as a U2N Relay UE;

● the U2N relay is able to connect/is connecting to gNB directly;

● the multi-hop U2N Relay Discovery Solicitation message #2 includes an indication indicating the end UE aims to discover a (multi-hop) U2N relay;

● the RSC contained in the multi-hop U2N Relay Discovery Solicitation message #2 is/matches the Specific RSC for multi-hop U2N relay. That is, the RSC contained in the multi-hop U2N Relay Discovery Solicitation message #2 matches any of the (pre) configured RSC (s) ;

● user information ID of the discoveree end UE contained in the multi-hop U2N Relay Discovery Solicitation message #2 is/matches the specific User information ID for multi-hop U2N relay. As one example, the user information ID contained in the multi-hop U2N Relay Discovery Solicitation message #2 matches any of the (pre) configured User information ID (s) .

In some embodiments, the multi-hop U2N Relay Discovery Response may contain the Type of Discovery Message, RSC, User Info ID of the discoverer 5G ProSe End UE (i.e., the remote terminal device 210) and User Info ID of discoveree 5G ProSe End UE (i.e., the U2N relay) .

Additionally, in some embodiments, the multi-hop U2N Relay Discovery Response may contain the serving cell of the discoveree 5G ProSe End UE ( (i.e., the U2N relay) , or RRC state of the discoveree 5G ProSe End UE (i.e., the U2N relay) .

Additionally, the U2U relay may receive multi-hop U2N Relay Discovery Response message and send another Response message (for example, adding an identity of the U2U relay) to the discoverer End UE (for example, the remote terminal device 210) .

In the following, how to transmit the Uu SRB (s) to the gNB will be discussed with reference to Step 2a to Step 8 in FIG. 3. In a case of original Uu SRB transmission, as there is no RRC configuration, the original Uu SRB transmission may be performed via a default/specific configuration. As one example embodiments, an (Uu) RRC signalings via (Uu) SRB0 (such as RRC SetupRequest and RRC Setup) may be transmitted via,

● a new SL-U2U-RLC, such as SL-U2U-RLC2 /SL-U2U-RLC1, according to a default/specific configuration (for example, the SL-U2U RLC may using Acknowledged mode (AM) or Unacknowledged (UM) and the logical channel ID value with 54 or 39) ;

● a new SL-SRB, such as SL-SRB5, and transmitted via legacy SL-U2U-RLC. That is, (Uu) RRC signalings are forwarded via new SL-SRB, which is transmitted via the SL-U2U-RLC;

● a legacy SL-U2U-RLC and legacy SL-SRB, while an indication (such as, an IE or a container) may be included to indicate the Uu SRB (s) ;

● a new SL-SRB, such as (E2E) SL-SRB5, and a new SL-U2U-RLC, such as SL-U2U-RLC2 /SL-U2U-RLC1. That is, (Uu) RRC signalings are forwarded via new SL-SRB, which is transmitted via the new SL-U2U-RLC2.

Additionally, in some embodiments, different (Uu) SRBs may be mapped to the same RLC or different RLCs.

In some embodiments, the RRC signalings via (Uu) SRB1 (such as RRC Setup Complete, SecurityModeCommand and RRCReconfiguration) are transmitted via at least one of the following:

● another new SL-U2U-RLC different from that for (Uu) SRB0, such as SL-U2U-RLC 3, according to a default/specific configuration;

● another new SL-U2U-RLC, different from that for (Uu) SRB0 such as SL-U2U-RLC 3, and another new SL-SRB different from that for (Uu) SRB0, such as SL-SRB6. That is, (Uu) RRC signalings are forward via new SL-SRB, which is transmitted via the new SL-U2U-RLC#2;

● a legacy SL-U2U-RLC and legacy SL-SRB, while an indication (such as, an IE or a container) may be included to indicate the Uu SRBx.

Additionally, (Uu) SRB2 (such as NAS signalling) may have related SL-U2U-RLC channel different from or the same as that of the SRB0/SRB1.

Additionally, in some embodiments, the index/bearer ID in SDAP PDU for Uu SRB(s) may be fixed, such as bearer ID for (Uu) SRB0 is 4, bearer ID for (Uu) SRB1 is 5 and bearer ID for (Uu) SRB2 is 6.

In some embodiments, all Uu SRBx may be forwarded via the same new SL-U2U-RLC/SL-SRBx.

As discussed above, the Uu RRC signalling needs to be transmitted according to the specific/default configuration. For example, at Step 5 of FIG. 3, the RRC SetupRequest for Remote UE need to be transmitted to the gNB via the U2N relay according to the specific/default configuration. In view of this, the remote UE, the U2U relay UE and the U2N relay need to apply the specific/default configuration at proper timepoints.

As for the U2N Remote UE, in some embodiments, the specific/default configuration may be applied upon initiation of the (RRC connection establishment) procedure.

In some embodiments, if the UE is acting as L2 U2N Remote UE, the UE always apply the default/specified configuration of new SL-U2U-RLC and/or another new SL-U2U-RLC.

Alternatively, or in addition, in some embodiments, if the UE is for/capable of multi-hop U2N relay, or if the UE selects a U2N Relay UE via at least one intermediate Relay UE (multi-hop U2N Relay UE) or if has established a Link with U2N Relay UE, the UE applies the default/specified configuration of new SL-U2U-RLC and/or another new SL-U2U-RLC.

Alternatively, or in addition, in some embodiments, the specific/default configuration may be applied upon a PC5-RRC connection establishment between (U2U) Remote UE the L2 U2U Relay UE (such as, Step2a in FIG. 3) .

In some embodiments, upon a PC5-RRC connection establishment, the UE always applies the default/specified configuration of new SL-U2U-RLC.

Alternatively, or in addition, in some embodiments, if the U2U Relay UE is acting as intermediate Relay UE and/or if the UE is U2N Remote UE, the UE may apply the default/specified configuration of new SL-U2U-RLC and/or another new SL-U2U-RLC.

As for the U2U Relay UE, in some embodiments, if the UE is acting as intermediate Relay UE, the UE always applies the default/specified configuration of new SL-U2U-RLC and/or another new SL-U2U-RLC.

Alternatively, or in addition, in some embodiments, if the Relay UE supports/is for/capable of multi-hop U2N relay transmission (not act as U2N Relay) , the UE may apply the default/specified configuration of new SL-U2U-RLC and/or another new SL-U2U-RLC.

Alternatively, or in addition, in some embodiments, the specific/default configuration may be applied upon PC5-RRC connection establishment between Remote UE and U2U Relay UE, and PC5-RRC connection establishment between U2U Relay UE and peer Remote UE (such as the U2N Relay UE) , and PC5-RRC connection establishment between U2U Relay UE and another U2U Relay UE (such as, Step2a and Step2b in FIG. 3) .

In some embodiments, the UE always applies the default/specified configuration of new SL-U2U-RLC and/or another new SL-U2U-RLC upon PC5-RRC connection establishment between Remote UE and U2U Relay UE.

Alternatively, or in addition, in some embodiments, if the U2U Relay UE is acting as intermediate Relay UE, and/or if the Remote UE is U2N Remote UE, and/or if the peer Remote UE is U2N Relay UE, and/or if the another U2U Relay UE is U2N Relay UE, the UE may apply the default/specified configuration of new SL-U2U-RLC and/or another new SL-U2U-RLC.

As for the U2N Relay UE, in some embodiments, if the UE is acting as U2N Relay UE or U2N Relay UE for multi-hop (transmission) , the UE may always apply the default/specified configuration of new SL-U2U-RLC and/or another new SL-U2U-RLC.

Alternatively, or in addition, in some embodiments, if the UE is for/capable of multi-hop U2N relay and/or if the UE is configured to be multi-hop U2N Relay UE, the UE may apply the default/specified configuration of new SL-U2U-RLC and/or another new SL-U2U-RLC.

Alternatively, or in addition, in some embodiments, upon PC5-RRC connection establishment between U2N Relay UE and Remote UE/U2U Relay UE (such as, Step2b in FIG. 3) , the UE may always apply the default/specified configuration of new SL-U2U-RLC and/or another new SL-U2U-RLC.

Alternatively, or in addition, in some embodiments, if the Remote UE/U2U Relay UE is acting as intermediate Relay UE, the UE may apply the default/specified configuration of new SL-U2U-RLC and/or another new SL-U2U-RLC.

It should be noted that the above mentioned procedure may also include: RRC connection reestablishment procedure and/or RRC connection resume procedure.

In some embodiments, a relay terminal device in a multi-hop U2N transmission may be in an RRC idle or inactive state. In this event, the relay terminal device needs to enter in the RRC connected state as discussed below.

In some embodiments, as for an L2 U2N Relay UE in RRC_IDLE (such as, Step5 in FIG. 3) , an RRC connection establishment is initiated in the following cases:

● if any message is received from the U2N Remote UE via a new SL-U2U-RLC, such as SL-U2U-RLC1 or SL-U2U-RLC2;

● if E2E PC5-RRC connection is established, such as for a Remote UE via another intermediate Relay UE, or

● if RemoteUEInformationSidelink containing the connectionForMultihop (U2N) is received from a U2N Remote UE or the intermediate Relay UE. That is, triggered by U2N remote UE or the intermediate Relay UE with a PC5-RRC message or a PC5-Signaling (PC5-S) message.

In some embodiments, as for U2N Relay UE in RRC_INACTIVE, an RRC connection establishment is resumed in the following cases:

Alternatively, only U2N Relay UE in RRC_CONNECTED can be selected by Remote UE for multi-hop U2N relay.

In addition to the U2N relay terminal device, the U2U relay terminal device also needs to transition to the RRC connected state to enable the U2N transmission, for example, to receive the dedicated configuration from the network device for the U2N transmission.

In some embodiments, as for U2U Relay UE in RRC_IDLE, an RRC connection establishment is initiated (or as for a U2U Relay UE in RRC_INACTIVE, an RRC connection establishment is resumed) if at least one of the following:

● (indication#0) its upper layer (such as PC5-S, ProSe, V2X, NAS) indicates it is selected for multi-hop U2N relay transmission/to perform as intermediate Relay UE (for multi-hop U2N relay transmission) ,

● if the PC5 connection with U2N Relay UE is established, such as for multi-hop U2N relay transmission,

● if the PC5 connection between the U2U Relay UE and U2N Remote is established, such as, step 2a in FIG. 3,

● (indication#1) If it is indicated by Remote UE or U2N Relay UE an E2E PC5 connection is established (for multi-hopU2N relay transmission or between Remote UE and U2N Relay UE via a PC5-RRC signaling, such as RemoteUEInformationSidelink or new PC5-RRC signaling, or via SCI, MAC CE, control PDU of RLC,

● (indication#2) if it is indicated by Remote UE or U2N Relay UE that it is selected for multi-hop U2N relay transmission,

● if the U2U Relay UE is connected to an U2N Relay UE directly, or

● if it determines that it is performing as intermediate Relay UE (for multi-hop U2N relay) , such as determined by the following cases: local ID is assigned to U2N Remote UE, or local ID pairs are assigned for multi-hop U2N Relay and Remote UE.

Alternatively, only U2U Relay UE in RRC_CONNECTED can be selected by Remote UE for multi-hop U2N relay transmission.

In some embodiments, the U2U relay may trigger the U2N Relay UE transition to the RRC connected state.

As discussed above, the U2U Relay UE may initiate RRC connection establishment procedure or RRC connection resume procedure. Then the legacy method (such asēmessages via SL-RLC0 or SL-RLC1) will trigger U2N Relay UE to enter RRC_CONNECTED.

Alternatively, in some embodiments, the U2U Relay UE may send an indication to trigger U2N Relay UE entering to the RRC connected state, via PC5-RRC signaling.

In some embodiments, U2U Relay UE may trigger U2N Relay UE entering to the RRC connected state if at least one of the following:

● (indication#0) its upper layer indicates it is selected for multi-hop U2N relay transmission/to perform as intermediate Relay UE (for multi-hop U2N relay transmission) ,

● (indication#1) If it is indicated by Remote UE or U2N Relay UE an E2E PC5 connection is established ( for multi-hopU2N relay transmission or between Remote UE and U2N Relay UE via a PC5-RRC signaling, such as RemoteUEInformationSidelink or new PC5-RRC signaling, or via SCI, MAC CE, control PDU of RLC,

● (indication#2) if it is indicated by Remote UE or U2N Relay UE that it is selected for multi-hop U2N relay,

● if the U2U Relay UE is connected to an U2N Relay directly, or,

EXAMPLE METHODS

FIG. 4 illustrates a flowchart of a communication method 400 implemented at a first relay terminal device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 400 will be described from the perspective of the first relay terminal device in FIG. 2.

At block 410, the first relay terminal device determines information about at least one second relay terminal device, wherein each second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device.

At block 420, transmit the information about at least one second relay terminal device. Each second relay terminal device is indicated by an indication that the second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, the information about the at least one second relay terminal device is associated with a specific relay service code (RSC) , or the information about the at least one second relay terminal device is comprised in a specific information element or a discovery announcement message specific to a multi-hop U2N transmission.

In some example embodiments, the processor is further configured to cause the first relay terminal device to: for a second relay terminal device of the at least one second relay terminal device, transmit further information about at least one of the following: a serving cell of the second relay terminal device, or a radio resource control (RRC) state of the second relay terminal device.

FIG. 5 illustrates a flowchart of a communication method 500 implemented at a remote terminal device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 500 will be described from the perspective of the remote terminal device in FIG. 2.

At block 510, the remote terminal device generates a first solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device. The first solicitation message comprises an indication that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the first solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission.

At block 520, the remote terminal device transmits the first solicitation message.

In some example embodiments, the processor is further configured to cause the remote terminal device to: receive a second response from a first relay terminal device, the second response comprises an identity of the second relay terminal device and at least one of the following: a serving cell of the second relay terminal device, a radio resource control (RRC) state of the second relay terminal device, or the second response is a discovery response message specific to a multi-hop U2N transmission, wherein the first relay terminal device is a multi-hop UE-to UE (U2U) relay terminal device.

FIG. 6 illustrates a flowchart of a communication method 600 implemented at a first relay terminal device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 600 will be described from the perspective of the first relay terminal device in FIG. 2.

At block 610, the first relay terminal device revives a first solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device. The first solicitation message comprises an indication that the remote terminal device aims to discover at least one second relay terminal device, the first solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the first solicitation message is a discovery solicitation message dedicated to a multi-hop U2N transmission.

At block 620, the first relay terminal device transmits a second solicitation message generated based on the first solicitation message by at least adding an identity of the first relay terminal device to the first solicitation message.

In some example embodiments, the first relay terminal device may transmit the second solicitation message if at least one of the following: the first solicitation message comprises the indication, the first solicitation message comprises the specific RSC, the first solicitation message comprises the specific user identity, the RSC indicated in the first solicitation message matches a pre-configured RSC, the first solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission, the first relay terminal device is not able communicate with a network device via a direct connection or not able of performing as a multi-hop U2N relay terminal device, or the first relay terminal device is able communicate with a network device via at least one another relay terminal device or able of performing as an intermediate relay terminal device for multi-hop transmission.

In some example embodiments, the first relay terminal device may receive a first response from a second relay terminal device of the at least one second relay terminal device, the first response comprising an identity of the second relay terminal device and at least one of the following: a serving cell of the second relay terminal device, or a radio resource control (RRC) state of the second relay terminal device; and transmit a second response generated based on the first response by at least adding an identity of the first relay terminal device to the first response.

FIG. 7 illustrates a flowchart of a communication method 700 implemented at a second relay terminal device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 700 will be described from the perspective of the second relay terminal device in FIG. 2.

At block 710, the second relay terminal device revives a second solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device. The second solicitation message comprises an indication that the remote terminal device aims to discover the at least one second relay terminal device, the second solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the second solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the second solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission.

At block 720, the second relay terminal device transmits, a first response to the second solicitation message.

In some example embodiments, the second relay terminal device may transmit the first response to the second solicitation message if at least one of the following: the second solicitation message comprises the indication and the second relay terminal device is able communicate with a network device via a direct connection or able of performing as a multi-hop U2N relay terminal device, the second solicitation message comprises the specific RSC and the second relay terminal device is able communicate with a network device via a direct connection or able of performing as a multi-hop U2N relay terminal device, the second solicitation message comprises the specific user identity and the second relay terminal device is able communicate with a network device via a direct connection or able of performing as a multi-hop U2N relay terminal device, the RSC indicated in the second solicitation message matches a pre-configured RSC, the second solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission, or the second relay terminal device is able communicate with a network device 230 via a direct connection or able of performing as a multi-hop U2N relay terminal device.

In some example embodiments, the first response comprises an identity of the second relay terminal device and at least one of the following: a serving cell of the second relay terminal device, or a radio resource control (RRC) state of the second relay terminal device.

FIG. 8 illustrates a flowchart of a communication method 800 implemented at a remote terminal device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 800 will be described from the perspective of the remote terminal device in FIG. 2.

At block 810, the remote terminal device generates a packet for carrying Uu interface data of a signalling radio bearer (SRB) . The packet comprising a specific sidelink bearer identity pre-defined for a Uu interface transmission, or the packet is submitted to a specific radio link control (RLC) channel pre-defined for a Uu interface transmission, or the packet comprises an indication that the packet carries the Uu interface data.

In some example embodiments, a first packet carrying Uu interface data of a signalling radio bearer with a first identity is submitted to a first RLC channel, and a second packet carrying Uu interface data of a signalling radio bearer with a second identity is submitted to a second RLC channel, the second RLC channel being different from or the same as the first RLC channel.

In some example embodiments, a first set of sidelink bearer identities are defined for sidelink transmission, and a second set of sidelink bearer identities are defined for Uu interface transmission, the second set of sidelink bearer identities being different from the first set of sidelink bearer identities.

FIG. 9 illustrates a flowchart of a communication method 900 implemented at a remote terminal device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 900 will be described from the perspective of the remote terminal device in FIG. 2.

At block 910, the remote terminal device applies a specific configuration for a Uu interface transmission in response to at least one of the following: an initiation a radio resource control (RRC) connection establishment, an RRC connection reestablishment or an RRC connection resuming procedure with a network device, a successful selection of a first relay terminal device, a successful selection of a second relay terminal device, an establishment of a connection with a first relay terminal device, an establishment of a connection with a second relay terminal device, an establishment of a connection between a first relay terminal device and a second relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) remote terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, the first relay terminal device is a multi-hop U2N intermediate relay terminal device.

FIG. 10 illustrates a flowchart of a communication method 1000 implemented at a first relay terminal device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 1000 will be described from the perspective of the first relay terminal device in FIG. 2.

At block 1010, the first relay terminal device applies a specific configuration for a Uu interface transmission in response to at least one of the following: an establishment of a connection with a remote terminal device, an establishment of a connection with a second relay terminal device, or performing as a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2U relay terminal device.

FIG. 11 illustrates a flowchart of a communication method 2100 implemented at a second relay terminal device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 2100 will be described from the perspective of the second relay terminal device in FIG. 2.

At block 1110, the second relay terminal device applies a specific configuration for a Uu interface transmission in response to at least one of the following: an establishment of a connection with a remote terminal device, an establishment of a connection with a first relay terminal device, or performing as a multi-hop user equipment (UE) -to-network (U2N) relay terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2U relay terminal device.

FIG. 12 illustrates a flowchart of a communication method 2200 implemented at a second relay terminal device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 2200 will be described from the perspective of the second relay terminal device in FIG. 2.

At block 1210, in accordance with a determination that the second relay terminal device is in a radio resource control (RRC) idle state or an RRC inactive state, the second relay terminal device initiates a transition to an RRC connected state in response to at least one of the following: an establishment of a PC5-RRC connection with a remote terminal device, an establishment of a PC5-RRC connection with a first relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) relay terminal device, receiving a PC5-RRC message or PC5-Signaling message from the remote terminal device, or receiving a message from the first relay terminal device, the message requesting the second relay terminal device to transition to the RRC connected state, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device.

FIG. 13 illustrates a flowchart of a communication method 2300 implemented at a first relay terminal device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 2300 will be described from the perspective of the first relay terminal device in FIG. 2.

At block 1310, in accordance with a determination that the first relay terminal device is in a radio resource control (RRC) idle state or an RRC inactive state, the first relay terminal device initiates a transition to an RRC connected state in response to at least one of the following: a successful selection of a second relay terminal device, an establishment of a PC5-RRC connection with a remote terminal device, an establishment of a PC5-RRC connection with a second relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device, being indicated that the first relay terminal device is selected for a multi-hop U2N transmission by one of the following: the remote terminal device, the second relay terminal device, an upper layer of the first relay terminal device, receiving a message from the second relay terminal device or the remote terminal device, the message requesting the second relay terminal device to transition to the RRC connected state, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device.

In some example embodiments, the first relay terminal device may transmit a message to the second relay terminal device, the message requesting the second relay terminal device to transition to the RRC connected state.

EXAMPLE DEVICES AND APPARATUS

FIG. 14 is a simplified block diagram of a device 1400 that is suitable for implementing embodiments of the present disclosure. The device 1400 can be considered as a further example implementation of any of the devices as shown in FIG. 2. Accordingly, the device 1400 can be implemented at or as at least a part of the remote terminal device 210, the relay terminal device 210-1 or the relay terminal device 220-2 or the network device 220.

As shown, the device 1400 includes a processor 1410, a memory 1420 coupled to the processor 1410, a suitable transceiver 1440 coupled to the processor 1410, and a communication interface coupled to the transceiver 1440. The memory 1420 stores at least a part of a program 1430. The transceiver 1440 may be for bidirectional communications or a unidirectional communication based on requirements. The transceiver 1440 may include at least one of a transmitter 1442 and a receiver 1444. The transmitter 1442 and the receiver 1444 may be functional modules or physical entities. The transceiver 1440 has at least one antenna to facilitate communication, though in practice an Access Node mentioned in this application may have several ones. The communication interface may represent any interface that is necessary for communication with other network elements, such as X2/Xn interface for bidirectional communications between eNBs/gNBs, S1/NG interface for communication between a Mobility Management Entity (MME) /Access and Mobility Management Function (AMF) /SGW/UPF and the eNB/gNB, Un interface for communication between the eNB/gNB and a relay node (RN) , or Uu interface for communication between the eNB/gNB and a terminal device.

The program 1430 is assumed to include program instructions that, when executed by the associated processor 1410, enable the device 1400 to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to FIGS. 1 to 14. The embodiments herein may be implemented by computer software executable by the processor 1410 of the device 1400, or by hardware, or by a combination of software and hardware. The processor 1410 may be configured to implement various embodiments of the present disclosure. Furthermore, a combination of the processor 1410 and memory 1420 may form processing means 1450 adapted to implement various embodiments of the present disclosure.

The memory 1420 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer readable storage medium, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one memory 1420 is shown in the device 1400, there may be several physically distinct memory modules in the device 1400. The processor 1410 may be of any type suitable to the local technical network, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 1400 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

According to embodiments of the present disclosure, a first relay terminal device comprising a circuitry is provided. The circuitry is configured to: determine information about at least one second relay terminal device, wherein each second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device; and transmit the information about at least one second relay terminal device, wherein, each second relay terminal device is indicated by an indication that the second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, the information about the at least one second relay terminal device is associated with a specific relay service code (RSC) , or the information about the at least one second relay terminal device is comprised in a specific information element or a discovery announcement message specific to a multi-hop U2N transmission. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the first relay terminal device as discussed above.

According to embodiments of the present disclosure, a remote terminal device comprising a circuitry is provided. The circuitry is configured to: generate a first solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, the first solicitation message comprises an indication that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the first solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission; and transmit the first solicitation message. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the remote terminal device as discussed above.

According to embodiments of the present disclosure, a first relay terminal device comprising a circuitry is provided. The circuitry is configured to: revive a first solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, the first solicitation message comprises an indication that the remote terminal device aims to discover at least one second relay terminal device, the first solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the first solicitation message is a discovery solicitation message dedicated to a multi-hop U2N transmission; transmit a second solicitation message generated based on the first solicitation message by at least adding an identity of the first relay terminal device to the first solicitation message. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the first relay terminal device as discussed above.

According to embodiments of the present disclosure, a second relay terminal device comprising a circuitry is provided. The circuitry is configured to: revive a second solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, the second solicitation message comprises an indication that the remote terminal device aims to discover the at least one second relay terminal device, the second solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the second solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the second solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission; and transmit, a first response to the second solicitation message. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the second relay terminal device as discussed above.

According to embodiments of the present disclosure, a remote terminal device comprising a circuitry is provided. The circuitry is configured to: generate a packet for carrying Uu interface data of a signalling radio bearer (SRB) , wherein, the packet comprising a specific sidelink bearer identity pre-defined for a Uu interface transmission, or the packet is submitted to a specific radio link control (RLC) channel pre-defined for a Uu interface transmission, or the packet comprises an indication that the packet carries the Uu interface data. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the remote terminal device as discussed above.

According to embodiments of the present disclosure, a remote terminal device comprising a circuitry is provided. The circuitry is configured to: apply a specific configuration for a Uu interface transmission in response to at least one of the following: an initiation a radio resource control (RRC) connection establishment, an RRC connection reestablishment or an RRC connection resuming procedure with a network device, a successful selection of a first relay terminal device, a successful selection of a second relay terminal device, an establishment of a connection with a first relay terminal device, an establishment of a connection with a second relay terminal device, an establishment of a connection between a first relay terminal device and a second relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) remote terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the remote terminal device as discussed above.

According to embodiments of the present disclosure, a first relay terminal device comprising a circuitry is provided. The circuitry is configured to: apply a specific configuration for a Uu interface transmission in response to at least one of the following: an establishment of a connection with a remote terminal device, an establishment of a connection with a second relay terminal device, or performing as a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2U relay terminal device. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the first relay terminal device as discussed above.

According to embodiments of the present disclosure, a second relay terminal device comprising a circuitry is provided. The circuitry is configured to: apply a specific configuration for a Uu interface transmission in response to at least one of the following: an establishment of a connection with a remote terminal device, an establishment of a connection with a first relay terminal device, or performing as a multi-hop user equipment (UE) -to-network (U2N) relay terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2U relay terminal device. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the second relay terminal device as discussed above.

According to embodiments of the present disclosure, a second relay terminal device comprising a circuitry is provided. The circuitry is configured to: in accordance with a determination that the second relay terminal device is in a radio resource control (RRC) idle state or an RRC inactive state, initiate a transition to an RRC connected state in response to at least one of the following: an establishment of a PC5-RRC connection with a remote terminal device, an establishment of a PC5-RRC connection with a first relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) relay terminal device, receiving a PC5-RRC message or PC5-Signaling message from the remote terminal device, or receiving a message from the first relay terminal device, the message requesting the second relay terminal device to transition to the RRC connected state, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the second relay terminal device as discussed above.

According to embodiments of the present disclosure, a first relay terminal device comprising a circuitry is provided. The circuitry is configured to: in accordance with a determination that the first relay terminal device is in a radio resource control (RRC) idle state or an RRC inactive state, initiate a transition to an RRC connected state in response to at least one of the following: a successful selection of a second relay terminal device, an establishment of a PC5-RRC connection with a remote terminal device, an establishment of a PC5-RRC connection with a second relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device, being indicated that the first relay terminal device is selected for a multi-hop U2N transmission by one of the following: the remote terminal device, the second relay terminal device, an upper layer of the first relay terminal device, receiving a message from the second relay terminal device or the remote terminal device, the message requesting the second relay terminal device to transition to the RRC connected state, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device. According to embodiments of the present disclosure, the circuitry may be configured to perform any method implemented by the first relay terminal device as discussed above.

The term “circuitry” used herein may refer to hardware circuits and/or combinations of hardware circuits and software. For example, the circuitry may be a combination of analog and/or digital hardware circuits with software/firmware. As a further example, the circuitry may be any portions of hardware processors with software including digital signal processor (s) , software, and memory (ies) that work together to cause an apparatus, such as a terminal device or a network device, to perform various functions. In a still further example, the circuitry may be hardware circuits and or processors, such as a microprocessor or a portion of a microprocessor, that requires software/firmware for operation, but the software may not be present when it is not needed for operation. As used herein, the term circuitry also covers an implementation of merely a hardware circuit or processor (s) or a portion of a hardware circuit or processor (s) and its (or their) accompanying software and/or firmware.

According to embodiments of the present disclosure, a first relay terminal apparatus is provided. The first relay terminal apparatus comprises means for determining information about at least one second relay terminal device, wherein each second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device; and means for transmitting the information about at least one second relay terminal device, wherein, means for each second relay terminal device is indicated by an indication that the second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, means for thing information about the at least one second relay terminal device is associated with a specific relay service code (RSC) , or means for thing information about the at least one second relay terminal device is comprised in a specific information element or a discovery announcement message specific to a multi-hop U2N transmission. In some embodiments, the first apparatus may comprise means for performing the respective operations of the method 400. In some example embodiments, the first apparatus may further comprise means for performing other operations in some example embodiments of the method 400. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a remote terminal apparatus is provided. The remote terminal apparatus comprises means for generateing a first solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, means for the first solicitation message comprises an indication that the remote terminal device aims to discover the at least one second relay terminal device, means for the first solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, means for the first solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or means for the first solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission; and means for transmitting the first solicitation message. In some embodiments, the second apparatus may comprise means for performing the respective operations of the method 500. In some example embodiments, the second apparatus may further comprise means for performing other operations in some example embodiments of the method 500. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a first relay terminal apparatus is provided. The first relay terminal apparatus comprises means for reviving a first solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, means for the first solicitation message comprises an indication that the remote terminal device aims to discover at least one second relay terminal device, means for the first solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, means for the first solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or means for the first solicitation message is a discovery solicitation message dedicated to a multi-hop U2N transmission; means for transmitting a second solicitation message generated based on the first solicitation message by at least adding an identity of the first relay terminal device to the first solicitation message. In some embodiments, the third apparatus may comprise means for performing the respective operations of the method 600. In some example embodiments, the third apparatus may further comprise means for performing other operations in some example embodiments of the method 600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a second relay terminal apparatus is provided. The second relay terminal apparatus comprises means for reviving a second solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, means for the second solicitation message comprises an indication that the remote terminal device aims to discover the at least one second relay terminal device, means for the second solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, means for the second solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or means for the second solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission; and means for transmitting, a first response to the second solicitation message. In some embodiments, the fourth apparatus may comprise means for performing the respective operations of the method 700. In some example embodiments, the fourth apparatus may further comprise means for performing other operations in some example embodiments of the method 700. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a remote terminal apparatus is provided. The remote terminal apparatus comprises means for generateing a packet for carrying Uu interface data of a signalling radio bearer (SRB) , wherein, means for the packet comprising a specific sidelink bearer identity pre-defined for a Uu interface transmission, or means for the packet is submitted to a specific radio link control (RLC) channel pre-defined for a Uu interface transmission, or means for the packet comprises an indication that the packet carries the Uu interface data. In some embodiments, the fifth apparatus may comprise means for performing the respective operations of the method 800. In some example embodiments, the fifth apparatus may further comprise means for performing other operations in some example embodiments of the method 800. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a remote terminal apparatus is provided. The remote terminal apparatus comprises means for applying a specific configuration for a Uu interface transmission in response to at least one of the following: means for an initiation a radio resource control (RRC) connection establishment, an RRC connection reestablishment or an RRC connection resuming procedure with a network device, means for aing successful selection of a first relay terminal device, means for aing successful selection of a second relay terminal device, means for an establishment of a connection with a first relay terminal device, means for an establishment of a connection with a second relay terminal device, means for an establishment of a connection between a first relay terminal device and a second relay terminal device, means for performing as a multi-hop user equipment (UE) -to-network (U2N) remote terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and means for the first relay terminal device is a multi-hop U2N intermediate relay terminal device. In some embodiments, the sixth apparatus may comprise means for performing the respective operations of the method 900. In some example embodiments, the sixth apparatus may further comprise means for performing other operations in some example embodiments of the method 900. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a first relay terminal apparatus is provided. The first relay terminal apparatus comprises means for applying a specific configuration for a Uu interface transmission in response to at least one of the following: means for an establishment of a connection with a remote terminal device, means for an establishment of a connection with a second relay terminal device, or means for performing as a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2U relay terminal device. In some embodiments, the seventh apparatus may comprise means for performing the respective operations of the method 1000. In some example embodiments, the seventh apparatus may further comprise means for performing other operations in some example embodiments of the method 1000. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a second relay terminal apparatus is provided. The second relay terminal apparatus comprises means for applying a specific configuration for a Uu interface transmission in response to at least one of the following: means for an establishment of a connection with a remote terminal device, means for an establishment of a connection with a first relay terminal device, or means for performing as a multi-hop user equipment (UE) -to-network (U2N) relay terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2U relay terminal device. In some embodiments, the eighth apparatus may comprise means for performing the respective operations of the method 2100. In some example embodiments, the eighth apparatus may further comprise means for performing other operations in some example embodiments of the method 2100. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a second relay terminal apparatus is provided. The second relay terminal apparatus comprises in accordance with a determination that the second relay terminal device is in a radio resource control (RRC) idle state or an RRC inactive state, means for initiating a transition to an RRC connected state in response to at least one of the following: means for an establishment of a PC5-RRC connection with a remote terminal device, means for an establishment of a PC5-RRC connection with a first relay terminal device, means for performing as a multi-hop user equipment (UE) -to-network (U2N) relay terminal device, means for receiving a PC5-RRC message or PC5-Signaling message from the remote terminal device, or means for receiving a message from the first relay terminal device, the message requesting the second relay terminal device to transition to the RRC connected state, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device. In some embodiments, the ninth apparatus may comprise means for performing the respective operations of the method 2200. In some example embodiments, the ninth apparatus may further comprise means for performing other operations in some example embodiments of the method 2200. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

According to embodiments of the present disclosure, a first relay terminal apparatus is provided. The first relay terminal apparatus comprises in accordance with a determination that the first relay terminal device is in a radio resource control (RRC) idle state or an RRC inactive state, means for initiating a transition to an RRC connected state in response to at least one of the following: means for aing successful selection of a second relay terminal device, means for an establishment of a PC5-RRC connection with a remote terminal device, means for an establishment of a PC5-RRC connection with a second relay terminal device, means for performing as a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device, means for being indicated that the first relay terminal device is selected for a multi-hop U2N transmission by one of the following: the remote terminal device, the second relay terminal device, an upper layer of the first relay terminal device, means for receiving a message from the second relay terminal device or the remote terminal device, the message requesting the second relay terminal device to transition to the RRC connected state, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device. In some embodiments, the tenth apparatus may comprise means for performing the respective operations of the method 2300. In some example embodiments, the tenth apparatus may further comprise means for performing other operations in some example embodiments of the method 2300. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In summary, embodiments of the present disclosure provide the following aspects.

In an aspect, it is proposed a first relay terminal device comprising: a processor configured to cause the terminal device to: determine information about at least one second relay terminal device, wherein each second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device; and transmit the information about at least one second relay terminal device, wherein, each second relay terminal device is indicated by an indication that the second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, the information about the at least one second relay terminal device is associated with a specific relay service code (RSC) , or the information about the at least one second relay terminal device is comprised in a specific information element or a discovery announcement message specific to a multi-hop U2N transmission.

In some embodiments, for a second relay terminal device of the at least one second relay terminal device, the first relay terminal device may transmit further information about at least one of the following: a serving cell of the second relay terminal device, or a radio resource control (RRC) state of the second relay terminal device.

In an aspect, it is proposed a remote terminal device comprising: a processor configured to cause the remote terminal device to: generate a first solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, the first solicitation message comprises an indication that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the first solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission; and transmit the first solicitation message.

In some embodiments, the remote terminal device mayreceive a second response from a first relay terminal device, the second response comprises an identity of the second relay terminal device and at least one of the following: a serving cell of the second relay terminal device, a radio resource control (RRC) state of the second relay terminal device, or the second response is a discovery response message specific to a multi-hop U2N transmission, wherein the first relay terminal device is a multi-hop UE-to UE (U2U) relay terminal device.

In an aspect, it is proposed a first relay terminal device comprising: a processor configured to cause the first relay terminal device to: revive a first solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, the first solicitation message comprises an indication that the remote terminal device aims to discover at least one second relay terminal device, the first solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the first solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the first solicitation message is a discovery solicitation message dedicated to a multi-hop U2N transmission; transmit a second solicitation message generated based on the first solicitation message by at least adding an identity of the first relay terminal device to the first solicitation message.

In some embodiments, the first relay terminal device may transmit the second solicitation message if at least one of the following: the first solicitation message comprises the indication, the first solicitation message comprises the specific RSC, the first solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission, the first solicitation message comprises the specific user identity, the RSC indicated in the first solicitation message matches a pre-configured RSC, the first relay terminal device is not able communicate with a network device via a direct connection or not able of performing as a multi-hop U2N relay terminal device, or the first relay terminal device is able communicate with a network device via at least one another relay terminal device or able of performing as an intermediate relay terminal device for multi-hop transmission.

In some embodiments, the first relay terminal device may receive a first response from a second relay terminal device of the at least one second relay terminal device, the first response comprising an identity of the second relay terminal device and at least one of the following: a serving cell of the second relay terminal device, or a radio resource control (RRC) state of the second relay terminal device; and transmit a second response generated based on the first response by at least adding an identity of the first relay terminal device to the first response.

In an aspect, it is proposed a second relay terminal device comprising: a processor configured to cause the second relay terminal device to: revive a second solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein, the second solicitation message comprises an indication that the remote terminal device aims to discover the at least one second relay terminal device, the second solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, the second solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or the second solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission; and transmit, a first response to the second solicitation message.

In some embodiments, the second relay terminal device maytransmit the first response to the second solicitation message if at least one of the following: the second solicitation message comprises the indication and the second relay terminal device is able communicate with a network device via a direct connection or able of performing as a multi-hop U2N relay terminal device, the second solicitation message comprises the specific RSC and the second relay terminal device is able communicate with a network device via a direct connection or able of performing as a multi-hop U2N relay terminal device, the second solicitation message comprises the specific user identity and the second relay terminal device is able communicate with a network device via a direct connection or able of performing as a multi-hop U2N relay terminal device, the RSC indicated in the second solicitation message matches a pre-configured RSC, the second solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission, or the second relay terminal device is able communicate with a network device 230 via a direct connection or able of performing as a multi-hop U2N relay terminal device.

In some embodiments, the first response comprises an identity of the second relay terminal device and at least one of the following: a serving cell of the second relay terminal device, or a radio resource control (RRC) state of the second relay terminal device.

In an aspect, it is proposed a remote terminal device comprising: a processor configured to cause the remote terminal device to: generate a packet for carrying Uu interface data of a signalling radio bearer (SRB) , wherein, the packet comprising a specific sidelink bearer identity pre-defined for a Uu interface transmission, or the packet is submitted to a specific radio link control (RLC) channel pre-defined for a Uu interface transmission, or the packet comprises an indication that the packet carries the Uu interface data.

In some embodiments, a first packet carrying Uu interface data of a signalling radio bearer with a first identity is submitted to a first RLC channel, and a second packet carrying Uu interface data of a signalling radio bearer with a second identity is submitted to a second RLC channel, the second RLC channel being different from or the same as the first RLC channel.

In some embodiments, a first set of sidelink bearer identities are defined for sidelink transmission, and a second set of sidelink bearer identities are defined for Uu interface transmission, the second set of sidelink bearer identities being different from the first set of sidelink bearer identities.

In an aspect, it is proposed a remote terminal device comprising: a processor configured to cause the remote terminal device to: apply a specific configuration for a Uu interface transmission in response to at least one of the following: an initiation a radio resource control (RRC) connection establishment, an RRC connection reestablishment or an RRC connection resuming procedure with a network device, a successful selection of a first relay terminal device, a successful selection of a second relay terminal device, an establishment of a connection with a first relay terminal device, an establishment of a connection with a second relay terminal device, an establishment of a connection between a first relay terminal device and a second relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) remote terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device.

In an aspect, it is proposed a first relay terminal device comprising: a processor configured to cause the first relay terminal device to: apply a specific configuration for a Uu interface transmission in response to at least one of the following: an establishment of a connection with a remote terminal device, an establishment of a connection with a second relay terminal device, or performing as a multi-hop user equipment (UE) -to- network (U2N) intermediate relay terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2U relay terminal device.

In an aspect, it is proposed a second relay terminal device comprising: a processor configured to cause the second relay terminal device to: apply a specific configuration for a Uu interface transmission in response to at least one of the following: an establishment of a connection with a remote terminal device, an establishment of a connection with a first relay terminal device, or performing as a multi-hop user equipment (UE) -to-network (U2N) relay terminal device, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2U relay terminal device.

In an aspect, it is proposed a second relay terminal device comprising: a processor configured to cause the second relay terminal device to: in accordance with a determination that the second relay terminal device is in a radio resource control (RRC) idle state or an RRC inactive state, initiate a transition to an RRC connected state in response to at least one of the following: an establishment of a PC5-RRC connection with a remote terminal device, an establishment of a PC5-RRC connection with a first relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) relay terminal device, receiving a PC5-RRC message or PC5-Signaling message from the remote terminal device, or receiving a message from the first relay terminal device, the message requesting the second relay terminal device to transition to the RRC connected state, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device.

In an aspect, it is proposed a first relay terminal device comprising: a processor configured to cause the first relay terminal device to: in accordance with a determination that the first relay terminal device is in a radio resource control (RRC) idle state or an RRC inactive state, initiate a transition to an RRC connected state in response to at least one of the following: a successful selection of a second relay terminal device, an establishment of a PC5-RRC connection with a remote terminal device, an establishment of a PC5-RRC connection with a second relay terminal device, performing as a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device, being indicated that the first relay terminal device is selected for a multi-hop U2N transmission by one of the following: the remote terminal device, the second relay terminal device, an upper layer of the first relay terminal device, receiving a message from the second relay terminal device or the remote terminal device, the message requesting the second relay terminal device to transition to the RRC connected state, wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device.

In some embodiments, the first relay terminal device may transmit a message to the second relay terminal device, the message requesting the second relay terminal device to transition to the RRC connected state.

In an aspect, a first relay terminal device comprises: at least one processor; and at least one memory coupled to the at least one processor and storing instructions thereon, the instructions, when executed by the at least one processor, causing the device to perform the method implemented by the first relay terminal device discussed above.

In an aspect, a remote terminal device comprises: at least one processor; and at least one memory coupled to the at least one processor and storing instructions thereon, the instructions, when executed by the at least one processor, causing the device to perform the method implemented by the remote terminal device discussed above.

In an aspect, a second relay terminal device comprises: at least one processor; and at least one memory coupled to the at least one processor and storing instructions thereon, the instructions, when executed by the at least one processor, causing the device to perform the method implemented by the second relay terminal device discussed above.

In an aspect, a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the first relay terminal device discussed above.

In an aspect, a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the remote terminal device discussed above.

In an aspect, a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the second relay terminal device discussed above.

In an aspect, a computer program comprising instructions, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the first relay terminal device discussed above.

In an aspect, a computer program comprising instructions, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the remote terminal device discussed above.

In an aspect, a computer program comprising instructions, the instructions, when executed on at least one processor, causing the at least one processor to perform the method implemented by the second relay terminal device discussed above.

Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it will be appreciated that the blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the process or method as described above with reference to FIGS. 1 to 14. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

The above program code may be embodied on a machine readable medium, which may be any tangible medium that may contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine readable medium may be a machine readable signal medium or a machine readable storage medium. A machine readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the machine readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the present disclosure has been described in language specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A first relay terminal device comprising:

a processor configured to cause the terminal device to:

determine information about at least one second relay terminal device, wherein each second terminal device is able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device; and

transmit the information about at least one second relay terminal device, wherein,

each second relay terminal device is indicated by an indication that the second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, or

the information about the at least one second relay terminal device is associated with a specific relay service code (RSC) , or

the information about the at least one second relay terminal device is comprised in a specific information element or a discovery announcement message specific to a multi-hop U2N transmission.
The first relay terminal device of claim 1, wherein the processor is further configured to cause the first relay terminal device to:

for a second relay terminal device of the at least one second relay terminal device, transmit further information about at least one of the following:

a serving cell of the second relay terminal device, or

a radio resource control (RRC) state of the second relay terminal device.
A remote terminal device comprising:

a processor configured to cause the remote terminal device to:

generate a first solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein,

the first solicitation message comprises an indication that the remote terminal device aims to discover the at least one second relay terminal device, or

the first solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, or

the first solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or

the first solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission; and

transmit the first solicitation message.
The remote terminal device of claim 3, wherein the processor is further configured to cause the remote terminal device to:

receive a second response from a first relay terminal device, the first relay terminal device being a multi-hop UE-to UE (U2U) relay terminal device,

wherein the second response comprises an identity of the second relay terminal device and at least one of the following:

a serving cell of the second relay terminal device,

a radio resource control (RRC) state of the second relay terminal device,

or wherein the second response is a discovery response message specific to a multi-hop U2N transmission.
A first relay terminal device comprising:

a processor configured to cause the first relay terminal device to:

revive a first solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein,

the first solicitation message comprises an indication that the remote terminal device aims to discover at least one second relay terminal device, or

the first solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, or

the first solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or

the first solicitation message is a discovery solicitation message dedicated to a multi-hop U2N transmission; and

transmit a second solicitation message generated based on the first solicitation message by at least adding an identity of the first relay terminal device to the first solicitation message.
The first relay terminal device of claim 5, wherein the processor is further configured to cause the first relay terminal device to:

transmit the second solicitation message if at least one of the following:

the first solicitation message comprises the indication,

the first solicitation message comprises the specific RSC,

the first solicitation message comprises the specific user identity,

the RSC indicated in the first solicitation message matches a pre-configured RSC,

the first solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission,

the first relay terminal device is not able communicate with a network device via a direct connection or not able of performing as a multi-hop U2N relay terminal device, or

the first relay terminal device is able communicate with a network device via at least one another relay terminal device or able of performing as an intermediate relay terminal device for multi-hop transmission.
The first relay terminal device of claim 5, wherein the processor is further configured to cause the first relay terminal device to:

receive a first response from a second relay terminal device of the at least one second relay terminal device, the first response comprising an identity of the second relay terminal device and at least one of the following:

a serving cell of the second relay terminal device, or

a radio resource control (RRC) state of the second relay terminal device; and

transmit a second response generated based on the first response by at least adding an identity of the first relay terminal device to the first response.
A second relay terminal device comprising:

a processor configured to cause the second relay terminal device to:

revive a second solicitation message for discovering at least one second relay terminal device being able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device, wherein,

the second solicitation message comprises an indication that the remote terminal device aims to discover the at least one second relay terminal device, or

the second solicitation message comprises a specific relay service code (RSC) implying that the remote terminal device aims to discover the at least one second relay terminal device, or

the second solicitation message comprises a specific user identity implying that the remote terminal device aims to discover the at least one second relay terminal device, or

the second solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission; and

transmit, a first response to the second solicitation message.
The second relay terminal device of claim 8, wherein the processor is further configured to cause the second relay terminal device to:

transmit the first response to the second solicitation message if at least one of the following:

the second solicitation message comprises the indication and the second relay terminal device is able communicate with a network device via a direct connection or able of performing as a multi-hop U2N relay terminal device,

the second solicitation message comprises the specific RSC and the second relay terminal device is able communicate with a network device via a direct connection or able of performing as a multi-hop U2N relay terminal device,

the second solicitation message comprises the specific user identity and the second relay terminal device is able communicate with a network device via a direct connection or able of performing as a multi-hop U2N relay terminal device,

the RSC indicated in the second solicitation message matches a pre-configured RSC,

the second solicitation message is a discovery solicitation message specific to a multi-hop U2N transmission, or

the second relay terminal device is able communicate with a network device 230 via a direct connection or able of performing as a multi-hop U2N relay terminal device.
The second relay terminal device of claim 8, wherein the first response comprises an identity of the second relay terminal device and at least one of the following:

a serving cell of the second relay terminal device, or

a radio resource control (RRC) state of the second relay terminal device.
A remote terminal device comprising:

a processor configured to cause the remote terminal device to:

generate a packet for carrying Uu interface data of a signalling radio bearer (SRB) , wherein,

the packet comprising a specific sidelink bearer identity pre-defined for a Uu interface transmission, or

the packet is submitted to a specific radio link control (RLC) channel pre-defined for a Uu interface transmission, or

the packet comprises an indication that the packet carries the Uu interface data.
The remote terminal device of claim 11, wherein,

a first packet carrying Uu interface data of a signalling radio bearer with a first identity is submitted to a first RLC channel, and

a second packet carrying Uu interface data of a signalling radio bearer with a second identity is submitted to a second RLC channel, the second RLC channel being different from or the same as the first RLC channel.
The remote terminal device of claim 11, wherein,

a first set of sidelink bearer identities are defined for sidelink transmission, and

a second set of sidelink bearer identities are defined for Uu interface transmission, the second set of sidelink bearer identities being different from the first set of sidelink bearer identities.
A remote terminal device comprising:

a processor configured to cause the remote terminal device to:

apply a specific configuration for a Uu interface transmission in response to at least one of the following:

an initiation a radio resource control (RRC) connection establishment, an RRC connection reestablishment or an RRC connection resuming procedure with a network device,

a successful selection of a first relay terminal device,

a successful selection of a second relay terminal device,

an establishment of a connection with a first relay terminal device,

an establishment of a connection with a second relay terminal device,

an establishment of a connection between a first relay terminal device and a second relay terminal device, or

performing as a multi-hop user equipment (UE) -to-network (U2N) remote terminal device,

wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device.
A first relay terminal device comprising:

a processor configured to cause the first relay terminal device to:

apply a specific configuration for a Uu interface transmission in response to at least one of the following:

an establishment of a connection with a remote terminal device,

an establishment of a connection with a second relay terminal device, or

performing as a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device,

wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2U relay terminal device.
A second relay terminal device comprising:

a processor configured to cause the second relay terminal device to:

apply a specific configuration for a Uu interface transmission in response to at least one of the following:

an establishment of a connection with a remote terminal device,

an establishment of a connection with a first relay terminal device, or

performing as a multi-hop user equipment (UE) -to-network (U2N) relay terminal device,

wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2U relay terminal device.
A second relay terminal device comprising:

a processor configured to cause the second relay terminal device to:

in accordance with a determination that the second relay terminal device is in a radio resource control (RRC) idle state or an RRC inactive state, initiate a transition to an RRC connected state in response to at least one of the following:

an establishment of a PC5-RRC connection with a remote terminal device,

an establishment of a PC5-RRC connection with a first relay terminal device,

performing as a multi-hop user equipment (UE) -to-network (U2N) relay terminal device,

receiving a PC5-RRC message or PC5-Signaling message from the remote terminal device, or

receiving a message from the first relay terminal device, the message requesting the second relay terminal device to transition to the RRC connected state,

wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device.
A first relay terminal device comprising:

a processor configured to cause the first relay terminal device to:

in accordance with a determination that the first relay terminal device is in a radio resource control (RRC) idle state or an RRC inactive state, initiate a transition to an RRC connected state in response to at least one of the following:

a successful selection of a second relay terminal device,

an establishment of a PC5-RRC connection with a remote terminal device,

an establishment of a PC5-RRC connection with a second relay terminal device,

performing as a multi-hop user equipment (UE) -to-network (U2N) intermediate relay terminal device,

being indicated that the first relay terminal device is selected for a multi-hop U2N transmission by one of the following: the remote terminal device, the second relay terminal device, an upper layer of the first relay terminal device,

receiving a message from the second relay terminal device or the remote terminal device, the message requesting the second relay terminal device to transition to the RRC connected state,

wherein, the second terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, and the first relay terminal device is a multi-hop U2N intermediate relay terminal device.
The first relay terminal device of claim 18, wherein the processor is further configured to cause the first relay terminal device to:

transmit a message to the second relay terminal device, the message requesting the second relay terminal device to transition to the RRC connected state.
A communication method implemented at a first relay terminal device, comprising:

determining information about at least one second relay terminal device, wherein each second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a user equipment (UE) -to-network (U2N) relay terminal device; and

transmitting the information about at least one second relay terminal device, wherein,

each second relay terminal device is indicated by an indication that the second relay terminal device is able to communicate with a network device via a direct connection or able of performing as a U2N relay terminal device, or

thing information about the at least one second relay terminal device is associated with a specific relay service code (RSC) , or

thing information about the at least one second relay terminal device is comprised in a specific information element or a discovery announcement message specific to a multi-hop U2N transmission.