Methods and apparatus for a discovery mechanism in a relay case having multiple hops

Abstract

Various aspects of the present disclosure relate to methods and apparatus for a discovery mechanism in a relay case having multiple hops. According to an embodiment of the present disclosure, a user device (UE) comprises at least one memory and at least one processor coupled to at least one memory, and the at least one processor is configured to cause the UE to transmit a discovery message; to establish a first PC5 connection between the UE and the relay UE and to establish a second PC5 connection between the UE and the remote UE, and a connection between the relay UE and the network node is established, and the remote UE is expected to establish an end-to-end connection to the network node through both the UE and the relay UE.

Description

Technology Field

[0001] The present disclosure relates to wireless communication, and more specifically, to methods and apparatus for a discovery mechanism in a relay case having multiple hops, for example, a layer-2 (L2) UE-to-network (U2N) relay case having multiple hops. Background Technology

[0002] A wireless communication system may include one or more network communication devices, such as base stations, capable of supporting wireless communication for one or more user communication devices, which may be otherwise known by other suitable terms, such as user equipment (UE). A wireless communication system may support wireless communication with one or more user communication devices by utilizing resources of the wireless communication system (e.g., time domain resources (e.g., symbols, slots, subframes, frames, etc.) or frequency domain resources (e.g., subcarriers, carriers, etc.). Additionally, a wireless communication system may support wireless communication across various radio access technologies, including 3rd generation (3G) radio access technology, 4th generation (4G) radio access technology, and 5th generation (5G) radio access technology, among other suitable radio access technologies beyond 5G (e.g., 6th generation (6G)).

[0003] Sidelink relays are introduced to support 5G ProSe UE-to-Network Relay (U2N) functionality, providing network connectivity to remote U2N UEs. The U2N relay UE will be in RRC_CONNECTED to perform relaying of unicast data. For path switching, a U2N relay UE in the RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED state can be selected as the target relay UE.

[0004] The article "a" preceding an element is understood to refer to "at least one" of the elements or "one or more" of the elements without limitation. The terms "a," "at least one," "one or more," and "at least one of one or more" may be interchangeable. As used herein, including in the claims, the word "or" as used in a list of items (e.g., a list of items followed by phrases such as "at least one of," "one or more of," or "one or both of") indicates a comprehensive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A, B, and C). Furthermore, as used herein, the phrase "based on" should not be interpreted as a reference to a closed set of conditions. For example, an exemplary step described as "based on condition A" may be based on both condition A and condition B without departing from the scope of this disclosure. That is, as used herein, the phrase “based on” should be interpreted in the same way as the phrase “at least partially based on”. Additionally, as used herein, including the claims, the “set” may include one or more elements.

[0005] Some embodiments of the present disclosure provide a first user device (UE). The first UE comprises at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to cause the first UE to transmit a discovery message; to establish a first PC5 connection between the first UE and a first relay UE and to establish a second PC5 connection between the first UE and a remote UE, and a connection between the first relay UE and a network node is established, and the remote UE is expected to establish an end-to-end connection to the network node through both the first UE and the first relay UE.

[0006] In some implementations of the first UE described in this specification, the processor of the first UE is configured to receive first information from a network node indicating whether the network node supports a multi-hop sidelink layer 2 (L2) relay UE.

[0007] In some implementations of the first UE described herein, the processor of the first UE is configured to determine whether the channel quality of the PC5 link between the first UE and the first relay UE is greater than or equal to a first threshold; and in response to the channel quality of the PC5 link between the first UE and the first relay UE being greater than or equal to the first threshold, to determine that the first UE can operate as a multi-hop relay UE.

[0008] In some implementations of the first UE described in this specification, in response to the fact that the first UE may operate as a multi-hop relay UE, the first UE is allowed to transmit a discovery message or monitor other discovery messages before establishing a first PC5 connection.

[0009] In some implementations of the first UE described herein, the processor of the first UE is configured to trigger the establishment of an end-to-end connection between the first UE and a network node in response to the establishment of a PC5 link between the remote UE and the first UE after the first UE transmits a discovery message.

[0010] In some implementations of the first UE described in this specification, the first threshold is a pre-configured threshold.

[0011] In some implementations of the first UE described herein, in response to the establishment of the first PC5 connection, the first UE is allowed to transmit a discovery message.

[0012] In some implementations of the first UE described herein, in response to the establishment of a first PC5 connection and the establishment of an end-to-end connection between the first UE and a network node, the first UE is allowed to transmit a discovery message.

[0013] In some implementations of the first UE described herein, the processor of the first UE is configured to determine whether the channel quality of the Uu link between the first UE and the network node is less than or equal to a second threshold; and in response to the channel quality of the Uu link between the first UE and the network node being less than or equal to the second threshold, to determine that the first UE can operate as a multi-hop relay UE.

[0014] In some implementations of the first UE described herein, in response to the first UE being able to operate as a multi-hop relay UE, the processor of the first UE is configured to determine whether the channel quality of the PC5 link between the first UE and the first relay UE is greater than or equal to a third threshold; and in response to the channel quality of the PC5 link between the first UE and the first relay UE being greater than or equal to the third threshold, the first UE is allowed to transmit a discovery message before establishing the first PC5 connection.

[0015] In some implementations of the first UE described herein, the processor of the first UE is configured to receive first configuration information from a network node, the first configuration information including a second threshold, a third threshold, or a combination thereof.

[0016] In some implementations of the first UE described herein, the first information, the first configuration information, or a combination thereof is received by the first UE from a network node via system information or dedicated signaling.

[0017] In some implementations of the first UE described herein, in response to the first UE being able to operate as a multi-hop relay UE, the first UE is allowed to transmit a discovery message in response to satisfying one of the following conditions: that a first PC5 connection is established before an end-to-end connection between the first UE and a network node is established; that an end-to-end connection between the first UE and a network node is established; or that the first UE is configured to transition to an RRC connected state, an RRC idle state, or an RRC inactive state.

[0018] In some implementations of the first UE described herein, the processor of the first UE is configured to receive an RRC setup request message from a remote UE; a first PC5 relay radio link control (RLC) channel for a PC5 link between the first UE and the first relay UE configured by a network; and to transmit the RRC setup request message to the first relay UE on a signaling radio bearer (SRB) 0 using one of the designated PC5 relay RLC channels.

[0019] In some implementations of the first UE described herein, the processor of the first UE is configured to receive an RRC setup message on SRB 0 using one of the designated PC5 relay RLC channels from the first relay UE; and a first PC5 relay RLC channel.

[0020] In some implementations of the first UE described herein, the discovery message comprises: information indicating whether the relay UE will allow access to the first UE so that the first UE can operate as a parent relay UE of the relay UE; information indicating, by reference to the network node, whether the first UE is an Out-of-Coverage (OOC) UE or an In-Coverage (IC) UE; information indicating whether the first UE is a single-hop relay UE or a multi-hop relay UE toward the network node; information indicating whether a backhaul (BH) is established between the first UE and the network node in response that the first UE is a multi-hop relay UE toward the network node; the total number of hops between the first UE and the network node; the duration for which the first UE can provide service if the first UE operates as a multi-hop relay UE; information indicating whether there is one or more connected remote UEs with which a PC5 connection is established between the first UE and the first UE; the total number of one or more connected remote UEs; and the channel quality of the PC5 link between the first UE and the first relay UE. In response to the fact that the first UE is within the coverage of the network node, the channel quality of the Uu link between the first UE and the network node; or a combination thereof.

[0021] Some embodiments of the present disclosure provide a processor for wireless communication, the processor comprises at least one controller coupled with at least one memory, and at least one controller is configured to cause the processor to transmit a discovery message; to establish a first PC5 connection between a first UE and a first relay UE and to establish a second PC5 connection between the first UE and a remote UE, and to establish a connection between the first relay UE and a network node, and the remote UE is expected to establish an end-to-end connection to the network node through both the first UE and the first relay UE.

[0022] Some embodiments of the present disclosure provide a method performed by a first user device (UE). The method comprises the steps of: transmitting a discovery message; and establishing a first PC5 connection between the first UE and a first relay UE and establishing a second PC5 connection between the first UE and a remote UE, wherein a connection between the first relay UE and a network node is established, and the remote UE is expected to establish an end-to-end connection toward the network node through both the first UE and the first relay UE.

[0023] Some embodiments of the present disclosure provide a first relay user device (UE). The first relay UE comprises at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to cause the first relay UE to transmit a first discovery message; and to establish a first PC5 connection between the first relay UE and a second relay UE, and a connection between the first relay UE and a network node is established, and a remote UE is expected to establish an end-to-end connection to the network node through both the second relay UE and the first relay UE.

[0024] In some implementations of the first relay UE described in this specification, the processor of the first relay UE is configured to receive first information from a network node indicating whether the network node supports a multi-hop sidelink layer 2 (L2) relay UE.

[0025] In some implementations of the first relay UE described herein, the processor of the first relay UE is configured to receive a second discovery message from the second relay UE before or after establishing the first PC5 connection.

[0026] In some implementations of the first relay UE described herein, a second discovery message is received from the second relay UE in response to the establishment of a first PC5 connection; the establishment of an end-to-end connection between the second relay UE and a network node; and the second relay UE transitioning to an RRC connected state, an RRC idle state, or an RRC inactive state.

[0027] In some implementations of the first relay UE described herein, the second discovery message comprises: information indicating whether the relay UE will allow access to the second relay UE so that the second relay UE can operate as the parent relay UE of the relay UE; information indicating whether the second relay UE is an Out-of-Coverage (OOC) UE or an In-Coverage (IC) UE with reference to the network node; information indicating whether the second relay UE is a single-hop relay UE or a multi-hop relay UE toward the network node; information indicating whether a backhaul (BH) is established between the second relay UE and the network node in response that the second relay UE is a multi-hop relay UE toward the network node; the total number of hops between the second relay UE and the network node; the duration for which the second relay UE can provide service if the second relay UE operates as a multi-hop relay UE; information indicating whether there is one or more connected remote UEs with which a PC5 connection is established between the second relay UE and the second relay UE; the total number of one or more connected remote UEs; and the channel quality of the PC5 link between the second relay UE and the first relay UE. In response to the second relay UE being within the coverage of the network node, the channel quality of the Uu link between the second relay UE and the network node; or a combination thereof.

[0028] In some implementations of the first relay UE described herein, the processor of the first relay UE is configured to receive, from the second relay UE, a first PC5 relay radio link control (RLC) channel for the PC5 link between the second relay UE and the first relay UE configured by the network; and an RRC setup request message on a signaling radio bearer (SRB) 0 using one of the designated PC5 relay RLC channels.

[0029] In some implementations of the first relay UE described herein, the processor of the first relay UE is configured to transmit an RRC setup message to the second relay UE on SRB 0 using one of the designated PC5 relay RLC channels; and a first PC5 relay RLC channel.

[0030] In some implementations of the first relay UE described herein, the first discovery message comprises: information indicating whether the relay UE allows access to the first relay UE so that the first relay UE can operate as the parent relay UE of the relay UE; information indicating, by reference to the network node, whether the first relay UE is an Out-of-Coverage (OOC) UE or an In-Coverage (IC) UE; information indicating whether the first relay UE is a single-hop relay UE or a multi-hop relay UE toward the network node; information indicating whether a backhaul (BH) is established between the first relay UE and the network node in response that the first relay UE is a multi-hop relay UE toward the network node; the total number of hops between the first relay UE and the network node; the duration for which the first relay UE can provide service if the first relay UE operates as a multi-hop relay UE; information indicating whether there is one or more connected remote UEs with which a PC5 connection is established between the first relay UE and the first relay UE; and the total number of one or more connected remote UEs. In response to the first relay UE being within the coverage of the network node, the channel quality of the Uu link between the first relay UE and the network node; or a combination thereof.

[0031] Some embodiments of the present disclosure provide a processor for wireless communication, the processor comprises at least one controller coupled with at least one memory, and at least one controller is configured to cause the processor to transmit a first discovery message; to establish a first PC5 connection between a first relay UE and a second relay UE, and a connection between the first relay UE and a network node is established, and a remote UE is expected to establish an end-to-end connection toward the network node through both the second relay UE and the first relay UE.

[0032] Some embodiments of the present disclosure provide a method performed by a first relay user device (UE). The method comprises the steps of: transmitting a first discovery message; and establishing a first PC5 connection between the first relay UE and a second relay UE, wherein a connection between the first relay UE and a network node is established, and the remote UE is expected to establish an end-to-end connection toward the network node through both the second relay UE and the first relay UE.

[0033] Some embodiments of the present disclosure provide a network node. The network node comprises at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to enable the network node to receive, from a user device (UE), the capability of a UE to support a multi-hop sidelink layer 2 (L2) relay UE; and to transmit information indicating whether the network node supports a multi-hop sidelink L2 relay UE.

[0034] In some implementations of the network node described in this specification, the UE includes at least one of a remote UE, a single-hop relay UE, or a multi-hop relay UE.

[0035] In some implementations of the network node described herein, the processor of the network node is configured to transmit to the UE at least one of: first configuration information regarding a first threshold associated with the channel quality of the PC5 link between the UE and the first relay UE; second configuration information regarding a second threshold associated with the channel quality of the Uu link between the UE and the network node; or third configuration information regarding a PC5 relay radio link control (RLC) channel configured for the PC5 link between the UE and the first relay UE.

[0036] In some implementations of the network node described in this specification, the first configuration information, the second configuration information, the third configuration information, or a combination thereof is transmitted via system information or dedicated signaling.

[0037] Some embodiments of the present disclosure provide a processor for wireless communication, the processor comprises at least one controller coupled with at least one memory, and the at least one controller is configured to cause the processor to receive from a user device (UE) the capability of a UE to support a multi-hop sidelink layer 2 (L2) relay UE; and to transmit information indicating whether a network node supports a multi-hop sidelink L2 relay UE.

[0038] Some embodiments of the present disclosure provide a method performed by a network node. The method comprises receiving, from a user device (UE), the capability of a UE to support a multi-hop sidelink Layer 2 (L2) relay UE; and transmitting information indicating whether the network node supports a multi-hop sidelink L2 relay UE. In embodiments of the present disclosure, the relay UE may be a UE-to-network relay UE that is a UE providing functionality to support connectivity to a network for U2N remote UE(s). Brief explanation of the drawing

[0039] FIG. 1 illustrates an example of a wireless communication system according to embodiments of the present disclosure. FIG. 2 illustrates an example of user equipment (UE) (200) according to embodiments of the present disclosure. FIG. 3 illustrates an example of a processor (300) according to embodiments of the present disclosure. FIG. 4 illustrates an example of network equipment (NE) (400) according to embodiments of the present disclosure. FIG. 5a illustrates a schematic diagram of a wireless communication system according to embodiments of the present disclosure. FIG. 5b illustrates a schematic diagram of a relay-based wireless communication system according to embodiments of the present disclosure. FIG. 5c illustrates an exemplary procedure for a notification message according to embodiments of the present disclosure. FIG. 6 illustrates a schematic diagram of a relay-based wireless communication system according to embodiments of the present disclosure. FIGS. 7 through 9 illustrate flowcharts of methods related to an L2 U2N relay case according to embodiments of the present disclosure. FIGS. 10 to 12 illustrate schematic diagrams of an L2 U2N relay case according to embodiments of the present disclosure. Specific details for implementing the invention

[0040] The detailed description of the accompanying drawings is intended to describe preferred embodiments of the present disclosure and is not intended to represent the only form in which the present disclosure may be practiced. It should be understood that identical or equivalent functions may be achieved by different embodiments intended to be included within the spirit and scope of the present disclosure.

[0041] Now, some embodiments of the present disclosure will be referenced in detail, and examples are illustrated in the accompanying drawings. For ease of understanding, embodiments are provided under specific network architectures and new service scenarios, such as the 3rd Generation Partnership Project (3GPP) 5G (NR), 3GPP Long Term Evolution (LTE) Release 8, etc. With the development of network architectures and new service scenarios, it is considered that all embodiments of the present disclosure are also applicable to similar technical problems; and also that terms cited in the present disclosure may be modified, and this should not affect the principles of the present disclosure.

[0042] FIG. 1 illustrates an example of a wireless communication system (100) according to embodiments of the present disclosure. The wireless communication system (100) may include one or more NEs (102), one or more UEs (104), and a core network (CN) (106). The wireless communication system (100) may support various radio access technologies. In some embodiments, the wireless communication system (100) may be a 4G network, such as an LTE network or an LTE-Advanced (LTE-A) network. In some other embodiments, the wireless communication system (100) may be an NR network, such as a 5G network, a 5G-Advanced (5G-A) network, or a 5G Ultra-Wideband (5G-UWB) network. In other implementations, the wireless communication system (100) may be a combination of a 4G network and a 5G network, or other suitable radio access technologies including IEEE (Institute of Electrical and Electronics Engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), and IEEE 802.20. The wireless communication system (100) may support radio access technologies beyond 5G, for example, 6G. Additionally, the wireless communication system (100) may support technologies such as TDMA (time division multiple access), FDMA (frequency division multiple access), or CDMA (code division multiple access).

[0043] One or more NEs (102) may be distributed across a geographical area to form a wireless communication system (100). One or more of the NEs (102) described herein may be network nodes, base stations, network elements, network functions, network entities, radio access networks (RAN), NodeB, eNodeB (eNB), next-generation NodeB (gNB), or other suitable terms, may include or be referred to as such. The NEs (102) and UEs (104) may communicate through a communication link that may be wireless or wired. For example, the NEs (102) and UEs (104) may perform wireless communication (e.g., receiving signaling, transmitting signaling) through a Uu interface.

[0044] The NE (102) may provide a geographic coverage area in which the NE (102) can support services for one or more UEs (104) within the geographic coverage area. For example, the NE (102) and the UE (104) may support wireless communication of signals related to services (e.g., voice, video, packet data, messaging, broadcast, etc.) according to one or more radio access technologies. In some implementations, the NE (102) may be mobile, for example, a satellite associated with a non-terrestrial network (NTN). In some implementations, different geographic coverage areas associated with the same or different radio access technologies may overlap, but different geographic coverage areas may be associated with different NEs (102).

[0045] One or more UEs (104) may be distributed across the entire geographical area of ​​the wireless communication system (100). The UE (104) may include or be referred to as a remote unit, mobile device, wireless device, remote device, subscriber device, transmitter device, receiver device, or some other suitable term. In some implementations, the UE (104) may be referred to as a unit, station, terminal, or client, among other examples. Additionally or alternatively, the UE (104) may be referred to as an Internet of Things (IoT) device, Internet of Everything (IoE) device, or Machine Communication (MTC) device, among other examples.

[0046] A UE (104) can directly support wireless communication with other UEs (104) via a communication link. For example, a UE (104) can directly support wireless communication with other UEs (104) via a device-to-device (D2D) communication link. In some implementations, such as vehicle-to-vehicle (V2V) deployments, vehicle-to-everything (V2X) deployments, or cellular-V2X deployments, the communication link may be referred to as a side link. For example, a UE (104) can directly support wireless communication with other UEs (104) via a PC5 interface.

[0047] The NE (102) may support communication with the CN (106), with another NE (102), or with both. For example, the NE (102) may interface with another NE (102) or CN (106) through one or more backhaul links (e.g., S1, N2, or network interface). In some implementations, the NEs (102) may communicate directly with each other. In some other implementations, the NEs (102) may communicate with each other or indirectly (e.g., through CN (106)). In some implementations, one or more NEs (102) may include subcomponents such as an access network entity, which may be an example of an access node controller (ANC). The ANC may communicate with one or more UEs (104) through one or more other access network transport entities, which may be referred to as a radio head, a smart radio head, or a transmit-receive point (TRP).

[0048] CN (106) may support user authentication, access authorization, tracking, connectivity, and other access, routing, or mobility functions. CN (106) may be an advanced packet core (EPC) or a 5G core (5GC), which may include a control plane entity that manages access and mobility (e.g., a mobility management entity (MME), access and mobility management functions (AMF)) and a user plane entity that routes packets or interconnects to external networks (e.g., a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), or a user plane function (UPF)). In some implementations, the control plane entity may manage non-access stratum (NAS) functions such as mobility, authentication, and bearer management (e.g., data bearers, signaling bearers, etc.) for one or more UEs (104) served by one or more NEs (102) associated with CN (106).

[0049] CN (106) may communicate with a packet data network through one or more backhaul links (e.g., through S1, N2, or other network interfaces). The packet data network may include an application server. In some implementations, one or more UEs (104) may communicate with the application server. The UE (104) may establish a session (e.g., a Protocol Data Unit (PDU) session) with CN (106) through NE (102). CN (106) may route traffic (e.g., control information, data, etc.) between the UE (104) and the application server using the established session (e.g., an established PDU session). A PDU session may be an example of a logical connection between the UE (104) and CN (106) (e.g., one or more network functions of CN (106)).

[0050] In a wireless communication system (100), NEs (102) and UEs (104) can perform various operations (e.g., wireless communication) using the resources of the wireless communication system (100) (e.g., time resources (e.g., symbols, slots, subframes, frames, etc.) or frequency resources (e.g., subcarriers, carriers)). In some implementations, NEs (102) and UEs (104) may support different resource structures. For example, NEs (102) and UEs (104) may support different frame structures. In some implementations, such as in 4G, NEs (102) and UEs (104) may support a single frame structure. In some other implementations, such as in 5G, and among other suitable radio access technologies, NEs (102) and UEs (104) may support various frame structures (i.e., multiple frame structures). The NEs (102) and UEs (104) can support various frame structures based on one or more numerologies.

[0051] One or more numerologies may be supported in the wireless communication system (100), and the numerologies may include a subcarrier interval and a cyclic prefix. A first numerology (e.g., μ=0) may be associated with a first subcarrier interval (e.g., 15 kHz) and a normal cyclic prefix. In some implementations, the first numerology (e.g., μ=0) associated with the first subcarrier interval (e.g., 15 kHz) may utilize one slot per subframe. A second numerology (e.g., μ=1) may be associated with a second subcarrier interval (e.g., 30 kHz) and a normal cyclic prefix. A third numerology (e.g., μ=2) may be associated with a third subcarrier interval (e.g., 60 kHz) and a normal cyclic prefix or an extended cyclic prefix. The fourth numerology (e.g., μ=3) may be associated with the fourth subcarrier interval (e.g., 120 kHz) and a normal cyclic prefix. The fifth numerology (e.g., μ=4) may be associated with the fifth subcarrier interval (e.g., 240 kHz) and a normal cyclic prefix.

[0052] Time intervals of a resource (e.g., a communication resource) can be organized according to frames (also referred to as radio frames). Each frame may have a duration, for example, 10 milliseconds (ms). In some implementations, each frame may contain multiple subframes. For example, each frame may contain 10 subframes, and each subframe may have a duration, for example, 1 ms. In some implementations, each frame may have the same duration. In some implementations, each subframe of a frame may have the same duration.

[0053] Additionally or alternatively, time intervals of a resource (e.g., a communication resource) may be organized according to slots. For example, a subframe may contain a number (e.g., a large number) of slots. The number of slots within each subframe may also depend on one or more numerologies supported by the wireless communication system (100). For example, first, second, third, fourth, and fifth numerologies (i.e., μ=0, μ=1, μ=2, μ=3, μ=4) associated with each of the subcarrier intervals of 15 kHz, 30 kHz, 60 kHz, 120 kHz, and 240 kHz may each utilize a single slot per subframe, two slots per subframe, four slots per subframe, eight slots per subframe, and sixteen slots per subframe, respectively. Each slot may contain a number (e.g., a large number) of symbols (e.g., OFDM symbols). In some implementations, the number of slots (e.g., quantity) for a subframe may depend on the numerology. For a normal cyclic prefix, a slot may contain 14 symbols. For an extended cyclic prefix (e.g., applicable to a 60 kHz subcarrier interval), a slot may contain 12 symbols. The relationship between the number of symbols per slot, the number of slots per subframe, and the number of slots per frame for the normal cyclic prefix and the extended cyclic prefix may depend on the numerology. It should be understood that a reference to a first numerology (e.g., μ=0) associated with a first subcarrier interval (e.g., 15 kHz) may be used interchangeably between subframes and slots.

[0054] In a wireless communication system (100), the electromagnetic (EM) spectrum may be divided into various classes, frequency bands, frequency channels, etc. based on frequency or wavelength. For example, the wireless communication system (100) may support one or more operating frequency bands such as frequency range designations FR1 (410 MHz - 7.125 GHz), FR2 (24.25 GHz - 52.6 GHz), FR3 (7.125 GHz - 24.25 GHz), FR4 (52.6 GHz - 114.25 GHz), FR4a or FR4-1 (52.6 GHz - 71 GHz), and FR5 (114.25 GHz - 300 GHz). In some implementations, NEs (102) and UEs (104) may perform wireless communication through one or more of the operating frequency bands. In some implementations, FR1 may be used by NEs (102) and UEs (104) among other equipment or devices for cellular communication traffic (e.g., control information, data). In some implementations, FR2 may be used by NEs (102) and UEs (104) among other equipment or devices for short-range, high data rate capabilities.

[0055] FR1 may be associated with one or more numerologies (e.g., at least three numerologies). For example, FR1 may be associated with a first numerology including a 15 kHz subcarrier interval (e.g., μ=0); a second numerology including a 30 kHz subcarrier interval (e.g., μ=1); and a third numerology including a 60 kHz subcarrier interval (e.g., μ=2). FR2 may be associated with one or more numerologies (e.g., at least two numerologies). For example, FR2 may be associated with a third numerology including a 60 kHz subcarrier interval (e.g., μ=2); and a fourth numerology including a 120 kHz subcarrier interval (e.g., μ=3).

[0056] FIG. 2 illustrates an example of a UE (200) according to embodiments of the present disclosure. The UE (200) may include a processor (202), memory (204), a controller (206), and a transceiver (208). The processor (202), memory (204), controller (206), or transceiver (208), or various combinations thereof, or various components thereof, may be examples of means for carrying out various embodiments of the present disclosure as described herein. These components may be coupled (e.g., operablely, communically, functionally, electronically, electrically) through one or more interfaces.

[0057] A processor (202), memory (204), controller (206), or transceiver (208), or various combinations or components thereof, may be implemented in hardware (e.g., circuits). The hardware may include a processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), or other programmable logic devices, or any combination thereof configured as a means for performing the functions described in this disclosure or otherwise supporting such functions.

[0058] The processor (202) may include an intelligent hardware device (e.g., a general-purpose processor, a DSP, a CPU, an ASIC, an FPGA, or any combination thereof). In some implementations, the processor (202) may be configured to operate memory (204). In some other implementations, memory (204) may be integrated into the processor (202). The processor (202) may be configured to execute computer-readable instructions stored in memory (204) to enable the UE (200) to perform various functions of the present disclosure.

[0059] Memory (204) may include volatile or non-volatile memory. Memory (204) may store computer-readable, computer-executable code containing instructions that enable the UE (200) to perform the various functions described herein when executed by the processor (202). The code may be stored in a non-transient computer-readable medium, such as memory (204) or other types of memory. A computer-readable medium includes both a non-transient computer storage medium and a communication medium, which include any medium that facilitates the transfer of a computer program from one place to another. A non-transient storage medium may be any available medium that can be accessed by a general-purpose or special-purpose computer.

[0060] In some implementations, the processor (202) and the memory (204) combined with the processor (202) may be configured to enable the UE (200) to perform one or more of the functions described herein (e.g., by the processor (202), execute instructions stored in the memory (204).

[0061] For example, the processor (202) may support wireless communication in the UE (200) according to the examples disclosed in connection with FIG. 7. The UE (200) may be configured to support means for transmitting discovery messages; and means for establishing a first PC5 connection between the first UE and the first relay UE and establishing a second PC5 connection between the first UE and the remote UE, and a connection between the first relay UE and the network node is established, and the remote UE is expected to establish an end-to-end connection toward the network node through both the first UE and the first relay UE.

[0062] For example, the processor (202) may support wireless communication in the UE (200) according to the examples disclosed in connection with FIG. 8. The UE (200) may be configured to support means for transmitting a first discovery message; and means for establishing a first PC5 connection between the first relay UE and the second relay UE, and a connection between the first relay UE and the network node is established, and the remote UE is expected to establish an end-to-end connection toward the network node through both the second relay UE and the first relay UE.

[0063] The controller (206) can manage input and output signals for the UE (200). The controller (206) can also manage peripherals not integrated into the UE (200). In some implementations, the controller (206) can use an operating system such as iOS®, ANDROID®, WINDOWS®, or other operating systems. In some implementations, the controller (206) can be implemented as part of the processor (202).

[0064] In some implementations, the UE (200) may include at least one transceiver (208). In some other implementations, the UE (200) may have more than one transceiver (208). The transceiver (208) may represent a wireless transceiver. The transceiver (208) may include one or more receiver chains (210), one or more transmitter chains (212), or a combination thereof. The means for receiving or the means for transmitting in the processor (202) described above may be implemented through at least one transceiver (208).

[0065] A receiver chain (210) may be configured to receive signals (e.g., control information, data, packets) through a wireless medium. For example, the receiver chain (210) may include one or more antennas for receiving signals through an airborne or wireless medium. The receiver chain (210) may include at least one amplifier (e.g., a low-noise amplifier (LNA)) configured to amplify the received signal. The receiver chain (210) may include at least one demodulator configured to obtain transmitted data by demodulating the received signal and inverting the modulation technique applied during the transmission of the signal. The receiver chain (210) may include at least one decoder for decoding and processing the demodulated signal to receive the transmitted data.

[0066] The transmitter chain (212) may be configured to generate and transmit signals (e.g., control information, data, packets). The transmitter chain (212) may include at least one modulator for modulating data on a carrier signal and preparing the signal for transmission over a wireless medium. The at least one modulator may be configured to support one or more digital modulation techniques, such as amplitude modulation (AM), frequency modulation (FM), or phase shift keying (PSK) or quadrature amplitude modulation (QAM). The transmitter chain (212) may also include at least one power amplifier configured to amplify the modulated signal to an appropriate power level suitable for transmission over a wireless medium. The transmitter chain (212) may also include one or more antennas for transmitting the amplified signal over the air or a wireless medium.

[0067] FIG. 3 illustrates an example of a processor (300) according to embodiments of the present disclosure. The processor (300) may be an example of a processor configured to perform various operations according to the examples described herein. The processor (300) may include a controller (302) configured to perform various operations according to the examples described herein. The processor (300) may optionally include at least one memory (304), which may be, for example, an L1 / L2 / L3 cache. Additionally or alternatively, the processor (300) may optionally include one or more arithmetic logic units (ALUs) (306). One or more of these components may be electronically communicated through one or more interfaces (e.g., buses) or otherwise coupled (e.g., operablely, communically, functionally, electronically, electrically).

[0068] The processor (300) may be a processor chipset and may include a protocol stack (e.g., a software stack) executed by the processor chipset to perform various operations (e.g., receiving, acquiring, searching, transmitting, outputting, forwarding, storing, determining, identifying, accessing, writing, reading) according to the examples described herein. The processor chipset may include one or more cores, one or more caches (e.g., memory local to or included in the processor chipset (e.g., processor (300)) or other memory (e.g., random access memory (RAM), read-only memory (ROM), dynamic RAM (DRAM), synchronous dynamic RAM (SDRAM), static RAM (SRAM), ferroelectric RAM (FeRAM), magnetic RAM (MRAM), resistive RAM (RRAM), flash memory, phase change memory (PCM), etc.).

[0069] A controller (302) may be configured to manage and coordinate various operations of the processor (300) (e.g., signaling, receiving, acquiring, searching, transmitting, outputting, forwarding, storing, determining, identifying, accessing, writing, reading) so that the processor (300) supports various operations according to the examples described herein. For example, the controller (302) may operate as a control unit of the processor (300) and generate control signals that manage the operations of various components of the processor (300). These control signals include enabling or disabling function units, selecting data paths, initiating memory access, and coordinating the timing of operations.

[0070] The controller (302) may be configured to fetch instructions from memory (304) (e.g., acquire, retrieve, receive) and determine subsequent instruction(s) to be executed to enable the processor (300) to support various operations according to the examples described herein. The controller (302) may be configured to track the memory addresses of instructions associated with memory (304). The controller (302) may be configured to decode instructions to determine the operations to be performed and the accompanying operands. For example, the controller (302) may be configured to interpret instructions and determine control signals to be output to other components of the processor (300) to enable the processor (300) to support various operations according to the examples described herein. Additionally or alternatively, the controller (302) may be configured to manage the flow of data within the processor (300). The controller (302) may be configured to control the transfer of data between the registers, arithmetic logic units (ALUs), and other functional units of the processor (300).

[0071] Memory (304) may include one or more caches (e.g., memory local to or contained in other memory such as RAM, ROM, DRAM, SDRAM, SRAM, MRAM, flash memory, etc.) or other memory such as the processor (300). In some implementations, memory (304) may reside in or on a processor chipset (e.g., local to the processor (300)). In some other implementations, memory (304) may reside outside the processor chipset (e.g., remotely from the processor (300)).

[0072] Memory (304) may store computer-readable, computer-executable code containing instructions that, when executed by the processor (300), cause the processor (300) to perform the various functions described herein. The code may be stored in a non-transient computer-readable medium, such as system memory or other types of memory. A controller (302) and / or a processor (300) may be configured to execute computer-readable instructions stored in memory (304) to cause the processor (300) to perform the various functions. For example, the processor (300) and / or the controller (302) may be coupled with or connected to memory (304), and the processor (300), the controller (302), and memory (304) may be configured to perform the various functions described herein. In some examples, the processor (300) may include multiple processors, and memory (304) may include multiple memories. One or more of the multiple processors may be combined with one or more of the multiple memories, and they may be configured to perform the various functions of this specification individually or collectively.

[0073] One or more ALUs (306) may be configured to support various operations according to the examples described herein. In some implementations, one or more ALUs (306) may reside within or on a processor chipset (e.g., processor (300)). In some other implementations, one or more ALUs (306) may reside outside the processor chipset (e.g., processor (300)). One or more ALUs (306) may perform one or more operations on data, such as addition, subtraction, multiplication, and division. For example, one or more ALUs (306) may receive input operands and an operation code that determines the operation to be executed. One or more ALUs (306) are composed of various logic and arithmetic circuits, including adders, subtractors, shifters, and logic gates, to process and manipulate data according to the operation. Additionally or alternatively, one or more ALUs (306) may support logical operations such as AND, OR, XOR (exclusive-OR), NOR (not-OR), and NAND (not-AND), so that one or more ALUs (306) can process conditional operations, comparisons, and bitwise operations.

[0074] The processor (300) can support wireless communication according to the examples disclosed in this specification.

[0075] In some implementations, the processor (300) may be configured to support means for performing operations of the UE as described in relation to FIG. 7. The processor (300) may be configured or operable to support means for transmitting discovery messages; and means for establishing a first PC5 connection between the first UE and the first relay UE and establishing a second PC5 connection between the first UE and the remote UE, and a connection between the first relay UE and the network node is established, and the remote UE is expected to establish an end-to-end connection toward the network node through both the first UE and the first relay UE.

[0076] In some implementations, the processor (300) may be configured to support means for performing operations of the UE as described in relation to FIG. 8. The processor (300) may be configured or operable to support means for transmitting a first discovery message; and means for establishing a first PC5 connection between the first relay UE and the second relay UE, and a connection between the first relay UE and the network node is established, and the remote UE is expected to establish an end-to-end connection toward the network node through both the second relay UE and the first relay UE.

[0077] In some implementations, the processor (300) may be configured to support means for performing the operations of the serving BS as described in connection with FIG. 9. The processor (300) may be configured or operable to support means for receiving from the user equipment (UE) the ability of the UE to support a multi-hop sidelink layer 2 (L2) relay UE; and means for transmitting information indicating whether the network node supports the multi-hop sidelink L2 relay UE.

[0078] A person skilled in the art should understand that, without departing from the spirit and scope of the present disclosure, the components of the exemplary processor (300) may be changed, for example, some of the components of the exemplary processor (300) may be omitted or modified, or new component(s) may be added to the exemplary processor (300). For example, in some embodiments, the processor (300) may not include ALUs (306).

[0079] FIG. 4 illustrates an example of an NE (400) according to embodiments of the present disclosure. The NE (400) may include a processor (402), a memory (404), a controller (406), and a transceiver (408). The processor (402), the memory (404), the controller (406), or the transceiver (408), or various combinations thereof, or various components thereof, may be examples of means for carrying out various embodiments of the present disclosure as described herein. These components may be coupled (e.g., operablely, communically, functionally, electronically, electrically) through one or more interfaces.

[0080] A processor (402), memory (404), controller (406), or transceiver (408), or various combinations or components thereof, may be implemented in hardware (e.g., circuits). The hardware may include a processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), or other programmable logic devices, or any combination thereof configured as a means for performing the functions described in this disclosure or otherwise supporting such functions.

[0081] The processor (402) may include an intelligent hardware device (e.g., a general-purpose processor, a DSP, a CPU, an ASIC, an FPGA, or any combination thereof). In some implementations, the processor (402) may be configured to operate memory (404). In some other implementations, memory (404) may be integrated into the processor (402). The processor (402) may be configured to execute computer-readable instructions stored in memory (404) to enable the NE (400) to perform various functions of the present disclosure.

[0082] Memory (404) may include volatile or non-volatile memory. Memory (404) may store computer-readable, computer-executable code containing instructions that, when executed by the processor (402), cause the NE (400) to perform the various functions described herein. The code may be stored in a non-transient computer-readable medium, such as memory (404) or other types of memory. Computer-readable media include both communication media and non-transient computer storage media, which include any medium that facilitates the transfer of a computer program from one place to another. Non-transient storage media may be any available medium that can be accessed by a general-purpose or special-purpose computer.

[0083] In some implementations, the processor (402) and the memory (404) coupled with the processor (402) may be configured to enable the NE (400) to perform one or more of the functions described herein (e.g., by the processor (402), to execute instructions stored in the memory (404)). For example, the processor (402) may support wireless communication in the NE (400) according to the examples disclosed herein. For example, the NE (400) may be configured to support means for performing operations such as those described in connection with FIGS. 7 and FIGS. 8 as described below.

[0084] In some implementations, the NE (400) may be a network node as described in connection with FIG. 9. The NE (400) may be configured or operable to support means for receiving from a user device (UE) the ability of a UE to support a multi-hop sidelink layer 2 (L2) relay UE; and means for transmitting information indicating whether the network node supports a multi-hop sidelink L2 relay UE.

[0085] The controller (406) can manage input and output signals for the NE (400). The controller (406) can also manage peripherals not integrated into the NE (400). In some implementations, the controller (406) can use an operating system such as iOS®, ANDROID®, WINDOWS®, or other operating systems. In some implementations, the controller (406) can be implemented as part of the processor (402).

[0086] In some implementations, the NE (400) may include at least one transceiver (408). In some other implementations, the NE (400) may have more than one transceiver (408). The transceiver (408) may represent a wireless transceiver. The transceiver (408) may include one or more receiver chains (410), one or more transmitter chains (412), or a combination thereof. The aforementioned means for receiving or means for transmitting in the processor (402) may be implemented through at least one transceiver (408).

[0087] A receiver chain (410) may be configured to receive signals (e.g., control information, data, packets) over a wireless medium. For example, the receiver chain (410) may include one or more antennas for receiving signals over an airborne or wireless medium. The receiver chain (410) may include at least one amplifier (e.g., a low-noise amplifier (LNA)) configured to amplify the received signal. The receiver chain (410) may include at least one demodulator configured to obtain transmitted data by demodulating the received signal and inverting the modulation technique applied during the transmission of the signal. The receiver chain (410) may include at least one decoder for decoding and processing the demodulated signal to receive the transmitted data.

[0088] The transmitter chain (412) may be configured to generate and transmit signals (e.g., control information, data, packets). The transmitter chain (412) may include at least one modulator for modulating data on a carrier signal and preparing the signal for transmission over a wireless medium. The at least one modulator may be configured to support one or more digital modulation techniques, such as amplitude modulation (AM), frequency modulation (FM), or phase shift keying (PSK) or quadrature amplitude modulation (QAM). The transmitter chain (412) may also include at least one power amplifier configured to amplify the modulated signal to an appropriate power level suitable for transmission over a wireless medium. The transmitter chain (412) may also include one or more antennas for transmitting the amplified signal over the air or a wireless medium.

[0089] A person skilled in the art should understand that, without departing from the spirit and scope of the disclosure, the components of the exemplary NE (400) may be changed, for example, some of the components of the exemplary NE (400) may be omitted or modified, or new component(s) may be added to the exemplary NE (400). For example, in some embodiments, the NE (400) may not include a controller (406).

[0090] FIG. 5a illustrates a schematic diagram of a wireless communication system according to embodiments of the present disclosure. As illustrated in FIG. 5a, the wireless communication system (100) may support sidelink communication. Sidelink communication supports direct UE-to-UE communication. In the context of the present disclosure, sidelink communication may be categorized according to the wireless communication technologies adopted. For example, sidelink communication may include NR sidelink communication and V2X sidelink communication.

[0091] NR sidelink communications (as specified, for example, in the 3GPP TS 38 series specifications) may refer to access stratum (AS) capabilities that enable at least vehicle-to-everything (V2X) communication between neighboring UEs using NR technology but without traversing any network node. V2X sidelink communications (as specified, for example, in the 3GPP TS 36 series specifications) may refer to AS capabilities that enable V2X communication between neighboring UEs using evolved-universal mobile telecommunication system (UMTS) terrestrial radio access (UTRA) technology but without traversing any network node. However, unless specified, "sidelink communications" may refer to NR sidelink communications, V2X sidelink communications, or any sidelink communications adopting other radio communication technologies.

[0092] Referring to FIG. 5a, the wireless communication system (100) may include a certain number of base stations (e.g., BS (105) and BS (103)) and a certain number of UEs (e.g., UE (101A), UE (101B), and UE (101C)). Although a specific number of UEs and BSs are shown in FIG. 5a, it is taken into consideration that any number of UEs and BSs may be included in the wireless communication system (100).

[0093] UEs and BSs may support communication based on, for example, 3G, LTE (long-term evolution), LTE-A (LTE-advanced), NR (new radio), or other suitable protocol(s). In some embodiments of the present disclosure, a BS (e.g., BS (105) or BS (103)) may be referred to as an access point, access terminal, base, base unit, macro cell, node-B, evolved node-B (eNB), gNB, ng-eNB, home node-B, relay node, or device, or may be described using other terms used in the art. A UE (e.g., UE (101A), UE (101B), or UE (101C)) may include, but is not limited to, a computing device, a wearable device, a mobile device, an IoT device, a vehicle, etc.

[0094] In the example of FIG. 5a, BS (105) and BS (103) may be included in a next-generation radio access network (NG-RAN). In some embodiments of the present disclosure, BS (105) may be a gNB and BS (103) may be an ng-eNB.

[0095] UE (101A) and UE (101B) may be inside coverage (e.g., inside NG-RAN). For example, as shown in FIG. 5a, UE (101A) may be inside the coverage of BS (105), and UE (101B) may be inside the coverage of BS (103). UE (101C) may be outside coverage (e.g., outside the coverage of NG-RAN). For example, as shown in FIG. 5a, UE (101C) may be outside the coverage of any BS, e.g., both BS (105) and BS (103). UE (101A) and UE (101B) may each be connected to BS (105) and BS (103) through a network interface, e.g., a Uu interface specified in the 3GPP specification. The control plane protocol stack at the Uu interface may include an RRC layer that may be referred to as Uu RRC. A link established between a UE (e.g., UE (101A)) and a BS (e.g., BS (105)) may be referred to as a Uu link. BS (105) and BS (103) may be connected to each other via a network interface, for example, an Xn interface specified in a 3GPP standard document. UE (101A), UE (101B), and UE (101C) may each be connected to each other via a PC5 interface specified in a 3GPP standard document, for example. The control plane protocol stack at the PC5 interface may include an RRC layer that may be referred to as PC5 RRC. A link established between two UEs (e.g., UE (101A) and UE (101B)) may be referred to as a PC5 link.

[0096] Support for V2X services over the PC5 interface may be provided, for example, by NR sidelink communication and / or V2X sidelink communication. NR sidelink communication may support one of the following three types of transmission modes for a pair of source Layer 2 identity and destination Layer 2 identity: unicast transmission, groupcast transmission, and broadcast transmission. Sidelink communication transmission and reception over the PC5 interface are supported when the UE is inside or outside the coverage. For example, a UE (101A) inside the coverage of BS (105) may perform sidelink transmission and reception (e.g., sidelink unicast transmission, sidelink groupcast transmission, or sidelink broadcast transmission) through the PC5 interface. A UE (101C) outside the coverage of both BS (105) and BS (103) may also perform sidelink transmission(s) and reception(s) through the PC5 interface.

[0097] A UE that supports sidelink communication and / or V2X communication may be referred to as a V2X UE. A V2X UE may be a cell phone, a vehicle, a roadmap device, a computer, a laptop, an IoT (Internet of Things) device, or other types of devices according to some other embodiments of the present disclosure.

[0098] As mentioned above, sidelink-based relay functions may be supported in a communication network. Sidelink relays can provide connectivity to the network for other UEs (remote UEs). In some embodiments of the present disclosure, UE-to-network (U2N) relays are supported. For example, an Out-of-Coverage (OOC) UE communicating with a remote UE (e.g., an Out-of-Coverage (OOC) UE or an IC UE) may function as a relay UE between the IC UE's serving BS and the remote UE. Thus, the remote UE may communicate with the BS through this relay UE. Data between the remote UE and the BS may be transmitted by the relay UE. In this scenario, the relay UE may be referred to as the remote UE's serving relay, and the relay UE's serving BS or serving cell may be referred to as the remote UE's serving BS or serving cell, respectively.

[0099] In the present disclosure, a remote UE may have RRC states such as the RRC_IDLE state, RRC_INACTIVE state, and RRC_CONNECTED state as defined in 3GPP specifications. The RRC_IDLE state may also be referred to as the RRC idle state, etc. The RRC_INACTIVE state may also be referred to as the RRC inactive state, etc. The RRC_CONNECTED state may also be referred to as the RRC connected state, etc. A relay UE may be in the RRC_CONNECTED state to perform relaying of unicast data.

[0100] In some embodiments, the following RRC state combinations may be supported for L2 U2N relay operation:

[0101] - To perform the transmission or reception of relayed unicast data, both the relay UE and the remote UE may be in the RRC_CONNECTED state;

[0102] - As long as all remote UEs connected to the relay UE are in either the RRC_INACTIVE or RRC_IDLE state, the relay UE may be in the RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED state.

[0103] A single unicast link can be established between one relay UE and one remote UE. Traffic from the remote UE and traffic from the relay UE through a given relay UE can be separated on different Uu relay radio link control (RLC) channels. In some embodiments, for an L2 U2N relay, the remote UE may be configured to use only resource allocation mode 2 for data to be relayed.

[0104] FIG. 5b illustrates a schematic diagram of a relay-based wireless communication system according to embodiments of the present disclosure. The details described in all the aforementioned embodiments of the present disclosure are applicable to the embodiments illustrated in FIG. 5b.

[0105] As illustrated in FIG. 5b, a wireless communication system may include a BS (e.g., BS #1) and some UEs (e.g., relay UE #1 and remote UE #1). Although a specific number of UEs and BSs are illustrated in FIG. 5b, it is taken into consideration that any number of UEs and BSs may be included in the wireless communication system. In some examples, relay UE #1 may function as the UE (101A) or UE (101B) illustrated in FIG. 5a, and remote UE #1 may function as the UE (101C) illustrated in FIG. 5a.

[0106] As shown in FIG. 5b, relay UE #1 is within the coverage of BS #1. For example, relay UE #1 and BS #1 can establish an RRC connection between them. Remote UE #1 is outside the coverage of BS #1. The wireless communication system of FIG. 5b can support sidelink communication. For example, relay UE #1 communicates via sidelink with remote UE #1. A PC5 RRC connection can be established between remote UE #1 and relay UE #1.

[0107] In some embodiments of the present disclosure, remote UE #1 may initiate a procedure to establish a connection with BS #1 through relay UE #1 (i.e., U2N relay). After such a procedure, remote UE #1 may access BS #1 (e.g., a cell of BS #1) through relay UE #1. This cell may be referred to as the serving cell of remote UE #1. Remote UE #1 and BS #1 may establish an RRC connection between them. Relay UE #1 may also be referred to as the relay UE, sidelink relay, or serving relay of remote UE #1.

[0108] Although a single relay node (e.g., relay UE #1) between remote UE #1 and BS #1 is illustrated in FIG. 5b, it should be understood by those skilled in the art that any number of relay nodes may be included. Although remote UE #1 is illustrated in FIG. 5b as being outside the coverage of BS #1, in some other embodiments of the present disclosure, remote UE #1 may be considered to be within the coverage of BS #1. In these embodiments, remote UE #1 may connect directly to BS #1 and / or connect to BS #1 through relay UE #1.

[0109] FIG. 5c illustrates an exemplary procedure for a notification message according to embodiments of the present disclosure. The details described in all the aforementioned embodiments of the present disclosure are applicable to the embodiments illustrated in FIG. 5c.

[0110] Referring to FIG. 5c, in some embodiments, in operation (511), the relay UE (503) may transmit a notification message to the UE (501). In some examples, the relay UE (503) may be a relay UE such as the U2N relay UE. In this scenario, the notification message may also be referred to as a "notification message for the sidelink" or a "notification message sidelink message," etc.

[0111] In some embodiments of the present disclosure, the relay UE (503) may initiate the exemplary procedure of FIG. 5c, for example, when one of the following conditions is satisfied:

[0112] - In response to Uu RLF as described below; or

[0113] - In response to the reception of an RRC reconfiguration message containing a reconfigurationWithSync information element (IE), such as a handover command; or

[0114] - In response to cell reselection in relay UE (503); or

[0115] - In response to an RRC connection failure in a relay UE (503), which may include, for example, an RRC connection rejection, the expiration of a timer for an RRC setup request (e.g., timer T300 specified in the 3GPP specification), and an RRC resumption failure.

[0116] The notification message may include a type indicator (e.g., "Indicator Type"), which may indicate that the notification message is due to one of relay Uu RLF, relay handover, relay cell reselection, and / or relay connection failure.

[0117] Currently, details regarding discovery mechanisms in Layer 2 (L2) UE-to-Network (U2N) relay cases (e.g., multi-hop L2 U2N relay cases) have not yet been specifically discussed in wireless communication systems. For example, the following issues need to be addressed: whether an Out-of-Coverage (OOC) UE can operate as a child L2 relay UE; if so, what criteria can be configured for the UE "to operate as a child L2 relay UE"; what conditions allow the OOC child relay UE to perform the discovery mechanism; whether an In-Coverage (IC) UE can operate as a child L2 relay UE; if so, what criteria can be configured for the UE "to operate as a child L2 relay UE"; what conditions allow the IC child relay UE to perform the discovery mechanism; and what information can be transmitted by the parent relay UE and / or child relay UE during the discovery mechanism.

[0118] Embodiments of the present disclosure aim to solve the aforementioned problems. In embodiments of the present disclosure, a remote UE may access a serving BS (e.g., serving gNB) through two relay UEs, e.g., a first relay UE and a second relay UE. The first relay UE connects to the serving BS through a Uu interface. The first relay UE may be referred to as a parent relay UE, parent L2 relay UE, parent L2 U2N relay UE, parent sidelink relay, first hop relay UE, or top relay UE, etc. The second relay UE connects to the serving BS through the first relay UE. The second relay UE may be referred to as a child relay UE, child L2 relay UE, child L2 U2N relay UE, child sidelink relay, or second hop relay UE, etc. In embodiments of the present disclosure, a discovery message may also be referred to as a "relay discovery message," etc. A PC5 connection may also be referred to as a "PC5 RRC connection," "PC5-S connection," etc.

[0119] For example, some embodiments of the present disclosure provide criteria for an OOC UE to "operate as an L2 U2N relay UE." Some embodiments provide one or more conditions that enable the OOC UE to transmit or monitor discovery messages. Some embodiments provide criteria for an IC UE to "operate as an L2 U2N relay UE." Some embodiments of the present disclosure provide one or more conditions that enable the IC UE to transmit or monitor discovery messages. Some embodiments of the present disclosure provide enhanced discovery messages, for example, additional information related to multiple hops is added to the discovery message. In some embodiments of the present disclosure, a network node (e.g., BS) may broadcast whether to support a multi-hop sidelink (SL) L2 U2N relay.

[0120] In some embodiments of the present disclosure, the relay UE may be a UE-to-network relay UE that is a UE providing functionality to support connectivity to a network for U2N remote UE(s). More details of the embodiments of the present disclosure will be illustrated in the following text in combination with the accompanying drawings.

[0121] FIG. 6 illustrates a schematic diagram of a relay-based wireless communication system according to embodiments of the present disclosure. The details described in all the aforementioned embodiments of the present disclosure are applicable to the embodiments illustrated in FIG. 6. The embodiments of FIG. 6 refer to a wireless communication system having an architecture similar to that of FIG. 5b. Some embodiments of the present disclosure aim to provide a discovery mechanism in the wireless communication system illustrated in FIG. 6. Specific examples are described as follows in the embodiments of FIG. 7 through 12.

[0122] The wireless communication system illustrated in FIG. 6 includes BS #1 and some UEs (e.g., relay UE #1, relay UE #2, relay UE #3, remote UE #1 and remote UE #2). Although a specific number of UEs and BSs are illustrated in FIG. 6, it is taken into consideration that any number of UEs and BSs may be included in the wireless communication system. In some examples, relay UE #1, relay UE #2 or relay UE #3 may function as the UE (101A) or UE (101B) illustrated in FIG. 5a, and remote UE #1 or remote UE #2 may function as the UE (101C) illustrated in FIG. 5a.

[0123] As shown in FIG. 6, relay UE #1 and relay UE #3 are within the coverage of BS #1, meaning they are IC UEs. For example, relay UE #1 and BS #1 can establish an RRC connection between them. Relay UE #2, remote UE #1, and remote UE #2 are outside the coverage of BS #1, meaning they are OOC UEs. The wireless communication system of FIG. 6 supports sidelink communication. For example, relay UE #2 communicates via sidelink with remote UE #1. A PC5 RRC connection can be established between remote UE #1 and relay UE #2. Relay UE #3 communicates via sidelink with remote UE #2. A PC5 RRC connection can be established between remote UE #2 and relay UE #3.

[0124] In some embodiments of the present disclosure, remote UE #1 may initiate a procedure to establish a connection with BS #1 through both relay UE #1 and relay UE #2 (i.e., U2N relay). After such a procedure, remote UE #1 may access BS #1 (e.g., a cell of BS #1) through relay UE #1 and relay UE #2. This cell may be referred to as the serving cell of remote UE #1. Remote UE #1 and BS #1 may establish an RRC connection between them. Relay UE #1 connects to serving BS #1 through a Uu interface. Relay UE #1 may also be referred to as the first relay UE of remote UE #1, the first hop relay UE, the top relay UE, the parent relay UE, the parent L2 relay UE, the parent L2 U2N relay UE, the parent sidelink relay, or the parent serving relay, etc. Relay UE #2 is connected to serving BS #1 through relay UE #1. Relay UE #2 may also be referred to as the second relay UE of remote UE #1, second hop relay UE, child relay UE, child L2 relay UE, child L2 U2N relay UE, child sidelink relay, or child serving relay, etc.

[0125] Figure 6 illustrates two relay nodes (e.g., relay UE #1 and relay UE #2) between remote UE #1 and BS #1, but it should be understood by those skilled in the art that any number of relay nodes may be included.

[0126] In some embodiments of the present disclosure, remote UE #2 may initiate a procedure to establish a connection with BS #1 through both relay UE #1 and relay UE #3 (i.e., U2N relay). After this procedure, remote UE #2 may access BS #1 (e.g., a cell of BS #1) through relay UE #1 and relay UE #3. This cell may be referred to as the serving cell of remote UE #2. Remote UE #1 and BS #1 may establish an RRC connection between them. Relay UE #1 connects to serving BS #1 through the Uu interface. Relay UE #1 may also be referred to as the parent serving relay of remote UE #2, etc. Relay UE #3 connects to serving BS #1 through relay UE #1. Relay UE #3 may also be referred to as the second relay UE of remote UE #1, second hop relay UE, child relay UE, child L2 relay UE, child L2 U2N relay UE, child sidelink relay, or child serving relay, etc.

[0127] Figure 6 illustrates two relay nodes (e.g., relay UE #1 and relay UE #3) between remote UE #2 and BS #1, but it should be understood by those skilled in the art that any number of relay nodes may be included.

[0128] FIG. 7 illustrates a flowchart of a method related to an L2 U2N relay case according to embodiments of the present disclosure. The operations of this method may be implemented by a UE (which can operate as a child relay UE) as described herein. The UE may be an OOC UE (e.g., relay UE #2 of FIG. 6) or an IC UE (e.g., relay UE #3 of FIG. 6). In some embodiments, the UE may execute a set of instructions to control functional elements of the UE to perform the described functions. In some embodiments, embodiments of operations (702 and 704) may be performed by the UE (200) as described with reference to FIG. 2. Each of operations (702 and 704) may be performed according to examples as described herein. Specific examples are described below in the embodiments of FIG. 10 through 12.

[0129] In operation (702), the method may include the step of transmitting a discovery message (indicated as discovery message #1 for simplification) by a UE (e.g., relay UE #2 or relay UE #3 in FIG. 6). The discovery message may also be named "relay discovery message," etc.

[0130] In operation (704), the method may include the step of establishing a PC5 connection (indicated as PC5 connection #1) between a UE and a relay UE (e.g., relay UE #1 in FIG. 6), and the step of establishing a PC5 connection (indicated as PC5 connection #2) between a UE and a remote UE (e.g., remote UE #1 or remote UE #2 in FIG. 6). In operation (704), a connection between a relay UE and a network node (e.g., BS #1 in FIG. 6) is established, for example, through a Uu interface. The remote UE is expected to establish an end-to-end connection (e.g., an end-to-end RRC connection) toward the network node through both the UE (acting as a child relay UE) and the relay UE (acting as a parent relay UE). For example, as illustrated in FIG. 6, remote UE #1 is expected to establish an end-to-end connection toward BS #1 through relay UE #2 and relay UE #1. Remote UE #2 is expected to establish an end-to-end connection to BS #1 through relay UE #3 and relay UE #1.

[0131] The order in which operations (702 and 704) are performed may differ in different embodiments. In some embodiments, discovery message #1 is transmitted by the UE before establishing PC5 connection #1 or PC5 connection #2. In some other embodiments, discovery message #1 is transmitted by the UE after establishing PC5 connection #1 or PC5 connection #2.

[0132] In some implementations, the UE may receive information from a network node indicating whether the network node supports a multi-hop sidelink L2 relay UE. For example, the network node broadcasts the information via system information (e.g., a System Information Block (SIB)) or dedicated signaling. Specific examples are described in the embodiments of FIG. 12 as follows.

[0133] In some implementations, the UE can determine whether the channel quality of the PC5 link between the UE and the relay UE is greater than or equal to a threshold (indicated as threshold #1). If the channel quality of the PC5 link is greater than or equal to threshold #1, the UE can determine that the UE can operate as a multi-hop relay UE (e.g., two or more hop relay UEs), that is, the UE is qualified to operate as a multi-hop relay UE. For example, the UE may be qualified to operate as a child relay UE, e.g., a second-hop relay UE or a third-hop relay UE, by reference to a parent relay UE.

[0134] For example, Threshold #1 is the Reference Signal Receive Power (RSRP) threshold. In an implementation, Threshold #1 is a pre-configured threshold, for example, if the UE is an OOC UE by referencing a network node. In another implementation, after the UE transitions to an RRC connected state, an RRC idle state, or an RRC disabled state, the UE may receive configuration information regarding Threshold #1 from the network node, i.e., via broadcast signaling (e.g., SIB) or private signaling.

[0135] In an implementation, if the UE determines that it can operate as a multi-hop relay UE, the UE is allowed to transmit discovery message #1 or monitor other discovery messages before establishing PC5 connection #1. In some embodiments, if a PC5 link between a remote UE and a UE is established after the UE transmits discovery message #1, the UE may trigger to establish an end-to-end connection (i.e., a control plane connection) between the UE (operating as a child relay UE) and the network node.

[0136] For example, as illustrated in FIG. 6, remote UE #1 may select relay UE #2 as a child relay UE after receiving discovery message #1 from relay UE #2 (e.g., when remote UE #1 receives one or more discovery messages from different candidate relay UEs), and a PC5 link between remote UE #1 and relay UE #2 may be established, for example, based on an NR sidelink PC5 unicast link establishment procedure. Then, relay UE #2 may trigger to establish an end-to-end connection between relay UE #2 and BS #1.

[0137] In some implementations, when PC5 connection #1 is established, the UE is allowed to transmit discovery message #1. For example, after PC5 connection #1 is established, the UE is allowed to transmit discovery message #1 before establishing an end-to-end connection between the UE and BS #1. After transmitting discovery message #1, the UE can monitor discovery messages from the remote UE (indicated as discovery message #2). Discovery message #2 may contain information or elements similar to those of discovery message #1. Specific examples are described in the embodiments of FIG. 10 as follows.

[0138] In some implementations, when PC5 connection #1 is established and an end-to-end connection between the UE and the network node is established, the UE is allowed to transmit discovery message #1. Specific examples are described in the embodiments of FIG. 11 as follows.

[0139] In some implementations, the UE can determine whether the channel quality of the Uu link between the UE and the network node is less than or equal to a threshold (indicated as Threshold #2) (e.g., if the UE is an IC UE referencing the network node). If the channel quality of the Uu link is less than or equal to Threshold #2, the UE can determine that the UE can operate as a multi-hop relay UE. That is, the UE will connect to the network node via a parent-child relay UE. Threshold #2 is the Uu link threshold, for example, the RSRP threshold. For example, Threshold #2 may be the minimum Uu RSRP threshold configured by the network node.

[0140] In another implementation, if the UE determines that it can operate as a multi-hop relay UE, the UE may also determine whether the channel quality of the PC5 link between the UE and the relay UE is greater than or equal to a threshold (indicated as Threshold #3). If the channel quality of the PC5 link is greater than or equal to Threshold #3, the UE is allowed to transmit Discovery Message #1 before establishing PC5 Connection #1. For example, the UE is allowed to transmit Discovery Message #1 in response to satisfying one of the following conditions:

[0141] (1) PC5 connection #1 is established before an end-to-end connection is established between the UE and the network node;

[0142] (2) Establishing an end-to-end connection between the UE and the network node;

[0143] (3) The UE is configured to transition to an RRC connection state;

[0144] (4) The UE is configured to transition to an RRC idle state; or

[0145] (5) The UE is configured to transition to an RRC inactive state.

[0146] Threshold #3 is a PC5 link threshold, e.g., an RSRP threshold. For example, a UE may receive configuration information including threshold #2 and / or threshold #3 from a network node, e.g., via system information (e.g., SIB) or dedicated signaling. Specific examples are described as follows in the embodiments of FIG. 12.

[0147] In some implementations, the UE receives an RRC setup request message from a remote UE and can send the RRC setup request message to the relay UE on SRB 0 using the following:

[0148] (1) PC5 relay RLC channel for the PC5 link between the UE configured by the network and the relay UE; or

[0149] (2) Designated PC5 relay RLC channel (e.g., default PC5 relay RLC channel).

[0150] In the implementation, the UE may additionally receive an RRC setup message on SRB 0 from the relay UE using the "PC5 relay RLC channel" or the "specified PC5 relay RLC channel".

[0151] In some implementations, discovery message #1 includes at least one of the following:

[0152] (1) Information indicating whether to allow a relay UE to access a UE so that the UE can operate as a parent relay UE of the relay UE, e.g., information indicating whether to allow a child relay UE to access the UE;

[0153] (2) Information indicating whether the UE is an OOC UE or an IC UE by referring to a network node;

[0154] (3) Information indicating whether the UE is a single-hop relay UE or a multi-hop relay UE toward a network node;

[0155] (4) Information indicating whether a backhaul (BH) between the UE and the network node is established (i.e., whether the BH has already been established) in response to the fact that the UE is a multi-hop relay UE toward the network node;

[0156] (5) Total number of hops between the UE and network nodes;

[0157] (6) If the UE operates as a multi-hop relay UE (e.g., as a parent or child relay UE), the duration for which the UE can provide service;

[0158] (7) Information indicating whether there is one or more connected remote UEs with which a PC5 connection between one or more connected remote UEs and a UE has been established;

[0159] (8) Total number of one or more connected remote UEs;

[0160] (9) Channel quality of the PC5 link between the UE and the relay UE (e.g., the PC5 link between relay UE #2 and relay UE #1 in FIG. 6); or

[0161] (10) Channel quality of the Uu link between the UE and the network node (e.g., Uu RSRP) in response to the UE being within the coverage of the network node (e.g., relay UE #3 in FIG. 6).

[0162] It should be noted that the method described in FIG. 7 describes possible implementations, and that operations and steps may be rearranged, removed or modified in other ways, and that other implementations are possible without departing from the spirit and scope of the present disclosure.

[0163] FIG. 8 illustrates a flowchart of a method related to an L2 U2N relay case according to embodiments of the present disclosure. The operations of this method may be implemented by a UE (which can operate as a parent relay UE) as described herein. In some embodiments, the UE may execute a set of instructions to control functional elements of the UE to perform the described functions. In some embodiments, embodiments of operations (802 and 804) may be performed by the UE (200) as described with reference to FIG. 2. Each of operations (802 and 804) may be performed according to examples as described herein. Specific examples are described below in the embodiments of FIG. 10 through 12.

[0164] In operation (802), the method may include the step of transmitting a discovery message (indicated as discovery message #3) by a relay UE (e.g., relay UE #1 in FIG. 6). In operation (804), the method may include the step of establishing a PC5 connection between a relay UE and another relay UE (e.g., relay UE #2 or relay UE #3 in FIG. 6). For simplification, the relay UE is denoted as relay UE #a, and this other relay UE is denoted as relay UE #b. Relay UE #a may operate as a parent relay UE. Relay UE #b may operate as a child relay UE of relay UE #a. The PC5 connection between relay UE #a and relay UE #b may be referred to as "PC5 connection #1" as described in the embodiments of FIG. 7.

[0165] In operation (804), a connection between relay UE #a and a network node (e.g., BS #1 in FIG. 6) is established, for example, through the Uu interface. A remote UE (e.g., remote UE #1 or remote UE #2 in FIG. 6) is expected to establish an end-to-end connection to the network node through these two relay UEs, namely relay UE #a and relay UE #b. For example, as shown in FIG. 6, remote UE #1 is expected to establish an end-to-end connection to BS #1 through relay UE #2 and relay UE #1. Remote UE #2 is expected to establish an end-to-end connection to BS #1 through relay UE #3 and relay UE #1.

[0166] The order in which operations (802 and 804) are performed may differ in different embodiments. In some embodiments, discovery message #3 is transmitted by relay UE #a (e.g., relay UE #1 in FIG. 6) before establishing a PC5 connection between relay UE #a and relay UE #b. In some other embodiments, discovery message #3 is transmitted by relay UE #a after establishing a PC5 connection between relay UE #a and relay UE #b.

[0167] In some implementations, relay UE #a may receive information from a network node indicating whether the network node supports a multi-hop sidelink L2 relay UE. For example, the network node broadcasts this information via system information (e.g., SIB) or dedicated signaling. Specific examples are described in the embodiments of FIG. 12 as follows.

[0168] In some implementations, relay UE #a may receive a discovery message (e.g., discovery message #1 as described in the embodiments of FIG. 7) from relay UE #b before or after establishing a PC5 connection between relay UE #a and relay UE #b. The information or elements contained in discovery message #1 as described in the embodiments of FIG. 7 are applicable to the embodiments of FIG. 8.

[0169] In some implementations, discovery message #1 is received from relay UE #b in response to satisfying the following conditions:

[0170] (1) PC5 connection between relay UE #a and relay UE #b is established;

[0171] (2) Establishing an end-to-end connection between relay UE #b and network node; and

[0172] (3) Relay UE #b transitioning to RRC connected state, RRC idle state, or RRC inactive state.

[0173] In some implementations, relay UE #a may receive an RRC setup request message on SRB 0 from relay UE #b using (1) a PC5 relay RLC channel for a PC5 link between relay UE #b and relay UE #a configured by a network; or (2) a designated PC5 relay RLC channel, e.g., a default PC5 relay RLC channel. In an implementation, relay UE #a may transmit an RRC setup message on SRB 0 to relay UE #b using the first PC5 relay RLC channel or a designated PC5 relay RLC channel.

[0174] In some implementations, discovery message #3 includes at least one of the following:

[0175] (1) Information indicating whether to allow a relay UE to access relay UE #a so that relay UE #a can operate as a parent relay UE of relay UE, e.g., information indicating whether to allow a child relay UE to access relay UE #a;

[0176] (2) Information indicating whether relay UE #a is an OOC UE or an IC UE by referring to a network node;

[0177] (3) Information indicating whether relay UE #a is a single-hop relay UE or a multi-hop relay UE toward a network node;

[0178] (4) Information indicating whether a backhaul (BH) is established between relay UE #a and the network node in response to relay UE #a being a multi-hop relay UE toward the network node;

[0179] (5) Total number of hops between relay UE #a and network node;

[0180] (6) If relay UE #a operates as a multi-hop relay UE, the duration for which relay UE #a can provide service;

[0181] (7) Information indicating whether there is one or more connected remote UEs for which a PC5 connection between one or more connected remote UEs and relay UE #a has been established;

[0182] (8) Total number of one or more connected remote UEs; or

[0183] (9) Channel quality of the Uu link between relay UE #a and the network node in response to relay UE #a being within the coverage of the network node (e.g., relay UE #1 in FIG. 6).

[0184] It should be noted that the method described in FIG. 8 describes possible implementations, and that operations and steps may be rearranged, removed or modified in other ways, and that other implementations are possible without departing from the spirit and scope of the present disclosure.

[0185] FIG. 9 illustrates a flowchart of a method related to an L2 U2N relay case according to embodiments of the present disclosure. The operations of this method may be implemented by a network node, e.g., a BS as described herein. In some embodiments, the BS may execute a set of instructions to control functional elements of the BS to perform the described functions. In some embodiments, embodiments of operations (902 and 904) may be performed by an NE (400) as described with reference to FIG. 4. Each of operations (902 and 904) may be performed according to examples as described herein. Specific examples are described below in the embodiments of FIG. 10 through 12.

[0186] In operation (902), the method may include the step of receiving from a network node (e.g., BS #1 in FIG. 6) the ability of a UE to support a multi-hop sidelink L2 relay UE. The UE may be as follows:

[0187] (1) Remote UE (e.g., remote UE #1 or remote UE #2 of FIG. 6);

[0188] (2) a single-hop relay UE (e.g., relay UE #1 of FIG. 6); and / or

[0189] (3) Multi-hop relay UE (e.g., relay UE #2 or relay UE #3 of FIG. 6).

[0190] In operation (904), this method may include the step of transmitting information by the network node indicating whether the network node supports a multi-hop sidelink L2 relay UE.

[0191] In some implementations, the network node may additionally transmit at least one of the following to the UE, for example, through system information (e.g., SIB) or dedicated signaling:

[0192] (1) Configuration information regarding threshold #1, which is associated with the channel quality of the PC5 link between the UE and the relay UE, for example as described in the embodiments of FIG. 7.

[0193] (2) Configuration information regarding threshold #2, for example, as described in the embodiments of FIG. 7, which is associated with the channel quality of the Uu link between the UE and the network node (e.g., when the UE is an IC UE). For example, this threshold may be the minimum Uu RSRP threshold configured by the network node.

[0194] (3) Configuration information regarding the PC5 relay RLC channel configured for the PC5 link between the UE and the relay UE (indicated as Configuration #1). Specific examples are described in the embodiments of FIGS. 10 to 12 as follows.

[0195] It should be noted that the method described in FIG. 9 describes possible implementations, and that operations and steps may be rearranged, removed or modified in other ways, and that other implementations are possible without departing from the spirit and scope of the present disclosure.

[0196] FIG. 10 illustrates a schematic diagram of an L2 U2N relay case according to embodiments of the present disclosure. Details described in all other embodiments of the present disclosure are applicable to the embodiments illustrated in FIG. 10.

[0197] In an exemplary flowchart (1000) as illustrated in FIG. 10, in operation (1011), a UE (1002) (e.g., relay UE #2 of FIG. 6) (which will operate as a child relay UE) can transmit a relay discovery message (e.g., discovery message #1 as described in the embodiments of FIG. 7) and can monitor a relay discovery message (e.g., discovery message #2 as described in the embodiments of FIG. 7) from a remote UE (e.g., UE (1001)) on a side link between UE (1001) and UE (1002). Different operations may be performed in operation (1011) according to different embodiments, e.g., options #1 and #2 as described below.

[0198] Option #1: There is a threshold (e.g., threshold #1) for the PC5 link of the UE (1002) toward the parent relay UE (1003). In some embodiments, when the UE (1002) is outside the coverage of the BS (1004) (e.g., BS #1 in FIG. 6) (i.e., when the UE (1002) is an OOC UE), this threshold is a pre-configured threshold. In some embodiments, after the UE (1002) transitions to an RRC connected state, an RRC idle state, or an RRC inactive state, the BS (1004) (e.g., gNB) may transmit or configure this threshold to the UE (1002) via broadcast signaling or private signaling.

[0199] In Option #1, if the channel quality of the PC5 link between the UE (1002) and the parent relay UE (1003) is greater than or equal to a threshold (e.g., threshold #1), the UE (1002) can operate as a child relay UE. Then, the child relay UE (1002) is allowed to transmit or monitor discovery messages from other UEs. In Option #1, the child relay UE (1002) (e.g., is outside the coverage of the BS (1004)) can transmit discovery messages before connecting to the BS (1004). Once a remote UE (e.g., remote UE (1001)) selects the child relay UE (1002), the child relay UE (1002) will be triggered to establish a connection toward the network node.

[0200] Option #2: The UE (1002) (which will act as a child relay UE) has established a PC5 connection toward the parent relay UE (1003). Next, the child relay UE (1002) is allowed to send relay discovery messages, for example, toward a remote UE (1001), and can monitor relay discovery messages from, for example, the remote UE (1001) via a sidelink. In Option #2, if a PC5 connection has been established between the child relay UE (1002) (for example, outside the coverage of BS (1004)) and the parent relay UE (1003), the child relay UE (1002) is allowed to send discovery messages.

[0201] In operation (1011) (e.g., option #1 or option #2), at least one of the following information may be included in a discovery message broadcast by the UE (1002):

[0202] (1) Information indicating whether to allow a relay UE to access UE (1002) so that UE (1002) can operate as a parent relay UE of a relay UE, e.g., information indicating whether to allow a child relay UE to access UE (1002);

[0203] (2) Information indicating whether the UE (1002) is an OOC UE or an IC UE by referring to BS (1004);

[0204] (3) Information indicating whether the UE (1002) is a single-hop relay UE or a multi-hop relay UE toward the BS (1004);

[0205] (4) Information indicating whether a backhaul (BH) is established between UE (1002) and BS (1004) in response to UE (1002) being a multi-hop relay UE;

[0206] (5) Total number of hops between UE (1002) and BS (1004);

[0207] (6) The duration for which the UE (1002) can provide service when the UE (1002) operates as a multi-hop relay UE;

[0208] (7) Information indicating whether there is one or more connected remote UEs for which a PC5 connection between these connected remote UEs and UE (1002) has been established;

[0209] (8) Total number of one or more connected remote UEs;

[0210] (9) Channel quality of the PC5 link between the UE (1002) and its parent relay UE (1003) (e.g., the PC5 link between relay UE #2 and relay UE #1 in FIG. 6); or

[0211] (10) Channel quality of the Uu link between UE (1002) and BS (1004) (e.g., Uu RSRP) when UE (1002) is within the coverage of BS (1004) (e.g., relay UE #3 in FIG. 6).

[0212] In some embodiments, when the UE (1002) is within the coverage of the BS (1004), the UE (1002) may receive information from the BS (1004) indicating whether the BS (1004) supports a multi-hop sidelink L2 relay UE, for example, via system information or dedicated signaling. In some other embodiments, when the UE (1002) is outside the coverage of the BS (1004) while an end-to-end connection between the UE (1002) and the BS (1004) is being established via the parent relay UE (1003), the UE (1002) may receive such information from the BS (1004) via the parent relay UE (1003), for example, via system information or dedicated signaling. For example, if system information is used, the BS (1004) may transmit such information via the following SIB:

[0213]

[0214] In operation (1012), the UE (1001) (i.e., a remote UE outside the coverage of the BS (1004)) receives a discovery message transmitted by the UE (1002) and can select the UE (1002) as a child relay UE. For example, if the remote UE (1001) receives two or more discovery messages from the child relay UE (1002) or other relay UEs, the remote UE (1001) can select the child relay UE (1002) as that relay UE toward the BS (1004).

[0215] In operation (1013), the PC5 connection between the remote UE (1001) and the child relay UE (1002) is established based on the NR sidelink PC5 unicast link establishment procedure.

[0216] In operation (1014), the remote UE (1001) may send an RRC message (indicated as message #1), for example, an SRB 0 message, to establish its connection with the BS (1004) through the child relay UE (1002) and the parent relay UE (1003).

[0217] In some embodiments of operation (1014), the remote UE (1001) transmits message #1 (i.e., an RRC setup request message) to the child relay UE (1002) to establish its connection with the BS (1004) using a designated PC5 relay RLC channel (e.g., a default PC5 relay RLC channel). After receiving message #1 from the remote UE (1001), the child relay UE (1002) may transmit message #1 to the BS (1004) via either the "configured PC5 relay RLC channel" or the "designated PC5 relay RLC channel (e.g., a default PC5 relay RLC channel)." For example, different embodiments, such as options #A and #B as described below, may exist.

[0218] Option #A: In some implementations, the child relay UE (1002) may send message #1 (e.g., an RRC setup request message) for establishing a connection with the BS (1004) (received from the remote UE (1001)) to the parent relay UE (1003) via a designated PC5 relay RLC channel through the PC5 link between the child relay UE (1002) and the parent relay UE (1003). Then, the parent relay UE (1003) sends message #1 to the BS (1004) via a designated Uu relay RLC channel through the Uu link between the parent relay UE (1003) and the BS (1004).

[0219] Option #B: In some implementations, when the child relay UE (1002) is not in an RRC state or is not connected to the BS (1004), it is necessary to establish an end-to-end RRC connection with the BS (1004) through the parent relay UE (1003) upon receipt of a message (e.g., message #1) on a designated PC5 relay RLC channel between the child relay UE (1002) and the remote UE (1001). For example, the child relay UE (1002) may transmit an RRC message (indicated as message #2) (e.g., an RRC setup request message) to establish a connection with the BS (1004) through a designated PC5 relay RLC channel between the child relay UE (1002) and the parent relay UE (1003). Next, the parent relay UE (1003) can transmit message #2 to the BS (1004) via a designated Uu relay RLC channel through the Uu link between the parent relay UE (1003) and the BS (1004). After receiving message #2, the BS (1004) can configure the PC5 relay RLC channel for the PC5 link between the child relay UE (1002) and the parent relay UE (1003). For example, the BS (1004) can transmit the corresponding configuration information (e.g., configuration #1 described in FIG. 9) to the child relay UE (1002) through the parent relay UE (1003). Next, the child relay UE (1002) can transmit message #1, that is, an SRB 0 message (e.g., an RRC setup request message) received from the remote UE (1001), to the BS (1004) through one of the “configured PC5 relay RLC channel” and “specified PC5 relay RLC channel (e.g., default PC5 relay RLC channel)” between the child relay UE (1002) and the parent relay UE (1003).

[0220] In some embodiments of Option #B, if the parent relay UE (1003) is not in the RRC_CONNECTED state, it is necessary to establish its own Uu RRC connection upon receiving a message (e.g., message #2) on the designated PC5 relay RLC channel between the child relay UE (1002) and the parent relay UE (1003). After completing the procedure to establish the RRC connection of the parent relay UE (1003), the BS (1004) may configure an SRB 0 to relay the Uu relay RLC channel to the parent relay UE (1003). In some embodiments, the parent relay UE (1003) may transmit a discovery message (e.g., discovery message #3 described in the embodiment of FIG. 8) before allowing the UE (1002) to access the parent relay UE (1003) and operate as a child relay UE.

[0221] In operation (1015), BS (1004) may respond to the remote UE (1001) with an RRC setup message. In some embodiments, BS (1004) may transmit the RRC setup message to the parent relay UE (1003) using SRB 0 relaying a Uu relay RLC channel (e.g., configured by BS (1004)) through a Uu link between BS (1004) and the parent relay UE (1003). Then, the parent relay UE (1003) may transmit the RRC setup message to the child relay UE (1002) through a PC5 link between the child relay UE (1002) and the parent relay UE (1003) using a configured PC5 relay RLC channel (configured by BS (1004)) or a designated PC5 relay RLC channel. After that, the child relay UE (1002) can send an RRC setup message to the remote UE (1001) using the designated PC5 relay RLC channel through the PC5 link between the child relay UE (1002) and the remote UE (1001).

[0222] In operation (1016), the remote UE (1001) can transmit data to the BS (1004) or receive data from the BS (1004) through an end-to-end RRC connection.

[0223] FIG. 11 illustrates a schematic diagram of an L2 U2N relay case according to embodiments of the present disclosure. Details described in all other embodiments of the present disclosure are applicable to the embodiments illustrated in FIG. 11.

[0224] In an exemplary flowchart (1100) as illustrated in FIG. 11, in operation (111), a UE (1102) (which will operate as a child relay UE) (e.g., relay UE #2 or relay UE #3 of FIG. 6) can transmit a relay discovery message (e.g., discovery message #1 as described in the embodiments of FIG. 7) and can monitor a relay discovery message (e.g., discovery message #2 as described in the embodiments of FIG. 7) from a remote UE (e.g., UE (1101)) on a side link between UE (1101) and UE (1102).

[0225] In some embodiments of operation (111), when the UE (1102) transitions to an RRC connected state (or an RRC idle state or an RRC inactive state), the UE (1102) is allowed to transmit a discovery message. That is, the condition for the UE (1102) operating as a child relay UE is that the UE (1102) transitions to an RRC connected state, an RRC idle state, or an RRC inactive state. For example, if a PC5 connection is established between the UE (1102) (i.e., child relay UE (1102)) and the UE (1103) (i.e., parent relay UE (1103)), and an end-to-end connection is established between the child relay UE (1102) and the BS (1104), when the child relay UE (1102) transitions to one of the “RRC connected state, RRC idle state, and RRC inactive state,” the child relay UE (1102) is allowed to transmit a discovery message.

[0226] In some implementations, when the child relay UE (1102) is in an RRC connection state, the PC5 relay RLC channel for the PC5 link between the child relay UE (1102) and the parent relay UE (1103) may be configured by BS (1104) for an SRB 0 message (e.g., an RRC setup request message) received from the remote UE (1101). Details are described below in option #Y.

[0227] In operation (111), at least one of the following information may be included in a discovery message broadcast by the UE (1102):

[0228] (1) Information indicating whether to allow a relay UE to access the UE (1102) so that the UE (1102) can operate as a parent relay UE of the relay UE, e.g., information indicating whether to allow a child relay UE to access the UE (1102);

[0229] (2) Information indicating whether the UE (1102) is an OOC UE or an IC UE by referring to BS (1104);

[0230] (3) Information indicating whether the UE (1102) is a single-hop relay UE or a multi-hop relay UE toward the BS (1104);

[0231] (4) Information indicating whether a backhaul (BH) is established between UE (1102) and BS (1104) in response to UE (1102) being a multi-hop relay UE;

[0232] (5) Total number of hops between UE (1102) and BS (1104);

[0233] (6) The duration for which the UE (1102) can provide service when the UE (1102) operates as a multi-hop relay UE;

[0234] (7) Information indicating whether there is one or more connected remote UEs with which a PC5 connection is established between the UE (1102) and the UE;

[0235] (8) Total number of one or more connected remote UEs;

[0236] (9) Channel quality of the PC5 link between the UE (1102) and the parent relay UE (1103) (e.g., the PC5 link between relay UE #2 and relay UE #1 in FIG. 6); or

[0237] (10) When UE (1102) is within the coverage of BS (1104) (e.g., relay UE #3 in FIG. 6), the channel quality of the Uu link between UE (1102) and BS (1104) (e.g., Uu RSRP value).

[0238] In some embodiments, when the UE (1102) is within the coverage of the BS (1104), the UE (1102) may receive information from the BS (1104) indicating whether the BS (1104) supports a multi-hop sidelink L2 relay UE, for example, via system information or dedicated signaling. In some other embodiments, when the UE (1102) is outside the coverage of the BS (1104) while an end-to-end RRC connection between the UE (1102) and the BS (1104) is being established via the parent relay UE (1103), the UE (1102) may receive such information from the BS (1104) via the parent relay UE (1103), for example, via system information or dedicated signaling. For example, if system information is used, the BS (1104) may transmit such information via the following SIB:

[0239]

[0240] In operation (112), the UE (1101) (i.e., a remote UE outside the coverage of the BS (1104)) receives a discovery message transmitted by the UE (1102) and can select the UE (1102) as a child relay UE. For example, if the remote UE (1101) receives two or more discovery messages from the child relay UE (1102) or other relay UEs, the remote UE (1101) can select the child relay UE (1102) as that relay UE toward the BS (1104).

[0241] In operation (113), the PC5 connection between the remote UE (1101) and the child relay UE (1102) is established based on the NR sidelink PC5 unicast link establishment procedure.

[0242] In operation (114), the remote UE (1101) may send an RRC message (indicated by message #a), for example, an SRB 0 message, to establish its connection with the BS (1104) through the child relay UE (1102) and the parent relay UE (1103).

[0243] In some embodiments of operation (114), the remote UE (1101) transmits message #a (i.e., an RRC setup request message) to the child relay UE (1102) to establish its connection with the BS (1104) using a designated PC5 relay RLC channel (e.g., a default PC5 relay RLC channel). After receiving message #a from the remote UE (1101), the child relay UE (1102) may transmit message #a to the BS (1104) via either the "configured PC5 relay RLC channel" or the "designated PC5 relay RLC channel (e.g., a default PC5 relay RLC channel)." For example, different embodiments, such as the following options #X and option #Y, may exist.

[0244] Option #X: In some implementations, the child relay UE (1102) may send message #a (e.g., an RRC setup request message) for establishing a connection with the BS (1104) (received from the remote UE (1101)) to the parent relay UE (1103) via a designated PC5 relay RLC channel through the PC5 link between the child relay UE (1102) and the parent relay UE (1103). Then, the parent relay UE (1103) sends message #a to the BS (1104) via a designated Uu relay RLC channel through the Uu link between the parent relay UE (1103) and the BS (1104).

[0245] Option #Y: In some implementations, when the child relay UE (1102) is not in an RRC state or is not connected to the BS (1104), for example, upon receiving a message (e.g., message #a) on a designated PC5 relay RLC channel from a remote UE (1101), it is necessary to establish an end-to-end RRC connection with the BS (1104) through the parent relay UE (1103). For example, the child relay UE (1102) may transmit an RRC message (indicated as message #b) (e.g., an RRC setup request message) to establish a connection with the BS (1104) through a designated PC5 relay RLC channel between the child relay UE (1102) and the parent relay UE (1103). Next, the parent relay UE (1103) transmits message #b to the BS (1104) via a designated Uu relay RLC channel through the Uu link between the parent relay UE (1103) and the BS (1104). After receiving message #b, the BS (1104) can configure the PC5 relay RLC channel for the PC5 link between the child relay UE (1102) and the parent relay UE (1103). For example, the BS (1104) can transmit the corresponding configuration information (e.g., configuration #1 described in FIG. 9) to the child relay UE (1102) through the parent relay UE (1103). After that, the child relay UE (1102) can transmit message #a, that is, an SRB 0 message (e.g., an RRC setup request message) received from the remote UE (1101), to the BS (1104) through the “configured PC5 relay RLC channel” or “specified PC5 relay RLC channel (e.g., default PC5 relay RLC channel)” between the child relay UE (1102) and the parent relay UE (1103).

[0246] In some embodiments of Option #Y, if the parent relay UE (1103) is not in the RRC_CONNECTED state, it is necessary to establish its own Uu RRC connection upon receiving a message (e.g., message #a or message #b) from the child relay UE (1102) on the designated PC5 relay RLC channel between the child relay UE (1102) and the parent relay UE (1103). After completing the procedure to establish the RRC connection of the parent relay UE (1103), the BS (1104) may configure an SRB 0 to relay the Uu relay RLC channel to the parent relay UE (1103). In some embodiments, the parent relay UE (1103) may transmit a discovery message (e.g., discovery message #3 described in the embodiment of FIG. 8) before allowing the UE (1102) to access the parent relay UE (1103) and operate as a child relay UE.

[0247] In operation (115), BS (1104) may respond to the remote UE (1101) with an RRC setup message. In some embodiments, BS (1104) may transmit the RRC setup message to the parent relay UE (1103) using SRB 0 relaying a Uu relay RLC channel (e.g., configured by BS (1104)) through a Uu link between BS (1104) and the parent relay UE (1103). Then, the parent relay UE (1103) may transmit the RRC setup message to the child relay UE (1102) through a PC5 link between the child relay UE (1102) and the parent relay UE (1103) using a configured PC5 relay RLC channel (configured by BS (1104)) or a designated PC5 relay RLC channel. After that, the child relay UE (1102) can send an RRC setup message to the remote UE (1101) using the designated PC5 relay RLC channel through the PC5 link between the child relay UE (1102) and the remote UE (1101).

[0248] In operation (116), the remote UE (1101) can transmit data to the BS (1104) or receive data from the BS (1104) through an end-to-end RRC connection.

[0249] FIG. 12 illustrates a schematic diagram of an L2 U2N relay case according to embodiments of the present disclosure. Details described in all other embodiments of the present disclosure are applicable to the embodiments illustrated in FIG. 12.

[0250] In the exemplary flowchart (1200) illustrated in FIG. 12, in operation (121), the UE (1202) accesses the serving BS (1204) (e.g., gNB) through the Uu interface. The UE (1202) is within the coverage of the BS (1204). That is, the UE (1202) is an IC UE (e.g., relay UE #3 in FIG. 6). For example, the UE (1202) may report one or more measurement results based on configuration information from the BS (1204). The measurement results may include measurement results for a cell or a candidate relay UE.

[0251] In some embodiments, the UE (1202) receives a configuration related to a multi-hop relay from the BS (1204). The BS (1204) may transmit information indicating whether to support a multi-hop L2 U2N relay (or child L2 U2N relay) via system information (e.g., SIB) or dedicated signaling. If system information is used, the BS (1204) may transmit this information via the following SIB.

[0252]

[0253] In some embodiments, the BS (1204) may transmit a threshold of Uu channel quality (e.g., threshold #2 described in the embodiment of FIG. 7) via system information (e.g., SIB) or dedicated signaling. For example, this threshold may be a "minimum Uu RSRP threshold" used for a UE operating as an L2 relay UE. If the channel quality of the Uu channel between the UE (1202) and the BS (1204) is less than or equal to the threshold, the UE (1202) is allowed to operate as a "child L2 relay UE," i.e., as a child relay (1202) (e.g., relay UE #3 in FIG. 6), and thus the condition for operating as a child relay UE is satisfied. That is, the UE (1202) needs to connect with the BS (1204) through a parent relay UE (e.g., relay UE #1 in FIG. 6). In some embodiments, the parent relay UE (1203) may transmit a discovery message (e.g., discovery message #3 described in the embodiment of FIG. 8) before allowing the UE (1202) to access the parent relay UE (1203) and operate as a child relay UE.

[0254] In operation (122), the child relay UE (1202) is allowed to transmit a discovery message (e.g., discovery message #1 as described in the embodiments of FIG. 7) and monitor a discovery message (e.g., discovery message #2 as described in the embodiments of FIG. 7) based on any of the following conditions, namely, condition #1, condition #2 and condition #3.

[0255] Condition #1: Conditions for operating as a child relay UE are satisfied (e.g., the channel quality of the Uu channel between UE (1202) and BS (1204) is less than or equal to threshold #2), and the channel quality of the PC5 link between the child relay UE (1202) and the parent relay UE (1203) is greater than or equal to the threshold (e.g., threshold #3 described in the embodiments of FIG. 7). The PC5 connection between the child relay UE (1202) and the parent relay UE (1203) has not yet been established. That is, when Condition #1 is satisfied, the child relay UE (1202) is allowed to transmit discovery messages and monitor discovery messages, whereas the PC5 connection between the child relay UE (1202) and the parent relay UE (1203) does not need to be established.

[0256] Condition #2: Conditions for operating as a child relay UE are satisfied (e.g., the channel quality of the Uu channel between the UE (1202) and the BS (1204) is less than or equal to threshold #2), the channel quality of the PC5 link between the child relay UE (1202) and the parent relay UE (1203) is greater than or equal to the threshold (e.g., threshold #3 described in the embodiments of FIG. 7), and the PC5 connection between the child relay UE (1202) and the parent relay UE (1203) is already established. However, the child relay UE (1202) connects to the BS (1204) via the Uu interface. That is, the child relay UE (1202) is allowed to transmit discovery messages and monitor discovery messages when condition #2 is satisfied, whereas the end-to-end connection between the child relay UE (1202) and the BS (1204) does not need to be established.

[0257] Condition #3: The child relay UE (1202) connects to the BS (1204) through the parent relay UE (1203). That is, an end-to-end connection is established between the child relay UE (1202) and the BS (1204). That is, when Condition #3 is satisfied, the child relay UE (1202) is allowed to transmit discovery messages and monitor discovery messages, where an end-to-end connection is established between the child relay UE (1202) and the BS (1204). After Condition #3 is satisfied, the child relay UE (1202) may be in one of the RRC_CONNECTED, RRC_IDLE, or RRC_INACTIVE states.

[0258] In operation (123), the remote UE (1201) receives a discovery message transmitted by the child relay UE (1202) and can select the UE (1202) as the child relay UE. For example, if the remote UE (1201) receives two or more discovery messages from the child relay UE (1202) or other relay UEs, the remote UE (1201) can select the UE (1202) as the child relay UE.

[0259] In operation (124), the PC5 connection between the remote UE (1201) and the child relay UE (1202) is established based on the NR sidelink PC5 unicast link establishment procedure.

[0260] In operation (125), the remote UE (1201) may send an RRC message (indicated by message #x), for example, an SRB 0 message, to establish its connection with the BS (1204) through the child relay UE (1202) and the parent relay UE (1203).

[0261] In some embodiments of operation (125), the remote UE (1201) transmits message #x (i.e., an RRC setup request message) to the child relay UE (1202) to establish its connection with the BS (1204) using a designated PC5 relay RLC channel (e.g., a default PC5 relay RLC channel). After receiving message #x from the remote UE (1201), the child relay UE (1202) may transmit message #x to the BS (1204) via either the "configured PC5 relay RLC channel" or the "designated PC5 relay RLC channel (e.g., a default PC5 relay RLC channel)." For example, different embodiments, such as options #M and #N as described below, may exist.

[0262] Option #M: In some implementations, the child relay UE (1202) may send message #x (e.g., an RRC setup request message) for establishing a connection with the BS (1204) (received from the remote UE (1201)) to the parent relay UE (1203) via a designated PC5 relay RLC channel through the PC5 link between the child relay UE (1202) and the parent relay UE (1203). Then, the parent relay UE (1203) sends message #x to the BS (1204) via a designated Uu relay RLC channel through the Uu link between the parent relay UE (1203) and the BS (1204).

[0263] Option #N: In some implementations, if the child relay UE (1202) is not in an RRC state or is not connected to the BS (1204), for example, upon receiving a message (e.g., message #x) on a designated PC5 relay RLC channel from a remote UE (1201), it is necessary to establish an end-to-end RRC connection with the BS (1204) through the parent relay UE (1203). For example, the child relay UE (1202) may transmit an RRC message (indicated by message #y) (e.g., an RRC setup request message) to establish a connection with the BS (1204) through a designated PC5 relay RLC channel between the child relay UE (1202) and the parent relay UE (1203). Next, the parent relay UE (1203) transmits message #y to the BS (1204) via a designated Uu relay RLC channel through the Uu link between the parent relay UE (1203) and the BS (1204). After receiving message #y, the BS (1204) can configure the PC5 relay RLC channel for the PC5 link between the child relay UE (1202) and the parent relay UE (1203). For example, the BS (1204) can transmit the corresponding configuration information (e.g., configuration #1 described in FIG. 9) to the child relay UE (1202) through the parent relay UE (1203). Next, the child relay UE (1202) can transmit message #x, that is, an SRB 0 message (e.g., an RRC setup request message) received from the remote UE (1201), to the BS (1204) through the “configured PC5 relay RLC channel” or “specified PC5 relay RLC channel (e.g., default PC5 relay RLC channel)” between the child relay UE (1202) and the parent relay UE (1203).

[0264] In some embodiments of Option #N, if the parent relay UE (1203) is not in the RRC_CONNECTED state, it is necessary to establish its own Uu RRC connection upon receiving a message (e.g., message #x or message #y) from the child relay UE (1202) on the designated PC5 relay RLC channel between the child relay UE (1202) and the parent relay UE (1203). After completing the procedure to establish the RRC connection of the parent relay UE (1203), the BS (1204) may configure an SRB 0 to relay the Uu relay RLC channel to the parent relay UE (1203).

[0265] In operation (126), BS (1204) may respond to the remote UE (1201) with an RRC setup message. In some embodiments, BS (1204) may transmit the RRC setup message to the parent relay UE (1203) using SRB 0 relaying a Uu relay RLC channel (e.g., configured by BS (1204)) through a Uu link between BS (1204) and the parent relay UE (1203). Then, the parent relay UE (1203) may transmit the RRC setup message to the child relay UE (1202) through a PC5 link between the child relay UE (1202) and the parent relay UE (1203) using a configured PC5 relay RLC channel (configured by BS (1204)) or a designated PC5 relay RLC channel. After that, the child relay UE (1202) can send an RRC setup message to the remote UE (1201) using the designated PC5 relay RLC channel through the PC5 link between the child relay UE (1202) and the remote UE (1201).

[0266] In operation (127), the remote UE (1201) can transmit data to the BS (1204) or receive data from the BS (1204) through an end-to-end RRC connection.

[0267] The description in this specification is provided to enable a person skilled in the art to make or use the disclosed content. Various modifications to the disclosed content will be apparent to a person skilled in the art, and the general principles defined in this specification may be applied to other variations without departing from the scope of the disclosed content. Accordingly, the disclosed content is not limited to the examples and designs described in this specification, but should be understood in the broadest scope consistent with the principles and novel features disclosed in this specification.

Claims

Claim 1 A first user device (UE) comprising at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor causes the first UE to transmit a discovery message; is configured to establish a first PC5 connection between the first UE and a first relay UE and establish a second PC5 connection between the first UE and a remote UE, and establish a connection between the first relay UE and a network node, and the remote UE is expected to establish an end-to-end connection toward the network node through both the first UE and the first relay UE. Claim 2 In claim 1, the processor of the first UE is configured to receive first information from the network node indicating whether the network node supports a multi-hop sidelink layer 2 (L2) relay UE. Claim 3 A first UE, wherein the processor of the first UE determines whether the channel quality of the PC5 link between the first UE and the first relay UE is greater than or equal to a first threshold; and the first UE is configured to determine that the first UE can operate as a multi-hop relay UE in response to the channel quality of the PC5 link between the first UE and the first relay UE being greater than or equal to the first threshold. Claim 4 In paragraph 3, in response to the fact that the first UE can operate as the multi-hop relay UE, the first UE is allowed to transmit the discovery message or monitor other discovery messages before establishing the first PC5 connection. Claim 5 In paragraph 4, the processor of the first UE is configured to trigger the establishment of an end-to-end connection between the first UE and the network node in response to the PC5 link between the remote UE and the first UE being established after the first UE transmits the discovery message. Claim 6 In paragraph 3, the first threshold is a first UE, which is a pre-configured threshold. Claim 7 In paragraph 1, the first UE is allowed to transmit the discovery message in response to the establishment of the first PC5 connection. Claim 8 In claim 1, the first UE is allowed to transmit the discovery message in response to the first PC5 connection being established and the end-to-end connection between the first UE and the network node being established. Claim 9 A first UE according to claim 1, wherein the processor of the first UE determines whether the channel quality of the Uu link between the first UE and the network node is less than or equal to a second threshold; and in response to the channel quality of the Uu link between the first UE and the network node being less than or equal to the second threshold, the first UE is configured to determine that the first UE can operate as a multi-hop relay UE. Claim 10 In claim 9, in response to the fact that the first UE can operate as the multi-hop relay UE, the processor of the first UE is configured to determine whether the channel quality of the PC5 link between the first UE and the first relay UE is greater than or equal to a third threshold; and in response to the fact that the channel quality of the PC5 link between the first UE and the first relay UE is greater than or equal to the third threshold, the first UE is allowed to transmit the discovery message before establishing the first PC5 connection. Claim 11 In claim 9 or 10, the processor of the first UE is configured to receive first configuration information including the second threshold, the third threshold, or a combination thereof from the network node, the first UE. Claim 12 In paragraph 2 or 11, the first information, the first configuration information, or a combination thereof is a first UE received by the first UE from the network node via system information or dedicated signaling. Claim 13 In claim 9, in response to the fact that the first UE can operate as the multi-hop relay UE, the first UE is allowed to transmit the discovery message in response to satisfying one of the following conditions: that the first PC5 connection is established before the end-to-end connection between the first UE and the network node is established; that the end-to-end connection between the first UE and the network node is established; or that the first UE is configured to transition to an RRC connected state, an RRC idle state, or an RRC inactive state. Claim 14 In any one of paragraphs 2 through 13, the processor of the first UE receives an RRC setup request message from the remote UE; A first PC5 relay radio link control (RLC) channel for a PC5 link between the first UE and the first relay UE configured by a network; and A first UE configured to transmit the RRC setup request message to the first relay UE on signaling radio bearer (SRB) 0 using one of the designated PC5 relay RLC channels. Claim 15 In paragraph 14, the processor of the first UE is, The above first PC5 relay RLC channel; and A first UE configured to receive an RRC setup message from the first relay UE on the SRB 0 using one of the designated PC5 relay RLC channels. Claim 16 In any one of claims 1 to 15, the discovery message comprises: information indicating whether the relay UE allows access to the first UE so that the first UE can operate as the parent relay UE of the relay UE; information indicating, with reference to the network node, whether the first UE is an Out-of-Coverage (OOC) UE or an In-Coverage (IC) UE; information indicating whether the first UE is a single-hop relay UE or a multi-hop relay UE toward the network node; information indicating whether a backhaul (BH) is established between the first UE and the network node in response to the first UE being the multi-hop relay UE toward the network node; the total number of hops between the first UE and the network node; the duration for which the first UE can provide service if the first UE operates as the multi-hop relay UE; information indicating whether there exists one or more connected remote UEs with which a PC5 connection is established between the first UE and the first UE; the total number of the one or more connected remote UEs; and the PC5 between the first UE and the first relay UE. A first UE comprising: the channel quality of a link; the channel quality of a Uu link between the first UE and the network node in response to the first UE being within the coverage of the network node; or a combination thereof. Claim 17 A first relay user device (UE) comprising at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to cause the first relay UE to transmit a first discovery message; and to establish a first PC5 connection between the first relay UE and a second relay UE, wherein a connection between the first relay UE and a network node is established, and a remote UE is expected to establish an end-to-end connection toward the network node through both the second relay UE and the first relay UE. Claim 18 In paragraph 17, the processor of the first relay UE is configured to receive first information from the network node indicating whether the network node supports a multi-hop sidelink layer 2 (L2) relay UE. Claim 19 A network node comprising: at least one memory; and at least one processor coupled to the at least one memory, wherein the at least one processor is configured to enable the network node to receive, from a user device (UE), the capability of the UE to support a multi-hop sidelink layer 2 (L2) relay UE; and to transmit information indicating whether the network node supports the multi-hop sidelink L2 relay UE. Claim 20 In paragraph 19, the processor of the network node is configured to transmit to the UE at least one of: first configuration information regarding a first threshold associated with the channel quality of a PC5 link between the UE and a first relay UE; second configuration information regarding a second threshold associated with the channel quality of a Uu link between the UE and the network node; or third configuration information regarding a PC5 relay radio link control (RLC) channel configured for the PC5 link between the UE and the first relay UE.

Images