Side Link Relay Channel Establishment Method and Device

Abstract

Embodiments of the present invention provide a method for establishing a sidelink relay channel and a user equipment. In a demonstration example, a relay UE establishes a sidelink relay channel when receiving a sidelink relay connection request. In one embodiment, the above request comes from a base station to a relay UE within the network coverage. In another embodiment, the above request comes from a remote UE that requests services from a relay UE outside the network coverage. The relay UE performs service relaying between two end nodes of a sidelink relay path at L2 or L3. In another embodiment, a specific PC5 RRC message is used to initiate a relay channel establishment process between the relay UE and the remote UE. In another embodiment, the network sends a relay channel configuration to the relay UE before the process starts. The relay UE maintains a mapping relationship between the relay channel ID and the end-to-end radio bearer index for bearer mapping. By utilizing the present invention, sidelink relay communication can be better carried out.

Description

Technical Field

[0001] The present invention relates to wireless communication, and more particularly to sidelink (SL) relay channel establishment. Background Art

[0002] 5G radio access technology will become a key component of modern access networks, which will address high traffic growth and the increasing demand for high-bandwidth connections. Wireless relays in cellular networks can provide extended coverage and improved transmission reliability. The Long Term Evolution (LTE) network introduced 3GPP SL, which is direct communication between two User Equipments (UEs) without signal relaying through a base station. In 3GPP New Radio (NR), SL continues to evolve. With new features being supported one after another, SL provides low latency, high reliability, and high throughput for communication between devices. Using SL for wireless relay can provide a reliable and efficient way for service forwarding. SL relay has evolved from the Proximity Services (ProSe) UE-to-Network relay at layer 3 (L3) to the UE-to-Network relay at layer 2 (L2), with the expectation of forwarding traffic between a remote UE and a base station at an adaptation layer between the Radio Link Control (RLC) layer and the Packet Data Convergence Protocol (PDCP) layer. In addition, the NR network also supports Integrated Access Backhaul (IAB) to support layer 2-based relay operations between UEs and base stations. A Backhaul Adaptation Protocol (BAP) layer is defined above the RLC on the Uu interface in the relay path. The RLC channel for relay in IAB is established before any relay operation of the UE. Existing link establishment protocols lack support for relay channel establishment.

[0003] Improvements and enhancements are needed to establish a sidelink relay channel to support sidelink relay communication. Summary of the Invention

[0004] Embodiments of the present invention provide a method for establishing a sidelink relay channel and a user equipment. In a demonstration example, a relay UE establishes a sidelink relay channel when receiving a sidelink relay connection request. In one embodiment, the above request comes from a base station to a relay UE within the network coverage. In another embodiment, the above request comes from a remote UE that requests services from a relay UE outside the network coverage. The relay UE performs service relaying between two end nodes of the sidelink relay path at L2 or L3. In one embodiment, the relay channel is an RLC channel with RLC and MAC logical channel configurations. A specific relay channel ID can be assigned to identify a specific relay channel. In another embodiment, a specific PC5 RRC message is used to initiate the relay channel establishment process between the relay UE and the remote UE. In one embodiment, the relay UE is within the coverage of the network. The network sends the configuration of the relay channel to the relay UE before the process starts. The relay UE maintains a mapping relationship between the relay channel ID and the end-to-end radio bearer index for bearer mapping. In another embodiment, a relay channel is established at L3 as one or more SLRBs between the relay UE and the remote UE for L3-based relay operations. The above relay channel configured as an SLRB includes the configurations of SDAP, PDCP, RLC, and MAC logical channels. The SLRB ID is used to identify a specific relay channel in this case.

[0005] In one embodiment, the relay UE receives a request to establish a sidelink relay path in the NR network, where the sidelink relay path includes the relay UE as a relay node for two end nodes; sends one or more sidelink relay channel establishment commands to one or more UEs to establish one or more corresponding sidelink relay channels for the sidelink relay path; activates the end-to-end sidelink relay channel of the sidelink relay path when one or more sidelink relay channels are established; and routes sidelink relay packets between the two end nodes through the end-to-end relay channel. In one embodiment, the request to establish the sidelink relay path is a Uu RRC message of a relay channel establishment command from the gNB, including the relay channel configuration of the sidelink relay path. In one embodiment, the request to establish the sidelink relay path is a PC5 RRC message of a relay channel establishment request from a remote UE end node.

[0006] This section does not define the present invention, which is defined by the claims.

[0007] By using the present invention, sidelink relay communication can be better performed. Description of the Drawings

[0008] The drawings illustrate embodiments of the present invention, where the same numbers indicate the same components.

[0009] Figure 1It is a schematic diagram of an exemplary NR wireless network for sidelink relay channel establishment according to an embodiment of the present invention.

[0010] Figure 2 It is a schematic diagram of an exemplary NR wireless system with a centralized upper layer having an NR radio interface stack according to an embodiment of the present invention.

[0011] Figure 3A It is a schematic diagram of an exemplary NR UE-to-network relay network with a relay connected to the network according to an embodiment of the present invention.

[0012] Figure 3B It is a schematic diagram of an exemplary NR UE-to-network relay network with a relay outside the network coverage area according to an embodiment of the present invention.

[0013] Figure 4 It is a schematic diagram of an exemplary top-level sidelink relay channel establishment for in-network-coverage relay UEs and out-of-network-coverage relay UEs according to an embodiment of the present invention.

[0014] Figure 5 It is a schematic flowchart of an exemplary establishment of an L2-based sidelink relay channel through an in-network-coverage relay UE according to an embodiment of the present invention.

[0015] Figure 6 It is a schematic flowchart of an exemplary establishment of an L3-based sidelink relay channel using an in-network-coverage relay UE according to an embodiment of the present invention.

[0016] Figure 7 It is a schematic flowchart of an exemplary establishment of an L2-based sidelink relay channel using an out-of-network-coverage relay UE according to an embodiment of the present invention.

[0017] Figure 8 It is a schematic flowchart of an exemplary establishment of an L3-based sidelink relay channel for an out-of-network-coverage relay UE according to an embodiment of the present invention.

[0018] Figure 9 It is a schematic flowchart of an exemplary sidelink relay channel establishment according to an embodiment of the present invention. Detailed Description of the Invention

[0019] Some embodiments of the present invention are now given in detail for reference, and their examples are described in the accompanying drawings.

[0020] Figure 1It is a system schematic diagram of an exemplary NR wireless network for sidelink relay channel establishment according to an embodiment of the present invention. The NR wireless system 100 includes one or more fixed infrastructure units that form a network distributed over a geographical area. The infrastructure units may also be referred to as access points, access terminals, base stations, Node B, evolved Node B (eNode-B), next-generation Node B (gNB), or other terms used in the art. The network may be a homogeneous network or a heterogeneous network and may be deployed using the same or different frequencies. gNBs 101, 102, and 103 are base stations in the NR network, and their service areas may or may not overlap with each other. Backhaul connections such as 131, 132, and 133 connect non-co-located receiving base stations such as gNBs 101, 102, and 103. These backhaul connections may be ideal or non-ideal. gNB 101 is connected to gNB 102 through the Xn interface 131 and to gNB 103 through the Xn interface 132. gNB 102 is connected to gNB 103 through the Xn interface 133.

[0021] The wireless network 100 also includes a plurality of communication devices or mobile stations, such as UEs 111, 112, 113, 117, 118, 121, 122, 123, and 128. The communication devices or mobile stations in the wireless network 100 may also refer to devices with wireless connections in vehicles, such as mobile devices 117, 118, and 128. The exemplary mobile devices in the wireless network 100 have SL functions. The mobile devices may establish one or more connections with one or more base stations (such as gNBs 101, 102, and 103). The mobile devices may also disconnect their access links from the base stations, but may send and receive data packets with one or more other mobile stations or one or more base stations through layer 2-based SL relaying.

[0022] The remote UE 111 and the gNB 103 form an end-to-end path 181 through layer 2-based SL relaying with the relay UE 121. The end-to-end path 181 includes an access link 135 between the gNB 103 and the relay UE 121, and a sidelink 171 between the remote UE 111 and the relay UE 121. In another embodiment, the configured sidelink relaying using the sidelink is layer 2 or layer 3-based UE-to-network multi-hop relaying. The remote UE 112 and the gNB 102 form an end-to-end path 182 through layer 2 or layer 3-based SL relaying with the relay UE 122 and another relay UE 123. The end-to-end path 182 includes an access link 136 between the gNB 102 and the relay UE 122, a sidelink 172 between the relay UE 122 and the relay UE 123, and a sidelink 173 between the remote UE 112 and the relay UE 123. In another embodiment, the relay mobile device is configured with multiple remote mobile devices or multiple end-node mobile devices. The relay UE 128 having an access link 137 with the gNB 101 is respectively configured with two remote UEs 117 and 118 through sidelinks 175 and 176. In other embodiments, the relay mobile device can be configured for multiple UE-to-UE relay paths. Different links can be established for the illustrated relay paths. The access link is a link between a base station (such as a gNB) and a mobile device (such as a UE), and the above UE can be a remote UE or a relay UE. The access link includes an uplink (UL) and a downlink (DL) between the base station and the mobile device. The interface of the access link is the NR Uu interface. In one embodiment, the remote UE also establishes an access link with the base station. The sidelink is a link between two mobile devices and uses the PC5 interface. The sidelink can be a link between a remote UE / end-node UE and a relay UE, or a link between two relay mobile devices / UEs in multi-hop relaying. The end-to-end link for the relay path can be a link between two end-node mobile devices for UE-to-UE relaying, or a link between a base station and a mobile device for UE-to-network relaying. The Xn link is a backhaul link between two base stations (such as gNBs using the Xn interface). In one embodiment, the candidate relay UE information is sent to the base station via the Xn link.

[0023] Figure 1A simplified block diagram of a base station and a mobile device / UE for sidelink relay channel establishment is further shown. The gNB 103 has an antenna 156 that transmits and receives radio signals. The RF transceiver circuit 153 coupled to the antenna receives RF signals from the antenna 156, converts the RF signals into baseband signals, and sends the baseband signals to the processor 152. The RF transceiver 153 also converts the baseband signals received from the processor 152 into RF signals and sends them to the antenna 156. The processor 152 processes the received baseband signals and calls different functional modules to perform the functional features in the gNB 103. The memory 151 stores program instructions and data 154 to control the operation of the gNB 103. The gNB 103 also includes a set of control modules 155 for performing functional tasks to communicate with the mobile station.

[0024] Figure 1 A simplified block diagram of a UE (such as relay UE 121 or remote UE 111) is also shown. The UE has an antenna 165 for transmitting and receiving radio signals. The RF transceiver circuit 163 coupled to the antenna receives RF signals from the antenna 165, converts the RF signals into baseband signals, and sends the baseband signals to the processor 162. In one embodiment, the RF transceiver may include two RF modules (not shown). The first RF module is for high frequency (HF) transmission and reception; the other RF module, different from the HF transceiver, is for transmission and reception in different frequency bands. The RF transceiver 163 also converts the baseband signals received from the processor 162 into RF signals and sends them to the antenna 165. The processor 162 processes the received baseband signals and calls different functional modules to perform the functional features in the UE. The memory 161 stores program instructions and data 164 to control the operation of the UE. The antenna 165 sends an uplink transmission to the antenna 156 of the gNB 103 and receives a downlink transmission from the antenna 156 of the gNB 103.

[0025] The UE also includes a set of control modules for performing functional tasks. These control modules can be implemented by circuits, software, firmware, or a combination of the above. The request receiving processor 191 receives a request to establish a sidelink relay path in the NR network, where the sidelink relay path includes the UE as a relay node between two end nodes. The command processor 192 sends one or more sidelink relay channel establishment commands to one or more UEs to establish one or more corresponding sidelink relay channels for the sidelink relay path. The relay path processor 193 activates the end-to-end sidelink relay channel for the sidelink relay path when one or more sidelink relay channel establishments are completed. The data routing processor 194 routes sidelink relay data packets between two end nodes through the end-to-end relay path.

[0026] Figure 2 It is a schematic diagram of an exemplary NR radio system with a centralized upper layer having an NR radio interface stack according to an embodiment of the present invention. There may be different protocol partitioning options between the central unit (CU) and the distributed unit (DU) of the gNB node. The functional partitioning between the CU and the DU of the gNB node may depend on the transport layer. Since the higher protocol layers have lower performance requirements for the transport layer in terms of bandwidth, latency, synchronization, and jitter, a low-performance transport between the CU and the DU of the gNB node can enable the higher protocol layers of the NR radio stack to be supported in the CU. In one embodiment, the service data adaptation protocol (SDAP) and the packet data convergence protocol (PDCP) layers are located in the CU, while the radio link control (RLC), media access control (MAC), and physical (PHY) layers are located in the DU. The core unit 201 is connected to the central unit 211 having the gNB upper layer 252. In one embodiment 250, the gNB upper layer 252 includes the PDCP layer and an optional SDAP layer. The central unit 211 is connected to the distributed units 221, 222, and 223, where the distributed units 221, 222, and 223 correspond to cells 231, 232, and 233 respectively. The distributed units 221, 222, and 223 include the gNB lower layer 251. In one embodiment, the gNB lower layer 251 includes the PHY, MAC, and RLC layers. In another embodiment 260, each gNB has a protocol stack 261 including the SDAP, PDCP, RLC, MAC, and PHY layers.

[0027] Figure 3AFIG. is a schematic diagram of a NR UE to network relay network with a relay connected to the network according to an embodiment of the present invention. The NR network 300 includes a gNB 301, a relay UE 302, and remote UEs 311, 312, and 313. The relay UE 302 is connected to the network through a Uu interface with UL and DL 331. In one embodiment, UEs outside the coverage area (such as UEs 311, 312, and 313) form a local group 310. The relay UE 302 schedules radio resources for the remote UE group (such as UEs 311, 312, and 313) according to the network configuration. The relay UE 302 can relay data and signaling between device members of the local group 310 outside the network coverage area. There is a NR Uu air interface between the gNB 301 and the relay UE 302. The relay UE operates as an L2 relay or an L3 relay. There are PC5 interfaces between the relay UE 302 and the remote UEs (such as UEs 311, 312, and 313), such as sidelinks 321, 322, and 323.

[0028] Figure 3B FIG. is a schematic diagram of a NR UE to network relay network with a relay outside the network coverage area according to an embodiment of the present invention. The NR network 350 includes a gNB 351, a relay UE 352, and remote UEs 361, 362, and 363. When establishing a sidelink relay path for the remote UE, the relay UE and the remote UE are not within the coverage area. In one embodiment, the relay UE 352 obtains the network configuration for sidelink relay according to its previous connection to the network. In another embodiment, the relay UE 352 obtains the network configuration for sidelink relay based on its pre-configuration. Remote UEs outside the coverage area (such as UEs 361, 362, and 363) form a local group 360. The relay UE 352 schedules radio resources for the remote UEs in the local group 360. The relay UE can relay data and signaling between device members of the local group 360 outside the network coverage area. In one embodiment, the relay UE 352 performs L2 sidelink relay or L3 sidelink relay with the remote UEs 361, 362, and 363 through sidelinks 371, 372, and 373 respectively.

[0029] In one exemplary example, the relay UE establishes a sidelink relay channel when receiving a sidelink relay connection request. In one embodiment, the above request comes from a base station / gNB for a relay UE within the network coverage area. In another embodiment, the above request comes from a remote UE requesting services for a relay UE outside the network coverage area. The relay UE relays traffic between the two end nodes of the sidelink relay path at L2 or L3.

[0030] Figure 4It is an exemplary schematic diagram for establishing a top-level sidelink relay channel for in-network coverage relay UEs and out-of-network coverage relay UEs according to an embodiment of the present invention. In step 410, the relay UE and one or two remote UEs perform PC5 signaling (PC5-S) discovery. For UE-to-network relay, the relay UE establishes a PC5-S link with the remote UE. For UE-to-UE relay, the relay UE establishes two PC5-S links with the remote UE. In other embodiments of multi-hop sidelink relay, the relay UE establishes PC5-S links with one or more relay UE nodes and / or remote UEs closest to it. In step 420, the relay UE establishes a relay channel for sidelink relay. In step 430, the end-to-end relay path is activated when the relay channel is successfully established. In one embodiment, the relay UE is an in-network coverage relay UE connected to the gNB of the NR network. For step 420, the relay UE follows process 460 for in-network coverage relay UEs. In step 461, the remote UE uses the established PC5-S link to send a relay request to the base station through the relay UE. In step 462, the base station / gNB sends a relay channel establishment command / request to the relay UE. In step 463, the relay UE sends a relay channel establishment command to one or two remote UEs. In another embodiment, the relay UE is an out-of-network coverage relay UE. For step 420, the relay UE follows process 480 for out-of-network coverage relay UEs. In step 481, the remote UE sends a relay request to the relay UE. In step 482, the relay UE sends a relay channel establishment command to one or more remote UEs.

[0031] Figure 5FIG. 0 is an exemplary flowchart of establishing an L2-based sidelink relay channel through a relay UE within a network coverage area according to an embodiment of the present invention. The NR network includes a gNB 503, a remote UE 501, and a relay UE 502. At step 511, discovery of the remote UE 501 and the relay UE 502 is completed. At step 521, the relay UE 502 sends an RRC message of sidelink UE Information (SUI) to the gNB 503 to establish a unicast link with the remote UE 501. The SUI includes a relay UE ID, a remote UE ID, and resource requests for TX and RX. Optionally, the SUI may further include the PC5 link quality of the relay UE-remote UE pair. The remote UE ID and the relay UE ID may be L2 UE IDs defined in 3GPP TS 23.003. The SUI report clearly describes the remote UE-relay UE pair, the roles of the two UEs, and the IDs of the two UEs. In one embodiment, the relay UE 502 reports the remote UE capabilities (including the supported frequency list) and / or the relay UE capabilities to the gNB 503 to obtain appropriate resources for subsequent relay operations between the remote 501 and the gNB 503. At step 522, the gNB 503 sends an RRC message including resource configuration to the relay UE 502 to allow the relay UE to establish a unicast link with the remote UE. Alternatively, a pre-configured or previously configured resource pool may be used. At step 523, a PC5 link is established between the relay UE 502 and the remote UE 501 based on the network-configured resources. During or after the PC5 link establishment (managed by PC5-S), the relay UE may use an access stratum (AS) procedure to indicate the received resource configuration to the remote UE 501. An RRC connection between the relay UE 502 and the remote UE 501 is established along with the establishment of the PC5 link.

[0032] In step 531, the remote UE 501 sends a service request non-access stratum (NAS) message to the gNB 503, which is forwarded by the relay UE 502 as an RRC message. The service request from the remote UE 501 is to establish the necessary quality of service (QoS) flows to support communication between the remote UE 501 and the gNB 503. In step 532, the 5G core network (5GC) of the NR network sends a NAS message to the remote UE 501 via the gNB 503, which is forwarded by the relay UE 502 as an RRC message. The service acceptance message is the network's confirmation of the service request and a command to the remote UE 501 to establish the necessary QoS flows between the remote UE and the gNB. To support L2 relay operation, the radio bearer (RB) establishment command includes the necessary configurations to establish an end-to-end QoS flow between the remote UE and the gNB. Assuming that L2 relay is performed at the RLC layer, the configurations in the RB establishment command include one or more of the following elements: SDAP configuration, PDCP configuration including security keys, end-to-end RB ID, and QoS information for each RB to be established. One RB can be established to carry multiple QoS flows. If the remote UE 501 does not initiate an initial registration before the service request message, then the initial registration process needs to be applied for before the service request message. After step 532 and before step 533, a security and / or authentication process can be performed between the UE and the network. In step 533, when the remote UE 501 establishes the QoS flows using the indicated configurations, an RRC message including establishment completion is sent to the gNB 503, where the above message is forwarded by the relay UE 502.

[0033] In step 541, gNB 503 sends a Uu RRC message (such as RRC reconfiguration) including a relay channel establishment command to relay UE 502 to configure the sidelink relay channel to establish the necessary relay channels to perform relaying between remote UE 501 and gNB 503. gNB 503 configures resource pools for both relay UE 502 and remote UE 501 in mode A or mode B to reconfigure the PC5 unicast link for relaying. If relay UE 502 and remote UE 501 are scheduled by mode B, sensing of the aligned resource pool for the UE pair needs to be provided through configuration. The relay channel configuration of the PC5 link between remote UE 501 and relay UE 502 includes the configuration of one or more relay channels. Each relay channel configuration includes information elements in sl-RLC-BearerConfig. Specifically, each relay channel configuration includes one or more of the following elements: the associated end-to-end Uu radio bearer index (such as ServedRadioBearer), the RLC layer index (such as SL-RLC-BearerConfigIndex), the RLC configuration (such as sl-RLC-Config), the MAC logical channel configuration (such as sl-MAC-LogicalChannelConfig), the sidelink logical channel ID, the relay channel ID, and the QoS profile of the QoS flow in each associated end-to-end Uu radio bearer. The associated end-to-end Uu radio bearer in each relay channel configuration can be an end-to-end Uu radio bearer or a list of end-to-end radio bearer IDs. The end-to-end configuration indicates to relay UE 502 the RLC channel carrying a specific end-to-end radio bearer, and relay UE 502 applies the above information during bearer mapping. In addition, gNB 503 notifies relay UE 502 of the QoS profile of the QoS flow in each end-to-end Uu radio bearer of the relay to allow relay UE to perform transmission ordering for the next-hop transmission. When the L2 relay UE forwards traffic at the RLC layer or at the adaptation layer between the RLC and PDCP layers, the relay channel of the L2 relay is configured as an RLC channel. In one embodiment, the relay channel configuration further includes the Uu radio bearer configuration between relay UE 502 and gNB 503. In another embodiment, relay UE 502 performs L2 relay at the MAC layer. The relay channel configuration of the PC5 link between remote UE 501 and relay UE 502 includes the MAC logical channel configuration (such as sl-MAC-LogicalChannelConfig), the sidelink logical channel ID, and the relay channel ID. In yet another embodiment, relay UE 502 performs L2 relay at the adaptation layer.The relay channel configuration of the PC5 link between the remote UE 501 and the relay UE 502 includes one or more of the following elements: MAC logical channel configuration (such as sl-MAC-LogicalChannelConfig), sidelink logical channel ID, relay channel ID, and adaptation layer configuration. In one embodiment, in order to identify the relay channel on the direct link PC5, the logical channel ID is used as the relay channel ID. The relay UE 502 allocates one or more specific logical channels on the PC5 for relaying. Alternatively, a specific relay channel ID is defined by a one-to-one mapping between the logical channel ID and the PC5 relay channel ID.

[0034] In step 551, the relay UE 502 applies the relay channel configuration and sends a PC5 RRC message including a relay channel establishment command to the remote UE 501 to establish a PC5 relay channel for relaying. The relay channel establishment command includes one or a set of relay channel configurations. Each relay channel configuration includes one or more of the following elements: the associated end-to-end Uu radio bearer index (such as ServedRadioBearer), RLC layer index (such as sl-RLC-BearerConfigIndex), RLC configuration (such as sl-RLC-Config), MAC logical channel configuration (such as sl-MAC-LogicalChannelConfig), sidelink logical channel ID, relay channel ID, and the QoS profile of the QoS flow within each associated end-to-end Uu radio bearer. The RLC configuration includes the RLC mode, SN length, etc. Optionally, the relay UE ID may also be included in the relay channel establishment command to indicate that the relay channel is established for a pair of remote UE and relay UE specific to one PC5 link. In one embodiment, in order to schedule the remote UE to use specific radio resources for sidelink communication, the resource pool (mode A or mode B) and / or the configured grant may be included in the relay channel establishment command. In one embodiment, a list of end-to-end radio bearer IDs is included within each relay channel configuration for each relay channel, which can tell the remote UE which RLC channel to use to carry a specific end-to-end radio bearer. In step 552, the remote UE 501 confirms to the relay UE 502 via a PC5 RRC message of the relay channel establishment completion message. In one embodiment, in step 553, the relay UE 502 responds via a sidelink configuration completion message (such as in the RRC configuration completion message) as an acknowledgement of the relay channel configuration provided in step 541. In one embodiment, when the Uu radio bearer configuration is provided between the relay UE 502 and the gNB 503 in step 541, the relay channel establishment completion message in step 553 further includes feedback on the completion of the radio bearer reconfiguration.

[0035] At step 561, gNB 503 sends an RRC message for RRC reconfiguration, such as adding an additional DRB for relay UE 502 to reconfigure the Uu radio bearer to carry relay services. At step 562, the relay UE sends an acknowledgement RRC message to gNB 503, i.e., the RRC reconfiguration is completed, to indicate the completion of the RRC reconfiguration. At step 571, the relay UE 502 transparently forwards the traffic between the remote UE 501 and gNB 503.

[0036] The remote UE 501 maintains the mapping relationship between the end-to-end Uu radio bearer ID and the relay channel ID. The relay UE 502 maintains the mapping relationship between the Uu radio bearer ID of the mapped radio bearer for relay between gNB 503 and the relay UE 502 and the relay channel ID. In one embodiment, the relay UE 502 maintains the mapping relationship between the ID of the end-to-end radio bearer between gNB 503 and the remote UE 501, the Uu radio bearer ID of the mapped radio bearer for relay between gNB 503 and the relay UE 502, and the relay channel ID. gNB 503 maintains the mapping relationship between the Uu radio bearer ID of the mapped radio bearer for relay (with the relay UE) and the Uu radio bearer ID of the end-to-end radio bearer (with the remote UE). To identify the radio bearers of different remote UEs, the relay UE 502 uses a combination of the remote UE ID, the Uu radio bearer ID of the mapped radio bearer for relay, and the Uu bearer ID of the end-to-end radio bearer. In addition, the mapping of QoS flows to radio bearers is performed at the SDAP of gNB503 and each remote UE.

[0037] Figure 6is an exemplary flowchart of establishing an L3-based sidelink relay channel using a relay UE within a network coverage according to an embodiment of the present invention. The NR network includes a gNB 603, a remote UE 601, and a relay UE 602. At step 611, the discovery of the remote UE 601 and the relay UE 602 is completed. At step 621, the relay UE 602 sends an RRC message of sidelink UE information (SUI) to the gNB 603, where the SUI includes a relay UE ID, a remote UE ID, and TX and RX resource requests for establishing a unicast link with the remote UE 601. Optionally, the SUI may also include the PC5 link quality of the relay UE-remote UE pair. The remote UE ID and the relay UE ID may be L2 UE IDs defined in 3GPP TS 23.003. The SUI report clearly describes the remote UE-relay UE pair, the roles of the two UEs, and the identities of the two UEs. In one embodiment, the relay UE 602 reports the remote UE capabilities (including the supported frequency list) and / or the relay UE capabilities to the gNB 603 to obtain appropriate resources for subsequent relay operations between the remote UE 601 and the gNB 603. At step 622, the gNB 603 sends an RRC message including resource configuration to the relay UE 602 to allow the relay UE to establish a unicast link with the remote UE. Alternatively, a pre-configured or previously configured resource pool may be used. At step 623, a PC5 link is established between the relay UE 602 and the remote UE 601 based on the resources configured by the gNB. During or after the PC5 link establishment (managed by PC5-S), the relay UE may use an AS layer procedure to indicate the received resource configuration to the remote UE 601. The RRC connection between the relay UE 602 and the remote UE 601 is established along with the establishment of the PC5 link.

[0038] In step 631, the remote UE 601 sends the NAS message (i.e., service request) encapsulated in the PC5 RRC as a NAS PDU to the relay UE 602. According to the appropriate indication of the received PC5 RRC message, the relay UE 602 parses the PC5 RRC message and forwards the NAS PDU as a Uu RRC message to the gNB 603. The service request indicates a request from the remote UE 601 to establish necessary QoS flows to support communication between the remote UE 601 and the gNB 603. In step 632, the network sends a NAS message (i.e., service acceptance) to the gNB 603, which is forwarded by the relay UE 602 as an RRC message. The service acceptance message indicates the network's confirmation of the service request. If the remote UE 601 has not initiated an initial registration before the service request message, the initial registration process needs to be performed between steps 631 and 632. A security and / or authentication process is also performed between steps 631 and 632.

[0039] In step 641, the gNB 603 sends a Uu RRC message (such as RRC reconfiguration) including a relay channel establishment command to the relay UE 602 to configure the sidelink relay channel, that is, the sidelink radio bearer (SLRB), so as to establish a necessary relay channel (i.e., SLRB) for sidelink relay. The gNB 503 configures a resource pool (mode A or mode B) for both the relay UE 602 and the remote UE 601 to reconfigure the PC5 unicast link between the relay UE 602 and the remote UE 601 for relay. If the relay UE 602 and the remote UE 601 are scheduled through mode B, it is necessary to provide an aligned resource pool for the UE pair through configuration for sensing. The relay channel (i.e., SLRB) configuration of the PC5 link between the relay UE 602 and the remote UE 601 includes one or more relay channel configurations. Each relay channel (i.e., SLRB) configuration includes one or a set of sidelink radio bearer configurations (SL-RadioBearerConfig), and / or one or a set of sidelink RLC bearer configurations (SL-RLC-BearerConfig). The SL-RadioBearerConfig includes one or more of the following elements: SDAP configuration, PDCP configuration (including security keys), and SLRB index (or ID). The SL-RLC-BearerConfig includes one or more of the following elements: the relevant sidelink radio bearer index (such as SL-ServedRadioBearer), the RLC layer index (such as sl-RLC-BearerConfigIndex), the RLC configuration (such as sl-RLC-Config), the MAC logical channel configuration (such as sl-MAC-LogicalChannelConfig), the sidelink logical channel ID, and the QoS profile of each QoS flow within the relevant end-to-end Uu radio bearer. In one embodiment, the configuration provided by the gNB 603 also includes the Uu radio bearer configuration between the relay UE and the BS.

[0040] In step 651, relay UE 602 applies the relay channel (i.e., SLRB) configuration and sends a PC5 RRC message including a relay channel establishment command to remote UE 601 to establish a PC5 relay channel (i.e., SLRB) for relaying. The relay channel establishment command includes the relay channel (i.e., SLRB) configuration. One radio bearer can be established to carry multiple QoS flows. Each relay channel (i.e., SLRB) configuration includes one or a set of SL-RadioBearerConfig, and / or one or a set of SL-RLC-BearerConfig. SL-RadioBearerConfig includes one or more of the following elements: SDAP configuration, PDCP configuration including a security key, and SLRB index (or ID). SL-RLC-BearerConfig includes one or more of the following elements: associated sidelink radio bearer index (such as SL-ServedRadioBearer), RLC layer index (such as sl-RLC-BearerConfigIndex), RLC configuration (such as sl-RLC-Config), MAC logical channel configuration (such as sl-MAC-LogicalChannelConfig), sidelink logical channel ID, and QoS profile of QoS flows within each associated end-to-end Uu radio bearer. Optionally, it may further include a relay UE ID for indicating the establishment of a relay channel for a pair of UEs specific to one PC5 link. In one embodiment, to schedule the remote UE to use specific radio resources for sidelink communication, a resource pool (mode A or mode B) and / or a configured grant are included in the relay channel establishment command. In step 652, the remote UE confirms to the relay UE 602 via a PC5 RRC message including a relay channel SLRB establishment completion message. In one embodiment, in step 653, the relay UE 602 sends a response indicating completion of sidelink configuration (such as in an RRC reconfiguration complete message) as an acknowledgement of the configuration by gNB 603. In one embodiment, when the configuration provided by the BS in step 641 includes the Uu radio bearer configuration between the relay UE 602 and gNB 603, step 653 may include indicating feedback of radio reconfiguration completion.

[0041] In step 661, gNB 603 sends an RRC message for RRC reconfiguration, such as adding an additional DRB, to the relay UE 602 to reconfigure the Uu radio bearer to carry relay traffic. In step 662, the relay UE 602 confirms to the gNB 603 via an RRC message (i.e., RRC reconfiguration complete) to indicate the completion of the reconfiguration. In step 671, the data between the gNB 603 and the remote UE 601 is forwarded by the relay UE 602.

[0042] Figure 7 It is an exemplary flowchart of establishing an L2-based sidelink relay channel using a relay UE outside the network coverage according to an embodiment of the present invention. The NR network includes a gNB 704, remote UEs 701 and 703, and a relay UE 702. At step 711, direct PC5 unicast links are established between the remote UE 701 and the relay UE 702 and between the remote UE 703 and the relay UE 702 for UE-to-UE sidelink relay, which is managed by PC5-S signaling. At step 721, the remote UE 701 sends a direct communication request to the remote UE 703. At step 722, the remote UE 703 sends a direct communication response to the remote UE 701. At step 723, a direct PC5 unicast link is established between the remote UE 701 and the remote UE 703.

[0043] The remote UE 701 initiates a relay-based application. At step 731, the remote UE 701 sends an RRC message for a relay channel establishment request from the AS layer to the relay UE 702. The PC5-S message for the service request is encapsulated in the RRC message, indicating the service request for a specific relay-based application. At step 732, the relay UE 702 sends an RRC message for the SUI to the gNB 704, where the SUI includes the relay UE ID, the remote UE ID, and a resource request (TX and RX) for the radio resources requested to establish the relay operation between the relay UE and the remote UE. The remote UE ID and the relay UE ID can be the L2 UE ID defined in 3GPP TS 23.003. The SUI report clearly describes the remote UE-relay UE pair, the roles of the two UEs, and the identities of the two UEs. In one embodiment, the relay UE 702 reports the remote UE capabilities (including the supported frequency list) and / or the relay UE capabilities to the gNB 704 to obtain appropriate resources for subsequent relay operations between the remote UEs. At step 733, the gNB 704 sends an RRC message to the relay UE 702 including the sidelink configuration for the relay, which may include a radio resource pool. The resource configuration can be based on mode A or based on mode B. Alternatively, a pre-configured or previously configured resource pool can be used. In one embodiment, when the relay UE 702 is an out-of-network-coverage relay UE, steps 732 and 733 are not performed. At steps 734 and 735, the relay UE 702 applies the relay channel configuration and sends PC5 RRC messages including relay channel establishment commands to the remote UEs 701 and 703 respectively to establish the corresponding PC5 relay channels for relaying. The same process as step 551 can be applied. The difference is that when a set of radio bearer IDs is included for each relay channel in each relay channel configuration, the radio bearer ID is the SLRB ID. It indicates to the remote UE which RLC channel to use to carry a specific SLRB. Each relay channel configuration includes one or more of the following elements: the associated end-to-end SLRB index (such as ServedRadioBearer), the RLC layer index (such as sl-RLC-BearerConfigIndex), the RLC configuration (such as sl-RLC-Config), the MAC logical channel configuration (e.g., sl-MAC-LogicalChannelConfig), the sidelink logical channel ID, the relay channel ID, and the QoS profile of the QoS flow within each associated end-to-end Uu radio bearer. The RLC configuration includes the RLC mode, the SN length, etc. At steps 736 and 737, in response, the remote UE 703 and the remote UE 701 respectively send PC5 RRC messages for the relay channel establishment completion message to the relay UE 702.

[0044] In step 741, the remote UE 701 sends a PC5 RRC message (such as an SLRB establishment command) to the remote UE 703, which is forwarded by the relay UE 702. The SLRB establishment command includes the radio bearers or QoS flows to be established to support the applications to be relayed. The SLRB establishment request includes one or a set of SL-RadioBearerConfig, and / or one or a set of SL-RLC-BearerConfig. The SL-RadioBearerConfig includes one or more of the following elements: SDAP configuration, PDCP configuration (including security keys, SLRB index (or ID), or any combination thereof). The SL-RLC-BearerConfig includes one or more of the following elements: the relevant sidelink radio bearer index (such as SL-ServedRadioBearer), the RLC layer index (such as sl-RLC-BearerConfigIndex), the RLC configuration (such as sl-RLC-Config), the MAC logical channel configuration (such as sl-MAC-LogicalChannelConfig), the sidelink logical channel ID, and the QoS profile of the QoS flow within each relevant end-to-end Uu radio bearer. In step 742, the remote UE 703 responds with a PC5 RRC message of an SLRB establishment completion message, which is forwarded by the relay UE 702. In step 751, an end-to-end SLRB is established for the remote UE 701 and the remote UE 703. In step 752, the relay UE 702 transparently forwards the traffic between the end-node remote UEs.

[0045] The remote UE 701 maintains a mapping relationship between the end-to-end sidelink radio bearer (i.e., SLRB) ID and the relay channel ID of the relay channel between the remote UE 701 and the relay UE 702. The remote UE 703 maintains a mapping relationship between the end-to-end sidelink radio bearer (i.e., SLRB) ID and the relay channel ID of the relay channel between the remote UE 703 and the relay UE 702. The relay UE 702 maintains a mapping relationship between the remote UE 701-relay UE 702 relay channel ID and the remote UE 703-relay UE 702 relay channel ID. In one embodiment, the relay UE 702 maintains a mapping relationship between the remote UE 701-relay UE 702 relay channel ID, the remote UE 703-relay UE 702 relay channel ID, and the end-to-end SLRB ID. In other embodiments, a combination of the remote UE ID, the relay channel ID of the ingress relay channel, and the relay channel ID of the egress relay channel is used. The mapping of QoS flows to radio bearers at the SDAP of the remote UE 701 and the remote UE 703 follows the existing procedures.

[0046] Figure 8An exemplary flowchart for establishing an L3-based sidelink relay channel with a relay UE outside the network coverage area according to an embodiment of the present invention. The NR radio network includes a remote UE 801, a relay UE 802, and a remote UE 803. In step 811, the PC5-S discovery of the remote UE and the relay UE is completed. Any UE that wants to use L3 UE-to-UE relay needs to establish a unicast L2 link for UE-to-UE relay through IP configuration. The L3 UE-to-UE relay assigns an IP address / prefix to the remote UE. In steps 812 and 813, a direct PC5 unicast link is established between the remote UE 801 and the relay UE 802, and between the remote UE 803 and the relay UE 802 for UE-to-UE-based relay, which is managed by PC5-S signaling. As part of the unicast L2 link establishment process, the relay UE 802 stores the association of the user information of the peer UE of the unicast link with the IP address / prefix assigned to the above UE into its domain name system (DNS) entry. The relay UE 802 can act as a DNS server for other UEs. In step 821, when the remote UE 801 needs to communicate with the remote UE 803 or needs to discover ProSe services through the relay UE 802, the remote UE 801 sends a DNS query to the relay UE 802 through the unicast link for the remote UE 803 or ProSe services. In step 822, the relay UE 802 returns the IP address / prefix of the remote UE 803 or ProSe services to the remote UE 801.

[0047] In step 831, from the perspective of the AS layer, the remote UE 801 sends an RRC message: Relay Channel Establishment Request to the relay UE 802. A PC5-S message (such as a service request) is encapsulated in this RRC message, indicating a service request for a specific relay-based application. The SLRB and / or the corresponding QoS flow in the above message support L3 IP routing for the UE pair indicated by the IP address / prefix pair. In step 832, the relay UE 802 sends a PC5 RRC message or a relay channel (SLRB) establishment command to the remote UE 803. In step 833, the relay UE 802 sends a PC5 RRC message or a relay channel (SLRB) establishment command to the remote UE 801. In step 834, the remote UE 803 confirms to the relay UE 802 via a PC5 RRC message of the relay channel establishment completion message. In step 835, the remote UE 801 confirms to the relay UE 802 via a PC5 RRC message of the relay channel establishment completion message. In step 841, the relay UE 802 routes traffic between the remote UE 801 and the remote UE 803 as an IP router. The relay UE 802 acts as an IP router and forwards data packets destined for the target UE to the corresponding unicast L2 link. Each unicast L2 link is regarded as an IP interface.

[0048] In one embodiment, one or more SLRBs are established between the remote UE 801 and the relay UE 802 for traffic between the remote UE 801 and the remote UE 803. In order to enable the relay UE 802 to perform transmission ordering for the received data stream of a specific SLRB (such as the SLRB between the remote UE 801 and the relay UE 802), the end-to-end SLRB ID can be inserted into the packet header (i.e., the IP header, the SDAP header, or the PDCP header). The relay UE 802 knows the QoS information of the end-to-end SLRB. The relay UE 802 performs transmission ordering for the next-hop transmission of the data stream, for example, it can be performed in the LCP of the MAC.

[0049] Figure 9 is an exemplary flowchart for sidelink relay channel establishment according to an embodiment of the present invention. In step 901, the relay UE receives a request to establish a sidelink relay path in the NR network, where the sidelink relay path includes the relay UE as a relay node for two end nodes. In step 902, the relay UE sends one or more sidelink relay channel establishment commands to one or more UEs to establish one or more corresponding sidelink relay channels for the sidelink relay path. In step 903, the relay UE activates the end-to-end sidelink relay channel for the sidelink relay path when one or more sidelink relay channels are established. In step 904, the relay UE routes sidelink relay data packets between the two end nodes via the end-to-end relay channel.

[0050] Although, for purposes of illustration, the present invention has been described in connection with specific embodiments, the present invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of the features of the described embodiments may be made without departing from the scope of the present invention as set forth in the claims.

Claims

1. A method for establishing a sidelink relay channel, for a relay user equipment, comprising: receiving, by the relay user equipment, a request to establish a sidelink relay path in a new radio network, wherein the sidelink relay path includes the relay user equipment as a relay node for two end nodes; sending, by the relay user equipment, one or more sidelink relay channel establishment commands to one or more user equipments to establish one or more corresponding sidelink relay channels for the sidelink relay path, wherein the sidelink relay channel establishment command is carried by a PC5 radio resource control message and includes one or more relay channel configurations for a PC5 link between an end node remote user equipment and the relay user equipment; activating, when one or more sidelink relay channels are established, an end-to-end sidelink relay channel for the sidelink relay path; and routing sidelink relay data packets between the two end nodes through the end-to-end sidelink relay channel, wherein the sidelink relay path is a layer 2 sidelink relay, and wherein the relay channel configuration includes one or more of the following elements: associated end-to-end Uu radio bearer index, radio link control index, radio link control configuration, media access control logical channel configuration, sidelink logical channel identifier, relay channel identifier, and quality of service profiles for one or more quality of service flows of each associated end-to-end Uu radio bearer.

2. The sidelink relay channel establishment method according to claim 1, wherein, the request to establish the sidelink relay path is a Uu radio resource control message of a relay channel establishment command from a gNB, and the Uu radio resource control message includes the relay channel configuration of the sidelink relay path.

3. The sidelink relay channel establishment method according to claim 1, wherein, the request to establish the sidelink relay path is a PC5 radio resource control message of a relay channel establishment request from an end node of a remote user equipment.

4. A user equipment, comprising: a transceiver for transmitting and receiving radio frequency signals in a new radio network; a request receiving processor for receiving, from a base station, a request to establish a sidelink relay path in the new radio network, wherein the sidelink relay path includes the relay user equipment as a relay node for two end nodes; A command processor for sending one or more sidelink relay channel establishment commands to one or more user devices to establish one or more corresponding sidelink relay channels for a sidelink relay path, wherein the sidelink relay channel establishment command is carried by a PC5 radio resource control message and includes one or more relay channel configurations for the PC5 link between an end-node remote user device and the relay user device, wherein the sidelink relay path is a layer 2 sidelink relay, and wherein the relay channel configuration includes one or more of the following elements: a related end-to-end Uu radio bearer index, a radio link control index, a radio link control configuration, a media access control logical channel configuration, a sidelink logical channel identifier, a relay channel identifier, and a quality of service profile for one or more quality of service flows of each related end-to-end Uu radio bearer; A relay path processor for activating an end-to-end sidelink relay channel for the sidelink relay path when one or more sidelink relay channel establishments are completed; and A data routing processor for routing sidelink relay data packets between the two end nodes through the end-to-end sidelink relay channel.

5. The user equipment according to claim 4, wherein the request for establishing the sidelink relay path is a Uu radio resource control message of a relay channel establishment command from a gNB, and the Uu radio resource control message includes a relay channel configuration of the sidelink relay path.

6. The user equipment according to claim 4, wherein the request for establishing the sidelink relay path is a PC5 radio resource control message of a relay channel establishment request from an end-node remote user device.

7. A storage medium storing a program which, when executed, causes a user equipment to perform the steps of the sidelink relay channel establishment method according to any one of claims 1-3.

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