Data communication method and device based on sidelink relay

Abstract

Embodiments of the present invention provide devices and methods for sidelink relay based UE-to-network communication. In one example, a relay UE determines to perform a delayed relay forwarding when a remote UE is in a DRX cycle based on a PC5 configuration. The relay UE buffers relay traffic and / or sends a suspension indication to a base station to request the base station to suspend relay traffic for the remote UE. In another example, a relay UE monitors a paging occasion configured for itself and receives a paging message from a network intended for a remote UE in a non-connected RRC state. The relay UE sends a PC5 paging message to the remote UE in the non-connected RRC state over an established SL based on the received paging message. In one embodiment, the network stores an SL association between the relay UE and the remote UE. By utilizing the present invention, data communication can be better performed.

Description

[0001] Cross-references

[0002] This application is filed pursuant to 35 USC §111(a), and claims priority to International Application No. PCT / CN2020 / 091597, filed May 21, 2020, entitled "Methods and Apparatus of Sidelink Relay Based Data Communication," pursuant to 35 USC §120 and §365(c), and the foregoing applications are incorporated herein by reference. Technical Field

[0003] This invention relates to wireless communication, and more particularly to data communication based on sidelink (SL) relay. Background Technology

[0004] 5G radio access technology will become a key component of modern access networks, addressing the growing demand for high traffic volume and high-bandwidth connectivity. In 3GPP New Radio (NR), SL (Short-Side Array) continues to evolve. With the support of new features, SL provides low latency, high reliability, and high throughput for communication between devices. NR Vehicle-to-Everything (V2X) supports sidelink measurement. V2X sidelink communication can be supported via unicast, multicast, and broadcast. Using SL for radio relay provides a reliable and efficient way to forward traffic. SL relay has evolved from Layer 3 (L3) Proximity Services (ProSe) UE-to-Network relay to Layer 2 (L2) UE-to-Network relay, anticipating forwarding traffic between remote UEs and base stations at the adaptation layer between the radio link control (RLC) layer and the packet data convergence protocol (PDCP) layer. For UE-to-network relay operations, an important issue is considering relay operations when the relay UE is operating in different radio resource control (RRC) states. Different procedures are required to establish the connection between the remote UE and the base station to enable relay operations at the relay UE.

[0005] Considering the different RRC states of relay UEs and remote UEs, it is necessary to improve and enhance the sidelink relay operation. Summary of the Invention

[0006] This invention provides apparatus and methods for UE-to-network communication based on sidelink relay. In one example, the relay UE performs delayed relay forwarding when it determines, based on a PC5 configuration, that the remote UE is in a DRX cycle. In one embodiment, delayed relay forwarding includes buffering relay services at the relay UE. In another embodiment, delayed relay forwarding includes sending a pause indication to the base station to request the base station to suspend relay services to the remote UE. Relay services are data services or signaling messages from the base station to the remote UE.

[0007] In another example, the relay UE monitors the paging timing configured for itself and receives a paging message from the network intended for a remote UE in a disconnected RRC state. Based on the received paging message, the relay UE sends a PC5 paging message to the remote UE in the disconnected RRC state via an established SL. In one embodiment, the relay UE reports the SL association between the relay UE and the remote UE when transitioning from an RRC connected state to a disconnected RRC state. In another embodiment, the paging message includes one or more of the following elements: the relay UE's ID, the remote UE's ID, and the SL association between the relay UE and the remote UE. In another embodiment, an RRC reconfiguration message including the remote UE ID and / or the remote UE-relay UE SL association is received from the gNB. In yet another embodiment, the paging message received by the relay UE indicates a paging or wake-up indication to the remote UE and is forwarded to the remote UE via a sidelink. Upon receiving the paging indication or wake-up indication, the remote UE sends an RRC recovery request or an RRC establishment request.

[0008] This section is not intended to define the invention; the invention is defined by the claims.

[0009] By utilizing this invention, data communication can be improved. Attached Figure Description

[0010] The accompanying drawings illustrate embodiments of the invention, wherein the same numbers indicate the same components.

[0011] Figure 1 This is a schematic diagram of an exemplary wireless network for data communication based on sidelink relay according to an embodiment of the present invention.

[0012] Figure 2 This 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.

[0013] Figure 3 This is an exemplary top-level functional diagram of communication based on sidelink relay according to an embodiment of the present invention.

[0014] Figure 4This is an exemplary signaling procedure according to an embodiment of the present invention for transmitting downlink data between a remote UE in a long DRX state and a base station via a relay UE.

[0015] Figure 5 This is an exemplary schematic diagram illustrating how a relay UE forwards a paging message from the network to a remote UE in a disconnected RRC state to wake up the remote UE, according to an embodiment of the present invention.

[0016] Figure 6A This is an exemplary flowchart of how a relay UE forwards a paging message from the network to a remote UE in an RRC inactive state to wake up the remote UE, according to an embodiment of the present invention.

[0017] Figure 6B This is an exemplary flowchart of a relay UE forwarding a paging message from the network to a remote UE in an RRC idle state to wake up the remote UE, according to an embodiment of the present invention.

[0018] Figure 7 This is an exemplary flowchart illustrating downlink data transmission between a remote UE in a long DRX state and a base station via a relay UE, according to an embodiment of the present invention.

[0019] Figure 8 This is an exemplary flowchart of a relay UE forwarding a paging message from the network to a remote UE in a disconnected RRC state, according to an embodiment of the present invention. Detailed Implementation

[0020] Some embodiments of the present invention are now given in detail for reference, examples of which are described in the accompanying drawings.

[0021] Figure 1 This is a schematic diagram of an exemplary wireless network for data communication based on sidelink relay according to an embodiment of the present invention. The wireless system 100 includes one or more fixed infrastructure units forming a network distributed over a geographical area. The infrastructure unit may also be referred to as an access point, access terminal, base station, Node B, evolved Node B (eNode-B), next-generation Node B (gNB), or other terms used in the art. The network can be homogeneous or heterogeneous, and can be deployed using the same or different frequencies. gNB 101 is an exemplary base station in an NR network.

[0022] Wireless network 100 also includes multiple communication devices or mobile stations, such as user equipment (UE) 111, 112, 113, 114, 115, 116, and 117. Exemplary mobile devices in wireless network 100 have SL (Single Link) functionality. Mobile devices can establish one or more connections with one or more base stations, such as gNB 101. UE 111 has an access link with gNB 101, including an uplink (UL) and a downlink (DL). UE 112, also served by gNB 101, can establish UL and DL with gNB 101. UE 111 also establishes a sidelink with UE 112. UE 111 and UE 112 are both within coverage area. Mobile devices in vehicles (such as mobile devices 113, 114, and 115) also have SL functionality. Mobile devices 113 and 114 are covered by gNB 101. Mobile device 113 within the coverage area establishes a side link with mobile device 114 within the coverage area. Mobile device 115 in the vehicle is outside the coverage area. Mobile device 114 within the coverage area establishes a side link with mobile device 115 outside the coverage area. In other embodiments, mobile devices such as UEs 116 and 117 may both be outside the coverage area, but can still send and receive data packets with one or more other mobile stations via side links.

[0023] Figure 1 A simplified block diagram of a base station and mobile device / UE for sidelink-based data communication is further shown. The gNB 101 has an antenna 156 that transmits and receives radio signals. An RF transceiver circuit 153 coupled to this antenna receives RF signals from the antenna 156, converts the RF signals into baseband signals, and sends the baseband signals to a processor 152. The RF transceiver 153 also converts 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 invokes different functional modules to execute functional features in the gNB 101. Memory 151 stores program instructions and data 154 to control the operation of the gNB 101. The gNB 101 also includes a set of control modules 155 for performing functional tasks to communicate with the mobile station.

[0024] UE 111 has an antenna 165 for transmitting and receiving radio signals. An RF transceiver circuit 163 coupled to this antenna receives RF signals from antenna 165, converts the RF signals into baseband signals, and sends the baseband signals to processor 162. In one embodiment, the RF transceiver may include two RF modules (not shown). A first RF module is used for high-frequency (HF) transmission and reception; another RF module, different from the HF transceiver, is used for transmission and reception in a different frequency band. RF transceiver 163 also converts baseband signals received from processor 162 into RF signals and sends them to antenna 165. Processor 162 processes the received baseband signals and invokes different functional modules to execute functional features in the UE. Memory 161 stores program instructions and data 164 to control the operation of the UE. Antenna 165 transmits uplink transmissions to antenna 156 of gNB 101 and receives downlink transmissions from antenna 156 of gNB 101.

[0025] The UE also includes a set of control modules for performing functional tasks. These control modules can be implemented via circuitry, software, firmware, or a combination thereof. The sidelink relay configuration module 191 configures a relay path between the remote UE and the base station, wherein the UE is connected to the base station via a Uu link in the wireless network. The sidelink controller 192 establishes an SL with the remote UE, where the SL is part of the relay path, and configures a discontinuous reception (DRX) period on the SL for the remote UE. The relay service receiver 193 receives relay services destined for the remote UE from the base station. The relay controller 194 performs delayed relay forwarding when it determines that the remote UE is in a DRX period configured on the SL. The paging module 195 receives a paging message for a remote UE from the wireless network at a paging occasion (PO) configured for the relay UE. The remote UE is in a disconnected RRC state, including both RRC_IDLE and RRC_INACTIVE states. The paging message is based on the SL association between the UE and the remote UE. Based on the received paging message, the module sends a PC5 paging message to the remote UE in the disconnected RRC state via the established SL.

[0026] Figure 2This 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. Different protocol partitioning options may exist between the central unit (CU) and distributed unit (DU) of the gNB node. The functional partitioning between the CU and DU of the gNB node may depend on the transport layer. Since higher protocol layers have lower performance requirements for the transport layer in terms of bandwidth, latency, synchronization, and jitter, low-performance transmission between the CU and DU of the gNB node can enable higher protocol layers of the NR radio stack to be supported in the CU. In one embodiment, the Service Data Adaptation Protocol (SDAP) and 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 a gNB upper layer 252. In one embodiment 250, the gNB upper layer 252 includes a PDCP layer and an optional SDAP layer. Central unit 211 is connected to distributed units 221, 222, and 223, which correspond to cells 231, 232, and 233, respectively. Distributed units 221, 222, and 223 include a gNB lower layer 251. In one embodiment, the gNB lower layer 251 includes PHY, MAC, and RLC layers. In another embodiment 260, each gNB has a protocol stack 261 including SDAP, PDCP, RLC, MAC, and PHY layers.

[0027] Figure 3 This is an exemplary top-level functional diagram of communication based on sidelink relay according to an embodiment of the present invention. In an NR network, relay UE 301 and remote UE 302 are connected to gNB 303 via Uu links 311 and 312, respectively. In one embodiment, a sidelink 313 is configured between relay UE 301 and remote UE 302. Because UE to network relay is network reachable, and remote UE is UE to network relay reachable, remote UE 302 should be network reachable, and can be reached via the network and can reach the network relay via UE-to. Generally, a remote UE can only be reached via the relay UE if a unicast PC5 link (such as sidelink 313) is established between the remote UE and the relay UE.

[0028] In one example, as shown in procedure 320, when the relay UE determines that the remote UE has entered DRX mode, it performs delayed relay forwarding via side link 313. As shown, the relay path includes Uu link 311 and relay link 313. The relay UE forwards relay services between gNB 303 and remote UE 302, including data services and signaling messages. The PC5 state of remote UE 302 is not visible to gNB 303. For example, for PC5 link side link 313, when no service is in progress, the PC5 link remains without service, which is the same as an inactive state. In some scenarios, the Uu RRC state between remote UE 302 and gNB 303 is maintained, regardless of the PC5 link state between remote UE 302 and relay UE 301. As shown in 361, remote UE 302, which is in RRC connection state from the Uu RRC perspective, enters long DRX mode from the PC5 perspective. When relay UE 301 is in an RRC connection state and the network wants to communicate with an associated remote UE, there may be a desynchronization between the Uu and PC5 of remote UE 302. In step 321, gNB 303 sends the relay service to remote UE 302 to relay UE 301. Relay UE 301 determines that remote UE 302 is in a DRX cycle configured on SL. In one example, relay UE 301 performs delayed relay forwarding when it determines that the remote UE is in a DRX cycle configured on SL. In one embodiment, in step 322, relay UE 301 buffers the relay service. In another embodiment 323, relay UE 301 sends a pause indication to base station 303 to request the base station to pause the relay service to remote UE 302. Relay UE 301 performs delayed relay forwarding by executing steps 322 and / or 323.

[0029] In another example, as shown in exemplary procedure 330, relay UE 301 forwards a paging message from the network to remote UE 302, which is in a disconnected RRC state 362, and wakes up the remote UE. The disconnected RRC state includes an RRC idle state and an RRC inactive state. In step 331, gNB 303 prepares to send a relay service to remote UE 302. In step 332, gNB 303 sends a paging message to relay UE 301 for remote UE 302, which is in a disconnected RRC state. The paging message is based on the SL association between the relay UE and the remote UE. In step 321, relay UE 301 forwards the paging message to remote UE 302 via PC5 side link 313. Remote UE 302 transitions to RRC connected (RRC_CONNECTED) state 363 based on the PC5 paging message.

[0030] Figure 4 This is an exemplary signaling procedure according to an embodiment of the present invention for transmitting downlink data between a remote UE and a base station via a relay UE in a long DRX state. The relay UE 401 is in an RRC connection state 413 and has an active Uu link with the gNB / base station 403. The remote UE 402 is in an RRC connection state at step 412, with no active service on the sidelink. At step 411, the remote UE 402 enters a long DRX mode on the sidelink to sleep according to the configured long DRX period. The state of the remote UE 402 is the inactive state during the RRC connection state. The network maintains the UE context of the remote UE. The base station / gNB 403 is unaware of the inactive state of the remote UE 402.

[0031] In step 421, gNB 403 initiates downlink data transmission to remote UE 402 via relay UE 401. Since remote UE 402 is in long DRX mode on the sidelink, relay UE 401 cannot transmit data to remote UE 402. In an example 430, relay UE 401 performs delayed relay forwarding when it determines in step 481 that remote UE 402 is in a DRX cycle configured on the SL. In one embodiment, in step 431, relay UE 401 stores downlink data in a buffer. It can be assumed that relay UE 401 knows when remote UE 402 wakes up based on the configured long DRX cycle. In one embodiment, the configured long DRX cycle is a MAC parameter configured via a PC5 RRC message when the PC5 relay link is established. The configured long DRX cycle can be provided by the gNB or determined by the relay UE. In any case, relay UE 401 is aware of the DRX cycles of one or more remote UEs with which it has established a sidelink.

[0032] In one embodiment, for example for downlink relay purposes, relay UE 401 sends periodic or event-based reports to gNB 403 regarding its buffer status. The buffer status enables gNB 403 and / or other network entities to determine whether to schedule downlink data transmission to relay UE 401 for relay service to remote UE 402 to avoid buffer overflow within relay UE 401. In one embodiment, in step 432, relay UE 401 sends a data pause request to a network entity (such as gNB 403) to pause data transmission to remote UE 402, awaiting wake-up from remote UE 402, where wake-up depends on the incoming DRX cycle. In one embodiment, the network reduces relay service through relay UE 401 to remote UE 402. In one embodiment, relay UE 401 determines whether the relay service from the network is manageable. If the relay service is manageable, relay UE 401 buffers the service without sending a pause request to the network.

[0033] In step 482, relay UE 401 determines that remote UE 402 has exited the DRX cycle. In step 441, relay UE 401 transmits buffered data to remote UE 402 via PC5. In step 442, relay UE 401 requests the network to resume downlink data transmission. In step 413, remote UE 402 returns to normal RRC connection state. In one embodiment, relay UE 402 indicates the data pause time according to the configured DRX cycle of remote UE 402. After the timer set according to the time indicated by relay UE 401 expires, the network automatically resumes downlink data transmission. Step 442 can be omitted. In yet another embodiment, relay UE 401 reports the DRX cycle of remote UE 402 to gNB 403. gNB 403 sends downlink data to remote UE 402 via relay UE 401 in a specified time pattern to avoid data buffering for relaying at relay UE 401.

[0034] In one example, a relay UE receives a paging message from the network destined for a remote UE in a disconnected state and forwards the paging message to the remote UE via a sidelink. When a remote UE is inactive with the network, i.e., in an RRC inactive / RRC idle state from the perspective of the indirect path to the network, its PC5 connection to the network relay can be maintained. Such a PC5 connection allows the forwarding of paging messages from the UE to the network relay to the remote UE. When the UE to the network relay is in an RRC connected state, a remote UE considered RRC inactive / RRC idle by the network will force the gNB to contact the remote UE via paging. One possible scenario for sidelink relay operation is that the relay UE has multiple associations with multiple remote UEs. For example, the head node (relay UE) of a fleet serves one of its member vehicles, and other member vehicles communicate with the network through the head node's relay. However, other member vehicles have no service at this stage and may remain in an RRC inactive / RRC idle state. During this period, the network can only contact these remote UEs via paging. Relay UEs need to monitor paging opportunities of remote UEs while in RRC connection mode. This places a significant burden on the relay UE because it requires the UE to monitor paging opportunities of multiple remote UEs via the network relay. This can lead to excessive complexity in the UE-to-network relay process, or it may compromise the reachability of the remote UEs themselves. In one embodiment, the network uses the relay UE's PO to send paging messages destined for remote UEs to the relay UE.

[0035] Figure 5 This is an exemplary schematic diagram illustrating how a relay UE forwards a paging message from the network to a remote UE in a disconnected RRC state to wake up the remote UE, according to an embodiment of the present invention. A Uu link is established between relay UE 501 and gNB 503. In step 561, relay UE 501 establishes one or more SLs with one or more remote UEs, including a side link with remote UE 502. The SL with remote UE 502 is part of the relay path. In step 562, remote UE 502 enters a disconnected RRC state. The disconnected RRC state may include an RRC inactive state and an RRC idle state. When a UE is in an RRC connected state when relaying to the network, a remote UE considered by the network to be in an RRC inactive / RRC idle state will force the gNB to use paging to contact the remote UE.

[0036] In step 563, one or more network entities, such as gNB 503, store the relay UE-remote UE SL association information. There is no PC5 RRC state on the PC5 link. Following this principle, the UE may exhibit different states on the Uu and PC5 links. For example, when a remote UE remains in or enters an RRC inactive or RRC idle state from the perspective of the Uu interface, the UE remains active on the PC5 link as long as the PC5 link between the remote UE and the relay UE is maintained. When a unicast PC5 link exists between the remote UE and the relay UE, the network (gNB and / or core network) needs to store the remote UE-remote UE SL association. Based on the stored remote UE-remote UE SL association information, the network always pagees the relay UE to locate the associated one or more remote UEs. The relay UE only needs to monitor its own PO and forward the paging message to the associated remote UE.

[0037] There are several ways for the network / gNB to obtain the PC5 SL association information between the relay UE and the remote UE. In one embodiment, when the relay UE 401 is in the RRC connection phase or decides to leave the connection state, it informs the network of the PC5 SL association between the relay UE and the remote UE. In another embodiment, during a state transition, such as entering an RRC inactive state, the relay UE reports a list of remote UEs maintaining a PC5 link with the relay UE to the gNB. In yet another embodiment, when the relay UE is in the RRC connection state, it dynamically updates the list of remote UEs maintaining a PC5 link with the relay UE to the gNB.

[0038] In another embodiment, each remote UE associated with a relay UE notifies the network, such as the 5G core network 5GC, during the RRC connection phase or when it decides to leave the connection state.

[0039] In another embodiment, each remote UE follows the RRC state of the relay UE. That is, if the relay UE remains in the RRC connected state, all associated remote UEs follow the same RRC state. When the relay UE enters the RRC inactive / RRC idle state, all remote UEs transition to the same RRC state as the relay UE. The relay UE cannot enter a disconnected state (including the RRC inactive / RRC idle state) as long as any remote UE has active traffic flow, because the relay UE needs to remain in the RRC connected state. In one embodiment, a large long DRX period can be configured to reduce the power consumption of inactive remote UEs. It can be assumed that the remote UE remains in the RRC connected state and has a long DRX period, while the UE to the network relay UE itself is in the RRC connected state.

[0040] Once the network obtains the remote UE-relay UE SL association, the network can page the unconnected remote UE by sending a paging message to the associated relay UE. In step 511, the network (e.g., gNB503) prepares to send a service to the remote UE 502 based on the stored remote UE-relay UE SL association information.

[0041] In step 521, gNB 503 sends a paging message to relay UE 501 via the Uu link between relay UE 501 and gNB 503. In one embodiment, relay UE 501 is also in a disconnected RRC state. The paging message from gNB 503 first initiates a random access channel (RACH) procedure 522 from relay UE 501. In one embodiment, the paging message from gNB 503 pagees both relay UE 501 and remote UE 502. The paging message includes one or more of the following elements: the identifier (ID) of the relay UE, the ID of the remote UE, and the SL association between the relay UE and the remote UE. In one embodiment, the paging message is sent at the PO configured for relay UE 501.

[0042] In another embodiment, the paging message includes a paging indication or wake-up indication for the remote UE 502. Upon receiving the paging message, the relay UE 501 forwards the paging indication or wake-up indication to the remote UE 502 via the PC5 side link. Upon receiving the paging indication or wake-up indication, the remote UE 502 uses a PC5 RRC message to send an RRC Resume Request or RRC Setup Request to the network via the relay UE 501. The relay UE 501 forwards the RRC Resume Request or RRC Setup Request to the network / gNB 503. The network continues the RRC process, causing the remote UE 502 to transition back to the RRC connection state 541.

[0043] In one embodiment, in step 523, gNB 503 sends an RRC reconfiguration message to relay UE 502 after the paging message. In one embodiment, the RRC reconfiguration message includes the remote UE ID and / or the remote UE-relay UE SL association. In step 531, relay UE 501 forwards the PC5 paging message to remote UE 502 via a sidelink. In step 532, remote UE 502 sends a PC5 RRC response message to relay UE 501. In step 533, relay UE 501 forwards the RRC response message from remote UE 501 to gNB 503. In step 541, remote UE 502 enters the RRC connection state. In step 551, gNB 503 sends relay services for remote UE 502 to relay UE 501. In step 552, relay UE 501 forwards the relay services to remote UE 502.

[0044] Figure 6A This is an exemplary flowchart illustrating how a relay UE forwards a paging message from the network to a remote UE in an RRC inactive state to wake up the remote UE, according to an embodiment of the present invention. A relay UE 601 in a disconnected RRC state 612 establishes a sidelink with a remote UE 602 in an RRC inactive state 611. The relay UE 601 is connected to the gNB / base station 603 via a Uu link in the wireless network. The remote UE 602 and the relay UE 601 maintain a PC5 sidelink at 613. In step 621, the gNB 603 sends a paging message to the relay UE 601, intending to wake up both the relay UE 601 and the remote UE 602 to transmit downlink data to the remote UE 602. If the relay UE 601 is in an RRC inactive state, the gNB 603 sends a paging message to wake up both the remote UE 602 and the relay UE 601. If relay UE 601 is in RRC idle state, gNB 603 sends a paging message to wake up remote UE 602 and relay UE 601. In one embodiment, the paging message includes a remote UE index or ID to allow relay UE 601 to identify which remote UE is the target of downlink data transmission. In another embodiment, gNB 603 sends the remote UE index or ID in a dedicated RRC message to identify which remote UE is the target of downlink data transmission.

[0045] In step 622, relay UE 601 performs a RACH procedure on gNB 603 in response to a paging message from gNB 603. In step 623, relay UE 601 sends message 5 (MSG5) to gNB 603 to establish an RRC connection with gNB 603. In step 613, relay UE 601 enters the RRC connection state. In one embodiment, in step 624, gNB 603 sends an RRC reconfiguration message including RRC recovery to the remote UE. In step 631, relay UE 601 forwards a PC5 paging message to the remote UE 602 based on the paging message of step 621 and (optionally) the RRC reconfiguration message of step 624. In one embodiment, the PC5 paging message includes RRC recovery. In step 632, remote UE 602 responds to the PC5 RRC to gNB 603 by encapsulating a Uu RRC recovery complete (RRCResumeComplete) message. In step 633, relay UE 601 forwards a Uu encapsulated RRC recovery completion message to gNB 603. In step 614, remote UE 602 with service access enters the RRC connection state.

[0046] In one embodiment, after receiving the paging message in step 621, the relay UE 601 and the remote UE 602 perform a handshake. After a successful handshake indicating a response from the remote UE, the remote UE 602 sends an RRC recovery request message to the relay UE 601 via a sidelink. The relay UE 601 forwards the RRC recovery request message to the gNB 603 via the Uu interface. In another embodiment, if the relay UE enters an RRC inactive state and the associated remote UE also enters an RRC inactive state, the gNB uses RAN-based paging to wake up the relay UE before paging the remote UE for downlink data transmission. When both the relay UE and the remote UE are in an RRC inactive state, the gNB knows the SL association between them. When both the relay UE and the remote UE are in an RRC inactive state, the gNB stores the SL association between the relay UE and the remote UE. The aforementioned SL association can be added to the UE context of the UE in the RRC inactive state stored in the gNB.

[0047] Figure 6BThis is an exemplary flowchart illustrating how a relay UE forwards a paging message from the network to a remote UE in an RRC idle state to wake up the remote UE, according to an embodiment of the present invention. A relay UE 651 in a disconnected RRC state 662 establishes a sidelink with a remote UE 652 in an RRC idle state 661. The relay UE 651 is connected to the gNB / base station 653 via a Uu link in the wireless network. The remote UE 652 and the relay UE 651 maintain a PC5 sidelink at 663. In step 671, the gNB 653 sends a paging message to the relay UE 651, intending to wake up both the relay UE 651 and the remote UE 652 to transmit downlink data to the remote UE 652. If the relay UE 651 is in an RRC idle state, the gNB 653 sends a RAN paging message to wake up both the remote UE 652 and the relay UE 651. If relay UE 651 is in RRC idle state, gNB 653 sends a paging message to wake up remote UE 652 and relay UE 651. In one embodiment, the paging message includes a remote UE index or ID to allow relay UE 651 to identify which remote UE is the target of downlink data transmission. In another embodiment, gNB 653 sends the remote UE index or ID in a dedicated RRC message to identify which remote UE is the target of downlink data transmission.

[0048] In step 672, relay UE 601 performs a RACH procedure on gNB 653 in response to a paging message from gNB 653. In step 673, relay UE 651 sends message 5 to gNB 653 to establish an RRC connection with gNB 653. In step 663, relay UE 651 enters the RRC connection state. In one embodiment, in step 674, gNB 653 sends an RRC reconfiguration message including RRC establishment to the remote UE RRC. In step 681, relay UE 651 forwards the PC5 paging message to the remote UE 652 based on the paging message of step 671 and (optionally) the RRC reconfiguration message of step 674. In one embodiment, the PC5 paging message includes RRC establishment. In step 682, remote UE 652 responds to PC5 RRC to gNB 653 with an encapsulated Uu RRC Setup Complete message. In step 683, relay UE 651 forwards a Uu encapsulated RRC establishment completion message to gNB 603. In step 664, the remote UE 664 with service access enters the RRC connection state.

[0049] In one embodiment, after receiving the paging message in step 671, the relay UE 651 and the remote UE 652 perform a handshake. After a successful handshake indicating a response from the remote UE, the remote UE 652 initiates an RRC establishment request message to the relay UE 651 via a sidelink. The relay UE 651 forwards the RRC establishment request message to the gNB 653 via the Uu interface. In another embodiment, if the relay UE enters an RRC idle state and the associated remote UE also enters an RRC idle state, the gNB uses paging to wake up the relay UE before paging the remote UE for downlink data transmission. When both the relay UE and the remote UE are in an RRC idle state, the gNB knows the SL association between them. When both the relay UE and the remote UE are in an RRC idle state, the gNB stores the SL association between the relay UE and the remote UE. The aforementioned SL association can be added to the UE context of the UE in the RRC idle state stored in the gNB.

[0050] Figure 7 This is an exemplary flowchart illustrating downlink data transmission between a remote UE and a base station in a long DRX state according to an embodiment of the present invention, via a relay UE. In step 701, the relay UE configures a relay path between the remote UE and the base station in the wireless network, wherein the relay UE is connected to the base station via a Uu link in the wireless network. In step 702, the relay UE establishes an SL with the remote UE, wherein the SL is part of the relay path, and wherein a DRX period on the SL is configured for the remote UE. In step 703, the relay UE receives relay traffic destined for the remote UE from the base station. In step 704, the relay UE performs delayed relay forwarding when it determines that the remote UE is in the DRX period configured on the SL.

[0051] Figure 8 This is an exemplary flowchart illustrating how a relay UE forwards a paging message from the network to a remote UE in a disconnected RRC state, according to an embodiment of the present invention. In step 801, the relay UE establishes a relay link (SL) with the remote UE, wherein the relay UE is connected to the base station via a Uu link in the wireless network. In step 802, the relay UE receives a paging message for the remote UE from the wireless network at a paging time configured for the relay UE, wherein the remote UE is in a disconnected RRC state including an RRC idle state and an RRC inactive state, and wherein the paging message is based on the SL association between the relay UE and the remote UE. In step 803, based on the received paging message, the relay UE sends a PC5 paging message to the remote UE in the disconnected RRC state via the established SL. In step 804, the relay UE forwards the relay service from the base station to the remote UE.

[0052] While the invention has been described in conjunction with specific embodiments for illustrative purposes, it is not limited thereto. Therefore, various modifications, adaptations, and combinations of the features of the described embodiments can be made without departing from the scope of the invention as set forth in the claims.

Claims

1. A data communication method based on sidelink relay, comprising: The relay user equipment configures a relay path between the remote user equipment and the base station in the wireless network, wherein the relay user equipment is connected to the base station through a Uu link in the wireless network; A side link is established with the remote user equipment, wherein the side link is part of the relay path, and wherein a discontinuous reception period of the side link is configured for the remote user equipment. The base station receives relay services destined for the remote user equipment, wherein the relay user equipment and the remote user equipment are in a radio resource control connection state; as well as When it is determined that the remote user equipment is in a sleep mode of discontinuous reception period, delayed relay forwarding is performed, wherein the relay user equipment is unable to transmit data to the remote user equipment in the mode, and the discontinuous reception period is configured on the side link.

2. The data communication method based on sidelink relay according to claim 1, characterized in that, The delayed relay forwarding performed by the relay user equipment includes buffering the relay service at the relay user equipment.

3. The data communication method based on sidelink relay according to claim 2, characterized in that, Further includes: When it is determined that the remote user equipment has exited the discontinuous reception period, the buffered relay service is forwarded and the relay service forwarding is resumed.

4. The data communication method based on sidelink relay according to claim 1, characterized in that, The delayed relay forwarding performed by the relay user equipment includes sending a pause instruction to the base station, requesting the base station to suspend the relay service to the remote user equipment.

5. The data communication method based on sidelink relay according to claim 4, characterized in that, When it is determined that the remote user equipment has exited the discontinuous reception period, a recovery instruction is sent to the base station to request the base station to restore the relay service to the remote user equipment.

6. The data communication method based on sidelink relay according to claim 1, characterized in that, The relay service is a data service or signaling message from the base station to the remote user equipment.

7. A user equipment, comprising: A transceiver is used to send and receive radio frequency signals in a wireless network; The sidelink relay configuration module is used to configure the relay path between the remote user equipment and the base station, wherein the user equipment is connected to the base station through the Uu link in the wireless network; A sidelink controller is configured to establish a sidelink with the remote user equipment, wherein the sidelink is part of the relay path, and wherein a discontinuous reception period of the sidelink is configured for the remote user equipment. A relay service receiver is used to receive relay services from the base station destined for the remote user equipment, wherein the user equipment and the remote user equipment are in a radio resource control connection state; as well as A relay controller is configured to perform delayed relay forwarding when the remote user equipment is in a sleep mode that determines the discontinuous reception period, wherein the user equipment is unable to transmit data to the remote user equipment in the mode, and the discontinuous reception period is configured on the side link.

8. The user equipment according to claim 7, characterized in that, The delayed relay forwarding involves one or more of the following processes: buffering the relay service at the user equipment, and sending a pause indication to the base station to request the base station to pause the relay service to the remote user equipment.

9. The user equipment according to claim 7, characterized in that, The relay service is a data service or signaling message from the base station to the remote user equipment.

10. The user equipment according to claim 9, characterized in that, The system further includes a paging module for receiving a paging message for a remote user equipment from the wireless network at a paging time configured for the relay user equipment, wherein the remote user equipment is in a disconnected RRC state including an RRC idle state and an RRC inactive state, and wherein the paging message is based on a sidelink association between the relay user equipment and the remote user equipment; and for sending a PC5 paging message to the remote user equipment in the disconnected RRC state via the established sidelink based on the received paging message.

11. The user equipment according to claim 10, characterized in that, The paging message includes one or more of the following elements: the identifier of the trunk user equipment, the identifier of the remote user equipment, and the sidelink association between the trunk user equipment and the remote user equipment.

12. A storage medium storing a program that, when executed, causes a user equipment to perform the steps of the data communication method based on sidelink relay as described in any one of claims 1-6.

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