Path Switching to Indirect Communication via a Relay User Equipment (UE) Device in a Radio Resource Control (RRC) Inactive Connection State

Abstract

A base station sends a radio access network (RAN)-based page to a target relay user equipment (UE) device to initiate a path switch from direct communication with the remote user equipment (UE) device to indirect communication through the target relay UE device. The relay UE device is in a radio resource control (RRC) connection state of RRC INACTIVE when it receives the page. The base station sends an RRC reconfiguration message to the remote UE device, and the remote UE device sends an RRC reconfiguration complete message to the base station via the target relay UE device.

Description

Claim of Priority

[0001] This application claims the priority of U.S. Provisional Application No. 63 / 222,303, filed on July 15, 2021, with docket number TPRO 00363 US and entitled "SERVICE CONTINUITY UNDER L2 SIDELINK RELAYING". The U.S. Provisional Application has been assigned to the assignee of this application and is hereby expressly incorporated by reference in its entirety.

Technical Field

[0002] The present invention generally relates to wireless communication, and more particularly to the management of wireless communication links using relay devices.

Background Art

[0003] Many wireless communication systems that employ multiple base stations to provide wireless services to user equipment (UE) devices enable sidelink communication between two or more UE devices where a UE device can communicate directly with other UE devices. In sidelink communication, UE devices transmit data signals to each other via a communication link using cellular resources instead of via a base station. Such proximity services (ProSe) communication is sometimes referred to as device-to-device (D2D). In addition, one or more UE devices can be used as a relay device between a UE device and a destination. The relay device transfers data between the UE device and the destination. The destination can be a communication network or another UE device (destination UE device). When the destination is a network, the relay function is typically referred to as UE-to-network (U2N) relay, and the relay UE device establishes a communication path between a remote UE and a base station (gNB) or cell. In some situations, for example, a UE device may be outside the service area of a base station, and the relay UE device provides a communication link routed from such out-of-coverage (OoC) UE device through the relay UE device to the base station. When the destination device is another UE device (target UE device), the relay function is usually referred to as UE-to-UE (U2U) relay. Summary of the Invention

[0004] The base station transmits a radio access network (RAN)-based page to a target relay user equipment (UE) device to initiate a path switch from direct communication with a remote user equipment (UE) device to indirect communication through the target relay UE device. When receiving the page, the relay UE device is in a radio resource control (RRC) connection state of RRC INACTIVE. The base station transmits an RRC reconfiguration message to the remote UE device, and the remote UE device transmits an RRC reconfiguration complete message to the base station via the target relay UE device. Brief Description of the Drawings

[0005]

Figure 1A

[0006]

Figure 1B

[0007]

Figure 1C

[0008]

Figure 1D

[0009]

Figure 1E

[0010]

Figure 2

[0011]

Figure 3

[0012]

Figure 4

[0013]

Figure 5

Embodiments for Carrying Out the Invention

[0014] As described above, the relay UE device provides a connection between the remote UE device and a destination that can be another UE device (destination UE device) or a network. When the destination is a network, the relay provides a connection to a cell provided by a base station (gNB) of the network. The relay connection between the remote UE device and the target UE device may be referred to as a UE-UE (U2U) relay connection. The relay connection between the remote UE device and the base station (gNB) may be referred to as a UE-network (U2N) relay connection. In some situations, the final destination is a target UE device via a base station. In a conventional system where the relay connects to a base station (gNB), the relay UE device needs to meet certain criteria to function as a relay. For example, the relay UE device must be within coverage and have a cellular (Uu) communication link to a base station of sufficient quality to be available for the U2N relay function.

[0015] The sidelink relay function enables a remote UE outside of coverage (OoC) to connect to a gNB or a base station via a relay UE device. In UE-network (U2N) relay, the relay UE is within the coverage of the cell and needs to be connected to the gNB. The relay connection from the remote UE device to the base station (gNB) includes a PC5 link (sidelink) between the remote UE device and the relay UE device and a Uu link between the relay UE device and the gNB.

[0016] In some situations, the remote UE device communicates directly with the base station (gNB) without communicating through the relay UE device, and the base station determines that the communication link to the remote UE device should be switched from a direct link to an indirect link through the relay UE device. However, when performing the switch to the indirect link, the base station can choose to switch to an indirect relay link provided by a relay UE device in an RRC state other than the RRC connected state (RRC CONN). Compared with switching to a relay connection through a relay UE device in the RRC CONN state, latency may be minimized when switching to a relay connection through a relay UE device in the RRC CONN state. However, in some situations, the path through the relay in the RRC INACTIVE state may be preferred. Therefore, the base station can choose a better path at the expense of latency. In other situations, the relay in the RRC CONN may not be available, and it is generally more power-efficient to keep the relay UE device in the IDLE or INACTIVE state when there is no remote UE device PC5-connected to the relay UE device, so the only indirect option includes the relay in the INACTIVE state. Also, the current communication standard does not stipulate that the remote UE device restricts the pool of candidate relay UE devices included in the measurement report to any specific RRC state such as RRC CONN, and does not stipulate that the remote UE indicates the state of the candidate relay UE devices listed in the measurement report.

[0017] In the example of this specification, the base station sends a radio access network (RAN)-based page to a target relay UE device in RRC INACTIVE to initiate a path switch from a direct link to a remote UE device to an indirect link via the target relay UE device to the remote UE device. The page triggers a resume procedure to transition the target relay UE to RRC CONN. The base station also sends a synchronization-based RRC reconfiguration message to the remote UE. The remote UE sends an RRC reconfiguration complete message to the base station via the target relay UE. The target relay UE sends an RRC reconfiguration complete message to the base station via the resumed Uu communication link.

[0018] The techniques described herein may be applied to various types of systems and communication specifications, but the example devices operate according to at least one revised version of the 3rd Generation Partnership Project (3GPP) New Radio (NR) V2X communication specification. Thus, the techniques described herein may be adopted by one or more future revisions of the communication specification, or the techniques may be applied to other communication specifications where sidelink or D2D is adopted. More specifically, the techniques may be applied to current and future releases of the 3GPP NR specification. For example, the techniques may also be applicable to 3GPP NR (3GPP Rel-17) and 3GPP Rel-18.

[0019] FIG. 1A is a block diagram of a communication system 100 for an example in which candidate relay UE devices 101-103 transmit reference signals 104-106 received by a remote UE device 108, and the candidate relay UE devices 101-103 may be in any one of the RRC connected states. The candidate relay UE devices 101-103 are within the cell coverage area 110 of a base station (gNB) 112. In this example, the first candidate relay UE device 101 is in the RRC inactive state (RRC INACTIVE), the second candidate relay UE device 102 is in the RRC connected state (RRC CONN), and the third candidate relay UE device 103 is in the RRC idle state (RRC IDLE).

[0020] The remote UE device 108 communicates with the base station 112 via the direct Uu communication link 114. Therefore, the remote UE device 108 is within the cell coverage area 110 when the scenarios of the examples described with reference to FIGS. 1A to 1E start. The remote UE device 108 receives the reference signals 104, 105, and 106 from each of the candidate relay UE devices 101, 102, and 103. In this example, the reference signals 104 to 106 are sidelink discovery signals, and the discovery signals can be model A discovery notification messages or model B response messages.

[0021] Figure 1B is a block diagram of a communication system 100 in which, in RRC INACTIVE, the remote UE device 108 transmits a measurement report 120 to the base station 112, and the base station 112 transmits a RAN-based page 121 to the selected target relay UE device 101. The remote UE device 108 generates the measurement report 120 based on the measured values of the reference signals 104-106 received at the remote UE device 108. As an example, the measurement report 120 is generated in accordance with at least one revised version of the 3GPP communication specification. The base station 112 receives the measurement report 120 and determines that the remote UE device 108 should switch from a direct communication path to the base station 112 to an indirect communication path via a relay UE device. In this example, the base station 112 selects the candidate relay UE device 101 as the target relay UE device for the indirect communication path. The base station 112 determines that the indirect communication link through the target relay UE device is a preferred connection to the remote UE device 108 and selects the target relay UE device based at least in part on the measurement report and the quality of service (QoS) requirements, as well as other factors. Since the candidate relay UE devices are served by the base station 112, the base station 112 is aware of the RRC connection status of each candidate relay UE device. In the example of this specification, the base station 112 refrains from selecting a relay UE device that is in RRC IDLE. The prior art is applied to switch communication to an indirect path through a relay UE device in RRC CONN. In the example described with reference to FIGS. 1A-1E, the base station 112 selects the relay UE device 101 that is in RRC INACTIVE. Thus, in this example, the relay UE device 101 is selected as the target relay UE device.

[0022] The base station 112 transmits the RAN-based paging 121 to the target relay UE device 101. The target relay UE device 101 in RRC INACTIVE monitors RAN paging using a complete non-active radio network temporary identifier (I-RNTI). The complete I-RNTI is part of the Pagingl)E-identity within the RAN-based paging message 121. The RAN assigned the I-RNTI to the target relay UE device 101 when the target relay UE device 101 transitioned to RRC INACTIVE.

[0023] Figure 1C is a block diagram of a communication system 100 in which the target relay UE device resumes RRC CONN and the base station 112 transmits an RRC reconfiguration message 122 by synchronization to the remote UE device 108. In response to receiving the RAN paging message 121, the target relay UE device 101 implements procedures to resume the RRC CONN state with the base station 112. In this example, the target relay UE device 101 implements the resume procedures according to at least one revised version of the 3GPP communication specification, which typically includes at least transmitting an RRC resume request message to the base station 112, receiving an RRC resume message from the base station 112, and transmitting an RRC resume completion message to the base station 112. After the procedures are implemented, the RRC CONN state 128 is resumed. The base station 112 transmits an RRC reconfiguration message 122 by synchronization instructing the remote UE device 108 to switch to an indirect path through the candidate relay UE device 101. Thus, in this example, the base station 112 selects the target relay UE device 101 in RRC INACTIVE, transmits the RAN page 121 to the target relay UE device 101, and initiates the resume procedure to bring the target relay UE device 101 to RRC CONN. Next, the base station 112 transmits an RRC reconfiguration message 122 by synchronization to the remote UE device 108. The base station 112 also transmits an RRC reconfiguration message 123 to the target relay UE device 101 to configure both the sidelink radio link control (RLC) configuration and the RLC configuration in the Uu link, as well as the remote UE identifier (ID) used for the relay operation.

[0024] FIG. 1D is a block diagram of a communication system 100 in which a remote UE device 108 transmits an RRC reconfiguration complete message 124 to a target relay UE device (candidate relay UE device 101) for relaying to a base station 112. In response to receiving the RRC reconfiguration message 122 by synchronization, the remote UE device 108 establishes a sidelink (PC5 link) 126 with the candidate relay UE device 101. After the PC5 link 126 is established, the remote UE device 108 uses the default settings of SL-RLC1 to transmit the RRC reconfiguration complete message 124 to the candidate relay UE device 101, which is directed to the base station 112.

[0025] FIG. 1E is a block diagram of the communication system 100, in which a target relay UE device (candidate relay UE device 101) transfers information related to the RRC reconfiguration complete message 124 in a remote reconfiguration complete relay transmission 130 to the base station 112. After receiving the RRC reconfiguration complete message 124, the target relay UE device (candidate relay UE device 101) relays the RRC reconfiguration complete message 124 to the base station 112, and an indirect communication path 132 is established between the remote UE device 108 and the base station 112 through the relay UE device 101. In this example, the remote reconfiguration complete relay transmission 130 is a signaling radio bearer 1 (SRB1) message transmitted using sidelink relay adaptation protocol (SRAP) technology.

[0026] FIG. 2 is a block diagram of an example of a base station 200 suitable for use as base station 112 and providing a cell or otherwise serving either UE devices. Base station 200 includes a control unit 204, a transmission unit 206, and a reception unit 208, as well as other electronic devices, hardware, and code. Base station 200 is any fixed device, mobile device, or portable device that implements the functions described herein. The various functions and operations of the blocks described with reference to base stations 112, 200 may be implemented in any number of devices, circuits, or elements. Two or more of the functional blocks may be integrated into a single device, and the functions described as being performed in any single device may be implemented across multiple devices. Base station 200 may be a fixed device or apparatus installed at a specific location during system deployment. Examples of such equipment include fixed base stations or fixed transceiver stations. Base stations may be referred to by different terms, but when operating in accordance with one or more communication specifications of 3GPP V2X operation, base stations are generally referred to as gNodeB or gNB. In some situations, base station 200 may be a mobile device temporarily installed at a specific location. Some examples of such equipment include mobile transceiver stations that may include power generation equipment such as generators, solar panels, and / or batteries. Larger and heavier versions of such equipment may be transported by trailers. In still other situations, base station 200 may be a portable device not fixed to any specific location.

[0027] The control unit 204 includes any combination of hardware, software, and / or firmware that executes the functions described herein and facilitates the overall functions of the base station 200. An example of a suitable control unit 204 includes a microprocessor connected to a memory or code executed on a processor configuration. The transmission unit 206 includes an electronic device configured to transmit a wireless signal. In some situations, the transmission unit 206 may include a plurality of transmission units. The reception unit 208 includes an electronic device configured to receive a wireless signal. In some situations, the reception unit 208 may include a plurality of reception units. The reception unit 208 and the transmission unit 206 receive and transmit signals via the antenna 210, respectively. The antenna 210 may include a separate transmission antenna and a reception antenna. In some situations, the antenna 210 may include a plurality of transmission antennas and reception antennas.

[0028] In the example of FIG. 2, the transmission unit 206 and the reception unit 208 perform radio frequency (RF) processing including modulation and demodulation. Accordingly, the reception unit 208 may include components such as a low noise amplifier (LNA) and a filter. The transmission unit 206 may include a filter and an amplifier. Other components may include isolators, matching circuits, and other RF components. These components may be combined with or cooperate with other components to perform the base station functions. The required components may depend on the specific functions required by the base station.

[0029] The transmission unit 206 includes a modulator (not shown), and the reception unit 208 includes a demodulator (not shown). The modulator can modulate a signal transmitted as part of a downlink signal and apply any one of a plurality of modulation orders. The demodulator demodulates any uplink signal received at the base station 200 according to one of the plurality of modulation orders.

[0030] The base station 200 includes a communication interface 212 for transmitting and receiving messages with other base stations. The communication interface 212 may be connected to a backhaul or network that enables communication with other base stations. In some situations, the link between base stations may include at least a portion of the radio portion. Accordingly, the communication interface 212 may include a wireless communication function and may utilize some of the components of the transmitter 206 and / or the receiver 208.

[0031] FIG. 3 is a block diagram of an example of a UE device 300 suitable for use as each of the UE devices 101-103, 108. In some examples, the UE device 300 is any wireless communication device such as a mobile phone, transceiver modem, personal digital assistant (PDA), tablet, or smartphone. In other examples, the UE device 300 is a machine type communication (MTC) device or an Internet of Things (IoT) device. The UE device 300 is thus any fixed, mobile, or portable device that performs the functions described herein. The various functions and operations of the blocks described with reference to the UE device 300 may be implemented in any number of devices, circuits, or elements. Two or more of the functional blocks may be integrated into a single device, and the functions described as being performed in any single device may be implemented across multiple devices.

[0032] The UE device 300 includes at least a control unit 302, a transmission unit 304, and a reception unit 306. The control unit 302 includes any combination of hardware, software, and / or firmware for executing the functions described in this specification and facilitating the overall functions of the communication device. An example of a suitable control unit 302 includes a microprocessor connected to a memory or code executed on a processor configuration. The transmission unit 304 includes an electronic device configured to transmit a radio signal. In some situations, the transmission unit 304 may include a plurality of transmission units. The reception unit 306 includes an electronic device configured to receive a radio signal. In some situations, the reception unit 306 may include a plurality of reception units. The reception unit 306 and the transmission unit 304 receive and transmit signals via an antenna 308, respectively. The antenna 308 may include a separate transmission antenna and a reception antenna. In some situations, the antenna 308 may include a plurality of transmission antennas and reception antennas.

[0033] In the example of FIG. 3, the transmission unit 304 and the reception unit 306 perform radio frequency (RF) processing including modulation and demodulation. Accordingly, the reception unit 306 may include components such as a low noise amplifier (LNA) and a filter. The transmission unit 304 may include a filter and an amplifier. Other components may include isolators, matching circuits, and other RF components. These components, in combination with or in cooperation with other components, perform the communication device functions. The required components may depend on the specific functions required by the communication device.

[0034] The transmitting unit 304 includes a modulator (not shown), and the receiving unit 306 includes a demodulator (not shown). The modulator can modulate a signal transmitted as part of the uplink signal by applying any one of a plurality of modulation orders. The demodulator demodulates the downlink signal according to one of the plurality of modulation orders. The UE device 300 includes a memory 310 in addition to the memory that is part of the control unit 302. It may be included in the remote reconfiguration completion relay transmission 130. Information such as a candidate relay priority list may be stored and maintained in the memory 310, the control unit 302, or a combination of the two.

[0035] Figure 4 is a message diagram 400 showing an example of relay link management for switching from a direct path to an indirect path when the target relay UE device is in RRC INACTIVE. Figure 4 shows three candidate relay UE devices 101 to 103, but any number of candidate relay devices may be involved in the messaging. This example starts with the remote UE device 108 communicating directly (402) with the base station (gNB) 112, the first candidate relay UE device 101 being in the RRC inactive state (RRC INACTIVE), the second candidate relay UE device 102 being in the RRC connected state (RRC CONN), and the third candidate relay UE device 103 being in the RRC idle state (RRC IDLE). Uplink data and downlink data are exchanged between the remote UE device 108 and the gNB 112 via the direct Uu communication link 402.

[0036] In transmission 404, a Model B discovery request is transmitted from the remote UE device 108 to nearby candidate relay UE devices. In some situations, the Model B discovery request may be omitted. Therefore, the arrow representing the Model B discovery request is shown as a dashed line to indicate that transmission may not be required. For example, when a Model A discovery message is received from a candidate relay UE device, the Model B request may not be required.

[0037] In transmission 406, a discovery message is transmitted from candidate relay UE device 102. In transmission 408, a discovery message is transmitted from candidate relay UE device 101. In transmission 410, a discovery message is transmitted from candidate relay UE device 103. The discovery messages in transmissions 406, 408, and 410 may be model A discovery notification messages or may be model B discovery response messages. Remote UE device 108 receives the discovery message and evaluates the received signals and information as part of the relay reselection procedure. As an example, remote UE device 108 measures the side link discovery reference signal received power (SD-RSRP) level of the received discovery message.

[0038] In transmission 412, remote UE device 108 transmits a measurement report to gNB 112, and the measurement report includes signal quality measurement values of candidate relay devices. Thus, the measurement report includes signal quality measurement values such as the SD-RSRP levels of discovery signals 406, 408, and 410.

[0039] In event 414, gNB 112 determines that the communication with remote UE device 108 should be switched from a direct connection to an indirect connection via a target relay UE device. The decision by gNB 112 to switch to indirect communication may be based on any combination of factors such as which event triggered the measurement report, the SD-RSRP level(s), the RRC connection status, and the congestion level of the candidate relay UE (the gNB may know how many remote UE devices are already connected to a particular candidate relay UE). In the example of Figure 4, gNB 112 selects candidate relay UE device (UE1) 101 as the target UE device.

[0040] In transmission 416, gNB 112 transmits a RAN-based page to target relay UE device 101. In response to receiving the RAN-based page, target relay UE device 101 starts the RRC resume procedure by transmitting an RRC resume request in transmission 418.

[0041] The target relay UE device 101 and the gNB 112 exchange messages to resume the RRC CONN. In this example, the gNB 112 transmits an RRC resume message at transmission 420, and the target relay UE device 101 transmits an RRC resume completion message 422. When the target relay UE device 101 is in the RRC CONN, a Uu communication link is established between the target relay UE device 101 and the gNB 112.

[0042] At transmission 423, the gNB 112 transmits an RRC reconfiguration message to the target relay UE device 101 to configure both the sidelink radio link control (RLC) configuration, the RLC configuration on the Uu link, and the remote UE identifier (ID) used for the relay operation.

[0043] At transmission 424, the gNB 112 transmits an RRC reconfiguration message by synchronization to the remote UE device 108. The RRC reconfiguration message by synchronization starts the switch from the direct communication link 402 to the indirect communication link via the target candidate relay UE device 101.

[0044] In event 426, a PC5 connection is established between the remote UE device 108 and the target candidate relay UE device 101. In some situations, the PC5 connection may already be established and event 426 is not required.

[0045] At transmission 428, the remote UE device 108 transmits an RRC reconfiguration completion message directed to the gNB 112 via the target relay UE device 101. The RRC reconfiguration completion message 428 is received at the target relay UE device 101 via the PC5 link.

[0046] In transmission 430, the target relay UE device 101 relays the RRC reconfiguration completion message received from the remote UE device 108 to the gNB 112. The communication between the remote UE device 108 and the gNB 112 continues via an indirect communication link 432 including a relay connection through the relay UE device 101.

[0047] Figure 5 is a flowchart of an example of a method for managing the path switching from a direct communication link to an indirect communication link. This method can provide a relay service to one or more remote UE devices and is implemented by a UE device in the RRC INACTIVE state. Therefore, in this example, the method may be implemented by a candidate relay UE device such as the candidate relay UE device (UE1) 101.

[0048] In step 502, the RRC INACTIVE connection state with the base station (gNB) 112 is maintained.

[0049] In step 504, it is determined whether a RAN-based page has been received from the base station (gNB) 112. If the RAN-based page is not received, the method returns to step 502. If the RAN-based page is received, the method proceeds to step 506.

[0050] In step 506, the relay UE device transmits an RRC resume request message to the gNB 112. The relay UE device starts a connection resumption procedure in response to receiving the RAN-based page. The connection resumption procedure proceeds to step 508, where an RRC resume message is received from the base station (gNB) 112.

[0051] In step 510, the relay UE device transmits RRC resume completion to the base station (gNB) 112. This procedure places the relay UE device in RRC CONN.

[0052] In step 512, a PC5 link with the remote UE device 108 is established. For example, the candidate relay UE device receives messages according to one or more revised versions of the 3GPP communication specifications to initiate the PC5 link.

[0053] In step 514, an RRC reconfiguration complete message is received from the remote UE device 108. The destination of the RRC reconfiguration complete is the base station (gNB) 112. In this example, the relay UE device determines whether the SL-RLC1 from the remote UE is received after the RRC reconfiguration complete is transmitted on the SL-RLC1 channel.

[0054] After the relay UE device enters RRC CONN, in response to receiving the RRC reconfiguration complete from the remote UE device, the relay UE device relays the RRC reconfiguration complete message received from the remote UE device to the gNB 112 in step 516. The communication between the remote UE device 108 and the gNB 112 continues via an indirect path through the relay UE device. The technology described above provides at least a mechanism for switching from direct communication to indirect communication through a candidate relay UE device that is at least in RRC INACTIVE.

[0055] Obviously, other embodiments and modifications of the present invention will readily occur to those skilled in the art in view of these teachings. The above description is illustrative and not restrictive. The present invention should be limited only by the appended claims, which should be considered in conjunction with the above specification and the accompanying drawings and include all such embodiments and modifications. Therefore, the scope of the present invention should not be determined with reference to the above description, but rather should be determined with reference to the appended claims along with the full scope of their equivalents.

Claims

1. A relay user equipment (UE) device, a transmission unit that transmits a signal to a remote UE device, a control unit that maintains the relay UE device in a radio resource control (RRC) INACTIVE state with a base station that has received a measurement report from the remote UE device via a Uu direct communication link, wherein the measurement report includes a measured value of the signal, the control unit, a reception unit that receives a radio access network (RAN)-based page from the base station, and comprises, the control unit performs an RRC resume procedure with the base station to transition the relay UE device to an RRC connected (CONN) state, after the relay UE device has transitioned to the RRC connected (CONN) state, the reception unit receives a first RRC reconfiguration message including settings for relaying communication of the remote UE device from the base station, the reception unit receives an RRC reconfiguration completion message directed to the base station from the remote UE device via a PC5 communication link, the transmission unit is configured to transmit the RRC reconfiguration completion message to the base station via a Uu communication link established in response to the RRC resume procedure, Relay UE device.

2. After the relay UE device has transitioned to the RRC connected (CONN) state, the control unit establishes the PC5 communication link with the remote user device The relay UE device according to claim 1.

3. The RRC reconfiguration completion message is transmitted by the remote UE device in response to receiving, at the remote UE device, a second RRC reconfiguration message transmitted from the base station via a Uu direct communication link between the base station and the remote UE device, and the second RRC reconfiguration message starts a path switch from a direct communication link between the remote UE device and the base station to an indirect communication link between the remote UE device and the base station via the relay UE device, The relay UE device according to claim 1.

4. The RAN-based page is transmitted by the base station to initiate a path switch from a direct communication link between the remote UE device and the base station to an indirect communication link between the remote UE device and the base station through the relay UE device. The relay UE device according to claim 1.

5. After the transmitting unit transmits an RRC resume request message, the receiving unit is further configured to receive an RRC resume message. After the receiving unit receives the RRC resume message, the transmitting unit is further configured to transmit an RRC resume completion message. The relay UE device according to claim 1.

6. The transmitting unit and the receiving unit are configured to operate according to at least one revised version of the 3rd Generation Partnership Project (3GPP) New Radio (NR) V2X communication specification. The relay UE device according to claim 1.

7. The signal is a discovery message. The relay UE device according to claim 1.

8. A base station, A receiving unit that receives a measurement report from a remote user equipment (UE) device via a Uu direct communication link, where the measurement report includes measurement values of signals received by the remote UE device from a relay UE device, and the receiving unit; A transmitting unit that transmits a radio access network (RAN)-based page to the relay UE device in a radio resource control (RRC) INACTIVE state; A control unit that performs an RRC resume procedure with the relay UE device to transition the relay UE device to an RRC connected (CONN) state. After the relay UE device transitions to the RRC connected (CONN) state, the transmitting unit transmits a first RRC reconfiguration message including settings for relaying the communication of the remote UE device to the relay UE device. The receiving unit receives an RRC reconfiguration complete message from the relay UE device via a Uu communication link established according to the RRC resume procedure. Base station. **Claim 9** The receiving unit receives the RRC reconfiguration complete message transmitted by the remote UE device and relayed by the relay UE device. The base station according to claim 8. **Claim 10** The transmitting unit transmits a second RRC reconfiguration message to the remote UE device via a Uu direct communication link between the base station and the remote UE device. The second RRC reconfiguration message starts a path switch from a direct communication link between the remote UE device and the base station to an indirect communication link between the remote UE device and the base station via the relay UE device. The base station according to claim 8. **Claim 11** The transmitting unit transmits the RAN-based page to start a path switch from a direct communication link between the remote UE device and the base station to an indirect communication link between the remote UE device and the base station via the relay UE device. The base station according to claim 8. **Claim 12** The receiving unit receives an RRC resume request message. The transmitting unit transmits an RRC resume message. The base station according to claim 8. **Claim 13** The transmitting unit and the receiving unit are configured to operate according to at least one revised version of the 3rd Generation Partnership Project (3GPP) New Radio (NR) V2X communication specification. The base station according to claim 8.

Images