Network device, relay user device and communication method

Abstract

An exemplary embodiment of the present disclosure relates to a communication method, wherein a first network device receives a first message that explicitly or implicitly indicates successful transmission of a path switch configuration to a first terminal device, the first terminal device being connected to the first network device via a relay path including a second terminal device, and the first network device is switched to a target path between the first terminal device and the second network device, and the first network device transmits to the second terminal device one of a second message used for reconfiguring the relay path and a third message used to trigger the second terminal device to apply the previously received second message used for reconfiguring the relay path.

Description

[Technical Field]

[0001] FIELD Embodiments of the present disclosure relate generally to the field of telecommunications, and more particularly to a method, apparatus, and computer storage medium for path switching. [Background technology]

[0002] In a wireless communication network device, a terminal device can communicate with a network device via a direct path or an indirect path. Specifically, in the case of a direct path, the terminal device communicates directly with the network device, while in the case of an indirect path, the terminal device communicates with the network device via at least one relay terminal device. Furthermore, the location and communication status of the terminal device may change over time. To maintain continuous communication with the network, the terminal device may switch to a new path or connect to a new network device, i.e., perform path switching. Summary of the Invention [Problem to be solved by the invention]

[0003] Generally speaking, when a path is switched, if the source path is an indirect path, the source path should be released after the path switch command is successfully sent to the terminal device. However, when the source network device and the target network device are located in different physical devices (also referred to as inter-gNB), and the source path is an indirect path, the source network device cannot determine whether the path switch command has been sent successfully, which may result in an unexpected situation in which the source path is released before the path switch command is successfully sent. Therefore, in the case of inter-gNB, further consideration is needed to determine how to control the release of the relay path during path switching. [Means for solving the problem]

[0004] Generally, embodiments of the present disclosure provide a method, apparatus, and computer storage medium for path switching.

[0005] In a first aspect, there is provided a method performed by a first network device, the method including: receiving, at the first network device, a first message that explicitly or implicitly indicates successful transmission of a path switch configuration to a first terminal device, the first terminal device being connected to the first network device via a relay path that includes a second terminal device, and transmitting to the second terminal device one of: a second message used for reconfiguring the relay path to be switched to a target path between the first terminal device and the second network device; and a third message used to trigger the second terminal device to apply the previously received second message used for reconfiguring the relay path.

[0006] In a second aspect, there is provided a method performed by a second network device, the method including: receiving, at the second network device, a fourth message that explicitly or implicitly indicates successful transmission of a path switch configuration to a first terminal device; the first terminal device is connected to the first network device via a relay path that includes the second terminal device and is switched to a target path between the first terminal device and the second network device; and transmitting, to the first network device, a first message that explicitly or implicitly indicates successful transmission of the path switch configuration to the first terminal device.

[0007] In a third aspect, there is provided a method performed by a second terminal device, the method including performing one of: determining, in the second terminal device, successful transmission of a path switch configuration to a first terminal device, the first terminal device being connected to a first network device via a relay path including the second terminal device and switched to a target path between the first terminal device and the second network device; transmitting a first message to the first network device indicating successful transmission of the path switch configuration to the first terminal device; and applying a previously received second message used for reconfiguring the relay path.

[0008] In a fourth aspect, a method is provided that is executed by a first terminal device, the method including: detecting, in the first terminal device, a failure of a PC5 path between the first terminal device and a second terminal device via a keep-alive procedure without receiving a path switching configuration from the second terminal device; and the first terminal device is connected to a first network device via the second terminal device, and initiating a re-establishment procedure with the second terminal device.

[0009] In a fifth aspect, there is provided a method performed by a core network (CN) device, the method including: generating, at the CN device, a first message that explicitly or implicitly indicates successful transmission of a path switch configuration to a first terminal device, the first terminal device being connected to a first network device via a relay path that includes a second terminal device, the first terminal device being switched to a target path between the first device and the second network device, and transmitting the first message to the first network device.

[0010] In a sixth aspect, there is provided a first network device, the first network device comprising: a processing unit; and a memory coupled to the processing unit and configured to store instructions, the instructions, when executed by the processing unit, causing the device to perform a method according to the first aspect.

[0011] In a seventh aspect, there is provided a second network device, the second network device comprising: a processing unit; and a memory coupled to the processing unit and storing instructions, the instructions, when executed by the processing unit, causing the device to perform the method of the second aspect.

[0012] In an eighth aspect, there is provided a second terminal device, the second terminal device comprising: a processing unit; and a memory coupled to the processing unit that stores instructions, the instructions, when executed by the processing unit, causing the device to perform the method of the third aspect.

[0013] In a ninth aspect, there is provided a first terminal device, the first terminal device comprising: a processing unit; and a memory coupled to the processing unit that stores instructions, the instructions, when executed by the processing unit, causing the device to perform the method of the fourth aspect.

[0014] In a tenth aspect, there is provided a CN apparatus, comprising: a processing unit; and a memory, coupled to the processing unit, storing instructions, the instructions, when executed by the processing unit, causing the apparatus to perform the method of the fifth aspect.

[0015] In an eleventh aspect, there is provided a computer-readable medium storing instructions that, when executed on at least one processor, cause the at least one processor to perform a method according to any of the first to fifth aspects above.

[0016] Other features of the present disclosure will become readily apparent from the following description. [Brief explanation of the drawings]

[0017] The above and other objects, features and advantages of the present disclosure will become more apparent through more detailed descriptions of several embodiments of the present disclosure in the accompanying drawings.

[0018] [Figure 1A] 1 illustrates a signaling chart showing a process for intra-gNB path switching in some embodiments.

[0019] [Figure 1B] 1 shows a signaling chart illustrating a process for inter-gNB path switching in some embodiments.

[0020] [Figure 1C] 10 shows another signaling chart illustrating a process for inter-gNB path switching in some embodiments.

[0021] [Figure 2A] 1 illustrates a block diagram of a communication environment in which embodiments of the present disclosure may be implemented.

[0022] [Figure 2B] 1 shows a signaling chart illustrating a process for communication according to some embodiments of the present disclosure.

[0023] [Figure 2C] FIG. 1 illustrates another block diagram of a communication environment in which embodiments of the present disclosure may be implemented.

[0024] [Figure 3] 1 shows a signaling chart illustrating a process for communication according to some embodiments of the present disclosure.

[0025] [Figure 4A] 1 shows a signaling chart illustrating a process for communication according to some embodiments of the present disclosure. [Figure 4B] 1 shows a signaling chart illustrating a process for communication according to some embodiments of the present disclosure. [Figure 4C] 1 shows a signaling chart illustrating a process for communication according to some embodiments of the present disclosure. [Figure 4D] 1 shows a signaling chart illustrating a process for communication according to some embodiments of the present disclosure. [Figure 4E]1 shows a signaling chart illustrating a process for communication according to some embodiments of the present disclosure. [Figure 4F] 1 shows a signaling chart illustrating a process for communication according to some embodiments of the present disclosure.

[0026] [Figure 5A] 1 shows a signaling chart illustrating a process for communication according to some embodiments of the present disclosure. [Figure 5B] 1 shows a signaling chart illustrating a process for communication according to some embodiments of the present disclosure.

[0027] [Figure 6] 1 illustrates an exemplary communication method implemented in a first network device according to some embodiments of the present disclosure.

[0028] [Figure 7] 10 illustrates an exemplary communication method implemented in a second network device according to some embodiments of the present disclosure.

[0029] [Figure 8] 10 illustrates an exemplary communication method implemented in a second terminal device according to some embodiments of the present disclosure.

[0030] [Figure 9] 1 illustrates an exemplary communication method implemented in a first terminal device according to some embodiments of the present disclosure.

[0031] [Figure 10] 1 illustrates an exemplary communication method implemented in a CN device according to some embodiments of the present disclosure.

[0032] [Figure 11] FIG. 1 is a simplified block diagram of an apparatus suitable for implementing embodiments of the present disclosure.

[0033] Throughout the drawings, the same or similar reference numbers represent the same or similar elements. DETAILED DESCRIPTION OF THE INVENTION

[0034] The principles of the present disclosure will now be described with reference to several embodiments. It should be understood that these embodiments are provided for illustrative purposes only, to help those skilled in the art understand and practice the present disclosure, and are not intended to imply any limitations on the scope of the present disclosure. The disclosure described herein can be implemented in various forms other than those described below.

[0035] In the following description and claims, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0036] As used herein, the term "terminal device" refers to any device with wireless or wired communication capabilities. Examples of terminal devices include user equipment (UE), personal computers, desktops, mobile phones, mobile phones, smartphones, personal digital assistants (PDAs), portable computers, tablets, wearable devices, Internet of Things (IoT) devices, Ultra-reliable and Low Latency Communication (URLLC) devices, Internet of Everything (IoE) devices, Machine Type Communication (MTC) devices, vehicle-mounted devices for V2X communications (where X represents pedestrian, vehicle, or infrastructure / network), Integrated Access and Backhaul (IAB) devices, High Altitude Platforms (HAPs) including Unmanned Aircraft Systems (UASs) and spacecraft or aircraft in Non-Terrestrial Networks (NTNs) with satellites, and extended reality (XR) including various types of reality such as Augmented Reality (AR), Mixed Reality (MR), and Virtual Reality (VR). This includes, but is not limited to, Reality devices, Unmanned Aerial Vehicles (UAVs), which are aircraft without a human pilot and are commonly known as drones, devices on High Speed ​​Trains (HST), image capture devices such as digital cameras, sensors, gaming devices, music storage and playback devices, or internet devices that enable wireless or wired internet access or browsing.A "terminal device" may also have "multicast / broadcast" features to support public safety, mission-critical, V2X applications, transparent IPv4 / IPv6 multicast distribution, IPTV, smart TV, wireless services, over-the-air software distribution, group communication, and IoT applications. It may also incorporate one or more Subscriber Identity Modules (SIMs), known as multi-SIMs. The term "terminal device" can be used interchangeably with UE, mobile station, subscriber station, mobile terminal, user terminal, or wireless device.

[0037] The term "network device" refers to a device that can provide or host a cell or coverage area over which terminal devices can communicate. Examples of network devices include, but are not limited to, a Node B (Node B or NB), an evolved Node B (eNode B or eNB), a next generation Node B (gNB), a Transmission Reception Point (TRP), a Remote Radio Unit (RRU), a Radio Head (RH), a Remote Radio Head (RRH), an IAB node, a low power node such as a femto node, a pico node, a Reconfigurable Intelligent Surface (RIS), etc.

[0038] A terminal device or network device may have artificial intelligence (AI) or machine learning capabilities, typically including models trained from a large amount of collected data for a particular function, which can be used to predict some information.

[0039] The terminal device or network device may operate in, for example, FR1 (410 MHz to 7125 MHz), FR2 (24.25 GHz to 71 GHz), frequency bands above 100 GHz, terahertz (THz), etc. Furthermore, it can also operate in licensed / unlicensed / shared frequency bands. In MR-DC (Multi-Radio Dual Connectivity) application scenarios, the terminal device may have more than one connection with the network device. The terminal device or network device can operate in full duplex, flexible duplex, and cross-division duplex modes.

[0040] Embodiments of the present disclosure may be implemented in test equipment, such as a signal generator, a signal analyzer, a spectrum analyzer, a network analyzer, a test terminal equipment, a test network equipment, or a channel emulator.

[0041] In some embodiments, the terminal device may be connected to a first network device and a second network device. One of the first network device and the second network device may be a master node, and the other may be a secondary node. The first network device and the second network device may use different radio access technologies (RATs). In some embodiments, the first network device may be a first RAT device, and the second network device may be a second RAT device. In some embodiments, the first RAT device is an eNB, and the second RAT device is a gNB. Information related to the different RATs may be transmitted to the terminal device from at least one of the first network device or the second network device. In some embodiments, the first information may be transmitted to the terminal device from the first network device, and the second information may be transmitted to the terminal device from the second network device directly or via the first network device. In some embodiments, information related to a configuration for the terminal device configured by the second network device may be transmitted from the second network device via the first network device. Information relating to the reconfiguration for the terminal device configured by the second network device may be transmitted to the terminal device directly from the second network device or via the first network device.

[0042] As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term "comprises" and variations thereof should be interpreted as an open term meaning "including, but not limited to." The term "based on" should be interpreted as "based at least in part on." The terms "one embodiment" and "embodiment" should be interpreted as "at least one embodiment." The term "another embodiment" should be interpreted as "at least one other embodiment." Terms such as "first," "second," etc. may refer to different or the same object. Other definitions, both explicit and implied, may be included below.

[0043] In some instances, values, procedures, or devices are referred to as "best," "lowest," "highest," "minimum," "maximum," etc. It is understood that such descriptions are intended to indicate that a selection can be made from among many functional options available, and that such a selection is not necessarily better, smaller, higher, or otherwise preferred than other options.

[0044] In a wireless communication network, a terminal device can communicate with the network via a direct network connection or an indirect network connection. Furthermore, in the case of a path switch, the communication path of the terminal device may be switched from a source network device to a target network device. In some embodiments, the source network device and the target network device are located within the same physical device (referred to as intra-gNB). Alternatively, in some other embodiments, the source network device and the target network device are located in different physical devices (referred to as inter-gNB).

[0045] In view of the above, path switching may be associated with any of the following: indirect-to-direct (I2D) path switching for intra-gNB, indirect-to-indirect (I2I) path switching for intra-gNB, direct-to-direct (D2D) path switching for intra-gNB, direct-to-indirect (D2I) path switching for intra-gNB, I2D for inter-gNB, I2I for inter-gNB, D2D for inter-gNB, D2I for inter-gNB.

[0046] As described above, generally speaking, when a path is switched, if the source path is an indirect path, the release of the source path should be performed after the path switch command is successfully sent to the terminal device.

[0047] FIG. 1A illustrates a signaling diagram illustrating a process 100 for intra-gNB path switching in some embodiments. As illustrated in FIG. 1A, a remote UE originally performs data transmission with a gNB via a relay UE (105). Next, a Uu measurement configuration and measurement reporting procedure is performed (110), evaluating both relay link and Uu link measurements. Specifically, if configured measurement reporting criteria are met, Layer 2 (L2) user-to-network (U2N) measurement results from the remote UE are reported. In some embodiments, a sidelink relay measurement report may include at least one of a source L2 identity (ID) of the L2 U2N relay UE, a serving cell ID (i.e., NR cell global identifier (NCGI) or NR cell identifier (NCI)), and sidelink measurement results. The sidelink measurement may be the sidelink-reference signal receiving power (SL-RSRP) of the serving L2 U2N relay UE; if SL-RSRP is unavailable, sidelink discovery (SD)-RSRP is used. Using the measurement results, the gNB decides to switch the L2 U2N remote UE to the direct Uu path (115).

[0048] The gNB then sends a radio resource control (RRC) reconfiguration message to the L2 U2N remote UE (120). After receiving the RRC reconfiguration message including the path switch configuration from the gNB, the L2 U2N remote UE stops uplink (UP) and control plane (CP) transmissions via the L2 U2N relay UE. In response to the RRC reconfiguration message, the L2 U2N remote UE synchronizes with the gNB and performs random access (RA) with the gNB (125).

[0049] The UE (i.e., the L2 U2N remote UE in the previous step) then sends an RRC Reconfiguration Complete message to the gNB via the established direct path using the settings provided in the RRC Reconfiguration message. From this step, the UE (i.e., the L2 U2N remote UE in the previous step) uses an RRC connection via the direct path to the gNB. The gNB sends an RRC Reconfiguration message to the L2 U2N Relay UE to reconfigure the connection between the L2 U2N Relay UE and the gNB (135).

[0050] In a specific embodiment, the RRC reconfiguration message to the L2 U2N relay UE may be sent any time after sending the RRC reconfiguration message (120) based on the gNB's implementation (e.g., to release Uu and PC5 relay RLC channel configuration for relay, bearer mapping configuration associated with the L2 U2N remote UE).

[0051] After receiving the RRCReconfiguration message from the gNB, the AS layer of the L2 U2N relay UE or L2 U2N remote UE can release the PC5-RRC connection (140) and instruct upper layers to release the PC5 unicast link. The timing of the link release is up to the UE implementation. Next, the data path between the UE (i.e., the previous L2 U2N remote UE) and the gNB is switched from an indirect path to a direct path. Re-establishment of PDCP (packet data convergence protocol) in the UL or PDCP data recovery, if configured by the gNB, is performed by the UE (i.e., the previous L2 U2N remote UE) for lossless delivery during the path switch (145).

[0052] In the specific embodiment of Figure 1A, since the source gNB also functions as the target gNB, the source gNB can reconfigure the relay UE to properly release the PC5 relay RLC channel after receiving an RRC reconfiguration complete message from the remote UE, which indicates successful transmission of the path switch command. In this way, it is guaranteed that the PC5 relay RLC channel is released (or the PC5 link initiated by the relay UE is released) after successful transmission of the path switch command.

[0053] In the inter-gNB case, the remote UE accesses the target gNB instead of the source gNB, but the release of the relay RLC channel / reconfiguration of the relay UE is controlled by the source gNB. Therefore, in the inter-gNB case where the source path is a relay path, the source network device does not know whether the path switch command was sent successfully or not. Reference is now made to Figures 1B and 1C, which show signaling charts illustrating processes 150 and 160 for inter-gNB path switching in some embodiments.

[0054] As shown in Figures 1B and 1C, if the transmission of the path switch command fails, an improper PC5 connection may be triggered. In other words, the PC5 relay RLC channel / PC5 ​​link is released before the successful transmission of the path switch command (e.g., initiated by the relay UE), which is an unexpected result. For example, without the successful transmission of the path switch command, the remote UE cannot trigger the establishment of a new connection with the target network device, but the source connection is released, which means that the remote UE's communication is interrupted. Furthermore, because the source connection is released, the source network device cannot resend the path switch command to the remote UE, which causes the remote UE's connection status information to become inconsistent with that of the source network side. Therefore, in the case of inter-gNBs, further consideration is needed to determine how to control the release of the relay path during path switching. In other words, the timing of the successful transmission of the path switch command and the timing of the relay release should be specified.

[0055] An embodiment of the present disclosure provides a solution for path switching. In the present disclosure, successful transmission of a path switch configuration to a terminal device may be determined and / or notified to a source network device and / or a relay terminal device. With respect to the source network device, the source network device may generate a second message used to reconfigure the relay path in response to successful transmission of the path switch configuration. Alternatively or additionally, the relay terminal device may apply the path switch configuration until successful transmission of the path switch configuration.

[0056] In this way, it is ensured that the relay path is released after the path switching configuration is successfully sent, thereby ensuring the continuity of communication for the remote UE.

[0057] For ease of discussion, some terms used in the following description are listed below. Direct network connection: Refers to a mode of network connection in which there is no relay terminal device / relay UE between the terminal device and the network device, and is sometimes called a direct path. Indirect network connection: Refers to a mode of network connection in which a relay terminal device / relay UE exists between a terminal device and a network device, and may also be called a relay path or an indirect path. First network device: refers to a network entity, and may be a source network device when switching paths. Second network device: Refers to a network entity, and may be a target network device when switching paths. A first terminal device refers to a terminal entity to be switched. In some embodiments, the first terminal device is originally connected to a first network device via a relay path (also referred to as a source path). The first terminal device is then switched to a target path so as to be connected to a second network device. In some embodiments, the target path is a direct path. Alternatively, in some other embodiments, the target path is an indirect path, and the first terminal device may be referred to as a remote terminal device. The second terminal device refers to a terminal entity that functions as a relay terminal device in the source path, and may also be referred to as a source relay terminal device. Another second terminal device refers to a terminal entity that functions as a relay terminal device in the target path, and may also be referred to as a target relay terminal device. Relay path: refers to either a path between a network device and a remote terminal device via a relay terminal device or multiple relay terminal devices, a path between a remote terminal device and a relay terminal device (i.e., PC5 connection / sidelink connection / D2D connection), or a path between a relay terminal device and a network device. Successful transmission of path switch configuration / command: refers to either the path switch configuration / command being successfully received by the terminal device, successful completion of path switch to the second network device / target device, successful accession to the second network device / target device, or successful / completion of path switch to the second network device / target device.

[0058] In the present disclosure, the terms "path switch configuration", "path switch command", "RRC reconfiguration including path switch command", and "RRC reconfiguration for path switch" can be used interchangeably, the terms "path switch" and "path switch" can be used interchangeably, and the terms "relay path" and "relaying path" can be used interchangeably.

[0059] In some embodiments, the message / signaling "HO Command" is used for I2D scenarios and the message / signaling "Path Switch" is used for I2I scenarios.

[0060] The principles and implementations of the present disclosure will be described in detail below with reference to the drawings.

[0061] Example of a communication network 2A illustrates an exemplary communication environment 200 in which exemplary embodiments of the present disclosure may be implemented. The communication environment 200 includes a plurality of terminal devices and network devices. As illustrated in FIG. 2A, the communication environment 200 includes a network device 210-1 and a network device 210-2. For ease of explanation, the network devices 210-1 and 210-2 will be collectively referred to as the network devices 210, or individually referred to as the first network device 210-1 (i.e., sometimes referred to as the source gNB) and the second network device 210-2 (i.e., sometimes referred to as the target gNB), respectively.

[0062] In the specific exemplary embodiment of FIG. 2A, the first network device 210-1 and the second network device 220-2 are located in different physical devices, and therefore, an inter-gNB network structure is supported in the communication environment 200.

[0063] The communication environment 200 further includes a terminal device 220-1, a terminal device 220-2, and a terminal device 220-3. At time T0, the terminal device 220-1 communicates with the first network device 210-1 via the terminal device 220-2, i.e., via an indirect path / relay path. Thereafter, as the terminal device 220-1 moves over time or the channel condition of the terminal device 220-1 deteriorates, it becomes necessary to change the connection between the terminal device 220-1 and the network device 210-1, for example, by switching the terminal device 220-1 to another path (also referred to as a target path).

[0064] 2A, at time T1, terminal device 220-1 may be switched to a target path that includes second network device 210-2. In some embodiments, the target path is a direct path, i.e., terminal device 210-1 communicates directly with second network device 210-2. Alternatively, in some other embodiments, the target path is an indirect path, i.e., terminal device 210-1 communicates with network device 210-2 via terminal device 220-3.

[0065] FIG. 2B shows a signaling chart illustrating a process 240 for communication according to some embodiments of the present disclosure.

[0066] As shown in Figure 2B, the source gNB issues a handover request message to the target gNB to pass a transparent RRC container containing information necessary for preparing the handover at the target side. This information includes at least the target cell ID, KgNB*, the UE's cell-radio network temporary identity (C-RNTI) in the source gNB, radio resource management (RRM) configuration including the UE's inactive time, basic AS configuration including antenna information and downlink (DL) carrier frequency, the current quality of service (QoS) flow-to-DRB mapping rule applied to the UE, signaling radio bearer 1 (SRB1) from the source gNB, the UE's capabilities for various RATs, protocol data unit (PDU) session-related information, and, if available, measurement information reported by the UE including beam-related information. The PDU session-related information includes slice information and QoS flow-level QoS profile(s). The source gNB may also request a dual active protocol stack (DAPS) handover for one or more data radio bearers (DRBs).

[0067] In some embodiments, admission control may be performed by the target gNB. If slice information is transmitted to the target gNB, slice-aware admission control must be performed. If a PDU session associates with an unsupported slice, the target gNB must reject such a PDU session.

[0068] In some embodiments, the target gNB prepares the handover at Layer 1 (L1) / L2 and sends a HANDOVER REQUEST ACKNOWLEDGE to the source gNB. This HANDOVER REQUEST ACKNOWLEDGE includes a transparent container that is sent to the UE as an RRC message to perform the handover. The target gNB also indicates whether or not it accepts the DAPS handover.

[0069] In some embodiments, the source gNB triggers the Uu handover by sending an RRCReconfiguration message to the UE, which includes information necessary to access the target cell (at least the target cell ID, the new C-RNTI, the target gNB's security algorithm identifier for the selected security algorithm), and may also include a set of dedicated RACH resources, an association of random access channel (RACH) resources with synchronization signal and PBCH block (SSB(s)), an association of RACH resources with UE-specific channel state information (CSI)-reference signal (RS) configuration(s), common RACH resources, system information of the target cell, etc.

[0070] In some embodiments, the UE synchronizes to the target cell and completes the RRC handover procedure by sending an RRCReconfigurationComplete message to the target gNB. In the case of a DAPS handover, the UE does not detach from the source cell upon receiving the RRCReconfiguration message. Upon receiving an explicit release from the target node, the UE releases the source resources and configuration and stops DL / UL reception / transmission with the source.

[0071] In some embodiments, in the case of a DAPS handover, the target gNB sends a HANDOVER SUCCESS message to the source gNB to notify that the UE has successfully accessed the target cell, and in return, the source gNB sends an SN STATUS TRANSFER message to the DAPS configured DRB.

[0072] In some embodiments, the 5GC (such as the Access and Mobility Management Function, AMF, or the User Plane Function, UPF) switches the DL data path towards the target gNB. The UPF sends one or more "end marker" packets on the old path per PDU session / tunnel to the source gNB and can then release any U-Plane / TNL resources towards the source gNB.

[0073] In some embodiments, upon receiving the PATH SWITCH REQUEST ACKNOWLEDGE message from the AMF, the target gNB sends a UE CONTEXT RELEASE to notify the source gNB of the successful handover. The source gNB can then release radio and C-Plane related resources associated with the UE context. Ongoing data transfers may continue.

[0074] Reference is now made to Figure 2C, which illustrates another exemplary communication environment 260. As shown in Figure 2C, path switching may be performed between direct and indirect paths, i.e., between I2D and D2I, and also between indirect and indirect paths, i.e., between I2I.

[0075] It should be understood that the number of devices and cells in Figures 2A-2C are given for illustrative purposes without implying any limitation of the present disclosure, and a communication network may include any suitable number of network devices and / or terminal devices suitable for carrying out implementations of the present disclosure.

[0076] In some embodiments, terminal device 220 and network device 210 may communicate with each other via channels, such as wireless communication channels over an air interface (e.g., a Uu interface). The wireless communication channels may include a Physical Uplink Control Channel (PUCCH), a Physical Uplink Shared Channel (PUSCH), a Physical Random-Access Channel (PRACH), a Physical Downlink Control Channel (PDCCH), a Physical Downlink Shared Channel (PDSCH), and a Physical Broadcast Channel (PBCH). Of course, any other suitable channels are also possible.

[0077] Communications in communication network 100 may conform to any suitable standard, including, but not limited to, Global System for Mobile Communications (GSM), Long Term Evolution (LTE), LTE-Evolution, LTE-Advanced (LTE-A), New Radio (NR), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access (CDMA), GSM EDGE Radio Access Network (GERAN), Machine Type Communication (MTC), etc. Embodiments of the present disclosure may be performed in accordance with any currently known or future-developed generation of communication protocols. Examples of communication protocols include, but are not limited to, first generation (1G), second generation (2G), 2.5G, 2.75G, third generation (3G), fourth generation (4G), 4.5G, fifth generation (5G) communication protocols, 5.5G, 5G-Advanced networks, or sixth generation (6G) networks.

[0078] Path switching processing example Although feature(s) / operation(s) are discussed individually in particular exemplary embodiments, it should be understood that, unless expressly indicated to the contrary, these feature(s) / operation(s) described in different exemplary embodiments may be used in any suitable combination.

[0079] Additionally, in the following description, several interactions are performed between terminal device 220 and network device 210 (e.g., exchanging configuration(s)). It should be understood that the interactions may be implemented in either a single signaling / message or multiple signaling / messages, including system information, Radio Resource Control (RRC) messages, Downlink Control Information (DCI) messages, Uplink Control Information (UCI) messages, Media Access Control (MAC) Control Elements (CEs), Sidelink Relay Adaptation Protocol (SRAP), etc. The disclosure is not limited in this respect.

[0080] In the following, some exemplary embodiments are described for an I2D scenario. It should be understood that the I2D scenario is merely illustrative without implying any limitation. That is, the exemplary embodiments described for I2D are also suitable for an I2I scenario. For the sake of brevity only, identical or similar content is omitted.

[0081] The principles and implementations of the present disclosure are described in detail below with reference to Figure 3, which shows a signaling chart illustrating a communication process 300 according to some exemplary embodiments of the present disclosure. For discussion purposes, process 300 will be described with reference to Figures 2A-2C.

[0082] The process 300 may include a first network device 210-1 (i.e., a source network device), a second network device 210-2 (i.e., a target network device), a first terminal device 220-1 (i.e., a remote terminal device), a second terminal device 220-2 (i.e., a source relay terminal device), and a CN device. Additionally, the process 300 may optionally include another second terminal device 220-3 (i.e., a target relay terminal device).

[0083] In the specific embodiment of FIG. 3, the first terminal device 220-1 is originally connected to the first network device 210-1 via the second terminal device 220-2.

[0084] In operation, the first terminal device 220-1 may be configured to selectively measure and report the measurement results (301). Based on the measurement results, the first network device 210-1 may decide to perform a path switch (302). Thereafter, the first network device 210-1 sends a handover (HO) request to the second network device 210-2 (303) and receives an HO acknowledgement (ACK) from the second network device 210-2 (304).

[0085] In some embodiments, the target path in a path switch is either a direct path or an indirect path.

[0086] In one embodiment, the first network device 210-1 transmits 305 a path switch configuration (e.g., an RRC reconfiguration for a path switch) to the first terminal device. However, the transmission of the path switch configuration may fail. In this case, a retransmission 305-1 of the path switch configuration is required, and the retransmission of the path switch configuration requires a PC5 connection between the first terminal device 220-1 and the second terminal device 220-2.

[0087] In one embodiment, the path switching configuration is associated with I2D path switching or I2I path switching.

[0088] In one embodiment, the path switching configuration is associated with inter-gNB path switching.

[0089] According to some embodiments of the present disclosure, release of a relay path (including any of the connection between the first terminal device 220-1 and the second terminal device 220-2, the connection between the first terminal device 220-1 and the first network device 210-1, and the connection between the second terminal device 220-2 and the first network device 210-1) may be controlled. In particular, release of the relay path may be performed after successful transmission of a path switching configuration.

[0090] In some embodiments, the first network device 210-1 may transmit a second message to the second terminal device 220-2, the second message being used to reconfigure the relay path, and the second message may trigger the release of the relay path in the second terminal device 220-2. In view of the above, the opportunity to transmit the second message may be controlled. In principle, the first network device 210-1 controls the transmission of the second message to be executed after the path switch configuration is successfully transmitted to the first terminal device 220-1. In other words, the first network device 210-1 controls the transmission of the second message to be executed after the first terminal device 220-1 successfully completes the path switch to the second network device 210-2 or the first terminal device 220-1 successfully joins the second network device 210-2. Some processing examples will be described below.

[0091] In some embodiments, the first network device 210-1 receives a first message indicating successful transmission of the path switch configuration to the first terminal device 220-1 and then transmits a second message to the second terminal device 220-2 used for reconfiguring the relay path (335). As a result, the PC5 connection between the first terminal device 220-1 and the second terminal device 220-2 may be released (350).

[0092] In some embodiments, the first message may indicate the successful transmission of the path switch configuration in an explicit manner, specifically, the first message includes an indication indicating the successful transmission of the path switch configuration to the first terminal device.

[0093] Alternatively, in some other embodiments, the first message may indicate successful transmission of the path switch configuration in an implicit manner. Specifically, some existing signaling may be reused to indicate the successful transmission. Furthermore, when existing signaling is reused, the existing signaling may also include an explicit indication of successful transmission of the path switch configuration.

[0094] Also, in some embodiments, the first message may be received from either the second network device 210-2, the second terminal device 220-2, or the CN device, as will be described in more detail below.

[0095] As shown in Figure 3, in some embodiments, a first message is received 320-3 from a second network device 210-2. For a better understanding, refer to Figure 4A, which illustrates a signaling diagram illustrating a communication process 400 according to some exemplary embodiments of the present disclosure. For purposes of discussion, process 400 will be described with reference to Figure 3. That is, like references in Figures 3 and 4A refer to the same physical meaning.

[0096] In some embodiments, after receiving the fourth message regarding successful transmission of the path switch configuration (or successful handover), the second network device 220-2 may send 410 a first message to the first network device 210-1, where the first message may indicate successful (sidelink relay) path switching (i.e., successful transmission of the path switch configuration).

[0097] Furthermore, in some embodiments, the second message is only sent in the case of an I2D / I2I path switching scenario.

[0098] As shown in FIG. 4A, upon receiving the first message, the first network device 210-1 may determine that the first terminal device 210 has successfully joined the target cell or that the path switch has been successful, and then the first network device 210-1 may send (335) a second message (e.g., an RRCReconfiguration message) to the second terminal device 220-2 to reconfigure the relay path (such as the connection between the second terminal device 220-2 and the first network device 210-1, and / or the connection between the second terminal device 220-2 and the first terminal device 220-1) (e.g., to release the PC5 relay RLC channel).

[0099] Further, in some embodiments, the second network device 210-2 may be notified by the first network device 210-1 that the first terminal device 220-1 was connected to the first network device 210-1 via an indirect path before the path switch.

[0100] Also, from the perspective of the second network device 210-2, the successful transmission of the path switch configuration may be implied / determined after receiving a fourth message from another device. As an example, the second network device 210-2 receives an RRC reconfiguration complete message from the first terminal device 220-1 (322), and the RRC reconfiguration complete message is sent in response to a random access (RA) 321 procedure of the second network device 210-2. As another example, the second network device 210-2 receives a PATH SWITCH REQUEST ACKNOWLEDGE from a CN device (such as an AMF).

[0101] In some embodiments, the target path is either a direct path or an indirect path. As shown in Figure 3, if the target path is an indirect path, a PC5 connection is established between the first terminal device 220-1 and another second terminal device 220-3 (i.e., a target relay terminal device) (323). The first terminal device 220-1 then transmits an RRC reconfiguration complete message to the other second terminal device 220-3 (324-1), which may then be forwarded to the second network device 210-2 (324-2). As described above, the forwarded RRC reconfiguration complete message may be used as the fourth message.

[0102] Furthermore, if the other second terminal device 220-3 is in an idle state or an inactive state, after receiving an RRC reconfiguration complete message from the first terminal device 220-1, the other second terminal device 220-3 sends an RRC Setup / Resume request to the second network device 210-2 (325). Then, after receiving an RRC Setup / Resume message from the second network device 210-1 (326), the other second terminal device 220-3 may send an RRC Setup / Resume complete to the second network device 210-2 (327). In light of this, if the other second terminal device 220-3 is in an idle state or an inactive state, the fourth message may be one of the following: an RRC setup request received from another second terminal device; an RRC resume request received from another second terminal device; an RRC setup complete received from another second terminal device, or > RRC resume complete received from another second terminal device.

[0103] In this case, as shown in Fig. 3, the second network device 210-2 may send a first message to the first network device to indicate the successful transmission of the path switch configuration (320-2). That is, the second network device 210-2 uses the joining of the target relay UE (i.e., another second terminal device 220-3) as a trigger to send the first message. In this case, the first message may be sent via a newly defined Xn message. Furthermore, the first message may be sent in the case of I2D path switching and / or I2I path switching.

[0104] For better understanding, refer to FIG. 4F, which shows a signaling chart illustrating a communication process 495 according to some exemplary embodiments of the present disclosure, in which the target path is an indirect path and the target relay terminal device (i.e., another second terminal device 220-3) is in an idle or inactive state.

[0105] Furthermore, as described above, some existing signaling may be reused to indicate successful transmission. In one embodiment, after receiving an RRC reconfiguration complete message from the first terminal device 220-1, the second network device 210-2 may send a HANDOVER SUCCESS message to the first network device 210-1. In consideration of this, the HANDOVER SUCCESS message may be reused as the first message because it may imply successful transmission of the path switch configuration. Furthermore, in the case of an I2D / I2I path switch, the first network device 210-1 may send (335) a second message to the first terminal device 220-1.

[0106] In some embodiments, the handover success message itself implies successful transmission of the path switch configuration. Alternatively, in some other embodiments, the handover success message includes an explicit indication of successful transmission of the path switch configuration.

[0107] For better understanding, reference is now made to Figure 4B, which illustrates a signaling chart illustrating a communication process 420 according to some exemplary embodiments of the present disclosure. As shown in Figure 4B, the second network device 210-2 sends a HANDOVER SUCCESS to the first network device 210-1 to indicate successful transmission of the path switch configuration.

[0108] In summary, the remote UE (i.e., the first terminal device 220-1) synchronizes to the target cell and completes the RRC handover procedure by sending an RRCReconfigurationComplete message to the target gNB (i.e., the second network device 210-2). In the case of a DAPS handover, the target gNB sends a HANDOVER SUCCESS message to the source gNB (i.e., the first network device 210-1) to notify that the UE (i.e., the first terminal device 220-1) has successfully accessed the target cell. In response, the source gNB sends an SN STATUS TRANSFER message to the DRB configured in DAPS. In the case of an I2D path switch or an I2I path switch, the target gNB sends a HANDOVER SUCCESS message to the source gNB to notify that the UE has successfully accessed the target cell. Upon receiving the HANDOVER SUCCESS message, the source gNB sends an RRCReconfiguration message (i.e., a second message) to the relay UE (i.e., the second terminal device 220-2), for example, to release the PC5 relay RLC channel.

[0109] In this way, the PC5 relay RLC channel or PC5 connection can be released at an appropriate time, and the resources of the relay UE can be released in a timely manner, and the signaling exchange can be performed with low complexity.

[0110] Alternatively, as shown in FIG. 2B , in one embodiment, upon receiving the SN STATUS TRANSFER message from the first network device 210-1, the second network device 210-2 may send a PATH SWITCH REQUEST to the CN device (e.g., AMF). Upon receiving the PATH SWITCH REQUEST, the CN device may send a PATH SWITCH REQUEST ACKNOWLEDGE to the second network device 210-2. The second network device 210-2 may then send a UE context release message to the first network device 210-1. In consideration of this, the UE context release message (UE CONTEXT RELEASE) may also be reused as the first message because it implies successful transmission of the path switch configuration. Furthermore, in the case of an I2D / I2I path switch, the first network device 210-1 may send (335) a second message to the first terminal device 220-1.

[0111] In some embodiments, the UE context release message itself implies successful transmission of the path switch configuration. Alternatively, in some other embodiments, the UE context release message includes an explicit indication of successful transmission of the path switch configuration.

[0112] For better understanding, reference is now made to Figure 4C, which illustrates a signaling chart illustrating a communication process 440 according to some exemplary embodiments of the present disclosure. As shown in Figure 4C, the second network device 210-2 sends a UE CONTEXT RELEASE to the first network device 210-1 to indicate successful transmission of the path switch configuration.

[0113] In summary, upon receiving a PATH SWITCH REQUEST ACKNOWLEDGE message from the CN device (e.g., AMF), the target gNB (i.e., the second network device 210-2) sends a UE CONTEXT RELEASE to notify the source gNB (i.e., the first terminal device 220-1) of the success of the handover. The source gNB can then release the radio and C-plane related resources associated with the UE context. In the case of an I2D / I2I path switch, the source gNB can then send an RRCReconfiguration message (i.e., the second message) to the relay UE (i.e., the second terminal device 220-2), for example, to release the PC5 relay RLC channel. Ongoing data transfer may continue.

[0114] In this way, the PC5 relay RLC channel is released at the appropriate time and signaling exchanges can be performed with reduced complexity.

[0115] In some embodiments, the timing of configuring the second terminal device 220-2 for inter-gNB D2I / I2I path switching is governed as follows: The configuration of the second terminal device 220-2 for inter-gNB path switching may be transmitted at any time after the source gNB (i.e., the first network device 210-1) receives a first message (e.g., UE CONTEXT RELEASE) or a first message (e.g., UE CONTEXT RELEASE including an explicit instruction) indicating successful transmission of the path switch configuration to the first network device 210-1. In other words, the first message itself implies successful transmission of the path switch configuration, or the first message includes an explicit instruction indicating successful transmission of the path switch configuration.

[0116] Alternatively, in some other embodiments, the timing of configuring the second terminal device 220-2 for inter-gNB D2I / I2I path switching is governed as follows: the configuration of the second terminal device 220-2 for inter-gNB path switching may be transmitted at any time after the UE (i.e., the first terminal device 210-1) transmits an RRCReconfigurationComplete message to the target gNB (i.e., the second network device 210-2).

[0117] Alternatively, in addition to receiving the first message from the second network device 210-2, the first network device 210-1 may also receive the first message 320-4 from the CN device.

[0118] In some specific embodiments, the CN device may send the first message, or the first message including an explicit indication indicating successful transmission of the path switch configuration, to the first network device 210-1. In other words, the first message itself implies successful transmission of the path switch configuration, or the first message includes an explicit indication indicating successful transmission of the path switch configuration.

[0119] Furthermore, similar to the second network device 210-2, the CN device may also reuse some existing signaling as the first message.

[0120] 2B, in an embodiment, upon receiving a PATH SWITCH REQUEST from the second terminal device, the AMF and UPF(s) may perform a path switch in the UPF. As a result, the UPF(s) send end marker packet(s) to the first network device 210-1. In view of this, the end marker packet(s) may be reused as the first message to imply successful transmission of the path switch configuration.

[0121] For better understanding, reference is now made to Figure 4D, which illustrates a signaling chart illustrating a communication process 460 according to some exemplary embodiments of the present disclosure. As shown in Figure 4D, the CN device sends an end marker packet to the first network device 210-1 to indicate successful transmission of the path switch configuration.

[0122] Further, in some embodiments, the source gNB determines the path switching to be successful when at least one "end marker" packet for each PDU session / tunnel is received from the UPF(s), which means that all associated PDU sessions / tunnels have been switched at the CN.

[0123] Alternatively, in some embodiments, the source gNB determines the path switching to be successful if at least one "end marker" packet for at least one PDU session / tunnel is received from the UPF(s), which means that at least a portion of the PDU session / tunnel has been switched at the CN.

[0124] In summary, in some embodiments, the core network (including the AMF and UPF) switches the DL data path to the target gNB (i.e., the second network device 210-2). The UPF sends one or more "end marker" packets on the old path to the source gNB (i.e., the first network device 210-1) for each PDU session / tunnel, and can then release any U-plane / TNL resources toward the source gNB. If the source gNB receives at least one "end marker" packet for each PDU session / tunnel, it determines the path switch is successful and sends an RRCReconfiguration message to the relay UE (i.e., the second terminal device 220-2) to, for example, release the PC5 relay RLC channel. In this way, the PC5 relay RLC channel can be released at the appropriate opportunity.

[0125] Alternatively, the first network device 210-1 may also receive a first message from the second terminal device 220-2 (320-1). For example, the second terminal device 220-2 may send the first message, or the first message including an explicit indication indicating successful transmission of the path switch configuration, to trigger the first network device 210-1 to send a second message (i.e., an RRC reconfiguration message). In other words, the first message itself implies successful transmission of the path switch configuration, or the first message includes an explicit indication indicating successful transmission of the path switch configuration.

[0126] For a better understanding, reference is now made to Figure 4E, which illustrates a signaling chart illustrating a communication process 480 according to some exemplary embodiments of the present disclosure. As shown in Figure 4E, if the path switch configuration is successfully transmitted, the second terminal device 220-2 transmits a first message indicating the successful transmission of the path switch configuration to the first network device 210-1 (490).

[0127] Furthermore, in some embodiments, the second terminal device 220-2 transmits the first message via MAC CE or RRC signaling (such as a Sidelink UE Information, SidelinkUEInformationNR message, or UE Assistance Information).

[0128] From the perspective of the second terminal device 220, several factors can be used to determine the successful transmission of the path switch configuration. Examples of factors include, but are not limited to: Element #1: The last packet data unit (PDU) for the PC5 radio link control (RLC) channel corresponding to the SRB (including at least one of SIB1, SIB2, SIB3, and control signaling) associated with the first terminal device is successfully transmitted to the first terminal device 220-1. In other words, the last RLC PDU for the PC5 relay RLC channel corresponding to the Uu RRC signaling / SRB1 is successfully transmitted. Element #2: An acknowledgement is received from the first terminal device for the last RLC PDU for the PC5 radio link control (RLC) channel corresponding to the SRB (including at least one of SIB1, SIB2, SIB3, and control signaling) associated with the first terminal device. In other words, a PC5 RLC ack is received from the remote UE (i.e., the first terminal device 220-1) for the last RLC PDU for the PC5 relay RLC channel of Uu RRC signaling / SRB1. > Element #3: There are no packets buffered for the PC5 RLC channel corresponding to the SRB (including at least one of SIB1, SIB2, SIB3, and control signaling) associated with the first terminal device 220-1. In other words, the buffer of the PC5 relay RLC channel of Uu RRC signaling / SRB1 is empty. Element #4: The length of time during which no packets are received for the PC5 Radio Link Control (RLC) channel corresponding to the SRB (including at least one of SIB1, SIB2, SIB3, and control signaling) associated with the first terminal device reaches a pre-configured length of time. In other words, no data / packets arrive for the PC5 relay RLC channel of Uu RRC signaling / SRB1 during a pre-defined period of time. Furthermore, the pre-configured length of time or the pre-defined period of time is set as a default value or by one of system information, RRC signaling, MAC CE, and downlink control information (DCI). > Element #5: The second terminal device is indicated by the upper layer regarding the release of the PC5 connection for the first terminal device, where the release of the PC5 connection may refer to either that the PC5 connection has been released or that the PC5 connection is to be released. > Element #6: Receiving a third message from the first network device, used to trigger the second terminal device to apply the previously received second message.

[0129] Furthermore, element #1 and element #3 may be used together when determining successful transmission of a path switch configuration. Alternatively, element #1 and element #4 may be used together when determining successful transmission of a path switch configuration. Alternatively, element #2 and element #3 may be used together when determining successful transmission of a path switch configuration. Alternatively, element #2 and element #4 may be used together when determining successful transmission of a path switch configuration.

[0130] It should be understood that the above example elements and combinations thereof are provided for illustrative purposes, without implying any limitation. Furthermore, the above elements and other suitable elements may be used separately or in combination.

[0131] In addition to controlling the transmission opportunity of the second message to ensure that the relay path is released appropriately, the application opportunity of the second message can also achieve the same technical effect.

[0132] 3, after transmitting (305) a path switch configuration (e.g., RRC reconfiguration) to the first terminal device 220-1, the first network device 210-1 transmits (310-1) a second message to the second terminal device 220-2 to reconfigure a relay path (such as the connection between the second terminal device 220-2 and the first network device 210-1 and / or the connection between the second terminal device 220-2 and the first terminal device 220-1) (e.g., to release the PC5 relay RLC channel). The second terminal device 220-2 stores the second message without applying it, or stores only a portion of the second message (e.g., the portion related to the relay path or the portion related to the release of the PC5 relay RLC channel). The second terminal device 220-2 may then apply (340) the previously received second message if it determines that the path switch configuration has been successfully transmitted to the first terminal device 220-1. How the second terminal device 220-2 determines whether the path switching configuration has been successfully transmitted to the first terminal device 220-1 has been fully explained earlier in this disclosure, and so the same content will be omitted here solely for the sake of brevity.

[0133] For better understanding, refer to FIG. 5A, which shows a signaling chart illustrating a communication process 500 according to some exemplary embodiments of the present disclosure, in which the second terminal device 220-2 determines that the path switching configuration has been successfully sent to the first terminal device 220-1 and applies the previously received second message (340).

[0134] Furthermore, applying the previously received second message may be triggered by a third message from the first network device 210-1. As shown in FIG. 3 , the first network device 210-1 determines that the path switch configuration has been successfully transmitted to the first terminal device 220-1 (330) and then transmits a third message (310-2) used to trigger the second terminal device 220-2 to apply the previously received second message or a portion of the second message. Upon receiving the third message, the second terminal device 220-2 applies the previously received second message or a portion of the second message (340). How the first network device 210-1 determines whether the path switch configuration has been successfully transmitted to the first terminal device 220-1 has been fully described earlier in this disclosure, and therefore will not be repeated here solely for the sake of brevity.

[0135] For better understanding, refer to FIG. 5B, which shows a signaling chart illustrating a communication process 500 according to some exemplary embodiments of the present disclosure, where, upon receiving the third message, the second terminal device 220-2 determines that the path switching configuration has been successfully sent to the first terminal device 220-1 and applies the previously received second message (340).

[0136] In some embodiments, the second terminal device 220-2: > Releasing the relay path, Releasing the connection between the second terminal device 220-2 and the first network device 210-1; Releasing the connection between the second terminal device 220-2 and the first terminal device 220-1; Releasing at least one of the PC5 relay RLC channel, the Uu relay RLC channel, and the bearer mapping information; > Releasing the PC5 channel, and > Releasing the PC5-RRC connection, a previously received second message by at least one of

[0137] In this way, the PC5 relay RLC channel can be released at the appropriate opportunity without incurring too much signaling overhead.

[0138] The above exemplary embodiments mainly relate to methods for avoiding improper release of relay paths. The following text describes exemplary embodiments for methods for dealing with improper release of relay paths.

[0139] In some embodiments, the first terminal device 220-1: > When the sidelink RLC entity indicates that the maximum number of retransmissions for a particular destination has been reached, or For example, when the MAC entity indicates that the maximum number of consecutive hybrid automatic repeat request (HARQ) discontinuous transmissions (DTX) to a particular destination has been reached. a sidelink RLF initiating an RRC re-establishment procedure for a second terminal device 220-2 in an RRC_CONNECTED state; > The keep-alive procedure For example, if timer T5080 expires, or If the maximum number of retransmissions of the PROSE DIRECT LINK KEEPALIVE REQUEST message is reached, Deciding to locally release the PC5-RRC connection; Based on at least one of the above, it is possible to locally detect a relay connection failure caused by the release of the PC5 relay RLC channel or the release of the PC5-RRC connection by the second terminal device 220-2.

[0140] In some embodiments, if the first terminal device 220-1 detects a failure of the PC5 path between the first terminal device 220-1 and the second terminal device 220-2 via a keep-alive procedure, it initiates a re-establishment procedure with the second terminal device 220-2.

[0141] In this way, improper release of relay paths can be dealt with gracefully.

[0142] Example of how to 6 illustrates a flowchart of an example method 600 according to some embodiments of the present disclosure. For example, the method 600 may be implemented in the first network device 210-1 shown in FIG.

[0143] In block 610, the first network device 210-1 receives a first message that explicitly or implicitly indicates successful transmission of a path switching configuration to the first terminal device 220-1, and the first terminal device 220-1 is connected to the first network device 210-1 via a relay path that includes the second terminal device 220-2, and is switched to a target path between the first terminal device 220-1 and the second network device 210-2.

[0144] In block 610, the first network device 210-1 sends to the second terminal device 220-2 one of a second message used for reconfiguring the relay path and a third message used to trigger the second terminal device 220-2 to apply the previously received second message used for reconfiguring the relay path.

[0145] In some embodiments, the first message includes an indication of successful transmission of the path switching configuration to the first terminal device 220-1, and receiving the first message by the first network device 210-1 includes receiving the first message from one of the second network device 210-2, the second terminal device 220-2, and the CN device.

[0146] In some embodiments, the first message is a handover success message or a UE context release message received from the second network device 210-2.

[0147] In some embodiments, the first message is at least one end marker packet corresponding to at least one respective PDU session of the first terminal device 220-1, and the first message is received from the CN device.

[0148] In some embodiments, the first message is received from second terminal device 220-2 via one of MAC CE and RRC signaling.

[0149] In some embodiments, the target path is either a direct path or an indirect path.

[0150] In some embodiments, the path switching configuration is associated with I2D path switching or I2I path switching.

[0151] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0152] 7 illustrates a flowchart of an example method 700 according to some embodiments of the present disclosure. For example, the method 700 may be implemented in the second network device 210-2 shown in FIG.

[0153] In block 710, the second network device 210-2 receives a fourth message that explicitly or implicitly indicates successful transmission of the path switching configuration to the first terminal device 220-1, and the first terminal device 220-1 is connected to the first network device 210-1 via a relay path that includes the second terminal device 220-2, and is switched to the target path between the first terminal device 220-1 and the second network device 210-2.

[0154] In block 710, the second network device 210-2 transmits a first message to the first network device 210-1, explicitly or implicitly indicating the successful transmission of the path switch configuration to the first terminal device 220-1.

[0155] In some embodiments, the fourth message is a configuration completion message corresponding to the path switching configuration and is received from one of the first terminal device 220-1 and another second terminal device 220-3 included in the target path and functioning as a relay device.

[0156] In some embodiments, the target path is an indirect path including another second terminal device 220-3, the other second terminal device 220-3 is in an idle or inactive state, and the fourth message is one of an RRC setup request received from the other second terminal device 220-3, an RRC resume request received from the other second terminal device 220-3, an RRC setup complete received from the other second terminal device 220-3, and an RRC resume complete received from the other second terminal device 220-3.

[0157] In some embodiments, the fourth message is a path switch confirmation message received from the CN device, the path switch confirmation message corresponding to a path switch request sent by the second network device 210-2 to the CN device.

[0158] In some embodiments, the first message includes an indication of successful transmission of the path switch configuration to the first terminal device 220-1.

[0159] In some embodiments, the first message is a handover success message or a UE context release message.

[0160] In some embodiments, the target path is either a direct path or an indirect path.

[0161] In some embodiments, the path switching configuration is associated with I2D path switching or I2I path switching.

[0162] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0163] 8 illustrates a flowchart of an exemplary method 800 according to some embodiments of the present disclosure. For example, the method 800 may be implemented in the second terminal device 220-2 illustrated in FIG. 2A.

[0164] In block 810, the second terminal device 220-2 determines successful transmission of the path switching setting to the first terminal device 220-1, and the first terminal device 220-1 is connected to the first network device 210-1 via a relay path including the second terminal device 220-2, and is switched to the target path between the first terminal device 220-1 and the second network device 210-2.

[0165] In block 820, the second terminal device 220-2 performs one of sending a first message to the first network device 210-1 indicating successful transmission of a path switching configuration to the first terminal device 220-1, and applying a previously received second message used for reconfiguring the relay path.

[0166] In some embodiments, applying the previously received second message includes at least one of releasing the relay path, releasing the connection between the second terminal device 220-2 and the first network device 210-1, and releasing the connection between the second terminal device 220-2 and the first terminal device 220-1.

[0167] In some embodiments, determining successful transmission of the path switch configuration includes determining that the last PDU for the PC5 RLC channel corresponding to the SRB associated with the first terminal device 220-1 is successfully transmitted to the first terminal device 220-1, receiving an acknowledgement from the first terminal device 220-1 for the last RLC PDU for the PC5 RLC channel corresponding to the SRB associated with the first terminal device 220-1, that there are no packets buffered for the PC5 RLC channel corresponding to the SRB associated with the first terminal device 220-1, and determining that the last RLC PDU for the PC5 RLC channel corresponding to the SRB associated with the first terminal device 220-1 is successfully transmitted to the first terminal device 220-1. The method includes determining successful transmission of the path switching configuration based on at least one of: a length of time during which no packets have been received for the RLC channel reaches a predetermined length of time; the second terminal device 220-2 being indicated by an upper layer about the release of the PC5 connection of the first terminal device 220-1; and receiving a third message from the first network device 210-1 used to trigger the second terminal device 220-2 to apply the previously received second message.

[0168] In some embodiments, the pre-configured time period is set as a default value or is set by one of system information, RRC signaling, MAC CE, and downlink control information.

[0169] In some embodiments, the first message includes an indication of successful transmission of the path switch configuration to the first terminal device 220-1.

[0170] In some embodiments, the target path is either a direct path or an indirect path.

[0171] In some embodiments, the path switching configuration is associated with I2D path switching or I2I path switching.

[0172] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0173] 9 illustrates a flowchart of an exemplary method 900 according to some embodiments of the present disclosure. For example, the method 900 may be implemented in the first terminal device 220-1 illustrated in FIG.

[0174] In block 910, the first terminal device 220-1 detects a failure in the PC5 path between the first terminal device 220-1 and the second terminal device 220-2 via a keep-alive procedure without receiving a path switching setting from the second terminal device 220-2, and the first terminal device 220-1 is connected to the first network device 210-1 via the second terminal device 220-2.

[0175] In block 920, the first terminal device 220-1 initiates a re-establishment procedure with the second terminal device 220-2.

[0176] In some embodiments, detecting the PC5 path failure includes detecting the PC5 path failure in response to at least one of timer T5080 expiring and the number of retransmissions of the PROSE DIRECT LINK KEEPALIVE REQUEST message reaching a third threshold number.

[0177] In some embodiments, the path switching configuration is associated with I2D path switching or I2I path switching.

[0178] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0179] In block 1010, the CN device generates a first message that explicitly or implicitly indicates successful transmission of a path switching configuration to the first terminal device 220-1, the first terminal device 220-1 being connected to the first network device 210-1 via a relay path including the second terminal device 220-2, and being switched to a target path between the first device and the second network device 210-2.

[0180] In block 1020, the CN device sends a first message to the first network device 210-1.

[0181] In some embodiments, the first message includes an indication of successful transmission of the path switch configuration to the first terminal device 220-1.

[0182] In some embodiments, the first message is at least one end marker packet corresponding to at least one respective PDU session of the first terminal device 220-1.

[0183] In some embodiments, the target path is either a direct path or an indirect path.

[0184] In some embodiments, the path switching configuration is associated with I2D path switching or I2I path switching.

[0185] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0186] Devices and Device Examples 11 is a simplified block diagram of an apparatus 1100 suitable for implementing embodiments of the present disclosure. The apparatus 1100 can be considered another exemplary implementation of the first terminal device 220-1, the second terminal device 220-2, the other second terminal device 220-3, the first network device 210-1, and the second network device 220-2 shown in FIG. 2A. Thus, the apparatus 1100 can be implemented in or as at least a portion of the first terminal device 220-1, the second terminal device 220-2, the other second terminal device 220-3, the first network device 210-1, and the second network device 220-2.

[0187] As shown, the apparatus 1100 comprises a processor 1110, a memory 1120 coupled to the processor 1110, a suitable transmitter (TX) / receiver (RX) 1140 coupled to the processor 1110, and a communication interface coupled to the TX / RX 1140. The memory 1110 stores at least a portion of a program 1130. The TX / RX 1140 is for bidirectional communication. The TX / RX 1140 has at least one antenna to facilitate communication, although in practice the access nodes referred to herein may have multiple antennas. The communication interface may represent any interface required for communication with other network elements, such as an X2 / Xn interface for bidirectional communication between eNBs / gNBs, an S1 / NG interface for communication between a Mobility Management Entity (MME) / Access and Mobility Management Function (AMF) / SGW / UPF and an eNB / gNB, an Un interface for communication between an eNB / gNB and a relay node (RN), or a Uu interface for communication between an eNB / gNB and a terminal device.

[0188] The program 1130 is assumed to include program instructions that, when executed by an associated processor 1110, enable the apparatus 1100 to operate in accordance with embodiments of the present disclosure, as described herein with reference to Figures 2A-10. The embodiments herein may be implemented by computer software executable by the processor 1110 of the apparatus 1100, by hardware, or by a combination of software and hardware. The processor 1110 may be configured to implement various embodiments of the present disclosure. Furthermore, the combination of the processor 1110 and the memory 1120 may form a processing means 1150 suitable for implementing various embodiments of the present disclosure.

[0189] Memory 1120 may be of any type suitable for a local technology network and may be implemented using any suitable data storage technology, including, by way of non-limiting example, non-transitory computer-readable storage media, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. While only one memory 1120 is shown in device 1100, device 1100 may have multiple physically distinct memory modules. Processor 1110 may be of any type suitable for a local technology network and may include, by way of non-limiting example, one or more of a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. Device 1100 may have multiple processors, such as application-specific integrated circuit chips, that are time-slaved to a clock that synchronizes the main processor.

[0190] In some embodiments, the first network device 210-1 comprises circuitry configured to receive a first message explicitly or implicitly indicating the successful transmission of a path switching configuration to the first terminal device 220-1, and the first terminal device 220-1 is connected to the first network device 210-1 via a relay path including the second terminal device 220-2, and is switched to a target path between the first terminal device 220-1 and the second network device 210-2, and to transmit to the second terminal device 220-2 one of a second message used for reconfiguring the relay path and a third message used to trigger the second terminal device 220-2 to apply a previously received second message used for reconfiguring the relay path.

[0191] In some embodiments, the first message includes an indication of successful transmission of the path switching configuration to the first terminal device 220-1, and receiving the first message by the first network device 210-1 includes receiving the first message from one of the second network device 210-2, the second terminal device 220-2, and the CN device.

[0192] In some embodiments, the first message is a handover success message or a UE context release message received from the second network device 210-2.

[0193] In some embodiments, the first message is at least one end marker packet corresponding to at least one respective PDU session of the first terminal device 220-1 and is received from the CN device.

[0194] In some embodiments 210-nts, the first message is received from the second terminal device 220-2 via one of MAC CE and RRC signaling.

[0195] In some embodiments, the target path is either a direct path or an indirect path.

[0196] In some embodiments, the path switching configuration is associated with I2D path switching or I2I path switching.

[0197] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0198] In some embodiments, the second network device 210-2 comprises circuitry configured to: receive a fourth message that explicitly or implicitly indicates successful transmission of a path switching configuration to the first terminal device 220-1; and the first terminal device 220-1 is connected to the first network device 210-1 via a relay path that includes the second terminal device 220-2 and is switched to a target path between the first terminal device 220-1 and the second network device 210-2; and send a first message to the first network device 210-1 that explicitly or implicitly indicates successful transmission of the path switching configuration to the first terminal device 220-1.

[0199] In some embodiments, the fourth message is a configuration completion message corresponding to the path switching configuration and is received from one of the first terminal device 220-1 and another second terminal device 220-3 that is included in the target path and functions as a relay device.

[0200] In some embodiments, the target path is an indirect path including another second terminal device 220-3, the other second terminal device 220-3 is in an idle or inactive state, and the fourth message is one of an RRC setup request received from the other second terminal device 220-3, an RRC resume request received from the other second terminal device 220-3, an RRC setup complete received from the other second terminal device 220-3, and an RRC resume complete received from the other second terminal device 220-3.

[0201] In some embodiments, the fourth message is a path switch confirmation message received from the CN device, the path switch confirmation message corresponding to a path switch request sent by the second network device 210-2 to the CN device.

[0202] In some embodiments, the first message includes an indication of successful transmission of the path switch configuration to the first terminal device 220-1.

[0203] In some embodiments, the first message is a handover success message or a UE context release message.

[0204] In some embodiments, the target path is either a direct path or an indirect path.

[0205] In some embodiments, the path switching configuration is associated with I2D path switching or I2I path switching.

[0206] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0207] In some embodiments, the second terminal device 220-2 comprises circuitry configured to perform one of determining successful transmission of a path switching configuration to the first terminal device 220-1, the first terminal device 220-1 being connected to the first network device 210-1 via a relay path including the second terminal device 220-2 and switched to a target path between the first terminal device 220-1 and the second network device 210-2, transmitting a first message to the first network device 210-1 indicating successful transmission of the path switching configuration to the first terminal device 220-1, and applying a previously received second message used for reconfiguring the relay path.

[0208] In some embodiments, applying the previously received second message includes at least one of releasing the relay path, releasing the connection between the second terminal device 220-2 and the first network device 210-1, and releasing the connection between the second terminal device 220-2 and the first terminal device 220-1.

[0209] In some embodiments, determining successful transmission of the path switch configuration includes determining that a last PDU for the PC5 RLC channel corresponding to the SRB associated with the first terminal device 220-1 is successfully transmitted to the first terminal device 220-1, receiving an acknowledgement from the first terminal device 220-1 for the last RLC PDU for the PC5 RLC channel corresponding to the SRB associated with the first terminal device 220-1, that there are no packets buffered for the PC5 RLC channel corresponding to the SRB associated with the first terminal device 220-1, and determining that a last RLC PDU for the PC5 RLC channel corresponding to the SRB associated with the first terminal device 220-1 is successfully transmitted to the first terminal device 220-1. The method includes determining successful transmission of the path switching configuration based on at least one of: a length of time during which no packets have been received for the RLC channel reaches a predetermined length of time; the second terminal device 220-2 being indicated by an upper layer about the release of the PC5 connection of the first terminal device 220-1; and receiving a third message from the first network device 210-1 used to trigger the second terminal device 220-2 to apply the previously received second message.

[0210] In some embodiments, the pre-configured time period is set as a default value or is set by one of system information, RRC signaling, MAC CE, and downlink control information.

[0211] In some embodiments, the first message includes an indication of successful transmission of the path switch configuration to the first terminal device 220-1.

[0212] In some embodiments, the target path is either a direct path or an indirect path.

[0213] In some embodiments, the path switching configuration is associated with I2D path switching or I2I path switching.

[0214] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0215] In some embodiments, the first terminal device 220-1 comprises circuitry configured to detect a failure of the PC5 path between the first terminal device 220-1 and the second terminal device 220-2 via a keep-alive procedure without receiving a path switching configuration from the second terminal device 220-2, and the first terminal device 220-1 is connected to the first network device 210-1 via the second terminal device 220-2 and initiate a re-establishment procedure with the second terminal device 220-2.

[0216] In some embodiments, detecting the PC5 path failure includes detecting the PC5 path failure in response to at least one of timer T5080 expiring or the number of retransmissions of the PROSE DIRECT LINK KEEPALIVE REQUEST message reaching a third threshold number.

[0217] In some embodiments, the path switching configuration is associated with I2D path switching or I2I path switching.

[0218] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0219] In some embodiments, the CN device comprises circuitry configured to generate a first message explicitly or implicitly indicating successful transmission of a path switching configuration to a first terminal device 220-1, the first terminal device 220-1 being connected to a first network device 210-1 via a relay path including a second terminal device 220-2 and being switched to a target path between the first device and the second network device 210-2, and to send the first message to the first network device 210-1.

[0220] In some embodiments, the first message includes an indication of successful transmission of the path switch configuration to the first terminal device 220-1.

[0221] In some embodiments, the first message is at least one end marker packet corresponding to at least one respective PDU session of the first terminal device 220-1.

[0222] In some embodiments, the target path is either a direct path or an indirect path.

[0223] In some embodiments, the path switching configuration is associated with I2D path switching or I2I path switching.

[0224] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0225] As used herein, the term "circuit" may refer to a hardware circuit and / or a combination of a hardware circuit and software. For example, a circuit may be a combination of analog and / or digital hardware circuitry and software / firmware. As another example, a circuit may be any portion of a hardware processor with software, where a hardware processor includes digital signal processor(s), software, and memory(s) that cooperate to enable a device, such as a terminal device or network device, to operate to perform various functions. As yet another example, a circuit may be a hardware circuit and / or processor, such as a microprocessor or portion of a microprocessor, that requires software / firmware for operation, but the software may not be present when not necessary for operation. As used herein, the term circuit also includes simply a hardware circuit or processor(s) or portion of a hardware circuit or processor(s) and its (or their) associated software and / or firmware implementation.

[0226] In summary, the embodiments of the present disclosure provide the following solutions:

[0227] In one solution, a communication method includes receiving, in a first network device, a first message that explicitly or implicitly indicates successful transmission of a path switching configuration to a first terminal device, the first terminal device being connected to the first network device via a relay path that includes a second terminal device, and transmitting to the second terminal device one of a second message used for reconfiguring the relay path to be switched to a target path between the first terminal device and the second network device, and a third message used to trigger the second terminal device to apply the previously received second message used for reconfiguring the relay path.

[0228] In some embodiments, the first message includes an indication of successful transmission of the path switching configuration to the first terminal device, and receiving the first message includes receiving the first message from one of the second network device, the second terminal device, and a core network (CN) device.

[0229] In some embodiments, the first message is a handover success message or a user equipment (UE) context release message received from the second network device.

[0230] In some embodiments, the first message is at least one end marker packet corresponding to at least one respective packet data unit (PDU) session of the first terminal device, and the first message is received from a core network (CN) device.

[0231] In some embodiments, the first message is received from the second terminal device via one of a media access control (MAC) control element (CE) and radio resource control (RRC) signaling.

[0232] In some embodiments, the target path is either a direct path or an indirect path.

[0233] In some embodiments, the path switching configuration is associated with indirect-to-direct (I2D) path switching or indirect-to-indirect (I2I) path switching.

[0234] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0235] In one solution, a communications device comprises a processor and a memory coupled to the processor that stores instructions that, when executed by the processor, cause the communications device to perform any of the above methods.

[0236] In one solution, a computer readable medium storing instructions that, when executed on at least one processor, cause the at least one processor to perform any of the methods set forth above.

[0237] In another solution, a communications device comprises a processor configured to cause the device to perform any of the above methods.

[0238] In one solution, a communication method includes receiving, in a second network device, a fourth message that explicitly or implicitly indicates successful transmission of a path switching setting to a first terminal device; and the first terminal device is connected to the first network device via a relay path that includes the second terminal device and is switched to a target path between the first terminal device and the second network device, and transmitting to the first network device a first message that explicitly or implicitly indicates successful transmission of the path switching setting to the first terminal device.

[0239] In some embodiments, the fourth message is a configuration completion message corresponding to the path switching configuration and is received from one of the first terminal device and another second terminal device that is included in the target path and functions as a relay device.

[0240] In some embodiments, the target path is an indirect path including another second terminal device, the other second terminal device is in an idle state or an inactive state, and the fourth message is one of a radio resource control (RRC) setup request received from the other second terminal device, an RRC resume request received from the other second terminal device, an RRC setup complete received from the other second terminal device, and an RRC resume complete received from the other second terminal device.

[0241] In some embodiments, the fourth message is a path switch confirmation message received from a core network (CN) device, the path switch confirmation message corresponding to a path switch request sent by the second network device to the CN device.

[0242] In some embodiments, the first message includes an indication of successful transmission of the path switch configuration to the first terminal device.

[0243] In some embodiments, the first message is a handover success message or a user equipment (UE) context release message.

[0244] In some embodiments, the target path is either a direct path or an indirect path.

[0245] In some embodiments, the path switching configuration is associated with indirect-to-direct (I2D) path switching or indirect-to-indirect (I2I) path switching.

[0246] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0247] In one solution, a communications device comprises a processor and a memory coupled to the processor that stores instructions that, when executed by the processor, cause the communications device to perform any of the above methods.

[0248] In one solution, a computer readable medium storing instructions that, when executed on at least one processor, cause the at least one processor to perform any of the methods set forth above.

[0249] In another solution, a communications device comprises a processor configured to cause the device to perform any of the above methods.

[0250] In one solution, a communication method includes performing one of the following: determining, in a second terminal device, successful transmission of a path switching setting to a first terminal device; the first terminal device being connected to a first network device via a relay path including the second terminal device and switched to a target path between the first terminal device and the second network device; transmitting a first message to the first network device indicating successful transmission of the path switching setting to the first terminal device; and applying a previously received second message used to reconfigure the relay path.

[0251] In some embodiments, applying the previously received second message includes at least one of releasing the relay path, releasing a connection between the second terminal device and the first network device, and releasing a connection between the second terminal device and the first terminal device.

[0252] In some embodiments, determining successful transmission of the path switch configuration includes determining that a last packet data unit (PDU) for a PC5 radio link control (RLC) channel corresponding to a signaling radio bearer (SRB) associated with the first terminal device is successfully transmitted to the first terminal device; receiving an acknowledgement from the first terminal device of the last RLC PDU for the PC5 radio link control (RLC) channel corresponding to the signaling radio bearer (SRB) associated with the first terminal device; The method includes determining successful transmission of the path switching configuration based on at least one of: there are no packets buffered for the RLC channel; a length of time during which no packets have been received for the PC5 radio link control (RLC) channel corresponding to the SRB associated with the first terminal device reaches a predetermined length of time; the second terminal device is indicated by an upper layer regarding the release of the PC5 connection for the first terminal device; and receiving a third message from the first network device used to trigger the second terminal device to apply the previously received second message.

[0253] In some embodiments, the pre-configured time length is set as a default value or is set by one of system information, radio resource control (RRC) signaling, media access control (MAC) control element (CE), and downlink control information.

[0254] In some embodiments, the first message includes an indication of successful transmission of the path switch configuration to the first terminal device.

[0255] In some embodiments, the target path is either a direct path or an indirect path.

[0256] In some embodiments, the path switching configuration is associated with indirect-to-direct (I2D) path switching or indirect-to-indirect (I2I) path switching.

[0257] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0258] In one solution, a communications device comprises a processor and a memory coupled to the processor that stores instructions that, when executed by the processor, cause the communications device to perform any of the above methods.

[0259] In one solution, a computer readable medium storing instructions that, when executed on at least one processor, cause the at least one processor to perform any of the methods set forth above.

[0260] In another solution, a communications device comprises a processor configured to cause the device to perform any of the above methods.

[0261] In one solution, a communication method includes detecting, in a first terminal device, a failure of a PC5 path between the first terminal device and a second terminal device via a keep-alive procedure without receiving a path switching setting from the second terminal device, and the first terminal device being connected to a first network device via the second terminal device and initiating a re-establishment procedure with the second terminal device.

[0262] In some embodiments, detecting the PC5 path failure includes detecting the PC5 path failure in response to at least one of timer T5080 expiring and the number of retransmissions of the PROSE DIRECT LINK KEEPALIVE REQUEST message reaching a third threshold number.

[0263] In some embodiments, the path switching configuration is associated with indirect-to-direct (I2D) path switching or indirect-to-indirect (I2I) path switching.

[0264] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0265] In one solution, a communications device comprises a processor and a memory coupled to the processor that stores instructions that, when executed by the processor, cause the communications device to perform any of the above methods.

[0266] In one solution, a computer readable medium storing instructions that, when executed on at least one processor, cause the at least one processor to perform any of the methods set forth above.

[0267] In another solution, a communications device comprises a processor configured to cause the device to perform any of the above methods.

[0268] In one solution, a communication method includes generating, in a core network (CN) device, a first message that explicitly or implicitly indicates successful transmission of a path switching setting to a first terminal device, the first terminal device being connected to a first network device via a relay path that includes a second terminal device, and being switched to a target path between the first device and the second network device, and transmitting the first message to the first network device.

[0269] In some embodiments, the first message includes an indication of successful transmission of the path switch configuration to the first terminal device.

[0270] In some embodiments, the first message is at least one end marker packet corresponding to at least one respective packet data unit (PDU) session of the first terminal device.

[0271] In some embodiments, the target path is either a direct path or an indirect path.

[0272] In some embodiments, the path switching configuration is associated with indirect-to-direct (I2D) path switching or indirect-to-indirect (I2I) path switching.

[0273] In some embodiments, the path switching configuration is associated with inter-gNB path switching.

[0274] In one solution, a communications device comprises a processor and a memory coupled to the processor that stores instructions that, when executed by the processor, cause the communications device to perform any of the above methods.

[0275] In one solution, a computer readable medium storing instructions that, when executed on at least one processor, cause the at least one processor to perform any of the methods set forth above.

[0276] In another solution, a communications device comprises a processor configured to cause the device to perform any of the above methods.

[0277] In general, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described using block diagrams, flowcharts, or some other pictorial representations, it should be understood that the blocks, devices, systems, techniques, or methods described herein may be implemented in, by way of non-limiting example, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller, or other computing device, or some combination thereof.

[0278] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer-executable instructions (e.g., computer-executable instructions included in program modules) that execute on a target real or virtual processor device to perform the processes or methods described above with reference to FIGS. 2A-10. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split among program modules as desired in various embodiments. The machine-executable instructions for the program modules may be executed in local or distributed devices. In a distributed device, the program modules may be located in both local and remote storage media.

[0279] Program code for implementing the methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus, so that when executed by the processor or controller, the program code performs the functions / acts specified in the flowcharts and / or block diagrams. The program code may be executed entirely on a machine, partially on a machine, as a stand-alone software package, partially on a machine and partially on a remote machine, or entirely on a remote machine or server.

[0280] The program code may be embodied in a machine-readable medium, which may be any tangible medium that can contain or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. The machine-readable medium includes, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination thereof. More specific examples of machine-readable storage media include an electrical connection having one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a CD-ROM (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0281] Additionally, while operations are depicted in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown, or sequentially, or that all of the operations depicted be performed, to achieve desirable results. In certain situations, multitasking and parallel processing may be advantageous. Similarly, while several specific implementation details are included in the above description, these should not be construed as limiting the scope of the disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination.

[0282] Although the present disclosure has been described in language specific to structural features and / or methodological operations, it is to be understood that the present disclosure, as defined in the appended claims, is not necessarily limited to the specific features or operations described above. Rather, the specific features and operations described above are disclosed as example forms of implementing the claims.

Claims

1. A means for receiving a message indicating a successful path switch from a first indirect path to a second path from a second network device by a remote user equipment (UE), the remote UE being connected to the first network device in the first indirect path and being connected to the second network device in the second path; means for transmitting a Radio Resource Control (RRC) reconfiguration message to the relay UE to release a Uu relay Radio Link Control (RLC) channel setup for relaying and a PC5 relay RLC channel setup.

2. The second path is a direct path or a second indirect path. The first network device of claim 1 .

3. The second network device is different from the first network device. The first network device of claim 1 .

4. The message is a UE CONTEXT RELEASE message. The first network device of claim 1 .

5. A method for transmitting a message indicating successful path switching from a first indirect path to a second path, wherein a remote user equipment (UE) is connected to the first network device on the first indirect path and connected to a second network device on the second path, and a Radio Resource Control (RRC) reconfiguration message is sent from the first network device to the relay UE to release a Uu relay Radio Link Control (RLC) channel setting and a PC5 relay RLC channel setting for relaying. A second network device.

6. The second path is a direct path or a second indirect path. The second network device of claim 5 .

7. The second network device is different from the first network device. The second network device of claim 5 .

8. The method of claim 7, wherein the message is a UE CONTEXT RELEASE message. The second network device of claim 5 .

9. A relay user equipment (UE: User Equipment), means for receiving a first Radio Resource Control (RRC) reconfiguration message from a first network device to trigger a path switch in which a remote UE switches from a first indirect path to a second path, the remote UE being connected to the first network device over the first indirect path and connected to a second network device over the second path; means for receiving a second RRC reconfiguration message from the first network device to release a Uu relay Radio Link Control (RLC) channel setup for relaying and a PC5 relay RLC channel setup; Relay UE.

10. The second path is a direct path or a second indirect path. The relay UE of claim 9.

11. The second network device is different from the first network device. The relay UE of claim 9.

12. A method of communication performed by a first network device, comprising: receiving a message from a second network device indicating a successful path switch in which a remote user equipment (UE) switches from a first indirect path to a second path, the remote UE being connected to the first network device over the first indirect path and connected to the second network device over the second path; sending a Radio Resource Control (RRC) reconfiguration message to the relay UE to release a Uu relay Radio Link Control (RLC) channel setup and a PC5 relay RLC channel setup for relaying; method.

13. The second path is a direct path or a second indirect path. The method of claim 12.

14. A method of communication performed by a second network device, comprising: a remote user equipment (UE) sending a message to a first network device indicating a successful path switch, the path switch being performed from a first indirect path to a second path, the remote UE being connected to the first network device on the first indirect path and connected to the second network device on the second path; and a radio resource control (RRC) reconfiguration message being sent from the first network device to the relay UE to release a Uu relay radio link control (RLC) channel configuration and a PC5 relay RLC channel configuration for relay. method.

15. A method of communication performed by a relay user equipment (UE), comprising: receiving a first Radio Resource Control (RRC) reconfiguration message from a first network device to trigger a path switch in which a remote UE switches from a first indirect path to a second path, wherein the remote UE is connected to the first network device on the first indirect path and to a second network device on the second path; receiving a second RRC reconfiguration message from the first network device to release a Uu relay Radio Link Control (RLC) channel setup for relaying and a PC5 relay RLC channel setup; method.

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