Mobility support in U2N relays

Abstract

Embodiments of the present disclosure relate to mobility support in a user equipment (UE) to a network relay (U2N relay). In an example embodiment, a network device determines to switch a relay terminal device from the network device to a target network device. The network device then determines a reconfiguration of the remote terminal device associated with the relay terminal device, the reconfiguration being caused by the handover. Further, the network device transmits a first radio resource control message to the relay terminal device, the first radio resource control message being separated from the network device based on determining that a last message for the remote terminal device is received from the network device or delivered to the remote terminal device.

Description

Technical Field

[0001] Various example instances relate to the field of telecommunications, and in particular to methods, devices, apparatuses, and computer-readable storage media for mobility support in a User Equipment (UE) to Network Relay (U2N Relay). Background Art

[0002] Sidelink relay is introduced to support U2N relay functionality to provide connectivity to the network for U2N remote UEs. User plane (UP) and control plane (CP) protocol stacks of Layer 2 (L2) U2N relay are introduced separately. For the remote UE, higher layer protocols such as Uu Service Data Adaptation Protocol (SDAP), Packet Data Convergence Protocol (PDCP) and Radio Resource Control (RRC) protocols are terminated end-to-end between the remote UE and the New Radio (NR) NodeB (gNB). Lower layer protocols such as Radio Link Control (RLC), Medium Access Control (MAC) and Physical Layer (PHY) protocols are terminated in each hop between the remote UE and the relay UE or between the relay UE and the gNB. There are also additional protocols such as Uu Sidelink Relay Application Protocol (SRAP) between the relay UE and the gNB and Proximity Service (ProSe) Communication 5 (PC5) SRAP between the remote UE and the relay UE are introduced in each hop to handle the traffic mapping of different bearers and remote UEs.

[0003] In addition, with the development of communication technology, a new network architecture has been developed to split the functions of the base station in the radio access network in order to improve the flexibility of deployment. Some functions of the base station are deployed on the central unit (CU), while other functions are deployed on the distributed unit (DU). For example, the CU can be responsible for some higher-layer protocol stack functions and the DU can be responsible for some lower-layer protocol stack functions. Summary of the invention

[0004] In general, example embodiments of the present disclosure provide a solution for mobility support in U2N relaying.

[0005] In a first aspect, a network device is provided. The network device includes at least one processor and at least one memory storing instructions, which, when executed by the at least one processor, causes the terminal device to at least: determine to switch a relay terminal device from the network device to a target network device; determine a reconfiguration of a remote terminal device associated with the relay terminal device, the reconfiguration being caused by the switch; and send a first radio resource control message to the relay terminal device, the first radio resource control message requesting the relay terminal device to detach from the network device based on determining that the last message for the remote terminal device is received from the network device and delivered to the remote terminal device.

[0006] In a second aspect, a relay terminal device is provided. The relay terminal device includes at least one processor and at least one memory storing instructions, and when the instructions are executed by the at least one processor, the relay terminal device at least: receives a first radio resource control message for switching from the network device to a target network device from a network device, the first radio resource control message requests the relay terminal device to detach from the network device based on determining that the last message for a remote terminal device associated with the relay terminal device is received from the network device or delivered to the remote terminal device; and detaches from the network device based on determining that the last message is received from the network device or delivered to the remote terminal device.

[0007] In a third aspect, a remote terminal device is provided. The remote terminal device includes at least one processor and at least one memory storing instructions, and when the instructions are executed by the at least one processor, the remote terminal device at least: receives a second radio resource control message for reconfiguration of the remote terminal device from a network device via a relay terminal device associated with the remote terminal device, the second radio resource control message instructing the remote terminal device to send an indication of last message delivery to the relay terminal device upon receiving the second radio resource control message; and sends an indication to the relay terminal device that the last message is delivered to the remote terminal device.

[0008] In a fourth aspect, a method implemented on a network device is provided. The method includes determining to switch a relay terminal device from the network device to a target network device; determining a reconfiguration of a remote terminal device associated with the relay terminal device, the reconfiguration being caused by the switch; and sending a first radio resource control message to the relay terminal device, the first radio resource control message requesting the relay terminal device to detach from the network device based on determining that a last message for the remote terminal device is received from the network device or delivered to the remote terminal device.

[0009] In a fifth aspect, a method implemented on a relay terminal device is provided. The method includes receiving a first radio resource control message from a network device for switching from the network device to a target network device, the first radio resource control message requesting the relay terminal device to detach from the network device based on determining that the last message for a remote terminal device associated with the relay terminal device is received from the network device or delivered to the remote terminal device; and detaching from the network device based on determining that the last message is received from the network device or delivered to the remote terminal device.

[0010] In a sixth aspect, a method implemented on a remote terminal device is provided. The method includes receiving a second radio resource control message for reconfiguration of the remote terminal device from a network device via a relay terminal device associated with the remote terminal device, the second radio resource control message indicating that the remote terminal device sends an indication of last message delivery to the relay terminal device upon receiving the second radio resource control message; and sending an indication that the last message is delivered to the remote terminal device to the relay terminal device.

[0011] In a seventh aspect, an apparatus is provided. The apparatus includes a component for determining, at a network device, that a relay terminal device is switched from the network device to a target network device; a component for determining a reconfiguration of a remote terminal device associated with the relay terminal device, the reconfiguration being caused by the switching; and a component for sending a first radio resource control message to the relay terminal device, the first radio resource control message requesting the relay terminal device to detach from the network device based on determining that a last message for the remote terminal device is received from the network device or delivered to the remote terminal device.

[0012] In an eighth aspect, an apparatus is provided. The apparatus includes a component for receiving a first radio resource control message from a network device at a relay terminal device to switch from the network device to a target network device, the first radio resource control message requesting the relay terminal device to detach from the network device based on determining that the last message for a remote terminal device associated with the relay terminal device is received from the network device or delivered to the remote terminal device; and a component for detaching from the network device based on determining that the last message is received from the network device or delivered to the remote terminal device.

[0013] In a ninth aspect, an apparatus is provided. The apparatus includes a component for receiving, at a remote terminal device, a last message for reconfiguration of the remote terminal device from a network device via a relay terminal device associated with the remote terminal device, the last message indicating that the remote terminal device sends an indication to the relay terminal device that the last message is delivered to the remote terminal device; and a component for sending an indication to the relay terminal device that the last message is delivered to the remote terminal device.

[0014] In a tenth aspect, a non-transitory computer-readable medium is provided, comprising program instructions for causing an apparatus to at least perform a method according to any one of the fourth to sixth aspects.

[0015] In an eleventh aspect, there is provided a computer program comprising instructions which, when executed by an apparatus, cause the apparatus to at least perform the method according to any one of the fourth to sixth aspects.

[0016] In a twelfth aspect, a network device is provided. The network device includes: a determining circuit device configured to determine at the network device that a relay terminal device is switched from the network device to a target network device; a determining circuit device configured to determine a reconfiguration of a remote terminal device associated with the relay terminal device, the reconfiguration being caused by the switching; and a sending circuit device configured to send a first radio resource control message to the relay terminal device, the first radio resource control message requesting the relay terminal device to detach from the network device based on determining that the last message for the remote terminal device is received from the network device or delivered to the remote terminal device.

[0017] In a thirteenth aspect, a relay terminal device is provided. The relay terminal device includes: a receiving circuit device configured to receive a first radio resource control message from a network device at the relay terminal device to switch from the network device to a target network device, the first radio resource control message requesting the relay terminal device to detach from the network device based on determining that the last message for a remote terminal device associated with the relay terminal device is received from the network device or delivered to the remote terminal device; and a detaching circuit device configured to detach from the network device based on determining that the last message is received from the network device or delivered to the remote terminal device.

[0018] In a fourteenth aspect, a remote terminal device is provided. The remote terminal device comprises: a receiving circuit device configured to receive, at the remote terminal device, a second radio resource control message for reconfiguration of the remote terminal device from a network device via a relay terminal device associated with the remote terminal device, the second radio resource control message instructing the remote terminal device to send an indication that a last message was delivered to the remote terminal device to the relay terminal device; and a sending circuit device configured to send an indication that a last message was delivered to the remote terminal device to the relay terminal device.

[0019] It should be understood that the invention summary is not intended to identify the key or essential features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become readily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Some example embodiments will now be described with reference to the accompanying drawings, in which:

[0021] Figure 1A illustrates an example network environment in which some example embodiments of the present disclosure may be implemented;

[0022] Figure 1Billustrates example scenarios in which some example embodiments of the present disclosure may be implemented;

[0023] Figure 1C illustrates a user plane protocol stack for L2 UE-to-network relay according to some example embodiments of the present disclosure;

[0024] Figure 1D illustrates a control plane protocol stack for L2 UE-to-network relay according to some example embodiments of the present disclosure;

[0025] Figure 2 illustrates signaling flows between devices according to some example embodiments of the present disclosure;

[0026] Figure 3 illustrates an example of an indication using a header of a Sidelink Relay Adaptation Protocol (SRAP) Protocol Data Unit (PDU) according to some example embodiments of the present disclosure;

[0027] Figure 4 illustrates an example of indication using a SRAP control PDU (C-PDU) according to some example embodiments of the present disclosure;

[0028] Figure 5 Illustrated are signaling flows between according to some other example embodiments of the present disclosure;

[0029] Figure 6 illustrates an example process for mobility support in a U2N relay with one remote UE according to some example embodiments of the present disclosure;

[0030] Figure 7 illustrates another example process for mobility support in a U2N relay with one remote UE according to some other example embodiments of the present disclosure;

[0031] Figure 8 illustrates an example process for mobility support in a U2N relay with multiple remote UEs according to some example embodiments of the present disclosure;

[0032] Fig. 9 illustrates another example process for mobility support in a U2N relay with multiple remote UEs according to some other example embodiments of the present disclosure;

[0033] Fig.10 illustrates a flow chart of a method implemented at a network device according to some example embodiments of the present disclosure;

[0034] Fig.11 A flowchart illustrating a method implemented at a relay terminal device according to some other exemplary embodiments of the present disclosure is shown;

[0035] Fig.12 illustrates a flow chart of a method implemented at a remote terminal device according to some other example embodiments of the present disclosure;

[0036] Fig.13 illustrates a simplified block diagram of a device suitable for implementing some example embodiments of the present disclosure; and

[0037] Fig.14 A block diagram illustrating an example of a computer readable medium according to some example embodiments of the present disclosure is illustrated.

[0038] Throughout the drawings, the same or similar reference numerals refer to the same or similar elements. DETAILED DESCRIPTION

[0039] The principles of the present disclosure will now be described with reference to some example embodiments. It should be understood that these embodiments are described only for illustrative purposes and help those skilled in the art to understand and implement the present disclosure, and do not represent any limitation on the scope of the present disclosure. The disclosure described herein can be implemented in various other ways except for the way described below.

[0040] In the following description and claims, unless defined otherwise, 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.

[0041] In this disclosure, references to "one embodiment," "an embodiment," and "an example embodiment" indicate that the described embodiment may include a particular feature, structure, or characteristic, but not every embodiment must include the particular feature, structure, or characteristic. In addition, such phrases do not necessarily refer to the same embodiment. In addition, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, those skilled in the art believe that it is within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in conjunction with other embodiments, whether or not explicitly described.

[0042] It should be understood that although the terms "first" and "second" etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, without departing from the scope of the example embodiments, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes any and all combinations of one or more of the listed terms.

[0043] The terms used herein are only used to describe specific embodiments, and are not intended to limit exemplary embodiments. The singular forms "a", "an" and "the" used herein also include plural forms, unless the context clearly states otherwise. It is further understood that the terms "comprises", "comprising", "has", "having", "includes" and / or "including" specify the presence of the features, elements and / or components when used herein, but do not exclude the presence or addition of one or more other features, elements, components and / or their combinations. As used herein, "at least one of the following: <list of two or more elements>" and "at least one of the lists of <two or more elements>" and similar wording (wherein the list of two or more elements is connected by "and" or "or") refer to at least any one of these elements, or at least any two or more of these elements, or at least all of these elements.

[0044] As used in this application, the term "circuitry" may refer to one or more or all of the following:

[0045] (a) a pure hardware circuit implementation (such as an implementation using only analog and / or digital circuit devices), and

[0046] (b) a combination of hardware circuitry and software such as (where applicable):

[0047] (i) a combination of analog and / or digital hardware circuits and software / firmware, and

[0048] (ii) any portion of hardware processor(s) (including digital signal processor(s)) with software, software and memory(s) that work together to enable a device (such as a mobile phone or server) to perform various functions),

[0049] as well as

[0050] (c) Hardware circuits and / or processor(s), such as microprocessor(s) or portions of microprocessor(s), that require software (e.g., firmware) to operate, but which may not be present when the software is not required for operation.

[0051] This definition of circuitry applies to all uses of the term in this application, including in any claims. As another example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its accompanying software and / or firmware. For example, if applicable to a particular claim element, the term circuitry also covers a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0052] As used herein, the term "communication network" refers to a network that complies with any suitable communication standard, such as Long Term Evolution (LTE), Advanced LTE (LTE-A), Wideband Code Division Multiple Access (WCDMA), High Speed ​​Packet Access (HSPA), Narrowband Internet of Things (NB-IoT), etc. In addition, the communication between the terminal equipment and the network equipment in the communication network can be performed according to any suitable generation of communication protocols, including but not limited to the third generation (3G), fourth generation (4G), 4.5G, future fifth generation (5G) communication protocols, and / or any other protocols currently known or to be developed in the future. The embodiments of the present disclosure can be applied to various communication systems. In view of the rapid development of communication, there will certainly be communication technologies and systems that can be used to embody future types of the present disclosure. It should not be regarded as limiting the scope of the present disclosure to the above-mentioned systems.

[0053] As used herein, the term "network device" refers to a node in a communication network via which a terminal device accesses the network and receives services from the network. Depending on the terminology and technology applied, a network device may refer to a base station (BS) or an access point (AP), such as a NodeB (NodeB or NB), an evolved NodeB (eNodeB or eNB), a new radio (NR) NB (also known as a gNB), a remote radio cell (RRU), a radio head (RH), a remote radio head (RRH), a relay, a low-power node (such as a femto, a pico), etc.

[0054] As used herein, the term "network device" refers to a device that can implement some functions of a network device, such as a CU or DU. For example, a CU may be responsible for some high-level protocol stack functions and a DU may be responsible for lower-level functions.

[0055] The term "terminal device" refers to any terminal device capable of wireless communication. As an example and not limitation, a terminal device may also be referred to as a communication device, a user equipment (UE), a subscriber station (SS), a portable subscriber station, a mobile station (MS), or an access terminal (AT). The terminal device may include, but is not limited to, a mobile phone, a cellular phone, a smart phone, a voice over IP (VoIP) phone, a wireless local loop phone, a tablet computer, a wearable terminal device, a personal digital assistant (PDA), a portable computer, a desktop computer, an image capture terminal device (such as a digital camera), a game terminal device, a music storage and playback device, a vehicle-mounted wireless terminal device, a wireless endpoint, a mobile station, a laptop embedded device (LEE), a laptop mounted device (LME), a USB dongle, a smart device, a wireless customer premises equipment (CPE), an Internet of Things (IoT) device, a watch or other wearable device, a head mounted display (HMD), a vehicle, a drone, medical equipment and applications (e.g., remote surgery), industrial equipment and applications (e.g., robots and / or other wireless devices operating in industrial and / or (multiple) automated processing chain environments), consumer electronic devices, equipment operating on commercial and / or industrial wireless networks, etc. In the following description, the terms "terminal device", "communication device", "terminal", "user equipment" and "UE" may be used interchangeably.

[0056] As mentioned above, SL relay is introduced to support U2N relay function to provide connectivity to the network for U2N remote UE. The following service mapping rules are specified in L2 U2N relay:

[0057] Through the Uu interface, the remote UE's service and the relay UE's service cannot be mapped to the same Uu-RLC channel.

[0058] Through the Uu interface, user plane traffic or control plane traffic of the same or different remote UEs can be mapped / multiplexed into the Uu-RLC channel of the same relay UE.

[0059] Through the Uu interface and the PC5 interface, UP services (corresponding to the data radio bearer (DRB) services of the remote UE) and the CP services of the remote UE (corresponding to the signaling radio bearer (SRB) services of the remote UE) cannot be mapped / multiplexed into the same RLC channel.

[0060] In the 3rd Generation Partnership Project (3GPP) Release 18 (Rel-18), NR SL relay enhancement has been discussed. The purpose of the work item (WI) is to enhance service continuity for L2UE-to-NW in a single hop for the following scenarios:

[0061] a) Inter-gNB to direct path handover (i.e., “remote UE <—> first relay UE <—> source gNB (S-gNB)” to “remote UE <—> target gNB (T-gNB)”)

[0062] b) Inter-gNB direct to indirect path handover (i.e., “remote UE <—> S-gNB” to “remote UE <—> first relay UE <—> T-gNB”)

[0063] c) Inter-gNB indirect-to-indirect path handover (i.e., “remote UE <—> first relay UE <—> S-gNB” to “remote UE <—> second relay UE <—> S-gNB”)

[0064] d) Inter-gNB indirect-to-indirect path handover (i.e., “remote UE <—> first relay UE <—> S-gNB” to “remote UE <—> second relay UE <—> T-gNB”)

[0065] Without specific optimizations, scenario d) above is supported by reusing solutions used for other scenarios.

[0066] When the remote UE has established a U2N relay link with the source gNB via the relay UE, the UP and CP traffic transmission between the remote UE and the original gNB is forwarded via the relay UE. When the relay UE is configured by the source gNB for handover to the target gNB, the remote UE needs to be reconfigured to perform handover to the same target gNB, or a path switch to the source gNB or another gNB for a direct path or a path switch to another indirect path via the reselected relay UE, etc. This will trigger the source gNB to initiate an RRC reconfiguration procedure for handover or path switch to the remote UE, while simultaneously initiating an RRC reconfiguration procedure for handover to the relay UE for handover to the target gNB.

[0067] In L2 U2N relay, the RRC reconfiguration procedure of the remote UE is terminated between the remote UE and the source gNB. The relay UE only provides relay functionality in the lower radio L2 protocol under PDCP. The relay UE is therefore unaware of which RRC procedure message has been initiated by the source gNB to the remote UE. When the relay UE receives its own RRC reconfiguration message (i.e., a handover command in the case of a handover) from the source gNB to configure the relay UE to perform the handover, the relay UE may perform the handover by detaching from the serving cell before it successfully receives the RRC reconfiguration message of the remote UE from the source gNB over the Uu interface. When this occurs, the remote UE will not be able to obtain the RRC reconfiguration message from the source gNB for the handover or path switch when the relay UE switches to the target gNB. Therefore, until the remote UE reestablishes the RRC connection, the RRC connection of the remote UE to the source gNB will be interrupted and the service continuity of the ongoing services of the remote UE will be affected.

[0068] The gNB implementation can solve the above problem by always triggering the RRC reconfiguration procedure of the remote UE for handover or path switch before the RRC reconfiguration procedure of the relay UE for handover. However, there are some limitations that make the gNB implementation solution impractical.

[0069] For example, if the gNB needs to wait for the completion of the RRC reconfiguration procedure of the remote UE, it may be too late to initiate the RRC reconfiguration procedure to the relay UE for handover. This can affect the robustness of the handover of the relay UE, especially in high mobility scenarios, which are typical of many vehicle-to-anything (V2X) use cases.

[0070] In addition, in a normal handover procedure, the RRC Reconfiguration Complete message from the UE is not sent to the source gNB but to the target gNB. In this case, regarding the handover of the remote UE, the source gNB cannot ensure that the RRC Reconfiguration message has been delivered to the remote UE before initiating the RRC Reconfiguration procedure to the relay UE for handover because there is no end-to-end RLC or MAC protocol between the gNB and the remote UE to allow the gNB to know the delivery of the RRC Reconfiguration message through Automatic Repeat Request (ARQ) or Hybrid Automatic Repeat Request (HARQ) feedback.

[0071] In addition, if the source gNB does not need to wait for the completion confirmation of the remote UE, but only initiates and delivers the RRC reconfiguration message of the remote UE to the lower layer before delivering the RRC reconfiguration message of the relay UE to the lower layer, this cannot ensure that the RRC reconfiguration message of the remote UE can always be sent to the relay UE by the lower layer protocol earlier than the relay UE's own RRC reconfiguration message. The reason is that the SRB of the relay UE and the SRB of the remote UE cannot be multiplexed into the same Uu-RLC channel, but the SRBs of different remote UEs can be multiplexed into the same Uu-RLC channel. For example, if multiple remote UEs are connected to the same relay UE, the transmission of the RRC message of the remote UE multiplexed into the same Uu-RLC channel may experience a longer delay in the lower layer protocol (e.g., in the MAC layer for multiplexing and logical channel priority) than the transmission of the RRC message of the relay UE mapped to different Uu-RLC channels and logical channels.

[0072] In addition, Release 17 stipulates that the relay UE sends a SL notification to the connected remote UE when one of the following conditions is met:

[0073] via Uu Radio Link Failure (RLF);

[0074] Receipt of an RRC reconfiguration message including a reconfigurationWithSync message;

[0075] Reselection by the community;

[0076] The RRC connection failure involving the relay UE includes RRC connection rejection, timer T300 expiration and RRC recovery failure.

[0077] When the remote UE receives the SL notification from the relay UE, it initiates the RRC reestablishment process or releases the PC5 connection with the relay UE according to the RRC state of the remote UE. 3GPP Release 17 specifies the SL notification, and the remote UE initiates the RRC reestablishment process upon receiving the SL notification because it agrees that the optimization features will not be pursued in Release 17 due to the time limit for completing WI in Release 17.

[0078] However, during a relay UE handover or failure situation, if the remote UE can only be triggered to initiate the RRC re-establishment process, the service continuity of the remote UE will be affected. Therefore, there is a service continuity enhancement target in the Release 18 SL relay WI. According to the Release 17 specification, when the relay UE is reconfigured for handover, there is no need to initiate the RRC reconfiguration process for the remote UE. Therefore, during the 3GPP Release 17 time frame, the above issues were not discussed. So far, there is no effective way to solve the above issues to further improve the communication performance of users.

[0079] According to an embodiment of the present disclosure, a scheme for mobility support in U2N relay is provided. With the scheme, a network device determines to switch a relay terminal device from the network device to a target network device; then, the network device determines a reconfiguration of a remote terminal device associated with the relay terminal device. The reconfiguration is caused by the switch. In addition, the network device sends a first radio resource control (RRC) message to the relay terminal device. The first RRC message requests the relay terminal device to separate from the network device based on determining that the last message for the remote terminal device is received from the network device or delivered to the remote terminal device.

[0080] Then, the relay terminal device is separated from the network device based on determining that the last message of the remote terminal device is delivered to the remote terminal device. This solution improves user experience by avoiding service interruption caused by failed delivery of the RRCReconfiguration message of the remote UE. In this way, it is possible to improve communication efficiency.

[0081] The principles and embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Figure 1A, which illustrates an example environment 100 in which example embodiments of the present disclosure may be implemented.

[0082] Environment 100, which may be part of a communication network, includes network device 105. In some example embodiments, network device 105 may include two network elements 110 and 120 that communicate with each other or with other devices via each other. For example, network element 120 may be under the control of network element 110. In some example embodiments, a CU of a network device (e.g., a gNB-CU) will be considered an example of network element 110, and a DU of a network device (e.g., a gNB-DU) will be considered an example of network element 120. In some example embodiments, network element 110 and network element 120 may be implemented as one network device 105, such as one base station, or a next generation Node B (i.e., gNB), etc.

[0083] Environment 100 also includes two terminal devices 130 and 140 that communicate with each other or with other devices via each other. Terminal device 140 can communicate with network device 105 via terminal device 130. For the purpose of discussion, terminal devices 130 and 140 will be referred to as relay terminal device 130 and remote terminal device 140, respectively. For example, relay terminal device 130 can be connected to first network element 110 via network element 120. Terminal device 140 can be connected to network element 110 via network element 120 and relay terminal device 130.

[0084] It should be understood that the devices shown in environment 100 are for illustration purposes only and do not represent any limitation on the scope of the present disclosure. In certain example embodiments, environment 100 may include additional devices to communicate information with one or more of the above-mentioned devices.

[0085] Communications in environment 100 may follow any suitable communication standard or protocol already in existence or to be developed in the future, such as Universal Mobile Telecommunications System (UMTS), Long Term Evolution (LTE), Advanced LTE (LTE-A), Fifth Generation (5G) New Radio (NR), Wireless Fidelity (Wi-Fi), and Worldwide Interoperability for Microwave Access (WiMAX) standards, and employ any suitable communication technology, including, for example, Multiple Input Multiple Output (MIMO), Orthogonal Frequency Division Multiplexing (OFDM), Time Division Multiplexing (TDM), Frequency Division Multiplexing (FDM), Code Division Multiplexing (CDM), Bluetooth, ZigBee, and Machine Type Communication (MTC), Enhanced Mobile Broadband (eMBB), Massive Machine Type Communication (mMTC), Ultra-Reliable Low Latency Communication (URLLC), Carrier Aggregation (CA), Dual Connectivity (DC), and New Radio Unlicensed (NR-U) technology.

[0086] Reference now Figure 1B, which illustrates an example scenario in which some example embodiments of the present disclosure will be implemented. For the purpose of discussion, reference will be made to Figure 1A describe Figure 1B .like Figure 1B As shown in FIG. 1 , the remote terminal device 140 has an indirect path to the source network device 105 via the relay terminal device 130. When the relay terminal device 130 is configured to switch to the target network device 160, the remote terminal device 140 is configured to simultaneously switch to the target network device 160. In this case, the remote terminal device 140 is directly connected to the target network device 160.

[0087] Figure 1C and Figure 1D The user plane and control plane protocol stacks of the L2U2N relay according to some example embodiments of the present disclosure are illustrated respectively. For the remote UE, higher layer protocols such as Uu SDAP, PDCP, and RRC protocols are terminated end-to-end between the remote UE and the new radio (NR) Node B (gNB). Lower layer protocols such as RLC, MAC, and PHY protocols are terminated in each hop between the remote UE and the relay UE or between the relay UE and the gNB. In addition, some protocols, such as Uu SRAP and PC5 SRAP, are supported in each hop to handle the service mapping of different bearers and remote UEs.

[0088] Figure 2 FIG. 2 illustrates a signaling flow 200 between devices according to some example embodiments of the present disclosure. For discussion purposes, reference will be made to Figure 1A Describe the signaling flow 200. Figure 2 As shown, the network device 105 determines (205) to switch the relay terminal device 130 from the network device 105 to the target network device. Then, the network device 105 determines (210) a reconfiguration of the remote terminal device 140 associated with the relay terminal device 130. The reconfiguration is caused by the switch. In addition, the network device 105 sends (215) a first RRC message 216 to the relay terminal device 130. Accordingly, the relay terminal device 130 receives (220) the first RRC message 216 from the network device 105. The first RRC message 216 requests the relay terminal device 130 to separate from the network device 105 based on determining that the last message for the remote terminal device is received from the network device 105.

[0089] The network device 105 then sends (225) a second RRC message 226 for the remote terminal device 140 to the relay terminal device 130, and an indication 227 that the second RRC message 226 is the last message delivered to the remote terminal device 140 via the relay terminal device 130. On the other side of the transmission, the relay terminal device 130 receives (230) the second RRC message 226 and the indication 227 from the network device 105. The relay terminal device 130 then sends (235) the second RRC message 226 to the remote terminal device 140. Accordingly, the remote terminal device 140 receives (240) the second RRC message 226 from the relay terminal device 130.

[0090] The relay terminal device 130 may determine that the last message for the remote terminal device 140 was received from the network device 105, and then detach from the network device 105 (245). For example, the relay terminal device 130 may detach from the network device 105 after receiving the indication 227 from the network device 105. In some example embodiments, the network device 105 may include a network element 110, such as a CU of the network device 105, and a network element 120, such as a DU of the network device 105. In this case, since the relay terminal device 130 is connected to the network element 110 via the network element 120, the detachment from the network device 105 also means that the relay terminal device 130 is detached from the network element 110 and / or the network element 120.

[0091] In some example embodiments, the network device 105 may determine whether it is necessary for the relay terminal device 130 to determine that the last message for the remote terminal device 140 is received from the network device 105 before detaching from the network device 105 based on the quality of service (QoS) or characteristics of the traffic of the remote terminal device 140 relayed by the relay terminal device 130. For example, if the traffic of the remote terminal device 140 requires strict service continuity, the network device 105 may configure the relay terminal device 130 to wait for an indication that the last message for the remote terminal device 140 is received from the network device 105 before detaching from the network device 105.

[0092] In some example embodiments, the first RRC message 216 may include a configuration for a timer. The timer may define a maximum duration for the last message received from the network device 105 before the relay terminal device 130 determines to be detached from the network device 105. In this case, the first RRC message 216 may also indicate to the relay terminal device 130 the detachment from the network device 105 based on the expiration of the timer. In an alternative, the timer may be preconfigured to the relay terminal device 130, using, for example, public or dedicated signaling from the network device 105, and the indication of the relay terminal device 130 using the timer and the first RRC message 216 may become implicit. Accordingly, upon expiration of the timer, the relay terminal device 130 may be detached from the network device 105 even if the relay terminal device 130 fails to determine that the last message for the remote terminal device 140 is received from the network device 105.

[0093] For example, the second RRC message 226 for the remote terminal device 140 may be a reconfiguration message for configuring the remote terminal device 140 to switch to the target network device and connect to the target network device via the relay terminal device 130. As another example, the second RRC message 226 for the remote terminal device 140 may be a reconfiguration message for configuring the remote terminal device 140 to switch to the target network device or another target network device / element and connect to the target network device or another target network via another relay terminal device. As another example, the second RRC message 226 for the remote terminal device 140 may be a reconfiguration message for configuring the remote terminal device 140 to directly connect to the network device 105, the target network device or another target network device. Alternatively or additionally, the second RRC message 226 for the remote terminal device 140 may be a reconfiguration message for configuring the remote terminal device 140 to perform a path switch to connect to the network device 105 via another relay terminal device.

[0094] In some example embodiments, the network device 105 may send an indication 227 to the relay terminal device 130 that the second RRC message 226 is the last message delivered to the remote terminal device 140 via the relay terminal device 130 in a variety of ways. For example, when the second RRC message 226 of the remote terminal device 140 is sent to the relay terminal device 130 over the Uu interface, the indication 227 may be sent using the enhanced SRAP protocol. When the second RRC message 226 of the remote terminal device 140 is terminated end-to-end between the remote terminal device 140 and the network device 105, the relay terminal device 130 may not identify that the second RRC message 226 of the remote terminal device 140 is sent from the network device 105. In this case, as an example, the network device 105 may send the indication 227 in the SRAP PDU header to the relay terminal device 130. As another example, the network device 105 may send the indication 227 in the SRAP C-PDU to the relay terminal device 130. It should be understood that other signaling or messages may be used to send the indication 227, and the scope of the present disclosure shall not be limited in this regard.

[0095] Figure 3 to Figure 4 An example of using an indication 227 of a SRAP PDU and a SRAP C-PDU, respectively, according to some example embodiments of the present disclosure is illustrated. For example, when the network device 105 initiates transmission of a second RRC message 226 of the remote terminal device 140 via the relay terminal device 130, the RRC layer entity of the network device may indicate to the Uu SRAP layer entity that the second RRC message 226 is the last message for the remote terminal device 140. When the Uu SRAP entity forms the SRAP PDU of the last message of the remote terminal device 140, it may set the "1" bit in the SRAP PDU header to provide such an indication. Figure 3 227, or use Figure 4 The SRAP C-PDU shown may be a last message with an implicit option of carrying indication 227, or may explicitly provide indication 227 together with the SRAP PDU carrying the last message. The Uu SRAP entity at the network device 105 may then send the last message and indication 227 to the relay terminal device 130 via the same Uu-RLC channel. Figure 3 to Figure 4 In the , the "D" bit refers to the data PDU, the "C" bit refers to the control PDU, and the "R" bit is a reserved bit. In this case, for example, Figure 3 As shown, the “I” bit may be used as a one-bit indication in the SRAP PDU header to indicate whether the transmitted SRAP PDU includes the last RRC message of the remote terminal device 140.

[0096] In some example embodiments, network device 105 may determine a plurality of reconfigurations of a plurality of remote terminal devices associated with relay terminal device 130. Remote terminal device 140 is one of the plurality of remote terminal devices. In this case, first RRC message 216 from network device 105 may request relay terminal network 130 to detach from network device 105 based on determining that a corresponding last message for each of the plurality of remote terminal devices was received from network device 105.

[0097] Accordingly, the relay terminal device 130 can determine that the last message for the corresponding remote terminal device is received from the network device 105 based on the corresponding indication, and then separate from the network device 105, the corresponding indication being that the corresponding second radio resource control message is the last message to be delivered from the network device 105 to the corresponding remote terminal device via the relay terminal device 130. In this way, it is possible to improve the user experience by avoiding the service interruption caused by the failed delivery of the reconfiguration message of the remote terminal device. In this way, it is possible to improve the communication efficiency.

[0098] Figure 5 FIG. 5 illustrates a signaling flow 500 between devices according to some other example embodiments of the present disclosure. For the purpose of discussion, the signaling flow 500 will refer to FIG. Figure 1A Described. Figure 5 As shown, the network device 105 determines (505) to switch the relay terminal device 130 from the network device 105 to the target network device. Then, the network device 105 determines (510) the reconfiguration of the remote terminal device 140 associated with the relay terminal device 130. The reconfiguration is caused by the switch. In addition, the network device 105 sends (515) a first RRC message 516 to the relay terminal device 130. Accordingly, the relay terminal device 130 receives (517) the first RRC message 516 from the network device 105. The first RRC message 516 requests the relay terminal device 130 to separate from the network device 105 based on determining that the last message for the remote terminal device 140 is delivered to the remote terminal device 140.

[0099] Then, the network device 105 sends (520) a second RRC message 521 for the remote terminal device 140 to the relay terminal device 130. The second RRC message 521 includes an indication that the remote terminal device 140 sent an indication of the last message delivery to the relay terminal 130 upon receiving the second RRC message 521. For example, the indication 521 can be implicit or explicit. On the other side of the transmission, the relay terminal device 130 receives (525) the second RRC message 521 from the network device 105. The relay terminal device 130 then sends (530) the second RRC message 521 to the remote terminal device 140. Accordingly, the remote terminal device 140 receives (535) the second RRC message 521 from the relay terminal device 130.

[0100] In addition, after receiving the second RRC message 521 indicating that the remote terminal device 140 sent the last message to the relay terminal device 130 via the relay terminal device 130 from the network device 105, the remote terminal device 140 sends (540) an indication 546 that the last message was delivered to the remote terminal device 140 to the relay terminal device 130. On the receiving side, the relay terminal device 130 receives (545) the indication 546 from the remote terminal device 140. The relay terminal device 130 may determine that the last message for the remote terminal device 140 was delivered to the remote terminal device 140 based on the indication 546, and then detach (550) from the network device 105. For example, the relay terminal device 130 may detach from the network device 105 after receiving the indication 546 from the remote terminal device 140.

[0101] In some example embodiments, the network device 105 may determine whether it is necessary for the relay terminal device 130 to determine that the last message for the remote terminal device 140 is delivered to the remote terminal device 140 before detaching from the network device 105 based on the QoS or characteristics of the traffic of the remote terminal device 140 relayed by the relay terminal device 130. For example, if the traffic of the remote terminal device 140 requires strict service continuity, the network device 105 may configure the relay terminal device 130 to wait for an indication that the last message for the remote terminal device 140 is delivered to the remote terminal device 140 before detaching from the network device 105.

[0102] In some example embodiments, the first RRC message 516 may include a configuration for a timer. The timer may define a maximum duration for the relay terminal device 130 to determine that the last message was delivered to the remote terminal device 140. In this case, the first RRC message 516 may also indicate to the relay terminal device 130, based on the expiration of the timer, that it is detached from the network device 105. In an alternative, the timer may be preconfigured to the relay terminal device 130, using, for example, public dedicated signaling from the network device 105, and the indication of the relay terminal device 130 using the timer and the first RRC message 216 may become implicit. Accordingly, upon expiration of the timer, the relay terminal device 130 may be detached from the network device 105 even if the relay terminal device 130 fails to determine that the last message for the remote terminal device 140 was delivered to the remote terminal device 140.

[0103] For example, the second RRC message 521 for the remote terminal device 140 may be a reconfiguration message for configuring the remote terminal device 140 to switch to the target network device and connect to the target network device via the relay terminal device 130. As another example, the second RRC message 521 for the remote terminal device 140 may be a reconfiguration message for configuring the remote terminal device 140 to switch to the target network device or another target network device / element and connect to the target network device or another target network via another relay terminal device. As another example, the second RRC message 521 for the remote terminal device 140 may be a reconfiguration message for configuring the remote terminal device 140 to directly connect to the network device 105, the target network device or another target network device. Alternatively or additionally, the second RRC message 521 for the remote terminal device 140 may be a reconfiguration message for configuring the remote terminal device 140 to perform a path switch and connect to the network device 105 via another relay terminal device.

[0104] In some example embodiments, upon receiving the second RRC message 521 via the relay terminal device 130, the remote terminal device 140 may be triggered to send an indication of receiving the last RRC message, i.e., an indication 546 that the last message was delivered to the remote terminal device 140, to the relay terminal device 130 through the PC5 interface. In order to trigger the remote terminal device 140 to send the indication 546, for example, when the network device 105 simultaneously initiates the handover process of the relay terminal device 130 and the RRC reconfiguration process of the remote terminal device 140, the network device 105 may mark the last RRC message of the remote terminal device 140, i.e., the second RRC message 521. (Multiple) marking bits may be introduced into the second RRC message 521 to indicate whether the remote terminal device 140 needs to send the indication 546 to the relay terminal device 140 after receiving the second RRC message 521 (i.e., the last message). Alternatively or additionally, the relay terminal device 130 may request the remote terminal device 140 to send the indication 546 upon receiving the first RRC message 516 for handover of the relay terminal device 130 .

[0105] In some example embodiments, the remote terminal device 140 may send the indication 546 that the last message was delivered to the remote terminal device 140 to the relay terminal device 130 in a variety of ways. For example, the remote network device 240 may send the indication 546 to the relay terminal device 130 in sidelink RRC signaling. As another example, the remote network device 240 may send the indication 546 to the relay terminal device 130 in a sidelink media access control (MAC) control element (CE). As another example, the remote network device 240 may send the indication 546 in a header of a SRAP PDU to the relay terminal device 130. Alternatively or additionally, the remote network device 240 may send the indication 546 in a SRAP C-PDU to the relay terminal device 130. It should be understood that other signaling or carriers may be used to send the indication 546, and the scope of the present disclosure will not be limited in this regard.

[0106] In some example embodiments, the network device 105 may determine a plurality of reconfigurations of a plurality of remote terminal devices associated with the relay terminal device 130. The remote terminal device 140 is one of the plurality of remote terminal devices. In this case, the first RRC message 516 from the network device 105 may request the relay terminal device 130 to separate from the network device 105 based on determining that the corresponding last message of each of the plurality of remote terminal devices is delivered to the corresponding remote terminal device. Accordingly, the relay terminal device 130 may separate from the network device 105 after receiving a corresponding indication 546 from each of the plurality of remote terminal devices that the last message for the corresponding remote terminal device is delivered to the corresponding remote terminal device. In this way, it is possible to improve the user experience by avoiding service interruption caused by failed delivery of the reconfiguration message of the remote terminal device. In this way, it is possible to improve communication efficiency.

[0107] Figure 6 An example process for mobility support in a U2N relay with a remote UE according to some example embodiments of the present disclosure is illustrated. For discussion purposes, process 600 will refer to Figure 1A In this case, the remote terminal device 140 is implemented by the remote UE 601, the relay terminal device 130 is implemented by the relay UE 603, and the network device 105 is implemented by the gNB 605. In this case, the relay UE 603 ​​is connected to the gNB 605, and the remote UE 601 has established an indirect path with the serving gNB 605 via the relay UE 603. In this example, the network element 110 and the network element 120 are implemented in the same network device (i.e., the gNB 605).

[0108] like Figure 6 As shown, at 610, the relay UE 603 ​​sends a measurement report to the gNB 605. At 612, the remote UE 601 sends a measurement report to the gNB 605 via the relay UE 603. At 614, based on the measurement reports from the relay UE 603 ​​and the remote UE 601, the gNB 605 makes a handover (HO) decision for the relay UE 603, and initiates an RRC reconfiguration procedure for the remote UE 601 due to the HO of the relay UE 603. The RRC reconfiguration procedure for the remote UE 601 may configure the remote UE 601 to perform a handover with the relay UE 603, or to switch the path to a direct path to the serving gNB 605 or a neighboring gNB, or to switch to another reselected relay UE to continue an indirect path with the same serving gNB 605 or another neighboring gNB.

[0109] At 616, when the gNB 605 sends the RRC reconfiguration message (i.e., the handover command) to the relay UE 603, the gNB 605 requests the relay UE 603 ​​to wait for an indication of the last RRC message for the connected remote UE 601, e.g., the RRC reconfiguration message from the gNB 605, before detaching from the serving gNB 605. In other words, the gNB 605 requests the relay UE 603 ​​to detach from the gNB 605 based on determining that the last RRC message for the remote UE 601 was received from the gNB 605. At 618, the gNB 605 logically sends the last RRC reconfiguration message for the remote UE 601 to the remote UE 601 via the relay UE 603, which can be physically implemented as follows. At 619, the gNB 605 generates an inter-layer indication of the last RRC message of the remote UE 601 and passes the last RRC message downward. In this case, the RRC layer entity of the gNB 605 may indicate to the Uu SRAP layer entity that the RRC message is the last message of the remote UE 601. When the Uu SRAP layer entity at the gNB 605 forms the SRAP PDU of the last RRC message of the remote UE 601 to be delivered to the relay UE 603, it may indicate in the SRAP PDU header or the SRAP C-PDU that this is the last RRC message of the remote UE 601 of the connection to be delivered to the remote UE 601.

[0110] Then, at 620, the Uu SRAP layer entity at the gNB 605 sends a SRAP PDU (and / or SRAP C-PDU) carrying the last RRC message and an indication of the last RRC message to the relay UE 603. The PC5 SRAP at the relay UE 603 ​​then forwards the last RRC message to the remote UE 601. At 622, the relay UE 603 ​​identifies the receipt of the last RRC message of the remote UE 601 based on the indication from the SRAP PDU header or the SRAP C-PDU. Then, at 624, the relay UE 603 ​​detaches from the gNB 605 based on determining that the last RRC message for the remote UE 601 was received from the gNB 605. The above reference Figures 2 to 4 All operations and features described are equally applicable to process 600 and have similar effects. For the sake of simplicity, details will be omitted.

[0111] Figure 7 Another example process for mobility support in a U2N relay with a remote UE according to some other example embodiments of the present disclosure is illustrated. For discussion purposes, process 700 will refer to Figure 1AIn this case, the remote terminal device 140 is implemented by the remote UE 701, the relay terminal device 130 is implemented by the relay UE 703, and the network device 105 is implemented by the gNB 605. In this case, the relay UE 703 is connected to the gNB 705, and the remote UE 701 has established an indirect path with the serving gNB 705 via the relay UE 703.

[0112] like Figure 7 As shown, at 710, the relay UE 703 sends a measurement report to the gNB 705. At 712, the remote UE 701 sends a measurement report to the gNB 705 via the relay UE 703. At 714, based on the measurement reports from the relay UE 703 and the remote UE 701, the gNB 705 makes a handover (HO) decision for the relay UE 703, and initiates an RRC reconfiguration procedure for the remote UE 701 due to the HO of the relay UE 703. The RRC reconfiguration procedure for the remote UE 701 may configure the remote UE 701 to perform a handover with the relay UE 703, to perform a path switch for a direct path to the serving gNB 705 or a neighboring gNB, or to switch to another reselected relay UE to continue an indirect path with the same serving gNB 705 or a neighboring gNB.

[0113] At 716, when the gNB 705 sends the RRC reconfiguration message (i.e., the handover command) to the relay UE 703, the gNB 705 requests the relay UE 703 to wait for an indication of the delivery of the last RRC message (e.g., the RRC reconfiguration message) of the connected remote UE 701 from the remote UE 701 before detaching from the serving gNB 705. In other words, the gNB 705 requests the relay UE 603 ​​to detach from the gNB 705 based on determining that the last RRC message for the remote UE 701 was delivered to the remote UE 701. At 718, the gNB 705 sends the RRC reconfiguration message for the remote UE 701 to the remote UE 701 via the relay UE 703.

[0114] At 720, the remote UE 701 sends an indication to the relay UE 703 that the last RRC message was delivered to the remote UE 701. At 722, the relay UE 703 identifies the receipt of the last RRC message of the remote UE 701 based on the indication from the remote UE 701. Then, at 724, the relay UE 703 detaches from the gNB 705. Figure 5 All operations and features described are equally applicable to process 700 and have similar effects. For the sake of simplicity, details will be omitted.

[0115] Figure 8An example process for mobility support in a U2N relay with multiple remote UEs according to some example embodiments of the present disclosure is illustrated. For discussion purposes, process 800 will refer to Figure 1A In this case, the remote terminal device 140 is implemented by a remote UE 801. The process 800 involves remote UEs 802 and 803. The relay terminal device 130 is implemented by a relay UE 803. The network element 120 is implemented by a DU of a source gNB (also denoted as source gNB-DU) 807. The network element 110 is implemented by a CU of a source gNB (also denoted as source gNB-CU) 809.

[0116] like Figure 8 As shown, at 810, remote UEs 801-803 are connected to relay UE 805 and are also connected to source gNB-CU 809 via source gNB-DU 807. At 812-816, remote UEs 801-803 send measurement reports to source gNB-CU 809. Then, at 818, source gNB-CU 809 decides to handover relay UE 805 and remote UEs 801 and 802 together. For example, source gNB-CU 809 may make this decision based on QoS or other feature requirements of the services of the respective remote UEs relayed by relay UE 805. In this case, the QoS or other features of the relayed services of remote UEs 801 and 803 relayed by relay UE 805 may require low service interruption, and thus source gNB-CU 809 may configure relay UE 805 to wait for an indication related to the delivery of the last RRC message of each remote UE 801 and 803 from the gNB. In addition, the QoS or other features of the relay service of the remote UE 802 relayed by the relay UE 805 may not require low service interruption, and therefore the source gNB-CU 809 may hand over the remote UE 802 to a different target gNB, or to the same target gNB but with possible interruption.

[0117] At 820, the source gNB-CU 809 initiates a handover preparation procedure for the relay UE 805 and the remote UEs 801 and 803. At 822, the source gNB-CU 809 sends an RRC message (e.g., an RRC reconfiguration message) to the relay UE 805 via the source gNB-DU 807, the RRC message requesting the relay UE 805 to wait for an indication from each of the remote UEs 801 and 803 of the gNB indicating that the corresponding last RRC message is the last message to be delivered to the corresponding remote UE before detaching from the source gNB-CU 809.

[0118] At 824, the source gNB-CU 809 sends an F1 Application Protocol (F1AP) message for the remote UE 801 including an RRC reconfiguration message for the remote UE 801 and an indication (also referred to as a first indication) that the RRC reconfiguration message is the last message delivered to the remote UE 801 via the relay UE 805 to the source gNB-DU 807. At 826, the source gNB-DU 807 sends the RRC message (i.e., the RRC reconfiguration message) and another indication (also referred to as a second indication) to the relay UE 805. The second indication indicates to the relay UE 805 that the received RRC message is the last message delivered to the remote UE 801 via the relay UE 805. For example, the first indication and the second indication may be sent in an SRAP PDU header or an SRAP C-PDU. Then at 828, the relay UE 805 sends the RRC reconfiguration message for the remote UE 801 to the remote UE 801.

[0119] Likewise, at 830, the source gNB-CU 809 sends a F1AP message for the remote UE 803 including an RRC reconfiguration message for the remote UE 803 and an indication (also referred to as a third indication) that the RRC reconfiguration message is the last message delivered to the remote UE 803 via the relay UE 805 to the source gNB-DU 807. At 832, the source gNB-DU 807 sends an RRC message (i.e., the RRC reconfiguration message) and another indication (also referred to as a fourth indication) to the relay UE 805. The fourth indication indicates to the relay UE 805 that the received RRC message is the last message delivered to the remote UE 803 via the relay UE 805. For example, the third indication and the fourth indication described above may be sent in an SRAP PDU header or an SRAP C-PDU. Then, at 834, the relay UE 805 sends the RRC reconfiguration message for the remote UE 803 to the remote UE 803. At 836, when the last RRC reconfiguration message has been delivered to the remote UEs 801 and 803, the relay UE 905 knows that the remote UEs 801 and 803 are ready for their reconfiguration and then detaches from the source gNB-CU 809. Figures 2 to 4 All operations and features described are equally applicable to process 800 and have similar effects. For the sake of simplicity, details will be omitted.

[0120] Fig. 9 Other example processes for mobility support in a U2N relay with multiple remote UEs are illustrated with reference to some other example embodiments of the present disclosure. For discussion purposes, process 900 will refer to Figure 1AIn this case, the remote terminal device 140 is implemented by a remote UE 901. The process 900 involves remote UEs 902 and 903. The relay terminal device 130 is implemented by a relay UE 903. The network element 120 is implemented by a DU of a source gNB (also denoted as source gNB-DU) 907. The network element 110 is implemented by a CU of a source gNB (also denoted as source gNB-CU) 909.

[0121] like Fig. 9 As shown, at 910, remote UEs 901-903 are connected to relay UE 905 and are also connected to source gNB-CU 909 via source gNB-DU 907. At 912-916, remote UEs 901-903 send measurement reports to source gNB-CU 909. Then, at 918, source gNB-CU 909 decides to handover relay UE 905 and remote UEs 901 and 902 together. For example, source gNB-CU 909 may make this decision based on QoS or other feature requirements of the services of the respective remote UEs relayed by relay UE 905. In this case, the QoS or other features of the relayed services of remote UEs 901 and 903 relayed by relay UE 905 may require low service interruption, and thus source gNB-CU 909 may configure relay UE 905 to wait for an indication related to the delivery of the last RRC message of each remote UE 901 and 903 from the gNB. In addition, the QoS or other features of the relay service of the remote UE 902 relayed by the relay UE 905 may not require low service interruption, and therefore the source gNB-CU 909 may hand over the remote UE 902 to a different target gNB, or to the same target gNB but with possible interruption.

[0122] At 920, the source gNB-CU 909 initiates a handover preparation procedure for the relay UE 905 and the remote UEs 901 and 903. At 922, the source gNB-CU 909 sends an RRC message (e.g., an RRC reconfiguration message) to the relay UE 905 via the source gNB-DU 907, the RRC message requesting the relay UE 905 to wait for an indication from each of the remote UEs 901 and 903 of the gNB indicating that the corresponding last RRC message is the last message to be received or delivered to the corresponding remote UE before detaching from the source gNB-CU 909.

[0123] At 924, the source gNB-CU 909 sends an F1 Application Protocol (F1AP) message for the remote UE 901 to the source gNB-DU 907, including an RRC reconfiguration message for the remote UE 901. The RRC reconfiguration message includes an indication that the remote UE 901 sent an indication of the last message delivered to the relay UE 905 upon receiving the RRC reconfiguration message, which causes the remote UE 901 to send another indication (e.g., a ready indication) to the relay UE 905. At 926, the source gNB-DU 907 sends the RRC reconfiguration message for the remote UE 901 to the relay UE 905. Then at 928, the relay UE 905 sends an RRC reset message for the remote UE 901 to the remote UE 901. At 930, the remote UE 901 sends another indication (e.g., a ready indication) to the relay UE 905 that the last message was delivered to the remote UE 901.

[0124] Similarly, at 932, the source gNB-CU 909 sends an F1 Application Protocol (F1AP) message for the remote UE 903 to the source gNB-DU 907, including an RRC reconfiguration message for the remote UE 903. The RRC reconfiguration message includes an indication that the remote UE 903 sent an indication of the last message delivered to the relay UE 905 upon receiving the RRC reconfiguration message, which causes the remote UE 903 to send another indication (e.g., a ready indication) to the relay UE 905. At 934, the source gNB-DU 907 sends the RRC reconfiguration message for the remote UE 903 to the relay UE 905. Then, at 936, the relay UE 905 sends the RRC reconfiguration message for the remote UE 903 to the remote UE 903. At 938, the remote UE 903 sends another indication (e.g., a ready indication) to the relay UE 905 that the last message was delivered to the remote UE 903. At 940, the relay UE 905 knows that the remote UEs 901 and 903 have received the corresponding RRC reconfiguration messages (e.g., preparing their reconfiguration), and then detach from the source gNB-CU 909. Figure 5 All operations and features described are equally applicable to process 900 and have similar effects. For the sake of simplicity, details will be omitted.

[0125] Fig.10 A flowchart 1000 of a method implemented at a network device 105 according to some embodiments of the present disclosure is illustrated. For discussion purposes, the method 1000 will refer to Figure 1A It is described from the perspective of network device 105 .

[0126] At block 1010, the network device 105 determines to switch the relay terminal device 130 from the network device 105 to the target network device. At block 1020, the network device 105 determines a reconfiguration of the remote terminal device 140 associated with the relay terminal device 130, the reconfiguration being caused by the switch. At block 1030, the network device 105 sends a first radio resource control message to the relay terminal device 130, the first radio resource control message requesting the relay terminal device 130 to detach from the network device 105 based on determining that the last message for the remote terminal device 140 was received from the network device 105 or delivered to the remote terminal device 140.

[0127] In some example embodiments, network device 105 sends to relay terminal device 130 a second radio resource control message for reconfiguration of remote terminal device 140 and an indication that the second radio resource control message is the last message delivered to remote terminal device 140 via the relay terminal device.

[0128] In some example embodiments, the network device 105 sends an indication to the relay terminal device in a header of a Sidelink Relay Adaptation Protocol SRAP, a Protocol Data Unit PDU, or in a SRAP Control PDU C-PDU.

[0129] In some example embodiments, network device 105 sends a second radio resource control message for reconfiguration of remote terminal device 140 to remote terminal device 140 via relay terminal device 130, the second radio resource control message including an indication of an indication of a last message delivered to relay terminal device 130 sent by remote terminal device 140 upon receiving the second radio resource control message.

[0130] In some example embodiments, the first radio resource control message includes a configuration for a timer that may define a maximum duration for the relay terminal device 130 to determine that the last message was received from the network device 105 or delivered to the remote terminal device 140, and wherein the first radio resource control message further indicates that the relay terminal device 130 is detached from the network device 105 based on the expiration of the timer.

[0131] In some example embodiments, the second radio resource control message for the remote terminal device 140 is a reconfiguration message including at least one of the following: configuring the remote terminal device 140 to switch to and connect with the target network device via the relay terminal device 130; configuring the remote terminal device 140 to switch to the target network device or another target network device, and connect with the target network device or another target network; configuring the remote terminal device 140 to directly connect to the network device 105, or the target network device, or another target network device; and configuring the remote terminal device 140 to perform path switching via another relay terminal device 130 to connect to the network device 105.

[0132] In some example embodiments, the network device 105 determines a plurality of reconfigurations of a plurality of remote terminal devices associated with the relay terminal device 130 , the remote terminal device 140 being one of the plurality of remote terminal devices.

[0133] In some example embodiments, the first radio resource control message requests the relay terminal device 130 to detach from the network device 105 based on determining that a respective last message for each of the plurality of remote terminal devices was received from the network device 105 or delivered to the respective remote terminal device.

[0134] Fig.11 FIG. 1 is a flowchart of a method implemented at a relay terminal device 130 according to some other exemplary embodiments of the present disclosure. For the purpose of discussion, the method 1100 will refer to Figure 1A It is described from the perspective of the relay terminal device 130 .

[0135] In block 1110, the relay terminal device 130 receives a first radio resource control message from the network device 105 to switch from the network device 105 to the target network device, the first radio resource control message requesting the relay terminal device to detach from the network device 105 based on determining that the last message for the remote terminal device 140 associated with the relay terminal device 130 was received from the network device 105 or delivered to the remote terminal device 140. In block 1120, the relay terminal device 130 detaches from the network device 105 based on determining that the last message was received from the network device 105 or delivered to the remote terminal device 140.

[0136] In some example embodiments, the relay terminal device 130 receives from the network device 105 a second radio resource control message for the remote terminal device 140, and an indication that the second radio resource control message is the last message delivered to the remote terminal device 140 via the relay terminal device 130, and sends the second radio resource control message to the remote terminal device 140. In addition, the relay terminal device 130 detaches from the network device 105 after receiving the indication from the network device 105.

[0137] In some example embodiments, the relay terminal device 130 receives the indication in a header of a Sidelink Relay Adaptation Protocol SRAP, a Protocol Data Unit PDU, or in a SRAP Control PDU C-PDU.

[0138] In some example embodiments, relay terminal device 130 receives an indication from remote terminal device 140 that the last message was delivered to terminal device 140 and relay terminal device 130 detaches from network device 105 after receiving the indication from remote terminal device 140 .

[0139] In some example embodiments, an indication is received from the remote terminal device 140 via a sidelink connection between the relay terminal device 130 and the remote terminal device 140 in one of the following: sidelink radio resource control RRC signaling; sidelink media access control MAC control element CE; a header, protocol data unit PDU of a sidelink relay adaptation protocol SRAP; or a SRAP control PDU C-PDU.

[0140] In some example embodiments, the first radio resource control message requests the relay terminal device 130 to detach from the network device 105 based on determining that a corresponding last message for each of the multiple remote terminal devices is received from the network device 105 or delivered to the corresponding remote terminal device, and the remote terminal device 140 is one of the multiple remote terminal devices.

[0141] In some example embodiments, the relay terminal device 130 is detached from the network device 105 based on determining that a respective last message for each of the plurality of remote terminal devices was received from the network device 105 or delivered to the respective remote terminal device.

[0142] In some example embodiments, the first radio resource control message includes a configuration for a timer that may define a maximum duration for the relay terminal device 130 to determine that the last message was received from the network device 105 or delivered to the remote terminal device 140, wherein the first radio resource control message also indicates that the relay terminal device 130 is detached from the network device 105 based on the expiration of the timer.

[0143] Fig.12 FIG. 1 is a flowchart of a method implemented at a remote terminal device 140 according to some other exemplary embodiments of the present disclosure. For the purpose of discussion, the method 1200 will refer to Figure 1A It is described from the perspective of the remote terminal device 140.

[0144] In block 1210, the terminal device 140 receives a second radio resource control message for reconfiguration of the remote terminal device 140 from the network device 105 via the relay terminal device 130 associated with the remote terminal device 140, the second radio resource control message indicating that the remote terminal device sends an indication of last message delivery to the relay terminal device upon receiving the second radio resource control message. In block 1220, the remote terminal device 140 sends an indication that the last message was delivered to the remote terminal device 140 to the relay terminal device 130.

[0145] In some example embodiments, the remote terminal device 140 sends an indication to the relay terminal device 130 via a sidelink connection between the relay terminal device 130 and the remote terminal device 140, in one of the following: sidelink radio resource control RRC signaling; sidelink media access control MAC control element CE; a header, protocol data unit PDU of a sidelink relay adaptation protocol SRAP; or a SRAP control PDU C-PDU.

[0146] In some example embodiments, the reconfiguration of the remote terminal device 140 includes at least one of the following: configuring the remote terminal device 140 to switch to the target network device and connect to the target network device via the relay terminal device 130; configuring the remote terminal device 140 to switch to the target network device and connect to the target network device via another relay terminal device; configuring the remote terminal device 140 to directly connect to the network device 105 or the target network device; and configuring the remote terminal device 140 to perform path switching to connect to the network device 105 via another relay terminal device.

[0147] In some example embodiments, an apparatus capable of executing method 1000 (e.g., network device 105) includes a component for executing the corresponding steps of method 1000. The component may be implemented in any suitable form. For example, the component may be implemented in a circuit device or a software module.

[0148] In some example embodiments, an apparatus includes: a component for determining at a network device to switch a relay terminal device from the network device to a target network device; a component for determining a reconfiguration of a remote terminal device associated with the relay terminal device, the reconfiguration being caused by the switching; and a component for sending a first radio resource control message to the relay terminal device, the first radio resource control message requesting the relay terminal device to detach from the network device based on determining that a last message for the remote terminal device was received from the network device or delivered to the remote terminal device.

[0149] In some example embodiments, the apparatus further comprises means for sending to the relay terminal device a second radio resource control message for reconfiguration of the remote terminal device and an indication that the second radio resource control message is the last message to be delivered to the remote terminal device via the relay terminal device.

[0150] In some example embodiments, the apparatus further comprises means for sending an indication to the relay terminal device in a header of a Sidelink Relay Adaptation Protocol (SRAP), a Protocol Data Unit (PDU), or in a SRAP Control PDU (C-PDU).

[0151] In some example embodiments, the apparatus further comprises means for sending a second radio resource control message for reconfiguration of the remote terminal device to the remote terminal device via the relay terminal device, the second radio resource control message comprising an indication of an indication of a last message delivered to the relay terminal device sent by the remote terminal device upon receiving the second radio resource control message.

[0152] In some example embodiments, the first radio resource control message includes a configuration for a timer that may define a maximum duration for the relay terminal device to determine that the last message was received from the network device or delivered to the remote terminal device, wherein the first radio resource control message further indicates that the relay terminal device is detached from the network device based on expiration of the timer.

[0153] In some example embodiments, the second radio resource control message for the remote terminal device is a reconfiguration message including at least one of the following: configuring the remote terminal device to switch to a target network device and connect to the target network device via a relay terminal device; configuring the remote terminal device to switch to the target network device or another target network device and connect to the target network device or another target network via another relay terminal device; configuring the remote terminal device to directly connect to the network device, or the target network device, or another target network device; and configuring the remote terminal device to perform path switching to connect to the network device via another relay terminal device.

[0154] In some example embodiments, the means for determining a reconfiguration of a remote terminal device associated with the relay terminal device includes means for determining multiple reconfigurations of multiple remote terminal devices associated with the relay terminal device, the remote terminal device being one of the multiple remote terminal devices.

[0155] In some example embodiments, the first radio resource control message requests the relay terminal device to detach from the network device based on determining that a respective last message of each remote terminal device of the plurality of remote terminal devices is delivered to the respective remote terminal device.

[0156] In some example embodiments, the apparatus further comprises means for performing other steps in some embodiments of method 1000. In some embodiments, the means comprises at least one processor and at least one memory comprising computer program code. The at least one memory and the computer program code are configured to enable execution of the apparatus with the at least one processor.

[0157] In some example embodiments, a device capable of executing method 1100 may include a component for executing the corresponding steps of method 1100. The component may be implemented in any suitable form. For example, the component may be implemented in a circuit device and a software module.

[0158] In some example embodiments, an apparatus includes: a component for receiving, at a relay terminal device, a first radio resource control message from a network device for switching from the network device to a target network device, the first radio resource control message requesting the relay terminal device to detach from the network device based on determining that a last message for a remote terminal device associated with the relay terminal device was received from the network device or delivered to the remote terminal device; and a component for detaching from the network device based on determining that a last message was received from the network device or delivered to the remote terminal device.

[0159] In some example embodiments, the apparatus further comprises means for receiving from the second network device a second radio resource control message for the remote terminal device and an indication that the second radio resource control message is the last message delivered to the remote terminal device via the relay terminal device; and means for sending the second radio resource control message to the remote terminal device. The means for detaching from the network device comprises means for detaching from the network device after receiving the indication from the network device.

[0160] In some example embodiments, the means for receiving the indication includes means for receiving the indication from the network device in a header of a Sidelink Relay Adaptation Protocol (SRAP), a Protocol Data Unit (PDU), or in a SRAP Control PDU (C-PDU).

[0161] In some example embodiments, the apparatus includes means for receiving an indication from the remote terminal device that a last message was delivered to the remote terminal device. The means for detaching from the network device includes means for detaching from the network device after receiving a third indication from the remote terminal device.

[0162] In some example embodiments, the component for receiving an indication includes receiving an indication from the remote terminal device through a sidelink connection between the relay terminal device and the remote terminal device, in one of the following: sidelink radio resource control RRC signaling; sidelink media access control MAC control element CE; a header, protocol data unit PDU of a sidelink relay adaptation protocol SRAP; or a SRAP control PDU C-PDU.

[0163] In some example embodiments, the first radio resource control message requests the relay terminal device to detach from the network device based on determining that a respective last message for each of the plurality of remote terminal devices was received from the network device or delivered to the respective remote terminal device.

[0164] In some example embodiments, means for detaching from the network device includes means for detaching from the network device based on determining that a respective last message for a remote terminal device of the plurality of remote terminal devices was received from the network device or delivered to the respective remote terminal device.

[0165] In some example embodiments, the first radio resource control message includes a configuration for a timer that defines a maximum duration for a relay terminal device to determine that a last message was received from a network device or delivered to a remote terminal device, and the apparatus further includes a component for detaching from the network device based on expiration of the timer.

[0166] In some example embodiments, the apparatus further comprises means for performing other steps in some embodiments of method 1100. In some embodiments, the means comprises at least one processor and at least one memory comprising computer program code. The at least one memory and the computer program code are configured to enable execution of the apparatus using the at least one processor.

[0167] In some example embodiments, an apparatus capable of executing method 1200 (e.g., remote terminal equipment 140) may include components for executing the corresponding steps of method 1200. The components may be implemented in any suitable form. For example, the components may be implemented in a circuit device or a software module.

[0168] In some example embodiments, the apparatus includes: a component for receiving, at a remote terminal device, a second radio resource control message for reconfiguration of the remote terminal device from a network device via a relay terminal device associated with the remote terminal device, the second radio resource control message indicating that the remote terminal device sends an indication of last message delivery to the relay terminal device upon receiving the second radio resource control message; and a component for sending an indication to the relay terminal device that the last message was delivered to the remote terminal device.

[0169] In some example embodiments, the component for sending an indication includes: a component for sending an indication to the relay terminal device through a sidelink connection between the relay terminal device and the remote terminal device, in one of the following: sidelink radio resource control RRC signaling; sidelink media access control MAC control element CE; a header, a protocol data unit PDU of a sidelink relay adaptation protocol SRAP; or a SRAP control PDU C-PDU.

[0170] In some example embodiments, the reconfiguration of the remote terminal device includes at least one of the following: configuring the remote terminal device to switch to a target network device and connect to the target network device via a relay terminal device; configuring the remote terminal device to switch to a target network device and connect to the target network device via another relay terminal device; configuring the remote terminal device to directly connect to the network device or the target network device; and configuring the remote terminal device to perform path switching to connect to the network device via another relay terminal device.

[0171] In some example embodiments, the apparatus further comprises means for performing, in some embodiments, the other steps of method 1200. In some embodiments, the means comprises at least one processor and at least one memory comprising computer program code. The at least one memory and the computer program code are configured to cause execution of the apparatus together with the at least one processor.

[0172] Fig.13 1 shows a simplified block diagram of a device 1300 suitable for implementing some example embodiments of the present disclosure. The device 1300 may be provided to implement a communication device, such as Figure 1A The network device 105, the relay terminal device 130, or the remote terminal device 140 is shown. As shown, the device 1300 includes one or more processors 1310, one or more memories 1320 coupled to the processor 1310, and one or more communication modules 1340 coupled to the processor 1310.

[0173] The communication module 1340 is used for two-way communication. The communication module 1340 has at least one antenna to facilitate communication. The communication interface may represent any interface required to communicate with other network elements.

[0174] Processor 1310 may be of any type suitable for the local technology network, and may include, as non-limiting examples, one or more of the following: 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 1300 may have multiple processors, such as application specific integrated circuit chips that are time slaved to a clock synchronized with a main processor.

[0175] The memory 1320 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memories include, but are not limited to, read-only memory (ROM) 1324, electrically programmable read-only memory (EPROM), flash memory, hard disk, compact disk (CD), digital video disk (DVD), and other magnetic and / or optical memories. Examples of volatile memories include, but are not limited to, random access memory (RAM) 1322 and other volatile memories that do not persist during power outages.

[0176] Computer program 1330 includes computer executable instructions executed by associated processor 1310. Program 1330 may be stored in ROM 1324. Processor 1310 may perform any suitable actions and processes by loading program 1330 into RAM 1322.

[0177] The embodiments of the present disclosure may be implemented by the program 1330 so that the device 1300 may execute the reference Figures 2 to 12 Any process of the present disclosure discussed. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0178] In some example embodiments, the program 1330 may be tangibly embodied in a computer-readable medium that may be included in the device 1300 (such as in the memory 1320) or in other storage devices accessible to the device 1300. The device 1300 may load the program 1330 from the computer-readable medium to the RAM 1322 for execution. The computer-readable medium may include any type of tangible non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc.

[0179] Fig.14 A block diagram of an example of a computer readable medium 1400 according to some example embodiments of the present disclosure is illustrated. The computer readable medium 1400 has stored thereon the program 1330. It is noteworthy that although the computer readable medium 1400 is shown in the form of a CD or DVD, the computer readable medium 1400 may be in any other form suitable for carrying or storing the program 730.

[0180] Generally, various embodiments of the present disclosure may be implemented using hardware or dedicated circuits, software, logic, or any combination thereof. Some aspects may be implemented using hardware, while other aspects may be implemented using firmware or software that may be executed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of the present disclosure are shown and described as block diagrams, flow charts, or using some other graphical representations, it should be understood that, as non-limiting examples, the blocks, devices, systems, techniques, or methods described herein may be implemented using hardware, software, firmware, dedicated circuits or logic, general-purpose hardware or controllers or other computing devices, or some combination thereof.

[0181] 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, such as instructions included in a program module, which are executed in a device on a target real or virtual processor to perform the above reference Fig.10 and Fig.12 The method described. Typically, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform specific tasks or implement specific abstract data types. In various embodiments, the functions of program modules can be combined or split between program modules as needed. The machine executable instructions of program modules can be executed in local or distributed devices. In distributed devices, program modules can be located in both local and remote storage media.

[0182] The program code for performing the disclosed method can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer or other programmable data processing device so that the program code, when executed by a processor or controller, enables the function / operation specified in the flow chart and / or block diagram to be realized. The program code can be executed completely on the machine, partially on the machine, as an independent software package, partially on the machine and partially on a remote machine, or completely on a remote machine or server.

[0183] In the context of the present disclosure, computer program codes or related data may be carried by any suitable carrier to enable a device, apparatus or processor to perform various processes and operations as described above. Examples of carriers include signals, computer readable media, etc.

[0184] Computer readable medium can be a computer readable signal medium or a computer readable storage medium. Computer readable medium can include but is not limited to electronic, magnetic, optical, electromagnetic, infrared or semiconductor systems, devices or equipment, or any suitable combination of the foregoing. A more specific example of a computer readable storage medium will include an electrical connection with one or more wires, a portable computer floppy 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 portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. The term "non-transient" used herein is a restriction on the medium itself (i.e., tangible, rather than a signal), rather than a restriction on data storage persistence (e.g., RAM and ROM).

[0185] In addition, although the operations are described in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown or in order or performing all the operations shown to obtain the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, although several specific implementation details are included in the above discussion, these should not be interpreted as limitations on the scope of the present disclosure, but rather descriptions of features that may be specific to a particular embodiment. Certain features described in the context of a separate embodiment may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable sub-combination.

[0186] Although the present disclosure has been described in language specific to structural features and / or methodological acts, it should be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Instead, the specific features or acts described above are disclosed as example forms of implementing the claims.

Claims

1. A network device, comprising: at least one processor; as well as at least one memory storing instructions, which, when executed by the at least one processor, cause the network device to at least: Determining to switch the relay terminal device from the network device to the target network device; determining a reconfiguration of a remote terminal device associated with the relay terminal device, the reconfiguration being caused by the switching; as well as A first radio resource control message is sent to the relay terminal device, the first radio resource control message requesting the relay terminal device to detach from the network device based on determining that a last message for the remote terminal device was received from the network device or delivered to the remote terminal device.

2. The network device according to claim 1, wherein the network device is further configured to: A second radio resource control message for the reconfiguration of the remote terminal is sent to the relay terminal device, together with an indication that the second radio resource control message is the last message delivered to the remote terminal device via the relay terminal device.

3. The network device of claim 2, wherein the network device is caused to send the indication by: The indication is sent to the relay terminal device in a header of a sidelink relay adaptation protocol SRAP, a protocol data unit PDU, or in a SRAP control PDU C-PDU.

4. The network device according to claim 1, wherein the network device is further configured to: A second radio resource control message for the reconfiguration of the remote terminal device is sent to the remote terminal device via the relay terminal device, the second radio resource control message comprising an indication that the remote terminal device sends a last message delivery indication to the relay terminal device upon receiving the second radio resource control message.

5. A network device according to any one of claims 1 to 4, wherein the first radio resource control message includes a configuration for a timer, the timer definition is used by the relay terminal device to determine the maximum duration of the last message received from the network device or delivered to the remote terminal device, and wherein the first radio resource control message also indicates: the relay terminal device is separated from the network device based on the expiration of the timer.

6. The network device according to any one of claims 1 to 5, wherein the second radio resource control message for the remote terminal device is a reconfiguration message including at least one of the following: configuring the remote terminal device to switch to the target network device and connect to the target network device via the relay terminal device; configuring the remote terminal device to switch to the target network device or another target network device, and connect to the target network device or another target network via another relay terminal device; configuring the remote terminal device to connect directly to the network device, or the target network device, or another target network device; as well as The remote terminal device is configured to perform path switching to connect to the network device via another relay terminal device.

7. The network device according to any one of claims 1 to 6, wherein the network device is caused to determine the reconfiguration of the remote terminal device associated with the relay terminal device by: A plurality of reconfigurations of a plurality of remote terminal devices associated with the relay terminal device are determined, the remote terminal device being one of the plurality of remote terminal devices.

8. The network device according to claim 7, wherein the first radio resource control message requests the relay terminal device to detach from the network device based on determining that the corresponding last message for each of the multiple remote terminal devices is received from the network device or delivered to the corresponding remote terminal device.

9. A relay terminal device, comprising: at least one processor; as well as At least one memory storing instructions, wherein when the instructions are executed by the at least one processor, the relay terminal device at least: receiving, from a network device, a first radio resource control message for handing over from the network device to a target network device, the first radio resource control message requesting the relay terminal network to detach from the network device based on determining that a last message for a remote terminal device associated with the relay terminal device was received from the network device or delivered to the remote terminal device; as well as Based on determining that the last message was received from the network device or delivered to the remote terminal device, detaching from the network device.

10. The relay terminal device according to claim 9, wherein the relay terminal device is further configured to: receiving from the network device a second radio resource control message for the remote terminal device and an indication that the second radio resource control message is the last message delivered to the remote terminal device via the relay terminal device; and sending the second radio resource control message to the remote terminal equipment, and The relay terminal device is separated from the network device by: The method further comprises separating from the network device after receiving the indication from the network device.

11. The relay terminal device according to claim 10, wherein the relay terminal device is caused to receive the indication by: The indication is received from the network device in a Sidelink Relay Adaptation Protocol (SRAP) header, a Protocol Data Unit (PDU), or in a SRAP Control PDU (C-PDU).

12. The relay terminal device according to claim 9, wherein the relay terminal device is further configured to: receiving from the remote terminal equipment an indication that the last message was delivered to the remote terminal equipment, and The relay terminal device is separated from the network device by: The method further comprises separating from the network device after receiving the instruction from the remote terminal device.

13. The relay terminal device according to claim 12, wherein the relay terminal device is caused to receive the indication by: The indication is received from the remote terminal device via a sidelink connection between the relay terminal device and the remote terminal device in one of the following: Sidelink Radio Resource Control RRC signaling; Sidelink media access control MAC control element CE; The header and protocol data unit (PDU) of the Sidelink Relay Adaptation Protocol (SRAP); or SRAP controls PDU C-PDU.

14. A relay terminal device according to any one of claims 9 to 13, wherein the first radio resource control message requests the relay terminal device to detach from the network device based on determining that the corresponding last message for each of a plurality of remote terminal devices is received from the network device or delivered to the corresponding remote terminal device, the remote terminal device being one of the plurality of remote terminal devices.

15. The relay terminal device according to claim 14, wherein the relay terminal device is caused to be separated from the network device by: Based on determining that the corresponding last message for each of the plurality of remote terminal devices was received from the network device or delivered to the corresponding remote terminal device, detaching from the network device.

16. The relay terminal device according to any one of claims 9 to 15, wherein the first radio resource control message includes a configuration for a timer, the timer defining a maximum duration for the relay terminal device to determine that the last message for the reconfiguration was received from the network device or delivered to the remote terminal device, and the relay terminal device is further caused to: Based on expiration of the timer, detaching from the network device.

17. A remote terminal device, comprising: at least one processor; as well as at least one memory storing instructions, which, when executed by at least one of the processors, cause the remote terminal device to at least: receiving, from a network device via a relay terminal device associated with the remote terminal device, a second radio resource control message for reconfiguration of the remote terminal device, the second radio resource control message instructing the remote terminal device to send an indication of last message delivery to the relay terminal device upon receiving the second radio resource control message; as well as An indication that the last message was delivered to the remote terminal device is sent to the relay terminal device.

18. The remote terminal device according to claim 17, wherein the remote terminal device is caused to send the indication by: The indication is sent to the relay terminal device through a sidelink connection between the relay terminal device and the remote terminal device in one of the following: Sidelink Radio Resource Control RRC signaling; Sidelink media access control MAC control element CE; The header and protocol data unit (PDU) of the Sidelink Relay Adaptation Protocol (SRAP); or SRAP controls PDU C-PDU.

19. The remote terminal device according to claim 17 or 18, wherein the reconfiguration of the remote terminal device comprises at least one of the following: Configuring the remote terminal device to switch to the target network device and connect to the target network device via the relay terminal device; Configuring the remote terminal device to switch to the target network device and connect to the target network device via another relay terminal device; Configuring the remote terminal device to directly connect to the network device or the target network device; as well as The remote terminal device is configured to perform path switching to connect to the network device via another relay terminal device.

20. A method comprising: At the network device, determining to switch the relay terminal device from the network device to the target network device; determining a reconfiguration of a remote terminal device associated with the relay terminal device, the reconfiguration being caused by the switching; as well as A first radio resource control message is sent to the relay terminal device, the first radio resource control message requesting the relay terminal device to detach from the network device based on determining that a last message for the remote terminal device was received from the network device or delivered to the remote terminal device.

21. A method comprising: receiving, at a relay terminal device, from a network device a first radio resource control message for switching from the network device to a target network device, the first radio resource control message requesting the relay terminal device to detach from the network device based on determining that a last message for a remote terminal device associated with the relay terminal device was received from the network device or delivered to the remote terminal device; as well as Disengaging from the network device based on determining that the last message was received from the network device or delivered to the remote terminal device.

22. A method comprising: receiving, at a remote terminal device, a last message for reconfiguration of the relay terminal device from a network device via a relay terminal device associated with the remote terminal device, the last message indicating that the remote terminal device sends an indication to the relay terminal device that the last message is delivered to the remote terminal device; as well as The indication that the last message was delivered to the remote terminal device is sent to the relay terminal device.

23. An apparatus comprising: A component for determining at a network device to switch a relay terminal device from the network device to a target network device; means for determining a reconfiguration of a remote terminal device associated with the relay terminal device, the reconfiguration being caused by the switching; as well as means for sending a first radio resource control message to the relay terminal device, the first radio resource control message requesting the relay terminal device to detach from the network device based on determining that a last message for the remote terminal device was received from the network device or delivered to the remote terminal device.

24. An apparatus comprising: means for receiving, at a relay terminal device, from a network device a first radio resource control message for handover from the network device to a target network device, the first radio resource control message requesting the relay terminal device to detach from the network device based on determining that a last message for the remote terminal device associated with the relay terminal device was received from the network device or delivered to the remote terminal device; as well as Means for detaching from the network device based on determining that the last message was received from the network device or delivered to the remote terminal device.

25. An apparatus comprising: means for receiving, at a remote terminal device, from a network device via a relay terminal device associated with the remote terminal device, a last message for reconfiguration of the remote terminal device, the last message indicating that the remote terminal device sends to the relay terminal device an indication that the last message is delivered to the remote terminal device; as well as The method is used for sending an indication to the relay terminal device that the last message is delivered to the remote terminal device.

26. A non-transitory computer-readable medium comprising program instructions for causing an apparatus to at least perform the method according to any one of claims 20 to 22.

Images