Communication method, system, and related device

Abstract

The present application relates to the technical field of communications. Provided are a communication method, a system and a related device, which are used for solving the problem of an increased delay caused by security key update when performing a cell handover between different base stations. The method provided in the present application comprises: in a cell handover process of a terminal device from a first base station to a second base station, determining whether the second base station is a non-anchor base station that is connected to a core network by means of the first base station; and if the second base station is a non-anchor base station that is connected to the core network by means of the first base station, cancelling security key update. On the basis of the method, the present application can reduce a delay of cell handover between different base stations by cancelling security key update.

Description

Communication method, system and related device

[0001] The present application claims priority to the Chinese Patent Application No. 202411402628.4, filed on September 30, 2024, and entitled "Communication method, system and related device", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of communication technology, in particular to a communication method, system and related device. BACKGROUND

[0003] The development of current mobile communication networks is constantly evolving towards high frequencies, and high-frequency cells have small coverage ranges, and terminal devices face more frequent cell reselection and handover. In 5G-A (5G Advance), a new handover procedure is introduced to reduce service interruption time for the above scenarios, which is called L1 / L2 triggered mobility (LTM, L1 / L2 Triggered Mobility). In Release 18, LTM is supported between different cells in one base station. LTM reduces the mobility latency by allowing the terminal device to synchronize with the target cell in advance. In Release 19, the LTM framework will be extended to support handover between cells in different base stations. Under the current network deployment architecture, when a terminal device performs inter-base station cell handover, access layer security key update is required. The signaling interaction and processing in the security key update process will bring additional latency, which is contrary to the purpose of reducing handover latency. SUMMARY

[0004] The present application provides a communication method, system and related device to achieve the purpose of reducing the latency caused by security key update in inter-base station cell handover.

[0005] A first aspect of the present application provides a communication method applied to a first base station, the first base station being a base station that has established a connection with a terminal device, and the first base station being an anchor base station, the anchor base station being a relay node base station between other base stations and a core network. The method comprises: determining whether a second base station is a non-anchor base station connected to the core network through the first base station during a cell handover process of the terminal device from the first base station to the second base station; and canceling security key update if the second base station is a non-anchor base station connected to the core network through the first base station.

[0006] When the terminal device is handed over from the first base station to the second base station, if the second base station is a non-anchor base station connected to the core network through the first base station, the security key update is cancelled. In the cell handover, the update of the security key increases the processing delay of the terminal device and the base station, and increases the mobility interruption time and the handover delay. The method provided in the present application can keep the PDCP layer connection of the security key unchanged in the anchor base station when the above conditions are met, and the terminal device and the base station continue to use the original security key, so that the security key update can be cancelled, and the processing delay and the mobility interruption time can be reduced. In the method provided in the present application, the security key update can be cancelled by continuing to use the original security key. In the method provided in the present application, the process of determining whether the second base station is a non-anchor base station connected to the core network through the first base station is performed outside the mobility interruption time, in the configuration and processing time in the early stage, so as to reduce the cell handover delay between base stations. At the same time, after the handover is performed in the embodiment, the second base station does not need to perform path change to the access and mobility management function AMF (Access and Mobility Management Function), and the core network does not need to update the downlink GPRS tunneling protocol user plane GTP-U (GPRS Tunneling Protocol), and the GTP-U address on the access network side is still the address of the first base station, thereby reducing the complexity of the handover.

[0007] In some optional embodiments, the cell handover includes an LTM cell handover.

[0008] In some optional embodiments, before determining whether the second base station is a non-anchor base station connected to the core network through the first base station, the method further includes: generating anchor connection relationship information, and the candidate target base station includes the second base station; and determining whether the second base station is a non-anchor base station connected to the core network through the first base station includes: determining whether the second base station is a non-anchor base station according to the anchor connection relationship information.

[0009] In the scheme provided in the present application, the first base station can determine the anchor information and generate the anchor connection relationship information by itself, reduce the signaling and data interaction between the first base station and the candidate target base station, and reduce the complexity.

[0010] In some optional embodiments, the anchor connection relationship information includes at least one of the following: an anchor connection relationship between the first base station and the candidate target base station; and an anchor connection relationship between the candidate target base stations.

[0011] The anchor connection relationship between the first base station and the candidate target base station can include an anchor connection relationship between the first base station and at least one candidate target base station. The anchor connection relationship between the candidate target base stations includes an anchor connection relationship between at least two candidate target base stations.

[0012] In some optional embodiments, before the anchor connection relationship information is generated, the method further includes: obtaining capability information of the terminal device supporting inter-base-station cell handover without security key update.

[0013] In some optional embodiments, before the anchor connection relationship information between the candidate target base station and the first base station is generated, the method further includes: sending an anchor information request to the candidate target base station, the anchor information request being used to obtain information about whether the candidate target base station is a non-anchor base station; receiving an anchor information request response sent by the candidate target base station, the anchor information request response including anchor information of the candidate target base station; or, receiving anchor information sent by the candidate target base station.

[0014] In addition to the anchor connection relationship information being determined by the original base station itself, the anchor connection relationship information can also be determined by the original base station through interaction with the candidate target base station. The anchor information in the present application can include the base station type of the candidate target base station, i.e., whether it is an anchor base station or a non-anchor base station, and the connection relationship between the candidate target base station and other base stations. Alternatively, the anchor information includes the base station type of the candidate target base station, i.e., whether it is an anchor base station or a non-anchor base station.

[0015] In some optional embodiments, the anchor information request is carried by an LTM cell handover request, and the anchor information request response is carried by an LTM cell handover response request.

[0016] The anchor information request and the anchor information request response multiplex the existing process, saving resources.

[0017] In some optional embodiments, after the anchor connection relationship information between the candidate target base station and the first base station is generated, the method further includes: sending the anchor connection relationship information to the terminal device, so that: if the terminal device determines, according to the anchor connection relationship information, that the first base station is an anchor base station and the second base station is a non-anchor base station connected to the core network through the first base station, the terminal device cancels the security key update; or, after the terminal device is handed over from the first base station to the second base station, and during the cell handover process from the second base station to the third base station again, if the terminal device determines, according to the anchor connection relationship information, that the second base station is a non-anchor base station connected to the core network through the first base station, the terminal device cancels the security key update. After the first base station generates the anchor connection relationship information, the first base station sends the information to the terminal device, so that the terminal device can determine whether to cancel the security key update according to the information.

[0018] In some optional embodiments, the anchor connection relationship information is carried by a radio resource control (RRC) reconfiguration message.

[0019] The anchor connection relationship information is multiplexed in the RRC reconfiguration message in the existing procedure, thereby saving resources.

[0020] In some optional embodiments, after determining whether the second base station is a non-anchor base station connected to the core network through the first base station, the method further comprises: sending the anchor connection relationship information to the candidate target base station.

[0021] The anchor connection relationship information is sent to the candidate target base station so as to be synchronized to the candidate target base station, and in a subsequent continuous handover scenario, the candidate target base station can determine whether to cancel the key update according to the information. For example, after the terminal device switches to the second base station, the second base station can determine whether to perform security key update in subsequent handover according to the received anchor connection relationship information, without repeating the acquisition of the anchor connection relationship information. In this way, the time delay of acquiring the anchor connection relationship information in subsequent handover can be reduced.

[0022] In some optional embodiments, canceling the security key update comprises: sending a security key update cancellation instruction to the terminal device.

[0023] The first base station notifies the terminal device to cancel the security key update in the current cell handover by sending the security key update cancellation instruction, thereby reducing the complexity of the procedure of the terminal device.

[0024] In some optional embodiments, the security key update cancellation instruction is carried by an LTM cell handover instruction. The existing procedure is multiplexed, thereby saving resources.

[0025] In some optional embodiments, before determining whether the second base station is a non-anchor base station connected to the core network through the first base station, the method further comprises: receiving measurement reporting information sent by the terminal device; after determining whether the second base station is a non-anchor base station connected to the core network through the first base station, the method further comprises: sending an RRC reconfiguration message to the terminal device; receiving an RRC reconfiguration complete message sent by the terminal device; and triggering the terminal device to initiate downlink synchronization and uplink synchronization with the second base station.

[0026] The second aspect of the present application provides a communication method, which is applied to a terminal device and includes: determining whether to cancel security key update in a cell handover process from a first base station to a second base station, wherein the first base station is a base station that has established a connection with the terminal device, and the first base station is an anchor base station, which is a relay node base station between other base stations and a core network; if the second base station is a non-anchor base station connected to the core network through the first base station, the security key update is cancelled; and if it is determined to cancel the security key update, a packet data convergence protocol (PDCP) layer re-establishment process is performed.

[0027] In the cell handover process, the update of the security key increases the processing delay of the terminal device and the base station, and increases the mobile interruption time and the handover delay. The method provided in the present application can keep the PDCP layer connection of the security key unchanged at the anchor base station when the above conditions are met, and the terminal device and the base station continue to use the original security key, so that the security key update can be cancelled, the processing delay and the mobile interruption time are reduced. In the method provided in the present application, the process of determining whether the second base station is a non-anchor base station connected to the core network through the first base station is performed outside the mobile interruption time, and is performed in the configuration and processing time in the early stage, so as to reduce the cell handover delay between the base stations. At the same time, after the handover is performed in the embodiment, the second base station does not need to perform path change to the AMF, and the core network does not need to update the downlink GTP-U, and the access network side GTP-U address is still the address of the first base station, thereby reducing the complexity of the handover.

[0028] In some optional embodiments, the cell handover includes an LTM cell handover.

[0029] In some optional embodiments, the determination of whether to cancel the security key update includes: receiving anchor connection relationship information sent by the first base station, the anchor connection relationship information being used to record the anchor connection relationship between the first base station and a candidate target base station, the candidate target base station including the second base station; determining whether the second base station is a non-anchor base station connected to the core network through the first base station according to the anchor connection relationship information; and if the second base station is a non-anchor base station, determining to cancel the security key update.

[0030] The terminal device receives the anchor connection relationship information sent by the base station, and the main function is to enable the terminal device to determine whether to cancel the security key update according to the information.

[0031] In some optional embodiments, before the determination of whether to cancel the security key update, the method includes: sending, to the first base station, capability information of inter-base-station cell handover supporting cancellation of the security key update.

[0032] In some optional embodiments, the anchor connection relationship information comprises at least one of the following: an anchor connection relationship between the first base station and a candidate target base station, the candidate target base station comprising the second base station; an anchor connection relationship between candidate target base stations.

[0033] In some optional embodiments, the anchor connection relationship information is carried by a radio resource control (RRC) reconfiguration message.

[0034] The anchor connection relationship information reuses the RRC reconfiguration message in the existing procedure, thereby saving resources.

[0035] In some optional embodiments, determining whether to cancel the security key update comprises receiving a security key update cancellation instruction sent by the first base station; and determining whether to cancel the security key update according to the security key update cancellation instruction.

[0036] In this embodiment, the terminal device performs the responsive security key update cancellation operation by receiving the instruction sent by the base station, thereby reducing the complexity of the procedure of the terminal device.

[0037] In some optional embodiments, the security key update cancellation instruction is carried by an LTM cell switching instruction. The existing procedure is reused, thereby saving resources.

[0038] In some optional embodiments, after the security key update is cancelled, the method further comprises: after the terminal device is switched from the first base station to the second base station, determining whether the second base station is a non-anchor base station connected to the core network through the first base station in a cell switching process from the second base station to a third base station; and if the second base station is a non-anchor base station, cancelling the security key update in the cell switching process.

[0039] In a continuous cell switching scenario, after the terminal device is switched from an anchor base station to a non-anchor base station connected to the anchor base station, the security key update can be cancelled in subsequent switching, thereby further reducing the switching delay of continuous cell switching.

[0040] In some optional embodiments, before determining whether to cancel the security key update, the method further comprises: sending measurement reporting information to the first base station; receiving an RRC reconfiguration message sent by the first base station; sending an RRC reconfiguration completion message to the first base station; performing downlink synchronization and uplink synchronization with the second base station; disconnecting the connection with the first base station; and performing a random access procedure with the second base station.

[0041] The third aspect of the present application provides a communication method applied to a second base station, the second base station being a non-anchor base station, the non-anchor base station being a base station that is not a relay node between other base stations and a core network, and the method comprising: after a terminal device is handed over from a cell of a first base station to a cell of the second base station, during a handover process of the terminal device from the cell of the second base station to a cell of a third base station, if the second base station is a non-anchor base station connected to the core network through the first base station, canceling security key updating during the handover process; and the first base station being an anchor base station, the anchor base station being a relay node between other base stations and the core network.

[0042] When the method provided by the present application meets the above conditions, the PDCP layer connection of the security key remains unchanged at the anchor base station, and the terminal device and the base station continue to use the original security key, so that the security key updating can be canceled, the processing delay and the mobile interruption time are reduced. In the method provided by the present application, the process of determining whether the second base station is a non-anchor base station connected to the core network through the first base station is performed outside the mobile interruption time, in the configuration and processing time in the early stage, so as to reduce the LTM cell handover delay between base stations. At the same time, after the handover is performed in the embodiment, the third base station does not need to perform path change to the AMF, and the core network does not need to update the downlink GTP-U, and the access network side GTP-U address is still the address of the first base station, thereby reducing the complexity of the handover. In the continuous cell handover scenario, after the terminal device is handed over from an anchor base station to a non-anchor base station connected to the anchor base station, whether the target base station of this handover is an anchor base station or a non-anchor base station, security key updating is not needed. In this way, the handover delay of the continuous cell handover is further reduced.

[0043] In some optional embodiments, before the security key updating during the cell handover process is canceled, the method further comprises: receiving an anchor information request sent by the first base station, the candidate target base station including the second base station; sending an anchor information request response to the first base station, the anchor information request response including anchor information of the second base station, so that the first base station generates anchor connection relationship information based on the anchor information request response; or sending anchor information to the first base station.

[0044] In some optional embodiments, the anchor connection relationship information includes at least one of the following: an anchor connection relationship between the first base station and the candidate target base station; and an anchor connection relationship between the candidate target base stations.

[0045] The first base station determines anchor information from the candidate target base stations, wherein the second base station is one of the candidate target base stations, and the second base station sends information to the first base station about whether it is a non-anchor base station, so that the first base station can generate anchor connection relationship information.

[0046] In some optional embodiments, the anchor point information request is carried by the LTM cell switching request; and the anchor point information request response is carried by the LTM cell switching request response. The existing process is multiplexed, and resources are saved.

[0047] In some optional embodiments, before the security key update in the canceling cell switching process, the method further comprises: receiving anchor connection relationship information sent by the first base station, the anchor connection relationship information being used to record an anchor connection relationship between the first base station and a candidate target base station, the candidate target base station including the second base station, and the first base station specifying the second base station as a non-anchor base station in the anchor connection relationship information.

[0048] In the continuous cell switching scenario, the second base station determines whether the security key update in the canceling cell switching process can be performed based on the received anchor connection relationship information.

[0049] In some optional embodiments, after the security key update in the canceling cell switching process, the method further comprises: sending a notification message to the third base station, the notification message being used to inform the third base station that the terminal device is connected to the core network through the first base station.

[0050] The fourth aspect of the present application provides a terminal device, the terminal device comprising a processor and a memory, the memory being used to store program code; the processor being used to run the program code, so that the terminal device implements the above method.

[0051] The fifth aspect of the present application provides a base station, the base station comprising a processor and a memory, the memory being used to store program code; the processor being used to run the program code, so that the base station implements the above method.

[0052] The sixth aspect of the present application provides a computer readable storage medium, the computer readable storage medium storing a computer program, the computer program being executed by a processor to implement the above method. BRIEF DESCRIPTION OF DRAWINGS

[0053] FIG. 1 is a structural schematic diagram of a 5G network base station;

[0054] FIG. 2 is a schematic diagram of an LTM cell switching process;

[0055] FIG. 3 is a schematic diagram of a conditional LTM cell switching process;

[0056] FIG. 4 is a schematic diagram of the connection relationship between an anchor base station and a non-anchor base station in the present application;

[0057] FIG. 5 is a schematic diagram of a communication method provided in an embodiment of the present application;

[0058] FIG. 6 is a schematic diagram of a second communication method provided in an embodiment of the present application;

[0059] FIG. 7 is a schematic diagram of a LTM cell switching communication method according to an embodiment of the present application;

[0060] FIG. 8 is a schematic diagram of a second LTM cell switching communication method according to an embodiment of the present application;

[0061] FIG. 9 is a schematic diagram of a third LTM cell switching communication method according to an embodiment of the present application;

[0062] FIG. 10 is a schematic diagram of a fourth LTM cell switching communication method according to an embodiment of the present application;

[0063] FIG. 11 is a schematic diagram of a fifth LTM cell switching communication method according to an embodiment of the present application;

[0064] FIG. 12 is a schematic diagram of a sixth LTM cell switching communication method according to an embodiment of the present application;

[0065] FIG. 13 is a signaling format diagram of a medium access control layer control unit;

[0066] FIG. 14 is a schematic diagram of a terminal device according to an embodiment of the present application;

[0067] FIG. 15 is a schematic diagram of a base station according to an embodiment of the present application. DETAILED DESCRIPTION

[0068] For the purpose of clearly describing the technical solutions of the embodiments of the present application, in the embodiments of the present application, the words "exemplary" or "for example" are used to represent an example, illustration or description. Any embodiment or design solution described as "exemplary" or "for example" in the present application should not be interpreted as being more preferred or more advantageous than other embodiments or design solutions. In fact, the words "exemplary" or "for example" are used to present the relevant concept in a specific manner.

[0069] In the embodiments of the present application, the words "first", "second" and the like are used to distinguish the same or similar items with basically the same function and role. For example, the first indication information and the second indication information are only used to distinguish different indication information, and do not limit the order. Those skilled in the art can understand that the words "first", "second" and the like do not limit the quantity and execution order, and the words "first", "second" and the like do not necessarily mean different.

[0070] In the embodiments of the present application, “at least one” means one or more, and “multiple” means two or more. “And / or” describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can represent the following three cases: A exists alone, A and B exist together, and B exists alone, where A and B can be singular or plural. The character “ / ” generally represents an “or” relationship between the front and rear associated objects. “At least one of the following” or similar expressions means any combination of these items, including any combination of single or multiple items. For example, at least one of a, b, or c can represent a, b, c, a-b, a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0071] The base station in the embodiments of the present application can refer to a public mobile communication network device, which is an interface device for terminal devices to access the Internet and is also a form of radio station. It refers to a wireless radio station that transmits information between terminal devices in a certain radio coverage area, including base stations (base station, BS), which can also be called base station devices. It is a device deployed in a radio access network (radio access network, RAN) to provide wireless communication functions. The device providing base station functions in 5G NR is gNB, and the continuously evolving NodeB (ng-eNB), where gNB and terminal devices communicate using NR technology, ng-eNB and terminal devices communicate using evolved universal terrestrial radio access network (evolved universal terrestrial radio access, E-UTRA) technology, and gNB and ng-eNB can be connected to a 5G core network. The base station in the embodiments of the present application also includes devices providing base station functions in future new communication systems, etc.

[0072] As shown in FIG. 1, the CU, DU separated network architecture in the 5G network includes a centralized unit (CU) and a distributed unit (DU). The CU and the DU are divided according to different protocol layers. The DU is responsible for the physical layer, the medium access control (MAC) layer, and the radio link control (RLC) layer. The CU is responsible for the packet data convergence protocol (PDCP) layer and the radio resource control (RRC) layer. There can be one or more cells under a DU.

[0073] The terminal device of the embodiments of the present application can include a handheld device with wireless communication function, a vehicle-mounted device, etc. For example, some terminal devices are: a mobile phone, a tablet computer, a palm computer, a notebook computer, a mobile internet device (MID), a wearable device, a VR device, an AR device, a wireless terminal in industrial control, a wireless terminal in unmanned driving, a wireless terminal in remote medical surgery, a wireless terminal in smart grid, a wireless terminal in transportation safety, a wireless terminal in smart city, a wireless terminal in smart home, a cellular phone, a cordless phone, a Session Initiation Protocol (SIP) phone, a Wireless Local Loop (WLL) station, a Personal Digital Assistant (PDA), a handheld device with wireless communication function, a computing device or other processing device connected to a wireless modem, a vehicle-mounted device, a wearable device, a terminal device in a 5G network, or a terminal device in a future evolved Public Land Mobile Network (PLMN), etc., and the embodiments of the present application are not limited thereto.

[0074] By way of example and not limitation, in the embodiments of the present application, the terminal device can also be a wearable device. The wearable device can also be referred to as a wearable smart device, which is a general term for devices that are designed and developed by applying wearable technology to daily wear, such as glasses, gloves, watches, clothing, and shoes. The wearable device is a portable device that is directly worn on the body or integrated into the user's clothes or accessories. The wearable device is not only a hardware device, but also a device that realizes powerful functions through software support and data interaction and cloud interaction. The general wearable smart device includes a device with full functions and large size, which can realize complete or partial functions without relying on a smart phone, such as a smart watch or smart glasses, and a device that focuses on a certain application function and needs to be used in cooperation with other devices, such as a smart phone, such as various smart wristbands and smart jewelry for monitoring vital signs.

[0075] In addition, in the embodiments of the present application, the terminal device can also be a terminal device in an Internet of Things (IoT) system. The IoT is an important part of future information technology development, and its main technical feature is to connect objects through communication technology and network, so as to realize the intelligent network of man-machine interconnection and object-object interconnection.

[0076] The terminal device in the embodiments of the present application can also be referred to as a user equipment (UE), a mobile station (MS), a mobile terminal (MT), an access terminal, a subscriber unit, a subscriber station, a mobile station, a mobile station, a remote station, a remote terminal, a mobile device, a user terminal, a terminal, a wireless communication device, a user agent, or a user apparatus, etc.

[0077] In the embodiments of the present application, the device for implementing the function of the terminal can be a terminal, or a device capable of supporting the terminal to implement the function, such as a chip system, which can be installed in the terminal.

[0078] In the embodiments of the present application, the network element involved in the handover process can be represented in units of cells or in units of base stations. In the network architecture of CU and DU separation, one base station includes one CU and all DUs connected to the CU. Therefore, in the network architecture of CU and DU separation, the anchor base station and the non-anchor base station can also be an anchor CU and a non-anchor CU. The definition of the anchor CU and the non-anchor CU implements the cell handover process between the CUs without performing security key update. The DU is a node directly interacting with the terminal for signaling and data transmission. The signaling interaction and information transmission between the original CU and the candidate target CU, such as the signaling interaction and information transmission between the original base station and the candidate target base station, will not be described here. The signaling interaction and information transmission between the original DU and the terminal, such as the signaling interaction and information transmission between the original base station and the terminal, will not be described here. The original CU transmits the signaling and information that need to be interacted with the terminal to the original DU, and then the original DU interacts with the terminal for signaling and information transmission.

[0079] Under the network structure as shown in FIG. 1, base stations are more densely deployed, and terminal devices will face more frequent cell switching. In order to ensure user experience and reduce the latency of cell switching, LTM cell switching within the same CU is proposed. The current LTM cell switching reduces the switching latency through early synchronization. In order to better illustrate the technical solutions provided by the embodiments of the present application, the related content of LTM is first described. FIG. 2 is an example of an LTM cell switching process. The first cell, the second cell, the third cell, etc. in FIG. 2 are for illustration, and the specific message sending and receiving subject is a network device. In FIG. 2, the candidate target cell contains two cells as an example, and the second cell is taken as the target cell as an example. How to select the target cell can be determined according to the measurement report of the terminal device, and the specific process is not described in detail.

[0080] The LTM switching process shown in FIG. 2 includes the following steps:

[0081] S201, the terminal device sends measurement reporting information to the first cell.

[0082] The terminal device performing LTM cell switching is already in a connected state and connected with the first cell. The terminal device will measure each candidate target cell and send the measurement reporting information to the first cell. Taking a 5G network as an example, the reference signal receiving power (RSRP) measurement and reporting are performed at layer one and layer three. In this step, the measurement reporting information can be one of layer one measurement reporting or layer three measurement reporting.

[0083] The first cell determines the support capability of the terminal device for LTM according to the measurement result, and determines to perform LTM according to the support capability of the terminal device for LTM, and performs a candidate target cell configuration preparation process including steps S202-S205.

[0084] S202, the first cell sends an LTM cell switching request to the second cell and the third cell.

[0085] S203, the second cell and the third cell send an LTM cell switching request response to the first cell.

[0086] In S203, the LTM cell switching request responses sent by the second cell and the third cell respectively include the configuration information of the second cell and the third cell.

[0087] S204, the first cell sends an RRC reconfiguration message to the terminal device.

[0088] The RRC reconfiguration message includes the configuration information of the candidate target cell.

[0089] S205, the terminal device sends an RRC reconfiguration complete message to the first cell.

[0090] The RRC reconfiguration complete message indicates that the terminal device has received the RRC reconfiguration message.

[0091] S206, the terminal device performs downlink synchronization for the candidate target cell.

[0092] S207, the terminal device performs uplink synchronization for the candidate target cell.

[0093] In some implementations, the RRC reconfiguration information indicates that the terminal device measures the uplink timing advance, the terminal measures the timing advance of the first cell, and determines the timing advance of the second cell according to the received time difference between the first cell and the second cell.

[0094] In another implementation, the contention-free random access (CFRA) is triggered by the first cell through a physical downlink control channel (PDCCH) order to obtain the timing advance of the candidate target cell, the terminal initiates CFRA to the candidate target cell to obtain the timing advance, and the network manages the validity of the timing advance.

[0095] S208, the terminal device sends a layer one measurement report to the first cell.

[0096] The terminal device performs layer one measurement on the first cell and the candidate target cell respectively, obtains the layer one measurement report and sends it to the first cell.

[0097] S209, the first cell sends an LTM cell switching instruction to the terminal device.

[0098] The first cell selects the target cell for this switching from the candidate target cells based on the L1 measurement report, and takes the second cell as an example. The switching instruction indicates that the terminal switches from the first cell to the second cell.

[0099] In some implementations, the switching instruction includes a MAC control element (MAC CE), which at least includes a timing advance (TA), a transmission configuration indication (TCI) state identifier (state id), CFRA resource information, and candidate target cell configuration information identifier.

[0100] The timing advance is a timing advance obtained by the terminal and still in a valid state, i.e., before S211, if the network determines that the TA obtained by the terminal before is still in a valid state, the TA is included in the MAC CE.

[0101] S210, the terminal device disconnects the connection with the first cell.

[0102] S211, the terminal device performs a random access procedure with the second cell.

[0103] In an alternative manner of S211, when the terminal receives the TA carried in the MAC CE of the LTM cell switching instruction, or when the terminal device self-tests the TA, the terminal device will initiate the cell switching without random access to the target cell.

[0104] S212, the terminal device completes the LTM cell switching.

[0105] When the target cell receives the RRC reconfiguration message sent by the terminal device, it means that the terminal device has completed the LTM cell switching. If step S211 is performed, when the random access procedure between the terminal device and the target cell is completed, it means that the LTM cell switching is completed. If the terminal device performs cell switching without random access, when the target cell receives the first uplink data sent by the terminal device, it means that the terminal device has completed the LTM cell switching.

[0106] In the above LTM cell switching, the terminal device needs to perform the operation of switching to the target cell according to the LTM cell switching instruction sent by the base station; in order to further improve the flexibility and robustness of mobility management, conditional LTM (Conditional LTM) is proposed. In conditional LTM, the terminal device is configured in advance with corresponding execution conditions for switching to each candidate target cell, and when the switching condition is met, the switching is performed. Figure 3 is an example of conditional LTM cell switching process.

[0107] The conditional LTM cell switching process shown in Figure 3 includes the following steps:

[0108] S301, the terminal device sends measurement reporting information to the first cell.

[0109] The specific content of the step can refer to step S201.

[0110] S302, the first cell sends a conditional LTM cell switching request to the second cell and the third cell.

[0111] S303, the second cell and the third cell send a conditional LTM cell switching request response to the first cell.

[0112] In the above step, the LTM cell handover request response of the conditions sent by the second cell and the third cell respectively includes the configuration information of the second cell and the third cell and the configuration information of the handover conditions. The original base station configures a certain number of candidate target cells and corresponding handover conditions according to the received LTM cell handover request response of the conditions.

[0113] One of the candidate target cells can correspond to one or more handover conditions. The handover condition can be set, for example, that the signal quality of the candidate target cell is better than that of the first cell. For another example, the signal quality of the first cell is less than an absolute threshold, and the signal quality of the candidate target cell is higher than an absolute threshold, and the like. The embodiments of the present application do not limit the specific handover conditions.

[0114] S304, the first cell sends an RRC reconfiguration message to the terminal device.

[0115] The RRC reconfiguration message includes the configuration information of each candidate target cell and the handover condition.

[0116] S305, the terminal device sends an RRC reconfiguration complete message to the first cell.

[0117] The RRC reconfiguration complete message is used to indicate that the terminal device has received the RRC reconfiguration message.

[0118] S306, downlink synchronization for the candidate target cell.

[0119] S307, uplink synchronization for the candidate target cell.

[0120] S308, the terminal device evaluates the handover condition and disconnects the connection with the first cell when the handover condition is met.

[0121] After receiving the RRC reconfiguration message, the terminal device evaluates the handover condition, and when at least one candidate target cell meets the response handover condition, the terminal device disconnects the connection with the first cell, starts to perform the LTM cell handover of the conditions on the determined candidate target cell, and releases the configuration information after completing the handover.

[0122] S309, the terminal device performs a random access procedure with the second cell.

[0123] S310, the terminal device completes the LTM cell handover of the conditions.

[0124] The specific contents of steps S309 and S310 can refer to steps S211 and S212.

[0125] Currently, no matter LTM cell switching or conditional LTM cell switching, in the cross-CU scenario, the update of the security key will be involved, and the update of the security key will cause the delay in the switching process. The biggest gain of the LTM cell switching mode is to reduce the switching delay, so in this scenario, how to reduce or avoid the delay problem caused by the security key update needs to be considered.

[0126] To solve the delay problem caused by the security key, the application first proposes the concepts of anchor base station and non-anchor base station. In the application, the anchor base station is a relay node base station connected to the core network as other base stations, more specifically, the anchor base station is a PDCP anchor connected to the core network as other base stations, that is, the PDCP layer connection between the terminal device connected to other base stations and the core network needs other base stations to be connected to the core network through the anchor base station, that is, the PDCP layer of the non-anchor base station is borne on the anchor base station. The non-anchor base station in the application is a base station that does not connect other base stations to the core network as a relay node, and the non-anchor base station can be a base station connected to the core network through the anchor base station, or directly connected to the core network, but not as a relay node to connect other base stations. Taking a 5G base station as an example, FIG. 4 is a schematic diagram of the connection relationship between the anchor base station and the non-anchor base station in the application.

[0127] In FIG. 4, base station 1 and base station 2 are anchor base stations, and base station 3, base station 4, base station 5 and base station 6 are non-anchor base stations. Among them, base station 3 is a non-anchor base station associated with base station 1; base stations 4 and 5 are non-anchor base stations associated with base station 2; and base station 6 is a non-anchor base station directly connected to the core network.

[0128] According to the above classification of base stations, there can be multiple possibilities when the terminal device switches between different base stations, such as switching from an anchor base station to a non-anchor base station, switching from an anchor base station to another anchor base station, and the like. In an embodiment of the application, since the access layer security key update process is implemented at the PDCP layer, when the terminal device switches from an anchor base station to a non-anchor base station connected to the anchor base station, there is no need to re-establish the PDCP layer connection, and the original security key is continued to be used. Therefore, the terminal device does not need to update the security key when performing LTM cell switching between base stations, and the specific implementation steps are shown in FIG. 5.

[0129] FIG. 5 includes the following steps:

[0130] S501, in a layer 1 or layer 2 triggered mobility LTM cell switching process from a first base station to a second base station, it is determined whether the second base station is a non-anchor base station connected to the core network through the first base station.

[0131] In this step, the first base station is a base station that has been in a connected state with the terminal device, and is the original base station in the LTM cell switching process. The second base station is the target base station in the LTM cell switching process. Before the terminal device performs switching, the first base station needs to determine whether the multiple candidate target base stations including the target base station are non-anchor base stations.

[0132] S502, if the second base station is a non-anchor base station connected to the core network through the first base station, cancel security key update.

[0133] In this step, the execution decision of canceling security key update can be made by the first base station or by the terminal device. If the first base station determines to cancel security key update, it needs to send a cancel security key update instruction to notify the terminal device to cancel security key update; if the terminal device determines to cancel security key update, the first base station does not need to send a cancel security key update instruction to the terminal device.

[0134] S503, if it is determined to cancel security key update, the terminal device performs a cancel packet data convergence protocol (PDCP) layer re-establishment process.

[0135] In the embodiments of the present application, canceling security key update mainly refers to canceling access stratum (AS) security key update. AS signaling security and data security are responsible by the PDCP layer. The activation and deactivation of PDCP layer security and the selection of security algorithms are controlled by the RRC layer. The base station updates the AS security by sending an RRC reconfiguration message, which contains security configuration and other activation information elements. The terminal device calculates security keys such as KUPint, KUPenc, KRRCint, and KRRCenc according to these information elements and configures them to the PDCP layer. At this time, it can be considered that the AS layer security update is completed. Therefore, in the embodiments of the present application, security key update can be canceled by canceling PDCP layer re-establishment when performing inter-base station cell switching. In the scheme provided in the present application, when the terminal device performs inter-base station cell switching, the PDCP layer connection remains unchanged at the anchor base station, and the terminal device and the base station continue to use the original security key to cancel security key update.

[0136] The LTM cell switching supports continuous switching. Based on the scheme shown in FIG. 5, the present application provides a technical scheme that can cancel security key update in a continuous LTM cell switching scenario. FIG. 6 is an example diagram of the scheme.

[0137] FIG. 6 includes the following steps:

[0138] S601, after the terminal device is handed over from the first base station to the LTM cell of the second base station, determining whether the second base station is a non-anchor base station connected to the core network through the first base station during the handover process from the second base station to the LTM cell of the third base station.

[0139] In this step, the terminal device has already performed LTM cell handover once, i.e., the aforementioned LTM cell handover from the first base station to the second base station shown in FIG. 5. At this time, the terminal device is in the connected state and is connected to the second base station, the second base station is the original base station of this handover, and the third base station is the target base station of this handover. The second base station can determine whether the second base station is a non-anchor base station connected to the core network through the first base station and send a security key cancellation instruction to the terminal device. The terminal device can also determine it according to the anchor connection relationship information sent by the base station.

[0140] S602, if the second base station is a non-anchor base station connected to the core network through the first base station, cancel the security key update during the LTM cell handover process.

[0141] If the condition in step S601 is met, the security key update is cancelled. In the continuous handover scenario, the security key update is cancelled, and the specific content is described above in step S503. The security key update is cancelled by cancelling the re-establishment of the PDCP layer.

[0142] The following further gives embodiments of the scheme proposed in the present application in specific scenarios. Since the technical scheme proposed in the present application is directed to the LTM cell handover scenario across base stations, in the following embodiments, “base station” is used to generally refer to a cell. It can be understood that one base station can include multiple cells. In the following embodiments, the handover of the terminal device from one base station to another base station represents the handover process of the terminal device from a cell under one base station to a cell under another base station.

[0143] FIG. 7 is an example diagram of a base station inter-LTM cell handover communication method provided by the present application. In the embodiment shown in FIG. 7, the anchor connection relationship information is obtained by multiplexing the original process.

[0144] FIG. 7 includes the following steps:

[0145] S701, the terminal device sends measurement reporting information to the first base station.

[0146] The terminal device in the connected state is currently connected to the first base station and reports the measurement report of each cell to the first base station. The measurement report can be one of a layer one measurement report, a layer three measurement report, or other kinds of measurement reports.

[0147] The first base station determines the support capability of the terminal device for the LTM according to the measurement report, and determines to perform the LTM cell switching according to the support capability of the terminal device for the LTM, and performs a configuration preparation process of a subsequent candidate target base station.

[0148] S702, the first base station sends an LTM cell switching request to the candidate target base station.

[0149] In order to support the LTM cell switching with cancellation of the security key update, the anchor information request is included in the LTM cell switching request in this step. The anchor information request is used to obtain information whether the candidate target base station is a non-anchor base station.

[0150] The candidate target base station includes the target base station of the LTM cell switching and other candidate target base stations.

[0151] S703, the candidate target base station sends an LTM cell switching request response to the first base station.

[0152] Correspondingly, the plurality of candidate target base stations carries the anchor information request response in the LTM cell switching request response after receiving the anchor information request.

[0153] In the scheme provided in the present application, the anchor information request response includes the anchor information of the base station, and the anchor information includes information whether the base station is a non-anchor base station of the first base station, or the anchor information includes information whether the base station is a non-anchor base station.

[0154] S704, the candidate target base station sends the anchor information to the first base station.

[0155] In another scheme provided in the present application, the anchor information is sent by the candidate target base station to the first base station, and when this method is used, the anchor information request and the anchor information request response can not be carried in the step S702 and the step S703.

[0156] S705, the first base station sends an RRC reconfiguration message to the terminal device.

[0157] After the first base station receives the LTM cell handover request response and the anchor point information request response included therein, the first base station generates anchor point connection relationship information according to the anchor point information of the first base station and the candidate target base stations. In terms of format, the anchor point connection relationship information can be a list including the anchor point base station identifiers or non-anchor point base station identifiers of the first base station and the candidate target base stations, and the association relationship between the base stations. For example, there are three candidate target base stations, which are base station A, base station B and base station C, wherein the base station A can serve as an anchor point base station, and the base station B and the base station C can only serve as non-anchor point base stations. After the first base station obtains the anchor point information of the three candidate target base stations, the association relationship is generated, for example, the base station B serves as a non-anchor point base station connected with the first base station, and the base station C serves as a non-anchor point base station connected with the base station A. The further generated anchor point connection relationship information includes the identifiers of the first base station and the base station A as anchor point base stations, and the identifiers of the base station B and the base station C as non-anchor point base stations; the identifier of the base station B and the identifier of the first base station have a mapping relationship in the table, and the identifier of the base station C and the identifier of the base station A have a mapping relationship in the table.

[0158] The anchor point connection relationship information described above is sent to the terminal device by an RRC reconfiguration message in the embodiment of the present application.

[0159] S706, the first base station sends the anchor point connection relationship information to the candidate target base stations.

[0160] In this step, the candidate target base stations can be one or more, and the purpose is to notify and update the configuration information in the network.

[0161] S707, the terminal device sends an RRC reconfiguration complete message to the first base station.

[0162] S708, the terminal device performs downlink synchronization for the candidate target cell.

[0163] S709, the terminal device performs uplink synchronization for the candidate target cell.

[0164] S710, the terminal device sends layer one measurement reporting information to the first base station.

[0165] S711, the first base station sends an LTM cell handover instruction to the terminal device.

[0166] After the first base station determines that the target base station is a non-anchor point base station of the first base station according to the anchor point connection relationship information described above, the first base station sends an LTM cell handover instruction to the terminal device.

[0167] S712, the terminal device disconnects the connection with the first base station and determines whether to cancel the security key update.

[0168] After receiving the LTM cell handover instruction in step S710, the terminal device disconnects the connection with the first base station, and judges whether to perform the LTM cell handover without security key update according to the identification of the target cell in the LTM cell handover instruction sent by the first base station and the anchor connection relationship information received in step S704. In this embodiment, it is determined that the second base station is the target base station, and when the second base station is a non-anchor base station connected with the core network through the first base station, the terminal device determines to cancel the security key update.

[0169] S713, the terminal device performs a random access procedure with the second base station.

[0170] S714, the LTM cell handover is completed.

[0171] When the target cell receives the RRC reconfiguration message sent by the terminal device, it means that the terminal device has completed the LTM cell handover. If step S712 is performed, when the random access procedure between the terminal device and the target cell is completed, it means that the LTM cell handover is completed. If the terminal device performs the cell handover without random access, i.e., step S712 is not performed, when the target cell receives the first uplink data sent by the terminal device, it means that the terminal device has completed the LTM cell handover.

[0172] FIG. 8 provides another embodiment, which can be applied in conditional LTM cell handover. In the embodiment shown in FIG. 8, the terminal device decides whether to perform LTM handover and whether to cancel the security key update during handover.

[0173] S801, the terminal device sends measurement reporting information to the first base station.

[0174] The content of this step can refer to step S701.

[0175] S802, the first base station sends a conditional LTM cell handover request to the candidate target base station.

[0176] The conditional LTM cell handover request includes an anchor information request.

[0177] S803, the candidate target base station sends a conditional LTM cell handover request response to the first base station.

[0178] The conditional LTM cell handover request response includes an anchor information request response. The first base station generates anchor connection relationship information according to the anchor information of itself and the candidate target base station.

[0179] In the above step, the LTM cell handover request response with conditions sent by the candidate target base station respectively comprises configuration information of the candidate target base station and configuration information of the handover conditions. The first base station configures a certain number of candidate target cells and corresponding handover conditions according to the received LTM cell handover request response with conditions.

[0180] One of the candidate target cells can correspond to one or more handover conditions. The handover condition can be set, for example, that the signal quality of the candidate target base station is better than the cell currently connected by the terminal device under the first base station. For another example, the signal quality of the cell currently connected by the terminal device under the first base station is less than an absolute threshold, and the signal quality of the target cell under the candidate target base station is higher than an absolute threshold, and the like. The embodiments of the present application do not limit the specific handover conditions.

[0181] S804, the candidate target base station sends anchor point information to the first base station.

[0182] The specific content can be referred to step S704.

[0183] S805, the first base station sends an RRC reconfiguration message to the terminal device.

[0184] In this step, in addition to the basic configuration information of the candidate target base station, the RRC reconfiguration message also carries anchor connection relationship information and handover condition information of each candidate target cell.

[0185] S806, the first base station sends anchor connection relationship information to the candidate target base station.

[0186] S807, the terminal device sends an RRC reconfiguration complete message to the first base station.

[0187] S808, the terminal device performs downlink synchronization for the candidate target cell.

[0188] S809, the terminal device performs uplink synchronization for the candidate target cell.

[0189] S810, the terminal device performs conditional LTM evaluation and decides to perform LTM cell handover; determines whether to cancel the security key update.

[0190] In this step, the terminal device determines and selects the cell that currently meets the handover condition for handover according to the handover condition information of each candidate target cell obtained in step S804, wherein the handover condition can refer to step S803. In this embodiment, taking the determination of the second base station as the target base station as an example, when the second base station is a non-anchor point base station connected to the core network through the first base station, the terminal device determines to cancel the security key update.

[0191] S811, the terminal device performs a random access procedure with the second base station.

[0192] S812, completing the LTM cell handover.

[0193] When the target cell receives the RRC reconfiguration message sent by the terminal device, it means that the terminal device has completed the LTM cell handover. If step S810 is performed, when the random access procedure between the terminal device and the target cell is completed, it means that the LTM cell handover is completed. If the terminal device performs the cell handover without random access, i.e., step S810 is not performed, when the target cell receives the first uplink data sent by the terminal device, it means that the terminal device has completed the LTM cell handover.

[0194] Another embodiment is provided in the present application. In the embodiment, the anchor connection relationship information within the range of the first base station and each candidate target base station is determined and generated by the first base station, and is sent to the terminal device and each candidate target base station. FIG. 9 is an example diagram of the present scheme.

[0195] FIG. 9 includes the following steps:

[0196] S901, the terminal device sends measurement reporting information to the first base station.

[0197] The specific content can be referred to step S701.

[0198] S902, the first base station sends an LTM cell handover request to the candidate target base station.

[0199] S903, the candidate target base station sends an LTM cell handover request response to the first base station.

[0200] S904, the first base station sends an RRC reconfiguration message to the terminal device.

[0201] In this step, the RRC reconfiguration message carries the anchor connection relationship information, which is generated by the first base station. The first base station specifies each candidate target base station as an anchor base station or a non-anchor base station, and the connection relationship is also configured by the first base station. The anchor connection relationship information includes the above-mentioned information. The specific content can be referred to step S704.

[0202] S905, the first base station sends the anchor connection relationship information to the candidate target base station.

[0203] S906, the terminal device sends an RRC reconfiguration complete message to the first base station.

[0204] S907, the terminal device performs downlink synchronization to the candidate target cell.

[0205] S908, the terminal device performs uplink synchronization to the candidate target cell.

[0206] S909, the terminal device sends layer one measurement reporting information to the first base station.

[0207] S910, the first base station sends LTM cell handover instruction to the terminal device.

[0208] S911, the terminal device disconnects the connection with the first base station.

[0209] Steps S905-S911 can refer to steps S706-S712.

[0210] S912, the terminal device performs random access procedure with the second base station.

[0211] S913, LTM cell handover is completed.

[0212] Specific content can refer to step S714.

[0213] For conditional LTM, FIG. 10 gives an example of an embodiment. Similar to the difference between FIG. 9 and FIG. 7, the difference between FIG. 10 and FIG. 8 is that the anchor connection relationship information in the method shown in FIG. 10 is determined and generated independently by the first base station.

[0214] S1001, the terminal device sends measurement reporting information to the first base station.

[0215] S1002, the first base station sends conditional LTM cell handover request to the candidate target base station.

[0216] In step S1002, the LTM cell handover request does not include anchor information request.

[0217] S1003, the candidate target base station sends conditional LTM cell handover request response to the first base station.

[0218] In step S1003, the LTM cell handover request response also does not include anchor information request response.

[0219] In steps S1002 and S1003, the conditional LTM cell handover request response sent by the candidate target base station respectively includes configuration information of the candidate target base station and configuration information of the handover condition. The first base station configures a certain number of candidate target cells and corresponding handover conditions according to the received conditional LTM cell handover request response.

[0220] One of the candidate target cells can be configured with one or more handover conditions. The handover conditions can be set, for example, that the signal quality of the candidate target base station is better than the cell to which the terminal device is currently connected under the first base station. For another example, the signal quality of the cell to which the terminal device is currently connected under the first base station is less than an absolute threshold, and the signal quality of the target cell under the candidate target base station is higher than an absolute threshold, and the like. The embodiments of the present application do not limit the specific handover conditions.

[0221] S1004, the first base station sends an RRC reconfiguration message to the terminal device.

[0222] S1005, the first base station sends anchor connection relationship information to the candidate target base station.

[0223] S1006, the terminal device sends an RRC reconfiguration completion message to the first base station.

[0224] S1007, the terminal device performs downlink synchronization for the candidate target cell.

[0225] S1008, the terminal device performs uplink synchronization for the candidate target cell.

[0226] The specific contents of steps S1004-S1008 can refer to steps S805-S809.

[0227] S1009, the terminal device performs conditional LTM evaluation and determines to perform LTM cell handover; and confirms whether the LTM cell handover with cancellation of security key update can be performed.

[0228] In this step, the terminal device determines and selects the cell that currently satisfies the handover condition for handover according to the handover condition information of each candidate target cell obtained in step S1004, wherein the handover condition can refer to step S1003. In the present embodiment, the second base station is taken as an example of the target base station, and when the second base station is a non-anchor base station connected to the core network through the first base station, the terminal device determines to cancel the security key update.

[0229] S1010, the terminal device performs a random access procedure with the second base station.

[0230] S1011, the LTM cell handover is completed.

[0231] For the scenario of continuous LTM handover, based on Fig. 6, embodiments of the present application provide a more specific implementation, as shown in Fig. 11. In Fig. 11, after the terminal device switches to the target base station (second base station) in Figs. 7-10, the LTM cell handover from the second base station to the third base station is performed again. The implementation shown in Fig. 11 is also the process of one LTM handover, and other steps shown in the figure are not described here, and can be specifically referred to the contents in Figs. 7-10 according to different scenarios. In the scenario of continuous LTM handover, RRC reconfiguration is not performed.

[0232] Fig. 11 includes the following steps:

[0233] S1101, the second base station sends an LTM cell handover instruction to the terminal device.

[0234] This step is an optional step, which is not executed in conditional LTM. The terminal device evaluates and decides to perform the handover. In non-conditional LTM, this step needs to be executed, and the terminal device is instructed to perform LTM cell handover through the LTM cell handover instruction.

[0235] S1102, the terminal device disconnects the connection with the second base station, and simultaneously confirms whether to perform the LTM cell handover with cancellation of security update.

[0236] In this step, if the terminal device performs conditional LTM cell handover, the cell currently satisfying the handover condition is judged and selected for handover according to the pre-configured handover condition of the candidate target cell, which can be referred to step S803. In this step, taking the determination of the target base station as the third base station as an example, when the second base station is a non-anchor base station connected with the core network through the first base station, the terminal device determines to cancel the security key update. The terminal device judges whether the second base station satisfies the above condition of canceling the security key update based on the anchor connection relationship information sent by the base station in the previous handover.

[0237] S1103, the terminal device or the second base station sends a notification message to the third base station.

[0238] The notification message can be sent by the terminal device to the third base station, or sent by the second base station to the third base station. The notification message is used to inform the third base station that the terminal device is connected with the core network through which anchor base station, and in this implementation, it is connected through the first base station.

[0239] In the mode of Fig. 11, the terminal device does not need to consider which base station is the target base station when determining whether to cancel the security key update in the scenario of continuous LTM cell handover, and only according to the currently connected base station, the more flexible LTM cell handover with cancellation of security key update can be realized.

[0240] For the unconditional LTM cell handover, the embodiment of the present application proposes another solution: the base station decides whether the terminal device cancels the security key update in this LTM cell handover, and indicates it to the terminal device through the LTM handover instruction. The implementation is shown in FIG. 12.

[0241] FIG. 12 includes the following steps:

[0242] S1201, the terminal device sends the measurement report information to the first base station.

[0243] The content of this step can refer to step S701.

[0244] S1202, the first base station sends the LTM cell handover request to the candidate target base station.

[0245] S1203, the candidate target base station sends the LTM cell handover request response to the first base station.

[0246] The implementation shown in FIG. 12 supports the two ways of obtaining the anchor connection relationship information shown in FIG. 7 and FIG. 9. If the anchor connection relationship information needs to be obtained by sending the anchor information request to the candidate target base station and obtaining the anchor information request response, the anchor information request is carried in the LTM cell handover request in step S1202, and refer to step S702; the anchor information request response is carried in the LTM cell handover request response in step S1203, and refer to step S703.

[0247] S1204, the first base station sends the RRC reconfiguration message to the terminal device.

[0248] In this step, the anchor connection relationship information is carried in the RRC reconfiguration message.

[0249] S1205, the first base station sends the anchor connection relationship information to the candidate target base station.

[0250] S1206, the terminal device sends the RRC reconfiguration complete message to the first base station.

[0251] S1207, the terminal device performs the downlink synchronization for the candidate target cell.

[0252] S1208, the terminal device performs the uplink synchronization for the candidate target cell.

[0253] S1209, the terminal device sends the layer one measurement report information to the first base station.

[0254] S1210, the security key update cancellation instruction.

[0255] In one implementation provided by the embodiments of the present application, the terminal device determines whether to cancel the security key update in the current handover according to the cancel security key update information sent by the base station. The cancel security key update information sent by the base station can be carried and transmitted through a special signaling, which can be a cancel security key update instruction.

[0256] In S1211, the first base station sends an LTM cell handover instruction to the terminal device.

[0257] In this step, the first base station selects a target cell from the candidate target cells based on the layer-1 measurement report information from the terminal device, and the handover instruction instructs the terminal device to switch from the first cell under the first base station to the target cell under the target base station. In this step, the LTM cell handover instruction carries the cancel security key update instruction.

[0258] In some implementations, the handover instruction includes a MAC CE. The format of the MAC CE is shown in FIG. 13, where the MAC CE can include the following fields: Target Config ID, Timing Advance Command, TCI state ID, UL TCI state ID, Random Access Preamble index, SS / PBCH index, PRACH Mask index, etc. Some bits in FIG. 13 are not allocated and are identified as “R”, i.e., reserved bits.

[0259] The cancel security key update instruction is indicated by the reserved bits of the MAC CE. For example, one reserved bit A is used to represent the cancel security key update instruction: when the reserved bit A is set to 1, it indicates that the terminal device cancels the security key update; when the reserved bit A is set to 0, it indicates that the terminal device needs to perform the security key update. For another example, two reserved bits A and B are used to represent the cancel security key update instruction, where one bit indicates whether the cancel security key update instruction carried by the LTM cell handover instruction is valid: when the reserved bit B is set to 0, the reserved bit A does not perform the cancel security key update regardless of whether it is set to 1 or 0; when the reserved bit B is set to 1, when the reserved bit A is set to 1, it indicates that the terminal device cancels the security key update; when the reserved bit A is set to 0, it indicates that the terminal device needs to perform the security key update.

[0260] According to the carried cancel security key update instruction, it is determined whether to perform the LTM cell handover without security key update.

[0261] S1212, the first base station sends a notification message to the second base station.

[0262] In this step, the notification message is used to inform the second base station that this LTM cell switching is a switching without performing security key update.

[0263] S1213, the terminal device disconnects the connection with the first base station, and determines whether to cancel the security key update.

[0264] In this step, different from step S711, the terminal device determines whether to cancel the security key update according to the cancel security key update instruction carried in the received LTM cell switching instruction.

[0265] S1214, the terminal device performs a random access procedure with the second base station.

[0266] S1215, the LTM cell switching is completed.

[0267] The contents in steps S1213-S1214 can refer to steps S712-S713. FIG. 14 is a structural example diagram of a terminal device disclosed in an embodiment of the present application. Taking a mobile phone as an example, the terminal device includes a processor 1401, an external memory interface 1403, an internal memory 1402, a display screen 1404, a camera 1405, an antenna 1, an antenna 2, a mobile communication module 1406, and a wireless communication module 1407, and the like.

[0268] It can be understood that the structure illustrated in the embodiment does not constitute a specific limitation on the terminal. In other embodiments, the terminal can include more or fewer components than those illustrated, or combine certain components, or split certain components, or different component arrangements. The illustrated components can be implemented in hardware, software, or a combination of software and hardware.

[0269] The processor 1401 can include one or more processing units, for example: the processor 1401 can include an application processor (AP), a modem processor, a graphics processing unit (GPU), an image signal processor (ISP), a controller, a video codec, a digital signal processor (DSP), a baseband processor, and / or a neural-network processing unit (NPU), etc. Different processing units can be independent devices, or can be integrated in one or more processors.

[0270] The external memory interface 1403 can be used to connect an external memory card, such as a Micro SD card, to expand the storage capacity of the terminal. The external memory card communicates with the processor 1401 through the external memory interface 1403 to implement a data storage function. For example, files such as music and videos are stored in the external memory card.

[0271] The internal memory 1402 can be used to store computer executable program code, which includes instructions. The processor 1401 executes various functional applications and data processing of the terminal by running the instructions stored in the internal memory 1402. The internal memory 1402 can include a program storage area and a data storage area. The program storage area can store an operating system, at least one application program required by a function (such as a sound playing function, an image playing function, etc.), and the like. The data storage area can store data created during use of the terminal (such as audio data, a phone book, etc.), and the like. In addition, the internal memory 1402 can include a high-speed random access memory, and can also include a non-volatile memory, such as at least one magnetic disk storage device, a flash memory device, a universal flash storage (UFS), and the like. The processor 1401 executes various functional applications and data processing of the terminal by running the instructions stored in the internal memory 1402 and / or the instructions stored in the memory disposed in the processor.

[0272] The wireless communication function of the terminal can be implemented through the antenna 1, the antenna 2, the mobile communication module 1406, the wireless communication module 1407, a modem processor, and a baseband processor, and the like.

[0273] The antenna 1 and the antenna 2 are used to transmit and receive electromagnetic wave signals. Each antenna in the terminal can be used to cover a single or multiple communication frequency bands. Different antennas can also be multiplexed to improve the utilization rate of the antennas. For example, the antenna 1 can be multiplexed as a diversity antenna of a wireless local area network. In some other embodiments, the antennas can be used in combination with a tuning switch.

[0274] The mobile communication module 1406 can provide a solution for wireless communication including 2G / 3G / 4G / 5G, etc. applied on the terminal. The mobile communication module 1406 can include at least one filter, switch, power amplifier, low noise amplifier (LNA), etc. The mobile communication module 1406 can receive electromagnetic waves by the antenna 1, and perform filtering, amplification, etc. on the received electromagnetic waves, and transfer to the modem processor for demodulation. The mobile communication module 1406 can also amplify the signal modulated by the modem processor, and radiate as electromagnetic waves through the antenna 1. In some embodiments, at least part of the function modules of the mobile communication module 1406 can be arranged in the processor 1401. In some embodiments, at least part of the function modules of the mobile communication module 1406 can be arranged in the same device as at least part of the modules of the processor 1401.

[0275] In some embodiments, the terminal initiates or receives a call request through the mobile communication module 1406 and the antenna 1.

[0276] In addition, on the above components, an operating system is running. For example, iOS operating system, Android operating system, Windows operating system, etc. Application programs can be installed and run on the operating system.

[0277] FIG. 15 is a structural example diagram of a base station 1500 disclosed in an embodiment of the present application, including a 1510 part, a 1520 part, and a 1530 part. The 1510 part is mainly used for baseband processing, controlling the base station, etc. The 1510 part is usually the control center of the base station, which can be usually referred to as a processor, used for controlling the base station to perform the processing operations of the network device side in the above method embodiments. The 1520 part is mainly used for storing computer program codes. The 1530 part is mainly used for transceiving radio frequency signals and converting radio frequency signals and baseband signals. The 1530 part can be usually referred to as a transceiver module, a transceiver, a transceiving circuit, or a transceiver, etc. The transceiver module of the 1530 part can also be referred to as a transceiver or a transceiver, etc., which includes an antenna 1533 and a radio frequency circuit (not shown in the figure), wherein the radio frequency circuit is mainly used for radio frequency processing. Optionally, the devices for realizing the receiving function in the 1530 part can be regarded as a receiver, and the devices for realizing the sending function can be regarded as a transmitter, that is, the 1530 part includes a receiver 1532 and a transmitter 1531. The receiver can also be referred to as a receiving module, a receiver, or a receiving circuit, etc., and the transmitter can be referred to as a transmitting module, a transmitter, or a transmitting circuit, etc.

[0278] The 1510 section and the 1520 section can include one or more boards, each of which can include one or more processors and one or more memories. The processors are configured to read and execute programs in the memories to implement baseband processing functions and control the base station. If there are multiple boards, the boards can be interconnected to enhance processing capability. As an optional implementation, the multiple boards can also share one or more processors, or share one or more memories, or share one or more processors and one or more memories at the same time.

[0279] For example, in an implementation, the transceiver module of the 1530 section is configured to perform the transceiver-related processes performed by the base station in the above-described embodiments. The processors of the 1510 section are configured to perform the processing-related processes performed by the base station in the above-described embodiments.

[0280] It should be understood that FIG. 15 is merely an example and is not limiting, and the above-described base station including processors, memories, and transceivers can not depend on the structure shown in FIG. 15.

[0281] The above merely provides a description of the specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any change or replacement within the technical scope disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A communication method characterized by comprising: The method is applied to a first base station, the first base station is a base station having established a connection with a terminal device, and the first base station is an anchor base station, which is a relay node base station between other base stations and a core network. The method comprises the following steps: In a cell handover process of the terminal device from the first base station to a second base station, it is determined whether the second base station is a non-anchor base station connected to the core network through the first base station; If the second base station is a non-anchor base station connected to the core network through the first base station, security key updating is cancelled.

2. The method of claim 1, wherein, The cell handover comprises layer 1 or layer 2 triggered mobility LTM cell handover.

3. The method according to claim 1 or 2, characterized in that, Before the step of determining whether the second base station is a non-anchor base station connected to the core network through the first base station, the method further comprises the following steps: Anchor connection relationship information is generated; The step of determining whether the second base station is a non-anchor base station connected to the core network through the first base station comprises the following step: According to the anchor connection relationship information, it is determined whether the second base station is a non-anchor base station connected to the core network through the first base station.

4. The method of claim 3, wherein, The anchor connection relationship information comprises at least one of the following: Anchor connection relationship information between the first base station and candidate target base stations; the candidate target base stations comprise the second base station; Anchor connection relationship information between the candidate target base stations.

5. The method of claim 3, wherein, Before the step of generating the anchor connection relationship information, the method further comprises the following step: Capability information of the terminal device supporting inter-base station cell handover with security key updating cancellation is acquired.

6. The method of claim 4, wherein, Before the step of generating the anchor connection relationship information between the first base station and the candidate target base stations, the method further comprises the following steps: Anchor information sent by the candidate target base stations is received; or Anchor information is sent to the candidate target base stations, the anchor information is used to acquire information about whether the candidate target base stations are non-anchor base stations, anchor information request responses sent by the candidate target base stations are received, and the anchor information request responses comprise anchor information of the candidate target base stations.

7. The method of claim 6, wherein: The anchor information request is carried by an LTM cell handover request; The anchor information request response is carried by an LTM cell handover response request.

8. The method according to any one of claims 4-7, characterized in that, After the step of generating the anchor connection relationship information between the first base station and the candidate target base stations, the method further comprises the following steps: The anchor connection relationship information is sent to the terminal device, so that: If the terminal device determines, according to the anchor connection relationship information, that the first base station is an anchor base station and the second base station is a non-anchor base station connected to the core network through the first base station, security key updating is cancelled by the terminal device; or After the terminal device is handed over from the first base station to the second base station and then performs a cell handover process from the second base station to a third base station, if the terminal device determines, according to the anchor connection relationship information, that the second base station is a non-anchor base station connected to the core network through the first base station, security key updating is cancelled by the terminal device.

9. The method of claim 8, wherein: The anchor connection relationship information is carried by a radio resource control (RRC) reconfiguration message.

10. The method according to any one of claims 4-7, characterized in that, After determining whether the second base station is a non-anchor base station connected to the core network through the first base station, the method further comprises: sending the anchor connection relationship information to the candidate target base station.

11. The method of claim 1 or 2, wherein, The canceling of the security key update further comprises: sending a canceling security key update instruction to the terminal device.

12. The method of claim 11, wherein, The canceling security key update instruction is carried by an LTM cell switching instruction.

13. The method of claim 1 or 2, wherein, Before determining whether the second base station is a non-anchor base station connected to the core network through the first base station, the method further comprises: receiving measurement report information sent by a terminal device; After determining whether the second base station is a non-anchor base station connected to the core network through the first base station, the method further comprises: sending an RRC reconfiguration message to the terminal device; receiving an RRC reconfiguration complete message sent by the terminal device; triggering the terminal device to initiate downlink synchronization and uplink synchronization with the second base station.

14. A communication method, comprising: The method is applied to a terminal device, and the method comprises: In a cell switching process from a first base station to a second base station, determining whether to cancel a security key update, wherein the first base station is a base station having established a connection with a terminal device, and the first base station is an anchor base station, and the anchor base station is a relay node base station between other base stations and a core network; if the second base station is a non-anchor base station connected to the core network through the first base station, canceling the security key update; if it is determined to cancel the security key update, performing a reestablishment procedure of a packet data convergence protocol (PDCP) layer.

15. The method of claim 14, wherein, The cell switching comprises layer 1 or layer 2 triggered mobility (LTM) cell switching.

16. The method according to claim 14 or 15, characterized in that The determining whether to cancel the security key update comprises: receiving anchor connection relationship information sent by the first base station; determining, according to the anchor connection relationship information, whether the second base station is a non-anchor base station connected to the core network through the first base station; if the second base station is the non-anchor base station, determining to cancel the security key update.

17. The method of claim 14 or 15, wherein, Before the determining whether to cancel the security key update, the method comprises: sending, to the first base station, capability information of inter-base station cell switching supporting canceling of the security key update.

18. The method of claim 16, wherein, The anchor connection relationship information comprises at least one of the following: an anchor connection relationship between the first base station and a candidate target base station, the candidate target base station comprising the second base station; an anchor connection relationship between the candidate target base stations.

19. The method of claim 16, wherein: The anchor connection relationship information is carried by a radio resource control (RRC) reconfiguration message.

20. The method of claim 14 or 15, wherein, The determining whether to cancel the security key update comprises: receiving a canceling security key update instruction sent by the first base station; determining, according to the canceling security key update instruction, to cancel the security key update.

21. The method of claim 20, wherein: The canceling security key update instruction is carried by an LTM cell switching instruction.

22. The method of any one of claims 16-21, wherein, After the canceling of the security key update, the method further comprises: After the terminal device is handed over from the first base station to the second base station, in a cell handover process from the second base station to a third base station, it is determined whether the second base station is a non-anchor base station connected to a core network through the first base station; If the second base station is the non-anchor base station, security key updating in the cell handover process is cancelled.

23. The method of claim 14 or 15, wherein, Before the determination of whether to cancel the security key updating, the method further comprises: sending measurement reporting information to the first base station; receiving an RRC reconfiguration message sent by the first base station; sending an RRC reconfiguration complete message to the first base station; performing downlink synchronization and uplink synchronization with the second base station; disconnecting the connection with the first base station and performing a random access procedure with the second base station.

24. A method of communication, comprising: The method is applied to a second base station, the second base station is a non-anchor base station, the non-anchor base station is a base station that is not a relay node for connection between other base stations and a core network, and the method comprises: After a terminal device is handed over from a first base station to a second base station, in a cell handover process from the second base station to a third base station, if the second base station is a non-anchor base station connected to a core network through the first base station, security key updating in the cell handover process is cancelled. The first base station is an anchor base station, and the anchor base station is a relay node for connection between other base stations and a core network.

25. The method of claim 24, wherein, The cell handover comprises layer 1 or layer 2 triggered mobility LTM cell handover.

26. The method of claim 24 or 25, wherein, Before the cancellation of the security key updating in the LTM cell handover process, the method further comprises: sending anchor information to the first base station; or receiving an anchor information request sent by the first base station, the candidate target base station comprising the second base station, sending an anchor information request response to the first base station, and the anchor information request response comprising anchor information of the second base station, so that the first base station generates anchor connection relationship information based on the anchor information request response.

27. The method of claim 26, wherein, The anchor connection relationship information comprises at least one of the following: an anchor connection relationship between the first base station and the candidate target base station; and an anchor connection relationship between the candidate target base stations.

28. The method of claim 26, wherein: the anchor information request is carried by an LTM cell handover request; and the anchor information request response is carried by an LTM cell handover request response.

29. The method of claim 24 or 25, wherein, Before the cancellation of the security key updating in the cell handover process, the method further comprises: receiving anchor connection relationship information sent by the first base station, the anchor connection relationship information being used to record anchor connection relationships of the first base station and candidate target base stations, the candidate target base stations comprising the second base station, and the first base station specifying the second base station as the non-anchor base station in the anchor connection relationship information.

30. The method of claim 24 or 25, wherein, After the cancellation of the security key updating in the cell handover process, the method further comprises: sending a notification message to the third base station, the notification message being used to inform the third base station that the terminal device is connected to the core network through the first base station, or that the terminal device cancels security key updating in the cell handover process from the second base station to the third base station.

31. A terminal device, comprising: The terminal device comprises a processor and a memory, the memory is used to store program code; the processor is used to run the program code, so that the terminal device implements the method in any one of claims 14-23.

32. A base station, comprising: The base station comprises a processor and a memory, the memory is used to store program code; the processor is used to run the program code, so that the base station implements the method in any one of claims 1-13, 24-30.

33. A computer-readable storage medium, characterized in that, The computer readable storage medium stores a computer program, when the computer program is executed by the processor, the method in any one of claims 1-30 is implemented.

Images