Communication method, system and related equipment

Abstract

The invention provides a communication method, a communication system and related equipment. Relates to the technical field of communication, and is used for solving the problem of time delay increase caused by security key update during cell switching among different base stations. The method comprises the following steps: in a cell switching process of terminal equipment from a first base station to a second base station, determining whether the second base station is a non-anchor base station connected with a core network through the first base station; and if the second base station is a non-anchor base station connected with the core network through the first base station, cancelling the updating of the security key. Based on the method, the time delay of cell switching between different base stations can be reduced by cancelling updating of the security key.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to a communication method, system and related equipment. Background Technology

[0002] The development of mobile communication networks is constantly evolving towards higher frequencies. High-frequency cells have smaller coverage areas, leading to more frequent cell reselection and handover for terminal devices. In 5G-A (5G Advance), a new handover procedure called L1 / L2 Triggered Mobility (LTM) was introduced to address this scenario and reduce service interruption time. Release 18 supports LTM between different cells within a single base station. LTM reduces mobility latency by enabling terminal devices to synchronize with the target cell in advance. Release 19 will extend the LTM framework to support handover between cells of different base stations. Under the current network deployment architecture, when terminal devices perform inter-base station cell handovers, access layer security key updates are required. The signaling interaction and processing during the security key update process introduce additional latency, which contradicts the goal of reducing handover latency. Summary of the Invention

[0003] This application provides a communication method, system, and related equipment to reduce the latency caused by security key updates during cell handover between base stations.

[0004] The first aspect of this 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 the core network, the method comprising: during the cell handover process of the terminal device 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; if the second base station is a non-anchor base station connected to the core network through the first base station, then canceling the security key update.

[0005] When a terminal device switches from a first base station to a second base station, if the second base station is a non-anchor base station that establishes a connection with the core network through the first base station, the security key update is cancelled. During cell handover, security key updates increase the processing latency of both the terminal device and the base station, increasing mobility interruption time and handover latency. The method provided in this application, when the above conditions are met, keeps the PDCP layer connection providing the security key unchanged at the anchor base station, and the terminal device and base station continue to use the original security key, thus cancelling the security key update and reducing processing latency and mobility interruption time. In the method provided in this application, cancellation of security key updates can be achieved by continuing to use the original security key. Furthermore, in the method provided in this application, the process of determining whether the second base station is a non-anchor base station that establishes a connection with the core network through the first base station is performed outside of the mobility interruption time, during the initial configuration and processing time, thereby reducing cell handover latency between base stations. Meanwhile, when switching is performed using this implementation method, the second base station does not need to perform path change to the Access and Mobility Management Function (AMF), and the core network does not need to update the downlink GPRS Tunneling Protocol User Plane (GTP-U). The GTP-U address on the access network side remains the address of the first base station, reducing the complexity of the handover.

[0006] In some alternative implementations, cell handover includes LTM cell handover.

[0007] In some optional implementations, 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, wherein the candidate target base station includes 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 includes: determining whether the second base station is a non-anchor base station based on the anchor connection relationship information.

[0008] In the solution provided in this application, the first base station can determine the anchor point information and generate the anchor point connection relationship information on its own, thereby reducing the signaling and data interaction with the candidate target base station and reducing complexity.

[0009] In some optional implementations, the anchor connection relationship information includes at least one of the following: the anchor connection relationship between the first base station and the candidate target base station; the anchor connection relationship between the candidate target base stations.

[0010] The anchor point connection relationship between the first base station and the candidate target base station can include the anchor point connection relationship between the first base station and at least one candidate target base station. The anchor point connection relationship between candidate target base stations includes the anchor point connection relationship between at least two candidate target base stations.

[0011] In some optional implementations, before generating anchor connection relationship information, the method further includes: obtaining information on the terminal device's ability to support inter-base station cell handover with the cancellation of security key updates.

[0012] In some optional implementations, before generating the anchor connection relationship information between the candidate target base station and the first base station, the method further includes: sending an anchor information request to the candidate target base station, the anchor information request being used to obtain information on 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 the anchor information of the candidate target base station; or, receiving the anchor information sent by the candidate target base station.

[0013] The proposed solution, in addition to allowing the original base station to determine the anchor connection information itself, can also allow the original base station to determine the anchor connection information through interaction with candidate target base stations. The anchor information in this application may 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 may 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.

[0014] In some alternative implementations, the anchor information request is carried by the LTM cell handover request; the anchor information request response is carried by the LTM cell handover response request.

[0015] Anchor information requests and anchor information request responses reuse existing processes, saving resources.

[0016] In some optional implementations, after generating the anchor connection relationship information between the candidate target base station and the first base station, the method further includes: sending the anchor connection relationship information to the terminal device, such that: if the terminal device determines, based on 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, during a cell handover process from the first base station to the second base station and then from the second base station to the third base station, if the terminal device determines, based on 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 generating the anchor connection relationship information, the first base station sends this information to the terminal device, enabling the terminal device to determine whether to cancel the security key update based on this information.

[0017] In some alternative implementations, anchor connection information is carried by the Radio Resource Control (RRC) reconfiguration message.

[0018] Anchor point connection information reuses existing RRC reconfiguration messages in the process, saving resources.

[0019] In some alternative implementations, 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 includes: sending anchor connection relationship information to the candidate target base station.

[0020] Anchor point connection relationship information is sent to candidate target base stations to ensure that the message is synchronized there. Furthermore, in subsequent continuous handover scenarios, candidate target base stations may use this information to determine whether to cancel key updates. For example, when a terminal device switches to a second base station, the second base station can use the received anchor point connection relationship information to decide whether to perform a security key update during subsequent handovers, without needing to repeatedly obtain the anchor point connection relationship information. This reduces the latency of obtaining anchor point connection relationship information during subsequent handovers.

[0021] In some alternative implementations, canceling a security key update includes sending a command to the terminal device to cancel the security key update.

[0022] The first base station notifies the terminal device to cancel the security key update for this cell handover by sending a cancellation security key update command, thereby reducing the process complexity for the terminal device.

[0023] In some alternative implementations, the security key update cancellation instruction is carried over to the LTM cell handover instruction. This reuses existing processes and saves resources.

[0024] In some optional implementations, 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: 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 includes: sending an RRC reconfiguration message to the terminal device; receiving an RRC reconfiguration completion message sent by the terminal device; and triggering the terminal device to initiate downlink synchronization and uplink synchronization with the second base station.

[0025] A second aspect of this application provides a communication method applied to a terminal device. The method includes: during a cell handover 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 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 the core network; if the second base station is a non-anchor base station connected to the core network through the first base station, then canceling the security key update; if it is determined to cancel the security key update, then executing a process to cancel the re-establishment of the Packet Data Convergence Protocol (PDCP) layer.

[0026] During cell handover, security key updates increase processing latency for terminal devices and base stations, leading to increased mobility interruption and handover delays. The method provided in this application, when the above conditions are met, maintains the PDCP layer connection providing the security key at the anchor base station, allowing the terminal device and base station to continue using the original security key, thus canceling the security key update and reducing processing latency and mobility interruption. In the method provided in this 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 of the mobility interruption time, during the initial configuration and processing period, thereby reducing cell handover latency between base stations. Furthermore, after handover using this implementation method, the second base station does not need to perform path changes to the AMF, and the core network does not need to update the downlink GTP-U; the access network-side GTP-U address remains the address of the first base station, reducing handover complexity.

[0027] In some alternative implementations, cell handover includes LTM cell handover.

[0028] In some optional implementations, determining whether to cancel the security key update includes: receiving anchor connection relationship information sent by a 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 a second base station; determining, based on 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 a non-anchor base station, then determining to cancel the security key update.

[0029] The terminal device receives anchor connection relationship information sent by the base station. Its main function is to enable the terminal device to determine whether to cancel the security key update based on this information.

[0030] In some alternative implementations, before determining to cancel the security key update, the process includes: sending inter-base station cell handover capability information that supports the cancellation of the security key update to the first base station.

[0031] In some optional implementations, the anchor connection relationship information includes at least one of the following: the anchor connection relationship between the first base station and the candidate target base station, wherein the candidate target base station includes the second base station; and the anchor connection relationship between the candidate target base stations.

[0032] In some alternative implementations, anchor connection information is carried by the Radio Resource Control (RRC) reconfiguration message.

[0033] Anchor point connection information reuses existing RRC reconfiguration messages in the process, saving resources.

[0034] In some optional implementations, determining whether to cancel the security key update includes receiving a cancellation security key update instruction sent by the first base station; and determining to cancel the security key update based on the cancellation security key update instruction.

[0035] In this embodiment, the terminal device executes a corresponding cancellation security key update operation by receiving instructions sent by the base station, thereby reducing the process complexity of the terminal device.

[0036] In some alternative implementations, the security key update cancellation instruction is carried over to the LTM cell handover instruction. This reuses existing processes and saves resources.

[0037] In some optional implementations, after canceling the security key update, the method further includes: during the cell handover process from the second base station to the third base station after the terminal device switches from the first base station to the second base station, determining whether the second base station is a non-anchor base station that connects to the core network through the first base station; if the second base station is a non-anchor base station, then canceling the security key update during the cell handover process.

[0038] In continuous cell handover scenarios, after a terminal device is switched from an anchor base station to a non-anchor base station connected to that anchor base station, the security key update can be canceled in subsequent handovers, further reducing the handover latency of continuous cell handover.

[0039] In some optional implementations, before determining whether to cancel the security key update, the method further includes: sending measurement reporting information to a 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 and uplink synchronization with a second base station; disconnecting the connection with the first base station and executing a random access procedure with the second base station.

[0040] A third aspect of this application provides a communication method applied to a second base station, wherein the second base station is a non-anchor base station, which is a base station that does not act as a relay node connecting other base stations to the core network. The method includes: after a terminal device performs a cell handover from a first base station to the second base station, during 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 the core network through the first base station, then the security key update during the cell handover process is cancelled; the first base station is an anchor base station, which is a relay node base station between other base stations and the core network.

[0041] The method provided in this application, when meeting the above conditions, ensures that the PDCP layer connection providing the security key remains unchanged at the anchor base station, and the terminal device and base station continue to use the original security key, thus canceling the security key update and reducing processing latency and mobility interruption time. In the method provided in this 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, during the initial configuration and processing time, thereby reducing the LTM cell handover latency between base stations. Simultaneously, after handover using this implementation method, 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; the access network-side GTP-U address remains the address of the first base station, reducing the complexity of handover. In continuous cell handover scenarios, after the terminal device switches from an anchor base station to a non-anchor base station connected to that anchor base station, regardless of whether the target base station for this handover is an anchor base station or a non-anchor base station, no security key update is required. This further reduces the handover latency of continuous cell handover.

[0042] In some optional implementations, before canceling the security key update during cell handover, the method further includes: receiving an anchor information request sent by a first base station, the candidate target base station including a 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.

[0043] In some optional implementations, the anchor connection relationship information includes at least one of the following: the anchor connection relationship between the first base station and the candidate target base station; the anchor connection relationship between the candidate target base stations.

[0044] The first base station determines anchor point information to the candidate target base station, wherein the second base station is one of the candidate target base stations. The second base station sends information to the first base station about whether it is a non-anchor point base station, so that the first base station can generate anchor point connection relationship information.

[0045] In some optional implementations, the anchor information request is carried by the LTM cell handover request; the anchor information request response is carried by the LTM cell handover request response. This reuses existing processes and saves resources.

[0046] In some optional implementations, before canceling the security key update during cell handover, the method further includes: receiving anchor connection relationship information sent by a 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 a second base station, the first base station specifying the second base station as a non-anchor base station in the anchor connection relationship information.

[0047] In continuous cell handover scenarios, the second base station determines whether cell handover with the security key update canceled can be performed based on the received anchor connection relationship information.

[0048] In some alternative implementations, after canceling the security key update during cell handover, the method further includes: sending a notification message to a third base station, the notification message informing the third base station terminal device that it is connected to the core network through the first base station.

[0049] A fourth aspect of this application provides a terminal device, which includes a processor and a memory, wherein the memory is used to store program code; and the processor is used to run the program code, thereby enabling the terminal device to implement the above-described method.

[0050] The fifth aspect of this application provides a base station, which includes a processor and a memory, wherein the memory is used to store program code; and the processor is used to run the program code, causing the base station to implement the above-described method.

[0051] A sixth aspect of this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the above-described method. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the structure of a 5G network base station;

[0053] Figure 2 This is a schematic diagram of the LTM cell handover process;

[0054] Figure 3 A schematic diagram of the LTM cell handover process under certain conditions;

[0055] Figure 4 This is a schematic diagram illustrating the connection relationship between anchor base stations and non-anchor base stations in this application;

[0056] Figure 5 This is a schematic diagram of a communication method provided in an embodiment of this application;

[0057] Figure 6 This is a schematic diagram of the second communication method provided in the embodiments of this application;

[0058] Figure 7 This is a schematic diagram of an LTM cell handover communication method provided in an embodiment of this application;

[0059] Figure 8 This is a schematic diagram of the second LTM cell handover communication method provided in the embodiments of this application;

[0060] Figure 9 This is a schematic diagram of the third LTM cell handover communication method provided in the embodiments of this application;

[0061] Figure 10 This is a schematic diagram of the fourth LTM cell handover communication method provided in the embodiments of this application;

[0062] Figure 11 This is a schematic diagram of the fifth LTM cell handover communication method provided in the embodiments of this application;

[0063] Figure 12 This is a schematic diagram of the sixth LTM cell handover communication method provided in the embodiments of this application;

[0064] Figure 13 This is a schematic diagram of the signaling format of a media access control layer control unit;

[0065] Figure 14 This is a schematic diagram of the structure of a terminal device disclosed in an embodiment of this application;

[0066] Figure 15 This is a schematic diagram of the structure of a base station disclosed in an embodiment of this application. Detailed Implementation

[0067] To facilitate a clear description of the technical solutions in the embodiments of this application, the terms "exemplary" or "for example" are used in the embodiments of this application to indicate that they are examples, illustrations, or descriptions. Any embodiment or design scheme described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0068] In the embodiments of this application, terms such as "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, "first instruction information" and "second instruction information" are used only to distinguish different instruction information and do not limit their order. Those skilled in the art will understand that terms such as "first" and "second" do not limit the quantity or execution order, and that terms such as "first" and "second" do not necessarily imply that they are different.

[0069] In this application embodiment, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, ab, a--c, bc, or abc, where a, b, and c can be single or multiple.

[0070] In this application's embodiments, a base station can refer to a public mobile communication network device, an interface device for terminal devices to access the Internet, and also a form of radio station, referring to a radio transceiver station that transmits information with terminal devices within a certain radio coverage area. This includes base stations (BS), also known as base station equipment, which is a device deployed in a radio access network (RAN) to provide wireless communication functions. In 5G NR, the gNB (gfortified network node) provides base station functionality, and the evolved Node B (ng-eNB) further evolves into a base station. The gNB communicates with the terminal device using NR technology, while the ng-eNB communicates with the terminal device using evolved universal terrestrial radio access (E-UTRA) technology. Both the gNB and ng-eNB can connect to the 5G core network. The base station in this application's embodiments also includes equipment that provides base station functionality in future new communication systems.

[0071] like Figure 1As shown, the 5G network architecture with separate CU and DU components comprises two parts: the centralized unit (CU) and the distributed unit (DU). The CU and DU are separated 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, while the CU is responsible for the Packet Data Convergence Protocol (PDCP) layer and the Radio Resource Control (RRC) layer. A single DU may contain one or more cells.

[0072] The terminal devices in this application embodiment may include handheld devices, vehicle-mounted devices, etc., that have wireless communication capabilities. For example, some terminal devices include: mobile phones, tablets, PDAs, laptops, mobile internet devices (MIDs), wearable devices, VR devices, AR devices, wireless terminals in industrial control, wireless terminals in autonomous driving, wireless terminals in remote medical surgery, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, wireless terminals in smart homes, cellular phones, cordless phones, Session Initiation Protocol (SIP) phones, Wireless Local Loop (WLL) stations, Personal Digital Assistants (PDAs), handheld devices with wireless communication capabilities, computing devices or other processing devices connected to a wireless modem, in-vehicle devices, wearable devices, terminal devices in 5G networks, or terminal devices in future evolved Public Land Mobile Networks (PLMNs), etc., and the embodiments of this application are not limited to these.

[0073] By way of example and not limitation, in this embodiment, the terminal device can also be a wearable device. Wearable devices, also known as wearable smart devices, are a general term for devices that utilize wearable technology to intelligently design and develop everyday wearables, such as glasses, gloves, watches, clothing, and shoes. Wearable devices are portable devices that are worn directly on the body or integrated into the user's clothing or accessories. Wearable devices are not merely hardware devices, but also achieve powerful functions through software support, data interaction, and cloud interaction. Broadly speaking, wearable smart devices include those that are feature-rich, large in size, and can achieve complete or partial functions without relying on a smartphone, such as smartwatches or smart glasses, as well as those that focus on a specific type of application function and require the use of other devices such as smartphones, such as various smart bracelets and smart jewelry for vital sign monitoring.

[0074] Furthermore, in this embodiment, the terminal device can also be a terminal device in an Internet of Things (IoT) system. IoT is an important component of the future development of information technology. Its main technical feature is to connect objects to the network through communication technology, thereby realizing an intelligent network of human-machine interconnection and object-to-object interconnection.

[0075] The terminal device in this application embodiment may also be referred to as: User Equipment (UE), Mobile Station (MS), Mobile Terminal (MT), Access Terminal, User Unit, User Station, Mobile Station, Mobile Station, Remote Station, Remote Terminal, Mobile Device, User Terminal, Terminal, Wireless Communication Equipment, User Agent, or User Equipment, etc.

[0076] In this embodiment of the application, the device for implementing the function of the terminal can be the terminal itself; or it can be a device that supports the terminal in implementing the function, such as a chip system, which can be installed in the terminal.

[0077] In this embodiment, the network elements involved in the handover process can be represented by cells or by base stations. In this embodiment, for a network architecture with separated CUs and DUs, a base station includes one CU and all DUs connected to that CU. Therefore, in a network architecture with separated CUs and DUs, anchor base stations and non-anchor base stations can also be anchor CUs and non-anchor CUs. Define anchor CUs and non-anchor CUs to implement cell handover between CUs without performing security key updates. A DU is a node with which the terminal directly interacts with signaling and transmits data. The signaling interaction and information transmission between the original CU and the candidate target CU are similar to those between the original base station and the candidate target base station, and will not be described further here. The signaling interaction and information transmission between the original DU and the terminal are similar to those between the original base station and the terminal, and will not be described further here. The original CU first transmits the signaling and information that needs to be interacted with the terminal to the original DU, and then the original DU interacts with the terminal.

[0078] In such Figure 1 In the network structure shown, base stations are deployed more densely, and terminal devices face more frequent cell handovers. To ensure user experience and reduce cell handover latency, LTM cell handover within the same CU has been proposed. Current LTM cell handover reduces handover latency through early synchronization. To better illustrate the technical solution provided by the embodiments of this application, the relevant content of LTM will be explained first. Figure 2 This is an example of the LTM cell handover process. In Figure 2, "first cell", "second cell", "third cell", etc. are for illustrative purposes only. The actual message sending and receiving entities are network devices. Figure 2 Taking a candidate target cell containing two cells as an example, and taking the second cell as the target cell as an example, the selection of the target cell can be determined based on the measurement report of the terminal device. The specific process will not be elaborated here.

[0079] Figure 2 The LTM switching process shown includes the following steps:

[0080] S201. The terminal device sends measurement reporting information to the first cell.

[0081] The terminal device performing LTM cell handover is already in a connected state and connected to the first cell. The terminal device will measure each candidate target cell and send the measurement report information to the first cell. Taking a 5G network as an example, the measurement and reporting of Reference Signal Receiving Power (RSRP) is performed at Layer 1 and Layer 3. In this step, the measurement report information can be either a Layer 1 measurement report or a Layer 3 measurement report, etc.

[0082] The first cell determines the terminal device's support capability for LTM based on the measurement results, and determines to execute LTM based on the terminal device's support capability for LTM, and executes the candidate target cell configuration preparation process, including steps S202-S205.

[0083] S202, the first cell sends an LTM cell handover request to the second and third cells.

[0084] S203, the second and third cells send an LTM cell handover request response to the first cell.

[0085] In S203, the LTM cell handover request responses sent by the second cell and the third cell respectively include the configuration information of the second cell and the third cell.

[0086] S204. The first cell sends an RRC reconfiguration message to the terminal device.

[0087] The RRC reconfiguration message includes the configuration information of the candidate target cell.

[0088] S205, The terminal device sends an RRC reconfiguration complete message to the first cell.

[0089] The RRC reconfiguration complete message indicates that the terminal device has received the RRC reconfiguration message.

[0090] S206. The terminal device performs downlink synchronization for the candidate target cell.

[0091] S207. The terminal device performs uplink synchronization for the candidate target cell.

[0092] In some implementations, the RRC reconfiguration information instructs the terminal device to measure the uplink timing advance, the terminal measures the timing advance of the first cell, and determines the timing advance of the second cell based on the reception time difference between the first and second cells.

[0093] In other implementations, the first cell triggers Contention-Free Random Access (CFRA) via a Physical Downlink Control Channel (PDCCH) Order to obtain the timing advance of candidate target cells. The terminal initiates CFRA with the candidate target cells to obtain the timing advance, and the network manages the validity of the timing advance.

[0094] S208. The terminal device sends a Layer 1 measurement report to the first cell.

[0095] The terminal device performs Layer 1 measurements on the first cell and the candidate target cell respectively, obtains a Layer 1 measurement report, and sends it to the first cell.

[0096] S209. The first cell sends an LTM cell handover command to the terminal device.

[0097] The first cell, based on L1 measurement and reporting messages, selects the target cell for this handover from the candidate target cells. Taking the second cell as an example, the handover command instructs the terminal to handover from the first cell to the second cell.

[0098] In some implementations, the handover instruction includes: a MAC control element (MAC CE), which includes at least a timing advance (TA), a transmission configuration indication (TCI) state id, CFRA resource information, and a candidate target cell configuration information identifier.

[0099] Among them, the timing advance is the timing advance that the terminal obtains and is still in a valid state. That is, before S211, if the network determines that the TA obtained by the terminal before is still in a valid state, then the TA is included in the MAC CE.

[0100] S210, The terminal device disconnects from the first cell.

[0101] S211. The terminal device and the second cell perform a random access procedure.

[0102] In an alternative S211 approach, when the terminal receives an LTM cell handover command and the MAC CE carries the TA, or when the terminal device self-tests the TA, the terminal device will initiate a cell handover to the target cell without random access.

[0103] S212, The terminal equipment completes the LTM cell handover.

[0104] When the target cell receives an RRC reconfiguration message from the terminal device, it indicates that the terminal device has completed the LTM cell handover. If step S211 is executed, the LTM cell handover is complete when the random access procedure between the terminal device and the target cell is completed. If the terminal device performs a cell handover without random access, the target cell receiving the first uplink data sent by the terminal device indicates that the terminal device has completed the LTM cell handover.

[0105] In the LTM cell handover described above, the terminal device needs to execute the handover operation to the target cell according to the LTM cell handover command sent by the base station. To further improve the flexibility and robustness of mobility management, Conditional LTM was proposed. In Conditional LTM, the terminal device is pre-configured with the corresponding execution conditions for handover to each candidate target cell, and the handover is executed when the handover conditions are met. Figure 3 This is an example of a conditional LTM cell handover process.

[0106] Figure 3 The LTM cell handover process under the given conditions includes the following steps:

[0107] S301. The terminal device sends measurement reporting information to the first cell.

[0108] For detailed steps, please refer to step S201.

[0109] S302, The first cell sends conditional LTM cell handover requests to the second and third cells.

[0110] S303, the second cell and the third cell send a conditional LTM cell handover request response to the first cell.

[0111] In the above steps, the conditional LTM cell handover request responses sent by the second and third cells respectively include configuration information of the second and third cells and configuration information of the handover conditions. The original base station configures a certain number of candidate target cells and corresponding handover conditions based on the received conditional LTM cell handover request responses.

[0112] One of the candidate target cells can be configured with one or more handover conditions. The handover conditions can be set as follows: for example, the signal quality of the candidate target cell is better than that of the first cell. Another example is that the signal quality of the first cell is less than an absolute threshold, while the signal quality of the candidate target cell is higher than an absolute threshold, and so on. This application does not limit the specific handover conditions.

[0113] S304. The first cell sends an RRC reconfiguration message to the terminal device.

[0114] The RRC reconfiguration message includes the configuration information and handover conditions for each candidate target cell.

[0115] S305, The terminal device sends an RRC reconfiguration complete message to the first cell.

[0116] The RRC reconfiguration complete message is used to indicate that the terminal device has received the RRC reconfiguration message.

[0117] S306. Downlink synchronization for candidate target cells.

[0118] S307, Uplink synchronization for candidate target cells.

[0119] S306. The terminal equipment evaluates the handover conditions and disconnects the connection with the first cell if the handover conditions are met.

[0120] Upon receiving an RRC reconfiguration message, the terminal device evaluates the handover conditions. When at least one candidate target cell meets the corresponding handover conditions, the terminal device disconnects from the first cell and begins LTM cell handover on the determined candidate target cell. After the handover is completed, the configuration information is released.

[0121] S307. The terminal equipment and the second cell perform a random access procedure.

[0122] S308, Terminal equipment completes LTM cell handover under certain conditions.

[0123] For details of steps S307 and S308, please refer to steps S211 and S212.

[0124] Currently, both LTM cell handover and conditional LTM cell handover involve security key updates in cross-CU scenarios, which introduce latency during the handover process. The greatest benefit of LTM cell handover lies in reducing handover latency; therefore, in this scenario, it is necessary to consider how to reduce or avoid the latency issues caused by security key updates.

[0125] To address the latency issue caused by security keys, this application first proposes the concepts of anchor base stations and non-anchor base stations. In this application, an anchor base station is a relay node base station that connects other base stations to the core network. More specifically, the anchor base station acts as a PDCP anchor point for connecting other base stations to the core network. That is, the connection between the terminal equipment connecting to other base stations and the PDCP layer of the core network requires other base stations to connect to the core network through the anchor base station; in other words, the PDCP layer of the non-anchor base station is carried on the anchor base station. In this application, a non-anchor base station is a base station that does not act as a relay node to connect other base stations to the core network. A non-anchor base station can be a base station connected to the core network through an anchor base station, or it can be directly connected to the core network but not act as a relay node connecting other base stations. Taking a 5G base station as an example... Figure 4 This is a schematic diagram illustrating the connection relationship between anchor base stations and non-anchor base stations in this application.

[0126] Figure 4 In this diagram, base stations 1 and 2 are anchor base stations, while base stations 3, 4, 5, and 6 are non-anchor base stations. Specifically, 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.

[0127] Based on the above classification of base stations, there may be various possibilities when a terminal device switches between different base stations, such as switching from an anchor base station to a non-anchor base station, or switching from an anchor base station to another anchor base station, etc. In a technical solution proposed in this application embodiment, since the access layer security key update process is implemented at the PDCP layer, when a terminal device switches from one anchor base station to a non-anchor base station connected to that anchor base station, there is no need to re-establish the PDCP layer connection; the original security key continues to be used. Therefore, the terminal device does not need to update the security key when performing LTM cell handover between base stations. The specific implementation steps are as follows: Figure 5 As shown.

[0128] Figure 5 Includes the following steps:

[0129] S501. During the LTM cell handover process triggered by the first base station to the second base station at layer 1 or layer 2, determine whether the second base station is a non-anchor base station connected to the core network through the first base station.

[0130] In this step, the first base station is the base station already connected to the terminal device and is the original base station in this LTM cell handover process. The second base station is the target base station in this LTM cell handover process. Before the terminal device performs the handover, the first base station needs to determine whether multiple candidate target base stations containing the target base station are non-anchor base stations.

[0131] S502. If the second base station is a non-anchor base station connected to the core network through the first base station, then the security key update is cancelled.

[0132] In this step, the decision to cancel the security key update can be made by either the first base station or the terminal device. If the first base station decides to cancel the security key update, it needs to send a cancellation command to the terminal device to notify it to cancel the security key update; if the terminal device decides to cancel the security key update, the first base station does not need to send a cancellation command to the terminal device.

[0133] S503. If it is determined that the security key update will be cancelled, the terminal device will execute the cancellation of the re-establishment process of the Packet Data Convergence Protocol (PDCP) layer.

[0134] In this embodiment, canceling the security key update mainly refers to canceling the Access Stratum (AS) security key update. AS signaling security and data security are handled 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 implements the AS security update process by sending RRC reconfiguration messages. These messages contain activation information elements such as security configuration. The terminal device calculates security keys such as KUPint, KUPenc, KRRCint, and KRRCenc based on these elements and configures them to the PDCP layer. At this point, the AS layer security update can be considered complete. Therefore, in this embodiment, the security key update can be canceled by canceling the PDCP layer re-establishment during inter-base station cell handover. In the solution provided in this application, when the terminal device performs inter-base station cell handover, 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 keys, thus canceling the security key update.

[0135] LTM cell handover supports continuous handover. Figure 5 Based on the scheme shown, this application proposes a technical solution that can cancel security key updates in continuous LTM cell handover scenarios. Figure 6 This is an example diagram of the scheme.

[0136] Figure 6 Includes the following steps:

[0137] S601. During the handover process from the second base station to the third base station after the terminal device has switched from the first base station to the LTM cell of the second base station, determine whether the second base station is a non-anchor base station that connects to the core network through the first base station.

[0138] In this step, the terminal device has already performed one LTM cell handover, as mentioned above. Figure 5 The diagram illustrates an LTM cell handover from the first base station to the second base station. At this time, the terminal device is in connected state, connected to the second base station, which is the original base station for this handover, and the third base station is the target base station. Whether the second base station is a non-anchor base station connected to the core network through the first base station can be determined by the second base station itself, which can then send a cancellation security key command to the terminal device. Alternatively, the terminal device can determine this based on the anchor connection relationship information sent by the base station.

[0139] S602. If the second base station is a non-anchor base station that connects to the core network through the first base station, then cancel the security key update during the LTM cell handover process.

[0140] If the conditions in step S601 are met, the security key update is cancelled. In continuous switching scenarios, the security key update is cancelled as described in step S503 above, by cancelling the re-establishment of the PDCP layer.

[0141] The following provides further embodiments of the proposed solution in specific scenarios. Since the technical solution proposed in this application is aimed at the LTM cell handover scenario across base stations, in the following embodiments, "base station" is used to refer to a cell in general. It can be understood that a base station can contain multiple cells. In the following embodiments, the handover of the terminal device from one base station to another base station means the handover process of the terminal device from a cell under one base station to a cell under another base station.

[0142] Figure 7 This is an example diagram illustrating an inter-base station LTM cell handover communication method provided in this application. Figure 7 In the implementation shown, anchor point connection information is obtained by reusing the original process.

[0143] Figure 7 Includes the following steps:

[0144] S701, The terminal device sends measurement reporting information to the first base station.

[0145] The terminal device in the connected state is currently connected to the first base station and reports measurement reports for each cell to the first base station. This measurement report can be one of the following: a Layer 1 measurement report, a Layer 3 measurement report, or other types of measurement reports.

[0146] The first base station determines the terminal equipment's support capability for LTM based on the measurement report, and determines to perform LTM cell handover based on the terminal equipment's support capability for LTM, and then performs the configuration preparation process for subsequent candidate target base stations.

[0147] S702, The first base station sends an LTM cell handover request to the candidate target base station.

[0148] To support LTM cell handover with security key updates cancelled, this step includes an anchor information request in the LTM cell handover request. The anchor information request is used to obtain information on whether the candidate target base station is a non-anchor base station.

[0149] Among them, the candidate target base stations include the target base station for this LTM cell handover and other candidate target base stations.

[0150] S703, The candidate target base station sends an LTM cell handover request response to the first base station.

[0151] Correspondingly, after receiving the above anchor information request, multiple candidate target base stations will carry the anchor information request response in the LTM cell handover request response.

[0152] In the solution provided in this application, the anchor information request response includes the anchor information of this base station, which includes information on whether this base station is a non-anchor base station of the first base station, or the anchor information includes information on whether this base station is a non-anchor base station.

[0153] S704. The candidate target base station sends anchor point information to the first base station.

[0154] In another scheme provided by this application, the anchor point information is sent from the candidate target base station to the first base station. When this method is adopted, the anchor point information request and anchor point information request response may not be carried in steps S702 and S703.

[0155] S705, the first base station sends an RRC reconfiguration message to the terminal device.

[0156] After receiving the LTM cell handover request response and the included anchor information request response, the first base station generates anchor connection relationship information based on its own and the anchor information of the candidate target base stations. In terms of format, the anchor connection relationship information can be a list containing the anchor base station identifiers or non-anchor base station identifiers of the first base station and the candidate target base stations, as well as the association relationships between the base stations. For example, there are three candidate target base stations: base station A, base station B, and base station C. Base station A can be an anchor base station, while base stations B and C can only be non-anchor base stations. After obtaining the anchor information of these three candidate target base stations, the first base station generates the association relationships: for example, base station B is a non-anchor base station connected to the first base station, and base station C is a non-anchor base station connected to base station A. The further generated anchor connection relationship information includes: the identifiers of the first base station and base station A as anchor base stations, and the identifiers of base stations B and C as non-anchor base stations; there is a mapping relationship between the identifier of base station B and the identifier of the first base station in the table, and a mapping relationship between the identifier of base station C and the identifier of base station A in the table.

[0157] In this embodiment of the application, the anchor point connection relationship information is sent to the terminal device by the RRC reconfiguration message.

[0158] S706. The first base station sends anchor point connection relationship information to the candidate target base station.

[0159] In this step, there can be one or more candidate target base stations, the purpose of which is to notify and update the configuration information in the network.

[0160] S707, The terminal device sends an RRC reconfiguration complete message to the first base station.

[0161] S708, The terminal device performs downlink synchronization for the candidate target cell.

[0162] S709, The terminal device performs uplink synchronization for the candidate target cell.

[0163] S710, the terminal equipment sends layer 1 measurement reporting information to the first base station.

[0164] S711, The first base station sends an LTM cell handover command to the terminal equipment.

[0165] After determining that the target base station is its own non-anchor base station based on the above anchor point connection relationship information, the first base station sends an LTM cell handover command to the terminal device.

[0166] S712. The terminal device disconnects from the first base station and determines whether to cancel the security key update.

[0167] After receiving the LTM cell handover instruction in step S710, the terminal device will disconnect from the first base station. Simultaneously, the terminal device will determine whether to perform an LTM cell handover to cancel the security key update based on the target cell identifier 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, taking the second base station as the target base station as an example, if the second base station is a non-anchor base station connected to the core network through the first base station, the terminal device will determine to cancel the security key update.

[0168] S713, The terminal equipment executes the random access procedure with the second base station.

[0169] S714, Complete LTM cell handover.

[0170] When the target cell receives an RRC reconfiguration message from the terminal device, it indicates that the terminal device has completed the LTM cell handover. If step S712 is executed, the LTM cell handover is complete when the random access procedure between the terminal device and the target cell is completed. If the terminal device performs a cell handover without random access, i.e., step S712 is not executed, the target cell receiving the first uplink data sent by the terminal device indicates that the terminal device has completed the LTM cell handover.

[0171] Figure 8 Another implementation method is provided, which can be applied to conditional LTM cell handover. Figure 8 In the embodiment shown, the terminal device decides whether to perform an LTM handover and whether to cancel the security key update during the handover.

[0172] S801, The terminal device sends measurement reporting information to the first base station.

[0173] This step can be found in step S701.

[0174] S802, The first base station sends a conditional LTM cell handover request to the candidate target base station.

[0175] Conditional LTM cell handover requests include anchor point information requests.

[0176] S803, The candidate target base station sends a conditional LTM cell handover request response to the first base station.

[0177] The conditional LTM cell handover request response includes an anchor information request response. The first base station generates anchor connection relationship information based on its own anchor information and that of the candidate target base station.

[0178] In the above steps, the conditional LTM cell handover request response sent by the candidate target base station includes 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 based on the received conditional LTM cell handover request response.

[0179] One of the candidate target cells can be configured with one or more handover conditions. The handover conditions can be set as follows: for example, the signal quality of the candidate target base station is better than the cell currently connected to by the terminal device under the first base station. Another example is that the signal quality of the cell currently connected to by the terminal device under the first base station is less than an absolute threshold, while the signal quality of the target cell under the candidate target base station is higher than an absolute threshold, and so on. This application does not limit the specific handover conditions.

[0180] S804. The candidate target base station sends anchor point information to the first base station.

[0181] For details, please refer to step S704.

[0182] S805, the first base station sends an RRC reconfiguration message to the terminal device.

[0183] In this step, in addition to the basic candidate target base station configuration information, the RRC reconfiguration message also carries anchor point connection relationship information and handover condition information for each candidate target cell.

[0184] S806. The first base station sends anchor point connection relationship information to the candidate target base station.

[0185] S807, The terminal device sends an RRC reconfiguration complete message to the first base station.

[0186] S808, The terminal device performs downlink synchronization for the candidate target cell.

[0187] S809, The terminal device performs uplink synchronization for the candidate target cell.

[0188] S810 and terminal equipment perform LTM condition assessment and decide to perform LTM cell handover; confirm whether LTM cell handover with security update cancellation can be performed.

[0189] In this step, the terminal device determines and selects a cell that currently meets the handover conditions for handover based on the handover condition information of each candidate target cell obtained in step S804. The handover conditions can be referred to in 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 base station connected to the core network through the first base station, the terminal device determines to cancel the security key update.

[0190] S811, The terminal device executes the random access procedure with the second base station.

[0191] S812, Complete LTM cell handover.

[0192] When the target cell receives an RRC reconfiguration message from the terminal device, it indicates that the terminal device has completed the LTM cell handover. If step S810 is executed, the LTM cell handover is complete when the random access procedure between the terminal device and the target cell is completed. If the terminal device performs a cell handover without random access, i.e., step S810 is not executed, the target cell receiving the first uplink data sent by the terminal device indicates that the terminal device has completed the LTM cell handover.

[0193] This application provides another implementation method. In this implementation method, the anchor point 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 sent to the terminal device and each candidate target base station. Figure 9 This is an example diagram of this solution.

[0194] Figure 9 Includes the following steps:

[0195] S901, The terminal device sends measurement reporting information to the first base station.

[0196] For details, please refer to step S701.

[0197] S902, The first base station sends an LTM cell handover request to the candidate target base station.

[0198] S903, The candidate target base station sends an LTM cell handover request response to the first base station.

[0199] S904, The first base station sends an RRC reconfiguration message to the terminal device.

[0200] In this step, the RRC reconfiguration message carries anchor connection relationship information. This information is generated by the first base station, which specifies whether each candidate target base station is an anchor base station or a non-anchor base station, and also configures their connection relationships. The anchor connection relationship information includes the information mentioned above. For details, please refer to step S704.

[0201] S905, The first base station sends anchor point connection relationship information to the candidate target base station.

[0202] S906, The terminal device sends an RRC reconfiguration complete message to the first base station.

[0203] S907, The terminal device performs downlink synchronization for the candidate target cell.

[0204] S908, The terminal device performs uplink synchronization for the candidate target cell.

[0205] S909, The terminal equipment sends Layer 1 measurement reporting information to the first base station.

[0206] S910, the first base station sends an LTM cell handover command to the terminal equipment.

[0207] S911, The terminal device disconnects from the first base station.

[0208] Steps S905-S911 can be referred to steps S706-S712.

[0209] S912, The terminal equipment executes the random access procedure with the second base station.

[0210] S913, Complete LTM cell handover.

[0211] For details, please refer to step S714.

[0212] Conditional LTM Figure 10 An example of one implementation method is given. (Compared to...) Figure 9 and Figure 7 The differences are similar. Figure 10 and Figure 8 The difference is Figure 10 In the method shown, the anchor point connection information is independently determined and generated by the first base station.

[0213] S1001, The terminal device sends measurement reporting information to the first base station.

[0214] S1002, The first base station sends a conditional LTM cell handover request to the candidate target base station.

[0215] In step S1002, the LTM cell handover request does not include an anchor point information request.

[0216] S1003, The candidate target base station sends a conditional LTM cell handover request response to the first base station.

[0217] In step S1003, the LTM cell handover request response does not include the anchor point information request response.

[0218] In steps S1002 and S1003, the conditional LTM cell handover request response sent by the candidate target base station includes configuration information of the candidate target base station and configuration information of the handover conditions, respectively. The first base station configures a certain number of candidate target cells and corresponding handover conditions based on the received conditional LTM cell handover request response.

[0219] One of the candidate target cells can be configured with one or more handover conditions. The handover conditions can be set as follows: for example, the signal quality of the candidate target base station is better than the cell currently connected to by the terminal device under the first base station. Another example is that the signal quality of the cell currently connected to by the terminal device under the first base station is less than an absolute threshold, while the signal quality of the target cell under the candidate target base station is higher than an absolute threshold, and so on. This application does not limit the specific handover conditions.

[0220] S1004, The first base station sends an RRC reconfiguration message to the terminal device.

[0221] S1005, The first base station sends anchor point connection relationship information to the candidate target base station.

[0222] S1006, The terminal device sends an RRC reconfiguration complete message to the first base station.

[0223] S1007. The terminal device performs downlink synchronization for the candidate target cell.

[0224] S1008, The terminal device performs uplink synchronization for the candidate target cell.

[0225] For details of steps S1004-S1008, please refer to steps S805-S809.

[0226] S1009. The terminal equipment performs an LTM assessment of the conditions and decides to perform an LTM cell handover; it confirms whether an LTM cell handover with the security key update canceled can be performed.

[0227] In this step, the terminal device determines and selects a cell that currently meets the handover conditions for handover based on the handover condition information of each candidate target cell obtained in step S1004. The handover conditions can be referred to in step S1003. 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 base station connected to the core network through the first base station, the terminal device determines to cancel the security key update.

[0228] S1010, The terminal device executes the random access procedure with the second base station.

[0229] S1011, Complete LTM cell handover.

[0230] For scenarios involving continuous LTM switching, in Figure 6 Based on this, embodiments of this application provide a more specific implementation method, such as... Figure 11 As shown. In Figure 11 In the middle, the terminal device switched to Figures 7-10 After the target base station (second base station) is reached, an LTM cell handover will be performed again from the second base station to the third base station. Figure 11 The implementation shown is also an LTM switching process. Other steps besides those shown in the figure will not be described in detail here. For specific details, please refer to the relevant documentation for different scenarios. Figures 7-10 The content in [the document] states that in scenarios with continuous LTM switching, RRC reconfiguration is not performed.

[0231] Figure 11 The process includes the following steps:

[0232] S1101, The second base station sends an LTM cell handover command to the terminal device.

[0233] This step is optional. In conditional LTM, this step is not performed; the terminal device evaluates and decides whether to perform the handover. In unconditional LTM, this step is required, and the terminal device is instructed to perform an LTM cell handover via an LTM cell handover command.

[0234] S1102. The terminal device disconnects from the second base station, and at the same time, the terminal device confirms whether to perform LTM cell handover to cancel security updates.

[0235] In this step, if the terminal device performs an LTM cell handover based on the pre-configured handover conditions for candidate target cells, it determines and selects a cell that currently meets the handover conditions for handover, as shown in step S803. Taking the determination of the target base station as the third base station as an example, if 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. The terminal device determines whether the second base station meets the aforementioned conditions for canceling the security key update based on the anchor connection relationship information sent by the base station during the previous handover.

[0236] S1103, The terminal device or the second base station sends a notification message to the third base station.

[0237] The notification message can be sent by the terminal device to the third base station, or by the second base station to the third base station. The notification message informs the third base station which anchor base station the terminal device connects to the core network through; in this embodiment, it connects through the first base station's core network.

[0238] exist Figure 11 In this approach, when the terminal device determines whether to cancel the security key update in a continuous LTM cell handover scenario, it does not need to consider the type of base station of the target base station, but only the base station currently connected, which enables more flexible LTM cell handover with cancellation of security key update.

[0239] For unconditional LTM cell handover, embodiments of this application propose another solution: the base station determines whether the terminal device should cancel the security key update during the LTM cell handover and instructs the terminal device via an LTM handover command. The implementation method is as follows: Figure 12 As shown.

[0240] Figure 12 Includes the following steps:

[0241] S1201, The terminal device sends measurement reporting information to the first base station.

[0242] This step can be found in step S701.

[0243] S1202, The first base station sends an LTM cell handover request to the candidate target base station.

[0244] S1203, The candidate target base station sends an LTM cell handover request response to the first base station.

[0245] Figure 12 The illustrated implementation supports Figure 7 and Figure 9 The two methods for obtaining anchor connection relationship information are shown. If the anchor connection relationship information needs to be obtained by sending an anchor information request to the candidate target base station and obtaining an anchor information request response, then the anchor information request is carried in the LTM cell handover request in step S1202, referring to step S702; the anchor information request response is carried in the LTM cell handover request response in step S1203, referring to step S703.

[0246] S1204, The first base station sends an RRC reconfiguration message to the terminal device.

[0247] In this step, the RRC reconfiguration message carries anchor connection relationship information.

[0248] S1205, The first base station sends anchor point connection relationship information to the candidate target base station.

[0249] S1206. The terminal device sends an RRC reconfiguration complete message to the first base station.

[0250] S1207. The terminal device performs downlink synchronization for the candidate target cell.

[0251] S1208, The terminal device performs uplink synchronization for the candidate target cell.

[0252] S1209. The terminal device sends Layer 1 measurement reporting information to the first base station.

[0253] S1210, Cancel security key update command.

[0254] In one embodiment provided by this application, when the terminal device determines whether to cancel the security key update in this handover based on the cancellation security key update information sent by the base station, the cancellation security key update information sent by the base station can be transmitted via a dedicated signaling, which can be a cancellation security key update instruction.

[0255] S1211, The first base station sends an LTM cell handover command to the terminal device.

[0256] 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. The handover command instructs the terminal device to switch from the first cell under the first base station to the target cell under the target base station. The LTM cell handover command in this step carries a command to cancel the security key update.

[0257] In some implementations, the switching command includes MAC CE. The format of MAC CE is as follows: Figure 13 As shown, the MAC CE can contain the following fields: Target Config ID, Timing Advance Command, Transmission Configuration Indicator State ID, Uplink Transmission Configuration Indicator State ID, Random Access Preamble Index, Synchronization Signal / Physical Broadcast Channel Index (SS / PBCH index), Physical Random Access Channel Mask Index, etc. Figure 13 Some bits are unallocated and are marked as "R", meaning reserved bits.

[0258] The aforementioned cancellation of security key update instruction is indicated by the reserved bits of the MAC CE. For example, using one reserved bit A to represent the cancellation of security key update instruction: when reserved bit A is set to 1, it indicates that the terminal device is instructed to cancel the security key update; when reserved bit A is set to 0, it indicates that the terminal device needs to perform a security key update. As another example, using two reserved bits A and B to represent the cancellation of security key update instruction, one bit indicates whether the cancellation of security key update instruction carried by the LTM cell handover instruction is valid: when reserved bit B is set to 0, then regardless of whether reserved bit A is 1 or 0, no cancellation of security key update is performed; when reserved bit B is set to 1, then when reserved bit A is set to 1, it indicates that the terminal device is instructed to cancel the security key update; when reserved bit A is set to 0, it indicates that the terminal device needs to perform a security key update.

[0259] The decision on whether to perform an LTM cell handover without security key update is determined based on the carried command to cancel security key update.

[0260] S1212, The first base station sends a notification message to the second base station.

[0261] In this step, the notification message is used to inform the second base station that this LTM cell handover will not perform a security key update.

[0262] S1213. The terminal device disconnects from the first base station and confirms whether to cancel the security key update.

[0263] In this step, unlike step S711, the terminal device determines whether to cancel the security key update based on the cancellation security key update instruction carried in the received LTM cell handover instruction.

[0264] S1214. The terminal device executes the random access procedure with the second base station.

[0265] S1215, Complete LTM cell handover.

[0266] The contents of steps S1213-S1214 can be found in steps S712-S713. Figure 14 This is a structural example diagram of a terminal device disclosed in an embodiment of this application. Taking a mobile phone as an example, it 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, etc.

[0267] It is understood that the structure illustrated in this embodiment does not constitute a specific limitation on the terminal. In other embodiments, the terminal may include more or fewer components than illustrated, or combine some components, or split some components, or have different component arrangements. The illustrated components may be implemented in hardware, software, or a combination of software and hardware.

[0268] Processor 1401 may include one or more processing units, such as application processor (AP), modem processor, graphics processing unit (GPU), image signal processor (ISP), controller, video codec, digital signal processor (DSP), baseband processor, and / or neural network processing unit (NPU). These different processing units may be independent devices or integrated into one or more processors.

[0269] The external storage interface 1403 can be used to connect an external storage card, such as a Micro SD card, to expand the terminal's storage capacity. The external storage card communicates with the processor 1401 through the external storage interface 1403 to perform data storage functions. For example, music, video, and other files can be saved on the external storage card.

[0270] Internal memory 1402 can be used to store executable program code, including instructions. Processor 1401 executes various functional applications and data processing of the terminal by running the instructions stored in internal memory 1402. Internal memory 1402 may include a program storage area and a data storage area. The program storage area may store the operating system, at least one application program required for a function (such as sound playback, image playback, etc.), etc. The data storage area may store data created during terminal use (such as audio data, phonebook, etc.). In addition, internal memory 1402 may include high-speed random access memory, and may also include non-volatile memory, such as at least one disk storage device, flash memory device, universal flash storage (UFS), etc. Processor 1401 executes various functional applications and data processing of the terminal by running instructions stored in internal memory 1402 and / or instructions stored in memory located in the processor.

[0271] The terminal's wireless communication function can be implemented through antenna 1, antenna 2, mobile communication module 1406, wireless communication module 1407, modem processor, and baseband processor.

[0272] Antenna 1 and antenna 2 are used to transmit and receive electromagnetic wave signals. Each antenna in the terminal can be used to cover one or more communication frequency bands. Different antennas can also be reused to improve antenna utilization. For example, antenna 1 can be reused as a diversity antenna for a wireless local area network. In some other embodiments, the antennas can be used in conjunction with a tuning switch.

[0273] The mobile communication module 1406 can provide solutions for wireless communication applications including 2G / 3G / 4G / 5G in terminals. The mobile communication module 1406 may include at least one filter, switch, power amplifier, low-noise amplifier (LNA), etc. The mobile communication module 1406 can receive electromagnetic waves via antenna 1, and perform filtering, amplification, and other processing on the received electromagnetic waves before transmitting them to a modem processor for demodulation. The mobile communication module 1406 can also amplify the signal modulated by the modem processor and convert it into electromagnetic waves for radiation via antenna 1. In some embodiments, at least some functional modules of the mobile communication module 1406 may be housed in the processor 1401. In some embodiments, at least some functional modules of the mobile communication module 1406 and at least some modules of the processor 1401 may be housed in the same device.

[0274] In some embodiments, the terminal initiates or receives call requests via the mobile communication module 1406 and the antenna 1.

[0275] In addition, an operating system runs on top of the aforementioned components. Examples include iOS, Android, and Windows. Applications can be installed and run on this operating system.

[0276] Figure 15This is a structural example diagram of a base station 1500 disclosed in an embodiment of this application, including parts 1510, 1520, and 1530. Part 1510 is mainly used for baseband processing and base station control; part 1510 is typically the control center of the base station, often referred to as a processor, used to control the base station to perform the processing operations on the network device side in the above method embodiments. Part 1520 is mainly used to store computer program code. Part 1530 is mainly used for the transmission and reception of radio frequency signals and the conversion between radio frequency signals and baseband signals; part 1530 can typically be referred to as a transceiver module, transceiver, transceiver circuit, or transceiver. The transceiver module of part 1530, also referred to as a transceiver or transceiver, 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 device in part 1530 used to implement the receiving function can be regarded as a receiver, and the device used to implement the transmitting function can be regarded as a transmitter, that is, part 1530 includes a receiver 1532 and a transmitter 1531. A receiver can also be called a receiving module, receiver, or receiving circuit, while a transmitter can be called a transmitting module, transmitter, or transmitting circuit.

[0277] Sections 1510 and 1520 may include one or more circuit boards, each of which may include one or more processors and one or more memories. The processors are used to read and execute programs from the memories to implement baseband processing functions and control the base station. If multiple circuit boards exist, they can be interconnected to enhance processing capabilities. As an alternative implementation, multiple circuit boards may share one or more processors, multiple circuit boards may share one or more memories, or multiple circuit boards may simultaneously share one or more processors.

[0278] For example, in one implementation, the transceiver module in section 1530 is used to execute the transceiver-related processes performed by the base station in the above embodiments. The processor in section 1510 is used to execute the processing-related processes performed by the base station in the above embodiments.

[0279] It should be understood that Figure 15 This is merely an example and not a limitation; the base station described above, including the processor, memory, and transceiver, may not depend on... Figure 15 The structure shown.

[0280] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A communication method, characterized in that, The method is applied to a first base station, which is a base station that has 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 the core network. The method includes: During the cell handover process from the first base station to the second base station for the terminal device, 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, then the security key update is cancelled.

2. The method according to claim 1, characterized in that, The cell handover includes mobility LTM cell handover triggered by layer 1 or layer 2.

3. The method according to claim 1 or 2, characterized in that, 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: Anchor point connection relationship information is generated, and the candidate target base station includes 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 includes: Based on the anchor point connection relationship information, determine whether the second base station is a non-anchor point base station connected to the core network through the first base station.

4. The method according to claim 1 or 2, characterized in that, The anchor point connection relationship information includes at least one of the following: The anchor point connection relationship between the first base station and the candidate target base station; The anchor point connection relationship between the candidate target base stations.

5. The method according to claim 3, characterized in that, Before generating the anchor point connection relationship information, the method further includes: Obtain information about the terminal device's ability to support inter-base station cell handover with the security key update cancelled.

6. The method according to claim 3, characterized in that, Before generating the anchor point connection information between the candidate target base station and the first base station, the method further includes: Receive the anchor point information sent by the candidate target base station; or, An anchor information request is sent to the candidate target base station. The anchor information request is used to obtain information on whether the candidate target base station is a non-anchor base station. An anchor information request response sent by the candidate target base station is received. The anchor information request response includes the anchor information of the candidate target base station.

7. The method according to claim 6, characterized in that: The anchor point information request is carried in the LTM cell handover request; The anchor point information request response is carried by the LTM cell handover response request.

8. The method according to any one of claims 3-7, characterized in that, After generating the anchor point connection information between the candidate target base station and the first base station, the method further includes: Send the anchor point connection relationship information to the terminal device so that: If the terminal device determines, based on 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, then the terminal device cancels the security key update; or, If, during the process of the terminal device switching from the first base station to the second base station and then switching from the second base station to the third base station, the terminal device determines, based on 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, then the terminal device cancels the security key update.

9. The method according to claim 8, characterized in that: The anchor point connection information is carried by the Radio Resource Control (RRC) reconfiguration message.

10. The method according to any one of claims 3-7, 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 includes: The anchor point connection relationship information is sent to the candidate target base station.

11. The method according to claim 1 or 2, characterized in that, The cancellation of security key update also includes: Send a command to the terminal device to cancel the security key update.

12. The method according to claim 11, characterized in that, The command to cancel security key update is carried by the LTM cell handover command.

13. The method according to claim 1 or 2, characterized in that, 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: Receive measurement reporting information sent by terminal devices; 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 includes: Send an RRC reconfiguration message to the terminal device; Receive the RRC reconfiguration complete message sent by the terminal device; The terminal device is triggered to initiate downlink and uplink synchronization with the second base station.

14. A communication method, characterized in that, The method is applied to a terminal device, and the method includes: During the cell handover process from the first base station to the second base station, it is determined whether to cancel the security key update. Here, 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 the core network. If the second base station is a non-anchor base station connected to the core network through the first base station, then the security key update is cancelled; If it is determined that the security key update will be cancelled, the process of cancelling the re-establishment of the Packet Data Convergence Protocol (PDCP) layer will be executed.

15. The method according to claim 14, characterized in that, The cell handover includes mobility LTM cell handover triggered by layer 1 or layer 2.

16. The method according to claim 14 or 15, characterized in that, The process of determining whether to cancel the security key update includes: Receive anchor point connection relationship information sent by the first base station; Based on the anchor point connection relationship information, determine whether the second base station is a non-anchor point base station connected to the core network through the first base station; If the second base station is the non-anchor base station, then the security key update is cancelled.

17. The method according to claim 14 or 15, characterized in that, Before determining whether to cancel the security key update, the method includes: Send information to the first base station regarding the ability to perform inter-base station cell handover that supports canceling security key updates.

18. The method according to claim 14 or 15, characterized in that, The anchor point connection relationship information includes at least one of the following: The anchor point connection relationship between the first base station and the candidate target base station, wherein the candidate target base station includes the second base station; The anchor point connection relationship between the candidate target base stations.

19. The method according to claim 16, characterized in that: The anchor point connection information is carried by the Radio Resource Control (RRC) reconfiguration message.

20. The method according to claim 14 or 15, characterized in that, The process of determining whether to cancel the security key update includes: Receive the command to cancel security key update sent by the first base station; The security key update is cancelled based on the cancellation security key update instruction.

21. The method according to claim 20, characterized in that: The command to cancel security key update is carried by the LTM cell handover command.

22. The method according to any one of claims 16-21, characterized in that, After canceling the security key update, the method further includes: During the cell handover process from the second base station to the third base station after the terminal device is switched from the first base station to the second base station, it is determined whether the second base station is a non-anchor base station that connects to the core network through the first base station. If the second base station is the non-anchor base station, then the security key update during the cell handover process is cancelled.

23. The method according to claim 14 or 15, characterized in that, Before determining whether to cancel the security key update, the method further includes: Send measurement reporting information to the first base station; Receive the RRC reconfiguration message sent by the first base station; Send an RRC reconfiguration complete message to the first base station; Perform downlink and uplink synchronization with the second base station; Disconnect from the first base station and execute the random access procedure with the second base station.

24. A communication method, characterized in that, Applied to a second base station, which is a non-anchor base station, the method includes: After the terminal device performs a cell handover from the first base station to the second base station, during the cell handover process from the second base station to the third base station, if the second base station is a non-anchor base station that connects to the core network through the first base station, the security key update during the cell handover process is cancelled. The first base station is an anchor base station, which is a relay node base station between other base stations and the core network.

25. The method according to claim 24, characterized in that, The cell handover includes mobility LTM cell handover triggered by layer 1 or layer 2.

26. The method according to claim 24 or 25, characterized in that, Before canceling the security key update during the LTM cell handover process, the method further includes: Send the anchor point information to the first base station; or, The system receives an anchor point information request sent by the first base station, wherein the candidate target base station includes the second base station, and sends an anchor point information request response to the first base station, wherein the anchor point information request response includes the anchor point information of the second base station, so that the first base station generates anchor point connection relationship information based on the anchor point information request response.

27. The method according to claim 26, characterized in that, The anchor point connection relationship information includes at least one of the following: The anchor point connection relationship between the first base station and the candidate target base station; The anchor point connection relationship between the candidate target base stations.

28. The method according to claim 26, characterized in that: The anchor point information request is carried in the LTM cell handover request; The anchor point information request response is carried in the LTM cell handover request response.

29. The method according to claim 24 or 25, characterized in that, Before canceling the security key update during cell handover, the method further includes: The system receives anchor connection relationship information sent by the first base station. The anchor connection relationship information is used to record the anchor connection relationship between the first base station and the candidate target base station. The candidate target base station includes the second base station. The first base station designates the second base station as the non-anchor base station in the anchor connection relationship information.

30. The method according to claim 24 or 25, characterized in that, After canceling the security key update during the cell handover process, the method further includes: A notification message is sent 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 the security key update during the cell handover process from the second base station to the third base station.

31. A terminal device, characterized in that, The terminal device includes a processor and a memory, the memory being used to store program code; the processor being used to run the program code, causing the terminal device to implement the method as described in any one of claims 14-23.

32. A base station, characterized in that, The base station includes a processor and a memory, the memory being used to store program code; the processor being used to run the program code, causing the base station to implement the method as described 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 that, when executed by a processor, implements the method as described in any one of claims 1 to 30.

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