Communication method and apparatus

Abstract

A communication method and an apparatus, used for solving the problem of communication failure caused by key misalignment between a terminal device and an access network device in subsequent handover or multiple handover processes. The method comprises: determining that a trigger condition for a target cell is met and a first message from a first access network device and used for indicating that key notification to a candidate access network device has been completed has been received; and, on the basis of the first message, determining to send to the target cell a second message used for accessing the target cell, the first access network device being an access network device to which a current serving cell of a terminal device belongs, and the target cell being one of candidate cells managed by the candidate access network device. The described method enables a terminal device and a target cell to perform communication on the basis of a same key, thereby improving the communication security.

Description

Communication method and device

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of the People's Republic of China on December 29, 2023, with application number 202311868620.2 and application name "A Communication Method and Device", the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of communication technology, and in particular to a communication method and device. Background Art

[0004] In mobile communication systems, the movement of terminal devices causes changes in the communication link between the terminal device and the access network device, necessitating a cell handover or access network device handover. When an access network device handover occurs, the terminal device typically needs to change its key. This means that different keys are used for data encryption and integrity protection when communicating with the source and target access network devices to ensure secure communication.

[0005] For mobility management technologies that support "subsequent handovers" or "multiple handovers," the access network device configures multiple candidate cells for the terminal. These candidate cells may be located on different access network devices. The terminal device can perform multiple handovers between these candidate cells. Aligning the keys used by the terminal device and the access network device to ensure normal communication is a worthy research issue. Summary of the Invention

[0006] The present application provides a communication method and apparatus for solving the problem of communication failure caused by misalignment of the key of a terminal device with that of an access network device during subsequent switching or multiple switching processes.

[0007] In a first aspect, a communication method is provided, the execution subject of the method can be a terminal device or a chip, chip system or circuit for the terminal device, and the method can be implemented by the following steps: determining that the trigger condition of the target cell is met and a first message has been received from the first access network device to indicate that the key notification to the candidate access network device has been completed, and determining to send a second message for accessing the target cell to the target cell based on the first message, the first access network device is the access network device to which the current service cell of the terminal device belongs, and the target cell is one of the candidate cells managed by the candidate access network device.

[0008] In this embodiment of the present application, the terminal device can determine through the first message that the access network device to which the target cell belongs has (or is about to) obtain the key for the next handover. The terminal device performs the cell handover after receiving the first message, which facilitates the terminal device and the target cell to communicate based on the same key, thereby improving communication security.

[0009] In one possible design, the first message includes second information, wherein the second information is used to indicate that key notification has been completed to the candidate access network device. In the above manner, the second information can explicitly indicate that key notification has been completed to the candidate access network device.

[0010] In one possible design, the first message includes second information and third information, wherein the second information is used to indicate that key notification has been completed to the candidate access network device, and the third information is used to indicate parameters related to the key update. The above design facilitates key derivation by the terminal device by carrying the third information, which can further facilitate communication between the terminal device and the target cell based on the same key, thereby improving communication security.

[0011] In one possible design, the first message includes third information, which is used to indicate parameters related to the key update. Carrying the third information facilitates key derivation by the terminal device, which further facilitates communication between the terminal device and the target cell based on the same key, thereby improving communication security. Furthermore, the third information can implicitly indicate that key notification has been completed to the candidate access network device, saving signaling overhead.

[0012] In one possible design, the third information includes at least one of the following: a next hop chain count, or a key set change indication.

[0013] In one possible design, the method further includes: determining a key for the target cell based on the target cell information and the third information. This design allows the terminal device to derive the same key rules as the access network device to which the source cell belongs, thereby further facilitating communication between the terminal device and the target cell based on the same key, thereby improving communication security.

[0014] In one possible design, the information of the target cell includes at least one of the following: the physical cell identifier of the target cell, or the downlink frequency information of the target cell.

[0015] In one possible design, the method further includes: determining a first message to be received when a key needs to be updated after switching to the target cell. Since in some scenarios, the terminal device does not need to update the key after switching to the target cell, such as same-site handover, the above-mentioned waiting for receiving the first message only when a key update is required, and not waiting for receiving the first message when a key update is not required, can reduce the delay of switching when a key update is not required.

[0016] In one possible design, determining that the key needs to be updated after switching to the target cell includes: determining that the access network device to which the target cell belongs is different from the first access network device.

[0017] In one possible design, the method further includes: sending a third message to the first access network device, the third message being used to request the first access network device to notify the candidate access network device of the key. In this manner, by requesting the first access network device to notify the candidate access network device of the key via the third message after the trigger condition of the target cell is met, the access network device to the target cell can obtain the key in a timely manner, thereby reducing handover latency.

[0018] In one possible design, the third message also indicates that the triggering condition of the target cell has been met. In this way, the third message can implicitly request the first access network device to notify the candidate access network device of the key by indicating that the triggering condition of the target cell has been met.

[0019] In one possible design, the method also includes: determining a first message to be received when the channel quality of the serving cell is greater than or equal to a threshold value.

[0020] Since there may be a time difference between meeting the trigger conditions of the target cell and receiving the first message, the above design waits for receiving the first message when the channel quality of the serving cell is good, so that the terminal device can continue to communicate with the network through the serving cell while waiting for the first message, thereby minimizing the impact of cell switching on the terminal device communication.

[0021] In one possible design, the method also includes: receiving a fourth message, where the fourth message is used to configure the triggering conditions of the target cell.

[0022] In a second aspect, a communication method is provided. The method may be performed by an access network device or a chip, chip system, or circuit for the access network device. The method may be implemented by the following steps: receiving first information from a second access network device, and determining a first key based on the first information, wherein the first information includes information about at least one candidate cell of a terminal device. The first key is sent to a candidate access network device to which the at least one candidate cell belongs, and after sending the first key, a first message is sent to the terminal device, the first message indicating that key notification has been completed to the candidate access network device.

[0023] In an embodiment of the present application, the access network device to which the source cell belongs obtains information about the candidate cell from the second access network device, so that the access network device to which the source cell belongs can deduce the key for the next handover of the terminal device based on the information about the candidate cell obtained from the second access network device, and send the key to the candidate access network device. In this way, the access network device to which the target cell belongs in a subsequent handover can obtain the same key as the terminal device, thereby facilitating the terminal device and the target cell to correctly decrypt or correctly complete the message integrity check.

[0024] Moreover, in the present application, the access network device to which the source cell belongs indicates to the terminal device through a first message that the key notification between access network devices has been completed after sending the key to the candidate access network device, so that the terminal device can determine through the first message that the access network device to which the target cell belongs has (or is about to) obtain the key for the next switching, thereby facilitating communication between the terminal device and the target cell based on the same key, and can improve communication security.

[0025] In one possible design, the first message includes second information, wherein the second information is used to indicate that key notification has been completed to the candidate access network device. In the above manner, the second information can explicitly indicate that key notification has been completed to the candidate access network device.

[0026] In one possible design, the first message includes second information and third information, wherein the second information is used to indicate that key notification has been completed to the candidate access network device, and the third information is used to indicate parameters related to the key update. The above design facilitates key derivation by the terminal device by carrying the third information, which can further facilitate communication between the terminal device and the target cell based on the same key, thereby improving communication security.

[0027] In one possible design, the first message includes third information, which is used to indicate parameters related to the key update. Carrying the third information facilitates key derivation by the terminal device, which further facilitates communication between the terminal device and the target cell based on the same key, thereby improving communication security. Furthermore, the third information can implicitly indicate that key notification has been completed to the candidate access network device, saving signaling overhead.

[0028] In one possible design, the third information includes at least one of the following: a next hop chain count, or a key set change indication.

[0029] In one possible design, the information of at least one candidate cell includes at least one of the following: a global cell identifier of at least one candidate cell, a physical cell identifier of at least one candidate cell, or downlink frequency information of at least one candidate cell.

[0030] On the third aspect, a communication method is provided, the execution subject of the method may be an access network device or a chip, chip system or circuit used for the access network device, and the method may be implemented by the following steps: sending first information to the first access network device, the first information including information of at least one candidate cell of the terminal device.

[0031] In an embodiment of the present application, the access network device to which the terminal device has historically accessed sends information about the candidate cell of the terminal device to a candidate access network device (such as the first access network device), so that in subsequent switching, the access network device to which the source cell belongs (one of the above-mentioned candidate access network devices, the first access network device in this application) can deduce the key for the next switching of the terminal device based on the obtained information about the candidate cell.

[0032] In one possible design, the information of at least one candidate cell includes at least one of the following: a global cell identifier of at least one candidate cell, a physical cell identifier of at least one candidate cell, or downlink frequency information of at least one candidate cell.

[0033] In a fourth aspect, a communication method is provided, the execution subject of the method may be a terminal device or a chip, chip system or circuit used for the terminal device, and the method may be implemented by the following steps: determining whether the trigger conditions of the target cell are met, and sending first information and second information to the first access network device to which the target cell belongs, the first information being used to access the target cell, and the second information being used by the first access network device to obtain a key from the second access network device, the second access network device being the access network device to which the source cell of the terminal device belongs.

[0034] In an embodiment of the present application, the terminal device sends relevant information of the source cell / terminal device (i.e., the above-mentioned second information) to the access network device to which the target cell belongs, so that the access network device to which the target cell belongs can determine the access network device to which the source cell belongs, thereby triggering the access network device to which the target cell belongs to request a key from the access network device to which the source cell belongs, which is beneficial for the terminal device and the target cell to correctly decrypt or correctly complete the message integrity check.

[0035] Moreover, the terminal device can trigger the access network device of the target cell to request the key from the access network device of the source cell in a timely manner through the second information, so that subsequent communications between the terminal device and the target cell can be based on the same key, thereby improving communication security.

[0036] In one possible design, the second information includes at least one of the following: information of the source cell, or information of the terminal device. In this way, the access network device to which the target cell belongs can determine the access network device to which the source cell belongs.

[0037] In one possible design, the information of the source cell includes an identifier of the source cell.

[0038] In one possible design, the information of the terminal device includes an identification of the terminal device.

[0039] In one possible design, the first information is not encrypted and / or not integrity protected. In this way, the first access network device can correctly obtain the content of the first information, facilitate subsequent key alignment, and achieve secure communication.

[0040] In one possible design, the method further includes: receiving third information from the first access network device, the third information being used to indicate parameters related to the key update; determining the key of the target cell based on the third information; and communicating with the target cell based on the key of the target cell. The above design allows the terminal device to derive keys in a manner consistent with the key derivation rules of the access network device to which the source cell belongs, thereby further facilitating communication between the terminal device and the target cell based on the same key, thereby improving communication security.

[0041] In one possible design, the third information includes at least one of the following: a next hop chain count, or a key set change indication.

[0042] In one possible design, the method further includes: determining the key of the target cell using a horizontal deduction method; and communicating with the target cell based on the key of the target cell. In the above method, if the key is derived using a horizontal deduction method, the first access network device does not need to send key update-related parameters (i.e., the third information) to the terminal device, thereby saving signaling overhead.

[0043] In one possible design, the method further includes: determining to send the first information and the second information after the triggering condition of the target cell is met when the channel quality of the serving cell is less than or equal to a threshold value.

[0044] The above design can minimize the impact of cell switching on terminal device communications by performing switching first when the channel quality of the serving cell is poor and triggering the access network device of the target cell to request a key.

[0045] In one possible design, the method also includes: receiving a first message, where the first message is used to configure the triggering conditions of the target cell.

[0046] In a fifth aspect, a communication method is provided. The execution subject of the method can be an access network device or a chip, chip system, or circuit for the access network device. The method can be implemented by the following steps: receiving first information and second information from a terminal device, and sending a request message to the second access network device, wherein the first information is used to access a target cell, the second information is used by the first access network device to obtain a key from the second access network device, the second access network device is the access network device to which the source cell of the terminal device belongs, the request message is used to request a key, and the request message carries fourth information, the fourth information is used to identify the terminal device. By receiving a response message to the request message, the key of the target cell of the terminal device can be obtained, the target cell being one of the candidate cells managed by the first access network device.

[0047] In the embodiment of the present application, the access network device to which the target cell belongs can determine the access network device to which the source cell belongs based on the relevant information of the source cell / terminal device (i.e., the second information described above), and thus can request a key from the access network device to which the source cell belongs. In this way, in subsequent handovers, the access network device to which the target cell belongs can actively obtain a key that is consistent with that of the terminal device, thereby facilitating the correct decryption or message integrity check between the terminal device and the target cell.

[0048] Moreover, the access network device to which the target cell belongs can promptly request a key from the access network device to which the source cell belongs when triggered by the second information, so that subsequent communications between the terminal device and the target cell can be based on the same key, thereby improving communication security.

[0049] In one possible design, the second information includes at least one of the following: information of the source cell, or information of the terminal device. In this way, the access network device to which the target cell belongs can determine the access network device to which the source cell belongs.

[0050] In one possible design, the information of the source cell includes an identifier of the source cell.

[0051] In one possible design, the information of the terminal device includes an identification of the terminal device.

[0052] In one possible design, the first information is not encrypted and / or not integrity protected. In this way, the first access network device can correctly obtain the content of the first information, facilitate subsequent key alignment, and achieve secure communication.

[0053] In one possible design, the response message further carries third information indicating parameters related to the key update; the method further includes: sending the third information to the terminal device; and communicating with the terminal device based on the key of the target cell. This design allows the terminal device to derive keys consistent with the key derivation rules of the access network device to which the source cell belongs, thereby further facilitating communication between the terminal device and the target cell based on the same key, thereby improving communication security.

[0054] In one possible design, the third information includes at least one of the following: a next hop chain count, or a key set change indication.

[0055] In a sixth aspect, a communication method is provided. The execution subject of the method can be an access network device or a chip, chip system, or circuit for the access network device. The method can be implemented by the following steps: after receiving a request message for requesting a key from a first access network device, determining the key of a target cell of the terminal device based on fourth information carried in the request message, and sending the key of the target cell to the first access network device via a response message to the request message. The fourth information is used to determine the terminal device. The target cell is one of the candidate cells managed by the first access network device.

[0056] In the embodiment of the present application, the access network device to which the source cell belongs can determine the terminal device based on the relevant information of the source cell / terminal device (i.e., the fourth information mentioned above), thereby being able to deduce the key for the next handover of the terminal device. In this way, the access network device to which the target cell belongs in subsequent handovers can obtain the same key as the terminal device, thereby facilitating the correct decryption or message integrity check between the terminal device and the target cell.

[0057] In one possible design, the fourth information includes at least one of the following: information of a source cell of the terminal device, or information of the terminal device, wherein the source cell is one of the cells managed by the second access network device. In this way, the access network device to which the source cell belongs can determine the terminal device.

[0058] In one possible design, the information of the source cell includes an identifier of the source cell.

[0059] In one possible design, the information of the terminal device includes an identification of the terminal device.

[0060] In one possible design, the key of the target cell of the terminal device is determined based on the fourth information, including: determining a next hop parameter based on the fourth information, and determining the key of the target cell based on the next hop parameter.

[0061] In one possible design, the response message also carries third information, which is used to indicate parameters related to the key update. This design can make the rules for deducing keys by the terminal device consistent with the rules for deducing keys by the access network device to which the source cell belongs, thereby further facilitating communication between the terminal device and the target cell based on the same key, thereby improving communication security.

[0062] In one possible design, the third information includes at least one of the following: a next hop chain count, or a key set change indication.

[0063] In one possible design, determining the key of the target cell of the terminal device based on the fourth information includes: determining the key of the source cell of the terminal device based on the fourth information; and determining the key of the target cell based on the key of the source cell of the terminal device using a horizontal deduction method. In the above method, if the key is deduced using the horizontal deduction method, the first access network device does not need to send key update-related parameters (i.e., the third information) to the terminal device, thereby saving signaling overhead.

[0064] In a seventh aspect, the present application further provides a communication device, which is a terminal device or a chip in a terminal device. The communication device has the function of implementing any of the methods provided in the first or fourth aspects above. The communication device can be implemented in hardware or by hardware executing corresponding software implementations. The hardware or software includes one or more units or modules corresponding to the above functions.

[0065] In one possible design, the communication device includes a processor configured to support the communication device in executing the corresponding functions of the terminal device in the method described above. The communication device may also include a memory, which may be coupled to the processor and stores program instructions and data necessary for the communication device. Optionally, the communication device also includes an interface circuit for supporting communication between the communication device and an access network device, such as the transmission and reception of data or signals. Exemplarily, the communication interface may be a transceiver, circuit, bus, module, or other type of communication interface.

[0066] In one possible design, the communication device includes corresponding functional modules for implementing the steps in the above method. The functions can be implemented by hardware or by hardware executing corresponding software implementations. The hardware or software includes one or more modules corresponding to the above functions.

[0067] In one possible design, the structure of the communication device includes a processing unit (or processing module) and a communication unit (or communication module). These units can perform the corresponding functions in the above method examples. For details, please refer to the description of the method provided in the first aspect or the fourth aspect, which will not be repeated here.

[0068] In an eighth aspect, the present application further provides a communication device, which is an access network device or a chip in an access network device. The communication device has the function of implementing any of the methods provided in the second aspect, the third aspect, the fifth aspect, or the sixth aspect. The communication device can be implemented in hardware or by hardware executing corresponding software. The hardware or software includes one or more units or modules corresponding to the above functions.

[0069] In one possible design, the communication device includes a processor configured to support the communication device in executing the corresponding functions of the access network device in the method described above. The communication device may also include a memory, which may be coupled to the processor and stores program instructions and data necessary for the communication device. Optionally, the communication device also includes an interface circuit for supporting communication between the communication device and a terminal device, such as the transmission and reception of data or signals. Exemplarily, the communication interface may be a transceiver, circuit, bus, module, or other type of communication interface.

[0070] In one possible design, the communication device includes corresponding functional modules for implementing the steps in the above method. The functions can be implemented by hardware or by hardware executing corresponding software implementations. The hardware or software includes one or more modules corresponding to the above functions.

[0071] In one possible design, the structure of the communication device includes a processing unit (or processing module) and a communication unit (or communication module). These units can perform the corresponding functions in the above method examples. For details, please refer to the description of the method provided in the second aspect, the third aspect, the fifth aspect or the sixth aspect, which will not be repeated here.

[0072] In the ninth aspect, a communication device is provided, comprising a processor and an interface circuit, the interface circuit being used to receive signals from other communication devices outside the communication device and transmit them to the processor or to send signals from the processor to other communication devices outside the communication device, the processor being used to implement the methods in the aforementioned first aspect or fourth aspect and any possible design through logic circuits or execution code instructions.

[0073] In the tenth aspect, a communication device is provided, comprising a processor and an interface circuit, the interface circuit being used to receive signals from other communication devices outside the communication device and transmit them to the processor or to send signals from the processor to other communication devices outside the communication device, the processor being used to implement the methods of the aforementioned second aspect, third aspect, fifth aspect, or sixth aspect and any possible design through logic circuits or execution code instructions.

[0074] In the eleventh aspect, a computer-readable storage medium is provided, which stores a computer program or instruction. When the computer program or instruction is executed by a processor, it implements the method in any one of the aforementioned aspects from the first to the sixth aspect and any possible design.

[0075] In the twelfth aspect, a computer program product storing instructions is provided, which, when executed by a processor, implements the method in any one of the aforementioned aspects 1 to 6 and any possible design.

[0076] In a thirteenth aspect, a chip system is provided, comprising a processor and possibly a memory, for implementing the method of any of the aforementioned aspects 1 to 6 and any possible design. The chip system may be composed of a chip alone or may include a chip and other discrete components.

[0077] In the fourteenth aspect, a communication system is provided, which includes the device described in the first aspect (such as a terminal device), the device described in the second aspect (such as an access network device), and the device described in the third aspect (such as an access network device).

[0078] In the fifteenth aspect, a communication system is provided, which includes the device described in the fourth aspect (such as a terminal device), the device described in the fifth aspect (such as an access network device), and the device described in the sixth aspect (such as an access network device).

[0079] The technical effects that can be achieved by the technical solutions in any of the above-mentioned aspects 7 to 15 can be described with reference to the technical effects that can be achieved by the technical solutions in the above-mentioned aspects 1 to 6, and the repetitions will not be repeated. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] FIG1 is a schematic diagram of a cell switching process according to an embodiment of the present application;

[0081] FIG2 is a schematic diagram of the architecture of a communication system according to an embodiment of the present application;

[0082] FIG3 is a schematic structural diagram of an access network device according to an embodiment of the present application;

[0083] FIG4 is a schematic diagram of a communication method according to an embodiment of the present application;

[0084] FIG5 is a schematic diagram of a cell switching process according to an embodiment of the present application;

[0085] FIG6 is a schematic diagram of a cell switching process according to an embodiment of the present application;

[0086] FIG7 is a schematic diagram of a communication method according to an embodiment of the present application;

[0087] FIG8 is a schematic diagram of a cell switching process according to an embodiment of the present application;

[0088] FIG9 is a schematic diagram of a cell switching process according to an embodiment of the present application;

[0089] FIG10 is a schematic structural diagram of a communication device according to an embodiment of the present application;

[0090] FIG11 is a schematic structural diagram of a communication device according to an embodiment of the present application. DETAILED DESCRIPTION

[0091] In order to better understand the embodiments of the present application, the following first introduces the application scenarios and existing problems of the embodiments of the present application. It should be noted that the application scenarios are intended to make the embodiments of the present application easier to understand and should not be regarded as limiting the scope of protection claimed by the present application.

[0092] In mobile communication systems, the movement of terminal devices causes changes in the communication link between the terminal device and the access network device, necessitating a cell handover or access network device handover. When an access network device handover occurs, the terminal device typically needs to change its key. This means that different keys are used for data encryption and integrity protection when communicating with the source and target access network devices to ensure secure communication.

[0093] Assume that the communication system includes access network devices 1 to 3. The mobility handover process triggered by the terminal device may be as shown in Figure 1, including:

[0094] S101, the terminal device communicates with access network device 1.

[0095] The serving cell / source cell of the terminal device is cell 1, which is managed by access network device 1. The terminal device uses Key 1 to encrypt and perform integrity protection on the communication data and signaling.

[0096] S102: Access network device 1 sends a handover request message to access network device 2 and access network device 3 respectively.

[0097] The handover request message sent by access network device 1 to access network device 2 carries key 2, which is used for the terminal device to communicate with access network device 2. The handover request message sent by access network device 1 to access network device 3 carries key 3, which is used for the terminal device to communicate with access network device 3.

[0098] Key 2 and Key 3 are both derived by access network device 1 based on Key 1 or next hop parameter (NH) 1. NH 1 is provided to access network device 1 by the access and mobility management function (AMF) network element and is used by access network device 1 to derive the key of the target cell.

[0099] S103 : Access network device 2 and access network device 3 send a handover request response message to access network device 1 .

[0100] The handover request response message carries the configuration information of the candidate cell.

[0101] Assume that the candidate cell managed by access network device 2 is cell 2, and the candidate cell managed by access network device 3 is cell 3. Then, the handover request response message sent by access network device 2 to access network device 1 carries the configuration information of cell 2, and the handover request response message sent by access network device 3 to access network device 1 carries the configuration information of cell 3.

[0102] Exemplarily, the configuration information of a cell may include a physical cell identifier (PCI) of the cell and downlink frequency information of the cell such as an absolute radio frequency channel number-downlink (ARFCN-DL).

[0103] The configuration information of the cell may also include the uplink physical channel configuration, downlink physical channel configuration, etc. that the terminal device needs to use when accessing the cell.

[0104] S104, access network device 1 sends a configuration message to the terminal device.

[0105] The configuration message carries the configuration information of the candidate cell and the corresponding trigger conditions. The configuration message also carries the next hop chaining count (NCC) 1. NCC 1 is provided by the AMF network element to access network device 1 and is used by the terminal device to deduce the key of the target cell.

[0106] S105, the terminal device evaluates whether the triggering conditions of the candidate cell are met.

[0107] Assume that the terminal device determines that the trigger condition of cell 2 has been met.

[0108] S106: The terminal device switches to cell 2.

[0109] Among them, the terminal device can deduce Key2 based on Key 1 or NCC 1.

[0110] S107 , access network device 2 sends a handover success message to access network device 1 .

[0111] S108 , access network device 1 , access network device 2 , and access network device 3 send a handover cancellation message.

[0112] S109, access network device 2 sends a path switching request message to the AMF network element.

[0113] The path switch request message is used to request the core network to switch the downlink path from access network device 1 to access network device 2.

[0114] S110, the AMF network element sends a path switching request response message to access network device 2.

[0115] The path switch request response message is used to respond to whether the path switch is successful or not.

[0116] Optionally, the path switch request response message may include NH 2 and NCC 2. NH 2 is used by the access network device 2 to derive a new key at the next handover; NCC 2 is used by the terminal device to derive a new key at the next handover.

[0117] Through the above process, the terminal device is switched from cell 1 managed by access network device 1 to cell 2 managed by access network device 2. The above switching process can be understood as one switching process.

[0118] Currently, the terminal device releases the configuration information of other candidate cells after successfully switching to Cell 2. If the terminal device needs to perform the next handover (for example, switching from cell 2 to cell 3), the above handover process needs to be executed again.

[0119] However, as the terminal device continues to move, the terminal device may trigger multiple switches within a short time interval. If the switching method described above is used, a certain switching delay will be caused. In response to this problem, a possible solution is that after the terminal device performs a cell switch (such as the successful switch to Cell2 described above), it may not release the configuration information of other candidate cells, thereby continuing to evaluate whether the triggering conditions of the candidate cells are met based on the configuration information of other candidate cells, and then performing the switch. That is, in subsequent switches, the terminal device may not perform the above-mentioned processes of S101 to S104. For example, after the above-mentioned S110, the following switching process may be performed:

[0120] S111, the terminal device evaluates whether the triggering conditions of the candidate cell are met.

[0121] Assume that the terminal device determines that the trigger condition of cell 3 has been met.

[0122] S112: The terminal device switches to cell 3.

[0123] Among them, the terminal device can deduce Key 3' based on Key 2 or NCC 2.

[0124] The above process can cause a misalignment between the keys of the terminal device and the target cell of the subsequent handover. For example, the key received by access network device 3 is Key 3 sent by access network device 1, and Key 3 is derived by the access network device based on Key 1 or NH 1. Therefore, Key 3 and Key 3' are different, and the terminal device and access network device 3 cannot decrypt or complete message integrity verification normally, resulting in communication failure.

[0125] Based on this, embodiments of the present application provide a communication method and apparatus for resolving the problem of communication failure caused by key misalignment between a terminal device and an access network device during subsequent handovers or multiple handovers. The method and apparatus are based on the same concept. Since the method and apparatus solve similar problems, the implementation of the apparatus and method can refer to each other, and any repetitions will not be repeated.

[0126] The communication method provided in this application can be applied to various communication systems, for example, the Internet of Things (IoT), narrowband Internet of Things (NB-IoT), long term evolution (LTE), fifth generation (5G) communication system, LTE and 5G hybrid architecture, 5G new radio (NR) system, and 6G or new communication systems emerging in future communication development. The communication system described in this application can also be a machine to machine (M2M) network, a non-terrestrial network (NTN) network, or other networks. As long as there is a cell switching demand in the communication system, the technical solutions of the embodiments of the present application can be adopted.

[0127] Referring to Figure 2, which is a schematic diagram of the architecture of a communication system provided in an embodiment of the present application, the communication system includes an access network device and a terminal device.

[0128] Among them, the access network equipment can be a base station, an evolved nodeB (eNodeB), a transmission reception point (TRP), the next generation base station (next generation NodeB, gNB) in the fifth generation (5G) mobile communication system, the next generation base station in the sixth generation (6G) mobile communication system, a base station in a future mobile communication system or an access node in a WiFi system, etc.; it can also be a module or unit that completes part of the functions of the base station, for example, it can be a centralized unit (CU) or a distributed unit (DU). The CU here completes the functions of the radio resource control (RRC) protocol and the packet data convergence protocol (PDCP) of the base station, and can also complete the function of the service data adaptation protocol (SDAP); the DU completes the functions of the radio link control (RLC) layer and the medium access control (MAC) layer of the base station, and can also complete the functions of part of the physical (PHY) layer or all of the physical layer. For the specific description of the above-mentioned protocol layers, please refer to the relevant technical specifications of the 3rd Generation Partnership Project (3GPP). The access network device can be a macro base station, a micro base station or an indoor station, a relay node or a donor node, etc. The embodiments of the present application do not limit the specific technology and specific device form adopted by the access network device.

[0129] In an embodiment of the present application, the access network device may adopt a CU-DU separation architecture, which may also be referred to as a distributed deployment architecture. For example, see Figure 3, which is a schematic diagram of a CU-DU separation architecture adopted by an access network device provided in an embodiment of the present application. As shown in Figure 3, the access network device may logically include a CU and one or more DUs, each DU may be connected to the CU via an F1 interface, and information interaction between different DUs may be completed based on the forwarding of the CU. The CU and the DU may be physically set together or physically separated, and there is no limitation. Among them, the CU may support the functions of RRC, PDCP, and SDAP; the DU may support the functions of the RLC layer protocol, the MAC layer protocol, and the PHY layer protocol.

[0130] Among them, the terminal device can also be called a terminal, user equipment (UE), mobile station, mobile terminal, etc. The terminal device can be widely used in various scenarios, for example, device-to-device (D2D), vehicle to everything (V2X) communication, machine-type communication (MTC), Internet of Things (IOT), virtual reality, augmented reality, industrial control, autonomous driving, telemedicine, smart grid, smart furniture, smart office, smart wearable, smart transportation, smart city, etc. The terminal device can be a mobile phone, a tablet computer, a computer with wireless transceiver function, a wearable device, a vehicle, a drone, a helicopter, an airplane, a ship, a robot, a robotic arm, a smart home device, etc. The embodiments of the present application do not limit the specific technology and specific device form adopted by the terminal device.

[0131] In the embodiments of the present application, the access network equipment and terminal devices can be fixed or mobile. They can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; on water; or in the air on aircraft, balloons, and satellites. The embodiments of the present application do not limit the application scenarios of the access network equipment and terminal devices.

[0132] The roles of access network devices and terminal devices can be relative. For example, a drone can be configured as a mobile access network device. For terminal devices that access the network through the drone, the drone is an access network device; but for the access network devices accessed by the drone, the drone is a terminal device.

[0133] The functions of an access network device can also be performed by a module (such as a chip) within the access network device, or by a control subsystem that includes the functions of the access network device. The control subsystem that includes the functions of the access network device here can be a control center in application scenarios such as smart grids, industrial control, intelligent transportation, and smart cities. The functions of a terminal device can also be performed by a module (such as a chip or modem) within the terminal device, or by a device that includes the functions of the terminal device.

[0134] In an embodiment of the present application, communication between a terminal device and an access network device refers to the terminal device sending an uplink signal or uplink information to the access network device, the uplink information being carried on an uplink channel, and / or the access network device sending a downlink signal or downlink information to the terminal device, the downlink information being carried on a downlink channel. In order to communicate with the access network device, the terminal device needs to establish a wireless connection with the cell controlled by the access network device (i.e., the terminal device resides in the cell controlled by the access network device). The cell that establishes a wireless connection with the terminal device is called the service cell of the terminal device (i.e., the cell that provides services to the terminal device).

[0135] The terminal device may be located within the coverage of one or more cells (carriers), and the cell providing services to the terminal device may be one or more. For example, in the scenario shown in Figure 2, the terminal device is simultaneously located within the coverage of cell 1 controlled by access network device 1, cell 2 controlled by access network device 2, and cell 3 controlled by access network device 3, and cell 1, cell 2, and cell 3 can all provide services for the terminal device. It should be noted that Figure 2 takes an access network device controlling only one cell as an example. In actual applications, an access network device can control multiple cells at the same time. When there are multiple cells providing services to the terminal device, the terminal device may operate in the manner of carrier aggregation (CA), dual connectivity (DC), or coordinated multiple points transmission / reception (CoMP), and one or more cells may provide the terminal device with one or more of the following tasks: wireless resources corresponding to more than one transmission parameter set.

[0136] Due to changes in the mobility of the terminal device and / or the cell channel conditions, the terminal device can switch the service cell, wherein the service cell where the terminal device originally resides (or the cell where the terminal device disconnects the wireless connection, or the cell cut out by the terminal device) is called the source cell, and the cell where the terminal device newly resides (or the cell where the terminal device newly establishes a wireless connection, or the cell into which the terminal device cuts in) is called the target cell, that is, the terminal device switching the service cell means that the terminal device switches from the source cell to the target cell. The terminal device can reside in only one cell or in multiple cells at the same time, and the multiple cells can be controlled by the same access network device or by different access network devices, which is not limited in the embodiments of the present application; accordingly, when performing service cell switching, the terminal device can switch only one service cell or switch multiple service cells at the same time, which is not limited in the embodiments of the present application.

[0137] In addition, communication between a cell and a terminal device (such as a cell sending a downlink signal to a terminal device, and / or a cell receiving an uplink signal from a terminal device) refers to communication between the access network device to which the cell belongs (such as a base station that controls the cell) and the terminal device. Communication between cells, such as communication between one cell and another cell, if the two cells belong to different access network devices (such as two cells controlled by different base stations), refers to communication between the access network device to which the one cell belongs and the access network device to which the other cell belongs (such as message transmission between the two access network devices); if the two cells belong to the same access network device (such as two cells controlled by the same base station), refers to signaling or data exchange between the functional module in the access network device that controls the one cell and the functional module that controls the other cell within the access network device.

[0138] The network architecture and business scenarios described in the embodiments of the present application are intended to more clearly illustrate the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided in the embodiments of the present application. A person skilled in the art will appreciate that, with the evolution of the network architecture and the emergence of new business scenarios, the technical solutions provided in the embodiments of the present application are equally applicable to similar technical problems.

[0139] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present application. The terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0140] References to "one embodiment" or "some embodiments" described in this specification mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. The terms "including", "comprising", "having" and their variations involved in this application all mean "including but not limited to", unless otherwise specifically emphasized. Words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions, and any embodiment or design described as "exemplary" or "for example" should not be interpreted as being more preferred or more advantageous than other embodiments or designs. The use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete way for easy understanding.

[0141] The multiple involved in the embodiments of the present application refers to greater than or equal to two. In view of this, in the embodiments of the present application, "multiple" can also be understood as "at least two". "At least one" can be understood as one or more, for example, as one, two or more. For example, including at least one means including one, two or more, and there is no limit on which ones are included. For example, including at least one of A, B and C, then the included ones may be A, B, C, A and B, A and C, B and C, or A and B and C. Similarly, the understanding of descriptions such as "at least one" is similar. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / ", unless otherwise specified, generally indicates that the related objects before and after are in an "or" relationship.

[0142] It should be noted that, unless otherwise specified, in the description of the embodiments of the present application, words such as "first" and "second", or numbers such as "1" and "2" are only used for the purpose of distinguishing the description, and cannot be understood as indicating or implying relative importance, nor can they be understood as indicating or implying order.

[0143] In addition, the term "used to indicate" mentioned in the description of the embodiments of the present application can include being used for direct indication and being used for indirect indication. When describing that a certain indication information is used to indicate A, it can include that the indication information directly indicates A or indirectly indicates A, and does not necessarily mean that the indication information carries A.

[0144] In the embodiments of the present application, the terms “system” and “network” may be used interchangeably.

[0145] The term "switching" as used in the embodiments of this application can be understood as updating, replacing, or changing. For example, a UE's path switching can refer to updating or replacing the UE's original path with the new path after determining the UE's new path, so that the UE can communicate via the new path. Therefore, the term "switching" can also be replaced with "updating" or other terms, and this application does not limit this.

[0146] The trigger condition may also be referred to as a handover trigger condition, a handover condition, etc. Meeting the trigger condition of the XX cell may also be described as triggering a handover process to the XX cell, etc.

[0147] It should be understood that in this application, the source cell and the target cell are relative concepts. In a handover, the cell accessed by the terminal device before the handover can be called the source cell, and the cell accessed after the handover can be called the target cell. For example, when the terminal device switches from cell 1 to cell 2, cell 1 can be understood as the source cell of this handover, and cell 2 can be understood as the target cell of this handover. When the terminal device switches from cell 2 to cell 3, cell 2 can be understood as the source cell of this handover, and cell 3 can be understood as the target cell of this handover.

[0148] In the present application, the terminal device may trigger multiple switches within a short time interval, and the multiple switches can be divided into a first switch and subsequent switches, wherein the subsequent switch refers to the second switch and subsequent switches.

[0149] In this application, determining a key, generating a key, and deducing a key can be understood as having the same meaning and can be replaced with each other.

[0150] In an exemplary description, the key involved in this application (such as the first key mentioned below) can be understood as an intermediate parameter, and the terminal device can further generate a user plane processing key Kup and an RRC layer processing key Krrc based on the parameter. Exemplarily, the key involved in this application (such as the first key mentioned below) is also referred to as KgNB, etc.

[0151] For ease of introduction, the following description uses the method performed by a network device and a terminal device as an example. See Figure 4, which is a flow chart of a communication method provided by this application. Assume that the terminal device is currently connected to a first access network device, that is, the first access network device is the access network device to which the terminal device's current serving cell belongs, and the access network device to which the target cell to which the terminal device is switching belongs is a third access network device. The following description uses the process of switching from the first access network device to the third access network device as an example.

[0152] The method described in FIG4 can be applied to subsequent handover processes, such as the second handover process and subsequent handover processes. In this scenario, the first access network device is the access network device to which the source cell belongs during the subsequent handover process. That is, the handover of the terminal device from the first access network device to the third access network device is a handover in the subsequent handover process.

[0153] Alternatively, the method described in FIG4 can be applied to any handover process, such as the first handover process, the second handover process, and subsequent handover processes. In this scenario, the first access network device can be the access network device to which the source cell belongs during the first handover process, that is, the handover of the terminal device from the first access network device to the third access network device can be the first handover. Alternatively, the first access network device can be the access network device to which the source cell belongs during a subsequent handover process, that is, the handover of the terminal device from the first access network device to the third access network device can be a handover in a subsequent handover process.

[0154] The method includes:

[0155] S401: A first access network device obtains first information.

[0156] The first information includes information about at least one candidate cell managed by the third access network device. Exemplarily, the candidate cell information includes at least one of the following: a global cell identifier (CGI) of the candidate cell, a PCI of the candidate cell, or downlink frequency information of the candidate cell, such as ARFCN-DL.

[0157] The following describes a method for obtaining the first information in combination with two application scenarios.

[0158] Scenario 1: The method described in Figure 4 is applied to a subsequent handover process. The first access network device may obtain the first information by: the second access network device sends information A to the first access network device. Information A may include the first information. Optionally, information A may also include information about candidate cells managed by other candidate access network devices, information about candidate cells managed by the first access network device, and so on.

[0159] The second access network device may be an access network device that the terminal device has previously accessed. For example, the second access network device may be the access network device that the terminal device initially accessed, or may be understood as the access network device to which the source cell belongs during the first handover, or may be understood as the access network device that initially performs handover-related configuration for the terminal device, such as the access network device that initially configures a candidate cell for the terminal device. For another example, the second access network device may be the access network device that the terminal device accessed last time, or may be understood as the access network device to which the source cell of the last handover belongs.

[0160] Optionally, the second access network device may obtain the first information in the following manner: the second access network device sends a handover request message to the third access network device. The third access network device sends a handover request response message to the second access network device, where the handover request response message carries configuration information of the candidate cell managed by the third access network device. Exemplarily, the cell configuration information may include at least one of the following: CGI, PCI, or downlink frequency information such as ARFCN-DL. Optionally, the candidate cell configuration information may also include uplink physical channel configuration, downlink physical channel configuration, etc. that the terminal device needs to use when accessing the cell.

[0161] Optionally, in scenarios such as carrier aggregation, the handover request response message may carry configuration information of a candidate cell group managed by a third access network device, specifically including configuration information of a candidate primary cell and configuration information of a candidate secondary cell managed by the third access network device. In this scenario, the first information may include information of the candidate primary cell managed by the third access network device.

[0162] Alternatively, the second access network device may also obtain the first information through an operation, administration, and maintenance (OAM) function.

[0163] It is understandable that the second access network device may also obtain information about candidate cells managed by other candidate access network devices in the above manner.

[0164] Scenario 2: The method described in FIG4 can be applied to any switching process.

[0165] If the first access network device is the access network device to which the source cell belongs during the first handover process, the first access network device can obtain the first information by: sending a handover request message to a third access network device. The third access network device sends a handover request response message to the first access network device, where the handover request response message carries configuration information of candidate cells managed by the third access network device. The cell configuration information is described above and is not repeated here.

[0166] Optionally, in scenarios such as carrier aggregation, the handover request response message may carry information about a candidate cell group managed by a third access network device, specifically including configuration information about candidate primary cells and candidate secondary cells managed by the third access network device. In this scenario, the first information may include configuration information about candidate primary cells managed by the third access network device.

[0167] Alternatively, the first access network device may also obtain the first information in the following manner: the first access network device obtains the first information through OAM.

[0168] If the first access network device is the access network device to which the source cell belongs in the subsequent switching process, the manner in which the first access network device obtains the first information can refer to the relevant description in scenario one.

[0169] S402: The first access network device determines a first key based on the first information.

[0170] For example, the first access network device may determine the first key based on the key of the first access network device and the first information. This method may be referred to as a horizontal deduction method.

[0171] Alternatively, the first access network device may also determine the first key based on the NH and the first information sent by the AMF network element. This method may be referred to as a vertical deduction method.

[0172] In one possible implementation, the first access network device can determine the key deduction method in the following manner: when the first access network device has an unused pair of parameters {NH, NCC}, the first access network device can use a vertical deduction method to determine the first key; when the first access network device does not have an unused pair of parameters {NH, NCC}, the first access network device can use a horizontal deduction method to determine the first key.

[0173] As a possible solution, S402 may be executed under the triggering of the following steps: the first access network device determines that the terminal device switches to the first access network device. For example, the first access network device receives a path switching request response message from the AMF network element.

[0174] As another possible solution, S402 can also be executed under the triggering of the following steps: the first access network device receives NH from the AMF network element.

[0175] S403: The first access network device sends the first key to the third access network device. Correspondingly, the third access network device receives the first key from the first access network device.

[0176] Optionally, if the second access network device also sends information about candidate cells managed by other candidate access network devices to the first access network device, the first access network device may also determine the keys of the other candidate access network devices and send them to the corresponding candidate access network devices.

[0177] As an optional step, after receiving the first key, the third access network device may send a response message to the first access network device, where the response message is used to confirm successful receipt of the first key. Further, the first access network device may execute S404 after receiving the response message.

[0178] S404: The first access network device sends a first message to the terminal device. Correspondingly, the terminal device receives the first message from the first access network device.

[0179] The first message indicates that key notification has been completed to the candidate access network device.

[0180] Exemplarily, the first message may be an RRC message, a media access control control element (MAC CE), a layer 1 (L1) message, such as downlink control information (DCI), or other types of downlink messages. This application does not limit the specific form of the first message.

[0181] The first message may include at least one of the following: second information or third information. The second information indicates that key notification has been completed to the candidate access network device. The third information indicates parameters related to key update, such as parameters for key update derivation for the next handover. Exemplarily, the third information includes at least one of the following: an NCC for key update derivation for the next handover, or a key set change indication for key update derivation for the next handover.

[0182] It can be understood that in the manner in which the first message includes the third information but does not include the second information, the third information may implicitly indicate that the key notification has been completed to the candidate access network device.

[0183] It should be noted that "the first message indicating that key notification has been completed to the candidate access network device" can also be described as "the first message indicating that a key has been sent to the candidate access network device", "the first message indicating that the key update of the candidate access network device is completed", "the key update and notification process between access network devices has been completed", etc. This application does not limit the specific meaning of the first message indication. As long as the terminal device can know that the first access network device has sent a key to the candidate access network device, it can be understood as the first message described in this application. Similarly, the second information is not limited to a specific indication meaning. As long as the terminal device can know that the first access network device has sent a key to the candidate access network device, it can be understood as the second information described in this application.

[0184] S405, the terminal device determines that the triggering condition of the target cell is met and has received the first message from the first access network device.

[0185] The target cell is one of the candidate cells managed by the third access network device.

[0186] In one implementation, the terminal device may determine that the triggering condition of the target cell is met through a measurement result of a reference signal of the target cell.

[0187] In order to better understand S405, four examples of triggering conditions of the target cell are introduced below.

[0188] For example, the triggering condition of the target cell may be that a measurement result of a reference signal of the target cell is higher than a measurement result of a serving cell.

[0189] Alternatively, the trigger condition of the target cell may be that the measurement result of the reference signal of the target cell is higher than that of the serving cell, and the difference between the measurement result of the reference signal of the target cell and the measurement result of the serving cell is greater than a first threshold.

[0190] Alternatively, the trigger condition of the target cell may be that the measurement result of the reference signal of the target cell is higher than the measurement result of the serving cell, and the difference between the measurement result of the reference signal of the target cell and the measurement result of the serving cell is greater than the first threshold, and the duration is greater than the time threshold.

[0191] Alternatively, the trigger condition of the target cell may be that the measurement result of the reference signal of the target cell is greater than the second threshold, the measurement result of the reference signal of the serving cell is less than the third threshold, and the second threshold is greater than the third threshold.

[0192] The measurement results may be parameters such as reference signal received power (RSRP), reference signal received quality (RSRQ), and signal to interference plus noise ratio (SINR).

[0193] The above triggering conditions are merely exemplary introductions, and this application does not limit the specific content of the triggering conditions.

[0194] It can be understood that the triggering conditions of other cells below are similar to the triggering conditions of the target cell and are not described one by one.

[0195] As a possible solution, if the terminal device determines that the triggering conditions for the target cell have been met but has not received the first message, the terminal device can send a third message to the first access network device. The third message is used to request the first access network device to notify the third access network device and other candidate access network devices of the key. In other words, the third message is used to request the first access network device to send the first message to the terminal device.

[0196] In one example, the third message may include at least one of the following information: information requesting the first access network device to notify the candidate access network device of the key, or information indicating that the triggering condition of the target cell has been met.

[0197] In one possible implementation, the terminal device may obtain the triggering conditions of the target cell in the following manner: the access network device to which the source cell of the first handover belongs sends configuration information to the terminal device, where the configuration information may include the triggering conditions of the candidate cell. Optionally, the configuration information may also include configuration information of the candidate cell, where the content of the configuration information may refer to the description of the configuration information in S401.

[0198] S406: The terminal device determines to send a second message to the target cell based on the first message.

[0199] The second message is used to access the target cell. For example, the second message may be a random access preamble, or an uplink message based on uplink grant-free scheduling or pre-configured uplink grant scheduling, or an uplink message based on dynamic grant scheduling, etc.

[0200] In an exemplary description, the determination to send the second message to the target cell based on the first message can be understood as follows: when the terminal device evaluates that the trigger condition of the target cell is met, if the terminal device has received the first message, the terminal device executes the handover process to the target cell, for example, sending the second message to the target cell. If the terminal device has not received the first message, the terminal device does not execute the handover process to the target cell until the terminal device receives the first message, at which time the terminal device begins the handover process to the target cell.

[0201] In one possible implementation, the receipt of the first message may be used as one of the conditions for cell switching. That is, the conditions for the terminal device to execute the switching to the target cell include condition 1 and condition 2, where condition 1 is the trigger condition of the target cell and condition 2 is the receipt of the first message. If both conditions 1 and 2 are met, the terminal device begins the switching process to the target cell. If either condition 1 or condition 2 is not met or both conditions are not met, the terminal device does not execute the switching process to the target cell.

[0202] It should be understood that this application does not limit the order in which the above-mentioned conditions 1 and 2 are evaluated. Condition 1 can be evaluated first, and condition 2 can be evaluated when condition 1 is satisfied. Alternatively, condition 2 can be evaluated first, and condition 1 can be evaluated when condition 2 is satisfied. Alternatively, conditions 1 and 2 can be evaluated simultaneously.

[0203] Optionally, the terminal device can determine to send a second message to the target cell based on the first message when it is determined that the key needs to be updated when switching to the target cell, that is, when the key needs to be updated after switching to the target cell, determine to wait for receiving the first message before executing the switch to the target cell.

[0204] The above implementation can be understood as follows: if the key needs to be updated after switching to the target cell, the terminal device determines to send a second message to the target cell based on the first message; if the key does not need to be updated after switching to the target cell, the terminal device can start the switching process to the target cell after the triggering conditions of the target cell are met (that is, send the second message to the target cell) without waiting to receive the first message.

[0205] An example of requiring a key update after switching to a target cell is that an access network device to which the target cell belongs is different from the first access network device.

[0206] Another example of requiring a key update after handover to a target cell is that the configuration of the target cell indicates that a key update is required.

[0207] Another example of a key update required after switching to a target cell is that the group identifier corresponding to the target cell is different from the group identifier corresponding to the source cell, and the terminal device determines that a key update is required.

[0208] Optionally, after the terminal device accesses the target cell, the terminal device and the target cell may communicate based on the target cell's key, i.e., the first key, and may use the first key to perform security processing (e.g., encryption) on the data content / signaling content. The terminal device and the first access network device may deduce the target cell's key based on the same rules.

[0209] For example, if both the terminal device and the first access network device use a horizontal deduction method, the terminal device can deduce the target cell's key based on the first access network device's key and the target cell's information. If both the terminal device and the first access network device use a vertical deduction method, the terminal device can deduce NH and then deduce the target cell's key based on NH and the target cell's information.

[0210] In one possible implementation, the terminal device may determine the key deduction method in the following manner: the terminal device may compare the NCC carried in the first message with the stored NCC; if they are the same, a horizontal deduction method is used; if they are different, a vertical deduction method is used.

[0211] In an embodiment of the present application, the access network device to which the source cell belongs (for example, the access network device to which the source cell belongs in a subsequent handover) can deduce the key of the candidate cell or the target cell based on the information of the candidate cell obtained in advance, and notify the access network device to which the candidate cell or the target cell belongs, so that the key obtained by the access network device of the target cell (for example, the target cell in a subsequent handover) is the same as the key deduced by the terminal device, thereby facilitating the correct decryption or correct completion of message integrity verification when the terminal device and the target cell communicate. Moreover, before switching to the target cell, the terminal device waits for the first message from the access network device to which the source cell belongs, so that the communication between the terminal device and the target cell is based on the same key, which can further facilitate the correct decryption or normal completion of message integrity verification between the terminal device and the target cell.

[0212] For ease of understanding, the following describes the first and second handover processes using a communication system including access network devices 1, 2, and 3 as an example, combining the two scenarios described above. The first handover can be from access network device 1 to access network device 2. The second handover can be from access network device 2 to access network device 3. It should be understood that other handovers can be performed after the second handover. For specific handover methods, please refer to the second handover process and will not be further described here.

[0213] Example 1:

[0214] In this embodiment, the method described in FIG4 can be applied to subsequent handovers (the second handover is taken as an example below). In embodiment 1, access network device 1 can correspond to the second access network device, access network device 2 corresponds to the first access network device, and access network device 3 corresponds to the third access network device.

[0215] As shown in FIG5 , the method includes:

[0216] Assuming that the terminal device initially accesses access network device 1, the terminal device may perform the first handover through the following steps S501 to S510:

[0217] S501: The terminal device communicates with access network device 1.

[0218] S502: Access network device 1 sends a handover request message to access network device 2 and access network device 3 respectively.

[0219] S503 : Access network device 2 and access network device 3 send a handover request response message to access network device 1 .

[0220] It should be noted that S501 to S503 are optional steps.

[0221] For the above S501 to S503 , please refer to the relevant description of S101 to S103 above, which will not be repeated here.

[0222] S504 , access network device 1 sends information about candidate cells to access network device 2 and access network device 3 .

[0223] The candidate cell information includes information about cell 2 and cell 3. The cell 2 information includes at least one of the following: a CGI of cell 2, a PCI of cell 2, or downlink frequency information of cell 2, such as ARFCN-DL. The cell 3 information includes at least one of the following: a CGI of cell 3, a PCI of cell 3, or downlink frequency information of cell 3, such as ARFCN-DL.

[0224] S505: Access network device 1 sends a configuration message to the terminal device.

[0225] S506: The terminal device determines that the triggering condition of cell 2 is met.

[0226] S507: The terminal device switches to cell 2.

[0227] S508 , access network device 2 sends a handover success message to access network device 1 .

[0228] S509, access network device 2 sends a path switching request message to the AMF network element.

[0229] S510, the AMF network element sends a path switching request response message to access network device 2.

[0230] It should be noted that S505 to S510 are optional steps.

[0231] For the above S505 to S508, reference may be made to the related description of S104 to S107 above, and for the above S509 to S510, reference may be made to the related description of S109 to S110 above, which will not be repeated here.

[0232] Through the above process, the terminal device switches from cell 1 managed by access network device 1 to cell 2 managed by access network device 2.

[0233] As a possible implementation, after the terminal device switches to cell 2, the terminal device and cell 2 can communicate based on key 2. The manner in which the terminal device generates key 2 can be found in the above description of S106 and will not be repeated here.

[0234] Afterwards, the terminal device may perform a second handover through the following steps S511 to S518:

[0235] S511 , the access network device 2 determines the key 3 ′ of the access network device 3 according to the information of the cell 3 .

[0236] The information in cell 3 corresponds to the first information in the previous text. Key 3' corresponds to the first key in the previous text.

[0237] The method for determining key 3' can refer to the relevant description of S402 and will not be repeated here.

[0238] S512 , access network device 2 sends key 3 ′ to access network device 3 .

[0239] S513 , access network device 3 sends a response message to access network device 2 .

[0240] This response message is used to confirm the successful receipt of key 3'.

[0241] It should be noted that S513 is an optional step.

[0242] S514, access network device 2 sends a first message to the terminal device.

[0243] The first message can be found in the relevant description of S404, which will not be repeated here.

[0244] S515: The terminal device determines that the trigger condition of cell 3 is met.

[0245] The cell 3 mentioned above corresponds to the target cell mentioned above.

[0246] This application does not limit the execution order of S514 and S515.

[0247] S516: The terminal device determines to send a second message to cell 3 according to the first message.

[0248] For details of the above S516, please refer to the relevant description of S406 above, which will not be repeated here.

[0249] Optionally, if the terminal device does not receive the first message after the trigger condition of cell 3 is met, the terminal device may send a third message to access network device 2. The third message is used to request access network device 2 to notify the candidate access network devices (i.e., access network device 3 and access network device 1) of the key. For details about the third message, please refer to the relevant description in S405 above. In other words, the third message is used to request the first access network device to send the first message to the terminal device.

[0250] In addition, the terminal device may determine to send the second message to cell 3 according to the first message when a key needs to be updated after switching to cell 3. For details, please refer to the relevant description of S406 above, which will not be repeated here.

[0251] S517 , access network device 3 sends a handover success message to access network device 2 .

[0252] S518, access network device 3 sends a path switching request message to the AMF network element.

[0253] S519, the AMF network element sends a path switching request response message to access network device 3.

[0254] It should be noted that S517 to S519 are optional steps.

[0255] For the above S517 to S519, reference may be made to the related descriptions of S107 and S109 to S110 above, which will not be repeated here.

[0256] Through the above process, the terminal device switches from cell 2 managed by access network device 2 to cell 3 managed by access network device 3.

[0257] As a possible implementation, after the terminal device switches to cell 3, the terminal device and cell 3 can communicate based on key 3'. The method for the terminal device to generate key 3' can refer to the method for the terminal device to determine the first key above, which will not be repeated here.

[0258] According to the method described in FIG5 , a terminal device can perform at least two handovers, and the first handover and subsequent handovers (e.g., the second handover) employ different methods. In the first handover, the terminal device performs the handover after determining that the triggering conditions of the target cell are met. In the subsequent handover, the terminal device waits for a first message from the access network device of the source cell after determining that the triggering conditions of the target cell are met, and then performs the handover after receiving the first message. The following describes a method for a terminal device to distinguish between the first handover and the subsequent handover.

[0259] In one possible approach, a terminal device may deem the access network device it accesses when it first receives candidate cell configuration information as the initial access network device. When the terminal device performs its first cell handover or access network device handover using the candidate cell configuration information, this can be considered an initial handover or first handover. When the terminal device performs a second cell handover or access network device handover using the previously provided candidate cell configuration information, this can be considered a second handover or subsequent handover. Similarly, the third, fourth, and other cell handovers or access network device handovers using the previously provided candidate cell configuration information can also be considered subsequent handovers.

[0260] Example 2:

[0261] The difference between Example 2 and Example 1 is that the first handover in Example 1 does not use the method described in Figure 4 , while the first handover in Example 2 can also use the method described in Figure 4 . In Example 2, for the first handover, access network device 1 can correspond to the first access network device, and access network device 2 can correspond to the third access network device. For subsequent handovers, using the second handover as an example, access network device 1 can correspond to the second access network device, access network device 2 can correspond to the first access network device, and access network device 3 can correspond to the third access network device.

[0262] As shown in FIG6 , the method includes:

[0263] Assuming that the terminal device initially accesses access network device 1, the terminal device may perform the first handover through the following steps S601 to S611:

[0264] S601: The terminal device communicates with access network device 1.

[0265] S602: Access network device 1 sends a handover request message to access network device 2 and access network device 3 respectively.

[0266] In one possible implementation, the handover request message sent by access network device 1 to access network device 2 may carry key 2 of access network device 2. The handover request message sent by access network device 1 to access network device 3 may carry key 3 of access network device 3.

[0267] This approach can minimize changes to the original protocol and thus improve forward compatibility.

[0268] In another possible implementation, the handover request message sent by access network device 1 to access network device 2 and access network device 3 may not carry the keys of access network device 2 and access network device 3.

[0269] Furthermore, if the switching request message does not carry the keys of access network device 2 and access network device 3, access network device 1 can send the corresponding keys to access network device 2 and access network device 3 respectively through other messages (such as key notification messages, etc.).

[0270] In this way, the access network device to which the source cell belongs can use the same rule to send the handover request message and notification key in the first handover and subsequent handovers, thereby reducing the processing complexity of the access network device.

[0271] S603 : Access network device 2 and access network device 3 send a handover request response message to access network device 1 .

[0272] It should be noted that S601 to S603 are optional steps.

[0273] For the above S601 to S603 , please refer to the relevant description of S101 to S103 above, which will not be repeated here.

[0274] S604, access network device 1 sends a first message to the terminal device.

[0275] The first message can refer to the related description of S404 above, which will not be repeated here.

[0276] S605 , access network device 1 sends information about candidate cells to access network device 2 and access network device 3 .

[0277] For details, please refer to the relevant description of S504 above.

[0278] S606: Access network device 1 sends a configuration message to the terminal device.

[0279] For details, please refer to the relevant description of S104 above.

[0280] S607: The terminal device determines that the triggering condition of cell 2 is met.

[0281] For the first handover, cell 3 may correspond to the target cell mentioned above.

[0282] S608: The terminal device determines to send a second message to cell 2 according to the first message.

[0283] For details of the above S608, please refer to the related description of S406 above.

[0284] Optionally, if the terminal device does not receive the first message from access network device 1 after the trigger condition of cell 2 is met, the terminal device may send a third message to access network device 1. The third message is used to request access network device 1 to notify the candidate access network devices (i.e., access network device 2 and access network device 3) of the key. For details about the third message, please refer to the relevant description in S405 above.

[0285] In addition, the terminal device may determine to send the second message to cell 2 according to the first message when the key needs to be updated after switching to cell 2. For details, please refer to the relevant description of S406 above, which will not be repeated here.

[0286] S609 , access network device 2 sends a handover success message to access network device 1 .

[0287] S610, access network device 2 sends a path switching request message to the AMF network element.

[0288] S611, the AMF network element sends a path switching request response message to access network device 2.

[0289] It should be noted that S609 to S611 are optional steps.

[0290] For the above S609 to S611, reference may be made to the related descriptions of S107 and S109 to S110 above, which will not be repeated here.

[0291] Through the above process, the terminal device switches from cell 1 managed by access network device 1 to cell 2 managed by access network device 2.

[0292] As a possible implementation, after the terminal device switches to cell 2, the terminal device and cell 2 can communicate based on key 2. The manner in which the terminal device generates key 2 can be found in the above description of S106 and will not be repeated here.

[0293] Afterwards, the terminal device may perform a second switching, specifically including steps S612 to S620. For the specific process, please refer to the relevant description of the second switching in Example 1, namely, the relevant description of S511 to S519, which will not be repeated here.

[0294] In an embodiment of the present application, the access network device that the terminal device has historically accessed (such as the second access network device) sends the information of the candidate cell of the terminal device to the candidate access network device, so that in the subsequent switching, the access network device to which the source cell belongs (one of the above-mentioned candidate access network devices, the first access network device in this application) can deduce the key for the next switching of the terminal device based on the information of the candidate cell obtained from the second access network device, and send the key to the access network device to which the target cell belongs (one of the above-mentioned candidate access network devices, the third access network device in this application). In this way, the access network device to which the target cell belongs in the subsequent switching can obtain a key that is consistent with that of the terminal device, which is conducive to the correct decryption or correct completion of message integrity verification by the terminal device and the target cell.

[0295] Furthermore, in the present application, after the first access network device sends the key to the access network device (i.e., the third access network device) to which the target cell belongs, the first access network device indicates to the terminal device through the first message that the key notification between access network devices has been completed, so that the terminal device can determine through the first message that the access network device to which the target cell belongs has (or is about to) obtain the key for the next handover. After receiving the first message, the terminal device performs a cell handover, so that the communication between the terminal device and the target cell is based on the same key, thereby improving the security of the communication.

[0296] The above describes a communication method for multiple handover communication scenarios. The following describes another communication method for multiple handover communication scenarios, as shown in Figure 7. Assume that a terminal device is currently connected to access network device B. That is, access network device B is the access network device of the terminal device's current serving cell, and the access network device of the target cell to which the terminal device is handovering belongs is access network device A. The following describes the handover process from access network device B to access network device A as an example.

[0297] The difference between the method described in Figure 7 and the method described in Figure 4 is that in the method described in Figure 4, the access network device to which the source cell belongs (especially the access network device to which the source cell belongs in subsequent switching) can deduce the key of the target cell based on the information of the candidate cell obtained in advance and notify the access network device to which the target cell belongs. In addition, the terminal device waits for the first message from the access network device to which the source cell belongs before switching to the target cell. In the method described in Figure 7, the terminal device sends some information to the target cell when switching to the target cell, so that the target cell can request the key from the source cell based on this information.

[0298] The method described in FIG7 can be applied to subsequent handover processes, such as the second handover process and subsequent handover processes. In this scenario, access network device B is the access network device of the source cell in the subsequent handover process, and access network device A is the access network device of the target cell in the subsequent handover process. That is, the handover of the terminal device from access network device B to access network device A is a handover in the subsequent handover.

[0299] Alternatively, the method described in FIG7 can be applied to any handover process, such as the first handover process, the second handover process, and subsequent handover processes. In this scenario, access network device B is the access network device to which the source cell belongs during the first handover process, and access network device A is the access network device to which the target cell belongs during the first handover process. That is, the handover of the terminal device from access network device B to access network device A can be the first handover. Alternatively, access network device B is the access network device to which the source cell belongs during a subsequent handover process, and access network device A is the access network device to which the target cell belongs during a subsequent handover process. That is, the handover of the terminal device from access network device B to access network device A can be a handover in a subsequent handover process.

[0300] As shown in FIG7 , another communication method for switching communication scenarios multiple times includes:

[0301] S701, the terminal device determines that the triggering conditions of the target cell are met.

[0302] The target cell is one of the candidate cells managed by the access network device A. The access network device A corresponds to the first access network device in the fourth to sixth aspects of the present invention.

[0303] In one possible implementation, the terminal device can obtain the triggering conditions of the target cell in the following manner: the access network device to which the source cell of the first handover belongs sends configuration information to the terminal device, and the configuration information may include the configuration information of the candidate cell and the corresponding triggering conditions.

[0304] S702: The terminal device sends information 1 to the access network device A. Correspondingly, the access network device A receives the information 1 from the terminal device.

[0305] Information 1 is used to access the target cell. For example, information 1 may be random access information such as a preamble, or uplink information based on uplink grant-free scheduling or preconfigured uplink grant scheduling, or uplink information based on dynamic grant scheduling, etc. Information 1 corresponds to the first information in aspects 4 to 6 of the present invention.

[0306] In one possible implementation, the information 1 may not be encrypted and / or integrity protected. This allows the access network device A to correctly obtain the content of the information 1, facilitates subsequent key alignment, and achieves secure communication.

[0307] S703: The terminal device sends information 2 to the access network device A. Correspondingly, the access network device A receives information 2 from the terminal device.

[0308] Information 2 is used by access network device A to obtain a key from access network device B. Access network device B is the access network device to which the source cell of the terminal device belongs. Information 2 corresponds to the second information in aspects 4 to 6 of the present invention. Access network device B corresponds to the second access network device in aspects 4 to 6 of the present invention.

[0309] Exemplarily, the information 2 includes at least one of the following: information of the source cell, or information of the terminal device. For example, the information of the source cell may include an identifier of the source cell. The information of the terminal device may include an identifier of the terminal device.

[0310] It should be noted that this application does not limit the order in which information 1 and information 2 are sent. Information 1 can be sent first and then information 2, or information 2 can be sent first and then information 1. Alternatively, information 1 and information 2 can be sent in the same message.

[0311] S704: Access network device A sends a request message to access network device B. Correspondingly, access network device B receives the request message from access network device A.

[0312] The request message is used to request a key, and the request message carries information 4, which is used to determine the terminal device. Information 4 corresponds to the fourth information in the fourth to sixth aspects of the invention.

[0313] Exemplarily, information 4 includes at least one of the following: information of a source cell, or information of a terminal device.

[0314] S705 , access network device B determines the key of the target cell of the terminal device according to information 4 .

[0315] In one possible implementation, access network device B can use vertical deduction to determine the key of the target cell. For example, it can determine the terminal device based on information 4, thereby determining the next hop parameter NH corresponding to the terminal device, and determine the key of the target cell based on the next hop parameter NH.

[0316] In one example, when the access network device B determines the key of the target cell according to the next hop parameter NH, it can determine the key of the target cell according to the next hop parameter NH and information of the target cell.

[0317] In another possible implementation method, access network device B can use horizontal deduction to determine the key of the target cell. For example, it can determine the terminal device based on information 4, and further determine the key of the source cell corresponding to the terminal device, and determine the key of the target cell based on the key of the source cell of the terminal device.

[0318] In one example, when access network device B determines the key of the target cell based on the key of the source cell of the terminal device, it can determine the key of the target cell based on the key of the source cell and information of the target cell.

[0319] As an optional solution, access network device B can determine the deduction method to be adopted in the following manner: when access network device B has an unused pair of parameters {NH, NCC}, access network device B can use the vertical deduction method; when access network device B does not have an unused pair of parameters {NH, NCC}, access network device B can use the horizontal deduction method.

[0320] The following describes how the access network device B obtains the target cell information in combination with two application scenarios.

[0321] Scenario A: The method described in Figure 7 is applied to the subsequent handover process. Access network device B can obtain target cell information in the following manner: Access network device C sends information A to access network device B. Information A may include information about candidate cells managed by access network device A. Because the target cell is included among the candidate cells managed by access network device A, information A includes the target cell information. Optionally, information A may also include information about candidate cells managed by other candidate access network devices, information about candidate cells managed by access network device B, and so on.

[0322] The access network device C may refer to the relevant description of the second access network device in the method described in Figure 4. The access network device C obtains the target cell information in a similar manner to the second access network device obtaining the first information in scenario 1 of the method described in Figure 4. For details, please refer to the above description and will not be elaborated here.

[0323] Scenario B: The method described in FIG7 can be applied to any handover process. In this scenario, the access network device B obtains the target cell information in a similar manner to the first access network device obtaining the first information in scenario 2 of the method described in FIG4. For details, please refer to the above description and will not be elaborated here.

[0324] S706 , access network device B sends a response message to the request message received to access network device A. Correspondingly, access network device A receives the response message to the request message from access network device B.

[0325] The response message carries the key of the target cell of the terminal device.

[0326] Optionally, if access network device B uses a vertical derivation method, access network device B may further send information 3 to access network device A, where information 3 is used to indicate parameters related to key update. Information 3 corresponds to the third information in aspects 4 to 6 of the present invention. Exemplarily, information 3 may include at least one of the following: an NCC for key update derivation during the next handover, or a key set change indication for key update derivation during the next handover.

[0327] For example, information 3 can be carried in the response message. After receiving information 3, access network device A sends information 3 to the terminal device. Information 3 can be carried in different types of messages, such as MAC CE, unencrypted and / or unintegrity-protected RRC messages, DCI, etc. The terminal device can deduce the key based on information 3, using the same derivation method as that used by access network device B.

[0328] Optionally, if the terminal device derives the key of the target cell, the terminal device may send a confirmation message of information 3 to access network device A, which is used to instruct the use of the new key for communication. Alternatively, the function of the confirmation message can also be described as instructing the use of the new key for encryption and / or integrity protection.

[0329] If access network device B uses the horizontal derivation method, access network device B does not need to send information 3 to access network device A. The terminal device can derive the key based on the key of the source cell, and the specific derivation method is the same as the derivation method used by access network device B.

[0330] In the embodiment of the present application, the terminal device sends the source cell / terminal device related information (i.e., the above-mentioned information 2) to the access network device to which the target cell belongs, so that the access network device to which the target cell belongs can determine the access network device to which the source cell belongs, and thus can request a key from the access network device to which the source cell belongs. In this way, in subsequent handovers, the access network device to which the target cell belongs can actively obtain a key that is consistent with that of the terminal device, thereby facilitating the correct decryption or message integrity check of the terminal device and the target cell.

[0331] Moreover, the terminal device can trigger the access network device of the target cell to request the key from the access network device of the source cell in a timely manner through information 2, so that subsequent communications between the terminal device and the target cell can be based on the same key, thereby improving communication security.

[0332] For ease of understanding, the following describes the first and second handover processes using a communication system including access network devices 1, 2, and 3 as an example, combining the two scenarios described above. The first handover can be from access network device 1 to access network device 2. The second handover can be from access network device 2 to access network device 3. It should be understood that other handovers can be performed after the second handover. For specific handover methods, please refer to the second handover process and will not be further described here.

[0333] Example A:

[0334] In this embodiment, the method described in FIG7 can be applied to subsequent handovers (the second handover is taken as an example below). In embodiment 1, access network device 1 can correspond to the access network device C, access network device 2 corresponds to the access network device B, and access network device 3 corresponds to access network device A.

[0335] As shown in FIG8 , the method includes:

[0336] Assume that the terminal device is currently connected to access network device 1. As the terminal device moves, the terminal device can perform the first switching, which specifically includes steps S801 to S810. The specific process can refer to the relevant description of the first switching in Example 1 of the method described in Figure 4, that is, the relevant description of S501 to S510, which will not be repeated here.

[0337] Afterwards, the terminal device can perform a second handover through the following steps S811 to S819:

[0338] S811: The terminal device determines that the trigger condition of cell 3 is met.

[0339] The cell 3 mentioned above corresponds to the target cell mentioned above.

[0340] S812, the terminal device sends information 1 to the access network device 3.

[0341] Information 1 is used to access cell 3. For information 1, please refer to the relevant description of S702 above, and will not be repeated here.

[0342] S813, the terminal device sends information 2 to the access network device 3.

[0343] Information 2 is used by access network device 3 to obtain a key from access network device 2. For information 2, please refer to the relevant description of S703 above, and will not be repeated here.

[0344] S814, access network device 3 sends a request message to access network device 2.

[0345] The request message is used to request a key, and the request message carries information 4, which is used to determine the terminal device. For information 4, please refer to the relevant description of S704 above, and will not be repeated here.

[0346] S815 , the access network device 2 determines the key 3 ′ of the target cell of the terminal device according to the information 4 .

[0347] The specific method can be found in the related description of S705 above, which will not be repeated here.

[0348] S816 , access network device 2 sends a response message to access network device 3 in response to the receiving request message.

[0349] The response message carries the key key 3' of the target cell of the terminal device.

[0350] Optionally, the response message may also carry information 3. The access network device 3 may send the information 3 to the terminal device. For information 3, please refer to the relevant description of S706 above, which will not be repeated here.

[0351] S817 , access network device 3 sends a switching success message to access network device 2 .

[0352] S818, access network device 3 sends a path switching request message to the AMF network element.

[0353] S819, the AMF network element sends a path switching request response message to access network device 3.

[0354] It should be noted that S817 to S819 are optional steps.

[0355] For the above S817 to S819, reference can be made to the relevant description of S517 to S519 above, which will not be repeated here.

[0356] Through the above process, the terminal device switches from cell 2 managed by access network device 2 to cell 3 managed by access network device 3.

[0357] As a possible implementation, after the terminal device switches to cell 3, the terminal device and cell 3 can communicate based on key 3'. The method for the terminal device to generate key 3' can refer to the method for generating the key of the target cell of the terminal device in S706 above, which will not be repeated here.

[0358] According to the method described in FIG8 , a terminal device can perform at least two handovers, and the first handover and subsequent handovers (e.g., the second handover) are performed in different ways. In the first handover, the terminal device performs the handover after determining that the triggering conditions of the target cell are met. In the subsequent handover, the terminal device sends the source cell information / terminal device information (i.e., information 2) to the access network device to which the target cell belongs after determining that the triggering conditions of the target cell are met, so that the access network device to which the target cell belongs requests a key from the access network device to which the source cell belongs. The following describes a method for a terminal device to distinguish between the first handover and the subsequent handover.

[0359] In one possible approach, a terminal device may deem the access network device it accesses when it first receives candidate cell configuration information as the initial access network device. When the terminal device performs its first cell handover or access network device handover using the candidate cell configuration information, this can be considered an initial handover or first handover. When the terminal device performs a second cell handover or access network device handover using the previously provided candidate cell configuration information, this can be considered a second handover or subsequent handover. Similarly, the third, fourth, and other cell handovers or access network device handovers using the previously provided candidate cell configuration information can also be considered subsequent handovers.

[0360] Example B:

[0361] The difference between Example B and Example A is that the first handover in Example A does not use the method described in Figure 7 , while the first handover in Example B can also use the method described in Figure 7 . In Example B, for the first handover, access network device 1 can correspond to the aforementioned access network device B, and access network device 2 can correspond to the aforementioned access network device A. For subsequent handovers, using the second handover as an example below, access network device 1 can correspond to the aforementioned access network device C, access network device 2 can correspond to the aforementioned access network device B, and access network device 3 can correspond to the aforementioned access network device A.

[0362] As shown in FIG9 , the method includes:

[0363] Assuming that the terminal device initially accesses access network device 1, the terminal device can perform the first handover through the following steps S901 to S911:

[0364] S901, the terminal device communicates with access network device 1.

[0365] S902: Access network device 1 sends a handover request message to access network device 2 and access network device 3 respectively.

[0366] In one possible implementation, the handover request message sent by access network device 1 to access network device 2 may carry key 2 of access network device 2. The handover request message sent by access network device 1 to access network device 3 may carry key 3 of access network device 3.

[0367] This approach can minimize changes to the original protocol and thus improve forward compatibility.

[0368] In another possible implementation, the handover request message sent by access network device 1 to access network device 2 and access network device 3 may not carry the keys of access network device 2 and access network device 3.

[0369] Since the access network device of the target cell (i.e., access network device 2) can obtain the key through S909 to S911 below, the above method does not carry the key of access network device 2 in the handover request message, which can save signaling overhead. In addition, this method can ensure that the access network device of the source cell uses the same rules to send handover request messages in the first handover and subsequent handovers, thereby reducing the processing complexity of the access network device.

[0370] S903 : Access network device 2 and access network device 3 send a handover request response message to access network device 1 .

[0371] It should be noted that S901 to S903 are optional steps.

[0372] For the above S901 to S903 , please refer to the relevant description of S501 to S503 above, which will not be repeated here.

[0373] S904 , access network device 1 sends information about candidate cells to access network device 2 and access network device 3 .

[0374] S905, access network device 1 sends a configuration message to the terminal device.

[0375] It should be noted that S904 to S905 are optional steps. For details, please refer to the relevant description of S504 to S505 above, and they will not be repeated here.

[0376] S906: The terminal device determines that the triggering condition of cell 2 is met.

[0377] In the first handover process, the cell 2 mentioned above corresponds to the target cell mentioned above.

[0378] S907, the terminal device sends information 1-1 to access network device 2.

[0379] Information 1-1 is used to access cell 2. For information 1-1, please refer to the description of information 1 in S702 above, and will not be repeated here.

[0380] S908, the terminal device sends information 2-1 to access network device 2.

[0381] The information 2-1 is used by the access network device 2 to obtain the key from the access network device 1. Exemplarily, the information 2-1 includes at least one of the following: information of the source cell 1, or information of the terminal device.

[0382] For details of information 2-1, please refer to the description of information 2 in S703 above, which will not be repeated here.

[0383] S909 , access network device 2 sends request message 1 to access network device 1 .

[0384] Request message 1 is used to request a key, and carries information 4-1, which is used to identify the terminal device. Exemplarily, information 4-1 includes at least one of the following: information about the source cell cell 1, or information about the terminal device.

[0385] For details of information 4-1, please refer to the description of information 4 in S704 above, which will not be repeated here.

[0386] S910, the access network device 1 determines the key key 2 of the target cell cell 2 of the terminal device according to the information 4-1.

[0387] The specific method can be found in the related description of S705 above, which will not be repeated here.

[0388] S911 , access network device 1 sends a response message 1 to access network device 2 in response to receiving request message 1 .

[0389] The response message 1 carries the key key 2 of the target cell cell 2 of the terminal device.

[0390] Optionally, the response message may also carry information 3-1. Access network device 2 may send information 3-1 to the terminal device. Exemplarily, information 3-1 may include at least one of the following: NCC 1 for key update deduction at the next handover, or key set change indication 1 for key update deduction at the next handover.

[0391] For information 3-1, please refer to the description of information 3 in S706 above, which will not be repeated here.

[0392] S912 , access network device 2 sends a handover success message to access network device 1 .

[0393] S913, access network device 2 sends a path switching request message to the AMF network element.

[0394] S914, the AMF network element sends a path switching request response message to access network device 2.

[0395] It should be noted that S912 to S914 are optional steps.

[0396] For the above S912 to S914, reference may be made to the related description of S508 to S510 above, which will not be repeated here.

[0397] Through the above process, the terminal device switches from cell 1 managed by access network device 1 to cell 2 managed by access network device 2.

[0398] As a possible implementation, after the terminal device switches to cell 2, the terminal device and cell 2 can communicate based on key 2. The method for the terminal device to generate key 2 can refer to the method for generating the key of the target cell of the terminal device in S706 above, which will not be repeated here.

[0399] Afterwards, the terminal device may perform a second handover through steps S915 to S923:

[0400] S915: The terminal device determines that the triggering condition of cell 3 is met.

[0401] In the second handover process, the cell 3 mentioned above corresponds to the target cell mentioned above.

[0402] S916, the terminal device sends information 1-2 to access network device 3.

[0403] Information 1-2 is used to access cell 3. Information 1-2 can refer to the description of information 1 in S702 above, and will not be repeated here.

[0404] S917, the terminal device sends information 2-2 to the access network device 3.

[0405] The information 2-2 is used by the access network device 3 to obtain the key from the access network device 2. Exemplarily, the information 2-2 includes at least one of the following: information of the source cell 2, or information of the terminal device.

[0406] For details of information 2-2, please refer to the description of information 2 in S703 above, which will not be repeated here.

[0407] S918 , access network device 3 sends request message 2 to access network device 2 .

[0408] Request message 2 is used to request a key, and carries information 4-2, which is used to identify the terminal device. Exemplarily, information 4-2 includes at least one of the following: information about the source cell cell 2, or information about the terminal device.

[0409] For information 4-2, please refer to the description of information 4 in S704 above, which will not be repeated here.

[0410] S919, the access network device 2 determines the key key 3' of the target cell cell 3 of the terminal device according to the information 4-2.

[0411] The specific method can be found in the related description of S705 above, which will not be repeated here.

[0412] S920 , access network device 2 sends a response message 2 to access network device 3 in response to receiving request message 2 .

[0413] The response message carries the key key 3' of the target cell cell 3 of the terminal device.

[0414] Optionally, the response message may also carry information 3-2. The access network device 3 may send the information 3-2 to the terminal device. Exemplarily, the information 3-2 may include at least one of the following: NCC 2 for performing key update deduction at the next handover, or key set change indication 2 for performing key update deduction at the next handover.

[0415] For information 3-2, please refer to the description of information 3 in S706 above, which will not be repeated here.

[0416] S921 , access network device 3 sends a handover success message to access network device 2 .

[0417] S922, access network device 3 sends a path switching request message to the AMF network element.

[0418] S923, the AMF network element sends a path switching request response message to access network device 3.

[0419] It should be noted that S921 to S923 are optional steps.

[0420] The above S921 to S923 can refer to the relevant description of S517 to S519 above, and will not be repeated here.

[0421] Through the above process, the terminal device switches from cell 2 managed by access network device 2 to cell 3 managed by access network device 3.

[0422] As a possible implementation, after the terminal device switches to cell 3, the terminal device and cell 3 can communicate based on key 3'. The method for the terminal device to generate key 3' can refer to the method for generating the key of the target cell of the terminal device in S706 above, which will not be repeated here.

[0423] In the embodiment of the present application, the terminal device sends the source cell / terminal device related information (i.e., the above-mentioned information 2) to the access network device to which the target cell belongs, so that the access network device to which the target cell belongs can determine the access network device to which the source cell belongs, and thus can request a key from the access network device to which the source cell belongs. In this way, in subsequent handovers, the access network device to which the target cell belongs can actively obtain a key that is consistent with that of the terminal device, thereby facilitating the correct decryption or message integrity check of the terminal device and the target cell.

[0424] Moreover, the terminal device can trigger the access network device of the target cell to request the key from the access network device of the source cell in a timely manner through information 2, so that subsequent communications between the terminal device and the target cell can be based on the same key, thereby improving communication security.

[0425] It should be noted that the method described in FIG. 4 and the method described in FIG. 7 can be implemented separately as independent solutions. Alternatively, the method described in FIG. 4 and the method described in FIG. 7 can be combined and implemented as a solution. For example, the terminal device can determine whether to use the method described in FIG. 4 or the method described in FIG. 7 based on preset conditions.

[0426] Exemplarily, the preset condition may be that the channel quality of the serving cell is greater than a threshold value, or the preset condition may be that the channel quality of the serving cell is greater than or equal to a threshold value. If the preset condition is met, the method described in FIG4 is adopted, that is, after the trigger condition of the target cell is met, the first message is waited for to be received, and the handover is performed after the first message is received. If the preset condition is not met, the method described in FIG7 is adopted, that is, after the trigger condition of the target cell is met, the handover is performed, and information 1 is sent to the access network device to which the target cell belongs, so as to trigger the access network device to which the target cell belongs to request a key from the access network device to which the source cell belongs.

[0427] It should be understood that the preset condition may have other variations. For example, the preset condition may be that the channel quality of the serving cell is less than a threshold value, or the preset condition may be that the channel quality of the serving cell is less than or equal to the threshold value. If the preset condition is not met, the method described in Figure 4 is adopted; if the preset condition is met, the method described in Figure 7 is adopted.

[0428] As an example, the channel quality of the serving cell may be represented by parameters such as RSRP, RSRQ, and SINR of a signal of the serving cell.

[0429] Optionally, the above threshold value can be defined by the protocol or configured by the access network device (for example, the access network device to which the source cell belongs in the first handover, or the access network device to which the source cell belongs in a subsequent handover, or the access network device to which the current service cell belongs, etc.), and this application does not make specific limitations.

[0430] Based on the same inventive concept as the method embodiment, an embodiment of the present application provides a communication device, the structure of which may be as shown in FIG10 , including a communication unit 1001 and a processing unit 1002 .

[0431] In one embodiment, the communication device can be specifically used to implement the method executed by the terminal device in the embodiment of Figure 4. The device can be the terminal device itself, or it can be a chip or chipset in the terminal device or a part of the chip used to execute the function of the relevant method. Among them, the processing unit 1002 is used to determine that the trigger condition of the target cell is met and a first message from the first access network device has been received through the communication unit 1001, the first message indicating that the key notification has been completed to the candidate access network device, the first access network device is the access network device to which the current service cell of the terminal device belongs, and the target cell is one of the candidate cells managed by the candidate access network device; and, based on the first message, determine to send a second message to the target cell through the communication unit 1001, the second message is used to access the target cell.

[0432] Optionally, the processing unit 1002 is further configured to determine a key of the target cell according to the information of the target cell and the third information.

[0433] Optionally, the processing unit 1002 is further configured to determine a first message to be received when a key needs to be updated after switching to a target cell.

[0434] Optionally, the communication unit 1001 is further configured to send a third message to the first access network device, where the third message is configured to request the first access network device to notify the candidate access network device of a key.

[0435] Optionally, the processing unit 1002 is further configured to determine a first message to be received when the channel quality of the serving cell is greater than or equal to a threshold value.

[0436] Optionally, the communication unit 1001 is further used to receive a fourth message, where the fourth message is used to configure a trigger condition of the target cell.

[0437] In one embodiment, a communication device can be specifically used to implement the method performed by the access network device in the embodiment of Figure 4. The device can be the access network device itself, or a chip, chipset, or a portion of a chip in the access network device that is used to perform the functions of the relevant method. The communication unit 1001 is configured to receive first information from a second access network device, the first information including information about at least one candidate cell of a terminal device; the processing unit 1002 is configured to determine a first key based on the first information; the communication unit 1001 is further configured to send the first key to a candidate access network device to which the at least one candidate cell belongs; and, to send a first message to the terminal device, the first message indicating that key notification has been completed to the candidate access network device.

[0438] In one embodiment, a communication device can be specifically used to implement the method executed by the terminal device in the embodiment of Figure 7. The device can be the terminal device itself, or a chip or chipset in the terminal device, or a portion of a chip used to execute the function of the relevant method. The processing unit 1002 is used to determine whether a trigger condition of a target cell is satisfied; the communication unit 1001 is used to send first information to a first access network device to which the target cell belongs, the first information being used to access the target cell; and the second information is sent to the first access network device, the second information being used for the first access network device to obtain a key from a second access network device, where the second access network device is the access network device to which the source cell of the terminal device belongs.

[0439] Optionally, the communication unit 1001 is further configured to receive third information from the first access network device, where the third information is used to indicate parameters related to the key update. The processing unit 1002 is further configured to determine a key of the target cell based on the third information, and to communicate with the target cell via the communication unit 1001 based on the key of the target cell.

[0440] Optionally, the processing unit 1002 is further configured to determine the key of the target cell by horizontal deduction; and communicate with the target cell through the communication unit 1001 based on the key of the target cell.

[0441] Optionally, the processing unit 1002 is further configured to determine, when the channel quality of the serving cell is less than or equal to a threshold value, to send the first information and the second information after a trigger condition of the target cell is met.

[0442] Optionally, the communication unit 1001 is further used to receive a first message, where the first message is used to configure a trigger condition of the target cell.

[0443] In one embodiment, a communication device can be specifically used to implement the method performed by the access network device in the embodiment of FIG. 7 . The device can be the access network device itself, or a chip, chipset, or a portion of a chip in the access network device that performs the functions of the related method. The communication unit 1001 is configured to send and receive signals. The processing unit 1002 is configured to receive first information from a terminal device via the communication unit 1001, the first information being used to access a target cell; and, via the communication unit 1001, receive second information from the terminal device, the second information being used for the first access network device to obtain a key from a second access network device, the second access network device being the access network device to which the source cell of the terminal device belongs; and, via the communication unit 1001, send a request message to the second access network device, the request message being used to request a key and carrying fourth information, the fourth information being used to identify the terminal device; and, via the communication unit 1001, receive a response message to the request message, the response message carrying a key of the target cell of the terminal device, the target cell being one of the candidate cells managed by the first access network device.

[0444] Exemplarily, the response message further carries third information, where the third information is used to indicate parameters related to the key update.

[0445] Optionally, the processing unit 1002 is further configured to send third information to the terminal device through the communication unit 1001; and communicate with the terminal device based on the key of the target cell.

[0446] The division of modules in the embodiments of the present application is schematic and is only a logical function division. In actual implementation, there may be other division methods. In addition, the functional modules in the various embodiments of the present application can be integrated into a processor, or can exist physically separately, or two or more modules can be integrated into one module. The above-mentioned integrated modules can be implemented in the form of hardware or in the form of software functional modules. It is understood that the functions or implementations of the various modules in the embodiments of the present application can be further referred to the relevant description of the method embodiment.

[0447] In one possible embodiment, a communication device may be as shown in FIG11 . The device may be a communication device or a chip within the communication device, wherein the communication device may be a terminal device or a network device in the above embodiments. The device includes a processor 1101 and a communication interface 1102, and may also include a memory 1103. The processing unit 1002 may be the processor 1101. The communication unit 1001 may be the communication interface 1102. Optionally, the processor 1101 and the memory 1103 may be integrated.

[0448] The processor 1101 may be a CPU, a digital processing unit, or the like. The communication interface 1102 may be a transceiver, an interface circuit such as a transceiver circuit, or a transceiver chip, or the like. The device further includes: a memory 1103 for storing programs executed by the processor 1101. The memory 1103 may be a non-volatile memory, such as a hard disk drive (HDD) or a solid-state drive (SSD), or a volatile memory (volatile memory), such as a random-access memory (RAM). The memory 1103 is any other medium that can be used to carry or store desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto.

[0449] The processor 1101 is used to execute the program code stored in the memory 1103, specifically to execute the actions of the processing unit 1002, which will not be described in detail in this application. The communication interface 1102 is specifically used to execute the actions of the communication unit 1001, which will not be described in detail in this application.

[0450] The specific connection medium between the communication interface 1102, processor 1101, and memory 1103 is not limited in the embodiments of the present application. In Figure 11, the embodiment of the present application shows that the memory 1103, processor 1101, and communication interface 1102 are connected via a bus 1104. The bus is represented by a bold line in Figure 11. The connection method between other components is only for schematic illustration and is not intended to be limiting. Buses can be divided into address buses, data buses, control buses, etc. For ease of representation, only one bold line is used in Figure 11, but this does not mean that there is only one bus or one type of bus.

[0451] An embodiment of the present invention further provides a computer-readable storage medium for storing computer software instructions required to be executed by the above-mentioned processor, which includes a program required to be executed by the above-mentioned processor.

[0452] An embodiment of the present application also provides a communication system, including a communication device for implementing the terminal device function in the embodiment of Figure 4 and a communication device for implementing the access network device function in the embodiment of Figure 4.

[0453] An embodiment of the present application also provides a communication system, including a communication device for implementing the terminal device function in the embodiment of Figure 7 and a communication device for implementing the access network device function in the embodiment of Figure 7.

[0454] Those skilled in the art will appreciate that the embodiments of the present application can be provided as methods, systems, or computer program products. Therefore, the present application can adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application can adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0455] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the present application. It should be understood that each flow and / or box in the flow chart and / or block diagram, as well as the combination of the flow chart and / or box in the flow chart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for implementing the functions specified in one or more flow charts and / or one or more boxes in the block diagram.

[0456] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce a product including an instruction device that implements the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0457] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in one or more processes in the flowchart and / or one or more boxes in the block diagram.

[0458] Obviously, those skilled in the art may make various changes and modifications to the present application without departing from the scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include these modifications and variations.

Claims

1. A communication method, characterized in that, The method includes: Determining that a triggering condition of a target cell is satisfied and a first message from a first access network device has been received, the first message indicating that key notification has been completed to a candidate access network device, the first access network device being the access network device to which the current serving cell of the terminal device belongs, and the target cell being one of the candidate cells managed by the candidate access network device; Determining, according to the first message, to send a second message to the target cell, the second message being used for accessing the target cell.

2. The method according to claim 1, characterized in that, The first message includes at least one of the following: second information, or third information, where the second information is used to indicate that key notification has been completed to the candidate access network device, and the third information is used to indicate parameters related to key update.

3. The method according to claim 2, wherein The third information includes at least one of the following: a next-hop chain count, or a key set change indication.

4. The method according to claim 2 or 3, characterized in that, The method further includes: Determining a key of the target cell according to information of the target cell and the third information.

5. The method according to claim 4, wherein The information of the target cell includes at least one of the following: a physical cell identifier of the target cell, or downlink frequency point information of the target cell.

6. The method according to any one of claims 1-5, characterized in that, The method further includes: Determining to receive the first message when a key needs to be updated after switching to the target cell.

7. The method according to any one of claims 1-6, characterized in that, The method further includes: Sending a third message to the first access network device, the third message being used to request the first access network device to notify a key to the candidate access network device.

8. The method according to claim 7, wherein The third message further indicates that the triggering condition of the target cell is satisfied.

9. The method according to any one of claims 1 to 8, characterized in that, The method further includes: Determining to receive the first message when the channel quality of the serving cell is greater than or equal to a threshold value.

10. The method according to any one of claims 1-9, characterized in that, The method further includes: Receiving a fourth message, the fourth message being used to configure the triggering condition of the target cell.

11. A communication method, characterized in that, The method includes: Receiving first information from a second access network device, the first information including information of at least one candidate cell of the terminal device; Determining a first key based on the first information; Sending the first key to candidate access network devices to which the at least one candidate cell belongs; Sending a first message to the terminal device, the first message indicating that key notification has been completed to the candidate access network device.

12. The method according to claim 11, wherein The first message includes at least one of the following: second information, or third information, where the second information is used to indicate that key notification has been completed to the candidate access network device, and the third information is used to indicate parameters related to key update.

13. The method according to claim 12, wherein The third information includes at least one of the following: a next-hop chain count, or a key set change indication.

14. The method according to any one of claims 11-13, characterized in that, The information of the at least one candidate cell includes at least one of the following: a global cell identifier of the at least one candidate cell, a physical cell identifier of the at least one candidate cell, or downlink frequency point information of the at least one candidate cell.

15. A communication method, characterized in that, The method includes: Determining that a triggering condition of a target cell is satisfied; Sending first information to a first access network device to which the target cell belongs, the first information being used for accessing the target cell; Send second information to the first access network device, where the second information is used for the first access network device to obtain a key from a second access network device, and the second access network device is the access network device to which the source cell of the terminal device belongs.

16. The method according to claim 15, characterized in that, The second information includes at least one of the following: information of the source cell, or information of the terminal device.

17. The method according to claim 15 or 16, characterized in that The first information is not encrypted and / or not integrity protected.

18. The method according to any one of claims 15 to 17, characterized in that, The method further includes: Receive third information from the first access network device, where the third information is used to indicate parameters related to key update; Determine the key of the target cell according to the third information; Communicate with the target cell based on the key of the target cell.

19. The method according to any one of claims 15 - 17, characterized in that, The method further includes: Determine the key of the target cell in a horizontal derivation manner; Communicate with the target cell based on the key of the target cell.

20. The method according to any one of claims 15-19, characterized in that, The method further includes: Determine to send the first information and the second information after the trigger condition of the target cell is met when the channel quality of the serving cell is less than or equal to a threshold.

21. The method according to any one of claims 15-20, characterized in that, The method further includes: Receive a first message, where the first message is used to configure the trigger condition of the target cell.

22. A communication method, characterized in that, The method includes: Receive first information from a terminal device, where the first information is used to access the target cell; Receive second information from the terminal device, where the second information is used for the first access network device to obtain a key from a second access network device, and the second access network device is the access network device to which the source cell of the terminal device belongs; Send a request message to the second access network device, where the request message is used to request a key, and the request message carries fourth information, and the fourth information is used to determine the terminal device; Receive a response message to the request message, where the response message carries the key of the target cell of the terminal device, and the target cell is one of the candidate cells managed by the first access network device.

23. The method according to claim 22, characterized in that, The first information includes at least one of the following: information of the source cell, or information of the terminal device.

24. The method according to claim 22 or 23, characterized in that, The fourth information includes at least one of the following: information of the source cell, or information of the terminal device.

25. The method according to any one of claims 22-24, characterized in that, The first information is not encrypted and / or not integrity protected.

26. The method according to any one of claims 22-25, characterized in that, The response message further carries third information, where the third information is used to indicate parameters related to key update; The method further includes: Send the third information to the terminal device; Communicate with the terminal device based on the key of the target cell.

27. A communication device, characterized in that, Includes a unit or module for executing the method according to any one of claims 1-10, or includes a unit or module for executing the method according to any one of claims 15-21.

28. A communication device, characterized in that, Includes a unit or module for executing the method according to any one of claims 11-14, or includes a unit or module for executing the method according to any one of claims 22-26.

29. A communication device, characterized in that, Includes a processor and a memory, where the memory is used to store program instructions, and when the processor executes the program instructions, the method according to any one of claims 1-10 is executed, or the method according to any one of claims 15-21 is executed.

30. A communication device, characterized in that, Comprising a processor and a memory, the memory being used for storing program instructions, the processor, when executing the program instructions, causes the method according to any one of claims 11-14 to be executed, or the method according to any one of claims 22-26 to be executed.

31. A computer-readable storage medium, characterized in that, Computer-readable instructions are stored in the computer storage medium, and when the computer-readable instructions run on a communication device, cause the method according to any one of claims 1-10 to be executed, or the method according to any one of claims 11-14 to be executed, or the method according to any one of claims 15-21 to be executed, or the method according to any one of claims 22-26 to be executed.

32. A computer program product, characterized in that, When the computer program product runs on a device, cause the device to execute the method according to any one of claims 1-10 or the method according to any one of claims 11-14 or the method according to any one of claims 15-21 or the method according to any one of claims 22-26.

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