Key management method and device

Abstract

The embodiment of the invention discloses a key management method and device. The method comprises the following steps: sending pre-configuration information and first key information of a plurality of candidate cells to terminal equipment; the first key information is used for deducing a communication key between the terminal equipment and the access network equipment; and sending the first key to a second access network device to which a target cell switched by the terminal device belongs, the first key being a key for communication between the terminal device and the second access network device, the plurality of candidate cells including the target cell. According to the method, subsequent switching can be supported, and the key can be effectively managed.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of communication technology, and in particular, to a method and device for key management. Background Art

[0002] In a mobile communication system, the movement of a terminal device will cause a change in the communication link between the terminal device and the access network device. For example, the access network device can instruct the terminal device to switch cells or access network devices according to the movement of the terminal device. When an access network device is switched, the terminal device usually needs to change the key, that is, the terminal device uses different keys to encrypt data, perform integrity protection, etc. when communicating with the source access network device and the target access network device to achieve secure communication.

[0003] At present, some switching methods can pre-configure multiple candidate cells for terminal devices to support subsequent switching of terminal devices (ie, multiple switching between multiple candidate cells). However, the current switching methods that support subsequent switching do not have an effective key management mechanism, making it difficult to ensure communication security. Summary of the invention

[0004] The embodiments of the present application disclose a method and device for key management, which can support subsequent switching and effectively manage keys.

[0005] The present application is introduced below from different aspects. It should be understood that the implementation methods and beneficial effects of the following different aspects can be referenced to each other.

[0006] In a first aspect, the present application discloses a method for key management, which can be executed by a first access network device or a module (for example, a chip) in the first access network device, and the method may include: sending pre-configuration information and first key information of multiple candidate cells to a terminal device; the first key information is used to derive a key for communication between the terminal device and the access network device; sending a first key to a second access network device to which a target cell to which the terminal device switches belongs, the first key being a key for communication between the terminal device and the second access network device, and the multiple candidate cells include the target cell.

[0007] In an embodiment of the present application, the first access network device can send pre-configuration information of multiple candidate cells to the terminal device to support the terminal device in subsequent switching (i.e., switching once or multiple times among multiple candidate cells), and the terminal device does not need to perform the steps of obtaining pre-configuration information multiple times in subsequent cell switching. The first access network device sends the first key information used to derive the key for this switching to the terminal device, which can ensure the key security of this switching. In this method, the first key information and the pre-configuration information are two independent parameters, which can support the terminal device to use other key information when using the above pre-configuration information in subsequent switching after this switching (i.e., accessing the above target cell), and can effectively manage the key to ensure communication security.

[0008] In combination with the first aspect, in a possible implementation manner, pre-configuration information of multiple candidate cells is used for a terminal device to perform one or more handovers among the multiple candidate cells.

[0009] In an embodiment of the present application, the first access network device can send pre-configuration information of multiple candidate cells to the terminal device to support the terminal device to switch once or multiple times among multiple candidate cells. The terminal device does not need to perform multiple steps of obtaining pre-configuration information during subsequent cell switching.

[0010] In combination with the first aspect, in a possible implementation manner, the pre-configuration information does not include the first key information.

[0011] In an embodiment of the present application, the pre-configuration information does not include the first key information. Then, when switching between multiple candidate cells, the terminal device can re-acquire the key information to align with the key of the access network device to be accessed. Different key information can also be used to avoid key duplication in subsequent switching processes. This method provides an effective key management mechanism to ensure communication security.

[0012] Exemplarily, the first key information may be the next hop chaining count (NCC), and the first key information is used to derive the first key; it may be the KgNB in ​​the new wireless NR (newradio) communication, the UE and the gNB use the KgNB to further derive the key Kup used for the user plane data and the key Krrc used for the radio resource control (RRC) layer signaling, the UE and the gNB use Kup to encrypt the user plane data, perform security processing such as integrity protection, and the UE and the gNB use Krrc to encrypt the RRC signaling, perform security processing such as integrity protection. In an embodiment of the present application, the terminal device may use a different NCC in each subsequent switch. Since the KgNB generated by different NCCs is different, the Kup and Krrc derived based on different KgNBs are also different. This method can avoid the problem of key reuse in subsequent switching processes and ensure communication security.

[0013] In combination with the first aspect, in a possible implementation manner, the multiple candidate cells belong to one or more access network devices.

[0014] In the embodiment of the present application, multiple candidate cells may be managed by one or more access network devices to support terminal devices switching between different cells or different access network devices.

[0015] In combination with the first aspect, in a possible implementation manner, sending a first key to a second access network device to which a target cell to which the terminal device is switched belongs includes:

[0016] After determining the target cell, the first key is sent to the second access network device.

[0017] In an embodiment of the present application, the target cell for the terminal device to switch can be determined by the service base station of the terminal device (i.e., the first access network device), and the first access network device can send the first key used for this switch to the second access network device after determining the target cell. It should be understood that if key interaction is performed in the pre-configuration stage, it will lead to a strong binding relationship between the key and the pre-configuration, making it difficult to change the key; and since the target cell is not determined in the pre-configuration stage, if keys are sent to multiple candidate access network devices at this time, additional data transmission will be added, resulting in insecure keys. In this method, the first access network device does not send the first key to the second access network device when obtaining the pre-configuration information of the cell it manages from the second access network device (referred to as the pre-configuration stage), but sends the first key after determining the target cell, which can protect the key and support key changes during subsequent switching of the terminal device to ensure switching security.

[0018] In combination with the first aspect, in a possible implementation, the first key information is carried by one of layer 1 signaling, layer 2 signaling and layer 3 signaling, or the first key information is carried by a switching command, and the switching command is used to indicate switching to a target cell.

[0019] In combination with the first aspect, in a possible implementation, before sending the first key to the second access network device to which the target cell to which the terminal device is switched belongs, the method further includes: receiving a first message sent by the terminal device, the first message being used to indicate switching to the target cell.

[0020] In the embodiment of the present application, the target cell for switching of the terminal device may be determined by the terminal device, and this switching may be triggered by the terminal device.

[0021] In combination with the first aspect, in a possible implementation, sending a first key to a second access network device to which a target cell to which a terminal device switches belongs includes: receiving a request message sent by the second access network device, the request message being used to request a key for communication between the terminal device and the second access network device; and sending the first key to the second access network device in response to the request message.

[0022] In an embodiment of the present application, the first access network device can send the first key to the second access network device in response to a request message sent by the second access network device. The method does not need to notify the second access network device of the first key after the terminal device communicates with the first access network device to determine the target cell, and can ensure that the terminal device successfully accesses the target cell when the wireless link between the terminal device and the first access network device fails.

[0023] In combination with the first aspect, in a possible implementation, the request message also includes an integrity message authentication code, and sending the first key to the second access network device includes: after the request message is verified based on the integrity message authentication code, sending the first key to the second access network device.

[0024] The embodiment of the present application can verify the second access network device through the integrity message authentication code to ensure the security of the first key.

[0025] In combination with the first aspect, in a possible implementation, the method also includes: sending a switching request message to the second access network device, the switching request message is used to request pre-configuration information of the cell corresponding to the second access network device; receiving a response message sent by the second access network device, the response message includes the pre-configuration message of the target cell.

[0026] In the second aspect, the present application discloses a method for key management, which can be executed by a terminal device or a module (for example, a chip) in the terminal device, and the method may include: receiving pre-configuration information and first key information of multiple candidate cells; the first key information is used to deduce the key for communication between the terminal device and the access network device; after receiving a switching command, deduce based on the first key information to obtain a first key corresponding to the first cell; the switching command is used to indicate switching to the first cell, the first cell belongs to the second access network device, and the first key is the key for communication between the terminal device and the second access network device.

[0027] In an embodiment of the present application, a terminal device can receive pre-configuration information of multiple candidate cells to support the terminal device to perform subsequent switching (i.e., switching to the above-mentioned first cell) after the current switching (i.e., switching once or multiple times among multiple candidate cells), and the terminal device does not need to perform the step of obtaining pre-configuration information multiple times in subsequent cell switching. In this method, the first key information and the pre-configuration information are two independent parameters, which can support the terminal device to use other key information when using the above-mentioned pre-configuration information in subsequent switching, and can effectively manage the key to ensure communication security.

[0028] In combination with the second aspect, in a possible implementation manner, pre-configuration information of multiple candidate cells is used for a terminal device to perform one or more handovers among the multiple candidate cells.

[0029] In combination with the second aspect, in a possible implementation manner, the pre-configuration information does not include the first key information.

[0030] In combination with the second aspect, in a possible implementation manner, the first key information is carried by one of layer 1 signaling, layer 2 signaling, and layer 3 signaling, or the first key information is carried by a handover command.

[0031] In combination with the second aspect, in a possible implementation manner, the multiple candidate cells belong to one or more access network devices.

[0032] In conjunction with the second aspect, in a possible implementation manner, the method further includes:

[0033] When it is determined that the handover of the first cell fails or the radio link fails, determining a second cell from a plurality of candidate cells, where the second cell belongs to a third access network device;

[0034] A second message is sent to the third access network device, where the second message is used to request access to the second cell.

[0035] In the embodiment of the present application, when determining that the handover fails or the radio link fails, the terminal device can determine the second cell from multiple candidate cells and initiate access to the third access network device corresponding to the second cell. This method can ensure that the terminal device successfully accesses other cells when the handover fails or the radio link fails.

[0036] In combination with the second aspect, in a possible implementation, the second message further includes an integrity message authentication code and / or an identifier of the terminal device.

[0037] In a third aspect, the present application discloses a method for key management, which can be executed by a terminal device or a module (for example, a chip) in the terminal device, and the method may include: receiving pre-configuration information and first key information of multiple candidate cells; sending a first message to a first access network device, the first message being used to indicate switching to the first cell; the first cell belongs to a second access network device; multiple candidate cells include the first cell; deducing based on the first key information to obtain a first key corresponding to the first cell; the first key is a key for communication between the terminal device and the second access network device; receiving second key information from the second access network device; sending a second message to the second access network device, the second message being used to indicate switching to the second cell; the second cell belongs to a third access network device; multiple candidate cells include the second cell; deducing based on the second key information to obtain a second key corresponding to the second cell; the second key is a key for communication between the terminal device and the third access network device.

[0038] In an embodiment of the present application, the terminal device re-acquires key information to deduce different keys each time the cell is switched, such as deducing the first key corresponding to the first cell through the first key information, and deducing the second key corresponding to the second cell through the second key information. This method can avoid the situation where the key is repeated when the terminal device switches multiple times between multiple candidate cells, thereby ensuring key security.

[0039] In combination with the third aspect, in a possible implementation, the method further includes: determining the first cell and / or the second cell from the multiple candidate cells based on pre-configuration information of the multiple candidate cells.

[0040] In combination with the third aspect, in a possible implementation manner, the multiple candidate cells belong to one or more access network devices.

[0041] In combination with the third aspect, in a possible implementation manner, the first key information and / or the second key information is carried by one of layer 1 signaling, layer 2 signaling, and layer 3 signaling.

[0042] In combination with the third aspect, in a possible implementation, the method also includes: when it is determined that switching the second cell fails or the wireless link fails, determining a third cell from multiple candidate cells, the third cell belongs to a fourth access network device; sending a third message to the fourth access network device, the third message is used to request access to the third cell.

[0043] In combination with the third aspect, in a possible implementation, the third message further includes an integrity message authentication code and / or an identifier of the terminal device.

[0044] In a fourth aspect, the present application provides a communication device, which may be a first device or a chip / circuit therein. The communication device is used to execute the method in the first aspect or any possible implementation of the first aspect. The communication device includes a unit having a function of executing the method in the first aspect or any possible implementation of the first aspect.

[0045] In a fifth aspect, the present application provides a communication device, which may be a second device or a chip / circuit therein. The communication device is used to execute the method in any possible implementation of the second aspect, the third aspect, or any aspect thereof. The communication device includes a unit having a method for executing the second aspect, the third aspect, or any possible implementation of any aspect thereof.

[0046] In the fourth aspect or the fifth aspect, the communication device may include a transceiver unit and a processing unit. For a specific description of the transceiver unit and the processing unit, reference may also be made to the device embodiment shown below. The beneficial effects of the fourth to fifth aspects may refer to the relevant descriptions of the first to third aspects, which will not be repeated here.

[0047] In a sixth aspect, the present application discloses a method for key management, which can be executed by a first access network device or a module (for example, a chip) in the first access network device, and the method may include: deducing based on an initial key of the first access network device to obtain a first key corresponding to the first access network device; the first key is a key for communication between the terminal device and the first access network device; sending first key information to the terminal device; the first key information is used to derive a second key for communication between the terminal device and the second access network device; deducing based on the second key information of the first access network device to obtain a third key corresponding to the first access network device; the third key is a key for communication between the terminal device and the first access network device; the first key is different from the second key.

[0048] In the embodiment of the present application, the first access network device can derive the key for communication with the terminal device by itself, and use different key information to derive different keys after each access of the terminal device. This method can avoid the problem of key reuse and ensure communication security.

[0049] In conjunction with the sixth aspect, in a possible implementation, the terminal device stores pre-configuration information of multiple candidate cells. The method can support subsequent switching of the terminal device. Exemplarily, the terminal device can store pre-configuration information of cells managed by the first access network device and the second access network device.

[0050] In combination with the sixth aspect, in a possible implementation, the first access network device may deduce the first key or the third key after receiving an access request from the terminal device.

[0051] In combination with the sixth aspect, in a possible implementation, the method also includes: sending a path switching request to the core network; receiving a response message from the core network, the response message including first key information and second key information, the first key information and the second key information corresponding to a first access network device, the first key information being used to derive a key when the terminal device accesses the first access network device, and the second key information being used to derive a key from the first access network device.

[0052] In the seventh aspect, the present application discloses a method for key management, which may include: deducing based on the initial key of the first access network device to obtain a first key corresponding to the first access network device; the first key is a key for communication between the terminal device and the first access network device; receiving first key information sent by the first access network device; the first key information is used to deduce a second key for communication between the terminal device and the second access network device; deducing based on the second key information to obtain a third key corresponding to the first access network device; the third key is a key for communication between the terminal device and the first access network device; the first key is different from the second key.

[0053] In the embodiment of the present application, the first access network device can derive the key for communication with the terminal device by itself, and use different key information to derive different keys after each access of the terminal device. This method can avoid the problem of key reuse and ensure communication security.

[0054] In conjunction with the seventh aspect, in a possible implementation, the terminal device stores pre-configuration information of multiple candidate cells. The method can support subsequent switching of the terminal device. Exemplarily, the terminal device can store pre-configuration information of cells managed by the first access network device and the second access network device.

[0055] In conjunction with the seventh aspect, in a possible implementation, the terminal device may obtain pre-configuration information of the cell managed by the first access network device and the second access network device from the source cell; and deduce the first key when receiving a handover command sent by the source cell or determining a target cell for handover. The handover command is used to indicate handover to the cell managed by the first access network device; and the target cell is a cell managed by the first access network device.

[0056] In an eighth aspect, the present application provides a communication device, which may be the sixth device or a chip / circuit therein. The communication device is used to execute the method in the sixth aspect or any possible implementation of the sixth aspect. The communication device includes a unit having a function of executing the method in the sixth aspect or any possible implementation of the sixth aspect.

[0057] In a ninth aspect, the present application provides a communication device, which may be the seventh device or a chip / circuit therein. The communication device is used to execute the method in the seventh aspect or any possible implementation of the seventh aspect. The communication device includes a unit having a function of executing the method in the seventh aspect or any possible implementation of the seventh aspect.

[0058] In the eighth aspect or the ninth aspect, the communication device may include a transceiver unit and a processing unit. For a specific description of the transceiver unit and the processing unit, reference may also be made to the device embodiment shown below. The beneficial effects of the eighth to ninth aspects may refer to the relevant descriptions of the sixth to seventh aspects, which are not repeated here.

[0059] In the tenth aspect, the present application provides a communication device, which may include a processor and an interface circuit, and the processor is connected to the interface circuit. Wherein, the interface circuit is used to interact (or send and receive or input and output) information or data, and the processor is used to run program instructions so that the communication device executes the method described in any possible implementation of the first aspect, the second aspect, the third aspect, the sixth aspect, the seventh aspect, or any of the aspects above. Wherein, the interface circuit may be a communication interface, or a transceiver. The transceiver may be a radio frequency module in a communication device, or a combination of a radio frequency module and an antenna, or an input and output interface of a chip or circuit.

[0060] In the eleventh aspect, the present application provides a readable storage medium having program instructions stored thereon, which, when executed on a computer, enables the computer to execute the method described in the first aspect, or the second aspect, or the third aspect, or the sixth aspect, or the seventh aspect, or any possible implementation manner of any one of the aspects above.

[0061] In the twelfth aspect, the present application provides a program product comprising program instructions, which, when executed, enables the method described in the first aspect, or the second aspect, or the third aspect, or the sixth aspect, or the seventh aspect, or any possible implementation of any one of the aspects above to be executed.

[0062] In a thirteenth aspect, the present application provides a device, which can be implemented in the form of a chip or in the form of a device, and the device includes a processor. The processor is used to read and execute a program stored in a memory to execute one or more of the above-mentioned first aspect, or the above-mentioned second aspect, or the above-mentioned third aspect, or the above-mentioned sixth aspect, or the above-mentioned seventh aspect, or, the information interaction method provided by one or more of any possible implementation methods of any aspect thereof. Optionally, the device also includes a memory, and the memory is connected to the processor through a circuit. Further optionally, the device also includes a communication interface, and the processor is connected to the communication interface. The communication interface is used to receive information to be processed, and the processor obtains the information from the communication interface, processes the information, and outputs the processing results through the communication interface. The communication interface can be an input and output interface.

[0063] In a possible implementation, the processor and memory may be physically independent units, or the memory may be integrated with the processor.

[0064] In a fourteenth aspect, the present application provides a communication system, which includes a first access network device and a terminal device; the first access network device is used to execute the method described in the first aspect, the sixth aspect, or any possible implementation of any one of the aspects above, and the terminal device is used to execute the method described in the second aspect, the third aspect, the seventh aspect, or any possible implementation of any one of the aspects above.

[0065] The technical effects achieved in the above-mentioned aspects can be referred to each other or to the beneficial effects in the method embodiments shown below, and will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1A This is a schematic diagram of a switching scenario provided by an embodiment of the present application;

[0067] Figure 1B It is a flowchart of a switching method provided in an embodiment of the present application;

[0068] Figure 2 It is a flowchart of a switching method provided in an embodiment of the present application;

[0069] Figure 3 is a schematic diagram of a network architecture of a communication system provided in an embodiment of the present application;

[0070] Figure 4 It is a flowchart of a key management method provided in an embodiment of the present application;

[0071] Figure 5 It is a flowchart of another key management method provided in an embodiment of the present application;

[0072] Figure 6 It is a flowchart of another key management method provided in an embodiment of the present application;

[0073] Figure 7 It is a flowchart of another key management method provided in an embodiment of the present application;

[0074] Figure 8 It is a flowchart of another key management method provided in an embodiment of the present application;

[0075] Fig. 9 is a schematic diagram of a structure of a communication device provided in an embodiment of the present application;

[0076] Fig.10 is another structural schematic diagram of a communication device provided in an embodiment of the present application;

[0077] Fig.11 This is another structural diagram of the communication device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0078] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0079] In the description of the present application, the words "first", "second", etc. are only used to distinguish different objects, and do not limit the quantity and execution order, and the words "first", "second", etc. do not necessarily limit them to be different. For example, the first information and the second information, the first PDC type and the second PDC type, etc. are only used to distinguish different information, and do not limit their order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or units inherent to these processes, methods, products or devices.

[0080] In the description of this application, unless otherwise specified, " / " means "or", for example, A / B can mean A or B. "And / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. 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, "at least one (item)", "the following one (item) or more (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, at least one item (item) of a, b, or c can mean: a, b, c; a and b; a and c; b and c; or a, b and c. Among them, a, b, c can be single or multiple.

[0081] In the description of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described in this application as "exemplary", "for example" or "for example" should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary", "for example" or "for example" is intended to present related concepts in a concrete way.

[0082] It can be understood that in the description of this application, "when", "if" and "if" all mean that the device will perform corresponding processing under certain objective circumstances, and do not limit the time, nor do they require that the device must have a judgment action when it is implemented, nor do they mean that there are other limitations. Among them, the device performs corresponding processing under certain objective circumstances, including: the corresponding processing can be performed when the objective situation is met; or the corresponding processing can be performed only when the objective situation and other situations are met.

[0083] The term “simultaneously” in the present application may be understood as at the same time point, within a period of time, or within the same cycle, and may be understood in conjunction with the context.

[0084] Elements used in the singular herein are intended to mean "one or more" rather than "one and only one" unless specifically stated otherwise.

[0085] Additionally, the terms "system" and "network" are often used interchangeably herein.

[0086] It can be understood that in each embodiment of the present application, "A corresponds to B", "A corresponds to B", "B corresponding to A" or similar expressions indicate that B is associated with A, and B can be determined according to A. Determining B according to A does not mean determining B only according to A, and B can also be determined according to A and / or other information.

[0087] At present, handover technologies such as layer 3 handover (L3 Handover) and conditional handover (Conditional Handover) are only for the handover process of a single handover cell, that is, each time a cell is switched, a handover request and a handover request response process between a source base station and a target base station need to be performed once. For the convenience of description, the present application embodiment refers to the above handover technology as a one-time handover technology.

[0088] The following exemplifies the one-time switching technology by taking L3 Handover as an example.

[0089] Figure 1A It is a schematic diagram of a switching scenario exemplarily provided in an embodiment of the present application.

[0090] like Figure 1A As shown, the initial serving cell of the user equipment (UE) is Cell1 (the serving access network device is gNB1), and the UE uses the key Key1 to encrypt communication with the serving cell / serving access network device; as the UE moves, the UE switches to Cell2 / gNB2, and the UE uses Key2 to communicate with Cell2 / gNB2. Since L3 Handover is a one-time process, this handover process is considered completed. The UE then continues to move to Cell1 / gNB1, and the above process needs to be repeated again. The UE uses Key3 to encrypt communication with Cell1 / gNB1. The specific processes of the above two handovers can be found below. Figure 1B The above keys Key1, Key2 and Key3 can be KgNB in ​​new radio NR (newradio) communication. UE and gNB use KgNB to further derive the key Kup used for user plane data and the key Krrc used for radio resource control (RRC) layer signaling. UE and gNB use Kup to encrypt user plane data, perform integrity protection and other security processing, and UE and gNB use Krrc to encrypt RRC signaling and perform integrity protection and other security processing.

[0091] Figure 1B : is a flowchart of a switching method provided by the present application. The method may include some or all of the following steps:

[0092] S101: UE communicates with gNB1 based on Key1.

[0093] It should be understood that the serving cell of the UE in this handover is Cell1, which is managed by gNB1, so gNB1 is also called serving gNB. The UE can use Key1 to perform encryption and integrity protection on the communication data and signaling. Optionally, when encrypting the data and signaling, the UE may use Key1 as a parameter to further generate a user plane processing key Kup and an RRC layer processing key Krrc. For user plane data, Kup is used for encryption, integrity protection and other security processing, and for RRC signaling, Krrc is used for encryption, integrity protection and other security processing. For gNB1, similarly, Key1 can also be used as a parameter to further generate a user plane processing key Kup and a radio resource control layer processing key Krrc. For user plane data, Kup is used for encryption, integrity protection and other security processing, and Krrc is used for encryption, integrity protection and other security processing.

[0094] S102: gNB1 derives the key Key2 of the target cell / target gNB.

[0095] In this switching, gNB1 can be called the source gNB, Cell1 can be called the source cell; gNB2 can be called the target gNB, Cell2 can be called the target cell.

[0096] S103: gNB1 sends a switching request message to gNB2, which includes Key2 and NCC2.

[0097] Among them, NCC2 is a next hop chaining count (NCC) provided by the access and mobility management function (AMF) to gNB1, which is used by the UE to derive Key2; Key2 is the key used by the UE when communicating with Cell2 / gNB2.

[0098] S104: gNB2 sends a switching request response message to gNB1, which includes the configuration information of the target cell (i.e. Cell2) and NCC2.

[0099] S105: gNB1 sends a switching command to the UE, which includes the configuration information of the target cell (i.e., Cell2) and NCC2.

[0100] S106: The UE performs switching according to the switching command and uses NCC2 to perform key derivation to obtain Key2.

[0101] It should be understood that when the UE performs encryption processing on data and signaling, Key2 can be used as a parameter to further generate a user plane processing key Kup and an RRC layer processing key Krrc.

[0102] S107: UE accesses Cell2 / gNB2.

[0103] S108: gNB2 sends a path switching request message to AMF to request the core network to switch the downlink path between the user plane function network element and the base station for the UE from gNB1 to gNB2.

[0104] S109: AMF sends a path switch request response message to gNB2 to respond to whether the path switch is successful or not.

[0105] Furthermore, the response message includes NH and NCC3. NH is the next hop parameter, which is used by gNB2 to deduce Key3 at the next handover; NCC3 is used by UE to deduce Key3 at the next handover.

[0106] Through S101 to S109, the UE completes a handover process from Cell1 / gNB1 to Cell2 / gNB2 (referred to as the first handover). For subsequent handovers, the UE, source cell / source gNB, and target cell / target gNB need to perform the same process as the first handover described above. The following example uses the next handover as an example to illustrate. For example, if the next handover is from Cell2 / gNB2 to Cell1 / gNB1, then Cell2 / gNB2 is called the source cell / source gNB, and Cell1 / gNB1 is called the target cell / target gNB. The specific process of the next handover can be found in S110 to S117 below.

[0107] S110: gNB2 derives Key3.

[0108] The deduction process of step S110 is similar to that of step S102. Specifically, gNB2 uses the cell identity information of NH and Cell1 obtained in S109 to deduce Key3.

[0109] S111: gNB1 sends a switching request message to gNB2, which includes Key3 and NCC3.

[0110] The specific implementation of step S111 is similar to step S103.

[0111] S112: gNB2 sends a switching request response message to gNB1, which includes the configuration information of the target cell (i.e. Cell1) and NCC3.

[0112] The specific implementation of step S112 is similar to step S104.

[0113] S113: gNB1 sends a switching command to the UE, which includes the configuration information of the target cell Cell1 and NCC3.

[0114] The specific implementation of step S113 is similar to that of step S105.

[0115] S114: The UE performs switching according to the switching command and uses NCC3 to perform key derivation to obtain Key3.

[0116] The specific implementation of step S114 is similar to step S106.

[0117] S115: UE accesses Cell1 / gNB1.

[0118] The specific implementation of step S115 is similar to step S107.

[0119] Steps S116 and S117 are similar to steps S108 and S109. Figure 1B Not shown.

[0120] Through S110~S117: the UE completes a switching process from Cell2 / gNB2 to Cell1 / gNB1.

[0121] It can be seen that the above one-time switching technology requires a new switching preparation process for the next switching (for example Figure 1B The handover request and handover request response of step S103 and step S104 in step S106 are performed, and the keys used by the UE and the target cell are aligned through the handover preparation process and the handover command. The above method does not support subsequent handover of the terminal device.

[0122] The following is an example of Figure 2 The handover method supporting subsequent handover is introduced by taking as an example. Supporting subsequent handover means pre-configuring multiple candidate cells for the terminal device to support multiple handovers of the terminal device between the multiple candidate cells.

[0123] See also Figure 2 , Figure 2 : is a flowchart of a switching method provided by the present application. The method may include some or all of the following steps:

[0124] S201: UE communicates with gNB1 based on Key1.

[0125] Exemplarily, the source cell is Cell1 and the source gNB is gNB1.

[0126] S202: gNB1 sends a handover request message to the candidate gNB. The handover request message is used to request the L1 / L2 triggered mobility management (LTM) pre-configuration information of the candidate cell. The handover request message includes the Key corresponding to the candidate gNB (such as Key2 corresponding to gNB2 or Key3 corresponding to gNB3) and the NCC used by the UE for the next handover (i.e., NCC2).

[0127] For example, Figure 2 It is shown that the candidate gNBs include gNB2 and gNB3. gNB1 can send a handover request message to gNB2, which includes Key2 and NCC2; gNB1 can send a handover request message to gNB3, which includes Key3 and NCC2.

[0128] It should be understood that gNB1 only obtains a pair of {NH, NCC} from the core network, so the NCC that gNB1 gives to gNB2 and gNB3 is the same, both are NCC2. NCC2 is the key information used by the UE for the next switching, and NCC2 corresponds to NH2.

[0129] S203: The candidate gNB sends a handover request response message to gNB1. The handover request response message is used to provide pre-configuration information of the candidate cell. The handover request response message includes NCC2 used by the UE for the next handover.

[0130] S204: gNB1 sends pre-configuration information of candidate cells to the UE, where the pre-configuration information includes NCC2.

[0131] S205: gNB1 sends a switching command to the UE, where the switching command is used to indicate switching to Cell2, which is managed by gNB2.

[0132] This switching is explained using the example where the target cell is Cell2 and the target base station is gNB2.

[0133] The switching command includes identification information corresponding to Cell2.

[0134] S206: gNB1 sends a notification message to gNB2, where the notification message is used to indicate UE access.

[0135] S207: The UE derives the key Key2 of Cell2 based on NCC2.

[0136] S208: UE accesses Cell2.

[0137] S209: gNB2 sends a path switching request message to AMF to request the core network to switch the downlink path between the user plane function network element and the base station for the UE from gNB1 to gNB2.

[0138] S210: AMF sends a path switch request response message to gNB2 to respond to whether the path switch is successful or not.

[0139] Through S201~S210, the UE completes a switching process from Cell1 / gNB1 to Cell2 / gNB2 (referred to as the first switching). For subsequent switching, the UE, source cell / source gNB and target cell / target gNB do not need to perform the same process as the first switching mentioned above. The following example uses the next switching as an example to illustrate. For example, the next switching (referred to as the second switching) is from Cell2 / gNB2 to Cell3 / gNB3, then Cell2 / gNB2 is called the source cell / source gNB, and Cell3 / gNB3 is called the target cell / target gNB. For the specific process, please refer to S211 to S214 below.

[0140] S211: gNB2 sends a switching command to the UE, where the switching command is used to indicate switching to Cell3, which is managed by gNB3.

[0141] S212: gNB2 sends a notification message to the target gNB (i.e. gNB3), where the notification message is used to indicate UE access.

[0142] S213: The UE derives the key of the target cell based on NCC2 and obtains Key4.

[0143] S214: The UE accesses the target cell (ie, Cell3).

[0144] In the above step S202, the Key3 obtained by gNB3 is derived by gNB1 based on Key1, while in the above step S213, the Key4 is derived by UE based on Key1 and NCC2. Key3 and Key4 are different (that is, the keys of the second handover are not aligned). It can be seen that Figure 2 The method shown will cause key misalignment when switching to other candidate gNBs. In addition, if the UE successfully switches to other cells, when the UE switches back to Cell1, gNB1 still uses Key1, which will cause key reuse.

[0145] It can be seen that the above-mentioned switching method supporting subsequent switching does not have an effective key management mechanism and it is difficult to ensure communication security.

[0146] In view of this, an embodiment of the present application provides a key management method and related devices. In this method, the UE re-acquires key information each time a switch is made, ensuring that the key for each switch is different. This can ensure key alignment between the terminal device and the target access network device and that the key is not reused in subsequent switches, thereby providing an effective key management mechanism that can ensure communication security.

[0147] Based on the above, in order to better understand the key management method and related devices proposed in this application, the network architecture applied in the embodiment of the present application is described below.

[0148] See also Figure 3 , Figure 3 It is a schematic diagram of a network architecture of a communication system provided in an embodiment of the present application.

[0149] like Figure 3 As shown, the network architecture may include a first access network device 101, a second access network device 102 and a terminal device 103. It should be understood that Figure 3 Only two access network devices are shown as examples. The network architecture may also include other access network devices. The embodiment of the present application does not limit the number of access network devices.

[0150] Among them, the terminal device 103 can switch in the cell of the first access network device 101 or the second access network device 102 based on the key management method provided in the embodiment of the present application.

[0151] The terminal device 103 may be connected to the first access network device 101 or the second access network device 102 in a wireless manner, and may be accessed to the core network through the first access network device 101 or the second access network device 102. The terminal device 103 may be fixed or movable.

[0152] The first access network device 101 and the second access network device 102 may be entities for transmitting or receiving signals, or may be devices for communicating with the terminal device 103. The network device may be a base transceiver station (BTS) in a global system for mobile communications (GSM) system or a code division multiple access (CDMA), or a base station (NodeB, NB) in a wideband code division multiple access (WCDMA) system, or an evolved NodeB (eNB or eNodeB) in an LTE system, or a wireless controller in a cloud radio access network (CRAN) scenario, or the network device may be a relay station, an access point, an on-board device, a wearable device, a network device in a 5G network, or a network device in a future evolved PLMN network, etc., which is not limited in the embodiments of the present application. The network device may be a device in a wireless network, such as a radio access network (RAN) node that connects the terminal device 103 to a wireless network. At present, some examples of RAN nodes are: base station, next generation base station gNB, transmission reception point (TRP), evolved Node B (eNB), home base station, baseband unit (BBU), or access point (AP) in WiFi system. In a network structure, the network equipment may include a centralized unit (CU) node, or a distributed unit (DU) node, or a RAN device including a CU node and a DU node. Among them, in the O-RAN system, CU can also be called O-CU, and DU can also be called O-DU.

[0153] The terminal device 103 is an entity on the user side for receiving or transmitting signals, and is mainly used to realize the function of wireless communication with the first access network device 101.

[0154] For example, terminal device 103 can be an access terminal, a subscriber unit, a subscriber station, a mobile station, a mobile station, a remote station, a remote terminal, a mobile device, a user terminal, a terminal, a wireless communication device, a user agent, or a user device. The terminal device 103 may also be a mobile phone, a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, a tablet computer (Pad), a computer with wireless transceiver function, a virtual reality (VR) terminal device, an augmented reality (AR) terminal device, a wireless terminal in industrial control, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device with wireless communication function, a computing device or other processing device connected to a wireless modem, an in-vehicle device, a wireless terminal in self-driving, a wireless terminal in remote medical, a wireless terminal in a smart grid, a wireless terminal in transportation safety, a wireless terminal in a smart city, a wireless terminal in a smart home, a wearable device (such as a smart watch, a smart bracelet, a pedometer, etc.), a terminal device in a 5G network, or a public land mobile communication network (public land mobile communication network) to be evolved in the future. The terminal device 103 may be a terminal device in a local mobile network (PLMN), etc., which is not limited in the embodiments of the present application. The terminal device 103 may be deployed on land, including indoors or outdoors, handheld, wearable or vehicle-mounted, or may be deployed on water (such as ships, etc.), or may be deployed in the air (for example, on airplanes, balloons, and satellites, etc.). In the embodiments of the present application, the terminal device 103 may be a legacy UE, or may be an RB-level partial frequency hopping (RPFS) UE that supports SRS coverage and capacity enhancement, or may be other UEs. The present application does not limit the type of the terminal device 103. Among them, legacy UE refers to user equipment that supports existing mechanisms, for example, user equipment that supports release-15 and release-16.

[0155] In the embodiment of the present application, any one of the first access network device 101, the second access network device 102 and the terminal device 103 may include a hardware layer, an operating system layer running on the hardware layer, and an application layer running on the operating system layer. The hardware layer includes hardware such as a central processing unit (CPU), a memory management unit (MMU) and a memory (also called main memory). The operating system may be any one or more computer operating systems that implement business processing through processes, such as a Linux operating system, a Unix operating system, an Android operating system, an iOS operating system or a Windows operating system. The application layer includes applications such as a browser, an address book, a word processing software, and an instant messaging software. Furthermore, the embodiments of the present application do not particularly limit the specific structure of the execution subject of the method provided in the embodiments of the present application. As long as it is possible to communicate according to the method provided in the embodiments of the present application by running a program that records the code of the method provided in the embodiments of the present application, for example, the execution subject of the method provided in the embodiments of the present application can be any one of the first access network device 101, the second access network device 102 and the terminal device 103, or it can be a functional module in any one of the first access network device 101, the second access network device 102 and the terminal device 103 that can call and execute the program.

[0156] It should be noted that Figure 3 The number and type of terminal devices 103 included in the network architecture shown are only examples, and the embodiments of the present application are not limited thereto. For example, more or fewer terminal devices 103 communicating with access network devices may also be included, which are not described one by one in the drawings for the sake of simplicity.

[0157] In addition, in Figure 3 In the network architecture shown, although any one of the first access network device 101, the second access network device 102 and the terminal device 103 is shown, the application scenario may not be limited to including any one of the first access network device 101, the second access network device 102 and the terminal device 103, for example, it may also include a core network device or a device for carrying virtualized network functions, wherein the core network device communicates with the terminal device 103 through the first access network device 101.

[0158] The technical solutions of the embodiments of the present application can be applied to various communication systems, such as: global system of mobile communication (GSM) system, code division multiple access (CDMA) system, wideband code division multiple access (WCDMA) system, general packet radio service (GPRS), long term evolution (LTE) system, LTE frequency division duplex (FDD) system, LTE time division duplex (TDD), universal mobile telecommunication system (UMTS), worldwide interoperability for microwave access (WiMAX) communication system, fifth generation (5G) system or new radio (NR) and future communication systems, etc., without limitation here.

[0159] In combination with the above network architecture, a key management method provided in an embodiment of the present application is described below.

[0160] See also Figure 4 , Figure 4 It is a flowchart of a key management method provided by an embodiment of the present application. The function performed by the terminal device in this embodiment can also be performed by a module (e.g., a chip) in the terminal device, and the function performed by the access network device in this application can also be performed by a module (e.g., a chip) in the access network device, such as the function performed by the first access network device in this application can also be performed by a module (e.g., a chip) in the first access network device.

[0161] like Figure 4 As shown, the key management method may include the following steps:

[0162] Step S401: The first access network device sends pre-configuration information and first key information of multiple candidate cells to the terminal device.

[0163] Correspondingly, the terminal device receives pre-configuration information and first key information of multiple candidate cells from the first access network device.

[0164] Optionally, the pre-configuration information of the multiple candidate cells is used for the terminal device to perform one or more handovers among the multiple candidate cells. Exemplarily, the pre-configuration information of the candidate cell may include physical channel configuration information, reference signal configuration information, etc. of the candidate cell.

[0165] Optionally, the preconfiguration information does not include the first key information. Exemplarily, the first key information may be a next hop chaining count (NCC).

[0166] Optionally, the pre-configuration information of the multiple candidate cells may include pre-configuration information of the cells managed by the first access network device.

[0167] Optionally, the first key information is carried by one of layer 1 signaling, layer 2 signaling and layer 3 signaling. Exemplarily, L3 signaling may be an RRC message, L2 signaling may be a media access control control element (Media Access ControlControl Element, MAC CE), and L1 signaling may be downlink control information (Downlink ControlInformation, DCI). Alternatively, the first key information is carried by a handover command, and the handover command is used to indicate handover to a target cell. For example, in LTM, the first access network device may send a handover command to the terminal device after determining the target cell to which the terminal device is to switch, and the handover command is used to indicate handover to the target cell, and the handover command may include the above-mentioned first key information.

[0168] It should be understood that the cell corresponding to the pre-configuration information obtained by the first access network device can be called a candidate cell. If the candidate cell is determined to be the cell to which the terminal device is about to switch, the candidate cell can be called a target cell.

[0169] Optionally, the multiple candidate cells belong to one or more access network devices, or in other words, the multiple candidate cells are managed by one or more access network devices.

[0170] In one implementation, before executing step S401, the first access network device may obtain pre-configuration information of the candidate cells from one or more candidate access network devices to obtain the pre-configuration information of the above-mentioned multiple candidate cells. Exemplarily, the first access network device obtains the pre-configuration information of the candidate cells, which can refer to steps S502 and S503 in the following embodiments.

[0171] For example, if the candidate access network device includes a second access network device, the first access network device may send a handover request message to the second access network device, the handover request message being used to request pre-configuration information of a cell managed by the second access network device, the cell managed by the second access network device including the target cell; and receive a response message sent by the second access network device, the response message including the pre-configuration information of the target cell. The handover request message does not include the first key information and the first key, and the response message does not include the first key information.

[0172] It should be understood that the embodiments of the present application can be applicable to switching technologies triggered by terminal devices (such as CHO) and switching technologies triggered by access network devices (such as LTM). Optionally, the specific content of the pre-configuration information can be related to the switching technology adopted. For example, the pre-configuration information can be L1 / L2 triggered mobility management (L1 / L2 Triggered Mobility, LTM) pre-configuration information, or conditional handover (Conditional Handover, CHO) pre-configuration information. The embodiments of the present application do not limit the switching technology adopted and the specific content of the pre-configuration information.

[0173] Step S402: the first access network device sends a first key to a second access network device to which a target cell to which the terminal device switches belongs. The first key is a key for communication between the terminal device and the second access network device. The multiple candidate cells include the target cell.

[0174] Correspondingly, the second access network device receives the first key from the first access network device. Exemplarily, in the NR communication system, the first key may be KgNB, which may be used to further derive Kup and Krrc.

[0175] In one implementation, the first access network device may send the first key to the second access network device after determining the target cell. For example, the first access network device may send a notification message to the second access network device, the notification message being used to indicate that the terminal device will access, and the notification message may carry the first key.

[0176] In another implementation, the first access network device may receive a first message sent by the terminal device, the first message being used to indicate switching to a target cell, the target cell belonging to the second access network device. Furthermore, the first access network device may send a first key to the second access network device. For example, the first access network device may send a notification message to the second access network device, the notification message carrying the first key.

[0177] Optionally, the notification message does not carry the first key information.

[0178] In another implementation, the first access network device may receive a request message sent by the second access network device, where the request message is used to request a key for communication between the terminal device and the second access network device; and in response to the request message, send a first key to the second access network device.

[0179] Optionally, the request message also includes an integrity message authentication code; the first access network device may send the first key to the second access network device after verifying the request message based on the integrity message authentication code.

[0180] For example, when determining that the handover fails or the radio link fails, the terminal device can determine the target cell from multiple candidate cells, and the target cell belongs to the second access network device; then, the terminal device can send a second message to the second access network device, and the second message is used to request access to the target cell; the second access network device can send the above second message to the first access network device to obtain the first key. Then, after the terminal device accesses the target cell, it can communicate with the target cell based on the first key. Optionally, the second message also includes an integrity message authentication code and / or an identifier of the terminal device.

[0181] Step S403: The terminal device deduce, based on the first key information, to obtain a first key corresponding to the target cell.

[0182] In some embodiments, the terminal device may deduce the first key based on the first key information and the cell information of the target cell (such as downlink frequency information, etc.) and then access the target cell and communicate with the target cell based on the first key.

[0183] In some other embodiments of the present application, when the terminal device fails to switch the above-mentioned target cell or the wireless link fails, the second cell can be determined from multiple candidate cells; assuming that the second cell belongs to a third access network device, the terminal device can send a third message to the third access network device, and the third message is used to request access to the second cell; the third access network device can send the above-mentioned third message to the first access network device to obtain the second key. The terminal device can deduce the second key based on the first key information and the cell information of the second cell; further, after the terminal device accesses the second cell, it can communicate with the second cell based on the second key. Optionally, the third message also includes an integrity message authentication code and / or an identifier of the terminal device.

[0184] It should be understood that the embodiments of the present application do not limit the method for key derivation of access network devices and terminal devices. For examples, please refer to the relevant description below.

[0185] above Figure 4 The method embodiment shown includes many possible implementation schemes. Figures 5 to 8Some of the implementation schemes are illustrated with examples. It should be noted that: Figures 5 to 8 For related concepts, operations or logical relationships that are not explained, please refer to Figure 4 The corresponding description in the illustrated embodiment.

[0186] Figure 4 The method embodiment shown is applicable to the switching technology triggered by the access network device, that is, the access network device sends a switching command to the terminal device to trigger the access network device to switch. For example, in the LTM switching technology, the terminal device can first obtain the LTM pre-configuration information of multiple candidate cells, and then the terminal device measures and reports the reference signal of the candidate cell, and the access network device sends a switching command to instruct the terminal device to switch to a certain candidate cell. For the specific process, please refer to Figure 5 The embodiment shown.

[0187] Figure 5 It is a flowchart of another key management method provided in an embodiment of the present application.

[0188] Among them, taking the terminal device as UE, the source access network device of the terminal device (that is, the above-mentioned first access network device) as gNB1, the target access network device for the terminal device switching (that is, the above-mentioned second access network device) as gNB2, and the core network device as AMF as an example, the key management method provided in the embodiment of the present application is introduced in detail.

[0189] like Figure 5 As shown, the key management method may include some or all of the following steps:

[0190] S501: UE communicates with gNB1 based on Key1.

[0191] Exemplarily, the serving cell (or source cell) of the UE is Cell1, which is managed by gNB1, so gNB1 can also be called serving gNB or source gNB. The UE can use Key1 to encrypt and perform integrity protection on the data and signaling of the communication. It should be understood that when the UE encrypts the data and signaling, it can use Key1 as a parameter to further generate the user plane processing key Kup and the RRC layer processing key Krrc.

[0192] S502: gNB1 sends a switching request message to candidate gNBs (such as gNB2 and gNB3), which is used to request LTM pre-configuration information.

[0193] Figure 5 In this example, gNB2 and gNB3 are used as candidate gNBs, and gNB1 is used as the source gNB. Figure 5As shown, gNB1 can send a switching request message to gNB2 and gNB3 respectively, which is used to request the provision of LTM pre-configuration information of the candidate cell.

[0194] It should be understood that Figure 2 What is different from the method shown is that in the embodiment of the present application, the message does not need to carry the key that should be used when the candidate cell / target cell communicates with the UE, nor does it need to carry the corresponding NCC.

[0195] In an embodiment of the present application, when a candidate cell is determined to be a cell to which a terminal device is to switch, the candidate cell may be referred to as a target cell, and the candidate gNB that manages the target cell may be referred to as a target gNB.

[0196] S503: The candidate gNB sends a handover request response message to gNB1, carrying the LTM pre-configuration information.

[0197] like Figure 5 As shown, gNB2 and gNB3 can respectively send a switching request response message to gNB1, which message can carry the LTM pre-configuration information of the cells managed by the gNB (i.e., multiple candidate cells).

[0198] Exemplarily, the message may carry LTM pre-configuration information of cells managed by gNB2 and gNB3. That is, the multiple candidate cells include cells managed by gNB2 and gNB3.

[0199] Optionally, the message may also carry LTM pre-configuration information of cells managed by gNB1 (i.e., multiple candidate cells). That is, the multiple candidate cells include cells managed by gNB1.

[0200] It should be understood that the embodiments of the present application are Figure 2 The difference is that, in the handover request response message in step S503 of the embodiment of the present application, there is no need to carry the NCC.

[0201] S504: gNB1 sends LTM pre-configuration information to UE.

[0202] Exemplarily, gNB1 may send LTM pre-configuration information of cells managed by gNB2 and gNB3 to the UE.

[0203] It should be understood that the embodiments of the present application are Figure 2 The difference is that the pre-configuration information in step S504 of the embodiment of the present application does not include the NCC corresponding to the candidate cell.

[0204] S505: gNB1 sends NCC2 to UE.

[0205] Among them, NCC2 is the key information used by the UE when switching cells this time, and is used by the UE to deduce the key for the UE's current switching.

[0206] It should be understood that when the UE receives NCC2, if the switching execution process has not yet been started, NCC2 is used by the UE to derive the key for the UE's next switching; when the UE receives NCC2, it has been determined to start the switching execution process, then NCC2 is used by the UE to derive the key for the UE's current switching.

[0207] Optionally, gNB1 may send NCC2 to the UE before determining the target cell for this switching.

[0208] In one implementation, gNB1 may send NCC2 to the UE via L3 / L2 / L1 signaling, for the UE to derive the key of the target cell.

[0209] For example, L3 signaling may be an RRC message, L2 signaling may be a MAC CE, and L1 signaling may be a DCI. Among them, NCC2 may be received by gNB1 from AMF. Figure 5 Not shown.

[0210] Optionally, after receiving NCC2, the UE may store the value of NCC2, and not use the NCC2 immediately for key derivation, nor replace the previously stored NCC. For example, before step S505, the UE stores NCC1, and after step S505, the UE may store both NCC1 and NCC2.

[0211] In a possible implementation, the NCC2 sent in step S505 may be sent via the switching command in step S507. In this case, step S505 and step S507 may be considered to be combined into one step.

[0212] S506: gNB1 derives the key Key2 corresponding to the first cell, and the first cell belongs to gNB2.

[0213] In some embodiments, gNB1 can deduce Key2 based on the physical cell identifier (PCI) and downlink frequency of the target cell, in combination with NH2 corresponding to NCC2 or in combination with Key1. Among them, NCC2 and NH2 are key information obtained by gNB1 from the core network. The embodiment of the present application does not limit the method for gNB and UE to deduce keys.

[0214] Exemplarily, gNB1 can determine the deduction method based on NCC2 and NH2, where the deduction method includes vertical deduction and horizontal deduction; further, when the deduction method is determined to be vertical deduction, gNB1 can deduce Key2 based on NH2 and parameters such as PCI and downlink frequency of the first cell; when the deduction method is determined to be horizontal deduction, gNB1 can deduce Key2 based on Key1 and parameters such as PCI and downlink frequency of the first cell.

[0215] Among them, when gNB1 has an unused pair of parameters {NH, NCC} (i.e., a new NCC and a new NH are received), gNB1 can use vertical deduction; when the source gNB does not have an unused pair of parameters {NH, NCC} (i.e., both the stored NH and NCC have been used), the source gNB uses horizontal deduction. Among them, the pair of parameters {NH, NCC} can be provided to gNB1 by AMF. It should be understood that the stored NH and NCC have been used, which means that the NH and NCC were used during intra-site switching.

[0216] S507: gNB1 sends a switching command to the UE, where the switching command is used to indicate switching to the first cell.

[0217] The first cell is the target cell of this handover. The handover command may also be called a LTM command (command, CMD), namely, LTMCMD.

[0218] It should be noted that Figure 5 Taking the LTM switching command as an example, the switching command may be an L1 / L2 message; in other switching technologies, the switching command may be an L1 / L2 / L3 message.

[0219] The handover command may include identification information corresponding to the target cell. For example, the identification information may be a pre-configured identification, indicating which set of pre-configurations received in step S504 is used by the UE.

[0220] S508: gNB1 sends a notification message to gNB2, carrying Key2.

[0221] The notification message includes key information (eg, Key2) that should be used when the target cell (ie, the first cell) communicates with the UE, and does not need to include the NCC.

[0222] In addition, the notification message may also include one or more of the following: UE identity information, target cell identity information, and target gNB identity information.

[0223] It should be noted that the embodiment of the present application does not limit the order in which step S507 and step S508 occur, nor does it limit the order in which step S507 and step S506 occur.

[0224] S509: The UE derives Key2 based on NCC2.

[0225] In some embodiments, the UE may determine the PCI and downlink frequency information of the target cell according to the target cell identity indicated in step S507; and then, in combination with the NCC2 received in step S505, derive the key (eg, Key2) of the target cell.

[0226] In one implementation, the UE may compare the newly received NCC (ie, NCC2) with the previously received and stored NCC value, and if they are the same, perform horizontal deduction; if they are different, perform vertical deduction.

[0227] S510: UE accesses the first cell.

[0228] In some embodiments, the UE may apply the target cell pre-configuration information received in step S504 to access the target cell.

[0229] S511: gNB2 sends a path switching request message to the AMF to request the core network to switch the downlink path between the user plane function network element and the base station for the UE from gNB1 to gNB2.

[0230] S512: AMF sends a path switch request response message (carrying NH3, NCC3) to gNB2.

[0231] Optionally, the path switch request response message may also carry indication information for indicating whether the path switch is successful.

[0232] The above steps S501 to S512 are the specific process of the first handover (UE switching from gNB1 to gNB2), and some steps of the second handover (UE switching from gNB2 to gNB3) (such as steps S513 to S518) are also exemplarily shown below. It should be understood that the cell switching after the first handover can be called a subsequent handover, and the LTM pre-configuration information of the multiple candidate cells received by the UE can be used in the subsequent handover of the UE after the first handover.

[0233] S513: gNB2 sends NCC3 to UE.

[0234] Among them, NCC3 is the key information during the second handover, which is used by the UE to deduce the key of the target cell of the second handover.

[0235] S514: gNB2 deduce the key Key3 corresponding to the second cell based on NH3, and the second cell belongs to gNB3.

[0236] S515: gNB2 sends a switching command to the UE to instruct switching to the second cell.

[0237] S516: gNB2 sends a notification message to gNB3, carrying Key3.

[0238] S517: UE derives Key3 based on NCC3.

[0239] It should be understood that the above-mentioned keys Key1, Key2 and Key3 can be KgNB in ​​NR communication. UE and gNB use KgNB to further derive the key Kup used for user plane data and the key Krrc used for RRC layer signaling. UE and gNB use Kup to encrypt user plane data, perform integrity protection and other security processing, and UE and gNB use Krrc to encrypt RRC signaling and perform integrity protection and other security processing.

[0240] S518: The UE accesses the second cell.

[0241] Figure 5 In the method shown, during the second handover, gNB2 sends NCC3 used in this handover to UE, and UE can deduce Key3 based on NCC3; and sends Key3 derived from NH3 corresponding to NCC3 to gNB3, which can ensure the key alignment of UE and gNB3.

[0242] After step S518, the second handover may also include that gNB3 may obtain NH4 and NCC4 from AMF and send NCC4 to UE. For details, refer to steps S511 to S513. Figure 5 Not shown.

[0243] Assume that the third handover is from the second cell of gNB3 to the first cell of gNB2. Since the key information used for the first handover to the first cell is NCC2 and the key information used for the third handover to the first cell is NCC4, the UE uses NCC2 to derive the key when it switches to the first cell for the first time and uses NCC4 to derive the key when it switches to the first cell for the third time. The obtained keys are different. Therefore, although the first handover and the third handover are switched to the same cell, key reuse can be avoided, thereby ensuring communication security.

[0244] In some embodiments of the present application, before step S505, the UE stores NCC1, which is the NCC corresponding to the key of the service cell of the current UE; after step S505, the UE stores two values, NCC1 and NCC2, and NCC2 is the NCC corresponding to the key of the target cell of LTM switching.

[0245] After step S505, if the source gNB triggers an L3 handover (e.g. Figure 1A If NCC3 is indicated in the switching command or key reconfiguration command of this L3 switching, the UE executes this L3 switching or key update, and updates the previously stored value of NCC1 to the value of NCC3 (if NCC1=NCC3, the update process can also be understood as maintaining the value of NCC1), and updates the previously stored value of NCC2 to the value of NCC3 (if NCC2=NCC3, the update process can also be understood as maintaining the value of NCC1).

[0246] The above technology can ensure that when LTM switching and L3 switching (or key change in the same cell) coexist, the subsequent key deduction results of the UE and the base station are consistent, avoiding the situation where the UE and the base station deduce different keys and avoid communication failure.

[0247] Figure 4 The method embodiment shown can also be applied to switching technologies triggered by terminal devices (such as CHO switching technology). Exemplarily, in the CHO switching technology, the access network device can provide the terminal device with the configuration of multiple candidate cells and corresponding trigger conditions. For example, the trigger condition can be that the reference signal of a candidate cell has a reference signal received power (RSRP) higher than the reference signal of the serving cell by a preset decibel (dB); then, when the terminal device determines that the trigger condition corresponding to a candidate cell is met, it selects the cell as the target cell and accesses the target cell. In switching technologies triggered by terminal devices such as CHO, there is no need for the access network device to issue a switching command to indicate the target cell to the terminal device. For the specific process, please refer to Figure 6 The embodiment shown.

[0248] Figure 6 This is a flow chart of another key management method provided in an embodiment of the present application.

[0249] Among them, taking the terminal device as UE, the source access network device of the terminal device (that is, the above-mentioned first access network device) as gNB1, the target access network device for the terminal device switching (that is, the above-mentioned second access network device) as gNB2, and the core network device as AMF as an example, the key management method provided in the embodiment of the present application is introduced in detail.

[0250] like Figure 6 As shown, the key management method may include some or all of the following steps:

[0251] S601: UE communicates with gNB1 based on Key1.

[0252] S602: gNB1 sends a switching request message to candidate gNBs (such as gNB2 and gNB3), which is used to request CHO pre-configuration information.

[0253] S603: The candidate gNB sends a handover request response message to gNB1, carrying CHO pre-configuration information.

[0254] Exemplarily, the message may carry LTM pre-configuration information of cells managed by gNB2 and gNB3. That is, the multiple candidate cells include cells managed by gNB2 and gNB3.

[0255] Optionally, the message may also carry LTM pre-configuration information of cells managed by gNB1 (i.e., multiple candidate cells). That is, the multiple candidate cells include cells managed by gNB1.

[0256] S604: gNB1 sends CHO pre-configuration information to UE.

[0257] S605: gNB1 sends NCC2 to UE.

[0258] S606: The UE determines that the first cell is the target cell, and the first cell belongs to gNB2.

[0259] In some embodiments, the UE may select a candidate cell as a target cell when evaluating and determining that a candidate cell satisfies a handover trigger condition. Exemplarily, the first cell managed by gNB2 is a candidate cell, and the UE evaluates and determines that the first cell satisfies the handover trigger condition, and selects the first cell as the target cell.

[0260] S607: The UE sends a first message to gNB1 to indicate switching to the first cell.

[0261] Among them, the first message may include at least one of the following information: identification information corresponding to the target cell selected by the UE (i.e., the first cell), and identification information corresponding to the target gNB selected by the UE (i.e., gNB2).

[0262] In the embodiment of the present application, the first message may also be referred to as a farewell message (Goodbye message), and the present application does not limit the naming of the first message.

[0263] S608: gNB1 derives Key2.

[0264] In some embodiments, gNB1 may perform key derivation based on the identification information corresponding to the target cell or target gNB in ​​the first message.

[0265] S609: gNB1 sends a notification message to gNB2, carrying Key2.

[0266] In some embodiments, gNB1 determines that the target gNB is gNB2 according to the identification information corresponding to the target cell (i.e., the first cell) or the target gNB (i.e., gNB2) indicated in the first message, and sends a notification message to gNB2. In the embodiment of the present application, the first message may also be referred to as CHO Notification, and the present application does not limit the naming of the first message.

[0267] Optionally, the notification message can be used to indicate that a terminal device will access the cell managed by gNB2.

[0268] S610: The UE derives Key2 based on NCC2.

[0269] S611: UE accesses the first cell.

[0270] S612: gNB1 sends a path switching request message to AMF to request the core network to switch the downlink path between the user plane function network element and the base station for the UE from gNB1 to gNB2.

[0271] S613: AMF sends a path switch request response message to gNB1, which carries NH3 and NCC3.

[0272] Among them, NH3 and NCC3 are both used to derive the key for communication between the terminal device and the access network device.

[0273] Optionally, the path switch request response message may also carry indication information for indicating whether the path switch is successful.

[0274] The above steps S601 to S612 are the specific process of the first handover (UE switching from gNB1 to gNB2), and some steps (such as steps S613 to S618) of the second handover (UE switching from gNB2 to gNB3) are also exemplarily shown below. It should be understood that the cell handover after the first handover can be called a subsequent handover, and the CHO pre-configuration information of the multiple candidate cells received by the UE can be used in the subsequent handover of the UE after the first handover.

[0275] S614: gNB2 sends NCC3 to UE.

[0276] S615: The UE determines that the second cell is the target cell, and the second cell belongs to gNB3.

[0277] gNB2 deduce the key Key3 corresponding to the second cell, and the second cell belongs to gNB3.

[0278] S616: The UE sends a second message to gNB2 to indicate switching to the second cell.

[0279] S617: gNB1 derives Key3 based on NH3.

[0280] S618: gNB1 sends a notification message to gNB3, carrying Key3.

[0281] S619: UE derives Key3 based on NCC3.

[0282] It should be understood that the above-mentioned keys Key1, Key2 and Key3 can be KgNB in ​​NR communication. UE and gNB use KgNB to further derive the key Kup used for user plane data and the key Krrc used for RRC layer signaling. UE and gNB use Kup to encrypt user plane data, perform integrity protection and other security processing, and UE and gNB use Krrc to encrypt RRC signaling and perform integrity protection and other security processing.

[0283] S620: The UE accesses the second cell.

[0284] The specific implementation of some steps in the embodiment of the present application (such as step S601 can refer to step S501) can be referred to Figure 5 The relevant content will not be repeated here.

[0285] Figure 6 In the method shown, during the second handover, gNB2 sends NCC3 used in this handover to UE, and UE can deduce Key3 based on NCC3; and sends Key3 derived from NH3 corresponding to NCC3 to gNB3, which can ensure the key alignment of UE and gNB3.

[0286] After step S620, the second handover may further include that gNB3 may obtain NH4 and NCC4 from AMF, and send NCC4 to UE. For details, refer to steps S612 to S614. Figure 6 Not shown.

[0287] Assume that the third handover is from the second cell of gNB3 to the first cell of gNB2. Since the key information used for the first handover to the first cell is NCC2 and the key information used for the third handover to the first cell is NCC4, the UE uses NCC2 to derive the key when it switches to the first cell for the first time and uses NCC4 to derive the key when it switches to the first cell for the third time. The obtained keys are different. Therefore, although the first handover and the third handover are switched to the same cell, key reuse can be avoided, thereby ensuring communication security.

[0288] In executing the above Figure 5 and Figure 6The handover failure may occur during the process, for example, the UE fails to successfully access the first cell or the second cell. The embodiment of the present application provides another key management method, which can be applied to be executed after the handover failure or the source base station communication failure. For details, please refer to Figure 7 .

[0289] Figure 7 FIG. 1 is a flow chart of another key management method provided in an embodiment of the present application. Figure 7 As shown, the key management method may include some or all of the following steps:

[0290] S701: The UE fails to access the first cell or a radio link failure occurs in the source cell.

[0291] Exemplarily, a switching failure occurs in the UE, such as in the above steps S510 or S611, the UE cannot successfully switch to the first cell managed by gNB2.

[0292] In a possible implementation, after receiving the handover command, the UE starts a timer; when the timer times out, if the UE still fails to switch successfully, the UE determines that the handover fails and performs a cell selection operation, namely step S702.

[0293] As another example, if the UE detects a radio link failure in the source cell, the UE may execute step S702.

[0294] S702: The UE determines the second cell as the target cell from multiple candidate cells, and the second cell belongs to gNB3.

[0295] In some embodiments, if the cell selected by the UE is a candidate cell that has been preconfigured previously, the UE may access the cell through subsequent steps S703 and S704.

[0296] S703: UE derives Key3 based on NCC2.

[0297] In some embodiments, the UE may deduce Key3 based on NCC2 and the cell information of the second cell (such as PCI, etc.).

[0298] S704: The UE initiates access to the second cell, carrying at least one of the following information: source cell ID, UE ID and MAC-I.

[0299] Among them, the source cell ID can be the identification information corresponding to the source cell / source gNB, the UE ID is the identity information of the UE, and the MAC-I is the integrity message authentication code (MAC-I, Message Authentication Code for integrity) generated by the UE using the key of the source cell to process the uplink message.

[0300] In some embodiments, the UE sends an uplink message to the second cell / gNB3, and the uplink message may carry the above-mentioned source cell ID. Optionally, the uplink message may also carry the UE ID and MAC-I.

[0301] In a possible implementation, the MAC-I is a short version of the MAC-I, that is, a portion of bits of a complete MAC-I are truncated.

[0302] S705: gNB3 sends a request message to gNB1 to request the key that the UE should use. The request message carries at least one of the following information: source cell ID, UE ID and MAC-I.

[0303] In some embodiments, gNB3 can determine to send the request message to gNB1 through the identification information corresponding to the source cell / gNB in ​​the message of step S704.

[0304] Optionally, the request message may carry the MAC-I in step E, which is used by gNB1 to verify whether the request is legal.

[0305] Optionally, the request message carries UE identity information, which is used by gNB1 to determine for which UE key derivation is performed.

[0306] S706: gNB1 derives Key3.

[0307] Optionally, gNB1 derives Key3 after successful verification based on MAC-I.

[0308] S707: gNB3 sends Key3 to gNB1.

[0309] It should be understood that the above-mentioned keys Key1, Key2 and Key3 can be KgNB in ​​NR communication. UE and gNB use KgNB to further derive the key Kup used for user plane data and the key Krrc used for RRC layer signaling. UE and gNB use Kup to encrypt user plane data, perform integrity protection and other security processing, and UE and gNB use Krrc to encrypt RRC signaling and perform integrity protection and other security processing.

[0310] In the embodiment of the present application, the UE can perform cell selection when the handover fails. If the selected cell is still a candidate cell pre-configured before, the UE can send an uplink message to the cell / gNB when accessing the cell to inform which source gNB should be obtained from the key information. This method can ensure that the UE can select a candidate cell for access after the handover fails, and still ensure the key alignment between the UE and the selected cell / gNB, thereby improving the robustness of the solution.

[0311] See also Figure 8 , Figure 8 It is a flow chart of another key management method provided in an embodiment of the present application.

[0312] This method can be applied to switching technologies triggered by terminal devices (such as CHO) and switching technologies triggered by access network devices (such as LTM). In an embodiment of the present application, the target access network device to which the terminal device switches can deduce the key to be used by itself without the need for notification from the source access network device of the terminal device. Among them, taking the terminal device as UE, the source access network device of the terminal device (that is, the above-mentioned first access network device) as gNB1, the target access network device to which the terminal device switches (that is, the above-mentioned second access network device) as gNB2, and the core network device as AMF as an example, the key management method provided in the embodiment of the present application is introduced in detail.

[0313] like Figure 8 As shown, taking LTM switching as an example, the key management method may include some or all of the following steps:

[0314] S81: The UE obtains the initial key of the candidate access network device.

[0315] Figure 8 The candidate access network devices are taken as gNB2 and gNB3 as an example.

[0316] In some embodiments, the AMF may provide initial keys to gNB2 and gNB3, which are respectively denoted as Root key2 and Root key3. For example, the currently serving gNB is gNB1, and the initial key used may be Root key1.

[0317] In one possible implementation method, AMF may provide Root key2 and Root key3 to gNB1, which in turn may be provided by gNB1 to gNB2 and gNB3.

[0318] In another possible implementation method, gNB2 and gNB3 respectively request initial keys from AMF, and AMF sends initial keys to gNB2 and gNB3 respectively.

[0319] Optionally, AMF can calculate Root key1 based on the two parameters K_AMF and NAS UPLINK COUNTER maintained by itself, calculate Root key2 based on the two parameters K_AMF and NAS UPLINK COUNTER+1, and calculate Root key3 based on the two parameters K_AMF and NAS UPLINK COUNTER+2. Among them, K_AMF is the key corresponding to AMF, and NAS UPLINK COUNTER is the uplink counter value of the non-access stratum (NAS).

[0320] It should be understood that the UE side also maintains the two parameters K_AMF and NAS UPLINK COUNTER, and Root key1, Root key2 and Root key3 can be calculated according to the above principles.

[0321] For example, Figure 8 As shown, S81 may include some or all of the following steps:

[0322] S811:AMF sends Root key2 corresponding to gNB2 and Root key3 corresponding to gNB3.

[0323] S812: UE communicates with gNB1 based on Key1.

[0324] S813: gNB1 sends a switching request message to gNB2. The switching request message is used to request LTM pre-configuration information. The switching request message carries Root key2.

[0325] For a detailed description of the LTM pre-configuration information, please refer to the relevant content above and will not be repeated here.

[0326] S814: gNB1 sends a switching request message to gNB3. The switching request message is used to request LTM pre-configuration information. The switching request message carries Root key3.

[0327] S815: gNB2 sends a handover request response message to gNB1, and the handover request response message carries the LTM pre-configuration information of the candidate cells managed by gNB2.

[0328] S816: gNB3 sends a handover request response message to gNB1, and the handover request response message carries the LTM pre-configuration information of the candidate cells managed by gNB3.

[0329] S817: gNB1 sends LTM pre-configuration information to UE.

[0330] Exemplarily, gNB1 sends to the UE the LTM pre-configuration information of the candidate cells managed by gNB2 and the LTM pre-configuration information of the candidate cells managed by gNB3.

[0331] S818: UE derives Root key2 and Root key3.

[0332] S82: The UE switches to the first cell for the first time, and the first cell belongs to gNB2.

[0333] In some embodiments, the UE may switch to the target cell / gNB for the first time ( Figure 8 In the example, gNB2 is used. The Root key corresponding to the target cell / gNB is used, and the PCI and downlink frequency information of the target cell are combined to generate the Key to be used.

[0334] For example, Figure 8 As shown, S82 may include some or all of the following steps:

[0335] S821: gNB1 sends a switching command to the UE, indicating switching to the first cell, which belongs to gNB2.

[0336] S822: UE derives Key2-1 based on Root key2.

[0337] This is the first time that the UE switches to gNB2. The UE can use Root key2, combined with the PCI and frequency information of the first cell, to generate Key2-1. It should be understood that the meaning of 2-1 in Key2-1 is: 2 represents gNB2; 1 represents the first access to gNB2.

[0338] S823: The UE accesses the first cell.

[0339] S824: gNB2 derives Key2-1.

[0340] In one implementation, gNB2, like the above-mentioned UE, also uses Root key2 and the PCI and frequency information of the first cell to generate Key2-1.

[0341] S825: gNB2 sends a path switching request message to AMF to request the core network to switch the downlink path between the user plane function network element and the base station for the UE from gNB1 to gNB2.

[0342] S826: AMF sends a path switch request response message to gNB2, which may carry NH for gNB2 and NCC for gNB2.

[0343] Among them, the NH is used when gNB2 derives Key2-2 the next time the UE switches to gNB2 (i.e. the second switch described below); the NCC is used when the UE derives Key2-2 the next time the UE switches to gNB2 (i.e. the second switch described below).

[0344] Optionally, the path switch request response message may also carry indication information for indicating whether the path switch is successful.

[0345] S827: gNB2 sends NCC for gNB2 to UE.

[0346] In one implementation, gNB2 may send the NCC corresponding to gNB2 to the UE via L1 / L2 / L3 signaling, where the signaling includes the NCC value and, optionally, an identity identifier (or a preconfigured identifier) ​​corresponding to gNB2.

[0347] S83: The UE switches to the second cell for the first time, and the second cell belongs to gNB3.

[0348] In some embodiments, when the UE switches to the second cell or gNB3 for the first time, it can use the Root key corresponding to the second cell / gNB3 and combine the PCI and downlink frequency information of the second cell to generate the Key to be used.

[0349] Similar to step S82, UE and gNB3 derive Key3-1 respectively, where the meaning of 3-1 in Key3-1 is: 3 identifies gNB3; 1 indicates the first switch to gNB3.

[0350] For example, Figure 8 As shown, S83 may include some or all of the following steps:

[0351] S831: gNB2 sends a switching command to the UE, indicating switching to the second cell, which belongs to gNB3.

[0352] S832: UE derives Key3-1 based on Root key3.

[0353] S833: The UE accesses the second cell.

[0354] S834: gNB3 derives Key3-1.

[0355] It should be noted that after step S834, gNB3 can obtain the NH and NCC corresponding to gNB3 from AMF, and send the NCC corresponding to gNB3 to UE. For details, please refer to steps S825, S826 and S827. Figure 8 Not shown.

[0356] S84: The UE switches to the second cell for the second time.

[0357] In some embodiments, when the UE switches to the first cell / gNB2 for the second time, it can calculate and deduce Key2-2 based on NCC for gNB2, PCI of the second cell and downlink frequency information, where 2-2 means: the first 2 represents gNB2, and the second 2 represents the second switch to gNB2; gNB2 can calculate and deduce Key2-2 based on NH for gNB2, PCI of the first cell and downlink frequency information.

[0358] For example, Figure 8 As shown, S84 may include some or all of the following steps:

[0359] S841: gNB3 sends a switching command to the UE, indicating switching to the first cell.

[0360] The switching command may include an identifier of the first cell.

[0361] S842: UE derives Key2-2 based on NCC for gNB2.

[0362] In some embodiments, the UE performs key derivation based on parameters such as NCC for gNB2, PCI of the first cell, and downlink frequency to obtain Key2-2.

[0363] S843: The UE accesses the first cell.

[0364] S844: gNB2 derives Key2-2 based on NH for gNB2.

[0365] It should be noted that after step S834, gNB3 can obtain the NH and NCC corresponding to gNB3 from AMF, and send the NH and NCC corresponding to gNB3 to UE. For details, see steps S825, S826 and S827. Figure 8 Not shown.

[0366] In some embodiments, when gNB2 monitors that the UE accesses the first cell, it can perform key derivation based on NH for gNB2 to obtain Key2-2; and communicate with the UE based on Key2-2.

[0367] It should be understood that the above-mentioned keys Key1, Key2 and Key3 can be KgNB in ​​NR communication. UE and gNB use KgNB to further derive the key Kup used for user plane data and the key Krrc used for RRC layer signaling. UE and gNB use Kup to encrypt user plane data, perform integrity protection and other security processing, and UE and gNB use Krrc to encrypt RRC signaling and perform integrity protection and other security processing.

[0368] It should be understood that the above Figure 8 The following is an example of LTM switching. The CHO switching method can be found in the above Figure 8 The method flow is as follows: Figure 8 The switching judgment in the process is changed to the UE making the judgment, that is, the above steps S821, S831 and S841 are changed to the UE determining the first cell.

[0369] The above content elaborates on the method provided by the present application. In order to facilitate the implementation of the above scheme of the embodiment of the present application, the embodiment of the present application also provides corresponding devices or equipment.

[0370] The present application divides the functional modules of the first access network device and the terminal device according to the above method embodiment. For example, each functional module can be divided according to each function, or two or more functions can be integrated into one processing module. The above integrated modules can be implemented in the form of hardware or software functional modules. It should be noted that the division of modules in the present application is schematic and is only a logical functional division. There may be other division methods in actual implementation. The following will be combined with Figures 9 to 11 The communication device according to the embodiment of the present application is described in detail.

[0371] See also Fig. 9 , Fig. 9 is a schematic diagram of a structure of a communication device provided in an embodiment of the present application. Fig. 9 As shown, the communication device may include a transceiver unit 10 and a processing unit 20 .

[0372] In some embodiments of the present application, the communication device may be the first access network device shown above or a chip or circuit disposed in the first access network device. That is, the communication device may be used to execute the steps or functions performed by the first access network device in the above method embodiment.

[0373] In one design, the transceiver unit 10 is used to: send pre-configuration information and first key information of multiple candidate cells to a terminal device; the first key information is used to deduce a key for communication between the terminal device and the access network device; send the first key to a second access network device to which a target cell to which the terminal device switches belongs, the first key being the key for communication between the terminal device and the second access network device, and the multiple candidate cells include the target cell.

[0374] Exemplarily, the pre-configuration information of multiple candidate cells is used for the terminal device to perform one or more handovers among the multiple candidate cells.

[0375] Exemplarily, the pre-configuration information does not include the first key information.

[0376] Exemplarily, the multiple candidate cells belong to one or more access network devices.

[0377] In a possible implementation, the transceiver unit 10 is specifically configured to: after determining the target cell, send the first key to the second access network device.

[0378] Exemplarily, the first key information is carried by one of layer 1 signaling, layer 2 signaling, and layer 3 signaling, or the first key information is carried by a handover command, and the handover command is used to indicate handover to a target cell.

[0379] In a possible implementation, before sending the first key to the second access network device to which the target cell to which the terminal device is switched belongs, the transceiver unit 10 is further used to: receive a first message sent by the terminal device, where the first message is used to indicate switching to the target cell.

[0380] In a possible implementation, the transceiver unit 10 is specifically used to: receive a request message sent by the second access network device, where the request message is used to request a key for communication between the terminal device and the second access network device;

[0381] In response to the request message, the first key is sent to the second access network device.

[0382] In a possible implementation, the transceiver unit 10 is specifically configured to: after the request message is verified based on the integrity message authentication code, send the first key to the second access network device.

[0383] In a possible implementation, the transceiver unit 10 is further used to: send a handover request message to the second access network device, where the handover request message is used to request pre-configuration information of a cell corresponding to the second access network device;

[0384] A response message sent by the second access network device is received, where the response message includes a pre-configuration message of the target cell.

[0385] In the embodiment of the present application, the description of the first key, pre-configuration information and the first key information can refer to the above Figures 4 to 7 The introduction in the illustrated method embodiment will not be described in detail here.

[0386] It is understood that the specific description of the transceiver unit and the processing unit shown in the embodiment of the present application is only an example. For the specific functions or execution steps of the transceiver unit and the processing unit, reference can be made to the above Figures 4 to 7 The method embodiment shown is not described in detail here. In addition, the technical effects of the embodiment of the present application can be found in the aforementioned Figures 4 to 7 For the sake of brevity, the technical effects in the illustrated method embodiment are not described in detail here.

[0387] Reuse Fig. 9In some other embodiments of the present application, the communication device may be the terminal device shown above or a chip or circuit disposed in the terminal device. That is, the communication device may be used to execute the steps or functions executed by the terminal device in the above method embodiment.

[0388] In one design, the transceiver unit 10 is used to: receive pre-configuration information and first key information of multiple candidate cells; the first key information is used to deduce a key for communication between the terminal device and the access network device;

[0389] The processing unit 20 is used to: after receiving the switching command, deduce based on the first key information to obtain the first key corresponding to the first cell; the switching command is used to indicate switching to the first cell, the first cell belongs to the second access network device, and the first key is the key for communication between the terminal device and the second access network device.

[0390] Exemplarily, the pre-configuration information of multiple candidate cells is used for the terminal device to perform one or more handovers among the multiple candidate cells.

[0391] Exemplarily, the pre-configuration information does not include the first key information.

[0392] Exemplarily, the first key information is carried by one of layer 1 signaling, layer 2 signaling, and layer 3 signaling, or the first key information is carried by a handover command.

[0393] Exemplarily, the multiple candidate cells belong to one or more access network devices.

[0394] In a possible implementation, the processing unit 20 is also used to: when it is determined that the switching of the first cell fails or the wireless link fails, determine a second cell from multiple candidate cells, and the second cell belongs to a third access network device; the transceiver unit 10 is also used to: send a second message to the third access network device, and the second message is used to request access to the second cell.

[0395] Exemplarily, the second message also includes an integrity message authentication code and / or an identifier of the terminal device.

[0396] It is understood that the specific description of the transceiver unit and the processing unit shown in the embodiment of the present application is only an example. For the specific functions or execution steps of the transceiver unit and the processing unit, reference can be made to the above Figure 4 , Figure 5 and Figure 7 The method embodiment shown is not described in detail here. In addition, the technical effects of the embodiment of the present application can be found in the aforementioned Figure 4 , Figure 5 and Figure 7 For the sake of brevity, the technical effects in the illustrated method embodiment are not described in detail here.

[0397] Reuse Fig. 9In some other embodiments of the present application, the communication device may be the terminal device shown above or a chip or circuit disposed in the terminal device. That is, the communication device may be used to execute the steps or functions executed by the terminal device in the above method embodiment.

[0398] In one design, the transceiver unit 10 is used to: receive pre-configuration information and first key information of multiple candidate cells; send a first message to a first access network device, the first message is used to indicate switching to the first cell; the first cell belongs to the second access network device; the multiple candidate cells include the first cell;

[0399] The processing unit 20 is used to: deduce based on the first key information to obtain a first key corresponding to the first cell; the first key is a key for communication between the terminal device and the second access network device;

[0400] The transceiver unit 10 is used to: receive second key information from a second access network device; send a second message to the second access network device, the second message is used to indicate switching to a second cell; the second cell belongs to a third access network device; the plurality of candidate cells include the second cell;

[0401] The processing unit 20 is used to: deduce based on the second key information to obtain the second key corresponding to the second cell; the second key is a key for communication between the terminal device and the third access network device.

[0402] In a possible implementation, the processing unit 20 is further configured to: determine the first cell and / or the second cell from the multiple candidate cells based on pre-configuration information of the multiple candidate cells.

[0403] Exemplarily, the multiple candidate cells belong to one or more access network devices.

[0404] Exemplarily, the first key information and / or the second key information is carried by one of layer 1 signaling, layer 2 signaling, and layer 3 signaling.

[0405] In a possible implementation, the processing unit 20 is also used to: when it is determined that switching the second cell fails or the wireless link fails, determine a third cell from multiple candidate cells, and the third cell belongs to a fourth access network device; the transceiver unit 10 is also used to: send a third message to the fourth access network device, and the third message is used to request access to the third cell.

[0406] Exemplarily, the third message also includes an integrity message authentication code and / or an identifier of the terminal device.

[0407] It is understood that the specific description of the transceiver unit and the processing unit shown in the embodiment of the present application is only an example. For the specific functions or execution steps of the transceiver unit and the processing unit, reference can be made to the above Figure 4 , Figure 6and Figure 7 The method embodiment shown is not described in detail here. In addition, the technical effects of the embodiment of the present application can be found in the aforementioned Figure 4 , Figure 6 and Figure 7 For the sake of brevity, the technical effects in the illustrated method embodiment are not described in detail here.

[0408] The first access network device and the terminal device of the embodiment of the present application are introduced above. The possible product forms of the first access network device and the terminal device are introduced below. It should be understood that any device having the above Fig. 9 Any product of the functions of the first access network device or the terminal device falls within the protection scope of the embodiments of the present application. It should also be understood that the following description is only an example and does not limit the product form of the communication device of the embodiments of the present application to this.

[0409] In one possible implementation, Fig. 9 In the communication device shown, the processing unit 20 may be one or more processors, the transceiver unit 10 may be a transceiver, or the transceiver unit 10 may also be a sending unit and a receiving unit, the sending unit may be a transmitter, the receiving unit may be a receiver, and the sending unit and the receiving unit are integrated into one device, such as a transceiver. In the embodiment of the present application, the processor and the transceiver may be coupled, etc., and the embodiment of the present application does not limit the connection mode of the processor and the transceiver. In the process of executing the above method, the process of sending information in the above method can be understood as the process of outputting the above information by the processor. When outputting the above information, the processor outputs the above information to the transceiver so that it is transmitted by the transceiver. After the above information is output by the processor, it may also need to be processed in other ways before it reaches the transceiver. Similarly, the process of receiving information in the above method can be understood as the process of the processor receiving the input information. When the processor receives the input information, the transceiver receives the above information and inputs it into the processor. Furthermore, after the transceiver receives the above information, the above information may need to be processed in other ways before it is input into the processor.

[0410] See also Fig.10 , Fig.10 is another structural diagram of the communication device provided in the embodiment of the present application. Fig.10 As shown, the communication device provided in the embodiment of the present application can be used to implement the method described in the above method embodiment, and the description in the above method embodiment can be referred to. The communication device can be a first access network device, or a terminal device, or a chip therein. Exemplarily, the communication device includes one or more processors 1001 and a transceiver 1002. The communication device may further include a memory 1003. In one implementation, the communication device also includes an input and output device ( Fig.10not indicated).

[0411] The processor 1001 is mainly used to process the communication protocol and communication data, and to control the entire communication device, execute the software program, and process the data of the software program. The memory 1003 is mainly used to store the software program and data. The transceiver 1002 may include a control circuit and an antenna. The control circuit is mainly used to convert the baseband signal and the radio frequency signal and process the radio frequency signal. The antenna is mainly used to send and receive radio frequency signals in the form of electromagnetic waves. The input and output devices, such as a touch screen, a display screen, a keyboard, etc., are mainly used to receive data input by the user and output data to the user.

[0412] When the communication device is turned on, the processor 1001 can read the software program in the memory 1003, interpret and execute the instructions of the software program, and process the data of the software program. When data needs to be sent wirelessly, the processor 1001 performs baseband processing on the data to be sent, and outputs the baseband signal to the radio frequency circuit. The radio frequency circuit performs radio frequency processing on the baseband signal and then sends the radio frequency signal outward in the form of electromagnetic waves through the antenna. When data is sent to the communication device, the radio frequency circuit receives the radio frequency signal through the antenna, converts the radio frequency signal into a baseband signal, and outputs the baseband signal to the processor 1001. The processor 1001 converts the baseband signal into data and processes the data.

[0413] In another implementation, the RF circuit and antenna may be arranged independently of the processor performing baseband processing. For example, in a distributed scenario, the RF circuit and antenna may be arranged remotely from the communication device.

[0414] The processor 1001 , the transceiver 1002 , and the memory 1003 may be connected via a communication bus.

[0415] Exemplarily, when the communication device is used to perform the above Figure 4 When the first access network device performs the steps, methods or functions in the embodiment shown, the transceiver 1002 can be used to perform Figure 4 Steps S401 and S402 in, and / or other processes for the technology described herein.

[0416] Exemplarily, when the communication device is used to perform the above Figure 4 When the terminal device executes the steps, methods or functions in the embodiment shown, the processor 1001 may be used to generate Figure 4 Step S403 in step S404, and / or other processes for performing the techniques described herein; the transceiver 1002 may be used to perform Figure 4 Step S401 in, and / or other processes for the technology described herein.

[0417] Exemplarily, when the communication device is used to perform the above Figure 8 When the first access network device executes the steps, methods or functions in the embodiment shown, the processor 1001 may be used to execute Figure 8 Step S824 in, and / or other processes for performing the techniques described herein; the transceiver 1002 may be used to perform Figure 8 Step S827 in, and / or other processes for the techniques described herein.

[0418] Exemplarily, when the communication device is used to perform the above Figure 8 When the terminal device executes the steps, methods or functions in the embodiment shown, the processor 1001 can be used to execute Figure 8 Steps S818, S822 and / or other processes for performing the techniques described herein; the transceiver 1002 may be used to perform Figure 8 Step S812, step S817, step S821, step S823, step S827, and / or other processes for the technology described in this article.

[0419] In any of the above implementations, the processor 1001 may include a transceiver for implementing the receiving and sending functions. For example, the transceiver may be a transceiver circuit, or an interface, or an interface circuit. The transceiver circuit, interface, or interface circuit for implementing the receiving and sending functions may be separate or integrated. The above transceiver circuit, interface, or interface circuit may be used for reading and writing code / data, or the above transceiver circuit, interface, or interface circuit may be used for transmitting or delivering signals.

[0420] In any of the above implementations, the processor 1001 may store instructions, which may be computer programs. The computer programs run on the processor 1001, and may enable the communication device to perform the method described in the above method embodiment. The computer program may be fixed in the processor 1001, in which case the processor 1001 may be implemented by hardware.

[0421] In one implementation, the communication device may include a circuit that can implement the functions of sending or receiving or communicating in the aforementioned method embodiment. The processor and transceiver described in the present application can be implemented in an integrated circuit (IC), an analog IC, a radio frequency integrated circuit (RFIC), a mixed signal IC, an application specific integrated circuit (ASIC), a printed circuit board (PCB), an electronic device, etc. The processor and transceiver can also be manufactured using various IC process technologies, such as complementary metal oxide semiconductor (CMOS), N-type metal oxide semiconductor (nMetal-oxide-semiconductor, NMOS), P-channel metal oxide semiconductor (positive channel metal oxide semiconductor, PMOS), bipolar junction transistor (bipolar junction transistor, BJT), bipolar CMOS (BiCMOS), silicon germanium (SiGe), gallium arsenide (GaAs), etc.

[0422] It is understandable that the communication device shown in the embodiment of the present application may also have Fig.10 The embodiments of the present application do not limit the number of components and the like. The methods executed by the processor and transceiver shown above are only examples, and the specific steps executed by the processor and transceiver can refer to the introduction of the above method embodiments.

[0423] In another possible implementation, Fig. 9 In the communication device shown, the processing unit 20 may be one or more logic circuits, and the transceiver unit 10 may be an input / output interface, or a communication interface, or an interface circuit, or an interface, etc. Alternatively, the transceiver unit 10 may also be a sending unit and a receiving unit, the sending unit may be an output interface, the receiving unit may be an input interface, and the sending unit and the receiving unit are integrated into one unit, such as an input / output interface.

[0424] See also Fig.11 , Fig.11 is another structural diagram of a communication device provided in an embodiment of the present application. Fig.11 As shown, Fig.11The communication device shown includes a logic circuit 901 and an interface 902. That is, the processing unit 20 can be implemented by the logic circuit 901, and the transceiver unit 10 can be implemented by the interface 902. The logic circuit 901 can be a chip, a processing circuit, an integrated circuit or a system on chip (SoC) chip, etc., and the interface 902 can be a communication interface, an input / output interface, a pin, etc. For example, Fig.11 The above communication device is taken as an example of a chip, and the chip includes a logic circuit 901 and an interface 902 .

[0425] In the embodiment of the present application, the logic circuit and the interface may also be coupled to each other. The embodiment of the present application does not limit the specific connection method between the logic circuit and the interface.

[0426] Exemplarily, when the communication device is used to perform the above Figure 4 When the first access network device executes the steps, methods or functions in the method embodiment shown, the logic circuit 901 is used to determine the first key; the interface 902 is used to send the pre-configuration information and the first key information of multiple candidate cells; the interface 902 is used to send the first key, and the first key is the key for communication between the terminal device and the second access network device.

[0427] Exemplarily, when the communication device is used to perform the above Figure 4 When the terminal device executes the steps, methods or functions in the method embodiment shown, the logic circuit 901 is used to determine the first key corresponding to the target cell by deduction based on the first key information; the interface 902 is used to receive the first key.

[0428] In the embodiment of the present application, the description of the first key, pre-configuration information and the first key information can refer to the above Figure 4 The description of the method embodiment shown in the figure will not be described in detail here. It is understood that the specific description of the logic circuit 901 and the interface 902 can also be referred to. Fig. 9 The description of the processing unit and the transceiver unit shown will not be repeated here.

[0429] It can be understood that the communication device shown in the embodiment of the present application can implement the method provided in the embodiment of the present application in the form of hardware, or can implement the method provided in the embodiment of the present application in the form of software, etc., and the embodiment of the present application is not limited to this.

[0430] for Fig.11 The specific implementation methods of the various embodiments shown can also refer to the above embodiments, which will not be described in detail here.

[0431] The embodiment of the present application also provides a communication system, which includes a first access network device and a terminal device, and the first access network device and the terminal device can be used to execute any of the above method embodiments ( Figures 4 to 8 ) in the method.

[0432] In addition, the present application also provides a computer program, which is used to implement the operations and / or processing performed by the first access network device in the method provided by the present application.

[0433] The present application also provides a computer program, which is used to implement the operations and / or processing performed by a terminal device in the method provided by the present application.

[0434] The present application also provides a computer-readable storage medium, in which computer code is stored. When the computer code is executed on a computer, the computer executes the operations and / or processing performed by the first access network device in the method provided in the present application.

[0435] The present application also provides a computer-readable storage medium, in which computer codes are stored. When the computer codes are executed on a computer, the computer executes the operations and / or processes performed by the terminal device in the method provided in the present application.

[0436] The present application also provides a computer program product, which includes a computer code or a computer program. When the computer code or the computer program runs on a computer, the operations and / or processing performed by the first access network device in the method provided by the present application are executed.

[0437] The present application also provides a computer program product, which includes a computer code or a computer program. When the computer code or the computer program runs on a computer, the operations and / or processing performed by the terminal device in the method provided by the present application are executed.

[0438] In the several embodiments provided in the present application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, or it can be an electrical, mechanical or other form of connection.

[0439] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the technical effects of the solutions provided in the embodiments of the present application.

[0440] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0441] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application is essentially or partly contributed to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a readable storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned readable storage medium includes: U disk, mobile hard disk, read-only memory (ROM), random access memory (RAM), disk or optical disk and other media that can store program code.

[0442] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A key management method, characterized in that: The method comprises: Sending pre-configuration information of multiple candidate cells and first key information to a terminal device; the first key information is used to deduce a key for communication between the terminal device and an access network device; A first key is sent to a second access network device to which a target cell to which the terminal device switches belongs, where the first key is a key for communication between the terminal device and the second access network device, and the multiple candidate cells include the target cell.

2. The method according to claim 1, characterized in that The pre-configuration information of the multiple candidate cells is used for the terminal device to perform one or more switching among the multiple candidate cells.

3. The method according to claim 1 or 2, characterized in that: The pre-configuration information does not include the first key information.

4. The method according to any one of claims 1 to 3, characterized in that: The multiple candidate cells belong to one or more access network devices.

5. The method according to any one of claims 1 to 4, characterized in that: The sending the first key to the second access network device to which the target cell to which the terminal device is handed over belongs includes: After determining the target cell, sending the first key to the second access network device.

6. The method according to any one of claims 1 to 5, characterized in that: The first key information is carried by one of layer 1 signaling, layer 2 signaling and layer 3 signaling, or the first key information is carried by a handover command, and the handover command is used to indicate handover to the target cell.

7. The method according to any one of claims 1 to 4, characterized in that: Before sending the first key to the second access network device to which the target cell to which the terminal device is switched belongs, the method further includes: Receive a first message sent by the terminal device, where the first message is used to indicate switching to the target cell.

8. The method according to any one of claims 1 to 4, characterized in that: The sending the first key to the second access network device to which the target cell to which the terminal device is handed over belongs includes: Receiving a request message sent by the second access network device, where the request message is used to request a key for communication between the terminal device and the second access network device; In response to the request message, the first key is sent to the second access network device.

9. The method according to claim 8, characterized in that The request message further includes an integrity message authentication code, and the sending the first key to the second access network device includes: After the request message is verified based on the integrity message authentication code, the first key is sent to the second access network device.

10. The method according to any one of claims 1 to 9, characterized in that: The method further comprises: Sending a handover request message to the second access network device, where the handover request message is used to request pre-configuration information of a cell corresponding to the second access network device; Receive a response message sent by the second access network device, where the response message includes a pre-configuration message of the target cell.

11. A key management method, characterized in that: The method comprises: Receiving pre-configuration information and first key information of a plurality of candidate cells; the first key information is used to deduce a key for communication between a terminal device and an access network device; After receiving the switching command, the first key corresponding to the first cell is deduced based on the first key information; the switching command is used to indicate switching to the first cell, the first cell belongs to the second access network device, and the first key is the key for communication between the terminal device and the second access network device.

12. The method according to claim 11, characterized in that The pre-configuration information of the multiple candidate cells is used for the terminal device to perform one or more switching among the multiple candidate cells.

13. The method according to claim 11 or 12, characterized in that: The pre-configuration information does not include the first key information.

14. The method according to any one of claims 11 to 13, characterized in that: The first key information is carried by one of layer 1 signaling, layer 2 signaling and layer 3 signaling, or the first key information is carried by the handover command.

15. The method according to any one of claims 11 to 14, characterized in that: The multiple candidate cells belong to one or more access network devices.

16. The method according to any one of claims 11 to 15, characterized in that: The method further comprises: When it is determined that the handover of the first cell fails or the radio link fails, determining a second cell from the multiple candidate cells, where the second cell belongs to a third access network device; A second message is sent to the third access network device, where the second message is used to request access to the second cell.

17. The method according to claim 16, characterized in that The second message also includes an integrity message authentication code and / or an identification of the terminal device.

18. A key management method, characterized in that: The method comprises: receiving pre-configuration information and first key information of a plurality of candidate cells; Sending a first message to a first access network device, where the first message is used to indicate switching to a first cell; the first cell belongs to a second access network device; and the multiple candidate cells include the first cell; Deducing based on the first key information, obtaining a first key corresponding to the first cell; the first key is a key for communication between the terminal device and the second access network device; Receiving second key information from the second access network device; Sending a second message to the second access network device, where the second message is used to indicate switching to a second cell; the second cell belongs to a third access network device; and the multiple candidate cells include the second cell; Based on the second key information, deduction is performed to obtain a second key corresponding to the second cell; the second key is a key for communication between the terminal device and the third access network device.

19. The method according to claim 18, characterized in that The method further comprises: Based on the pre-configuration information of the multiple candidate cells, the first cell and / or the second cell is determined from the multiple candidate cells.

20. The method according to claim 18 or 19, characterized in that The multiple candidate cells belong to one or more access network devices.

21. The method according to any one of claims 18 to 20, characterized in that: The first key information and / or the second key information is carried by one of layer 1 signaling, layer 2 signaling and layer 3 signaling.

22. The method according to any one of claims 18 to 21, characterized in that: The method further comprises: When it is determined that the switching of the second cell fails or the radio link fails, determining a third cell from the multiple candidate cells, where the third cell belongs to a fourth access network device; A third message is sent to the fourth access network device, where the third message is used to request access to the third cell.

23. The method according to claim 22, characterized in that The third message also includes an integrity message authentication code and / or an identification of the terminal device.

24. A communication device, characterized in that: Comprising modules or units for executing the method according to any one of claims 1 to 23.

25. A communication device, characterized in that: It includes a processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices and transmit them to the processor or send signals from the processor to other communication devices, and the processor is used to implement the method as described in any one of claims 1 to 23 through a logic circuit or executing code instructions.

26. A readable storage medium, characterized in that: Used to store a program, the program being executed by one or more processors so that a device including the one or more processors performs the method according to any one of claims 1 to 23.

27. A communication system, characterized in that: include: A first access network device for executing the method described in any one of claims 1 to 10, and a terminal device for executing the method described in any one of claims 11 to 23.

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