Cell handover method and communication apparatus

Abstract

The present application relates to the field of communications. Provided are a cell handover method and a communication apparatus, which facilitate a reduction in the time consumed in a cell handover. The method comprises: a terminal device receiving, from a source cell (e.g., a first cell), first information used for instructing the terminal device to perform a cell handover, and the terminal device sending, to a target cell (e.g., a second cell) by means of a common control channel, a first message used for requesting the establishment of a radio resource control (RRC) connection, such that the terminal device can access the second cell in a similar manner to which the RRC connection is initiated in an RRC_IDLE state, or access the second cell in a similar manner to which RRC connection resume is initiated in an RRC_INACTIVE state. In this way, when being required to hand over from a first cell to a second cell, a terminal device can access the second cell without going through a handover preparation procedure, thereby reducing interaction procedures or steps, and thus reducing the time consumed in a cell handover.

Description

Cell handover method and communication apparatus

[0001] The present application claims priority from the Chinese patent application No. 202411266392.6 filed on September 10, 2024, and entitled "Cell handover method and communication apparatus", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] Embodiments of the present application relate to the field of communications, in particular to a cell handover method and a communication apparatus in the field of communications. BACKGROUND

[0003] Some geographical areas can be deployed with non-terrestrial networks (NTNs) and terrestrial networks (TNs).

[0004] Non-terrestrial devices in the NTN can be satellites. The movement of the satellite can cause the physical area covered by the satellite to change. In a case where the movement of one satellite causes the one satellite to be unable to cover a user equipment (UE), the UE can switch to another cell covering the UE to maintain the communication connection. The other cell can be a cell of another satellite or a TN cell.

[0005] However, in some implementations, there is a handover delay when the UE switches from a cell of one satellite to another cell, which can affect the communication function of the UE. SUMMARY

[0006] The present application provides a cell handover method and a communication apparatus, which can reduce the handover time of cell handover.

[0007] In a first aspect, a cell handover method is provided. The method comprises: receiving first information from a first cell, the first information being used to instruct a terminal device to perform cell handover; and sending a first message to a second cell through a common control channel, the first message being used to request establishment of a radio resource control (RRC) connection.

[0008] The cell switching method of the present application, in the case that the terminal device receives the first information from the first cell, the terminal device can send the first message (such as RRC establishment request) to the second cell through the common control channel (CCCH), so that the terminal device can access the second cell in a manner similar to initiating RRC connection in RRC_IDLE state or in a manner similar to initiating RRC connection recovery in RRC_INACTIVE state. In this way, in the case that the terminal device needs to switch from the first cell to the second cell, the terminal device can access the second cell without going through the switching preparation process, reducing the interaction process or steps, and thus reducing the switching time of cell switching.

[0009] In addition, the terminal device accesses the second cell in a manner similar to initiating RRC connection in RRC_IDLE state, that is, the terminal device accesses the second cell from RRC_IDLE state, and the access of the terminal device to the second cell does not affect the connection between the terminal device and the first cell. Alternatively, the terminal device accesses the second cell in a manner similar to initiating RRC connection recovery in RRC_INACTIVE state, that is, the terminal device accesses the second cell from RRC_INACTIVE state, and the access of the terminal device to the second cell does not affect the connection between the terminal device and the first cell. That is, during the process of the terminal device accessing the second cell and after the terminal device accesses the second cell, the terminal device can still maintain connection and communication with the first cell, so that the impact on the transmission of downlink user plane data sent by the source core network can also be reduced.

[0010] In combination with the first aspect, in some embodiments of the first aspect, the method further comprises: receiving a second message from the second cell, the second message being a response to the first message, and the second message being transmitted through the common control channel.

[0011] In this way, the terminal device can establish an RRC connection with the second cell in a manner similar to RRC_IDLE state to access the second cell.

[0012] In combination with the first aspect, in some embodiments of the first aspect, before sending the first message or before receiving the second message, the terminal device maintains connection with the first cell.

[0013] In this way, in the case that the terminal device receives the information (such as the first information) for indicating cell switching, or during the process of the terminal device accessing the second cell and after the terminal device accesses the second, the terminal device can still maintain connection and communication with the first cell, so that the impact of the transmission of downlink user plane data sent by the source core network can be reduced, and the probability of occurrence of data transmission delay in the interaction between the terminal device and the source core network can be reduced.

[0014] With reference to the first aspect, in some embodiments of the first aspect, after sending the first message to the second cell, or after receiving the second message from the second cell, the method further includes receiving second information from the first cell, and disconnecting the connection with the first cell based on the second information.

[0015] In this way, the wireless resources used for wireless transmission between the terminal device and the first cell can be released, so as to realize effective utilization of the wireless resources.

[0016] With reference to the first aspect, in some embodiments of the first aspect, after receiving the second message from the second cell, the method further includes sending data packets of the first data stream to the second cell.

[0017] In this way, in the case that the terminal device accesses the second cell, the terminal device can timely interact with the second cell to realize the service related to the interaction data, such as the first service corresponding to the first data stream, so as to reduce the probability of service interruption caused by the fact that the base station of the first cell cannot cover the geographical area where the terminal device is located.

[0018] With reference to the first aspect, in some embodiments of the first aspect, the method further includes: in the case that the data packets in the second data stream are completely transmitted to the first cell, sending third information to the first cell, the third information being used to indicate that the data packets in the second data stream are completely transmitted, the second data stream being a data stream transmitted by the terminal device to the first cell. And / or, receiving fourth information from the first cell, the fourth information being used to indicate that the data packets in the third data stream are completely transmitted, the third data stream being a data stream transmitted by the first cell to the terminal device.

[0019] In this way, the terminal device and the first cell can determine that the uplink data (such as the second data stream) and / or the downlink data (such as the third data stream) transmitted between the terminal device and the first cell are completely transmitted, so as to execute subsequent procedures of releasing the RRC connection.

[0020] With reference to the first aspect, in some embodiments of the first aspect, the method further includes sending first user equipment (UE) capability information to the first cell, the first UE capability information being UE capability information corresponding to the connection between the terminal device and the first cell when the terminal device accesses the first cell and the second cell.

[0021] In this way, the source base station (or the first cell) can update the transmission parameters and resources configured for the terminal device based on the first UE capability information, so as to reduce the waste of resources.

[0022] In some embodiments of the first aspect, the method further comprises: receiving, by the access stratum (AS) layer, a first packet of the fourth data stream from the second cell. In a case that the RRC connection with the first cell is released, and / or a second packet of the fourth data stream from the first cell has been delivered to the upper layer, the first packet of the fourth data stream is transmitted to the upper layer by the AS layer.

[0023] In this way, the packets in the fourth data stream can be transmitted and processed in the terminal device in the preset packet order, and thus the occurrence probability of the fourth service interruption or failure corresponding to the fourth data stream can be reduced.

[0024] In some embodiments of the first aspect, the first information comprises a first cell list, and the first cell list comprises the second cell. Alternatively, the first information comprises a first public land mobile network (PLMN) list, and the cells indicated by the first PLMN list comprise the second cell.

[0025] In this way, the terminal device can send the first message to the second cell indicated by the first information to access the second cell.

[0026] Optionally, before receiving the first information from the first cell, the method further comprises: receiving information from the first cell for indicating a measurement configuration, the measurement configuration comprising frequency point information of at least one frequency point, and the frequency points in the measurement configuration being determined based on the first PLMN list.

[0027] In this way, the terminal device can perform frequency point measurement based on the measurement configuration, and thus the first cell can indicate the second cell to be accessed by the terminal device to the terminal device based on the measurement result of the frequency point measurement of the terminal device.

[0028] Optionally, before receiving the first information from the first cell, the method further comprises: sending sixth information to the first cell, the sixth information comprising measurement results of respective cells corresponding to respective frequency points in the measurement configuration or measurement results of at least one neighbor cell measured by the terminal device.

[0029] In this way, the first cell can indicate the second cell to be accessed by the terminal device to the terminal device based on the measurement result of the terminal device.

[0030] In some embodiments of the first aspect, the method further comprises: in a case that the terminal device fails to access a cell in a second cell list or fails to access any cell in the second cell list within a first time length, sending information indicating a cell handover failure to the first cell, the second cell list comprising the second cell, the second cell list being determined by the terminal device, or the second cell list being indicated by the first information.

[0031] In this way, the terminal device can fall back to the communication capability of the terminal device in the source network before receiving the first information (or the handover command), so as to fully utilize the communication capability.

[0032] With reference to the first aspect, in some embodiments of the first aspect, the method further includes: sending, to the first cell, second UE capability information, the second UE capability being corresponding UE capability information of the terminal device in connection with the first cell when the terminal device only accesses the first cell.

[0033] In this way, the source base station (or the first cell) can update the transmission parameters and resources configured for the terminal device based on the second UE capability information, so that the terminal device can fall back to the communication capability of the terminal device in the source network before receiving the first information (or the handover command).

[0034] With reference to the first aspect, in some embodiments of the first aspect, the method further includes: before disconnecting the connection with the first cell, and in a case where it is determined that a radio link failure occurs between the terminal device and the first cell, sending, to a third cell, a first request, the first request being used to request RRC reestablishment, the third cell and the first cell both belonging to a non-terrestrial network or a terrestrial network.

[0035] In this way, before the terminal device disconnects the connection with the first cell, and in a case where the terminal device determines that a radio link failure occurs between the terminal device and the first cell, the terminal device can select the third cell in the source network to trigger RRC reestablishment, so that the terminal device can continue to perform the process of switching from the source network to the target network (such as accessing the second cell), and the time length of the data transmission delay of the interaction between the source network and the terminal device can be reduced, the influence of the data transmission of the interaction between the source network and the terminal device can be reduced, and the occurrence probability of the data packet loss of the interaction between the source network and the terminal device can be reduced.

[0036] The second aspect of the present application provides a cell handover method, which includes: determining first information, the first information being used to instruct a terminal device to perform cell handover; and sending the first information to the terminal device, so that the terminal device sends a first message to a second cell through a common control channel, the first message being used to request to establish an RRC connection.

[0037] With reference to the second aspect, in some embodiments of the second aspect, the determining of the first information includes: receiving information used to indicate a first PLMN list from a first core network device, the first PLMN list including a PLMN supported by the terminal device; and determining the first information based on the first PLMN list.

[0038] With reference to the second aspect, in some embodiments of the second aspect, the first information comprises a first cell list, the first cell list comprises the second cell, and the first cell list is determined based on the first PLMN list. Alternatively, the first information comprises a first PLMN list, and the cells indicated by the first PLMN list comprise the second cell.

[0039] Optionally, before sending the first information to the terminal device, the method further comprises: sending information indicating a measurement configuration, the measurement configuration comprising frequency point information of at least one frequency point, the frequency points in the measurement configuration being determined based on the first PLMN list.

[0040] Optionally, before sending the first information to the terminal device, the method further comprises: receiving sixth information from the terminal device, the sixth information comprising measurement results of respective cells corresponding to respective frequency points in the measurement configuration or measurement results of at least one neighbor cell measured by the terminal device.

[0041] With reference to the second aspect, in some embodiments of the second aspect, after sending the first information to the terminal device, the method further comprises: receiving first UE capability information from the terminal device, the first UE capability information being UE capability information corresponding to connection of the terminal device to the first cell when the terminal device accesses the first cell and the second cell.

[0042] With reference to the second aspect, in some embodiments of the second aspect, the method further comprises: receiving information from the first core network device indicating release of a UE context. Sending second information to the terminal device, the second information indicating release of an RRC connection.

[0043] With reference to the second aspect, in some embodiments of the second aspect, receiving the information from the first core network device indicating release of the UE context comprises: receiving fifth information from the first core network device, the fifth information indicating that transmission of data packets in a third data flow is complete, the third data flow being a data flow to be transmitted to the terminal device. Sending information to the first core network device requesting release of the UE context. Receiving the information from the first core network device indicating release of the UE context.

[0044] With reference to the second aspect, in some embodiments of the second aspect, sending the information to the first core network device requesting release of the UE context comprises: based on the fifth information and completion of transmission of the data packets in the third data flow to the terminal device, sending the information to the first core network device requesting release of the UE context.

[0045] In some embodiments of the second aspect, the sending the information for requesting the release of the UE context to the first core network device comprises: receiving third information from the terminal device, the third information being used to indicate that the sending of the data packets in the second data stream is completed, the second data stream being a data stream transmitted by the terminal device to the first cell; and based on the third information, the fifth information, and the sending of the data packets in the third data stream to the terminal device being completed, the sending of the information for requesting the release of the UE context to the first core network device.

[0046] In some embodiments of the second aspect, the method further comprises: receiving information from the terminal device indicating a failure of the cell handover.

[0047] In some embodiments of the second aspect, the method comprises: receiving second UE capability information from the terminal device, the second UE capability being UE capability information corresponding to a connection of the terminal device in the first cell when the terminal device only accesses the first cell.

[0048] In a third aspect, a communication apparatus is provided, which is configured to execute the method in any possible implementation of the first aspect or the second aspect. Specifically, the apparatus includes modules for performing the method in any possible implementation of the first aspect or the second aspect.

[0049] In a fourth aspect, another communication apparatus is provided, which includes a processor configured to execute instructions to implement the method in any possible implementation of the first aspect, the second aspect, or the third aspect. Optionally, the apparatus further includes a memory, and the processor is coupled to the memory. The memory stores the instructions.

[0050] In one implementation, the apparatus is a terminal device or a network device (e.g., a source base station). The communication interface can be a transceiver, or an input / output interface.

[0051] In another implementation, the apparatus is a chip configured in a terminal device or a chip configured in a network device (e.g., a source base station). When the apparatus is a chip configured in a terminal device or a chip configured in a network device (e.g., a source base station), the communication interface can be an input / output interface.

[0052] In a fifth aspect, a processor is provided, which includes an input circuit, an output circuit, and a processing circuit. The processing circuit is configured to receive a signal through the input circuit and transmit a signal through the output circuit, so that the processor executes the method in any possible implementation of the first aspect or the second aspect.

[0053] In the implementation process, the processor can be a chip, the input circuit can be an input pin, the output circuit can be an output pin, and the processing circuit can be a transistor, a gate circuit, a flip-flop, and various logic circuits. The input signal received by the input circuit can be received and input by, for example but not limited to, a receiver, the output signal output by the output circuit can be output to and transmitted by, for example but not limited to, a transmitter, and the input circuit and the output circuit can be the same circuit which is used as the input circuit and the output circuit at different times. The embodiments of the present application do not limit the specific implementation of the processor and various circuits.

[0054] In a sixth aspect, a processing apparatus is provided, including a processor and a memory. The processor is configured to read instructions stored in the memory, and can receive signals through a receiver and transmit signals through a transmitter to perform the method in any possible implementation manner of the first aspect or the second aspect.

[0055] Optionally, the processor is one or more, and the memory is one or more.

[0056] Optionally, the memory can be integrated with the processor, or the memory and the processor are separately arranged.

[0057] In the implementation process, the memory can be a non-transitory memory, for example, a read only memory (ROM), which can be integrated with the processor on the same chip or arranged separately on different chips. The type of the memory and the arrangement of the memory and the processor are not limited in the present application.

[0058] It should be understood that the related data interaction process, for example, the sending of the indication information can be a process of outputting the indication information from the processor, and the receiving of the capability information can be a process of receiving the input capability information by the processor. Specifically, the processed output data can be output to the transmitter, and the input data received by the processor can come from the receiver. The transmitter and the receiver can be collectively referred to as a transceiver.

[0059] The processing apparatus in the sixth aspect can be a chip, and the processor can be implemented by hardware or software. When implemented by hardware, the processor can be a logic circuit or an integrated circuit. When implemented by software, the processor can be a general-purpose processor which is implemented by reading software codes stored in the memory. The memory can be integrated in the processor or exist independently.

[0060] In a seventh aspect, a computer program product is provided. The computer program product includes a computer program (which can also be referred to as code or instructions) that, when executed by a computer, causes the computer to perform the method in any possible implementation of the first aspect or the second aspect.

[0061] In an eighth aspect, a computer-readable storage medium is provided. The computer-readable storage medium stores a computer program (which can also be referred to as code or instructions) that, when executed on a computer, causes the computer to perform the method in any possible implementation of the first aspect or the second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0062] FIG. 1 is a schematic diagram of binding of a cell identity and / or broadcasted area identity in a satellite to a geographical area according to an embodiment of the present application;

[0063] FIG. 2 is a schematic diagram of binding of a cell identity and / or broadcasted area identity in a satellite to a satellite according to an embodiment of the present application;

[0064] FIG. 3 is a schematic diagram of a communication system architecture related to transparent satellites according to an embodiment of the present application;

[0065] FIG. 4 is a schematic diagram of a communication system architecture related to regenerative satellites according to an embodiment of the present application;

[0066] FIG. 5 is a schematic diagram of a scenario of co-deployment of NTN and TN according to an embodiment of the present application;

[0067] FIG. 6 is a schematic diagram of a handover preparation procedure according to an embodiment of the present application;

[0068] FIG. 7 is a schematic diagram of a handover execution procedure according to an embodiment of the present application;

[0069] FIG. 8 is a schematic diagram of a cell handover method according to an embodiment of the present application;

[0070] FIG. 9 is another schematic diagram of a cell handover method according to an embodiment of the present application;

[0071] FIG. 10 is a schematic diagram of a scenario of multi-hop interaction between a source base station and a ground device according to an embodiment of the present application;

[0072] FIG. 11 is a schematic diagram of another cell handover method according to an embodiment of the present application;

[0073] FIG. 12 is a schematic diagram of another cell handover method according to an embodiment of the present application;

[0074] FIG. 13 is a schematic diagram of a structure of a communication apparatus according to an embodiment of the present application;

[0075] FIG. 14 is another structural schematic diagram of a communication device according to an embodiment of the present application;

[0076] FIG. 15 is a schematic diagram of an architecture of an O-RAN system according to an embodiment of the present application. DETAILED DESCRIPTION

[0077] The technical solutions in the present application will be described below with reference to the drawings.

[0078] In the embodiments of the present application, the same items or similar items with basically the same functions and effects are distinguished by using "first", "second", and the like. For example, the first value and the second value are only used to distinguish different values, and the order is not limited. Those skilled in the art can understand that "first", "second", and the like do not limit the quantity and execution order, and "first", "second", and the like do not necessarily mean different.

[0079] It should be noted that in the embodiments of the present application, "exemplarily" or "for example" and the like are used to represent as an example, illustration or description. Any embodiment or design scheme described as "exemplarily" or "for example" in the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. Rather, the use of "exemplarily" or "for example" and the like is intended to present the relevant concept in a specific manner.

[0080] In the embodiments of the present application, "at least one" means one or more, and "multiple" means two or more. "And / or" describes the association relationship between the associated objects, which means that there can be three kinds of relationships, for example, A and / or B, which can represent the following three cases: A exists alone, A and B exist together, and B exists alone, where A and B can be singular or plural. The character "or" generally represents the relationship between the preceding and following associated objects as "or". "At least one of the following" or the like means any combination of these items, including any combination of single item or multiple items. For example, at least one of a, b, or c can represent a, b, c, a-b, a-c, b-c, or a-b-c, where a, b, and c can be single or multiple.

[0081] The technical solutions of the embodiments of the present application can be applied to various communication systems, for example: a long term evolution (LTE) system, an LTE frequency division duplex (FDD) system, an LTE time division duplex (TDD), a universal mobile telecommunication system (UMTS), a worldwide interoperability for microwave access (WiMAX) communication system, a 5th generation (5G) system or a new radio (NR) or a future evolved communication system, and the like.

[0082] The communication system can include a radio access network (RAN) and a core network (CN). The RAN can include at least one NTN corresponding base station, at least one TN corresponding base station and / or at least one terminal device. The terminal device can be connected to the RAN node in a wireless manner. The RAN node can be connected to the core network in a wireless or wired manner.

[0083] The terminal device in the embodiments of the present application can also be referred to as: user equipment (UE), mobile station (MS), mobile terminal (MT), access terminal, subscriber unit, subscriber station, mobile station, mobile station, remote station, remote terminal, mobile device, user terminal, terminal, wireless communication device, user agent or user equipment, etc.

[0084] The terminal device can be a device that provides voice and / or data connectivity to a user, such as a handheld phone, a car-mounted device, etc. Currently, some examples of terminal devices include mobile phones, tablets, laptops, palmtops, mobile internet devices (MIDs), wearable devices, virtual reality (VR) devices, augmented reality (AR) devices, wireless terminals in industrial control, wireless terminals in self driving, wireless terminals in remote medical surgery, wireless terminals in smart grid, wireless terminals in transportation safety, wireless terminals in smart city, wireless terminals in smart home, helicopters, airplanes, ships, robots, mechanical arms, smart home devices, cellular phones, cordless phones, session initiation protocol (SIP) phones, wireless local loop (WLL) stations, personal digital assistants (PDAs), handheld devices with wireless connectivity, computing devices or other processing devices connected to wireless modems, car-mounted devices, wearable devices, terminal devices in a 5G network, or terminal devices in a future evolved public land mobile network (PLMN), etc. The present application is not limited thereto.

[0085] By way of example, and without limitation, in the present application, the terminal device can be a terminal device in an internet of things (IoT) system. The internet of things is an important component of future information technology development, and its main technical feature is to connect objects through communication technology and network, so as to realize the intelligent network of man-machine interconnection and object-object interconnection. Illustratively, the terminal device in the embodiments of the present application can be a wearable device. The wearable device can also be referred to as a wearable smart device, which is a general term for smart devices that can be worn, such as glasses, gloves, watches, clothing, and shoes, which are designed and developed by applying wearable technology to daily wear. The wearable device is a portable device that can be directly worn on the body or integrated into the user's clothes or accessories. The wearable device is not only a hardware device, but also can realize powerful functions through software support and data interaction and cloud interaction. The general wearable smart device includes a full function, large size, and can realize complete or partial functions without relying on a smart phone, such as a smart watch or smart glasses, and only focuses on a certain application function, and needs to cooperate with other devices such as a smart phone, such as various smart wristbands, smart jewelry, and the like for monitoring vital signs.

[0086] By way of example, and without limitation, in the embodiments of the present application, the terminal device can also be a terminal device in machine type communication (MTC). In addition, the terminal device can also be a vehicle-mounted module, a vehicle-mounted module group, a vehicle-mounted component, a vehicle-mounted chip, or a vehicle-mounted unit, etc. built-in as one or more components or units in a vehicle, and the vehicle can implement the method provided in the present application through the built-in vehicle-mounted module, vehicle-mounted module group, vehicle-mounted component, vehicle-mounted chip, or vehicle-mounted unit, etc. Therefore, the embodiments of the present application can also be applied to the Internet of Vehicles, such as vehicle to everything (V2X), long term evolution-vehicle (LTE-V), vehicle-to-vehicle (V2V) technology, etc.

[0087] The RAN node involved in the present application can be a device in communication with a terminal device, and the RAN node can also be referred to as a RAN entity, an access node, an access network device, or a wireless access network device, etc. The RAN node can be a base station, and can also be a transmission reception point (TRP), and can also be an evolved NodeB (eNB or eNodeB) in an LTE system, and can also be a home base station (for example, a home evolved NodeB, or a home NodeB, HNB), a baseband unit (BBU), and can also be a wireless controller in a cloud radio access network (CRAN) scenario, or the network device can be a relay station, an access point, a vehicle-mounted device, a wearable device, a network device in a 5G network, or a network device in a future evolved PLMN network, etc., and can also be an access point (AP) in a WLAN, and can also be a 5G base station (next generation NodeB, gNB) in a new radio (NR) system, etc. The RAN node described above can also be a city base station, a micro base station, a pico base station, a femto base station, etc., and the present application does not limit this.

[0088] Optionally, the access network can be an open access network (O-RAN). The open access network (O-RAN) aims to realize an intelligent and open access network. The O-RAN architecture can separate software and hardware, and can realize virtualization of network functions and standardization of hardware. In addition, the O-RAN can also introduce artificial intelligence (AI).

[0089] The core network device involved in the present application can be a device in the core network that provides service support for a terminal device. At present, some core network devices are, for example: access and mobility management function (AMF) entities, session management function (SMF) entities, user plane function (UPF) entities, etc., which are not listed one by one here.

[0090] Among them, the AMF entity can be responsible for access management and mobility management of the terminal. The SMF entity can be responsible for session management, such as session establishment of a user, etc. The UPF entity can be a functional entity of the user plane, mainly responsible for connecting external networks.

[0091] It should be noted that the entity in the present application can also be referred to as a network element or a functional entity, for example, the AMF entity can also be referred to as an AMF network element or an AMF functional entity, the SMF entity can also be referred to as an SMF network element or an SMF functional entity, and the like, and the UPF entity can also be referred to as a UPF network element or a UPF functional entity, and the like.

[0092] In the embodiments of the present application, the AMF network element can be referred to as AMF for short. The SMF network element can be referred to as SMF for short. The UPF network element can be referred to as UPF for short. For example, the source AMF network element can be referred to as source AMF for short. The target AMF network element can be referred to as target AMF for short.

[0093] Firstly, some technical terms and symbols involved in the present application are introduced.

[0094] 1、Uu interface, NR Uu interface and NG interface

[0095] The Uu interface can be understood as a wireless interface between a user equipment (UE) and a base station in a communication system. The Uu interface can include an NR Uu interface. The Uu interface can be referred to as Uu for short.

[0096] The NR Uu interface can be understood as a wireless interface between a UE and a gNB in a 5G new radio (5G NR) system.

[0097] The NR Uu interface can carry user data and control signaling to realize transmission of user data and / or control signaling between a user equipment and a base station.

[0098] The NR Uu interface can support handover of a user equipment between different base stations.

[0099] The NG interface can be understood as a communication interface between a 5G base station and a 5G core network.

[0100] 2、Non-terrestrial network (NTN) and non-terrestrial equipment in NTN

[0101] Non-terrestrial communication based on non-terrestrial network has the advantages of wide coverage, long communication distance, high reliability, great flexibility, high throughput, etc., and can make communication not affected by geographical environment, climate conditions and natural disasters. The introduction of NTN into the communication system can provide communication services for areas that are difficult to cover by terrestrial networks, can enhance the reliability of communication, for example, can provide more stable and better communication services for trains, airplanes and users on these vehicles, and can also provide more data transmission resources to support a larger number of connections.

[0102] The non-terrestrial equipment in the NTN can be a satellite, a drone or a high-altitude platform, etc.

[0103] Taking a non-ground device as an example, a satellite, the orbit of the satellite can be divided into three types according to the height:

[0104] (1) Low Earth Orbit (LEO): the orbit height is 160-2 000 km;

[0105] (2) Medium Earth Orbit (MEO): the orbit height is 2 000-35 786 km;

[0106] (3) Geostationary Orbit (GEO): the orbit height is 35 786 km, and the relative position of the satellite running on the orbit to the earth is not affected by the rotation of the earth.

[0107] In ground communication, one base station can have multiple cells, and generally, the physical cell identifier (PCI), broadcasted area identifier or tracking area identity (TAI) of the cells will not change in a long time. The broadcasted area identifier is, for example, a tracking area code (TAC).

[0108] In satellite communication, since the satellite is moving at a high speed, the geographical area covered by the satellite signal is changing. The geographical area covered by the satellite signal can also be referred to as the geographical area covered by the satellite. For the identification of the cell in the satellite and the broadcasted area identifier, there are two deployment modes at present:

[0109] Deployment mode one: the identification of the cell in the satellite and / or the broadcasted area identifier is bound to the geographical area. That is, for a certain geographical area, the cell identification and / or the broadcasted area identifier corresponding to the area is unchanged. When a satellite (referred to as an old satellite) moves away, another satellite (referred to as a new satellite) can provide services for the area. The cell identification and / or the broadcasted area identifier in the new satellite are the same as those in the old satellite.

[0110] In this way, for a certain geographical area, in the case that the position of the UE is unchanged, since the cell perceived by the UE is unchanged, the network side does not need to trigger the cell switching process for the UE, thereby reducing the number of switching in the network and reducing the signaling overhead of the Uu interface. The cell in the following deployment mode can also be referred to as a quasi-earth fixed cell.

[0111] FIG. 1 shows a schematic diagram of the identification of the cell in the satellite and / or the broadcasted area identifier bound to the geographical area according to an embodiment of the present application.

[0112] As shown in FIG. 1, at 10:00:00, satellite A covers geographical area 1, and the cell of satellite A corresponding to the geographical area 1 is cell #1. Wherein, #1 is the PCI of cell #1 of satellite A.

[0113] At 10:15:00, satellite A covers geographical area 2, and the cell of satellite A corresponding to the geographical area 2 is cell #2. Wherein, #2 is the PCI of cell #2 of satellite A.

[0114] At 10:30:00, satellite A covers geographical area 3, and the cell of satellite A corresponding to the geographical area 3 is cell #3. Wherein, #3 is the PCI of cell #3 of satellite A.

[0115] As can be seen from FIG. 1, the identification of the cell in satellite A and / or the broadcasted area identification is bound to the geographical area covered by satellite A.

[0116] It should be noted that the quasi-ground fixed cell can also refer to that, for the cell, the covered geographical area of the cell is unchanged within a period of time. After a period of time, the covered geographical area of the cell becomes another geographical area.

[0117] Deployment mode two: the identification of the cell in satellite and / or the broadcasted area identification is bound to the satellite. When the satellite moves and causes the change of the geographical area covered by the satellite signal, the identification of the cell in satellite and the broadcasted area identification do not change. In the deployment mode two, it can be understood that the identification of the cell in satellite and / or the broadcasted area identification is scanned on the geographical area covered by the satellite along with the movement of the satellite.

[0118] In this way, even if the position of the UE is unchanged, since the satellite is moving, when the satellite can no longer cover the UE, the network side needs to inform the UE to perform cell switching, so that the UE switches to other cells to maintain the communication connection.

[0119] FIG. 2 shows a schematic diagram of the identification of the cell in satellite and the broadcasted area identification bound to the satellite provided by the embodiments of the present application.

[0120] As shown in FIG. 2, at 10:00:00, satellite B covers geographical area 1, and the cell of satellite B corresponding to the geographical area 1 is cell #1. Wherein, #1 is the PCI of cell #1 of satellite B.

[0121] At 10:15:00, satellite B covers geographical area 2, and the cell of satellite B corresponding to the geographical area 2 is also cell #1.

[0122] At 10:30:00, satellite B covers geographical area 3, and the cell of satellite B corresponding to the geographical area 3 is also cell #1.

[0123] As shown in FIG. 2, the identity of the cell in satellite B and / or the broadcasted area identity is bound to satellite B.

[0124] It should be noted that the cell in the second deployment mode can be referred to as an earth moving cell. The earth moving cell can also refer to a coverage area of a certain cell that slides on the earth surface along with the satellite.

[0125] Exemplarily, in the embodiments of the present application, according to the working mode of the satellite, the type of the satellite can include a transparent satellite or a regenerative satellite. It should be noted that the satellite is only taken as an example herein. For the NTN network, the type of the NTN network can include a transparent NTN network or a regenerative NTN network.

[0126] The transparent satellite can be used to forward the information of the cell of the ground network device. The ground network device is, for example, a base station deployed on the ground. The transparent satellite can perform radio frequency filtering, frequency conversion and amplification, that is, the transparent satellite can serve as a physical layer relay (L1 relay) to regenerate the physical layer signal for signal forwarding. The transparent satellite does not have the function of a higher protocol layer. The transparent satellite can be referred to as a transparent satellite for short. The communication system architecture related to the transparent satellite can be referred to FIG. 2.

[0127] FIG. 3 shows a schematic diagram of a communication system architecture related to a transparent satellite according to an embodiment of the present application.

[0128] Taking the 5G network as an example, as shown in FIG. 3, the architecture related to the transparent satellite can include a UE 301, a remote radio unit (RRU), a gNB 304 deployed on the ground, a 5G core network (5G CN) 305 and a data network 306. The remote radio unit can include a transparent satellite 302 and a gateway station (NTN gateway) 303.

[0129] The NR Uu interface information of the cell of the gNB 304 can be forwarded to the UE 301 through the transparent satellite 302. The information transmitted between the transparent satellite 302 and the gNB 304 can be forwarded through the gateway station (NTN gateway) 303.

[0130] The gNB 304 and the 5G core network 305 can communicate through the NG interface.

[0131] The 5G core network 305 can be in communication with a data network 306, e.g., the Internet. The 5G core network 305 can be in direct communication with the data network 306, or can communicate via a 5G access and mobility management function (AMF) 310. The 5G core network 305 can include, or can be known as, a next generation core (NGC).

[0132] The remote radio unit and the gNB 304 can each belong to a next generation radio access network (NG-RAN).

[0133] The regenerative satellite can have the processing function of the base station. The regenerative satellite can be referred to as a regenerative satellite for short.

[0134] According to the regenerative mode, the regenerative satellite can include a regenerative satellite without an inter-satellite link (ISL) or a regenerative satellite with an inter-satellite link.

[0135] The regenerative satellite without the inter-satellite link does not have an inter-satellite link between the regenerative satellites.

[0136] The regenerative satellite with the inter-satellite link has an interface between the regenerative satellites with the inter-satellite link to realize data interaction between the regenerative satellites with the inter-satellite link through the interface. The interface between the regenerative satellites with the inter-satellite link can be an Xn interface. The regenerative satellite with the inter-satellite link has the distributed unit (DU) processing function of the base station, and therefore, the regenerative satellite with the inter-satellite link can serve as a DU. The communication system architecture related to the regenerative satellite can be referred to FIG. 4.

[0137] FIG. 4 shows a communication system architecture related to a regenerative satellite according to an embodiment of the present application.

[0138] Still taking the 5G network as an example, as shown in FIG. 4, the architecture related to the regenerative satellite can include a UE 401, a regenerative satellite 402, a gateway station 403, a 5G core network 404, a data network 405, a UE 406, a regenerative satellite 407, a gateway station 408, a 5G core network 409, and a data network 510.

[0139] The UE 401 and the regenerative satellite 402 can communicate through an NR Uu interface, that is, the NR Uu interface information generated by the regenerative satellite 402 is directly sent to the UE 401.

[0140] The NG interface communication between the regenerative satellite 402 and the 5G core network 404 can be implemented through a satellite radio interface (SRI) between the regenerative satellite 402 and the gateway station 403, and a wired link between the gateway station 403 and the 5G core network 404, that is, NG over SRI.

[0141] Optionally, the NG interface communication between the regenerative satellite 402 and the 5G core network 404 can also be implemented through a feeder link between the regenerative satellite 402 and the gateway station 403, and a wired link between the gateway station 403 and the 5G core network 404.

[0142] The 5G core network 404 and the data network 405 can communicate through an N6 interface.

[0143] The communication principles between the UE 406 and the regenerative satellite 407, between the regenerative satellite 407 and the 5G core network 409, and between the 5G core network 409 and the data network 510 can refer to the corresponding communication principles in the communication link composed of the UE 401, the regenerative satellite 402, the gateway station 403, the 5G core network 404, and the data network 405, and will not be described here.

[0144] The Xn interface between regenerative satellites with inter-satellite links is the Xn interface shown in FIG. 4.

[0145] In the case of the regenerative satellite 402 and / or the regenerative satellite 407 being a regenerative satellite without an inter-satellite link, there is no inter-satellite link between the regenerative satellite 402 and the regenerative satellite 407, that is, no Xn interface.

[0146] In the case of the regenerative satellite 402 and the regenerative satellite 407 both being regenerative satellites with inter-satellite links, there is an inter-satellite link between the regenerative satellite 402 and the regenerative satellite 407, that is, there is an Xn interface. The regenerative satellite 402 and the regenerative satellite 407 can communicate through the Xn interface. The Xn interface communication between the regenerative satellite 402 and the regenerative satellite 407 can be implemented through an inter-satellite link between the regenerative satellite 402 and the regenerative satellite 407, that is, Xn (over ISL).

[0147] 3. Scenario of co-deployment of NTN and TN

[0148] The scenario of co-deployment of NTN and TN can be understood as a scenario in which a non-terrestrial network and a terrestrial network are co-deployed in a geographical area, or can be understood as a scenario in which a non-terrestrial network and a non-terrestrial network are simultaneously present around a geographical area.

[0149] FIG. 5 shows a schematic diagram of a scenario of co-deployment of NTN and TN according to an embodiment of the present application.

[0150] As shown in FIG. 5, the scenario can include a satellite 501 and at least one base station deployed on the ground. The at least one base station deployed on the ground, for example, base station 502, base station 503, base station 504 and base station 505 in FIG. 5. It should be understood that the satellite 501 is a non-terrestrial device in a non-terrestrial network. Each of the at least one base station deployed on the ground is a device in a terrestrial network.

[0151] Each of the at least one base station can include a plurality of TN cells. The TN cell, for example, TN cell 507 in FIG. 5.

[0152] The geographical area covered by the satellite 501, for example, area 506 in FIG. 5.

[0153] The geographical area covered by the satellite 501 (such as area 506) is large, and the area 506 can include a plurality of TN cells 507. The plurality of TN cells 507 can include at least two TN cells with the same PCI. The at least two TN cells with the same PCI, for example, two TN cells 507 with PCI #2 (PCI: #2) shown in FIG. 5.

[0154] During the movement of the satellite 501, a UE in the area 506 can be handed over from a cell of the satellite 501 to a TN cell 507, i.e., the UE can be handed over from an NTN cell to a TN cell. It can be understood that the cell of the satellite can be referred to as an NTN cell.

[0155] In the embodiments of the present application, the source network can include a source access network and a source core network. The target network can include a target access network and a target core network. The source access network can include a source access network device or a source access network network element. The target access network can include a target access network device or a target access network network element. The source network can be an NTN network, and the target network can be a TN network.

[0156] In a possible implementation, the handover procedure of the NTN cell to the TN cell can include a handover preparation procedure and a handover execution procedure. The handover preparation procedure can be referred to FIG. 6, and the handover execution procedure can be referred to FIG. 7.

[0157] FIG. 6 shows a schematic diagram of a handover preparation procedure according to an embodiment of the present application.

[0158] As shown in Figure 6, the source access network equipment can be a source base station. A source base station, for example, is a source next-generation radio access network (S-NG-RAN) device. When the source network is an NTN network, the source base station can be a non-terrestrial device in the regenerating satellite network, such as satellite 501, or a terrestrial base station providing cell information to non-terrestrial devices in the transparent network. The cell of the source base station can be called the source cell or the old cell. A non-terrestrial device in the transparent network, for example, is satellite 302 in Figure 3.

[0159] The source core network may include source AMF network elements (S-AMF), SMF network elements, source UPF network elements (S-UPF), and / or UPF (PSA) network elements. PSA stands for Session Anchor (PDU). The UPF (PSA) network element can be a relay station between the source base station and the source UPF network element in the source access network, or it can be a relay station between the source base station and the PSA in the source core network.

[0160] The target access network equipment can be a target base station. A target base station may be, for example, a target next-generation radio access network (T-NG-RAN) device. In the case of a TN network, the target base station can be a terrestrial base station, such as base station 502, base station 503, base station 504, or base station 505. The cell of the target base station can be called a target cell or a new cell. The target core network may include target AMF network elements (T-AMF), SMF network elements, and target UPF network elements (T-UPF).

[0161] When a UE accesses the source network, the UE can transmit uplink user plane data to the source core network through the source base station, and the source core network can transmit downlink user plane data to the UE through the source base station.

[0162] Within a preset time period before the source base station (satellite 501 in Figure 5) leaves the geographical area to which the UE belongs (area 506 in Figure 5), the source base station can make a handover decision, such as deciding to trigger a cell handover. If the source base station decides to trigger a cell handover via the N2 interface, it can prepare for the handover according to the process shown in Figure 6, negotiating with the target base station to prepare handover-related configurations and parameters, so that the target base station can perform verification and availability checks to determine and serve the UE handover from the source cell to the target cell.

[0163] As shown in Figure 6, the handover preparation process may include:

[0164] S601. The source base station sends a handover request (or handover required) to the source AMF network element to request the target base station to allocate resources for the UE in the target cell. Correspondingly, the source AMF network element receives the handover request from the source base station.

[0165] A handover request may include the identifier of the target base station and the identifier of the target cell.

[0166] S602. The source AMF network element selects the target AMF network element. For example, the source AMF network element can determine the target AMF network element corresponding to the target base station based on the identifier of the target base station.

[0167] S603. The source AMF network element sends a UE context creation request to the target AMF network element. Correspondingly, the target AMF network element can receive the UE context creation request from the source AMF network element.

[0168] S604, the source core network and the target core network interact to realize the context update of relevant protocol data unit (PDU) sessions, N4 session modification and N4 session establishment.

[0169] The source AMF and the target AMF can be the same AMF network element. The source core network and the target core network can be the same core network.

[0170] S605 monitors the PDU session handover response of the target AMF network element and the target UPF network element.

[0171] S606. The target AMF network element can send a handover request to the target base station. Correspondingly, the target base station receives the handover request from the target AMF network element.

[0172] The target base station can check whether the target cell has sufficient resources to accept the UE. If it is determined that the target cell has sufficient resources to accept the UE, i.e., handover is allowed, the target base station can allocate radio resources, including temporary identifiers, to the UE in the target cell.

[0173] S607. The target base station may send a handover request acknowledgement to the target AMF network element to confirm that the handover preparation of the target base station is successful and to notify the target core network that it can accept the handover. Correspondingly, the target AMF network element receives the handover request acknowledgement from the target base station.

[0174] S608, the source core network and the target core network interact to realize the context update of relevant PDU sessions and the modification of N4 sessions.

[0175] S609. The target AMF network element can send a UE context creation response to the source AMF network element, so as to enable the target core network to notify the source core network that the target core network can accept the UE for cell handover. Correspondingly, the source AMF network element can receive the UE context creation response from the target AMF network element.

[0176] As shown in Figure 6, the source base station sends a handover request to the target base station through the source core network and the target core network, requesting the target base station to provide a connection for the UE. Upon receiving the handover request, the target base station determines that handover is permitted and allocates radio resources for the UE in the target cell. With the target base station permitting cell handover, the target core network can perform context updates for the PDU session and N4 session modifications to facilitate data transmission and processing after successful cell handover. After completing the handover preparation process as shown in Figure 6, the UE can interact with the source and target networks as shown in Figure 7 to achieve handover from the source cell to the target cell.

[0177] Figure 7 shows a schematic diagram of a switching execution flow provided in an embodiment of this application.

[0178] As shown in Figure 7, the switching execution process may include:

[0179] S701, the source AMF network element can send a handover command to the source base station. Correspondingly, the source base station can receive the handover command from the source AMF network element.

[0180] The handover command may include the target base station's configuration information, such as the radio resources allocated by the target base station to the UE in the target cell.

[0181] S702. The source base station can send a handover command to the UE. Correspondingly, the UE can receive the handover command from the source base station.

[0182] Upon receiving a handover command, the UE can disconnect its radio resource control (RRC) connection with the source base station. The UE can then synchronize with the target cell (the new cell) in the target base station for time and frequency synchronization. The UE can then establish an RRC connection with the target cell. In this way, during the handover process, the UE first disconnects its RRC connection with the source cell and then establishes an RRC connection with the target cell, reducing conflicts and interference during cell handover and enabling the UE to access the target cell.

[0183] When the UE accesses the target cell, the UE can execute S704.

[0184] Optionally, when the source base station sends a handover instruction to the UE, the source base station may execute S702a.

[0185] S702a. The source base station can transmit information indicating the uplink RAN ​​status to the source AMF network element. Correspondingly, the source AMF network element can receive information indicating the uplink RAN ​​status from the source base station.

[0186] S702b, the source AMF network element and the target AMF network element transmit N1N2 messages.

[0187] S702c: The target AMF network element can transmit information indicating the downlink RAN ​​status to the target base station. Correspondingly, the target base station can receive information indicating the downlink RAN ​​status from the target AMF network element.

[0188] Before the UE synchronizes with the target cell, the source core network can continue to transmit downlink user plane data to the source base station. Correspondingly, the source base station can receive downlink user plane data from the source core network. Since the UE disconnects its RRC connection with the source base station before accessing the target cell, the downlink user plane data from the source core network cannot be transmitted to the UE through the source base station. Therefore, the source base station can forward the received downlink user plane data to the target base station via the direct data forwarding method shown in S703a or the indirect data forwarding method shown in S703b, so that the downlink user plane data from the source core network can be transmitted to the UE through the target base station after the UE accesses the target cell.

[0189] S703a: The source base station can forward the received downlink user plane data to the target base station via direct data forwarding. Correspondingly, the target base station can receive the downlink user plane data received by the source base station.

[0190] S703b: The source base station can forward the received downlink user plane data to the target base station via indirect data forwarding. Correspondingly, the target base station can receive the downlink user plane data received by the source base station.

[0191] The source base station forwards the received downlink user plane data to the target base station through indirect data forwarding. For example, the source base station can forward the received downlink user plane data to the target base station through the source UPF network element and the target UPF network element.

[0192] S704. The UE can send a handover confirmation to the target base station, indicating that the UE has accessed the target cell of the target base station. Correspondingly, the target base station can receive the handover confirmation from the UE.

[0193] When the target base station receives a handover confirmation from the UE, it can transmit downlink user plane data from the source base station to the UE, such as the downlink user plane data forwarded by the source base station as shown in S703a or S703b. The handover confirmation can be an RRC reconfiguration complete message sent via the dedicated control channel (DCCH).

[0194] When a UE accesses a target cell, the UE can transmit uplink user plane data to the target core network through the target base station.

[0195] S705. The target base station can send a handover notification to the target AMF network element to inform the target core network UE that it has accessed the target network's cell. Correspondingly, the target AMF network element can receive the handover notification from the target base station.

[0196] S706, the target core network and the source core network interact to realize the context release of relevant PDU sessions, the context update of PDU sessions, and the modification of N4 sessions.

[0197] The target core network can transmit downlink user plane data to the UE through the target base station.

[0198] S707 and UE can execute the registration process.

[0199] S708a. Once the registration process is complete, the SMF network element can send an N4 session release request to the source UPF network element. Correspondingly, the source UPF network element can receive an N4 session release request from the SMF network element.

[0200] S708a. The source UPF network element can send an N4 session release response to the SMF network element. Correspondingly, the SMF network element can receive an N4 session release response from the source UPF network element.

[0201] S709a. Upon completion of the registration process, the source AMF network element can send a UE context release command to the source base station. Correspondingly, the source base station can receive the UE context release command from the source AMF network element.

[0202] S709a. The source base station can send a response to the source AMF network element indicating that the UE context release is complete. Correspondingly, the source AMF network element can receive the response from the source base station indicating that the UE context release is complete.

[0203] S710a. Once the registration process is complete, the SMF network element can send an N4 session modification request to the target UPF network element. Correspondingly, the target UPF network element can receive the N4 session modification request from the SMF network element.

[0204] S710a. The target UPF network element can send an N4 session modification response to the SMF network element. Correspondingly, the SMF network element can receive the N4 session modification response from the target UPF network element.

[0205] Through the interaction process shown in Figure 7, the UE can switch from the source cell to the target cell.

[0206] As shown in Figures 6 and 7, the source base station negotiates and prepares with the target base station through the source core network and the target core network, as shown in Figure 6. After confirming that the target base station can accept the UE handover and provide services to the UE, the UE hands over from the source cell to the target cell through the handover execution process shown in Figure 7. The entire process involves many interactions and a long handover time, affecting handover performance, and may even lead to handover failure. In addition, for the UE handover from NTN to TN scenarios, before S601, since there may be multiple ground base stations with the same PCI under the coverage of the source base station, the source base station will notify the UE to read the information carried in the system message broadcast by the target cell to obtain the target base station identifier. This process takes a long time, resulting in a long handover process and affecting handover performance. In particular, there may be multiple ground base stations with the same PCI under the coverage of the source base station. For example, there may be at least two TN cells with the same PCI in the geographical area covered by the source base station, and the base stations of these at least two TN cells are different.

[0207] In view of this, embodiments of this application provide a cell handover method. A terminal device can receive information from a first cell instructing it to perform a cell handover. The terminal device can send a message to a second cell requesting the establishment of an RRC connection via a common control channel. Sending this message to the second cell via the common control channel allows the terminal device to access the second cell in a manner similar to initiating an RRC connection in the Radio Resource Control (RRC) idle state (RRC_IDLE) or initiating an RRC connection recovery manner similar to initiating an RRC connection in the Radio Resource Control (RRC_INACTIVE) inactive state. This allows the terminal device to access the second cell without a handover preparation process or obtaining the base station identifier of the target cell when it needs to hand over from the first cell to the second cell, reducing interaction processes or steps and thus reducing handover time.

[0208] The cell handover method provided in this application will be described in detail below with reference to Figures 8 to 15. The embodiments shown in this application illustrate the cell handover method provided in this application from the perspective of device interaction. The specific form and number of each device shown are merely examples and should not constitute any limitation on the implementation of the method provided in this application.

[0209] It should be understood that the terminal device can be the terminal device itself, or a chip, chip system or processor that supports the terminal device in implementing the cell handover method, or a logic module or software that can implement all or part of the terminal device; the network device (such as the source base station or the target base station) can be the network device itself, or a chip, chip system or processor that supports the network device in implementing the cell handover method, or a logic module or software that can implement all or part of the network device, and this application does not make specific limitations in this regard.

[0210] Figure 8 shows a flowchart of a cell handover method provided in an embodiment of this application.

[0211] As shown in Figure 8, the cell handover method provided in this application embodiment may include S801-S802.

[0212] S801, the first cell can send first information to the terminal device. The first information is used to instruct the terminal device to perform a cell handover. Correspondingly, the terminal device can receive the first information from the first cell.

[0213] For example, the first information may be a handover command. The first information does not carry configuration information for the second cell. Configuration information for the second cell may include time-frequency domain resources, RRC layer configuration information, packet data convergence protocol (PDCP) layer configuration information, radio link control (RLC) layer configuration information, media access control (MAC) layer configuration information, and / or physical layer configuration information, etc. For instance, the source base station corresponding to the first cell will not send a handover request to the target base station corresponding to the second cell, and the target base station corresponding to the second cell will not send the second cell's configuration information to the source base station.

[0214] After receiving the first information, the terminal device does not immediately disconnect from the first cell. Thus, even if the terminal device receives a handover command that does not carry configuration information for the second cell, it can continue to maintain its connection with the first cell. Compared to the embodiment shown in Figure 7, where the UE disconnects from the source cell upon receiving a handover command, causing a delay in data transmission (such as downlink user plane data) between the UE and the source network, the cell handover method provided in this application maintains communication between the terminal device and the first cell upon receiving the handover command, thereby reducing the probability of data transmission delays between the terminal device and the source network.

[0215] It is understandable that the first cell can be the cell of the source base station, and the second cell can be the cell of the target base station. The first cell sending the first information to the terminal device can be understood as the source base station sending the first information to the terminal device. The terminal device receiving the first information from the first cell can be understood as the terminal device receiving the first information from the source base station.

[0216] For example, taking satellite 501 as the source base station and base station 502 as the target base station as shown in Figure 5, the first cell can be the cell of satellite 501 and the second cell can be the cell of base station 502.

[0217] The first cell can send the first information to the terminal device at the first moment. Taking the moment when satellite 501 leaves the geographical area of ​​the terminal device as the second moment as an example, the first moment is the moment before the second moment, and the duration between the first moment and the second moment can be a preset duration.

[0218] Optionally, the first cell may send first information to the terminal device when the signal quality of the signal transmitted by the receiving terminal device is less than or equal to a first quality threshold, and / or when the measured downlink signal quality of the first cell transmitted by the receiving terminal device is less than or equal to the first quality threshold, and / or when the measured downlink signal quality of the neighboring cells of the first cell transmitted by the receiving terminal device is higher than the first quality threshold. If the signal quality of the signal transmitted by the receiving terminal device is less than or equal to the first quality threshold, and / or the measured downlink signal quality of the first cell transmitted by the receiving terminal device is less than or equal to the first quality threshold, and / or the measured downlink signal quality of the neighboring cells of the first cell transmitted by the receiving terminal device is higher than the first quality threshold, it may indicate that the source base station will leave the geographical area to which the terminal device belongs.

[0219] It is understandable that the first quality threshold can be predefined by the source base station.

[0220] After receiving the first information, the terminal device can perform cell handover in two ways.

[0221] Method 1: The terminal device immediately performs cell handover.

[0222] Method 2: The terminal device determines whether to perform cell handover based on the first condition. Optionally, the first information may carry configuration information of the first condition for the terminal device to perform cell handover.

[0223] The first condition includes one or more of the following:

[0224] The downlink signal quality of the first cell measured by the terminal device is less than or equal to the first quality threshold;

[0225] The downlink signal quality of the neighboring cells of the first cell measured by the terminal device is higher than the first quality threshold;

[0226] The downlink signal quality of the neighboring cells of the first cell measured by the terminal device is higher than the second quality threshold, and the downlink signal quality of the first cell measured is less than or equal to the third quality threshold.

[0227] The difference between the downlink signal quality of the neighboring cells of the first cell measured by the terminal equipment and the downlink signal quality of the first cell measured by the terminal equipment is greater than or equal to the fourth quality threshold.

[0228] It should be understood that in Method 2, the terminal device does not immediately perform cell handover after receiving the first information, but performs cell handover after the first condition is met.

[0229] The second, third, and fourth quality thresholds can all be predefined by the terminal device or agreed upon in advance by the terminal device and the base station (such as the source base station).

[0230] Optionally, after receiving the first information, the terminal device's access stratum (AS) can send a fifth indication message to the upper layer, indicating that the terminal device can access the second cell using the cell handover method provided in this application. The upper layer is, for example, a non-access stratum (NAS). Correspondingly, the upper layer of the terminal device can receive the fifth indication message from the terminal device's AS layer. The upper layer of the terminal device can send a trigger request to the terminal device's AS layer to trigger step S802.

[0231] Optionally, after receiving the first information, the AS layer of the terminal device can trigger step S802.

[0232] S802. The terminal device can send a first message to the second cell via the common control channel (CCCH). This first message is used to request the establishment of a Radio Resource Control (RRC) connection. Correspondingly, the second cell can receive the first message from the terminal device.

[0233] For example, the terminal device can send a first message to the second cell via the uplink common control channel (UL-CCCH). The UL-CCCH can also be referred to as the common control channel in the uplink. The first message can be an RRC connection request or an RRC resume request.

[0234] For example, in one possible scenario, the terminal device is in the RRC_INACTIVE state for the target base station or the second cell. The terminal device in the RRC_INACTIVE state can retain the context of some access network devices (such as the target base station or the second cell). Correspondingly, the target core network to which the target base station belongs can also retain the context of the terminal device. Upon receiving the first information, the terminal device in the RRC_INACTIVE state can send an RRC recovery request to the second cell through the common control channel to achieve rapid access to the second cell.

[0235] In another possible scenario, the terminal device is in the RRC_IDLE state for the target base station or the second cell. Upon receiving the first information, the terminal device can send an RRC establishment request to the second cell via the common control channel to achieve rapid access to the second cell.

[0236] Optionally, regardless of its state, upon receiving the first information, the terminal device can send an RRC establishment request to the second cell via the common control channel to achieve rapid access to the second cell.

[0237] Optionally, before sending the first message, the terminal device may first perform a random access procedure with the second cell. The random access procedure can be understood as a contention-based random access procedure.

[0238] For example, the terminal device can perform the following four-step random access process:

[0239] The terminal device can send a random access preamble to the second cell. The random access preamble can be used to convey the terminal device's random access request to the second cell, enabling the second cell to estimate the transmission delay between itself and the terminal device. This allows access network equipment (such as the base station to which the second cell belongs or the target base station) to calibrate uplink timing based on the random access preamble. The target base station can transmit a timing advance command to the terminal device. The timing advance command can carry calibration information, such as the calibrated uplink timing.

[0240] The second cell can send a random access response (RAR) to the terminal device. Correspondingly, the terminal device can receive the RAR sent by the second cell. For example, the terminal device can use the random access radio network temporary identifier (RA-RNTI) to monitor the physical downlink control channel (PDCCH). If the terminal device receives its own scheduling information, such as downlink control information (DCI), it can receive the RAR message from the network device (such as the target base station) on the physical downlink shared channel (PDSCH) based on the DCI information.

[0241] The DCI information may include resource block (RB) allocation information and modulation and coding scheme (MCS) related content. The RAR may include uplink timing advance, uplink grant (UL grant) allocated for the next uplink message, and temporary cell radio network temporary identifier (temporary C-RNTI) allocated by the network side.

[0242] The terminal device can send a scheduled transmission-based message (such as a first message) to the second cell. For example, the terminal device sends the first message to the network device via the physical uplink shared channel (PUSCH) based on the uplink grant and uplink timing advance information in the RAR. Correspondingly, the second cell can receive the first message from the terminal device. Optionally, the first message may include the contention resolution identifier of the terminal device, so that after receiving the contention resolution message, the terminal device can determine that it randomly accesses the second cell based on the fact that the contention resolution identifier contained in the contention resolution message is the same as the contention resolution identifier of the terminal device.

[0243] The second cell can send a contention resolution message to the terminal device. Correspondingly, the terminal device can receive the contention resolution message sent by the second cell. The contention resolution message may include part or all of the content of the first message.

[0244] It should be understood that when multiple terminal devices initiate random access using the same preamble, contention occurs. At most one terminal device can successfully access the network among those competing for the same resources. Once that terminal device successfully accesses the network, the second cell can send a contention resolution message to that terminal device via the PDSCH.

[0245] For example, after sending the first message, the terminal device can start a contention resolution timer and monitor the PDCCH based on the temporary cell radio network temporary identifier (TRANTI) indicated in the RAR. If the terminal device receives a contention resolution message from the second cell before the contention resolution timer expires, the random access procedure is considered successful.

[0246] C-RNTI stands for Cell Radio Network Temporary Identifier.

[0247] Optionally, the terminal device may perform the following two-step random access process:

[0248] The terminal device can send message A (MsgA) to network devices (such as the target base station or a second cell). Correspondingly, the second cell can receive MsgA from the terminal device.

[0249] Message A may include a random access signal and a first message. The random access signal may include a preamble and / or a demodulation reference signal (DMRS). The random access signal can be used for receiving payload data. For example, the random access signal can be used to determine the transmission boundaries of the payload data or for demodulation. The transmission boundaries of the payload data include, for example, the start and end positions of the time slots used to transmit the payload data.

[0250] The second cell can send message B (MsgB) to the terminal device. Correspondingly, the terminal device can receive message B from the second cell.

[0251] Message B can be used to carry a response message for random access signals and payload data. This response message can include at least one of the following: temporary C-RNTI information, timing advance command (TA) information, uplink grant information, and contention resolution ID information. The contention resolution ID can be part or all of the content of the first message. Optionally, the response message may also include an RRC setup message or an RRC resume message.

[0252] Before the terminal device sends the first message, the terminal device first performs a random access procedure to the second cell. If the terminal device successfully accesses the second cell, it does not need to execute S802, that is, it does not need to send the first message to the second cell through the common control channel.

[0253] Before the terminal device sends the first message, the terminal device first performs a random access procedure with the second cell. If the random access fails, the terminal device can execute S802.

[0254] It should be noted that the terminal device accesses the second cell in a manner similar to initiating an RRC connection in the Radio Resource Control (RRC) idle state (RRC_IDLE) or initiating an RRC connection recovery in a manner similar to initiating an RRC connection recovery in the Radio Resource Control (RRC_INACTIVE) inactive state. That is, the terminal device sends a message to the second cell through the common control channel to request the establishment of an RRC connection.

[0255] The first information may indicate the second cell. Alternatively, the first information may not indicate the second cell.

[0256] Taking the example of how the first piece of information can indicate the second cell.

[0257] For example, the first information may include a first cell list. The first cell list may include one or more cells, among which a second cell is included. For instance, the first cell list may include the identifiers of each cell in the one or more cells. Optionally, the first cell list may be determined based on a first public land mobile network (PLMN) list.

[0258] Alternatively, the first information may include a first PLMN list or a second PLMN list. The cells indicated by the first PLMN list include second cells. The cells indicated by the second PLMN list include second cells.

[0259] Both the first PLMN list and the second PLMN list can include PLMNs supported by the terminal device. PLMNs supported by the terminal device can include PLMNs that support the cell handover method provided in this application embodiment. PLMNs supporting the cell handover method provided in this application embodiment can be understood as PLMNs that the terminal device supports executing the cell handover method provided in this application embodiment between cells within these PLMNs and between cells between these PLMNs. The first PLMN list can be obtained from the source core network by the source base station corresponding to the first cell. Both the first PLMN list and the second PLMN list can include the identifiers of each PLMN in one or more PLMNs. The PLMN identifier may be, for example, a PLMN identifier (public land mobile network identifier).

[0260] The second PLMN list can be obtained from the source core network by the source base station corresponding to the first cell. The second PLMN list can also be determined by the source core network based on the first PLMN list and the measurement results obtained from the source base station for the corresponding cells. The measurement results can include the downlink signal quality of neighboring cells of the first cell measured by the terminal equipment.

[0261] If the first information received by the terminal device includes a cell identifier, the terminal device can send a first message to the cell corresponding to that cell identifier via the common control channel. It should be understood that the cell corresponding to that cell identifier is the second cell.

[0262] If the first information received by the terminal device includes the identifiers of each cell among multiple cells, the terminal device can select one of these cells as the second cell. For example, it can select the second cell with the highest signal quality strength or the highest priority, or randomly select a cell as the second cell. The terminal device can send the first message to the second cell through the common control channel.

[0263] If the first information received by the terminal device includes a first PLMN list or a second PLMN list, the terminal device can send a first message to the cell corresponding to a PLMN via the common control channel. It should be understood that the cell corresponding to this PLMN is the second cell. Optionally, the terminal device can select the PLMN with the highest signal quality strength or the highest priority from multiple PLMNs, or randomly select a PLMN. The terminal device can then send the first message to the second cell corresponding to the selected PLMN via the common control channel.

[0264] Taking the example that the first information may not indicate the second cell.

[0265] For example, upon receiving the first information, the terminal device can select the neighboring cell with the highest signal quality strength from the measurement results of each of the one or more neighboring cells, i.e., the second cell. The terminal device can then send the first message to this second cell via a common control channel.

[0266] Alternatively, if the terminal device receives the first information, and the first information does not indicate a second cell, the terminal device may randomly select one of one or more neighboring cells as the second cell. The terminal device may then send a first message to this second cell via a common control channel.

[0267] Understandably, an increasing number of terminal devices support the installation of dual Universal Subscriber Identity Modules (USIMs). Taking a terminal device supporting two Subscriber Identity Module (SIM) cards as an example, there are several possible implementation methods, such as dual SIM single standby (DSSS) mode, dual SIM dual standby (DSDS) mode, or dual SIM dual active (DSDA) mode.

[0268] DSSS indicates that although the terminal device has two SIM cards, it can only be active in the communication system of one SIM card at a time. Users can choose to be active in different SIM card communication systems at different times. DSDS indicates that the terminal device can be active in the communication systems of two SIM cards simultaneously, but only one SIM card's communication system can be in communication mode at a time. For example, when using one SIM card for internet access, the other SIM card cannot be used to answer phone calls. DSDA indicates that the terminal device can not only be active in multiple SIM card communication systems simultaneously, but also communicate in multiple SIM card communication systems simultaneously. For example, when using one SIM card for internet access, another SIM card can be used to answer phone calls.

[0269] In this embodiment, the terminal device can be a terminal device with one SIM card installed, meaning it supports one user identity. Alternatively, the terminal device can be a terminal device with two SIM cards installed, meaning it supports two user identities. It is understood that there is a one-to-one correspondence between the SIM card and the user identity.

[0270] Taking a terminal device supporting two user identities as an example, these two user identities are referred to as the first user identity and the second user identity, respectively. The first user identity can be understood as the user identity that the terminal device has after installing SIM card 1, and the second user identity can be understood as the user identity that the terminal device has after installing SIM card 2.

[0271] In other possible embodiments of this application, if the terminal device has two or more SIM cards installed, then the terminal device also supports two or more user identities. For example, the terminal device supports three, four or more user identities and can register in two or more networks, wherein each user identity can be registered in one network.

[0272] This application describes embodiments based on a terminal device supporting two user identities. When a terminal device supports more than two user identities, its specific implementation can refer to the relevant description of a terminal device supporting two user identities, which may require some simple adaptation, but it is still within the protection scope of this application. Specifically, when the terminal device's user identity is the first user identity, from the network device's perspective, the terminal device can be understood as one user (from the protocol's perspective, it is one terminal device, for example, referred to as the first user); when the terminal device's user identity is the second user identity, from the network device's perspective, the terminal device can be understood as yet another user (for example, referred to as the second user). The terminal device can register as the first user identity on a first network and as the second user identity on a second network. In this application embodiment, the terminal device supporting one user identity can also be described as the terminal device having one user identity. Similarly, the terminal device supporting two user identities can also be described as the terminal device having two user identities. In this embodiment of the application, the terminal device may receive first information as a first user (i.e., the terminal device accesses the source base station as a first user and interacts with the source core network through the source base station as a first user), and send the first message as a second user (i.e., the terminal device accesses the target base station as a second user and interacts with the target core network through the target base station as a second user), or the terminal device may receive first information as a first user and send the first message as a first user.

[0273] As shown in Figure 8, in the cell handover method, when the terminal device receives the first information from the first cell, it can send a first message (such as an RRC establishment request) to the second cell via the common control channel (CCCH). This allows the terminal device to access the second cell either by initiating an RRC connection in a manner similar to the RRC_IDLE state or by initiating an RRC connection recovery in a manner similar to the Radio Resource Control inactive state (RRC_INACTIVE). This allows the terminal device to access the second cell without going through a handover preparation process or obtaining the base station identifier of the target cell when it needs to hand over from the first cell. This reduces the interaction process or steps, thereby reducing handover time.

[0274] Furthermore, the terminal device can access the second cell in a manner similar to initiating an RRC connection in the RRC_IDLE state. This means the terminal device can access the second cell from the RRC_IDLE state without affecting the connection between the terminal device and the first cell. Alternatively, the terminal device can access the second cell in a manner similar to initiating an RRC connection recovery in the RRC_INACTIVE state. This also means the terminal device can access the second cell from the RRC_INACTIVE state without affecting the connection between the terminal device and the first cell. In other words, the terminal device can maintain connection and communication with the first cell during and after accessing the second cell, thus reducing the impact on the transmission of downlink user plane data sent by the source core network. Compared to the cell handover process shown in Figures 6 and 7, where the UE disconnects from the source base station before accessing the target cell, and the downlink user plane data received by the source base station before the UE accesses the target cell needs to be forwarded to the UE by the target base station after the UE accesses the target cell, resulting in a longer data packet transmission delay between the UE and the source core network. In the cell handover method shown in Figure 8, the terminal device can still maintain connection and communication with the first cell during the process of accessing the second cell and after accessing the second cell, which can reduce the probability of data or data packet transmission delay between the UE and the source core network.

[0275] The cell handover methods shown in S801-S802 will be explained below with reference to Figures 9-13.

[0276] Figure 9 shows another flowchart of the cell handover method provided in the embodiments of this application.

[0277] It is understood that the source network can include the source base station (S-RAN) and source core network as shown in Figure 9. The source core network can include source AMF network elements (S-AMF), source SMF network elements (S-SMF), and source UPF network elements (S-UPF(PSA)). The target network can include the target base station (T-RAN) and target core network. The target core network can include target AMF network elements (T-AMF) and target UPF network elements (T-UPF). The source AMF and target AMF can be the same AMF network element or different AMF network elements. The source UPF and target UPF can be the same UPF network element or different UPF network elements. The source core network and target core network can be the same core network or different core networks.

[0278] Taking the terminal device as a UE as an example, as shown in Figure 9, the cell handover method may include:

[0279] S901, Terminal devices can access the source network.

[0280] When a terminal device is connected to the source network, the terminal device can transmit uplink user plane data to the source core network through the source base station, and the source core network can transmit downlink user plane data to the terminal device through the source base station.

[0281] S902a: The terminal device can send sixth information to the source base station. The sixth information may include measurement results, thus enabling the terminal device to report measurement results to the source base station. Correspondingly, the source base station can receive the sixth information from the terminal device.

[0282] For example, taking a first cell as the source base station where the terminal device accesses the source network and the cell providing services to the terminal device is the source base station, the terminal device can send sixth information to the first cell. Correspondingly, the first cell can receive the sixth information from the terminal device.

[0283] It should be understood that when a terminal device accesses the source network, and the cell providing services to the terminal device is the first cell of the source base station, the terminal device sends information to the source base station, that is, it sends information to the first cell. The terminal device also receives information from the source base station, that is, it receives information from the first cell.

[0284] In one embodiment of this application, the sixth information may include the measurement results of at least one neighboring cell.

[0285] For example, the terminal device can perform neighbor cell measurements at a preset frequency or according to the measurement configuration configured by the source base station to obtain measurement results for at least one neighbor cell. The terminal device can then send sixth information containing the measurement results of at least one neighbor cell to the source base station.

[0286] Neighbor cell measurement can be understood as measuring the signal quality and / or strength of neighboring cells.

[0287] Optionally, when the signal quality of the first cell degrades to a fifth quality threshold, the terminal device may perform neighbor cell measurements to obtain measurement results for at least one neighbor cell. The terminal device may then send sixth information containing the measurement results of at least one neighbor cell to the source base station.

[0288] Upon receiving sixth information containing measurement results of at least one neighboring cell, the source base station may send seventh information to the source core network. The seventh information may include the identifiers of each neighboring cell in the at least one neighboring cell and / or the PLMN identifiers corresponding to each neighboring cell in the at least one neighboring cell. The seventh information is used to request confirmation as to whether each neighboring cell in the at least one neighboring cell supports the cell handover method provided in this application embodiment. Correspondingly, the source core network may receive the seventh information from the source base station. The source core network may send eighth information or first information to the source base station. Both the eighth information and the first information may include a second PLMN list. The second PLMN list contains the PLMN identifiers corresponding to each cell in the at least one cell. The cells included in the second PLMN list may be cells selected by the source core network from the at least one neighboring cell in the seventh information that support the cell handover method provided in this application embodiment. That is, the cells included in the second PLMN list may be determined by the source core network based on the seventh information. The second PLMN list may be the intersection of the first PLMN list and the seventh information. The cells included in the second PLMN list are some or all of the cells in the at least one neighboring cell of the seventh information.

[0289] Understandably, the fifth quality threshold can be predefined by the terminal device.

[0290] In one embodiment of this application, the sixth information may include the measurement results of the cells corresponding to each frequency point in at least one frequency point of the measurement configuration.

[0291] For example, before the terminal device sends the sixth information to the source base station, the source base station may send a measurement configuration to the terminal device. Correspondingly, the terminal device may receive the measurement configuration from the source base station. The measurement configuration may include frequency point information for at least one frequency point and / or reporting conditions. The reporting conditions may be the first condition mentioned above.

[0292] Upon receiving a measurement configuration, the terminal device can perform frequency point measurements on the frequencies specified in the configuration and obtain the measurement results for each frequency point. These frequency point measurements may include signal strength, signal quality, and / or interference levels at the measured frequency point. Since each frequency point corresponds to a cell, the terminal device can obtain the measurement results for the cell corresponding to each frequency point.

[0293] The terminal device can send sixth information to the source base station. This sixth information contains the measurement results of the corresponding cells for each frequency point that meet the reporting conditions in the measurement configuration. Correspondingly, the source base station can receive the sixth information from the terminal device.

[0294] It should be understood that the sixth piece of information sent by the terminal device to the source base station may include the measurement results of the cells in the target network.

[0295] The frequency points in the measurement configuration can be determined by the source base station based on the first PLMN list.

[0296] For example, if the first PLMN list includes PLMNs supported by the terminal device, and the terminal-supported PLMNs include PLMNs that support the cell handover method provided in the embodiments of this application and PLMNs that do not support the cell handover method provided in the embodiments of this application, the source base station can select a PLMN that supports the cell handover method provided in the embodiments of this application from the first PLMN list. The source base station can configure the frequency point information of the frequency point corresponding to the PLMN that supports the cell handover method provided in the embodiments of this application in the measurement configuration.

[0297] When the first PLMN list includes PLMNs supported by the terminal device, and the PLMNs supported by the terminal only include PLMNs that support the cell handover method provided in the embodiments of this application, the source base station can configure the frequency point information of the frequency points corresponding to the PLMNs in the first PLMN list in the measurement configuration.

[0298] The number of PLMNs supporting the cell handover method provided in this application embodiment can be one or more. The first PLMN list can be obtained by the source base station from the source core network.

[0299] For example, still taking satellite 501 as the source base station in Figure 5, the first cell can be a cell of satellite 501. The source base station can send measurement configuration to the terminal device at the first moment.

[0300] In S902b, the source AMF network element in the source core network can send the first PLMN list to the source base station. Correspondingly, the source base station can receive the first PLMN list from the source AMF network element.

[0301] For example, the source core network may send a first PLMN list to the source base station when establishing the context of the terminal device. This allows the source base station to indicate a second cell to the terminal device via the first information upon receiving the sixth information sent by the terminal device. The second cell may be determined by the terminal device based on the sixth information and the first PLMN list, and the second cell is a cell contained in the intersection of the sixth information and the first PLMN list.

[0302] Optionally, the source base station may send a request for a first PLMN list to the source AMF network element. Correspondingly, the source AMF network element may receive the request for a first PLMN list from the source base station. The source AMF network element may also send information indicating the first PLMN list to the source base station. In this way, the source base station can obtain the first PLMN list. It should be understood that when the source core network is the first core network, the source AMF network element belongs to the first core network equipment.

[0303] For example, when the source base station receives sixth information from the terminal device containing measurement results of at least one neighboring cell, the source base station can send information requesting a first PLMN list to the source AMF network element. In this way, the source base station can select at least one cell corresponding to the PLMN supporting the cell handover method provided in this application embodiment from the measurement results of at least one neighboring cell based on the received first PLMN list. This at least one cell includes a second cell. It should be understood that in this example, the execution order of S902a and S902b can be S902a executed first, followed by S902b.

[0304] Optionally, when the terminal device accesses the source network, the source base station can send a request for a first PLMN list to the source AMF network element. In this way, the source base station can configure the frequency point information of the PLMN corresponding to the frequency point supporting the cell handover method provided in this application embodiment in the measurement configuration based on the received first PLMN list, so that the source base station can send the measurement configuration to the terminal device before S902a. It should be understood that in this example, the execution order of S902a and S902b can be S902b executed first, followed by S902a.

[0305] S902a and S902b are optional. S902a and S902b may not exist simultaneously.

[0306] Optionally, the source AMF network element in the source core network can send a first request message to the SMF (such as the source SMF network element) in the source core network to request the terminal device to support the PLMN list of the cell handover method provided in this application embodiment. Correspondingly, the SMF in the source core network can receive the first request message from the source AMF network element. The SMF in the source core network can send a first PLMN list to the source AMF network element. Correspondingly, the source AMF network element can receive the first PLMN list from the SMF in the source core network. The source AMF network element in the source core network can send the first PLMN list to the source base station.

[0307] Optionally, the source base station sends a second request message to the source AMF network element in the source core network to request the adoption of the cell handover method provided in this application. Correspondingly, the source AMF network element can receive the second request message from the source base station. The source AMF sends a first confirmation message to the source base station to confirm or allow the adoption of the cell handover method provided in this application. Correspondingly, the source base station can receive the first confirmation message from the source AMF. This allows the source base station to adopt the cell handover method provided in this application to realize cell handover of the terminal device or access to the target cell (such as the second cell). In this implementation, S902a and S902b are optional.

[0308] S903. The source base station can send first information to the terminal device. Correspondingly, the terminal device can receive the first information from the source base station.

[0309] For example, the source base station can determine the first information and send the first information to the terminal device. This allows the terminal device to send the first message to the second cell via the common control channel. For the specific implementation principle of the terminal device sending the first message to the second cell via the common control channel, please refer to the specific implementation principle of S801.

[0310] For example, when the source base station selects at least one cell from the measurement results of at least one neighboring cell based on the received first PLMN list, the source base station can send first information to the terminal device. The first information includes a first cell list, which includes the at least one cell selected by the source base station. It should be understood that the first cell list includes a second cell. This enables the source base station to determine the first information based on the received first PLMN list, facilitating the terminal device to access the second cell based on the first information. It should be understood that this example may include S902a, S902b, and S903.

[0311] Optionally, after the source base station receives the first PLMN list and the measurement results of at least one neighboring cell, the source base station may send first information to the terminal device, the first information including the first PLMN list. In this way, the terminal device can obtain the first PLMN list from the received first information and, based on the first PLMN list, select at least one cell corresponding to the PLMN supporting the cell handover method provided in this application embodiment from the measurement results of at least one neighboring cell. This facilitates the terminal device's access to the second cell. It should be understood that this example may include S902a, S902b, and S903. S902a and S902b can be executed concurrently, or S902a can be executed first and then S902b, or S902b can be executed first and then S902a.

[0312] Optionally, after the source base station sends the measurement configuration to the terminal device and receives the measurement results from the terminal device for each frequency point's corresponding cell, the source base station can select the second cell with the highest signal quality strength from the measurement results for each frequency point's corresponding cell. The source base station can send first information to the terminal device, the first information including the identifier of the second cell with the highest signal quality strength selected by the source base station. It should be understood that in this example, S902b, S902a, and S903 may be included.

[0313] Optionally, the first information may not indicate the second cell. If the first information does not indicate the second cell, the cell handover method provided in this application embodiment may not include S902a and S902b.

[0314] If the first information does not indicate a second cell, the terminal device can select neighboring cells with signal quality higher than a fifth quality threshold from the measurement results of at least one neighboring cell to form a second cell list.

[0315] It should be understood that, in cases where the first information indicates a second cell, the list of the second cell is the same as the list of the first cell.

[0316] Optionally, the first information may be a handover command. The handover command may be generated by the source base station or by the source core network.

[0317] When the handover command is generated by the source base station, the handover command may include a first cell list, a first PLMN list, and / or a second PLMN list.

[0318] When the switching command is generated by the source core network, the switching command may include a first PLMN list and / or a second PLMN list.

[0319] The first PLMN list may include PLMN identifiers from the second PLMN list. It should be noted that when the handover command is generated by the source core network, the source base station transparently transmits the first PLMN list and / or the second PLMN list to the terminal device.

[0320] Optionally, the first information may include frequency point information and / or the identifier of the second cell. The identifier of the second cell may be, for example, PCI.

[0321] S904. The terminal device can send first UE capability information to the source base station. The first UE capability information can be the UE capability information corresponding to the connection between the terminal device and the first cell when accessing both the first and second cells. Correspondingly, the source base station can receive the first UE capability information from the terminal device. It should be noted that the first UE capability information can be the UE capability information corresponding to the connection between the terminal device and the first cell when accessing both the first and second cells; it does not mean that the terminal device only connected to the first cell. The terminal device can also connect to other cells in the source base station corresponding to the first cell. For example, the terminal device may have performed multi-carrier communication with the source base station corresponding to the first cell.

[0322] For example, taking the cell of the source base station serving the terminal device as the first cell and the cell of the target base station as the second cell, the terminal device can send first UE capability information to the first cell. Correspondingly, the first cell receives the first UE capability information from the terminal device.

[0323] The UE capabilities in this application embodiment may include multiple-input multiple-output (MIMO) capabilities. MIMO capabilities may include antenna configuration, MIMO mode, signal processing capabilities, and dynamic adaptation capabilities, etc.

[0324] This allows the source base station to update the transmission parameters and resources configured for the terminal device based on the first UE capability information, thereby reducing resource waste.

[0325] Optionally, before sending the first information to the terminal device, the source base station may send a ninth information to the terminal device. The ninth information is used to request a change in the UE's capabilities. The ninth information may include a reason for the request. The reason for the request could be that the terminal device's switch from the source network to the target network necessitates a change in the UE's capabilities. Correspondingly, the terminal device may receive the ninth information from the source base station.

[0326] Upon receiving the ninth information and the first information, the terminal device can send the first UE capability information to the source base station.

[0327] The terminal device can also send the first UE capability information to the source base station after receiving the ninth information and before receiving the first information.

[0328] Optionally, if the first information carries the first condition, the terminal device sends the first UE capability information to the source base station if the first condition for performing cell handover is met.

[0329] Optionally, before the source base station sends the first information to the terminal device, the source base station obtains the second UE capability information (which can be referred to as capability information #a) corresponding to the connection between the terminal device and the first cell when the terminal device is only connected to the first cell. It should be noted that capability information #a does not mean that the terminal device is only connected to the first cell; the terminal device may also be connected to other cells in the source base station corresponding to the first cell. For example, the terminal device may have performed multi-carrier communication with the source base station corresponding to the first cell.

[0330] S905. The terminal device can send a first message to the target base station through the common control channel. This first message is used to request the establishment of a Radio Resource Control (RRC) connection. Correspondingly, the target base station can receive the first message from the terminal device.

[0331] Since the second cell is the target base station's cell, exemplarily, the terminal device can send a first message to the second cell via a common control channel. Correspondingly, the second cell can receive the first message from the terminal device.

[0332] For details on the implementation principle of this step, please refer to the implementation principle of S802, which will not be repeated here.

[0333] Understandably, upon receiving the first information (or handover command) from the source base station, the terminal device does not disconnect its RRC connection with the source base station. That is, the terminal device maintains its connection with the first cell before sending the first message.

[0334] The source core network can still send downlink user plane data (i.e., downlink data) to terminal devices through the source base station. For example, the source UPF network element can send downlink data to the source base station. Correspondingly, the source base station receives downlink data from the source UPF network element. The source base station can send downlink data to the terminal device. Correspondingly, the terminal device can receive downlink data from the source base station.

[0335] Thus, compared to the embodiment shown in Figure 7, where the source base station cannot send downlink user plane data from the source core network to the UE after receiving the handover command but before the UE accesses the target cell, resulting in downlink user plane data transmission delay, the cell handover method provided in this application embodiment allows the source base station to still send downlink user plane data from the source core network to the terminal device after receiving the handover command but before the terminal device accesses the second cell. This reduces the probability of downlink user plane data transmission delay.

[0336] Optionally, the terminal device may send a second indication message to the target base station to indicate that the terminal device is switching from the source network to the target network or to indicate that the scheme in this application has been adopted to perform the switch from the source network to the target network. For example, the second indication message may be carried in the first message or in other messages (e.g., in the RRC establishment completion message). Correspondingly, the target base station may receive the second indication message from the terminal device.

[0337] S906. The target base station can send a second message to the terminal device. The second message can be a response to the first message. Correspondingly, the terminal device can receive the second message from the target base station.

[0338] For example, the second cell can send a second message to the terminal device. Correspondingly, the terminal device can receive the second message from the second cell.

[0339] In one implementation of this application, the second message may be transmitted via a common control channel. For example, the second message may be transmitted by the second cell via a downlink common control channel (DL-CCCH). DL-CCCH can also be referred to as the common control channel in the downlink. The second message may carry configuration information of the second cell. The second message may be an RRC establishment message.

[0340] In another implementation of this application, the second message may be transmitted via a dedicated control channel. For example, the second message may be transmitted by the second cell via a downlink dedicated control channel (DL-DCCH). DL-DCCH can also be referred to as a dedicated control channel in the downlink. The second message may carry configuration information of the second cell. The second message may be an RRC recovery message.

[0341] This enables terminal devices to access the second cell.

[0342] Understandably, the terminal device can maintain its connection with the first cell before receiving the second message. This allows the terminal device to continue exchanging data with the source network.

[0343] S907. The target base station can send a fourth message to the target AMF network element of the target core network. This fourth message can be used to forward information sent by the terminal device to the target core network. Correspondingly, the target AMF network element can receive the fourth message from the target base station. This information sent by the terminal device to the target core network may include, for example, the second indication information or the NAS message carried in the RRC establishment completion message.

[0344] Optionally, the target base station may send a third indication message to the target core network to indicate that the terminal device is switching from the source network to the target network or to indicate that the scheme in this application is used to perform the switch from the source network to the target network. For example, the third indication message may be carried in a fourth message or in other messages. The target base station can determine the third indication message based on the second indication message.

[0345] Optionally, the terminal device can send third indication information to the target core network through the target base station, without the target base station being aware of the third indication information. For example, the third indication information can be carried in a non-access stratum (NAS) message sent by the terminal device to the target core network.

[0346] Optionally, S906 and S907 can be executed concurrently.

[0347] S908. The target AMF network element can send information for requesting UE context to the source AMF network element in the source core network. Correspondingly, the source AMF network element can receive information for requesting UE context from the target AMF network element.

[0348] S909. The source AMF network element can send a response requesting the UE context to the target AMF network element. Correspondingly, the target AMF network element can receive the response requesting the UE context from the source AMF network element.

[0349] The response requesting the UE context can carry the UE context.

[0350] In this way, the target core network can obtain the UE context, enabling it to execute relevant procedures for receiving terminal device access and subsequently manage the accessed terminal device based on the UE context. For example, the target core network can authenticate the terminal device and subsequently manage its mobility based on the UE context.

[0351] In one embodiment of this application, the target AMF network element and the source AMF network element may be the same. When the target AMF network element and the source AMF network element are the same, the cell handover method provided in this application embodiment may not include S908 and S909. When the target AMF network element receives a fourth message from the target base station, the target core network can execute the relevant procedures for receiving terminal equipment access and subsequently manage the accessed terminal equipment based on the UE context on the target AMF network element.

[0352] In another embodiment of this application, when the first message is an RRC recovery request, the cell handover method provided in this application embodiment may also exclude S908 and S909.

[0353] Optionally, the source SMF network element can send the downlink address information of the target core network user plane (target UPF) to the PSA. The PSA can then send downlink data to the target UPF network element based on this downlink address information. Optionally, the source SMF network element can assign downlink address information to the target UPF itself, or the source SMF network element can obtain the downlink address information from the target UPF network element.

[0354] S910, the target AMF network element can send a fifth message to the target base station. The fifth message can be a response to the fourth message. Correspondingly, the target base station can receive the fifth message from the target AMF network element.

[0355] For example, after the target core network has completed the relevant procedures for receiving terminal equipment access, the target AMF network element can send a fifth message to the target base station.

[0356] S911. The source AMF network element can send a path modification request to the source SMF network element. Correspondingly, the source SMF network element can receive a path modification request from the source AMF network element.

[0357] Among them, the path modification request can be used to indicate that downlink data from the source core network can be sent to the target UPF network element of the target core network.

[0358] For example, after the target core network completes the relevant procedures for receiving terminal equipment access, the target AMF network element can send information to the source AMF network element indicating that the received terminal equipment has accessed. The source AMF network element can send a path modification request to the source SMF network element.

[0359] S912. The source SMF network element can send a path modification request to the source UPF network element. Correspondingly, the source UPF network element can receive a path modification request from the source SMF network element.

[0360] The path modification request can carry the data tunnel address of the target core network user plane.

[0361] In this way, the source UPF network element can send downlink data to the target UPF network element according to the data tunnel address of the target core network user plane. This downlink data can be the downlink data that the source UPF network element is about to transmit to the terminal device. Correspondingly, the target UPF network element can receive the downlink data from the source UPF network element. The target UPF network element can send this downlink data to the target base station. Correspondingly, the target base station can receive the downlink data from the target UPF network element. The target base station can send the downlink data from the target UPF network element to the terminal device.

[0362] This application does not strictly limit the order of S909 to S912.

[0363] S913, terminal equipment can exchange data with the target network.

[0364] For example, when a terminal device accesses a second cell of the target network and establishes a session with the target network, the terminal device can send uplink data to the target network.

[0365] It should be understood that the session established between the terminal device and the target network may include, but is not limited to: radio resource control sessions, transport layer sessions, PDU sessions, session management procedures, and other possible sessions (such as IMS sessions). The process of establishing a session between the terminal device and the target network is not shown in Figure 9. The process of establishing a session between the terminal device and the target network can be executed concurrently with the S911-S912 process, or the terminal device can establish a session with the target network during the execution of S911-S912.

[0366] This refers to the uplink data sent by the terminal device to the target network, such as data packets in the first data stream. In this embodiment, the data stream can be a data stream corresponding to a service. In this embodiment, the service is, for example, a user viewing an application page. The first data stream is, for example, a data stream corresponding to a first service.

[0367] Optionally, if the terminal device is transmitting partial data packets of the second data stream to the first cell of the source network before sending the first message, the terminal device may continue transmitting data packets of the second data stream to the first cell before establishing a session with the target network. After establishing a session with the target network, the terminal device may begin transmitting data packets of the second data stream to the second cell. The data packets of the second data stream transmitted by the terminal device to the second cell may be the remaining data packets in the second data stream that have not been transmitted to the first cell after the terminal device has transmitted partial data packets of the second data stream through the first cell, or data packets of the second data stream received by the AS layer of the terminal device from the upper layer. The second data stream may be one of the uplink data streams. After establishing a session with the target network, for those data packets of the second data stream that have already been transmitted through the first cell of the source network, the terminal device continues to transmit these data packets of the second data stream through the first cell of the source network before the first cell has correctly received them. Afterwards, when the terminal device has transmitted all the data packets in the second data stream to the first cell, the terminal device may execute S914 to send third information to the first cell. The third information is used to indicate that the data packets in the second data stream have been sent (i.e., all data packets in the second data stream transmitted through the first cell have been sent). The second data stream is the data stream transmitted by the terminal device to the first cell. The second data stream can be the data stream corresponding to the second service. The first data stream can be the same data stream as the second data stream, or they can be different data streams. The third information can be an end marker.

[0368] The third type of information can be data stream level information, radio bearer level information, session level information, or UE level information.

[0369] For example, the third information can be used to indicate that all data packets of the second data stream of a radio bearer have been sent (i.e., all data packets of the second data stream in a radio bearer transmitted through the first cell have been sent). The third information can be sent through the radio bearer, or it can carry data stream identification information. That is, the third information is specific to a particular second data stream. As another example, the third information can be used to indicate that all data packets of a certain radio bearer have been sent (i.e., all data packets of a certain radio bearer transmitted through the first cell have been sent). The third information can be sent through the radio bearer, or it can carry radio bearer identification information. As yet another example, the third information can be used to indicate that all data packets of all data streams of a certain session have been sent (i.e., all data packets of all data streams of a certain session transmitted through the first cell have been sent). The third information can be sent through the radio bearer of that session or generated and sent to the source base station at a protocol layer of that session (e.g., the Service Data Adaptation Protocol (SDAP) layer), or it can carry session identification information. As yet another example, the third information can be used to indicate that all data packets transmitted by the UE have been sent (i.e., all data packets of all data streams transmitted through the first cell have been sent).

[0370] In this way, based on the third information, the first cell can determine that the uplink data transmission between the terminal device and the first cell is complete, so that the first cell can execute the relevant procedures for releasing the RRC connection. For example, when the third information is used to indicate that all data packets of the second data stream of the radio bearer have been sent, or to indicate that all data packets of all data streams of a certain session have been sent, the first cell can determine that the uplink data transmission between the terminal device and the first cell is complete when it receives the third information carrying the radio bearer or the session.

[0371] Optionally, before the terminal device establishes a session with the target network, the first cell may send data packets of a third data stream to the terminal device. The third data stream is the data stream corresponding to the third service. Correspondingly, the terminal device may receive data packets of the third data stream from the first cell.

[0372] When the first cell has finished sending all data packets in the third data stream to the terminal device, the first cell may send a fourth message to the terminal device. The fourth message indicates that the data packets in the third data stream have been sent. Correspondingly, the terminal device may receive the fourth message from the first cell.

[0373] The fourth information can be an end marker. This fourth information can be data stream-level, radio bearer-level, session-level, or UE-level. For example, the fourth information can indicate that all data packets of the third data stream of a radio bearer have been transmitted (i.e., all data packets of the third data stream in a radio bearer transmitted through the first cell have been transmitted). The fourth information can be transmitted through the radio bearer, or it can carry data stream identification information. That is, the fourth information is specific to a particular third data stream. As another example, the fourth information can indicate that all data packets of a certain radio bearer have been transmitted (i.e., all data packets of a certain radio bearer transmitted through the first cell have been transmitted). The fourth information can be transmitted through the radio bearer, or it can carry radio bearer identification information. As yet another example, the fourth information can indicate that all data packets of all data streams of a certain session have been transmitted (i.e., all data packets of all data streams of a certain session transmitted through the first cell have been transmitted). The fourth information can be transmitted through the radio bearer of the session, or generated and transmitted to the UE at a protocol layer (e.g., SDAP layer) of the session, or it can carry session identification information. For example, the fourth information can be used to indicate that all data packets transmitted in the first cell for this UE have been sent (i.e., all data packets of all data streams sent through the first cell have been sent).

[0374] The third data stream can also be a data stream sent from the source core network to the source base station. Taking the source core network as the first core network as an example, the third data stream can be a data stream sent from the first core network equipment to the source base station. The first core network equipment may include source UPF network elements. The third data stream is a data stream to be sent to the terminal equipment. After the source UPF network element has completed transmitting the data packets in the third data stream to the source base station, the source UPF network element can send fifth information to the source base station. The fifth information is used to indicate that the data packets in the third data stream have been transmitted. Correspondingly, the source base station can receive the fifth information from the source UPF network element. Based on the fifth information and the transmission status of the data packets in the third data stream sent by the first cell to the UE, the first cell can determine the fourth information.

[0375] In this way, based on the fourth information, the terminal device can determine that the downlink data (such as the third data stream) exchanged between the terminal device and the first cell has been transmitted, so that the AS of the terminal device can determine the time to send the data of the third data stream received from the second cell to the upper layer.

[0376] Optionally, when the source UPF network element sends the fifth information to the source base station, the source AMF network element can execute S915 so that the source base station can execute S916 after sending the data packets in the third data stream to the terminal device.

[0377] Optionally, before receiving the second message, the first cell may send a second data packet of the fourth data stream to the terminal device. The fourth data stream may be the data stream corresponding to the fourth service. Correspondingly, the terminal device may receive the second data packet of the fourth data stream from the first cell.

[0378] After the terminal device establishes a session with the target network, it can receive the first data packet of the fourth data stream from the second cell through the access layer (AS). This first data packet is distinct from the second data packet. The establishment of the session between the terminal device and the target network can occur after the terminal device receives the second message.

[0379] Upon releasing the RRC connection with the first cell, and / or after all data packets (including the second data packet) of the fourth data stream from the first cell have been delivered to the upper layer and information indicating that all data packets in the fourth data stream have been sent has been received, the terminal device transmits the first data packet of the fourth data stream to the upper layer via the AS layer. For ease of understanding, the release of the RRC connection between the terminal device and the first cell will be described later.

[0380] This reduces the likelihood of data packets in the fourth data stream being transmitted and processed within the terminal device in a pre-defined data packet order, thereby reducing the probability of interruption or failure of the fourth service corresponding to the fourth data stream.

[0381] Optionally, before disconnecting communication with the first cell, and while the terminal device is communicating with both the first and second cells, independent MAC, RLC, and PDCP layer protocol stacks are used between the terminal device and the first and second cells respectively. That is, when the terminal device communicates with the first and second cells, each link has its own protocol stack. This reduces interference between the terminal device's communication with the first cell and its communication with the second cell. It also reduces the coupling between the terminal device's communication with the first cell and its communication with the second cell, thereby reducing the complexity of the terminal device.

[0382] There are two links: one for communication between the terminal device and the first cell, and another for communication between the terminal device and the second cell. The RRC layer and the SDAP layer can use their own independent protocol stacks or a shared protocol stack.

[0383] Optionally, when the terminal device communicates with the first cell and the second cell, the two links have independent keys. This ensures the security of data transmission on both links. For example, when the target network generates a key for the terminal device, it re-initializes and allocates a new key for the terminal device, rather than deriving a new key based on the terminal device's key in the source network. Optionally, the terminal device's key in the target network is derived from the key in the source network.

[0384] Optionally, after the terminal device establishes a session with the target network, the upper layer of the terminal device's AS layer can send uplink data to the AS protocol stack corresponding to the link between the terminal device and the second cell of the target network. This enables the terminal device to send uplink data to the second cell. The AS protocol stack corresponding to the link between the terminal device and the second cell can be, for example, a PDCP layer or an SDAP layer.

[0385] Optionally, the terminal device can receive a fourth indication message from the second cell, which instructs the terminal device to disconnect from the source cell. In one embodiment, steps S914-S916 are not required. In another embodiment, after receiving the fourth indication message, the terminal device sends an indication message to the first cell, requesting the release of the connection. For example, the indication message is carried in the UE assistance information message sent by the terminal device to the first cell. Then, step S916 can be executed.

[0386] S914. After the terminal device has finished transmitting the data packets in the second data stream to the source base station, the terminal device may send third information to the source base station. Correspondingly, the source base station may receive the third information from the terminal device.

[0387] For example, after the terminal device has finished transmitting the data packets in the second data stream to the first cell, the terminal device can send third information to the first cell. Correspondingly, the first cell can receive the third information from the terminal device.

[0388] It should be understood that S914 is an optional step.

[0389] S915, the source AMF network element can send information to the source base station indicating the release of the UE context. Correspondingly, the source base station can receive information from the source AMF network element indicating the release of the UE context.

[0390] For example, taking the source core network as the first core network, the first core network equipment may also include source AMF network elements.

[0391] Before the source AMF network element sends information indicating the release of the UE context to the source base station, the source base station may send information requesting the release of the UE context to the source AMF network element. Correspondingly, the source AMF network element may receive information from the source base station requesting the release of the UE context.

[0392] For example, when the source base station receives the fifth information from the source UPF network element, the source base station can send information to the source AMF network element to request the release of the UE context. Correspondingly, the source AMF network element can receive the information from the source base station to request the release of the UE context.

[0393] Optionally, based on the fifth information and after the source base station has sent the data packets in the third data stream to the terminal device, the source base station may send information to the source AMF network element to request the release of the UE context.

[0394] Optionally, the source base station may send information to the source AMF network element to request the release of the UE context based on third information.

[0395] Optionally, the source base station may send information to the source AMF network element to request the release of the UE context based on the third information, the fifth information, and the data packets in the third data stream sent to the terminal device.

[0396] S916. The source base station may send second information to the terminal device. The second information may be used to indicate disconnection from the source base station or to indicate release of the UE's connection. Correspondingly, the terminal device may receive the second information from the source base station. The terminal device may disconnect from the source base station based on the second information.

[0397] For example, the first cell may send second information to the terminal device. The second information may be used to indicate disconnection from the first cell. Correspondingly, the terminal device may receive the second information from the first cell and disconnect from the first cell based on the second information.

[0398] This frees up wireless resources that would otherwise be used for wireless transmission between the terminal device and the first cell, thus enabling more efficient use of those resources.

[0399] As shown in Figure 9, in the cell handover method provided in this application embodiment, the source base station can determine or generate first information. This first information can be determined by the source base station based on measurement results reported by the terminal device and / or a first PLMN list sent by the source core network. Upon receiving the first information from the source base station regarding the first cell, the terminal device can send a first message to the second cell via the common control channel, enabling the terminal device to access the second cell in a manner similar to initiating an RRC connection in RRC_IDLE state, or to access the second cell in a manner similar to initiating an RRC connection recovery in RRC_INACTIVE state. When the terminal device accesses the second cell, it can send uplink data to the second cell. After the terminal device accesses the second cell, and after all uplink data transmitted from the terminal device to the source base station has been transmitted and / or all downlink data transmitted from the source core network to the terminal device through the source base station has been transmitted, the source base station can request the release of the UE context from the source core network. Upon receiving information from the source core network indicating the release of the UE context, the source base station can instruct the terminal device to disconnect from the first cell of the source base station. The terminal device can then disconnect from the first cell. In the cell handover method provided in this application embodiment, when a terminal device accesses a second cell, it can maintain its connection with the first cell and disconnect from the first cell after the data transmission between the terminal device and the source network is completed. This enables the terminal device to hand over from the first cell to the second cell. The entire process eliminates the need for a handover preparation procedure, reducing handover time. The disconnection of the terminal device from the first cell occurs after the data transmission between the terminal device and the source network is complete. Therefore, it does not affect the transmission of data between the terminal device and the source network, and thus does not affect the transmission of downlink user plane data to be transmitted from the source core network to the terminal device. The data exchanged between the terminal device and the source network may include the second data packet of the fourth data stream, the second data stream, and / or the third data stream.

[0400] It is understandable that the source network can be an NTN network and the destination network can be a TN network. Alternatively, the source network can be a TN network and the destination network can be an NTN network.

[0401] Taking a satellite as the source base station and a TN base station as the target base station as an example, in a geographical area covered by the satellite, there can be at least two TN cells with the same PCI, and the PCI of the target cell is one of these at least two TN cells. In this case, the UE can report the measurement results of the target cell to the source base station (such as an NTN base station). For example, in the geographical area covered by the satellite 501 shown in Figure 5, there are at least two TN cells 507 with PCI #2 (i.e., PCI: #2) included in the geographical area 506 covered by the satellite 501.

[0402] Since the PCI of the target cell is the same as that of at least one TN cell in the geographical area covered by the satellite, in the handover preparation process shown in Figure 6, the source base station can send the identifier of the target base station corresponding to the target cell to the source core network and the target core network when sending the handover request to the target base station through the source core network and the target core network. Therefore, the source base station may obtain the identifier of the target base station corresponding to the target cell in the following way: The source base station instructs the UE to read the target's system message. The system message may carry the global cell identifier. The global cell identifier may carry the base station identifier. The UE can send the global cell identifier of the target cell to the source base station. In this way, the source base station can obtain the identifier of the target base station. However, this process of obtaining the global cell identifier is also time-consuming. For example, for cells in the FR1 band, the process of obtaining the global cell identifier takes 2 seconds. For cells in the FR2 band, the process of obtaining the global cell identifier takes 16 seconds. This makes the cell handover time long, which may affect the timing of the cell handover and thus affect the cell handover performance, for example, causing the cell handover to fail. The FR1 band can be understood as the frequency range between 440MHz and 6GHz. The FR2 band can be understood as the frequency range between 24.25 GHz and 52.6 GHz, and can also be called the millimeter wave (mm wave) band.

[0403] The terminal device performs cell handover using the cell handover method shown in Figure 8 or Figure 9. The source base station can determine the first information and indicate the target base station to the terminal device through the first information, which can also reduce the handover time of cell handover.

[0404] In addition, the source base station may encounter the following scenario: The source base station (such as a satellite) needs to interact with ground equipment (such as network elements of the source core network) through multiple hops. For example, the source base station needs to interact with network elements of the source core network through inter-satellite links. Scenario 1 can be seen in Figure 10, which will be described later for ease of understanding.

[0405] In Scenario 1, the cell handover process shown in Figures 6 and 7 results in a longer handover time for the terminal device and also consumes valuable inter-satellite transmission resources. The cell handover method provided in the embodiments shown in Figures 8 or 9 allows the terminal device to perform cell handover, reducing handover time and minimizing the consumption of inter-satellite transmission resources.

[0406] Furthermore, the cell handover method shown in Figure 8 or Figure 9 can also be applied to cell handover when the source network and the target network belong to different operators. This simplifies the handover process from a source cell in the source network to a target cell in the target network, reducing handover time.

[0407] Figure 10 illustrates a scenario where a source base station interacts with ground equipment via multiple hops, as provided in an embodiment of this application. As shown in Figure 10, satellite C, acting as the source base station, can interact with network elements of the source core network via satellite D, ..., satellite N, and the gateway station. The gateway station is not shown in Figure 10. The source core network and the target core network can interact. It should be understood that in the process shown in Figure 7, the source core network can send downlink user plane data to satellite C via the gateway station, satellite N, ..., satellite D. Due to the interruption of the connection between the source base station and UE 1002, satellite C transmits the downlink user plane data to the target base station 1001 via satellite D, ..., satellite N, the gateway station, the source core network, and the target core network, so that UE 1002 can receive the downlink user plane data transmitted by the target base station 1001 when accessing the target base station 1001.

[0408] The cell handover method shown in Figure 8 will be explained below with reference to Figure 11.

[0409] Figure 11 shows another schematic flowchart of the cell handover method provided in the embodiments of this application.

[0410] As shown in Figure 11, the cell handover method may include:

[0411] S901, Terminal devices can access the source network.

[0412] S902a: The terminal device can send sixth information to the source base station. The sixth information may include measurement results, thus enabling the terminal device to report measurement results to the source base station. Correspondingly, the source base station can receive the sixth information from the terminal device.

[0413] In S902b, the source AMF network element in the source core network can send the first PLMN list to the source base station. Correspondingly, the source base station can receive the first PLMN list from the source AMF network element.

[0414] S903. The source base station can send first information to the terminal device. Correspondingly, the terminal device can receive the first information from the source base station.

[0415] S904. The terminal device can send first UE capability information to the source base station. The first UE capability information can be the UE capability information corresponding to the connection between the terminal device and the first cell when accessing the first cell and the second cell. Correspondingly, the source base station can receive the first UE capability information from the terminal device.

[0416] The specific implementation principles and technical effects of each step in S901-S904, namely S901, S902a, S902b, and S903-S904, can be found in the specific implementation principles and technical effects of the corresponding steps in the embodiment shown in Figure 9, and will not be repeated here.

[0417] S1101. The terminal device can send a first message to a cell (such as a second cell) of the target network through a common control channel. Correspondingly, the cell of the target network can receive the first message from the terminal device.

[0418] For example, taking cell #1 (T-RAN #1) of the target network shown in Figure 11 as an example, where #1 is the identifier or sequence number of this cell in the target network, the terminal device can send a first message to cell #1 via UL-CCCH to initiate the connection establishment process between the terminal device and cell #1. Correspondingly, cell #1 can receive the first message from the terminal device. The connection establishment process between the terminal device and cell #1 can be found in the process shown in S906-S912 of Figure 9, and will not be repeated here.

[0419] If the terminal device fails to establish a connection with cell #1, the terminal device can execute S1102.

[0420] S1102. The terminal device can send a first message to another cell in the target network through the common control channel. Correspondingly, the other cell in the target network can receive the first message from the terminal device.

[0421] For example, taking cell #2 (T-RAN #2) of the target network as shown in Figure 11 as another cell in the target network, where #2 is the identifier or sequence number of this other cell in the target network, the terminal device can send a first message to cell #2 via UL-CCCH to initiate the connection establishment process between the terminal device and cell #2. Correspondingly, cell #2 can receive the first message from the terminal device. The connection establishment process between the terminal device and cell #2 can also be seen in the process shown in S906-S912 of Figure 9, and will not be repeated here.

[0422] In this way, if the terminal device fails to access one cell in the list indicating the second cell, it can attempt to access other cells in the list. If the terminal device fails to access all cells in the list indicating the second cell, or if the terminal device fails to access any cell in the list indicating the second cell within a first time period, the terminal device can execute S1103. The first time period can be a preset value or carried in the first information.

[0423] It should be understood that the list indicating the second cell can be a first PLMN list, a first cell list, or a second cell list. The second cell list includes at least one cell, and that at least one cell includes the second cell. The second cell list can be determined by the terminal device, or the second cell list can be indicated by first information. When the second cell list is indicated by first information, the second cell list is the same as the first cell list.

[0424] S1103. The terminal device can send information indicating cell handover failure to the source base station. Correspondingly, the source base station can receive information from the terminal device indicating cell handover failure.

[0425] The information used to indicate a cell handover failure can be a failure indicator.

[0426] For example, the terminal device may send information indicating a cell handover failure to the first cell. Correspondingly, the first cell may receive the information indicating a cell handover failure from the terminal device. Optionally, the cell handover failure information may include a list of cells where the terminal device has failed to access the target network.

[0427] S1104. The terminal device can send second UE capability information to the source base station to change the UE capability. The second UE capability is the UE capability information corresponding to the terminal device in the first cell when the terminal device only accesses the first cell of the source base station. Correspondingly, the source base station can receive the second UE capability information from the terminal device.

[0428] It should be understood that a terminal device only connecting to the first cell of the source base station includes the terminal device connecting to the first cell and also connecting to other cells in the source base station corresponding to the first cell. For example, the terminal device performs multi-carrier communication with the source base station corresponding to the first cell.

[0429] For example, the terminal device can send second UE capability information to the first cell. Correspondingly, the first cell can receive the second UE capability information from the terminal device.

[0430] This allows the source base station to update the transmission parameters and resources configured for the terminal device based on the second UE capability information, so that the terminal device can revert to its ability to communicate in the source network before receiving the first information (or handover command).

[0431] Optionally, after the terminal device sends the second UE capability information to the source base station, the source base station may send information to the terminal device indicating the fallback of UE capabilities. Correspondingly, the terminal device may receive the information from the source base station indicating the fallback of UE capabilities. The terminal device may update its communication capabilities in the source network; for example, the terminal device may perform antenna configuration updates and MIMO mode updates.

[0432] S1104 is optional. The source base station can determine whether the UE's current capability information can be updated based on the information indicating cell handover failure sent by the terminal device. And based on the second UE capability information obtained before sending the first information to the terminal device (e.g., the second UE capability information before step S904), the transmission parameters and resources configured for the terminal device are updated so that the terminal device can fall back to the capability of the terminal device to communicate in the source network before receiving the first information (or handover command).

[0433] As shown in the embodiment of Figure 11, in the cell handover method, after a terminal device fails to access a target cell (such as a second cell), it can attempt to access other target cells to improve the handover success rate. When the terminal device fails to access all target cells indicated by the first information or all target cells determined by the terminal device, the terminal device falls back to its communication capabilities in the source network before receiving the first information (or handover command) to fully utilize its communication capabilities.

[0434] The cell handover method shown in Figure 8 will be explained below with reference to Figure 12.

[0435] Figure 12 shows another schematic flowchart of the cell handover method provided in the embodiments of this application.

[0436] As shown in Figure 12, the cell handover method may include:

[0437] S901, Terminal devices can access the source network.

[0438] S902a: The terminal device can send sixth information to the source base station. The sixth information may include measurement results, thus enabling the terminal device to report measurement results to the source base station. Correspondingly, the source base station can receive the sixth information from the terminal device.

[0439] In S902b, the source AMF network element in the source core network can send the first PLMN list to the source base station. Correspondingly, the source base station can receive the first PLMN list from the source AMF network element.

[0440] S903. The source base station can send first information to the terminal device. Correspondingly, the terminal device can receive the first information from the source base station.

[0441] S904. The terminal device can send first UE capability information to the source base station. The first UE capability information can be the UE capability information corresponding to the connection between the terminal device and the first cell when accessing the first cell and the second cell. Correspondingly, the source base station can receive the first UE capability information from the terminal device.

[0442] S1101. The terminal device can send a first message to a cell (such as a second cell or cell #1) of the target network through a common control channel. Correspondingly, the cell of the target network can receive the first message from the terminal device.

[0443] The specific implementation principles and technical effects of each step in S901-S904 and S1101, namely S901, S902a, S902b, S903-S904 and S1101, can be found in the specific implementation principles and technical effects of the corresponding steps in the embodiment of Figure 11, and will not be repeated here.

[0444] During the process of establishing a connection between the terminal device and cell #1, before the terminal device disconnects from the first cell, if a radio link failure occurs between the terminal device and the first cell, the terminal device may execute S1201.

[0445] S1201, the terminal device can select the third cell in the source network.

[0446] For example, if the terminal device detects a failure in the radio link with the source network before receiving the second information or before disconnecting from the first cell, the terminal device can perform cell selection. For instance, the terminal device can perform signal quality measurements on at least one cell in the source network other than the first cell, obtaining measurement results for at least one cell in the source network. The terminal device can select a third cell with the best signal quality from the measurement results of at least one cell in the source network, or select a cell whose signal quality meets certain conditions as the third cell. Selecting a cell whose signal quality meets certain conditions as the third cell could be, for example, selecting a cell whose signal quality is greater than or equal to a sixth quality threshold. The sixth quality threshold can be predefined by the terminal device or pre-agreed upon by the terminal device and the base station (such as the source base station). The sixth quality threshold can be the same as the first quality threshold.

[0447] It should be understood that the cell selection performed by the terminal device only selects cells in the source network, not cells in the target network.

[0448] S1202, The terminal device may send a first request to a third cell in the source network. The first request is used to request RRC reconstruction. Correspondingly, the third cell receives the first request from the terminal device. For example, the first request may be an RRC reconstruction request message.

[0449] In this context, both the third cell and the first cell belong to either a non-terrestrial network or a terrestrial network; that is, the third cell and the first cell belong to the same network. For example, both the third cell and the first cell belong to the source network. The source network can be either a non-terrestrial network or a terrestrial network.

[0450] The base station belonging to the third cell can be the same as or different from the base station belonging to the first cell.

[0451] If the base station belonging to the third cell is the same as the base station belonging to the first cell, the base station belonging to the third cell may not need to execute S1203.

[0452] If the base station of the third cell is different from the base station of the first cell, the base station of the third cell can execute S1203.

[0453] The third cell, such as cell #3 (S-RAN#3) of the source network shown in Figure 12, is the identifier or sequence number of the third cell of the source network.

[0454] In this way, before disconnecting from the first cell and if it is determined that the wireless link between the terminal device and the first cell has failed, the terminal device can send a first request to the third cell to establish a connection with the third cell, thereby reducing the data transmission delay between the source network and the terminal device.

[0455] S1203. The base station belonging to the third cell can send information for requesting UE context to the base station belonging to the first cell. Correspondingly, the base station belonging to the first cell can receive information for requesting UE context from the base station belonging to the third cell.

[0456] S1204. The base station belonging to the first cell can send a response message requesting UE context to the base station belonging to the third cell. Correspondingly, the base station belonging to the third cell can receive the response message requesting UE context from the base station belonging to the first cell.

[0457] The response message requesting UE context sent by the base station of the first cell may carry first indication information. This first indication information can be used to indicate that the terminal device is executing the cell handover method provided in this embodiment to switch from the source network to the target network. The response message requesting UE context sent by the base station of the first cell may also carry the UE context, so that the third cell can execute the relevant procedures for rebuilding the terminal device and subsequently manage the terminal device based on the UE context.

[0458] S1205. The third cell can send a first response to the terminal device. The first response is the response to the first request; it can also be called a reconstruction response. Correspondingly, the terminal device can receive the first response from the third cell. For example, the first response could be an RRC reconstruction message.

[0459] This enables the terminal device to connect to the third cell.

[0460] As shown in the embodiment of Figure 12, the cell handover method allows the terminal device to select a third cell in the source network to trigger RRC reconstruction before the terminal device receives information (such as second information) indicating the disconnection from the first cell. This allows the terminal device to continue the handover process from the source network to the target network (such as accessing the second cell) before detecting a failure of the radio link with the source network. This reduces the duration of data transmission delay between the source network and the terminal device, minimizes the impact on data transmission between the source network and the terminal device, and reduces the probability of data packet loss during the interaction between the source network and the terminal device.

[0461] It is understood that in the cell handover method provided in this application embodiment, the connection between the terminal device and the first cell of the source base station may involve the terminal device connecting to the first cell of the source base station and also connecting to other cells of the source base station besides the first cell. The first cell may be a primary cell, and the other cells may be secondary cells. Upon receiving the second information, the terminal device may disconnect from the first cell and also disconnect from the other cells of the source base station to conserve resources.

[0462] It should also be understood that the order of the methods listed above does not imply the order of execution. The execution order of each process should be determined by its function and internal logic.

[0463] The cell handover method of this application embodiment has been described in detail above with reference to Figures 8 to 12. The communication device of this application embodiment will be described in detail below with reference to Figures 13 and 14. The communication device includes modules or units for performing each part of the above embodiments. Modules or units can be software, hardware, or a combination of software and hardware. The following is only a brief illustrative description of the communication device; for details of the implementation, please refer to the description of the foregoing method embodiments, which will not be repeated below.

[0464] Figure 13 is a schematic diagram of a communication device provided in an embodiment of this application. As shown in Figure 13, the communication device may include a processing module 1301 and a transceiver module 1302.

[0465] In one possible implementation, the communication device is used to implement the steps corresponding to the terminal equipment in the cell handover method shown in S801-S802 above.

[0466] The transceiver module 1302 can be used to receive first information from the first cell, which is used to instruct the terminal device to perform cell handover.

[0467] The transceiver module 1302 can also be used to send a first message to the second cell through the common control channel. The first message is used to request the establishment of a Radio Resource Control (RRC) connection.

[0468] Optionally, the transceiver module 1302 can also be used to receive a second message from the second cell, which is a response to the first message and is transmitted through a common control channel.

[0469] Optionally, the communication device maintains a connection with the first cell before the transceiver module 1302 sends the first message or receives the second message.

[0470] Optionally, after the transceiver module 1302 sends the first message to the second cell, or after the transceiver module 1302 receives the second message from the second cell, the transceiver module 1302 may also be used to receive the second information from the first cell and disconnect the connection with the first cell based on the second information.

[0471] Optionally, after receiving the second message from the second cell, the transceiver module 1302 can also be used to send data packets of the first data stream to the second cell.

[0472] Optionally, after transmitting the data packets in the second data stream to the first cell, the transceiver module 1302 can also be used to send third information to the first cell. The third information is used to indicate that the data packets in the second data stream have been transmitted. The second data stream is the data stream transmitted by the terminal device to the first cell.

[0473] And / or, the transceiver module 1302 can also be used to receive fourth information from the first cell, the fourth information being used to indicate that the data packets in the third data stream have been sent, the third data stream being the data stream sent by the first cell to the terminal device.

[0474] Optionally, the transceiver module 1302 can also be used to send first user equipment (UE) capability information to the first cell. The first UE capability information is the UE capability information corresponding to the connection between the terminal device and the first cell when accessing the first cell and the second cell.

[0475] Optionally, the processing module 1301 can be used to receive the first data packet of the fourth data stream from the second cell through the access layer AS.

[0476] In the event that the transceiver module 1302 releases the RRC connection with the first cell, and / or the second data packet of the fourth data stream from the first cell has been delivered to the upper layer, the processing module 1301 can also be used to transmit the first data packet of the fourth data stream to the upper layer through the AS layer.

[0477] Optionally, the first information includes a first cell list, which includes a second cell. Alternatively, the first information includes a first Public Land Mobile Network (PLMN) list, where the cells indicated by the first PLMN list include the second cell.

[0478] Optionally, if the communication device fails to access a cell in the second cell list, or fails to access any cell in the second cell list within a first time period, the transceiver module 1302 may also be used to send information indicating cell handover failure to the first cell. The second cell list includes a second cell, and the second cell list is determined by the terminal device, or the second cell list is indicated by the first information.

[0479] Optionally, the transceiver module 1302 can also be used to send second UE capability information to the first cell. The second UE capability is the UE capability information corresponding to the terminal device in the connection of the first cell when the terminal device only accesses the first cell.

[0480] Optionally, before the transceiver module 1302 disconnects from the first cell and determines that a radio link failure has occurred with the first cell, the transceiver module 1302 may also send a first request to the third cell. The first request is used to request RRC reconstruction. Both the third cell and the first cell belong to a non-terrestrial network or a terrestrial network.

[0481] In another possible implementation, the communication device is used to implement the steps corresponding to the source base station or the second cell in the cell handover method shown in S801-S802 above.

[0482] The processing module 1301 can be used to determine first information, which is used to instruct the terminal device to perform cell handover.

[0483] The transceiver module 1302 can be used to send first information to the terminal device so that the terminal device can send a first message to the second cell through the common control channel. The first message is used to request the establishment of an RRC connection.

[0484] Optionally, determining the first information includes: the transceiver module 1302 receiving information from the first core network device indicating a first PLMN list, the first PLMN list including PLMNs supported by the terminal device. The processing module 1301 determines the first information based on the first PLMN list.

[0485] Optionally, the first information includes a first cell list, which includes second cells, and the first cell list is determined based on a first PLMN list. Alternatively, the first information includes a first PLMN list, and the cells indicated by the first PLMN list include second cells.

[0486] Optionally, after the transceiver module 1302 sends the first information to the terminal device, the transceiver module 1302 can also be used to receive the first UE capability information from the terminal device. The first UE capability information is the UE capability information corresponding to the connection between the terminal device and the first cell when accessing the first cell and the second cell.

[0487] Optionally, the transceiver module 1302 can also be used to receive information from the first core network device indicating the release of the UE context.

[0488] The transceiver module 1302 can also be used to send a second message to the terminal device, which is used to indicate the release of the RRC connection.

[0489] Optionally, receiving information from the first core network device indicating the release of the UE context includes: the transceiver module 1302 receiving fifth information from the first core network device, the fifth information indicating that data packets in the third data stream have been sent, the third data stream being the data stream to be sent to the terminal device. The transceiver module 1302 sends information to the first core network device requesting the release of the UE context. The transceiver module 1302 receives information from the first core network device indicating the release of the UE context.

[0490] Optionally, the transceiver module 1302 sends information to the first core network device to request the release of the UE context, based on the fifth information and after sending the data packets in the third data stream to the terminal device.

[0491] Optionally, the first core network device is sent with information to request the release of the UE context, including: the transceiver module 1302 receiving third information from the terminal device, the third information indicating that the data packets in the second data stream have been sent, the second data stream being the data stream transmitted by the terminal device to the first cell.

[0492] Based on the third information, the fifth information, and after sending the data packets in the third data stream to the terminal device, the transceiver module 1302 sends information to the first core network device to request the release of the UE context.

[0493] Optionally, the transceiver module 1302 can also be used to receive information from the terminal device indicating a cell handover failure.

[0494] Optionally, the transceiver module 1302 can also be used to receive second UE capability information from the terminal device. The second UE capability is the UE capability information corresponding to the terminal device in the connection of the first cell when the terminal device only accesses the first cell.

[0495] It should be understood that the communication device described here is embodied in the form of a functional module. The term "module" here can refer to application-specific integrated circuits (ASICs), electronic circuits, processors (e.g., shared processors, proprietary processors, or group processors) and memories for executing one or more software or firmware programs, integrated logic circuits, and / or other suitable components supporting the described functions. In an alternative example, those skilled in the art will understand that the communication device can specifically be the terminal device or source base station in the above embodiments. The communication device can be used to execute the various processes and / or steps corresponding to the terminal device or source base station in the above method embodiments; to avoid repetition, these will not be described again here.

[0496] The aforementioned communication device has the function of implementing the corresponding steps performed by the terminal device or source base station in the above method; the above functions can be implemented by hardware or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above functions. In embodiments of this application, the communication device in FIG13 can also be a chip, such as a system-on-a-chip (SOC).

[0497] Figure 14 shows another schematic diagram of the communication device provided in an embodiment of this application. The communication device includes a processor 1401, a transceiver 1402, and a memory 1403. The processor 1401, transceiver 1402, and memory 1403 communicate with each other through an internal connection path. The memory 1403 is used to store instructions, and the processor 1401 is used to execute the instructions stored in the memory 1403 to control the transceiver 1402 to send and / or receive signals.

[0498] It should be understood that the device 1400 may specifically be a terminal device or a source base station in the above embodiments, and may be used to execute the various steps and / or processes corresponding to the terminal device or source base station in the above method embodiments. Optionally, the memory 1403 may include a read-only memory and a random access memory, and provide instructions and data to the processor. A portion of the memory may also include non-volatile random access memory. For example, the memory may also store device type information. The processor 1401 may be used to execute instructions stored in the memory, and when the processor 1401 executes instructions stored in the memory, the processor 1401 is used to execute the various steps and / or processes in the above method embodiments. The transceiver 1402 may include a transmitter, a receiver, and an antenna. The transmitter may be used to implement the various steps and / or processes corresponding to the transceiver for performing a transmission action, and the receiver may be used to implement the various steps and / or processes corresponding to the transceiver for performing a reception action. The transmitter may also be referred to as a transmitter, and the receiver may also be referred to as a receiver.

[0499] It should be understood that, in the embodiments of this application, the processor may be a central processing unit (CPU), or it may be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor.

[0500] In implementation, each step of the above method can be completed by integrated logic circuits in the processor's hardware or by instructions in software. The steps of the method disclosed in the embodiments of this application can be directly manifested as execution by a hardware processor, or as a combination of hardware and software modules within the processor. The software modules can reside in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. This storage medium is located in memory, and the processor executes the instructions in the memory, combining them with its hardware to complete the steps of the above method. To avoid repetition, detailed descriptions are omitted here.

[0501] Figure 15 shows a schematic diagram of the architecture of an O-RAN system provided in an embodiment of this application.

[0502] As shown in Figure 15, this architecture may include components such as a service management and orchestration framework (SMO), a near-real-time RAN intelligent controller (near-real-time RIC), an O-RAN central unit control plane (O-CU-CP), an O-RAN central unit user plane (O-CU-UP), an O-RAN distributed unit (O-DU), an O-RAN radio unit (O-RU), an open cloud infrastructure platform (O-cloud), and an O-eNB. The SMO may also include a non-real-time RAN intelligent controller (non-real-time RIC).

[0503] Among them, O-CU-CP and O-CU-UP belong to the Open Access Network Control Unit (O-RAN central unit or O-RAN control unit, O-CU). O-CU can also be called Open Access Network Aggregation Unit or Open Access Network Central Unit.

[0504] O-CU can be used to implement the radio resource control (RRC) layer, packet data convergence protocol (PDCP) layer, service data adaptation protocol (SDAP) layer, and other control functions in the 3GPP standard.

[0505] O-CU-CP is similar to CU-CP in the NR system and can be used to implement the functions of the RRC layer and the control plane functions of the PDCP layer.

[0506] O-CU-UP is similar to CU-UP in the NR system and can be used to implement the functions of the SDAP layer and the user plane functions of the PDCP layer.

[0507] O-DU is based on low-layer function segmentation and can be used to implement radio link control (RLC) layer functions, media access control (MAC) layer functions, and higher-layer (closer to the MAC) functions of the physical layer (PHY) in the 3GPP standard. Among them, the higher-layer functions of the physical layer include one or more of the following: forward error correction (FEC) encoding / decoding, scrambling / descrambling, or modulation / demodulation.

[0508] O-RU is based on low-level function segmentation and can be used to implement low-level (near radio frequency) functions of the Physical Layer (PHY) in 3GPP standards, as well as radio frequency functions. The low-level PHY functions include one or more of the following: Fast Fourier Transform (FFT) / Inverse Fast Fourier Transform (iFFT), digital beamforming, or extraction and filtering of the Physical Random Access Channel (PRACH). O-DU can be similar to a Transmission Reception Point (TRP) or Remote Radio Head (RRH) in 3GPP, but includes low-level PHY functions such as FFT / iFFT or PRACH extraction.

[0509] A non-real-time RAN intelligent controller, also known as a non-RT RIC or NRT RIC, is used to implement non-real-time intelligent management of RAN functions. It can also implement AI / ML workflows, including model training and model updates, and guide applications / functions within the nRT RIC based on policies.

[0510] A near-real-time RAN intelligent controller, also known as a near-RT RIC or nRT RIC, is used to achieve near-real-time intelligent management of the RAN. Through data collection and related operations on the E2 interface, it enables near-real-time control and optimization of O-RAN modules and resources.

[0511] The interfaces in the open access network shown in Figure 15 may include:

[0512] The NG interface can be understood as the interface between 5G and future mobile communication systems, such as the interface between a 5G base station and the 5G core network. For example, in a 5G mobile communication system, the NG interface can be understood as the communication interface between New Radio Access Network (NR RAN) equipment (such as base stations, CUs, CU-CPs, or CU-UPs) and the 5G core network (5GC).

[0513] The NG interface may include the NG control plane (NG-c) or the NG user plane (NG-u).

[0514] NG-c can be used to transmit control signaling. NG-u can be used to transmit user data.

[0515] Xn interface: The interface between NR RAN devices (such as base stations, CUs, CU-CPs, or CU-UPs). The Xn interface may include the Xn control plane interface (Xn-c) or the Xn user plane interface (Xn-u).

[0516] Xn-c can be used to transmit control signaling. Xn-u can be used to transmit user data.

[0517] X2 Interface: The interface between LTE RAN devices; X2-u is the user plane X2 interface, and X2-c is the control plane X2 interface. In NR, the X2 interface is mainly used in Evolved Universal Terrestrial Radio Access Network - New Radio Dual Connectivity (EN-DC) scenarios, where the master station is an LTE RAN device that connects to the LTE core network via the X2 interface.

[0518] E1 interface: The interface between CU-CP and CU-UP.

[0519] F1-C interface: The interface between CU-CP and DU.

[0520] F1-U interface: The interface between CU-UP and DU.

[0521] O1 Interface: The communication interface between the SMO and O-RAN components (such as O-CU, O-DU, O-RU). The SMO can perform configuration management, fault management, performance management, and other operations through the O1 interface to ensure the normal operation and maintenance of the network.

[0522] O2 Interface: The communication interface between the SMO and the open cloud infrastructure platform (O-cloud). Virtual Infrastructure Manager (VIM) is used, for example, on the open cloud infrastructure platform (O-cloud).

[0523] E2 interface: Communication interface between the near real-time RAN intelligent controller and CU-CP, CU-UP, or DU.

[0524] A1 interface: Communication interface between the non-real-time RAN intelligent controller and the near-real-time RAN intelligent controller.

[0525] It should be understood that in the O-RAN system, CU can be called O-CU, CU-CP can be called O-CU-CP, CU-UP can be called O-CU-UP, and DU can be called O-DU.

[0526] As shown in Figure 15, the components in the open access network can communicate with each other through their respective interfaces. For example, the SMO can communicate with the O-eNB, near real-time RAN Intelligent Controller, O-CU-CP, O-CU-UP, O-DU, and / or O-RU through the O1 interface. The SMO can communicate with the open cloud infrastructure platform through the O2 interface. The non-real-time RAN Intelligent Controller can communicate with the near real-time RAN Intelligent Controller through the A1 interface. The near real-time RAN Intelligent Controller can communicate with the O-eNB, O-CU-CP, O-CU-UP, and / or O-DU through the E2 interface. The O-CU-CP can communicate with the O-DU through the F1-C interface. The O-CU-UP can communicate with the O-DU through the F1-U interface. The O-DU can communicate with the O-RU through the open fronthaul control, user, and synchronization plane (open FH CUS-plane) interface and / or the open fronthaul management plane (open FH M-plane) interface. The O-CU-CP can communicate with the O-CU-UP through the E1 interface. The O-CU-CP can communicate with the core network through the NG-c interface. The O-CU-UP can communicate with the core network via the NG-u interface. The open fronthaul control, user, and synchronization plane (open FH CUS-plane) can also be called the open FH CUS plane. The open fronthaul management plane (open FH M-plane) can also be called the open FH M plane.

[0527] This application also provides a computer-readable storage medium for storing a computer program for implementing the methods shown in the above-described method embodiments.

[0528] This application also provides a computer program product, which includes a computer program (also referred to as code or instructions) that, when run on a computer, allows the computer to perform the methods shown in the above-described method embodiments.

[0529] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0530] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and modules described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0531] In the embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or modules may be electrical, mechanical, or other forms.

[0532] The modules described as separate components may or may not be physically separate. Similarly, the components shown as modules may or may not be physical modules; they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0533] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0534] If a function is implemented as a software module 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 this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0535] The above description is merely a specific embodiment of this application, but the protection scope of the embodiments of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of this application should be included within the protection scope of the embodiments of this application. Therefore, the protection scope of the embodiments of this application should be determined by the protection scope of the claims.

Claims

A cell handover method, characterized in that, include: Receive first information from the first cell, the first information being used to instruct the terminal device to perform cell handover; A first message is sent to the second cell via the common control channel. The first message is used to request the establishment of a Radio Resource Control (RRC) connection. The method according to claim 1, characterized in that, The method further includes: A second message is received from the second cell, the second message being a response to the first message, and the second message is transmitted via a common control channel. The method according to claim 2, characterized in that, Before sending the first message or receiving the second message, the terminal device maintains a connection with the first cell. The method according to claim 3, characterized in that, After sending the first message to the second cell, or after receiving the second message from the second cell, the method further includes: Receive second information from the first cell, and disconnect from the first cell based on the second information. The method according to any one of claims 2 to 4, characterized in that, After receiving the second message from the second cell, the method further includes: Send the data packets of the first data stream to the second cell. The method according to any one of claims 1 to 5, characterized in that, The method further includes: Upon completion of transmitting all data packets in the second data stream to the first cell, a third message is sent to the first cell. This third message indicates that the transmission of data packets in the second data stream has been completed. The second data stream is the data stream transmitted by the terminal device to the first cell. And / or The system receives fourth information from the first cell, which indicates that the data packets in the third data stream have been sent. The third data stream is the data stream sent by the first cell to the terminal device. The method according to any one of claims 1 to 6, characterized in that, The method further includes: Send first user equipment (UE) capability information to the first cell. The first UE capability information is the UE capability information corresponding to the connection between the terminal device and the first cell when accessing the first cell and the second cell. The method according to any one of claims 1 to 7, characterized in that, The method further includes: The first data packet of the fourth data stream from the second cell is received through the access layer AS; In the event that the RRC connection with the first cell is released, and / or the second data packet of the fourth data stream from the first cell has been delivered to the upper layer, the first data packet of the fourth data stream is transmitted to the upper layer through the AS layer. The method according to any one of claims 1 to 8, characterized in that, The first information includes a first cell list, which includes the second cell list; or, The first information includes a first Public Land Mobile Network (PLMN) list, and the cells indicated by the first PLMN list include the second cell. The method according to any one of claims 1 to 9, characterized in that, The method further includes: If a user fails to access a cell in the second cell list, or fails to access any cell in the second cell list within a first time period, the user sends information indicating a cell handover failure to the first cell. The second cell list includes the second cell and is determined by the terminal device, or the second cell list is indicated by the first information. The method according to claim 10, characterized in that, The method further includes: Send the second UE capability information to the first cell. The second UE capability is the UE capability information corresponding to the terminal device in the connection of the first cell when the terminal device only accesses the first cell. The method according to any one of claims 1 to 11, characterized in that, The method further includes: Before disconnecting from the first cell, and in the event that a radio link failure has occurred with the first cell, a first request is sent to the third cell. The first request is used to request RRC reconstruction. Both the third cell and the first cell belong to a non-terrestrial network or a terrestrial network. A cell handover method, characterized in that, include: Determine the first information, which is used to instruct the terminal device to perform cell handover; The first information is sent to the terminal device so that the terminal device sends a first message to the second cell through the common control channel. The first message is used to request the establishment of an RRC connection. The method according to claim 13, characterized in that, The determination of the first information includes: Receive information from a first core network device indicating a first PLMN list, the first PLMN list including PLMNs supported by the terminal device; Based on the first PLMN list, the first information is determined. The method according to claim 14, characterized in that, The first information includes a first cell list, which includes the second cell list, and the first cell list is determined based on the first PLMN list; or, The first information includes a first PLMN list, and the cells indicated by the first PLMN list include the second cell. The method according to any one of claims 13 to 15, characterized in that, After sending the first information to the terminal device, the method further includes: The terminal device receives first UE capability information, which is the UE capability information corresponding to the connection between the terminal device and the first cell when accessing the first cell and the second cell. The method according to any one of claims 13 to 16, characterized in that, The method further includes: Receive information from the first core network device indicating the release of the UE context; Send a second message to the terminal device, the second message being used to instruct the release of the RRC connection. The method according to claim 17, characterized in that, The receipt of information from the first core network device indicating the release of the UE context includes: The system receives fifth information from the first core network device, the fifth information being used to indicate that the data packets in the third data stream have been sent, the third data stream being the data stream to be sent to the terminal device. Send information to the first core network device to request the release of the UE context; Receive information from the first core network device indicating the release of the UE context. The method according to claim 18, characterized in that, Sending information to the first core network device to request the release of the UE context includes: Based on the fifth information and after sending the data packets in the third data stream to the terminal device, information for requesting the release of the UE context is sent to the first core network device. The method according to claim 18 or 19, characterized in that, Sending information to the first core network device to request the release of the UE context includes: The terminal device receives third information, which indicates that the data packets in the second data stream have been sent. The second data stream is the data stream transmitted by the terminal device to the first cell. Based on the third information, the fifth information, and after sending the data packets in the third data stream to the terminal device, information for requesting the release of the UE context is sent to the first core network device. The method according to any one of claims 13 to 20, characterized in that, The method further includes: Receive information from the terminal device indicating a cell handover failure. The method according to claim 21, characterized in that, The method includes: The terminal device receives second UE capability information, where the second UE capability is the UE capability information corresponding to the terminal device's connection in the first cell when the terminal device only accesses the first cell. A communication device, characterized in that, include: It includes modules for performing the method as described in any one of claims 1 to 12, or the method as described in any one of claims 13 to 22. A communication device, characterized in that, include: A processor, which, when invoking a computer program, causes the apparatus to perform the method of any one of claims 1 to 12, or the method of any one of claims 13 to 22. A computer-readable storage medium, characterized in that, Used to store computer programs, the computer programs including instructions for implementing the method as described in any one of claims 1 to 12, or the method as described in any one of claims 13 to 22. A computer program product, the computer program product comprising instructions, characterized in that, When the instructions are executed on a computer, the computer causes the computer to implement the method as described in any one of claims 1 to 12, or the method as described in any one of claims 13 to 22.

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