WO2022056863A1

WO2022056863A1 - Switching method and apparatus

Info

Publication number: WO2022056863A1
Application number: PCT/CN2020/116283
Authority: WO
Inventors: 黄曲芳; 酉春华
Original assignee: 华为技术有限公司
Priority date: 2020-09-18
Filing date: 2020-09-18
Publication date: 2022-03-24

Abstract

Provided in the embodiments of the present application are a switching method and apparatus. The method comprises: a target access network device determining second time information according to first time information from a source access network device, wherein the second time information is used for a terminal device to initiate random access; and the target access network device sending a switching response message to the source access network device, wherein the switching response message comprises the second time information. By means of the method in the embodiments, a target access device instructs, by means of second time information, a terminal device to initiate random access, such that an increase in the delay of a service frame transmitted during a random access process that is caused by the terminal device being switched to the target access network device at any moment by means of initiating random access can be prevented, and thus, the transmission delay of data during a switching process can be reduced.

Description

A switching method and device

technical field

The present application relates to the field of wireless communication technologies, and in particular, to a handover method and device.

Background technique

In a mobile communication system such as a new radio (new radio) system or a long term evolution (long term evolution, LTE) system, an access network device can provide mobile data transmission services for terminal devices. After the terminal device is connected to the network, it may switch from one access network device to another access network device. The handover process includes processes such as establishing a wireless connection between the terminal device and the target access network device, and establishing a data channel between the target access network device and the service gateway. Therefore, the downlink data transmission delay of the terminal device will increase significantly.

The increase in the downlink data transmission delay of the terminal equipment will reduce the user's service experience. For example, when a terminal device provides an extended reality (XR) service for a user, during the switching process, due to the increased transmission delay, the user may feel dizzy, video frame skip, video freeze, etc., which affects experience.

SUMMARY OF THE INVENTION

The purpose of the present application is to provide a handover method and device to reduce the data transmission delay in the handover process.

In a first aspect, the present application provides a handover method, which is applied to handover of a terminal device from a source network device to a target network device. The execution body of the method is the target access network device or a module in the target access network device, and the description is made by taking the target access network device as the execution body as an example. The target access network device receives the handover request message from the source access network device, and the handover request message includes first time information, and the first time information can be used to determine the first time. The first time is when the first service frame arrives at the source access network. The time of the network access device, or the first time is the time when the second service frame reaches the target access network device; the target access network device can determine the second time information according to the first time information; the second time information is used for the terminal device to initiate random access; the target access network device sends a handover response message to the source access network device; the handover response message includes second time information. The service frame may be an XR service frame transmitted periodically.

By implementing the method described in the first aspect, the target access network device can determine the time when the last service frame arrives at the source access network device or the time when the first service frame arrives at the target access network device. The second time information of random access prevents the terminal device from switching to the target access network device by initiating random access at any time, resulting in the service frame transmitted during the switching process cannot be transmitted to the terminal device, resulting in an increase in the delay of the service frame. It can reduce the data transmission delay during the handover process.

In a possible implementation manner of the first aspect, the second time information includes one or more of the following: the time when the first service frame transmitted to the terminal device through the target access network device reaches the first core network device; The time when the first service frame arrives at the target access network device; the time when the first service frame arrives at the source access network device if the terminal device does not switch; the last time when the first service frame is transmitted to the terminal device through the source access network device The moment when a service frame arrives at the first core network device; the moment when the last service frame arrives at the source access network device.

By implementing this method, the second time information can indirectly indicate the moment when the terminal device initiates random access to the target access network device. When initiating random access, the terminal device can determine the time when the service frame arrives at the source access network device or the target access network device according to the second time information, so as to flexibly determine the time when random access is initiated.

In a possible implementation manner of the first aspect, the second time information includes a second time, the second time is the time when the terminal device initiates random access to the target access network device, and the second time is equal to the time when the terminal device initiates random access to the target access network device. The moment when the last service frame transmitted by the device to the terminal device arrives at the source access network device.

By implementing this method, the second time information can directly indicate the moment when the terminal device initiates random access to the target access network device. According to the second time information, it can be known that the moment when the terminal device initiates random access is between the transmission intervals of two service frames, and there is no service frame transmission in this transmission interval, so that the data transmission can be greatly reduced during the handover process. time delay.

In a possible implementation manner of the first aspect, the moment when the first service frame reaches the target access network device is determined according to the first moment and the transmission period; the transmission period is the period of the service corresponding to the first service frame ; Or, the moment when the second service frame reaches the target access network device is determined according to the first moment, the transmission period, the first delay and the second delay; the first delay is the time from the source access network device to the first core The delay between network devices, and the second delay is the delay between the target access network device and the first core network device.

In a possible implementation manner of the first aspect, the second time information is used to determine the second time, the second time is the time when the terminal device initiates random access to the target access network device, and the second time is the time when the terminal device initiates random access to the target access network device. The last service frame transmitted by the network access device to the terminal device arrives at any time after the time when the source access network device arrives.

By implementing this method, the moment of initiating random access can be flexibly determined to avoid interference to data transmission.

In a possible implementation manner of the first aspect, the target access network device is determined to be in the target cell of the target access network device, and transmits service frames to other terminal devices at the same time, and the transmission period is the same as that of transmitting the service frames to the terminal device. The transmission period is the same. If the target access network device determines that the service frame of the terminal device and the service frames of other terminal devices arrive at the same time or overlap, the target access network device may also send adjustment instruction information to the server or the first core network device, and the adjustment instruction information is used for Instruct the server to advance or delay the sending time of the service frame sent to the terminal device by Y milliseconds from the third moment or from the third service frame; wherein, Y is greater than 0 and less than the transmission period of the service corresponding to the first service frame , the third time is any time after the first time, and the third service frame is any service frame after the first service frame.

By implementing this method, it can be avoided that the target access network device transmits service frames to multiple terminal devices in the same time period, which causes the target access network device to have an excessively high load. By advancing or delaying the sending time of the service frame sent to the terminal device by Y milliseconds, the load of the target access network device can be reduced, thereby improving the reliability of data transmission.

In a possible implementation manner of the first aspect, the method further includes: before receiving the random access request from the terminal device, the target access network device sends a path switch request message to the second core network device; the path switch request message It is used to request the second core network device to initiate a path switch before the last service frame transmitted to the terminal device through the source access network device reaches the source access network device, and the data transmission path of the terminal device is transferred from the source access network device to the source access network device. The data transmission path between the device and the first core network device is switched to the data transmission path between the target access network device and the first core network device; or, the path switching request message is used to request the second core network device to pass The path switching is completed before the time when the first service frame transmitted by the target access network device to the terminal device reaches the target access network device.

By implementing this method, when the terminal device initiates random access, the target access network device initiates a path switching request, which can reduce the time required for handover and further reduce the data transmission delay.

In a possible implementation manner of the first aspect, the path switching request message includes second time information.

In a second aspect, the present application provides a handover method, which is applied to handover of a terminal device from a source network device to a target network device. The execution body of the method is the source access network device or a module in the source access network device, and the description is made by taking the source access network device as the execution body as an example. The source access network device sends a handover request message to the target access network device, where the handover request message includes first time information, the first time information is used to determine the first time, and the first time is when the first service frame arrives at the source access network device or the first time is the time when the second service frame reaches the target access network device; the source access network device receives the handover response message from the target access network device, and the handover response message includes the second time information; the second time The information is determined according to the first time information.

By implementing the method described in the second aspect, the source access network device can instruct the terminal device to initiate random access according to the second time information, so as to prevent the terminal device from switching to the target access network device by initiating random access at any time, resulting in The service frame transmitted during the handover process cannot be transmitted to the terminal device, which causes the delay of the service frame to increase, thereby reducing the data transmission delay during the handover process.

In a possible implementation manner of the second aspect, the source access network device sends a handover command to the terminal device; the handover command includes second time information, and the handover command is used to instruct the terminal device to send the target access network to the target access network according to the second time information The device initiates random access.

By implementing this method, the source access network device sends the second indication information, and the terminal device can determine the time when the service frame arrives at the source access network device or the target access network device according to the second time information, so as to flexibly determine the initiation The moment of random access.

In a possible implementation manner of the second aspect, the source access network device sends a handover command to the terminal device, and sends indication information to the terminal device; the indication information is used to indicate the end of transmission of the last video frame transmitted to the terminal device; The handover command is used to instruct the terminal device to initiate random access to the target access network device after the transmission of the last service frame is completed, and the last service frame is determined according to the second time information.

By implementing this method, the source access network device instructs the terminal device to initiate random access at the end of transmission of the last service frame through the indication information. Since there is no service frame between the end of transmission of the last service frame and the start of transmission of the next service frame Transmission can minimize the delay of service frames caused by handover and reduce the delay of data transmission.

In a possible implementation manner of the second aspect, the second time information includes one or more of the following: the moment when the first service frame transmitted to the terminal device through the target access network device reaches the first core network device; The time when the first service frame arrives at the target access network device; the time when the first service frame arrives at the source access network device if the terminal device does not switch; the last time when the first service frame is transmitted to the terminal device through the source access network device The moment when a service frame arrives at the first core network device; the moment when the last service frame arrives at the source access network device.

In a possible implementation manner of the second aspect, the method further includes: the source access network device sends a handover command to the terminal device; the handover command includes a system frame number and a time slot number; the time slot number is used to instruct the terminal device to initiate a random For the access time slot, the system frame number is used to indicate the radio frame where the time slot is located; the system frame number and the time slot number are determined according to the second time information.

By implementing this method, time synchronization is not required between the source access network device and the terminal device, and the terminal device can also determine when to initiate random access according to the system frame number and time slot number, thereby reducing the complexity of system implementation.

In a possible implementation manner of the second aspect, the second time information is used to determine the second time, and the second time is the time when the terminal device initiates random access to the target access network device.

In a possible implementation manner of the second aspect, the second time is any time after the time when the last service frame transmitted by the source access network device to the terminal device arrives at the source access network device; or, the first The second time is the start time of the time slot corresponding to the time slot number in the radio frame indicated by the system frame number.

In a third aspect, the present application provides a handover method, which is applied to handover of a terminal device from a source network device to a target network device. The execution body of the method is a terminal device or a module in the terminal device, and the description is made by taking the terminal device as the execution body as an example. The terminal device receives a handover command from the source access network device; the handover command includes second time information; the handover command is used to instruct the terminal device to initiate random access to the target access network device; the terminal device accesses the target according to the second time information The network device initiates random access.

By implementing the method described in the third aspect, the terminal device can initiate random access according to the second time information, so as to prevent the terminal device from switching to the target access network device by initiating random access at any time, resulting in the transmission of data during the switching process. The service frame cannot be transmitted to the terminal device, which increases the delay of the service frame, thereby reducing the data transmission delay during the switching process.

In a possible implementation manner of the third aspect, the second time information includes one or more of the following: the time when the first service frame transmitted by the target access network device to the terminal device reaches the first core network device; The time when the first service frame arrives at the target access network device; the time when the first service frame arrives at the source access network device if the terminal device does not switch; the last time when the first service frame is transmitted to the terminal device through the source access network device The moment when a service frame arrives at the first core network device; the moment when the last service frame arrives at the source access network device.

In a possible implementation manner of the third aspect, the terminal device initiates random access to the target access network device according to the second time information, including: the terminal device initiates random access to the target access network device within a random access opportunity after the second time point The device initiates random access; the second time is determined according to the second time information.

In a possible implementation manner of the third aspect, the second time is any time after the time when the last service frame transmitted by the source access network device to the terminal device arrives at the source access network device.

In a fourth aspect, the present application provides a handover method, which is applied to handover of a terminal device from a source network device to a target network device. The execution body of the method is a terminal device or a module in the terminal device, and the description is made by taking the terminal device as the execution body as an example. The terminal device receives the handover command from the source access network device; the handover command includes the system frame number and time slot number; the time slot number is used to indicate the time slot where the terminal device initiates random access, and the system frame number is used to indicate the time slot where Radio frame; the handover command is used to instruct the terminal device to initiate random access to the target access network device; the terminal device initiates random access to the target access network device within the random access opportunity after the time slot in the radio frame.

By implementing the method described in the fourth aspect, the terminal device can determine the time slot and radio frame for initiating random access, and the terminal device and the source access network device do not need time synchronization, thereby reducing the complexity of system implementation.

In a possible implementation manner of the fourth aspect, the system frame number and time slot number are determined according to the arrival time of the last service frame transmitted by the source access network device to the terminal device, or the system frame number and time slot number is determined according to the second time information.

By implementing this method, since there is no service frame transmission between the end of transmission of the last service frame and the start of transmission of the next service frame, the delay of the service frame caused by handover can be minimized, and the delay of data transmission can be reduced.

In a fifth aspect, the present application provides a handover method, which is applied to handover of a terminal device from a source network device to a target network device. The execution body of the method is the source access network device or a module in the source access network device, and the description is made by taking the source access network device as the execution body as an example. The source access network device determines the last service frame transmitted to the terminal device through the source access network device; the source access network device sends a handover command to the terminal device, and sends indication information to the terminal device; the indication information is used to indicate the last service frame The frame transmission ends; the handover command is used to instruct the terminal device to initiate random access to the target access network device after the transmission of the last service frame ends.

By implementing the method described in the fifth aspect, by instructing the terminal device to start random access after the transmission of the last service frame, the service frame delay caused by handover can be minimized, and the data transmission delay can be reduced. In a possible implementation manner of the fifth aspect, the last service frame includes at least one data packet; when the last service frame is encoded in the first coding manner, the indication information is used to indicate the last service frame corresponding to the last service frame The data packet transmission ends; or, when the last service frame is encoded in the second encoding manner, the indication information is used to indicate that the transmission of the last data packet of the base layer data corresponding to the last service frame ends.

In a sixth aspect, the present application provides a handover method, which is applied to handover of a terminal device from a source network device to a target network device. The execution body of the method is a terminal device or a module in the terminal device, and the description is made by taking the terminal device as the execution body as an example. The terminal device receives the indication information from the source access network device and the handover command; the indication information is used to indicate the end of the transmission of the last service frame; the handover command is used to instruct the terminal device to send the target access network device after the end of the transmission of the last service frame. Initiate random access; the terminal device initiates random access to the target access network device within the random access opportunity after the last service frame transmission ends according to the handover command.

By implementing the method described in the sixth aspect, the terminal device starts random access after the transmission of the last service frame, which can minimize the delay of the service frame caused by the handover and reduce the delay of data transmission.

In a possible implementation manner of the sixth aspect, the handover command includes a handover condition, and the handover condition is a condition that the terminal device needs to meet to perform the handover; when the handover condition is satisfied, the terminal device randomly after the transmission of the last service frame ends Initiate random access to the target access network device within the access opportunity.

In a possible implementation manner of the sixth aspect, the last service frame includes at least one data packet; when the last service frame is encoded in the first encoding manner, the indication information is used to indicate the last service frame corresponding to the last service frame. The data packet transmission ends; or, when the last service frame is encoded in the second encoding manner, the indication information is used to indicate that the transmission of the last data packet of the base layer data corresponding to the last service frame ends.

In a possible implementation manner of the sixth aspect, the handover condition includes one or more of the following: the received power of the reference signal of the cell in the target access network device is greater than the first threshold; the reference signal of the cell in the target access network device The reception quality is greater than the second threshold; the signal-to-interference-noise ratio of the cell in the target access network device is greater than the third threshold.

In a seventh aspect, a communication apparatus is provided, including functional modules for implementing the method in the foregoing first aspect and any possible implementation manner of the first aspect.

In an eighth aspect, a communication apparatus is provided, including functional modules for implementing the method in the foregoing second aspect and any possible implementation manner of the second aspect.

In a ninth aspect, a communication device is provided, including functional modules for implementing the method in the foregoing third aspect and any possible implementation manner of the third aspect.

In a tenth aspect, a communication apparatus is provided, including functional modules for implementing the method in the foregoing fourth aspect and any possible implementation manner of the fourth aspect.

In an eleventh aspect, a communication device is provided, including functional modules for implementing the method in the foregoing fifth aspect and any possible implementation manner of the fifth aspect.

A twelfth aspect provides a communication apparatus, including functional modules for implementing the method in any possible implementation manner of the sixth aspect and the sixth aspect.

A thirteenth aspect provides a communication device, comprising a processor and an interface circuit, the interface circuit is configured to receive signals from other communication devices other than the communication device and transmit to the processor or transfer signals from the processor Sent to other communication devices other than the communication device, the processor is used to implement the method in the first aspect or any possible implementation manner of any one of the foregoing aspects through a logic circuit or executing code instructions.

A fourteenth aspect provides a communication device, comprising a processor and an interface circuit, the interface circuit is configured to receive signals from other communication devices other than the communication device and transmit to the processor or transfer signals from the processor Sent to other communication devices other than the communication device, the processor is used to implement the functional modules of the method in the foregoing second aspect and any possible implementation manner of the second aspect through logic circuits or executing code instructions.

A fifteenth aspect provides a communication device, comprising a processor and an interface circuit, the interface circuit is configured to receive signals from other communication devices other than the communication device and transmit to the processor or transfer signals from the processor Sent to other communication devices other than the communication device, the processor is used to implement the functional modules of the third aspect and the method in any possible implementation manner of the third aspect through logic circuits or executing code instructions.

A sixteenth aspect provides a communication device, comprising a processor and an interface circuit, the interface circuit is configured to receive signals from other communication devices other than the communication device and transmit to the processor or transfer signals from the processor Sent to other communication devices other than the communication device, the processor uses logic circuits or executes code instructions to implement the functional modules of the fourth aspect and the method in any possible implementation manner of the fourth aspect.

A seventeenth aspect provides a communication device, comprising a processor and an interface circuit, the interface circuit is configured to receive signals from other communication devices other than the communication device and transmit to the processor or transfer signals from the processor Sent to other communication devices other than the communication device, the processor is used to implement the functional modules of the methods in the fifth aspect and any possible implementation manner of the fifth aspect through logic circuits or executing code instructions.

In an eighteenth aspect, a communication device is provided, comprising a processor and an interface circuit, the interface circuit is configured to receive signals from other communication devices other than the communication device and transmit to the processor or transfer signals from the processor Sent to other communication devices other than the communication device, the processor is used to implement the functional modules of the methods in the sixth aspect and any possible implementation manner of the sixth aspect through logic circuits or executing code instructions.

A nineteenth aspect provides a computer-readable storage medium, where a computer program or instruction is stored, and when the computer program or instruction is executed by a processor, the aforementioned first to sixth aspects are implemented A method in any aspect, any possible implementation of any aspect.

A twentieth aspect provides a computer program product comprising instructions, when the instructions are executed by a processor, to implement any one of the foregoing first to sixth aspects, or any possible implementation manner of any aspect. method.

A twenty-first aspect provides a chip system, where the chip system includes a processor, and may further include a memory, for implementing the method described in any one of the foregoing first to sixth aspects. The chip system can be composed of chips, and can also include chips and other discrete devices.

According to a twenty-second aspect, a communication system is provided, the system comprising the apparatus of the seventh aspect (eg, target access network equipment), the apparatus of the eighth aspect (eg, source access network equipment), and the ninth aspect The apparatus (eg, terminal device) described in the aspect.

According to a twenty-third aspect, a communication system is provided, the system comprising the apparatus of the seventh aspect (eg, a target access network device), the apparatus of the eighth aspect (eg, a source access network device), and the tenth aspect The apparatus (eg, terminal device) described in the aspect.

A twenty-fourth aspect provides a communication system, where the system includes the apparatus (eg, source access network device) described in the eleventh aspect and the apparatus (eg, terminal device) described in the twelfth aspect.

Description of drawings

FIG. 1 is a schematic diagram of the architecture of a mobile communication system applicable to an embodiment of the present application;

FIG. 2 is a schematic diagram of time delay at different stages provided by an embodiment of the present application;

Fig. 3 is a kind of handover flow schematic diagram in the prior art;

FIG. 4 is a schematic flowchart of a switching method provided by an embodiment of the present application;

5 is a schematic diagram of a transmission period of a video frame provided by an embodiment of the present application;

FIG. 6 is a schematic flowchart of a switching method provided by an embodiment of the present application;

FIG. 7 is a schematic flowchart of a switching method provided by an embodiment of the present application;

FIG. 8 is a schematic structural diagram of a communication device according to an embodiment of the present application;

FIG. 9 is a schematic structural diagram of a communication device according to an embodiment of the present application.

detailed description

The embodiments of the present application will be described in further detail below with reference to the accompanying drawings.

The technical solutions of the embodiments of the present application can be applied to various mobile communication systems, for example, a long term evolution (LTE) system, an LTE frequency division duplex (FDD) system, an LTE time division duplex (LTE) system duplex, TDD) and fifth generation (5th generation, 5G) systems, such as NR systems, are not limited here.

To facilitate understanding of the embodiments of the present application, firstly, a communication system applicable to the embodiments of the present application is described by taking the mobile communication system shown in FIG. 1 as an example. FIG. 1 exemplarily shows a schematic diagram of the architecture of a mobile communication system applicable to the embodiments of the present application. As shown in FIG. 1 , in the 5G system architecture, a terminal device can communicate with a core network via an access network device, and the terminal device Can refer to user equipment (UE), access terminal, subscriber unit, subscriber station, mobile station, mobile station, remote station, remote terminal, mobile device, user terminal, session initiation protocol (SIP) phone , wireless local loop (WLL) stations, personal digital assistants (PDAs), handheld devices with wireless communication capabilities, computing devices or other processing devices connected to wireless modems, in-vehicle devices, wearable devices equipment, terminal equipment in the future 5G network, etc. For convenience of description, only one terminal device is illustrated in FIG. 1 . In an actual network, multiple terminal devices may coexist, which will not be repeated here.

Access network (AN) equipment, access network equipment can also be called radio access network (radio access network, RAN) equipment, hereinafter collectively referred to as access network equipment, mainly responsible for providing wireless connections for terminal equipment, Ensure reliable transmission of uplink and downlink data of terminal equipment, etc. The access network equipment may be a next-generation base station (generation Node B, gNB), an evolved Node B (evolved Node B, eNB), or the like.

When the access network equipment is a gNB, it can be composed of a centralized unit (CU) and a distributed unit (DU), that is, the functions of the base station in the original access network are split, and the part of the base station is divided. Functions are deployed in one CU, the remaining functions are deployed in DUs, and multiple DUs share one CU, which can save costs and facilitate network expansion. The segmentation of CU and DU can be divided according to the protocol stack, radio resource control (radio resource control, RRC), service data adaptation protocol (service data adaptation protocol, SDAP) and packet data convergence protocol (packet data convergence protocol, PDCP) The layer is deployed in the CU, and the rest of the radio link control (radio link control, RLC) layer, medium access control (media access control, MAC) layer and physical layer (physical, PHY) are deployed in the DU. The CU and DU are connected through the F1 interface. CU represents that the gNB is connected to the core network through the NG interface, and the CU represents that the gNB is connected to other gNBs through the Xn interface.

A session management function (SMF) network element, which can select an appropriate user plane function (UPF) network element for the terminal device according to the location information of the terminal device.

The main functions of the UPF network element include packet routing and forwarding, and quality of service (QoS) processing of user plane data.

Access and mobility management function (AMF) network element, the main functions include the termination point of the wireless access network control plane, the termination point of non-access signaling, mobility management, lawful interception, access authorization or authentication, etc.

The policy control function (PCF) network element is mainly responsible for the establishment, release and modification of user plane transmission paths.

Authentication server function (authentication server function, AUSF) network element, its main functions include user authentication and so on.

The user data management (UDM) network element is mainly responsible for managing the subscription data of users.

A data network (DN) may refer to a network that provides services for terminal devices.

FIG. 1 is just an example, and may also include other network elements, such as an application function (application function, AF) network element, etc., which will not be illustrated one by one here.

Figure 1 also shows the interfaces between various network elements, such as the N2 interface between the access network device and the AMF network element, the N3 interface between the access network device and the UPF network element, etc., which are not repeated here. One more elaboration.

The network architecture shown in FIG. 1 can provide a variety of business services for the terminal device, for example, can transmit the data required by the XR service for the terminal device. In XR, the terminal device is connected to an XR display device, for example, through a universal serial bus (Universal Serial Bus, USB) or through a Bluetooth or wireless connection. The XR display device can be a device similar to a helmet. The terminal device can provide the XR display device with video data and audio data, and the XR display device can display the acquired video data to the XR display device through three-dimensional dynamic scene, entity behavior interaction, etc. Users, providing users with an immersive application experience.

The XR display device and the terminal device can be physically integrated or separate. Sensors in the XR display device sense the user's position, movement changes, etc., and generate user feedback information, where the movement changes include but are not limited to changes in viewing angle, line of sight, and movement rate. The terminal device transmits the obtained feedback information to the XR server through the mobile communication system. The XR server generates corresponding video data and audio data according to the user's position, action changes and other feedback information, combined with the user's scene in the game or in the real scene, and transmits the corresponding video data and audio data to the XR display device connected to the terminal device through the mobile communication system. The XR display device is shown to the user.

As shown in Figure 2, for the XR service, the delay of each stage includes three parts:

1. Terminal-side delay: It consists of two parts. The first part includes the sensor in the XR display device, which generates feedback information according to the user's position, motion information, and action changes, encodes the feedback information, and delivers the encoded data to the access point. The delay caused by the layer waiting for transmission, etc.; the second part includes the delay caused by the terminal equipment buffering, video and audio decoding, and display after receiving the data from the XR server. The total delay of the two parts is about 25-30 milliseconds (ms).

2. Network side delay: It consists of two parts. The first part corresponds to the uplink transmission. After the terminal device receives the data (such as user location, motion information, etc.) from the upper layer (such as the application layer), it transmits the data through the mobile communication network. To the XR server; the second part corresponds to the downlink transmission. After the access network device receives the response data from the XR server, it transmits the response data to the terminal device, and the access layer of the terminal device submits it to the upper layer of the terminal, as shown by XR equipment. The total delay of the two parts is about 14ms.

3. Server side delay: After the XR server receives the feedback information from the XR display device (including the user's position, line of sight information, etc.), it takes time to generate a response after processing. Specifically, the processing of the XR server includes generating original video and audio data, rendering and enhancing virtual objects for the original video data, video encoding, audio encoding, and packaging to form a streaming media file, which takes about 26-34 ms in total.

It should be noted that the above only takes the XR service as an example for illustration. The delay in the transmission process of other services is similar to that of the XR service. For details, please refer to the description of the XR service.

At present, the process of switching the access network device by the terminal device can be as shown in Figure 3, which mainly includes the following processes:

S301: The terminal device sends a measurement report (measurement report) to the source access network device. The measurement report includes information such as reference signal received power (RSRP).

S302: The source access network device determines to perform handover according to information such as RSRP in the measurement report. It should be noted that, as to whether the source access network device needs to switch the access network device according to the measurement report, reference may be made to the description in the prior art, which will not be repeated here.

S303: The source access network device sends a handover request (handover request) message to the target access network device. The handover request message may be used to request the target access network device to prepare for handover, and the handover request message may include information such as the identification of the terminal device, and for details, refer to the description in the prior art.

S304: The target access network device sends a handover response (handover response) message to the source access network device.

S305: The source access network device sends a handover command (handover command) to the terminal device. The handover command can be used to instruct the terminal device to handover to the target access network device.

Optionally, S306: if the source access network device receives downlink data that needs to be sent to the terminal device before the terminal device switches to the target access network device, the received downlink data may be forwarded to the target access network device .

S307: The terminal device accesses the target access network device through a random access process. The terminal device establishes a wireless connection with the target access network device through the random access process, so that the target terminal device can transmit data for the terminal device.

S308: After the target access network device determines that the terminal device is connected, it sends a path switch request (path switch request) message to the UPF network element. The path switch request message is used to request to switch the data transmission path of the terminal equipment from the data transmission path between the source access network equipment and the UPF network element to the data transmission path between the target access network equipment and the UPF network element.

S309: Perform path switching between the UPF network element and the AMF network element, and the specific process will not be repeated.

S310: After the path switching is completed, the UPF network element sends a path switching completion message to the target access network device.

The above handover process mainly includes the following two stages:

1. It takes about 10-15ms for the terminal device to establish a wireless connection with the target access network device.

2. It takes about 10-15ms for the target access network device to establish a data channel with the service gateway.

It can be seen from the above S306 that during the switching process, if the video frames sent by the XR server to the terminal device reach the UPF network element, these video frames will be transmitted to the source access network device through the UPF network element, and then forwarded to the source access network device by the source access network device. The target access network device is finally transmitted to the terminal device via the target access network device. As can be seen from the foregoing description, due to the switching process, the delay of these video frames is relatively large, and the user experiences the phenomenon of video frame skipping and freezing, which reduces the user experience. To this end, the present application proposes a method to reduce the data delay in the handover process and improve the user experience, which will be described in detail below.

The network architecture and service scenarios described in the embodiments of the present application are for the purpose of illustrating the technical solutions of the embodiments of the present application more clearly, and do not constitute a limitation on the technical solutions provided by the embodiments of the present application. The evolution of the architecture and the emergence of new business scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

In the embodiments of the present application, the interaction between a terminal device and an access network device and other devices is used as an example for description. The methods provided in the embodiments of the present application can also be applied to the interaction between other execution subjects, such as a terminal device chip. Or module, and the interaction between the chip or module in the access network device, when the execution body is the chip or the module, reference may be made to the description in the embodiments of this application, and details are not repeated here.

Example 1:

As shown in FIG. 4 , a schematic flowchart of a handover method provided by an embodiment of the present application is shown. In the process of FIG. 4 , the time synchronization of nodes such as terminal equipment, source access network equipment, and target access network equipment, that is, each node maintains its own clock, and the time values indicated by these clocks at the same time are the same.

In the flow of FIG. 4 , the source access network device is the access network device currently accessed by the terminal device; the target access network device is the access network device accessed by the terminal device after switching. The first core network device may be a UPF network element, the first core network device may provide a data transmission service for the terminal device, and the second core network device may be an AMF network element.

In the process of FIG. 4, taking the XR service as an example, when the XR server (not shown in the figure) provides the terminal equipment with the XR service through the mobile communication system, before the terminal equipment switches, the service frame of the XR service is sent by the XR server. The first core network device transmits the service frame to the source access network device, and finally the source access network device transmits the received service frame to the terminal device. After the terminal device switches, the first core network device transmits the service frame to the target access network device, and then the target access network device transmits the received service frame to the terminal device. The service frames of the XR service are transmitted according to a certain transmission period, for example, at a rate of 60 frames per second, that is, the transmission period is 16.67ms. The service frame of the XR service includes at least one of video data and audio data, and may also include other types of data, which is not limited in this application. Referring to Figure 4 in conjunction with the foregoing description, the method includes:

S401: The source access network device sends a handover request message to the target access network device.

The handover request (handover request) message may be used to request the target access network device to prepare for handover. The handover request message may be sent when the source access network device determines that the terminal device needs to perform handover.

It should be noted that how the source access network device specifically determines that the terminal device needs to switch the access network device is not limited in this embodiment of the present application. For example, the source access network device may receive measurement reports from the terminal device. The measurement report includes information such as RSRP. The source access network device can determine whether the terminal device needs to switch the access network device according to the RSRP and other information in the measurement report. For details, refer to the description in the prior art, which is not repeated here.

The above handover request message includes first time information, where the first time information is used to determine the first moment. The first moment is the moment when the first service frame arrives at the source access network device, or the first moment is the moment when the second service frame arrives at the target access network device. The first service frame may be any service frame transmitted by the source access network device to the terminal device; the second service frame may be the first service frame to be transmitted by the target access network device to the terminal device.

It should be noted that if the first moment is the moment when the second service frame arrives at the target access network device, when S401 is executed, the second service frame has not been transmitted, and the first moment is the moment estimated by the source access network device. For example, before the handover, the time of the last service frame received by the source access network device is 11:25:14:442ms, and the transmission period is 16.67ms, assuming the transmission delay from the source access network device to the first core network device , which is the same as the transmission delay from the target access network device to the first core network device, then the time when the second service frame reaches the target access network device is 11:25:14:458ms.

In this embodiment of the present application, the first time information may be implemented in multiple ways. In one possible implementation, the first time information may be used to directly determine the first time. For example, the first time information is the arrival source of the first service frame. The time of the access network device, or the time when the second service frame reaches the target access network device, for example, the first time information is 11:25:14:442ms. In another possible implementation manner, the first time information may be used to indirectly determine the first moment, for example, each moment may correspond to an index value, and the first time information may be an index value corresponding to the first moment, for example, the first The time is 11:25:14:442ms, the corresponding index value is 0011, then the first time information is 0011.

For example, the source access network device may use the most recently received service frame before sending the handover request message as the first service frame. Correspondingly, the source access network device may take the reception moment of the service frame as the first moment.

It should be noted that a service frame includes multiple data packets, and these data packets arrive at the source access network device in sequence, and the arrival times of different data packets may be different. For example, taking the XR service as an example, the downlink data transmitted by the XR service includes video data generated by the XR server, and may also include audio data. The amount of audio data is relatively small, and the audio data and video data can be encapsulated together. The XR server can generate a service frame including video data at a rate of 60 frames per second, that is, a service frame is generated every 16.67ms. After the service frame is encoded by the XR server, due to the limitation of the data packet size by the Internet protocol (IP), the encoded data stream is divided into multiple data packets according to the standard of a data packet size of 1500 bytes. Considering the header overhead, the actual data payload in the packet is less than 1500 bytes. From the perspective of the mobile communication network, the UPF network element receives a cluster of downlink data packets belonging to the same service frame from the XR server every 16.67ms, and a cluster of data packets includes multiple data packets with a size of about 1500 bytes. Correspondingly, the access layer of the terminal device receives a cluster of uplink data packets from the upper layer every 16.67ms, and a cluster of data packets includes a plurality of data packets with a size of about 1500 bytes. For details, reference may be made to FIG. 5 . In FIG. 5 , the rate of 60 frames per second is used as an example for description. The XR service is a periodic service. The transmission of the data included in the service frame is periodic, and little or no data is transmitted between the periods. The generation rate of the service frame may also exist in other situations, for example, 30 frames per second, or 90 frames per second, and so on. At 30 frames per second, the corresponding transmission period is 33.33ms; at 90 frames per second, the corresponding transmission period is 11.11ms, and so on for other cases, and will not be repeated here.

In combination with the above description, the source access network device may take any of the following moments as the first moment: the moment when the first data packet in the first service frame arrives; the moment when the last data packet in the first service frame arrives; The median or average value from the arrival time of the first data packet in a service frame to the arrival time of the last data packet in the first service frame; the arrival time of any data packet in the first service frame.

It should be noted that the first service frame and the second service frame may belong to the same service, for example, belong to the XR service. The service frame of the service is transmitted from the source access network device to the terminal device according to a certain transmission period. The specific value of the transmission period is determined according to the actual situation. For example, when the service frame of this service is generated at a rate of 60 frames per second, the transmission period is 16.67ms; when the service frame of this service is generated at a rate of 90 frames per second, the transmission period is 11.11ms.

Optionally, the handover request message may further include a first delay, where the first delay is a data transmission delay between the source access network device and the first core network device. Certainly, the handover request message may also include other information, which is not limited in this embodiment of the present application.

S402: The target access network device receives a handover request message from the source access network device.

S403: The target access network device determines the second time information according to the first time information, and sends a handover response message to the source access network device.

The handover response message includes second time information, and the second time information is used by the terminal device to initiate random access. The second time information may be used to determine the second time. In an implementation manner, the second moment may be the moment when the terminal device initiates random access to the target access network device.

Specifically, the target access network device may determine, according to the first time information, the time when each service frame transmitted to the terminal device through the source access network device reaches the source access network device. The target access network device may determine any time between the arrival times of two consecutive service frames arriving at the source access network device as the second time.

Optionally, the absolute value of the difference between the second moment and the arrival moment of the nearest service frame is less than or equal to H. Optionally, the absolute value of the difference between the second moment and the arrival moment of the previous service frame among the arrival moments of two consecutive service frames is less than or equal to H. H is greater than or equal to 0 and less than the transmission period of the service frame. For example, H is 1/10 of the transmission period of the service frame. Optionally, the target access network device may also determine the arrival time of a service frame arriving at the source access network device as the second time.

For example, the first time information is the reception time of the most recently received service frame before the source access network device sends the handover request message: 11:25:14:442ms. The transmission period of the service frame is 16.67ms, then the target access network device can determine the next service frame, and the time to arrive at the source access network device is 11:25:14:458ms, 11:25:14:475ms, 11 :25:14:491ms etc. The target access network device may determine any moment between 11:25:14:458ms and 11:25:14:475ms as the second moment; the target access network device may also determine 11:25:14:475ms Any time between 11:25:14:491ms is determined as the second time, etc., and other situations will not be repeated. Alternatively, the target access network device may also determine 11:25:14:458ms or 11:25:14:475ms or 11:25:14:491ms as the second moment.

In the embodiment of the present application, the service frame transmitted before the second time is transmitted by the source access network device to the terminal device; the service frame transmitted after the second time is transmitted by the target access network device to the terminal device. For this reason, among the service frames transmitted by the source access network equipment to the terminal equipment before the second time, the service frame with the smallest difference between the time when it arrives at the source access network and the second time is the service frame sent by the source access network equipment to the terminal equipment. The last service frame transmitted by the terminal device. After the second time, among the service frames transmitted through the target access network device to the terminal device, the service frame with the smallest difference between the time when it reaches the target access network and the second time is the service frame transmitted through the target access network device to the terminal device. the first service frame. The second time may also be equal to the time when the service frame transmitted to the terminal device through the source access network device reaches the source access network. In this embodiment of the present application, the second time may be used as the second time information, and at this time, the second time information directly indicates the second time.

In this embodiment of the present application, the second time may also be indirectly indicated by the second time information. For example, one or more of the following may be used as the second time information: the first time transmitted through the target access network device to the terminal device. The time when a service frame arrives at the first core network device; the time when the first service frame arrives at the target access network device; the time when the first service frame arrives at the source access network device when the terminal device does not switch ; the time when the last service frame transmitted by the source access network device to the terminal device reaches the first core network device; the time when the last service frame arrives at the source access network device.

How the target access network device specifically determines one or more of the above is not limited in this application. For example, when the first time is the time when the first service frame arrives at the source access network device, the time T1 when the first service frame arrives at the first core network device can satisfy the following forms:

T1=T2+(n+1)×T-D1...(1)

Wherein, T2 is the first moment, T is the transmission period, D1 is the first delay, and n is the number of service frames included between the first service frame and the first service frame.

The time T3 when the first service frame arrives at the target access network device can satisfy the following forms:

T3=T2+(n+1)×T-D1+D2...(2)

Wherein, D2 is the second delay, and the second delay is the transmission delay between the target access network device and the first core network device.

If the first delay and the second delay are not considered, or the first delay and the second delay are considered equal, the formula (2) can be simplified as follows:

T3=T2+(n+1)×T...(3)

Correspondingly, when the terminal device does not switch, the time T4 when the first service frame arrives at the source access network device can satisfy the following form:

T4=T2+(n+1)×T...(4)

For example, the first time T2 determined according to the first time information is 11:25:14:442ms, T is 16.67ms, the handover request message includes the first delay D1 as 2ms, the second delay D2 as 3ms, and n as 1. Then according to the above formula (1), it can be determined that T1 is 11:25:14:456ms; according to the above formula (2), it can be determined that T3 is 11:25:14:459ms, or according to the above formula (3), T3 can be determined is 11:25:14:458ms; according to the above formula (4), it can be determined that T4 is 11:25:14:458ms.

It should be noted that, if the first moment is the moment when the second service frame reaches the target access network device, and the handover request message includes the first delay, then the target access network device can also determine the first moment according to the first delay. Make corrections. Specifically, the difference between the second delay minus the first delay and the cumulative sum of the first time delay may be used as the corrected first time. For example, combining the above example, the first moment before the correction is 11:25:14:442ms, and the first moment after the correction is 11:25:14:443ms.

Further, in combination with the foregoing description, the first moment is the moment when the second service frame arrives at the target access network device, and the moment T5 when the last service frame transmitted to the terminal device through the source access network device arrives at the first core network device. , which can satisfy the following forms:

T2=T5+(m+1)×T-D1...(5)

Wherein, T2 is the first moment, T is the transmission period, D1 is the first delay, and m is the number of service frames included between the last service frame and the second service frame.

The time T6 when the last service frame arrives at the source access network device can satisfy the following forms:

T2=T6+(m+1)×T...(6)

Of course, the above is just an example, and the above various moments can also be determined in other ways, which will not be repeated here.

Optionally, the target access network device may also combine the first time determined according to the first time information and the arrival time of the service frames included in the services of other terminal devices to determine whether to instruct the server to respond to the service frames sent to the terminal device. to adjust the sending time. The server is used to generate a service frame of the service provided to the terminal device, and when the service is an XR service, the server may be an XR server.

For example, the target access network device determines that it is in the target cell of the target access network device, and simultaneously transmits service frames to other terminal devices (hereinafter referred to as terminal device A), and the transmission period is the same as that to the terminal device (hereinafter referred to as terminal device A). Device B) transmits the service frame with the same transmission period. If the target access network device determines that the service frame of terminal device B and the service frame of terminal device A arrive at the same time or overlap, the target access network device may instruct the server to respond to the service frame sent to terminal device A or terminal device B. Adjust the sending time.

If the target access network device determines to adjust the arrival time of the video frame of the terminal device (the preceding terminal device B), the target access network device can directly request the server to adjust the arrival time of the service frame, or it can notify the source access network device, by The source access network device requests the server to adjust the arrival time of the service frame. For details, please refer to the following methods 1 and 2.

Manner 1: The target access network device sends adjustment indication information to the first core network device or the second core network device or the server corresponding to the terminal device.

The adjustment instruction information is used to instruct the server to advance or delay the sending time of the service frame sent to the terminal device by Y milliseconds from the third time or from the third service frame. Y is greater than 0 and less than the transmission period of the service corresponding to the first service frame, the third time is any time after the first time, and the third service frame is any service frame after the first service frame.

In a second manner, the target access network device sends a notification message to the source access network device, where the notification message is used to instruct the source access network device to request the server to adjust the arrival time of the service frame of the terminal device.

In this way, the source access network device can send adjustment indication information to the first core network device or the second core network device or the server corresponding to the terminal device, so as to advance or delay the sending time of the service frame sent to the terminal device by Y milliseconds Y ms.

It should be noted that the unit of Y may not be milliseconds, but may be other time units, which are not limited in this application. When the first core network device is a UPF network element, the transmission path of the adjustment instruction information may be: from the target access network device or the source access network device, to the UPF network element, to the AMF network element, to the SMF network element, to the server .

If the target access network device determines to adjust the arrival time of the video frames of other terminal devices (the preceding terminal device A), the target access network device may send adjustment instruction information to the first core network device or the server corresponding to the other terminal devices, thereby Advance or delay the sending time of service frames sent to other terminal devices by X milliseconds. X is greater than 0 and less than the transmission period of service frames of other terminal equipment.

S404: The source access network device receives the handover response message from the target access network device, and sends a handover command to the terminal device.

In implementation manner 1, the handover command includes second time information, and the handover command is used to instruct the terminal device to initiate random access to the target access network device according to the second time information.

In the second implementation, the handover command does not include the second time information. In this case, the source access network device may also determine the last service frame transmitted to the terminal device according to the second time information, and send indication information to the terminal device.

The indication information may be used to indicate the end of transmission of the last service frame transmitted to the terminal device. In this implementation manner, the handover command may be used to instruct the terminal device to initiate random access to the target access network device after the transmission of the last service frame ends.

For example, when the second time information directly indicates the second time, if the second indication information is the time when the last service frame transmitted by the source access network device to the terminal device arrives at the source access network device, or if the second time The indication information is the time when the first service frame transmitted to the terminal device through the target access network device reaches the target access network device, and the source access network device can directly determine the last service frame according to the second information.

For example, if the second time information includes at least one of the following: the time when the last service frame transmitted to the terminal device through the source access network device reaches the first core network device, the time when the last service frame arrives at the source access network device moment.

At this time, the source access network device can directly determine the last service frame transmitted to the terminal device.

For another example, if the second time information includes at least one of the following: the time when the first service frame transmitted to the terminal device through the target access network device reaches the first core network device, the time when the first service frame arrives at the target access network device. The moment of the access network device, and the moment when the first service frame arrives at the source access network device if the terminal device does not switch.

At this time, the source access network device may determine the arrival time of the last service frame transmitted to the terminal device according to the second time information and the transmission period, so as to determine the last service frame.

It should be noted that, as mentioned above, since the encoded data stream of one service frame is transmitted through at least one data packet, one service frame corresponds to at least one data packet. The transmission of the last data packet has ended, and the implementation indicates that the transmission of the last service frame has ended.

Specifically, in the first possible implementation manner, when the last service frame is encoded in the first encoding manner, the indication information may be used to indicate that the transmission of the last data packet corresponding to the last service frame is completed, thereby realizing the indication of the last The service frame transmission ends. Optionally, the source access network device may send indication information when transmitting the last data packet corresponding to the last service frame. Optionally, the indication information may also be located in the last data packet corresponding to the last service frame.

In the second possible implementation manner, when the last service frame is encoded in the second encoding manner, the indication information can be used to indicate the end of transmission of the last data packet of the base layer data corresponding to the last service frame, thereby realizing the indication of the last data packet. A service frame transmission ends. Optionally, the source access network device may send indication information when transmitting the last data packet of the base layer data corresponding to the last service frame. Optionally, the indication information may also be located in the last data packet of the base layer data corresponding to the last service frame.

It should be noted that, in this application, the service frame may be encoded using the first encoding mode or the first encoding mode, and the first encoding mode may refer to the "non-layered" encoding mode; the second encoding mode may refer to the "layered" encoding mode "Encoding. "Layered" encoding refers to dividing video data into base layer data and enhancement layer data, which are independently encoded. The most basic information of video is located in the base layer data, and the base layer data can provide lower quality video images; on the basis of the base layer data, combined with the enhancement layer data, high and low quality video images can be obtained. In the case of low bandwidth, only the base layer data can be transmitted, that is to say, the base layer data cannot be discarded, while the enhancement layer data can be discarded. Correspondingly, "non-layered" encoding refers to encoding according to the original video data without layering the video data.

How the instruction information is specifically transmitted is not limited in this embodiment of the present application. For example, the indication information can be transmitted through an extra bit in a control element (CE), which can be a medium access control (MAC), or a MAC header, and can also be controlled through a radio link control (RLC). Unit, packet data convergence protocol (packet data convergence protocol, PDCP) control unit, service data application protocol (service data adaptation protocol, SDAP) control unit, radio resource control (radio resource control, RRC) message transmission.

S405: The terminal device receives the handover command from the source access network device, and initiates random access to the target access network device.

Specifically, the following two cases may exist: Case 1: When the handover command includes the second time information, the terminal device may initiate random access to the target access network device according to the second time information.

Specifically, when the second time information includes the second time, the terminal device may directly determine the second time as the time at which the random access is initiated. When the second time information does not include the second time, but indirectly indicates the second time, the terminal device can determine the last service frame received according to the second time information, and send the last service frame transmitted to the terminal device through the source access network device. For a service frame, the time at which the first random access resource is located after the time when it arrives at the source access network device is determined as the time at which random access is initiated. In this case, the terminal device may determine the last received service frame according to the second time information, and initiate random access to the target access network device within the random access opportunity after the last received service frame.

At this time, the terminal device can directly determine the last service frame transmitted to the terminal device.

At this time, the terminal device may determine the arrival time of the last service frame transmitted by the source access network device to the terminal device according to the second time information and the transmission period, thereby determining the last service frame.

It should be noted that the access network device may broadcast some time-frequency resources for initiating random access, and the terminal device may initiate random access on these time-frequency resources. There are two kinds of random access opportunities, one is public, and any terminal device can initiate random access by using the public random access opportunity. The other is dedicated. Only when the network notifies the terminal device to use the random access opportunity, the terminal device can initiate random access through the dedicated random access opportunity. During handover, the target access network device can determine the dedicated random access opportunity, notify the terminal device through the source access network device, and the terminal device initiates random access through the dedicated random access opportunity. For the specific content of the above process, reference may be made to the description in the prior art, which will not be repeated here.

Case 2: When the handover command does not include the second time information, the terminal device can also receive the indication information. In this case, since the indication information is used to indicate the end of transmission of the last service frame transmitted to the terminal device, when the terminal device receives the indication information, it can determine that the last service frame is received. When the terminal device determines to receive the last service frame, it can initiate random access to the target access network device within the random access opportunity after the transmission of the last service frame ends.

Optionally, S406 is further included: the target access network device sends a path switching request message to the second core network device.

After receiving the handover request message in S402, the target access network device may send a path switch request message before receiving the random access request from the terminal device. Optionally, the target access network device may send the path switching request message when sending the path switching request message at the second moment.

In this embodiment of the present application, the path switching request message may include information such as second time information. The path switch request message may be used to request the second core network device to initiate a path switch before the last service frame transmitted to the terminal device through the source access network device reaches the source access network device. Or the path switch request message is used to request the second core network device to complete the path switch before the time when the first service frame transmitted to the terminal device through the target access network device reaches the target access network device. The path switching is used to switch the data transmission path of the terminal equipment from the data transmission path between the source access network equipment and the first core network equipment to the data transmission path between the target access network equipment and the first core network equipment .

Optionally, S407 is further included: the second core network device initiates a path switching process according to the second time information.

After the second core network device completes the path switching, it may also send a path switching completion message to the target access network device.

For example, the second time information includes the time when the first service frame transmitted by the target access network device to the terminal device reaches the target access network device, for example, 11:25:14:458ms, then the second core network device Path switching can be completed before 11:25:14:458ms. The above example assumes that the transmission delay between the first core network device and the target access network device is zero. If the transmission delay between the first core network device and the target access network device is not 0, for example, the delay is 2ms, the second core network device needs to complete the path switch before 11:25:14:456ms.

For another example, if the second time information includes at least one of the following: the time when the last service frame transmitted by the source access network device to the terminal device arrives at the first core network device, the time when the last service frame arrives at the source access network device moment. At this time, the second core network device can determine the time when the first service frame transmitted to the terminal device through the target access network device reaches the target access network device according to the second time information and the transmission period, so as to complete the path before this time. switch.

For example, the time when the last service frame included in the second time information reaches the source access network device is 11:25:14:450ms, and the transmission period is 16ms. Then the second core network device can determine that the time when the first service frame reaches the target access network device is 11:25:14:466ms=11:25:14:450ms+16ms, so that it can be reached at 11:25:14:466ms Complete the path switch before.

For example, the time when the last service frame included in the second time information reaches the first core network device is 11:25:14:450ms, the transmission period is 16ms, and the time between the target access network device and the first core network device is The transmission delay is 3ms. Then the second core network device can determine that the time when the first service frame reaches the target access network device is 11:25:14:469ms=11:25:14:450ms+16ms+3ms, so that it can be reached at 11:25:14 : The path switch is completed before 469ms.

Optionally, S408 is further included: after the second core network device completes the path switching, the second core network device may also send a path switching completion message to the target access network device.

It should be noted that S404 and S406 can be executed at the same time, and there is no order of precedence; S405 and S407 can be executed at the same time, and there is no order of precedence. Through this method, when the terminal device initiates random access, the target access network device initiates a path switching request, which can reduce the time required for handover and reduce the data transmission delay.

Through the above process, starting from the next service frame, the first core network device transmits the service frame to the target access network device through the newly established data channel, and then the target access network device transmits the service frame to the terminal device.

In the above process, the target access network device can determine the second time information for the terminal device to initiate random access according to the moment when the service frame arrives at the source access network device, so as to prevent the terminal device from initiating random access handover at any time. To the target access network device, the delay of the service frame transmitted in the random access process increases, so that the data transmission delay in the handover process can be reduced. Further, when the terminal device is instructed by the second time information to initiate random access at the moment of the last service frame received by the source access network device, the periodicity of service frame transmission can be used to transmit two service frames. Switching between intervals greatly reduces the data transmission delay. Further, when the terminal device initiates random access, the target access network device initiates a path switching request, which can reduce the time required for handover and further reduce the data transmission delay.

Embodiment 2:

In the previous embodiment, the time of each node is required to be kept synchronized. The present application can also be applied to the scenario where only the source access network device and the target access network device are required to maintain clock synchronization, and no synchronization requirement is required for other nodes. The following will be described in detail.

As shown in FIG. 6 , a schematic flowchart of a handover method provided by an embodiment of the present application is shown. In the process of FIG. 6 , the time synchronization of the source access network device and the target access network device may or may not be maintained by other nodes. In addition, the process of FIG. 6 is the same as the other backgrounds of the process of FIG. 4 , and for details, reference may be made to the foregoing description, which will not be repeated here.

The process shown in Figure 6 and the process shown in Figure 4, except that all nodes do not need to maintain time synchronization, the biggest difference is that in the process shown in Figure 6, the implementation of the second time information is different. For the description, see Figure 6, the method includes:

S601: The source access network device sends a handover request message to the target access network device.

S602: The target access network device receives a handover request message from the source access network device.

For the specific content of S601 to S602, reference may be made to the descriptions in S401 to S402, which will not be repeated here.

S603: The target access network device determines the second time information according to the first time information, and sends a handover response message to the source access network device.

The handover response message includes second time information, and the second time information is used by the terminal device to initiate random access.

S604: The source access network device receives the handover response message from the target access network device, and sends a handover command to the terminal device.

The switching command includes the system frame number and the time slot number. Specifically, the source access network device may convert the second time indicated by the second time information into the cell in the source access network device, the system frame number and the time slot number corresponding to the time. The source access network device may also determine the arrival time of the last service frame transmitted by the source access network device to the terminal device according to the second time information, and convert the time to the cell in the source access network device, which is the same as the time. The corresponding system frame number and time slot number. The time slot number is used to indicate the time slot in which the terminal device initiates random access, and the system frame number is used to indicate the radio frame where the time slot is located. That is to say, the system frame number and time slot number refer to: the terminal device is required to start from the time slot corresponding to the time slot number in the radio frame corresponding to the system frame number in the source access network device cell, and select a random number after the time slot. At the access opportunity, initiate random access to the target access network device.

It should be noted that, when the present application is applied to a 4G system, the time slot number may also be replaced with a subframe number, which is used to indicate the subframe in which the terminal device initiates random access.

S605: The terminal device receives the handover command from the source access network device, and initiates random access to the target access network device within the random access opportunity after the time slot in the radio frame. For the specific random access process, reference may be made to the description in the prior art, which will not be repeated here.

Optionally, S606 is further included: the target access network device sends a path switching request message to the second core network device.

Optionally, S607 is further included: the second core network device initiates a path switching process according to the second time information.

Optionally, S608 is further included: after the second core network device completes the path switching, it may also send a path switching completion message to the target access network device.

For the specific content of S604, S606 to S607, reference may be made to the descriptions in S404, S406 to S407, and details are not repeated here. It should be noted that S604 and S606 can be executed at the same time, and there is no order of precedence; S605 and S607 can be executed at the same time, and there is no order of precedence.

In the above process, the source access network device can determine the time slot and radio frame for the terminal device to initiate random access according to the second time information sent by the target access network device, so as to prevent the terminal device from initiating random access handover at any time. To the target access network device, the delay of the service frame transmitted in the random access process increases, so that the data transmission delay in the handover process can be reduced. Further, when the time slot is the time slot after the time of the last service frame received by the terminal device through the source access network device, the periodicity of the service frame transmission can be used, and the transmission interval between two service frames can be used. Switching, greatly reducing the data transmission delay. Further, when the terminal device initiates random access, the target access network device initiates a path switching request, which can reduce the time required for handover and further reduce the data transmission delay.

The embodiment of the present application also provides a method, in which the source access network device and the target access network device may not maintain time synchronization, and after the terminal device receives the handover command, it does not immediately send the target access network The device initiates random access, but initiates random access to the target access network device when it is determined that the last service frame transmitted to the terminal device through the source access network device is received, which will be described in detail below.

Embodiment three:

As shown in FIG. 7 , a schematic flowchart of a handover method provided by an embodiment of the present application is shown. The background of the process of FIG. 7 is the same as that of the process of FIG. 4 . For details, reference may be made to the foregoing description, which will not be repeated here. Referring to Figure 7 in conjunction with the foregoing description, the method includes:

S701: The source access network device determines the last service frame transmitted to the terminal device through the source access network device.

It should be noted that, before S701, the source access network device may receive the measurement report of the terminal device, so as to determine the handover according to the measurement report, and the specific process will not be repeated.

After the source access network device determines to perform the handover, it may send a handover request message to the target access network device. The source access network device may determine the service frame received after sending the handover request message as the last service frame. Certainly, the source access network device may also determine the last service frame in other manners, which is not limited in this embodiment of the present application.

S702: The source access network device sends a handover command to the terminal device, and sends indication information to the terminal device.

The source access network device may send the handover command first, and then send the instruction information, or may send the handover command and the instruction information at the same time. The indication information is used to indicate the end of transmission of the last service frame.

Specifically, it is possible to indicate that the transmission of the last data packet corresponding to the last service frame has ended through the indication information, so as to indicate the end of the transmission of the last service frame. Specifically, in the first possible implementation manner, when the last service frame is encoded in the "non-layered" encoding method, the indication information can be used to indicate that the transmission of the last data packet corresponding to the last service frame is completed, so as to realize Indicates the end of the transmission of the last service frame. Optionally, the source access network device may send indication information when transmitting the last data packet corresponding to the last service frame. Optionally, the indication information may also be located in the last data packet corresponding to the last service frame.

In the second possible implementation manner, when the last service frame is encoded in a "layered" coding manner, the indication information can be used to indicate that the transmission of the last data packet of the base layer data corresponding to the last service frame is completed, thereby realizing Indicates the end of the transmission of the last service frame. Optionally, the source access network device may send indication information when transmitting the last data packet of the base layer data corresponding to the last service frame. Optionally, the indication information may also be located in the last data packet of the base layer data corresponding to the last service frame.

It should be noted that the source access network device may send an indication message to indicate the end of the transmission of the service frame at the end of the transmission of each service frame; the source access network device may also send each service frame after the switching command is sent. When the frame transmission ends, an indication message is sent to indicate the end of the service frame transmission; the source access network device may also send indication information to indicate the end of the last service frame transmission when the last service frame transmission ends.

S703: The terminal device receives the indication information and the handover command from the source access network device.

S704: The terminal device initiates random access to the target access network device within the random access opportunity after the transmission of the last service frame ends.

It should be noted that, after the terminal device accesses the target access network device, the target access network device also needs to initiate a path switching process. For details, please refer to the previous description, which will not be repeated here.

Optionally, the handover command further includes a handover condition, and the handover condition is a condition that the terminal device needs to meet to perform handover.

When the terminal device satisfies the handover condition, the terminal device initiates random access to the target access network device within the random access opportunity after the transmission of the last service frame ends.

It should be noted that, when the handover command includes the handover condition, the moment when the terminal device initiates random access is determined by the terminal device, not by the target access network device, so the target access network device cannot use this moment. If the source access network device is notified in advance, the source access network device cannot determine which service frame is the last service frame sent to the terminal device. For this reason, the source access network device needs to send an indication message indicating the end of the transmission of the service frame at the end of the transmission of each service frame, so that the terminal device can determine the indication information corresponding to a service frame and determine whether the service frame is Transmission ends.

Further, when the handover command includes the handover condition, the last service frame transmitted to the terminal device through the source access network device is determined by the terminal device. The terminal device may take a service frame after the moment when the switching condition is satisfied as the last service frame to be received, that is, the last service frame transmitted to the terminal device through the source access network device. Of course, the terminal device may also select a service frame as the last service frame to be received from the service frames after the moment when the switching condition is satisfied according to the actual situation, which is not limited in this embodiment of the present application.

The specific content of the switching condition is not limited in this embodiment of the present application. For example, the handover condition may include one or more of the following: the RSRP of the cell in the target access network device is greater than the first threshold; the reference signal received quality (RSRQ) of the cell in the target access network device is greater than The second threshold; the signal to interference plus noise ratio (SINR) of the cell in the target access network device is greater than the third threshold.

When the terminal device determines that the RSRP of the cell in the source access network device is less than or equal to the first threshold, and any one of the handover conditions is satisfied, it initiates random access to the target access network device. Or, when the terminal device determines that the RSRQ of the cell in the source access network device is less than or equal to the second threshold, and any one of the handover conditions is satisfied, it initiates random access to the target access network device. Or, when the terminal device determines that the SINR of the cell in the source access network device is less than or equal to the third threshold, and any one of the handover conditions is satisfied, it initiates random access to the target access network device. For specific values of the first threshold, the second threshold, and the third threshold, reference may be made to the description in the prior art, and details are not repeated here.

In the above process, by instructing the terminal device to start switching after the transmission of the last service frame, the delay of the service frame caused by the switching can be minimized, and the delay of data transmission can be reduced.

It can be understood that, in order to implement the functions in the foregoing embodiments, the network device and the terminal device include corresponding hardware structures and/or software modules for performing each function. Those skilled in the art should easily realize that the units and method steps of each example described in conjunction with the embodiments disclosed in the present application can be implemented in the form of hardware, software, or a combination of hardware and software. Whether a function is performed by hardware, software, or computer software-driven hardware depends on the specific application scenarios and design constraints of the technical solution.

FIG. 8 and FIG. 9 are schematic structural diagrams of possible communication apparatuses provided by embodiments of the present application. These communication apparatuses can be used to implement the functions of the terminal device or the source access network device or the target access network device in the above method embodiments, and thus can also achieve the beneficial effects of the above method embodiments. In the embodiments of the present application, the communication device may be a terminal device, a source access network device or a target access network device, or a terminal device or a source access network device or a target access network device applied to modules (such as chips) in .

As shown in FIG. 8 , the communication apparatus 800 includes a processing unit 801 and a communication unit 802 . The communication apparatus 800 is configured to implement the functions of the terminal device or the source access network device or the target access network device in the method embodiments shown in FIGS. 4 to 7 above. Alternatively, the communication apparatus 800 may include a module for implementing any function or operation of the terminal device or the source access network device or the target access network device in the method embodiments shown in FIGS. 4 to 7 , and the modules may all or in part through software, hardware, firmware, or any combination thereof.

When the communication apparatus 800 is configured to implement the function of the target access network device in the method embodiment shown in FIG. 4 or 6, the communication unit 802 is configured to receive a handover request message from the source access network device, where the handover request message includes the first Time information, the first time information is used to determine the first time, and the first time is the time when the first service frame arrives at the source access network device, or the first time is the time when the second service frame arrives at the target access network device; processing The unit 801 is used to determine the second time information according to the first time information; the second time information is used for the terminal device to initiate random access; the communication unit 802 is used to send a handover response message to the source access network device; the handover response message includes Second time information.

When the communication apparatus 800 is configured to implement the function of the source access device in the method embodiment shown in FIG. 4 or 6, the communication unit 802 is configured to send a handover request message to the target access network device, where the handover request message includes the first time information , the first time information is used to determine the first time, and the first time is the time when the first service frame arrives at the source access network device, or the first time is the time when the second service frame arrives at the target access network device; the communication unit 802 It is used for receiving a handover response message from the target access network device, where the handover response message includes second time information; the second time information is determined according to the first time information.

When the communication apparatus 800 is used to implement the function of the terminal device in the method embodiment shown in FIG. 4 , the communication unit 802 is used to receive a handover command from the source access network device; the handover command includes second time information; the handover command is used for Instruct the terminal device to initiate random access to the target access network device; the processing unit 801 is configured to initiate random access to the target access network device according to the second time information.

When the communication apparatus 800 is used to implement the function of the terminal device in the method embodiment shown in FIG. 6, the communication unit 802 is used to receive a handover command from the source access network device; the handover command includes a system frame number and a time slot number; The slot number is used to indicate the time slot in which the terminal device initiates random access, and the system frame number is used to indicate the radio frame where the time slot is located; the handover command is used to instruct the terminal device to initiate random access to the target access network device; the processing unit 801 uses the In the random access opportunity after the time slot in the radio frame, the random access is initiated to the target access network device.

When the communication apparatus 800 is configured to implement the function of the source access network device in the method embodiment shown in FIG. 7 , the processing unit 801 is configured to determine the last service frame transmitted to the terminal device through the source access network device; the communication unit 802 It is used to send a handover command to the terminal device and send indication information to the terminal device; the indication information is used to indicate the end of the transmission of the last service frame; the handover command is used to instruct the terminal device to send the target access network after the transmission of the last service frame is completed. The device initiates random access.

When the communication apparatus 800 is used to implement the function of the terminal device in the method embodiment shown in FIG. 7 , the communication unit 802 is used to receive the indication information from the source access network device and the handover command; the indication information is used to indicate the last The service frame transmission ends; the handover command is used to instruct the terminal device to initiate random access to the target access network device after the end of the last service frame transmission; the processing unit 801 is used to, according to the handover command, randomly Initiate random access to the target access network device within the access opportunity.

More detailed descriptions of the above-mentioned processing unit 801 and communication unit 802 can be obtained directly by referring to the relevant descriptions in the method embodiments shown in FIGS. 4 to 7, and details are not repeated here.

As shown in FIG. 9 , the communication device 900 includes a processor 910 and an interface circuit 920 . The processor 910 and the interface circuit 920 are coupled to each other. It can be understood that the interface circuit 920 can be a transceiver or an input-output interface. Optionally, the communication apparatus 900 may further include a memory 930 for storing instructions executed by the processor 910 or input data required by the processor 910 to execute the instructions or data generated after the processor 910 executes the instructions.

When the communication apparatus 900 is used to implement the methods shown in FIGS. 4 to 7 , the processor 910 is used to implement the functions of the above-mentioned processing unit 801 , and the interface circuit 920 is used to implement the functions of the above-mentioned communication unit 802 .

When the above communication device is a chip applied to a terminal device, the terminal device chip implements the functions of the terminal device in the above method embodiments. The terminal device chip receives information from other modules (such as a radio frequency module or an antenna) in the terminal device, and the information is sent by the network device to the terminal device; or, the terminal device chip sends information to other modules (such as a radio frequency module or an antenna) in the terminal device antenna) to send information, the information is sent by the terminal equipment to the network equipment.

When the above communication device is a chip applied to a network device, the network device chip implements the functions of the network device in the above method embodiments. The network device chip receives information from other modules (such as a radio frequency module or an antenna) in the network device, and the information is sent by the terminal device to the network device; or, the network device chip sends information to other modules in the network device (such as a radio frequency module or an antenna). antenna) to send information, the information is sent by the network equipment to the terminal equipment.

It can be understood that the processor in the embodiments of the present application may be a central processing unit (Central Processing Unit, CPU), and may also be other general-purpose processors, digital signal processors (Digital Signal Processor, DSP), application-specific integrated circuits (Application Specific Integrated Circuit, ASIC), Field Programmable Gate Array (Field Programmable Gate Array, FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. A general-purpose processor may be a microprocessor or any conventional processor.

In the embodiment of the present application, the processor may be a random access memory (Random Access Memory, RAM), a flash memory, a read-only memory (Read-Only Memory, ROM), a programmable read-only memory (Programmable ROM, PROM), an erasable memory In addition to programmable read-only memory (Erasable PROM, EPROM), electrically erasable programmable read-only memory (Electrically erasable programmable read-only memory (Electrically EPROM, EEPROM), registers, hard disk, removable hard disk, CD-ROM or any other form of storage medium known in the art middle. An exemplary storage medium is coupled to the processor, such that the processor can read information from, and write information to, the storage medium. Of course, the storage medium can also be an integral part of the processor. The processor and storage medium may reside in an ASIC. Alternatively, the ASIC may be located in a network device or in an end device. Of course, the processor and the storage medium may also exist in the network device or the terminal device as discrete components.

As will be appreciated by those skilled in the art, the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to the present application. It will be understood that each flow and/or block in the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flow of the flowcharts and/or the block or blocks of the block diagrams.

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

Claims

A handover method, characterized in that the method is applied to a target network device or a chip in the target network device, and the method includes:

Receive a handover request message from a source access network device, where the handover request message includes first time information, where the first time information is used to determine a first time, and the first time is when the first service frame arrives at the source The time of the access network device, or the first time is the time when the second service frame reaches the target access network device;

Determine second time information according to the first time information; the second time information is used for the terminal device to initiate random access;

Send a handover response message to the source access network device; the handover response message includes the second time information.
The method according to claim 1, wherein the second time information comprises one or more of the following:

The moment when the first service frame transmitted by the target access network device to the terminal device reaches the first core network device;

the moment when the first service frame arrives at the target access network device;

The moment when the first service frame arrives at the source access network device when the terminal device does not perform handover;

The moment when the last service frame transmitted by the source access network device to the terminal device reaches the first core network device;

The time when the last service frame arrives at the source access network device.
The method according to claim 2, wherein the moment when the first service frame arrives at the target access network device is determined according to the first moment and a transmission period; and the transmission period is the The period of the service corresponding to the first service frame;

Or, the moment when the second service frame reaches the target access network device is determined according to the first moment, the transmission period, the first delay, and the second delay; the first delay is The delay between the source access network device and the first core network device, and the second delay is the delay between the target access network device and the first core network device.
The method according to any one of claims 2 to 3, wherein the second time information is used to determine a second time, and the second time is when the terminal device initiates random access to the target access network device. access time.
The method according to claim 4, wherein the second time is the last service frame transmitted to the terminal device through the source access network device, after the time when the source access network device arrives at any time.
The method according to any one of claims 1 to 5, wherein the method further comprises:

Send adjustment instruction information to the server or the first core network device, where the adjustment instruction information is used to instruct the server to advance the sending time of the service frame sent to the terminal device from the third moment or from the third service frame Or delay Y milliseconds;

Wherein, Y is greater than 0 and less than the transmission period of the service corresponding to the first service frame, the third time is any time after the first time, and the third service frame is the first service Any traffic frame after the frame.
The method according to any one of claims 1 to 6, wherein the method further comprises:

before receiving the random access request from the terminal device, sending a path switching request message to the second core network device;

The path switching request message is used to request the second core network device to initiate a path before the last service frame transmitted to the terminal device through the source access network device reaches the source access network device. switching, switching the data transmission path of the terminal equipment from the data transmission path between the source access network equipment and the first core network equipment to the data transmission path between the target access network equipment and the first core network equipment data transmission path between.
The method according to claim 7, wherein the path switching request message includes the second time information.
A switching method, characterized in that the method is applied to a source-target network device or a chip in the source-target network device, and the method comprises:

Send a handover request message to the target access network device, where the handover request message includes first time information, and the first time information is used to determine a first time, and the first time is when the first service frame arrives at the source connection. The time of the network access device, or the first time is the time when the second service frame reaches the target access network device;

A handover response message from the target access network device is received, where the handover response message includes second time information; the second time information is determined according to the first time information.
The method according to claim 9, wherein the method further comprises:

Send a handover command to the terminal device, where the handover command includes the second time information, and the handover command is used to instruct the terminal device to initiate a random connection to the target access network device according to the second time information. enter.
The method according to claim 9, wherein the method further comprises:

sending a handover command to the terminal device;

Send indication information to the terminal device, where the indication information is used to indicate the end of the transmission of the last video frame transmitted to the terminal device; the switching command is used to instruct the terminal device to end the transmission of the last service frame After that, initiate random access to the target access network device, and the last service frame is determined according to the second time information.
The method according to any one of claims 9 to 11, wherein the second time information comprises one or more of the following:

The moment when the first service frame transmitted by the target access network device to the terminal device reaches the first core network device;

the moment when the first service frame arrives at the target access network device;

The moment when the first service frame arrives at the source access network device when the terminal device does not perform handover;

The moment when the last service frame transmitted by the source access network device to the terminal device reaches the first core network device;

The time when the last service frame arrives at the source access network device.
The method according to claim 9, wherein the method further comprises:

Send a handover command to the terminal device, where the handover command includes a system frame number and a time slot number, the time slot number is used to indicate the time slot in which the terminal device initiates random access, and the system frame number is used to indicate The radio frame where the time slot is located, the system frame number and the time slot number are determined according to the second time information.
The method according to any one of claims 12 to 13, wherein the second time information is used to determine a second time, and the second time is when the terminal device initiates random access to the target access network device. access time.
The method according to claim 14, wherein the second time is the last service frame transmitted to the terminal device through the source access network device, after the time when it arrives at the source access network device at any time;

Or, the second time is the start time of the time slot corresponding to the time slot number in the radio frame indicated by the system frame number.
A switching method, characterized in that the method is applied to a terminal device or a chip in the terminal device, and the method includes:

receiving a handover command from a source access network device, where the handover command includes second time information, and the handover command is used to instruct the terminal device to initiate random access to the target access network device;

Initiating random access to the target access network device according to the second time information.
The method according to claim 16, wherein the second time information comprises one or more of the following:

The moment when the first service frame transmitted by the target access network device to the terminal device reaches the first core network device;

the moment when the first service frame arrives at the target access network device;

The moment when the first service frame arrives at the source access network device when the terminal device does not perform handover;

The moment when the last service frame transmitted by the source access network device to the terminal device reaches the first core network device;

The time when the last service frame arrives at the source access network device.
The method according to claim 17, wherein the initiating random access to the target access network device according to the second time information comprises:

Initiating random access to the target access network device within the random access opportunity after the second time; the second time is determined according to the second time information.
The method according to claim 18, wherein the second time is any time after the time when the last service frame transmitted to the terminal device through the source access network device arrives at the source access network device a moment.
A switching method, characterized in that the method is applied to a terminal device or a chip in the terminal device, and the method includes:

Receive a handover command from the source access network device, the handover command includes a system frame number and a time slot number, the time slot number is used to indicate the time slot for the terminal device to initiate random access, and the system frame number is used. In order to indicate the radio frame where the time slot is located, the handover command is used to instruct the terminal device to initiate random access to the target access network device;

In the random access opportunity after the time slot in the radio frame, a random access is initiated to the target access network device.
A switching method, characterized in that the method is applied to a source-target network device or a chip in the source-target network device, and the method comprises:

determining the last service frame transmitted to the terminal device through the source access network device;

sending a handover command to the terminal device;

Send indication information to the terminal device, where the indication information is used to indicate the end of the transmission of the last service frame; the handover command is used to instruct the terminal device to access the target after the transmission of the last service frame ends The network device initiates random access.
The method according to claim 21, wherein the last service frame includes at least one data packet;

When the last service frame is encoded in the first encoding manner, the indication information is used to indicate that the transmission of the last data packet corresponding to the last service frame ends;

Or, when the last service frame is encoded in the second encoding manner, the indication information is used to indicate that the transmission of the last data packet of the base layer data corresponding to the last service frame is ended.
A switching method, characterized in that the method is applied to a terminal device or a chip in the terminal device, and the method includes:

Receive the indication information from the source access network device and the handover command;

The indication information is used to indicate the end of transmission of the last service frame; the handover command is used to instruct the terminal device to initiate random access to the target access network device after the end of transmission of the last service frame;

According to the handover command, a random access is initiated to the target access network device within a random access opportunity after the transmission of the last service frame ends.
The method according to claim 23, wherein the handover command includes a handover condition, and the handover condition is a condition that the terminal device needs to meet to perform handover, and the method further comprises;

When the switching condition is satisfied, a random access is initiated to the target access network device within a random access opportunity after the transmission of the last service frame ends.
The method according to claim 23 or 24, wherein the last service frame includes at least one data packet;

When the last service frame is encoded in the first encoding manner, the indication information is used to indicate that the transmission of the last data packet corresponding to the last service frame ends;

Or, when the last service frame is encoded in the second encoding manner, the indication information is used to indicate that the transmission of the last data packet of the base layer data corresponding to the last service frame is ended.
The method according to claim 24, wherein the switching condition comprises one or more of the following:

The reference signal received power RSRP of the cell in the target access network device is greater than the first threshold;

The reference signal reception quality RSRQ of the cell in the target access network device is greater than the second threshold;

The signal-to-interference-noise ratio SINR of the cell in the target access network device is greater than the third threshold.
A communication device, characterized by comprising a module for performing the method according to any one of claims 1 to 8.
A communication device, characterized by comprising a module for performing the method according to any one of claims 9 to 15 or 21-22.
A communication device, characterized by comprising a module for performing the method according to any one of claims 16 to 20 or 23 to 26.
A communication device, characterized by comprising a processor and a memory, wherein the processor and the memory are coupled, and the processor is configured to implement the method according to any one of claims 1 to 8.
A communication device, characterized by comprising a processor and a memory, wherein the processor and the memory are coupled, and the processor is configured to implement the method according to any one of claims 9 to 15 or 21-22.
A communication device, characterized by comprising a processor and a memory, wherein the processor and the memory are coupled, and the processor is configured to implement the method according to any one of claims 16 to 20 or 23 to 26.
A communication device, characterized by comprising a processor and an interface circuit, wherein the interface circuit is configured to receive signals from other communication devices other than the communication device and transmit to the processor or transfer signals from the processor The signal is sent to other communication devices other than the communication device, and the processor is used to implement the method according to any one of claims 1 to 8 by means of a logic circuit or executing code instructions.
A communication device, characterized by comprising a processor and an interface circuit, wherein the interface circuit is configured to receive signals from other communication devices other than the communication device and transmit to the processor or transfer signals from the processor The signal is sent to other communication devices than the communication device, and the processor is used to implement the method according to any one of claims 9 to 15 or 21-22 by means of a logic circuit or executing code instructions.
A communication device, characterized by comprising a processor and an interface circuit, wherein the interface circuit is configured to receive signals from other communication devices other than the communication device and transmit to the processor or transfer signals from the processor The signal is sent to other communication devices than the communication device, and the processor is used to implement the method as claimed in any one of claims 16 to 20 or 23 to 26 through logic circuits or executing code instructions.
A communication system, characterized by comprising the communication device according to any one of claims 27, 30, and 33, the communication device according to any one of claims 28, 31, and 34, and the The communication device of any one of claims 29, 32, and 35.
A computer-readable storage medium, characterized in that, a computer program or instruction is stored in the storage medium, and when the computer program or instruction is executed by a communication device, any one of claims 1 to 26 is implemented. Methods.
A computer program product, characterized in that the computer program product includes instructions that, when executed by a processor, implement the method of any one of claims 1 to 26.