Communication method and communication apparatus

Abstract

A communication method and a communication apparatus. Before a terminal performs cell handover, a network device acquires, in a sensing manner, information (parameters) required for the cell handover, for example, comprising at least one of a timing advance (TA) of an uplink transmission performed by the terminal to a target network device, a measurement result of the target network device, or a large-scale feature of a channel between the terminal and the target network device. When the terminal performs the cell handover, the TA is notified to the terminal by means of a handover command, which prevents the terminal and the network device from acquiring the described information by means of signaling interaction during cell handover, and reduces steps that need to be executed for the cell handover, thereby reducing the handover delay and the duration of data transmission interruption during the cell handover by the terminal, and improving the cell handover efficiency.

Description

Communication methods and communication devices

[0001] This application claims priority to Chinese Patent Application No. 202510239075.3, filed on February 27, 2025, entitled "Communication Method and Communication Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of communications, and more specifically, to a communication method and a communication device. Background Technology

[0003] Due to the mobility of terminals, they need to hand over to cells covered by different network devices (such as base stations). For example, a terminal needs to hand over from a cell covered by a source base station (source cell) to a cell covered by a target base station (target cell). Currently, during cell handover, the handover latency or data transmission interruption time is relatively long, resulting in low cell handover efficiency. Summary of the Invention

[0004] This application provides a communication method and a communication device that can reduce the handover latency and data transmission interruption time during cell handover, thereby improving cell handover efficiency.

[0005] Firstly, a communication method is provided. The executing entity of this method can be a terminal device, which can be a terminal equipment, a component (chip, chip system, or processor) supporting the implementation of this method in the terminal equipment, or a logic module or software capable of implementing all or part of the functions of the terminal equipment. The method includes: the terminal device receiving a handover command, which instructs the terminal device to begin handover from a source network device to a target network device, or in other words, the handover command instructs the terminal device to handover from the source network device to the target network device. The handover command includes a timing advance (TA) for uplink transmission from the terminal device to the target network device, which is determined based on a first sensing signal sent by the target network device to the terminal device; the terminal device, according to the handover command, begins a cell handover process, or in other words, performs or executes a cell handover process; and the terminal device sends a handover completion indication information to the target network device.

[0006] The communication method provided in the first aspect allows the timing advance (TA) for uplink transmission from the terminal device to the target network device to be obtained through sensing signals and notified to the terminal device via a handover command. This avoids the terminal device obtaining the TA through signaling interaction (e.g., random access procedure) during cell handover, reducing the steps required during handover and thus lowering handover latency and data transmission interruption time, thereby improving cell handover efficiency. During cell handover, the terminal device can use the TA to establish uplink synchronization with the target network device. For example, the terminal device can use the TA to determine the uplink transmission timing when transmitting uplink data to the target network device.

[0007] In one possible implementation of the first aspect, the uplink and / or downlink signals between the target network device and the terminal device maintain a quasi-co-location (QCL) relationship with a second sensing signal, which is used for downlink synchronization between the terminal device and the target network device. For example, before and during cell handover, the target network device can continuously transmit a sensing signal (the second sensing signal) to the terminal device, maintaining continuous beam coverage of the sensing signal over the terminal device. By maintaining a QCL relationship between the uplink and / or downlink signals between the target network device and the terminal device and the sensing signal, the terminal device can use the sensing signal to perform downlink synchronization with the target network device. During downlink synchronization, the terminal device can determine the large-scale characteristics of the channel with the target network device (e.g., Doppler shift / multipath characteristics). On the one hand, the terminal device can determine the large-scale characteristics of the channel between itself and the target network device by measuring the sensed signal, avoiding the need for the terminal device to obtain the large-scale characteristics of the channel by activating the TCI-state indication. This avoids the need for signaling interaction between the terminal device and the network device to obtain the large-scale characteristics of the channel, thus reducing signaling overhead. On the other hand, the terminal device can measure the sensed signal before cell handover and use it for downlink synchronization. This means that downlink synchronization can be performed before the terminal device begins cell handover (during which the large-scale characteristics of the channel can be obtained). During handover, the terminal device does not need to perform downlink synchronization based on the received SSB, reducing the steps required during handover. This further reduces handover latency and data transmission interruption time, improving cell handover efficiency.

[0008] For example, in Rel-15 hard handover, before cell handover, the downlink synchronization performed by the terminal device using sensing signals includes: establishing slot-level downlink synchronization with the target network device (e.g., determining the downlink slot, subframe, and / or radio frame boundary timing of the target network device), precise time-frequency alignment, and establishing radio frame-level downlink synchronization (e.g., determining the radio frame number of the target network device's downlink radio frame). During the precise time-frequency alignment and radio frame-level downlink synchronization using sensing signals, large-scale characteristics of the channel between the terminal device and the target network device can be determined. The cell handover process does not include: the terminal device determining the downlink slot, subframe, and / or radio frame boundary timing of the target network device, or the terminal device determining the radio frame number of the network device's downlink radio frame.

[0009] For example, in LTM handover, before cell handover, the downlink synchronization performed by the terminal device using sensing signals includes: the terminal device can use sensing signals for time-frequency fine alignment and establish radio frame-level downlink synchronization (e.g., determining the radio frame number of the target network device's downlink radio frame). During the time-frequency fine alignment and radio frame-level downlink synchronization processes using sensing signals, large-scale characteristics of the channel between the terminal device and the target network device can be determined. The cell handover process does not include: the terminal device determining the radio frame number of the network device's downlink radio frame.

[0010] In one possible implementation of the first aspect, before cell handover, for Rel-15 hard handover, the terminal device can also use sensing signals to adjust automatic gain control (AGC) parameters. In this implementation, the terminal device does not need to adjust AGC parameters according to the received synchronization signal block (SSB) during the handover process, further reducing the steps that need to be performed during the handover process. This can further reduce the latency and data transmission interruption time when the terminal device performs cell handover, and improve cell handover efficiency.

[0011] In one possible implementation of the first aspect, the cell handover process includes: the terminal device reading and verifying the handover command, loading and adjusting the software and hardware of the terminal device according to the handover command, and establishing uplink synchronization with the target network device using the TA.

[0012] In one possible implementation of the first aspect, the handover command is carried in a Radio Resource Control (RRC) reconfiguration message or a Media Access Control (MAC) CE. For example, in LTM handover, the handover command can be carried in the MAC CE. The verification and interpretation time of the handover command includes the HARQ feedback time to the MAC CE and the MAC CE reading time. For LTM handover, the verification and interpretation time of the handover command also includes the processing delay of the RRC reconfiguration message (the second RRC message), which is received before the terminal device receives the MAC CE. The RRC reconfiguration message includes the RRC configuration required for handover.

[0013] In one possible implementation of the first aspect, the handover completion indication information is carried in the RRC reconfiguration completion message.

[0014] Secondly, a communication method is provided. The executing entity of this method can be a target network device, which can be a target network equipment, a component (chip, chip system, or processor) supporting the target network device in implementing the method, or a logical node, logical module, or software capable of implementing all or part of the target network equipment's functions. The method includes: the target network device sending a first sensing signal to a terminal device; the target network device receiving an echo signal corresponding to the first sensing signal; the target network device determining a timing advance (TA) for uplink transmission from the terminal device to the target network device based on the echo signal and the first sensing signal, the TA being used for cell handover by the terminal device; and the target network device sending indication information, including the TA, to a source network device, the source network device being the network device providing communication services to the terminal device before cell handover. During cell handover, the terminal device can use the TA to establish uplink synchronization with the target network device. For example, the terminal device can use the TA to determine the uplink transmission timing when transmitting uplink data to the target network device.

[0015] The second aspect provides a communication method in which the target network device can obtain the TA (Transmission Aspect) for uplink transmission from the terminal device to the target network device using a single-site sensing approach and send it to the terminal device through the source network device. This avoids the terminal device obtaining the TA through signaling interaction (e.g., RACH procedure), saving signaling overhead during handover and avoiding handover latency caused by signaling interaction. This reduces handover latency and data transmission interruption time during cell handover, thereby improving cell handover efficiency.

[0016] Thirdly, a communication method is provided. The executing entity of this method can be a target network device, which can be a target network equipment, a component (chip, chip system, or processor) supporting the target network equipment in implementing the method, or a logical node, logical module, or software capable of implementing all or part of the target network equipment's functions. The method includes: the target network device sending a third sensing signal to a terminal device; the target network device receiving an echo signal corresponding to the third sensing signal; the target network device determining the channel quality between the terminal device and the target network device based on the echo signal and the third sensing signal; the target network device determining whether cell handover is permitted for the terminal device based on the channel quality; and, if cell handover is permitted, the target network device sending indication information to a source network device. This indication information indicates that the terminal device is permitted to handover to the target network device. The indication information includes a timing advance (TA) for uplink transmission from the terminal device to the target network device. The target network device is the target network device for the terminal device during cell handover, and the source network device is the network device that provides communication services to the terminal device before cell handover. During cell handover, the terminal device can establish uplink synchronization with the target network device using the TA. For example, a terminal device can use TA to determine the uplink transmission timing when making uplink transmissions to a target network device.

[0017] The third aspect provides a communication method in which the target network device can acquire the channel quality between the terminal device and the target network device using a single-site sensing approach, and manage cell handover by utilizing the channel quality between the terminal device and the target network device. This avoids the terminal device measuring and reporting the target cell based on measurement configuration. In other words, it avoids the terminal device acquiring and reporting the channel quality between the terminal device and the target network device through signaling interaction, avoiding handover delays caused by signaling interaction, reducing the requirements on the terminal device's capabilities, and improving cell handover efficiency.

[0018] In one possible implementation of the second or third aspect, the channel quality includes the reference signal received power (RSRP), which includes absolute RSRP and / or relative RSRP.

[0019] In one possible implementation of the second or third aspect, the uplink and / or downlink signals between the target network device and the terminal device maintain a QCL relationship with the first or third sensing signal. In this implementation, the terminal device can utilize the sensing signal to perform downlink synchronization before the handover process begins, determining the large-scale characteristics of the channel between itself and the target network device (e.g., Doppler shift / multipath characteristics) based on the sensing signal. On one hand, the terminal device can determine the large-scale characteristics of the channel between itself and the target network device by measuring the sensing signal, avoiding the need for the terminal device to use activated TCI-state indication to obtain the large-scale characteristics of the channel, thus avoiding signaling overhead by avoiding signaling interaction between the terminal device and the network device to obtain the large-scale characteristics of the channel. On the other hand, the terminal device can measure the sensing signal before cell handover and use the sensing signal for downlink synchronization, meaning the downlink synchronization process can be performed before the terminal device begins cell handover (the downlink synchronization process can obtain the large-scale characteristics of the channel). During the handover process, the terminal device does not need to perform downlink synchronization based on the received SSB, reducing the steps required during handover; that is, downlink synchronization is not required during handover. This can further reduce the handover latency and data transmission interruption time when the terminal device performs cell handover, thereby improving cell handover efficiency.

[0020] Fourthly, a communication method is provided. The executing entity of this method can be a source network device, which can be a source network equipment, a component (chip, chip system, or processor) supporting the source network equipment in implementing this method, or a logical node, logical module, or software capable of implementing all or part of the functions of the source network equipment. The method includes: the source network device receiving a first echo signal reflected by a first sensing signal from a terminal device; the first sensing signal being a sensing signal sent by a target network device to the terminal device; the source network device being a network device providing communication services to the terminal device before cell handover; and the target network device being a target network device during cell handover; the source network device sending a fourth sensing signal to the terminal device; the source network device receiving a fourth echo signal corresponding to the fourth sensing signal; and the source network device determining a timing advance (TA) for uplink transmission from the terminal device to the target network device based on the fourth sensing signal, the fourth echo signal, the first sensing signal, and the first echo signal. The TA is used by the terminal device for cell handover. During cell handover, the terminal device can use the TA to establish uplink synchronization with the target network device. For example, the terminal device can use the TA (Transmission Aspect Ratio) to determine the uplink transmission timing when making uplink transmissions to the target network device. The communication method provided in the fourth aspect allows the source network device to use bi-site sensing to determine the TA for uplink transmissions from the terminal device to the target network device and send it to the terminal device. This avoids the terminal device obtaining the TA through signaling interaction (e.g., the RACH procedure), saving signaling overhead during handover and avoiding handover latency caused by signaling interaction. This reduces handover latency and data transmission interruption time during cell handover, lowers the requirements on terminal device capabilities, and improves cell handover efficiency.

[0021] In one possible implementation of the fourth aspect, the source network device receives the transmission time of the first sensing signal from the target network device.

[0022] In one possible implementation of the fourth aspect, the uplink and / or downlink signals between the target network device and the terminal maintain a QCL relationship with the first sensing signal. In this implementation, the terminal device can utilize the sensing signal to perform downlink synchronization before or during the handover process, and determine the large-scale characteristics of the channel between itself and the target network device (e.g., Doppler shift / multipath characteristics) based on the sensing signal. This saves signaling overhead during handover, thereby reducing latency and data transmission interruption time during cell handover, lowering the requirements on terminal device capabilities, and improving cell handover efficiency.

[0023] Fifthly, a communication method is provided. The executing entity of this method can be a source network device, which can be a source network equipment, a component (chip, chip system, or processor) supporting the source network equipment in implementing the method, or a logical node, logical module, or software capable of implementing all or part of the functions of the source network equipment. The method includes: the source network device receiving a fifth echo signal reflected by a fifth sensing signal from a terminal device, wherein the fifth sensing signal is a sensing signal sent by a target network device to the terminal device; the source network device is a network device that provides communication services to the terminal device before cell handover; and the target network device is a target network device for the terminal device during cell handover. A network device; a source network device sends a sixth sensing signal to a terminal device; the source network device receives a sixth echo signal corresponding to the sixth sensing signal; the source network device determines the channel quality between the terminal device and the target network device based on the sixth sensing signal, the sixth echo signal, the fifth sensing signal, and the fifth echo signal; the source network device determines whether cell handover is permitted for the terminal device based on the channel quality; if cell handover is permitted, the source network device sends a handover command to the terminal device, which instructs the terminal device to begin handover from the source network device to the target network device, or in other words, the handover command instructs the terminal device to handover from the source network device to the target network device. The handover command includes a timing advance (TA) for uplink transmission from the terminal device to the target network device. After receiving the handover command, the terminal device begins the cell handover process, or in other words, after receiving the handover command, the terminal device performs or executes the cell handover process. During the cell handover process, the terminal device can use the TA to establish uplink synchronization with the target network device. For example, the terminal device can use the TA to determine the uplink transmission timing when transmitting uplink data to the target network device. The fifth aspect provides a communication method in which the source network device can determine the channel quality between the terminal device and the target network device using bi-site sensing. The source network device uses channel quality management to enable the terminal device to perform cell handover. This avoids the terminal device measuring and reporting the target cell based on measurement configuration. It saves signaling overhead during handover, avoids handover delays caused by signaling interaction, reduces the requirements on terminal device capabilities, and improves cell handover efficiency.

[0024] In one possible implementation of the fifth aspect, the channel quality includes the reference signal received power (RSRP), which includes absolute RSRP and / or relative RSRP.

[0025] In one possible implementation of the fifth aspect, the method further includes: the source network device receiving the transmission power of a fifth sensing signal from the target network device.

[0026] In one possible implementation of the fifth aspect, the uplink and / or downlink signals between the target network device and the terminal device maintain a QCL relationship with the fifth sensing signal. In this implementation, the terminal device can utilize the sensing signal to perform downlink synchronization before the handover process begins, and determine the large-scale characteristics of the channel between itself and the target network device (e.g., Doppler shift / multipath characteristics) based on the sensing signal. This saves signaling overhead during the handover process, thereby reducing the latency and data transmission interruption time during cell handover by the terminal device, lowering the requirements on the terminal device's capabilities, and improving cell handover efficiency.

[0027] Sixthly, a communication method is provided. The executing entity of this method can be a terminal device, which can be a terminal equipment, a component (chip, chip system, or processor) supporting the implementation of the method in the terminal equipment, or a logic module or software capable of implementing all or part of the functions of the terminal equipment. The method includes: if the terminal device has measured the sensing signal and has obtained the timing advance (TA) for uplink transmission from the terminal device to the target network device according to the handover command, the terminal device determines a handover delay, wherein the time length between the terminal device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay, the handover delay including the verification and interpretation time of the handover command and the interrupt time, and the uplink and / or downlink signals between the target network device and the terminal device maintaining a QCL relationship with the sensing signal; or...

[0028] If the terminal device has already measured the sensed signal, the terminal device determines the handover delay, wherein the time length between the terminal device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay. The handover delay includes the verification and interpretation time of the handover command, the interruption time, and the time for obtaining the timing advance (TA) for uplink transmission from the terminal device to the target network device. The uplink and / or downlink signals between the target network device and the terminal device maintain a QCL relationship with the sensed signal; or...

[0029] If the terminal device has obtained the timing advance (TA) for uplink transmission to the target network device according to the handover command, the terminal determines the handover delay. The time between the terminal device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay. The handover delay includes the verification and interpretation time of the handover command, the interruption time, and the time for downlink synchronization between the terminal device and the target network device.

[0030] During cell handover, the terminal device can establish uplink synchronization with the target network device using the TA (Transmission Timing). For example, the terminal device can use the TA to determine the uplink transmission timing when transmitting uplink data to the target network device.

[0031] The communication method provided in the sixth aspect allows the TA to acquire and transmit handover commands to the terminal device through sensing signals, and / or the terminal device can use sensing signals for downlink synchronization. The handover delay of the terminal device during cell handover is short, thereby reducing the handover delay and data transmission interruption time when the terminal device performs cell handover, and improving cell handover efficiency.

[0032] In one possible implementation of the sixth aspect, the switching command is carried in a first RRC message (RRC reconfiguration message), and the verification and interpretation time of the switching command includes the processing delay of the first RRC message.

[0033] In one possible implementation of the sixth aspect, the switching command is carried in the MAC CE, and the verification and interpretation time of the switching command includes: the HARQ feedback time of the MAC-CE and the reading time of the MAC-CE.

[0034] In one possible implementation of the sixth aspect, the verification and interpretation time of the handover command also includes the processing delay of a second RRC message (RRC reconfiguration message), which is received before the terminal receives the MAC CE, and includes the RRC configuration required for the handover.

[0035] In one possible implementation of the sixth aspect, the interruption time includes: the time for the terminal device to load and adjust software and hardware according to the first RRC message or the second RCC message, and the time for waiting for transmission resources to make the first uplink transmission to the target network device.

[0036] In a seventh aspect, a communication method is provided. The execution subject of this method can be a terminal device, which can be a terminal equipment, a component (chip, chip system, or processor) supporting the implementation of the method in the terminal equipment, or a logic module or software capable of implementing all or part of the functions of the terminal equipment. The method includes: if the terminal device has obtained a timing advance (TA) for uplink transmission from the terminal device to the target network device according to a handover command, the terminal device determines a handover delay, wherein the time length between the terminal device receiving the handover command and sending a handover completion indication is less than or equal to the handover delay, and the handover delay does not include the time length for obtaining the TA; and / or, if the terminal device has measured a sensing signal, and the uplink and / or downlink signals between the target network device and the terminal device maintain a quasi-co-addressable (QCL) relationship with the sensing signal, the terminal device determines a handover delay, wherein the time length between the terminal device receiving the handover command and sending the handover completion indication is less than or equal to the handover delay, and the handover delay does not include the time for downlink synchronization between the terminal and the target network device.

[0037] The communication method provided in the seventh aspect allows the TA to be acquired through sensing signals and transmitted to the terminal device via a handover command. The terminal device can use the sensing signals for downlink synchronization. Therefore, the cell handover process may not include the time for acquiring the TA and / or performing downlink synchronization. The handover delay of the terminal device during the cell handover process is shorter, thereby reducing the handover delay and the duration of data transmission interruption when the terminal device performs cell handover, and improving cell handover efficiency.

[0038] Eighthly, a communication device is provided, the device comprising: a module (e.g., including a processing module and a communication module) for performing any of the first to seventh aspects above, or any possible implementation of any of the first to seventh aspects.

[0039] Ninthly, a communication apparatus is provided, the apparatus including at least one processor, the at least one processor being configured to execute: the method provided in any one of the first to seventh aspects above, or the method in any possible implementation of any one of the first to seventh aspects.

[0040] In one possible implementation, the communication device may further include a memory storing a computer program, and at least one processor executes the method provided by any one of the first to seventh aspects above, or the method in any possible implementation of any one of the first to seventh aspects, by executing the computer program stored in the memory. Optionally, the processor and the memory may be integrated together.

[0041] In one possible implementation, at least one processor executes, via logic circuitry or processing circuitry, the method provided by any one of the first to seventh aspects above, or the method in any possible implementation of any one of the first to seventh aspects.

[0042] In one possible implementation, the communication device may further include an interface circuit for performing specific signal transmission and reception.

[0043] For example, the communication device can be a terminal, a component (chip, chip system, or processor) in the terminal, or a logic module or software that can realize all or part of the terminal's functions.

[0044] For example, the communication device can be a network device, a component (chip, chip system, or processor) in a network device, or a logical node, logical module, or software that can implement all or part of the functions of a network device.

[0045] In one possible implementation, the communication device provided in the eighth aspect and the communication device provided in the ninth aspect can be the aforementioned terminal device, source network device, or target network device.

[0046] In a tenth aspect, a computer program product is provided, comprising a computer program that, when executed by a processor, performs the method provided in any one of the first to seventh aspects, or the method in any possible implementation of any one of the first to seventh aspects.

[0047] Eleventhly, a computer-readable storage medium is provided, which stores a computer program that, when executed, performs the method provided in any one of the first to seventh aspects above, or the method in any possible implementation of any one of the first to seventh aspects.

[0048] In a twelfth aspect, a chip is provided, comprising: a processor for calling and running a computer program from a memory, causing a communication device having the chip mounted to perform: the method provided in any one of the first to seventh aspects above, or the method in any possible implementation of any one of the first to seventh aspects.

[0049] In a thirteenth aspect, a chip or system-on-a-chip is provided, comprising: logic circuitry for implementing the method provided in any one of the first to seventh aspects, or any possible implementation of any one of the first to seventh aspects. Optionally, the chip or system-on-a-chip may further include interface circuitry.

[0050] In a fourteenth aspect, a communication system is provided, comprising: a terminal device and a source network device, wherein the terminal device is configured to perform the method of the first aspect or any possible implementation thereof, and / or to perform the method provided in the sixth or seventh aspect. The source network device is configured to perform the method provided in the fourth or fifth aspect, or any possible implementation thereof.

[0051] Optionally, the communication system further includes a target network device for performing the method provided in the second or third aspect above, or any possible implementation thereof. Attached Figure Description

[0052] Figure 1 is a schematic flowchart of a terminal performing cell handover.

[0053] Figure 2 is a schematic diagram of a single-site network device awareness.

[0054] Figure 3 is a schematic diagram of a dual-site sensing system with two network devices.

[0055] Figure 4 is a schematic diagram of the steps that the terminal needs to perform during a Rel-15 hard handover.

[0056] Figure 5 is a schematic diagram of the steps that the terminal needs to perform during an LTM handover process.

[0057] Figure 6 is a schematic diagram of a communication architecture applicable to an embodiment of this application.

[0058] Figure 7 is a schematic flowchart of a communication method provided in an embodiment of this application.

[0059] Figure 8 is a schematic diagram of the downlink receiving timing of a terminal device and the downlink transmitting timing of a target network device according to an embodiment of this application.

[0060] Figure 9 shows a scenario where a target network device sends two sensing signals according to an embodiment of this application.

[0061] Figure 10 is a schematic flowchart of another communication method provided in an embodiment of this application.

[0062] Figure 11 shows an example of a scenario where a target network device and a source network device are sensed through dual stations, as provided in an embodiment of this application.

[0063] Figure 12 is a schematic flowchart of another communication method provided in an embodiment of this application.

[0064] Figure 13 is a schematic diagram of the steps that the terminal needs to perform during a Rel-15 hard handover using the method provided in this application.

[0065] Figure 14 is a schematic diagram of the steps that the terminal needs to perform during LTM handover using the method provided in this application.

[0066] Figure 15 is a schematic block diagram of a communication device provided in an embodiment of this application.

[0067] Figure 16 is a schematic block diagram of another communication device provided in an embodiment of this application.

[0068] Figure 17 is a schematic block diagram of a terminal provided in an embodiment of this application.

[0069] Figure 18 is a schematic block diagram of a network device provided in an embodiment of this application. Detailed Implementation

[0070] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0071] In the description of the embodiments of this application, unless otherwise stated, " / " means "or", for example, A / B can mean A or B; "and / or" in this document is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.

[0072] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this embodiment, unless otherwise stated, "a plurality of" means two or more.

[0073] In this article, the terms "system" and "network" are often used interchangeably.

[0074] In this embodiment, the terminal or network device may include a hardware layer, an operating system layer running on top of the hardware layer, and an application layer running on top of the operating system layer. The hardware layer includes hardware such as a central processing unit (CPU), a memory management unit (MMU), and memory (also called main memory). The operating system can be any one or more computer operating systems that implement business processing through processes, such as Linux, Unix, Android, iOS, or Windows. The application layer includes applications such as browsers, address books, word processing software, and instant messaging software. Furthermore, this embodiment does not specifically limit the specific structure of the execution entity of the method provided in this embodiment, as long as it can communicate according to the method provided in this embodiment by running a program that records the code of the method provided in this embodiment. For example, the execution entity of the method provided in this embodiment can be a terminal or network device, or a functional module in the terminal or network device that can call and execute a program.

[0075] Furthermore, various aspects or features of this application can be implemented as methods, apparatus, or articles of manufacture using standard programming and / or engineering techniques. The term "article of manufacture" as used herein encompasses a computer program accessible from any computer-readable device, carrier, or medium. For example, computer-readable media may include, but are not limited to: magnetic storage devices (e.g., hard disks, floppy disks, or magnetic tapes), optical discs (e.g., compact discs (CDs), digital versatile discs (DVDs), etc.), smart cards, and flash memory devices (e.g., erasable programmable read-only memory (EPROMs), cards, sticks, or key drives, etc.). Additionally, the various storage media described herein may represent one or more devices and / or other machine-readable media for storing information. The term "machine-readable medium" may include, but is not limited to, wireless channels and various other media capable of storing, containing, and / or carrying instructions and / or data.

[0076] Due to the mobility of terminals, the radio access network (RAN) equipment (taking a base station as an example) providing network services to terminals may change. To ensure service continuity for the terminals, it is necessary to change the terminal's serving cell. The mobility procedure changes the terminal's serving cell (or, in other words, changes the base station serving the terminal device) so that the terminal can enjoy uninterrupted service regardless of its movement within network coverage. The mobility procedure may include various interactive processes to ensure service continuity for the terminals.

[0077] Depending on the radio resource control (RRC) state of the terminal, the mobility process in the RRC idle state (RRC_IDLE) refers to the cell selection / reselection process. In the RRC connected state (RRC_CONNECTED), it refers to the handover process, that is, the terminal hands over (HO) from the area covered by one base station (e.g., the source base station or source network device) to the area (cell) covered by another base station (e.g., the target base station or target network device).

[0078] For example, Figure 1 shows a schematic flowchart of a terminal performing cell handover. The example shown in Figure 1 is an intra-NR handover process, that is, the handover process of a terminal from one NR cell to another NR cell.

[0079] As shown in Figure 1, before the terminal performs cell handover, the terminal's (e.g., user equipment (UE)) user data is transmitted to core network equipment via the source gNB, including access and mobility function (AMF) network elements and user plane function (UPF) network elements. The AMF provides the source gNB with the terminal's mobility control information.

[0080] Step 1: The source base station configures the terminal to perform mobility measurement and report the measurement results (Measurement control and Reports).

[0081] For example, the source base station can send a measurement configuration to the terminal, and the terminal performs a measurement on the target base station according to the measurement configuration. After obtaining the measurement results, the terminal will report the measurement results to the source base station.

[0082] Step 2: The source base station decides whether to handover based on the measurement results reported by the terminal.

[0083] Step 3: If a handover is initiated, the source base station sends a handover request to the target base station (target gNB), informing the target base station of the parameters required for the handover, such as: basic access layer parameters of the terminal, quality of service flow (QoS flow) information, etc.

[0084] Step 4: The target base station performs an access permission control process to confirm whether handover is permitted.

[0085] Step 5: If handover is permitted, the target base station configures its own Layer 1 / Layer 2 protocol stack, sends a handover request confirmation message (HANDOVER REQUEST ACKNOWLEDGE) to the source base station, and also informs the source base station of the RRC parameters required for the terminal to handover.

[0086] Step 6: Begin RAN Handover Initiation.

[0087] In step 6, the source base station sends a message (e.g., an RRC Reconfiguration message) to the terminal to trigger a handover of the Uu interface, i.e., to trigger the terminal to perform a cell handover. The Uu interface is the interface between the terminal and the base station. The message carries the RRC configuration parameters provided by the target base station, and the terminal initiates the cell handover based on this message.

[0088] For example, during cell handover, the terminal synchronously separates from the source cell to the target cell. The source base station transfers buffered data and new data from the UPF to the target base station. The source cell is the cell providing network services to the source base station, and the target cell is the cell providing network services to the target base station.

[0089] Step 7: The source base station sends a sequence number (SN) state transition message to the target base station to transfer the SNs of the uplink and downlink packet data convergence protocol (PDCP) data packets of each radio bearer to the target base station.

[0090] Step 8: Complete the cell handover (RAN Handover Completion).

[0091] In step 8, the terminal can establish uplink and downlink synchronization with the target base station and transmit a handover completion message to the target base station, such as an RRC Reconfiguration Complete message, to indicate that the cell handover (RRC handover) is complete.

[0092] Step 9: The target base station sends a path switch request to the AMF, requesting that the downlink data path of the core network and the terminal be switched to the target base station.

[0093] Step 10: The AMF and UPF switch the downlink data path to the target base station (Path Switch in UPF).

[0094] Step 11: The AMF sends a PATH SWITCH REQUEST ACKNOWLEDGE message to the target base station to indicate that the downlink data path switch was successful.

[0095] Step 12: The target base station sends an indication message to the source base station to release the terminal's context (UE CONTEXT RELEASE), and the source base station releases the terminal's context according to the message.

[0096] From the terminal's perspective, only the measurement configuration and reporting in step 1, the cell handover process in step 6, and the transmission of the handover completion message to the target base station in step 8 are tasks that the terminal needs to perform.

[0097] The 3rd Generation Partnership Project (3GPP) protocol release 19 supports integrated sensing and communication (ISAC). ISAC technology is considered one of the key technologies for expanding the service capabilities of mobile communication networks. The core idea of ​​this technology is to add sensing capabilities to the mobile communication network, building the ability to detect and image targets, thereby integrating communication and sensing capabilities into a single network, achieving harmonious coexistence, and even mutual benefit.

[0098] The principles of sensing technology and communication technology differ somewhat. Communication technology primarily involves the transmitter modulating information onto radio waves and sending it to the receiver. The receiver then demodulates the signal (or communication signal) carried on the radio waves to obtain the information. Sensing technology, on the other hand, requires the transmitter to send radio waves (or sensing signals) in a specific direction. When these radio waves strike a target surface, they create reflected waves (or echo signals). The receiver then receives and processes these reflected waves to obtain the sensing results, such as information about the target's position, speed, and type.

[0099] The so-called integrated sensing and communication refers to reusing the network services / infrastructure of the 5G system (5GS) currently used to provide communication services to provide sensing services. Sensing services can include determining parameters such as the distance, angle, and instantaneous speed / direction of the sensed target. Sensed targets include device-free targets that are not connected to the 5GS network (such as vehicles, people, animals, drones, buildings, etc.).

[0100] 5GS sensing services support both radio frequency (RF) based and non-RF based sensing technologies. RF-based and non-RF-based sensing technologies can complement each other.

[0101] For example, radio frequency (RF) signal-based sensing technology can be implemented using radar technology, which utilizes radio wave detection and ranging. Network devices (such as base stations) or terminals transmit radio waves with known signal structures, and then, based on the radio waves reflected / refracted / diffracted by the sensed target (or echo signals), estimate the target's distance, angle, and instantaneous velocity.

[0102] Sensing technologies that are not based on radio frequency signals can utilize sensors that are not based on radio frequency signals, such as time-of-flight (ToF) cameras, accelerometers, gyroscopes, and lidar, on base stations or terminals for target perception.

[0103] Sensing can generally be divided into two modes: monostatic sensing and bistatic sensing. Monostatic sensing is characterized by the same device serving as both the transmitter and receiver of the sensing signal; they are co-located and belong to the same entity. In terms of signal transmission, the sensing station both transmits and receives the signal reflected from the target surface; therefore, monostatic sensing can also be called a self-transmitting and self-receiving mode. In bistatic sensing, the transmitter and receiver are two different devices; they are not co-located and belong to different entities. In terms of signal transmission, after sensing station A transmits a signal, the signal reflected from the target surface is received by sensing station B; therefore, bistatic sensing is also called the A-transmit, B-receive mode.

[0104] For example, Figure 2 shows a schematic diagram of a single-site sensing operation of a network device. As shown in Figure 2, the network device and the terminal communicate using communication signals. The network device sends a sensing signal (or a combined sensing signal) to the target to be sensed. The target to be sensed reflects the sensing signal to form an echo signal. The network device receives the echo signal and uses the echo signal and the sensing signal to sense the target.

[0105] For example, Figure 3 shows a schematic diagram of dual-site sensing using two network devices. As shown in Figure 3, network device A and the terminal communicate using communication signals. Network device A sends a sensing signal (or a combined sensing signal) to the target to be sensed. The target to be sensed reflects the sensing signal to form an echo signal. Network device B receives the echo signal and uses the echo signal and the sensing signal to sense the target.

[0106] The following is a brief explanation of several cell handover schemes related to this application.

[0107] Option 1: In the baseline assumptions of RAN work group 4 (RAN4), the terminal needs to perform the following steps during the measurement reporting process and RRC handover (i.e., cell handover) as shown in Figure 4. The process shown in Figure 4 can also be referred to as the cell handover process in Release 15 or Rel-15 hard handover.

[0108] Step 1: Layer 3 (L3) Measurement Reporting. The terminal performs measurements on the target base station according to the measurement configuration provided by the network and reports the measurement results to the source base station.

[0109] By measuring the target base station, the terminal can obtain the following information:

[0110] Downlink timing at the slot level of the target base station;

[0111] Automatic gain control (AGC) parameters when receiving downlink (DL) signals from the target base station;

[0112] Measurement results of the target base station include, for example, reference signal receiving power (RSRP), reference signal receiving quality (RSRQ), signal-noise ratio (SNR), and signal-to-interference plus noise ratio (SINR).

[0113] After obtaining the measurement results, the terminal reports the results to the source base station, thereby enabling the source base station to obtain the following information:

[0114] The configured reporting criteria and the measurement results of the target base station are used by the source base station to decide whether to trigger the handover process.

[0115] It should be understood that measurement result reporting is an auxiliary process to support the handover process, and it is not part of the handover process itself. Therefore, the network can also trigger the handover process directly without the support of measurement result reporting, which is called blind handover. In other words, step 1 is an optional step.

[0116] In one possible implementation, the impact of the terminal's beam-based reception needs to be considered in the frequency range 2 (FR2) defined by 5G. Therefore, the L3 measurement delay is relaxed (or increased) based on the frequency range 1 (FR1) to allow the terminal enough time to perform beam scanning. The specific relaxation factor (or amplification factor) is related to the terminal's power control (PC) and is generally 5 to 8 times.

[0117] Subsequently, the terminal can receive an RRC reconfiguration message sent by the source base station. The RRC reconfiguration message may carry a handover command. The handover command instructs the terminal to begin cell handover, marking the start of the cell handover process (RAN handover process) and the commencement of RAN handover delay calculation. In other words, the moment the terminal receives the RRC reconfiguration message from the source base station can be understood as the moment the cell handover delay calculation begins (the starting point of RAN handover delay calculation).

[0118] Step 2: RRC configuration read verification.

[0119] The terminal verifies the validity of the RRC reconfiguration message and can obtain the following information from it:

[0120] Configuration parameters for each layer of the protocol stack provided to the terminal by the target base station;

[0121] The dedicated random access resources and configurations required for subsequent random access initiation, where the random access resources and configurations are the resources and configurations on the random access channel (RACH).

[0122] Optionally, step 2 can also be referred to as reading and verifying the switching command. The delay in the RRC configuration reading and verification process can also be called the RRC procedure delay, which is calculated using T... RRC procedure express.

[0123] Step 3: Loading and adjusting software and hardware.

[0124] In step 3, the terminal reconfigures the radio frequency / baseband / software according to the configuration provided by the network (the configuration in the RRC reconfiguration message). The latency of loading and adjusting the software and hardware can be referred to as the processing latency (T). processing ).

[0125] Step 4: Adjust AGC parameters.

[0126] RAN4 assumes that the terminal adjusts the RF channel based on the received power of the synchronization signal block (SSB) of the target cell (i.e., the cell where the target base station provides network services), setting appropriate gain parameters for the RF channel. The terminal can obtain the AGC parameters through step 4.

[0127] It should be understood that AGC parameter adjustments can also be obtained during the L3 measurement process. Therefore, RAN4 assumes that if the terminal has already performed measurements and reported the target cell before the handover process begins, the AGC parameter adjustment step can be skipped. In other words, step 4 is an optional step.

[0128] Step 5: Establish downlink synchronization at the slot level.

[0129] RAN4 assumes that the terminal obtains the downlink timing of the target cell based on the reception of the target cell's SSB. Through step 5, the terminal can obtain the slot-level downlink timing of the target base station and establish slot-level downlink synchronization with the target base station. For example, establishing slot-level downlink synchronization with the target cell may include: determining the downlink time slot timing of the target base station based on the target cell's SSB, as well as the timing of subframe and / or radio frame boundaries, etc.

[0130] It should be understood that the slot-level downlink timing of the target base station can also be obtained during the measurement process. Therefore, RAN4 assumes that if the terminal has already performed measurements and reported the target cell before the handover process begins, then step 5 (i.e., the downlink synchronization step) can be skipped. In other words, step 5 is an optional step.

[0131] The sum of the delays in steps 4 and 5 can be called T. search .

[0132] It should be understood that if the target cell meets known conditions, such as the terminal performing L3 measurement on the target cell and reporting the measurement results 5 seconds before handover, and the target cell remaining detectable during handover, then the protocol assumes that the terminal has completed AGC parameter adjustment and downlink synchronization during the L3 measurement. Therefore, T... search =0.

[0133] Step 6: Time and frequency fine alignment, establish downlink synchronization at the wireless frame level.

[0134] For complexity reasons, the terminal typically does not read the payload of the physical broadcast channel (PBCH) contained in the SSB of the target cell during the L3 measurement process or downlink synchronization process (i.e., step 5). This means that the terminal has not yet obtained the half-frame and radio frame information of the detected SSB. However, complete frame structure information must be obtained before data transmission and reception can be performed. In addition, the time / frequency synchronization established by the terminal during L3 measurement and downlink synchronization may have a large deviation, and the terminal needs to perform time-frequency fine alignment to compensate for time-frequency timing errors caused by factors such as Doppler frequency shift / multipath. Therefore, in step 6, the terminal receives and reads the SSB of the target cell to obtain information such as the Doppler frequency shift / multipath information and the complete frame structure of the target cell. For example, time-frequency fine alignment and establishing radio frame-level downlink synchronization may include determining the radio frame number of the downlink radio frame of the target cell based on the SSB of the target cell.

[0135] Optionally, in this application, time-frequency precision alignment can also be referred to as time-frequency precision coverage.

[0136] As shown in Figure 4, the time delay corresponding to step 6 is T. Δ +2ms, where the 2ms time period is the SSB post-processing margin.

[0137] During the process of precise time-frequency alignment and establishing downlink synchronization at the radio frame level (i.e., in step 6), the terminal can implicitly determine the large-scale channel characteristics between itself and the target base station based on the received SSB through precise time-frequency synchronization. In other words, during the handover process, the target cell's channel / signal and the target cell's SSB maintain a quasi-co-location (QCL) relationship. The QCL relationship indicates that multiple resources or signals share one or more identical or similar communication characteristics. For multiple resources or signals with a QCL relationship, the same or similar communication configurations can be adopted. In step 6, the QCL relationship can be understood as: the target cell's uplink and / or downlink channels and the SSB share the same large-scale channel characteristics, such as Doppler shift, multipath characteristics, and time delay. The terminal can receive the target cell's uplink and / or downlink signals, such as control signals and / or data, based on the SSB's channel characteristics.

[0138] The length of the time from the end of step 6 to the arrival of the terminal's first transmission opportunity is T. Iu In other words, T IuThis can be understood as the time length between the end of the time-frequency alignment and the establishment of downlink synchronization at the radio frame level, and the arrival of the terminal's first transmission opportunity. The terminal's first transmission opportunity can be understood as the random access occasion (RO) for the terminal to first send the preamble. RO can be understood as the time-frequency resources used by the terminal for random access (i.e., for sending the preamble). Optionally, T... Iu This can also be referred to as the delay or duration of waiting for associated ROs.

[0139] In T Iu At the end of the process, the terminal can send a preamble to the target base station on the RO (Remote Access Resource). The preamble is carried by the physical random access channel (PRACH). The terminal can use the private / public random access resource configuration provided in the RRC reconfiguration message to send the preamble to the target base station. There is a correlation between the RO and the SSB (Secure Access Resource Block), and the terminal can determine the RO based on the received SSB, thus sending the preamble on the RO.

[0140] As shown in Figure 4, T Iu The end time, or the time when the terminal sends the preamble to the target base station, is the end time of the RAN handover delay. In other words, T Iu The end time, or the time when the terminal sends the preamble to the target base station, can be understood as the end time of cell handover delay calculation (RAN handover delay calculation endpoint).

[0141] As shown in Figure 4, T processing +T search +T Δ +2ms+T Iu The sum is T interrupt T interrupt This can be understood as the undesirable interruption time for the terminal to transmit or receive data in the source cell (i.e., the cell where the source base station provides network services).

[0142] In the example shown in Figure 4, the handover delay includes the time length D between the terminal device receiving the handover command and initiating the first transmission (i.e., the first preamble transmission) to the target base station. handover D handover =T RRC procedure +T interrupt .

[0143] Step 7: The terminal performs a competition-free random access (CFRA) procedure.

[0144] After the terminal sends the preamble, it receives a random access response (RAR) from the target base station. The RAR carries the timing advance (TA) required for the terminal to perform uplink (UL) transmission to the target base station, as well as the uplink transmission grant (UL grant) provided to the terminal. The terminal can then send information to the target base station on the transmission resources indicated by the uplink transmission grant (UL grant).

[0145] For example, after receiving the preamble sent by the terminal, the target base station calculates the TA required by the terminal device for uplink transmission based on the time domain location of the RACH resource used by the terminal and the reception timing of the preamble. Then, the target base station can inform the terminal of the TA amount through RAR and provide the terminal with uplink transmission grant (UL grant) in RAR.

[0146] Step 8: The terminal uses TA to establish uplink synchronization.

[0147] Generally, the terminal establishes uplink synchronization with the target base station using a random access procedure. After receiving the RAR, the terminal obtains the TA from the RAR and then determines that the terminal's uplink transmission timing equals the terminal's downlink reception timing plus the TA amount. After establishing uplink synchronization with the target base station, the terminal uses the UL grant provided by the target base station to transmit an RRC Reconfiguration Complete message. The RRC Reconfiguration Complete message indicates that the cell handover is complete, thus ending the RRC handover process. In other words, the moment the terminal sends the RRC Reconfiguration Complete message can be understood as the moment the cell handover is completed. After the terminal sends the RRC Reconfiguration Complete message, the cell handover process ends (the RAN handover process ends).

[0148] Steps 7 and 8 can be understood as the process by which the terminal obtains the TA and uses the TA for uplink synchronization (i.e., obtaining the TA through the RACH process).

[0149] After the handover is complete, the target base station can indicate to the terminal via the transmission configuration indicator state (TCI state) which reference signal and channel of the target cell maintain a QCL relationship. The TCI state can be used to indicate the QCL relationship between two reference signals. The target base station can configure a list of TCI states for the terminal via higher-layer signaling (such as RRC messages) and can activate one or more TCI states via medium access control-control element (MAC CE) signaling. The TCI state can be used to indicate the QCL relationship between two reference signals. In this application, MAC CE can also be represented as MAC-CE, and both have the same meaning.

[0150] For example, after cell handover is complete, the target base station can send RRC signaling to the terminal. The RRC signaling can include multiple TCI-states, each associated with a reference signal. The terminal can measure the RS associated with different TCI-states based on the reference signals (RS) configured in the RRC signaling and feed the measurement results back to the target base station. The target base station can then instruct the terminal to activate one or more TCI states based on the measurement results via MAC CE. An activated TCI state can be understood as one where the target cell's signal / channel and the associated reference signal share several large-scale characteristics, such as Doppler frequency shift / multipath characteristics. The terminal can receive uplink and / or downlink signals from the target cell, such as control signals and / or data, based on the channel characteristics of the reference signal associated with the TCI state.

[0151] Option 2: Dual active protocol stack (DAPS) switching.

[0152] The DAPS handover scheme configures the terminal with dual RF / baseband hardware resources, enabling it to maintain RRC connections with both the source and target base stations simultaneously. This means the terminal maintains connections with both base stations for a short period, and the connection with the source base station is only disconnected (released) after the connection with the target base station is established. This significantly reduces data transmission and reception interruption time during handover, achieving a so-called "0ms handover interruption." However, this applies to the entire user plane transmission; in reality, due to the inevitable RF adjustments, there will still be some transmission interruption time (typically around 0.5ms). But the steps performed during handover are consistent with the scheme, so the handover latency remains almost unchanged.

[0153] Option 3: Conditional handover (CHO).

[0154] The initial purpose of conditional handover was to address the timeliness issue of measurement results. The network informs the terminal of the target cell's RRC configuration in advance. When conditions are met, the terminal immediately and autonomously triggers the RRC handover process without waiting for the network's RRC message (i.e., handover command). This avoids the poor timeliness of measurement reporting in Rel-15 hard handover, where the terminal's previous measurement reports may be outdated by the time the network initiates the handover. However, conditional handover does not improve handover latency / interruption; the latency is essentially the same as Rel-15 hard handover.

[0155] Option 4: L1 / L2-triggered mobility (LTM) handover.

[0156] During L1 / L2-triggered mobility (LTM) handover, the source base station can provide the target cell's RRC configuration (via an RRC reconfiguration message) to the terminal beforehand. The terminal then initiates cell handover by performing L1-RSRP measurement (L1 measurement) or L3-RSRP measurement, reporting the measurement results, and the source base station sending a MAC-CE trigger. Layer 1 (L1) includes the physical (PHY) layer, and Layer 2 (L2) includes the media access control (MAC) layer, radio link control (RLC) layer, packet data convergence protocol (PDCP) layer, and service data adaptation protocol (SDAP) layer. In LTM, Layer 2 specifically refers to the MAC layer, and Layer 3 specifically refers to Layer 3 of the access stratum (AS), i.e., the RRC layer. Optionally, Layer 3 signaling can also be called RRC layer signaling or higher layer signaling, Layer 2 can also be called MAC layer signaling (e.g., MAC-CE), and Layer 1 can also be called physical layer signaling.

[0157] During the LTM handover process, the terminal needs to perform the steps shown in Figure 5.

[0158] Step 1: Report L1 or L3 measurements.

[0159] Similar to Re-15 hard handover, the terminal can perform measurements on the target base station based on the measurement configuration provided by the source base station (configured to the terminal by the source base station via RRC reconfiguration messages) to obtain the target base station's slot-level downlink timing, AGC parameters, and channel measurement results (such as RSRP). The terminal then reports these measurement results to the source base station. However, the difference is that LTM handover can be based on both L3 and L1 measurements.

[0160] It should be understood that although theoretically LTM can be initiated directly without measurement reporting support (also known as blind LTM handover), meaning step 1 is optional, RAN4 only defines LTM handover latency / interruption metrics when measurement reporting results are available. Therefore, blind LTM handover has no minimum performance guarantee.

[0161] Step 2: UL / DL TCI-state identification.

[0162] The RRC reconfiguration signaling (or RRC reconfiguration message) received by the terminal can carry individual UL TCI-states and DL TCI-states, or joint uplink / downlink TCI-states, to indicate the QCL relationship of the target base station's uplink / downlink. In other words, the RRC reconfiguration signaling can include multiple TCI-states, each of which can be associated with a reference signal. The terminal can measure the RS associated with different TCI-states according to the reference signals (RS) configured by the RRC reconfiguration signaling and feed the measurement results back to the source base station. The source base station can then indicate to the terminal, via subsequent MAC CE, that one or more TCI states should be activated. An activated TCI state can be understood as having the same large-scale channel characteristics as the target cell's signal / channel and the reference signal associated with that TCI state, such as Doppler shift, multipath characteristics, time delay, Doppler spread, beam direction, etc.

[0163] Step 3: Acquiring TA in advance.

[0164] If the terminal's capabilities support it, LTM handover allows the terminal to obtain the TA (Target Access Transaction) amount for uplink transmission to the target base station before the LTM handover is triggered. Currently, the protocol supports two acquisition methods. One is that the terminal acquires it itself (e.g., the terminal calculates the target base station's TA amount based on the source base station's TA amount and the timing difference between the source and target base stations). The other is that the source base station sends a command (PDCCH order) to the terminal on the physical downlink control channel (PDCCH), triggering the terminal to initiate a random access procedure (RACH) at the target base station. After the target base station calculates the TA amount, it informs the source base station, which then forwards it to the terminal (carried through the MAC CE in subsequent steps), thus allowing the terminal to obtain the TA amount for uplink transmission. It should be understood that step 3 is optional. For example, if the terminal's capabilities do not support it, it cannot obtain the TA before the LTM handover is triggered.

[0165] Step 4: Configure and verify RRC reading in advance.

[0166] Since the RRC configuration (i.e., the RRC reconfiguration message) has been pre-configured to the terminal, if the terminal's capabilities allow, it can verify the validity of the RRC reconfiguration message before receiving the LTM message (i.e., before the LTM handover is triggered). From this, it can obtain the configuration parameters of each layer of the protocol stack, random access resources and configurations, and uplink grants (UL grants) required for subsequent transmissions provided by the target base station to the terminal. For example, configured grants.

[0167] It should be understood that step 4 is optional. For example, if the terminal does not support it, RRC configuration reading verification cannot be performed before the LTM handover is triggered.

[0168] After step 4 (or step 2), the source base station can send an LTM message to the terminal to trigger the terminal to begin cell handover (i.e., LTM handover triggers handover). For example, the source base station can send a MAC CE to the terminal, which may carry a handover command to instruct the terminal to begin cell handover. The cell handover process begins (RAN handover process begins), and the RAN handover delay begins to be calculated. In other words, the moment the terminal receives the LTM message (i.e., MAC CE) sent by the source base station can be understood as the moment when the cell handover delay calculation begins (the starting point of the RAN handover delay calculation). Optionally, the MAC CE can be called an LTM switch trigger message or simply an LTM message.

[0169] Step 5: Hybrid Automatic Repeat Request (HARQ) feedback.

[0170] Since MAC-CE is carried at the physical layer by the physical downlink shared channel (PDSCH), the terminal receiving MAC-CE first needs to send a HARQ feedback to the source base station. The HARQ feedback delay can be expressed as T. HARQ .

[0171] Step 6: MAC-CE reading.

[0172] The terminal's MAC layer interprets the MAC-CE to obtain the configuration parameters required for performing LTM handover. Typically, the MAC-CE reading latency is 3ms. Optionally, step 6 can also be referred to as reading and verifying the handover command.

[0173] Step 7: RRC configuration read verification.

[0174] Similar to Rel-15 hard handover, the terminal needs to verify the validity of the RRC reconfiguration message. From this message, it obtains the configuration parameters of each layer of the protocol stack provided by the target base station, random access resources and configurations, and uplink grants (UL grants) required for subsequent transmissions. The latency of the RRC configuration reading and verification process in the LTM handover procedure can also be referred to as the RRC process latency in LTM handover, and can be expressed as T. LTM-RRC- procedure .

[0175] It should be understood that if the terminal has already performed RRC configuration read verification (i.e., step 4) before the LTM handover trigger, then step 7 does not need to be executed. LTM -RRC-procedure=0, meaning step 7 is an optional step.

[0176] Step 8: Loading and adjusting software and hardware.

[0177] Similar to Rel-15 hard handover, the terminal reconfigures the RF / baseband / software based on the configuration provided by the network (the configuration provided in the RRC reconfiguration message). The latency of loading and adjusting the software and hardware can be expressed as T. LTM-processing .

[0178] Step 9: Time and frequency fine alignment, establish wireless frame-level downlink synchronization.

[0179] Similar to Rel-15 hard handover (the process shown in Figure 4), the terminal needs to perform time-frequency fine alignment based on the SSB to determine the large-scale channel characteristics between the terminal and the target base station in order to obtain the Doppler frequency offset / multipath information and the complete frame structure of the target cell. In step 9, the terminal receives and reads the SSB of the target cell to obtain the Doppler frequency offset / multipath information and the complete frame structure of the target cell.

[0180] It should be understood that if the terminal has previously determined which TCI-state (or QCL relationship) in the activated TCI-state list is active via the TCI-state indication in the LTM message (i.e., MAC CE), then it can be considered that the terminal has already completed time-frequency fine synchronization with the target base station based on the TCI-state indication. In this case, step 9 can be omitted, i.e., step 9 is optional. The TCI-state list can be configured and notified to the terminal by the source base station via an RRC reconfiguration message. Subsequently, the source base station activates a certain TCI-state in the list via MAC CE, thereby ensuring that the terminal determines that the signal / channel of the target cell and the reference signal associated with the activated TCI-state have the same large-scale channel characteristics, such as Doppler frequency shift / multipath characteristics. The terminal can receive the uplink and / or downlink signals of the target cell based on the channel characteristics of the reference signal associated with the activated TCI-state.

[0181] As shown in Figure 5, the time delay corresponding to step 9 is T. first-RS +2ms, where T first-RSThis indicates the delay when the terminal receives the first SSB, with 2ms representing the post-processing margin for the SSB. If the terminal has previously determined which TCI-state (or QCL relationship) in the active TCI state list is active via the TCI-state indication in the LTM message, then T... first-RS =0, and there is no need to calculate the delay of SSB post-processing margin.

[0182] It should also be understood that the latency index defined by RAN4 is applicable only if the target base station and the original base station have the same system frame number (SFN), that is, assuming that the terminal infers the target base station frame structure based on the original base station frame structure.

[0183] After step 9, there are two possible implementation methods:

[0184] One possible implementation is as follows: the terminal obtains the TA through the RACH procedure and uses the TA to establish uplink synchronization, which can also be called RACH-based LTM handover. The specific process can be the same as steps 7 and 8 shown in Figure 4. For detailed explanations, please refer to the corresponding steps in Figure 4; for brevity, they will not be repeated here. In this case, the length of the time from the end of step 9 to the arrival of the terminal device's first transmission opportunity is T. LTM-Iu T LTM-Iu This can be understood as the time length between the end of the time-frequency alignment and the establishment of downlink synchronization at the radio frame level, and the arrival of the terminal's first transmission opportunity. The terminal's first transmission opportunity can be the random access opportunity (RO) at which the terminal first sends the preamble; optionally, T... LTM-Iu This can also be referred to as the delay or duration of waiting for associated ROs. LTM-Iu The end time (or the time when the terminal sends the preamble to the target base station) is the end time of the RAN handover delay. In other words, T LTM-Iu The end time, or the time when the terminal sends the preamble to the target base station, can be understood as the end time of cell handover delay calculation (RAN handover delay calculation endpoint).

[0185] As shown in Figure 5, T LTM-RRC-procedure +T LTM-processing +T first-RS +2ms+T LTM-Iu The sum is T LTM-interrupt T LTM-interrupt This can be understood as the time during which the terminal does not expect to transmit or receive data in the source cell during LTM handover.

[0186] In the example shown in Figure 5, the handover delay includes the time length D between the terminal device receiving the handover command and initiating the first transmission (i.e., the first preamble transmission) to the target base station. handover D handover＝ T HARQ +3ms+T LTM-interrupt .

[0187] After uplink synchronization is established, the terminal uses the UL grant provided by the target base station to transmit an RRC Reconfiguration Complete message. The RRC Reconfiguration Complete message indicates that cell handover is complete, thus ending the RRC handover process. The moment the terminal sends the RRC Reconfiguration Complete message can be understood as the moment the cell handover is completed; after the terminal sends the RRC Reconfiguration Complete message, the cell handover process ends (RAN handover process ends).

[0188] Another possible implementation is as follows: If the terminal has already obtained the TA through step 3, in this case, the terminal no longer needs to initiate the RACH procedure to obtain the TA and can directly use the previously obtained TA for uplink synchronization. This method can also be called establishing uplink synchronization without the RACH procedure, or RACH-free LTM handover (RACH-less LTM). After establishing uplink synchronization, the terminal uses the UL grant provided by the target base station to transmit an RRC Reconfiguration Complete message. The RRC Reconfiguration Complete message indicates that the cell handover is complete, thus ending the RRC handover step. After the terminal sends the RRC Reconfiguration Complete message, the cell handover process ends (RAN handover process ends). In this case, the time when the terminal sends the RRC Reconfiguration Complete message is the end time of the RAN handover delay (the end point of RAN handover delay calculation), that is, the end time of the cell handover process and the end time of the RAN handover delay are the same.

[0189] After the cell handover is completed, the target base station can also indicate to the terminal via TCI state which reference signal the target cell's channel / signal maintains a QCL relationship with.

[0190] As shown in Figures 4 and 5, LTM handover, compared to Rel-15 hard handover, does not differ significantly in overall baseline timing. However, with terminal capability support, many actions (such as steps 1 to 4 in Figure 5) can be performed before LTM handover is triggered, thereby reducing the time required for the LTM handover process. With terminal capability support, LTM handover can significantly shorten the latency or data transmission interruption time during handover compared to Rel-15 hard handover. However, without terminal capability support, the latency reduction advantage of LTM handover compared to Rel-15 hard handover is very limited.

[0191] In summary, during the current cell handover process, the handover latency (e.g., D) of the terminal is... handover Or the data transmission interruption lasts for a long time (e.g., T). interrupt Or T LTM-interrupt This method requires high-performance terminals and has low cell handover efficiency.

[0192] As can be seen from Figures 4 and 5, the handover latency or data transmission interruption during cell handover is mainly caused by various preparatory actions performed by the terminal or base station to obtain the necessary handover information (or parameters). Some of these preparatory actions involve signaling interaction between the terminal and the network, leading to a series of problems. For example, signaling interaction between the terminal and the base station increases handover latency / interruption time; terminal measurements may require the support of measurement gaps / scheduling restrictions, during which data cannot be transmitted between the terminal and the base station, potentially causing frequent data transmission interruptions and affecting data transmission and reception; signaling flow interaction between the terminal and the base station increases signaling overhead; the terminal needs to report measurements as support for handover decisions, which itself increases the terminal's power consumption; requiring terminal support also means relying on the terminal's capabilities, affecting applicability.

[0193] For example, Table 1 shows the information required during a cell handover process, as well as the methods for obtaining this information in Rel-15 hard handover and LTM handover.

[0194] Table 1

[0195] As shown in Table 1, some of this information (parameters) can be obtained independently by the base station or the terminal, or it may require signals from the other party but does not involve signaling interaction. The information obtained in steps involving terminal-base station interaction includes the following three types:

[0196] The first type: the quality of the target cell (e.g., RSRP, RSRQ, etc.), which is obtained through measurement reporting. For L3 measurement reporting, the source base station needs to send RRC measurement configuration to the terminal, and then the terminal sends the measurement results to the source base station. For L1 measurement reporting, the source base station needs to send measurement configuration (CSI-measConfig configuration) to the terminal, and then the terminal sends the measurement results to the source base station.

[0197] The second method involves identifying large-scale channel characteristics (such as Doppler shift / multipath characteristics), which is obtained by activating TCI-state indication. Under the current NR mechanism, the base station needs to send a list of TCI states to the terminal, including multiple TCI states. The terminal needs to measure the RS associated with different TCI-states and feed the measurement results back to the base station. Based on the measurement results, the base station can instruct the terminal to activate one or more TCI states via MAC CE. The terminal can then determine the large-scale characteristics of the base station channel based on the activated TCI states.

[0198] For Rel-15 hard handover, the terminal acquires the large-scale characteristics of the channel during the handover process by implicitly determining the SSB associated with the RO (step 6 in Figure 4), thus not involving interaction between the base station and the terminal. For LTM handover, the large-scale characteristics of the channel are acquired during the handover process by either implicitly determining the SSB associated with the RO (step 9 in Figure 5) or by relying on the active TCI-state indication in the MAC CE. The active TCI-state indication method in the MAC CE involves interaction between the base station and the terminal (step 2 in Figure 5 and the base station's use of the active TCI-state indication in the MAC CE).

[0199] The third method involves the TA (Trusted Access Transaction). For Rel-15 hard handover, the terminal needs to send a preamble, and the target base station feeds back the RAR (Random Access Transaction) based on the preamble. The RAR carries the TA. In other words, the TA is obtained through the RACH (Random Access Transaction) procedure. For LTM handover, one method is for the terminal to obtain the TA itself, without interaction between the base station and the terminal. Another method involves obtaining the TA through the RACH procedure, which involves interaction between the base station and the terminal. A third method involves the source base station sending a command (PDCCH order) to the terminal, triggering the terminal to initiate a Random Access Transaction (RACH) at the target base station. The target base station calculates the TA and informs the source base station, which then forwards it to the terminal via MAC-CE. This also involves interaction between the base station and the terminal.

[0200] In view of this, this application provides a communication method and a communication device. In cell handover, the network device obtains information (parameters) that require interaction between the terminal and the network device through sensing, such as at least one of TA, measurement results of the target base station, or large-scale characteristics of the channel. During the cell handover process of the terminal, the terminal and the network device are prevented from obtaining the above information through signaling interaction, thereby reducing the handover latency and data transmission interruption time when the terminal performs cell handover, reducing the requirements on the terminal's capabilities, and improving cell handover efficiency.

[0201] To facilitate understanding of the embodiments of this application, the communication system applicable to the embodiments of this application will be briefly introduced first.

[0202] For example, FIG6 is a schematic diagram of a communication system 60 applicable to an embodiment of this application. As shown in FIG6, the communication system 60 includes: a radio access network (RAN) 600, a core network (CN) 630, and an Internet 640. RAN 600 includes at least one RAN node (nodes 610a and 610b in FIG6, collectively referred to as 610) and at least one terminal (660a-660j in FIG6, collectively referred to as 660). RAN 600 may also include other RAN nodes, such as wireless relay devices and / or wireless backhaul devices (not shown in FIG6), etc. For example, a "node" can also be referred to as a "network element". For example, nodes 610a and 610b can also be referred to as network elements 610a and 610b, and nodes 660a-660j can also be referred to as network elements 660a-660j.

[0203] Terminal 660 connects to RAN node 610 via wireless or wired means. Different terminals communicate with each other via wireless or wired means. RAN node 610 connects to core network 630 via wireless or wired means. The core network equipment in core network 630 and RAN node 610 in RAN 600 can be different physical devices, or the functions of core network equipment and the logical functions of RAN node 610 can be integrated into the same physical device, or a single physical device can integrate some of the functions of core network equipment and some of the functions of RAN node 610.

[0204] RAN 600 can be a cellular system related to the 3rd generation partnership project (3GPP), such as Long Term Evolution (LTE) systems, LTE Frequency Division Duplex (FDD) systems, LTE Time Division Duplex (TDD) systems, 4G, 5G mobile communication systems (including standalone and non-standalone networks), New Radio (NR), Future Communications Networks, cloud radio access networks (CRAN), or it can be an open radio access network (O-RAN or ORAN) system, or it can be a communication system integrating two or more of the above systems. The embodiments in this application are not limited thereto.

[0205] RAN node 610, sometimes also referred to as access network equipment, radio access network equipment, network equipment, RAN entity, or access node, constitutes part of the communication system and is used to help terminals achieve wireless access. Multiple RAN nodes 610 in the communication system 60 can be of the same type or different types.

[0206] In some scenarios, the roles of RAN node 610 and terminal 660 are relative. For example, in Figure 6, network element 660i can be a helicopter or drone, which can be configured as a mobile base station. For terminals 660j that access RAN 600 through network element 660i, network element 660i is a base station; however, for base station 610a, network element 660i is a terminal. That is, base station 610a and terminal 660i communicate via a radio interface protocol. Of course, base station 610a and network element 660i can also communicate via a base station-to-base station interface protocol. In this case, relative to 610a, network element 660i is also a base station. RAN node 610 and terminal 660 are sometimes referred to as communication devices. For example, in Figure 6, network elements 610a and 610b can be understood as communication devices with base station functions, and network elements 660a-660j can be understood as communication devices with terminal functions.

[0207] In one possible scenario, the RAN node can be a base station, an evolved NodeB (eNodeB), an access point (AP), a transmission reception point (TRP), a next-generation NodeB (gNB), or a base station in a future communication network. The RAN node can be a macro base station (as shown in Figure 6, 610a), a micro base station or indoor station (as shown in Figure 6, 610b), a relay node or donor node, or a radio controller in a CRAN scenario. Optionally, the RAN node can also be a server, wearable device, vehicle, or in-vehicle equipment. For example, the access network equipment in vehicle-to-everything (V2X) technology can be a roadside unit (RSU). All or part of the functions of the RAN node in this application can also be implemented through software functions running on hardware, or through virtualization functions instantiated on a platform (e.g., a cloud platform). The RAN node in this application can also be a logical node, logical module, or software capable of implementing all or part of the RAN node functions.

[0208] In another possible scenario, multiple RAN nodes collaborate to assist the terminal in achieving wireless access, with each RAN node performing a portion of the base station's functions. For example, RAN nodes can be central units (CUs), distributed units (DUs), CU-control plane (CPs), CU-user plane (UPs), or radio units (RUs), etc. CUs and DUs can be separate entities or included in the same network element, such as a baseband unit (BBU). RUs can be included in radio frequency equipment or radio frequency units, such as remote radio units (RRUs), active antenna units (AAUs), or remote radio heads (RRHs).

[0209] The CU and DU can be configured according to the protocol layer functions of the wireless network they implement: for example, the CU can be configured to implement the functions of the PDCP layer and above, such as the RRC layer and / or SDAP layer; the DU can be configured to implement the functions of the protocol layers below the PDCP layer, such as the RLC layer, MAC layer, and / or PHY layer. Alternatively, the CU can be configured to implement the functions of the protocol layers above the PDCP layer (such as the RRC layer and / or SDAP layer), and the DU can be configured to implement the functions of the PDCP layer and below (such as the RLC layer, MAC layer, and / or PHY layer).

[0210] When a CU includes CU-CP and CU-UP, CU-CP is used to implement the control plane functions of the CU, and CU-UP is used to implement the user plane functions of the CU. For example, when a CU is configured to implement the functions of the PDCP layer, RRC layer, and SDAP layer, CU-CP is used to implement the RRC layer functions and the control plane functions of the PDCP layer, and CU-UP is used to implement the SDAP layer functions and the user plane functions of the PDCP layer.

[0211] In different systems, CU (or CU-CP and CU-UP), DU, or RU may have different names, but those skilled in the art will understand their meaning. For example, in an ORAN system, CU can also be called O-CU (open CU), DU can also be called O-DU, CU-CP can also be called O-CU-CP, CU-UP can also be called O-CU-UP, and RU can also be called O-RU. For ease of description, this application uses CU, CU-CP, CU-UP, DU, and RU as examples. Any of the units among CU (or CU-CP, CU-UP), DU, and RU in this application can be implemented through software modules, hardware modules, or a combination of software and hardware modules.

[0212] The CU-CP can interact with network elements in the core network used to implement control plane functions. These network elements can be access and mobility function (AMF) network elements, such as the AMF in a 5G system. These AMF network elements are responsible for mobility management in the mobile network, such as terminal location updates, terminal registration with the network, and terminal handover.

[0213] CU-UP can interact with network elements in the core network used to implement user plane functions. These network elements, such as the UPF in a 5G system, are responsible for forwarding and receiving data in the terminal.

[0214] The above CU and DU configurations are merely examples; the functions of the CU and DU can be configured as needed. For instance, the CU or DU can be configured to have more protocol layer functions, or only some protocol layer processing functions. For example, some RLC layer functions and protocol layer functions above the RLC layer can be placed in the CU, while the remaining RLC layer functions and protocol layer functions below the RLC layer can be placed in the DU. Furthermore, the functions of the CU or DU can be divided according to service type or other system requirements, such as by latency. Functions that require low latency can be placed in the DU, while functions that do not require low latency can be placed in the CU.

[0215] In the example shown in Figure 6, terminal 660 can utilize the method provided in this application during handover. For example, terminal 660 utilizes the method provided in this application during the handover process from communication services provided by node 610a to communication services provided by node 610b.

[0216] For example, RAN nodes (or network devices) and terminals can be fixed or mobile. RAN nodes and terminals can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; they can also be deployed on water; and they can also be deployed on aircraft, balloons, and satellites. The embodiments of this application do not limit the application scenarios of RAN nodes and terminals.

[0217] In the embodiments of this application, the functions of the RAN node can be executed by modules (such as chips) within the RAN node, or by a control subsystem that includes RAN node functions. For example, a control subsystem that includes RAN node functions can be a control center in application scenarios such as smart grids, industrial control, intelligent transportation, and smart cities. The functions of the terminal can also be executed by modules (such as chips or modems) within the terminal, or by a device that includes terminal functions.

[0218] In one possible implementation of this application, the network device (or RAN) may include CU, DU, and RU, etc. In another possible implementation, the network device (or RAN) may be CU, DU, or RU, etc. This application does not impose any limitations on the implementation.

[0219] In the embodiments of this application, the terminal may also be referred to as a terminal device, user equipment (UE), mobile station (MS), mobile terminal (MT), etc., or a device used to provide voice or data connectivity to a user. It may also be an Internet of Things (IoT) device, or an entity on the user side used to receive or transmit signals, for sending uplink signals to network devices, receiving downlink signals from network devices, sending signals to another terminal device, receiving signals from another terminal device, or receiving echo signals of signals transmitted by itself. For example, terminal devices include handheld devices with wireless connectivity, vehicle-mounted devices, etc. Terminals can be widely used in various scenarios, such as device-to-device (D2D), vehicle-to-everything (V2X) communication, machine-type communication (MTC), Internet of Things (IoT), virtual reality (VR), augmented reality (AR), industrial control, self-driving, remote medical, smart grid, smart furniture, smart office, smart wearables, smart transportation, and smart city.

[0220] For example, terminal devices can be: mobile phones, tablets, laptops, PDAs, mobile internet devices (MIDs), wearable devices (such as smartwatches, smart bracelets, pedometers, smart glasses, etc.), in-vehicle equipment (such as cars, bicycles, electric vehicles, airplanes, ships, trains, high-speed trains, etc.), satellite terminals, VR devices, AR devices, point-of-sale (POS) machines, customer-premises equipment (CPE), light user equipment (light UE), reduced capability UE (RedCap UE), wireless terminals in industrial control, smart home devices (such as refrigerators, televisions, air conditioners, electricity meters, etc.), smart robots, robotic arms, workshop equipment, wireless terminals in autonomous driving, wireless terminals in telemedicine, wireless terminals in smart grids, wireless terminals in transportation safety, wireless terminals in smart cities, or wireless terminals in smart homes, surveillance cameras in intelligent transportation and smart cities, and flying equipment (such as smart robots, hot air balloons, drones, airplanes), etc. The terminal device can also be a vehicle device, such as a complete vehicle device, an in-vehicle module, an in-vehicle chip, an on-board unit (OBU), or a telematics box (T-BOX). The terminal device can also be other devices with terminal functions; for example, it can be a device that functions as a terminal in D2D communication. The embodiments of this application do not limit the form of the terminal device.

[0221] It should be understood that the communication system shown in Figure 6 is merely exemplary and should not impose any limitations on the communication systems applicable to the embodiments of this application. For example, the communication system shown in Figure 6 may also include more or fewer network nodes, such as terminals, network devices (access network devices), etc. The network devices or terminals included in Figure 6 may be the various forms of RAN nodes or terminal devices described above. The embodiments of this application are not shown one by one in the figures.

[0222] The following section uses specific examples to illustrate the communication method provided in this application.

[0223] It should be understood that in this application, network devices and terminal devices are used as examples to illustrate the method. As examples and not limitations, the terminal device in this application can be a terminal equipment, a component (chip, chip system, or processor) that supports the terminal equipment in implementing the method, or a logic module or software that can implement all or part of the terminal equipment's functions. Similarly, the network device in this application can be a network device, a component (chip, chip system, or processor) that supports the network device in implementing the method, or a logic module or software that can implement all or part of the network device's functions, such as a CU, DU, or RU. The embodiments in this application are not limited herein.

[0224] It should also be understood that after the terminal device completes the handover, the terminal device actually disconnects from the source network device and establishes a communication connection with the target network device. At this time, the "target network device" is the "source network device" for the next handover, or the "current network device (current station)" that serves the terminal device.

[0225] It should also be understood that, in this application, the target network device may also be referred to as or replaced by the first network device, and the source network device may also be referred to as or replaced by the second network device.

[0226] Figure 7 is a schematic flowchart of a communication method according to an embodiment of this application. In the example shown in Figure 7, the target network device uses a single-site sensing method to determine the TA (Transmission Aspect Ratio) for uplink transmission from the terminal device to the target network device and / or the channel quality between the terminal device and the target network device. The TA and / or channel quality are used to manage cell handover by the terminal device. This avoids the terminal device obtaining the TA through RACH (Rapid Access Communication), and / or avoids the terminal device measuring and reporting the target cell according to the measurement configuration. In other words, it avoids the terminal device and the network device obtaining the above information through signaling interaction. During cell handover, the TA can be used to establish uplink synchronization between the terminal device and the target network device. For example, the terminal device can use the TA to determine the uplink transmission timing when transmitting uplink to the target network device. The uplink transmission timing when transmitting uplink from the terminal device to the target network device can be equal to the downlink reception timing of the terminal device + the TA.

[0227] As shown in Figure 7, method 700 may include steps S710 to S740a or S710 to S740b, meaning that only one step in S740a or S740b may be performed. The steps in method 700 will be described in detail below with reference to Figure 7.

[0228] S710, the target network device sends a sensing signal to the terminal device. Correspondingly, the terminal device receives the sensing signal.

[0229] Optionally, the sensing signal in S710 can also be referred to as the first sensing signal.

[0230] Optionally, in this embodiment, the target network device is a network device that provides network services to the terminal device after the terminal device performs cell handover.

[0231] After the terminal device receives the sensing signal, it reflects the sensing signal to form an echo signal, which the target network device can receive.

[0232] In one possible implementation, the target network device can determine the time to send the sensing signal, assuming the time to send the sensing signal is t.

[0233] In one possible implementation, the target network device can determine the power of the transmitted sensing signal, assuming the power of the transmitted sensing signal (the transmission power of the sensing signal) is P, for example, the unit of power can be decibels (dB).

[0234] In one possible implementation, the sensing signal in S710 can also be replaced with a synesthetic signal.

[0235] S720, the target network device receives the echo signal corresponding to the sensing signal.

[0236] In one possible implementation, the target network device can determine the time when the echo signal is received, assuming the time when the echo signal is received is t′.

[0237] In one possible implementation, the target network device can determine the power of the received echo signal, assuming the power of the received echo signal is P′.

[0238] S730, the target network device determines the TA for uplink transmission from the terminal device to the target network device and / or the channel quality between the terminal device and the target network device based on the echo signal and the sensing signal.

[0239] For a given TA (Target Aspect Ratio), the time (or duration) at which the target network device receives the echo signal is t′. Then, the round trip time (RTT) T for the sensing signal from the target network device to the terminal device and back is... RTT For t′-t, that is, T RTT =t′-t. The reason for introducing timing advance during the uplink transmission of the terminal device is to compensate for the uplink transmission delay of the terminal device to ensure that the uplink transmission of the terminal device and the downlink transmission of the target network device are aligned at the frame boundary of the target network device.

[0240] For example, as shown in Figure 8, the difference between the downlink receiving timing of the terminal device and the downlink transmitting timing of the target network device is approximately equal to the transmission delay between the target network device and the terminal device (using T). P (represented by T), and the difference between the uplink transmission timing of the terminal device and the downlink transmission timing of the target network device is also T. P Among them, 2T P =T RTT Since the uplink transmission timing of the terminal device is advanced by TA relative to the downlink reception timing of the terminal device, the value of TA is equal to the difference T between the downlink reception timing of the terminal device and the downlink transmission timing of the target network device. P The phase difference T between the uplink transmission timing of the terminal device and the downlink transmission timing of the target network device. P The sum, i.e., TA = 2T P =T RTT In other words, the TA quantity equals the RTT time, TA = T RTT = t′-t.

[0241] For determining the channel quality between the terminal device and the target network device, RSRP is used as an example. It should be understood that in other implementations of this application, the channel quality may include other parameters, which can also be obtained or determined using the methods provided in this application. This application does not impose any limitations on these embodiments.

[0242] If the power of the transmitted sensing signal is P and the power of the received echo signal is P′, then P and P′ satisfy the following formula (1): PP′=PL DL +PL UL +σ RCS (1)

[0243] In formula (1), PL DL and PL UL Let σ represent the path loss (PL) experienced by the uplink transmission (the echo signal reflected from the terminal device to the target network device) and the downlink transmission (the sensing signal sent from the target network device to the terminal device), respectively. RCS This represents the additional loss determined by the radar cross section (RCS) of the terminal device, and is a value related to factors such as the size, material, surface treatment, or signal incidence angle of the terminal device. It is typically assumed that PL... DL =PL UL =PL, so formula (1) becomes formula (2) as follows: PP′=2PL+σ RCS (2)

[0244] RSRP includes absolute RSRP and relative RSRP. Absolute RSRP can be understood as the absolute received power of the reference signal at the antenna port of the terminal device. Absolute RSRP satisfies the following formula (3): Absolute RSRP = P - PL (3)

[0245] In one possible implementation, the target network device can estimate σ RCS The value of σ can be set in various ways. For example, typical reference values ​​can be set for different targets, such as vehicles, people, mobile phones, tablets, etc. Alternatively, the target network device can estimate σ based on the uplink channel / signal before the terminal device. RCS The value of σ. In other words, the target network device can obtain or determine the value of σ corresponding to the terminal device. RCS The value of .

[0246] After obtaining σ RCS The value of (e.g., from σ) RCS After obtaining the estimated value, the absolute RSRP can satisfy the following formula (4): Absolute RSRP = P - (PP′ - σ RCS ) / twenty four)

[0247] The relative RSRP can be understood as the difference in power between two received reference signals at the antenna port of the terminal device. When the interval between the two measurements is short, the position and incident angle of the terminal device can be considered to change very little; therefore, σ can be considered... RCS The signal remains unchanged between the two measurements. Therefore, the target network device needs to send two (or two) sensing signals to the terminal device. The terminal device reflects the two sensing signals to obtain two (two) echo signals, and the target network device receives the two (two) echo signals. For example, Figure 9 shows a scenario where the target network device sends two sensing signals.

[0248] Assume the power of the sensing signal first transmitted by the target network device (e.g., the sensing signal transmitted in S710 above) is P1, the power of the first echo signal corresponding to the first sensing signal received is P′1, the power of the sensing signal second transmitted by the target network device is P2, and the power of the second echo signal corresponding to the second sensing signal received is P′2. Then P1, P′1, P2, and P′2 satisfy the following formulas (5) and (6) respectively: P1-P′1=2PL1+σ RCS (5) P2-P′2=2PL2+σ RCS (6)

[0249] In formulas (5) and (6), PL1 and PL2 are the path losses corresponding to the two sensing signals, respectively. Since σ RCSThe values ​​of PL1 and PL2 have been determined. Using formulas (5) and (6), the values ​​of PL1 and PL2 can be determined. The relative RSRP can satisfy the following formula (7): Relative RSRP = (P1 - PL1) - (P2 - PL2) (7)

[0250] It should be understood that, for TA, the target network device can determine the transmission and reception times corresponding to the first sensing signal and the first echo signal, respectively, or it can determine the transmission and reception times corresponding to the second sensing signal and the second echo signal, respectively. This application does not impose any limitations on the embodiments herein.

[0251] After the target network device determines the TA and / or the channel quality between the terminal device and the target network device, there may be two possible implementation methods:

[0252] One possible implementation is shown in S740a of Figure 7: the target network device manages the terminal device to perform cell handover based on the TA and / or the channel quality between the terminal device and the target network device.

[0253] For example, the target network device determines whether to allow the terminal device to perform cell handover based on channel quality (e.g., RSRP). For instance, if the RSRP is greater than or equal to a threshold, the terminal device is allowed to perform cell handover and hand over to the target network device. Alternatively, if the RSRP is less than or equal to the threshold, the terminal device is not allowed to perform cell handover. When cell handover is allowed, the target network device can send indication information to the source network device, indicating that the terminal device is allowed to handover to the target network device, and the indication information includes a TA (Transfer Targeting). After receiving the indication information, the source network device can send a handover command to the terminal device, instructing the terminal device to begin handover from the source network device to the target network device, and the handover command carries the TA.

[0254] Another possible implementation is shown in S740b of Figure 7: the target network device sends the TA and the channel quality between the terminal device and the target network device to the source network device. The source network device manages the terminal device to perform cell handover based on the TA and the channel quality between the terminal device and the target network device. The specific process is similar to the target network device managing the terminal device to perform cell handover based on channel quality, and will not be described in detail here for simplicity.

[0255] One possible implementation is that the uplink and / or downlink signals between the target network device and the terminal device can maintain a QCL relationship with the sensing signals sent by the target network device to the terminal device (e.g., the first and / or second sensing signals mentioned above). For example, the target network device can obtain sensing results about the terminal device based on the sensing signals and echo signals, including information such as RTT delay, path loss, and the terminal device's location / movement speed / direction. Based on these sensing results, the target network device continuously adjusts the sensing signals to maintain continuous sensing of the terminal device, and continuously adjusts the uplink and / or downlink signals between the target network device and the terminal device, ensuring that the uplink and / or downlink signals between the target network device and the terminal device maintain a QCL relationship with the sensing signals. In other words, through continuous sensing of the terminal device, the continuous coverage of the terminal device by the beams of the sensing signals and the uplink and / or downlink signals is guaranteed, and the uplink and / or downlink beams always maintain a QCL relationship with the beams of the sensing signals. The uplink and / or downlink signals between the target network device and the terminal device maintain a QCL relationship with the sensing signals sent by the target network device to the terminal device. Since the sensing signals can be continuously sent to the terminal device before and during cell handover, the terminal device can use these signals to perform downlink synchronization before the handover process begins. This includes establishing slot-level downlink synchronization with the target network device, performing time-frequency alignment, establishing radio frame-level downlink synchronization, and adjusting AGC parameters. During downlink synchronization, the large-scale characteristics of the channel between the terminal device and the target network device (e.g., Doppler shift, multipath characteristics, delay, Doppler spread, beam direction, etc.) can be determined based on the sensing signals. During handover, the terminal device does not need to perform downlink synchronization based on the received SSB, reducing the steps required during handover. This saves signaling overhead during handover, thereby reducing latency and data transmission interruption time during cell handover and improving handover efficiency.

[0256] One possible implementation is that during or after cell handover, and before receiving further instructions, the uplink and / or downlink signals between the target network device and the terminal device maintain a continuous QCL relationship with the sensing signals sent by the target network device to the terminal device. For example, the target network device or the source network device may send an instruction to the terminal device instructing it to stop transmitting sensing signals. Upon receiving the instruction, the terminal device determines that it is no longer receiving sensing signals, and it further determines that the QCL relationship between the uplink and / or downlink signals between the target network device and the terminal device and the sensing signals has terminated.

[0257] The communication method provided in this application allows the target network device to acquire the TA (Transmission Aspect) for uplink transmission from the terminal device to the target network device and / or the channel quality between the terminal device and the target network device using a single-site sensing approach. The target network device or the source network device uses the TA and / or the channel quality between the terminal device and the target network device to manage cell handover for the terminal device. This avoids the terminal device acquiring the TA through signaling interaction (e.g., RACH procedure), and / or avoids the terminal device measuring and reporting the target cell based on measurement configuration. In other words, it avoids the terminal device acquiring the TA and / or the channel quality between the terminal device and the target network device through signaling interaction, saving signaling overhead during handover, avoiding handover latency caused by signaling interaction, thereby reducing handover latency and data transmission interruption time during cell handover, reducing the requirements on terminal device capabilities, and improving cell handover efficiency.

[0258] It should be understood that in the example shown in Figure 7, the same sensing signal is used to obtain the channel quality between the TA, the terminal device, and the target network device. In other implementations of this application, different sensing signals may be used to obtain the channel quality between the TA, the terminal device, and the target network device; that is, obtaining the TA and the channel quality may be two separate processes. For example, the target network device may obtain the TA using a first sensing signal sent to the terminal device and the corresponding echo signal, and obtain the channel quality using other sensing signals sent to the terminal device (e.g., a third sensing signal) and the corresponding echo signal. After obtaining the TA, in one possible implementation, the target network device may send the TA to the source network device. After obtaining the channel quality, in one possible implementation, the target network device may send the channel quality to the source network device; in another possible implementation, the target network device determines whether to allow the terminal device to perform cell handover based on the channel quality. If cell handover is allowed, the target network device may send indication information to the source network device, indicating that the terminal device is allowed to handover to the target network device. Optionally, the indication information includes the TA.

[0259] Figure 10 is a schematic flowchart of a communication method according to another embodiment of this application. In the example shown in Figure 10, the target network device and the source network device use bi-site sensing to determine the TA (Transmission Aspect Ratio) for uplink transmission from the terminal device to the target network device and / or the channel quality between the terminal device and the target network device. The TA and / or channel quality are used to manage cell handover by the terminal device. This avoids the terminal device obtaining the TA through RACH (Rapid Access Control), and / or avoids the terminal device measuring and reporting the target cell according to the measurement configuration. In other words, it avoids the terminal device and the network device obtaining the above information through signaling interaction. During cell handover, the TA can be used to establish uplink synchronization between the terminal device and the target network device. For example, the terminal device can use the TA to determine the uplink transmission timing when transmitting uplink to the target network device.

[0260] As shown in Figure 10, the method 1000 illustrated in Figure 10 may include steps S1010 to S1060. The various steps in method 1000 will be described in detail below with reference to Figure 10.

[0261] S1010, the target network device sends a first sensing signal to the terminal device. Correspondingly, the terminal device receives the first sensing signal.

[0262] After the terminal device receives the first sensing signal, it reflects the first sensing signal to form a first echo signal, and the source network device can receive the first echo signal.

[0263] In one possible implementation, the target network device can determine the time when to send the first sensing signal and notify the source network device of that time. Assume that the time when the target network device sends the first sensing signal is t1.

[0264] In one possible implementation, the target network device can determine the transmission power of the first sensing signal and notify the source network device of the transmission power of the first sensing signal. Assume the transmission power of the first sensing signal is P. 1t .

[0265] In one possible implementation, the sensing signal in S1010 can also be replaced with a synesthetic signal.

[0266] S1020, the source network device receives the first echo signal corresponding to the first sensing signal. The source network device is a network device that provides network services to the terminal device before the terminal device performs cell handover.

[0267] In one possible implementation, the source network device can determine the time when the first echo signal is received, assuming the time of receiving the first echo signal is t′1. Then t′1 and t1 satisfy the following formula (8): t′1-t1=T BSt-UE +T BSs-UE(8)

[0268] In formula (8), T BSt-UE T represents the propagation delay of the channel between the target network device and the terminal device. BSs-UE This indicates the propagation delay of the channel between the source network device and the terminal device.

[0269] In one possible implementation, the source network device can determine the power of the received first echo signal, assuming the power of the first echo signal received by the source network device is P′. 1t .

[0270] Then P 1t and P′ 1t Satisfies the following formula (9): P 1t -P′ 1t =PL 1BSt-UE +PL BSs-UE +σ RCS (9)

[0271] In formula (9), PL 1BSt-UE PL represents the path loss between the target network device and the terminal device when the target network device sends the first sensing signal. BSs-UE This represents the path loss between the source network device and the terminal device. σ RCs This represents the additional loss determined by the RCS of the terminal device. The source network device can acquire or determine the σ corresponding to this terminal device. RCS The value of .

[0272] S1030, the source network device sends a sensing signal (for example, it can be called a fourth sensing signal) to the terminal device. Correspondingly, the terminal device receives the fourth sensing signal.

[0273] After the terminal device receives the fourth sensing signal, it will reflect the fourth sensing signal to form a fourth echo signal, and the source network device can receive the fourth echo signal.

[0274] In one possible implementation, the source network device can determine the time when to send the fourth sensing signal, assuming the time when the source network device sends the fourth sensing signal is t4.

[0275] In one possible implementation, the source network device can determine the transmission power of the fourth sensing signal, assuming the transmission power of the fourth sensing signal is P. 4s .

[0276] S1040, the source network device receives the fourth echo signal corresponding to the fourth sensing signal.

[0277] In one possible implementation, the source network device can determine the time when the fourth echo signal is received, assuming the time of receiving the fourth echo signal is t′4. Then t′4 and t4 satisfy the following formula (10): t′4-t4=2T BSs-UE (10)

[0278] In one possible implementation, the source network device can determine the power of the received fourth echo signal, assuming the power of the fourth echo signal received by the source network device is P′. 4s Then P 4s and P′ 4s Satisfying the following formula (11): P 4s -P′ 4s =2PL BSs-UE +σ RCS (11)

[0279] For example, Figure 11 shows a scenario where the target network device and the source network device are sensed by two stations.

[0280] S1050, the source network device determines the TA for uplink transmission from the terminal device to the target network device and / or the channel quality between the terminal device and the target network device based on the first sensing signal, the first echo signal, the fourth sensing signal and the fourth sensing signal.

[0281] For a given TA, TA can satisfy the following formula (12): TA = 2T BSt-UE =2(t′1-t1)-(t′4-t4) (12)

[0282] Using the formula (12) above, the source network device can determine the value of TA for the terminal device to transmit uplink data to the target network device.

[0283] For determining the channel quality between the terminal device and the target network device, RSRP is used as an example for illustration.

[0284] For absolute RSRP, the following formula (13) applies: Absolute RSRP = P 1t -PL 1BSt-UE (13)

[0285] Combining the above formula (9), formula (13) is transformed into formula (14): Absolute RSRP = P′ 1t +PL BSs-UE +σ RCS (14)

[0286] Based on the above formula (11), PL can be determined. BSs-UE The value of PL BSs-UEBy substituting the value of into formula (14), the absolute RSRP can be determined.

[0287] For relative RSRP, the target network device needs to send two (or two) sensing signals to the terminal device. The terminal device reflects the two sensing signals to obtain two (two) echo signals, and the source network device receives the two (two) echo signals. Assume the first sensing signal sent by the target network device is the first sensing signal described above, and the transmission power of the second sensing signal sent by the target network device to the terminal device is P. 3t The power of the echo signal corresponding to the second sensing signal received by the source network device is P′. 3t Then P 3t and P′ 3t Satisfying the following formula (15): P 3t -P′ 3t =PL 3BSt-UE +PL BSs-UE +σ RCS (15)

[0288] In formula (15), PL 3BSt-UE This indicates the path loss between the target network device and the terminal device when the target network device sends the third sensing signal.

[0289] The relative RSRP can satisfy the following formula (16): Relative RSRP = (P 1t -PL 1BSt-UE )-(P 3t -PL 3BSt-UE (16)

[0290] Based on the above formula (11), PL can be determined. BSs-UE The value of PL BSs-UE Substituting the value of into formula (15) will determine PL. 3BSt-UE The value of PL. BSs-UE Substituting the value of into formula (9), we can determine PL. 1BSt-UE The value of PL. 3BSt-UE The value of PL 1BSt-UE By substituting the value of into formula (16), the relative RSRP can be determined.

[0291] The relative RSRP or absolute RSRP determined by the source network device mentioned above can be called the relative RSRP or absolute RSRP of the target base station, that is, the sensing signal is sent by the target network device.

[0292] S1060, the source network device manages the terminal device to perform cell handover based on the TA and / or the channel quality between the terminal device and the target network device.

[0293] For example, the target network device determines whether to allow the terminal device to perform cell handover based on channel quality (e.g., RSRP). If cell handover is allowed, the source network device can send a handover command to the terminal device, instructing the terminal device to begin handover from the source network device to the target network device, and the handover command carries a TA (Transfer Transaction).

[0294] Optionally, in some possible implementations, the source network device may also utilize the sensing signals sent to the terminal device (e.g., including the fourth sensing signal mentioned above) and determine the absolute RSRP / relative RSRP of the source network device based on the echo signal reflected by the terminal device (e.g., the fourth echo signal mentioned above). The absolute / relative RSRP of the source network device and the absolute / relative RSRP of the target network device are jointly used to determine whether the terminal device is allowed to perform cell handover. The determination process is similar to the process described above, and for simplicity, it will not be repeated here.

[0295] One possible implementation is that the uplink and / or downlink signals between the target network device and the terminal device maintain a QCL relationship with the sensing signals (such as the first sensing signal mentioned above) sent by the target network device to the terminal device. For a detailed explanation, please refer to the corresponding section of method 700; for brevity, it will not be elaborated further here.

[0296] The communication method provided in this application allows the target network device and the source network device to determine the TA (Transmission Aspect Ratio) for uplink transmission from the terminal device to the target network device and / or the channel quality between the terminal device and the target network device using bi-site sensing. The source network device uses the TA and / or channel quality management to manage cell handover by the terminal device. This avoids the terminal device obtaining the TA through signaling interaction (e.g., RACH procedure) and / or avoids the terminal device measuring and reporting the target cell according to the measurement configuration. In other words, it avoids the terminal device obtaining the TA and / or the channel quality between the terminal device and the target network device through signaling interaction, saving signaling overhead during handover, avoiding handover delay caused by signaling interaction, thereby reducing handover delay and data transmission interruption time during cell handover by the terminal device, reducing the requirements on the terminal device's capabilities, and improving cell handover efficiency.

[0297] It should be understood that in the example shown in Figure 10, the same sensing signal is used to obtain the TA, the terminal device, and the target network device. In other implementations of this application, different sensing signals can be used to obtain the TA, the terminal device, and the channel quality; that is, obtaining the TA and the channel quality can be two separate processes or separate processes. For example, the source network device can obtain the TA using a first sensing signal sent by the target network device to the terminal device and a fourth sensing signal sent by itself to the terminal device, i.e., the process shown in method 1000 above. The channel quality is obtained using other sensing signals (e.g., a fifth sensing signal) sent by the target network device to the terminal device and a sensing signal (e.g., a sixth sensing signal) sent by itself to the terminal device. After obtaining the channel quality, the source network device can determine whether cell handover is allowed for the terminal device based on the channel quality. If cell handover is allowed for the terminal device, the target network device can send a handover command to the source network device. The handover command instructs the terminal device to begin handover from the source network device to the target network device, and the handover command includes the TA.

[0298] Figure 12 is a schematic flowchart of a communication method according to another embodiment of this application. In the example shown in Figure 12, the terminal device performs cell handover, that is, switches from the source network device to the target network device. The terminal device does not need to obtain the TA for uplink transmission to the target network device through RACH; the TA can be obtained through the method 700 or method 1000 described above. That is, the terminal device and the network device are avoided from obtaining the TA through signaling interaction.

[0299] As shown in Figure 12, method 1200 may include steps S1210 to S1230. The steps of method 1200 will be described in detail below with reference to Figure 12.

[0300] S1210, the source network device sends a handover command to the terminal device. The handover command instructs the terminal device to begin handover from the source network device to the target network device; in other words, the handover command instructs the terminal device to handover from the source network device to the target network device. The handover command includes a TA (Translation Aspect). The TA is determined based on a sensing signal (e.g., the first sensing signal described above) sent by the target network device to the terminal device. Accordingly, the terminal device receives the handover command.

[0301] It should be understood that in the embodiments of this application, the source network device or the target network device can obtain the TA (Transmission Acquisition Signal) based on the sensing signal sent to the terminal device (e.g., the first sensing signal in method 700 above, or the first sensing signal and the fourth sensing signal in method 1000). The source network device can also notify the terminal device of the TA via a handover command. For details, please refer to the descriptions of method 700 or method 1000 above. For simplicity, these details are not elaborated here. By using sensing signals to obtain the TA and notify the terminal device, the network device avoids obtaining the TA through signaling interaction (e.g., the RACH procedure) during handover, saving signaling overhead during handover and thus avoiding handover latency caused by signaling interaction. This reduces handover latency and data transmission interruption time during cell handover by the terminal device.

[0302] In one possible implementation, either the source network device or the target network device can obtain the channel quality between the terminal device and the target network device based on the sensing signal. If the channel quality determines that the terminal device is allowed to perform cell handover, the handover command in S1210 is sent to the terminal device. The specific process can be referred to the descriptions of methods 700 or 1000 above; for brevity, they will not be repeated here. In this case, the terminal device does not need to perform L1 or L3 measurements of the target cell according to the measurement configuration and report the measurement results (i.e., the channel quality between the terminal device and the target network device). This method avoids the terminal device and network device obtaining the channel quality through signaling interaction, reducing the requirements on the terminal device's capabilities, avoiding handover delays caused by signaling interaction, and improving cell handover efficiency.

[0303] S1220, after receiving the handover command, the terminal device begins cell handover.

[0304] After receiving a handover command, the terminal device begins the cell handover process; in other words, after receiving the handover command, the terminal device performs or executes the cell handover process. It should be understood that the terminal does not need to acquire the Technical Aspect Ratio (TA) during the cell handover process, thus avoiding the need for the terminal device and network device to acquire the TA through signaling interaction. During the cell handover process, the terminal device can use the TA to establish uplink synchronization with the target network device. For example, the terminal device can use the TA to determine the uplink transmission timing when transmitting uplink data to the target network device.

[0305] For example, the cell handover process may include: the terminal device reading and verifying the handover command, the terminal device loading and adjusting software and hardware, and the terminal device determining the downlink time slot, subframe and / or radio frame boundary timing of the target network device, or the terminal device determining the radio frame number of the downlink radio frame of the network device.

[0306] For example, in Rel-15 hard handover, the handover command can be carried in an RRC reconfiguration message. In this case, the cell handover process may include: the terminal device reading and verifying the RRC reconfiguration message; loading and adjusting the terminal device's software and hardware according to the RRC reconfiguration message; performing downlink synchronization (the terminal device determines the downlink time slot, subframe and / or radio frame boundary timing of the target network device, and determines the radio frame number of the network device's downlink radio frame); and establishing uplink synchronization with the target cell using the TA. After the terminal device and the target cell establish uplink synchronization, the terminal device uses the UL grant provided by the target network device to transmit an RRC reconfiguration complete message. The RRC reconfiguration complete message indicates that the cell handover is complete, thereby ending the cell handover process.

[0307] For example, in LTM handover mode, the handover command can be carried in the MAC CE. In this case, the cell handover process includes: HARQ feedback from the terminal device to the MAC-CE, reading the MAC-CE, reading and verifying the RRC reconfiguration message, loading and adjusting the software and hardware of the terminal device using the RRC reconfiguration message, performing downlink synchronization (the terminal device determines the radio frame number of the downlink radio frame of the network device), and establishing uplink synchronization with the target cell using the TA. The RRC reconfiguration message is sent to the terminal device by the source network device before sending the handover command, and includes the RRC configuration required for handover. In one possible implementation, if the terminal device has already read and verified the RRC reconfiguration message before receiving the handover command, the above cell handover process does not include the step of reading and verifying the RRC reconfiguration message by the terminal device. After the terminal device and the target cell establish uplink synchronization, the terminal device uses the UL grant provided by the target network device to transmit an RRC Reconfiguration Complete message. The RRC Reconfiguration Complete message indicates that the cell handover is complete, thereby ending the cell handover process.

[0308] S1230, the terminal device sends a handover completion indication message to the target network device.

[0309] In one possible implementation, after the cell handover process is completed, the terminal device sends a handover completion indication message to the target network device.

[0310] For example, after the terminal device and the target cell establish uplink synchronization, the terminal device uses the UL grant provided by the target network device to transmit an RRC Reconfiguration Complete message. The RRC Reconfiguration Complete message can indicate that the cell handover is complete, thereby ending the cell handover process. In other words, the indication information can be implemented using the RRC Reconfiguration Complete message.

[0311] The communication method provided in this application embodiment allows the timing advance (TA) for uplink transmission from the terminal device to the target network device to be obtained through sensing signals and notified to the terminal device through a handover command. This avoids the terminal device obtaining the TA through signaling interaction (e.g., RACH process) during cell handover, reducing the steps that need to be performed during the handover process. As a result, the handover latency and data transmission interruption time during cell handover can be reduced, thereby improving cell handover efficiency.

[0312] In one possible implementation, before and during cell handover, the target network device can continuously send sensing signals (e.g., a second sensing signal) to the terminal device. The target network device can maintain continuous coverage of the terminal device by the beam of the sensing signal and the beams of the uplink and / or downlink signals. For example, the target network device can adjust the uplink and / or downlink signals between itself and the terminal device based on information such as the terminal device's location, speed, and direction, so that the uplink and / or downlink signals between the target network device and the terminal device maintain a QCL relationship with the sensing signal. Exemplarily, the second sensing signal can be the same as or different from the sensing signal (e.g., the first sensing signal, the third sensing signal, or the fifth sensing signal) sent by the target network device to the terminal device in method 700 or method 1000; this embodiment of the application does not impose any limitations on this.

[0313] In one possible implementation, if the uplink and / or downlink signals between the target network device and the terminal device maintain a QCL relationship with the sensing signals sent by the target network device to the terminal device, and since the sensing signals can be sent to the terminal device before cell handover, downlink synchronization can be performed between the terminal device and the target network device if the terminal device has already measured the sensing signals before the handover begins. During downlink synchronization, the terminal device can determine the large-scale characteristics of the channel with the target network device (e.g., Doppler shift, multipath characteristics, delay, Doppler spread, beam direction, etc.). In this case, the cell handover process includes: the terminal device reading and verifying the handover command, the terminal device loading and adjusting software and hardware, and establishing uplink synchronization with the target cell using the TA. In this implementation, the terminal device may not need to obtain the TA through signaling interaction during the handover process, and may also not need to perform a downlink synchronization process. Because the uplink and / or downlink signals between the target network device and the terminal device maintain a QCL relationship with the sensing signals sent by the target network device to the terminal device, on the one hand, the terminal device can determine the large-scale characteristics of the channel with the target network device by measuring the sensing signals. This avoids the terminal device using the activation of TCI-state indication to obtain the large-scale characteristics of the channel, thus avoiding the need for signaling interaction between the terminal device and the network device to obtain the large-scale characteristics of the channel, thereby reducing signaling overhead. On the other hand, the terminal device can measure the sensing signals before initiating cell handover (i.e., before receiving the handover command). The terminal device can use the sensing signals for downlink synchronization, meaning that the downlink synchronization process can be performed based on the sensing signals before initiating cell handover (the downlink synchronization process can obtain the large-scale characteristics of the channel). During the handover process, the terminal device does not need to perform the downlink synchronization process based on the received SSB, reducing the steps required during the handover process. This further reduces the handover latency and data transmission interruption time during cell handover, improving cell handover efficiency.

[0314] For example, in Rel-15 hard handover, before cell handover, the terminal device can use sensing signals to establish slot-level downlink synchronization with the target network device (e.g., determining the downlink time slot, subframe, and / or radio frame boundary timing of the target network device), perform time-frequency fine alignment, and establish radio frame-level downlink synchronization (e.g., determining the radio frame number of the target network device's downlink radio frame). During the time-frequency fine alignment and radio frame-level downlink synchronization using sensing signals, large-scale characteristics of the channel between the terminal device and the target network device can be determined. The cell handover process does not include: the terminal device determining the downlink time slot, subframe, and / or radio frame boundary timing of the target network device, or the terminal device determining the radio frame number of the network device's downlink radio frame.

[0315] For example, in LTM handover, before cell handover, the terminal device uses sensing signals to perform time-frequency fine alignment and establish downlink synchronization at the radio frame level (e.g., determining the radio frame number of the downlink radio frame of the target network device). During downlink synchronization using sensing signals, the terminal device determines the large-scale characteristics of the channel with the target network device. The cell handover process does not include: the terminal device determining the radio frame number of the downlink radio frame of the network device.

[0316] In one possible implementation, for Rel-15 hard handover, the terminal device can adjust AGC parameters using sensing signals before cell handover. In this implementation, the terminal device does not need to adjust AGC parameters based on the received SSB during handover, further reducing the steps required during handover. This can further reduce latency and data transmission interruption time during cell handover, improving cell handover efficiency. The cell handover process does not include the AGC parameter adjustment process.

[0317] In one possible implementation, where there is no QCL relationship between the uplink and / or downlink signals between the target network device and the terminal device, and the sensing signals sent by the target network device to the terminal device, the cell handover process includes: the terminal device reading and verifying the handover command; the terminal device loading and adjusting software and hardware; the terminal device performing downlink synchronization with the target network device using the SBB (downlink synchronization can acquire large-scale channel characteristics); and establishing uplink synchronization with the target cell using the TA. In this implementation, the terminal device does not need to perform L1 or L3 measurements of the target cell and report the measurement results during the handover process, nor does it need to obtain the TA through signaling interaction. This reduces the steps required during the handover process, thereby reducing the handover latency and data transmission interruption time during cell handover, and improving cell handover efficiency.

[0318] In one possible implementation, after cell handover is completed, the target network device or the source network device can send an indication message to the terminal device. This indication message instructs the sensing signal (second sensing signal) to cease transmission. Upon receiving the indication message, the terminal device determines that it will no longer receive sensing signals, and the QCL relationship between the uplink and / or downlink signals between the target network device and the terminal device, and the sensing signal sent by the target network device to the terminal device, is terminated. After sending the indication message to the terminal device, the target network device can indicate to the terminal device via the TCI state which reference signal the target cell's channel / signal maintains a QCL relationship with.

[0319] Using the method provided in the embodiments of this application, the terminal device can determine the handover delay. Several possible implementation methods for the handover delay will be described in detail below.

[0320] One possible implementation involves the terminal device determining the handover delay if it has already measured the sensed signal and acquired the TA according to the handover command. This handover delay includes the verification and interpretation time of the handover command and the interruption time. The uplink and / or downlink signals between the target network device and the terminal device maintain a QCL relationship with the sensed signal. Measuring the sensed signal can be understood as the terminal device using the sensed signal to perform downlink synchronization with the target network device. The handover delay does not include the downlink synchronization delay or the TA acquisition delay. Before cell handover, the terminal device has already performed downlink synchronization with the target network device during the sensed signal measurement process.

[0321] One possible implementation involves the terminal device determining a handover delay if it has already measured the sensed signal. The handover delay occurs when the time between receiving the handover command and sending a handover completion indication message (e.g., an RRC reconfiguration completion message) is less than or equal to the handover delay. The handover delay includes the terminal device's verification and interpretation time of the handover command, interruption time, and the time for the terminal device to acquire the TA (Target Acquisition Context). Uplink and / or downlink signals between the target network device and the terminal device maintain a QCL (Quick Closed-Loop) relationship with the sensed signal. The handover delay does not include the delay for downlink synchronization by the terminal device. Before cell handover, the terminal device has already performed downlink synchronization with the target network device during the measurement of the sensed signal.

[0322] One possible implementation involves the terminal device determining the handover delay if it has already acquired the TA according to the handover command. The time between the terminal device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay. The handover delay includes the verification and interpretation time of the handover command, the interruption time, and the time for downlink synchronization between the terminal device and the target network device. The handover delay does not include the delay of the terminal device acquiring the TA.

[0323] For example, in the Rel-15 hard handover mode, the handover command can be carried in the RRC reconfiguration message (first RRC message), and the verification and interpretation time of the handover command includes the processing delay of the RRC reconfiguration message.

[0324] For example, in LTM switching mode, the switching command can be carried in the MAC CE. The verification and interpretation time of the switching command includes: the HARQ feedback time to the MAC-CE and the MAC-CE reading time.

[0325] For example, in LTM handover mode, the verification and interpretation time of the handover command also includes the processing delay of the RRC reconfiguration message (the second RRC message), which is received before the terminal device receives the MAC CE. The RRC reconfiguration message includes the RRC configuration required for handover.

[0326] For example, the interruption time includes: the time for the terminal device to load and adjust software and hardware according to the RRC reconfiguration message (first RRC message or second RRC message), and the time for waiting for transmission resources to make the first uplink transmission to the target network device. For example, the transmission resources for the terminal device to make the first uplink transmission can be understood as: the random access opportunity (RO) for the preamble sent by the terminal or the transmission resources for sending the handover completion indication information (uplink grant).

[0327] One possible implementation is that if the terminal device has already obtained the TA according to the handover command, the terminal device determines the handover delay, wherein the time length between the terminal device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay, and the handover delay does not include the time length (delay) for the terminal device to obtain the TA.

[0328] One possible implementation involves the terminal device measuring the sensed signal. The uplink and / or downlink signals between the target network device and the terminal device maintain a QCL relationship with the sensed signal. The terminal device determines the handover delay. The time between the terminal device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay. The handover delay does not include the downlink synchronization time between the terminal device and the target network device. Before cell handover, the terminal device has already performed downlink synchronization with the target network device during the measurement of the sensed signal.

[0329] One possible implementation involves the terminal device acquiring the TA (Transfer Attack) according to the handover command, and the terminal device measuring the sensing signal. The uplink and / or downlink signals between the target network device and the terminal device maintain a QCL (Quick Closed Chain) relationship with the sensing signal. The terminal device determines the handover delay. The time between the terminal device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay. The handover delay does not include the downlink synchronization time between the terminal device and the target network device (delay) or the time for acquiring the TA (delay). Before cell handover, the terminal device has already performed downlink synchronization with the target network device during the measurement of the sensing signal.

[0330] In summary, the communication method provided in this application can reduce the handover latency of the terminal device during cell handover and improve the cell handover efficiency.

[0331] The following uses Rel-15 hard handover and LTM handover as examples to illustrate the methods provided in this application.

[0332] Figure 13 shows a schematic diagram of a Rel-15 hard handover process using the method provided in this application.

[0333] Before cell handover, the source network device or the target network device can obtain the channel quality between the terminal device and the target network device based on the sensing signals. If the channel quality determines that the terminal device is allowed to perform cell handover, a handover command is sent to the terminal device. The handover command can be carried in an RRC Reconfiguration message, which includes a TA (Translation Address), also determined by the source network device or the target network device based on the sensing signals. Furthermore, the uplink and / or downlink signals between the target network device and the terminal device during handover maintain a quasi-co-located QCL (Quasi-Co-location Channel) relationship with the sensing signals sent by the target network device to the terminal device. For details, please refer to the descriptions of methods 700, 1000, or 1200 above; they will not be repeated here.

[0334] As shown in Figure 13, before cell handover begins, the terminal device can measure the received sensing signals to determine the large-scale characteristics of the channel with the target network device, i.e., perform downlink synchronization. This process can be called sensing-based handover preparation. Furthermore, the terminal device can also establish uplink synchronization with the target network device using the TA (Transmission Aspect) and adjust ACG (Animation and Compression) parameters using the sensing signals.

[0335] The source network device sends a handover command (RRC reconfiguration message) to the terminal device. This handover command instructs the terminal device to begin cell handover. Upon receiving the handover command, the cell handover process begins (RAN handover process begins), and RAN handover delay calculation starts. In other words, the moment the terminal device receives the RRC reconfiguration message from the source network device can be understood as the moment the cell handover delay calculation begins (the starting point for RAN handover delay calculation). It should be understood that the handover command includes the TA (Translation Acquisition).

[0336] Step 1: The terminal device reads and verifies the RRC reconfiguration message.

[0337] For example, the terminal device can obtain the following information from the RRC reconfiguration message:

[0338] The target network device provides configuration parameters for each layer of the protocol stack to the terminal device;

[0339] The uplink grant (UL grant) is the transmission resource (uplink grant) that the terminal device subsequently transmits to the target network device. For example, the uplink grant (UL grant) can be configured through the configured grant (CG) of the RRC reconfiguration message or the dynamic grant (DG) of the target network device, etc., and this application embodiment does not impose any limitations.

[0340] The read verification latency of the RRC configuration can also be called the RRC procedure delay, which is calculated using T. RRC procedure express.

[0341] Step 2: Loading and adjusting software and hardware.

[0342] In step 2, the terminal device reconfigures the radio frequency / baseband / software according to the configuration provided by the network (the configuration in the RRC reconfiguration message).

[0343] The latency of loading and adjusting software and hardware can be referred to as the processing latency (T). processing ).

[0344] The length of the time from the end of step 2 to the arrival of the first uplink transmission resource (UL grant) of the terminal device is T. Iu The initial uplink transmission resource of the terminal device can be determined through the RRC reconfiguration message in step 1. In other words, TIu can also be understood as the delay of the terminal device waiting for the initial uplink transmission resource (UL grant), or the length of time between the end of the loading and adjustment of software and hardware and the initial uplink transmission time of the terminal device.

[0345] When uplink transmission resources arrive, the terminal device can send an RRC Reconfiguration Complete message to the target network device on those resources. This message indicates that the cell handover is complete, thus ending the RRC handover process. After the terminal device sends the RRC Reconfiguration Complete message, the cell handover process ends (the RAN handover process ends), and RAN handover delay calculation stops. In other words, the moment the terminal sends the RRC Reconfiguration Complete message can be understood as the end point of RAN handover delay calculation and the end time of the cell handover process.

[0346] As shown in Figure 13, T processing +T Iu The sum is T interrupt T interrupt This can be understood as the undesirable interruption time for the terminal to transmit or receive data in the source cell (i.e., the cell where the source network device provides network services).

[0347] In the example shown in Figure 13, the handover delay includes: the time length D between the terminal device receiving the handover command and initiating the first transmission to the target network device. handover D handover =T RRC procedure +T interrupt .

[0348] Comparing the processes and time delays shown in Figures 13 and 4, it can be seen that, using the method provided in this application, T interrupt The time length is much shorter than T shown in Figure 3. interrupt The length of time, T, is determined using the method provided in this application. interrupt The time length may not include T shown in Figure 3. search +T Δ The +2ms reduction decreases the number of steps required during handover, thereby reducing handover latency and data transmission interruption time, and improving handover efficiency.

[0349] Figure 14 shows a schematic diagram of an LTM switching process using the method provided in this application.

[0350] Before cell handover, the source network device or the target network device can obtain the channel quality between the terminal device and the target network device based on the sensing signals. If the channel quality determines that the terminal device is allowed to perform cell handover, a handover command is sent to the terminal device. The handover command can be carried in the MAC CE. The handover command includes TA, which is also determined by the source network device or the target network device based on the sensing signals. Furthermore, the uplink and / or downlink signals between the target network device and the terminal device during handover maintain a quasi-co-addressable (QCL) relationship with the sensing signals sent by the target network device to the terminal device. For specific details, please refer to the descriptions of methods 700, 1000, or 1200 above, which will not be repeated here.

[0351] As shown in Figure 14, before the handover begins, the terminal device can measure the received sensing signals to determine the large-scale characteristics of the channel between itself and the target network device, i.e., perform downlink synchronization. Furthermore, the terminal device can also establish uplink synchronization with the target network device using the TA (Translation Address).

[0352] Since the RRC configuration (i.e., the RRC reconfiguration message) has been pre-configured to the terminal, if the terminal's capabilities support it, the validity of the RRC reconfiguration message can be verified before receiving the handover command, i.e., the RRC configuration read verification can be performed in advance. From this, the configuration parameters of each layer of the protocol stack, random access resources and configurations, and uplink grants (UL grants) required for subsequent uplink transmissions from the terminal to the target network device can be obtained.

[0353] Optionally, the above-mentioned use of sensing signals for downlink synchronization and advance RRC configuration reading verification can be referred to as a sensing-based handover preparation process.

[0354] It should be understood that, for example, if the terminal's capabilities do not support it, then RRC configuration reading verification cannot be performed before the handover is triggered (before the handover command is received).

[0355] The source network device sends a handover command (MAC CE) to the terminal device, instructing the terminal device to initiate cell handover. Upon receiving the handover command, the cell handover process begins (RAN handover process begins), and RAN handover delay calculation starts. In other words, the moment the terminal device receives the MAC CE from the source network device can be understood as the moment the cell handover delay calculation begins (RAN handover delay calculation start point). It should be understood that the handover command includes a TA (Transitional Message). Optionally, the MAC CE can be called an LTM switch trigger message.

[0356] Step 1: Hybrid Automatic Repeat Request (HARQ) feedback. The latency of HARQ feedback can be expressed as T. HARQ .

[0357] Step 2: MAC-CE reading.

[0358] The terminal device's MAC layer interprets the MAC-CE to obtain the configuration parameters required for performing LTM handover. Typically, the latency for reading the MAC-CE is 3ms.

[0359] Step 3: RRC configuration read verification:

[0360] The terminal device needs to verify the validity of the RRC reconfiguration message. The latency for RRC configuration read verification can be expressed as T. LTM- RRC-procedure.

[0361] It should be understood that if the terminal has already performed RRC configuration read verification before the LTM handover is triggered, then step 3 does not need to be executed. LTM-RRC-procedure=0, meaning step 3 is an optional step.

[0362] Step 4: Loading and adjusting software and hardware.

[0363] The terminal device reconfigures its radio frequency / baseband / software according to the configuration provided by the network (the configuration provided in the RRC reconfiguration message). The latency of loading and adjusting the software and hardware can be expressed as T. LTM-processing .

[0364] The length of the time from the end of step 4 to the arrival of the terminal device's first uplink transmission resource (UL grant) is T. LTM-Iu The initial uplink transmission resources of the terminal device can be determined through an RRC reconfiguration message. In other words, T LTM-Iu It can also be understood as: the delay of the terminal device waiting for the first uplink transmission resource (UL grant), or the length of time between the end of the loading and adjustment of software and hardware and the moment of the terminal device's first uplink transmission.

[0365] When uplink transmission resources arrive, the terminal device can send an RRC Reconfiguration Complete message to the target network device on those resources. This message indicates that the cell handover is complete, thus ending the RRC handover process. After the terminal device sends the RRC Reconfiguration Complete message, the cell handover process ends (the RAN handover process ends), and RAN handover delay calculation stops. In other words, the moment the terminal sends the RRC Reconfiguration Complete message can be understood as the end point of RAN handover delay calculation and the end time of the cell handover process.

[0366] As shown in Figure 14, T LTM-processing +T LTM-Iu The sum is T LTM-interrupt T LTM-interrupt This can be understood as the undesirable interruption time for the terminal to transmit or receive data in the source cell (i.e., the cell where the source network device provides network services).

[0367] In the example shown in Figure 14, the handover delay includes: the time length D between the terminal device receiving the handover command and initiating the first transmission to the target network device. handover D handover＝ T HARQ +3ms+T LTM-RRC-procedure +T LTM-interrupt It should be understood that if the terminal has already performed RRC configuration read verification before the LTM handover is triggered, then T LTM-RRC-processing =0.

[0368] Comparing the processes and time delays shown in Figures 14 and 5, it can be seen that, using the method provided in this application, T LTM-interrupt The time length is much shorter than T shown in Figure 5. LTM-interrupt The handover delay determined using the method provided in this application may not include T shown in Figure 5, given the duration of the handover. first-RS The +2ms reduction decreases the number of steps required during handover, thereby reducing handover latency and data transmission interruption time, and improving handover efficiency.

[0369] It should be understood that the above description is merely to help those skilled in the art better understand the embodiments of this application, and is not intended to limit the scope of the embodiments of this application. Based on the examples given above, those skilled in the art can obviously make various equivalent modifications or changes. For example, some steps in the above method embodiments may be unnecessary, or new steps may be added. Alternatively, any combination of two or more of the above embodiments may be used. Such modifications, changes, or combinations also fall within the scope of the embodiments of this application.

[0370] It should also be understood that the methods, situations, categories, and classifications of embodiments in this application are for the convenience of description only and should not constitute a special limitation. Various methods, categories, situations, and features in embodiments can be combined without contradiction.

[0371] It should also be understood that the various numerical designations used in the embodiments of this application are merely for descriptive convenience and are not intended to limit the scope of the embodiments of this application. The order of the process numbers described above does not imply the order of execution; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0372] It should also be understood that the above description of the embodiments of this application focuses on highlighting the differences between the various embodiments. Any similarities or differences not mentioned can be referred to each other. For the sake of brevity, they will not be repeated here.

[0373] The communication method of the present application embodiment has been described in detail above with reference to Figures 1 to 14. The communication device of the present application embodiment will be described in detail below with reference to Figures 15 to 18.

[0374] This embodiment can divide the terminal device and network-side device (including source network device and target network device) into functional modules according to the above method. For example, each function can be divided into its own functional module, or two or more functions can be integrated into one processing module. The integrated module can be implemented in hardware. It should be noted that the module division in this embodiment is illustrative and only represents one logical functional division; other division methods may be used in actual implementation.

[0375] It should be noted that the relevant content of each step involved in the above method embodiments can be referenced from the functional description of the corresponding functional module, and will not be repeated here.

[0376] The terminal device and network-side device provided in this application embodiment are used to execute any of the communication methods provided in the above-described method embodiments, thus achieving the same effect as the above-described implementation method. When using integrated units, the terminal device and network-side device may include a processing module, and optionally a storage module and a communication module. The processing module can be used to control and manage the actions of the terminal device and network-side device. For example, it can be used to support the terminal device and network-side device in executing the steps executed by the processing unit. The storage module can be used to support the storage of program code and data, etc. The communication module can be used to support communication between the terminal device and network-side device and other devices.

[0377] It should be understood that the network-side device provided in this application may be a network device (including a source network device and a target network device), a component (chip, chip system, or processor) that supports the network device in implementing the method, or a logical node, logical module, or software that can implement all or part of the functions of the network device.

[0378] It should also be understood that the terminal device in this application may be a terminal device, a component (chip, chip system, or processor) that supports the terminal device in implementing the method, or a logic module or software that can implement all or part of the functions of the terminal device.

[0379] The processing module can be a processor or a controller. It can implement or execute various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this application. The processor can also be a combination that implements computing functions, such as a combination of one or more microprocessors, a combination of digital signal processing (DSP) and a microprocessor, etc. The storage module can be a memory. The communication module can specifically be a radio frequency circuit, a Bluetooth chip, or a device that interacts with other electronic devices.

[0380] For example, FIG15 shows a schematic block diagram of a communication device 1500 according to an embodiment of the present application. As shown in FIG15, the communication device 1500 includes a processing unit 1510 and a transceiver unit 1520. The transceiver unit 1520 is used to perform operations related to information transmission and reception under the control of the processing unit 1510. The processing unit may also be referred to as a processing module, and the transceiver unit may also be referred to as a communication unit, communication module, or communication interface, etc.

[0381] In some embodiments, the communication device 1500 may correspond to the target network device described in method 700 above, or it may be a component (chip, chip system, or processor) applied to the target network device, or it may be a logic module or software that can implement all or part of the functions of the target network device. Furthermore, each module or unit in the communication device 1500 is used to execute the actions or processes performed by the target network device in method 700 above.

[0382] The processing unit 1510 is used to generate a first sensing signal.

[0383] The transceiver unit 1520 is used to: send a first sensing signal to the terminal device; and receive the echo signal corresponding to the first sensing signal.

[0384] The processing unit 1510 is further configured to: determine the timing advance TA for the terminal device to perform uplink transmission to the target network device based on the echo signal and the first sensing signal, wherein the TA is used by the terminal device to perform cell handover.

[0385] The transceiver unit 1520 is also used to: send indication information to the source network device, the indication information including TA, the source network device being a network device that provides communication services to the terminal device before cell handover.

[0386] The communication device provided in this application embodiment can obtain the TA (Transmission Aspect) for uplink transmission from the terminal device to the target network device using a single-site sensing method, and send it to the terminal device through the source network device. This avoids the terminal device obtaining the TA through signaling interaction (e.g., RACH procedure), saving signaling overhead during handover and avoiding handover latency caused by signaling interaction. This reduces handover latency and data transmission interruption time during cell handover, lowers the requirements on terminal device capabilities, and improves cell handover efficiency.

[0387] In other embodiments, the processing unit 1510 is used to generate a third sensing signal.

[0388] The transceiver unit 1520 is used to: send a third sensing signal to the terminal device; and receive the echo signal corresponding to the third sensing signal.

[0389] The processing unit 1510 is further configured to: determine the channel quality between the terminal device and the target network device based on the echo signal and the third sensing signal; determine whether the terminal device is allowed to perform cell handover based on the channel quality; and, if the terminal device is allowed to perform cell handover, control the transceiver unit 1520 to send indication information to the source network device. The indication information is used to indicate that the terminal device is allowed to handover to the target network device. The indication information includes a timing advance (TA) for the terminal device to perform uplink transmission to the target network device. The target network device is the target network device of the terminal device during the cell handover process, and the source network device is the network device that provides communication services to the terminal device before the cell handover.

[0390] The communication apparatus provided in this application embodiment can acquire the channel quality between the terminal device and the target network device using a single-site sensing method, and manage cell handover by utilizing the channel quality between the terminal device and the target network device. This avoids the terminal device measuring and reporting the target cell based on measurement configuration. In other words, it avoids the terminal device communicating with the target network device about channel quality through signaling interaction, saving signaling overhead during handover and avoiding handover latency caused by signaling interaction. This reduces handover latency and data transmission interruption time during cell handover, thereby improving cell handover efficiency.

[0391] In one possible implementation, the channel quality includes the reference signal received power (RSRP), which includes absolute RSRP and / or relative RSRP.

[0392] In one possible implementation, the uplink and / or downlink signals between the target network device and the terminal device maintain a QCL relationship with the first sensing signal or the third sensing signal.

[0393] In one possible implementation, the specific process by which each unit in the communication device 1500 performs the above-mentioned corresponding steps is described in the previous description of the target network device in conjunction with the relevant embodiments of method 700. For the sake of brevity, it will not be repeated here.

[0394] In some embodiments, the communication device 1500 may correspond to the source network device described in method 1000 above, or it may be a component (chip, chip system, or processor) applied to the source network device, or it may be a logic module or software that can implement all or part of the functions of the source network device. Furthermore, each module or unit in the communication device 1500 is used to execute the actions or processes performed by the target network device in method 1000 above.

[0395] The transceiver unit 1520 is used to: receive a first echo signal reflected by the terminal device from the first sensing signal, wherein the first sensing signal is a sensing signal sent by the target network device to the terminal device, and the target network device is the target network device of the terminal device during the cell handover process.

[0396] The processing unit 1510 is used to generate a fourth sensing signal.

[0397] The transceiver unit 1520 is used to: send a fourth sensing signal to the terminal device; and receive a fourth echo signal corresponding to the first sensing signal.

[0398] The processing unit 1510 is further configured to: determine the timing advance TA for the terminal device to perform uplink transmission to the target network device based on the fourth sensing signal, the fourth echo signal, the first sensing signal and the first echo signal, wherein the TA is used by the terminal device to perform cell handover.

[0399] The communication device provided in this application embodiment can obtain the TA (Transmission Availability) for uplink transmission from the terminal device to the target network device using a dual-site sensing method with the target network device. This avoids the terminal device obtaining the TA through signaling interaction (e.g., RACH procedure), saving signaling overhead during handover and avoiding handover latency caused by signaling interaction. Therefore, it can reduce handover latency and data transmission interruption time during cell handover, and improve cell handover efficiency.

[0400] In one possible implementation, the transceiver unit 1520 is further configured to: receive the transmission time of the first sensing signal from the target network device.

[0401] In one possible implementation, the uplink and / or downlink signals between the target network device and the terminal maintain a QCL relationship with the first sensing signal.

[0402] In one possible implementation, the specific process by which each unit in the communication device 1500 performs the above-mentioned corresponding steps is described in the previous description of the source network device in conjunction with the relevant embodiments of method 1000. For the sake of brevity, it will not be repeated here.

[0403] In some embodiments, the communication device 1500 may correspond to the terminal device described in method 1200 above, or it may be a component (chip, chip system, or processor) applied to the terminal device, or it may be a logic module or software that can implement all or part of the functions of the terminal device. Furthermore, each module or unit in the communication device 1500 is used to execute the actions or processing procedures performed by the terminal device in method 1200 above.

[0404] The transceiver unit 1520 is configured to: receive a handover command, which instructs the terminal device to begin handover from the source network device to the target network device. The handover command includes a timing advance TA for the terminal device to perform uplink transmission to the target network device. The TA is determined based on a first sensing signal sent by the target network device to the terminal device.

[0405] Processing unit 1510 is used to: initiate cell handover process according to the handover command;

[0406] The transceiver unit 1520 is also used to send a handover completion indication message to the target network device.

[0407] The communication device provided in this application embodiment can obtain the timing advance (TA) for uplink transmission to the target network device through sensing signals and notify the communication device through a handover command. This avoids the communication device obtaining the TA through signaling interaction (e.g., RACH process) during cell handover, reduces the steps that need to be performed during the handover process, thereby reducing the handover latency and the duration of data transmission interruption when the communication device performs cell handover, and improving cell handover efficiency.

[0408] In one possible implementation, the uplink and / or downlink signals between the target network device and the terminal device maintain a QCL relationship with the second sensing signal, which is used for downlink synchronization between the terminal device and the target network device. The second sensing signal is sent from the target network device to the terminal device.

[0409] In one possible implementation, the downlink synchronization includes: the terminal device determining the downlink time slot, subframe and / or radio frame boundary timing of the target network device based on the second sensing signal, or the terminal device determining the radio frame number of the downlink radio frame of the target network device based on the second sensing signal.

[0410] In one possible implementation, the second sensing signal is also used by the terminal device to adjust the automatic gain control (AGC) parameters.

[0411] In one possible implementation, the cell handover process includes: the terminal device reading and verifying the handover command, loading and adjusting the software and hardware of the terminal device according to the handover command, and establishing uplink synchronization with the target network device using the TA.

[0412] In one possible implementation, the handover command is carried in a Radio Resource Control (RRC) reconfiguration message or a MAC CE.

[0413] In one possible implementation, the handover completion indication information is carried in an RRC reconfiguration completion message.

[0414] In one possible implementation, if the communication device has measured the sensing signal and has obtained the timing advance (TA) for uplink transmission from the communication device to the target network device according to the handover command, the communication device determines the handover delay, wherein the time length between the communication device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay, and the handover delay includes the verification and interpretation time of the handover command and the interrupt time, the uplink and / or downlink signals between the target network device and the communication device, and the quasi-co-addressable (QCL) relationship between the sensing signal and the signal.

[0415] In one possible implementation, if the communication device has measured the sensing signal, the communication device determines the handover delay, wherein the time length between the communication device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay. The handover delay includes the verification and interpretation time of the handover command, the interruption time, and the time to obtain the timing advance (TA) for the communication device to transmit uplink data to the target network device. The uplink and / or downlink signals between the target network device and the communication device maintain a quasi-co-addressable (QCL) relationship with the sensing signal.

[0416] In one possible implementation, if the communication device has obtained the timing advance (TA) for the terminal to transmit uplink data to the target network device according to the handover command, the terminal determines the handover delay. The time between the communication device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay. The handover delay includes the verification and interpretation time of the handover command, the interruption time, and the time for the communication device and the target network device to perform downlink synchronization.

[0417] In one possible implementation, the interruption time includes: the time for the terminal device to load and adjust software and hardware based on the first RRC message or the second RCC message, and the time for waiting for transmission resources to be used for the first uplink transmission to the target network device. The first RRC message or the second RCC message includes an RRC reconfiguration message.

[0418] In one possible implementation, if the communication device has already obtained the timing advance (TA) for uplink transmission from the communication device to the target network device according to the handover command, the communication device determines the handover delay, wherein the time length between the terminal receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay, and the handover delay does not include the time length for obtaining the TA; and / or; if the communication device has measured the sensing signal, and the uplink and / or downlink signals between the target network device and the terminal maintain a QCL relationship with the sensing signal, the communication device determines the handover delay, wherein the time length between the terminal receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay, and the handover delay does not include the time for downlink synchronization between the terminal and the target network device.

[0419] In one possible implementation, the specific process by which each unit in the communication device 1500 performs the above-mentioned corresponding steps is described in the previous description of the terminal device in conjunction with the relevant embodiments of method 1200. For the sake of brevity, it will not be repeated here.

[0420] Furthermore, the communication device 1500 may also include a storage unit, and the transceiver unit 1520 may be a transceiver, an input / output interface, pins, or interface circuitry. The storage unit is used to store instructions executed by the transceiver unit 1520 and the processing unit 1510. The transceiver unit 1520, the processing unit 1510, and the storage unit are coupled to each other. The storage unit stores instructions, the processing unit 1510 executes the instructions stored in the storage unit, and the transceiver unit 1520 performs specific signal transmission and reception under the control of the processing unit 1510.

[0421] It should be understood that the transceiver unit 1520 may be a transceiver, an input / output interface, or an interface circuit. The storage unit may be a memory. The processing unit 1510 may be implemented by a processor.

[0422] As shown in Figure 16, the communication device 1600 may include a processor 1610. Optionally, the communication device 1600 may also include a memory 1620 and a transceiver 1630. The dashed lines in Figure 16 indicate that this unit or module is optional. The communication device 1600 can be used to implement the methods described in the above method embodiments.

[0423] The communication device 1500 shown in Figure 15 or the communication device 1600 shown in Figure 16 can implement the steps performed by the source network device or the target network device in the aforementioned method 700 and / or method 1200. Alternatively, it can implement the steps performed by the terminal device in the aforementioned method 1200; similar descriptions can be found in the descriptions of the corresponding methods described above. To avoid repetition, further details are omitted here.

[0424] In some possible implementations, the communication device 1500 shown in FIG15 or the communication device 1600 shown in FIG16 may be a terminal device, or the terminal device may include the communication device 1500 shown in FIG15 or the communication device 1600 shown in FIG16.

[0425] In some possible implementations, the communication device 1500 shown in FIG15 or the communication device 1600 shown in FIG16 can be a network-side device, or the network-side device can include the communication device 1500 shown in FIG15 or the communication device 1600 shown in FIG16.

[0426] It should also be understood that the division of units in the above device is merely a logical functional division. In actual implementation, they can be fully or partially integrated into a single physical entity, or they can be physically separated. Furthermore, all units in the device can be implemented entirely through software calls from processing elements; all units can be implemented entirely in hardware; or some units can be implemented through software calls from processing elements, while others are implemented in hardware. For example, each unit can be a separate processing element, or it can be integrated into a chip within the device. Alternatively, it can be stored as a program in memory, and its function can be called and executed by a processing element within the device. Here, the processing element can also be called a processor, which can be an integrated circuit with signal processing capabilities. In the implementation process, each step of the above method or each of the above units can be implemented through integrated logic circuits in the processor element or through software calls from processing elements.

[0427] In one example, a unit in any of the above devices can be one or more integrated circuits configured to implement the methods described above, such as one or more application-specific integrated circuits (ASICs), or one or more DSPs, or one or more field-programmable gate arrays (FPGAs), or a combination of at least two of these forms of integrated circuits. As another example, when a unit in the device can be implemented in the form of a processing element scheduler, the processing element can be a general-purpose processor, such as a CPU or other processor capable of calling programs. Furthermore, these units can be integrated together to implement a system-on-a-chip (SOC).

[0428] Figure 17 is a schematic diagram of the structure of a terminal device 1700 provided in this application. The aforementioned communication device 1500 or communication device 1600 can be configured in the terminal device 1700. Alternatively, the communication device 1500 or communication device 1600 itself can be the terminal device 1700. In other words, the terminal device 1700 can perform the actions performed by the terminal device in the aforementioned method 1200. Optionally, for ease of explanation, Figure 17 only shows the main components of the terminal device. As shown in Figure 17, the terminal device 1700 includes a processor, memory, control circuitry, antenna, and input / output devices.

[0429] The processor is primarily used to process communication protocols and data, control the entire terminal device, execute software programs, and process the data within those programs. For example, it supports the terminal in performing the actions described in the aforementioned communication method embodiments. The memory is primarily used to store software programs and data, such as the handover commands described in the aforementioned embodiments and large-scale characteristics of the channel between the terminal and the target network device. The control circuit is primarily used for converting baseband signals to radio frequency signals and processing radio frequency signals. The control circuit and antenna together can also be called a transceiver, primarily used for transmitting and receiving radio frequency signals in the form of electromagnetic waves. For example, it sends the handover completion indication information described in the aforementioned embodiments and receives the handover commands described in the aforementioned embodiments. Input / output devices, such as touchscreens, displays, and keyboards, are primarily used to receive user input data and output data to the user.

[0430] When the terminal device is powered on, the processor can read the software program from the storage unit, interpret and execute the instructions of the software program, and process the data of the software program. When data needs to be transmitted wirelessly, the processor performs baseband processing on the data to be transmitted (such as handover completion indication information) and outputs the baseband signal to the radio frequency (RF) circuit. The RF circuit processes the baseband signal and transmits the RF signal outward in the form of electromagnetic waves through the antenna. When a signal (such as the aforementioned handover command, sensing signal, etc.) is sent to the terminal device, the RF circuit receives the RF signal through the antenna, converts the RF signal into a baseband signal, and outputs the baseband signal to the processor. The processor converts the baseband signal into data and processes the data.

[0431] Those skilled in the art will understand that, for ease of explanation, Figure 17 only shows one memory and processor. In actual terminal devices, multiple processors and memories may exist. Memory may also be referred to as storage medium or storage device, etc., and the embodiments of this application do not limit this.

[0432] For example, a processor may include a baseband processor and a central processing unit (CPU). The baseband processor is mainly used for processing communication protocols and communication data, while the CPU is mainly used for controlling the entire terminal device, executing software programs, and processing the data in those programs. The processor in Figure 17 integrates the functions of both a baseband processor and a CPU. Alternatively, the baseband processor and CPU can be independent processors interconnected via technologies such as buses. A terminal device may include multiple baseband processors to adapt to different network standards, and multiple CPUs to enhance its processing capabilities. The various components of the terminal device can be connected via various buses. The baseband processor can also be described as a baseband processing circuit or a baseband processing chip. The CPU can also be described as a central processing circuit or a central processing chip. The function of processing communication protocols and communication data can be built into the processor or stored as software programs in a storage unit, with the processor executing the software programs to implement the baseband processing function.

[0433] For example, in this embodiment, the antenna and control circuit with transceiver functions can be regarded as the transceiver unit 1701 of the terminal device 1700, and the processor with processing functions can be regarded as the processing unit 1702 of the terminal device 1700. As shown in FIG17, the terminal device 1700 includes the transceiver unit 1701 and the processing unit 1702. The transceiver unit can also be referred to as a transceiver, transceiver device, transceiver apparatus, etc. Optionally, the device in the transceiver unit 1701 used to implement the receiving function can be regarded as the receiving unit, and the device in the transceiver unit 1701 used to implement the transmitting function can be regarded as the transmitting unit, that is, the transceiver unit 1701 includes a receiving unit and a transmitting unit. For example, the receiving unit can also be referred to as a receiver, receiver circuit, etc., and the transmitting unit can be referred to as a transmitter, transmitter, or transmitting circuit, etc.

[0434] Figure 18 is a schematic diagram of a network device 1800 provided in an embodiment of this application, which can be used to implement the functions of the target network device or source network device in the above method. The network device 1800 includes one or more radio frequency (RF) units 1801 and one or more processing units 1802. The RF unit 1801 can be referred to as a transceiver unit, transceiver, transceiver circuit, or transceiver, etc., and may include at least one antenna 18011 and an RF unit 18012. The RF unit 1801 is mainly used for transmitting and receiving RF signals and converting RF signals to baseband signals, such as sending switching commands and sensing signals to the terminal as described in the above embodiments. The processing unit 1802 is mainly used for baseband processing and controlling the network device. The RF unit 1801 and the processing unit 1802 can be physically arranged together or physically separated, i.e., a distributed network device.

[0435] The processing unit 1802 is the control center of the network device, also known as the baseband unit. It is mainly used to perform baseband processing functions, such as channel coding, multiplexing, modulation, spreading, etc. For example, the processing unit 1802 can be used to control the network device to execute the operation flow of the target network device or the source network device in the above method embodiments.

[0436] In one example, the processing unit 1802 may consist of one or more single boards. Multiple single boards can collectively support a single access standard wireless access network (such as an LTE system or a 5G system), or they can each support wireless access networks with different access standards. The processing unit 1802 also includes a memory 18021 and a processor 18022. The memory 18021 stores necessary instructions and data. For example, the memory 18021 stores handover commands, transfer actions (TAs), channel quality between the terminal device and the target network device, etc., as described in the above embodiments. The processor 18022 controls the network device to perform necessary actions, such as controlling the network device to execute the operation procedures related to the target network device or the source network device as described in the above method embodiments. The memory 18021 and the processor 18022 can serve one or more single boards. That is, each single board can have its own memory and processor, or multiple single boards can share the same memory and processor. Furthermore, each single board can also have necessary circuitry.

[0437] In one possible implementation, with the development of SoC technology, all or part of the functions of the 1802 and 1801 parts can be implemented by SoC technology, for example, by a network device function chip. This network device function chip integrates a processor, memory, antenna interface, and other devices. The program for the network device-related functions is stored in the memory, and the processor executes the program to implement the relevant functions of the network device. Optionally, the network device function chip can also read external memory to implement the relevant functions of the network device.

[0438] It should be understood that the network device structure illustrated in Figure 18 is only one possible configuration and should not be construed as limiting the embodiments of this application. This application does not exclude the possibility of other network-side device structures that may appear in the future.

[0439] It should be understood that in the embodiments of this application, the processor can be a CPU, but it can also be other general-purpose processors, DSPs, ASICs, FPGAs, microprocessors (MPUs), microcontroller units (MCUs), graphics processing units (GPUs), artificial intelligence processors (AI processors), neural processing units (NPUs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor.

[0440] It should also be understood that the memory in the embodiments of this application can be volatile memory or non-volatile memory, or may include both volatile and non-volatile memory. Non-volatile memory can be read-only memory (ROM), programmable read-only memory (PROM), EPROM, electrically erasable programmable read-only memory (EEPROM), or flash memory. Volatile memory can be cache or random access memory (RAM) (which serves as an external cache). By way of example, but not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous linked dynamic random access memory (SLDRAM), and direct rambus RAM (DR RAM).

[0441] This application also provides a communication system, which includes the aforementioned terminal device and network-side device. The network-side device may include a target network device and a source network device, and optionally, may also include a source network device.

[0442] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, as a computer program product. This computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer program are loaded or executed on a computer, all or part of the processes or functions according to the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., infrared, wireless, microwave, etc.) means.

[0443] This application also provides a computer-readable medium for storing computer program code, the computer program including instructions for executing any of the communication methods provided in the embodiments of this application. The readable medium may be the memory described in the examples above, and this application does not limit this to such methods.

[0444] This application also provides a computer program product including instructions that, when executed, cause a terminal device to perform operations corresponding to the terminal device operations in the above-described method, or cause a target network device or a source network device to perform operations corresponding to the corresponding device operations in the above-described method.

[0445] This application also provides a chip comprising a processing unit and a communication unit. The processing unit may be, for example, a processor, and the communication unit may be, for example, an input / output interface, pins, or circuitry. The processing unit can execute computer instructions to cause the chip within the communication device to perform any of the communication methods provided in the embodiments of this application.

[0446] Optionally, any of the communication devices provided in the above embodiments of this application may include the chip.

[0447] Optionally, the computer instructions are stored in a storage unit.

[0448] Optionally, the storage unit can be an internal storage unit within the chip, such as a register or cache. Alternatively, it can be an external storage unit within the communication device, such as ROM or other types of static storage devices capable of storing static information and instructions, like RAM. The processing unit and the storage unit can be decoupled and located on different physical devices, connected via wired or wireless means to implement their respective functions, thus supporting the chip in performing the various functions described in the above embodiments. Alternatively, the processing unit and the memory can also be coupled to the same device.

[0449] In this application, various objects such as messages / information / devices / systems / apparatus / actions / operations / processes may be named. It is understood that these specific names do not constitute a limitation on the relevant objects. The names may be changed depending on the scenario, context, or usage habits. The understanding of the technical meaning of the technical terms in this application should be mainly determined from their functions and technical effects embodied / performed in the technical solution.

[0450] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0451] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0452] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A communication method, characterized in that, The method includes: The terminal device receives a handover command, which instructs the terminal device to begin handover from the source network device to the target network device. The handover command includes a timing advance (TA) for the terminal device to perform uplink transmission to the target network device. The TA is determined based on a first sensing signal sent by the target network device to the terminal device. The terminal device initiates the cell handover process according to the handover command; The terminal device sends a handover completion indication message to the target network device.

2. The method according to claim 1, characterized in that, The uplink and / or downlink signals between the target network device and the terminal device maintain a quasi-co-address (QCL) relationship with the second sensing signal. The second sensing signal is used for downlink synchronization between the terminal device and the target network device and is sent by the target network device to the terminal device.

3. The method according to claim 2, characterized in that, The downlink synchronization includes at least one of the following: the terminal device determining the downlink time slot, subframe and / or radio frame boundary timing of the target network device based on the second sensing signal, or the terminal device determining the radio frame number of the downlink radio frame of the target network device based on the second sensing signal.

4. The method according to claim 2 or 3, characterized in that, The second sensing signal is also used by the terminal device to adjust the automatic gain control (AGC) parameters.

5. The method according to any one of claims 1 to 4, characterized in that, The cell handover process includes: The terminal device reads and verifies the handover command, loads and adjusts the software and hardware of the terminal device according to the handover command, and establishes uplink synchronization with the target network device using the TA.

6. The method according to any one of claims 1 to 5, characterized in that, The handover command is carried in a Radio Resource Control (RRC) reconfiguration message or a Media Access Control (MAC) CE element.

7. The method according to any one of claims 1 to 6, characterized in that, The handover completion indication information is carried in the RRC reconfiguration completion message.

8. A communication method, characterized in that, The method includes: The first network device sends a first sensing signal to the terminal device; The first network device receives the echo signal corresponding to the first sensing signal; The first network device determines the timing advance (TA) for the terminal device to perform uplink transmission to the first network device based on the echo signal and the first sensing signal. The TA is used by the terminal device to perform cell handover. The first network device sends an instruction message to the source network device, the instruction message including the TA, the source network device being the network device that provides communication services to the terminal device before cell handover.

9. A communication method, characterized in that, The method includes: The first network device sends a third sensing signal to the terminal device; The first network device receives the echo signal corresponding to the third sensing signal; The first network device determines the channel quality between the terminal device and the target network device based on the echo signal and the third sensing signal; The first network device determines whether to allow the terminal device to perform cell handover based on the channel quality. When the terminal device is allowed to perform cell handover, the first network device sends an indication message to the source network device. The indication message is used to indicate that the terminal device is allowed to handover to the first network device. The indication message includes a timing advance (TA) for the terminal device to perform uplink transmission to the first network device. The first network device is the target network device of the terminal device during the cell handover process, and the source network device is the network device that provides communication services to the terminal device before the cell handover.

10. The method according to claim 8 or 9, characterized in that, The channel quality includes the reference signal received power (RSRP), which includes absolute RSRP and / or relative RSRP.

11. The method according to any one of claims 8 to 10, characterized in that, The uplink and / or downlink signals between the target network device and the terminal device maintain a quasi-co-located (QCL) relationship with the first sensing signal or the third sensing signal.

12. A communication method, characterized in that, The method includes: The source network device receives a first echo signal reflected by the terminal device in response to the first sensing signal. The first sensing signal is a sensing signal sent by the first network device to the terminal device. The source network device is a network device that provides communication services to the terminal device before cell handover. The first network device is a target network device for the terminal device during cell handover. The source network device sends a fourth sensing signal to the terminal device; The source network device receives the fourth echo signal corresponding to the fourth sensing signal; The source network device determines the timing advance (TA) for the terminal device to perform uplink transmission to the first network device based on the fourth sensing signal, the fourth echo signal, the first sensing signal, and the first echo signal. The TA is used by the terminal device to perform cell handover.

13. The method according to claim 12, characterized in that, The method further includes: The source network device receives the transmission time of the first sensing signal from the first network device.

14. The method according to claim 12 or 13, characterized in that, The uplink and / or downlink signals between the target network device and the terminal maintain a quasi-co-addressable (QCL) relationship with the first sensing signal.

15. A communication method, characterized in that, The method includes: The source network device receives the fifth echo signal reflected by the terminal device in response to the fifth sensing signal. The fifth sensing signal is a sensing signal sent by the first network device to the terminal device. The source network device is a network device that provides communication services to the terminal device before cell handover. The first network device is the target network device of the terminal device during cell handover. The source network device sends a sixth sensing signal to the terminal device; The source network device receives the sixth echo signal corresponding to the sixth sensing signal; The source network device determines the channel quality between the terminal device and the target network device based on the sixth sensing signal, the sixth echo signal, the fifth sensing signal, and the fifth echo signal. The source network device determines whether to allow the terminal device to perform cell handover based on the channel quality. When the terminal device is allowed to perform cell handover, the source network device sends a handover command to the terminal device. The handover command is used to instruct the terminal device to start handover from the source network device to the first network device. The handover command includes a timing advance (TA) for the terminal to perform uplink transmission to the first network device.

16. The method according to claim 15, characterized in that, The channel quality includes the reference signal received power (RSRP), which includes absolute RSRP and / or relative RSRP.

17. The method according to claim 15 or 16, characterized in that, The method further includes: The source network device receives the transmission power of the fifth sensing signal from the first network device.

18. The method according to any one of claims 15 to 17, characterized in that, The uplink and / or downlink signals between the first network device and the terminal device maintain a quasi-co-address (QCL) relationship with the fifth sensing signal.

19. A communication method, characterized in that, The method includes: If the terminal device has already measured the sensed signal, and the terminal device has obtained the timing advance (TA) for uplink transmission to the target network device according to the handover command, the terminal device determines the handover delay, wherein the time length between the terminal device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay, the handover delay including the verification and interpretation time and interruption time of the handover command, and the uplink and / or downlink signals between the target network device and the terminal device maintain a quasi-co-addressable (QCL) relationship with the sensed signal; or... If the terminal device has already measured the sensed signal, the terminal device determines the handover delay, wherein the time length between the terminal device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay, the handover delay including the verification and interpretation time of the handover command, the interruption time, and the time for obtaining the timing advance (TA) for the terminal device to transmit uplink data to the target network device, the uplink and / or downlink signals between the target network device and the terminal device maintaining a quasi-co-addressable (QCL) relationship with the sensed signal; or... If the terminal device has obtained the timing advance (TA) for uplink transmission from the terminal to the target network device according to the handover command, the terminal determines the handover delay, wherein the time length between the terminal device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay, and the handover delay includes the verification and interpretation time of the handover command, the interruption time, and the time for the terminal device and the target network device to perform downlink synchronization.

20. The method according to claim 19, characterized in that, The switching command is carried in the first RRC message, and the verification and interpretation time of the switching command includes the processing delay of the first RRC message.

21. The method according to claim 19, characterized in that, The switching command is carried in the MACCE, and the verification and interpretation time of the switching command includes: the HARQ feedback time of the MAC-CE and the MAC-CE reading time.

22. The method according to claim 21, characterized in that, The verification and interpretation time of the switching command also includes the processing delay of the second RRC message, which is received before the terminal receives the MACCE. The second RRC message includes the RRC configuration required for the switching.

23. The method according to any one of claims 20 to 22, characterized in that, The interruption time includes: the time for the terminal device to load and adjust software and hardware according to the first RRC message or the second RCC message, and the time for waiting for transmission resources to make the first uplink transmission to the target network device.

24. The method according to any one of claims 20 to 23, characterized in that, The first RRC message or the second RRC message includes an RRC reconfiguration message.

25. A communication method, characterized in that, The method includes: If the terminal device has already obtained the timing advance (TA) for uplink transmission to the target network device according to the handover command, the terminal device determines the handover delay, wherein the time length between the terminal device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay, and the handover delay does not include the time length for obtaining the TA; and / or If the terminal device has already measured the sensing signal, the uplink and / or downlink signals between the target network device and the terminal device being switched by the terminal device maintain a quasi-co-addressable (QCL) relationship with the sensing signal. The terminal device determines the handover delay, wherein the time between the terminal device receiving the handover command and sending the handover completion indication information is less than or equal to the handover delay, and the handover delay does not include the time for the terminal and the target network device to perform downlink synchronization.

26. A communication device, characterized in that, include: A unit for performing the method as described in any one of claims 1 to 7, or a unit for performing the method as described in any one of claims 8 to 11, or a unit for performing the method as described in any one of claims 12 to 18, or a unit for performing the method as described in any one of claims 19 to 25.

27. A communication device, characterized in that, Includes a processor for causing the communication device to perform the method as claimed in any one of claims 1 to 7, or the method as claimed in any one of claims 8 to 11, or the method as claimed in any one of claims 12 to 18, or the method as claimed in any one of claims 19 to 25 by executing a computer program and / or by logic circuitry.

28. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, the computer program including program instructions that, when executed by a processor, cause the processor to perform: the method of any one of claims 1 to 7, or the method of any one of claims 8 to 11, or the method of any one of claims 12 to 18, or the method of any one of claims 19 to 25.

29. A computer program product, characterized in that, include: A computer program, when run on a computer, causes the computer to perform: the method as claimed in any one of claims 1 to 7, or the method as claimed in any one of claims 8 to 11, or the method as claimed in any one of claims 12 to 18, or the method as claimed in any one of claims 19 to 25.

Images