Communication method and apparatus

Abstract

The present application relates to the field of communications, and provides a communication method and apparatus, which can reduce a handover interruption delay when a terminal device is handed over, and are applicable to terrestrial communication and non-terrestrial communication scenarios. In the method, a terminal device can receive, from a first network device corresponding to a source cell, first configuration information used for configuring a time-domain position of a reference signal corresponding to a target cell, wherein a transmission time interval of the reference signal is less than a transmission period or an SMTC period of a synchronization signal of the target cell, so that the terminal device can receive the reference signal at the corresponding time-domain position and perform downlink synchronization with the target cell, thereby achieving the purpose of reducing the handover interruption delay.

Description

Communication method and apparatus

[0001] This application claims priority to the Chinese Patent Application No. 202411379930.2, filed on September 29, 2024, and entitled "Communication method and apparatus", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of communication, in particular to a communication method and apparatus. BACKGROUND

[0003] In satellite communication, since the satellite is moving at a high speed, the coverage physical area of the satellite is changing, which causes the terminal device to connect to the satellite to be switched, or the cell to be switched due to the switching of the satellite. For example, in a quasi-earth fixed cell scenario, the terminal device located in the cell will be switched to a satellite, but the cell will not be switched, at this time, it can still be considered that the cell is switched, and the source cell and the target cell are the same. For another example, in an earth moving cell scenario, the cell will move with the satellite, and the terminal device will be switched to a satellite due to the movement of the satellite, thereby causing the cell to be switched.

[0004] In the satellite switching process, the terminal device needs to be synchronized with the target cell in downlink and uplink before accessing the target cell, so that the terminal device has a switching interruption delay, which mainly depends on the time required by the terminal device to perform downlink synchronization. The time delay of the terminal device to perform downlink synchronization is related to the time length from determining to switch the satellite to receiving the SSB from the target satellite and the SMTC period length based on the SSB-based measurement timing configuration (SMTC) period length of the synchronization signal and physical broadcast channel (PBCH) block (SSB).

[0005] However, the SMTC period length is usually the same as the transmission period of the SSB, and when the transmission period of the SSB is relatively long, the switching interruption delay is relatively large, which will affect the communication experience of the user. Therefore, how to reduce the switching interruption delay of the terminal device is an urgent research topic. SUMMARY

[0006] The application provides a communication method and device, which can reduce the switching interruption delay of a terminal device and improve user communication experience.

[0007] To achieve the above object, the application adopts the following technical scheme:

[0008] In a first aspect, a communication method is provided, which can be applied to a terminal device side, such as a terminal device or a communication module in the terminal device, or a circuit or chip responsible for communication function in the terminal device (such as a modem chip, also known as a baseband chip, or a system on chip (SoC) chip or a system in package (SIP) chip containing a modem core). Taking the case where the method is applied to a terminal device, in the method: first configuration information from a first network device is received, the first configuration information is used to configure the time domain position of a reference signal corresponding to a target cell, and the first network device is a network device corresponding to a source cell of the terminal device. The reference signal from a second network device is received according to the first configuration information, the second network device is a network device corresponding to the target cell. Downlink synchronization is performed with the target cell according to the reference signal.

[0009] In the method, when cell switching occurs, the terminal device can receive first configuration information from a first network device corresponding to a source cell, which is used to configure the time domain position of a reference signal corresponding to a target cell, and the transmission time interval of the reference signal is less than the transmission period or SMTC period of a synchronization signal of the target cell, so that the terminal device can receive the reference signal at the corresponding time domain position to perform downlink synchronization with the target cell, without waiting for a long time to receive a synchronization signal to perform downlink synchronization with the target cell, which can reduce the switching interruption delay of the terminal device, improve the communication experience of the user, and ensure the continuity of user services.

[0010] In a possible design, the first configuration information can include time domain position information of at least one reference signal, and the time domain position information of the reference signal includes an offset value of the time domain starting position of the reference signal relative to a first time or a first time domain starting position. The first time is a time when the first network device stops providing coverage services for the source cell, and the first time domain starting position is a starting time domain position of a first synchronization signal sent by the first network device or a starting time domain position of a second synchronization signal sent by the second network device. In this way, the time domain position of the reference signal can be indicated by the offset value relative to the first time, or the synchronization signal sent by the first network device, or the synchronization signal sent by the second network device, i.e., the relative time domain position, without directly indicating the time domain position of each reference signal, which can save signaling overhead.

[0011] In a possible design, the first configuration information can further include a timing offset of the synchronization signal, where the timing offset of the synchronization signal is a time offset between a time domain position of the synchronization signal of the first network device and a time domain position of the synchronization signal of the second network device. In this way, the first configuration information can further include the timing offset of the synchronization signal between the first network device and the second network device, for the terminal device to perform downlink synchronization with the target cell.

[0012] In a possible design, the first configuration information can be carried in a broadcast message, for example, a system information block (SIB) 19, and can be applicable to a scenario where the terminal device performs handover based on hard handover or soft handover in a quasi-ground fixed cell scenario of satellite communication, or applicable to a scenario where the terminal device performs intra-site handover in ground communication.

[0013] In a possible design, the first configuration information can be carried in a radio resource control (RRC) message, where the RRC message is used to instruct the terminal device to perform handover to the target cell, and can be applicable to a scenario where the terminal device performs handover based on a layer 3 handover command in a quasi-ground fixed cell scenario of satellite communication, or applicable to a scenario where the terminal device performs inter-site handover in ground communication. It should be understood that the RRC message can be referred to as a handover command, and the disclosure does not limit this.

[0014] In a possible design, the downlink synchronization with the target cell according to the reference signal can include: performing fine time tracking of the target cell and obtaining all timing information according to the reference signal; or performing fine time tracking of the target cell and obtaining all timing information according to the reference signal and a second synchronization signal sent by the second network device. Before performing the fine time tracking of the target cell and obtaining all timing information, the method in the first aspect can further include: obtaining downlink timing of the target cell according to the ephemeris information of the first network device, the ephemeris information of the second network device, and the timing offset of the synchronization signal, where the timing offset of the synchronization signal is a time offset between a time domain position of the synchronization signal of the first network device and a time domain position of the synchronization signal of the second network device.

[0015] That is, before performing the fine time tracking of the target cell and obtaining all timing information according to the reference signal or according to the reference signal and the synchronization signal, the terminal device can obtain the downlink timing of the target cell according to the ephemeris information of the first network device, the ephemeris information of the second network device, and the timing offset of the synchronization signal.

[0016] Thus, when the terminal device performs downlink synchronization with the target cell, the terminal device does not need to wait for receiving the reference signal or the synchronization information of the target cell to perform downlink coarse synchronization, but only needs to wait for receiving the reference signal or the synchronization signal (i.e., the signal that arrives earliest among the reference signal and the synchronization signal) once to perform downlink fine synchronization, so that the downlink synchronization with the target cell can be completed, and the switching interruption delay of the terminal device can be reduced.

[0017] In a possible design, the downlink synchronization with the target cell according to the reference signal can include: performing downlink synchronization with the target cell according to the reference signal and the synchronization signal sent by the second network device. That is, the terminal device can perform downlink coarse synchronization (obtain the downlink timing of the target cell) and downlink fine synchronization (perform fine time tracking of the target cell and obtain all timing information) according to the signal that arrives earliest among the reference signal and the synchronization signal. At this time, the terminal device needs to wait for receiving the reference signal or the synchronization signal (i.e., which signal arrives earliest among the reference signal and the synchronization signal) once to perform downlink coarse synchronization, and then wait for receiving the reference signal or the synchronization signal (i.e., which signal arrives earliest among the reference signal and the synchronization signal) once to perform downlink fine synchronization, so that the downlink synchronization with the target cell can be completed.

[0018] In a possible design, the transmission time interval of the reference signal is less than the transmission period of the synchronization signal of the second network device or the measurement timing configuration (SSB-based measurement timing configuration, SMTC) period of the synchronization signal and the synchronization signal and the physical broadcast channel (physical broadcast channel, PBCH) block (synchronization signal and PBCH block, SSB), so that the switching interruption delay of the terminal device can be reduced.

[0019] In a possible design, the reference signal can be a channel state information-reference signal (channel state information-reference signal, CSI-RS) or a tracking reference signal (tracking reference signal, TRS).

[0020] In a second aspect, a communication method is provided, which can be applied to a network side, for example, a first network device of the network side, a module (for example, a circuit, a processor, a chip or a chip system, etc.) in the first network device, or a logic node, a logic module or software capable of realizing all or part of the functions of the first network device. Taking the case where the method is applied to the first network device, in the method: the first network device obtains first configuration information, the first configuration information being used to configure a time domain position of a reference signal corresponding to a target cell, the reference signal being used for downlink synchronization between a terminal device and the target cell, and the first network device being a network device corresponding to a source cell of the terminal device. The first network device sends the first configuration information to the terminal device.

[0021] In a possible design, the first configuration information can include time domain position information of at least one reference signal, the time domain position information of the reference signal including an offset value of a time domain starting position of the reference signal relative to a first time or a first time domain starting position, the first time being a time at which the first network device stops providing services for the source cell of the terminal device, and the first time domain starting position being a starting time domain position of a first synchronization signal sent by the first network device or a starting time domain position of a second synchronization signal sent by a second network device, the second network device being a network device corresponding to the target cell.

[0022] In a possible design, the first configuration information can further include a timing offset of a synchronization signal, the timing offset of the synchronization signal being a time offset between a time domain position of a synchronization signal of the first network device and a time domain position of a synchronization signal of the second network device.

[0023] In a possible design, the first configuration information can be carried in a broadcast message and sent.

[0024] In a possible design, the first configuration information can be carried in an RRC message, and the RRC message is used to instruct the terminal device to switch to the target cell.

[0025] In a possible design, a transmission time interval of the reference signal is less than a transmission period or SMTC period of a synchronization signal of the second network device, the second network device being a network device corresponding to the target cell.

[0026] In a possible design, the reference signal can be a CSI-RS or a TRS.

[0027] The technical effects of the method in the second aspect can be referred to the description of the technical effects in the first aspect, and details are not repeated.

[0028] In a third aspect, a communication method is provided, which can be applied to a network side, for example, a second network device of the network side, a module (for example, a circuit, a processor, a chip or a chip system, etc.) in the second network device, or a logic node, a logic module or software capable of realizing all or part of the functions of the second network device. Taking the case where the method is applied to the second network device, in the method: the second network device generates a reference signal, and the second network device is a network device corresponding to a target cell. The second network device sends the reference signal to a terminal device, and the reference signal is used for the terminal device to perform downlink synchronization with the target cell.

[0029] In the method, the second network device corresponding to the target cell can send the reference signal to the terminal device at a corresponding time domain position, and the transmission time interval of the reference signal is less than the transmission period or SMTC period of the synchronization signal of the target cell, so that the terminal device can receive the reference signal at the corresponding time domain position to perform downlink synchronization with the target cell, without waiting for a long time to receive the synchronization signal to perform downlink synchronization with the target cell, which can reduce the switching interruption delay of the terminal device, improve the communication experience of the user, and ensure the continuity of the user service.

[0030] In a possible design, the method of the third aspect can further include: the second network device obtaining area information of the terminal device. The second network device sending the reference signal to the terminal device can include: the second network device sending the reference signal to an area where the terminal device is located according to the area information, and the area where the terminal device is located is a part of the coverage range of the target cell. In this way, the second network device can send the reference signal according to the location of the terminal device, or send more intensive reference signals, so that the terminal device can quickly search for the signal of the target cell, and shorten the switching interruption delay.

[0031] In a possible design, the second network device obtaining the area information of the terminal device can include: the second network device receiving a switching request from a first network device, the switching request being used to request switching of the terminal device to the target cell, and the switching request including the area information, and the first network device being a network device corresponding to a source cell of the terminal device. This design scheme can be applied to the case where the terminal device performs switching based on hard switching.

[0032] In a possible design, the second network device sending the reference signal to the terminal device can include: the second network device sending the reference signal to the terminal device from a first time, and the first time being a time when the first network device stops providing coverage services for the source cell of the terminal device, and the first network device being a network device corresponding to the source cell of the terminal device. This design scheme can be applied to the case where the terminal device performs switching based on soft switching.

[0033] In a possible design, the second network device can send the reference signal to the terminal device, which can include: the second network device sends the reference signal to the terminal device from a second time point, the second time point being a time point at which the second network device provides coverage service for a target cell, and the second network device being a network device corresponding to the target cell. This design can be applicable to a case where the terminal device performs handover based on a layer 3 handover command.

[0034] In a possible design, the second network device can send the reference signal to the terminal device, which can include: the second network device sends the reference signal to the terminal device from a third time point, the third time point being determined according to at least one of the following: the first time point, the second time point, a transmission delay between the first network device and the second network device, or an air interface transmission delay between the first network device and the terminal device, and the first network device being a network device corresponding to a source cell of the terminal device.

[0035] In a possible design, after the terminal device in the first area accesses the target cell, the second network device stops sending the reference signal to the first area, and the first area belongs to the target cell. That is, the second network device can stop sending the reference signal to a specific area or the target cell after determining that all terminal devices in the specific area or the target cell access the target cell.

[0036] In a possible design, a transmission time interval of the reference signal is less than a transmission period or SMTC period of a synchronization signal of the second network device.

[0037] In a possible design, the reference signal can be a CSI-RS or a TRS.

[0038] In a fourth aspect, a communication apparatus is provided for implementing the methods described above. The communication apparatus can be the terminal device in the first aspect, or an apparatus including the terminal device, or an apparatus included in the terminal device, such as a chip. The communication apparatus includes corresponding modules, units, or means for implementing the methods described in the first aspect, which can be implemented by hardware, software, or by executing corresponding software by hardware. The hardware or software includes one or more modules or units corresponding to the functions described above.

[0039] In some possible design, the communication apparatus includes a processing module and a transceiver module. The transceiver module is configured to receive first configuration information from a first network device, the first configuration information being used to configure a time domain position of a reference signal corresponding to a target cell, and the first network device being a network device corresponding to a source cell of the terminal device. The transceiver module is further configured to receive the reference signal from a second network device according to the first configuration information, and the second network device being a network device corresponding to the target cell. The processing module is configured to perform downlink synchronization with the target cell according to the reference signal.

[0040] In a possible design, the first configuration information can include time domain position information of at least one reference signal, and the time domain position information of the reference signal includes an offset value of a time domain starting position of the reference signal relative to a first time or a first time domain starting position. The first time is a time at which the first network device stops providing coverage service for the source cell, and the first time domain starting position is a starting time domain position of a first synchronization signal sent by the first network device or a starting time domain position of a second synchronization signal sent by the second network device.

[0041] In a possible design, the first configuration information can further include a timing offset of a synchronization signal, and the timing offset of the synchronization signal is a time offset between a time domain position of a synchronization signal of the first network device and a time domain position of a synchronization signal of the second network device.

[0042] In a possible design, the first configuration information can be sent in a broadcast message.

[0043] In a possible design, the first configuration information can be carried in an RRC message, and the RRC message is used to instruct the terminal device to switch to the target cell.

[0044] In a possible design, the processing module configured to perform downlink synchronization with the target cell according to the reference signal can include: the processing module configured to perform fine time tracking of the target cell and obtain all timing information according to the reference signal; or perform fine time tracking of the target cell and obtain all timing information according to the reference signal and the second synchronization signal sent by the second network device. Before performing fine time tracking of the target cell and obtaining all timing information, the processing module is further configured to obtain downlink timing of the target cell according to ephemeris information of the first network device, ephemeris information of the second network device, and the timing offset of the synchronization signal, and the timing offset of the synchronization signal is a time offset between a time domain position of a synchronization signal of the first network device and a time domain position of a synchronization signal of the second network device.

[0045] In a possible design, the processing module, configured to perform downlink synchronization with the target cell according to the reference signal, can include: a processing module configured to perform downlink synchronization with the target cell according to the reference signal and a synchronization signal sent by the second network device.

[0046] In a possible design, the transmission time interval of the reference signal is less than the transmission period or SMTC period of the synchronization signal of the second network device.

[0047] In a possible design, the reference signal can be a CSI-RS or a TRS.

[0048] In a possible design, the transceiver module can include a receiving module and a sending module. The sending module is configured to implement the sending function of the communication apparatus in the fourth aspect, and the receiving module is configured to implement the receiving function of the communication apparatus in the fourth aspect.

[0049] In a possible design, the communication apparatus in the fourth aspect can further include a storage module that stores a program or an instruction. When the processing module executes the program or the instruction, the communication apparatus in the fourth aspect can execute the method in the first aspect.

[0050] In the fifth aspect, a communication apparatus is provided for implementing the above-described various methods. The communication apparatus can be the first network device in the second aspect, or a device containing the first network device, or a device contained in the first network device, such as a chip. The communication apparatus includes corresponding modules, units, or means for implementing the method in the second aspect, which can be implemented by hardware, software, or by hardware executing corresponding software. The hardware or software includes one or more modules or units corresponding to the above functions.

[0051] In some possible designs, the communication apparatus includes a processing module and a transceiver module. The processing module is configured to acquire first configuration information, the first configuration information being used to configure a time domain position of a reference signal corresponding to a target cell, the reference signal being used for downlink synchronization between a terminal device and the target cell, and the communication apparatus being a network device corresponding to a source cell of the terminal device. The transceiver module is configured to send the first configuration information to the terminal device.

[0052] In a possible design, the first configuration information can include time domain position information of the at least one reference signal, and the time domain position information of the reference signal includes an offset value of a time domain starting position of the reference signal relative to a first time or a first time domain starting position. The first time is a time when the communication apparatus stops providing service for a source cell of the terminal device. The first time domain starting position is a starting time domain position of a first synchronization signal sent by the communication apparatus, or a starting time domain position of a second synchronization signal sent by a second network device. The second network device is a network device corresponding to the target cell.

[0053] In a possible design, the first configuration information can further include a timing offset of the synchronization signal, where the timing offset is a time offset between a time domain position of the synchronization signal of the communication apparatus and a time domain position of the synchronization signal of the second network device.

[0054] In a possible design, the first configuration information can be carried in a broadcast message.

[0055] In a possible design, the first configuration information can be carried in an RRC message, where the RRC message is used to instruct the terminal device to switch to the target cell.

[0056] In a possible design, a transmission time interval of the reference signal is less than a transmission period or SMTC period of the synchronization signal of the second network device. The second network device is a network device corresponding to the target cell.

[0057] In a possible design, the reference signal can be a CSI-RS or a TRS.

[0058] In a possible design, the transceiver module can include a receiving module and a sending module. The sending module is configured to implement the sending function of the communication apparatus in the fifth aspect, and the receiving module is configured to implement the receiving function of the communication apparatus in the fifth aspect.

[0059] In a possible design, the communication apparatus in the fifth aspect can further include a storage module that stores a program or an instruction. When the processing module executes the program or the instruction, the communication apparatus in the fifth aspect can execute the method in the second aspect.

[0060] In a sixth aspect, a communication apparatus is provided for implementing the methods described above. The communication apparatus can be a network device in the third aspect, or a chip containing the network device, or a chip included in the network device. The communication apparatus includes corresponding modules, units, or means for implementing the methods of the third aspect, which can be implemented by hardware, software, or by executing corresponding software with hardware. The hardware or software includes one or more modules or units corresponding to the functions described above.

[0061] In some possible designs, the communication apparatus includes a processing module and a transceiver module. The processing module is configured to generate a reference signal, and the communication apparatus is a network device corresponding to a target cell. The transceiver module is configured to send the reference signal to a terminal device, and the reference signal is used by the terminal device to perform downlink synchronization with the target cell.

[0062] In a possible design, the processing module is further configured to obtain area information of the terminal device. The transceiver module is configured to send the reference signal to the terminal device, and the transceiver module can include a transceiver module configured to send the reference signal to an area where the terminal device is located according to the area information, and the area where the terminal device is located is a part of a coverage range of the target cell.

[0063] In a possible design, the processing module is configured to obtain the area information of the terminal device, and the processing module can include a processing module configured to control the transceiver module to receive a handover request from a first network device, the handover request being used to request to hand over the terminal device to the target cell, and the handover request including the area information, and the first network device being a network device corresponding to a source cell of the terminal device.

[0064] In a possible design, the transceiver module is configured to send the reference signal to the terminal device, and the transceiver module can include a transceiver module configured to send the reference signal to the terminal device starting from a first time, and the first time being a time when a first network device stops providing coverage service for a source cell of the terminal device, and the first network device being a network device corresponding to the source cell of the terminal device.

[0065] In a possible design, the transceiver module is configured to send the reference signal to the terminal device, and the transceiver module can include a transceiver module configured to send the reference signal to the terminal device starting from a second time, and the second time being a time when the communication apparatus provides coverage service for the target cell.

[0066] In a possible design, the transceiver module, configured to send the reference signal to the terminal device, can include: a transceiver module, configured to send the reference signal to the terminal device starting from a third time, and the third time is determined according to at least one of the following: the first time, the second time, a transmission delay between the first network device and the communication apparatus, or an air interface transmission delay between the first network device and the terminal device, and the first network device is a network device corresponding to a source cell of the terminal device.

[0067] In a possible design, after the terminal device in the first area accesses the target cell, the transceiver module is further configured to stop sending the reference signal to the first area, and the first area belongs to the target cell.

[0068] In a possible design, a transmission time interval of the reference signal is less than a transmission period of a synchronization signal of the communication apparatus or an SMTC period.

[0069] In a possible design, the reference signal can be a CSI-RS or a TRS.

[0070] In a possible design, the transceiver module can include a receiving module and a sending module. The sending module is configured to implement the sending function of the communication apparatus in the sixth aspect, and the receiving module is configured to implement the receiving function of the communication apparatus in the sixth aspect.

[0071] In a possible design, the communication apparatus in the sixth aspect can further include a storage module, which stores a program or an instruction. When the processing module executes the program or the instruction, the communication apparatus in the sixth aspect can execute the method in the third aspect.

[0072] In a seventh aspect, a communication apparatus is provided, which includes an interface circuit and one or more processors. The one or more processors are coupled with a memory. The memory is configured to store part or all of necessary computer programs or instructions for implementing functions related to the first aspect. The one or more processors can execute the computer programs or instructions, and when the computer programs or instructions are executed, the communication apparatus implements the method in any possible design or implementation manner in the first aspect. The interface circuit is configured to implement a communication function within the communication apparatus and / or a communication function of the communication apparatus with other devices or components.

[0073] In a possible design, the processor is configured to communicate with other devices or components through the interface circuit.

[0074] In a possible design, the communication apparatus can further include the memory.

[0075] The communication device can be a terminal device, a communication module in the terminal device, or a chip responsible for communication functions in the terminal device, such as a modem chip (also known as a baseband chip) or a SoC or SIP chip containing a modem module.

[0076] In an eighth aspect, a communication device is provided, which includes an interface circuit and one or more processors. The one or more processors are coupled with a memory. The memory is configured to store part or all of the computer programs or instructions necessary to implement the functions described in the second aspect or the third aspect. The one or more processors can execute the computer programs or instructions, which, when executed, cause the communication device to implement the method in any possible design or implementation manner of the second aspect or the third aspect. The interface circuit is configured to implement the communication function within the communication device and / or the communication function of the communication device with other devices or components.

[0077] In a ninth aspect, a communication system is provided, which includes a terminal device for implementing the method described in the first aspect, a first network device for implementing the method described in the second aspect, and a second network device for implementing the method described in the third aspect.

[0078] In a tenth aspect, a chip is provided, in which instructions are stored, which, when the chip is running on a communication device, cause the method described in any one of the first aspect to the third aspect to be implemented.

[0079] In an eleventh aspect, a computer-readable storage medium is provided, in which computer-readable instructions are stored, which, when read and executed by a computer, cause the computer to execute the method in any possible design of the first aspect to the third aspect.

[0080] In a twelfth aspect, a computer program product containing instructions is provided, which, when read and executed by a computer, cause the computer to execute the method in any possible design of the first aspect to the third aspect. BRIEF DESCRIPTION OF DRAWINGS

[0081] FIG. 1 is a schematic diagram of an architecture of a working mode of a satellite according to an embodiment of the present application;

[0082] FIG. 2 is a schematic diagram of a scenario between a satellite and a cell according to an embodiment of the present application;

[0083] FIG. 3 is a schematic diagram of a scenario of TA application according to an embodiment of the present application;

[0084] FIG. 4 is a schematic diagram of a scenario of TA calculation in NTN communication according to an embodiment of the present application;

[0085] FIG. 5 is a schematic diagram of a satellite switching scenario in a quasi-ground fixed cell scenario according to an embodiment of the present application;

[0086] FIG. 6 is a schematic diagram of a satellite polling SSB scenario according to an embodiment of the present application;

[0087] FIG. 7 is a schematic diagram of an architecture of a communication system according to an embodiment of the present application;

[0088] FIG. 8 is a schematic diagram of an architecture of a CU-DU according to an embodiment of the present application;

[0089] FIG. 9 is a schematic diagram of an O-RAN architecture according to an embodiment of the present application;

[0090] FIG. 10 is a schematic diagram of a flow of a communication method according to an embodiment of the present application;

[0091] FIG. 11 is a schematic diagram of a reference signal transmission scenario according to an embodiment of the present application;

[0092] FIG. 12 is a schematic diagram of a structure of a communication apparatus according to an embodiment of the present application;

[0093] FIG. 13 is a schematic diagram of another structure of a communication apparatus according to an embodiment of the present application. DETAILED DESCRIPTION

[0094] In order to better understand the embodiments of the present application, the following points are explained before the embodiments of the present application are introduced.

[0095] First, in the embodiments of the present application, the first, second, and various numbers are only for distinguishing and are not used to limit the scope of the embodiments of the present application. For example, the first network device and the second network device are only used to distinguish different network devices and do not limit the order. Those skilled in the art can understand that the words “first”, “second”, etc. do not limit the number and execution order, and the words “first”, “second”, etc. do not necessarily mean different.

[0096] Second, in the embodiments of the present application, the descriptions such as “when”, “in the case of”, “if”, and “whether” mean that the device (such as a terminal device or a network device) will make corresponding processing under certain objective circumstances, and are not limited to time, and do not require the device (such as a terminal device or a network device) to have a judgment action when implemented, and do not mean that there are other limitations.

[0097] Third, in the embodiments of the present application, the word "exemplary" or "for example" is used to mean "an example of" or "an example, only. Any embodiment or design solution described in the embodiments of the present application as "exemplary" or "for example" should not be interpreted as being more preferred or superior to other embodiments or design solutions. Rather, the use of "exemplary" or "for example" is intended to present relevant concepts in a concrete manner, facilitating understanding.

[0098] Fourth, in the embodiments of the present application, "at least one" means one or more, and "multiple" means two or more. The association relationship between the associated objects is described, which means that there can be three kinds of relationships, for example, A and / or B, which can represent the following three cases: A exists alone, A and B exist together, and B exists alone, wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it. "At least one of the following" or similar expressions means any combination of multiple items, including any combination of single item or multiple items. For example, at least one of a, b, or c can represent a, b, c, a-b, a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple.

[0099] Finally, the network architecture and business scenarios described in the embodiments of the present application are used to more clearly illustrate the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided by the embodiments of the present application. Those skilled in the art can know that, with the evolution of network architecture and the appearance of new business scenarios, the technical solutions provided by the embodiments of the present application are also applicable to similar technical problems.

[0100] The embodiments of the present application will present various aspects, embodiments or features around a system which can include multiple devices, components, modules, etc. It should be understood and appreciated that each system can include additional devices, components, modules, etc., and / or can not include all the devices, components, modules, etc. discussed in connection with the drawings. In addition, combinations of these solutions can also be used.

[0101] The technical solutions of the embodiments of the present application can be applied to non-ground network communication systems and ground network communication systems, for example, non-terrestrial network (NTN) communication systems, such as satellite communication systems, 4th generation (4G) mobile communication systems, such as long term evolution (LTE) systems, worldwide interoperability for microwave access (WiMAX) communication systems, 5th generation (5G) mobile communication systems, such as new radio (NR) systems, and future communication systems, etc.

[0102] For the convenience of understanding, the related terms, concepts or technologies that may be involved in the embodiments of the present application will be introduced first as follows:

[0103] 1. NTN communication

[0104] NTN communication has the advantages of wide coverage, long communication distance, high reliability, great flexibility, high throughput, etc., and is not affected by geographical environment, climate conditions and natural disasters, and has been widely used in aviation communication, maritime communication, military communication and other fields. Introducing NTN into 5G mobile networks can improve the performance of communication systems. Satellite communication systems and high altitude platform communication systems (HAPS) are typical non-ground communication systems. On the one hand, satellite networks can provide communication services for areas that are difficult for ground networks to cover, such as oceans, forests, deserts or remote areas, etc.; on the other hand, satellite networks can enhance the reliability of 5G communication, such as providing more stable communication services for users in high-speed mobile scenarios such as trains and airplanes. In addition, satellite networks can also provide more data transmission resources to support a larger number of connections. In the subsequent description, the satellite communication system is taken as an example of a non-ground communication system, but it can be extended to other non-ground communication systems, i.e., the satellite mentioned in the subsequent description can be extended to other non-ground network devices.

[0105] Generally speaking, the higher the orbit of a satellite, the larger its coverage area, but the longer the communication delay. According to the orbit height, satellites can be divided into:

[0106] (1) Low Earth Orbit (LEO): orbit height of 160-2000 kilometers (km);

[0107] (2) Medium Earth Orbit (MEO): orbit height of 2000-35786 km;

[0108] (3) Geostationary Earth Orbit (GEO): orbit height is 35786 km;

[0109] Wherein, GEO is a synchronous earth satellite orbit, the satellite running on this orbit is stationary relative to the ground; LEO and MEO are collectively referred to as non-geostationary orbit (NGSO), the satellite running on such orbit moves at high speed relative to the ground.

[0110] For NGSO, according to whether the satellite beam moves with the satellite, it can be further divided into earth moving cell and quasi earth fixed cell (also can be called quasi ground stationary cell). For earth moving cell, the cell is moving relative to the ground, and the satellite beam pointing follows the satellite movement; for earth fixed cell, the cell is fixed relative to the ground within a certain time, and the satellite antenna can use its beamforming capability to point the beam to a certain area fixed on the ground within a certain time.

[0111] By deploying a large number of satellites in low orbit, medium-high orbit, an NTN network is formed.

[0112] According to the working mode, the satellite can be generally divided into two categories. The first type is transparent, as shown in (a) of FIG. 1, for example, in the 5G system, the satellite transmits the information of the cell of the ground network device (such as base station), the gNB connects the data network (DN) communication through the 5G core network (CN), and the role of the satellite is wireless frequency filtering, frequency conversion and amplification, that is, the satellite mainly acts as layer 1 relay (L1 relay), regenerates the physical layer signal, and does not have other higher protocol layers, at this time, the satellite, NTN gateway and base station are equivalent to next generation (NG)-radio access network (RAN).

[0113] The second type is regenerative, the satellite has the processing function of a base station, equivalent to NG-RAN, and can communicate with a DN through a 5G CN. In the regenerative mode, it can be further divided into a regenerative satellite without an inter-satellite link (ISL), i.e., there is no inter-satellite link between satellites, as shown in (b) of FIG. 1; a regenerative satellite with an inter-satellite link, i.e., there is an interface between satellites that can directly interact with data, where the inter-satellite link is an Xn interface, as shown in (c) of FIG. 1; and a satellite with only the distributed unit (DU) processing function of a base station, where the satellite acts as a DU in this scenario.

[0114] For ease of description, the satellite in transparent forwarding mode will be referred to as a transparent satellite, and the regenerative satellite with the base station function will be referred to as a regenerative satellite in the embodiments of the present application.

[0115] In ground communication, a ground network device can have multiple cells, and generally, the identities of these cells, such as a physical cell identifier (PCI) and a broadcasted area identifier (such as a tracking area code (TAC) or a tracking area identity (TAI)), do not change for a long time. In satellite communication, the satellite is moving at a high speed, resulting in a change in the physical area covered by the satellite. For the identities of the cells and the broadcasted area identifier in satellite communication, there are currently two solutions as follows.

[0116] Scheme one: the identity is bound with the physical area. For a certain physical area, the cell identity corresponding to the area and the broadcasted area identity are unchanged. When a satellite (referred to as old satellite) moves away, other satellites (referred to as new satellite) provide services for the area, the cell identity in the new satellite and the broadcasted area identity are the same as the old satellite, as shown in (a) of FIG. 2, satellite 1 covers the cell #1 bound with geographical position 1 at 10:00:00, satellite 1 moves to cover the cell #2 bound with geographical position 2 at 10:15:00, satellite 1 moves to cover the cell #3 bound with geographical position 3 at 10:30:00, if satellite 2 moves to cover the cell #1 bound with geographical position 1, then the PCI and the area identity of the cell #1 are the same at satellite 1 and satellite 2, and the satellite coverage of the cell #2 and the cell #3 is similar. The main advantage of this scheme is that, for a certain physical area, assuming the position of the terminal device is unchanged, since the terminal device senses the unchanged cells, the network side does not need to trigger the cell switching process for the terminal device, thereby reducing the number of switching in the network and reducing the signaling overhead of the Uu interface. In this scheme, generally, a satellite covers a certain physical area in a time period, when the satellite cannot provide coverage for the physical area due to the movement of the satellite, other satellites provide services for the physical area. The cell under this scheme is also referred to as quasi-ground fixed cell.

[0117] Scheme two: the identity is bound with the satellite. When the satellite moves and the coverage area of the satellite changes, the identity in the satellite does not change, as shown in (b) of FIG. 2, satellite 1 covers geographical position 1 at 10:00:00, at this time, the cell of geographical position 1 is cell #1, satellite 1 moves to cover geographical position 2 at 10:15:00, at this time, the cell #1 becomes the cell corresponding to geographical position 2, satellite 1 moves to cover geographical position 3 at 10:30:00, at this time, the cell #1 becomes the cell corresponding to geographical position 3, the cell identity and the area identity of each coverage area of satellite 1 do not change during the movement. In this scheme, it can be understood that the identity is scanned on the physical coverage area along with the movement of the satellite. In this scheme, even if the position of a certain terminal device is unchanged, since the satellite is moving, when the satellite cannot cover the terminal device, the network side needs to inform the terminal device to switch to other cell. The cell under this scheme is also referred to as ground moving cell.

[0118] 2. Timing advance (TA)

[0119] TA is used for terminal device uplink transmission, which means that the uplink frame sent by the terminal device is ahead of the downlink frame received by a certain time. In order to maintain the synchronization of the uplink time of the terminal device, the uplink frame of the terminal device needs to be sent ahead of the downlink frame by a TA time length, as shown in FIG. 3, the terminal device sends the uplink frame ahead of the downlink frame by a T TA time length. After the terminal device is turned on, it first performs cell search, obtains downlink time synchronization through the synchronization signal broadcast by the cell, and then performs uplink time synchronization with the cell.

[0120] When TA is not used, because the distances from the terminal devices at different positions in the cell to the base station are different, the time delays of the signals sent by the terminal devices to the network device are different, causing the uplink signals of the terminal devices to be misaligned in time when reaching the network device.

[0121] When TA is used, the signals sent by the terminal devices at different positions in the cell reach the network device in time, so that the network device can process all the terminal devices in the same cell according to one time. Generally, the TA value is the time delay caused by the two-way distance between the network device and the terminal device, which is the reason for introducing TA.

[0122] In the ground communication network, T TA =(N TA +N TA,offset )T c ;

[0123] In the NTN,

[0124] wherein, N TA is a TA adjustment amount, which is calculated by the network side according to the time of the actually received uplink data and the TA value reported by the terminal device. In the random access response or in the media access control (MAC) control element (CE) of the absolute value adjustment of TA, the network device carries the absolute value T A to the terminal device, T A = 0, 1, 2,..., 3846, N TA =T A ·16·64 / 2μ, μ is the subcarrier spacing (SCS) number, in NR, the SCS corresponding to the SCS number μ is 2 μ ·15 kilo hertz (kHz). It can be considered that for initial access, N TA = 0.

[0125] N TA,offset is a fixed uplink-downlink frame offset configured by the network side, a limited number of fixed values in a time division duplexing (TDD) system, and the parameter is 0 in a frequency division duplexing (FDD). Indicated by the information element n-TimingAdvanceOffset in the system message of the serving cell; if not provided, the terminal device uses the default value.

[0126] T c is the minimum time unit, which can be a fixed value predefined in the 3rd generation partnership project (3GPP) technical specification (TS) (for example, 0.509 nanoseconds (ns) in the 3GPP technical specification).

[0127] is the TA that needs to be additionally calculated and compensated by the terminal device in the satellite communication scenario, is the transmission delay from the satellite to the reference point (RP), represented by Common TA, which is calculated by the network side and delivered to the terminal device, is the transmission delay from the terminal device to the satellite, which is the service link transmission delay, calculated by the terminal device according to global navigation satellite system (GNSS) information and ephemeris information.

[0128] As shown in FIG. 4, it is a schematic diagram of TA in NTN. The link between the terminal device and the satellite is called a service link, and the ephemeris information of the satellite is delivered in the system message. The terminal device can calculate the round-trip time (RTT) between the terminal device and the satellite through its own location and the ephemeris parameters of the satellite. The link between the satellite and the NTN gateway is called a feeder link, wherein the feeder link is divided into two segments by the RP, the Common TA of the cell is delivered in the system message, and the RP corresponds to a time point, and the Common TA corresponding to the time point and the offset (ta-commonDrift) and the offset change (ta-commonDriftVariant). The terminal device calculates the RTT between the satellite and the reference point at the current time point, that is, the Common TA, according to these parameters.

[0129] The RTT delay between the RP and the NTN gateway is compensated by the ground network device.

[0130] When the satellite is in transparent mode, the terminal device needs to compensate for the service link delay and Common TA; when the satellite is in regenerative mode, the terminal device only needs to compensate for the service link delay, and the Common TA can be considered as 0, because the satellite assumes all functions of the DU or base station.

[0131] In the embodiments of the present application, the RP is also referred to as an uplink timing reference point, and no limitation is made thereto.

[0132] 3、SMTC

[0133] In order to ensure that the terminal device accurately and completely measures all SSB beams under each cell, when the network issues a measurement configuration, in addition to indicating the SSB frequency points that need to be measured, it will also indicate the timing position and duration of starting SSB measurement, thereby introducing the concept of SMTC. SMTC information is used to indicate the window configured by the network device for the terminal device to perform SSB-based measurement. Through the configuration of SMTC, the time window for the terminal device to search for SSB can be effectively indicated, and unnecessary measurement power consumption of the terminal device can be reduced.

[0134] The SMTC information can include one or more of the length of the measurement window of the SSB of the cell, the period of the measurement window, and the offset. One or more of the period of the measurement window and the offset can be used to determine the time domain starting position of the measurement window. The time domain starting position and the length of the measurement window can be used to determine the time domain position of the measurement window.

[0135] Taking SSB-based measurement as an example, the SMTC information can also be extended to indicate the measurement window configured by the network device for the terminal device to perform measurement based on other downlink reference signals, such as CSI-RS, demodulation reference signal (DMRS), etc. When extended to the measurement window of other reference signals, SMTC can be another name.

[0136] The system frame number (SFN) where the measurement window is located satisfies the following formula: SFN mod T = floor(offset / 10). SFN is the system frame number where the measurement window is located, mod is a remainder operation, floor is a down-rounding operation, offset is an offset, T = ceil(periodicity / 10). ceil is an up-rounding operation, and periodicity is the period of the measurement window. If the period of the measurement window is greater than 5 subframes, the subframe number where the measurement window is located satisfies the following formula: subframe = offset mod 10. If the period of the measurement window is less than or equal to 5 subframes, the subframe number where the measurement window is located satisfies the following formula: subframe = offset, or subframe = offset + 5. subframe is the subframe number where the measurement window is located. offset and periodicity are configured by the network to the terminal device.

[0137] 4. Handover

[0138] In a terrestrial communication scenario, the terminal device will undergo cell handover in the process of movement. The cell handover can be an intra-station cell handover, i.e., the terminal device switches between different cells of the same network device. The source network device and the target network device are the same, and the source cell and the target cell are different. The cell handover can also be an inter-station cell handover, i.e., the terminal device switches between cells of different network devices. The source network device and the target network device are different, and the source cell and the target cell are different.

[0139] In a satellite communication scenario, the movement of the satellite will also cause the terminal device to undergo cell handover.

[0140] In a quasi-terrestrial fixed cell scenario, the satellite will adjust its beam so that the range of the beam coverage remains unchanged for a period of time, and then the next satellite will provide coverage when it cannot provide service. As shown in FIG. 5, satellite 1 covers cell #1. In the process of movement, satellite 1 will adjust the beam direction to maintain coverage of cell #1 for a period of time, until satellite 1 cannot provide coverage service for cell #1, and satellite 2 provides coverage service for cell #1.

[0141] If the satellite is a transparent satellite, the ground network device (such as a ground base station) corresponding to the cell #1 remains unchanged, that is, the satellite 1 and the satellite 2 provide coverage services for the cell #1 while connecting to the same ground network device. In the 3GPP protocol version (R) 17, the change of the satellite is also a handover for the ground terminal device, which can be considered as a handover without changing the serving cell (that is, the source cell and the target cell are the same), and the layer (L) 3 handover signaling process needs to be introduced, which will face the problem of signaling storm caused by simultaneous handover of many terminals.

[0142] In the quasi-ground fixed cell scenario, the ground network device before and after the satellite handover remains unchanged, and the satellite only undertakes the function of signal amplification, so the PCI of the cell does not need to be changed before and after the satellite handover, and the L3 signaling handover does not need to be introduced. The terminal device only needs to synchronize with the ground network device again after the new satellite (target satellite) comes, and the configuration on the terminal device and the ground network device side remains unchanged, which can solve the problem of signaling storm caused by handover in this scenario. In other words: all configurations of the cell remain unchanged, only the distance of signal transmission to the terminal device changes, and the terminal device synchronizes with the ground network device again, so the handover process does not need to be triggered, and there is no L3 signaling in the whole process.

[0143] In the quasi-ground fixed cell scenario, the terminal device has the following two satellite handover modes:

[0144] (1) Hard handover

[0145] For hard handover, the terminal device disconnects the connection with the source satellite after the time t-service, and synchronizes with the target satellite. The time parameter t-service represents the time when the source satellite stops serving the current coverage area (serving cell). At this time, the handover interruption delay of the terminal device mainly includes two parts: one part is the time required for the terminal device to search for the signal of the target satellite (that is, T search , which is equivalent to coarse synchronization), and this part of the delay depends on the end time (that is, T first_SSB ) of the terminal device searching for the first complete SSB burst set of the target satellite; the other part is the time for the terminal device to perform fine time tracking and obtain all timing information of the target cell (that is, T Δ , which is equivalent to fine synchronization), which generally equals to the SMTC period. For details, please refer to the related description in TS38.133 in 3GPP, which will not be described here.

[0146] The handover interruption delay of the hard handover should be less than T interrupt : T interrupt = T search+T IU +T processing +T Δ +T margin milliseconds (ms); wherein, T IU is the interruption uncertainty when acquiring the first uplink transmission resource, which can be a configured grant physical uplink shared channel (PUSCH) based on network configuration or scheduling, a dynamic grant based PUSCH, a scheduling request (SR) based on physical uplink control channel (PUCCH), or a physical random access channel (PRACH) if the TA timer is not running and there is no SR of PUCCH; T processing is the processing time of the terminal device, which can reach 10 ms; T margin is the SSB post-processing time, which can reach 2 ms.

[0147] (2) Soft handover

[0148] For soft handover, the ground network device broadcasts a time t-start to the terminal device through the source satellite, t-start representing the time when the target satellite starts to provide coverage for the current service cell. The terminal device performs downlink synchronization (including coarse synchronization and fine synchronization) with the current cell through the target satellite at a time between t-start and t-service, but the terminal device does not disconnect the connection with the source satellite between [t-start, t-service] and disconnects the connection with the source satellite after t-service. At this time, the handover interruption delay of the terminal device is related to the interval between [t-start, t-service] in addition to the time delay required for coarse synchronization and fine synchronization.

[0149] The handover interruption delay of soft handover should be less than T soft_switch : T soft_switch = (t-service-t-start, T search + T Δ + T margin )+ T IU + T processing ms, and the related parameters are introduced above for hard handover.

[0150] In the hard handover scenario, the handover scheme with unchanged PCI has no interference, and for the soft handover, there may be signal interference due to different satellites covering the same area. To solve this problem, the PCI of the cell can be changed before and after the satellite handover, but the terminal device configuration remains unchanged or changes a little (the part strongly related to PCI can be changed). The network side indicates the unchanged or slightly changed PCI after the satellite handover configuration. The terminal device searches for the changed PCI and performs downlink or uplink synchronization, and does not need L3 signaling process. The subsequent unified PCI change or unchanged handover without L3 handover command is called L3 signaling-free handover.

[0151] The above-mentioned hard handover and soft handover can be called L3 signaling-free handover, or unchanged PCI handover, or satellite change requiring resynchronization handover.

[0152] It should be understood that if the satellite is a regenerative satellite, the satellite has the function of a base station, and at this time there is no ground network equipment connected between the satellites before and after the handover, and the source satellite and the target satellite are respectively the source network equipment and the target network equipment, and the terminal device performs downlink synchronization with the target satellite in the service cell during handover.

[0153] In addition, for the handover with L3 handover command, the handover interruption delay of the terminal device also mainly includes coarse synchronization and fine synchronization, but both of them depend on the SMTC period length. The handover interruption delay should be less than T interrupt : T interrupt = T search + T IU + T processing + T Δ + T margin ms; wherein T search is the time from receiving the handover command by the terminal device to searching for the target cell; for random access-based handover, T IU is the interruption uncertainty when the first available PRACH occasion is acquired in the new cell, which can reach the sum of the SSB and PRACH occasion association period and 10ms, and for random access-free handover, T IU is the interruption uncertainty when the first uplink transmission resource is acquired, which can be a configured grant physical uplink shared channel based on network configuration or scheduling, a PUSCH based on dynamic grant, a PUCCH-based SR, or if the TA timer is not running and there is no PUCCH-based SR, the uplink transmission resource is PRACH; T processing is the processing time of the terminal device, which can reach 20ms; T Δ is the time for fine time tracking and acquiring all timing information of the target cell; T marginis the time of SSB post-processing, which can reach 2 ms.

[0154] In the earth moving cell scenario, the cell moves with the moving of the transparent satellite, and when the terminal device switches between two cells, the network device corresponding to the source cell sends L1 (for example, indicates through a physical layer channel) signaling or L2 signaling (for example, indicates through a MAC layer control unit) to the terminal device, instructing the terminal device to switch from the source cell to the target cell. When the terminal device switches from the source cell to the target cell, only the PCI of the cell needs to be changed, but the configuration of the terminal device remains unchanged or changes a little (the part related to PCI can be changed). In this switching process, the length of the switching interruption delay depends on the length of time from the terminal device determining to switch the satellite to receiving the SSB from the target satellite and the length of the SMTC cycle.

[0155] Therefore, whether in a ground communication scenario or a satellite communication scenario, the terminal device may switch due to the movement of the terminal device or the movement of the satellite, and the length of the switching interruption delay depends on the time of downlink synchronization of the terminal device with the target network device in the target cell. The downlink synchronization time is related to the length of time from the terminal device determining to switch the cell or the satellite to receiving the SSB from the target satellite or the target cell and the length of the SMTC cycle. The length of the SMTC cycle is usually the same as the transmission period of the SSB. When the transmission period of the SSB is relatively long, the switching interruption delay is relatively large, which affects the communication experience of the user. In some scenarios, due to the limited power of the satellite, the satellite can only transmit SSB in a limited area at the same time, so each area needs to poll the transmission of the SSB, as shown in FIG. 6. In this way, the SSB period needs to be expanded from 20 ms to 640 ms, which makes the switching interruption delay larger.

[0156] When the terminal device switches between cells or satellites, how to solve the problem of a relatively large downlink synchronization delay caused by a relatively long SSB transmission period, thereby causing a relatively large switching interruption delay, is a problem to be studied.

[0157] Therefore, an embodiment of the present application provides a communication method and device, which configures a temporary reference signal for downlink synchronization with a target cell when the terminal device switches, and can solve the problem of a relatively large switching interruption delay caused by a relatively long SSB transmission period, thereby improving the communication experience of the user.

[0158] In order to facilitate understanding of the embodiments of the present application, a communication system shown in FIG. 7 is taken as an example to explain the communication system applicable to the embodiments of the present application in detail. As shown in FIG. 7, the communication system includes a terminal device, a first network device, and a second network device, which can directly communicate with each other or indirectly communicate with each other, and the present application does not limit the communication mode. The first network device is a network device corresponding to the source cell of the terminal device, and the second network device is a network device corresponding to the target cell of the terminal device.

[0159] In a terrestrial communication network, the first network device and the second network device can be network nodes located on the ground, which can be referred to as terrestrial network devices, and the terrestrial network devices are generally arranged at a position close to the ground. For example, the terrestrial network devices can be installed on or in a building or a tower. The terrestrial communication network or the terrestrial network devices can also be referred to as being located on land or on the ground, and can additionally or alternatively include networks or devices implemented on or in water.

[0160] In this scenario, when the terminal device performs intra-site handover, the first network device and the second network device are the same network device, and the source cell and the target cell are different cells under the same network device; when the terminal device performs inter-site handover, the first network device and the second network device are different network devices, and the source cell and the target cell are different cells under different network devices.

[0161] In a non-terrestrial communication network, taking satellite communication as an example:

[0162] In the case where the satellite is a transparent satellite, the first network device and the second network device are terrestrial network devices, and one satellite is connected before and after the terminal device switches, and the terminal device communicates with the satellite. In this case, it can also be divided into the following two scenarios:

[0163] In the scenario of quasi-terrestrial fixed cells, the movement of the satellite will not cause the cell to move within a period of time, the first network device and the second network device are the same terrestrial network device, and are used to serve the terminal devices in the quasi-terrestrial fixed cells. The terminal device will perform cell switching due to the change of the satellite, at this time, the source cell and the target cell of the cell switching are the same cell, and the satellite connected with the terrestrial network device changes, and the terminal device needs to perform cell-level downlink synchronization with the terrestrial network device through the switched satellite (target satellite). In the scenario of quasi-terrestrial fixed cells, the first network device and the second network device can also be different terrestrial network devices, and the terminal device will perform cell switching due to its own movement, at this time, the source cell and the target cell of the cell switching are different cells, and the terminal device needs to perform cell-level downlink synchronization with the terrestrial network device through the switched satellite.

[0164] In the scenario of a ground moving cell, the movement of the satellite causes the cell to move, the first network device and the second network device can be different ground network devices, or the first network device and the second network device can be the same ground network device, the terminal device will perform cell switching due to the movement of the satellite, the first network device is connected to the satellite before switching (source satellite), and the second network device is connected to the satellite after switching (target satellite), at this time, if the first network device and the second network device are different ground network devices, the source cell and the target cell are different cells under different network devices, and if the first network device and the second network device are the same ground network device, the source cell and the target cell are cells under the same ground network device, so the terminal device still needs to perform cell-level downlink synchronization with the ground network device through the satellite after switching (target satellite).

[0165] In the case of a satellite being a regenerative satellite, the first network device and the second network device can be a satellite or a network device deployed on the satellite, and can be similar to a ground network device in structure and function. In this case, whether it is a quasi-ground fixed cell scenario or a ground moving cell scenario, the terminal device performs cell-level downlink synchronization with the target satellite when switching.

[0166] In addition, when the regenerative satellite only has a DU function, the first network device and the second network device can be a satellite with a DU function, or can be a network device with a CU function.

[0167] In the embodiments of the present application, the network device can also be referred to as a RAN node, an access network device, a RAN entity or an access node, etc., which is located at the network side of the above communication system, used to help the terminal device to realize wireless access, and is a device with wireless transceiving function or a chip or chip system that can be arranged in the device. The network device can include but is not limited to: a base station, an evolved NodeB (eNodeB), an access point (AP), a transmission reception point (TRP), a next generation Node-B (gNB), a base station in a future mobile communication system, etc. The network device can be a macro base station, a micro base station or an indoor station, a relay node or a donor node, an open radio access network (O-RAN) or a centralized radio access network (C-RAN) scenario wireless controller. Optionally, the RAN node can also be a server, a wearable device, a vehicle or a vehicle-mounted device, etc. For example, the network device in vehicle to everything (V2X) technology can be a road side unit (RSU). All or part of the functions of the network device in the present application can also be realized by software functions running on hardware, or by virtualized functions instantiated on a platform (such as a cloud platform). The network device in the present application can also be a logical node, a logical module or software that can realize all or part of the functions of the network device.

[0168] In another possible scenario, multiple RAN nodes cooperate to assist terminal devices to realize wireless access, and different RAN nodes respectively realize part of the functions of the base station. For example, the RAN node can be a central unit (CU), a DU, a CU-control plane (CP), a CU-user plane (UP), or a radio unit (RU), etc. The CU and the DU can be separately arranged, or can be included in the same network element, such as a baseband unit (BBU). The RU can be included in a radio frequency device or a radio frequency unit, such as a remote radio unit (RRU), an active antenna processing unit (AAU) or a remote radio head (RRH).

[0169] In different systems, the CU (or CU-CP and CU-UP), DU or RU can also have different names, but those skilled in the art can understand their meanings. For example, in the O-RAN system, the CU can also be referred to as O-CU (open CU), the DU can also be referred to as O-DU, the CU-CP can also be referred to as O-CU-CP, the CU-UP can also be referred to as O-CU-UP, and the RU can also be referred to as O-RU. For the convenience of description, the CU, CU-CP, CU-UP, DU and RU are taken as examples for description in this application. Any one of the CU (or CU-CP, CU-UP), DU and RU in this application can be implemented by a software module, a hardware module, or a combination of a software module and a hardware module.

[0170] The form of the network device is not limited in the embodiments of the present application. The device for implementing the function of the network device can be the network device; or can be a device capable of supporting the network device to implement the function, such as a chip system. The device can be installed in the network device or used in matching with the network device.

[0171] In the embodiments of the present application, the terminal device is a terminal with wireless transceiving function or a chip or chip system that can be provided in the terminal, which accesses the above communication system. The terminal device can also be referred to as a user equipment (UE), a user apparatus, an access terminal, a user unit, a user station, a mobile station, a mobile station, a remote station, a remote terminal, a mobile device, a user terminal, a terminal, a wireless communication device, a user agent or a user apparatus. The terminal device in the embodiments of the present application can be a mobile phone, a tablet computer (Pad), a computer with wireless transceiving function, a virtual reality (VR) terminal device, an augmented reality (AR) terminal device, a wireless terminal in industrial control, a wireless terminal in self-driving, a wireless terminal in remote medical treatment, a wireless terminal in smart grid, a wireless terminal in transportation safety, a wireless terminal in smart city, a wireless terminal in smart home, a vehicle-mounted terminal, a RSU with terminal function, etc. The terminal device in the present application can also be a vehicle-mounted module, a vehicle-mounted component, a vehicle-mounted chip or a vehicle-mounted unit built in a vehicle as one or more components or units, and the vehicle can implement the method provided in the present application through the built-in vehicle-mounted module, vehicle-mounted component, vehicle-mounted chip or vehicle-mounted unit.

[0172] Embodiments of the present application do not limit the device form of the terminal device, and the device for implementing the function of the terminal device can be a terminal device; or can be a device capable of supporting the terminal device to implement the function, such as a chip system. The device can be installed in the terminal device or used in matching with the terminal device. In embodiments of the present application, the chip system can be composed of a chip, or can include a chip and other discrete devices.

[0173] In embodiments of the present application, when cell switching occurs, the terminal device can receive the reference signal sent by the second network device according to the first configuration information for configuring the time domain position of the reference signal corresponding to the target cell received from the first network device, so as to perform downlink synchronization with the target cell according to the configured reference signal, without searching for SSB to perform downlink synchronization according to the SMTC period or the SSB transmission period, and can reduce the switching interruption delay of the terminal device.

[0174] Further, embodiments of the present application also provide a CU-DU architecture diagram suitable for the above network device. As shown in FIG. 8, by dividing the protocol stack, the network device includes a CU and a DU, wherein the CU can be further divided into a CU-CP and a CU-UP. The CU-CP and the DU can communicate through an interface 1, the CU-UP and the DU can communicate through an interface 2, and the CU-CP and the CU-UP can communicate through an interface 3. Optionally, the network device can be a gNB, at this time the interface 1 can be an F1-C interface, the interface 2 can be an F1-U interface, and the interface 3 can be an E1 interface.

[0175] Among them, the CU-CP includes an RRC layer and a packet data convergence protocol (PDCP)-control (C) layer, the CU-UP includes a service data adaptation protocol (SDAP) layer and a PDCP-user (U) layer, and the DU includes a radio link control (RLC) layer, a MAC layer and a physical (PHY) layer.

[0176] Embodiments of the present application also provide an O-RAN architecture diagram suitable for the above network device, and the main feature of the O-RAN architecture is the separation of software and hardware, which realizes the virtualization of network functions and the standardization of hardware. In addition, the O-RAN also introduces artificial intelligence (AI) / model learning (ML).

[0177] As shown in FIG. 9, the O-RAN includes a service management and orchestration framework (SMO), a non-real-time RAN intelligent controller (Non-RT RIC), a near real-time RAN intelligent controller (Near-RT-RIC), an O-CU, an O-CU-CP, an O-CU-UP, an O-DU, an O-RU, and an (O-RAN Cloud, O-Cloud).

[0178] Among them, the SMO: its function is similar to network management, mainly responsible for the operation and maintenance management of each communication module in the O-RAN system.

[0179] The Non-RT RIC: used to implement non-real-time intelligent management of RAN functions, can implement AI / ML workflow including model training and model updating, and guide applications / functions in the Near-RT RIC based on policies. The Non-RT RIC is located in the SMO module.

[0180] The Near-RT RIC: used to implement near real-time intelligent management of RAN, through data collection and related operations on the E2 interface, to realize near real-time control and optimization of modules and resources of the O-RAN.

[0181] The O-CU: used to implement the RRC layer, the PDCP layer, and the SDAP layer and other control functions in the 3GPP standard.

[0182] The O-CU-CP: similar to the CU-CP in the NR system, used to implement the functions of the RRC layer, and the control plane functions of the PDCP layer, and belongs to the O-CU.

[0183] The O-DU: based on low-layer function segmentation, used to implement the RLC layer, the MAC layer, and the higher physical layer (higher PHY) in the 3GPP standard. Among them, the higher physical layer functions include one or more of the following: forward error correction (FEC) encoding / decoding, scrambling / descrambling, or modulation / demodulation.

[0184] O-RU: Based on low-layer function split, used to implement the lower physical layer (Lower PHY) function and radio frequency function in the 3GPP standard. Among them, the lower physical layer function includes one or more of the following: fast Fourier transform (FFT) transform / inverse fast Fourier transform (IFFT) transform, digital beamforming, or extraction and filtering of PRACH, etc. Similar to the transmission reception point (TRP) or remote radio head (RRH) in 3GPP, but it includes low physical layer functions such as FFT / IFFT or PRACH extraction.

[0185] O-Cloud: As a cloud computing platform, it includes physical infrastructure nodes for hosting O-RAN functions such as RAN intelligent controller (RIC), O-DU, etc., supporting software components (such as operating systems, virtual machine monitors, container runtimes), management and orchestration functions.

[0186] The interfaces included in FIG. 9 are: A1 interface, E1 interface, E2 interface, O1 interface, O2 interface, open fronthaul control user synchronization plane (open FH CUS-Plane) interface, open fronthaul management plane (open FH M-Plane) interface, F1-c interface, F1-u interface, X2-c interface, X2-u interface, NG-u interface, Xn-u interface, Xn interface, NG-c interface, etc.

[0187] Among them, the A1 interface: the interface between the Non-RT RIC and the Near-RT RIC, used for intelligent and dynamic control of O-RAN internal wireless resources; the Non-RT RIC provides policies, rich information and ML model updates, etc. to the Near-RT RIC through the A1 interface, and the Near-RT RIC provides policy feedback to the Non-RT RIC through the A1 interface.

[0188] E2 interface: an open interface between two endpoints, used to connect the Near-RT RIC and the RAN node. The RAN node can include, for example, the CU in 5G, the DU, the O-RAN compatible eNB in 4G, the O-CU (O-CU-CP and / or O-CU-UP) and / or O-DU in O-RAN, etc. The RIC can obtain RAN node data collection and feedback through the E2 node, and the RAN node can obtain control feedback of the Near-RT RIC through the E2 node.

[0189] O1 interface: an interface between the management entity in the SMO and the O-RAN module, used for operation management, through which FCAPS management, software management, and file management are implemented.

[0190] O2 interface: an interface between the SMO and the infrastructure management framework supporting the O-RAN virtual network function.

[0191] open FH CUS-plane interface: including the control plane (C-Plane), user plane (U-Plane), and synchronization plane (S-Plane) interface. Among them, the control plane is used for real-time control between the O-DU and the O-RU, for example, for the O-DU to transmit the weight value to the O-RU for beamforming, or for the O-DU to perform power control on the O-RU, etc.; the user plane is used for transmitting communication data between the access network device and the terminal between the DU and the RU; the synchronization plane is used for the O-DU to provide clock synchronization to the O-RU.

[0192] It can be understood that the above is an introduction to the A1 interface, the E2 interface, the O1 interface, the O2 interface, and the open FH CUS-Plane interface. The related introduction of other interfaces in FIG. 9, such as the E1 interface, the open FH M-Plane interface, the F1-c interface, the F1-u interface, the X2-c interface, the X2-u interface, the NG-u interface, the Xn-u interface, the Xn interface, the NG-c interface, etc. can refer to the prior art, and will not be described here.

[0193] It can be understood that the above FIGS. 7-9 are only simplified schematic diagrams for ease of understanding, and other devices or modules or chips, etc. not shown in FIGS. 7-9 can also be included.

[0194] It should be pointed out that the scheme in the embodiments of the present application can also be applied to other communication systems, and the corresponding name can also be replaced by the name of the corresponding function in other communication systems.

[0195] The communication method provided by the embodiments of the present application will be described in detail below with reference to FIGS. 10 and 11.

[0196] Exemplarily, FIG. 10 is a flow diagram of a communication method provided by an embodiment of the present application. It can be understood that the network device and the terminal device shown in FIG. 7 are taken as an example to illustrate the execution subject of the interaction, but the present application does not limit the execution subject of the interaction. For example, the method executed by the network device in the present application can also be implemented by a module (such as a circuit, a processor, a chip or a chip system, etc.) in the network device, or a logic node, a logic module or software capable of realizing all or part of the functions of the network device; the method executed by the terminal device in the present application can also be implemented by a communication module in the terminal device or a circuit or chip (such as a modem chip (also known as a baseband chip), or a SoC chip containing a modem core, or a SIP chip) responsible for communication functions in the terminal device.

[0197] As shown in FIG. 10, the communication method comprises:

[0198] S1001, the first network device sends first configuration information to the terminal device. Correspondingly, the terminal device receives the first configuration information from the first network device.

[0199] The first network device is a network device corresponding to a source cell of the terminal device, which can also be referred to as a source network device, and this is not limited. The first configuration information is used to configure the time domain position of a reference signal corresponding to a target cell, and the reference signal is used for downlink synchronization between the terminal device and the target cell. For example, the reference signal can be a CSI-RS, a TRS or other reference signal except SSB, or the reference signal is an SSB corresponding to a switching purpose, which is different from the SSB for initial access, for example, the transmission time is different. In the present application, the reference signal can also be referred to as a temporary reference signal, that is, a reference signal introduced for switching (that is, a reference signal introduced for switching of a terminal device in a connected state. When there is no terminal device in a connected state that needs to be switched, the target cell can stop sending the reference signal, and this is not limited.

[0200] That is, the network device corresponding to the source cell, that is, the first network device, obtains the first configuration information and sends it to the terminal device, so that the terminal device to be switched receives the reference signal according to the first configuration information, thereby performing downlink synchronization with the target cell.

[0201] The first configuration information can include time domain position information of the at least one reference signal. The time domain position information of the reference signal can be represented by a time domain starting position and a time domain resource size. The time domain starting position can be a relative time domain starting position or an absolute time domain starting position, and the time domain resource size refers to a quantity of time domain resources occupied by the reference signal, such as a quantity of OFDM (Orthogonal Frequency Division Multiplexing) symbols. In this embodiment of this application, the OFDM symbol can also be referred to as a symbol. In the absence of a special description, the symbol described hereinafter is an OFDM symbol. In addition, for a periodically transmitted reference signal, the first configuration information can further include a periodically transmitted time domain starting position and a periodic duration, and the first configuration information is not limited in this regard.

[0202] In a satellite communication scenario, the time domain position information of the reference signal can include an offset value of the time domain starting position of the reference signal relative to a first time or a first time domain starting position, such as an offset value of subframes, slots, symbols, or milliseconds. Alternatively, the time domain position of the reference signal can include an offset value of the reference signal relative to a first synchronization signal of the first network device. Alternatively, the time domain position of the reference signal can include an offset value of the reference signal relative to a second synchronization signal of the second network device. The first time can be a time at which the first network device stops providing coverage services for the source cell. The first time can be t-service in the above related technology 4, which is configured by the first network device or predefined by a protocol, and the first time is not limited in this regard. If the working mode of the satellite is a transparent forwarding form, the first network device is a ground network device connected to a satellite (a source satellite) that provides coverage services for the source cell. If the working mode of the satellite is a regenerative form, the first network device is the source satellite or a DU or CU corresponding to the source satellite. Therefore, the first time can also be considered as a time at which the terminal device disconnects the connection with the source satellite or starts to perform cell-level downlink synchronization with a target satellite at the first time.

[0203] In a ground communication scenario, the time domain position of the reference signal can include an offset value of the time domain starting position of the reference signal relative to a first time domain starting position. Alternatively, the time domain position of the reference signal can include an offset value of the reference signal relative to a first synchronization signal transmitted by the first network device. Alternatively, the time domain position of the reference signal can include an offset value of the reference signal relative to a second synchronization signal of the second network device.

[0204] The first time domain starting position can be a starting time domain position of a first synchronization signal sent by the first network device, or a starting time domain position of a second synchronization signal sent by the second network device. It should be noted that the first synchronization signal and the second synchronization signal, the synchronization signal of the first network device and the synchronization signal of the second network device can also be other reference signals (such as CSI-RS, TRS), and are not limited to synchronization signals.

[0205] The synchronization signal can be an SSB in NR. Since the synchronization signal is periodically scanned and sent, the network device will send multiple synchronization signals with the same frequency domain position but different time domain positions in one period. The multiple synchronization signals are sent in different beam directions, and the terminal device can synchronize with the cell in downlink by searching for the synchronization signal. Therefore, the first synchronization signal can be a synchronization signal selected by the terminal device from the multiple synchronization signals periodically sent by the first network device, which can complete downlink synchronization with the source cell, such as the synchronization signal with the largest received signal strength. The first synchronization signal can also be called a service synchronization signal or a best synchronization signal, which is not limited. Alternatively, the multiple synchronization signals periodically sent by the first network device are all first synchronization signals, and there are multiple first time domain starting positions. At this time, one offset value corresponds to one first time domain starting position and the time domain starting position information of the reference signal includes multiple offset values of the reference signal.

[0206] It should be understood that the time domain starting position of the first synchronization signal used to represent the time domain starting position of the reference signal is usually the synchronization signal sent by the first network device received by the terminal device in the last period before downlink synchronization with the target cell.

[0207] The second synchronization signal can refer to a synchronization signal with the same index as the first synchronization signal among the multiple synchronization signals periodically sent by the second network device. At this time, the offset value of the time domain starting position of the reference signal relative to the second synchronization signal can be represented by the offset value of the time domain starting position of the second synchronization signal relative to the time domain starting position of the first synchronization signal, and the offset value of the time domain starting position of the first synchronization signal relative to the time domain starting position of the reference signal, or by the offset value of the time domain position of the second synchronization signal relative to the time domain position of the first synchronization signal, and the offset value of the time domain position of the first synchronization signal relative to the time domain position of the reference signal, which is not limited. It should be understood that when the multiple synchronization signals periodically sent by the second network device are all second synchronization signals, there are multiple first time domain starting positions, and each second synchronization signal corresponds to an offset value of the reference signal.

[0208] It should be understood that, in addition to including a parameter for characterizing the time-domain starting position of each reference signal, the time-domain position information of the reference signal can also include the time-domain resource size of each reference signal.

[0209] In order to shorten the switching interruption delay of the terminal device, in a possible design, the transmission time interval of the reference signal is less than the transmission period of the synchronization signal of the second network device or the SMTC period. It should be understood that the transmission period of the synchronization signal is usually the same as the SMTC period.

[0210] Alternatively, the reference signal can also be periodically transmitted like the synchronization signal, and one or more reference signals can be transmitted in one transmission period. In this case, the transmission time interval of the reference signal can refer to the transmission period of the reference signal, that is, the transmission period of the reference signal is less than the transmission period of the synchronization signal transmitted by the second network device or the SMTC period used to configure the synchronization signal measurement window. Alternatively, the reference signal can also be non-periodically transmitted, and the transmission time interval between adjacent two reference signals is also less than the transmission period of the synchronization signal transmitted by the second network device or the SMTC period used to configure the synchronization signal measurement window, which is not limited. It should be understood that the time-frequency domain resource size occupied by each reference signal is the same.

[0211] Alternatively, in the case of non-periodically transmitting multiple reference signals, the time-domain position of the reference signal can also be indicated by the offset value between adjacent two time-domain positions, which is not limited.

[0212] The above mainly indicates the time-domain position of the reference signal by the offset value between the time-domain starting positions. It should be understood that the time-domain position of the reference signal can also be indicated by the offset value between the time-domain ending positions, or the offset value between the time-domain starting position and the time-domain ending position, which is not limited.

[0213] It should also be understood that the first configuration information can also include the information of the target cell, the frequency-domain position information of the reference signal, etc. The multiple reference signals can be transmitted at the same frequency-domain position or at different frequency-domain positions, which is not limited.

[0214] Alternatively, when the first network device is not synchronized with the synchronization signal transmitted by the second network device, the first configuration information can also include the timing offset of the synchronization signal, which is the time offset between the time-domain position of the synchronization signal of the first network device and the time-domain position of the synchronization signal of the second network device. For example, in satellite communication, the timing offset of the synchronization signal represents the time offset of the synchronization signal corresponding to the target satellite at its uplink timing reference point relative to the synchronization signal corresponding to the source satellite at its uplink timing reference point. In the example, in the satellite communication scenario, the uplink timing reference point can be RP in FIG. 4.

[0215] There are two cases for how the first network device acquires the first configuration information.

[0216] Case 1: The first network device acquires the first configuration information locally. This case 1 can be applicable to the following cell switching scenarios of terminal devices:

[0217] Scenario 1: In a scenario where a terminal device in ground communication performs intra-site switching, the first network device and the second network device are the same ground network device, and the source cell and the target cell are different cells under the same ground network device. At this time, the first network device can locally generate the first configuration information of the reference signal of the target cell for the switching of the terminal device.

[0218] Scenario 2: In a quasi-ground fixed cell scenario of satellite communication, a terminal device performs switching (cell switching) of a transmissive satellite based on soft switching or hard switching or L3 switching signaling, that is, the terminal device performs switching from communicating with a source transmissive satellite to communicating with a target transmissive satellite through the same ground network device based on soft switching or hard switching or L3 switching signaling in the same cell. At this time, the first network device and the second network device are also the same ground network device. At this time, the first network device can also locally generate the first configuration information of the reference signal of the target cell for the switching of the terminal device.

[0219] Scenario 3: In a quasi-ground fixed cell scenario of satellite communication, a terminal device performs switching (cell switching) of a regenerative satellite based on soft switching or hard switching, that is, the terminal device performs switching from communicating with a source regenerative satellite to communicating with a target regenerative satellite based on soft switching or hard switching in the same cell. At this time, the first network device is the source regenerative satellite, and the second network device is the target regenerative satellite. At this time, the first network device can also locally generate the first configuration information of the reference signal of the target cell for the switching of the terminal device.

[0220] In scenario 3, if the regenerative satellite only has a DU function, the first configuration information can be generated by the DU or CU corresponding to the source regenerative satellite. At this time, the first network device can be the DU or CU corresponding to the source regenerative satellite, and the second network device can be the DU or CU corresponding to the target regenerative satellite.

[0221] Case 2: The first network device acquires the first configuration information from the second network device.

[0222] In this case 2, the second network device can interact with the first network device to learn that the terminal device needs to switch and that the target cell is a cell served by the second network device, so as to generate the first configuration information for the switching and send it to the first network device.

[0223] This case 2 can be applicable to the following cell switching scenarios of terminal devices:

[0224] Scenario 1, in the scenario of inter-station handover of terminal equipment in ground communication, the first network device and the second network device are different ground network devices, the first network device is a source network device, and the second network device is a target network device. At this time, the first configuration information is generated by the second network device and sent to the first network device. In a possible implementation, in the handover preparation process of the first network device and the second network device, the second network device can generate the first configuration information according to the handover request sent by the first network device, and send the first configuration information to the first network device in the handover request response (or handover request confirmation).

[0225] Scenario 2, in the scenario of quasi-ground fixed cell in satellite communication, the terminal equipment performs handover of regenerative satellite (cell handover, source cell and target cell are the same cell) based on L3 handover signaling, that is, the terminal equipment switches from communication with a source regenerative satellite to communication with a target regenerative satellite in the same cell based on L3 handover signaling. At this time, the first network device is the source regenerative satellite, and the second network device is the target regenerative satellite. At this time, the first configuration information can also be generated by the second network device and sent to the first network device.

[0226] In scenario 2, if the regenerative satellite only has DU function, the first configuration information can be generated by the CU corresponding to the source regenerative satellite, rather than the CU corresponding to the target regenerative satellite. At this time, the first network device can be the CU corresponding to the source regenerative satellite, and the second network device can be the CU corresponding to the target regenerative satellite.

[0227] Scenario 3, in the scenario of ground mobile cell in satellite communication, the terminal equipment performs handover of transparent satellite (cell handover, source cell and target cell are different cells). In this scenario, the satellite can change or not change, and the ground network device connected to the transparent satellite can change or not change. If the ground network device changes, the second network device (target ground network device) generates the first configuration information.

[0228] Scenario 4, in the scenario of ground mobile cell in satellite communication, the terminal equipment can perform handover of regenerative satellite (cell handover, source cell and target cell are different cells) based on L3 handover command, that is, the terminal equipment switches from the source cell of the source regenerative satellite to the target cell of the target regenerative satellite. At this time, the first network device is the source regenerative satellite, and the second network device is the target regenerative satellite. At this time, the first configuration information can also be generated by the second network device and sent to the first network device.

[0229] Thus, after the first network device acquires the first configuration information, the first network device can send the first configuration information to the terminal device. There can be two possible designs for the sending manner of the first network device sending the first configuration information as follows.

[0230] Design 1: The first configuration information can be sent in a broadcast message. That is, the first network device can send the first configuration information in the form of broadcast. For example, the broadcast message can be a system message, such as SIB19. This design 1 can be applicable to all scenarios in scenario 1.

[0231] Design 2: The first configuration information can be carried in an RRC message, which is used to instruct the terminal device to switch to a target cell. That is, the first network device can send the first configuration information based on RRC signaling instructing the terminal device to switch. This design 2 can be applicable to cell switching based on L3 switching signaling in scenario 2 of scenario 1 and all scenarios in scenario 2. In this design 2, the RRC message can be referred to as a handover command, which is not limited. It should be understood that in some implementations, the handover command can also be indicated by other high-layer signaling, such as MAC signaling, which is not limited.

[0232] S1002: The second network device sends a reference signal to the terminal device. Correspondingly, the terminal device receives the reference signal from the second network device according to the first configuration information.

[0233] The second network device generates and sends the reference signal. The second network device can send based on the configured time-domain position of the reference signal, such as the second network device sending the reference signal to the terminal device according to the second configuration information, the second configuration information being used to configure the time-domain position of the sending of the reference signal, the second configuration information and the first configuration information can be the same or different, or in some implementations, the second configuration information is the first configuration information, and in some implementations, the second configuration information is not the first configuration information. For example, the second configuration information configures the time-domain position of the sending of the reference signal to be more intensive than the time-domain position of the sending of the reference signal configured by the first configuration information.

[0234] The second network device can locally configure to acquire the second configuration information, such as the second network device learning that the target cell to which the terminal device needs to switch is a cell served by the second network device, and then locally configuring the second configuration information and sending the second configuration information to the first network device, so that the first network device can determine the first configuration information according to the second configuration information, or acquire the first configuration information from the first network device and determine the second configuration information according to the first configuration information, which is not limited. Thus, the second network device sends the reference signal to the terminal device according to the second configuration information.

[0235] After the second network device learns that the target cell for the terminal device to switch to is a cell served by the second network device, the second network device can send a reference signal to the terminal device at a time-frequency domain location of the reference signal configured in the second configuration information in a preset time, so that the terminal device can complete downlink synchronization with the target cell according to the reference signal.

[0236] To further shorten the interruption delay of the terminal device in switching, the second network device can send the reference signal to a region where the terminal device is located, or adjust the beam transmission direction of the reference signal according to the location or region where the terminal device is located, and send the reference signal to the region where the terminal device is located, without sending the reference signal to the entire region of the target cell. That is, the second network device only sends the reference signal to a region corresponding to a terminal device that needs to switch in an RRC connected state (RRC_CONNECTED) at present, without sending the reference signal to the entire region of the target cell, so as to shorten the period of sending the reference signal and shorten the time from performing switching to receiving the reference signal from the target cell.

[0237] In a possible design, the second network device can obtain the region information of the terminal device, so that the second network device sends the reference signal to the region where the terminal device is located according to the region information. The region where the terminal device is located is a part of the coverage of the target cell.

[0238] The region information of the terminal device can also be referred to as the location information of the terminal device, and is used to indicate the location or region of the terminal device in the target cell. The region information can be absolute region information or relative region information, which is not limited. The region information of the terminal device can be reported by the terminal device to the second network device, or reported by the terminal device to the first network device and then sent by the first network device to the second network device, or measured or calculated by the second network device or the first network device, which is not limited.

[0239] In a possible design, the second network device obtaining the region information of the terminal device can include: the second network device receiving a switching request from the first network device, the switching request being used to request switching of the terminal device to the target cell, and the switching request including the region information. That is, the second network device can obtain the region information of the terminal device from the switching request for the terminal device received from the first network device.

[0240] For example, as shown in (a) of FIG. 11, taking a quasi-geostationary fixed cell scenario of satellite communication as an example, the source regenerative satellite, i.e., the first network device, moves away from the cell where the terminal device is located, and the second network device continues to provide services for the cell as the target regenerative satellite. When the target regenerative satellite transmits the reference signal, the beam direction of the reference signal can be indicated according to the location or area where the terminal device is located, or the reference signal can be transmitted in the location or area where the terminal device is located. For example, the target cell can be divided into multiple areas according to the beam coverage direction, and there are terminal devices to be handed over in area 1 and area 2. Then, the beam direction of the reference signal of the target regenerative satellite is directed to the area 1 and area 2, so that the terminal devices located in the area 1 and area 2 can quickly receive the reference signal. For other areas without terminal devices to be handed over, the target regenerative satellite can not need to transmit the reference signal to these areas.

[0241] For another example, as shown in (b) of FIG. 11, taking a ground mobile cell scenario of satellite communication as an example, the source regenerative satellite, i.e., the first network device, moves to cause the cell to move, and the second network device moves and its corresponding cell covers the terminal device as the target cell. When the target regenerative satellite transmits the reference signal, the beam direction of the reference signal can be indicated according to the location or area where the terminal device is located, or the reference signal can be transmitted in the location or area where the terminal device is located. For example, the target cell can be divided into multiple areas according to the beam coverage direction, and there are terminal devices to be handed over in area 1 and area 2. Then, the beam direction of the reference signal of the target regenerative satellite is directed to the area 1 and area 2, so that the terminal devices located in the area 1 and area 2 can quickly receive the reference signal. For other areas without terminal devices to be handed over, the target regenerative satellite can not need to transmit the reference signal to these areas.

[0242] It should be understood that if the satellite is a transmissive satellite, the second network device is a ground network device, and then the second network device can indicate the beam direction of the reference signal transmitted by the target transmissive satellite connected according to the location or area where the terminal device is located, so as to transmit the reference signal in the specified area. It should also be understood that in the intra-station handover and inter-station handover scenarios of ground communication, the second network device transmits the reference signal in a manner similar to the above regenerative satellite scenario, and details are not described herein.

[0243] For the preset time of transmitting the reference signal by the second network device, in the quasi-geostationary fixed cell scenario of satellite communication:

[0244] In a case where the terminal device performs the handover based on the hard handover manner, the preset time is the first moment, the first moment is a moment at which the first network device stops providing coverage service for the source cell of the terminal device, and the first moment can refer to the related description of the first moment in S1001, which will not be repeated here. That is, the second network device starts to send the reference signal to the terminal device from the first moment.

[0245] In a case where the terminal device performs the handover based on the soft handover manner, the preset time is the second moment, the second moment is a moment at which the second network device provides coverage service for the target cell, and the second moment can be t-start in the related technology 4, the terminal device is connected to the source satellite between [t-start, t-service] and is disconnected from the source satellite after t-service. That is, the second network device starts to send the reference signal to the terminal device from the second moment.

[0246] In a case where the terminal device performs the handover based on the L3 handover command, the preset time is the third moment, and the third moment is determined according to at least one of the following: the first moment, the second moment, a transmission delay between the first network device and the second network device, or an air interface transmission delay between the first network device and the terminal device. That is, the second network device can start to send the reference signal to the terminal device from the third moment.

[0247] In a ground mobile cell scenario of satellite communication or an inter-site handover scenario of ground communication, the preset time at which the second network device sends the reference signal can be determined by considering a time for the first network device and the second network device to complete handover preparation, an air interface transmission delay between the first network device and the terminal device, and the like, which will not be limited. In an intra-site handover scenario of ground communication, the preset time at which the second network device sends the reference signal can be determined by considering a time for determining that the terminal device performs the handover, an air interface transmission delay between the first network device (that is, the second network device) and the terminal device, and the like, which will not be limited.

[0248] S1003, the terminal device performs downlink synchronization with the target cell according to the reference signal.

[0249] The terminal device receives the reference signal from the target cell at the corresponding time-frequency domain position according to the first configuration information, and performs downlink synchronization according to the received reference signal.

[0250] The downlink synchronization includes coarse synchronization and fine synchronization. The coarse synchronization obtains a general existing range of the reference signal, the fine synchronization can determine a relatively accurate time domain start and end position of the synchronization signal OFDM symbol, and finally, a decimal multiple frequency offset estimation and compensation correct the position of the center frequency point detected based on the reference signal reception strength in precision.

[0251] In satellite communication, a terminal device performs downlink synchronization with a target cell, and there are two design schemes as follows.

[0252] In a possible design scheme 1, the terminal device can obtain downlink timing of the target cell according to ephemeris information of a first network device, ephemeris information of a second network device, and timing deviation of a synchronization signal, and at this time, the terminal device performs cell search and downlink coarse synchronization with the target cell. After obtaining the downlink timing of the target cell, the terminal device can further perform fine time tracking and obtain all timing information of the target cell according to a reference signal, that is, the terminal device performs downlink fine synchronization with the target cell, and at this time, the handover interruption delay of the terminal device mainly depends on the length of time that the terminal device waits to receive a reference signal once. Alternatively, the terminal device can perform fine time tracking and obtain all timing information of the target cell according to the reference signal and a second synchronization signal sent by the second network device, that is, the terminal device performs downlink fine synchronization with the target cell, and at this time, the terminal device can perform downlink fine synchronization with the target cell according to the earliest received signal in the reference signal and the synchronization signal, and the handover interruption delay of the terminal device mainly depends on the length of time that the terminal device waits to receive a reference signal or a synchronization signal (that is, which signal arrives earliest in the reference signal and the synchronization signal).

[0253] That is, before performing fine time tracking and obtaining all timing information of the target cell according to the reference signal or according to the reference signal and the synchronization signal, the terminal device can obtain downlink timing of the target cell according to ephemeris information of a first network device, ephemeris information of a second network device, and timing deviation of a synchronization signal.

[0254] Therefore, when performing downlink synchronization with the target cell, the terminal device does not need to wait to receive a reference signal or synchronization information of the target cell for downlink coarse synchronization, but only needs to wait to receive a reference signal or a synchronization signal once for downlink fine synchronization, so as to complete the downlink synchronization with the target cell, and the handover interruption delay of the terminal device can be reduced. The timing deviation of the synchronization signal can be referred to the related description in S1001, which is not described herein again. It should be understood that in the transparent satellite scenario, the first network device and the second network device are both ground network devices, and the ephemeris information of the first network device refers to ephemeris information of a source satellite connected with the first network device, and the ephemeris information of the second network device refers to ephemeris information of a target satellite connected with the second network device.

[0255] For example, based on the above design scheme 1, in the handover interruption delay formula in the above technical solution 4, the value of T search is 0, or T search does not need to be considered in the handover interruption delay formula, or T searchis the internal processing time of the terminal device for calculating the downlink timing according to the ephemeris information and the timing offset of the synchronization signal. The processing time is very short, and T search is considered to be 0, and the value of T Δ is changed to the length of time for waiting for a reference signal or SSB (i.e., the time of the earliest arrival of the reference signal and SSB). Thus, the interruption delay of the terminal device switching is reduced.

[0256] In a possible design scheme 2, the terminal device can perform downlink synchronization with the target cell according to the reference signal and the synchronization signal sent by the second network device. That is, the terminal device can complete downlink coarse synchronization (obtain the downlink timing of the target cell) according to the earliest received signal of the reference signal and the synchronization signal, and after the coarse synchronization, complete downlink fine synchronization (perform fine time tracking of the target cell and obtain all timing information) according to the earliest received signal of the reference signal and the synchronization signal. At this time, the terminal device needs to wait for receiving a reference signal or a synchronization signal (i.e., which of the reference signal and the synchronization signal arrives earliest) to perform downlink coarse synchronization, and then wait for receiving a reference signal or a synchronization signal (i.e., which of the reference signal and the synchronization signal arrives earliest) to perform downlink fine synchronization, so as to complete the downlink synchronization with the target cell. Optionally, the reference signals for performing the downlink coarse synchronization and the downlink fine synchronization can be the same or different.

[0257] In order to reduce the interruption delay of the terminal device switching, the transmission time interval of the reference signal is less than the transmission time interval of the synchronization signal. In the embodiment of the present application, the first received signal and the second received signal can exist in the following three cases:

[0258] Case 1: the first received signal is the reference signal for downlink coarse synchronization, and the second received signal is the synchronization signal for downlink fine synchronization;

[0259] Case 2: the first received signal is the synchronization signal for downlink coarse synchronization, and the second received signal is the reference signal for downlink fine synchronization;

[0260] Case 3: the first received signal and the second received signal are both the reference signal, and the downlink coarse synchronization and the downlink fine synchronization are performed according to the reference signal, respectively.

[0261] Thus, when the terminal device performs downlink synchronization with the target cell, the interruption delay of the terminal device switching mainly depends on the length of time for waiting for receiving the two signals.

[0262] For example, based on the above design scheme 2, in the interruption delay formula of the terminal device switching in the above technical solution 4, the value of T search is changed to the length of time for waiting for the first received signal or SSB (i.e., the signal of the earliest arrival of the reference signal and SSB). The value of T ΔThe value of the time length becomes the time length of waiting for the second reference signal or SSB (i.e. the earliest signal among the reference signals and SSBs). Thus, the interruption delay of the terminal device switching is reduced.

[0263] In the ground communication scenario, the terminal device can perform downlink synchronization with the target cell in the manner of the above-described design scheme 2, and the downlink synchronization is not limited.

[0264] It should be understood that after the terminal device performs downlink synchronization with the target cell, the terminal device can also perform uplink synchronization with the target cell, so as to complete the access to the target cell. The terminal device performs uplink synchronization with the target cell in two ways.

[0265] Way 1: The terminal device initiates a random access process to the target cell. The terminal device determines the TA according to the T TA of the technical 2, assuming that the T TA is 0, and sends a random access preamble to the target cell according to the TA. The terminal device receives a random access response sent by the target cell. Optionally, before the terminal device sends the random access process to the target cell, the terminal device receives a physical downlink control channel (PDCCH) order from the target cell, which triggers the terminal device to initiate a random access to the target cell.

[0266] Way 2: The terminal device does not need to initiate a random access process, and the terminal device sends uplink data to the target cell according to the uplink grant sent by the target cell to the terminal device. The terminal device determines the TA according to the T TA of the technical 2, assuming that the T TA is 0, and sends uplink data to the target cell according to the TA.

[0267] Optionally, after the second network device determines that the terminal device accesses the target cell, the second network device stops sending the reference signal to the terminal device. For example, when the second network device determines that all the terminal devices that need to be switched in the area 1 access the target cell, the second network device stops sending the reference signal of the target cell to the area 1. Or when the second network device determines that all the terminal devices that need to be switched access the target cell, the second network device stops sending the reference signal of the target cell.

[0268] That is, after the terminal device in the first area accesses the target cell, the second network device can stop sending the reference signal to the first area, and the first area belongs to the target cell. It can be understood that the first area is part of the target cell, or is the target cell, and when the second network device determines that all terminal devices in the first area access the target cell, it is not necessary to send the reference signal to the first area.

[0269] In the communication method shown in FIG. 10, when the cell switching occurs, the terminal device can receive first configuration information for configuring the time domain position of the reference signal of the target cell from the first network device corresponding to the source cell, and the transmission time interval of the reference signal is less than the transmission period or SMTC period of the synchronization signal of the target cell, so that the terminal device can receive the reference signal at the corresponding time domain position to synchronize with the target cell in the downlink, without waiting for a long time to receive the synchronization signal to synchronize with the target cell in the downlink. The switching interruption delay of the terminal device can be reduced, the communication experience of the user can be improved, and the continuity of the user service can be ensured.

[0270] It can be understood that the methods and / or steps implemented by the network device in the above embodiments can also be implemented by components (such as processors, chips, chip systems, circuits, logic modules, or software) available for the network device; the methods and / or steps implemented by the terminal device can also be implemented by components (such as processors, chips, chip systems, circuits, logic modules, or software) available for the terminal device.

[0271] The above mainly introduces the schemes provided by the present application. Correspondingly, the present application also provides a communication apparatus, which is used to implement various methods in the above method embodiments. The communication apparatus can be the network device in the above method embodiments, or an apparatus containing the network device, or a component available for the network device, such as a chip or a chip system. Or, the communication apparatus can be the terminal device in the above method embodiments, or an apparatus containing the terminal device, or a component available for the terminal device, such as a chip or a chip system.

[0272] It can be understood that the communication apparatus contains the hardware structure and / or software module for executing the corresponding functions in order to implement the above functions. Those skilled in the art should easily realize that, in combination with the units and algorithm steps of the examples described in the embodiments disclosed herein, the present application can be realized in the form of hardware or a combination of hardware and computer software. Whether a certain function is executed in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0273] The embodiments of the present application can divide the functional modules of the communication device according to the method embodiments described above. For example, each functional module can be divided according to each function, or two or more functions can be integrated into one processing module. The integrated module can be implemented in the form of hardware or in the form of a software functional module. It should be noted that the division of the modules in the embodiments of the present application is illustrative, and is only a logical functional division. Actual implementation can have another division manner.

[0274] Taking the communication device as the network device or the terminal device in the method embodiments described above, FIG. 12 is a structural schematic diagram of a communication device provided by an embodiment of the present application. As shown in FIG. 12, the communication device 1200 includes a processing module 1201 and a transceiver module 1202. The processing module 1201 is configured to perform the processing functions of the network device or the terminal device in the method embodiments described above. The transceiver module 1202 is configured to perform the transceiving functions of the network device or the terminal device in the method embodiments described above. The related content of each step involved in the method embodiments described above can be referred to the function description of the corresponding functional module, and will not be repeated here.

[0275] In a possible design, the transceiver module 1202 in the embodiments of the present application can include a receiving module and a sending module (not shown in FIG. 12). The sending module and the receiving module are respectively configured to implement the sending function and the receiving function of the communication device 1200.

[0276] In a possible design, the communication device 1200 can further include a storage module (not shown in FIG. 12), which stores a program or instructions. When the processing module 1201 executes the program or instructions, the communication device 1200 can perform the functions of the network device or the terminal device in the method shown in FIG. 10.

[0277] In some embodiments, the processing module 1201 involved in the communication device 1200 can be implemented by a processor or a processor-related circuit component, and can be a processor or a processing unit. The transceiver module 1202 can be implemented by a transceiver or a transceiver-related circuit component, and can be a transceiver or a transceiving unit.

[0278] Exemplarily, FIG. 13 is a structural schematic diagram of another communication apparatus provided by the embodiments of the present application. The communication apparatus can be the network device or the terminal device in the method embodiments, or can be a chip (system) or other components or assemblies that can be arranged in the network device or the terminal device. As shown in FIG. 13, the communication apparatus 1300 can include a processor 1301, a bus 1302, a communication interface 1303, and a memory 1304. The processor 1301, the memory 1304, and the communication interface 1303 communicate through the bus 1302. The communication apparatus 1300 can be the network device or the terminal device. It should be understood that the number of processors and memories in the communication apparatus 1300 is not limited by the present application.

[0279] The bus 1302 can be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, only one line is shown in FIG. 13, but it does not mean that there is only one bus or only one type of bus. The bus 1302 can include a path for transmitting information between various components (for example, the memory 1304, the processor 1301, and the communication interface 1303) of the communication apparatus 1300.

[0280] The processor 1301 can include any one or more of a central processing unit (CPU), a graphics processing unit (GPU), a microprocessor (MP), or a digital signal processor (DSP) processor, etc.

[0281] The memory 1304 can include a volatile memory (for example, a random access memory (RAM)), and the processor 1301 can further include a non-volatile memory (for example, a read-only memory (ROM), a flash memory, a hard disk drive (HDD), or a solid state drive (SSD)).

[0282] The communication interface 1303 uses a transceiver module such as, but not limited to, a network interface card or a transceiver to implement the communication between the communication apparatus 1300 and other devices or communication networks.

[0283] The executable program code stored in the memory 1304 is executed by the processor 1301 to realize the functions of the network device or the terminal device in the foregoing method embodiments respectively. That is, the instructions for executing the communication method are stored in the memory 1304.

[0284] In another aspect, the embodiments of the present application further provide a computer program product containing instructions, which, when executed on a communication device, enable the communication device to perform the method described in the foregoing embodiments.

[0285] In another aspect, the embodiments of the present application further provide a computer readable storage medium. The computer readable storage medium stores computer programs or instructions, which, when executed on a communication device, enable the communication device to perform the method described in the foregoing embodiments.

[0286] In the foregoing embodiments, the implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented by using a software program, the implementation can be achieved entirely or partially in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the entire or partial process or function according to the embodiments of the present application is generated. The computer can be a general purpose computer, a special purpose computer, a computer network, or other programmable apparatus. The computer instructions can be stored in a computer readable storage medium or transferred from one computer readable storage medium to another computer readable storage medium, for example, the computer instructions can be transferred from one website, computer, server, or data center to another website, computer, server, or data center through a wired (for example, coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (for example, infrared, wireless, microwave, etc.) manner. The computer readable storage medium can be any available medium that can be accessed by a computer or data storage device, such as one or more servers, data centers, etc., integrated with one or more media. The available medium can be a magnetic medium (for example, floppy disk, hard disk, magnetic tape), an optical medium (for example, digital video disk (DVD)), or a semiconductor medium (for example, solid state disk (SSD)), etc.

[0287] Those skilled in the art can clearly understand that the units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0288] Those skilled in the art can clearly understand that, for the convenience and brevity of the description, the specific working processes of the above-described system, device and unit can refer to the corresponding processes in the foregoing method embodiments, which will not be repeated here.

[0289] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division, and there can be another division manner in actual implementation. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or other forms.

[0290] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e. they can be located in one place or distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment. In addition, the functional units in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present alone, or two or more units can be integrated in one unit.

[0291] If the functions are realized in the form of software function units and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application essentially or the parts that make contributions to the prior art or parts of the technical solutions can be embodied in the form of software products. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The foregoing storage medium includes: a U disk, a mobile hard disk, a ROM, a random access memory RAM, a magnetic disk or an optical disk, and various storage medium that can store program codes.

[0292] Although the application has been described in connection with various embodiments thereof, it will be understood that the application is capable of further modifications and that this application is intended to cover any and all such variations, using the scope of the claims. In the claims, the term comprising does not exclude the presence of other elements or steps than those listed in a claim. The term "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. A single processor or other unit can fulfil the functions of several items recited in the claims. A plurality of recited means, structural elements, or acts can be provided by a single item to perform the recited functions. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

[0293] Although the application has been described in connection with specific features thereof, it will be evident to those skilled in the art that various modifications and changes can be made to the application without departing from the spirit and scope of the application. Accordingly, it is intended that all possible modifications and changes be encompassed by the following claims, and that the application be limited only by the claims.

Claims

1. A communication method characterized by comprising: The method comprises: receiving first configuration information from a first network device, the first configuration information being used for configuring a time domain position of a reference signal corresponding to a target cell, the first network device being a network device corresponding to a source cell of a terminal device; receiving the reference signal from a second network device according to the first configuration information, the second network device being a network device corresponding to the target cell; performing downlink synchronization with the target cell according to the reference signal.

2. The method of claim 1, wherein, The first configuration information is carried in a broadcast message and sent.

3. The method of claim 1, wherein, The first configuration information is carried in a radio resource control (RRC) message, and the RRC message is used for instructing the terminal device to switch to the target cell.

4. The method according to any one of claims 1 to 3, characterized in that, The downlink synchronization with the target cell according to the reference signal comprises: performing fine time tracking and acquiring all timing information of the target cell according to the reference signal; or performing fine time tracking and acquiring all timing information of the target cell according to the reference signal and a second synchronization signal sent by the second network device. Before performing the fine time tracking and acquiring all timing information of the target cell, the method further comprises: acquiring downlink timing of the target cell according to ephemeris information of the first network device, ephemeris information of the second network device, and a timing deviation of a synchronization signal, the timing deviation of the synchronization signal being a time offset between a time domain position of a synchronization signal of the first network device and a time domain position of a synchronization signal of the second network device.

5. The method according to any one of claims 1-3, characterized in that, The downlink synchronization with the target cell according to the reference signal comprises: performing the downlink synchronization with the target cell according to the reference signal and a synchronization signal sent by the second network device.

6. A communication method characterized by comprising: The method comprises: a first network device acquiring first configuration information, the first configuration information being used for configuring a time domain position of a reference signal corresponding to a target cell, the reference signal being used for a terminal device to perform downlink synchronization with the target cell, the first network device being a network device corresponding to a source cell of the terminal device; the first network device sending the first configuration information to the terminal device.

7. The method of claim 6, wherein, The first configuration information is carried in a broadcast message and sent.

8. The method of claim 6, wherein, The first configuration information is carried in an RRC message, and the RRC message is used for instructing the terminal device to switch to the target cell.

9. The method according to any one of claims 1-8, characterized in that, The first configuration information comprises time domain position information of at least one reference signal, the time domain position information of the reference signal comprising an offset value of a time domain starting position of the reference signal relative to a first time or a first time domain starting position, the first time being a time at which the first network device stops providing services for the source cell of the terminal device, and the first time domain starting position being a starting time domain position of a first synchronization signal sent by the first network device or a starting time domain position of a second synchronization signal sent by a second network device, the second network device being a network device corresponding to the target cell.

10. The method of claim 9, wherein, The first configuration information further includes a timing offset of a synchronization signal, the timing offset of the synchronization signal being a time offset between a time domain position of a synchronization signal of the first network device and a time domain position of a synchronization signal of the second network device.

11. A communication method, comprising: The method comprises: The second network device generates a reference signal, the second network device being a network device corresponding to a target cell; The second network device sends the reference signal to a terminal device, the reference signal being used for downlink synchronization between the terminal device and the target cell.

12. The method of claim 11, wherein, The method further comprises: The second network device obtains area information of the terminal device; The second network device sends the reference signal to the terminal device, comprising: The second network device sends the reference signal to an area where the terminal device is located according to the area information, the area where the terminal device is located being a part of a coverage range of the target cell.

13. The method of claim 12, wherein, The second network device obtains area information of the terminal device, comprising: The second network device receives a handover request from a first network device, the handover request being used for requesting to hand over the terminal device to the target cell, the handover request including the area information, the first network device being a network device corresponding to a source cell of the terminal device.

14. The method according to any one of claims 11-13, characterized in that, The second network device sends the reference signal to the terminal device, comprising: The second network device starts to send the reference signal to the terminal device from a first time point, the first time point being a time point at which a first network device stops providing coverage service for a source cell of the terminal device, the first network device being a network device corresponding to the source cell of the terminal device.

15. The method according to any one of claims 11-13, characterized in that, The second network device sends the reference signal to the terminal device, comprising: The second network device starts to send the reference signal to the terminal device from a second time point, the second time point being a time point at which the second network device provides coverage service for the target cell.

16. The method of any one of claims 11-13, wherein, The second network device sends the reference signal to the terminal device, comprising: The second network device starts to send the reference signal to the terminal device from a third time point, the third time point being determined according to at least one of the following: the first time point, the second time point, a transmission delay between the first network device and the second network device, or an air interface transmission delay between the first network device and the terminal device, the first network device being a network device corresponding to a source cell of the terminal device.

17. The method according to any one of claims 11-16, characterized in that, The method further comprises: After a terminal device in a first area accesses the target cell, the second network device stops sending the reference signal to the first area, the first area belonging to the target cell.

18. The method of any one of claims 1-17, wherein, A transmission time interval of the reference signal is less than a transmission period of a synchronization signal of a second network device or a synchronization signal based measurement timing configuration (SMTC) period, the second network device being a network device corresponding to the target cell.

19. The method of any one of claims 1-18, wherein, The reference signal is a channel state information-reference signal (CSI-RS) or a tracking reference signal (TRS).

20. A communications device, characterized by The apparatus comprises means for performing the method of any one of claims 1-19.

21. A communications device, characterized by The apparatus comprises: a processor; The processor is configured to execute computer programs or instructions to cause the method of any one of claims 1-19 to be implemented.

22. A communication chip, comprising: The chip has instructions stored therein that, when executed on a communication device, cause the method of any one of claims 1-19 to be implemented.

23. A computer-readable storage medium, characterized in that, The computer readable storage medium has computer programs or instructions stored therein that, when executed by a communication device, implement the method of any one of claims 1-19.

24. A computer program product, characterised in that, The computer program product comprises computer program code that, when executed on a communication device, causes the communication device to implement the method of any one of claims 1-19.

Images