Time advance reporting method and communication apparatus

Abstract

Embodiments of the present application provide a time advance reporting method and a communication apparatus, capable of achieving time advance reporting in a cell handover process. The method comprises: receiving a handover command from an access network device, wherein the handover command is used for instructing a terminal device to hand over from a source cell to a target cell; and when the handover command carries first indication information and / or second instruction information, triggering time advance reporting, wherein the time advance is a time advance corresponding to the target cell, the first indication information is used for indicating an offset threshold of the time advance reported by the terminal device, and the second instruction information is used for instructing the terminal device to report the time advance.

Description

Timing advance reporting method and communication device

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on August 11, 2023, with application number 202311018454.7 and application name “Timing Advance Reporting Method and Communication Device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The embodiments of the present application relate to the field of communications, and in particular to a timing advance reporting method and a communication device. Background Art

[0003] Timing advance (TA) is used for uplink transmissions from terminal devices. It means that the system frame of uplink data sent by the terminal device is a certain amount of time ahead of the downlink frame received. In non-terrestrial network (NTN) communication systems, TA includes the transmission delay from the terminal device to the satellite and the transmission delay from the satellite to the reference point (RP). The transmission delay from the terminal device to the satellite is the service link round-trip time (RTT), which can be expressed as RTT and is calculated by the terminal device based on global navigation satellite system (GNSS) information and ephemeris information. The transmission delay from the satellite to the RP is represented by Common TA, which is calculated by the network side and sent to the terminal device.

[0004] In NTN, the current 3rd Generation Partnership Project (3GPP) protocol stipulates the following three triggering conditions for terminal devices to report TA: (1) When the terminal device receives a TA report indication from the network, TA reporting is triggered; (2) When the terminal device receives the configuration of a TA offset threshold (offsetThresholdTA) and the terminal device has not reported TA in the current serving cell, TA reporting is triggered; (3) When the network configures TA for the terminal device and the change in the current TA estimate of the terminal device compared with the last reported TA value exceeds the threshold offsetThresholdTA, TA reporting is triggered.

[0005] Among the three conditions for triggering TA reporting mentioned above, condition (1) is the TA reporting process of the terminal device during the random access phase, and conditions (2) and (3) are the TA reporting processes of the terminal device in the connected state and non-handover scenarios. However, none of the three conditions for triggering TA reporting clearly defines the TA reporting triggering conditions of the terminal device during the cell handover process. Therefore, how to implement TA reporting during the cell handover process has become an urgent problem to be solved.

[0006] Summary of the Invention

[0007] The embodiments of the present application provide a timing advance reporting method and a communication device, which can implement TA reporting during cell switching.

[0008] To achieve the above objectives, this application adopts the following technical solutions:

[0009] On the first aspect, a timing advance reporting method is provided, which can be executed by a terminal device, or by a component of the terminal device, such as a processor, chip, or chip system of the terminal device, or can be implemented by a logic module or software that can realize all or part of the terminal device functions. The method includes: receiving a switching command from an access network device. The switching command is used to instruct the terminal device to switch from a source cell to a target cell. When the switching command carries the first indication information and / or the second indication information, the timing advance reporting is triggered. The timing advance is the timing advance corresponding to the target cell, the first indication information is used to indicate the offset threshold of the timing advance reported by the terminal device, and the second indication information is used to instruct the terminal device to report the timing advance.

[0010] Based on this timing advance reporting method, a process for determining whether a terminal device reports the timing advance corresponding to a target cell when a handover command carries a timing advance offset threshold (such as the first indication information) and / or a timing advance reporting indication (such as the second indication information) is clarified, thereby ensuring that accurate timing advance reporting is triggered during cell handover. It should be understood that in the embodiment of the present application, the access network device that sends the handover command is the access network device corresponding to the source cell.

[0011] In one possible design, when the handover command carries the first indication information and / or the second indication information, triggering the timing advance reporting may include: if the handover command carries the first indication information, triggering the timing advance reporting during the random access process to the target cell or after the random access to the target cell is successful. Based on this design, when the handover command carries the first indication information, the terminal device may trigger the timing advance reporting during the random access process to the target cell or after the random access is completed.

[0012] In one possible design scheme, when the handover command carries the first indication information and / or the second indication information, triggering the timing advance reporting may include: if the handover command carries the first indication information and the second indication information, triggering the timing advance reporting during the random access to the target cell or after the random access to the target cell is successful. Based on the design scheme, when the handover command carries the first indication information and the second indication information, the terminal device may trigger the timing advance reporting during the random access to the target cell or after the random access is completed.

[0013] In one possible design, triggering timing advance reporting when a handover command carries first indication information and / or second indication information may include: when a terminal device is configured for cell handover based on RACH-less, if the handover command carries first indication information and / or second indication information, triggering timing advance reporting after the cell handover is completed. Based on this design, when the terminal device performs cell handover based on RACH-less, the terminal device may trigger timing advance reporting after the cell handover is completed.

[0014] In one possible design scheme, the switching command may be a radio resource control RRC reconfiguration message carrying synchronization reconfiguration.

[0015] On the second aspect, a timing advance reporting method is provided, which can be executed by an access network device, or by a component of the access network device, such as a processor, chip, or chip system of the access network device, or can be implemented by a logic module or software that can realize all or part of the functions of the access network device. The method includes: sending a switching command to a terminal device. The switching command is used to instruct the terminal device to switch from a source cell to a target cell, and the switching command carries a first indication information and / or a second indication information. Receive the timing advance from the terminal device. The timing advance is the timing advance corresponding to the target cell, the first indication information is used to indicate the offset threshold of the timing advance reported by the terminal device, and the second indication information is used to instruct the terminal device to report the timing advance.

[0016] Among them, the technical effects of the second aspect can refer to the description of the technical effects in the first aspect, and will not be elaborated on here.

[0017] On the third aspect, a timing advance reporting method is provided, which can be executed by a terminal device, or by a component of the terminal device, such as a processor, chip, or chip system of the terminal device, or can be implemented by a logic module or software that can realize all or part of the terminal device functions. The method includes: receiving a radio resource control RRC reconfiguration message from an access network device, wherein the RRC reconfiguration message is used to instruct the terminal device to switch from a source cell to a target cell. In the case where the RRC reconfiguration message carries the first indication information but does not carry the second indication information, it is determined that the timing advance reporting is not triggered. The timing advance is the timing advance corresponding to the target cell, the first indication information is used to indicate the offset threshold of the timing advance reported by the terminal device, and the second indication information is used to instruct the terminal device to report the timing advance.

[0018] In one possible design, the RRC reconfiguration message may carry synchronous reconfiguration.

[0019] In a fourth aspect, a communication method is provided, which can be executed by a terminal device, or by a component of the terminal device, such as a processor, chip, or chip system of the terminal device, or by a logic module or software that can implement all or part of the terminal device functions. The method includes: receiving a handover command from an access network device. The handover command is used to instruct the terminal device to switch from a source cell to a target cell. When the handover command does not carry the second indication information and the terminal device reuses the configuration of the source cell, it is determined that the access network device has configured the offset threshold of the timing advance of the target cell. The second indication information is used to instruct the terminal device to report the timing advance.

[0020] In one possible design scheme, the switching command may be a radio resource control RRC reconfiguration message carrying synchronization reconfiguration.

[0021] In a fifth aspect, a communication device is provided. The communication device includes: a module, unit, or means for executing the method described in any one of the first to fourth aspects, and the module, unit, or means can be implemented by hardware, software, or by executing the corresponding software implementation through hardware. The hardware or software includes one or more modules or units corresponding to the above functions, such as a transceiver module and a processing module. For example, the transceiver module is used to indicate the transceiver function of the communication device, and the processing module is used to perform functions of the communication device other than the transceiver function.

[0022] In one possible design solution, the transceiver module may include a receiving module and a sending module, wherein the sending module is used to implement the sending function of the communication device described in the fifth aspect, and the receiving module is used to implement the receiving function of the communication device described in the fifth aspect.

[0023] In one possible design, the communication device described in the fifth aspect may further include a storage module that stores a program or instruction. When the processing module executes the program or instruction, the communication device described in the fifth aspect can execute the method described in any one of aspects 1 to 4.

[0024] Among them, the communication device described in the fifth aspect can be a terminal device or an access network device, or it can be a chip (system) or other parts or components that can be set in the terminal device or access network device, or it can be a device that includes a terminal device or an access network device. This application does not limit this.

[0025] In the sixth aspect, a communication device is provided, comprising: a processor and a communication interface; the communication interface is used to communicate with a module outside the communication device; the processor is used to execute a computer program or instruction so that the communication device executes the method described in any one of the first to fourth aspects above.

[0026] In a seventh aspect, a communication device is provided (for example, the communication device may be a chip or a chip system), which includes a processor for implementing the functions involved in any one of the above-mentioned first to fourth aspects.

[0027] In some possible designs, the communication device includes a memory for storing necessary program instructions and / or data.

[0028] In one possible design, the processor can be integrated with the memory.

[0029] In some possible designs, when the communication device is a chip system, it can be composed of a chip, or it can include a chip and other discrete devices.

[0030] In an eighth aspect, a communication device is provided, comprising: a transceiver and a processor, wherein the transceiver is used to exchange information between the communication device and other communication devices, and the processor executes program instructions to perform the method described in any one of the first to fourth aspects above.

[0031] In one possible design, the communication device described in aspect 11 may further include a memory. The memory may be integrated with the processor or provided separately. The memory may be used to store the computer program and / or data involved in the method described in any one of aspects 1 to 4 above.

[0032] It should be understood that the sixth to eighth aspects above include modules, units, or means for implementing the methods described in any one of the first to fourth aspects above, and the modules, units, or means may be implemented by hardware, software, or by hardware executing the corresponding software implementation. The hardware or software includes one or more modules or units for performing the functions involved in the above methods.

[0033] It can be understood that when the communication device provided in any one of the sixth to eighth aspects is a chip, the above-mentioned sending action / function can be understood as output, and the above-mentioned receiving action / function can be understood as input.

[0034] In the ninth aspect, a computer-readable storage medium is provided, which stores a computer program or instruction. When the computer-readable storage medium is run on a communication device, the communication device can execute the method described in any one of the first to fourth aspects above.

[0035] In a tenth aspect, a computer program product comprising instructions is provided, which, when executed on a communication device, enables the communication device to execute the method described in any one of the first to fourth aspects above.

[0036] In the eleventh aspect, a communication system is provided, comprising a terminal device for executing the method described in the first aspect and an access network device for executing the method described in the second aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] FIG1 is a schematic diagram of an architecture of two satellite communications provided by an embodiment of the present application;

[0038] FIG2 is a schematic diagram of a scenario of TA calculation in NTN communication provided by an embodiment of the present application;

[0039] FIG3 is a schematic diagram of a cell switching process provided by an embodiment of the present application;

[0040] FIG4 is a schematic diagram of a four-step random access process according to an embodiment of the present application;

[0041] FIG5 is a schematic diagram of a two-step random access process provided by an embodiment of the present application;

[0042] FIG6 is a schematic diagram of the architecture of a communication system provided in an embodiment of the present application;

[0043] FIG7 is a schematic structural diagram of an access network device based on a CU-DU separation architecture provided in an embodiment of the present application;

[0044] FIG8 is a flow chart of a timing advance reporting method provided in an embodiment of the present application;

[0045] FIG9 is a flow chart of another timing advance reporting method provided in an embodiment of the present application;

[0046] FIG10 is a schematic structural diagram of a communication device provided in an embodiment of the present application;

[0047] FIG11 is a schematic structural diagram of another communication device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0048] The following describes the related technologies involved in the embodiments of this application.

[0049] 1. NTN communication

[0050] Non-terrestrial communications have the advantages of wide coverage, long communication distance, high reliability, great flexibility, and high throughput. They are not affected by geographical environment, climatic conditions, or natural disasters, and have been widely used in aviation communications, maritime communications, military communications, and other fields. Introducing NTN into the fifth-generation (5G) mobile network can improve the performance of the communication system. Satellite communication systems and high altitude platform station (HAPS) communication systems are typical non-terrestrial communication systems. On the one hand, satellite networks can provide communication services to areas that are difficult for terrestrial networks to cover, such as oceans, forests, deserts, or remote areas. On the other hand, satellite networks can enhance the reliability of 5G communications, such as providing more stable communication services to users in high-speed mobile scenarios such as trains and airplanes. In addition, satellite networks can also provide more data transmission resources and support a larger number of connections.

[0051] Generally speaking, the higher the satellite's orbit, the larger its coverage area, but the longer the communication delay. Based on the orbital altitude, satellites can be divided into:

[0052] (1) Low Earth orbit (LEO): orbital altitude is 160 to 2000 kilometers (km);

[0053] (2) Medium Earth Orbit (MEO): orbital altitude is 2000~35786km;

[0054] (3) Geostationary Earth orbit (GEO): orbital altitude is 35786 km;

[0055] Among them, GEO is a synchronous earth satellite orbit, and the satellites operating in this orbit are stationary relative to the ground; LEO and MEO are collectively referred to as non-geostationary orbits (NGSO), and the satellites operating in such orbits move at high speed relative to the ground.

[0056] NGSOs are further categorized as Earth Moving Cells (EMCs) and Earth Fixed Cells (EFCs), depending on whether the satellite's beam moves with it. In EMCs, the cell moves relative to the ground, and the satellite's beam follows its movement. In EFCs, the cell remains fixed relative to the ground for a specified period of time, and the satellite antenna uses its beamforming capabilities to direct the beam to a fixed area on the ground for a specified period of time.

[0057] Satellites can generally be divided into two categories based on their working mode. The first type is transparent forwarding, as shown in (a) of Figure 1. Satellites forward cell information from ground network equipment (such as the next generation Node-B (gNB)). The role of the satellite is wireless frequency filtering, frequency conversion, and amplification. That is, the satellite mainly acts as a layer 1 relay (L1 relay) to regenerate the physical layer signal and does not have other higher protocol layers. The second type is regenerative, in which the satellite has the processing function of a base station. In the regenerative working mode, it can be further divided into regenerative satellites without inter-satellite links, that is, there is no inter-satellite link (ISL) between satellites, as shown in (b) of Figure 1; regenerative satellites with inter-satellite links, that is, there is an interface between satellites that can directly exchange data, where the inter-satellite link is the Xn interface; there is also an architecture in which the satellite only has the distributed unit (DU) processing function of the base station. In this scenario, the satellite acts as a DU.

[0058] 2. TA

[0059] A key feature of uplink transmission is that uplink transmissions from different terminal devices in the same cell do not interfere with each other. To ensure orthogonality in uplink transmissions and avoid intra-cell interference, the base station requires that signals from different terminal devices in the same subframe but different frequency domain resources (different resource blocks (RBs)) arrive at the base station at essentially aligned times. As long as the base station receives the uplink data sent by the terminal device within the cyclic prefix (CP) range, it can correctly decode the uplink data. Therefore, uplink synchronization requires that the arrival times of signals from different terminal devices in the same subframe at the base station all fall within the cyclic prefix range.

[0060] To ensure time synchronization on the receiving side (base station side), Long Term Evolution (LTE) / New Radio (NR) introduces an uplink timing advance (TA) mechanism. From the perspective of the terminal device, TA is essentially a negative offset between the start time of the received downlink subframe and the time of the uplink subframe transmission. By appropriately controlling the offset for each terminal device, the base station can control the time when uplink signals from different terminal devices arrive at the base station. For terminal devices farther away from the base station, due to the larger transmission delay, they need to send uplink data earlier than terminal devices closer to the base station.

[0061] In a terrestrial network (TN), a base station sends a timing advance command to a terminal device in two ways:

[0062] (1) During the random access process, the base station determines the TA value by measuring the received preamble and sends it to the terminal via the Timing Advance Command field in the random access response (RAR). This process is called the "initial uplink synchronization process."

[0063] (2) In the radio resource control (RRC) connected state (RRC_CONNECTED), the base station needs to maintain TA information. Although the terminal device and the base station achieve uplink synchronization during the random access process, the timing of the uplink signal reaching the base station may change over time. Therefore, the terminal device needs to continuously update its uplink timing advance to maintain uplink synchronization. In LTE / NR, the base station determines the TA value of each terminal device based on measuring the uplink transmission of the corresponding terminal device. In theory, any signal sent by the terminal device, such as the sounding reference signal (SRS) / demodulation reference signal (DMRS) / channel quality indicator (CQI) / acknowledgement (ACK) / negative acknowledgement (NACK) / downlink physical shared channel (PUSCH), etc., can be used to measure TA. If a specific terminal device needs correction, the base station will send a Timing Advance Command to the terminal device, requesting it to adjust the uplink transmission timing. The Timing Advance Command is sent to the terminal device via a timing advance command media access control (MAC) control element (CE) (Timing Advance Command MAC-CE).

[0064] In NTN, as shown in Figure 2, TA includes the transmission delay from the terminal device to the satellite and the transmission delay from the satellite to the RP. Specifically, TA can be determined according to the following formula:

[0065] TA=N_TA+N_TA,offset+N_TA,adj^Common+N_TA,adj^UE;

[0066] Wherein, N_TA is the TA adjustment value, which is calculated by the network side based on the time of the actual received uplink data and the TA value reported by the terminal device; N_TA,offset is the fixed uplink and downlink frame offset configured by the network side, which has a finite number of fixed values ​​in the time division duplexing (TDD) system and is 0 in the frequency division duplexing (FDD) system; N_TA,adj^Common is the transmission delay from the satellite to the RP, expressed as the common TA, which is calculated by the network side and sent to the terminal device; N_TA,adj^UE is the transmission delay from the terminal device to the satellite, which is the service link transmission delay and is calculated by the terminal device based on GNSS information and ephemeris information.

[0067] The terminal device can report the TA through MAC-CE. Before reporting the TA, a MAC-CE for the TA report must be generated. The MAC-CE always uses the latest TA report to assemble the package. In other words, when multiple TA reports are triggered, the latest TA is always used for assembling the package. The generation process of the MAC-CE for TA reporting is as follows:

[0068] - If at least one TA report is triggered and the triggered TA report has not been cancelled;

[0069] - If the uplink shared channel (UL-SCH) is available and the UL-SCH resources are sufficient to carry the TA report;

[0070] - A TA reporting MAC CE (Timing Advance Report MAC CE) is generated; - Otherwise, a scheduling request may be triggered to request UL-SCH resources.

[0071] The UL-SCH resource availability condition is: if the MAC entity has configured, received or confirmed the uplink grant (UL Grant), the UL-SCH resource is considered available. In addition, if the MAC packet data unit (PDU) carrying the TA reporting MAC-CE has been sent, the previously triggered TA report will be cancelled.

[0072] 3. Cell switching

[0073] Due to the movement of the terminal device, the signal quality of the network currently accessed by the terminal device may deteriorate, and it is necessary to switch to a cell with better signal quality to obtain service. For the traditional switching process, the switching of the terminal device is controlled by the access network device, that is, the access network device instructs the terminal device which cell to switch to and how to switch by sending a switching command. As shown in Figure 3, after receiving the switching command, the terminal device accesses the target cell according to the content contained in the switching command. Therefore, the network side needs to obtain the target cell identifier. The specific switching steps include the following:

[0074] S301: The source base station sends an RRC reconfiguration message to the terminal device. Correspondingly, the terminal device receives the RRC reconfiguration message from the source base station.

[0075] The source base station sends an RRC reconfiguration message to the terminal device in the connected state to instruct the terminal device to perform measurement, wherein the RRC reconfiguration message includes parameters such as measurement object, report configuration, and measurement identifier.

[0076] S302: The terminal device sends a measurement report to the source base station. Correspondingly, the source base station receives the measurement report from the terminal device.

[0077] After the terminal device measures the cell according to the RRC reconfiguration message, it generates a measurement report to report various events to the source base station.

[0078] S303: The source base station executes a handover decision.

[0079] After receiving the measurement report, the source base station determines, based on the measurement report, to perform a cell handover, ie, handover from the source base station to the target base station.

[0080] S304: The source base station sends a handover request (Handover Request) to the target base station. Correspondingly, the target base station receives the handover request from the source base station.

[0081] S305: The target base station performs admission control.

[0082] The target base station determines whether to allow the terminal device to access based on the handover request. If the judgment result is allowed, it sends a handover confirmation message to the source base station. The handover request confirmation includes parameters such as the new cell-radio network temporary identifier (C-RNTI) and the target base station security-related algorithm.

[0083] S306: The target base station sends a handover request acknowledgment (Handover Request ACK) to the source base station. Correspondingly, the source base station receives the handover request acknowledgment from the target base station.

[0084] S307: The source base station sends an RRC reconfiguration message to the terminal device. Correspondingly, the terminal device receives the RRC reconfiguration message from the source base station.

[0085] After receiving the handover confirmation message from the target base station, the source base station sends an RRC reconfiguration message (handover command) to the terminal device. The content contained in the RRC reconfiguration message comes from the handover request confirmation of S306. Specifically, the handover command in the NR system contains relevant information of the target cell and the relevant configuration parameters required for the terminal device to access the target cell. For example, target cell information (such as the physical cell identifier (PCI) of the target cell and the frequency information corresponding to the target cell), the C-RNTI allocated by the target cell to the terminal device, the random access channel (RACH) resource information required to access the target cell (such as dedicated RACH resources and / or public RACH resources), etc.

[0086] S308: The terminal device performs random access to the target base station.

[0087] The terminal device initiates random access to the target base station according to the handover command. In the existing handover process, the terminal device will disconnect from the source base station, and there will be a brief interruption in the terminal device's data transmission and reception before successfully accessing the target base station.

[0088] S309: The terminal device sends an RRC reconfiguration complete message to the target base station. Correspondingly, the target base station receives the RRC reconfiguration complete message from the terminal device.

[0089] The above is an overview of the existing cell handover process. For specific implementation, please refer to the description in the relevant existing technology, which will not be described in detail.

[0090] Cell switching can be intra-site switching or inter-site switching. Intra-site switching may refer to the source cell and the target cell belonging to the same access network device (such as a base station), wherein the source cell and the target cell may be the same cell or different cells; inter-site switching refers to the source cell and the target cell belonging to different access network devices (such as base stations). This application does not limit this. It should be understood that the cell is the coverage area of ​​the access network device, the source cell corresponds to the source access network device (such as the source base station), and the target cell corresponds to the target access network device (such as the target base station). In the embodiment of the present application, cell switching mainly refers to inter-site switching.

[0091] It should also be understood that the source cell and the target cell may belong to the same access network device, or in other words, the source cell and the target cell may be co-located. In this case, for a certain terminal device, the TA corresponding to the target cell may be equal to the TA corresponding to the source cell. The target cell may also be a small cell, in which case, for a certain terminal device, the TA of the target cell may be 0.

[0092] 4. Random access (RA)

[0093] Random access is the process from when a terminal device begins sending a random access preamble to the access network device it is attempting to access, until a connection is established between the terminal device and the access network device. Random access can occur during handover, RRC re-establishment, and other processes.

[0094] Random access includes contention-based random access (CBRA) and non-contention-based random access (CFRA). CBRA can be applied to scenarios such as cell handover or downlink data transmission needs but synchronization loss. CFRA refers to random access initiated by a terminal device using a preamble designated for non-contention-based random access at a random access occasion (RO) specified by the access network device.

[0095] The following takes a terrestrial network (TN) as an example to introduce 4-step random access and 2-step random access of contention-based random access.

[0096] For example, Figure 4 is a flow chart of a 4-step random access process. As shown in Figure 4, the 4-step random access process may include the following steps:

[0097] S401: The terminal device sends an RA preamble to the access network device. Correspondingly, the access network device receives the RA preamble from the terminal device.

[0098] Among them, the RA preamble code can be used to estimate the uplink time difference between the terminal device and the access network device.

[0099] The RA preamble may also be referred to as the first message or message (Msg) 1 or message one in the RA process.

[0100] S402: In response to the RA preamble, the access network device sends a random access response (RAR) to the terminal device. Correspondingly, the terminal device receives the RAR from the access network device.

[0101] The RAR includes the TA, uplink (UL) grant, and cell-radio network temporary identifier (C-RNTI), etc. The RAR can also be used to indicate that the access network device has successfully received the RA preamble from the terminal device.

[0102] RAR is also known as message 2 in the RA process, or Msg2, or the second message. The RAR can be carried on the physical downlink shared channel (PDSCH). It is understood that the same PDSCH can carry the RARs corresponding to multiple terminal devices.

[0103] S403: The terminal device sends a third message to the access network device. Correspondingly, the access network device receives the third message from the terminal device.

[0104] Message three is also known as Msg3 or the third message in the RA process. Here, the content of Msg3 may also be different depending on the terminal device status and application scenarios. For the RRC_IDLE / INACTIVE state, when the terminal device initiates random access, Msg3 carries the common control channel (CCCH) service data unit (SDU) content. For the RRC_CONNECTED state, when the terminal device initiates random access, Msg3 carries the C-RNTI.

[0105] S404: The access network device sends message 4 to the terminal device. Correspondingly, the terminal device receives message 4 from the access network device.

[0106] Message 4 may also be referred to as a contention resolution message, Msg4, or a fourth message in the RA process.

[0107] If Msg3 carries a CCCH SDU, then Msg4 carries the content or part of the content of Msg3. If the content of Msg4 received by the terminal device matches that of Msg3, the contention is considered resolved and the random access process is successful. If Msg3 carries a C-RNTI, then Msg4 carries the physical downlink control channel (PDCCH) addressed to the C-RNTI (the PDCCH transmission is addressed to the C-RNTI). If Msg4 carries the PDCCH addressed to the C-RNTI of the terminal device, the contention is considered resolved and the random access process is successful.

[0108] It should be understood that, based on the different random access triggering scenarios, except that Msg1 is used to transmit the preamble and remains unchanged, the messages corresponding to Msg2 / 3 / 4 may be different from Msg2 / 3 / 4 in the random access process used for cell access. For example, in the reconstruction process, Msg2 is RAR, and Msg3 is the "RRCReestablishmentRequest" message, and Msg4 includes the content or part of the content of the "RRCReestablishmentRequest" message; in the random access process initiated by a terminal device in the RRC_IDLE state, Msg2 is RAR, and Msg3 is the "RRCSetupRequest" message, and Msg4 includes the content or part of the content of the "RRCSetupRequest" message. In the random access process initiated by a terminal device in the RRC_INACTIVE state, Msg2 is RAR, and Msg3 is the RRC resume request message, and Msg4 includes the content or part of the content of the RRC resume request message. In the random access process initiated by the terminal device in the RRC_CONNECTED state, Msg2 is the RAR, Msg3 is the MAC-CE carrying the C-RNTI, and Msg4 is the PDCCH addressed to the C-RNTI of the UE.

[0109] FIG4 shows a contention-based random access process. For non-contention-based random access, the contention resolution step is omitted, that is, there is no process described in S404 , which will not be described in detail.

[0110] In an NTN, terminal devices receive satellite ephemeris information and the transmission delay from the satellite to a reference point (e.g., Common TA) through system messages, allowing them to estimate the TA. Furthermore, the terminal device compensates for the TA when sending the preamble. The terminal device can report the TA value to the network via MAC-CE. The terminal device can report the TA in Msg3, Msg5, or other uplink transmission processes.

[0111] For example, Figure 5 is a schematic diagram of the process of 2-step random access. As shown in Figure 5, 2-step random access includes the following steps:

[0112] S501: The terminal device sends MsgA to the access network device. Correspondingly, the access network device receives MsgA from the terminal device.

[0113] MsgA sends the above-mentioned Msg1 and Msg3 together, including preamble and data.

[0114] S502: The access network device sends MsgB to the terminal device. Correspondingly, the terminal device receives MsgB from the access network device.

[0115] Among them, MsgB is sent together with the above-mentioned Msg2 and Msg4, including relevant information for resolving contention between terminal devices.

[0116] 5. RACH-less handover (RACH-less HO)

[0117] In order to reduce the delay caused by the random access process, the terminal device can initiate a handover from the source cell to the target cell based on the RACH-less handover, that is, the terminal device can skip (not perform) the random access process with the target cell. The terminal device can determine the TA value through the ephemeris information and GNSS position information and the commonTA broadcast by the network device. After receiving the handover command, the terminal device can use the UL grant indicated in the handover command, such as the RRC reconfiguration message described above, to send a TA value or an RRC reconfiguration completion message to the target access network device without performing the random access process. Optionally, the handover message may include indication information, which is used to instruct the terminal device to perform RACH-less handover.

[0118] 6. NTN's TA reporting mechanism

[0119] The 3GPP protocol specifies the following three triggering conditions for terminal devices to report TA:

[0120] (1) When the terminal device receives the TA report (TA-report) instruction from the network, it triggers TA reporting;

[0121] (2) When the terminal device receives the configuration of the TA offset threshold (offsetThresholdTA) and the terminal device has not reported the TA in the current serving cell, the TA reporting is triggered;

[0122] (3) When the change between the current TA of the terminal device and the last reported TA value (the latest reported TA) exceeds the threshold offsetThresholdTA, TA reporting is triggered.

[0123] In the above condition (1), the TA-report indication can be carried in the system information block (SIB) 19 message. If SIB19 carries the indication information, the terminal device reports the TA during the random access process during the RRC connection establishment, RRC connection re-establishment, and RRC connection recovery process. The TA-report indication can also be carried in dedicated signaling, for example, it can be carried in the handover command. If the UE handover command carries the ta-report indication, the UE reports the TA during the random access process during the handover process. Therefore, this condition determines whether it is necessary to trigger the TA report during the random access process based on whether the ta-report indication is configured.

[0124] Among the three conditions for triggering TA reporting mentioned above, condition (1) is the TA reporting process of the terminal device in the random access phase, and conditions (2) and (3) are the TA reporting processes of the terminal device in the connected state and non-switching scenarios. However, none of the three conditions for triggering TA reporting clearly specify the TA reporting triggering conditions when the terminal device does not configure TA-report during the cell switching process but configures offsetThresholdTA. Based on the understanding of the three triggering TA reports described in the above protocol, if the access network device configures offsetThresholdTA in the switching command, whether the terminal device reports TA, or when it reports it, can be understood as follows:

[0125] If the current serving cell is understood as the source cell (because the terminal device has not yet completed the cell handover and is still accessing the source cell), since the terminal device has previously accessed the source cell, it is likely that the TA corresponding to the source cell has been reported. In this case, there is no need to report the TA. If the current cell is understood as the target cell (because the terminal device has the target cell configuration in effect at this time, the target cell can be considered the current serving cell), the terminal device needs to judge condition (2). If the terminal device has not reported the TA corresponding to the target cell, the terminal device may need to report the TA corresponding to the target cell. Based on different understandings, it is unclear whether the TA is reported, and it is also unclear whether the TA of the source cell or the target cell is reported. If the terminal device and the access network device are based on different understandings, the actual behavior of the terminal device may be inconsistent with the terminal device behavior expected by the access network device.

[0126] In addition, according to the current protocol, the judgment shown in condition (2) is executed when the terminal device receives offsetThresholdTA for the first time. That is, when the terminal device receives the TA reporting offset threshold for the first time, it is considered to have configured the value, and receiving offsetThresholdTA again is considered to be reconfiguration, that is, reconfiguration. For reconfiguration, the terminal device does not trigger the evaluation of condition (2), and therefore does not trigger TA reporting. If the terminal device receives the configuration of the source cell in the current serving cell and then receives the configuration of the target cell, it is unclear whether the received configuration of the target cell is the first configuration or reconfiguration, and whether the TA reporting should be triggered in the current protocol.

[0127] Furthermore, according to the current protocol, if the RRC reconfiguration message does not carry the timing advance reporting configuration (TAR-Config), then the terminal device reuses or inherits the previous configuration (which includes offsetThresholdTA). How can we understand whether the access network device has configured offsetThresholdTA during a cell handover? In other words, does the terminal device's reuse of the previous configuration count as configuring this parameter? The current protocol description is unclear.

[0128] Therefore, it is unclear whether the cell handover process triggers TA reporting and whether to report the TA of the source cell or the target cell. To this end, the embodiments of the present application provide a timing advance reporting method to solve the TA problem during cell handover. The method provided in the embodiments of the present application can be applied to transparent satellite architecture and regenerative satellite architecture, and can also be applied to Earth Moving Cell and Quasi-Earth Fixed Cell scenarios.

[0129] In order to better understand the embodiments of the present application, the following explanations are made before introducing the embodiments of the present application.

[0130] First, in the embodiments of the present application, "used to indicate" can include being used for direct indication and being used for indirect indication. When describing a certain "indication information" as being used to indicate A, it can include the indication information directly indicating A or indirectly indicating A, and does not necessarily mean that the indication information carries A.

[0131] The information indicated by the indication information is called the information to be indicated. In the specific implementation process, there are many ways to indicate the information to be indicated, such as but not limited to, directly indicating the information to be indicated, such as the information to be indicated itself or the index of the information to be indicated. The information to be indicated can also be indirectly indicated by indicating other information, wherein there is an association between the other information and the information to be indicated. It is also possible to indicate only a part of the information to be indicated, while the other parts of the information to be indicated are known or agreed in advance. For example, it is also possible to use the arrangement order of each piece of information agreed in advance (such as specified in the protocol) to achieve the indication of specific information, thereby reducing the indication overhead to a certain extent. At the same time, it is also possible to identify the common parts of each piece of information and indicate them uniformly to reduce the indication overhead caused by indicating the same information separately.

[0132] In addition, the specific indication method can also be various existing indication methods, such as but not limited to the above-mentioned indication methods and various combinations thereof. The specific details of the various indication methods can be referred to the prior art and will not be repeated herein. As can be seen from the above, for example, when it is necessary to indicate multiple information of the same type, there may be a situation where the indication methods for different information are different. In the specific implementation process, the required indication method can be selected according to specific needs. The embodiment of the present application does not limit the selected indication method. In this way, the indication method involved in the embodiment of the present application should be understood to cover various methods that can enable the party to be indicated to obtain the information to be indicated.

[0133] The information to be indicated can be sent as a whole, or divided into multiple sub-information and sent separately, and the sending period and / or sending time of these sub-information can be the same or different. The specific sending method is not limited in this application. Among them, the sending period and / or sending time of these sub-information can be predefined, for example, predefined according to the protocol, or configured by the transmitting device by sending configuration information to the receiving device. Among them, the configuration information can, for example, but not limited to, include one or a combination of at least two of radio resource control (RRC) signaling, MAC layer signaling and physical layer signaling. Among them, MAC layer signaling, for example, includes MAC-CE; physical (PHY) layer signaling, for example, includes downlink control information (DCI).

[0134] Second, in the embodiments of the present application, the first, second, and various numerical numbers are merely distinctions made for ease of description and are not intended to limit the scope of the embodiments of the present application. For example, different indication information is used to distinguish one from another. For another example, the first indication information and the second indication information are merely used to distinguish different areas and do not limit their order of precedence. Those skilled in the art will understand that words such as "first" and "second" do not limit the quantity and order of execution, and words such as "first" and "second" do not necessarily limit them to be different.

[0135] Third, in the embodiments of the present application, descriptions such as "when...", "in the case of...", "if" and "if" all mean that the device (such as a terminal device or an access network device) will make corresponding processing under certain objective circumstances. It does not limit the time, and does not require the device (such as a terminal device or an access network device) to have a judgment action when implementing it, nor does it mean that there are other limitations.

[0136] At the same time, in the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner to facilitate understanding.

[0137] Finally, the network architecture and business scenarios described in the embodiments of this application are intended to more clearly illustrate the technical solutions of the embodiments of this application, and do not constitute a limitation on the technical solutions provided in the embodiments of this application. Ordinary technicians in this field can know that with the evolution of network architecture and the emergence of new business scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0138] The following first introduces the system architecture involved in the embodiments of the present application:

[0139] The embodiments of the present application will present various aspects, embodiments, or features around a system that may include multiple devices, components, modules, etc. It should be understood and appreciated that each system may include additional devices, components, modules, etc., and / or may not include all of the devices, components, modules, etc. discussed in conjunction with the figures. Furthermore, combinations of these solutions may also be used.

[0140] Please refer to Figure 6, which is a schematic diagram of the architecture of a communication system used in an embodiment of the present application. As an example, as shown in Figure 6, the communication system includes an access network device and multiple terminal devices that communicate with the access network device. Optionally, the communication system may also include a core network device that communicates with the access network device.

[0141] The communication system shown in FIG6 can be applied to various communication systems, such as wireless fidelity (Wi-Fi) systems, vehicle-to-everything (V2X) communication systems, device-to-device (D2D) communication systems, Internet of Vehicles (IoV) communication systems, 4th generation (4G) mobile communication systems such as LTE systems, worldwide interoperability for microwave access (WiMAX) communication systems, 5G mobile communication systems such as NR systems, and future communication systems such as 6th generation (6G) mobile communication systems. In different networks, the core network devices, access network devices, and terminal devices in the above communication systems may have different names. Those skilled in the art will understand that different devices can be divided according to their functions, and the names do not limit the devices themselves.

[0142] Among them, the core network device referred to in the embodiment of the present application is a device deployed in the core network to provide services to terminal devices. In systems using different wireless access technologies, the names of core network devices with similar wireless communication functions may be different. For example, when the communication method of the embodiment of the present application is applied to a 5G system, the core network device can be an access and mobility management function (AMF) network element, a session management function (SMF) network element, a user plane function (UPF) network element, etc. Among them, the UPF network element processes user plane data. The AMF network element and the SMF network element process control plane signaling. When the precoding method of the embodiment of the present application is applied to an LTE system, the core network device can be a mobility management entity (MME). For the convenience of description only, in the embodiment of the present application, the above-mentioned devices that can provide services to terminal devices are collectively referred to as core network devices.

[0143] Access network equipment is a device deployed in a wireless access network to provide wireless communication functions. Access network equipment can also be called access network node, RAN node, RAN entity or access node, etc. It is located on the network side of the above-mentioned communication system to help terminal equipment achieve wireless access, and has a device with wireless transceiver function or a chip or chip system that can be set on the device. The access network equipment includes but is not limited to: base station (base station), evolved NodeB (eNodeB), access point (AP), TRP or transmission point (TP), gNB, next-generation base station in 6G mobile communication system, base station in future mobile communication system, or access node in Wi-Fi system, etc. The access network equipment can be a macro base station, a micro base station or an indoor station, a relay node or a donor node, or a wireless controller in a centralized radio access network (CRAN) scenario. The access network device may also be one or a group of antenna panels (including multiple antenna panels) of a base station in 5G, or a network node constituting a gNB, TRP, TP, or transmission measurement function (TMF), such as a central unit (CU), DU, CU-control plane (CP), CU-user plane (UP), or radio unit (RU), or a road side unit (RSU) with base station functions. Optionally, the access network device may also be a server, wearable device, vehicle, or on-board device. For example, the access network device in V2X technology may be an RSU. All or part of the functions of the access network device in this application may also be implemented by software functions running on hardware, or by virtualization functions instantiated on a platform (e.g., a cloud platform). The access network device in this application may also be a logical node, logical module, or software that can implement all or part of the functions of the access network device. In the NTN, all or part of the functional modules of the access network device may be deployed on an airborne platform or satellite, or other forms of communication equipment deployed at high altitude. Accordingly, the access network device may refer to an airborne platform, satellite, or other similar device that connects the terminal device to the core network device. The airborne platform may include at least one of the following: a satellite, a drone, or a hot air balloon.

[0144] Among them, the CU and DU can be set separately, or can also be included in the same network element, such as a baseband unit (BBU). The CU and DU can be divided according to logical functions (such as the implemented protocol layer functions). 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 unit (AAU) or a remote radio head (RRH). It can be understood that the access network device can be a CU node, a DU node, or a device including a CU node and a DU node. In addition, the CU can be divided into an access network device in the access network RAN, or the CU can be divided into an access network device in the CN, and there is no limitation here.

[0145] In different systems, CU (or CU-CP and CU-UP), DU or RU may also have different names, but those skilled in the art can understand their meanings. For example, in an open RAN (open-RAN, O-RAN) system, CU may also be called O-CU (open CU), DU may also be called O-DU, CU-CP may also be called O-CU-CP, CU-UP may also be called O-CU-UP, and RU may also be called O-RU. For the convenience of description, this application uses CU, CU-CP, CU-UP, DU and RU as examples for description. Any unit of 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.

[0146] The embodiments of this application do not limit the form of the access network device. The device used to implement the functions of the access network device can be the access network device; it can also be a device that supports the access network device to implement the functions, such as a chip system. The device can be installed in the access network device or used in conjunction with the access network device.

[0147] The terminal device may be a terminal device with transceiver functions, or may be a chip or chip system provided in the terminal device. The terminal device may also be referred to as UE, access terminal, subscriber unit, user station, mobile station (MS), mobile station, remote station, remote terminal, mobile device, user terminal, terminal, wireless communication device, user agent or user equipment. The terminal device in the embodiments of the present application can be a mobile phone, a cellular phone, a smart phone, a tablet computer, a wireless data card, a personal digital assistant (PDA), a wireless modem, a handheld device (handset), a laptop computer, a machine type communication (MTC) terminal, a computer with wireless transceiver function, a virtual reality (VR) terminal, an augmented reality (AR) terminal, a smart home device (for example, a refrigerator, a television, an air conditioner, an electric meter, etc.), an intelligent robot, a robotic arm, a workshop equipment, a wireless terminal in unmanned driving, a wireless terminal in industrial control, a wireless terminal in self-driving, a wireless terminal in remote medical care, a wireless terminal in smart grid, a wireless terminal in transportation safety, a wireless terminal in a smart city, a wireless terminal in a smart home, a vehicle-mounted terminal, a roadside unit with terminal function, a roadside control unit (ROU), ... The terminal device of the present application may also be an onboard module, onboard module, onboard component, onboard chip or onboard unit built into a vehicle as one or more components or units. The terminal device may also be other devices with terminal functions, for example, a terminal device may also be a device that functions as a terminal in D2D communication.

[0148] The embodiments of this application do not limit the device form factor of the terminal. The device used to implement the functions of the terminal device can be the terminal device; it can also be a device that supports the terminal device to implement the functions, such as a chip system. The device can be installed in the terminal device or used in conjunction with the terminal device. In the embodiments of this application, the chip system can be composed of chips or include chips and other discrete devices.

[0149] In the system architecture shown in Figure 6, the system also includes a ground gateway and a data network (DN). Here, the interface for the terminal device to communicate with the access network device can be an air interface. The interface for the access network device to communicate with the ground gateway can be an NG interface. The interface for the ground gateway to communicate with the core network device can be an NG interface. The core network device can be connected to only one ground gateway. In this case, the access network device can be connected to the core network device through one ground gateway, as shown in Figure 6. The core network device can be connected to more than one ground gateway. In this case, the access network device can be connected to the core network device through any one of the more than one ground gateways (not shown in Figure 6). The core network device (such as the UPF network element) can communicate with the entities or network elements in the DN through an interface (such as the N6 interface).

[0150] It should be noted that the above only lists some communication methods between network elements. Other network elements can also communicate through certain connection methods, which will not be repeated here in the embodiments of this application.

[0151] Furthermore, Figure 7 is a schematic diagram of the structure of an access network device based on a CU-DU separation architecture provided in an embodiment of the present application. As shown in Figure 7, by dividing the protocol stack, the access network device includes a CU-CP, a CU-UP, and a DU. The CU-CP and the DU can communicate through interface 1, the CU-UP and the DU can communicate through interface 2, and the CU-CP and the CU-UP can communicate through interface 3. Optionally, the access network device can be a gNB, in which case interface 1 can be an F1-C interface, interface 2 can be an F1-U interface, and interface 3 can be an E1 interface.

[0152] Among them, CU-CP is responsible for the control plane functions, including the RRC layer and the PDCP-control (C) layer. Among them, PDCP-C is mainly responsible for encryption and decryption, integrity protection, data transmission, etc. of the control plane data.

[0153] CU-UP is responsible for user plane functions, including the SDAP layer and the PDCP-user (U) layer. SDAP is mainly responsible for processing core network data and mapping flows to bearers, while PDCP-U is mainly responsible for encryption and decryption, integrity protection, header compression, sequence number maintenance, data transmission, etc. on the data plane.

[0154] The DU includes the radio link control (RLC), MAC, and PHY layers. As can be seen, both the CU-CP and CU-UP contain the PDCP layer. The RRC layer sits above the PDCP layer in the CU-CP. RRC messages are processed by the PDCP layer and encapsulated into PDCP data PDUs. PDCP data PDUs can be sent by both the CU-CP and CU-UP. The PDCP control PDU is generated by the PDCP-U layer and is used to convey robust header compression (ROHC) context information, among other things.

[0155] The system architecture and business scenarios described in the embodiments of this application are intended to more clearly illustrate the technical solutions of the embodiments of this application and do not constitute a limitation on the technical solutions provided by the embodiments of this application. Those skilled in the art will appreciate that with the evolution of network architecture and the emergence of new business scenarios, the technical solutions provided in the embodiments of this application are equally applicable to similar technical problems.

[0156] The timing advance reporting method provided in the embodiment of the present application will be described in detail below with reference to FIG8 and FIG9 .

[0157] For example, Figure 8 is a flow chart of a timing advance reporting method provided in an embodiment of the present application. The timing advance reporting method is illustrated by taking the communication between the access network device and the terminal device shown in Figure 6 as an example. Of course, the subject that executes the terminal device action in this method can also be a device / module in the terminal device, such as a chip, processor, processing unit, etc. in the terminal device; the subject that executes the access network device action in this method can also be a device / module in the access network device, such as a chip, processor, processing unit, etc. in the access network device, and the embodiment of the present application does not make specific limitations on this. For example, as shown in Figure 8, the timing advance reporting method includes:

[0158] S801: The access network device sends a handover command to the terminal device. Correspondingly, the terminal device receives the handover command from the access network device.

[0159] The handover command is used to instruct the terminal device to switch from the source cell to the target cell. In the embodiment of the present application, the handover of the terminal device from the source cell to the target cell can be based on RACH handover or RACH-less handover. Therefore, the handover command can carry information instructing the terminal device to initiate RACH handover from the source cell to the target cell, or information instructing the terminal device to initiate RACH-less handover from the source cell to the target cell. In other words, the access network device can configure the cell handover mode of the terminal device to be based on RACH handover or RACH-less handover through the handover command.

[0160] In addition, the switching command may include relevant information of the target cell and relevant configuration parameters required for the terminal device to access the target cell, such as information of the target cell (such as the PCI of the target cell and the frequency information corresponding to the target cell), the C-RNTI allocated by the target cell to the terminal device, the RACH resource information required to access the target cell (such as dedicated RACH resources and / or public RACH resources), or UL grant information for RACH-less switching, etc. Among them, the UL grant information is used to indicate the UL grant, and the UL grant may include at least one of the following: time-frequency resources (PUSCH resources), modulation coding scheme (MCS), new data indicator (NDI), the time for initiating uplink transmission (such as a subframe or time slot), the interval of uplink scheduling, etc. The embodiment of the present application does not limit the specific content contained in the UL grant for RACH-less switching.

[0161] For example, the handover command may be an RRC message. For example, in NR, the handover command may be an RRC reconfiguration message carrying a synchronization reconfiguration (reconfigurationWithSync) information element. In LTE, the handover command may be an RRC connection reconfiguration message carrying mobility control information (mobility control info). The embodiment of the present application does not limit the specific name of the handover command.

[0162] In the embodiment of the present application, the handover command is taken as an example to describe the process of the terminal device triggering TA reporting during the cell handover process. It should be understood that the handover command can also be replaced by other messages or signaling, and there is no limitation on this.

[0163] It should be understood that in the embodiments of the present application, when a terminal device performs a cell handover, the access network device is the access network device of the source cell. In other words, after the access network device of the source cell determines that the terminal device needs to perform a cell handover, it sends a handover command to the terminal device to instruct the terminal device to handover from the source cell to the target cell. The process of the access network device of the source cell performing a cell handover decision can be found in the relevant description of the existing implementation method, and will not be described in detail here.

[0164] S802: When the handover command carries the first indication information and / or the second indication information, the terminal device triggers timing advance reporting.

[0165] Among them, the timing advance (TA) is the timing advance corresponding to the target cell, the first indication information is used to indicate the offset threshold of the timing advance reported by the terminal device (such as offsetThresholdTA), and the offset threshold of the timing advance can be used by the terminal device to compare the threshold value of the change between the currently estimated timing advance and the last reported timing advance, and the second indication information is used to instruct the terminal device to report the timing advance (such as TA-report).

[0166] In an embodiment of the present application, after receiving a handover command, the terminal device parses the handover command to determine whether the handover command carries the first indication information and / or the second indication information. In the case that the handover command carries the first indication information and / or the second indication information, the terminal device determines to trigger the timing advance report corresponding to the target cell. Otherwise, the timing advance report corresponding to the target cell is not triggered. For example, if the configured condition for triggering the timing advance report corresponding to the target cell is that the handover command carries the first indication information, thus, if the handover command received by the terminal device does not carry the first indication information, the timing advance report corresponding to the target cell is not triggered. It should be understood that the implementation of not triggering the timing advance report corresponding to the target cell should refer to the condition setting for triggering the timing advance report corresponding to the target cell by the handover command, and no limitation is made to this.

[0167] Among them, triggering the reporting of the timing advance corresponding to the target cell can refer to directly reporting the timing advance corresponding to the target cell, or it can refer to the terminal device preparing to report the timing advance corresponding to the target cell and reporting the timing advance corresponding to the target cell at a certain time thereafter. The specific time at which the terminal device reports the timing advance corresponding to the target cell can be determined based on the allocated available resources, and there is no limitation on this. It should be understood that the embodiments of the present application are directed to reporting the timing advance corresponding to the target cell. The timing advance corresponding to the target cell can be determined by referring to the calculation formula of TA in the NTN scenario described above, and this will not be described in detail.

[0168] In one possible design scheme, when the handover command carries the first indication information and / or the second indication information, the terminal device can immediately trigger the reporting of the timing advance corresponding to the target cell. In other words, after the terminal device receives the first indication information and / or the second indication information, it immediately triggers the reporting of the timing advance corresponding to the target cell. At this time, the terminal device can be configured for RACH-based cell handover or RACH-less cell handover.

[0169] In this design, in one possible scenario 1, the terminal device may only determine whether the handover command contains the first indication information. Regardless of whether the handover command contains the second indication information, as long as the first indication information is present, the terminal device immediately triggers reporting of the timing advance corresponding to the target cell. Alternatively, the terminal device may only determine whether the handover command contains the second indication information. Regardless of whether the handover command contains the first indication information, as long as the second indication information is present, the terminal device immediately triggers reporting of the timing advance corresponding to the target cell.

[0170] Exemplarily, if the RRCReconfiguration message (handover command) carrying reconfigurationWithSync received by the terminal device carries offsetThresholdTA (first indication information), and TA has not been reported in the current serving cell, the terminal device immediately triggers TA (TA corresponding to the target cell) reporting. Alternatively, if the handover command received by the terminal device carries offsetThresholdTA, and TA has not been reported in the current serving cell, the terminal device immediately triggers TA (TA corresponding to the target cell) reporting. Optionally, the current serving cell refers to the target cell.

[0171] For another example, if the RRCReconfiguration message (handover command) carrying reconfigurationWithSync received by the terminal device carries offsetThresholdTA (first indication information), the terminal device immediately triggers TA (TA corresponding to the target cell) reporting. Alternatively, if the handover command received by the terminal device carries offsetThresholdTA, the terminal device immediately triggers TA (TA corresponding to the target cell) reporting.

[0172] In one possible scenario 2, after receiving a handover command, the terminal device determines that the handover command contains the first indication information and does not contain the second indication information. The terminal device immediately triggers reporting of the timing advance corresponding to the target cell. In this case, the terminal device needs to determine that the handover command contains the first indication information and does not contain the second indication information before immediately triggering reporting of the timing advance corresponding to the target cell.

[0173] For example, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device carries offsetThresholdTA, does not carry TA-report, and TA has not been reported in the current serving cell, the terminal device immediately triggers the TA report corresponding to the target cell. Alternatively, if the switching command received by the terminal device carries offsetThresholdTA, does not carry TA-report, and TA has not been reported in the current serving cell, the terminal device immediately triggers the TA report corresponding to the target cell. Optionally, the current serving cell refers to the target cell.

[0174] As another example, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device carries offsetThresholdTA but does not carry TA-report, the terminal device immediately triggers the TA report corresponding to the target cell. Alternatively, if the switching command received by the terminal device carries offsetThresholdTA but does not carry TA-report, the terminal device immediately triggers the TA report corresponding to the target cell.

[0175] Alternatively, the terminal device receives a handover command and determines that the handover command does not contain the first indication information, but contains the second indication information. The terminal device immediately triggers reporting of the timing advance corresponding to the target cell. In this case, the terminal device needs to determine that the handover command contains the second indication information and does not contain the first indication information before immediately triggering reporting of the timing advance corresponding to the target cell.

[0176] For example, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device carries a TA-report but does not carry offsetThresholdTA, and TA has not been reported in the current serving cell, the terminal device immediately triggers the TA report corresponding to the target cell. Alternatively, if the switching command received by the terminal device carries a TA-report but does not carry offsetThresholdTA, and TA has not been reported in the current serving cell, the terminal device immediately triggers the TA report corresponding to the target cell. Optionally, the current serving cell refers to the target cell.

[0177] As another example, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device carries a TA-report but does not carry offsetThresholdTA, the terminal device immediately triggers the TA report corresponding to the target cell. Alternatively, if the switching command received by the terminal device carries a TA-report but does not carry offsetThresholdTA, the terminal device immediately triggers the TA report corresponding to the target cell.

[0178] In a possible scenario 3, after receiving the handover command, the terminal device immediately triggers reporting of the timing advance corresponding to the target cell when it determines that the handover command contains both the first indication information and the second indication information.

[0179] Exemplarily, the terminal device is configured for RACH-less-based cell switching. If the RRCReconfiguration message of reconfigurationWithSync received by the terminal device carries offsetThresholdTA and TA-report, and TA has not been reported in the current serving cell, the terminal device immediately triggers the TA report corresponding to the target cell. Alternatively, the terminal device is configured for RACH-less-based cell switching. If the switching command received by the terminal device carries TA-report and offsetThresholdTA, and TA has not been reported in the current serving cell, the terminal device immediately triggers the TA report corresponding to the target cell. Optionally, the current serving cell refers to the target cell.

[0180] As another example, the terminal device is configured for RACH-less cell switching. If the RRCReconfiguration message of reconfigurationWithSync received by the terminal device carries offsetThresholdTA and TA-report, the terminal device immediately triggers the TA report corresponding to the target cell. Alternatively, the terminal device is configured for RACH-less cell switching. If the switching command received by the terminal device carries TA-report and offsetThresholdTA, the terminal device immediately triggers the TA report corresponding to the target cell.

[0181] In an embodiment of the present application, the above-mentioned immediate triggering may mean that when the terminal device receives the above-mentioned switching command, the terminal device triggers the TA reporting of the target cell.

[0182] In another possible design scheme, when the switching command carries the first indication information and / or the second indication information, the terminal device may not immediately trigger the reporting of the timing advance corresponding to the target cell, but may trigger the reporting of the timing advance corresponding to the target cell in a subsequent process or at a certain moment.

[0183] When the terminal device is configured for random access-based cell handover (or the terminal device is RACH-based cell handover), the terminal device may trigger reporting of the timing advance based on the following situations:

[0184] In one possible scenario 1, if the switching command carries the first indication information, the terminal device triggers the reporting of the timing advance corresponding to the target cell during the process of random access to the target cell, or the terminal device triggers the reporting of the timing advance corresponding to the target cell after successfully randomly accessing the target cell.

[0185] At this time, it can be considered that the terminal device confirms that the handover command only carries the first indication information and no second indication information, or it can be considered that the terminal device only determines whether the handover command contains the first indication information, and if the first indication information is present, it does not matter whether the handover command also contains the second indication information. Thus, the terminal device triggers the reporting of the timing advance corresponding to the target cell during the random access process or after the random access is completed.

[0186] Exemplarily, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device carries offsetThresholdTA, and TA has not been reported in the current serving cell, the terminal device triggers the TA reporting corresponding to the target cell during the RACH period with the target cell or after the RACH ends. Alternatively, if the switching command received by the terminal device carries offsetThresholdTA, and TA has not been reported in the current serving cell, the terminal device triggers the TA reporting corresponding to the target cell during the RACH period with the target cell or after the RACH ends. Optionally, the current serving cell refers to the target cell.

[0187] As another example, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device carries offsetThresholdTA, the terminal device triggers the TA reporting corresponding to the target cell during the RACH period with the target cell or after the RACH ends. Alternatively, if the handover command received by the terminal device carries offsetThresholdTA, the terminal device triggers the TA reporting corresponding to the target cell during the RACH period with the target cell or after the RACH ends.

[0188] As another example, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device carries offsetThresholdTA, does not carry TA-report, and TA has not been reported in the current serving cell, the terminal device triggers the TA report corresponding to the target cell during the RACH period with the target cell or after the RACH ends. Alternatively, if the switching command received by the terminal device carries offsetThresholdTA, does not carry TA-report, and TA has not been reported in the current serving cell, the terminal device triggers the TA report corresponding to the target cell during the RACH period with the target cell or after the RACH ends. Optionally, the current serving cell refers to the target cell.

[0189] As another example, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device carries offsetThresholdTA but does not carry TA-report, the terminal device triggers the TA report corresponding to the target cell during the RACH period with the target cell or after the RACH ends. Alternatively, if the switching command received by the terminal device carries offsetThresholdTA but does not carry TA-report, the terminal device triggers the TA report corresponding to the target cell during the RACH period with the target cell or after the RACH ends.

[0190] In one possible scenario 2, if the handover command carries the first indication information and the second indication information, the terminal device triggers the reporting of the timing advance corresponding to the target cell during the process of random access to the target cell, or the terminal device triggers the reporting of the timing advance corresponding to the target cell after successfully random accessing the target cell. In this case, the terminal device needs to determine that the handover command contains both the first indication information and the second indication information before triggering the reporting of the timing advance corresponding to the target cell.

[0191] Exemplarily, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device carries offsetThresholdTA and TA-report, and TA has not been reported in the current serving cell, the terminal device triggers the TA report corresponding to the target cell during the RACH period with the target cell or after the RACH ends. Alternatively, if the switching command received by the terminal device carries offsetThresholdTA and TA-report, and TA has not been reported in the current serving cell, the terminal device triggers the TA report corresponding to the target cell during the RACH period with the target cell or after the RACH ends. Optionally, the current serving cell refers to the target cell.

[0192] As another example, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device carries offsetThresholdTA and TA-report, the terminal device triggers the TA report corresponding to the target cell during the RACH period with the target cell or after the RACH ends. Alternatively, if the handover command received by the terminal device carries offsetThresholdTA and TA-report, the terminal device triggers the TA report corresponding to the target cell during the RACH period with the target cell or after the RACH ends.

[0193] Based on the above scenario 1 or scenario 2, the terminal device triggers the timing advance report corresponding to the target cell during the process of random access to the target cell (such as during RACH), which can be that the terminal device triggers the timing advance report corresponding to the target cell at any time between sending Msg1 and receiving Msg4, or the terminal device triggers the timing advance report corresponding to the target cell at any time between sending MsgA and receiving MsgB. The terminal device triggers the timing advance report corresponding to the target cell after successfully randomly accessing the target cell (such as after the RACH ends), which can be that the terminal device triggers the timing advance report corresponding to the target cell after receiving Msg4 or after receiving MsgB.

[0194] When the terminal device is configured for RACH-less cell handover (or the terminal device is performing RACH-less cell handover), the terminal device may trigger reporting of the timing advance based on the following scenarios:

[0195] In a possible scenario 1, if the handover command carries the first indication information or the second indication information, the terminal device triggers the reporting of the timing advance corresponding to the target cell after the cell handover is completed. That is to say, as long as there is the first indication information or the second indication information in the handover command, the terminal device can trigger the reporting of the timing advance corresponding to the target cell after completing the cell handover. For example, the terminal device triggers the reporting of the timing advance corresponding to the target cell when sending a handover completion message (such as an RRC reconfiguration completion message) to the access network device corresponding to the target cell. At this time, the terminal device can report the timing advance corresponding to the target cell based on the UL grant resources configured by the access network device.

[0196] In this scenario 1, the terminal device only determines whether the handover command contains the first indication information. If the first indication information is present, the reporting of the timing advance corresponding to the target cell is triggered regardless of whether the handover command contains the second indication information. Alternatively, the terminal device only determines whether the handover command contains the second indication information. If the second indication information is present, the reporting of the timing advance corresponding to the target cell is triggered regardless of whether the handover command contains the first indication information.

[0197] Exemplarily, the terminal device is configured for RACH-less-based cell switching. If the RRCReconfiguration message of reconfigurationWithSync received by the terminal device carries a TA-report, and no TA has been reported in the current serving cell, the terminal device triggers a TA report corresponding to the target cell after the cell switching is completed. Alternatively, the terminal device is configured for RACH-less-based cell switching. If the switching command received by the terminal device carries a TA-report, and no TA has been reported in the current serving cell, the terminal device triggers a TA report corresponding to the target cell after the cell switching is completed. Optionally, the current serving cell refers to the target cell.

[0198] As another example, the terminal device is configured for RACH-less cell switching. If the RRCReconfiguration message of reconfigurationWithSync received by the terminal device carries a TA-report, the terminal device triggers the TA report corresponding to the target cell after the cell switching is completed. Alternatively, the terminal device is configured for RACH-less cell switching. If the switching command received by the terminal device carries a TA-report, the terminal device triggers the TA report corresponding to the target cell after the cell switching is completed.

[0199] As another example, the terminal device is configured for RACH-less-based cell switching. If the RRCReconfiguration message of reconfigurationWithSync received by the terminal device carries offsetThresholdTA, and TA has not been reported in the current serving cell, the terminal device triggers the TA reporting corresponding to the target cell after the cell switching is completed. Alternatively, the terminal device is configured for RACH-less-based cell switching. If the switching command received by the terminal device carries offsetThresholdTA, and TA has not been reported in the current serving cell, the terminal device triggers the TA reporting corresponding to the target cell after the cell switching is completed. Optionally, the current serving cell refers to the target cell.

[0200] As another example, the terminal device is configured for RACH-less cell switching. If the RRCReconfiguration message of reconfigurationWithSync received by the terminal device carries offsetThresholdTA, the terminal device triggers the TA reporting corresponding to the target cell after the cell switching is completed. Alternatively, the terminal device is configured for RACH-less cell switching. If the switching command received by the terminal device carries offsetThresholdTA, the terminal device triggers the TA reporting corresponding to the target cell after the cell switching is completed.

[0201] In one possible scenario 2, if the handover command carries the first indication information and the second indication information, the terminal device triggers the reporting of the timing advance corresponding to the target cell after the cell handover is completed. In other words, only when the handover command contains both the first indication information and the second indication information, the terminal device triggers the reporting of the timing advance corresponding to the target cell after the cell handover is completed.

[0202] Exemplarily, the terminal device is configured for RACH-less-based cell switching. If the RRCReconfiguration message of reconfigurationWithSync received by the terminal device carries offsetThresholdTA and TA-report, and TA has not been reported in the current serving cell, the terminal device triggers the TA report corresponding to the target cell after the cell switching is completed. Alternatively, the terminal device is configured for RACH-less-based cell switching. If the switching command received by the terminal device carries offsetThresholdTA and TA-report, and TA has not been reported in the current serving cell, the terminal device triggers the TA report corresponding to the target cell after the cell switching is completed. Optionally, the current serving cell refers to the target cell.

[0203] As another example, the terminal device is configured for RACH-less cell switching. If the RRCReconfiguration message of reconfigurationWithSync received by the terminal device carries offsetThresholdTA and TA-report, the terminal device triggers the TA report corresponding to the target cell after the cell switching is completed. Alternatively, the terminal device is configured for RACH-less cell switching. If the switching command received by the terminal device carries offsetThresholdTA and TA-report, the terminal device triggers the TA report corresponding to the target cell after the cell switching is completed.

[0204] The timing advance reporting method shown in Figure 8 clarifies the process of whether the terminal device reports the timing advance corresponding to the target cell when the switching command carries a timing advance offset threshold (such as the first indication information) and / or a timing advance reporting indication (such as the second indication information), which can ensure that accurate timing advance reporting is triggered during cell switching.

[0205] The communication method shown in Figure 8 is described below in conjunction with specific application scenarios. The access network device that sends the handover command is the source base station (the base station to which the source cell belongs), and the base station to which the target cell belongs is the target base station.

[0206] Exemplarily, when the terminal device is configured for RACH-based cell switching, as shown in (a) of FIG9 , the following steps are included:

[0207] S901a: The source base station sends a handover command to the terminal device. Correspondingly, the terminal device receives the handover command from the source base station.

[0208] The handover command is used to instruct the terminal device to switch from the source cell to the target cell, and the handover command carries first indication information or first indication information and second indication information, the first indication information is used to indicate the offset threshold (such as offsetThresholdTA) of the timing advance reported by the terminal device, and the second indication information is used to instruct the terminal device to report the timing advance (such as TA-report). For a description of the handover command, please refer to the relevant description in S801 above, which will not be repeated here.

[0209] S902a. The terminal device triggers reporting of the timing advance corresponding to the target cell.

[0210] Exemplarily, after receiving the handover command, the terminal device determines that the handover command carries the first indication information or the first indication information and the second indication information, and triggers the reporting of the timing advance corresponding to the target cell during the process of initiating random access with the target base station. For example, the terminal device triggers the reporting of the timing advance corresponding to the target cell after sending Msg1 or MsgA, and the terminal device carries the timing advance corresponding to the target cell when sending Msg3 or MsgB. It should be understood that after the terminal device sends Msg1, there are other random access steps between the terminal device and the target base station, such as the target base station sending Msg2 to the terminal device, and there are subsequent random access processes after completing Msg3, until the terminal device completes the access to the target cell. For the specific implementation process, please refer to the relevant descriptions in Figures 3 and 4 above, which will not be elaborated on.

[0211] As another example, after receiving the handover command, the terminal device determines that the handover command carries the first indication information or the first indication information and the second indication information, and triggers the reporting of the timing advance corresponding to the target cell.

[0212] As another example, after receiving the switching command, the terminal device determines that the switching command carries the first indication information or the first indication information and the second indication information. After the random access is completed, the terminal device triggers the reporting of the timing advance corresponding to the target cell.

[0213] As another example, in the case where the terminal device is configured for RACH-less based cell switching, as shown in (b) of FIG9 , the following steps are included:

[0214] S901b: The source base station sends a handover command to the terminal device. Correspondingly, the terminal device receives the handover command from the source base station.

[0215] The handover command is used to instruct the terminal device to switch from the source cell to the target cell, and the handover command carries first indication information and / or second indication information, the first indication information is used to indicate the offset threshold (such as offsetThresholdTA) of the timing advance reported by the terminal device, and the second indication information is used to instruct the terminal device to report the timing advance (such as TA report). For a specific description of the handover command, please refer to the relevant description in S801 above and will not be repeated here.

[0216] After receiving the switching command, the terminal device determines that the switching command carries the first indication information and / or the second indication information, and then determines that after the cell switching is completed, such as after executing the following S902b, the timing advance corresponding to the target cell is reported.

[0217] S902b: The terminal device sends an RRC reconfiguration completion message to the target base station. Correspondingly, the target base station receives the RRC reconfiguration completion message from the terminal device.

[0218] The RRC reconfiguration complete message is used to instruct the terminal device to complete the cell handover and access the target cell. The specific implementation process can be found in the description of the relevant prior art, which will not be described in detail. It should be understood that the embodiment of the present application exemplarily uses the RRC reconfiguration complete message to instruct the terminal device to complete the cell handover. In addition, other messages or signaling can also be used to achieve this, and this is not limited to this.

[0219] S903b: The terminal device sends the timing advance corresponding to the target cell to the target base station. Correspondingly, the target base station receives the timing advance corresponding to the target cell from the terminal device.

[0220] That is, after sending the RRC reconfiguration complete message, the terminal device reports the timing advance corresponding to the target cell. For example, the timing advance corresponding to the target cell can be carried in the RRC message, MAC signaling or other signaling, which is not limited.

[0221] The above scheme is defined based on the terminal device triggering the reporting of the timing advance corresponding to the target cell during the cell switching process. In addition, the embodiment of the present application can also define a mechanism in which the terminal device does not trigger the reporting of the timing advance corresponding to the target cell during the cell switching process, so as to clarify the issue of whether the terminal device reports the timing advance corresponding to the target cell in the existing protocol.

[0222] In one possible design scheme, the terminal device receives a handover command from the access network device, and when the handover command carries the first indication information but does not carry the second indication information, determines not to trigger the reporting of the timing advance corresponding to the target cell. That is, when the terminal device determines that the handover command carries the first indication information but does not carry the second indication information, it does not trigger the reporting of the timing advance corresponding to the target cell. Alternatively, once the terminal device determines that there is no second indication information in the handover command, it does not trigger the reporting of the timing advance corresponding to the target cell, regardless of whether there is the first indication information. In other words, after the terminal device receives the handover command from the access network device, whether the terminal device triggers reporting the timing advance of the target cell to the target cell only needs to consider the second indication information.

[0223] For this design, the triggering condition (2) of the TA of the three types of NTN defined in the above existing protocol can be modified as follows: in a non-handover scenario, when the terminal device receives the configuration of the TA offset threshold (offsetThresholdTA) and the terminal device has not reported TA in the current serving cell, TA reporting is triggered; or modified as follows: when the terminal device receives the configuration of the TA offset threshold (offsetThresholdTA) in an RRCReconfiguration message that does not carry reconfigurationWithSync and the terminal device has not reported TA in the current serving cell, TA reporting is triggered. In other words, TA reporting is triggered only when the RRC reconfiguration message of the non-handover command carries offsetThresholdTA, and the RRC reconfiguration message of the non-handover command can be an RRCReconfiguration message that does not carry reconfigurationWithSync.

[0224] In this design, in one possible scenario, under the condition that the source cell and the target cell belong to the same satellite corresponding to the same access network device, since the TA corresponding to the source cell is the same as the TA corresponding to the target cell, the access network device may not configure the terminal device to report the TA, that is, the access network device does not configure the second indication information (such as TA-report) for the terminal device in the handover command. In this case, when the terminal device receives the first indication information in the handover command, it may not trigger the TA reporting to the target cell.

[0225] For example, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device carries offsetThresholdTA but does not carry ta-report, and TA has not been reported in the current serving cell, the terminal device does not trigger TA reporting.

[0226] In another possible design scheme, the terminal device receives a switching command from the access network device. When the switching command does not carry the first indication information, the terminal device determines not to trigger the timing advance reporting corresponding to the target cell.

[0227] Exemplarily, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device does not carry offsetThresholdTA, the terminal device does not trigger TA reporting.

[0228] For this design scheme, correspondingly, the terminal device receives an RRC reconfiguration message of a non-handover command from the access network device. The RRC reconfiguration message of the non-handover command carries the first indication information, and when the terminal device has not reported the timing advance in the current serving cell, the terminal device triggers the timing advance reporting. Among them, the RRC reconfiguration message of the non-handover command can be an RRCReconfiguration message that does not carry reconfigurationWithSync. At this time, the reported timing advance is the timing advance corresponding to the source cell.

[0229] For example, if the RRCReconfiguration message carrying offsetThresholdTA received by the terminal device does not carry reconfigurationWithSync, and the terminal device has not reported TA in the current serving cell, the terminal device triggers TA reporting. Alternatively, if the terminal device receives the configuration of offsetThresholdTA, and the terminal device has not reported TA in the current serving cell, the terminal device triggers TA reporting. In other words, TA reporting will be triggered only if the RRC reconfiguration message of a non-switching command carries offsetThresholdTA, and TA reporting will not be triggered if the switching command carries offsetThresholdTA.

[0230] In one possible scenario, when the handover command does not carry the second indication information and the terminal device reuses the configuration of the source cell, regardless of whether the handover command carries the first indication information, the terminal device determines that the access network device has configured the offset threshold of the timing advance corresponding to the target cell. In other words, because the terminal device reuses the configuration of the source cell, the terminal device may use the offset threshold of the timing advance corresponding to the source cell as the offset threshold of the timing advance corresponding to the target cell, and deems that the access network device has configured the offset threshold of the timing advance during the cell handover process.

[0231] In addition, for the triggering condition (3) of the TA of the three types of NTN defined in the above-mentioned existing protocol, the terminal device will compare the current TA estimation value with the TA reported last time (also referred to as the latest reported). However, in the cell switching scenario, the most recently reported TA may be understood as the TA most recently reported in the source cell, or it may be understood as the TA most recently reported in the target cell. Therefore, the embodiment of the present application further defines how to determine which TA is the most recently reported.

[0232] In one possible design, the trigger condition (3) of TA is modified as follows: when the difference between the current TA estimate of the terminal device and the last reported TA value in the same cell (the latest reported TA) exceeds a threshold offsetThresholdTA, TA reporting is triggered. Alternatively, it is modified as follows: when the difference between the current TA estimate of the terminal device and the last reported TA value in the same cell (the latest reported TA) exceeds a threshold offsetThresholdTA, TA reporting is triggered.

[0233] In this design, for the switching scenario (i.e., when the terminal device receives a switching command), even if the change in the TA of the terminal device in the target cell exceeds the threshold offsetThresholdTA compared to the TA value last reported by the terminal device in the source cell, the terminal device does not trigger the TA report in the target cell.

[0234] In another possible design, the most recently reported TA includes the TA last reported by the terminal device in the source cell in a handover scenario, and also includes the TA last reported by the terminal device in the same cell in a non-handover scenario.

[0235] The access network device sends a handover command to the terminal device. Accordingly, the terminal device receives the handover command from the access network device. The handover command instructs the terminal device to handover from the source cell to the target cell. It should be understood that the handover command may include relevant information about the target cell and configuration parameters required for the terminal device to access the target cell. For details, please refer to the relevant description in S801 above and will not be repeated here.

[0236] In the scenario where the cell switching is an inter-station switching, that is, the source cell and the target cell correspond to different access network devices, and the terminal device accesses different access network devices, in a possible design scheme, when the switching command carries the first indication information, the terminal device determines that the last reported timing advance is the timing advance corresponding to the target cell. The first indication information is used to indicate the offset threshold (such as offsetThresholdTA) of the timing advance reported by the terminal device. That is to say, when the terminal device receives a switching command carrying the first indication information, and the change between the current timing advance estimate of the terminal device and the timing advance corresponding to the last reported target cell is greater than the offset threshold, the terminal device triggers the timing advance report. At this time, the reported timing advance is the timing advance corresponding to the target cell.

[0237] Exemplarily, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device carries offsetThresholdTA, and the change between the current TA estimation value and the latest reported TA value of the target cell is greater than the threshold offsetThresholdTA, TA reporting is triggered.

[0238] Correspondingly, when the handover command does not carry the first indication information, but the first indication information is carried in other signaling or messages, the terminal device determines that the last reported timing advance is the timing advance corresponding to the source cell. In this case, the first indication information can be carried in an RRC reconfiguration message that is not a handover command (such as an RRC reconfiguration message that does not carry reconfigurationWithSync). That is, when the terminal device receives the first indication information, and the change between the current timing advance estimate of the terminal device and the timing advance corresponding to the last reported source cell is greater than the offset threshold, the terminal device triggers the timing advance report. At this time, the reported timing advance is the timing advance corresponding to the source cell.

[0239] For example, if the terminal device receives the configuration of offsetThresholdTA, and the change between the current TA estimate and the latest reported TA value of the source cell is greater than the threshold offsetThresholdTA, the terminal device triggers TA reporting; or, if the terminal device receives the configuration of offsetThresholdTA in an RRCReconfiguration message that does not carry reconfigurationWithSync, and the change between the current TA estimate and the latest reported TA value of the source cell is greater than the threshold offsetThresholdTA, the terminal device triggers TA reporting.

[0240] In a scenario where the cell handover is an intra-site handover, that is, the source cell and the target cell correspond to the same access network device, and the terminal device accesses the same access network device, in one possible design scheme, when the handover command carries first indication information, the terminal device determines that the last reported timing advance is the timing advance corresponding to the source cell. In other words, when the terminal device receives a handover command carrying the first indication information, and the difference between the current timing advance estimate of the terminal device and the last reported timing advance corresponding to the source cell is greater than the offset threshold, the terminal device triggers timing advance reporting.

[0241] For example, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device carries offsetThresholdTA, and the change between the current TA estimation value and the latest reported TA value of the source cell is greater than the threshold offsetThresholdTA, the terminal device triggers TA reporting.

[0242] In another possible design, the trigger condition (3) of the TA in the existing protocol is only for non-handover scenarios. In the handover scenario, the new indication information can be used to control whether to compare the current timing advance estimate with the timing advance corresponding to the source cell to trigger the reporting of the TA to the target cell. For example, the trigger condition (3) can be modified as follows: in the non-handover scenario (for example, no RRCReconfiguration message carrying reconfigurationWithSync is received), when the difference between the current TA estimate of the terminal device and the last reported TA value (the most recently reported TA) exceeds the threshold offsetThresholdTA, TA reporting is triggered.

[0243] In a handover scenario (for example, receiving an RRCReconfiguration message carrying reconfigurationWithSync), the terminal device determines, according to the third indication information, whether to trigger a TA report in the target cell when the change in the current TA estimate value compared to the last reported TA value of the source cell (the latest reported TA) exceeds the threshold offsetThresholdTA, specifically:

[0244] The access network device sends a handover command to the terminal device. Accordingly, the terminal device receives the handover command from the access network device. The handover command is used to instruct the terminal device to handover from the source cell to the target cell, and the handover command carries third indication information. The third indication information is used to instruct the terminal device whether to compare the current timing advance estimate with the timing advance corresponding to the source cell, or to indicate whether to trigger timing advance reporting in the target cell when the change between the current timing advance estimate and the last reported timing advance of the source cell (the latest reported TA) exceeds an offset threshold (threshold offsetThresholdTA). Thus, the terminal device determines, based on the third indication information, whether to perform a threshold comparison between the current timing advance estimate and the timing advance corresponding to the source cell, or whether to trigger timing advance reporting in the target cell when the change between the current timing advance estimate and the last reported timing advance of the source cell (the latest reported TA) exceeds an offset threshold (threshold offsetThresholdTA). It should be understood that the handover command may also carry first indication information to indicate the offset threshold of the timing advance.

[0245] When the third indication information is used to indicate a threshold comparison between the current timing advance estimate of the terminal device and the timing advance corresponding to the source cell, the terminal device compares the change between the current timing advance estimate and the timing advance corresponding to the last reported source cell with the offset threshold. When the change between the current timing advance estimate and the timing advance corresponding to the last reported source cell is greater than the offset threshold, the terminal device triggers the timing advance reporting.

[0246] Alternatively, when the third indication information is used to indicate that the change between the current timing advance estimate and the last reported timing advance of the source cell (the latest reported TA) exceeds the offset threshold, triggering the timing advance reporting in the target cell, if the change between the current timing advance estimate and the timing advance corresponding to the last reported source cell is greater than the offset threshold, the terminal device triggers the timing advance reporting in the target cell.

[0247] Thus, the access network device can configure the last reported timing advance of the terminal device in the handover command as the timing advance corresponding to the source cell. That is, when the terminal device receives a handover command carrying third indication information, and the third indication information is used to indicate a threshold comparison between the current timing advance estimate and the timing advance corresponding to the source cell, if the difference between the current timing advance estimate of the terminal device and the last reported timing advance corresponding to the source cell is greater than the offset threshold, the terminal device triggers a timing advance report. At this time, the reported timing advance is the timing advance corresponding to the target cell.

[0248] Alternatively, when the terminal device receives a handover command carrying third indication information, and the third indication information is used to indicate that the change between the current timing advance estimate and the last reported timing advance of the source cell exceeds the offset threshold, the timing advance report in the target cell is triggered. If the change between the current timing advance estimate of the terminal device and the last reported timing advance corresponding to the source cell is greater than the offset threshold, the terminal device triggers the timing advance report. At this time, the reported timing advance is the timing advance corresponding to the target cell.

[0249] Exemplarily, taking the third indication information as indication, if the third indication information is used to indicate that the current TA estimation value of the terminal device is compared with the TA value corresponding to the source cell for a threshold comparison or used to indicate that the change in the current TA estimation value compared with the TA value of the source cell last reported exceeds the threshold offsetThresholdTA, the TA reporting in the target cell is triggered, then the third indication information is indicated as indication-y; if the third indication information is used to indicate that the current TA estimation value of the terminal device is compared with the TA value corresponding to the target cell for a threshold comparison or used to indicate that the change in the current TA estimation value compared with the TA value of the source cell last reported in the source cell (the latest reported TA) exceeds the threshold offsetThresholdTA, the TA reporting in the target cell is not triggered, then the third indication information is indicated as indication-n or the switching command does not carry indication-y. Therefore, if the RRCReconfiguration message carrying reconfigurationWithSync received by the terminal device carries offsetThresholdTA and indication-y, and the change between the current TA estimation value and the latest reported TA value of the source cell is greater than the threshold offsetThresholdTA, the terminal device triggers TA reporting.

[0250] It can be understood that in each of the above embodiments, the methods and / or steps implemented by the terminal device can also be implemented by components that can be used for the terminal device (such as a processor, chip, chip system, circuit, logic module, or software); the methods and / or steps implemented by the access network device can also be implemented by components that can be used for the access network device (such as a processor, chip, chip system, circuit, logic module, or software).

[0251] The above mainly introduces the solution provided by this application. Accordingly, this application also provides a communication device, which is used to implement the various methods in the above method embodiments. The communication device can be the terminal device in the above method embodiments, or a device including the terminal device, or a component that can be used for the terminal device, such as a chip or chip system. Alternatively, the communication device can be the access network device in the above method embodiments, or a device including the access network device, or a component that can be used for the access network device, such as a chip or chip system.

[0252] It is understandable that, in order to realize the above functions, the communication device includes hardware structures and / or software modules corresponding to the execution of each function. It should be easily appreciated by those skilled in the art that, in combination with the units and algorithm steps of each example described in the embodiments disclosed herein, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a 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 and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0253] The embodiment of the present application can divide the functional modules of the communication device according to the above method embodiment. For example, each functional module can be divided according to each function, or two or more functions can be integrated into one processing module. The above integrated modules can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of modules in the embodiment of the present application is schematic and is only a logical functional division. In actual implementation, there may be other division methods.

[0254] Taking the communication device as a terminal device or access network device in the above method embodiment as an example, Figure 10 is a schematic diagram of the structure of a communication device provided in an embodiment of the present application. As shown in Figure 10, the communication device 1000 includes: a processing module 1001 and a transceiver module 1002. The processing module 1001 is used to perform the processing functions of the terminal device or access network device in the above method embodiment. The transceiver module 1002 is used to perform the transceiver functions of the terminal device or access network device in the above method embodiment.

[0255] Among them, all relevant contents of each step involved in the above method embodiment can be referred to the functional description of the corresponding functional module and will not be repeated here.

[0256] Since the communication device 1000 provided in this embodiment can execute the above method, the technical effects that can be obtained can refer to the above method embodiments and will not be repeated here.

[0257] In one possible design solution, in the embodiment of the present application, the transceiver module 1002 may include a receiving module and a sending module (not shown in FIG10 ). The transceiver module is used to implement the sending and receiving functions of the communication device 1000 .

[0258] In one possible design, the communication device 1000 may further include a storage module (not shown in FIG. 10 ) storing a program or instruction. When the processing module 1001 executes the program or instruction, the communication device 1000 may perform the functions of the terminal device or access network device in the method shown in FIG. 8 or FIG. 9 .

[0259] It should be understood that the processing module 1001 involved in the communication device 1000 can be implemented by a processor or a processor-related circuit component, which can be a processor or a processing unit; the transceiver module 1002 can be implemented by a transceiver or a transceiver-related circuit component, which can be a transceiver or a transceiver unit.

[0260] For example, FIG11 is a schematic diagram of the structure of another communication device provided in an embodiment of the present application. The communication device may be a terminal device or an access network device, or may be a chip (system) or other component or assembly that can be provided in the terminal device or the access network device. As shown in FIG11 , the communication device 1100 may include a processor 1101. In one possible design scheme, the communication device 1100 may further include a memory 1102 and / or a transceiver 1103. The processor 1101 is coupled to the memory 1102 and the transceiver 1103, such as by a communication bus.

[0261] The following is a detailed introduction to the various components of the communication device 1100 with reference to FIG11 :

[0262] The processor 1101 is the control center of the communication device 1100 and can be a single processor or a collective term for multiple processing elements. For example, the processor 1101 can be one or more central processing units (CPUs), an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application, such as one or more digital signal processors (DSPs) or one or more field programmable gate arrays (FPGAs).

[0263] In one possible design, the processor 1101 may execute various functions of the communication device 1100 by running or executing software programs stored in the memory 1102 and calling data stored in the memory 1102 .

[0264] In a specific implementation, as an embodiment, the processor 1101 may include one or more CPUs, such as CPU0 and CPU1 shown in FIG11 .

[0265] In a specific implementation, as an embodiment, the communication device 1100 may also include multiple processors, such as the processor 1101 and the processor 1104 shown in FIG11 . Each of these processors may be a single-core processor (single-CPU) or a multi-core processor (multi-CPU). The processor herein may refer to one or more devices, circuits, and / or processing cores for processing data (e.g., computer program instructions).

[0266] Among them, the memory 1102 is used to store the software program for executing the solution of this application, and the execution is controlled by the processor 1101. The specific implementation method can refer to the above method embodiment and will not be repeated here.

[0267] In one possible design, the memory 1102 may be a read-only memory (ROM) or other type of static storage device that can store static information and instructions, a random access memory (RAM) or other type of dynamic storage device that can store information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, an optical disc storage (including a compact disc, laser disc, optical disc, digital versatile disc, Blu-ray disc, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto. The memory 1102 may be integrated with the processor 1101 or exist independently and be coupled to the processor 1101 via an interface circuit (not shown in FIG. 11 ) of the communication device 1100. This embodiment of the present application does not specifically limit this.

[0268] Transceiver 1103 is used for communication with other communication devices. For example, if communication device 1100 is a terminal device, transceiver 1103 can be used to communicate with an access network device or another terminal device. For another example, if communication device 1100 is an access network device, transceiver 1103 can be used to communicate with a terminal device or another access network device.

[0269] In one possible design, transceiver 1103 may include a receiver and a transmitter (not separately shown in FIG11 ), wherein the receiver is configured to implement a receiving function, and the transmitter is configured to implement a transmitting function.

[0270] In one possible design scheme, the transceiver 1103 can be integrated with the processor 1101, or it can exist independently and be coupled to the processor 1101 through the interface circuit of the communication device 1100 (not shown in Figure 11). This embodiment of the present application does not specifically limit this.

[0271] It should be noted that the structure of the communication device 1100 shown in FIG11 does not constitute a limitation on the communication device. An actual communication device may include more or fewer components than shown in the figure, or combine certain components, or arrange the components differently.

[0272] In addition, the technical effects of the communication device 1100 can refer to the technical effects of the methods described in the above method embodiments, and will not be repeated here.

[0273] An embodiment of the present application further provides a computer-readable storage medium on which a computer program or instruction is stored. When the computer program or instruction is executed by a computer, the functions of the above-mentioned method embodiment are realized.

[0274] The embodiments of the present application also provide a computer program product, which implements the functions of the above method embodiments when executed by a computer.

[0275] In the above embodiments, all or part of the embodiments can be implemented by software, hardware, firmware, or any combination thereof. When implemented using a software program, all or part of the embodiments can be implemented 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, all or part of the processes or functions according to the embodiments of the present application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via a wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) method. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that includes one or more media integrated therein. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a DVD), or a semiconductor medium (eg, a solid state disk (SSD)).

[0276] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0277] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0278] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0279] The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0280] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0281] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or an access network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0282] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art may understand and implement other variations of the disclosed embodiments by reviewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0283] Although the present application has been described with reference to specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present application. Accordingly, this specification and the drawings are merely illustrative of the present application as defined by the appended claims and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present application. Obviously, those skilled in the art may make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, the present application is intended to include such modifications and variations as fall within the scope of the claims of the present application and their equivalents.

Claims

1. A timing advance reporting method, characterized in that: The method comprises: Receiving a handover command from an access network device, the handover command being used to instruct a terminal device to handover from a source cell to a target cell; When the switching command carries the first indication information and / or the second indication information, the timing advance reporting is triggered; wherein the timing advance is the timing advance corresponding to the target cell, the first indication information is used to indicate the offset threshold of the timing advance reported by the terminal device, and the second indication information is used to indicate the timing advance reported by the terminal device.

2. The method according to claim 1, characterized in that In a case where the handover command carries the first indication information and / or the second indication information, triggering the timing advance reporting includes: If the handover command carries the first indication information, the timing advance reporting is triggered during the process of randomly accessing the target cell or after the random access to the target cell is successful.

3. The method according to claim 1, characterized in that In a case where the handover command carries the first indication information and / or the second indication information, triggering the timing advance reporting includes: If the handover command carries the first indication information and the second indication information, the timing advance reporting is triggered during the process of randomly accessing the target cell or after the random access to the target cell is successful.

4. The method according to claim 1, characterized in that In a case where the handover command carries the first indication information and / or the second indication information, triggering the timing advance reporting includes: In the case where the terminal device is configured for cell switching based on a random access channel-less RACH, if the switching command carries the first indication information and / or the second indication information, the timing advance reporting is triggered after the cell switching is completed.

5. A timing advance reporting method, characterized in that: The method comprises: Receiving a radio resource control (RRC) reconfiguration message from an access network device, where the RRC reconfiguration message is used to instruct the terminal device to switch from a source cell to a target cell; In a case where the RRC reconfiguration message carries the first indication information but does not carry the second indication information, it is determined that the timing advance reporting is not triggered; wherein the timing advance is the timing advance corresponding to the target cell, the first indication information is used to indicate the offset threshold of the timing advance reported by the terminal device, and the second indication information is used to indicate the timing advance reported by the terminal device.

6. The method according to claim 5, characterized in that The RRC reconfiguration message carries synchronization reconfiguration.

7. A communication device, characterized in that: include: Processing module and transceiver module; wherein, The transceiver module is used to receive a handover command from an access network device, where the handover command is used to instruct the terminal device to handover from a source cell to a target cell; The processing module is used to trigger the reporting of the timing advance when the switching command carries the first indication information and / or the second indication information; wherein the timing advance is the timing advance corresponding to the target cell, the first indication information is used to indicate the offset threshold of the timing advance reported by the terminal device, and the second indication information is used to indicate the timing advance reported by the terminal device.

8. The device according to claim 7, characterized in that The processing module is configured to trigger the reporting of the timing advance when the handover command carries the first indication information and / or the second indication information, including: If the handover command carries the first indication information, the processing module is used to trigger the reporting of the timing advance during the process of randomly accessing the target cell or after the random access to the target cell is successful.

9. The device according to claim 7, characterized in that The processing module is configured to trigger the reporting of the timing advance when the handover command carries the first indication information and / or the second indication information, including: If the handover command carries the first indication information and the second indication information, the processing module is used to trigger the reporting of the timing advance during the process of randomly accessing the target cell or after the random access to the target cell is successful.

10. The device according to claim 7, characterized in that The processing module is configured to trigger the reporting of the timing advance when the handover command carries the first indication information and / or the second indication information, including: In the case where the terminal device is configured for cell switching based on a random access channel RACH-less, if the switching command carries the first indication information and / or the second indication information, the processing module is used to trigger the timing advance reporting after the cell switching is completed.

11. A communication device, characterized in that: include: Processing module and transceiver module; wherein, The transceiver module is used to receive a handover command from an access network device, where the handover command is used to instruct the terminal device to handover from a source cell to a target cell; The processing module is used to determine not to trigger the reporting of the timing advance when the switching command carries the first indication information but does not carry the second indication information; wherein the timing advance is the timing advance corresponding to the target cell, the first indication information is used to indicate the offset threshold of the timing advance reported by the terminal device, and the second indication information is used to indicate the timing advance reported by the terminal device.

12. The device according to claim 11, characterized in that The handover command is a radio resource control RRC reconfiguration message carrying synchronization reconfiguration.

13. A communication device, characterized in that: It includes a processor and an interface circuit, wherein the interface circuit is used to receive signals from other communication devices outside the communication device and transmit them to the processor or send signals from the processor to other communication devices outside the communication device, and the processor is used to implement the method as described in any one of claims 1 to 6 through a logic circuit or executing code instructions.

14. A communication device, characterized in that: include: A processor, wherein the processor is configured to execute a computer program so that the communication device executes the method according to any one of claims 1 to 6.

15. A communication chip, characterized in that: Instructions are stored therein, and when the chip is run on a communication device, the method according to any one of claims 1 to 6 is implemented.

16. A computer-readable storage medium, characterized in that: The storage medium stores a computer program or instruction. When the computer program or instruction is executed by the communication device, the method according to any one of claims 1 to 6 is implemented.

17. A computer program product, characterized in that The device comprises a computer program code. When the computer program code is executed on a communication device, the communication device implements the method according to any one of claims 1 to 6.

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