Communication method and apparatus

Abstract

The present application relates to the technical field of communications, and provides a communication method and apparatus. In the method, a first DU may receive first information from a second DU. For example, the first DU receives information related to a TA used by a first terminal device for multiple accesses to a second cell, which indicates that a handover failure (e.g., an LTM handover failure) may occur in the first terminal device. Alternatively, the first DU receives information related to a plurality of TAs used by the first terminal device to execute uplink transmission in the second cell, which indicates that TA adjustment may occur when the first terminal device executes the uplink transmission. Therefore, TA-related information indicated by the first information enables the first DU to optimize a TA validity period management mechanism, thereby reducing the occurrence probability of a handover failure.

Description

A communication method and apparatus

[0001] This application claims priority to Chinese Patent Application No. 202510381632.5, filed on March 27, 2025, entitled "A Communication Method and Apparatus", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of communication technology, and in particular to a communication method and apparatus. Background Technology

[0003] Currently, when terminal devices perform L1 / L2 triggered mobility (LTM) handover, such as handover from a cell managed by the source distributed unit (DU) to a cell managed by the target DU, LTM handover failure may occur, or there may be potential LTM handover failure scenarios.

[0004] Optimizing the relevant parameters of LTM switching to reduce the probability of LTM switching failure is an urgent problem to be solved. Summary of the Invention

[0005] This application provides a communication method and apparatus that can optimize relevant parameters of LTM handover to reduce the probability of LTM handover failure.

[0006] Firstly, a communication method is provided. This method can be executed by a first DU (Digital Unit), for example, by the first DU itself, or by a module applied to the first DU (e.g., a processor, chip, or chip system), or by a logical node, logical module, or software capable of implementing all or part of the functions of the first DU. For ease of description, the following description assumes that the method is executed by the first DU. The method includes: sending a handover instruction to a first terminal device, the handover instruction instructing the first terminal device to handover from a first cell to a second cell; and receiving first information from a second DU. The first cell is a cell managed by the first DU, and the second cell is a cell managed by the second DU. The first information indicates information about the timing advance (TA) used by the first terminal device for multiple accesses to the second cell, or the first information indicates information about multiple TAs used by the first terminal device for uplink transmission in the second cell.

[0007] Based on the method described in the first aspect, the first DU can receive first information from the second DU. For example, if the first DU receives information about the TAs used by the first terminal device to access the second cell multiple times, it indicates that the first terminal device may have experienced a handover failure (such as an LTM handover failure). Alternatively, if the first DU receives information about multiple TAs used by the first terminal device to perform uplink transmission in the second cell, it indicates that the first terminal device may have experienced TA adjustments during uplink transmission. Thus, the TA information indicated by the first information can facilitate the first DU in optimizing the TA validity management mechanism to reduce the probability of handover failure.

[0008] Optionally, the first information may include at least one of the following: first indication information, first TA, second TA, or first difference. The first indication information indicates that the failure of the first terminal device to handover to the second cell without random access was caused by an invalid TA; the first TA is the TA used by the first terminal device when it failed to handover to the second cell without random access; the second TA is the TA used by the first terminal device to access the second cell through random access; and the first difference is the difference between the first TA and the second TA.

[0009] It is understood that the first information can indicate TA-related information to the first terminal device in the case where the failure of handover to the second cell without random access is caused by an invalid TA. The first terminal device can be a terminal, which can increase the frequency and efficiency of the first DU performing root cause analysis of invalid TA, and also increase the frequency and efficiency of the management mechanism for optimizing the validity period of TA, so as to reduce the probability of handover failure without random access.

[0010] Optionally, the first information may include at least one of the following: second indication information, N third TAs, N fourth TAs, or information related to N second differences. The second indication information indicates that the failure of the N terminal devices to handover to the second cell without random access was caused by an invalid TA. The i-th third TA among the N third TAs is the TA used when the i-th terminal device among the N terminal devices fails to handover to the second cell without random access; the i-th fourth TA among the N fourth TAs is the TA used when the i-th terminal device among the N terminal devices accesses the second cell through random access, where 1 ≤ i ≤ N and are integers. The information related to the N second differences indicates at least one of the following: the average of the N second differences, the maximum value among the N second differences, or the minimum value among the N second differences. The i-th second difference among the N second differences is the difference between the i-th third TA and the i-th fourth TA.

[0011] It is understandable that the first piece of information could be a summary of TA-related information from N terminal devices in cases where the failure to switch to the second cell via random access is caused by an invalid TA, which can reduce signaling overhead.

[0012] Optionally, the first information may include at least one of the following: third indication information, fifth TA, sixth TA, or third difference, wherein the third indication information indicates that the first terminal device performs TA adjustment within a preset time after performing the first uplink transmission, the fifth TA is the timing advance used by the first terminal device to perform the first uplink transmission, the sixth TA is the timing advance used by the first terminal device to perform the second uplink transmission after the TA adjustment, and the third difference is the difference between the fifth TA and the sixth TA. The first uplink transmission is the uplink transmission performed by the first terminal device when accessing the second cell using a non-random access method.

[0013] It is understood that the first information can indicate the TA-related information of the first terminal device in the case of TA adjustment within a preset time after the first uplink transmission. The first terminal device can be a terminal, which can increase the frequency and efficiency of the first DU to perform root cause analysis of TA invalidity, and improve the frequency and efficiency of the management mechanism for optimizing TA validity period, so as to reduce the probability of random access handover failure.

[0014] Optionally, the first information may include at least one of the following: fourth indication information, M seventh TAs, M eighth TAs, or information related to M fourth differences; wherein, the fourth indication information is used to indicate that a TA adjustment occurs within a preset time after the M terminal devices perform the first uplink transmission. The j-th seventh TA among the M seventh TAs is: the time advance used by the j-th terminal device among the M terminal devices to perform the first uplink transmission; the j-th eighth TA among the M eighth TAs is: the time advance used by the j-th terminal device among the M terminal devices to perform the second uplink transmission after the TA adjustment occurs, where 1≤j≤M and are integers. The information related to the M fourth differences indicates at least one of the following: the average of the M fourth differences, the maximum value among the M fourth differences, or the minimum value among the M fourth differences; wherein, the j-th fourth difference among the M fourth differences is the difference between the j-th seventh TA and the j-th eighth TA.

[0015] It is understandable that the first information can be a summary message of TA-related information when TA adjustment occurs within a preset time after M terminal devices perform the first uplink transmission, which can reduce signaling overhead.

[0016] Secondly, a communication method is provided, which can be executed by a second DU, for example, by the second DU itself, or by a module applied to the second DU (e.g., a processor, chip, or chip system), or by a logical node, logical module, or software capable of implementing all or part of the functions of the second DU. For ease of description, the following description assumes that the method is executed by the second DU. The method includes: sending first information to a first DU, where the first DU is a device instructing a first terminal device to switch from a first cell to a second cell. The first cell is a cell managed by the first DU, and the second cell is a cell managed by the second DU. The first information indicates information related to the timing advance (TA) used by the first terminal device for multiple accesses to the second cell, or the first information indicates information related to multiple TAs used by the first terminal device for uplink transmission in the second cell.

[0017] Based on the method in the second aspect, the second DU can send first information to the first DU. For example, the first information may include information about the TAs used by the first terminal device to access the second cell multiple times, indicating that the first terminal device may experience a handover failure (e.g., LTM handover failure). Alternatively, the first information may include information about multiple TAs used by the first terminal device to perform uplink transmission in the second cell, indicating that a TA adjustment may occur when the first terminal device performs uplink transmission. Thus, the TA information indicated by the first information can facilitate the first DU in optimizing the TA validity management mechanism to reduce the probability of handover failure.

[0018] In one possible implementation, sending the first information to the first DU may include: sending the first information when it is detected that the first terminal device accesses the second cell in a random access manner; or sending the first information when it is detected that the failure of the first terminal device to hand over to the second cell in a random access manner is caused by an invalid TA.

[0019] Thus, whenever the second DU detects that the first terminal device accesses the second cell via random access, or detects that the failure of the first terminal device to hand over to the second cell via random access is caused by an invalid TA, it sends the TA-related information of the first terminal device to the first DU. This can improve the efficiency of the first DU in performing root cause analysis of invalid TAs and optimizing the management mechanism of TA validity period, thereby improving the efficiency of the first DU in optimizing parameters related to non-random access and reducing the probability of non-random access handover failure.

[0020] Optionally, the first information may include at least one of the following: first indication information, first TA, second TA, or first difference; wherein, the first indication information is used to indicate that the failure of the first terminal device to hand over to the second cell without random access is caused by an invalid TA, the first TA is the TA used by the first terminal device when it fails to hand over to the second cell without random access, the second TA is the TA used by the first terminal device to access the second cell through random access, and the first difference is the difference between the first TA and the second TA.

[0021] It is understood that the first information can indicate TA-related information to the first terminal device in the case where the failure of handover to the second cell without random access is caused by an invalid TA. The first terminal device can be a terminal, which can increase the frequency and efficiency of the first DU performing root cause analysis of invalid TA, and also increase the frequency and efficiency of the management mechanism for optimizing the validity period of TA, so as to reduce the probability of handover failure without random access.

[0022] In one possible implementation, sending the first information to the first DU may include: sending the first information when N terminal devices are detected accessing the second cell via random access; or sending the first information when it is detected that the failure of N terminal devices to hand over to the second cell via random access is caused by an invalid TA. Here, the N terminal devices include the first terminal device, and N is an integer greater than 1.

[0023] Thus, when the second DU detects that N terminal devices access the second cell via random access, or when it detects that the failure of N terminal devices to switch to the second cell via random access is caused by invalid TAs, it can summarize the TA-related information of the N terminal devices and send a first message, thereby reducing signaling overhead.

[0024] Optionally, the first information may include at least one of the following: second indication information, N third TAs, N fourth TAs, or information related to N second differences. The second indication information indicates that the failure of the N terminal devices to handover to the second cell without random access was caused by an invalid TA. The i-th third TA among the N third TAs is the TA used when the i-th terminal device among the N terminal devices fails to handover to the second cell without random access; the i-th fourth TA among the N fourth TAs is the TA used when the i-th terminal device among the N terminal devices accesses the second cell through random access, where 1 ≤ i ≤ N and are integers. The information related to the N second differences indicates at least one of the following: the average of the N second differences, the maximum value among the N second differences, or the minimum value among the N second differences; wherein the i-th second difference among the N second differences is the difference between the i-th third TA and the i-th fourth TA.

[0025] It is understandable that the first message could be a summary of TA-related information from N terminal devices in cases where the failure of handover to the second cell without random access is caused by an invalid TA, which can reduce signaling overhead. Furthermore, after receiving the first message, the first DU can perform root cause analysis of the invalid TA based on the first message, optimize the TA validity management mechanism, and reduce the probability of handover failure without random access.

[0026] In one possible implementation, sending the first information to the first DU may include: sending the first information when a TA adjustment occurs within a preset time after the first terminal device performs the first uplink transmission, wherein the first uplink transmission is the uplink transmission performed by the first terminal device when it accesses the second cell in a manner that does not require random access.

[0027] Thus, when the second DU detects that the first terminal device has undergone TA adjustment within a preset time after performing the first uplink transmission, it sends the TA-related information of the first terminal device to the first DU. This can improve the efficiency of the first DU in performing root cause analysis of TA adjustment and improve the efficiency of the first DU's management mechanism for optimizing TA validity period, thereby reducing the probability of handover failure without random access.

[0028] Optionally, the first information may include at least one of the following: third indication information, fifth TA, sixth TA, or third difference, wherein the third indication information indicates that the first terminal device performs TA adjustment within a preset time after performing the first uplink transmission, the fifth TA is the time advance used by the first terminal device to perform the first uplink transmission, the sixth TA is the time advance used by the first terminal device to perform the second uplink transmission after the TA adjustment, and the third difference is the difference between the fifth TA and the sixth TA.

[0029] It is understood that the first information can indicate the TA-related information of the first terminal device in the case of TA adjustment within a preset time after the first uplink transmission. The first terminal device can be a terminal, which can increase the frequency and efficiency of the first DU to perform root cause analysis of TA invalidity, and improve the frequency and efficiency of the management mechanism for optimizing TA validity period, so as to reduce the probability of random access handover failure.

[0030] In one possible implementation, sending the first information to the first DU may include: sending the first information when a TA adjustment occurs within a preset time after M terminal devices have performed a first uplink transmission; the first uplink transmission is an uplink transmission performed by the M terminal devices when they access the second cell using a non-random access method. Here, the M terminal devices include the first terminal device, and M is an integer greater than or equal to 1.

[0031] Thus, when the second DU detects that a TA adjustment has occurred within a preset time after M terminal devices have performed the first uplink transmission, it can summarize the TA-related information of the M terminal devices and send a first message, thereby reducing signaling overhead.

[0032] Optionally, the first information may include at least one of the following: fourth indication information, M seventh TAs, M eighth TAs, or information related to M fourth differences; wherein, the fourth indication information is used to indicate that a TA adjustment occurs within a preset time after the M terminal devices perform the first uplink transmission. The j-th seventh TA among the M seventh TAs is: the time advance used by the j-th terminal device among the M terminal devices to perform the first uplink transmission; the j-th eighth TA among the M eighth TAs is: the time advance used by the j-th terminal device among the M terminal devices to perform the second uplink transmission after the TA adjustment occurs, where 1≤j≤M and are integers. The information related to the M fourth differences indicates at least one of the following: the average of the M fourth differences, the maximum value among the M fourth differences, or the minimum value among the M fourth differences; wherein, the j-th fourth difference among the M fourth differences is the difference between the j-th seventh TA and the j-th eighth TA.

[0033] It is understandable that the first information can be a summary message of TA-related information in the case where TA adjustments occur within a preset time after M terminal devices perform the first uplink transmission, which can reduce signaling overhead. Furthermore, after receiving the first information, the first DU can perform root cause analysis of invalid TAs based on the first information, optimize the TA validity period management mechanism, and reduce the probability of handover failure without random access.

[0034] The technical effects of the method described in the second aspect above can also be found in the description of the first aspect above, and will not be repeated here.

[0035] Thirdly, a communication method is provided, which can be executed by a first DU, for example, by the first DU itself, or by a module applied to the first DU (e.g., a processor, chip, or chip system), or by a logical node, logical module, or software capable of implementing all or part of the functions of the first DU. For ease of description, the following description uses the execution of the method by the first DU as an example. The method includes: sending a handover instruction to a first terminal device, the handover instruction being used to instruct the first terminal device to handover from a first cell to a second cell. The first cell is a cell managed by the first DU, and the second cell is a cell managed by the second DU. Receiving first information from the second DU. Wherein, the first information indicates information related to the beams used by the first terminal device to access the second cell multiple times, or, the first information indicates information related to multiple beams used by the first terminal device in the beam failure recovery process within a preset time after handover to the second cell based on a non-random access method.

[0036] Based on the method in the third aspect, the first DU can receive first information from the second DU. For example, if the first DU receives information about the beams used by the first terminal device when accessing the second cell multiple times, it indicates that the first terminal device may have experienced a handover failure (such as an LTM handover failure). Alternatively, if the first DU receives information about multiple beams used in the beam failure recovery process after the first terminal device has handed over to the second cell within a preset time, it indicates that beam selection needs to be optimized. Thus, the beam information indicated by the first information can facilitate the first DU's mechanism for optimizing beam selection, thereby reducing the probability of handover failure.

[0037] Optionally, the first information may include at least one of the following: first indication information, information for indicating a first beam, information for indicating a second beam, or a first beam offset. The first indication information indicates that the failure of the first terminal device to handover to the second cell without random access was caused by an incorrect beam. The first beam is the beam used by the first terminal device when it failed to handover to the second cell without random access, the second beam is the beam used by the first terminal device to access the second cell via random access, and the first beam offset is the offset between the first beam and the second beam.

[0038] It is understood that the first information can indicate beam-related information to the first terminal device in the case that the failure of handover to the second cell without random access is caused by an incorrect beam. The first terminal device can be a terminal, which can increase the frequency and efficiency of the first DU to perform root cause analysis of incorrect beams, and increase the frequency and efficiency of the mechanism for optimizing beam selection, so as to reduce the probability of handover failure without random access.

[0039] Optionally, the first information may include at least one of the following: second indication information, information for indicating N third beams, information for indicating N fourth beams, information for indicating the beam that appears most frequently among the N third beams, information for indicating the beam that appears most frequently among the N fourth beams, or information related to the offset of N second beams. The second indication information indicates that the failure of the N terminal devices to handover to the second cell without random access was caused by an incorrect beam. The i-th third beam among the N third beams is the beam used by the i-th terminal device when it failed to handover to the second cell without random access. The i-th fourth beam among the N fourth beams is the beam used by the i-th terminal device to access the second cell through random access, where 1 ≤ i ≤ N and are integers. The information related to the offset of N second beams indicates the average offset of the N second beams; where the i-th second beam offset among the N second beam offsets is the offset between the i-th third beam and the i-th fourth beam.

[0040] It is understandable that the first piece of information could be a message summarizing beam-related information from N terminal devices in the case where the failure to switch to the second cell via random access is caused by an incorrect beam, which can reduce signaling overhead.

[0041] Optionally, the first information may include at least one of the following: third indication information, information for indicating the fifth beam, information for indicating the sixth beam, or a third beam offset. The third indication information is used to instruct the first terminal device to perform a beam failure recovery procedure within a preset time after handover to the second cell using a non-random access method. The fifth beam is the beam used by the first terminal device when handover to the second cell using a non-random access method, the sixth beam is the beam used by the first terminal device when performing the beam failure recovery procedure, and the third beam offset is the offset between the fifth and sixth beams.

[0042] It is understood that the first information can indicate beam-related information when the first terminal device performs a beam failure recovery procedure within a preset time after handover to the second cell using a non-random access method. The first terminal device can be a terminal, which can increase the frequency and efficiency of the first DU performing root cause analysis of erroneous beams, and also increase the frequency and efficiency of the beam optimization mechanism, so as to reduce the probability of non-random access handover failure.

[0043] Optionally, the first information may include at least one of the following: fourth indication information, information for indicating M seventh beams, information for indicating M eighth beams, information for indicating the beam that appears most frequently among the M seventh beams, information for indicating the beam that appears most frequently among the M eighth beams, or information related to the offset of the M fourth beams. The fourth indication information is used to indicate that a beam failure recovery process occurs within a preset time after the M terminal devices handover to the second cell using a non-random access method. The j-th seventh beam among the M seventh beams is the beam used by the j-th terminal device among the M terminal devices when handover to the second cell using a non-random access method; the j-th eighth beam among the M eighth beams is the beam used by the j-th terminal device among the M terminal devices when performing the beam failure recovery process, where 1 ≤ j ≤ M and are integers. The information related to the offset of the M fourth beams indicates the average value of the offsets of the M fourth beams; where the j-th fourth beam offset among the M fourth beam offsets is the offset between the j-th seventh beam and the j-th eighth beam.

[0044] It is understandable that the first information could be a summary message of beam-related information in the case where beam failure recovery occurs within a preset time after M terminal devices switch to the second cell using a non-random access method, which can reduce signaling overhead.

[0045] Optionally, the first information may further include fifth indication information, which is used to indicate the beam failure recovery ratio. The beam failure recovery ratio is the ratio of the number of times M terminal devices perform the beam failure recovery process within a preset time after handing over to the second cell using the non-random access method, to the number of times L terminal devices successfully hand over to the second cell using the non-random access method. The L terminal devices include M terminal devices, and L is an integer greater than or equal to M.

[0046] Thus, by statistically analyzing the proportion of beam failure recovery, the first DU can better perform root cause analysis of erroneous beams, thereby enabling the first DU to optimize the beam selection mechanism and reduce the probability of beam failure.

[0047] Fourthly, a communication method is provided. This method can be executed by a second DU, for example, by the second DU itself, or by a module applied to the second DU (e.g., a processor, chip, or chip system), or by a logical node, logical module, or software capable of implementing all or part of the functions of the second DU. For ease of description, the following description uses the execution of the method by the second DU as an example. The method includes: sending first information to a first DU, where the first DU is a device instructing a first terminal device to switch from a first cell to a second cell. The first cell is a cell managed by the first DU, and the second cell is a cell managed by the second DU. The first information indicates information about the beams used by the first terminal device to access the second cell multiple times, or the first information indicates information about multiple beams used by the first terminal device in a beam failure recovery process within a preset time after switching to the second cell using a non-random access method.

[0048] Based on the method in the fourth aspect, the second DU can send first information to the first DU. For example, the first information may include information about the beams used by the first terminal device when accessing the second cell multiple times, indicating that the first terminal device may experience a handover failure (e.g., LTM handover failure). Alternatively, the first information may include information about multiple beams used by the first terminal device during the beam failure recovery process within a preset time after handover to the second cell using a non-random access method, indicating that the beam selection mechanism needs optimization. Thus, the beam information indicated by the first information can facilitate the first DU in optimizing the beam selection mechanism to reduce the probability of handover failure.

[0049] In one possible implementation, sending the first information to the first DU may include: sending the first information when it is detected that the first terminal device accesses the second cell in a random access manner; or sending the first information when it is detected that the failure of the first terminal device to hand over to the second cell in a random access manner is due to an incorrect beam.

[0050] Optionally, the first information may include at least one of the following: first indication information, information for indicating a first beam, information for indicating a second beam, or a first beam offset. The first indication information indicates that the failure of the first terminal device to handover to the second cell without random access was caused by an incorrect beam. The first beam is the beam used by the first terminal device when it failed to handover to the second cell without random access, the second beam is the beam used by the first terminal device to access the second cell via random access, and the first beam offset is the offset between the first beam and the second beam.

[0051] In one possible implementation, sending the first information to the first DU may include: sending the first information when N terminal devices are detected accessing the second cell via random access; or sending the first information when it is detected that the failure of N terminal devices to hand over to the second cell via random access is due to an incorrect beam. Here, the N terminal devices include the first terminal device, and N is an integer greater than or equal to 1.

[0052] Optionally, the first information may include at least one of the following: second indication information, information for indicating N third beams, information for indicating N fourth beams, information for indicating the beam that appears most frequently among the N third beams, information for indicating the beam that appears most frequently among the N fourth beams, or information related to the offset of N second beams. The second indication information indicates that the failure of the N terminal devices to handover to the second cell without random access was caused by an incorrect beam. The i-th third beam among the N third beams is the beam used by the i-th terminal device when it failed to handover to the second cell without random access. The i-th fourth beam among the N fourth beams is the beam used by the i-th terminal device to access the second cell through random access, where 1 ≤ i ≤ N and are integers. The information related to the offset of N second beams indicates the average offset of the N second beams; where the i-th second beam offset among the N second beam offsets is the offset between the i-th third beam and the i-th fourth beam.

[0053] In one possible implementation, sending the first information to the first DU may include: sending the first information after detecting that the first terminal device has switched to the second cell using a non-random access method and has performed a beam failure recovery procedure within a preset time.

[0054] Optionally, the first information may include at least one of the following: third indication information, information for indicating the fifth beam, information for indicating the sixth beam, or a third beam offset. The third indication information is used to instruct the first terminal device to perform a beam failure recovery procedure within a preset time after handover to the second cell using a non-random access method; the fifth beam is the beam used by the first terminal device when handover to the second cell using a non-random access method; the sixth beam is the beam used by the first terminal device when performing the beam failure recovery procedure; and the third beam offset is the offset between the fifth and sixth beams.

[0055] In one possible implementation, sending the first information to the first DU may include: sending the first information if a beam failure recovery process occurs within a preset time after detecting that M terminal devices have switched to the second cell using a non-random access method. Here, the M terminal devices include the first terminal device, and M is an integer greater than or equal to 1.

[0056] Optionally, the first information may include at least one of the following: fourth indication information, information for indicating M seventh beams, information for indicating M eighth beams, information for indicating the beam that appears most frequently among the M seventh beams, information for indicating the beam that appears most frequently among the M eighth beams, or information related to the offset of the M fourth beams. The fourth indication information is used to indicate that a beam failure recovery process occurs within a preset time after the M terminal devices handover to the second cell using a non-random access method. The j-th seventh beam among the M seventh beams is the beam used by the j-th terminal device among the M terminal devices when handover to the second cell using a non-random access method; the j-th eighth beam among the M eighth beams is the beam used by the j-th terminal device among the M terminal devices when performing the beam failure recovery process, where 1 ≤ j ≤ M and are integers. The information related to the offset of the M fourth beams indicates the average value of the offsets of the M fourth beams; where the j-th fourth beam offset among the M fourth beam offsets is the offset between the j-th seventh beam and the j-th eighth beam.

[0057] Optionally, the first information may further include fifth indication information, which is used to indicate the beam failure recovery ratio. The beam failure recovery ratio is the ratio of the number of times M terminal devices perform the beam failure recovery process within a preset time after handing over to the second cell using the non-random access method, to the number of times L terminal devices successfully hand over to the second cell using the non-random access method. The L terminal devices include M terminal devices, and L is an integer greater than or equal to M.

[0058] The technical effects of the method in the fourth aspect mentioned above can also be found in the relevant introduction in the third aspect mentioned above, and will not be repeated here.

[0059] Fifthly, a communication device is provided. The communication device includes a processor configured to perform the method according to any one of the embodiments of the first to fourth aspects.

[0060] In one possible implementation, the communication device of the fifth aspect may further include a transceiver. This transceiver may be a transceiver circuit or an interface circuit. The transceiver can be used by the communication device of the fifth aspect to communicate with other communication devices.

[0061] In one possible implementation, the communication device of the fifth aspect may further include a memory. This memory may be integrated with the processor or disposed separately. The memory may be used to store computer programs and / or data relating to the methods of any of the embodiments of the first to fourth aspects.

[0062] In the embodiments of this application, the communication device of the fifth aspect can be an access network device of any one of the first to fourth aspects, or a chip (system) or other component or assembly disposed in the access network device, or a device containing the access network device.

[0063] Furthermore, the technical effects of the communication device in the fifth aspect can be referred to the technical effects of any of the embodiments in the first to fourth aspects, and will not be repeated here.

[0064] A sixth aspect provides a communication device. The communication device includes a processor coupled to a memory, the processor being configured to execute a computer program or instructions stored in the memory, causing the communication device to perform the method of any one of the embodiments of the first to fourth aspects.

[0065] In one possible implementation, the communication device may further include a transceiver. The transceiver may be a transceiver circuit or an interface circuit. The transceiver can be used for communication between the communication device described in the sixth aspect and other communication devices.

[0066] In one possible implementation, the communication device further includes the memory for storing the aforementioned computer program or instructions. Optionally, the memory and processor are integrated together.

[0067] In the embodiments of this application, the communication device described in the sixth aspect may be an access network device described in any one of the first to fourth aspects, or a chip (system) or other component or assembly disposed in the access network device, or a device containing the access network device.

[0068] Furthermore, the technical effects of the communication device described in the sixth aspect can be referred to the technical effects of any of the embodiments in the first to fourth aspects, and will not be repeated here.

[0069] A seventh aspect provides a communication system. The communication system includes: a first DU for performing the method described in any one of the embodiments of the first and third aspects, and a second DU for performing the method described in any one of the embodiments of the second and fourth aspects.

[0070] Eighthly, a computer-readable storage medium is provided, comprising: a computer program or instructions; when the computer program or instructions are executed, causing the method as described in any of the first to fourth aspects above to be implemented.

[0071] Ninth aspect, a computer program product is provided, including a computer program or instructions that, when executed, cause the method as described in any of the first to fourth aspects above to be implemented.

[0072] In a tenth aspect, a chip is provided, including a processor connected to a memory for storing a computer program, the processor for executing the computer program stored in the memory, such that the method described in any of the first to fourth aspects above is implemented. Attached Figure Description

[0073] Figure 1 is a schematic diagram of the LTM switching failure process;

[0074] Figure 2 is a flowchart illustrating the process of BFR occurring shortly after a successful LTM switchover.

[0075] Figure 3 is a flowchart illustrating the process of TA adjustment occurring shortly after a successful LTM switchover.

[0076] Figure 4 is a schematic diagram of the architecture of a communication system to which the method provided in the embodiments of this application is applicable;

[0077] Figure 5 is a schematic diagram of the architecture of a communication system to which the method provided in the embodiments of this application is applicable;

[0078] Figure 6 is a schematic diagram of the NR protocol stack in an architecture where the CU and DU of the base station are separated;

[0079] Figure 7 is a schematic diagram of the O-RAN system architecture;

[0080] Figure 8 is a flowchart illustrating the communication method provided in an embodiment of this application;

[0081] Figure 9 is a schematic flowchart of the communication method provided in an embodiment of this application;

[0082] Figure 10 is a schematic flowchart of the communication method provided in the embodiment of this application;

[0083] Figure 11 is a schematic flowchart of the communication method provided in an embodiment of this application;

[0084] Figure 12 is a flowchart illustrating the communication method provided in an embodiment of this application.

[0085] Figure 13 is a schematic flowchart of the communication method provided in an embodiment of this application;

[0086] Figure 14 is a schematic diagram of the communication device provided in an embodiment of this application;

[0087] Figure 15 is a schematic diagram of the structure of the communication device provided in the embodiment of this application. Detailed Implementation

[0088] The technical solutions of this application embodiment 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, vehicle-to-everything (V2X) communication systems, fourth-generation (4G) mobile communication systems, such as long-term evolution (LTE) systems, worldwide interoperability for microwave access (WiMAX) communication systems, fifth-generation (5G) mobile communication systems, such as new radio (NR) systems, and future communication systems.

[0089] For ease of understanding, the technical terms involved in the embodiments of this application will be introduced below.

[0090] 1. Mobile robustness optimization (MRO) mechanism:

[0091] Currently, 5G mobile communication systems support the MRO mechanism to detect and correct the following mobility anomalies: connection failures (including handover failures and radio link failures) caused by unreasonable network parameter settings, unnecessary cross-system handovers, cross-system ping-pong handovers, failures to add / change primary / secondary cells, failures to provide voice fallback across systems, failures to recover fast primary cell groups, suboptimal handovers, and suboptimal addition / changes of primary / secondary cells.

[0092] When a terminal device experiences the aforementioned mobility anomaly, it reports mobility-related information (also known as a MRO report) to the network. Network devices can then autonomously analyze and optimize mobility parameters based on the mobility-related information reported by the terminal device. For example, an MRO report may include a radio link failure report (RLF), secondary cell group failure information (SCG failure information), a successful handover report (SHR), and a successful primary secondary cell (PSCell) addition / change report (SPR).

[0093] The MRO mechanism supports RAN analysis and correction of connection failures, such as when the RAN detects connection failures in terminal devices as early handover, late handover, or handover to the wrong cell. One approach is for the RAN to analyze and correct connection failures based on the RLF reports submitted by the terminal devices. Another approach involves information exchange between RANs and between centralized units (CUs) and distributed units (DUs), with the network side analyzing and correcting connection failures based on the information exchanged between nodes.

[0094] 2. Layer (L1) / L2 triggered mobility (LTM) switching:

[0095] In 3GPP release R17 and earlier, several different L3 handover types were introduced. L3 handover types include basic handover, conditional handover (CHO), and dual active protocol stack (DAPS) handover.

[0096] In L3 handover, the change of serving cell is triggered by L3 measurements and completed based on radio resource control (RRC) signaling (including RRC reconfiguration messages with synchronization cells). This change can be either a primary cell change or a primary / secondary cell change. L3 handover requires reconfiguration of higher layers (i.e., the RRC layer / packet data convergence protocol (PDCP)) and / or reset of lower layers (e.g., the medium access control (MAC) layer, physical layer). Therefore, compared to beam handover without explicit RRC signaling, L3 handover results in longer latency, greater signaling overhead, and longer downtime.

[0097] LTM handover was introduced in 3GPP Release 18 to reduce mobility latency. LTM handover can also be called LTM random access-less (RA-less) handover or random access-free LTM handover, without any restriction. LTM enables serving cell changes based on L1 / L2 signaling. Specifically, the next-generation node B (gNB) DU receives the L1 measurement report reported by the terminal device. The gNB DU instructs the terminal device to change the serving cell (from the source cell to the target cell) through a cell switch command carried by the MAC control element (MAC CE). This cell switch command indicates a gNB candidate cell configuration, which is one of at least one candidate cell configuration that the gNB has pre-sent to the terminal device via RRC signaling.

[0098] LTM handover supports intra-DU mobility handover managed by the same CU, meaning the source and destination cells belong to the same DU during the handover process. It also supports cross-DU mobility handover managed by the same CU, meaning the source and destination cells belong to different DUs during the handover process. Furthermore, it supports continuous LTM handover, which refers to the terminal device handover multiple times between candidate cells without requiring RRC reconfiguration on the network side during the handover process. It should be understood that in LTM handover scenarios, the candidate cell LTM can also be called an LTM candidate cell.

[0099] 3. Scenarios for LTM switching:

[0100] The following describes three scenarios for LTM switching: Scenario 1, Scenario 2, and Scenario 3.

[0101] Scenario 1: LTM switching failure scenario.

[0102] Figure 1 is a flowchart illustrating the LTM handover failure process. As shown in Figure 1, the process includes S101-S109, as follows:

[0103] S101, the CU sends an RRC Reconfiguration message to the user equipment (UE).

[0104] The RRC reconfiguration message includes the configuration of one or more candidate cells pre-configured by the gNB.

[0105] S102, the source DU instructs the UE to initiate early timing advance (TA) acquisition from one or more candidate DUs.

[0106] Among them, the source DU can be the DU to which the source cell belongs, and the candidate DU can be the DU to which the candidate cell belongs.

[0107] Specifically, the source DU sends indication information to the UE, which instructs the UE to initiate early access acquisition (TA) to one or more candidate DUs. In turn, the UE initiates early access acquisition to one or more candidate DUs, such as sending a random access preamble to one or more candidate DUs.

[0108] S103, the candidate DU indicates TA-related information to the source DU through the CU.

[0109] After receiving the random access preamble from the UE, the candidate DU indicates the TA-related information to the source DU via the CU. It can be understood that when there are multiple candidate DUs, the TA-related information can include the TA-related information determined by each candidate DU among the multiple candidate DUs; correspondingly, the TA-related information can include the TA-related information of each candidate cell among the multiple candidate cells.

[0110] S104, Source DU executes switching decision.

[0111] The source DU can make handover decisions based on the L1 measurement report reported by the UE and / or auxiliary information indicated by the CU (such as L3 measurement results or LTM target cell information).

[0112] S105, the source DU sends an LTM handover command to the UE.

[0113] Specifically, the source DU sends an LTM handover command to the UE via L2 MAC CE signaling.

[0114] The LTM handover command indicates the configuration of the target cell, which is one of the candidate cells mentioned above. The target cell can also be called the LTM target cell.

[0115] LTM handover commands may also include the identifier of the LTM target cell, the TA (Transmission Acquisition Target) of the LTM target cell, and beam information to enable the UE to perform random access-free operation. The TA of the LTM target cell can be used by the UE for subsequent LTM handover. The beam information is included in the transmission configuration indicator state (TCI state) information. The TCI state information can be used to indicate the quasi-co-address reference signal and quasi-co-address type to the UE. The quasi-co-address reference signal can be a synchronization signal and a physical broadcast channel (PBCH) block (SSB) or a channel state information reference signal (CSI-RS).

[0116] S106, the source DU sends a handover notification to the target DU through the CU.

[0117] The target DU can be the DU to which the target cell belongs. The handover notification information can include information about the target cell and beam information, etc.

[0118] S107, UE failed to perform LTM handover.

[0119] S108, UE performs cell selection.

[0120] S109, the UE sends an RRC re-establishment request message to the target DU or performs LTM handover based on the random access channel (RACH).

[0121] The UE attempts to access the selected cell. If the cell selected by the UE is not an LTM candidate cell, the UE executes the RRC re-establishment procedure, that is, sends an RRC re-establishment request message to the gNB to which the selected cell belongs. The cell selected by the UE can belong to the same CU (i.e., the source CU) as the source cell / LTM candidate cell, or it can belong to a different CU.

[0122] If the cell selected by the UE is an LTM candidate cell, the UE performs an LTM handover based on the random access channel. The selected cell may belong to the same DU as the LTM target cell in S105, or a different DU.

[0123] Optionally, if the cell selected by the UE is an LTM candidate cell, the LTM candidate cell can also be the LTM target cell indicated in S105. In this case, the UE will attempt to access the LTM target cell again. One possible approach is for the UE to perform an LTM handover based on the random access channel. Another possible approach is for the UE to initiate an RRC Re-establishment procedure to access the LTM target cell; this application does not impose any restrictions on this approach.

[0124] Scenario 2: A scenario in which beam failure recovery (BFR) occurs shortly after a successful LTM handover.

[0125] Figure 2 is a flowchart illustrating the BFR (Browser Free) process that occurs shortly after a successful LTM (Low-Temperature Transition) switchover. As shown in Figure 2, this process includes steps S201-S209, as detailed below:

[0126] S201, gNB-CU sends an RRC reconfiguration message to the UE.

[0127] S202, the source DU instructs the UE to initiate an early TA acquisition from one or more candidate DUs.

[0128] S203, the candidate DU indicates TA-related information to the source DU through the CU.

[0129] S204, Source DU executes switching decision.

[0130] S205, the source DU sends an LTM handover command to the UE.

[0131] S206, the source DU sends a handover notification to the target DU through the CU.

[0132] The specific implementations of S201-S206 can be found in the specific implementations of S101-S106, which will not be elaborated upon here.

[0133] S207, UE successfully performed LTM handover.

[0134] S208, the UE detected a beam failure.

[0135] Soon, if the UE detects a beam failure within a preset time, that is, if the UE performs beam failure detection (BFD) and detects a beam failure with the beam indicated by the LTM handover command in S205, the preset time can be a time period / range set based on actual experience.

[0136] S209, the UE executes the beam failure recovery procedure.

[0137] The UE performs beam failure recovery, selects a new beam, and initiates a beam failure recovery request to the target DU.

[0138] Scenario 3: A scenario where a TA adjustment occurs shortly after a successful LTM switchover.

[0139] Figure 3 is a flowchart illustrating the process of TA adjustment occurring shortly after a successful LTM switchover. As shown in Figure 3, this process includes S301-S309, as detailed below:

[0140] S301, gNB-CU sends an RRC reconfiguration message to the UE.

[0141] S302, the source DU instructs the UE to initiate early TA acquisition from one or more candidate DUs.

[0142] S303, the candidate DU indicates TA-related information to the source DU through the CU.

[0143] S304, Source DU executes switching decision.

[0144] S305, the source DU sends an LTM handover command to the UE.

[0145] S306, the source DU sends a handover notification to the target DU through the CU.

[0146] The specific implementations of S301-S306 can be found in the specific implementations of S101-S106, which will not be elaborated upon here.

[0147] S307, UE successfully performed LTM handover.

[0148] When the UE successfully performs an LTM handover, that is, the UE successfully performs its first uplink transmission based on the TA included in the LTM handover command, such as the LTM handover command including the TA value 1.

[0149] S308, the target DU sends a TA adjustment command to the UE.

[0150] The TA adjustment command instructs the UE to adjust the TA value. The target DU instructs the UE to adjust the TA value via the MAC CE command, specifically instructing the UE to adjust the TA value to TA 5.

[0151] Specifically, the target DU determines the UE's TA value by measuring the UE's uplink transmissions. If a specific UE needs calibration, a timing advance command (TAC) is sent to that UE, instructing the UE to adjust the TA value used for uplink transmissions. This timing advance command is sent to the UE via a timing advance command MAC control element (TAC MAC CE) command.

[0152] The target DU may be sent after the first uplink transmission, sending a TA adjustment command; or, the target DU may be sent after the first N uplink data packet transmissions, where N is an integer greater than or equal to 1; or, the target DU may be sent after a preset period of time, and this application does not impose any restrictions.

[0153] S309, the UE performs subsequent uplink transmission based on TA value 5.

[0154] As can be seen from the above, for scenario 1: after the UE fails to hand over to the LTM target cell, it selects the LTM target cell and attempts to access the LTM target cell in a random access manner. This may be due to an invalid TA value or incorrect beam information during the LTM handover.

[0155] For scenario 2: When the UE successfully performs an LTM handover, and a BFR / BFD occurs in the target cell within a preset time, the UE selects a new beam. This may be due to inappropriate beam information during the LTM handover, such as the UE being located in the edge area of ​​the beam coverage indicated by the beam information.

[0156] For scenario 3: When the UE successfully performs LTM handover, a TA adjustment occurs within a preset time. The UE performs subsequent uplink transmissions based on the adjusted TA. This may be due to an inappropriate TA during LTM handover, such as the TA included in the LTM handover command becoming invalid shortly after the first uplink transmission is successfully executed.

[0157] If an event (e.g., BFD / BFR / TA adjustment) occurs within a preset time period after a successful LTM handover (in scenarios 2 and 3, a successful handover without random access), it is equivalent to the aforementioned event occurring shortly after a successful LTM handover. The preset time period can be after the UE's first uplink data transmission (i.e., after successful UE access without random access), after the UE's first N uplink data packet transmissions to the target DU (i.e., after the UE has performed N-1 uplink transmissions after successful UE access without random access), or within a specific time interval after the first uplink data transmission (i.e., within the preset time period after successful UE access without random access). This scheme does not impose any restrictions. N is an integer greater than 1. This preset time period is pre-configured in the access network equipment; it can be determined by the access network equipment itself or pre-configured by the core network or operation, management, and maintenance equipment. This scheme does not impose any restrictions.

[0158] It is understandable that the source DU is responsible for managing the TA validity period and selecting the beam of the target cell. The source DU uses LTM handover commands to indicate to the UE the TA value and beam information of the target cell that the source DU considers valid. When scenarios 1-3 above occur, the source DU cannot obtain the relevant information to perform LTM MRO root cause analysis and mobility parameter optimization.

[0159] To address the aforementioned technical problems, this application proposes the following technical solutions, which will be described below with reference to the accompanying drawings.

[0160] In the embodiments of this application, "instruction" can include direct and indirect instructions, as well as explicit and implicit instructions. The information indicated by a certain piece of information is called the information to be instructed. In the specific implementation process, there are many ways to instruct the information to be instructed, such as, but not limited to, directly instructing the information to be instructed, such as the information to be instructed itself or its index. It can also indirectly instruct the information to be instructed by instructing other information, where there is a correlation between the other information and the information to be instructed. It can also instruct only a part of the information to be instructed, while the other parts are known or pre-agreed upon. For example, the instruction of specific information can be achieved by using a pre-agreed (e.g., protocol-defined) arrangement of various pieces of information, thereby reducing instruction overhead to some extent. At the same time, common parts of various pieces of information can be identified and uniformly indicated to reduce the instruction overhead caused by individually indicating the same information.

[0161] Furthermore, the specific instruction method can also be any existing instruction method, such as, but not limited to, the above-mentioned instruction methods and their various combinations. As described above, for example, when multiple pieces of information of the same type need to be indicated, the instruction methods for different pieces of information may differ. In the specific implementation process, the required instruction method can be selected according to specific needs. This application embodiment does not limit the selected instruction method. Therefore, the instruction methods involved in this application embodiment should be understood to cover various methods that enable the party to be instructed to obtain the information to be indicated.

[0162] The information to be instructed can be sent as a whole or divided into multiple sub-information messages, and the sending period and / or timing of these sub-information messages can be the same or different. The specific sending method is not limited in this application embodiment. The sending period and / or timing of these sub-information messages can be predefined, for example, according to a protocol, or configured by the sending node device by sending configuration information to the receiving node device.

[0163] In this application, "sending information" can be understood as one device sending information to another device, or it can also be understood as one logical module within a device sending information to another logical module. For example, "network device sending information" can be understood as a network device sending information to another device (such as a terminal device or other network devices), or it can be understood as logical module 1 in the network device sending information to logical module 2 in the network device.

[0164] In this application, "receiving information" can be understood as one device receiving information from another device, or it can also be understood as a logical module within a device receiving information from another logical module. For example, "network device receiving information" can be understood as a network device receiving information from another device (such as a terminal device or other network devices), or it can be understood as logical module 1 in the network device receiving information from logical module 2 in the network device.

[0165] In this application, the phrase "sending information to... (e.g., a terminal device)" or the related illustrations in the accompanying drawings can be understood as the destination of the information being the terminal device. This can include sending information directly or indirectly to the terminal device. Similarly, "receiving information from... (e.g., a terminal device)," "receiving information from... (e.g., a terminal device)," or "receiving information sent (e.g., by a terminal device)," or the related illustrations in the accompanying drawings, can be understood as the source of the information being the terminal device. This can include receiving information directly or indirectly from the terminal device. Information may undergo necessary processing between the source and destination, such as format changes, but the destination can understand the valid information from the source. Similar expressions in this application can be interpreted similarly, and will not be elaborated further here.

[0166] "Predefined" or "pre-configured" can be achieved by pre-saving corresponding codes, tables, or other means that can be used to indicate relevant information in the device. This application does not limit the specific implementation method. "Saving" can refer to saving in one or more memories. These memories can be separate installations or integrated into the encoder, decoder, processor, or communication device. Alternatively, some memories can be separately installed, while others are integrated into the decoder, processor, or communication device. The type of memory can be any form of storage medium, and this application does not limit this.

[0167] The “protocol” mentioned in the embodiments of this application may refer to a protocol family in the field of communication, a standard protocol with a similar protocol family frame structure, or a related protocol applied to future communication systems. The embodiments of this application do not specifically limit this.

[0168] In the embodiments of this application, descriptions such as "when," "under the circumstances," "if," and "if" all refer to the device making corresponding processing under certain objective circumstances, and are not limited to a specific time. They do not require the device to make a judgment action during implementation, nor do they imply any other limitations.

[0169] In the description of the embodiments of this application, unless otherwise stated, " / " indicates that the objects before and after are in an "or" relationship. For example, A / B can represent A or B. "And / or" in the embodiments of this application is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone, where A and B can be singular or plural. Furthermore, in the description of the embodiments of this application, unless otherwise stated, "multiple" refers to two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple. Additionally, to facilitate a clear description of the technical solutions of the embodiments of this application, the terms "first" and "second" are used in the embodiments of this application to distinguish identical or similar items with essentially the same function and effect. Those skilled in the art will understand that the terms "first," "second," etc., do not limit the quantity or order of execution, and that "first," "second," etc., are not necessarily different. Furthermore, in the embodiments of this application, words such as "exemplary" or "for example" are used to indicate that something is being used as an example, illustration, or description. Any embodiment or implementation described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or implementations. Specifically, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner for ease of understanding.

[0170] The network architecture and business scenarios described in the embodiments of this application are for the purpose of more clearly illustrating 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. As those skilled in the art will know, 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.

[0171] To facilitate understanding of the embodiments of this application, the communication system applicable to the embodiments of this application will be described in detail first using the communication system shown in FIG4 as an example. For example, FIG4 is a schematic diagram of the architecture of a communication system to which the method provided in the embodiments of this application is applicable.

[0172] As shown in Figure 4, the communication system mainly includes a first DU and a second DU. The first DU and the second DU can belong to the same CU. In this embodiment, the first DU can also be replaced with other possible terms, such as a source DU; the second DU can also be replaced with other possible terms, such as a target DU, and there is no limitation on this. The communication system may also include a first terminal device.

[0173] It is understood that Figure 4 is a simplified schematic diagram for ease of understanding. The communication system may also include other devices, such as other DUs besides the first DU and the second DU, and other terminal devices besides the first terminal device, etc., which are not shown in Figure 4.

[0174] In one possible scenario, this communication system can be applied to 5G or future communication systems. For example, Figure 5 is a schematic diagram of the architecture of a communication system to which the method provided in this application is applicable. As shown in Figure 5, the communication system 10 includes a RAN 100, a core network (CN) 200, and an Internet 300. The RAN 100 includes at least one RAN node (110a and 110b in Figure 5, collectively referred to as 110) and at least one terminal device (120a-120j in Figure 5, collectively referred to as 120). The RAN 100 may also include other RAN nodes, such as wireless relay devices and / or wireless backhaul devices (not shown in Figure 5). The terminal device 120 is wirelessly connected to the RAN node 110. The RAN node 110 is wirelessly or wiredly connected to the core network 200. The core network devices in the core network 200 and the RAN node 110 in the RAN 100 can be different physical devices, or they can be the same physical device integrating core network logical functions and wireless access network logical functions.

[0175] RAN 100 can be a 3GPP-related cellular system, such as a 4G or 5G mobile communication system, or a future-oriented evolution system (such as a future mobile communication system). RAN 100 can also be an open access network (open RAN, O-RAN, or ORAN), a cloud radio access network (CRAN), or a Wi-Fi system. RAN 100 can also be a communication system that integrates two or more of the above systems.

[0176] RAN node 110, sometimes also referred to as access network equipment, RAN entity, or access node, constitutes part of the communication system and is used to help terminal devices achieve wireless access. Multiple RAN nodes 110 in communication system 10 can be of the same type or different types. In some scenarios, the roles of RAN node 110 and terminal device 120 are relative. For example, network element 120i in Figure 5 can be a helicopter or drone, which can be configured as a mobile base station. For terminal devices 120j accessing RAN 100 through network element 120i, network element 120i is a base station; but for base station 110a, network element 120i is a terminal device. RAN node 110 and terminal device 120 are sometimes both referred to as communication devices. For example, network elements 110a and 110b in Figure 5 can be understood as communication devices with base station functions, and network elements 120a-120j can be understood as communication devices with terminal device functions.

[0177] In one possible scenario, the RAN node can be a base station, an evolved NodeB (eNodeB), a transmission reception point (TRP), a next-generation NodeB (gNB), a next-generation base station in a future mobile communication system, a base station in a future mobile communication system, or an access point (AP) in a Wi-Fi system. The RAN node can be a macro base station (as shown in Figure 5, 110a), a micro base station or indoor station (as shown in Figure 5, 110b), a relay node or donor node, or a radio controller in a CRAN scenario. Optionally, the RAN node can also be a server, wearable device, vehicle, or in-vehicle equipment. For example, the access network equipment in vehicle-to-everything (V2X) technology can be a roadside unit (RSU). All or part of the functions of the RAN node in this application can also be implemented through software functions running on hardware, or through virtualization functions instantiated on a platform (e.g., a cloud platform). The RAN node in this application can also be a logical node, logical module, or software capable of implementing all or part of the RAN node functions.

[0178] In another possible scenario, multiple RAN nodes collaborate to assist terminal devices in achieving wireless access, with different RAN nodes each implementing some of the base station's functions. For example, RAN nodes can be CUs, DUs, CUs (control plane, CP), CUs (user plane, UP), or radio units (RUs). CUs and DUs can be configured separately or included in the same network element, such as a baseband unit (BBU). RUs can be included in radio frequency equipment or radio frequency units, such as RRUs, active antenna units (AAUs), or remote radio heads (RRHs).

[0179] The CU and DU separate the protocol layer of the base station. Some of the protocol layer functions are centrally controlled by the CU, while the remaining part or all of the protocol layer functions are distributed in the DU, which is centrally controlled by the CU.

[0180] For example, Figure 6 is a schematic diagram of the NR protocol stack in a base station architecture where the CU and DU are separated. As shown in Figure 6(a), the CU includes CU-CP and CU-UP. CU-CP deploys the RRC layer and PDCP-control (C) layer of the protocol stack, while CU-UP deploys the Service Data Adaptation Protocol (SDAP) layer and PDCP-user (U) layer. CU-CP and CU-UP are connected via an E1 interface. The DU deploys the Radio Link Control Protocol (RLC) layer, MAC layer, and Physical Layer (PHY) of the protocol stack. CU-CP and DU are connected via an F1-C interface, and CU-UP and DU are connected via an F1-U interface. Thus, CU-CP has RRC and PDCP-C processing capabilities, CU-UP has SDAP and PDCP-U processing capabilities, and DU has RLC, MAC, and PHY processing capabilities.

[0181] A single CU (Core Unit) of a base station can connect to multiple DUs (Dedicated Units). Figure 6(b) illustrates this using two DUs as an example. As shown in Figure 6(b), the CU deploys the RRC, SDAP, and PDCP layers of the protocol stack. The DU deploys the RLC, MAC, and PHY layers of the protocol stack. The CU and DU are connected via an F1 interface. Thus, the CU has RRC, SDAP, and PDCP processing capabilities, while the DU has RLC, MAC, and PHY processing capabilities.

[0182] It is understood that the above functional division is only an example and does not constitute a limitation on CU and DU.

[0183] In different systems, CU (or CU-CP and CU-UP), DU, or RU may have different names, but those skilled in the art will understand their meaning. For example, in an ORAN system, CU can also be called an O-RAN central unit (O-CU) (open CU), DU can also be called an O-RAN distributed unit (O-DU), CU-CP can also be called an O-RAN central unit control plane (O-CU-CP), CU-UP can also be called an O-RAN central unit user plane (O-CU-UP), and RU can also be called an O-RAN radio unit (O-RU). For ease of description, this application uses CU, CU-CP, CU-UP, DU, and RU as examples. Any of the units among CU (or CU-CP, CU-UP), DU, and RU in this application can be implemented through software modules, hardware modules, or a combination of software and hardware modules.

[0184] It is understood that the RAN node mentioned above can be a newly defined name, and RAN nodes can also be described in different ways, such as access node, network device, wireless access node, etc., without limitation. Unless otherwise specified in this application, network device will be used as the term.

[0185] Figure 7 is a schematic diagram of the O-RAN system architecture. The following are examples of the network elements included in the O-RAN system. The O-RAN system includes:

[0186] Service Management and Orchestration Framework (SMO): Its function is similar to that of a network management system.

[0187] The non-real-time RAN intelligent controller (Non-RT RIC) is used for non-real-time intelligent management of RAN functions. It enables artificial intelligence (AI) or machine learning (ML) workflows, including model training and updates, and guides applications / functions within the Near-RT RIC based on policies. The Non-RT RIC is located within the SMO module.

[0188] Near-Real-Time RAN Intelligent Controller (Near-RT RIC): Used to achieve near-real-time intelligent management of the RAN. Through data collection and related operations on the E2 interface, it enables near-real-time control and optimization of O-RAN modules and resources.

[0189] O-CU: Used to implement the RRC layer, PDCP layer, SDAP layer and other control functions in the 3GPP standard.

[0190] O-CU-CP: Similar to CU-CP in the NR system, it is used to implement the functions of the RRC layer and the control plane functions of the PDCP layer. It is part of O-CU.

[0191] O-CU-UP: Similar to CU-UP in the NR system, it is used to implement the functions of the SDAP layer and the user plane functions of the PDCP layer. It is part of O-CU.

[0192] O-DU: Based on low-layer function segmentation, it is used to implement the RLC layer, MAC layer, and higher physical layer (Higher PHY) in the 3GPP standard. Among them, the higher physical layer functions include one or more of the following: forward error correction (FEC) encoding / decoding, scrambling / descrambling, or modulation / demodulation.

[0193] O-RU: Based on low-layer function segmentation, it is used to implement lower physical layer (PHY) functions and radio frequency (RF) functions in the 3GPP standard. The PHY functions include one or more of the following: Fast Fourier Transform (FFT) / Inverse Fast Fourier Transform (IFFT), digital beamforming, or extraction and filtering of the Physical Random Access Channel (PRACH). It is similar to the TRP or Remote Radio Head (RRH) in 3GPP, but includes PHY functions such as FFT, IFFT, or PRACH extraction.

[0194] O-RAN Cloud (O-Cloud): As a cloud computing platform, it includes physical infrastructure nodes for hosting O-RAN functions such as RIC and O-DU; it supports software components (such as operating systems, virtual machine monitoring, container runtimes), management and orchestration functions.

[0195] The O-RAN architecture diagram shown in Figure 7 above includes the following interfaces:

[0196] A1 Interface: The interface between Non-RT RIC and Near-RT RIC, used for intelligent and dynamic control of radio resources within the O-RAN. Non-RT RIC provides policies, rich information, and ML model updates to Near-RT RIC through the A1 interface, while Near-RT RIC provides policy feedback to Non-RT RIC through the A1 interface.

[0197] E2 Interface: The E2 interface is an open interface between two endpoints used to connect the Near-RT RIC and the RAN node. RAN nodes include, for example, CU and DU in 5G, O-RAN compatible eNB in ​​4G, O-CU (O-CU-CP and / or O-CU-UP) in O-RAN, and / or O-DU, etc. The RIC can obtain data collection and feedback from the RAN node through the E2 node, and the RAN node can obtain control feedback from the Near-RT RIC through the E2 node.

[0198] O1 Interface: The interface between the management entity in the SMO and the O-RAN module is used for operation management. Through this interface, fault management, configuration management, accounting management, performance management, security management (FCAPS), software management, and file management are implemented.

[0199] O2 Interface: The interface between the SMO and the infrastructure management framework that supports O-RAN virtual network functionality.

[0200] The Open Fronthaul Control, User, and Synchronization Plane (Open Fronthaul CUS-Plane) interface (i.e., Open FH CUS-Plane interface) includes the Control Plane (C-Plane), User Plane (U-Plane), and Synchronization Plane (S-Plane) interfaces. The Control Plane is used for real-time control between the O-DU and O-RU, such as transmitting beamforming weights from the O-DU to the O-RU or performing power control from the O-DU to the O-RU. The User Plane is used to transmit communication data between the DU and RU for access network equipment and terminal equipment. The Synchronization Plane is used by the O-DU to provide clock synchronization for the O-RU.

[0201] The Open Fronthaul M-Plane interface (Open FH M-Plane) is primarily responsible for management and control functions. Through configuration management, performance management, fault management, dynamic resource allocation, security control, software updates, and maintenance, the M-Plane interface ensures the efficient, secure, and stable operation of the fronthaul network.

[0202] For other 3GPP interfaces, for example, implementations of other 3GPP interfaces can be found in the 3GPP TS 38.401 protocol description.

[0203] NG interface: The interface between NR RAN equipment (such as base stations, CUs, CU-CPs, or CU-UPs) and the NR core network; among them, NG-u is the user plane NG interface, and NG-c is the control plane NG interface.

[0204] Xn interface: The interface between NR RAN devices (such as base stations, CUs, CU-CPs, or CU-UPs); where Xn-u is the user plane Xn interface and Xn-c is the control plane Xn interface.

[0205] X2 Interface: The interface between LTE RAN devices; X2-u is the user plane X2 interface, and X2-c is the control plane X2 interface. In NR, the X2 interface is mainly used in the evolved UMTS Terrestrial Radio Access Network (E-UTRAN) New Radio Dual Connectivity (E-UTRA-NR dual connectivity, E-UTRA-NR dual connectivity / EN-DC) scenario, where the master station is an LTE RAN device, which connects to the LTE core network through the X2 interface.

[0206] E1 interface: The interface between CU-CP and CU-UP.

[0207] F1-C interface: The interface between CU-CP and DU.

[0208] F1-U interface: The interface between CU-UP and DU.

[0209] Terminal devices can also be called terminals, user equipment (UE), mobile stations, mobile terminal devices, etc. Terminal devices can be widely used in various scenarios, such as device-to-device (D2D), V2X communication, machine-type communication (MTC), Internet of Things (IoT), point-of-sale (POS) machines, customer-premises equipment (CPE), virtual reality, augmented reality, industrial control, autonomous driving, telemedicine, smart grids, smart furniture, smart offices, smart wearables (e.g., smartwatches, smart bracelets, pedometers, smart glasses), smart transportation, smart cities, etc. Terminal devices can be mobile phones, tablets, computers with wireless transceiver capabilities, wearable devices, vehicle devices (e.g., vehicle units, in-vehicle modules, in-vehicle chips, on-board units (OBUs) or telematics boxes (T-BOXs)), drones, helicopters, airplanes, ships, robots, robotic arms, smart home devices, satellite terminal devices, etc. The embodiments of this application do not limit the device form of the terminal device.

[0210] In this communication system, the first DU can receive first information from the second DU. For example, if the first DU receives information about the TAs used by the first terminal device to access the second cell multiple times, it indicates that the first terminal device may have experienced a handover failure (such as an LTM handover failure). Alternatively, if the first DU receives information about multiple TAs used by the first terminal device to perform uplink transmission in the second cell, it indicates that the first terminal device may have experienced TA adjustments during uplink transmission. Thus, the TA information indicated by the first information can facilitate the first DU in optimizing the TA validity management mechanism to reduce the probability of handover failure.

[0211] Alternatively, the first DU may receive first information from the second DU, such as information about the beams used by the first terminal device when accessing the second cell multiple times, indicating that the first terminal device may have experienced a handover failure (e.g., LTM handover failure). Or, the first DU may receive information about multiple beams used in the beam failure recovery process after the first terminal device has handed over to the second cell within a preset time, indicating that beam selection needs optimization. In this way, the beam information indicated by the first information can facilitate the first DU's mechanism for optimizing beam selection, thereby reducing the probability of handover failure.

[0212] The interaction process between various network elements / devices in the above-described communication system will be specifically described below with reference to Figures 8-13, through method embodiments. The communication method provided in this application embodiment can be applied to the above-described communication system and specifically applied to various scenarios / processes mentioned in the above-described communication system, which will be described in detail below.

[0213] Figure 8 is a schematic flowchart of a communication method provided in an embodiment of this application. This communication method is applicable to the above-mentioned communication system and mainly involves the interaction between a first terminal device, a first DU, and a second DU.

[0214] As shown in Figure 8, the flow of this communication method is as follows:

[0215] S801, the first DU sends a handover command to the first terminal device, and the first terminal device receives the handover command from the first DU.

[0216] The handover instruction is used to instruct the first terminal device to hand over from the first cell to the second cell. The handover instruction can be carried in Layer 2 MAC CE signaling, meaning the first DU can send the handover instruction to the first terminal device via Layer 2 MAC CE signaling. Of course, the handover instruction can also be carried in RRC signaling, or in other possible signaling formats in future communication systems; there are no restrictions on this.

[0217] Optionally, the handover instruction is used to instruct the first terminal device to hand over from the first cell to the second cell in a manner that avoids random access, or the handover instruction is used to instruct the first terminal device to perform LTM handover and hand over from the first cell to the second cell.

[0218] Optionally, the handover instruction may further include the identifier of the second cell, the TA information corresponding to the second cell, and the beam information, to enable the first terminal device to handover from the first cell to the second cell without random access. The TA value indicated by the TA information and the beam indicated by the beam information are used for the first terminal device's no-random-access procedure.

[0219] The switching instructions can be found in the description of the LTM switching command in S105, which will not be repeated here.

[0220] In the embodiments of this application, the switching instruction may also be replaced with other possible expressions, such as switching command, LTM switching command, switching indication information, etc., and there is no limitation on this.

[0221] Among them, the first community is the community managed by the first DU, or in other words, the first DU is the DU to which the first community belongs. The second community is the community managed by the second DU, or in other words, the second DU is the DU to which the second community belongs.

[0222] In the embodiments of this application, the first cell can also be replaced with other possible terms, such as the source cell; the second cell can also be replaced with other possible terms, such as the target cell, and there is no limitation on this.

[0223] S802, the second DU sends the first information to the first DU, and correspondingly, the first DU receives the first information from the second DU.

[0224] The first information indicates the relevant information of the TA used by the first terminal device to access the second cell multiple times (denoted as TA information #1), or the first information indicates the relevant information of multiple TAs used by the first terminal device to perform uplink transmission in the second cell (denoted as TA information #2).

[0225] Optionally, the second DU sends first information to the first DU through the first CU, and correspondingly, the first DU receives first information from the second DU through the first CU. Here, the first CU refers to the CU to which both the first DU and the second DU belong.

[0226] Thus, the first DU can receive first information from the second DU. For example, if the first DU receives information about the TA used by the first terminal device to access the second cell multiple times, it indicates that the first terminal device may have experienced an access failure (such as an LTM handover failure). Alternatively, if the first DU receives information about multiple TAs used for uplink transmission in the second cell, it indicates that the first terminal device may have experienced TA adjustment during uplink transmission. In this way, the TA information indicated by the first information can facilitate the first DU in optimizing the TA validity management mechanism to reduce the probability of handover failure.

[0227] The following describes the cases of the first information indicating TA information #1 and the first information indicating TA information #2, including the following cases 1 and 2.

[0228] Scenario 1: The first information indicates TA information #1.

[0229] The term "multiple times" in "the first terminal device accesses the second cell multiple times" can refer to two or more times. The access methods for the first terminal device to access the second cell multiple times can include random access and non-random access methods. Random access methods can include LTM handover based on random access (which can be RACH-based LTM execution), RRC re-establishment, beam failure recovery, etc. Non-random access methods can be LTM handover methods based on non-random access.

[0230] The TA used by the first terminal device to access the second cell multiple times can be different each time. For example, the TA used by the first terminal device to access the second cell for the first time is TA value 1, and the TA used by the first terminal device to access the second cell for the second time is TA value 2. TA information #1 can be used to indicate the TA used by the first terminal device to access the second cell each time, as will be explained later.

[0231] Optionally, the multiple accesses of the first terminal device to the second cell may include: the first terminal device accessing the second cell once using a method to avoid random access, and accessing the second cell at least once using a method to randomly access. For example, if the first terminal device fails to access the second cell using a method to avoid random access, it may then access the second cell again using a method to randomly access. Accordingly, TA information #1 can be used to indicate the TA used by the first terminal device when it failed to access the second cell once using a method to avoid random access, and the TA used by the first terminal device when it accessed the second cell using a method to randomly access.

[0232] Alternatively, the multiple accesses of the first terminal device to the second cell may include: the first terminal device accessing the second cell multiple times using a method to avoid random access. For example, the first terminal device fails to access the second cell using the method to avoid random access, and then attempts to access the second cell again using the same method. Accordingly, TA information #1 can be used to indicate the TA used by the first terminal device when it failed to access the second cell using the method to avoid random access, and the TA used by the first terminal device to access the second cell using the same method.

[0233] The following describes how the second DU triggers the sending of the first information to the first DU in case 1, such as implementation method 1 to implementation method 4.

[0234] Optionally, if the second DU and the first DU are managed by the same CU (i.e., the first CU), when the second DU sends the first information to the first DU through the first CU, that is, the second DU sends the first information to the first CU, and the first CU sends the first information to the first DU.

[0235] Optionally, if the CUs managing the second DU and the first DU are the first CU and the second CU respectively, the second DU sends the first information to the first DU through the second CU and the first CU, that is, the second DU sends the first information to the second CU, the second CU sends the first information to the first CU, and the first CU sends the first information to the first DU.

[0236] For example, the first information sent by the second DU to the second CU or the first CU may include one or more of the following: a handover success message (Access Success message), an uplink RRC message transfer message (UL RRC MESSAGE TRANSFER message), or an access and mobility indication message (DU-CU Access and Mobility Indication message). The first information sent by the second CU or the first CU to the second DU may include one or more of the following: a downlink RRC message transfer message (DL RRC MESSAGE TRANSFER message) or an access and mobility indication message (Access and Mobility Indication message). The first information sent by the second CU to the first CU may include one or more of the following: a handover success message (HANDOVER SUCCESS message) or an access and mobility indication message (Access and Mobility Indication message).

[0237] In implementations 3 and 4, since the UE-specific F1 interface context has been released, non-UE-associated signaling is more suitable for sending the first information. The first information sent by the second DU to the second CU or the first CU may include a mobility indication message (DU-CU Access and Mobility Indication message). The first information sent by the second CU or the first CU to the second DU may include an access and mobility indication message. The first information sent by the second CU to the first CU may include an access and mobility indication message.

[0238] Implementation method 1: When the second DU detects that the first terminal device accesses the second cell in a random access manner, it sends the first information to the first DU, and the first DU receives the first information from the second DU.

[0239] Among them, the first terminal device accessing the second cell in a random access manner can be caused by the occurrence of event 1: after the first terminal device fails to switch to the second cell in a random access manner, it accesses the second cell again in a random access manner.

[0240] In other words, if the second DU detects event 1 occurring on the first terminal device each time, it will trigger the sending of the first information to the first DU. There is no limit to the number of times event 1 occurs on the first terminal device. For example, the second DU will trigger the sending of the first information to the first DU each time it detects event 1 occurring on the first terminal device.

[0241] Optionally, before the second DU detects a random access operation / non-random access operation of the first terminal device, it receives a handover command / notification message from the first DU. The second DU can determine, through this handover command / notification message, that a non-random access (e.g., LTM handover) operation of the first terminal device should be detected. Therefore, if the second DU detects that the first terminal device accesses the second cell via random access, it can determine that the first terminal device has failed to access the second cell via random access and has instead accessed the second cell via random access, thereby sending the first information to the first DU.

[0242] Thus, when the second DU detects that event 1 has occurred on the first terminal device, it sends the TA-related information of event 1 to the first DU. This can improve the efficiency of the first DU in performing root cause analysis of invalid TAs and optimizing the management mechanism of TA validity period, thereby improving the efficiency of the first DU in optimizing parameters related to non-random access and reducing the probability of non-random access handover failure.

[0243] Implementation Method 2: When the second DU detects that the failure of the first terminal device to switch to the second cell in order to avoid random access is caused by an invalid TA, it sends the first information to the first DU, and the first DU receives the first information from the second DU.

[0244] In other words, the second DU will send the first information to the first DU each time it detects event 2 (that the failure to handover to the second cell via random access is caused by an invalid TA) on the first terminal device. There is no limit to the number of times event 2 occurs on the first terminal device. For example, the second DU will send the first information to the first DU every time it detects event 2 on the first terminal device.

[0245] The second DU detects that the TA (denoted as the first TA) used by the first terminal device for handover to the second cell without random access is invalid, thus determining that the failure of the first terminal device's handover without random access was caused by the invalid TA. The determination mechanism by which the second DU determines the first TA to be invalid can be determined by the CU to which the second DU belongs.

[0246] For example, if the second DU fails to detect the first terminal device during the validity period of the first TA to avoid handover to the second cell via random access, the second DU determines / confirms that the first TA is invalid. As another example, if the TA (denoted as the second TA) used by the first terminal device to handover to the second cell via random access is different from the first TA, the second DU determines that the first TA is invalid. Alternatively, if the difference between the first TA and the second TA is greater than a threshold, the second DU determines that the first TA is invalid. This application does not restrict the decision mechanism by which the second DU determines the first TA to be invalid. The first TA and the second TA will be described in detail later and will not be repeated here.

[0247] Thus, when the second DU detects that event 2 has occurred on the first terminal device, it sends the TA-related information of event 2 to the first DU. This can improve the efficiency of the first DU in performing root cause analysis of invalid TAs and improve the efficiency of the first DU in optimizing the management mechanism of TA validity period, thereby reducing the probability of handover failure without random access.

[0248] Optionally, corresponding to implementation methods 1 and 2, the first information may include at least one of the following: first indication information, first TA, second TA, or first difference. The first indication information is used to indicate that the failure of the first terminal device to handover to the second cell without random access was caused by an invalid TA. The first TA is the TA used by the first terminal device when it failed to handover to the second cell without random access. The second TA is the TA used by the first terminal device to access the second cell through random access. The first difference is the difference between the first TA and the second TA.

[0249] In other words, TA information #1 may include at least one of the following: first indication information, first TA, second TA, or first difference. In the embodiments of this application, the first TA can be replaced with a first TA value, and the second TA can be replaced with a second TA value, without limitation.

[0250] Example 1: The first information may include first indication information. Example 1 corresponds to Implementation 2; that is, if the first information includes first indication information, it indicates that the second DU sends this first information when it detects that the failure of the first terminal device to handover to the second cell without random access is caused by an invalid TA. After receiving the first indication information, the first DU can perform root cause analysis of the invalid first TA based on the first indication information and optimize the TA validity period management mechanism to reduce the probability of handover failure without random access.

[0251] If the second DU triggers the sending of first information to the first DU through the above implementation method 1, the first information may not include the first indication information.

[0252] Optionally, the first instruction information may not be sent from the second DU to the first DU, but rather sent by the first CU itself to the first DU.

[0253] Example 2: The first information may include a first TA and a second TA. Example 2 corresponds to Implementation 1 and Implementation 2. That is, if the second DU triggers the sending of first information to the first DU through Implementation 1 or Implementation 2, the first information may include the first TA and the second TA.

[0254] The first TA can be the TA received by the first DU from the second DU when the first DU instructs the first terminal device to initiate an early TA acquisition from the second DU. For example, after receiving the random access preamble sent by the first terminal device, the second DU detects the first TA and instructs the first TA to the first DU through the first CU. Accordingly, the first DU receives the first TA.

[0255] Optionally, the first TA can be one of the TAs received by the first DU from the second DU multiple times when the first DU repeatedly instructs the first terminal device to initiate early TA acquisition from the second DU. This could be the latest TA received from the second DU, or any TA received from the second DU multiple times; there is no restriction on this. It should be understood that the first DU may initiate early TA acquisition multiple times to ensure the validity of the first TA due to the high movement speed of the first terminal device. For example, the first DU may initiate early TA acquisition 3 or 5 times within 20 seconds to ensure the validity of the latest acquired TA.

[0256] The second TA can be the TA used by the first terminal device to access the second cell via random access after failing to access the second cell via non-random access. It can be understood that the second TA can be the real-time TA obtained by the second DU when the first terminal device accesses the second cell via random access, such as the real-time TA detected by the second DU when the first terminal device sends a random access preamble to the second DU and receives the random access preamble from the UE.

[0257] In this way, after receiving the first TA and the second TA, the first DU can analyze whether the first TA is invalid, and perform root cause analysis in the case of invalid first TA, and optimize the management mechanism of TA validity period to reduce the probability of handover failure without random access.

[0258] Example 3: The first information may include a first difference, that is, the difference between the first TA and the second TA. Example 3 corresponds to Implementation 1 and Implementation 2. That is, if the second DU triggers the sending of first information to the first DU through Implementation 1 or Implementation 2, the first information may include the first difference.

[0259] Thus, after receiving the first difference, the first DU can analyze whether the first TA is invalid, and perform root cause analysis in the case of invalid first TA, and optimize the management mechanism of TA validity period to reduce the probability of handover failure without random access.

[0260] Example 4: The first information may include a first TA, a second TA, and a first difference. Example 4 corresponds to Implementation 1 and Implementation 2. That is, if the second DU triggers the sending of the first information to the first DU through Implementation 1 or Implementation 2, the first information may include the first TA, the second TA, and the first difference. After receiving the first information, the first DU can analyze whether the first TA is invalid based on the first TA, the second TA, and the first difference, and perform root cause analysis in the case of an invalid first TA. Furthermore, it can optimize the TA validity period management mechanism to reduce the probability of handover failure without random access.

[0261] Example 5: The first information may include a first TA, a second TA, a first difference, and first indication information. Example 5 corresponds to implementation method 2. That is, if the second DU triggers the sending of the first information to the first DU through the above implementation method 2, the first information may include the first TA, the second TA, the first difference, and the first indication information. After receiving the first information, the first DU can perform root cause analysis for the invalid first TA based on the first TA, the second TA, the first difference, and the first indication information, and optimize the TA validity period management mechanism to reduce the probability of handover failure without random access.

[0262] It should be understood that the second DU will only trigger the sending of the first information to the first DU if it detects that the first terminal device has experienced event 1 or event 2 multiple times. Correspondingly, the first TA may include the TA used when the first terminal device fails to hand over to the second cell multiple times using the non-random access method, and the second TA may include the TA used when the first terminal device accesses the second cell multiple times using the random access method. The first difference may include the difference between the first TA and the second TA associated with each access to the second cell in the multiple accesses to the second cell. For example, taking two accesses as an example, the first difference includes: the difference between TA1 used by UE1 when it failed to hand over to the second cell for the first time using the non-random access method and TA2 used by UE1 when it accessed the second cell for the first time using the random access method; and the difference between TA3 used by UE1 when it failed to hand over to the second cell for the second time using the non-random access method and TA4 used by UE1 when it accessed the second cell for the second time using the random access method.

[0263] Of course, the first information may also contain only the first TA, or only the second TA, and the first DU may optimize the management mechanism of the TA validity period based on the first TA or the second TA.

[0264] It should be understood that the above are only examples of a few types of content contained in the first information. There are other possible combinations of content contained in the first information, which will not be elaborated here.

[0265] Implementation methods 1 and 2 are implementation methods in case 1, where the second DU sends the first information every time it detects event 1 or event 2 occurring on the first terminal device. The following describes implementation methods 3 and 4, where the second DU sends the first information only when it detects multiple (two or more) events 1 or event 2 occurring on the first terminal device.

[0266] Implementation Method 3: When the second DU detects that N terminal devices have accessed the second cell via random access, it sends first information to the first DU. Correspondingly, the first DU receives the first information from the second DU. Here, the N terminal devices include the first terminal device, and N is an integer greater than 1. The value of N can be set based on experience or actual needs and is not restricted.

[0267] Among them, N terminal devices accessing the second cell in a random access manner can be N terminal devices experiencing event 1: after failing to switch to the second cell in a random access manner, they access the second cell again in a random access manner.

[0268] There is no limit to the number of times each of the N terminal devices experiences Event 1, nor is there a limit to the number of times the N terminal devices send Event 1. For example, if each of the N terminal devices experiences Event 1 at least once, the second DU, upon detecting Event 1 events on the N terminal devices, can aggregate the TA-related information of Event 1 events on the N terminal devices and send a first message, thereby reducing signaling overhead.

[0269] Implementation method 4: If the failure of the second DU to switch to the second cell in the manner of avoiding random access to N terminal devices is caused by invalid TA, the second DU sends the first information to the first DU. Correspondingly, the first DU receives the first information from the second DU.

[0270] In other words, if the second DU detects that N terminal devices have experienced event 2 (the failure to switch to the second cell via random access is caused by an invalid TA), it will trigger the sending of the first information to the first DU.

[0271] There is no limit to the number of times event 2 occurs on each of the N terminal devices. For example, event 2 occurs at least once on each of the N terminal devices.

[0272] The second DU detects that the TA (denoted as the third TA) used by N terminal devices for handover to the second cell without random access is invalid, thus determining that the failure of the handover without random access for the N terminal devices is caused by the invalid TA. The decision mechanism of the second DU to determine that the third TA is invalid can refer to the decision mechanism of the second DU to determine that the first TA is invalid, and will not be elaborated here.

[0273] Thus, when the second DU detects that event 2 has occurred on N terminal devices, it can summarize the TA-related information of event 2 on the N terminal devices and send a first message, which can reduce signaling overhead.

[0274] Optionally, corresponding to implementation methods 3 and 4, the first information includes at least one of the following: second indication information, N third TAs, N fourth TAs, or information related to N second differences.

[0275] In other words, TA information #1 may include at least one of the following: second indication information, N third TAs, N fourth TAs, or information related to N second differences. In the embodiments of this application, the third TA can be replaced with the third TA value, and the fourth TA can be replaced with the fourth TA value, without limitation.

[0276] Example 1: The first information may include second indication information. The second indication information indicates that the failure of N terminal devices to handover to the second cell without random access was caused by an invalid TA. This second indication information corresponds to implementation 4; that is, if the first information includes the second indication information, it means that the second DU sends the first information when it detects that the failure of N terminal devices to handover to the second cell without random access was caused by an invalid TA. After receiving the second indication information, the first DU can perform root cause analysis of invalid TAs based on the second indication information and optimize the TA validity period management mechanism to reduce the probability of handover failure without random access.

[0277] If the second DU triggers the sending of first information to the first DU through the above implementation method 3, the first information may not include the second indication information.

[0278] Optionally, the second instruction information may not be sent from the second DU to the first DU, but rather sent by the first CU to the first DU itself.

[0279] Example 2: The first information may include N third TAs and N fourth TAs. Example 2 corresponds to implementation methods 3 and 4. That is, if the second DU triggers the sending of the first information to the first DU through the above implementation method 3 or implementation method 4, the first information may include N third TAs and N fourth TAs.

[0280] The i-th third TA among N third TAs is the TA used when the i-th terminal device among N terminal devices fails to hand over to the second cell using a non-random access method, where 1 ≤ i ≤ N and is an integer. In other words, the N third TAs can include the third TA used by each of the N terminal devices when it fails to hand over to the second cell using a non-random access method. The description of each of the N third TAs can be referenced from the description of the first TA above, and will not be repeated here.

[0281] The i-th fourth TA among N fourth TAs is the TA used by the i-th terminal device among N terminal devices when it accesses the second cell via random access. In other words, the N fourth TAs can include the fourth TA used by each of the N terminal devices when it fails to hand over to the second cell via a non-random access method. The description of each of the N fourth TAs can be referenced from the description of the second TA above, and will not be repeated here.

[0282] Optionally, the third TA and the fourth TA are in one-to-one correspondence, or in other words, the third TA and the fourth TA corresponding to each of the N terminal devices are respectively matched. For example, the third TA used when the first terminal device among the N terminal devices fails to hand over to the second cell using a method without random access (such as without random access #1) corresponds to the fourth TA used when the first terminal device among the N terminal devices accesses the second cell using a method without random access (such as random access #1). That is, after the first terminal device fails to hand over using the method without random access #1, it then performs random access #1.

[0283] Thus, after receiving N third TAs and N fourth TAs, the first DU can analyze whether the N third TAs are invalid, and perform root cause analysis in the case where there are invalid third TAs among the N third TAs, and optimize the management mechanism of TA validity period to reduce the probability of handover failure without random access.

[0284] Example 3: The first information may include information related to N second differences. The information related to the N second differences indicates at least one of the following: the average of the N second differences, the maximum value among the N second differences, or the minimum value among the N second differences; wherein, the i-th second difference among the N second differences is the difference between the i-th third TA and the i-th fourth TA.

[0285] Example 3 corresponds to Implementation 3 and Implementation 4. That is, if the second DU triggers the sending of first information to the first DU through Implementation 3 or Implementation 4, the first information may include information related to N second differences.

[0286] The N second differences can include the difference between each of the N third TAs and its corresponding fourth TA (the third TA and the fourth TA correspond to the same terminal device). For example, taking N=2, the difference between the third TA#1 used by the first terminal device in the two terminals when it fails to hand over to the second cell using a non-random access method and the fourth TA#1 used by the first terminal device in the two terminals when it accesses the second cell using a random access method; and the difference between the third TA#2 used by the second terminal device in the two terminals when it fails to hand over to the second cell using a non-random access method and the fourth TA#2 used by the second terminal device in the two terminals when it accesses the second cell using a random access method.

[0287] The relevant information for N second differences can include one or more of the following: the average of the N second differences, the maximum value among the N second differences, and the minimum value among the N second differences. For example, the relevant information for N second differences includes the average of the N second differences; or, the relevant information for N second differences includes the average of the N second differences and the maximum value among the N second differences; or, the relevant information for N second differences includes the maximum value among the N second differences and the minimum value among the N second differences. More examples will not be elaborated here.

[0288] Thus, after receiving relevant information from N second differences, the first DU can analyze whether the N third TAs are invalid, and perform root cause analysis in the case of invalid third TAs among the N third TAs, and optimize the management mechanism of TA validity period to reduce the probability of handover failure without random access.

[0289] Example 4: The first information may include information related to N second differences, N third TAs, and N fourth TAs. Example 4 corresponds to implementation methods 3 and 4. After receiving the first information, the first DU can analyze whether the N third TAs are invalid based on the information related to the N second differences, the N third TAs, and the N fourth TAs, as well as perform root cause analysis if any of the N third TAs are invalid, and optimize the TA validity period management mechanism to reduce the probability of handover failure without random access.

[0290] Example 5: The first information may include second indication information, N third TAs, N fourth TAs, and information related to N second differences. Example 5 corresponds to implementation method 4. After receiving the first information, the first DU can perform root cause analysis on the invalidity of the N third TAs based on the second indication information, the information related to the N third TAs, the N fourth TAs, and the information related to the N second differences, and optimize the TA validity period management mechanism to reduce the probability of handover failure without random access.

[0291] It should be understood that the second DU will only trigger the sending of the first information to the first DU if it detects that N terminal devices have experienced event 1 or event 2 multiple times. Correspondingly, the N third TAs can include the third TAs used by the N terminal devices when they fail to hand over to the second cell multiple times using a non-random access method, such as the third TA used by each of the N terminal devices each time they fail to hand over to the second cell using a non-random access method. The N fourth TAs can include the fourth TAs used by the N terminal devices when they access the second cell multiple times using a random access method, such as the fourth TA used by each of the N terminal devices each time they access the second cell using a random access method.

[0292] Correspondingly, the N second differences can include the differences between the third TA and the fourth TA associated with each event 1 / event 2 in multiple occurrences of event 1 / event 2 for each of the N terminal devices. For example, taking two access attempts for each of the two terminals as an example, the N second differences include: the difference between the third TA1 used by UE1 when it failed to hand over to the second cell for the first time based on the non-random access method and the fourth TA1 used by UE1 when it first accessed the second cell based on the random access method; the difference between the third TA2 used by UE1 when it failed to hand over to the second cell for the second time based on the non-random access method and the fourth TA2 used by UE1 when it second accessed the second cell based on the random access method; the difference between the third TA3 used by UE2 when it failed to hand over to the second cell for the first time based on the non-random access method and the fourth TA3 used by UE2 when it first accessed the second cell based on the random access method; and the difference between the third TA4 used by UE2 when it failed to hand over to the second cell for the second time based on the non-random access method and the fourth TA4 used by UE2 when it second accessed the second cell based on the random access method.

[0293] It should be understood that the above are only examples of a few types of content contained in the first information. There are other possible combinations of content contained in the first information, which will not be elaborated here.

[0294] Scenario 2: The first information indicates TA information #2. That is, the first information indicates the relevant information of multiple TAs used by the first terminal device to perform uplink transmission in the second cell (denoted as TA information #2).

[0295] The uplink transmission performed by the first terminal device in the second cell may include the uplink transmission performed when the first terminal device accesses the second cell using a random access method or a non-random access method, as well as subsequent uplink transmissions. Multiple TAs may include the TAs used by the first terminal device each time it performs an uplink transmission in the second cell.

[0296] The following describes how the second DU triggers the sending of the first information to the first DU in case 2, as shown in methods 1 to 2.

[0297] Optionally, if the second DU and the first DU are managed by the same CU (i.e., the first CU), when the second DU sends the first information to the first DU through the first CU, that is, the second DU sends the first information to the first CU, and the first CU sends the first information to the first DU.

[0298] Optionally, if the CUs managing the second DU and the first DU are the first CU and the second CU respectively, the second DU sends the first information to the first DU through the second CU and the first CU, that is, the second DU sends the first information to the second CU, the second CU sends the first information to the first CU, and the first CU sends the first information to the first DU.

[0299] For example, the first information sent by the second DU to the second CU or the first CU may include one or more of the following: a handover success message (Access Success message), an uplink RRC message transfer message (UL RRC MESSAGE TRANSFER message), or an access and mobility indication message (DU-CU Access and Mobility Indication message). The first information sent by the second CU or the first CU to the second DU may include one or more of the following: a downlink RRC message transfer message (DL RRC MESSAGE TRANSFER message) or an access and mobility indication message (Access and Mobility Indication message). The first information sent by the second CU to the first CU may include one or more of the following: a handover success message (HANDOVER SUCCESS message) or an access and mobility indication message (Access and Mobility Indication message).

[0300] In Method 2, since the UE-specific F1 interface context has been released, non-UE-associated signaling is more suitable for sending the first information. The first information sent by the second DU to the second CU or the first CU may include a mobility indication message (DU-CU Access and Mobility Indication message). The first information sent by the second CU or the first CU to the second DU may include an access and mobility indication message. The first information sent by the second CU to the first CU may include an access and mobility indication message.

[0301] Method 1: When the second DU detects that a TA adjustment occurs within a preset time after the first terminal device performs the first uplink transmission, it sends the first information. The first uplink transmission is the uplink transmission performed by the first terminal device when it accesses the second cell in a non-random access manner.

[0302] It is understood that the first terminal device successfully accesses the second cell using a non-random access method and performs the first uplink transmission. A TA adjustment occurs within a preset time after the first uplink transmission; for example, the preset time could be 1 millisecond (ms), 10 ms, etc., without limitation. That is, the second DU performs a TA adjustment shortly after detecting that the first terminal device has performed the first uplink transmission. The TA adjustment can be based on the mobility of the first terminal device; for example, if the first terminal device moves quickly, a TA adjustment may occur shortly after it successfully accesses the second cell using the non-random access method. Optionally, the second DU sends a TA adjustment command to the first terminal device, which instructs the first terminal device to perform uplink transmission based on the adjusted TA.

[0303] The second DU sends the first information each time it detects event 3 (TA adjustment occurring within a preset time after the first uplink transmission) on the first terminal device. There is no limit to the number of times event 3 occurs on the first terminal device. For example, the second DU will trigger the sending of the first information to the first DU each time it detects event 3 on the first terminal device.

[0304] Thus, when the second DU detects that event 3 has occurred on the first terminal device, it sends the TA-related information of event 3 to the first DU. This can improve the efficiency of the first DU in performing root cause analysis for TA adjustment and improve the efficiency of the first DU's management mechanism for optimizing the TA validity period, thereby reducing the probability of handover failure without random access.

[0305] Optionally, corresponding to Method 1, the first information includes at least one of the following: third indication information, fifth TA, sixth TA, or third difference. The third indication information indicates that the first terminal device performs a TA adjustment within a preset time after performing the first uplink transmission; the fifth TA is the time advance used by the first terminal device to perform the first uplink transmission; the sixth TA is the time advance used by the first terminal device to perform the second uplink transmission after the TA adjustment; and the third difference is the difference between the fifth TA and the sixth TA.

[0306] In other words, TA information #2 may include at least one of the following: third indication information, fifth TA, sixth TA, or third difference. In the embodiments of this application, the fifth TA can be replaced with the fifth TA value, and the sixth TA can be replaced with the sixth TA value, without limitation.

[0307] Example 1: The first information may include third indication information. After receiving the third indication information, the first DU can optimize the management mechanism of the TA validity period based on the third indication information to reduce the probability of handover failure without random access.

[0308] Example 2: The first information may include a fifth TA and a sixth TA. The fifth TA may be the TA used by the first terminal device when performing the first uplink transmission based on a random access-free method to access the second cell. It should be understood that since the first terminal device undergoes TA adjustment within a preset time after performing the first uplink transmission, the fifth TA is the TA that needs adjustment, or in other words, an unsuitable TA, such as the fifth TA becoming invalid within the preset time. The fifth TA may be the TA received by the first DU from the second DU when the first DU instructs the first terminal device to initiate an early TA acquisition from the second DU. For details, please refer to the relevant description of the first TA; further elaboration is omitted here.

[0309] The sixth TA is the TA used by the first terminal device to perform the second uplink transmission after a TA adjustment occurs. For example, the second DU sends a TA adjustment command to the first terminal device. The TA adjustment command is used to instruct the first terminal device to perform uplink transmission based on the adjusted sixth TA.

[0310] Thus, after receiving the fifth and sixth TAs, the first DU can perform root cause analysis on the fifth TA based on the fifth and sixth TAs, and optimize the management mechanism of the TA validity period to reduce the probability of handover failure without random access.

[0311] Example 3: The first information may include the third difference, i.e., the difference between the fifth TA and the sixth TA. After receiving the third difference, the first DU can perform root cause analysis on the fifth TA based on the third difference and optimize the TA validity period management mechanism to reduce the probability of handover failure without random access.

[0312] Example 4: The first information may include the fifth TA, the sixth TA, and the third difference. After receiving the first information, the first DU can perform root cause analysis on the fifth TA based on the fifth TA, the sixth TA, and the third difference, and optimize the TA validity period management mechanism to reduce the probability of handover failure without random access.

[0313] Example 5: The first information may include the fifth TA, the sixth TA, the third difference, and the first indication information. After receiving the first information, the first DU can perform root cause analysis on the fifth TA based on the fifth TA, the sixth TA, the third difference, and the first indication information, and optimize the TA validity period management mechanism to reduce the probability of handover failure without random access.

[0314] It should be understood that the second DU will only trigger the sending of the first information to the first DU if it detects that the first terminal device has experienced event 3 multiple times. Correspondingly, the fifth TA may include the TA used when the first terminal device performs the first uplink transmission when event 3 has occurred multiple times, and the sixth TA may include the TA used when the first terminal device performs the second uplink transmission when event 3 has occurred multiple times. The third difference may include the difference between the fifth TA and the sixth TA associated with each occurrence of event 3 in the multiple occurrences of event 3. For example, taking the occurrence of event 3 twice as an example, the third difference may include: the difference between TA1 used by UE1 when it first accesses the second cell using the non-random access method to perform the first uplink transmission and TA2 used by UE1 when it first performs the second uplink transmission using the adjusted TA; and the difference between TA3 used by UE1 when it second accesses the second cell using the non-random access method to perform the first uplink transmission and TA4 used by UE1 when it second performs the second uplink transmission using the adjusted TA.

[0315] It should be understood that the above are only examples of a few types of content contained in the first information. There are other possible combinations of content contained in the first information, which will not be elaborated here.

[0316] Method 2: If the second DU detects that a TA adjustment occurs within a preset time after M terminal devices have performed the first uplink transmission, it sends the first information to the first DU. The first uplink transmission is the uplink transmission performed by the M terminal devices when they access the second cell using a non-random access method. Here, the M terminal devices include the first terminal device, and M is an integer greater than 1. The value of M can be set based on experience or actual needs and is not restricted.

[0317] The second DU detected event 3 in M ​​terminal devices: a TA adjustment occurred within a preset time after the first uplink transmission was performed.

[0318] There is no limit to the number of times event 3 occurs on each of the M terminal devices. For example, each of the M terminal devices must have experienced event 3 at least once. For instance, when the second DU detects that the total number of times event 3 has occurred on the M terminal devices reaches a certain threshold, it will trigger the sending of the first information to the first DU. Alternatively, the second DU may detect that event 3 has occurred on M terminal devices within a certain time interval after the last sending of the first information, and trigger the sending of the first information to the first DU.

[0319] Thus, when the second DU detects that event 3 has occurred on M terminal devices, it can summarize the TA-related information of event 3 on the M terminal devices and send a first message, which can reduce signaling overhead.

[0320] Optionally, corresponding to method 2, the first information includes at least one of the following: fourth indication information, M seventh TAs, M eighth TAs, or information related to M fourth differences.

[0321] In other words, TA information #2 may include at least one of the following: fourth indication information, M seventh TAs, M eighth TAs, or information related to M fourth differences. In the embodiments of this application, the seventh TA can be replaced with the seventh TA value, and the eighth TA can be replaced with the eighth TA value, without limitation.

[0322] Example 1: The first information may include fourth indication information. This fourth indication information instructs the M terminal devices to perform a TA adjustment within a preset time after performing the first uplink transmission. Upon receiving the fourth indication information, the first DU can perform root cause analysis of the TA adjustment based on this information, optimizing the TA validity period management mechanism to reduce the probability of handover failure without random access.

[0323] Example 2: The first information may include M seventh TAs and M eighth TAs. The j-th seventh TA among the M seventh TAs is: the timing advance used by the j-th terminal device among the M terminal devices to perform the first uplink transmission, where 1 ≤ j ≤ M and is an integer. In other words, the M seventh TAs may include the seventh TA used by each of the M terminal devices to perform the first uplink transmission. Each of the M seventh TAs can also refer to the description of the fifth TA above, and will not be repeated here.

[0324] The j-th eighth TA in the M eighth TAs is: the time advance used by the j-th terminal device among the M terminal devices to perform the second uplink transmission after a TA adjustment occurs. In other words, the M eighth TAs can include the eighth TA used by each of the M terminal devices to perform the second uplink transmission. Each of the M eighth TAs can also refer to the description of the sixth TA above, and will not be repeated here.

[0325] Optionally, the seventh TA and the eighth TA are in one-to-one correspondence, or in other words, the seventh TA and the eighth TA correspond to each of the M terminal devices. For example, the seventh TA used by the first terminal device among the M terminal devices to perform the first uplink transmission corresponds to the eighth TA used by the first terminal device among the M terminal devices to perform the second uplink transmission. That is, after the first terminal device performs the first uplink transmission, a TA adjustment occurs, and the second uplink transmission is performed based on the adjusted TA.

[0326] Thus, after receiving M seventh TAs and M eighth TAs, the first DU can perform root cause analysis on TA adjustment based on the M seventh TAs and M eighth TAs, and optimize the TA validity period management mechanism to reduce the probability of handover failure without random access.

[0327] Example 3: The first information may include information about the M fourth differences. The information about the M fourth differences indicates at least one of the following: the average of the M fourth differences, the maximum value among the M fourth differences, or the minimum value among the M fourth differences; wherein the j-th fourth difference among the M fourth differences is the difference between the j-th seventh TA and the j-th eighth TA.

[0328] The M fourth differences can include the difference between each of the M seventh TAs and its corresponding eighth TA (the seventh TA and the eighth TA correspond to the same terminal device). For example, taking M=2, the difference between the seventh TA#1 used by the first terminal device in the two terminals to perform the first uplink transmission and the eighth TA#1 used by the first terminal device in the two terminals to perform the second uplink transmission; and the difference between the seventh TA#2 used by the second terminal device in the two terminals to perform the first uplink transmission and the eighth TA#2 used by the second terminal device in the two terminals to perform the second uplink transmission.

[0329] The relevant information for M fourth differences can include one or more of the following: the average of the M fourth differences, the maximum value among the M fourth differences, and the minimum value among the M fourth differences. For example, the relevant information for M fourth differences includes the average of the M fourth differences; or, the relevant information for M fourth differences includes the average of the M fourth differences and the maximum value among the M fourth differences; or, the relevant information for M fourth differences includes the maximum value among the M fourth differences and the minimum value among the M fourth differences. More examples will not be elaborated here.

[0330] Thus, after receiving relevant information from M fourth differences, the first DU can perform root cause analysis for TA adjustment based on the relevant information from the M fourth differences, and optimize the management mechanism for TA validity period to reduce the probability of handover failure without random access.

[0331] Example 4: The first information may include information related to M fourth differences, M seventh TAs, and M eighth TAs. After receiving the first information, the first DU can perform root cause analysis for TA adjustment based on the information related to the M fourth differences, the M seventh TAs, and the M eighth TAs, and optimize the TA validity period management mechanism to reduce the probability of handover failure without random access.

[0332] Example 5: The first information may include fourth indication information, M seventh TAs, M eighth TAs, and information related to M fourth differences. After receiving the first information, the first DU can perform root cause analysis for TA adjustment based on the fourth indication information, M seventh TAs, M eighth TAs, and M fourth differences, and optimize the TA validity period management mechanism, thereby optimizing the parameters related to non-random access handover to reduce the probability of non-random access handover failure.

[0333] It should be understood that the second DU will only trigger the sending of the first information to the first DU if it detects that event 3 has occurred multiple times across M terminal devices. Correspondingly, the M seventh TAs can include the seventh TAs used by the M terminal devices when performing the first uplink transmission multiple times, such as the seventh TA used by each of the M terminal devices each time it performs the first uplink transmission. The M eighth TAs can include the eighth TAs used by the M terminal devices when performing the second uplink transmission multiple times, such as the eighth TA used by each of the M terminal devices each time it performs the second uplink transmission.

[0334] Correspondingly, the M fourth differences can include the differences between the seventh TA and the eighth TA associated with each of the M terminal devices in multiple occurrences of event 3. For example, taking two accesses of each of the two terminals as an example, the M fourth differences include: the difference between the seventh TA1 used by UE1 to perform the first uplink transmission when event 3 occurs for the first time and the eighth TA1 used by UE1 to perform the second uplink transmission; the difference between the seventh TA2 used by UE1 to perform the first uplink transmission when event 3 occurs for the second time and the eighth TA2 used by UE1 to perform the second uplink transmission; the difference between the seventh TA3 used by UE2 to perform the first uplink transmission when event 3 occurs for the first time and the eighth TA3 used by UE2 to perform the second uplink transmission; and the difference between the seventh TA4 used by UE2 to perform the first uplink transmission when event 3 occurs for the second time and the eighth TA4 used by UE2 to perform the second uplink transmission.

[0335] It should be understood that the above are only examples of a few types of content contained in the first information. There are other possible combinations of content contained in the first information, which will not be elaborated here.

[0336] The various implementation methods in this application embodiment can be used in combination, and the combination form of the various implementation methods in the above embodiments is not limited.

[0337] The overall flow of the communication method provided in the embodiments of this application has been described above with reference to Figure 8. The specific flow of the communication method provided in the embodiments of this application under specific application scenarios is described in detail below with reference to Figures 9 and 10.

[0338] Application scenario applicable to case 1:

[0339] Figure 9 is a schematic flowchart of the communication method provided in an embodiment of this application. The flowchart shown in Figure 9 mainly involves the interaction between the UE (such as the first terminal device mentioned above), the source DU (such as the first DU mentioned above), the target DU (such as the second DU mentioned above), and the CU (such as the first CU mentioned above). The source DU, the target DU, and the CU are located in the same gNB, and the CU manages the source DU and the target DU.

[0340] Specifically, as shown in Figure 9, the flow of this communication method is as follows:

[0341] S901, the CU sends an RRC Reconfiguration message to the UE.

[0342] The RRC reconfiguration message includes the configuration of one or more candidate cells pre-configured by the gNB.

[0343] S902, the source DU instructs the UE to initiate early TA acquisition from one or more candidate DUs.

[0344] Among them, the source DU can be the DU to which the source cell belongs, and the candidate DU can be the DU to which the candidate cell belongs.

[0345] Specifically, the source DU sends indication information to the UE, which instructs the UE to initiate early access acquisition (TA) to one or more candidate DUs. In turn, the UE initiates early access acquisition to one or more candidate DUs, such as sending a random access preamble to one or more candidate DUs.

[0346] S903, the candidate DU indicates TA-related information to the source DU through the CU.

[0347] After receiving the random access preamble from the UE, the candidate DU indicates the TA-related information to the source DU via the CU. It can be understood that when there are multiple candidate DUs, the TA-related information can include the TA-related information determined by each candidate DU among the multiple candidate DUs; correspondingly, the TA-related information can include the TA-related information of each candidate cell among the multiple candidate cells.

[0348] S904, the source DU executes the switching decision.

[0349] The source DU can make handover decisions based on the L1 measurement report reported by the UE and / or auxiliary information indicated by the CU (such as L3 measurement results or LTM target cell information).

[0350] S905, the source DU sends an LTM handover command to the UE.

[0351] Specifically, the source DU sends an LTM handover command to the UE via L2 MAC CE signaling.

[0352] The LTM handover command indicates the configuration of the target cell (such as the second cell mentioned above). The target cell belongs to the candidate cells mentioned above and can also be called the LTM target cell.

[0353] The LTM handover command may also include the identifier of the LTM target cell, the TA#1 of the LTM target cell (as described in the first TA above), and beam information to enable the UE to perform random access-free operation. The TA#1 of the LTM target cell can be used for subsequent LTM handover operations by the UE.

[0354] S906, the source DU sends a handover notification to the target DU through the CU.

[0355] The target DU can be the DU to which the target cell belongs. The handover notification information can include information about the target cell and beam information, etc.

[0356] S907, UE failed to perform LTM handover.

[0357] S908, UE performs cell selection.

[0358] S909, the UE sends an RRC re-establishment request message to the target DU or performs a RACH-based LTM handover.

[0359] In other words, the UE attempts to access the selected cell via random access based on TA#2 (as described in the second TA above). The cell selected by the UE can be the target cell indicated in S905. One possible approach is for the UE to perform an LTM handover based on the random access channel. Another possible approach is for the UE to initiate an RRC re-establishment procedure to access the target cell; this application does not limit the approach.

[0360] S910, the target DU sends TA-related information (as described in the first information above) to the source DU.

[0361] If the target DU detects that the UE has accessed the target cell through random access or detects an invalid TA (such as the difference between TA#1 and TA#2 exceeding a threshold), the target DU sends TA-related information to the source DU.

[0362] The TA-related information may include at least one of the following: first indication information, TA#1, TA#2, or the difference between TA#1 and TA#2. The first indication information indicates that the UE's failure to hand over to the second cell via random access was caused by an invalid TA#1. TA#1 is the TA used by the UE when LTM handover fails in S907, and TA#2 is the TA used by the UE to access the second cell via random access in S909.

[0363] For more information on TA, please refer to the relevant introduction in the first information of S802, which will not be elaborated here.

[0364] It is understood that if the target DU detects that the UE accesses the target cell via random access each time or detects an invalid TA each time, the target DU sends TA-related information to the source DU. Alternatively, if the target DU repeatedly detects that the UE accesses the target cell via random access or repeatedly detects invalid TAs, the target DU sends TA-related information to the source DU. This application does not impose any restrictions on this.

[0365] Application scenario applicable to case 2:

[0366] Figure 10 is a flowchart illustrating the communication method provided in this application embodiment. The flowchart shown in Figure 10 mainly involves the interaction between the UE (such as the first terminal device mentioned above), the source DU (such as the first DU mentioned above), the target DU (such as the second DU mentioned above), and the CU (such as the first CU mentioned above). The source DU, the target DU, and the CU are located in the same gNB, and the CU manages the source DU and the target DU.

[0367] Specifically, as shown in Figure 10, the communication method flow is as follows:

[0368] S1001, the CU sends an RRC reconfiguration message to the UE.

[0369] S1002, the source DU instructs the UE to initiate early TA acquisition from one or more candidate DUs.

[0370] S1003, the candidate DU indicates TA-related information to the source DU through the CU.

[0371] S1004, Source DU executes a switching decision.

[0372] S1005, the source DU sends an LTM handover command to the UE.

[0373] S1006, the source DU sends a handover notification to the target DU through the CU.

[0374] For S1001-S1006, please refer to the introduction of S901-S906, which will not be repeated here.

[0375] S1007, UE successfully performed LTM handover.

[0376] At this point, the UE successfully performed an uplink transmission based on TA#1.

[0377] S1008, the target DU sends a TA adjustment command to the UE.

[0378] The TA adjustment command instructs the UE to adjust the TA value, such as from TA#1 to TA#2 (as mentioned above, the second TA).

[0379] S1009, the UE performs uplink transmission based on TA#2.

[0380] S1010, the target DU sends TA-related information (as described in the first information above) to the source DU.

[0381] If the target DU detects that the UE has successfully performed LTM handover, that is, successfully accessed the target cell through the non-random access method, and then a TA adjustment occurs soon afterward (such as within a preset time), the target DU sends TA-related information to the source DU.

[0382] The TA-related information may include at least one of the following: second indication information, TA#3, TA#4, or the difference between TA#3 and TA#4. The second indication information is used to indicate that a TA adjustment will occur shortly after the UE successfully performs an LTM handover.

[0383] The first information can also be referred to in the description of the first information in S802, which will not be repeated here.

[0384] It is understood that if the target DU detects a successful LTM handover by the UE and a TA adjustment occurs soon afterward, the target DU will send TA-related information to the source DU. Alternatively, if the target DU detects multiple successful LTM handovers by the UE and a TA adjustment occurs soon afterward, the target DU will send TA-related information to the source DU. This application does not impose any restrictions on this.

[0385] The above describes a scheme where the second DU indicates first TA-related information or second-related information to the first DU. The following describes a scheme where the second DU indicates beam information to the first DU.

[0386] Figure 11 is a schematic flowchart of the communication method provided in an embodiment of this application. This communication method is applicable to the aforementioned communication system and mainly involves the interaction between a first terminal device, a first DU, and a second DU. It is understood that terms such as "first" and "second" are expressions at the embodiment level. For example, the content indicated by "first information" in the embodiment corresponding to Figure 11 may differ from that in the embodiment corresponding to Figure 8. Similarly, the content indicated by "event 2" in the embodiment corresponding to Figure 11 may differ from that in the embodiment corresponding to Figure 8. Further details will not be elaborated upon here.

[0387] As shown in Figure 11, the flow of this communication method is as follows:

[0388] S1101, the first DU sends a handover command to the first terminal device, and the first terminal device receives the handover command from the first DU.

[0389] The switching instructions can be found in the description of switching instructions in S801, and will not be repeated here.

[0390] S1102, the second DU sends the first information to the first DU, and correspondingly, the first DU receives the first information from the second DU.

[0391] The first information indicates the relevant information of the beam used by the first terminal device to access the second cell multiple times (denoted as beam-related information #1), or the first information indicates the relevant information of multiple beams used by the first terminal device in the beam failure recovery process within a preset time after switching to the second cell based on the non-random access method (denoted as beam-related information #2).

[0392] The following describes the cases of the first information indicator beam related information #1 and the first information indicator beam related information #2, including the following cases 1 and 2.

[0393] Case 1: First information indicates beam-related information #1.

[0394] The term "multiple times" in "the first terminal device accesses the second cell multiple times" can refer to two or more times. The access methods for the first terminal device to access the second cell multiple times can include random access and non-random access methods. Random access methods can include LTM handover based on random access, RRC re-establishment, beam failure recovery, etc. Non-random access methods can be LTM handover based on non-random access.

[0395] The beam used by the first terminal device to access the second cell multiple times can be different each time. For example, the first terminal device may use beam 1 when accessing the second cell for the first time, and beam 2 when accessing the second cell for the first time. Beam-related information #1 can be used to indicate the beam used by the first terminal device to access the second cell each time, as will be explained later.

[0396] Optionally, the multiple accesses of the first terminal device to the second cell may include: the first terminal device accessing the second cell once using a method to avoid random access, and accessing the second cell at least once using a method to randomly access. For example, if the first terminal device fails to access the second cell using a method to avoid random access, it then accesses the second cell again using a method to randomly access. Accordingly, beam-related information #1 can be used to indicate the beam used by the first terminal device when it failed to access the second cell once using a method to avoid random access, and the beam used by the first terminal device when it accesses the second cell using a method to randomly access.

[0397] Alternatively, the multiple accesses of the first terminal device to the second cell may include: the first terminal device accessing the second cell multiple times using a method to avoid random access. For example, the first terminal device fails to access the second cell using the method to avoid random access, and then attempts to access the second cell again using the same method. Accordingly, beam-related information #1 can be used to indicate the beam used by the first terminal device when it fails to access the second cell using the method to avoid random access, and the beam used by the first terminal device when it attempts to access the second cell using the same method.

[0398] The following describes how the second DU triggers the sending of the first information to the first DU in case 1, such as implementation method 1 to implementation method 4.

[0399] Optionally, if the second DU and the first DU are managed by the same CU (i.e., the first CU), when the second DU sends the first information to the first DU through the first CU, that is, the second DU sends the first information to the first CU, and the first CU sends the first information to the first DU.

[0400] Optionally, if the CUs managing the second DU and the first DU are the first CU and the second CU respectively, the second DU sends the first information to the first DU through the second CU and the first CU, that is, the second DU sends the first information to the second CU, the second CU sends the first information to the first CU, and the first CU sends the first information to the first DU.

[0401] For example, the first information sent by the second DU to the second CU or the first CU may include one or more of the following: a handover success message (Access Success message), an uplink RRC message transfer message (UL RRC MESSAGE TRANSFER message), or an access and mobility indication message (DU-CU Access and Mobility Indication message). The first information sent by the second CU or the first CU to the second DU may include one or more of the following: a downlink RRC message transfer message (DL RRC MESSAGE TRANSFER message) or an access and mobility indication message (Access and Mobility Indication message). The first information sent by the second CU to the first CU may include one or more of the following: a handover success message (HANDOVER SUCCESS message) or an access and mobility indication message (Access and Mobility Indication message).

[0402] In implementations 3 and 4, since the UE-specific F1 interface context has been released, non-UE-associated signaling is more suitable for transmitting the first information. The first information sent from the second DU to the second CU or the first CU may include a mobility indication message (DU-CU Access and Mobility Indication message). The first information sent from the second CU or the first CU to the second DU may include an access and mobility indication message. The first information sent from the second CU to the first CU may include an access and mobility indication message.

[0403] Implementation method 1: When the second DU detects that the first terminal device accesses the second cell in a random access manner, it sends the first information to the first DU, and the first DU receives the first information from the second DU.

[0404] The first terminal device accessing the second cell via random access can be achieved by the occurrence of event 1. This prevents the device from re-accessing the second cell via random access after a failed handover. There is no limit to the number of times event 1 occurs on the first terminal device. For example, each time the second DU detects event 1 occurring on the first terminal device, it will trigger the sending of first information to the first DU.

[0405] Thus, when the second DU detects that event 1 has occurred in the first terminal device, it sends the beam-related information of event 1 to the first DU. This can improve the efficiency of the first DU in performing root cause analysis of erroneous beams and optimizing the beam selection mechanism, thereby improving the efficiency of the first DU in optimizing parameters related to non-random access and reducing the probability of non-random access handover failure.

[0406] Implementation Method 2: When the second DU detects that the failure of the first terminal device to switch to the second cell in order to avoid random access is due to an incorrect beam, it sends the first information to the first DU, and the first DU receives the first information from the second DU.

[0407] In other words, the second DU will send the first information to the first DU each time it detects event 2 (the failure to handover to the second cell via random access is due to an incorrect beam) on the first terminal device. There is no limit to the number of times event 2 occurs on the first terminal device. For example, the second DU will send the first information to the first DU every time it detects event 2 on the first terminal device.

[0408] The second DU detects that the beam (denoted as the first beam) used by the first terminal device to handover to the second cell in the manner of avoiding random access is an incorrect beam, thereby determining that the failure of the first terminal device to handover in the manner of avoiding random access is caused by the incorrect beam. The decision mechanism by which the second DU determines that the first beam is incorrect can be determined by the CU to which the second DU belongs.

[0409] For example, if the second DU fails to detect the first terminal device within its beam coverage area to avoid handover to the second cell via random access, the second DU determines / identifies that the first beam is incorrect. As another example, if the beam used by the first terminal device to handover to the second cell via random access (denoted as the second beam) is different from the first beam, the second DU determines that the first beam is incorrect. Alternatively, if the offset between the first and second beams exceeds a threshold, the second DU determines that the first beam is incorrect. This application does not restrict the decision mechanism by which the second DU determines the first beam is incorrect. The first and second beams will be described in detail later and will not be repeated here.

[0410] Thus, when the second DU detects that event 2 has occurred in the first terminal device, it sends the beam-related information of event 2 to the first DU. This can improve the efficiency of the first DU in performing root cause analysis of erroneous beams and improve the efficiency of the first DU's beam selection mechanism, thereby reducing the probability of handover failure without random access.

[0411] Optionally, corresponding to implementation methods 1 and 2, the first information may include at least one of the following: first indication information, information for indicating the first beam, information for indicating the second beam, or a first beam offset. The first indication information indicates that the failure of the first terminal device to handover to the second cell without random access was caused by an incorrect beam. The first beam is the beam used by the first terminal device when it failed to handover to the second cell without random access, the second beam is the beam used by the first terminal device to access the second cell via random access, and the first beam offset is the offset between the first beam and the second beam.

[0412] In other words, beam-related information #1 may include at least one of the following: first indication information, information for indicating the first beam, information for indicating the second beam, or first beam offset.

[0413] Example 1: The first information may include first indication information. Example 1 corresponds to Implementation 2; that is, if the first information includes first indication information, it indicates that the second DU sends this first information when it detects that the failure of the first terminal device to handover to the second cell without random access is caused by an incorrect beam. After receiving the first indication information, the first DU can perform root cause analysis of the first beam error based on the first indication information and optimize the beam selection mechanism to reduce the probability of handover failure without random access.

[0414] If the second DU triggers the sending of first information to the first DU through the above implementation method 1, the first information may not include the first indication information.

[0415] Example 2: The first information may include information indicating the first beam and information indicating the second beam. Example 2 corresponds to Implementation 1 and Implementation 2. That is, if the second DU triggers the transmission of the first information to the first DU through Implementation 1 or Implementation 2, the first information may include information indicating the first beam and information indicating the second beam.

[0416] Thus, after receiving the first information, the first DU can analyze whether the first beam is erroneous based on the information used to indicate the first beam and the information used to indicate the second beam, as well as perform root cause analysis in the case of a first beam error, and optimize the beam selection mechanism to reduce the probability of handover failure without random access.

[0417] Example 3: The first information may include a first beam offset, that is, the offset between the first beam and the second beam.

[0418] In this embodiment, the offset between two beams can be calculated using codebook indexing. For example, the offset between the first and second beams can be calculated using the index values ​​of the first and second beams. For instance, the offset between beam 2 and beam 3 is smaller than the offset between beam 2 and beam 8. Alternatively, it can be calculated using phase difference, angle, etc. This application does not limit the method of calculating the offset between two beams.

[0419] Example 3 corresponds to Implementation 1 and Implementation 2. That is, if the second DU triggers the transmission of first information to the first DU through Implementation 1 or Implementation 2, the first information may include the first beam offset.

[0420] Thus, after receiving the first beam offset, the first DU can perform root cause analysis of beam errors based on the first beam offset and optimize the beam selection mechanism to reduce the probability of handover failure without random access.

[0421] Example 4: The first information may include information indicating the first beam, information indicating the second beam, and the first beam offset. Example 4 corresponds to Implementation 1 and Implementation 2. That is, if the second DU triggers the transmission of the first information to the first DU via Implementation 1 or Implementation 2, the first information may include information indicating the first beam, information indicating the second beam, and the first beam offset. After receiving the first information, the first DU can perform root cause analysis of beam errors based on the information indicating the first beam, the information indicating the first beam, and the first beam offset, and optimize the beam selection mechanism to reduce the probability of handover failure without random access.

[0422] Example 5: The first information may include information indicating the first beam, information indicating the second beam, the first beam offset, and the first indication information. Example 5 corresponds to Implementation 2. That is, if the second DU triggers the transmission of the first information to the first DU via Implementation 2, the first information may include information indicating the first beam, information indicating the second beam, the first beam offset, and the first indication information. After receiving the first information, the first DU can perform root cause analysis of beam errors based on the information indicating the first beam, the information indicating the second beam, the first beam offset, and the first indication information, and optimize the beam selection mechanism to reduce the probability of handover failure without random access.

[0423] It should be understood that the second DU will only trigger the sending of the first information to the first DU if it detects that the first terminal device has experienced event 1 or event 2 multiple times. Correspondingly, the first beam may include the beam used by the first terminal device when it fails to hand over to the second cell multiple times using the non-random access method, and the second beam may include the beam used by the first terminal device when it accesses the second cell multiple times using the random access method. The first beam offset may include the offset between the first beam and the second beam associated with each access to the second cell in the multiple accesses to the second cell. For example, taking two accesses as an example, the first beam offset includes: the offset between beam 1 used by UE1 when it fails to hand over to the second cell for the first time using the non-random access method and beam 2 used by UE1 when it accesses the second cell for the first time using the random access method; and the offset between beam 3 used by UE1 when it fails to hand over to the second cell for the second time using the non-random access method and beam 4 used by UE1 when it accesses the second cell for the second time using the random access method.

[0424] Of course, the first information may also contain only information for indicating the first beam, or only information for indicating the second beam, and the first DU optimizes the beam selection mechanism based on the information for indicating the first beam or the information for indicating the first beam.

[0425] It should be understood that the above are only examples of a few types of content contained in the first information. There are other possible combinations of content contained in the first information, which will not be elaborated here.

[0426] Implementation methods 1 and 2 are implementation methods in case 1, where the second DU sends the first information every time it detects event 1 or event 2 occurring on the first terminal device. The following describes implementation methods 3 and 4, where the second DU sends the first information only when it detects multiple (two or more) events 1 or event 2 occurring on the first terminal device.

[0427] Implementation Method 3: When the second DU detects that N terminal devices have accessed the second cell in a random access manner, it sends first information to the first DU. Correspondingly, the first DU receives the first information from the second DU. Here, the N terminal devices include the first terminal device, and N is an integer greater than 1.

[0428] In this scenario, N terminal devices accessing the second cell via random access can be defined as N terminal devices experiencing event 1. There is no limit to the number of times each of the N terminal devices experiences event 1. For example, each of the N terminal devices must have experienced event 1 at least once.

[0429] Thus, when the second DU detects that N terminal devices have experienced event 1, it can summarize the beam-related information of the N terminal devices experiencing event 1 and send a first message, which can reduce signaling overhead.

[0430] Implementation method 4: If the failure of the second DU to switch to the second cell in order to avoid random access by detecting N terminal devices is due to an incorrect beam, the second DU sends the first information to the first DU. Correspondingly, the first DU receives the first information from the second DU.

[0431] In other words, if the second DU detects that N terminal devices have experienced event 2 (the failure to switch to the second cell via random access is caused by an incorrect beam), it will trigger the sending of the first information to the first DU.

[0432] There is no limit to the number of times event 2 occurs on each of the N terminal devices. For example, each of the N terminal devices must have experienced event 2 at least once.

[0433] The second DU detects that the beam used by N terminal devices to handover to the second cell without random access (denoted as the third beam) is an incorrect beam, thus determining that the handover failure of the N terminal devices without random access is caused by the incorrect beam. The decision mechanism of the second DU in determining the third beam error can refer to the decision mechanism of the second DU in determining the first beam error, and will not be elaborated here.

[0434] Thus, when the second DU detects that N terminal devices have experienced event 2, it can summarize the beam-related information of the N terminal devices experiencing event 2 and send a first message, which can reduce signaling overhead.

[0435] Optionally, corresponding to implementation methods 3 and 4, the first information may include at least one of the following: second indication information, information for indicating N third beams, information for indicating N fourth beams, information for indicating the beam that appears most frequently among the N third beams, information for indicating the beam that appears most frequently among the N fourth beams, or information related to the offset of N second beams.

[0436] Example 1: The first information may include second indication information. The second indication information indicates that the failure of N terminal devices to handover to the second cell without random access was caused by an incorrect beam. This second indication information corresponds to implementation 4; that is, if the first information includes the second indication information, it means that the second DU sends the first information when it detects that the failure of N terminal devices to handover to the second cell without random access was caused by an incorrect beam. After receiving the second indication information, the first DU can perform root cause analysis of the incorrect beam based on the second indication information and optimize the beam selection mechanism to reduce the probability of handover failure without random access.

[0437] If the second DU triggers the sending of first information to the first DU through the above implementation method 3, the first information may not include the second indication information.

[0438] Example 2: The first information may include information indicating N third beams and information indicating N fourth beams. Example 2 corresponds to implementations 3 and 4. That is, if the second DU triggers the transmission of the first information to the first DU through implementation 3 or 4, the first information may include information indicating N third beams and information indicating N fourth beams.

[0439] The i-th third beam among N third beams is the beam used by the i-th terminal device among N terminal devices when the handover to the second cell fails using a non-random access method, where 1 ≤ i ≤ N and is an integer. In other words, the N third beams can include the third beam used by each of the N terminal devices when the handover to the second cell fails using a non-random access method. The description of each of the N third beams can be referenced from the description of the first beam above, and will not be repeated here.

[0440] The i-th fourth beam among the N fourth beams is the beam used by the i-th terminal device among the N terminal devices to access the second cell using random access. In other words, the N fourth beams can include the fourth beam used by each of the N terminal devices when the handover to the second cell fails using a non-random access method. The description of each of the N fourth beams can be referenced from the description of the second beam above, and will not be repeated here.

[0441] Optionally, the third beam and the fourth beam are in one-to-one correspondence, or in other words, the third beam and the fourth beam correspond to each of the N terminal devices. For example, the third beam used by the first terminal device among the N terminal devices when it fails to hand over to the second cell using a method without random access (such as without random access #1) corresponds to the fourth beam used by the first terminal device among the N terminal devices when it accesses the second cell using a method with random access (such as random access #1). That is, after the first terminal device fails to hand over using the method without random access #1, it attempts to access the second cell again using random access #1.

[0442] Thus, after receiving information indicating N third beams and information indicating N fourth beams, the first DU can perform analysis on whether the N third beams are erroneous, and root cause analysis in the case of erroneous beams among the N third beams, and optimize the beam selection mechanism to reduce the probability of handover failure without random access.

[0443] Example 3: The first information may include information for indicating the beam that appears most frequently among the N third beams, and information for indicating the beam that appears most frequently among the N fourth beams.

[0444] Example 3 corresponds to Implementation 3 and Implementation 4. That is, if the second DU triggers the transmission of first information to the first DU through Implementation 3 or Implementation 4, the first information may include relevant information of N second beam offsets.

[0445] The beam that appears most frequently among the N third beams indicates that the probability of that third beam being an erroneous beam is high, and the beam that appears most frequently among the N fourth beams indicates that the probability of that fourth beam being an erroneous beam is low (e.g., the beam quality is good). This facilitates the mechanism for the first DU to optimize beam selection.

[0446] Example 4: The first information may include information related to N second beam offsets. The information related to the N second beam offsets indicates the average value of the N second beam offsets; wherein, the i-th second beam offset among the N second beam offsets is the offset between the i-th third beam and the i-th fourth beam.

[0447] Example 4 corresponds to implementation methods 3 and 4. That is, if the second DU triggers the transmission of first information to the first DU through implementation method 3 or implementation method 4, the first information may include relevant information of N second beam offsets.

[0448] The N second beam offsets can include the offset between each of the N third beams and its corresponding fourth beam (the third and fourth beams correspond to the same terminal device). For example, taking N=2, the offset between the third beam #1 used by the first terminal device in the two terminals when it fails to hand over to the second cell using a non-random access method, and the fourth beam #1 used by the first terminal device in the two terminals when it accesses the second cell using a random access method; and the offset between the third beam #2 used by the second terminal device in the two terminals when it fails to hand over to the second cell using a non-random access method, and the fourth beam #2 used by the second terminal device in the two terminals when it accesses the second cell using a random access method.

[0449] Thus, after receiving the average of N second beam offsets, the first DU can optimize the beam selection mechanism based on the average of N second beam offsets to reduce the probability of handover failure without random access.

[0450] It should be understood that the second DU will only trigger the sending of the first information to the first DU if it detects that N terminal devices have repeatedly experienced Event 1 or Event 2. Correspondingly, the N third beams can include the third beams used by the N terminal devices when they repeatedly fail to hand over to the second cell using a non-random access method, such as the third beam used by each of the N terminal devices each time they fail to hand over to the second cell using a non-random access method. The N fourth beams can include the fourth beams used by the N terminal devices when they repeatedly access the second cell using a random access method, such as the fourth beam used by each of the N terminal devices each time they access the second cell using a random access method.

[0451] Correspondingly, the N second beam offsets can include the offsets between the third and fourth beams associated with each of the N terminal devices in multiple occurrences of event 1 / event 2. For example, taking two access attempts for each of the two terminals, the N second beam offsets include: the offset between the third beam 1 used by UE1 when it first fails to hand over to the second cell using the non-random access method and the fourth beam 1 used by UE1 when it first accesses the second cell using the random access method; the offset between the third beam 2 used by UE1 when it second fails to hand over to the second cell using the non-random access method and the fourth beam 2 used by UE1 when it second accesses the second cell using the random access method; the offset between the third beam 3 used by UE2 when it first fails to hand over to the second cell using the non-random access method and the fourth beam 3 used by UE2 when it first accesses the second cell using the random access method; and the offset between the third beam 4 used by UE2 when it second fails to hand over to the second cell using the non-random access method and the fourth beam 4 used by UE2 when it second accesses the second cell using the random access method.

[0452] It should be understood that the above are only examples of a few types of content contained in the first information. There are other possible combinations of content contained in the first information, which will not be elaborated here.

[0453] Case 2: First information indicates beam-related information #2.

[0454] The following describes how the second DU triggers the sending of the first information to the first DU in case 2, as shown in methods 1 to 2.

[0455] Optionally, if the second DU and the first DU are managed by the same CU (i.e., the first CU), when the second DU sends the first information to the first DU through the first CU, that is, the second DU sends the first information to the first CU, and the first CU sends the first information to the first DU.

[0456] Optionally, if the CUs managing the second DU and the first DU are the first CU and the second CU respectively, the second DU sends the first information to the first DU through the second CU and the first CU, that is, the second DU sends the first information to the second CU, the second CU sends the first information to the first CU, and the first CU sends the first information to the first DU.

[0457] For example, the first information sent by the second DU to the second CU or the first CU may include one or more of the following: a handover success message (Access Success message), an uplink RRC message transfer message (UL RRC MESSAGE TRANSFER message), or an access and mobility indication message (DU-CU Access and Mobility Indication message). The first information sent by the second CU or the first CU to the second DU may include one or more of the following: a downlink RRC message transfer message (DL RRC MESSAGE TRANSFER message) or an access and mobility indication message (Access and Mobility Indication message). The first information sent by the second CU to the first CU may include one or more of the following: a handover success message (HANDOVER SUCCESS message) or an access and mobility indication message (Access and Mobility Indication message).

[0458] In Method 2, since the UE-specific F1 interface context has been released, non-UE-associated signaling is more suitable for sending the first information. The first information sent by the second DU to the second CU or the first CU may include a mobility indication message (DU-CU Access and Mobility Indication message). The first information sent by the second CU or the first CU to the second DU may include an access and mobility indication message. The first information sent by the second CU to the first CU may include an access and mobility indication message.

[0459] Method 1: When the second DU detects that the first terminal device has switched to the second cell using a non-random access method and performs a beam failure recovery procedure within a preset time, it sends first information to the first DU. Correspondingly, the first DU receives the first information from the second DU.

[0460] It is understandable that the first terminal device successfully hands over to the second cell using the non-random access method, but performs a beam failure recovery procedure within a preset time. For example, the preset time can be 1 millisecond (ms), 10 ms, etc., without limitation. That is to say, the second DU will experience beam failure / beam failure recovery shortly after detecting that the first terminal device has successfully handed over to the second cell using the non-random access method.

[0461] The second DU sends the first information each time it detects event 3 (the beam failure recovery procedure is executed within a preset time after handover to the second cell via a non-random access method) on the first terminal device. There is no limit to the number of times event 3 occurs on the first terminal device. For example, the second DU will trigger the sending of the first information to the first DU every time it detects event 3 on the first terminal device.

[0462] Thus, when the second DU detects that event 3 has occurred in the first terminal device, it sends the beam-related information of event 3 to the first DU. This can improve the efficiency of the first DU in performing root cause analysis for beam failure recovery and improve the efficiency of the first DU's mechanism for optimizing beam selection, thereby reducing the probability of handover failure without random access.

[0463] Optionally, corresponding to Method 1, the first information includes at least one of the following: the first information includes at least one of the following: third indication information, information for indicating the fifth beam, information for indicating the sixth beam, or third beam offset. Wherein, the third indication information is used to instruct the first terminal device to perform a beam failure recovery procedure within a preset time after handover to the second cell using a non-random access method. The fifth beam is the beam used by the first terminal device when handover to the second cell using a non-random access method, the sixth beam is the beam used by the first terminal device when performing the beam failure recovery procedure, and the third beam offset is the offset between the fifth beam and the sixth beam.

[0464] Example 1: The first information may include third indication information. After receiving the third indication information, the first DU can optimize the beam selection mechanism based on the third indication information to reduce the probability of handover failure without random access.

[0465] Example 2: The first information may include information indicating the fifth beam and information indicating the sixth beam. The fifth beam may be the beam used by the first terminal device to access the second cell using a non-random access method.

[0466] It should be understood that since the first terminal device experiences beam failure recovery within a preset time after accessing the second cell in a non-random access manner, the fifth beam is the beam that caused the first terminal device to experience beam failure, or in other words, an unsuitable beam.

[0467] The sixth beam is the beam selected by the first terminal device after beam failure recovery. For example, after selecting a new beam, the first terminal device sends a random access request to the second DU based on the new beam, that is, the first terminal device executes the beam failure recovery process.

[0468] Thus, after receiving the fifth and sixth beams, the first DU can perform root cause analysis on the beam failure of the fifth beam based on the fifth and sixth beams, and optimize the beam selection mechanism to reduce the probability of handover failure without random access.

[0469] Example 3: The first information may include the third beam offset. After receiving the third beam offset, the first DU can perform root cause analysis on the beam failure recovery based on the third beam offset and optimize the beam selection mechanism to reduce the probability of handover failure without random access.

[0470] It should be understood that the second DU will only trigger the sending of the first information to the first DU if it detects that the first terminal device has experienced event 3 multiple times. Correspondingly, the fifth beam may include the beam used by the first terminal device to hand over to the second cell without random access when event 3 has occurred multiple times, and the sixth beam may include the beam used when performing beam failure recovery when event 3 has occurred multiple times. The third beam offset may include the offset between the fifth beam and the sixth beam associated with each occurrence of event 3 in the multiple occurrences of event 3. For example, taking the occurrence of event 3 twice as an example, the third beam offset may include: the offset between beam 1 used by UE1 when it first handovers to the second cell without random access and beam 2 used by UE1 when it first performs beam failure recovery; and the offset between beam 3 used by UE1 when it second handovers to the second cell without random access and beam 4 used by UE1 when it second performs beam failure recovery.

[0471] It should be understood that the above are only examples of a few types of content contained in the first information. There are other possible combinations of content contained in the first information, which will not be elaborated here.

[0472] Method 2: If the second DU detects that M terminal devices have switched to the second cell using a non-random access method and a beam failure recovery process occurs within a preset time, the second DU sends first information to the first DU. Here, the M terminal devices include the first terminal device, and M is an integer greater than 1.

[0473] The second DU detected event 3 occurring on M terminal devices: a beam failure recovery process occurred within a preset time after handover to the second cell via a non-random access method. There is no limit to the number of times event 3 occurs on each of the M terminal devices. For example, each of the M terminal devices must have experienced event 3 at least once.

[0474] Thus, when the second DU detects that event 3 has occurred in M ​​terminal devices, it can summarize the beam-related information of event 3 in the M terminal devices and send a first message, which can reduce signaling overhead.

[0475] Optionally, corresponding to mode 2, the first information may include at least one of the following: fourth indication information, information for indicating M seventh beams, information for indicating M eighth beams, information for indicating the beam that appears most frequently among the M seventh beams, information for indicating the beam that appears most frequently among the M eighth beams, or information related to the offset of the M fourth beams.

[0476] Example 1: The first information may include fourth indication information. This fourth indication information is used to instruct M terminal devices to complete a beam failure recovery process within a preset time after handover to the second cell using a non-random access method. Upon receiving the fourth indication information, the first DU can perform root cause analysis of beam failure recovery based on the fourth indication information, optimizing the beam selection mechanism to reduce the probability of non-random access handover failure.

[0477] Example 2: The first information may include information for indicating the M seventh beams and information for indicating the M eighth beams.

[0478] The j-th seventh beam among the M seventh beams is the beam used by the j-th terminal device among the M terminal devices when handing over to the second cell using a non-random access method, where 1 ≤ j ≤ M and is an integer. In other words, the M seventh beams can include the seventh beam used by each of the M terminal devices when handing over to the second cell using a non-random access method. The description of each of the M seventh beams can also be referenced to the description of the fifth beam above, and will not be repeated here.

[0479] The j-th eighth beam among the M eighth beams is the beam used by the j-th terminal device among the M terminal devices when executing the beam failure recovery procedure. In other words, the M eighth beams can include the eighth beam used by each of the M terminal devices when executing the beam failure procedure. Each of the M eighth beams can also refer to the description of the sixth beam above, and will not be repeated here.

[0480] Optionally, the seventh beam and the eighth beam are in one-to-one correspondence, or in other words, the seventh beam and the eighth beam correspond to each of the M terminal devices. For example, the seventh beam #1 used by the first terminal device among the M terminal devices when it hands over to the second cell using a non-random access method corresponds to the eighth beam #1 used by the first terminal device among the M terminal devices when it performs beam failure recovery.

[0481] Thus, after receiving information indicating M seventh beams and information indicating M eighth beams, the first DU can perform root cause analysis for beam failure recovery based on the information indicating M seventh beams and information indicating M eighth beams, and optimize the beam selection mechanism to reduce the probability of handover failure without random access.

[0482] Example 3: The first information may include information for indicating the beam that appears most frequently among the M seventh beams, and information for indicating the beam that appears most frequently among the M eighth beams.

[0483] The beam that appears most frequently among the M seventh beams indicates that the seventh beam is likely to be an erroneous beam. The beam that appears most frequently among the M eighth beams indicates that the eighth beam is likely to be an erroneous beam (e.g., the beam quality is good). This facilitates the mechanism for the first DU to optimize beam selection.

[0484] Example 4: The first information may include information related to the offsets of the M fourth beams. The information related to the offsets of the M fourth beams indicates the average value of the offsets of the M fourth beams. Among the M fourth beam offsets, the offset of the j-th fourth beam is the offset between the j-th seventh beam and the j-th eighth beam.

[0485] The M fourth beam offsets can include the offset between each of the M seventh beams and its corresponding eighth beam (the seventh and eighth beams correspond to the same terminal device). For example, taking M=2, the offset between the seventh beam #1 used by the first terminal device in the two terminals when handing over to the second cell using a non-random access method and the eighth beam #1 used by the first terminal device in the two terminals when performing beam failure recovery procedures; and the offset between the seventh beam #2 used by the second terminal device in the two terminals when handing over to the second cell using a non-random access method and the eighth beam #2 used by the second terminal device in the two terminals when performing beam failure recovery procedures.

[0486] Thus, after receiving the relevant information of M fourth beam offsets, the first DU can perform root cause analysis of beam failure recovery based on the relevant information of M fourth beam offsets, and optimize the beam selection mechanism to reduce the probability of handover failure without random access.

[0487] It should be understood that the second DU will only trigger the sending of the first information to the first DU if it detects that event 3 has occurred multiple times across M terminal devices. Correspondingly, the M seventh beams can include the seventh beams used by the M terminal devices when they repeatedly handover to the second cell using a non-random access method, such as the seventh beam used by each of the M terminal devices each time they handover to the second cell using a non-random access method. The M eighth beams can include the eighth beams used by the M terminal devices when they repeatedly execute beam failure recovery procedures, such as the eighth beam used by each of the M terminal devices each time they execute a beam failure recovery procedure.

[0488] Correspondingly, the M fourth offset values ​​can include the offset values ​​between the seventh beam and the eighth beam associated with each of the M terminal devices in multiple occurrences of event 3. For example, taking two accesses of each of the two terminals as an example, the M fourth offset values ​​include: the offset value between the seventh beam #1 used by UE1 to switch to the second cell using the non-random access method when event 3 occurs for the first time, and the eighth beam #1 used by UE1 to perform the beam failure recovery procedure; the offset value between the seventh beam #2 used by UE1 to switch to the second cell using the non-random access method when event 3 occurs for the second time, and the eighth beam #2 used by UE1 to perform the beam failure recovery procedure; the offset value between the seventh beam #3 used by UE2 to switch to the second cell using the non-random access method when event 3 occurs for the first time, and the eighth beam #3 used by UE2 to perform the beam failure recovery procedure; and the offset value between the seventh beam #4 used by UE2 to switch to the second cell using the non-random access method when event 3 occurs for the second time, and the eighth beam #4 used by UE2 to perform the beam failure recovery procedure.

[0489] Optionally, the first information may further include fifth indication information, which is used to indicate the beam failure recovery ratio. The beam failure recovery ratio is the ratio of the number of times M terminal devices perform the beam failure recovery process within a preset time after handing over to the second cell using the non-random access method, to the number of times L terminal devices successfully hand over to the second cell using the non-random access method. The L terminal devices include M terminal devices, and L is an integer greater than or equal to M.

[0490] The beam failure recovery ratio can be calculated based on a single beam failure recovery process involving M / L terminal devices. For example, L is 10 and M is 5. Ten terminal devices successfully handover to the second cell using a non-random access method. Among these ten terminal devices, three of them execute the beam failure recovery process within a preset time after handover to the second cell using the non-random access method. Therefore, the beam failure recovery ratio can be 3:10.

[0491] Alternatively, the beam failure recovery ratio can be calculated based on multiple beam failure recovery procedures for M / L terminal devices. For example, L is 10 and M is 5. Ten terminal devices successfully handover to the second cell a total of 20 times using the non-random access method. Among these, three terminal devices execute the beam failure recovery procedure within a preset time after handover to the second cell using the non-random access method, and these three terminal devices execute the beam failure recovery procedure a total of 7 times. Therefore, the beam failure recovery ratio can be 7:20.

[0492] The proportion of beam failure recovery can be calculated in other ways, and this application does not limit this.

[0493] Thus, by statistically analyzing the proportion of beam failure recovery, the first DU can better perform root cause analysis of erroneous beams, thereby enabling the first DU to optimize the beam selection mechanism and reduce the probability of beam failure.

[0494] It should be understood that the above are only examples of a few types of content contained in the first information. There are other possible combinations of content contained in the first information, which will not be elaborated here.

[0495] The various implementation methods in this application embodiment can be used in combination, and the combination form of the various implementation methods in the above embodiments is not limited.

[0496] The overall flow of the communication method provided in the embodiments of this application has been described above with reference to Figure 11. The specific flow of the communication method provided in the embodiments of this application under specific application scenarios is described in detail below with reference to Figures 12 and 13.

[0497] Application scenario applicable to case 1:

[0498] Figure 12 is a flowchart illustrating the communication method provided in this application embodiment. The flowchart shown in Figure 12 mainly involves the interaction between the UE (such as the first terminal device mentioned above), the source DU (such as the first DU mentioned above), the target DU (such as the second DU mentioned above), and the CU (such as the first CU mentioned above). The source DU, the target DU, and the CU are located in the same gNB, and the CU manages the source DU and the target DU.

[0499] Specifically, as shown in Figure 12, the communication method flow is as follows:

[0500] S1201, the CU sends an RRC reconfiguration message to the UE.

[0501] S1202, the source DU instructs the UE to initiate an early TA acquisition from one or more candidate DUs.

[0502] S1203, the candidate DU indicates TA-related information to the source DU through the CU.

[0503] S1204, Source DU executes a switching decision.

[0504] The specific implementations of S1201-S1204 can be found in the specific implementations of S901-S904, and will not be elaborated upon here.

[0505] S1205, the source DU sends an LTM handover command to the UE.

[0506] Specifically, the source DU sends an LTM handover command to the UE via L2 MAC CE signaling.

[0507] The LTM handover command indicates the configuration of the target cell (such as the second cell mentioned above). The target cell belongs to the candidate cells mentioned above and can also be called the LTM target cell.

[0508] The LTM handover command may also include the identifier of the LTM target cell, the TA of the LTM target cell, and beam information, wherein the beam information is used to indicate beam #1 (as described above as the first beam) to enable the UE to perform random access-free operation.

[0509] S1206, the source DU sends a handover notification to the target DU through the CU.

[0510] The target DU can be the DU to which the target cell belongs. The handover notification information can include information about the target cell and beam information, etc.

[0511] S1207, UE failed to perform LTM handover.

[0512] S1208, UE performs cell selection.

[0513] S1209, the UE sends an RRC re-establishment request message to the target DU or performs a RACH-based LTM handover.

[0514] In other words, the UE attempts to access the selected cell using random access based on beam #2 (as described above as the second beam). The cell selected by the UE can be the target cell indicated in S1205. One possible approach is for the UE to perform an LTM handover based on the random access channel. Another possible approach is for the UE to initiate an RRC re-establishment procedure to access the target cell; this application does not limit the approach.

[0515] S1210, the target DU sends beam-related information (as described in the first information above) to the source DU.

[0516] If the target DU detects that the UE has accessed the target cell through random access or detects an incorrect beam (such as the offset between beam #1 and beam #2 exceeding a threshold), the target DU sends beam-related information to the source DU.

[0517] The beam-related information may include at least one of the following: first indication information, information indicating beam #1, information indicating beam #2, or the offset between beam #1 and beam #2. The first indication information indicates that the UE's failure to hand over to the second cell without random access was caused by an incorrect beam #1.

[0518] The first information can also be referred to in the description of the first information in S1102, which will not be repeated here.

[0519] It is understood that if the target DU detects that the UE accesses the target cell via random access each time or detects an erroneous beam each time, the target DU sends beam-related information to the source DU. Alternatively, if the target DU repeatedly detects that the UE accesses the target cell via random access or repeatedly detects an erroneous beam, the target DU sends beam-related information to the source DU. This application does not impose any restrictions on this.

[0520] Application scenario applicable to case 2:

[0521] Figure 13 is a schematic flowchart of the communication method provided in the embodiment of this application. The flowchart shown in Figure 13 mainly involves the interaction between the UE (such as the first terminal device mentioned above), the source DU (such as the first DU mentioned above), the target DU (such as the second DU mentioned above), and the CU (such as the first CU mentioned above). The source DU, the target DU, and the CU are located in the same gNB, and the CU manages the source DU and the target DU.

[0522] Specifically, as shown in Figure 10, the communication method flow is as follows:

[0523] S1301, the CU sends an RRC reconfiguration message to the UE.

[0524] S1302, the source DU instructs the UE to initiate an early TA acquisition from one or more candidate DUs.

[0525] S1303, the candidate DU indicates TA-related information to the source DU through the CU.

[0526] S1304, Source DU executes a switching decision.

[0527] S1305, the source DU sends an LTM handover command to the UE.

[0528] LTM switching commands can include information for indicating beam #1.

[0529] S1306, the source DU sends a handover notification to the target DU through the CU.

[0530] For S1301-S1306, please refer to the introduction of S901-S906, and they will not be repeated here.

[0531] S1307, UE successfully performed LTM handover.

[0532] S1308, the UE detected a beam failure event between itself and beam #1.

[0533] S1309, the UE executes the beam failure recovery procedure.

[0534] S1310, the target DU sends beam-related information (as described in the first information above) to the source DU.

[0535] If the target DU detects that the UE has successfully performed LTM handover, that is, successfully accessed the target cell through the non-random access method, and then a beam failure recovery process occurs soon (such as within a preset time), the target DU sends beam-related information to the source DU.

[0536] The beam-related information may include at least one of the following: second indication information, information indicating beam #3, information indicating beam #4, or the offset between beam #3 and beam #4. The second indication information is used to indicate that a beam failure recovery procedure will occur shortly after the UE successfully performs an LTM handover.

[0537] The beam-related information can also be found in the description in the first information of S1102, which will not be repeated here.

[0538] It is understandable that if the target DU detects a successful LTM handover by the UE and then quickly experiences a beam failure recovery process, the target DU will send beam-related information to the source DU. Alternatively, if the target DU detects multiple successful LTM handovers by the UE and then quickly experiences a beam failure recovery process, the target DU will send beam-related information to the source DU. This application does not impose any restrictions on this.

[0539] In this application, the embodiments corresponding to FIG8 and FIG11 can be used in combination, which will not be described in detail here.

[0540] The method provided by the embodiments of this application has been described in detail above with reference to Figures 8-13. The communication apparatus used to perform the communication method provided by the embodiments of this application is described in detail below with reference to Figures 14-15.

[0541] Figure 14 is a schematic diagram of the structure of a communication device provided in an embodiment of this application. As exemplarily shown in Figure 14, the communication device 1400 includes a transceiver module 1401 and a processing module 1402. For ease of explanation, Figure 14 only shows the main components of the communication device.

[0542] The transceiver module 1401 is used to perform the transceiver function of the method shown in Figure 8 or Figure 11, and the processing module 1402 is used to perform other functions of the method shown in Figure 8 or Figure 11 besides the transceiver function.

[0543] Optionally, the transceiver module 1401 may include a transmitting module (not shown in FIG. 14) and a receiving module (not shown in FIG. 14). The transmitting module is used to implement the transmitting function of the communication device 1400, and the receiving module is used to implement the receiving function of the communication device 1400.

[0544] Optionally, the communication device 1400 may further include a storage module (not shown in FIG. 14) that stores programs or instructions. When the processing module 1402 executes the program or instructions, the communication device 1400 can perform the functions of the terminal device or network device in the methods shown in FIG. 8 or FIG. 11 described above.

[0545] It is understood that the communication device 1400 may be a terminal device or a network device, or a chip (system) or other component or assembly that can be disposed in a terminal device or a network device, or a device that includes a terminal device or a network device. This application does not limit this.

[0546] Furthermore, the technical effects of the communication device 1400 can be referred to the technical effects of the communication method shown in Figure 8 or Figure 11, and will not be repeated here.

[0547] Figure 15 is a second schematic diagram of the structure of the communication device provided in an embodiment of this application. Exemplarily, the communication device can be a terminal device, or a chip (system) or other component or assembly that can be disposed in the terminal device. As shown in Figure 15, the communication device 1500 may include a processor 1501. Optionally, the communication device 1500 may also include a memory 1502 and / or a transceiver 1503. The processor 1501 is coupled to the memory 1502 and / or the transceiver 1503, for example, by means of a communication bus, an internal chip interface, or other communication lines. Optionally, the memory 1502 may be integrated with the processor 1501.

[0548] The following is a detailed description of each component of the communication device 1500, with reference to Figure 15:

[0549] The processor 1501 is the control center of the communication device 1500. It can be a single processor or a collective term for multiple processing elements. For example, the processor 1501 can be one or more central processing units (CPUs), application-specific integrated circuits (ASICs), or one or more integrated circuits configured to implement the embodiments of this application, such as one or more digital signal processors (DSPs), or one or more field-programmable gate arrays (FPGAs).

[0550] Optionally, the processor 1501 can perform various functions of the communication device 1500 by running or executing software programs stored in the memory 1502 and calling data stored in the memory 1502, such as performing the communication methods shown in FIG8 or FIG11 above.

[0551] In a specific implementation, as one embodiment, processor 1501 may include one or more CPUs, such as CPU0 and CPU1 shown in FIG15.

[0552] In a specific implementation, as one embodiment, the communication device 1500 may also include multiple processors, such as processors 1501 and 1504 shown in FIG. 15. Each of these processors may be a single-core processor (single-CPU) or a multi-core processor (multi-CPU). Here, a processor may refer to one or more devices, circuits, and / or processing cores for processing data (e.g., computer program instructions).

[0553] The memory 1502 is used to store the software program that executes the solution of this application, and is controlled by the processor 1501 to execute it. The specific implementation method can be referred to the above method embodiment, and will not be repeated here.

[0554] Optionally, the memory 1502 may be a read-only memory (ROM) or other type of static storage device capable of storing static information and instructions, random access memory (RAM) or other type of dynamic storage device capable of storing information and instructions, or electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer, but not limited thereto. The memory 1502 may be integrated with the processor 1501 or may exist independently and be coupled to the processor 1501 through the interface circuit of the communication device 1500 (not shown in FIG. 15). This application embodiment does not specifically limit this.

[0555] Transceiver 1503 is used for communication with other communication devices. For example, if communication device 1500 is a terminal device, transceiver 1503 can be used to communicate with a network device or with another terminal device. As another example, if communication device 1500 is a network device, transceiver 1503 can be used to communicate with a terminal device or with another network device.

[0556] Optionally, transceiver 1503 may include a receiver and a transmitter (not shown separately in Figure 15). The receiver is used to implement the receiving function, and the transmitter is used to implement the transmitting function.

[0557] Optionally, the transceiver 1503 can be integrated with the processor 1501 or exist independently and be coupled to the processor 1501 through the interface circuit of the communication device 1500 (not shown in FIG15). This application embodiment does not specifically limit this.

[0558] It is understood that the structure of the communication device 1500 shown in Figure 15 does not constitute a limitation on the communication device. Actual communication devices may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0559] Furthermore, the technical effects of the communication device 1500 can be referred to the technical effects of the method described in the above method embodiments, and will not be repeated here.

[0560] It should be understood that the processor in the embodiments of this application can be a central processing unit (CPU), or it can be other general-purpose processors, DSPs, ASICs, FPGAs, or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor, etc.

[0561] It should also be understood that the memory in the embodiments of this application can be volatile memory or non-volatile memory, or may include both volatile and non-volatile memory. Non-volatile memory can be ROM, programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), EEPROM, or flash memory. Volatile memory can be random access memory (RAM), which is used as an external cache. By way of example, but not limitation, many forms of RAM are available, such as static RAM (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous linked dynamic random access memory (SLDRAM), and direct rambus RAM (DR RAM).

[0562] The above embodiments can be implemented, in whole or in part, by software, hardware (such as circuits), firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more sets of available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium. A semiconductor medium can be a solid-state drive.

[0563] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0564] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0565] It should be understood that in the various embodiments of this application, the order of the above-mentioned processes does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0566] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0567] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0568] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or units may be electrical, mechanical, or other forms.

[0569] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0570] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0571] If the aforementioned functions are implemented as 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 this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes all the various possible memories described above.

Claims

1. A communication method characterized by comprising: Applied to the first distribution unit DU, including: A handover instruction is sent to a first terminal device, the handover instruction being used to instruct the first terminal device to hand over from a first cell to a second cell; the first cell is a cell managed by the first DU, and the second cell is a cell managed by the second DU; Receive first information from the second DU; Wherein, the first information indicates information related to the timing advance (TA) used by the first terminal device to access the second cell multiple times, or the first information indicates information related to multiple TAs used by the first terminal device to perform uplink transmission in the second cell.

2. A communication method characterized by comprising: Applied to the second distribution unit DU, including: Send first information to the first DU, where the first DU is a device that instructs the first terminal device to switch from the first cell to the second cell; the first cell is a cell managed by the first DU, and the second cell is a cell managed by the second DU; Wherein, the first information indicates information related to the timing advance (TA) used by the first terminal device to access the second cell multiple times, or the first information indicates information related to multiple TAs used by the first terminal device to perform uplink transmission in the second cell.

3. The method of claim 2, wherein, Sending the first information to the first DU includes: If the first terminal device is detected to have accessed the second cell via random access, the first information is sent; or If the failure of the first terminal device to switch to the second cell in order to avoid random access is detected as being caused by an invalid TA, the first information is sent.

4. The method according to claim 3, characterized in that, The first information includes at least one of the following: first indication information, first TA, second TA, or first difference; wherein, the first indication information is used to indicate that the failure of the first terminal device to hand over to the second cell without random access is caused by an invalid TA, the first TA is the TA used by the first terminal device when it fails to hand over to the second cell without random access, the second TA is the TA used by the first terminal device to access the second cell through random access, and the first difference is the difference between the first TA and the second TA.

5. The method of claim 2, wherein, Sending the first information to the first DU includes: If N terminal devices are detected accessing the second cell in a random access manner, the first information is sent; or If it is detected that the failure of the N terminal devices to switch to the second cell in order to avoid random access is caused by an invalid TA, the first information is sent; The N terminal devices include the first terminal device, where N is an integer greater than 1.

6. The method according to claim 5, characterized in that, The first information includes at least one of the following: second indication information, N third TAs, N fourth TAs, or information related to N second differences; wherein, the second indication information is used to indicate that the failure of the N terminal devices to hand over to the second cell in order to avoid random access was caused by invalid TAs; The i-th third TA among the N third TAs is the TA used when the i-th terminal device among the N terminal devices fails to switch to the second cell using a non-random access method; the i-th fourth TA among the N fourth TAs is the TA used when the i-th terminal device among the N terminal devices accesses the second cell using a random access method; where 1≤i≤N and are integers; The relevant information of the N second differences indicates at least one of the following: the average value of the N second differences, the maximum value among the N second differences, or the minimum value among the N second differences; wherein, the i-th second difference among the N second differences is the difference between the i-th third TA and the i-th fourth TA.

7. The method of claim 2, wherein, Sending the first information to the first DU includes: If a TA adjustment occurs within a preset time after the first terminal device performs the first uplink transmission, the first information is sent. The first uplink transmission is the uplink transmission performed by the first terminal device when it accesses the second cell using a non-random access method.

8. The method according to claim 7, characterized in that, The first information includes at least one of the following: third indication information, fifth TA, sixth TA, or third difference; wherein, the third indication information indicates that the first terminal device performs TA adjustment within the preset time after performing the first uplink transmission, the fifth TA is the time advance used by the first terminal device to perform the first uplink transmission, the sixth TA is the time advance used by the first terminal device to perform the second uplink transmission after the TA adjustment, and the third difference is the difference between the fifth TA and the sixth TA.

9. The method of claim 2, wherein, Sending the first information to the first DU includes: If a TA adjustment occurs within a preset time after M terminal devices perform the first uplink transmission, the first information is sent; the first uplink transmission is the uplink transmission performed by the M terminal devices when they access the second cell in a non-random access manner. The M terminal devices include the first terminal device, where M is an integer greater than or equal to 1.

10. The method according to claim 9, characterized in that, The first information includes at least one of the following: fourth indication information, M seventh TAs, M eighth TAs, or information related to M fourth differences; wherein, the fourth indication information is used to indicate that the M terminal devices perform TA adjustment within the preset time after performing the first uplink transmission; The j-th seventh TA among the M seventh TAs is: the time advance used by the j-th terminal device among the M terminal devices to perform the first uplink transmission; the j-th eighth TA among the M eighth TAs is: the time advance used by the j-th terminal device among the M terminal devices to perform the second uplink transmission after TA adjustment; where 1≤j≤M and are integers; The relevant information of the M fourth differences indicates at least one of the following: the average value of the M fourth differences, the maximum value among the M fourth differences, or the minimum value among the M fourth differences; wherein, the j-th fourth difference among the M fourth differences is the difference between the j-th seventh TA and the j-th eighth TA.

11. A communication method, comprising: Applied to the first distribution unit DU, including: A handover instruction is sent to a first terminal device, the handover instruction being used to instruct the first terminal device to hand over from a first cell to a second cell; the first cell is a cell managed by the first DU, and the second cell is a cell managed by the second DU; Receive first information from the second DU; The first information indicates information about the beams used by the first terminal device to access the second cell multiple times, or the first information indicates information about multiple beams used by the first terminal device in the beam failure recovery process within a preset time after switching to the second cell in a non-random access manner.

12. A communication method characterized by comprising: Applied to the second DU, including: Send first information to the first DU, where the first DU is a device that instructs the first terminal device to switch from the first cell to the second cell; the first cell is a cell managed by the first DU, and the second cell is a cell managed by the second DU; The first information indicates information about the beams used by the first terminal device to access the second cell multiple times, or the first information indicates information about multiple beams used by the first terminal device in the beam failure recovery process within a preset time after switching to the second cell in a non-random access manner.

13. The method of claim 12, wherein, Sending the first information to the first DU includes: If the first terminal device is detected to have accessed the second cell via random access, the first information is sent; or If the failure of the first terminal device to switch to the second cell in order to avoid random access is detected as being due to an incorrect beam, the first information is sent.

14. The method according to claim 13, characterized in that, The first information includes at least one of the following: first indication information, information for indicating the first beam, information for indicating the second beam, or first beam offset; The first indication information is used to indicate that the failure of the first terminal device to hand over to the second cell without random access was caused by an incorrect beam. The first beam is the beam used by the first terminal device when it fails to hand over to the second cell without random access, the second beam is the beam used by the first terminal device to access the second cell with random access, and the first beam offset is the offset between the first beam and the second beam.

15. The method of claim 12, wherein, Sending the first information to the first DU includes: If N terminal devices are detected accessing the second cell in a random access manner, the first information is sent; or If it is detected that the failure of the N terminal devices to switch to the second cell in order to avoid random access is due to an incorrect beam, the first information is sent; The N terminal devices include the first terminal device, where N is an integer greater than or equal to 1.

16. The method according to claim 15, characterized in that, The first information includes at least one of the following: second indication information, information for indicating N third beams, information for indicating N fourth beams, information for indicating the beam that appears most frequently among the N third beams, information for indicating the beam that appears most frequently among the N fourth beams, or information related to the offset of N second beams; The second indication information is used to indicate that the failure of the N terminal devices to switch to the second cell in order to avoid random access was caused by an incorrect beam. The i-th third beam among the N third beams is the beam used by the i-th terminal device among the N terminal devices when it fails to switch to the second cell using a non-random access method; the i-th fourth beam among the N fourth beams is the beam used by the i-th terminal device among the N terminal devices to access the second cell using a random access method; where 1≤i≤N and are integers; The relevant information of the N second beam offsets indicates the average value of the N second beam offsets; wherein, the i-th second beam offset among the N second beam offsets is the offset between the i-th third beam and the i-th fourth beam.

17. The method of claim 12, wherein, Sending the first information to the first DU includes: If the first terminal device performs a beam failure recovery procedure within the preset time after switching to the second cell using a non-random access method, the first information is sent.

18. The method according to claim 17, characterized in that, The first information includes at least one of the following: third indication information, information for indicating the fifth beam, information for indicating the sixth beam, or third beam offset; The third indication information is used to instruct the first terminal device to perform a beam failure recovery process within the preset time after switching to the second cell using a non-random access method; the fifth beam is the beam used by the first terminal device when switching to the second cell using a non-random access method; the sixth beam is the beam used by the first terminal device when performing the beam failure recovery process; and the third beam offset is the offset between the fifth beam and the sixth beam.

19. The method according to claim 12, characterized in that, If a beam failure recovery process occurs within the preset time after detecting that M terminal devices have switched to the second cell using a non-random access method, the first information is sent. The M terminal devices include the first terminal device, where M is an integer greater than or equal to 1.

20. The method according to claim 19, characterized in that, The first information includes at least one of the following: fourth indication information, information for indicating M seventh beams, information for indicating M eighth beams, information for indicating the beam that appears most frequently among the M seventh beams, information for indicating the beam that appears most frequently among the M eighth beams, or information related to the offset of the M fourth beams; The fourth indication information is used to indicate that after the M terminal devices switch to the second cell in a non-random access manner, the beam failure recovery process occurs within the preset time. The j-th seventh beam among the M seventh beams is the beam used by the j-th terminal device among the M terminal devices when it switches to the second cell using a non-random access method; the j-th eighth beam among the M eighth beams is the beam used by the j-th terminal device among the M terminal devices when it executes the beam failure recovery procedure; where 1≤j≤M and are integers; The relevant information of the M fourth beam offsets indicates the average value of the M fourth beam offsets; wherein, the j-th fourth beam offset among the M fourth beam offsets is the offset between the j-th seventh beam and the j-th eighth beam.

21. The method of claim 19 or 20, wherein, The first information also includes a fifth indication information, which is used to indicate the beam failure recovery ratio. The beam failure recovery ratio is the ratio of the number of times the M terminal devices execute the beam failure recovery process within the preset time after switching to the second cell using the non-random access method, to the number of times the L terminal devices successfully switch to the second cell using the non-random access method. The L terminal devices include the M terminal devices, and L is an integer greater than or equal to M.

22. A communications device, characterized by The apparatus includes: a module for performing the method as described in any one of claims 1-10, or a module for performing the method as described in any one of claims 11-21.

23. A communications device, characterized by The communication device includes a processing unit and a storage unit; the storage unit is used to store computer instructions, which, when executed by the processing unit, cause the method as described in any one of claims 1-10 to be executed, or cause the method as described in any one of claims 11-21 to be executed.

24. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a computer program or instructions that, when executed on a computer, cause the computer to perform the method as claimed in any one of claims 1-10, or cause the computer to perform the method as claimed in any one of claims 11-21.

25. A computer program product, characterised in that, The computer program product includes a computer program or instructions that, when executed on a computer, cause the method as described in any one of claims 1-10 to be performed, or cause the method as described in any one of claims 11-21 to be performed.

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