CN117676723A

CN117676723A - Communication method and device

Info

Publication number: CN117676723A
Application number: CN202210951896.6A
Authority: CN
Inventors: 毛颖超; 强鹂; 常俊仁; 李娇娇; 酉春华
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2022-08-09
Filing date: 2022-08-09
Publication date: 2024-03-08
Also published as: WO2024032271A1

Abstract

The application provides a communication method and device, which are used for reducing the power consumption of terminal equipment and improving the switching performance. The method comprises the following steps: the terminal equipment receives indication information from first network equipment, wherein the indication information is used for indicating information of a target cell for switching, and the target cell is configured for the terminal equipment; and the terminal equipment determines uplink resources for sending the message indicating the completion of the switching according to the configuration condition of the first pre-configured resources of the target cell, and sends the message indicating the completion of the switching on the uplink resources.

Description

Communication method and device

Technical Field

The present disclosure relates to the field of communications, and in particular, to a communication method and apparatus.

Background

In a wireless communication system, during the movement of a terminal device, the terminal device may be handed over from a current serving cell to a target cell in order to provide a better network service to a user.

Currently, the network device may refer to a measurement report of the terminal device, determine a target cell for handover of the terminal device, and send a handover command for indicating handover to the target cell to the terminal device. The terminal device can switch to the target cell according to the switch command and send a switch completion message to the network device where the target cell is located. In the layer 1 or layer2 (layer 1/layer2, L1/L2) based handover procedure, after receiving an L1/L2 based handover command message of the network device, the terminal device switches to the target cell according to the handover command message. Because the target cell of the terminal device is one cell in the preconfigured candidate cells, the terminal device cannot determine uplink resources for sending a message indicating that the handover is completed based on the handover command message, and further cannot accurately determine when to start monitoring the physical downlink control channel of the target cell, which may result in waste of power consumption of the terminal device.

Disclosure of Invention

The embodiment of the application provides a communication method and a communication device, which are used for reducing power consumption of terminal equipment.

In order to achieve the above purpose, the embodiments of the present application adopt the following technical solutions:

in a first aspect, a communication method is provided, which may be performed by a terminal device, or a component of the terminal device, such as a processor, a chip, or a system-on-chip of the terminal device, or a logic module or software capable of implementing all or part of the functions of the terminal device. The following description will be made with an example in which the method is executed by the terminal device. The communication method comprises the following steps: the terminal device receives first indication information from the first network device for indicating information of a target cell for handover of the terminal device. The target cell is a cell of a plurality of candidate target cells configured by the terminal device before receiving the first indication information. And the terminal equipment determines uplink resources for sending the message indicating the completion of the switching according to the configuration condition of the first pre-configuration authorization of the target cell, and sends the message indicating the completion of the switching on the uplink resources.

That is, in the present application, after receiving the first indication information, the terminal device may accurately determine, according to the configuration condition of the pre-configured grant, uplink resources for sending a message indicating that the handover is completed. The terminal device determines an uplink resource for transmitting a message indicating that the handover is completed, and may transmit the message indicating that the handover is completed on the uplink resource. In this way, the network device in which the target cell is located may receive a message from the terminal device on the uplink resource indicating that the handover is complete.

In one possible implementation, the configuration of the first pre-configured grant includes configuring the first pre-configured grant or not configuring the first pre-configured grant.

Based on this possible implementation, when configuring the first pre-configuration grant, the terminal device may delay listening to the configured resources, thereby reducing power consumption. When the first pre-configuration authorization is not configured, the terminal equipment can acquire the authorized resources according to the dynamic scheduling of the network equipment, and the resource waste can be avoided because the authorization is not required to be configured in advance for the terminal equipment.

In one possible implementation, the terminal device configures the first pre-configuration grant and the first pre-configuration grant is valid, and the terminal device determines that an uplink resource that sends a message indicating that the handover is completed is a resource corresponding to the first pre-configuration grant. Alternatively, the terminal device configures the first pre-configured grant and the first pre-configured grant is invalid, the terminal device may monitor a physical downlink control channel (physical downlink control channel, PDCCH) of the target cell for indicating the second uplink grant resource, and determine that the second uplink grant is an uplink resource for transmitting a message indicating that the handover is completed.

Based on this possible implementation, in case the terminal device configures the first pre-configured grant and the first pre-configured grant is valid, the terminal device may send a message on the first pre-configured grant indicating that the handover is completed, completing the handover faster. In case the first pre-configured grant configured by the terminal device is invalid, the terminal device may determine the second grant resources by listening to a PDCCH of the target cell for indicating the second grant. Therefore, the terminal equipment can send the message indicating the switching completion on the second authorized resource, and provide the uplink resource of the access target cell for the terminal equipment, so that the terminal equipment does not need to perform a random access process in the switching process, the switching time delay is saved, and the switching performance of the terminal equipment is improved.

In one possible implementation, the terminal device does not configure the first pre-configured grant, and the terminal device may monitor the PDCCH of the target cell for indicating the second grant resource, and determine that the second grant resource is an uplink resource for transmitting a message indicating that handover is completed.

Based on the possible implementation manner, under the condition that the terminal equipment is not configured with the pre-configuration authorization, the terminal equipment can determine the authorization resource for sending the message indicating the completion of the switching through the dynamic scheduling of the network equipment, and send the message indicating the completion of the switching on the authorization resource, so that the terminal equipment does not need to perform a random access process in the switching process, the switching time delay is saved, and the switching performance of the terminal equipment is improved.

In one possible implementation, the first pre-configured grant validity may include one or more of the following: the reference signal received power (reference signal receiving power, RSRP) of the synchronization signal block (synchronization signal block, SSB) associated with the first pre-configured grant is above a first pre-set threshold, the first pre-configured grant does not overlap with physical random access channel (physical random access channel, PRACH) resources, or the first pre-configured grant does not overlap with physical uplink shared channel (physical uplink shared channel, PUSCH) resources of message a (message a, msgA).

Based on the possible implementation manner, the terminal device can determine whether the first pre-configuration authorization is valid according to the above conditions, and the terminal device accurately determines to send uplink resources indicating the handover complete message.

In one possible implementation, the terminal device configures the first pre-configuration grant, and the first pre-configuration grant is valid, and the offset between the time domain position of the terminal device receiving the first indication information and the time domain position of the first pre-configuration grant (or the first occasion of the first pre-configuration grant) is smaller than the second pre-set threshold, and the terminal device may determine that the first pre-configuration grant is an uplink resource for transmitting a message indicating that the handover is completed. Or the terminal device configures the first pre-configuration grant, the first pre-configuration grant is valid, the offset between the time domain position of the first indication information received by the terminal device and the time domain position of the first pre-configuration grant (or the first time of the first pre-configuration grant) is greater than or equal to a second preset threshold, the terminal device may monitor the PDCCH of the target cell for indicating the second uplink resource grant, and determine that the uplink resource for sending the handover complete message is the second uplink grant resource.

Based on this possible implementation manner, in the case where the first pre-configuration grant configured by the terminal device is valid, if the offset between the time domain position of the terminal device receiving the first indication information (i.e. the handover command) and the time domain position of the first pre-configuration grant or the time domain position of the first occasion of the first pre-configuration grant is smaller than the threshold, the terminal device may send a message indicating that the handover is completed on the first pre-configuration grant, and the terminal device does not need to monitor the PDCCH of the target cell, and may reduce power consumption. If the offset between the time domain position of the first indication information (i.e. the handover command) received by the terminal device and the time domain position of the first pre-configured grant or the time domain position of the first occasion of the first pre-configured grant is greater than or equal to a threshold value, it is indicated that the time domain position of the first pre-configured grant is longer than the time duration between the time domain position of the terminal device receiving the handover command. In the application, the terminal device can immediately monitor the PDCCH for indicating the uplink grant resource, and takes the uplink grant resource indicated by the PDCCH as a message for sending the indication of the completion of the handover. Compared with the method that the first pre-configuration authorization is used for sending the message indicating the switching completion, the method can reduce the time delay for sending the message indicating the switching completion by using the uplink authorization resource indicated by the PDCCH by the terminal equipment.

In one possible implementation, the terminal device sends a message on the uplink resource indicating that the handover is complete through a first hybrid automatic repeat request (hybrid automatic repeat request, HARQ) process.

In one possible implementation, the method further includes: the terminal device does not receive a response message indicating the handover completion message, and may receive a third uplink grant resource for the target cell on the PDCCH scrambled by the C-RNTI. The third uplink grant resource is associated with either the first HARQ process or the third uplink grant is associated with either one of the HARQ processes, and the third uplink grant resource is indicated for a new transmission. And the terminal equipment resends the message indicating the completion of the switching on the third uplink authorized resource.

The response message may be carried in a media access control (media access control, MAC) Control Element (CE) or downlink control information (downlink control information, DCI). Any one HARQ process may be the first HARQ process, or may be another HARQ process different from the first HARQ process. The new transmission may refer to an uplink message different from the message indicating handover completion, or to multiplexing and assembling the message indicating handover completion for transmission.

Based on the possible implementation manner, when the terminal device does not receive the response message for indicating that the message indicating the completion of the handover is received, the terminal device may monitor a PDCCH scrambled by a cell radio network temporary identifier (cell-radio network temporary identifier, C-RNTI), receive a third uplink grant resource of the target cell, and resend the message indicating the completion of the handover on the third uplink grant resource. In this way, the probability of successful transmission of a message indicating completion of handover is improved.

In one possible implementation, the method further includes: the terminal device does not receive a response message indicating that the switching is completed, and the terminal device does not receive the third uplink grant resource, the second time of the first pre-configuration grant is valid, and the terminal device can retransmit the message indicating that the switching is completed on the second time. The second occasion is an authorization occasion in the first pre-configured authorization.

Based on this possible implementation, when the terminal device does not receive a response message indicating the handover completion message, the terminal device also does not receive the uplink grant resources on the PDCCH of the target cell. In case the second occasion of the first pre-configuration grant is valid, the terminal device may retransmit a message indicating that the handover is complete on the valid occasion. As such, for a scenario in which the first pre-configured grant includes multiple occasions, the terminal device may retransmit a message indicating that the handover is complete on a valid occasion of the multiple occasions. The probability of successful transmission of a message indicating completion of handover is improved.

In one possible implementation manner, the first pre-configured grant is a dedicated uplink grant of the terminal device within a valid duration of a first timer corresponding to the first pre-configured grant.

For example, the effective duration of the first timer may comprise a starting offset, which is an offset value for the terminal device to receive the first pre-configured grant configuration. The validity duration may be in units of integer multiples or symbols of a preconfigured grant (CG) period. I.e. an integer multiple of the symbol, or of the frame, or may be a positive integer, or in seconds.

Based on the possible implementation manner, the effective duration is set for the first pre-configuration authorization, and in the effective duration, the first pre-configuration authorization is the special uplink authorization of the terminal equipment, so that the resource of the terminal equipment for sending the uplink message indicating the completion of switching is ensured not to conflict with the resource of other terminal equipment for sending the uplink message.

In one possible implementation, the first timer expires, and the terminal device cannot continue to use the first pre-configured grant or the first pre-configured grant is a common uplink grant.

It should be noted that, the common uplink grant may also configure grant resources for competing uplink grant resources or Type-1 (Type-1).

Based on this possible implementation, when the first timer expires, i.e. the duration of the first pre-configured grant exceeds the valid duration. The first pre-configured grant may be a common uplink grant, i.e. other terminal devices may also use the first pre-configured grant. In this way, the first pre-configured authorization can be fully used. The problem that when the terminal equipment does not use the first pre-configuration authorization, other terminal equipment cannot use the first pre-configuration authorization, so that resource waste is caused is avoided.

In a second aspect, a communication method is provided, where the method may be performed by the second network device, or may be performed by a component of the second network device, for example, a processor, a chip, or a system-on-chip of the second network device, or may be implemented by a logic module or software that may implement all or part of the functionality of the second network device. The method is described below as an example of being performed by the second network device. The communication method comprises the following steps: the second network device receives second indication information from the first network device. The second indication information is used for indicating information of a target cell for switching the terminal equipment. The target cell is a cell of a plurality of candidate target cells.

Based on the method, the second network device can accurately determine the target cell for terminal device handover based on the second indication information from the first network device. The second network device can accurately and dynamically schedule uplink resources, and the switching success probability of the terminal device is improved.

In a possible implementation manner, the second network device receives a message indicating that the handover is completed from the terminal device on the uplink resource according to the configuration condition of the first pre-configuration grant of the target cell.

Based on the possible implementation manner, the second network device can accurately receive the message indicating the completion of the handover from the terminal device according to the configuration condition of the first pre-configuration authorization of the target cell. The alignment of the terminal device with the second network device is ensured.

In one possible implementation, the configuration of the first pre-configured grant may include configuring the first pre-configured grant or not configuring the first pre-configured grant.

In one possible implementation, the terminal device configures a first pre-configured grant on which the second network device receives a message indicating that the handover is complete. Or the terminal device does not configure the first pre-configuration grant, the second network device may schedule the PDCCH of the target cell for indicating the second uplink grant resource, and receive a message indicating that the handover is completed on the second uplink grant resource.

Based on the possible implementation manner, when the second network device configures the first pre-configuration authorization for the terminal device, the second network device may receive a message sent by the terminal device and indicating that the switching is completed on the first pre-configuration authorization, so as to reduce the complexity of blind detection of the second network device. When the second network device configures the first pre-configuration grant for the terminal device, the second network device may schedule a PDCCH for indicating a target cell of the second uplink grant resources. Thus, the second network device can accurately receive the message indicating the completion of the handover from the terminal device on the second uplink grant resource.

In one possible implementation, the terminal device configures a first pre-configuration grant, and the terminal device receives a first indication information indicating information of the target cell, the time domain position of which is offset from the time domain position of the first pre-configuration grant (or the first occasion of the first pre-configuration grant) by less than a second pre-set threshold, and the second network device may receive a message indicating that the handover is completed on the first pre-configuration grant. Or the terminal equipment configures the first pre-configuration grant, the offset between the time domain position of the first indication information received by the terminal equipment and the time domain position of the first pre-configuration is greater than or equal to a second preset threshold, and the second network equipment can schedule the PDCCH of the target cell for indicating the second uplink grant and receive a message for indicating that the switching is completed on the second uplink grant.

Based on the possible implementation manner, under the condition that the second network device configures the first pre-configuration authorization for the terminal device and the offset between the time domain position of the first indication information received by the terminal device and the time domain position of the first pre-configuration authorization is smaller than a second pre-set threshold, the terminal device is indicated to possibly send a message indicating that the switching is completed on the first pre-configuration authorization. In this way, the second network device can receive the message indicating the completion of the handover on the first pre-configuration authorization, which is simple and convenient. In the case that the second network device configures the first pre-configuration grant for the terminal device, and the offset between the time domain position of the first indication information received by the terminal device and the time domain position of the first pre-configuration grant is greater than or equal to a second preset threshold, in order to reduce the time delay, the second network device may schedule the second uplink grant resource for the terminal device. In this way, the terminal device may send a message indicating that the handover is completed on the second uplink grant resource. Correspondingly, the second network device can also receive the message indicating the switching completion sent by the terminal device on the second uplink authorized resource, thereby reducing the waiting time. Thereby, the switching time delay of the terminal equipment can be reduced.

In one possible implementation, the second network device receives a message associated with the first HARQ process indicating that the handoff is complete.

In one possible implementation, the method further includes: and the second network equipment sends a third uplink grant resource through the PDCCH scrambled by the scheduling C-RNTI. The third uplink grant resource is associated with the first HARQ process or any one HARQ process and is indicated for a new transmission.

Based on the possible implementation manner, the second network device sends the uplink message by scheduling the new authorized resource for the terminal device, and the second network device detects the uplink message on the scheduled new authorized resource, so that the second network device accurately receives the message of the terminal device on the new authorized resource, and blind detection complexity is reduced.

Based on the possible implementation manner, the effective duration is set for the first pre-configured grant, and the first pre-configured grant is a dedicated uplink grant of the terminal device in the effective duration, so that the second network device can provide sufficient uplink resources for the terminal device to send the uplink message.

Based on this possible implementation, when the first timer expires, i.e. the duration of the first pre-configured grant exceeds the valid duration. In order to avoid affecting the resource allocation of other terminal devices, the first pre-configured grant may be a common uplink grant, i.e. the other terminal devices may also use the first pre-configured grant. Thus, the first pre-configuration authorization can be fully used, and resource waste is reduced. The problem that when the terminal equipment does not use the first pre-configuration authorization to send a message to the second network equipment, other terminal equipment cannot use the first pre-configuration authorization, so that the waste of resources of the second network equipment is caused is avoided.

In a third aspect, a communication method is provided, where the method may be performed by a first network device, or a component of the first network device, for example, a processor, a chip, or a system-on-chip of the first network device, or implemented by a logic module or software that can implement all or part of the functions of the first network device. The method is described below as an example of being performed by the first network device. The communication method comprises the following steps: the first network device transmits second indication information indicating information of a target cell for terminal device handover to the second network device. The target cell is a cell of the plurality of candidate cells.

In an application scenario, the first network device may be a first distribution unit DU. The second network device may be a second DU. The first DU and the second DU may be the same or different. The first DU and the second DU correspond to the same central unit CU.

Based on the method, the first network device may send information for indicating a target cell for handover of the terminal device to the second network device. Thus, the second network device can accurately determine the target cell for switching the terminal device.

In one possible implementation, the method further includes: the first network device transmits first indication information for indicating information of the target cell to the terminal device.

In one example, the first indication information may be carried in a MAC CE or DCI.

Based on the possible implementation manner, the first network device may send indication information for indicating information of the target cell to the terminal device, so that the terminal device may determine the target cell for handover according to the indication information. Since the indication information does not include the authorized resource, the data size is smaller, and the resources occupied by transmitting the indication information can be saved.

In a fourth aspect, a communication device is provided, and advantageous effects may be seen from the description of the first aspect, which is not repeated here. The communication device has the functionality to implement the actions in the method example of the first aspect described above. The functions may be implemented by hardware, or may be implemented by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the functions described above. In one possible design, the communication device includes: and the receiving and transmitting module is used for receiving first indication information from the first network equipment, wherein the first indication information is used for indicating the information of the target cell for switching the terminal equipment. The target cell is a cell of a plurality of candidate target cells configured by the terminal equipment before receiving the first indication information; the processing module is configured to determine, according to a configuration condition of the first pre-configuration grant of the target cell, an uplink resource for sending a message indicating that handover is completed, and send, on the uplink resource, a message indicating that handover is completed. These modules may perform the corresponding functions in the method examples of the first aspect, which are specifically referred to in the detailed description of the method examples and are not described herein.

In a fifth aspect, a communication device is provided, and advantageous effects may be seen in the description of the second aspect and are not repeated here. The communication device has the functionality to implement the behavior in the method example of the second aspect described above. The functions may be implemented by hardware, or may be implemented by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the functions described above. In one possible design, the communication device includes: and the transceiver module is used for receiving the second indication information from the first network equipment. The second indication information is used for indicating information of a target cell for switching the terminal equipment. The target cell is a cell of a plurality of candidate target cells. And the processing module is used for receiving a message indicating that the switching is finished of the terminal equipment on the uplink resource through the receiving and transmitting module according to the configuration condition of the first pre-configuration authorization of the target cell. These modules may perform the corresponding functions in the method examples of the second aspect, which are specifically referred to in the method examples and are not described herein.

In a sixth aspect, a communication device is provided, and advantageous effects may be seen in the description of the third aspect and are not repeated here. The communication device has the functionality to implement the behavior in the method example of the third aspect described above. The functions may be implemented by hardware, or may be implemented by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the functions described above. In one possible design, the communication device includes: and the processing module is used for sending second indication information for indicating the information of the target cell switched by the terminal equipment to the second network equipment through the receiving and transmitting module. The target cell is a cell of the plurality of candidate cells. The processing module is further configured to send first indication information for indicating information of the target cell to the terminal device. These modules may perform the corresponding functions in the method examples of the third aspect, which are specifically referred to in the method examples and are not described herein.

In a seventh aspect, a communication device is provided. The communication device may be the terminal device in the above embodiment of the method, or a chip provided in the terminal device. The communication device includes: at least one processor; the processor is configured to execute a computer program or instructions stored in the memory, to cause the communication device to perform the communication method according to the first aspect. The memory may be coupled to the processor or may be separate from the processor. The communication means may be a terminal device as in the first aspect or a device, such as a chip, comprised in the terminal device.

In a possible implementation, the communication device further includes the memory.

In one possible implementation, the communication device further comprises a communication interface.

In an eighth aspect, a communication device is provided. The communication device may be the second network device in the above embodiment of the method, or a chip provided in the second network device. The communication device includes: at least one processor; the processor is configured to execute a computer program or instructions stored in the memory to cause the communication device to perform the communication method according to the ninth aspect. The memory may be coupled to the processor or may be separate from the processor. The communication means may be the second network device of the second aspect or a device, such as a chip, comprised in the second network device.

In a ninth aspect, a communication apparatus is provided. The communication device may be the first network device in the above method embodiment, or a chip disposed in the first network device. The communication device includes: at least one processor; the processor is configured to execute a computer program or instructions stored in the memory to cause the communication device to perform the communication method according to the ninth aspect. The memory may be coupled to the processor or may be separate from the processor. The communication means may be the first network device of the third aspect or a device, such as a chip, comprised in the first network device.

In one possible implementation, the communication device further includes a memory.

In one possible implementation, the communication device further comprises a transceiver.

In a tenth aspect, there is provided a computer readable storage medium having stored therein a computer program or instructions which, when run on a communication device, enable the communication device to perform the method of the first or second or third aspects described above.

In an eleventh aspect, there is provided a computer program product comprising instructions which, when run on a communications apparatus, cause the communications apparatus to perform the method of the first or second or third aspects described above.

In a twelfth aspect, the present application provides a chip system, where the chip system includes a processor, and the processor is configured to implement a function of a terminal device in the method in the above aspects. In one possible design, the chip system further includes a memory for holding program instructions and/or data. The chip system can be composed of chips, and can also comprise chips and other discrete devices.

In a thirteenth aspect, the present application provides a chip system, where the chip system includes a processor, and the processor is configured to implement the functions of the first network device or the second network device in the methods in the foregoing aspects. In one possible design, the chip system further includes a memory for holding program instructions and/or data. The chip system can be composed of chips, and can also comprise chips and other discrete devices.

In a fourteenth aspect, the present application provides a communication method, including:

the first network equipment sends second indication information to the second network equipment, wherein the second indication information is used for indicating information of a target cell switched by the terminal equipment, and the target cell is a cell in a plurality of candidate target cells;

The first network equipment sends first indication information to terminal equipment, wherein the first indication information is used for indicating information of a target cell switched by the terminal equipment, and the target cell is a cell in a plurality of candidate target cells configured by the terminal equipment before receiving the first indication information;

the terminal equipment determines uplink resources for sending a message indicating that the switching is completed according to the configuration condition of the first pre-configuration authorization of the target cell, and sends the message indicating that the switching is completed to the second network equipment on the uplink resources;

and the second network equipment receives a message indicating that the switching is completed from the terminal equipment according to the configuration condition of the first pre-configuration authorization of the target cell.

In a fifteenth aspect, the present application provides a communication system comprising the communication device of the fifth aspect and the communication device of the sixth aspect. The system further comprises the communication device of the fourth aspect.

Drawings

Fig. 1 is a schematic architecture diagram of a communication system according to an embodiment of the present application;

fig. 2 is a schematic architecture diagram of a communication system according to an embodiment of the present application;

fig. 3 is a schematic architecture diagram of a network device according to an embodiment of the present application;

Fig. 4 is a schematic architecture diagram of a communication device according to an embodiment of the present application;

fig. 5 is a schematic flow chart of a communication method according to an embodiment of the present application;

fig. 6 is a flow chart of another communication method according to an embodiment of the present application;

fig. 7 is a flow chart of another communication method according to an embodiment of the present application;

fig. 8 is a flow chart of another communication method according to an embodiment of the present application;

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

fig. 10 is a schematic architecture diagram of yet another communication system according to an embodiment of the present application;

fig. 11 is a flow chart of another communication method according to an embodiment of the present application;

FIG. 12 is a flowchart of determining the effective time and the effective duration of the first pre-configured grant according to an embodiment of the present application;

fig. 13 is a flow chart of another communication method according to an embodiment of the present application;

fig. 14 is a flow chart of yet another communication method according to an embodiment of the present application;

fig. 15 is a schematic architecture diagram of a communication device according to an embodiment of the present application;

fig. 16 is a schematic architecture diagram of another communication device according to an embodiment of the present application.

Detailed Description

The technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application. Wherein, in the description of the present application, "/" means that the related objects are in a "or" relationship, unless otherwise specified, for example, a/B may mean a or B; the term "and/or" in this application is merely an association relation describing an association object, and means that three kinds of relations may exist, for example, a and/or B may mean: there are three cases, a alone, a and B together, and B alone, wherein a, B may be singular or plural. Also, in the description of the present application, unless otherwise indicated, "a plurality" means two or more than two. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, at least one (one) of a, b, or c may represent: a, b, c, a-b, a-c, b-c, or a-b-c, wherein a, b, c may be single or plural. In addition, in order to clearly describe the technical solutions of the embodiments of the present application, in the embodiments of the present application, the words "first", "second", and the like are used to distinguish the same item or similar items having substantially the same function and effect. It will be appreciated by those of skill in the art that the words "first," "second," and the like do not limit the amount and order of execution, and that the words "first," "second," and the like do not necessarily differ.

In addition, the network architecture and the service scenario described in the embodiments of the present application are for more clearly describing the technical solution of the embodiments of the present application, and do not constitute a limitation on the technical solution provided in the embodiments of the present application, and as a person of ordinary skill in the art can know, with evolution of the network architecture and appearance of a new service scenario, the technical solution provided in the embodiments of the present application is also applicable to similar technical problems.

The technical solution of the embodiments of the present application may be applied to various communication systems, such as a universal mobile telecommunications system (universal mobile telecommunications system, UMTS), a code division multiple access (code division multiple access, CDMA) system, a wireless local area network (wireless local area network, WLAN), a wireless fidelity (wireless fidelity, wi-Fi) system, a wired network, a vehicle-to-arbitrary object (vehicle to everything, V2X) communication system, an inter-device (D2D) communication system, a car networking communication system, a 4th generation (4th generation,4G) mobile communication system, such as a long term evolution (long term evolution, LTE) system, an evolved LTE (eete), a worldwide interoperability for microwave access (worldwide interoperability for microwave access, wiMAX) communication system, a fifth generation (5th generation,5G) mobile communication system, such as a new air interface (NR) system, a new radio access technology (new radio access technology, NR) and future communication systems, such as a sixth generation (6th generation,6G) mobile communication system, and the like. The network device of the eLTE can be connected to the core network of the LTE and the core network of the future 5G at the same time.

The present application will present various aspects, embodiments, or features about a system that may include multiple devices, components, or modules, etc. It is to be understood and appreciated that the various systems may include additional devices, components, modules, etc. and/or may not include all of the devices, components, modules etc. discussed in connection with the figures. Furthermore, combinations of these schemes may also be used.

In addition, in the embodiments of the present application, words such as "exemplary," "for example," and the like are used to indicate an example, instance, or illustration. Any embodiment or design described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, the term use of an example is intended to present concepts in a concrete fashion.

In the embodiments of the present application, "of", "corresponding" and "corresponding" may be sometimes used in combination, and it should be noted that the meaning to be expressed is consistent when the distinction is not emphasized.

To facilitate understanding of the embodiments of the present application, a communication system suitable for the embodiments of the present application will be described in detail first with reference to the communication system shown in fig. 1 as an example. Fig. 1 is a schematic diagram of a communication system to which the communication method according to the embodiment of the present application is applicable.

As shown in fig. 1, the communication system includes a plurality of network devices (such as network device 1, network device 2, network device 3 in fig. 1) and terminal devices.

Wherein the terminal device may be communicatively connected to a plurality of network devices. For example, the terminal device may be located within a common coverage area of the network device 1, the network device 2, and the network device 3.

The network device may also be referred to as an access device, an access network device, or a wireless network device. A network device is an entity on the network side for transmitting or receiving signals. The network device can manage wireless resources, provide access service for the terminal device, and complete the forwarding of data between the terminal and the core network. For example, the network device may be a base station, an Access Point (AP), etc., a next generation radio access network (next generation radio access network, NG-RAN).

The network device in the embodiment of the present application may be any communication device having a wireless transceiver function for communicating with a terminal device. The network devices include, but are not limited to: an evolved Node B (eNB), a radio network controller (radio network controller, RNC), a Node B (Node B, NB), a base station controller (base station controller, BSC), a base transceiver station (base transceiver station, BTS), a home evolved Node B, heNB, or home Node B, HNB), a Base Band Unit (BBU), an Access Point (AP) in a wireless fidelity (wireless fidelity, WIFI) system, a wireless relay Node, a wireless backhaul Node, a transmission point (transmission point, TP) or a transmission reception point (transmission and reception point, TRP), etc., may also be 5G, such as a next generation base station (the next Generation Node B, gNB) in an NR system, a transmission point (TRP or TP), or one or a group of base stations (including multiple antenna panels) in a 5G system, or may also be a network Node constituting a gNB or transmission point, such as a BBU, or a distributed unit (BBU), or a satellite, or an unmanned DU, etc.

In one example, the network device may be a gNB or may be part of a device in a gNB. The gNB may be a Centralized Unit (CU) and a Distributed Unit (DU) split architecture. As shown in fig. 2, the gNB may include one CU and a plurality of DUs (e.g., DU1 and DU2 in fig. 2). A CU is communicatively connected to a plurality of DUs, for example, CU and DUs may be communicatively connected via an F1 interface. Only 2 DUs are shown in fig. 2, the gNB may also include a larger number of DUs. When the network device is part of a device in the gNB, the network device may be a DU in the gNB. For example, the network device may be DU1 or DU2 in fig. 2.

Wherein the CU may implement part of the functionality of the gNB. For example, the CU is responsible for handling non-real time protocols and services, implementing the functions of the radio resource control (radio resource control, RRC), packet data convergence layer protocol (packet data convergence protocol, PDCP) layer. For example, as shown in fig. 3, a CU may include an RRC layer, a PDCP layer.

Wherein the DU may implement part of the functionality of the gNB. For example, the DU is responsible for handling physical layer protocols and real-time services, implementing the functions of a radio link control (radio link control, RLC), medium access control (media access control, MAC) and Physical (PHY) layers. For example, as shown in fig. 3, the DU may include an RLC layer, a MAC layer, and a PHY layer.

Further, the gNB may also include an active antenna unit (active antenna unit, AAU). The AAU realizes part of physical layer processing function, radio frequency processing and related functions of the active antenna. As shown in fig. 3, the AAU may include a lower physical layer (i.e., low-PHY layer), a Radio Frequency unit (RF) and an antenna.

In an example, according to a protocol stack hierarchy, the physical Layer may be Layer 1 (Layer 1, L1), and the MAC Layer, RLC Layer, and PDCP Layer may be L2 layers. The RRC layer may be an L3 layer.

The information of the RRC layer is generated by the CU, and finally becomes PHY layer information through PHY layer encapsulation of the DU, or is converted from the PHY layer information. Thus, under the architecture of fig. 3, higher layer signaling, such as RRC layer signaling, may also be considered to be sent by a DU, or by a du+aau. It is understood that the network device may be a device comprising one or more of a CU node, a DU node, or an AAU node. In addition, the CU may be divided into network devices in the access network, or may be divided into network devices in the core network, which is not limited in this application.

In one example, when the terminal device needs to perform cell switching, cell switching may be performed based on L1 or L2, or cell switching may be performed based on layer 3. Cell handover based on the L1 layer/L2 layer generally refers to a procedure of handover through MAC CE or DCI. Specifically, reference may be made to the following technical schemes of fig. 5 or fig. 6. Cell handover based on the L3 layer refers to a procedure of handover through RRC. Specifically, reference may be made to the following technical scheme of fig. 7.

The terminal is an entity on the user side for receiving or transmitting signals. For example, the terminal device may be a mobile terminal, a handset, a sensor with network access function, etc. A terminal device in this application may also be referred to as a terminal, user Equipment (UE), access terminal, subscriber unit, subscriber station, mobile station, remote terminal, mobile device, user terminal, wireless communication device, user agent, or user equipment. The terminals in the embodiments of the present application may be mobile phones (mobile phones), tablet computers (pad), unmanned aerial vehicles, computers with wireless transceiving functions, customer premise equipment (customer premise equipment, CPE), virtual Reality (VR) terminals, augmented reality (augmented reality, AR) terminals, wireless terminals in industrial control (industrial control), wireless terminals in unmanned aerial vehicles (self driving), wireless terminals in telemedicine (remote media), wireless terminals in smart grid (smart grid), wireless terminals in transportation security (transportation safety), wireless terminals in smart city (smart city), wireless terminals in smart home (smart home), cellular phones, cordless phones, session initiation protocol (session initiation protocol, SIP) phones, wireless local loop (wireless local loop, WLL) stations, personal digital assistants (personal digital assistant, PDA), handheld devices with wireless communication functions, computing devices or other processing devices connected to wireless modems, wireless terminals in smart media (remote media), wireless terminals in smart home (transportation safety), wireless terminals in smart city (smart home), wireless terminals in smart home (smart home), wireless phones, cordless phones, session Initiation Protocol (SIP) phones, wireless Local Loop (WLL) terminals, wireless local area phones, wireless terminals in future-mode or other wireless terminals.

For another example, the terminal device in the present application may be an express terminal in smart logistics (e.g., a device that can monitor the position of a cargo vehicle, a device that can monitor the temperature and humidity of the cargo, etc.), a wireless terminal in smart agriculture (e.g., a wearable device that can collect data related to livestock, etc.), a wireless terminal in smart architecture (e.g., a smart elevator, a fire monitoring device, and a smart meter, etc.), a wireless terminal in smart medical (e.g., a wearable device that can monitor the physiological state of a person or animal), a wireless terminal in smart transportation (e.g., a smart bus, a smart vehicle, a sharing bicycle, a charging pile monitoring device, a smart traffic light, and a smart monitoring and parking device, etc.), a wireless terminal in smart retail (e.g., a vending machine, a self-service checkout machine, and an unmanned convenience store, etc.). For another example, the terminal device in the present application may be an in-vehicle module, an in-vehicle component, an in-vehicle chip, or an in-vehicle unit that is built in a vehicle, and the method provided in the present application may be implemented by the in-vehicle module, the in-vehicle component, the in-vehicle chip, or the in-vehicle unit. The terminal equipment in the application can be intelligent internet of things (smart internet of things, SIoT) terminal equipment or non-SIoT terminal equipment, and has certain computing and storage capabilities. The non-SIoT terminal device may collect data through the gateway of the internet of things, for example, the non-SIoT terminal device may be a terminal with limited computing power, such as a sensor with a single function, etc. Alternatively, the SIoT terminal device may be built in with a data proxy network element, or the SIoT terminal device may implement the function of the data proxy network element.

It should be appreciated that fig. 1 is a simplified schematic diagram that is merely illustrative for ease of understanding, and that other devices may be included in the communication system, e.g., as shown in fig. 2, and that a core network may also be included. The core network may be a 5G core network (5G core,5 gc). The gNB may be communicatively coupled to the 5GC via a NG interface.

It should be noted that, the communication method provided in the embodiment of the present application may be applied to the communication systems shown in fig. 1 to 3, and specific implementation may refer to the following method embodiments, which are not described herein again.

It should be noted that the solution in the embodiments of the present application may also be applied to other communication systems, and the corresponding names may also be replaced by names of corresponding functions in other communication systems.

In a specific implementation, each device shown in fig. 1 or fig. 2, such as a terminal and a network device, may adopt the constituent structure shown in fig. 4 or include the components shown in fig. 4. Fig. 4 is a schematic diagram of a composition of a communication apparatus 400 provided in an embodiment of the present application, where the communication apparatus 400 has a function of a terminal device described in an embodiment of the present application, the communication apparatus 400 may be a terminal device or a chip or a system on a chip in the terminal device. When the communication apparatus 400 has the function of the network device described in the embodiments of the present application, the communication apparatus 400 may be a network device or a chip or a system on a chip in the network device. As shown in fig. 4, the communication apparatus 400 includes a processor 401, a communication interface 402, and a communication line 403.

Further, the communication device 400 may also include a memory 404. The processor 401, the memory 404, and the communication interface 402 may be connected by a communication line 403.

The processor 401 is a central processing unit (central processing unit, CPU), a general purpose processor network processor (network processor, NP), a digital signal processor (digital signal processing, DSP), a microprocessor, a microcontroller, a programmable logic device (programmable logic device, PLD), or any combination thereof. The processor 401 may also be any other device having a processing function, such as a circuit, a device, or a software module, without limitation.

A communication interface 402 for communicating with other devices or other communication networks. The other communication network may be an ethernet, a radio access network (radio access network, RAN), a wireless local area network (wireless local area networks, WLAN), etc. The communication interface 402 may be a module, a circuit, a communication interface, or any device capable of enabling communication.

Communication line 403 for transmitting information between the components included in communication device 400.

Memory 404 for storing instructions. Wherein the instructions may be computer programs.

The memory 404 may be, but is not limited to, a read-only memory (ROM) or other type of static storage device capable of storing static information and/or instructions, a random access memory (random access memory, RAM) or other type of dynamic storage device capable of storing information and/or instructions, an EEPROM, a CD-ROM (compact disc read-only memory) or other optical disk storage, an optical disk storage (including compact disk, laser disk, optical disk, digital versatile disk, blu-ray disk, etc.), a magnetic disk storage medium or other magnetic storage device, etc.

It is noted that the memory 404 may exist separately from the processor 401 or may be integrated with the processor 401. Memory 404 may be used to store instructions or program code or some data, etc. The memory 404 may be located within the communication device 400 or may be located outside the communication device 400, without limitation. A processor 401 is configured to execute instructions stored in a memory 404 to implement the time-slot-free measurement method provided in the following embodiments of the present application.

In one example, processor 401 may include one or more CPUs, such as CPU0 and CPU1 in fig. 4.

As an alternative implementation, the communication apparatus 400 includes a plurality of processors, for example, the processor 407 may be included in addition to the processor 401 in fig. 4.

As an alternative implementation, the communication apparatus 400 further comprises an input device 405 and an output device 406. Illustratively, the input device 405 is a keyboard, mouse, microphone, or joystick device, and the output device 406 is a display screen, speaker (spaker), or the like.

It should be noted that the communication apparatus 400 may be a desktop computer, a portable computer, a web server, a mobile phone, a tablet computer, a wireless terminal, an embedded device, a chip system, or a device having a similar structure as in fig. 4. Furthermore, the constituent structure shown in fig. 4 does not constitute a limitation of the terminal device, and the terminal device may include more or less components than those shown in fig. 4, or may combine some components, or may be arranged in different components, in addition to those shown in fig. 4.

In the embodiment of the application, the chip system may be formed by a chip, and may also include a chip and other discrete devices.

Further, actions, terms, etc. referred to between embodiments of the present application may be referred to each other without limitation. In the embodiment of the present application, the name of the message or the name of the parameter in the message, etc. interacted between the devices are only an example, and other names may also be adopted in the specific implementation, and are not limited.

The terms first, second, third and the like in the description and in the claims and in the above drawings are used for distinguishing between different objects and not necessarily for describing a particular sequential or chronological order.

In the embodiments of the present application, words such as "exemplary" or "such as" are used to mean serving as examples, illustrations, or descriptions. Any embodiment or design described herein as "exemplary" or "for example" should not be construed as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "such as" is intended to present related concepts in a concrete fashion.

The communication method provided in the embodiment of the present application is described below with reference to the communication system shown in fig. 1 or fig. 2. The network device and the terminal device described in the following embodiments may be provided with the components shown in fig. 4, which are not described in detail. In the embodiment of the present application, the name of the message or the name of the parameter in the message, etc. interacted between the devices are only an example, and other names may also be adopted in the specific implementation, and are not limited. The actions involved in the embodiments of the present application are just an example, and other names may be used in specific implementations, for example: the "carried on" in the embodiments of the present application may also be replaced by "carried on" or "included on" or the like.

In a scenario, when performing cell handover based on the L3 layer, a network device adjacent to a source network device currently accessed by a terminal device is one, as shown in fig. 5, and the communication method includes the following steps:

s501, the source network device sends measurement configuration information to the terminal device. Correspondingly, the terminal device receives measurement configuration information from the source network device.

For example, the measurement configuration information may be used to instruct the terminal device to measure the measurement object. The measurement configuration information may include one or more types of parameters: the method comprises the steps of measuring objects, reporting configuration, measuring identification, measuring quantity configuration, measuring interval or S measuring configuration. The measurement object provides an object list, and the terminal device performs measurement on the objects of the list.

The reporting configuration provides a reporting configuration list, and each measurement object can have one or more reporting configurations. The reporting configuration may include reporting criteria, reporting format, reference signal type, etc.

The measurement identifiers provide a measurement identifier list, wherein each measurement identifier is associated with a measurement object with a reporting configuration, and the terminal device can include the corresponding measurement identifier in the measurement report triggered to report as a reference to the network.

The measurement quantity configurations may be different measurement quantities, for example, the measurement parameters may include RSRP, reference signal received quality (reference singnal received quality, RSRQ), and different filter coefficients for each cell and each beam measurement.

The S measurement configuration is used to control a special cell (SpCell) RSRP measurement threshold when the terminal device performs measurement on the non-serving cell. The SpCell may include a primary cell (PCell) or a secondary primary cell (primary secondary cell, PSCell).

Wherein the measurement interval represents a period of time that the terminal device is likely to be used to perform the measurement.

S502, the terminal equipment sends a measurement report to the source network equipment.

The terminal device can measure according to the measurement configuration to obtain a measurement report, and send the measurement report to the source network device. Correspondingly, the source network device receives the measurement report from the terminal device.

For example, the terminal device performing measurement according to the measurement configuration may refer to the terminal device performing measurement on the signal quality of the cell provided by the measurement object. The measurement report may include the measurement quantity type (e.g., RSRP/RSRQ, etc.) and measurement results for the cell and/or beam, as well as other relevant information such as the maximum number of cells that can be reported and the maximum number of beams per cell, etc.

S503, the source network device performs switching judgment.

Optionally, the source network device refers to the measurement report to make a handover decision. The handover decision is used to determine that the terminal device performs handover to the target network device, or the handover decision is used to determine that the terminal device performs handover to the target cell. The target cell is a cell under the target network device.

In one example, the source network device may determine that the terminal device is handed over to the target network device based on the measurement object in the measurement report and the measurement result of the measurement quantity.

For example, when the RSRP of the target cell of the target network device in the measurement report is greater than or equal to the preset threshold, the source network device determines that the terminal device may perform handover to the target network device. When the RSRP is less than the preset threshold, the source network device may determine that the terminal device cannot perform handover to the target network device. The preset threshold may be set as desired, for example, may be 90 decibel milliwatts (dbm), 100dbm, etc., without limitation.

S504, the source network device sends a switching request message to the target network device.

The source network device determines that the terminal device can switch to the target network device. The source network device sends a handover request message to the target network device. Accordingly, the target network device receives the handover request message from the source network device.

The handover request message may be used to request handover of the terminal device to the target network device. For example, the handover request message may include information related to handover preparation. For example, the handover preparation related information may include one or more of an identity of the target cell, a key, an identity of the terminal device at the source cell, or an access stratum configuration.

The source cell of the terminal equipment is a cell of the source network equipment. The source network device may assign an identity of the source cell to the terminal device. The same terminal device may have different identities under different cells. The access stratum configuration may include configuration information required for the terminal device to switch to the target network device. For example, random access resources, access layer related information may be included.

S505, the target network device performs admission control.

Admission control may refer to, among other things, a target network device determining whether to allow or disallow a terminal device to handover to a target cell under the target network device. For example, the target network device may determine to allow handover of the terminal device based on configuration information of the target network device. For example, the configuration information of the target network device may include a bearer capability of the target network device, a bandwidth usage situation, and the like.

S506, the target network device sends a switching request response message to the source network device.

The target network equipment performs switching preparation and sends a switching request response message to the source network equipment.

The handover preparation may refer to a preparation performed by the target network device for handover of the terminal device to the target cell. For example, the terminal device may be assigned an identity, random access channel (random access channel, RACH) resources, cell group configuration information for the access target cell, etc. The handover request acknowledgement message may be used to instruct the target network device to allow handover of the terminal device.

S507, the source network device sends a switching command to the terminal device. Correspondingly, the terminal device receives a handover command from the source network device.

Wherein the handover command is generated by the target network device and transmitted through the source network device (specifically, may be sent through an RRC reconfiguration message containing synchronization information). The source base station may perform the necessary encryption and integrity protection for the message. The handover command includes information needed for accessing the target cell, for example, at least including the target cell identifier, the new UE ID, the security algorithm identifier of the target base station, and possibly carrying dedicated random access channel (Random Access Channel, RACH) resources for accessing the target cell, etc.

In one example, the source network device may also send SN (sequence number) status information to the target network device upon receiving the handover request acknowledgement message. The SN status information may be used to indicate data information transmitted by the source network device to the terminal device.

S508, the terminal equipment receives the switching command and performs synchronization with the target network equipment.

Wherein the synchronization of the terminal device with the target network device may be used to ensure communication synchronization after a successful handover of the terminal device to the target network device.

In one example, a terminal device may send a random access preamble to a target network device. The target network device, after receiving the random access preamble from the terminal device, may send a random access response (random access response, RAR) for resource allocation and timing advance.

S509, the terminal device sends RRC reconfiguration complete information to the target network device. Correspondingly, the target network device receives the RRC reconfiguration complete message from the terminal device.

The RRC reconfiguration complete message may be used to indicate that the terminal device switches to the target network device, and may be accompanied by an uplink buffer status report (buffer status report, BSR). The target network device confirms that the handover procedure is successful by receiving the RRC reconfiguration complete message. To this end, the target base station may begin transmitting data to the terminal.

S510, the target network device sends a path conversion request message to the core network. Accordingly, the core network receives the path switch request message from the target network device.

The interaction between the target network device and the core network in S510 may be an interaction between the target network device and a network element in the core network. For example, interaction of the target network device with the authentication management function (Authentication Management Function, AMF), user plane function (User Plane Function, UPF) may be provided.

In one example, the above S510 may be implemented through the following procedure.

And step 11, the target network equipment sends a path conversion request message to the AMF. Accordingly, the AMF receives the path switch request message from the target network device.

The path switching request message may be used to request a handover path or the terminal device changes cells. The path switch request may trigger a core network (5 GC) to switch a Downlink (DL) data path to the target network device and establish an NG-C interface to the target network device. The switching of the air interface has been successfully completed at this time.

Step 12, the AMF sends a User Plane (UP) update request message to the UPF. Accordingly, the UPF receives the UP update request message from the AMF.

Step 13, the UPF switches the DL data path to the target network device and sends one or more end marks to the source cell, and then the UP resources or transport network layer resources between the source cell and the source network device can be released.

Step 14, the UPF sends an UP update response message to the AMF. Accordingly, the AMF receives the UP update response message from the UPF.

And step 15, the AMF sends a path switching ACK message to the target network equipment.

And step 16, after receiving the path conversion ACK message, the target network equipment sends a UE context release message to the source network equipment, informs the source network equipment that the switching is successful and triggers the source network equipment to release the UE context.

In step 17, after receiving the UE context release message, the source network device may release the radio bearer and Control Plane (CP) resources related to the UE context.

If the data forwarding is not completed, the source network device does not release the related resources, and continues the data forwarding until the data forwarding is completed and then releases the related resources.

Based on the technical scheme of fig. 5, when switching is performed based on the L3 layer, the source network device may implement switching of the terminal device through interaction with the target network device and interaction with the terminal device.

In yet another scenario, in the L3 layer based handover procedure, the terminal device is performing a cell handover, which may be performed through a random access channel (RACH-less). Fig. 6 is an exemplary flowchart of RACH-less access provided in an embodiment of the present application. The method may include the following steps.

S601, the terminal equipment sends a measurement report to the source network equipment.

The measurement report may be obtained by the terminal device performing measurement based on a measurement configuration of the network device. Specifically, reference may be made to S501 and S502 described above.

S602, the source network equipment performs switching judgment according to the measurement report.

Herein, S602 may refer to S503, and is not described herein.

S603, the source network device sends switching request information to the target network device. Accordingly, the target network device receives the handover request information from the source network device.

The switching request information may refer to the description of S504, and will not be described herein.

S604, the target network device may perform admission control when receiving a handover request message from the source network device.

S605, the target network device sends a switching request confirmation message to the source network device. Accordingly, the source network device receives a handover request acknowledge message from the target network device.

Wherein the handover request confirm message may be used to indicate that the target network device allows handover of the terminal device. For example, the handover request confirm message may include information of a cell radio network temporary identity (cell radio network temporary identifier, C-RNTI), a security algorithm, random access channel (random access channel, RACH) resources, access layer configuration, system message blocks (system information block, SIBs), and the like.

In one example, when the target network device configures RACH-less handover, the handover request confirm message may also include a timing adjustment indication and/or uplink grant information. Wherein RACH-less means that random access is not performed in the handover procedure of the terminal device. The uplink grant may be used to indicate uplink resources. The uplink resource may be used to carry information/data sent by the terminal device to the target network device. The target network device configuring RACH-less handover may be that the target network device instructs the terminal device to skip the random access procedure.

S606, the target network equipment generates an RRC reconfiguration complete message and sends the RRC reconfiguration complete message to the terminal equipment through the source network equipment.

The RRC reconfiguration complete message may refer to the description of S509, and will not be described again.

In one example, the RRC reconfiguration message may also include a timing advance adjustment indication when the target network device is configured with RACH-less handover.

In yet another example, the RRC reconfiguration complete message may or may not include an uplink grant.

S607, the terminal equipment receives the RRC reconfiguration message and executes the switching.

In an example, when the RRC reconfiguration complete message includes information of the configured uplink grant resources, the terminal device may perform uplink transmission on the configured uplink grant resources, and access the target network device. When the RRC reconfiguration complete message does not include information of the configured uplink grant resources, the terminal device may receive the uplink grant by monitoring a physical downlink control channel (physical downlink control channel, PDCCH) of the target network device, and access the target network device through the received uplink grant resources.

In yet another example, if the target network device configures RACH-less handover, the terminal device sends an RRC reconfiguration complete message to the target network device through the pre-configured uplink grant resources or the dynamically scheduled uplink grant resources. The dynamically scheduled uplink grant resource may refer to an uplink grant resource received by the terminal device through monitoring the PDCCH of the target cell.

After receiving the RRC reconfiguration complete message, the target network device can interact with the core network to realize data path switching and air interface switching between the target network device and the core network. Specifically, reference may be made to the description of S510 above, and details are not repeated.

Based on the technical solution of fig. 6, in the RACH-less handover process based on the L3 layer, the source network device may interact with the target network device, so that the target network device may accurately know that the terminal device will perform handover to the target network device. Therefore, the target network device can accurately allocate uplink grant for the terminal device or accurately determine the time for dynamically scheduling the uplink grant.

In yet another scenario, based on Layer 1 or Layer 2 (Layer 1/Layer 2, L1/L2) handover, L1/L2 handover is relative to L3RRC handover, which means that the handover procedure is completed by a MAC Control Element (CE) or downlink control information (downlink control information, DCI), the gain of which is to reduce the delay of access, thereby reducing interruption of traffic and reducing signaling overhead.

In connection with the communication system shown in fig. 2, an inter-DU handover may refer to a handover of a terminal device from a cell of a source DU to a cell of a target DU, or to a handover of a terminal device from a source DU to a target DU. As shown in fig. 7, the method may include the steps of:

S701, the CU sends measurement configuration information to the terminal device. Correspondingly, the terminal device receives measurement configuration information from the CU.

The measurement configuration information may be used to instruct the terminal device to measure multiple target cells (e.g. one or more cells of the target DU1, one or more cells of the target DU 2). Specifically, reference may be made to the description of the measurement configuration information in S501, which is not repeated.

S702, the terminal equipment reports a measurement report to the CU.

Wherein the measurement report is used to assist the CU in making handover decisions and determination of candidate cells.

Wherein the measurement report may include measurements of one or more cells of each of the plurality of candidate DUs. Specifically, reference may be made to the description of S502 above, and details are not repeated.

S703, the CU transmits a handover request message or a candidate cell addition request to one or more candidate DUs (including the target DU).

Herein, S703 may refer to the description of S504, and will not be described herein.

For any one of the one or more candidate DUs, the candidate DU may perform S704 and S705 described below.

S704, the candidate DU performs handover admission control upon receiving a handover request message from the CU.

Here, S704 may refer to the description of S505, and will not be described herein.

S705, the candidate DU sends a handover request confirm message to the CU.

In S705, reference may be made to the description of S506 above, which is not repeated.

S706, the CU sends L1/L2 switching pre-configuration information to the terminal equipment.

The L1/L2 handover pre-configuration information may include a plurality of candidate cells and configuration information of the plurality of candidate cells. The L1/L2 pre-configuration information may be included in the RRC reconfiguration message. And after receiving the L1/L2 pre-configuration information, the UE continues to keep data transmission with the source cell. The UE may perform measurements according to the configuration of the network device, assisting the network device in making handover decisions.

S707, the source DU sends an L1/L2 switching command to the terminal equipment. Correspondingly, the terminal device receives an L1/L2 handover command from the source DU.

The L1/L2 handover command is used to instruct the terminal device to handover to the target cell under the target DU, or may be used to instruct the terminal device to complete cell change through L1/L2 handover. Specifically, S707 may refer to S507 described above, and will not be described again. Further, S707 and S507 are different: in S507, a handover command based on L3 (e.g., RRC reconfiguration message), and in S707, a L1/L2 handover command (e.g., MAC CE or DCI).

S708, the terminal equipment executes a random access procedure or a RACH-less procedure to establish connection with the target cell.

Optionally, the terminal device disconnects the data transmission with the source cell after receiving the L1/L2handover command.

Herein, S708 may refer to S508 to S509 described above, and will not be described in detail.

S709, after the terminal equipment establishes connection with the target DU, the terminal equipment performs data transmission with the target DU.

In one example, when the terminal device needs to perform a continuous L1/L2handover (sub sequence L1/L2 handover), the terminal device does not need to release the L1/L2 pre-configuration information after completing access of the target DU once. In this way, the terminal device can continue to switch according to the L1/L2 pre-configuration information.

S710, the CU executes path switching.

Optionally, the CU performs data path switching.

The CU sends a path switching request to the core network. S710 may refer to the description of S510, and will not be repeated.

The execution order of S709 and S710 is not limited. S709 may be performed first, and S710 may be performed later. Alternatively, S710 may be performed first, and S709 may be performed second.

Based on the technical scheme of fig. 7, the terminal device configures a plurality of candidate DUs, and the terminal device can complete cell handover according to the L1/L2 candidate cell configuration information.

Besides the above-mentioned L1/L2handover between DUs, there is also an L1/L2handover within DUs, i.e. the handover target cell and the source cell belong to the same DU, and the source DU and the target DU in FIG. 7 are replaced with the source cell and the target cell, respectively.

As can be seen from the RACH-less handover procedure based on the L3 layer in fig. 6, the source network device may interact with the target network device in time before issuing the handover command, and the configuration information of the target cell is issued in the handover command, so that the target network device may accurately determine that the terminal device is about to be handed over to the target network. Therefore, the target network device can accurately configure the pre-configured authorization for the terminal device or accurately determine the time for dynamically scheduling the uplink authorization. In addition, the target network device includes an indication of skipping the RACH in the handover command, and timing advance information and uplink grant resources of the target cell enable the terminal device to accurately determine uplink resources for transmitting the handover completion message.

But this approach is not applicable to L1/L2 based handover procedures. For an L1/L2 based handover procedure, the pre-configured grant is pre-configured when one or more candidate cells under one or more candidate DUs are configured for the terminal device. When the pre-configuration grant is a periodic configuration resource, if each candidate cell reserves the pre-configuration grant resource for the terminal device, resource waste is caused. In addition, since the L1/L2 handover command is issued to the terminal device by the source DU, the candidate DU (including the target DU) does not know when the terminal device will be handed over to the candidate DU. If the source DU issues an L1/L2 handover command indicating that the terminal device is handed over to a target cell of a target DU (one of the candidate DUs), the target DU needs to schedule grant resources for the terminal device by dynamic scheduling if a pre-configured grant is not configured or cannot be used for the target cell, but the target DU cannot determine when the source DU transmits a handover command to the terminal device and when the terminal device is handed over to the target DU. Because the target DU cannot determine the time of performing dynamic scheduling, the terminal device cannot accurately determine the time of monitoring the dynamic scheduling resource of the target DU, and the terminal device cannot be aligned with the target DU.

In view of this, the embodiment of the application provides a communication scheme, and the method is used for an L1/L2 handover process, if the handover is not performed in a random access process, the terminal device determines uplink resources for sending a handover complete message, and the terminal device determines to monitor a physical downlink control channel of a target cell, so that power consumption of the terminal device is saved, and alignment between the terminal device and a target DU is ensured. The method comprises the following steps: the first network device transmits indication information for indicating information of the target cell to the second network device and the terminal device, respectively. After receiving the indication information, the terminal device may send a message indicating that the handover is completed to the second network device according to the pre-configuration authorization. The second network device also receives a message from the terminal device indicating the completion of the handover according to the indication information of the first network device.

In an application scenario, a first network device is a source DU and a second network device is a target DU. The target DU and the terminal equipment can accurately determine the target cell switched by the terminal equipment according to the indication information. The problem that the terminal equipment and the target DU cannot be aligned is avoided.

The method provided in the embodiment of the present application is described below with reference to the communication system of fig. 2.

As shown in fig. 8, the method may include S801 to S804.

S801, the first network device sends second indication information to the second network device. Accordingly, the second network device receives the second indication information from the first network device.

Wherein the first network device and the second network device may be DUs in fig. 2. The first network device and the second network device may be identical, e.g. both are DU1 in fig. 2, in this case cell handover within the same DU. The first network device and the second network device may also be different, for example, the first network device may be DU1 in fig. 2 and the second network device may be DU2 in fig. 2.

The second indication information may be used to indicate information of a target cell for handover of the terminal device. For example, the first indication information may include an identification of the target cell.

The target cell is a cell of the second network device. The target cell may be a cell of the configured plurality of candidate cells. The plurality of candidate cells may include a cell of a first network device, a cell of a second network device, or a cell of another network device.

In one example, for ease of management, the first network device may divide the plurality of candidate cells into a plurality of candidate cell groups.

For example, as shown in fig. 9, the plurality of candidate cells may include cell 1 to cell 7. The terminal equipment is located in the coverage area of cell 1. And the cells 2 to 7 are candidate cells. Wherein cell 2, cell 3 and cell 4 belong to candidate cell group 1. Cell 5 and cell 6 belong to candidate cell group 2. Cell 7 belongs to candidate cell group 3.

In yet another example, before sending the second indication information to the second network device, in order to ensure that the terminal device is switched, the first network device reduces the delay of access, thereby reducing interruption of service and reducing signaling overhead, and the first network may configure one or more candidate network devices for the terminal device, and configure one or more cells of the one or more candidate network devices as candidate cells.

For example, the first network device may determine one or more candidate network devices (i.e., the second network device may be a network device of the one or more candidate network devices) according to one or more of deployment conditions of the network devices, topology information of the network devices, and movement trajectories of the terminal devices, and configure one or more cells of the one or more candidate network devices as candidate cells. The one or more candidate network devices may include the first network device and/or other network devices.

The deployment situation of the network device may include the network device, coverage of a cell of the network device, a distance between the network devices, and the like. The topology information of the network device may refer to networking information between nodes. For example, the topology information of the network devices may include identification of the network devices, link information between the network devices, and the like. The deployment situation and topology information of the network device may be preconfigured for the first network device, or may be obtained from other devices for the first network device. For example, the first network device may be acquired from a core network. For another example, when the first network device is a DU, the first network device may also obtain from the corresponding CU, without limitation.

For example, when a coverage area of a certain network device has an overlapping area with a coverage area of a first network device, or a distance between the network device and the first network device is smaller than a preset distance, the first network device may regard the network device as a candidate network device. The preset distance may be 50 meters, 60 meters, etc., without limitation.

For another example, the first network device may consider a certain network device as a candidate network device when the network device is in the same topology as the first network device or the network device has a direct link with the first network device.

For another example, when the movement track of the terminal device is a road a, the first network device may be a network device having a distance from the road a smaller than a preset distance, as a candidate network device.

Further, the first network device may also send a handover request to the one or more candidate network devices after determining the one or more candidate network devices. The candidate network device may perform access control after receiving the handover request and transmit handover request acknowledgement information to the first network device. The first network device may determine candidate network devices allowing the terminal device to switch according to the handover request acknowledgement information of the one or more candidate network devices. Specifically, reference may be made to the embodiment of fig. 7, which is not described in detail.

In yet another example, the terminal device sends a measurement report to the first network device, which may be an L1 measurement report, for example. The measurement report assists the first network device in determining a target cell from a plurality of candidate cells. Specifically, reference may be made to the description of the above embodiments, and details are not repeated.

In yet another example, in some handovers, the serving cell of the terminal device is unchanged, but the beam information of the corresponding serving cell of the terminal device is changed. That is, the target cell may be a serving cell of the terminal device.

In an application scenario, the first network device is a first DU and the second network device is a second DU. The first DU and the second DU may be the same DU or different DUs. When the first DU and the second DU are different DUs, the first DU and the second DU may correspond to the same CU. For example, as shown in fig. 2, the first DU may be DU1 and the second DU may be DU2. The CU corresponding to the first DU and the second DU is the CU in fig. 2.

In a possible implementation manner, in connection with the application scenario described above, the first network device (or the first DU) may send the first indication information to the second network device (or the second DU) through the CU.

S802, the first network equipment sends first indication information to the terminal equipment.

Correspondingly, the terminal device receives the first indication information from the first network device.

The first indication information may be used to indicate information of a target cell for handover of the terminal device. For example, the first indication information may be a handover command in the above-described embodiment. That is, the first indication information may also be used to instruct the terminal device to handover to the target cell. For example, the first indication information may include an identification of the target cell. The target cell may be a cell of a plurality of candidate cells configured by the terminal device before receiving the first indication information.

In one example, when the target cell is a cell of the candidate cell group, the first indication information may further include group information of the candidate cell group. For example, the group information may include an identification of the candidate cell group, an identification of each candidate cell included in the candidate cell group, and the like.

In a possible implementation manner, if the method is applied in an L1/L2 based handover procedure, the first indication information may be carried in a MAC CE or DCI. The first indication information may be a separate signaling, which is not limited.

It should be noted that, the first network device may execute S801 described above first, and then execute S802. S802 may be executed first, and S801 may be executed later. Alternatively, the first network device may perform the above S801 and S802 synchronously, without limitation.

S803, the terminal equipment determines uplink resources for sending a message indicating that the switching is completed according to the configuration condition of the first pre-configuration authorization of the target cell, and sends the message indicating that the switching is completed on the uplink resources.

The first pre-configuration authorization may also be referred to as configuration authorization or configuration authorization. The first pre-configuration authorization is pre-configured for the second network device for the terminal device.

The uplink resource may be used for the terminal device to send a message indicating that the handover is completed to the second network device. The message indicating the completion of the handover is a handover completion message for indicating the terminal device to handover to the target cell, or a synchronization completion message for indicating the terminal device to complete synchronization with the target cell. The message indicating completion of the handover may be carried in a MAC CE or DCI, for example, may be a 1-bit indication information in the handover-completed MAC CE or DCI.

Wherein, the uplink resource may be a first pre-configured grant. The first pre-configured grant may also be referred to as a first pre-configured grant resource.

The configuration condition of the first pre-configuration authorization may include that the terminal device configures the first pre-configuration authorization or that the terminal device does not configure the first pre-configuration authorization.

The configuration information of the first pre-configuration authority may be configured in the L1/L2 pre-configuration information, for example, configured in S706. It is also understood that the first pre-configured grant is configured during the candidate cell configuration procedure, e.g. S703-S706. The first pre-configuration grant of the terminal device for the handover target cell is configured when the target cell is configured as a candidate cell. The configuration information of the first pre-configuration grant includes time domain information, frequency domain information, period, etc. of the first pre-configuration grant. For example, if the first pre-configured grant is configured as a periodic resource, it may include one or more opportunities.

In one possible implementation manner, if the terminal device configures the first pre-configuration authorization and the first pre-configuration authorization is valid, the terminal device may determine that an uplink resource that sends a message indicating that handover is completed is an uplink resource indicated by the first pre-configuration authorization.

The configuration of the first pre-configuration authorization by the terminal device may also be described as the second network device pre-configuring the first pre-configuration authorization for the terminal device. For example, after receiving the second indication information of the first network device, if the second network device allows the access of the terminal device, the second network device may configure the first pre-configuration authorization for the terminal device and send a message indicating the first pre-configuration authorization to the first network device. For example, the message indicating the first pre-configuration grant may be carried in the handover request confirm information, or may be separate signaling. The first network device may forward the message indicating the first pre-configured grant to the terminal device after receiving the message indicating the first pre-configured grant. For example, the message for indicating the first pre-configuration authorization may be carried in the measurement configuration information of S801, or may be a separate signaling, which is not limited.

In one example, the first pre-configured grant validity may include one or more of the following: the RSRP of the SSB associated with the first pre-configured grant is above a first pre-set threshold, the first pre-configured grant does not overlap PRACH resources, and the first pre-configured grant does not overlap msgA PUSCH resources. The first preset threshold may be configured by the network or a preset threshold.

For example, if the terminal device configures the first pre-configuration grant and the RSRP of the SSB associated with the first pre-configuration grant is higher than a preset threshold, or the first pre-configuration grant does not overlap the PRACH resource, or the first pre-configuration grant does not overlap the msgmappsch resource, the terminal device may determine that the uplink resource that sends the message indicating that the handover is completed is the first pre-configuration grant resource.

For another example, if the terminal device configures the first pre-configured grant, and the RSRP of the SSB associated with the first pre-configured grant is higher than the preset threshold, and the first pre-configured grant does not overlap the PRACH resource, the terminal device may determine that the uplink resource that sends the message indicating that the handover is completed is the first pre-configured grant.

For another example, if the terminal device configures the first pre-configuration grant, and the RSRP of the SSB associated with the first pre-configuration grant is higher than the preset threshold, and the first pre-configuration grant and the msgA PUSCH resource do not overlap, the terminal device may determine that the uplink resource that sends the message indicating that the handover is completed is the first pre-configuration grant.

For another example, if the terminal device configures the first pre-configuration grant, and the first pre-configuration grant does not overlap the PRACH resource, and the first pre-configuration grant does not overlap the msgA PUSCH resource, the terminal device may determine that the uplink resource that sends the message indicating that the handover is completed is the first pre-configuration grant.

For another example, if the terminal device configures the first pre-configuration grant, and the RSRP of the SSB associated with the first pre-configuration grant is higher than the preset threshold, and the first pre-configuration grant does not overlap the PRACH resource, and the first pre-configuration grant does not overlap the msgAPUSCH resource, the terminal device may determine that the uplink resource that sends the message indicating that the handover is completed is the first pre-configuration grant resource.

In yet another possible implementation, if the first pre-configured grant is not a periodic resource, for example, it may be understood that the first pre-configured grant corresponds to a time-frequency resource, or to a pre-configured grant occasion. The terminal device configures the first pre-configuration grant, the first pre-configuration grant is valid, and the offset between the time domain position of the first indication information received by the terminal device and the time domain position of the first pre-configuration grant is smaller than a second preset threshold, the terminal device can determine that the uplink resource sending the message indicating the completion of the handover is the uplink resource indicated by the first pre-configuration grant. In particular, reference may be made to the following description of embodiments, which are not repeated here.

In another possible implementation, if the first pre-configured grant is a periodic resource, it may be understood that the first pre-configured grant corresponds to a plurality of time-frequency resources, or to a plurality of pre-configured grant occasions, for example. The terminal device configures the first pre-configuration grant, the first pre-configuration grant is valid, and the offset between the time domain position of the first occasion when the terminal device receives the first indication information and the time domain position of the first occasion when the first pre-configuration grant is smaller than the second pre-set threshold, the terminal device can determine that the uplink resource sending the message indicating that the switching is completed is the uplink resource indicated by the first pre-configuration grant.

In another possible implementation manner, if the terminal device does not configure the first pre-configuration grant or the first pre-configuration grant is invalid, the terminal device may monitor the PDCCH of the target cell for indicating the second uplink grant resource, and at this time, the terminal device sends a message for indicating that the handover is completed to the second network device, where the message uplink resource is the second uplink resource. In particular, reference may be made to the following description of embodiments, which are not repeated here. The second preset threshold may be network configured or a preset threshold.

In another possible implementation manner, the terminal device does not configure the first pre-configuration grant, or the first pre-configuration grant is invalid, or the offset (may also be referred to as an offset value) between the time domain position of the first indication information and the time domain position of the first pre-configuration grant received by the terminal device is greater than or equal to a second preset threshold, the terminal device monitors the PDCCH of the target cell for indicating the second uplink grant resource, and the terminal device may determine that the uplink resource sending the message indicating that the handover is completed is the second uplink grant resource. In particular, reference may be made to the following description of embodiments, which are not repeated here.

In another possible implementation, if the first pre-configured grant is a periodic resource, it may be understood that the first pre-configured grant corresponds to a plurality of time-frequency resources, or to a plurality of pre-configured grant occasions, for example. The terminal equipment does not configure the first pre-configuration grant, or the first pre-configuration grant is invalid, or the offset between the time domain position of the first indication information received by the terminal equipment and the time domain position of the first opportunity of the first pre-configuration grant is larger than or equal to a second preset threshold, and the terminal equipment monitors the PDCCH of the target cell for indicating the second uplink grant resource. In this way, the terminal device may determine that the uplink resource that transmits the message indicating that the handover is completed is the second uplink grant resource. Reference may be made to the following description of embodiments, which are not repeated here.

S804, the second network device receives a message from the terminal device indicating that the switching is completed.

In a possible implementation manner, the second network device detects an uplink message of the terminal device. For example, the second network device detects a message from the terminal device indicating that the handover is complete on the first pre-configured grant and/or the second network device detects a message from the terminal device indicating that the handover is complete on the second uplink resource. Optionally, the second network device starts to detect a message from the terminal device indicating that the handover is completed after receiving the second indication information from the first network device.

In a possible implementation manner, the second network device receives a message indicating that the handover is completed from the terminal device on the uplink resource according to the configuration condition of the first pre-configuration grant.

The configuration of the first pre-configuration grant may include the second network device configuring the first pre-configuration grant for the terminal device or the second network device not configuring the first pre-configuration grant for the terminal device. The second network device configures a first pre-configured grant for the terminal device, and the uplink resource may include the first pre-configured grant. The second network device does not configure the first pre-configured grant for the terminal device, and the uplink resource is a grant resource dynamically scheduled by the second network device.

In a possible implementation, the second network device configures the first pre-configured authorization for the terminal device. The second network device receives a message sent by the terminal device on the first pre-configured grant for indicating that the handover is completed (in this process, the uplink resource is the first pre-configured grant). If the second network device does not receive the message for indicating the completion of the handover within the time domain range corresponding to the first pre-configured grant, the second network device may dynamically schedule the second uplink grant resource, and receive the message for indicating the completion of the handover on the second uplink grant resource (in this process, the uplink resource is a resource dynamically scheduled by the second network device).

In one example, the second network device configures a first pre-configured grant for the terminal device, and the terminal device determines that the first pre-configured grant is valid. The terminal device sends a message indicating that the handover is complete on the first pre-configured grant. Accordingly, the second network device may receive a message from the terminal device indicating that the handover is complete on the first pre-configured grant.

In yet another example, the second network device configures a first pre-configured grant for the terminal device, but the terminal device receives the first indication information with a time domain position offset from the time domain position of the first pre-configured grant by less than a second pre-set threshold, the terminal device may send a message on the first pre-configured grant indicating that the handover is complete. Accordingly, the second network device may receive a message on the first pre-configured grant indicating that the handover is complete.

In yet another possible implementation manner, the second network device configures the first pre-configuration grant for the terminal device, but the second network device does not receive a message from the terminal device for indicating that the handover is completed on the first pre-configuration grant, or the second network device does not configure the first pre-configuration grant for the terminal device, and the second network device may schedule the PDCCH of the target cell for indicating the second uplink grant resource. In this way, the terminal device may send a message indicating that the handover is completed on the second uplink resource. Accordingly, the second network device may receive a message indicating that the handover is completed on the second uplink grant resource (in this process, the uplink resource is a resource dynamically scheduled by the second network device).

The second network device configures a first preset authorization for the terminal device, but the second network device does not receive a message from the terminal device indicating that the handover is completed on the first preset authorization may include: the terminal equipment configures a first pre-configuration authorization, and the terminal equipment determines that the first pre-configuration authorization is invalid; or the terminal equipment configures the first pre-configuration authorization, the first pre-configuration authorization is valid, but the time domain position of the terminal equipment receiving the first indication information and the time domain position of the first pre-configuration authorization are larger than or equal to a second preset threshold value; or the terminal device first pre-configured grant sent a message indicating that the handover is complete, and for some reason (e.g. poor signal quality or interference), the second network device did not receive the message sent by the terminal device indicating that the handover is complete.

Based on the technical solution shown in fig. 8, the second network device may accurately determine, after receiving the second indication information from the first network device, the target cell for handover of the terminal device according to the second indication information. Meanwhile, after receiving the first indication information, the terminal device can accurately determine uplink resources for sending a message indicating that the switching is completed according to the configuration condition of the pre-configuration authorization. The terminal device determines an uplink resource for transmitting a message indicating that the handover is completed, and may transmit the message indicating that the handover is completed on the uplink resource. Thus, the second network device can accurately receive the message indicating the completion of the handover from the terminal device according to the configuration condition of the first pre-configuration grant of the target cell. The alignment of the terminal device with the second network device is ensured.

In a possible embodiment, in S803, if the terminal device does not configure the first pre-configuration grant or the first pre-configuration grant is invalid, the terminal device may monitor the PDCCH of the target cell to obtain the second uplink grant resource, and take the second uplink grant resource as the uplink resource, which may specifically include the following multiple cases.

Case 1, the terminal device does not configure the first pre-configured grant.

When the second network device does not pre-configure the first pre-configuration grant for the terminal device, the second network device may dynamically schedule the second uplink grant resource. In this way, the terminal device may monitor the PDCCH of the target cell, determine a second uplink grant resource, and send a message indicating that the handover is completed on the second uplink grant resource. Accordingly, the second network device may receive a message indicating that the handover is complete on the second uplink grant resource.

And 2, configuring a first pre-configured authorized resource by the terminal equipment, wherein the first pre-configured authorized resource is invalid.

Wherein the first preconfigured authorization invalidation may comprise one or more of: the RSRP of the SSB associated with the first pre-configured grant is below a first pre-set threshold, the first pre-configured grant overlaps PRACH resources, or the first pre-configured grant overlaps MSGA PUSCH resources.

In one example, when the second network device configures the first pre-configured grant for the terminal device, and the terminal device determines that the first pre-configured grant is invalid. The terminal device does not send a message indicating that the handover is complete on the first pre-configured grant.

For example, when the RSRP of the SSB associated with the first pre-configured grant is lower than or equal to a first pre-set threshold, or the first pre-configured grant overlaps with the PRACH resource, or the first pre-configured grant overlaps with the msgA PUSCH resource, the terminal device determines that the first pre-configured grant is invalid.

For another example, when the RSRP of the SSB associated with the first pre-configured grant is lower than or equal to the first pre-set threshold, and the first pre-configured grant overlaps the PRACH resource, the terminal device determines that the first pre-configured grant is invalid.

For another example, when the RSRP of the SSB associated with the first pre-configured grant is lower than or equal to the first pre-set threshold, and the first pre-configured grant overlaps with the msgA PUSCH resource, the terminal device determines that the first pre-configured grant is invalid.

For another example, when the first pre-configured grant overlaps with the PRACH resource and the first pre-configured grant overlaps with the msgA PUSCH resource, the terminal device determines that the first pre-configured grant is invalid.

For another example, when the RSRP of the SSB associated with the first pre-configured grant is lower than or equal to a first pre-set threshold, and the first pre-configured grant overlaps the PRACH resource, and the first pre-configured grant overlaps the msgA PUSCH resource, the terminal device determines that the first pre-configured grant is invalid.

When the terminal device does not send a message indicating that the handover is completed on the first pre-configured grant. The second network device cannot receive a message indicating that the handover is complete on the first pre-configured grant.

In one example, the second network device detects a message indicating that the handover is complete within a range of time domain locations (including a start location and an end location) corresponding to the first pre-configured grant. If the second network device does not detect the message for indicating that the handover is completed in the time domain location range corresponding to the first pre-configured grant, the second network device may schedule the PDCCH for indicating the target cell of the second uplink grant resource. In this way, the terminal device may receive the second uplink grant resource by monitoring the PDCCH of the target cell. The end point device may send a message on the second uplink grant indicating that the handover is complete. Accordingly, the second network device may receive a message on the second uplink grant indicating that the handover is complete.

In yet another example, this embodiment may also include case 3.

In case 3, the offset (may also be referred to as an offset value) between the time domain position of the first indication information and the time domain position of the first preset grant received by the terminal device is greater than or equal to a second preset threshold, then the terminal device may monitor the PDCCH of the target cell for indicating the second uplink grant resource, so as to obtain the second uplink grant resource, and use the second uplink grant resource as the uplink resource. It should be noted that, the embodiments of the present application may be implemented alone or in combination with the corresponding embodiments of fig. 5 to 7 and fig. 10 to 14.

In a possible embodiment, as shown in fig. 10, in the method provided in the embodiment of the present application, in S803, the terminal device sends a message indicating that handover is completed on an uplink resource, which may specifically include:

s1001, the terminal equipment sends a message indicating that the switching is completed on an uplink resource through a first HARQ process.

Wherein the first HARQ process may be determined for the terminal device based on configuration information of the first pre-configured grant resource. For example, the configuration information of the first pre-configuration grant may include a period of the first pre-configuration grant, the number of HARQ processes, a time domain configuration, and a frequency domain configuration.

In one example, the first pre-configured authorized HARQ process is calculated as follows:

the HARQ process ID associated with the first symbol of the uplink transmission is derived from the following equation:

HARQ process id= [ current_symbol/periodicity) ] module nrofharq-Processes.

Wherein floor is rounded down. Modulo is modulo. Current_symbol= (sfn×number ofslotsperframe×number ofsymbol perslot+ slot number in the frame ×number ofsymbol perslot+ symbol number in the slot).

Where nrofharq-Processes is the number of HARQ Processes. The Periodicity is the period of the configuration grant. SFN is the system frame number. number Of Slots PerFrame is the number of consecutive slots in each frame. number Of Symbols PerSlot is the number of consecutive symbols in each slot. slot number in the frame is the slot number in the frame where the first symbol of the uplink transmission is located. symbol number in the slot is the symbol number in the slot where the first symbol of the uplink transmission is located. The above calculation formula is merely exemplary and is not limited thereto.

In one example, the message indicating that the handoff is complete may carry information for the first HARQ process. For example, the message indicating the completion of the handover may include an ID of the first HARQ process.

Correspondingly, in S804, the terminal device receives a message indicating that the handover is completed on the uplink resource, which may specifically include: the second network device receives a message associated with the first HARQ process on an uplink resource indicating that the handoff is complete. The second network device determines the first HARQ process upon receiving a message indicating that the handover is complete.

In a possible embodiment, as shown in fig. 11, the method provided in the embodiment of the present application may further include, if the second network device receives a message indicating that the handover is completed:

s1101, the second network device sends a first response message to the terminal device.

Correspondingly, the terminal device receives the first response message from the second network device.

Wherein the first response message may be used to indicate that the second network device received a message indicating that the handover is complete. For example, the first response message may be a handover complete acknowledgement message or a contention resolution message. For another example, the first response message may include a first character. The first character may be used to identify that the second network device received a message indicating that the handoff is complete, without limitation. The first response message may be carried in a MAC CE or DCI.

Based on this embodiment, the second network device may feedback receipt of the message indicating completion of the handover after receiving the message indicating completion of the handover. Therefore, after receiving the response message fed back by the second network device, the terminal device can accurately determine that the second network device receives the message indicating that the switching is completed, and the terminal device can perform data transmission with the second network device.

In a possible embodiment, the terminal device may monitor the PDCCH scrambled by the C-RNTI and receive a third uplink grant resource for the target cell.

Optionally, after sending a message indicating that the handover is completed, the terminal device monitors the PDCCH of the target cell. For example, if the terminal device does not receive the first response message, the terminal device may monitor the PDCCH scrambled by the C-RNTI and receive a third uplink grant resource for the target cell. The third uplink grant resource is indicated for a new transmission (also called a new transmission). Optionally, the second network device includes a new data indication (new data indicator, NDI) in downlink control information (downlink control information, DCI) scheduling the third uplink grant resource. For example, if NDI for the same HARQ process flips, then it is considered a new transmission resource; or for example, the new data indication is set to 0 to indicate new transmission, set to 1 to indicate retransmission, or the new data indication is set to 1 to indicate new transmission, and set to 0 to indicate retransmission.

The third uplink grant resource may be associated with the first HARQ process, or may be associated with any HARQ process. Any one HARQ process may be the same as or different from the first HARQ process. The terminal equipment does not receive the first response message of the network, and the third uplink grant is received through the PDCCH scrambled by the C-RNTI, and the terminal equipment sends a message indicating that the switching is completed again on the third uplink grant resource.

Optionally, the terminal device considers the retransmission of the message indicating the completion of the handover on the third uplink grant resource as a new transmission.

In a possible implementation manner, the terminal device may monitor the PDCCH scrambled by the C-RNTI and receive a third uplink grant resource for the target cell.

Optionally, after sending a message indicating that the handover is completed, the terminal device monitors the PDCCH of the target cell. For example, if the terminal device does not receive the first response message, the terminal device may monitor the PDCCH scrambled by the C-RNTI and receive a third uplink grant resource for the target cell. The third uplink grant resource is indicated for retransmission. Optionally, the third uplink grant resource is associated with the first HARQ process. The terminal equipment does not receive the first response message of the network, and the third uplink grant is received through the PDCCH scrambled by the C-RNTI, and retransmits the message indicating the completion of the switching on the third uplink grant resource. Alternatively, the retransmission is considered a retransmission.

This possible implementation is illustrated below in connection with examples:

example 1, a terminal device sends a message on an uplink resource indicating that a handover is complete through a first HARQ process. The second network device detects a message indicating that the handover is complete on the uplink resource, but does not successfully parse or successfully receive the message indicating that the handover is complete. The second network device may schedule the uplink grant resources (i.e., the third uplink grant resources) associated with the first HARQ process. After receiving the uplink grant resource, the terminal device may resend a message indicating that the handover is completed on the uplink grant resource. In this example, the third uplink grant resource is a retransmission resource.

Example 2, the terminal device sends a message indicating that the handover is completed on the uplink resource through the first HARQ process. The second network device does not detect a message on the uplink resource indicating that the handover is complete. The second network device may schedule the uplink grant resources associated with the first HARQ process or the second network device may schedule the uplink grant resources associated with any one HARQ process. If the terminal device does not receive the first response message of the second network device, the terminal device can retransmit a message indicating that the switching is completed on the uplink authorized resource. Alternatively, the retransmission is considered a new transmission.

For example, the uplink grant resource scheduled by the second network device is associated with the first HARQ process. The terminal device may transmit a message indicating that the handover is completed on the uplink grant resource through the first HARQ process.

For example, the second network device schedules uplink grant resources associated with any one HARQ process. For example, the uplink grant resource scheduled by the second network is associated with the second HARQ process, and the terminal device may retransmit a message indicating that the handover is completed on the uplink grant resource through the second HARQ process. For another example, the uplink grant resource scheduled by the second network is associated with the third HARQ process, and the terminal device may retransmit a message indicating that the handover is completed on the uplink grant resource through the third HARQ process.

In yet another possible implementation, the terminal device does not receive the first response message, and does not receive the PDCCH schedule scrambled by the C-RNTI of the second network or the third uplink grant resource. The terminal device may retransmit a message indicating that the handover is complete on the uplink grant resource associated with the next first HARQ process.

In one example, the first preconfigured authority may include a plurality of opportunities. The plurality of opportunities may be periodic opportunities. Each occasion is associated with one HARQ process. For example, the terminal device sends a message indicating that the handover is complete on a first occasion associated with the first HARQ process of the first pre-configured grant. The terminal device does not receive the first response message, and the terminal device does not receive the third uplink grant resource. The terminal device may retransmit a message indicating that the handover is complete on the next occasion of associating the first HARQ process in the first pre-configured grant.

Based on the possible embodiment, the terminal device does not receive the response message indicating that the second network device receives the message indicating that the switching is completed, and the terminal device can retransmit the message indicating that the switching is completed, thereby improving the switching success rate.

In a possible embodiment, the first pre-configured grant may also be provided with a corresponding validity duration and/or validation time.

In one possible implementation, this embodiment may be implemented by the following procedure.

Step 1: the second network device configures the timer.

In an example, the second network device configures a candidate cell for the terminal device, where the candidate cell configuration includes first preconfigured grant configuration information, and optionally, may further include a first timer duration (i.e., a valid duration) and/or a start offset corresponding to the first preconfigured grant.

The first timer duration and/or the effective time corresponding to the first preset authorization may be: the second network device is configured for each candidate cell, or for each candidate cell group, when configuring candidate cells for the terminal device.

The valid duration may refer to a time when the terminal device uses the first pre-configured authorization. That is, the first pre-configured grant may be a dedicated uplink grant of the terminal device within the valid duration. The effective duration may be an integer multiple of the CG period or the symbol, i.e. an integer multiple of the symbol, or the frame, or an integer multiple of the frame, or may be a positive integer, or the unit of seconds.

The effective time may refer to a time that the first pre-configured grant may be configured for use by the terminal device, such as a first symbol. For example, the validation time may be a compensation (offset) duration. After receiving the first indication information, the terminal device may use the first preset authorization after the offset duration.

In one example, the first pre-configured grant is a dedicated uplink grant for the terminal device within a validity period of the first pre-configured grant. The duration of the first pre-configured grant used by the terminal device exceeds the effective duration, and the terminal device cannot continue to use the first pre-configured grant or the first pre-configured grant is a shared uplink grant.

Wherein, the common uplink grant may mean that both the terminal device and other terminal devices may use the first pre-configured grant. For example, the first pre-configured grant may be a contended uplink grant, or may be a Type-1 configured grant.

In a possible implementation manner, the first network device includes, in the configuration of the candidate cell of the terminal device, the configuration of the first timer corresponding to the candidate cell. The first timer may be used to control the validity duration of the use of the first pre-configured grant by the terminal device. It is understood that during the run time of the first timer, the first pre-configured grant is a dedicated grant resource for the terminal device.

The first timer may be configured for each candidate cell, or may be configured for a candidate cell group. The candidate cell group may be obtained by grouping a plurality of candidate cells for the first network device. For example, the first network device may group the plurality of candidate cells according to network device deployment or topology information of the network device or information such as a movement track of the terminal device.

For example, the first network device may divide cells having overlapping coverage areas into one candidate cell group. For another example, the first network device may divide a plurality of cells of a network device in the same topology or having a direct link into one candidate cell group. For another example, when the movement track of the terminal device is a road a, the first network device may divide a plurality of cells of the network device having a distance from the road a smaller than a preset distance into one candidate cell group.

In one example, a first network device configures a timer. That is, the first network device configures a starting offset (i.e., an effective time) and a valid duration for the first timer. For example, the starting offset and the valid duration may be carried/contained in the RRC reconfiguration message, or may be a separate signaling, or may be carried/contained in another message, without limitation. The starting offset is validated based on the configuration of the terminal device reception candidate cell. The terminal device starts a first timer after an offset time elapses after receiving a message containing candidate cell configuration information. The message containing the candidate cell configuration information may be an RRC reconfiguration message, or may also be a separate message, or may also be another message, without limitation.

Wherein the first timer is configured for each candidate cell, each candidate cell may be configured with a starting offset and/or a validity period. The first timer is configured for each candidate cell group, then each candidate cell group may be configured with a starting offset and/or a validity period.

In yet another example, the first network device is not configured with the first timer. That is, the first network device does not configure the starting offset and/or the effective duration for the first timer.

For example, the first network device does not configure the effective duration of the first timer, but configures the starting offset of the first timer, when the terminal device receives the configuration of the candidate cell, the first pre-configuration grant starts to take effect, and the first pre-configuration grant is always a dedicated grant resource of the terminal device.

For another example, the first network device does not configure the starting offset, but configures the effective duration of the first timer, and the terminal device starts to take effect when receiving the first pre-configured grant of the candidate cell. And if the operation duration exceeds the effective duration, the terminal equipment cannot continue to use the first pre-configured grant or the first pre-configured grant is used as the shared grant resource.

For another example, the first network device does not configure the starting offset and does not configure the effective duration of the first timer, and when the terminal device receives the first pre-configured grant of the candidate cell, the first pre-configured grant starts to take effect, and the first pre-configured grant is always a dedicated grant resource of the terminal device.

Step 2: the terminal device applies a timer.

In a possible implementation manner, the terminal device determines the effective time and the effective duration of the first pre-configuration authorization according to the configuration of the second network device.

In one example, the first pre-configured authorization configures a corresponding validity duration and sets a validation time. The terminal equipment receives the message containing the configuration of the candidate cell or starts a first timer after receiving the first pre-configuration authorization of the first network equipment aiming at the candidate cell/group and the effective time passes, and the first pre-configuration authorization starts to be effective. The terminal device may send a message indicating that the handover is complete on the first pre-configured grant for a valid duration.

For example, as shown in a in fig. 12, the target cell is cell 2, and the first timer duration of the first preconfigured grant configuration of cell 2 or the candidate cell group 1 where cell 2 is located is 2 times the duration of CG resources (which may also be described as a CG period of 2 times), and offset 1=0. The terminal device, upon receiving the message containing the candidate cell configuration information, the first pre-configured grant for cell 2 becomes active (i.e. the first pre-configured grant is a dedicated uplink grant referring to the terminal device). After a duration of 2 CG periods, the first pre-configured grant for cell 2 expires (i.e., the first pre-configured grant is a common uplink grant or the terminal device does not need to continue using the first pre-configured grant).

In yet another example, the first pre-configured grant does not configure the validity duration of the first timer, but configures the starting offset of the first timer, then the terminal device starts the first timer (i.e. the first pre-configured grant starts to take effect) when receiving the message containing the candidate cell configuration information, and the first pre-configured grant is always a dedicated grant resource for the terminal device.

For example, as shown in b in fig. 12, the target cell is cell 3, and the timer duration of the first preconfigured grant configuration of cell 3 or the candidate cell group 1 where cell 3 is located is 3 times CG period, offset 2=2 (i.e. 2 times CG period). The terminal device, after 2 times of CG period duration, validates the first preconfigured grant of cell 3, i.e. starts the first timer, when receiving the first indication information. After a duration of 3 CG periods after the first timer is started, the first pre-configured grant for cell 3 is disabled.

In yet another example, the first pre-configuration grant does not configure the starting offset, but configures the validity duration of the first timer, and the terminal device starts the first timer when receiving a message containing candidate cell configuration information. And when the running time of the first timer exceeds the effective time, the terminal equipment cannot continue to use the first pre-configuration authorization or the first pre-configuration authorization is used as the shared authorized resource.

For example, as shown in c in fig. 12, the target cell is cell 5, and the first timer duration of the first pre-configured grant configuration of cell 5 or the candidate cell group 2 where cell 5 is located is CG period n times, offset 3=m. n and m are positive integers. That is, the first pre-configuration grant takes effect after a duration of n times CG period upon receiving a message containing candidate cell configuration information. After a duration of m times the CG period, the first preconfigured authority fails.

In yet another example, the first network device does not configure the starting offset, and does not configure the effective duration of the first timer, and the terminal device starts the first timer when receiving the configuration information including the candidate cell. The first pre-configured grant is always a dedicated grant resource for the terminal device.

For example, as shown in d of fig. 12, the target cell is cell 7, and the first pre-configured grant of cell 7 or the candidate cell group 3 in which cell 7 is located does not configure the first timer duration and the validation time. The terminal device, upon receiving the message containing the candidate cell configuration information, the first pre-configuration grant of the cell 7 becomes effective, and in the period of time in which the cell 7 is the serving cell of the terminal device, the first pre-configuration grant is always a dedicated uplink resource of the terminal device.

Based on the possible embodiment, the effective duration and the effective time are configured for the first pre-configuration authorization of the target cell, so that the simultaneous effective pre-configuration authorization of a plurality of candidate cells is avoided, and the resource waste is caused, thereby improving the resource utilization rate.

It should be noted that, the embodiments corresponding to fig. 10 and fig. 11 may be implemented separately, or may be combined with any one or more embodiments in the embodiments of the present application, and the two embodiments may also be combined with each other.

In one embodiment, the method provided in the embodiment of the present application is described below with reference to the communication system of fig. 2, taking the source DU of the first network device and the destination DU of the second network device as examples.

As shown in fig. 13, a communication method provided in an embodiment of the present application includes:

s1301, the source DU pre-configures a plurality of candidate cells for the terminal equipment.

After determining the plurality of candidate cells of the terminal device, the source DU may send configuration information of the plurality of candidate cells to the terminal device through an RRC reconfiguration message. The configuration information of the candidate cell may include a configuration of a first pre-configuration grant configured by the candidate cell for the terminal device.

The implementation of S1301 may refer to S701 to S706, and will not be described herein.

S1302, the terminal equipment sends a measurement report to the source DU.

Alternatively, the measurement report may be a layer 1 measurement report.

And the terminal equipment measures a plurality of candidate cells according to the measurement configuration information to obtain a measurement result. Alternatively, the measurement is a layer 1 measurement. The terminal device sends a measurement report to the source DU. The source DU receives measurement reports from the terminal device.

S1303, the source DU makes a switching decision.

The source DU refers to a measurement report reported by the terminal equipment, decides to execute switching, and determines a target cell for switching.

S1304, the source DU transmits second instruction information;

optionally, the source DU sends the second indication information to the target DU where the target cell is located through the CU.

Wherein the target DU sends the second indication information to the CU, which forwards the second indication information to the target DU.

S1305, the source DU sends first indication information to the terminal device. Correspondingly, the terminal device receives the first indication information from the source DU.

The execution sequence of S1304 and S1305 is not sequential.

S1306, the terminal equipment determines to perform cell switching to the target DU according to the first indication information.

In one example, the terminal device may start the second timer when performing cell handover, and apply the running duration of the second timer. And when the terminal equipment is not successfully switched to the target cell within the operation time, determining that the cell switching fails. Optionally, the second timer is a MAC layer timer.

S1307, the terminal device transmits a message indicating that the handover is completed.

And the terminal equipment sends a message indicating that the switching is completed on the uplink resource according to the configuration condition of the first pre-configuration authorization.

In one example, the terminal device configures a first pre-configured grant and the first pre-configured grant is valid, and the terminal device sends a message on the first pre-configured grant indicating that the handover is complete.

Further, the terminal device starts to monitor the PDCCH scrambled by the C-RNTI on the x-th slot after the message indicating the completion of the handover is sent on the first pre-configured grant, so as to receive the schedule of the target DU. Wherein x is an integer.

In yet another example, the terminal device does not configure the first pre-configured grant, or the first pre-configured grant is invalid, the terminal device may monitor the PDCCH scrambled by the C-RNTI, to receive a second uplink grant resource for the target cell from the target DU, and send a message indicating that handover is complete on the second uplink grant resource.

S1308, the target DU receives a message indicating handover completion from the terminal device.

The target cell may receive, on the uplink resource, a message indicating that handover is complete according to the configuration condition of the first pre-configuration grant.

In one example, the target DU configures a first pre-configuration grant for the terminal device and the target DU does not receive a message on the first pre-configuration grant indicating that the handoff is complete. The target DU may schedule the C-RNTI scrambled PDCCH, send a second uplink grant resource to the terminal device, and receive a message indicating that handover is completed on the second uplink grant resource.

S1309, the target DU sends a response message to the terminal device.

Optionally, after receiving the message indicating that the handover is completed, the target DU sends a response message to the terminal device. Wherein, the response message may be carried in DCI or MAC CE. The response message indicates that the target DU receives a message indicating that the handover is completed.

S1310, the CU performs path switching.

The specific implementation method of each step in fig. 13 may refer to the description of the foregoing embodiments, which is not repeated. S1301 to S1304, S1308, S1309, S1310 are optional steps.

Based on the technical solution of fig. 13, the target DU may determine when to schedule resources for the terminal device according to the second indication information. The terminal device can determine the time of monitoring the PDCCH through the configuration condition of the pre-configured authorized resource. The time for the terminal equipment to monitor the PDCCH is reduced, and the purpose of saving power consumption is achieved. In addition, the terminal equipment can confirm to send the uplink resource of the message indicating the switching completion to the target DU through the configuration condition of the pre-configuration authorization, thereby improving the switching success rate.

In one example, the source DU and the target DU may be the same DU. In this case, cell handover within the DU is understood. Alternatively, in the corresponding procedure, the source DU and the target DU may be replaced with the source cell and the target cell, respectively.

As shown in fig. 14, another communication method provided in an embodiment of the present application includes:

s1401, a source DU configures a plurality of candidate cells for the terminal device.

The implementation of S1401 may refer to S701 to S706, and will not be described again.

S1402, the terminal device sends a measurement report to the source DU.

In S1402, reference may be made to S1302 above, and details are not described herein.

S1403, the source DU makes a switching decision.

The source DU refers to a measurement report reported by the terminal equipment and decides a target cell for executing the determined handover of the handover.

S1404, the source DU sends second indication information to the target DU where the target cell is located. Accordingly, the target DU receives the second indication information from the source DU.

S1405, the source DU sends first indication information to the terminal device. Correspondingly, the terminal device receives the first indication information from the source DU.

The execution sequence of S1404 and S1405 is not sequential.

S1406, the terminal equipment performs cell switching to the target DU according to the first indication information.

In one example, the terminal device may start the second timer when performing cell handover, and apply the running duration of the second timer. And when the terminal equipment is not successfully switched to the target cell within the operation time, determining that the cell switching fails.

For example, the terminal device receives the first indication information and starts the second timer. Optionally, the second timer is a timer maintained by the MAC layer. If the second timer is overtime, the terminal equipment is not successfully switched to the target cell, and the switching process is failed. And if the terminal equipment is successfully switched to the target cell, stopping the second timer.

S1407, the terminal equipment sends a message indicating that the handover is completed to the target DU.

In an example, the terminal device configures a first pre-configuration grant, the first pre-configuration grant is valid, and the time domain position of the terminal device receiving the first indication information and the time domain position of the first pre-configuration grant are smaller than a second pre-set threshold, and the terminal device sends a message indicating that the handover is completed on the first pre-configuration grant.

Further, after the terminal device sends the message indicating the completion of the handover on the first pre-configured grant, the terminal device may monitor the PDCCH scrambled by the C-RNTI through x slots, so as to receive the uplink resource of the subsequent transmission data.

In yet another example, the terminal device does not configure the first pre-configured grant, or the first pre-configured grant is invalid, or the time domain position of the first indication information received by the terminal device and the time domain position of the first pre-configured grant are greater than or equal to a second preset threshold, the terminal device may monitor the PDCCH scrambled by the C-RNTI, receive a second uplink grant resource for the target cell from the target DU, and send a message indicating that the handover is completed on the second uplink grant resource.

S1408, the target DU receives a message from the terminal device indicating that the handover is completed.

For example, the target DU may receive a message on the uplink resource indicating that the handover is complete according to the configuration of the first pre-configured grant.

In S1404 and S1408 described above, since there is a difference in transmission time between the source DU and the target DU and between the source DU and the terminal device, the time at which the target DU receives the second instruction information and the terminal device receives the first instruction information are different. Thereby causing the terminal device to monitor the resources scheduled by the second network device and the time dynamically scheduled by the second network device to be different. In order to ensure that the terminal device and the second network device are aligned, the power consumption of the terminal device for monitoring the PDCCH is reduced, and the following technical scheme can be adopted.

In the first mode, after receiving a handover instruction of a source DU, a target DU starts scheduling a PDCCH of a target cell. When the target DU configures the first pre-configuration authorization for the terminal device, the target DU detects the first pre-configuration authorization and is used for receiving a message indicating that the switching is completed. When the target DU dynamically schedules uplink grant, the target DU detects a message carried on a Dynamic Grant (DG) resource.

And configuring compensation time delay for the terminal equipment by the target DU. For example, the RRC reconfiguration message in S1401 may include the backoff delay α of the terminal device. Alpha may be twice the transmission time between the source DU and the CU. And the terminal equipment does not need to monitor the PDCCH in the alpha time of receiving the first indication information. After the α time, the terminal device may monitor the PDCCH. For example, the terminal device may listen to the PDCCH on a specific search space. The specific search space may be a dedicated search space of the terminal device.

And thirdly, configuring an offset value for the terminal equipment by the target DU. For example, the RRC reconfiguration message in S1401 may include an offset value for instructing the terminal device to listen to the PDCCH. And the terminal equipment does not need to monitor the PDCCH in the time of receiving the offset value of the first indication information. After the offset time, the terminal device may monitor the PDCCH. For example, the terminal device may listen to the PDCCH on a specific search space.

In a fourth mode, when the time domain position of the first indication information received by the terminal device and the time domain position of the first preset authorization (or the first time of the first preset authorization) are greater than a second preset threshold, the terminal device monitors the PDCCH when receiving the first indication information.

S1409, the target DU sends a response message of the handover complete message to the terminal device.

In combination with S1406 described above, the second timer does not timeout and the terminal device does not receive the response message, the terminal device may resend the message indicating that the handover is completed.

In one scenario, the terminal device sends a message indicating that the handover is completed on the uplink resource through the first HARQ process in S1407. The second network device detects a message on the uplink resource indicating that the handover is complete, but fails decoding/reception.

In one example, the second network device may dynamically schedule the first HARQ process and transmit a second uplink grant resource associated with the first HARQ process. After receiving the second uplink grant resource associated with the first HARQ process, the terminal device retransmits a message indicating that the handover is completed in the second uplink grant.

In yet another scenario, in S1407, the terminal device sends a message indicating that the handover is completed on the uplink resource through the first HARQ process. The second network device does not detect a message on the uplink resource indicating that the handover is complete.

In one example, the terminal device does not receive the response message, but receives a second uplink grant resource from the second network device for scheduling the first HARQ process. The terminal device may retransmit a message indicating that the handover is complete on the second uplink grant resource.

After the terminal device sends the message indicating the completion of the handover on the uplink resource, the SDU corresponding to the message indicating the completion of the handover may be stored. In this way, the terminal device may continue to transmit a message indicating that the handover is completed after not receiving the response message.

In yet another example, the terminal device does not receive the response message, but receives the second uplink grant resource from any HARQ process scheduled by the second network device. The terminal device may retransmit a message indicating that the handover is complete on the second uplink grant resource.

Any HARQ process may be the first HARQ process or the second HARQ process. The first HARQ process is different from the second HARQ process.

In yet another scenario, the terminal device does not receive the response message, and the terminal device does not receive the second uplink grant resource of the HARQ process scheduled by the second network device. The terminal device may indicate a handover complete message on the grant occasion of the next first HARQ process.

Further, after receiving the response message, the terminal device determines that the handover is successful, and stops the operation of the second timer.

The specific implementation method of each step in fig. 14 may refer to the description of the foregoing embodiments, which is not repeated. S1401 to S1405, S1408, S1409 are optional steps.

Based on the technical solution of fig. 14, in the case that the terminal device determines that the first preset authorization is valid, the terminal device determines to send a message indicating that the handover is completed by determining an offset value between the time when the first indication information is received and the time of the first preset authorization. When the offset value is too large, the dynamically scheduled uplink grant resource of the target DU can be monitored, and a message indicating that the switching is completed is sent on the received uplink grant resource. The time delay may be reduced for the handover as compared to when the message indicating the completion of the handover is sent using the first pre-configured grant after a longer period of time.

In addition, through a feedback mechanism, the terminal device can determine whether to successfully send a message indicating that the handover is completed according to the response message. It is avoided that the target DU does not receive a message indicating handover completion.

It should be noted that, in the embodiment of the present application, in the description that the preset threshold is used as the judgment condition, for example, higher may be replaced by higher or equal, and lower or equal may be replaced by lower; greater than or equal to can be replaced by greater than, less than can be replaced by less than or equal to; higher than or equal to can be replaced by higher than, lower than can be replaced by lower than or equal to; greater than or equal to may be replaced with greater than or equal to, less than or equal to, and less than or equal to may be replaced with less than.

In one example, the condition that the first preset authorization is valid includes that the RSRP of the SSB associated with the first preset authorization is higher than a first preset threshold, and the condition that the first preset authorization is invalid includes that the RSRP of the SSB associated with the first preset authorization is lower than or equal to the first preset threshold, may be replaced by: the condition that the first pre-configured grant is valid includes that the RSRP of the SSB associated with the first pre-configured grant is greater than or equal to a first pre-set threshold, and the condition that the first pre-configured grant is invalid includes that the RSRP of the SSB associated with the first pre-configured grant is less than the first pre-set threshold.

In yet another example, the offset value is greater than or equal to the second preset threshold value, and the offset value is less than the second preset threshold value, may be replaced by: the offset value is greater than a second preset threshold value, and the offset value is less than or equal to the second preset threshold value.

In the embodiments of the present application, the same or similar parts between the embodiments may be referred to each other unless specifically described otherwise. In the various embodiments and the various implementation/implementation methods in the various embodiments in this application, if no special description and logic conflict exist, terms and/or descriptions between different embodiments and between the various implementation/implementation methods in the various embodiments may be consistent and may be mutually referred to, technical features in the different embodiments and the various implementation/implementation methods in the various embodiments may be combined to form new embodiments, implementations, implementation methods, or implementation methods according to their inherent logic relationships. The above-described embodiments of the present application are not intended to limit the scope of the present application. In each of the embodiment steps, it may be partially performed (for example, the terminal device may not perform the steps performed by the terminal device in the above embodiments). The order of execution of the different steps may be altered. The embodiments described herein may be combined with other embodiments, and the steps of the different embodiments herein may also be combined.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.

It will be appreciated that in the various embodiments above, the methods and/or steps implemented by the terminal device may also be implemented by means (e.g., a processor, chip, system on chip, circuit, logic module, or software) available to the terminal device. The methods and/or steps implemented by the first network device may also be implemented by components (e.g., processors, chips, systems on a chip, circuits, logic modules, or software) that may be used in the first network device. The methods and/or steps implemented by the second network device may also be implemented by a component (e.g., a processor, chip, system on a chip, circuit, logic module, or software) that is available to the second network device.

The foregoing has mainly described the solutions provided in this application. Correspondingly, the application also provides a communication device, which is used for realizing the various methods in the method embodiment. The communication means may be the terminal device in the above-described method embodiments, or an apparatus comprising the terminal device, or a component usable with the terminal device, such as a chip or a chip system. The communication means may be the first network device in the above-described method embodiments, or an apparatus comprising the first network device, or a component, such as a chip or a chip system, that may be used for the first network device. The communication means may be the second network device in the above-described method embodiments, or an apparatus comprising the second network device, or a component, such as a chip or a chip system, usable with the second network device.

It will be appreciated that the communication device, in order to achieve the above-described functions, comprises corresponding hardware structures and/or software modules performing the respective functions. Those of skill in the art will readily appreciate that the elements and algorithm steps of the examples described in connection with the embodiments disclosed herein may be implemented as hardware or combinations of hardware and computer software. Whether a function is implemented as hardware or computer software driven hardware depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.

The embodiment of the application may divide the functional modules of the communication device according to the embodiment of the method, for example, each functional module may be divided corresponding to each function, or two or more functions may be integrated into one processing module. The integrated modules may be implemented in hardware or in software functional modules. It should be noted that, in the embodiment of the present application, the division of the modules is schematic, which is merely a logic function division, and other division manners may be implemented in actual implementation.

Fig. 15 and 16 are schematic structural diagrams of possible communication devices according to embodiments of the present application. The communication devices can realize the functions of the terminal equipment, the first network equipment or the second network equipment in the method embodiment, so that the beneficial effects of the method embodiment can be realized. In this embodiment of the present application, the communication device may be a terminal device as shown in fig. 1, a network device as shown in fig. 1, or a module (such as a chip) applied to the terminal device or the network device.

As shown in fig. 15, the communication apparatus 1500 includes a transceiver module 1501 and a processing module 1502. The communication apparatus 1500 may be configured to implement the functions of the terminal device or the first network device or the second network device in the method embodiments shown in fig. 8, 10 or 11.

When the communication apparatus 1500 is used to implement the functions of the terminal device in the embodiment of the method described in fig. 8: a transceiver module 1501 for receiving first indication information from a first network device. A processing module 1502 is configured to determine, according to a configuration condition of a first pre-configuration grant of a target cell, uplink resources for sending a message indicating that handover is completed. The transceiver module 1501 is further configured to send a message indicating that the handover is completed on the uplink resource.

When the communication apparatus 1500 is used to implement the functionality of the first network device in the embodiment of the method described in fig. 8: a transceiver module 1501 for transmitting second indication information to a second network device; the transceiver module 1501 is further configured to send the first indication information to the terminal device.

When the communication apparatus 1500 is used to implement the functionality of the second network device in the embodiment of the method described in fig. 8: a transceiver module 1501, configured to receive second indication information from the first network device, and receive a message from the terminal device that indicates that handover is completed on the uplink resource.

When the communication apparatus 1500 is used to implement the functions of the terminal device in the embodiment of the method illustrated in fig. 10: a transceiver module 1501, configured to receive first indication information, the processing module 1502 is configured to determine, according to a configuration condition of a first pre-configuration grant of a target cell, an uplink resource for sending a message indicating that handover is completed, and the transceiver module 1501 is configured to send, through a first HARQ process, the message indicating that handover is completed on the uplink resource.

When the communication apparatus 1500 is used to implement the functionality of the second network device in the embodiment of the method described in fig. 10: a transceiver module 1501, configured to receive second indication information from the first network device, and send a message indicating that handover is completed on an uplink resource by the receiving terminal device through the first HARQ process.

When the communication apparatus 1500 is used to implement the functionality of the second network device in the embodiment of the method described in fig. 11: the transceiver module 1501 is further configured to send the first response message to the terminal device.

For a more detailed description of the transceiver module 1501 and the processing module 1502, reference should be made to the relevant description of the method embodiments described above, which will not be described here.

As shown in fig. 16, the communication device 1600 includes a processor 1610 and interface circuitry 1620. Processor 1610 and interface circuitry 1620 are coupled to each other. It is understood that the interface circuit 1620 may be a transceiver or an input-output interface. Optionally, the communication device 1600 may also include a memory 1630 for storing instructions to be executed by the processor 1610 or for storing input data required by the processor 1610 to execute instructions or for storing data generated upon execution of instructions by the processor 1610.

When the communication device 1600 is used to implement the method in the method embodiment described above, the processor 1610 is configured to perform the functions of the processing module 1502, and the interface circuit 1620 is configured to perform the functions of the transceiver module 1501.

When the communication device is a chip applied to the terminal equipment, the terminal equipment chip realizes the functions of the terminal equipment in the embodiment of the method. The terminal device chip receives information from other modules (such as a radio frequency module or an antenna) in the terminal device, and the information is sent to the terminal device by the network device; alternatively, the terminal device chip sends information to other modules (e.g., radio frequency modules or antennas) in the terminal device, which is sent by the terminal device to the network device.

When the communication device is a chip applied to the first network device, the first network device chip implements the functions of the network device in the method embodiment. The first network device chip receives information from other modules (such as a radio frequency module or an antenna) in the first network device, and the information is sent to the first network device by the terminal device; alternatively, the first network device chip sends information to other modules (e.g., radio frequency modules or antennas) in the first network device, where the information is sent by the first network device to the terminal device.

When the communication device is a chip applied to the second network device, the second network device chip implements the functions of the network device in the method embodiment. The first network device chip receives information from other modules (such as radio frequency modules or antennas) in the second network device, the information being sent by the first network device to the second network device; alternatively, the second network device chip sends information to other modules (e.g., radio frequency modules or antennas) in the second network device, where the information is sent by the second network device to the terminal device.

It is to be appreciated that the processor in embodiments of the present application may be a central processing unit (central processing unit, CPU), but may also be other general purpose processors, digital signal processors (digital signal processor, DSP), application specific integrated circuits (application specific integrated circuit, ASIC), field programmable gate arrays (field programmable gate array, FPGA) or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The general purpose processor may be a microprocessor, but in the alternative, it may be any conventional processor.

The method steps in the embodiments of the present application may be implemented by hardware, or may be implemented by a processor executing software instructions. The software instructions may be comprised of corresponding software modules that may be stored in random access Memory (random access Memory, RAM), flash Memory, read-Only Memory (ROM), programmable ROM (PROM), erasable Programmable ROM (EPROM), electrically Erasable Programmable ROM (EEPROM), registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. In addition, the ASIC may reside in an access network device or a terminal device. The processor and the storage medium may reside as discrete components in an access network device or terminal device.

In the above embodiments, it may be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer programs or instructions. When the computer program or instructions are loaded and executed on a computer, the processes or functions described in the embodiments of the present application are performed in whole or in part. The computer may be a general purpose computer, a special purpose computer, a computer network, or other programmable apparatus. The computer program or instructions may be stored in or transmitted across a computer-readable storage medium. The computer readable storage medium may be any available medium that can be accessed by a computer or a data storage device such as a server that integrates one or more available media. The usable medium may be a magnetic medium, e.g., floppy disk, hard disk, tape; but also optical media such as DVD; but also semiconductor media such as Solid State Disks (SSDs).

In the various embodiments of the application, if there is no specific description or logical conflict, terms and/or descriptions between the various embodiments are consistent and may reference each other, and features of the various embodiments may be combined to form new embodiments according to their inherent logical relationships.

In the present application, "at least one" means one or more, and "a plurality" means two or more. "and/or", describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate: a alone, a and B together, and B alone, wherein a, B may be singular or plural. In the text description of the present application, the character "/", generally indicates that the associated object is an or relationship; in the formulas of the present application, the character "/" indicates that the front and rear associated objects are a "division" relationship.

It will be appreciated that the various numerical numbers referred to in the embodiments of the present application are merely for ease of description and are not intended to limit the scope of the embodiments of the present application. The sequence number of each process does not mean the sequence of the execution sequence, and the execution sequence of each process should be determined according to the function and the internal logic.

Claims

1. A method of communication, the method comprising:

the terminal equipment receives first indication information from first network equipment, wherein the first indication information is used for indicating information of a target cell switched by the terminal equipment, and the target cell is a cell in a plurality of candidate target cells configured by the terminal equipment before receiving the first indication information;

The terminal equipment determines uplink resources for sending a message indicating that the switching is completed according to the configuration condition of the first pre-configuration authorization of the target cell;

and the terminal equipment sends the message indicating the completion of the switching on the uplink resource.

2. The method of claim 1, wherein the configuration of the first pre-configured grant comprises configuring the first pre-configured grant or not configuring the first pre-configured grant.

3. The method according to claim 2, wherein the determining, by the terminal device, uplink resources for sending a message indicating that handover is completed according to the configuration of the first pre-configured grant of the target cell, includes:

the terminal equipment configures the first pre-configuration authorization, the first pre-configuration authorization is valid, and the terminal equipment determines that the uplink resource for sending the message indicating the completion of the switching is the resource corresponding to the first pre-configuration authorization; or,

the terminal equipment configures the first pre-configuration authorization, wherein the first pre-configuration authorization is invalid, monitors a Physical Downlink Control Channel (PDCCH) of the target cell for indicating a second uplink authorization resource, and determines the uplink resource as the second uplink authorization resource.

4. The method according to claim 2, wherein the determining, by the terminal device, uplink resources for sending a message indicating that handover is completed according to the configuration of the first pre-configured grant of the target cell, includes:

the terminal equipment does not configure the first pre-configuration grant, monitors the PDCCH of the target cell for indicating a second uplink grant resource, and determines the uplink resource as the second uplink grant resource.

5. A method according to claim 3, wherein the first pre-configured authorization valid includes one or more of: the reference signal received power RSRP of the synchronization signal block SSB associated with the first pre-configured grant is higher than a first preset threshold, the first pre-configured grant does not overlap with the physical random access channel PRACH resource or the first pre-configured grant does not overlap with the physical uplink shared channel PUSCH resource of the message a.

6. The method according to any of claims 2-5, wherein the determining, by the terminal device, uplink resources for sending a message indicating that handover is complete according to the configuration of the first pre-configured grant of the target cell, includes:

The terminal equipment configures the first pre-configuration authorization, the first pre-configuration authorization is effective, the deviation value is smaller than a second preset threshold, and the terminal equipment determines that the uplink resource is a resource corresponding to the first pre-configuration authorization; or,

the terminal equipment configures the first pre-configuration authorization, the first pre-configuration authorization is effective, the deviation value is larger than or equal to the second preset threshold, monitors a PDCCH (physical downlink control channel) of the target cell for indicating a second uplink authorization resource, and determines the uplink resource as the second uplink authorization resource; the offset value is an offset between the time domain position of the first indication information received by the terminal device and the time domain position of the first preset authorization; or, the offset value is an offset between the time domain position of the first indication information received by the terminal device and the time domain position of the first occasion of the first preset authorization.

7. The method according to any of claims 1-6, wherein the terminal device sends a message on the uplink resource indicating that handover is complete, comprising

And the terminal equipment sends the message indicating the completion of the switching on the uplink resource through a first hybrid automatic repeat request (HARQ) process.

8. The method of claim 7, wherein the method further comprises:

the terminal equipment does not receive the response message of the message indicating the completion of the switching, and receives a third uplink grant resource aiming at the target cell on a PDCCH scrambled by a cell radio network temporary identifier C-RNTI, wherein the third uplink grant resource is associated with the first HARQ process and is indicated to be used for new transmission, and the terminal equipment resends the message indicating the completion of the switching on the third uplink grant resource; or,

and the terminal equipment receives the third uplink grant resource on the PDCCH scrambled by the C-RNTI, wherein the third uplink grant resource is associated with any HARQ process, the third uplink grant resource is indicated to be used for new transmission, and the terminal equipment resends the message indicating the completion of switching on the third uplink grant resource.

9. The method of claim 8, further comprising,

the terminal equipment does not receive the response message of the message indicating the completion of the switching, and the terminal equipment does not receive the third uplink grant resource, the second time of the first pre-configuration grant is valid, the terminal equipment retransmits the message indicating the completion of the switching on the second time, and the second time is the grant time in the first pre-configuration grant.

10. A method of communication, the method comprising:

the second network equipment receives second indication information from the first network equipment, wherein the second indication information is used for indicating information of a target cell switched by the terminal equipment, and the target cell is a cell in a plurality of candidate target cells;

and the second network equipment receives a message indicating that the switching is completed from the terminal equipment on an uplink resource according to the configuration condition of the first pre-configuration authorization of the target cell.

11. The method of claim 10, wherein the configuration of the first pre-configured grant comprises configuring the first pre-configured grant or not configuring the first pre-configured grant.

12. The method according to claim 11, wherein the second network device receives a message from the terminal device indicating that handover is complete on an uplink resource according to the configuration of the first pre-configured grant of the target cell, comprising:

the terminal equipment configures a first pre-configuration authorization, and the second network equipment receives the message indicating the completion of the switching on the first pre-configuration authorization; or,

The terminal equipment does not configure the first pre-configuration grant, the second network equipment schedules the PDCCH of the target cell for indicating a second uplink grant resource, and receives the message indicating the completion of the switching on the second uplink grant resource.

13. The method according to claim 11 or 12, wherein the second network device receives a message from the terminal device on an uplink resource indicating that handover is complete according to the configuration of the first pre-configured grant of the target cell, comprising:

the terminal equipment configures the first pre-configuration authorization, the deviation value is smaller than a second preset threshold value, and the second network equipment receives the message indicating the completion of switching on the first pre-configuration authorization; or,

the terminal equipment configures the first pre-configuration grant, the deviation value is larger than or equal to the second preset threshold value, the second network equipment schedules the PDCCH of the target cell for indicating a second uplink grant, and receives the message indicating that the switching is completed on the second uplink grant; the offset value is an offset between a time domain position of the terminal device receiving the first indication information and a time domain position of the first pre-configuration authorization; or, the offset value is an offset between a time domain position of the first indication information received by the terminal device and a time domain position of a first occasion of the first preset authorization, where the first indication information is used to indicate information of the target cell.

14. The method according to any of claims 10-13, wherein the second network device receiving a message from the terminal device indicating that handover is complete, comprises:

the second network device receives the message indicating that the handover is completed in association with the first HARQ process.

15. The method of claim 14, wherein the method further comprises:

the second network device sends a third uplink grant resource through a PDCCH scrambled by the scheduling C-RNTI, wherein the third uplink grant resource is associated with the first HARQ process and is indicated to be used for new transmission; or,

and the second network equipment sends the third uplink grant resource through a PDCCH scrambled by the scheduling C-RNTI, the third uplink grant resource is associated with any HARQ process, and the third uplink grant resource is indicated for new transmission.

16. The method according to any of claims 1-15, wherein the first pre-configured grant is a dedicated uplink grant of the terminal device within a valid duration of a first timer corresponding to the first pre-configured grant.

17. The method of claim 16, wherein the first timer expires, wherein the terminal device is unable to continue using the first pre-configured grant or wherein the first pre-configured grant is a common uplink grant.

18. A method of communication, the method comprising:

the first network device sends second indication information to the second network device, where the second indication information is used to indicate information of a target cell for handover of the terminal device, and the target cell is a cell in a plurality of candidate target cells.

19. The method of claim 18, wherein the method further comprises:

the first network device sends first indication information to the terminal device, wherein the first indication information is used for indicating information of the target cell.

20. A communication device comprising means for performing the method of any of claims 1 to 9 or 10 to 17 or 18 to 19.

21. A communication device comprising a processor and a communication interface for receiving signals from other communication devices than the communication device and transmitting to the processor or sending signals from the processor to other communication devices than the communication device, the processor being configured to implement the method of any one of claims 1 to 9 or 10 to 17 or 18 to 19 by logic circuitry or execution of code instructions.

22. A communication system comprising a first network device for performing the method of claim 18 or 19, and a second network device for performing the method of any of claims 10 to 17, and a terminal device for indicating the method of any of claims 1 to 9.

23. A computer readable storage medium, characterized in that the computer readable storage medium stores a computer program which, when run, implements the method of any one of claims 1 to 9 or 10 to 17 or 18 to 19.

24. A computer program product, the computer program product comprising: computer program code which, when executed, implements the method of any of claims 1 to 9 or 10 to 17 or 18 to 19.