WO2021018283A1 - Procédé de communication et appareil de communication - Google Patents

Procédé de communication et appareil de communication Download PDF

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Publication number
WO2021018283A1
WO2021018283A1 PCT/CN2020/106162 CN2020106162W WO2021018283A1 WO 2021018283 A1 WO2021018283 A1 WO 2021018283A1 CN 2020106162 W CN2020106162 W CN 2020106162W WO 2021018283 A1 WO2021018283 A1 WO 2021018283A1
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WO
WIPO (PCT)
Prior art keywords
cell
terminal device
rach
network device
target cell
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PCT/CN2020/106162
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English (en)
Chinese (zh)
Inventor
严乐
耿婷婷
曾清海
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华为技术有限公司
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Publication of WO2021018283A1 publication Critical patent/WO2021018283A1/fr

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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W76/00—Connection management
    • H04W76/20—Manipulation of established connections
    • H04W76/27—Transitions between radio resource control [RRC] states
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access
    • H04W74/08—Non-scheduled access, e.g. ALOHA
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access
    • H04W74/08—Non-scheduled access, e.g. ALOHA
    • H04W74/0833—Random access procedures, e.g. with 4-step access
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W36/00—Hand-off or reselection arrangements
    • H04W36/0005—Control or signalling for completing the hand-off
    • H04W36/0055—Transmission or use of information for re-establishing the radio link

Definitions

  • This application relates to the communication field, and more specifically, to a communication method and communication device in the communication field.
  • the traditional handover process often includes a random access process, that is, after receiving the handover message, the terminal device will use the relevant information of the target cell contained in the handover message (such as the physical cell identification, frequency information, and frequency information of the target cell). Random access resource information required for handover to the target cell, etc.), and a random access procedure with the target cell.
  • the handover message can include uplink (UL) grant information and the timing advance (TA) of the target cell.
  • the terminal device can directly send a radio resource control (radio resource control, RRC) reconfiguration complete message to the network device to which the target cell belongs based on the UL grant in the handover message without performing random Access process. Therefore, the time consumed by the random access procedure in the handover process can be reduced, and the handover interruption time delay can be shortened.
  • RACH-less random access channel-less handover
  • RACH-less handover may fail.
  • how the terminal device can resume communication in a reasonable manner is a problem to be solved urgently.
  • the present application provides a communication method and communication device, in order to provide a reasonable recovery mechanism for the terminal device in the case of a RACH-less handover failure of the terminal device.
  • a communication method is provided, which may be executed by a terminal device, or may also be executed by a component (such as a chip or a circuit) configured in the terminal device. This application does not limit this.
  • the method includes: receiving a radio resource control RRC message, the RRC message instructing a terminal device to initiate a random access channel-free RACH-less handover from a source cell to a target cell; determining that the RACH-less handover fails; and the first network device Communication, wherein the first network device is: the network device to which the source cell belongs, or the network device to which the target cell belongs, or the network device to which the reestablished cell belongs, the reestablished cell is a cell that meets a predetermined criterion, and the reestablished cell It is a cell that is requested to be accessed after the terminal device fails to attempt to communicate with the network device to which the source cell belongs and/or the random access to the target cell fails.
  • the first network device is: the network device to which the source cell belongs, or the network device to which the target cell belongs, or the network device to which the reestablished cell belongs, the reestablished cell is a cell that meets a predetermined criterion, and the reestablished cell It is a cell that
  • the communication method provided in the embodiments of the present application provides a variety of ways for the terminal device to resume communication when the terminal device fails in the RACH-less handover from the source cell to the target cell.
  • the terminal device can communicate with the network device by falling back to the source cell or randomly accessing the target cell.
  • the terminal device may also initiate RRC re-establishment to achieve communication with the network device. Therefore, after the RACH-less handover fails, the terminal device can try to restore the normal communication with the network device in a more reasonable manner to minimize the communication interruption time delay.
  • the fallback source cell fails or the random access to the target cell fails the RRC re-establishment process can still be used to restore normal communication with the network device.
  • the terminal device If the terminal device maintains an RRC connection with the source cell, it still resumes normal communication through a complicated RRC re-establishment process, or if the terminal device can access the target cell through a random access process, but through a complicated
  • the RRC re-establishment process to resume communication will on the one hand cause communication interruption to the user and affect the user experience; on the other hand, it will also cause the complexity of the terminal device implementation and increase the power consumption of the terminal device. This communication interruption and power consumption can be avoided or reduced. Therefore, the technical solution provided in this application provides a reasonable recovery mechanism for terminal devices that fail RACH-less handover, which is beneficial to improve user experience.
  • the first network device is a network device to which the source cell belongs. That is, the first network device is the source network device.
  • the terminal device can resume normal communication by, for example, falling back to the source cell.
  • the implementation method of falling back to the source cell is suitable for having the make-before-break (MBB) capability or enhanced make-before-break (eMBB) capability. Capable of terminal equipment. That is, when the terminal device initiates the RACH-less handover from the source cell to the target cell, it still has the ability to maintain the RRC connection with the source cell.
  • MBB make-before-break
  • eMBB enhanced make-before-break
  • the method further includes: in a case where it is determined that there is an RRC connection between the terminal device and the source cell, falling back to the source cell.
  • the terminal device can directly fall back to the source cell when there is an RRC connection with the source cell. Thus, the terminal device can quickly resume communication.
  • the method further includes: determining that there is no beam with a signal quality higher than a first preset threshold in the target cell.
  • the terminal device can determine whether there is a possibility of random access to the target cell before returning to the source cell. If the terminal device does not detect a beam with a signal quality higher than the first preset threshold in the target cell, the terminal device may choose not to initiate random access, but fall back to the source cell to communicate with the source network device.
  • the method further includes: determining that the cell signal quality of the source cell is higher than a second preset threshold.
  • the terminal device can determine whether the cell signal quality of the source cell is good before returning to the source cell. If the terminal device determines that the cell signal quality of the source cell is higher than the second preset threshold, the terminal device may consider the cell signal quality of the source cell to be better, and preferentially consider falling back to the source cell to communicate with the source network device.
  • the method further includes: the random access procedure initiated to the target cell fails.
  • the terminal device can also try to access the target cell through random access before returning to the source cell. However, if the random access to the target cell fails, because RRC re-establishment is more time-consuming and more complicated than the fallback to the source cell, the terminal device can give priority to fallback to the source cell, and the source network Device communication.
  • the method before initiating the random access procedure to the target cell, the method further includes: determining that there is a beam with a signal quality higher than a first preset threshold in the target cell, or determining that the cell signal quality of the source cell is not higher than the first preset threshold. 2. Preset threshold.
  • the terminal device can initiate random access to the target cell based on certain preset conditions. For example, when the target cell has a beam with good signal quality, for example, when the target cell has a beam with a signal quality higher than the first preset threshold, or when the cell signal quality of the source cell is poor, such as when the signal quality of the source cell is poor, When the signal quality of the cell is not higher than the second preset threshold, the terminal device may give priority to random access to the target cell to communicate with the target network device.
  • the first network device is a network device to which the target cell belongs.
  • the network device to which the target cell belongs and the network device to which the source cell belongs may be the same network device or different network devices.
  • the network equipment is deployed in the form of centralized unit (CU) + distributed unit (DU)
  • the network equipment to which the target cell belongs and the network equipment to which the source cell belongs can be the same CU but different DUs It can also be the same CU and the same DU, or different CUs and different DUs. This application does not limit this.
  • the method further includes: initiating a random access procedure to the target cell; after the random access is successful, communicating with a network device to which the target cell belongs. That is, the first network device is the target network device. That is, the terminal device can resume normal communication by randomly accessing to the target cell, for example.
  • the method before initiating a random access procedure to the target cell, the method further includes: determining that the signal quality of the source cell is not higher than a second preset threshold.
  • the terminal device can initiate random access to the target cell based on certain preset conditions. For example, when the cell signal quality of the source cell is poor, such as when the cell signal quality is not higher than the second preset threshold, the terminal device may give priority to random access with the target cell to communicate with the target network device.
  • the method before initiating a random access procedure to the target cell, the method further includes: determining that there is a beam with a signal quality higher than a first preset threshold in the target cell; and the initiating a random access procedure to the target cell includes: Based on the first beam and the RACH resource, a random access procedure is initiated to the target cell, where the first beam is one of one or more beams in the target cell whose signal quality is higher than a first preset threshold.
  • the terminal device can initiate random access to the target cell based on certain preset conditions. For example, when the target cell has a beam with good signal quality, for example, when the target cell has a beam with a signal quality higher than the first preset threshold, the terminal device may give priority to random access with the target cell to communicate with the target network. Device communication.
  • the terminal device When the terminal device performs random access with the target cell, it may specifically perform random access with the target cell based on a beam with a signal quality higher than the first preset threshold (the first beam as described above) and RACH resources.
  • the terminal device performs random access based on the beam with the signal quality higher than the first preset threshold, which may specifically include: the terminal device is based on the non-competitive random access (contention free random access, CFRA) resource association and the signal quality is higher than the first A beam with a preset threshold performs random access, and/or the terminal device performs random access based on a beam with a signal quality higher than a first preset threshold and contention-based random access (CBRA) resources.
  • CFRA contention free random access
  • CBRA contention-based random access
  • CFRA and CBRA are two types of random access.
  • the beams used by the terminal equipment for random access based on CFRA resources and CBRA resources may be different, but they are all beams with signal quality higher than the first preset threshold.
  • the method before initiating a random access procedure to the target cell, the method further includes: determining that the RRC connection between the terminal device and the source cell is disconnected.
  • the terminal device since the terminal device cannot fall back to the source cell when the RRC connection between the terminal device and the source cell is disconnected, it can choose one of RRC re-establishment and random access to resume communication.
  • the terminal device may prioritize random access to the target cell when it is determined that the RRC connection with the source cell is disconnected.
  • the first network device is a network device to which a reestablished cell belongs.
  • the terminal device can resume normal communication by means of RRC re-establishment, for example.
  • the re-established cell may be a cell requested to be accessed after the terminal device fails to attempt to communicate with the network device to which the source cell belongs and/or fails random access with the target cell.
  • the re-established cell may be a cell that the terminal device requests to access when the fallback source cell fails and/or the random access with the target cell fails.
  • the re-established cell may be the source cell, the target cell, or other cells except the source cell and the target cell.
  • the network device to which the re-established cell belongs may be a source network device, a target network device, or other network devices except the source network device and the target network device. This application does not limit this.
  • the method further includes: initiating an RRC re-establishment procedure to the re-established cell; and communicating with a network device to which the re-established cell belongs.
  • the terminal device can access the re-established cell through the RRC re-establishment process to communicate with the network device to which the re-established cell belongs.
  • the method before initiating an RRC re-establishment procedure to the re-established cell, the method further includes: determining that the RRC connection between the terminal device and the source cell is disconnected.
  • the terminal device cannot fall back to the source cell when the RRC connection between the terminal device and the source cell is disconnected, so it can choose one of RRC re-establishment and random access. Resume communication.
  • the terminal device may, in the case of determining that the RRC connection with the source cell is disconnected, give priority to restoring the communication of the terminal device through the RRC re-establishment procedure.
  • the method before initiating the RRC re-establishment procedure to the re-established cell, the method further includes: determining that there is no beam with a signal quality higher than the first preset threshold in the target cell.
  • the terminal device may further consider whether there is a beam with better signal quality in the target cell for random access. In the case where the terminal device determines that there is no beam with good signal quality in the target cell, such as a beam with a signal quality higher than the first preset threshold, the RRC re-establishment procedure may be initiated.
  • the method before initiating the RRC re-establishment procedure to the re-established cell, the method further includes: initiating a random access procedure to the target cell, but the random access fails.
  • the terminal device can give priority to random access with the target cell, but in the case of a random access failure with the target cell, the terminal device can resume communication through the RRC re-establishment procedure.
  • the method before initiating the RRC re-establishment procedure to the re-established cell, more specifically, before giving priority to random access with the target cell, the method further includes: determining that there is a signal quality in the target cell higher than the first predetermined Threshold beam.
  • the terminal device can give priority to random access with the target cell when there is a beam with better signal quality in the target cell. For example, the terminal device may preferentially perform random access with the target cell when there is a beam with a signal quality higher than the first preset threshold in the target cell.
  • the method further includes: determining that the cell signal quality of the source cell is not higher than a second preset threshold; initiating a random access procedure to the target cell, but the random access fails; initiating an RRC re-establishment procedure.
  • the terminal device may prioritize fallback to the source cell.
  • the cell signal quality in the source cell is poor. If the cell signal quality is not higher than the second preset threshold, the terminal device may also initiate a random access procedure to the target cell. However, if the random access fails, the terminal device can initiate an RRC re-establishment procedure.
  • the method further includes: sending RACH-less handover failure related information, where the RACH-less handover failure related information includes one or more of the following:
  • Timing advance obtained in advance by the terminal equipment for RACH-less handover
  • the cell identity includes but is not limited to: physical cell identity (PCI) and frequency information, and/or cell global identity (CGI).
  • PCI physical cell identity
  • CGI cell global identity
  • RACH-less handover failure include but are not limited to: there is no beam with signal quality higher than the third preset threshold and associated with uplink grant (UL grant) in the target cell, handover failure (HOF) or radio link failure (radio) link failure, RLF).
  • UL grant uplink grant
  • HAF handover failure
  • radio link failure radio link failure
  • the third preset threshold is specifically a preset threshold used to determine the signal quality of the beam of the target cell.
  • the terminal device detects that there is a beam with a signal quality higher than the third preset threshold in the target cell, and the beam is configured with associated uplink grant UL grant information (for example, configured through a handover message), the terminal device can be based on The beam and the UL grant associated with the beam perform RACH-less handover.
  • the UL grant information described here is used to indicate UL grant.
  • the UL grant may include at least one of the following: time-frequency resources (such as physical uplink share channel (PUSCH) resources), modulation coding scheme (MCS), new data indicator (new data indicator) , NDI), the time when the uplink transmission is initiated (such as a subframe or a time slot (slot)), the interval of uplink scheduling, and so on.
  • time-frequency resources such as physical uplink share channel (PUSCH) resources
  • MCS modulation coding scheme
  • new data indicator new data indicator
  • NDI new data indicator
  • This application does not limit the specific content included in the UL grant for RACH-less handover.
  • the third preset threshold, the first preset threshold and the second preset threshold described above are only named for the convenience of distinguishing different thresholds, and should not constitute any limitation on the magnitude relationship of the preset thresholds.
  • the time information related to the RACH-less handover failure is related to the process performed by the terminal device in the process of resuming communication. If the terminal device falls back to the source cell, the time information related to RACH-less handover failure may include, for example, one or more of the first time interval, the second time interval, and the third time interval.
  • the first time interval is the time interval from the moment when the terminal device receives the RRC message to the moment when the RACH-less handover fails.
  • the second time interval is the time interval from the moment when the RACH-less handover fails to the moment when the terminal device reverts to the source cell.
  • the third time interval is the time interval from the moment when the terminal device retreats to the source cell to the moment when the terminal device reports the information about the RACH-less handover failure.
  • the time information related to the RACH-less handover failure may include, for example, one or more of the first time interval, the fourth time interval, and the fifth time interval.
  • the fourth time interval is the time interval from the moment when the RACH-less handover fails to the moment when the terminal device and the target cell are successfully randomly accessed.
  • the fifth time interval is the time interval from the moment when the terminal device succeeds in random access to the moment when the terminal device reports the information related to the RACH-less handover failure.
  • the time information related to the RACH-less handover failure may include, for example, one or more of the first time interval, the sixth time interval, and the seventh time interval.
  • the sixth time interval is the time interval from the moment when the RACH-less handover fails to the moment when the terminal device initiates RRC re-establishment.
  • the seventh time interval is the time interval from the moment when the terminal device initiates RRC re-establishment to the moment when the terminal device reports the failure information related to the RACH-less handover.
  • the method further includes: receiving a request message, where the request message is used to request information about the RACH-less handover failure.
  • the terminal device can actively send the RACH-less handover failure related information to the network device, such as the first network device, or can send the RACH-less handover failure related information based on the request of the network device, such as the above request message. This is not limited.
  • the network device that receives the information about the RACH-less handover failure may forward part or all of the information about the RACH-less handover failure to the network device that has demand, for example, the source network device and/ Or the target network device.
  • the source network device and/or the target network device can adjust the handover parameters based on the information related to the RACH-less handover failure, so that the next RACH-less handover uses more reasonable parameters, so that the handover performance is better, and then the RAHC- The success rate and reliability of less switching.
  • a communication method is provided, which may be executed by a network device, or may also be executed by a component (such as a chip or a circuit) configured in the network device.
  • the method includes: receiving a first release instruction, the first release instruction is used to instruct the network device to which the target cell belongs to release the UL grant, and the UL grant is used for the terminal device to switch from the source cell to the target cell through RACH-less handover ; Release the UL grant.
  • the release of the UL grant mentioned here may specifically include the release of the uplink resources scheduled by the UL grant and other information contained in the UL grant, such as the modulation and coding scheme (MCS), new data indication (NDI), and the time when the uplink transmission is initiated (such as subframes or time slots (slots), uplink scheduling intervals, and so on.
  • MCS modulation and coding scheme
  • NDI new data indication
  • time when the uplink transmission is initiated Such as subframes or time slots (slots), uplink scheduling intervals, and so on.
  • the target network device can release the UL grant after determining that the RACH-less handover of the terminal device fails. That is, the UL grant that the terminal device will not use is released for the uplink transmission of other terminal devices. Since the target network device can release the uplink resources scheduled by the UL grant for other terminal devices or other scheduling scenarios, resource utilization can be improved.
  • the receiving the first release instruction includes: receiving the first release instruction from a first network device, the first network device being the source cell or Establish network equipment to which the cell belongs.
  • the first network device may send the first release instruction to the target network device, so that the target network device can release the UL grant.
  • the receiving the first release indication includes: receiving indication information from the terminal device for indicating RACH-less handover failure, the indication information being used to indicate: The terminal device fails the RACH-less handover from the source cell to the target cell to indicate the release of the UL grant.
  • the terminal device can directly send the indication information for indicating the failure of the RACH-less handover to the target network device, so that the target network device can release the UL grant.
  • the first release indication may be, for example, the above-mentioned RACH-less handover failure related information, or part or all of the RACH-less handover failure related information, or may also be based on the RACH-less handover failure. Information generated by failure related information. This application does not limit this.
  • a communication method is provided, which may be executed by a network device, or may also be executed by a component (such as a chip or a circuit) configured in the network device.
  • the method includes: receiving a second release indication for instructing a network device to which the target cell belongs to release a random access channel RACH resource, where the RACH resource is used by the terminal device to initiate a random access procedure to the target cell. Resources used; release the RACH resource.
  • the target network device determines that the terminal device has access to other cells other than the target cell, it can release the RACH resources required to access the target cell, that is, release the RACH resources that the terminal device will not use. Can improve resource utilization.
  • the receiving the second release instruction includes: receiving the second release instruction from the first network device, which is the source cell or re-established The network equipment to which the cell belongs.
  • the first network device may send a second release instruction to the target network device to instruct the target network device to release RACH resources.
  • the second release indication may be, for example, the above-mentioned RACH-less handover failure related information, or part or all of the RACH-less handover failure related information, or may also be based on the RACH-less handover Information generated by failure related information. This application does not limit this.
  • a communication device which includes modules or units for executing the method in the first aspect and any one of the possible implementation manners of the first aspect.
  • a communication device which includes modules or units for executing the second aspect and the method in any one of the possible implementation manners of the second aspect.
  • a communication device including various modules or units for executing the third aspect and the method in any one of the possible implementation manners of the third aspect.
  • a communication device including a processor.
  • the processor is coupled with the memory and can be used to execute instructions or data in the memory to implement the foregoing first aspect and the method in any one of the possible implementation manners of the first aspect.
  • the communication device further includes a memory.
  • the communication device further includes a communication interface, and the processor is coupled with the communication interface.
  • the communication device is a terminal device.
  • the communication interface may be a transceiver, or an input/output interface.
  • the communication device is a chip configured in a terminal device.
  • the communication interface may be an input/output interface.
  • the transceiver may be a transceiver circuit.
  • the input/output interface may be an input/output circuit.
  • a communication device including a processor.
  • the processor is coupled to the memory, and can be used to execute instructions or data in the memory to implement the second aspect and the method in any one of the possible implementation manners of the second aspect.
  • the communication device further includes a memory.
  • the communication device further includes a communication interface, and the processor is coupled with the communication interface.
  • the communication device is a network device.
  • the communication interface may be a transceiver, or an input/output interface.
  • the communication device is a chip configured in a network device.
  • the communication interface may be an input/output interface.
  • the transceiver may be a transceiver circuit.
  • the input/output interface may be an input/output circuit.
  • a communication device including a processor.
  • the processor is coupled to the memory and can be used to execute instructions or data in the memory to implement the third aspect and the method in any one of the possible implementation manners of the third aspect.
  • the communication device further includes a memory.
  • the communication device further includes a communication interface, and the processor is coupled with the communication interface.
  • the communication device is a network device.
  • the communication interface may be a transceiver, or an input/output interface.
  • the communication device is a chip configured in a network device.
  • the communication interface may be an input/output interface.
  • the transceiver may be a transceiver circuit.
  • the input/output interface may be an input/output circuit.
  • a processor including: an input circuit, an output circuit, and a processing circuit.
  • the processing circuit is configured to receive a signal through the input circuit and transmit a signal through the output circuit, so that the processor executes any one of the first aspect to the third aspect and the first aspect to the third aspect. The method in the way.
  • the above-mentioned processor can be one or more chips
  • the input circuit can be an input pin
  • the output circuit can be an output pin
  • the processing circuit can be a transistor, a gate circuit, a flip-flop, and various logic circuits, etc.
  • the input signal received by the input circuit may be received and input by, for example, but not limited to, a receiver
  • the signal output by the output circuit may be, for example, but not limited to, output to and transmitted by the transmitter
  • the circuit can be the same circuit, which is used as an input circuit and an output circuit at different times.
  • the embodiments of the present application do not limit the specific implementation manners of the processor and various circuits.
  • a processing device including a processor and a memory.
  • the processor is used to read instructions stored in the memory, receive signals through a receiver, and transmit signals through a transmitter, so as to implement any one of the first to third aspects and any one of the possible implementation manners of the first to third aspects Method in.
  • processors there are one or more processors and one or more memories.
  • the memory may be integrated with the processor, or the memory and the processor may be provided separately.
  • the memory can be a non-transitory (non-transitory) memory, such as a read only memory (ROM), which can be integrated with the processor on the same chip, or can be set in different On the chip, the embodiment of the present application does not limit the type of memory and the setting mode of the memory and the processor.
  • ROM read only memory
  • sending instruction information may be a process of outputting instruction information from the processor
  • receiving capability information may be a process of the processor receiving input capability information.
  • the data output by the processor can be output to the transmitter, and the input data received by the processor can come from the receiver.
  • the transmitter and receiver can be collectively referred to as a transceiver.
  • the processing device in the above-mentioned eleventh aspect may be one or more chips.
  • the processor in the processing device can be implemented by hardware or software.
  • the processor may be a logic circuit, integrated circuit, etc.; when implemented by software, the processor may be a general-purpose processor, which is implemented by reading software codes stored in the memory, and the memory may Integrated in the processor, can be located outside of the processor, and exist independently.
  • a computer program product includes: a computer program (also called code, or instruction), which when the computer program is executed, causes a computer to execute the first aspect to The third aspect and the method in any one of the possible implementation manners of the first to third aspects.
  • a computer program also called code, or instruction
  • a computer-readable medium stores a computer program (also called code, or instruction) when it runs on a computer, so that the computer executes the first aspect to The third aspect and the method in any one of the possible implementation manners of the first to third aspects.
  • a computer program also called code, or instruction
  • a communication system including the aforementioned network equipment and terminal equipment.
  • FIG. 1 is a schematic diagram of a communication system suitable for the communication method and communication device provided by the embodiments of the present application;
  • FIG. 11 is a schematic block diagram of a communication device provided by an embodiment of the present application.
  • FIG. 12 is a schematic structural diagram of a terminal device provided by an embodiment of the present application.
  • FIG. 13 is a schematic structural diagram of a network device provided by an embodiment of the present application.
  • LTE Long Term Evolution
  • FDD frequency division duplex
  • UMTS Universal Mobile Telecommunication System
  • WiMAX Worldwide Interoperability for Microwave Access
  • NR new wireless Access technology
  • V2X can include vehicle-to-network (V2N) and vehicle-to-vehicle (V2V) , Vehicle to Infrastructure (V2I), Vehicle to Pedestrian (V2P), etc.
  • LTE-V Long Term Evolution-Vehicle
  • LTE-V Long Term Evolution-Vehicle
  • MTC Machine Communication
  • IoT Internet of Things
  • LTE-M Long Term Evolution-Machine
  • M2M Machine to Machine
  • the communication system 100 may include at least two network devices, such as the network device 110 and the network device 120 shown in FIG. 1; the communication system 100 may also include at least one terminal device, such as the one shown in FIG. Terminal equipment 130. Wherein, the terminal device 130 may be mobile or fixed.
  • the network device 110 and the network device 120 are both devices that can communicate with the terminal device 130 via a wireless link, such as a base station or a base station controller. Each network device can provide communication coverage for a specific geographic area, and can communicate with terminal devices located in the coverage area (cell).
  • Figure 1 exemplarily shows two network devices and one terminal device.
  • the communication system 100 may include at least one network device and the coverage of each network device may include other numbers of terminal devices. The embodiment does not limit this.
  • Each of the aforementioned communication devices may be configured with multiple antennas.
  • the plurality of antennas may include at least one transmitting antenna for transmitting signals and at least one receiving antenna for receiving signals.
  • each communication device additionally includes a transmitter chain and a receiver chain.
  • Those of ordinary skill in the art can understand that they can all include multiple components related to signal transmission and reception (such as processors, modulators, multiplexers). , Demodulator, demultiplexer or antenna, etc.). Therefore, multiple antenna technology can be used to communicate between network devices and terminal devices.
  • the wireless communication system 100 may also include other network entities such as a network controller and a mobility management entity, and the embodiment of the present application is not limited thereto.
  • the network device may be any device with wireless transceiver function.
  • the equipment includes, but is not limited to: evolved Node B (eNB), Radio Network Controller (RNC), Node B (Node B, NB), Base Station Controller (BSC) , Base transceiver station (Base Transceiver Station, BTS), home base station (for example, Home evolved NodeB, or Home Node B, HNB), baseband unit (BaseBand Unit, BBU), wireless fidelity (Wireless Fidelity, WIFI) system Access point (Access Point, AP), wireless relay node, wireless backhaul node, transmission point (transmission point, TP) or transmission and reception point (transmission and reception point, TRP), etc., can also be 5G, such as NR ,
  • the gNB may include a centralized unit (CU) and a DU.
  • the gNB may also include an active antenna unit (AAU).
  • CU implements some functions of gNB
  • DU implements some functions of gNB.
  • CU is responsible for processing non-real-time protocols and services, implementing radio resource control (RRC), and packet data convergence protocol (PDCP) The function of the layer.
  • RRC radio resource control
  • PDCP packet data convergence protocol
  • the DU is responsible for processing physical layer protocols and real-time services, and realizes the functions of the radio link control (RLC) layer, media access control (MAC) layer, and physical (PHY) layer.
  • RLC radio link control
  • MAC media access control
  • PHY physical
  • the network device may be a device that includes one or more of a CU node, a DU node, and an AAU node.
  • the CU can be divided into network equipment in an access network (radio access network, RAN), or the CU can be divided into network equipment in a core network (core network, CN), which is not limited in this application.
  • the network equipment provides services for the cell, and the terminal equipment communicates with the cell through the transmission resources (for example, frequency domain resources, or spectrum resources) allocated by the network equipment.
  • the cell may belong to a macro base station (for example, a macro eNB or a macro gNB, etc.) , It may also belong to the base station corresponding to the small cell, where the small cell may include: metro cell, micro cell, pico cell, femto cell, etc. These small cells have the characteristics of small coverage and low transmit power, and are suitable for providing high-speed data transmission services.
  • terminal equipment may also be referred to as user equipment (UE), access terminal, user unit, user station, mobile station, mobile station, remote station, remote terminal, mobile equipment, user terminal, Terminal, wireless communication equipment, user agent or user device.
  • the terminal device in the embodiment of the present application may be a mobile phone (mobile phone), a tablet computer (pad), a computer with wireless transceiver function, a virtual reality (VR) terminal device, and an augmented reality (AR) terminal Equipment, wireless terminals in industrial control, wireless terminals in unmanned driving (self-driving), wireless terminals in remote medical, wireless terminals in smart grid, transportation safety ( Wireless terminal in transportation safety), wireless terminal in smart city, wireless terminal in smart home (smart home), cellular phone, cordless phone, session initiation protocol (SIP) phone, wireless local Loop (wireless local loop, WLL) stations, personal digital assistants (personal digital assistants, PDAs), handheld devices with wireless communication functions, computing devices or other processing devices connected to wireless modems, in-vehicle devices
  • wearable devices can also be called wearable smart devices, which are the general term for using wearable technology to intelligently design daily wear and develop wearable devices, such as glasses, gloves, watches, clothing and shoes.
  • a wearable device is a portable device that is directly worn on the body or integrated into the user's clothes or accessories.
  • Wearable devices are not only a hardware device, but also realize powerful functions through software support, data interaction, and cloud interaction.
  • wearable smart devices include full-featured, large-sized, complete or partial functions that can be achieved without relying on smart phones, such as smart watches or smart glasses, and only focus on a certain type of application function, and need to cooperate with other devices such as smart phones. Use, such as various smart bracelets and smart jewelry for physical sign monitoring.
  • the terminal device may also be a terminal device in an Internet of Things (IoT) system.
  • IoT Internet of Things
  • Its main technical feature is to connect objects to the network through communication technology, so as to realize the intelligent network of human-machine interconnection and interconnection of things.
  • This application does not limit the specific form of the terminal device.
  • Random access is the process from the terminal device starting to send a random access preamble index to the network device trying to access to the connection between the terminal device and the network device.
  • the random access procedure may occur in procedures such as handover and RRC re-establishment, for example.
  • Random access can be divided into contention-based random access (CBRA) and non-competition random access (CFRA).
  • CFRA contention-based random access
  • CFRA resources are dedicated RACH resources.
  • CFRA resources may specifically include preamble index and time-frequency resources.
  • CFRA resources may be CFRA resources associated with a certain beam of a cell. If the network device configures CFRA resources for the terminal device, the terminal device can use the CFRA resource to initiate a CFRA process. If CFRA fails or CFRA resources are not configured, the terminal device can initiate CBRA.
  • CBRA resources can be understood as public resources, and terminal devices can use CBRA resources to initiate CBRA procedures through competition. During the handover, the CFRA process and/or CBRA process can be performed.
  • the contention-based random access procedure may specifically include steps one to four described below.
  • Step 1 The terminal device sends a random access preamble (or random access preamble sequence) index to the network device through a physical random access channel (PRACH).
  • PRACH physical random access channel
  • Step 2 The network device sends a random access response to the terminal device.
  • the random access response may include timing advance (TA), UL grant, and temporary cell-radio network temporary identifier (C-RNTI) of the response.
  • TA timing advance
  • C-RNTI temporary cell-radio network temporary identifier
  • Step 3 Based on the received random access response, the terminal device sends a message/data on the UL grant resource allocated by the network device, for example, sending an RRC establishment request message, which may include the identification information of the terminal device.
  • the identification information may be, for example, the temporary C-RNTI described above.
  • Step 4 After the network device receives the message/data sent by the terminal device on the allocated UL grant resource, if there is no conflict (or no competition), the network device sends a contention resolution message to the terminal device, for example, the network device sends the terminal device Send RRC setup message. After that, the terminal device can communicate with the network device.
  • the CFRA process can specifically include steps (1) to (2) described below.
  • Step (1) The terminal device sends a random access preamble index (or called a random access preamble sequence) to the network device through PRACH.
  • a random access preamble index (or called a random access preamble sequence)
  • the random access preamble index is allocated to the terminal device in advance by the network device. In other words, the random access preamble index is dedicated.
  • Step (2) The network device sends a random access response to the terminal device.
  • the random access response may include TA, UL grant, etc. of the response.
  • the UL grant may specifically include at least one of the following: time-frequency resources, modulation and coding scheme (MCS), new data indication (NDI), the time at which the uplink transmission is initiated (such as a subframe or slot), and Uplink scheduling interval, etc.
  • time-frequency resource included in the UL grant may specifically refer to the time-frequency location of the uplink resource scheduled through the UL grant.
  • the uplink resources scheduled by the UL grant may be PUSCH resources, for example.
  • RRC re-establishment When a terminal device fails to switch, RLF, RRC reconfiguration fails, etc., the terminal device can initiate an RRC re-establishment process.
  • the RRC re-establishment process may include the following steps:
  • Step 1 The terminal device sends an RRC re-establishment request message to the re-established cell (or the network device to which the cell belongs);
  • Step 2 Re-establish the cell to allow the terminal device's request, then send an RRC re-establishment message to the terminal device;
  • Step 3 The terminal device sends an RRC re-establishment complete message to the re-established cell.
  • the re-established cell may be a cell determined by the terminal device through cell search or detection.
  • the re-established cell may be a cell that meets predetermined criteria, such as the cell selection S criteria in the NR protocol TS38.304-f30.
  • predetermined criteria such as the cell selection S criteria in the NR protocol TS38.304-f30.
  • the embodiment of the beam in the NR protocol can be a spatial filter, or a spatial filter or a spatial parameter.
  • the beam used to transmit the signal can be called the transmission beam (Tx beam), can be called the spatial transmission filter (spatial domain transmit filter) or the spatial transmission parameter (spatial domain transmit parameter);
  • the beam used to receive the signal can be It is called a receive beam (reception beam, Rx beam), and can be called a spatial domain receive filter or a spatial domain receive parameter.
  • a beam can be understood as a spatial resource, and can refer to a transmission or reception precoding vector with energy transmission directivity.
  • the transmission or reception precoding vector can be identified by index information, and the index information can correspond to a resource identification (identity, ID) configured to the terminal.
  • ID resource identification
  • the index information can correspond to a configured synchronization signal block (synchronization signal block). block, SSB) identifier or resource; it can also correspond to the configured channel state information reference signal (channel state information reference signal, CSI-RS) identifier or resource; it can also correspond to the configured uplink sounding reference signal (sounding reference signal, SRS) identification or resource.
  • the index information may also be index information that is explicitly or implicitly carried by a signal or channel carried by a beam.
  • the energy transmission directivity may refer to precoding processing of the signal to be sent by the precoding vector, the precoding processing signal has a certain spatial directivity, and receiving the precoding processing after the precoding vector
  • the signal has good received power, such as meeting the signal-to-noise ratio of receiving and demodulation, etc.; the energy transmission directivity may also mean that the same signal sent from different spatial positions received through the precoding vector has different received power.
  • the same communication device (such as a terminal device or a network device) may have different precoding vectors, and different devices may also have different precoding vectors, that is, corresponding to different beams.
  • a communication device can use one or more of multiple different precoding vectors at the same time, that is, one beam or multiple beams can be formed at the same time.
  • beams can be divided into transmitting beams and receiving beams.
  • the transmitting beam may refer to the distribution of signal strength in different directions in space after a signal is transmitted through the antenna
  • the receiving beam may refer to the signal strength distribution of the wireless signal received from the antenna in different directions in space.
  • the beam may be a wide beam, or a narrow beam, or other types of beams.
  • the beam forming technology may be beamforming technology or other technologies.
  • the beamforming technology may specifically be a digital beamforming technology, an analog beamforming technology, or a hybrid digital/analog beamforming technology, etc. Different beams can be considered as different resources. The same information or different information can be sent through different beams.
  • multiple beams with the same or similar communication characteristics are regarded as one beam.
  • One or more antenna ports can be included in a beam for transmitting data channels, control channels, and sounding signals.
  • One or more antenna ports forming a beam can also be regarded as an antenna port set.
  • each network device can be divided into one or more cells, and each cell can correspond to one or more frequency points, in other words, each cell can be regarded as the coverage area of one or more frequency points.
  • the formed area can be divided into one or more cells, and each cell can correspond to one or more frequency points, in other words, each cell can be regarded as the coverage area of one or more frequency points. The formed area.
  • the cell may be an area within the coverage of the wireless network of the network device.
  • different cells may correspond to the same or different network devices.
  • the network equipment to which cell #1 belongs and the network equipment to which cell #2 belongs may be different network equipment, such as a base station. That is, cell #1 and cell #2 can be managed by different base stations.
  • the network equipment that manages cell #1 and the network equipment that manages cell #2 may also be different radio frequency processing units of the same base station, for example, a radio remote unit (RRU), that is, Cell #1 and cell #2 can be managed by the same base station, have the same baseband processing unit and intermediate frequency processing unit, but have different radio frequency processing units.
  • RRU radio remote unit
  • the network device to which cell #1 belongs and the network device to which cell #2 belongs may be the same network device, such as a base station.
  • the cell #1 and the cell #2 can be managed by the same base station.
  • gNB may include CU and DU in some possible deployments.
  • cell #1 and cell #2 can be managed by the same CU and the same DU, that is, share CU and share DU; cell #1 and cell #2 can be managed by the same CU and different DUs, That is, they share CU but do not share DU; cell #1 and cell #2 may also be managed by different CUs and different DUs, that is, do not share CU and do not share DU.
  • Handover In a wireless communication system, when a terminal device moves/closes from one cell to another cell, in order to keep the communication of the terminal device uninterrupted, it needs to be switched.
  • the source cell refers to a cell that provides services for the terminal device before handover
  • the target cell refers to a cell that provides services for the terminal device after the handover.
  • Relevant information of the target cell can be indicated by a handover message, which is the network device to which the source cell belongs (That is, the source network device) sent to the terminal device.
  • Handover can be intra-station handover or inter-station handover.
  • In-site handover means that the source cell and target cell belong to the same network equipment (such as a base station), where the source cell and target cell can be the same cell or different cells;
  • inter-site handover means that the source cell and target cell belong to different Network equipment (such as base stations). This application does not limit this.
  • the cell is the coverage area of the network equipment
  • the source cell corresponds to the source network equipment (for example, the source base station)
  • the target cell corresponds to the target network equipment (for example, the target base station).
  • the source cell and the target cell may belong to the same network device, or in other words, the source cell and the target cell may be co-sited.
  • the TA corresponding to the target cell may be equal to the TA corresponding to the source cell.
  • the target cell may also be a small cell.
  • the TA of the target cell may be 0.
  • the mobility management of the terminal equipment is controlled by the network equipment. That is, the network device instructs the terminal device to switch to which cell and how to switch by sending a handover message.
  • the source network device sends a handover message to the terminal device to control the terminal device to switch from the source cell to the target cell.
  • the handover message may be an RRC message.
  • the RRC message may be an RRC connection reconfiguration message that carries mobility control information (mobility control info); in an NR system, the RRC message may be a synchronization reconfiguration information element (reconfiguration with sync) RRC reconfiguration message.
  • the handover message contains the parameters required by the target network device (that is, the network device to which the target cell belongs) configured for the terminal device to access the target cell, for example, including the information of the target cell (such as the physical cell identifier of the target cell). identifier (PCI) and frequency information corresponding to the target cell, the C-RNTI allocated by the target network device to the terminal device), RACH resource information (such as dedicated RACH resources and/or public RACH resources) required to access the target cell, etc.
  • the terminal device initiates a random access procedure to the target network device according to the content contained in the handover message.
  • NR introduces beam characteristics, and the target network device can consider the beam characteristics when configuring the RACH resource information required to access the target cell. For example, when configuring CFRA resources, the target network device may configure RACH resources associated with beams (such as SSB or CSI-RS) under the target cell.
  • the handover message and the foregoing RRC message for indicating handover are described from different perspectives.
  • the handover message is described from a functional perspective, and aims to express that the message is used to instruct the terminal device to switch.
  • the RRC message is described from the perspective of message type, and aims to express that the message is high-level signaling.
  • the RRC reconfiguration message is an enumeration of RRC messages. In other words, the handover message is sent to the terminal device through high-level signaling.
  • RRC messages are listed above, such as RRC connection reconfiguration messages in LTE, RRC reconfiguration messages in NR, etc. These messages are only examples for ease of understanding and should not constitute any limitation to this application. This application does not limit the specific name of the RRC message used to instruct the terminal device to initiate the handover process.
  • RACH-less handover (RACH-less HO): As mentioned earlier, in order to reduce the delay caused by the random access process, the terminal device can initiate handover from the source cell to the target cell based on the RACH-less handover, namely The terminal device can skip (do not perform) the RACH process with the target cell. After receiving the handover message, the terminal device can use the UL grant indicated in the message to send the RRC reconfiguration complete message to the target network device according to the handover message, such as the RRC reconfiguration message described above, without performing random access. Into the process.
  • the handover message may include indication information, and the indication information is used to instruct the terminal device to perform RACH-less handover.
  • the terminal device cannot successfully access/handover to the target cell, that is, the target cell cannot subsequently provide services for the terminal device.
  • the handover message may include UL grant information associated with the beam of the target cell.
  • the handover message may also include a preset threshold.
  • the terminal device can use the signal quality in the target cell (the signal quality can be evaluated by reference signal receiving power (RSRP) or reference signal receiving quality (RSRQ), etc.) higher than the preset
  • RSRP reference signal receiving power
  • RSRQ reference signal receiving quality
  • the UL grant associated with the threshold beam sends an RRC reconfiguration complete message to the target network device.
  • This RACH-less handover failed if there is no beam with a signal quality higher than the preset threshold among the beams configured by the target cell that is associated with the UL grant, or in other words, there is no beam associated with the UL grant and the signal quality is higher than the preset threshold in the target cell, then This RACH-less handover failed.
  • RRC connection Before the terminal device communicates normally, it can establish an RRC connection with a network device, or in other words, an RRC connection with a cell. When the RRC connection is disconnected, the terminal device cannot communicate normally.
  • the terminal device determines whether there is an RRC connection with the source cell after the RACH-less handover.
  • the terminal device determines whether there is an RRC connection with the source cell, which mainly depends on two factors: 1) whether the source cell has RLF; 2) after receiving the handover message, whether the terminal device is in the process of trying to access the target cell, The ability to connect with the source cell can still be maintained. For example, whether the terminal device has the ability to keep connected before disconnection (MBB), or whether the terminal device has the ability to keep connected before disconnection (eMBB) enhanced.
  • the terminal device having MBB capability may specifically refer to that the terminal device can still maintain the RRC connection (or data scheduling) with the source cell before sending the random access preamble index;
  • the terminal device having eMBB capability may specifically refer to:
  • the terminal device can maintain the RRC connection (or data scheduling) with the source cell while performing the random access process with the target cell, for example, until the source cell has RLF, or until the source network device or the target network device notifies the terminal The device releases the RRC connection with the source cell. Before that, the terminal device can still maintain the RRC connection (or data scheduling) with the source cell.
  • the terminal device if the terminal device is capable of MBB or eMBB, if the signal quality of the source cell is good, it can maintain the RRC connection with the source cell, or it can also disconnect the RRC connection with the source cell. It depends on the realization of the terminal equipment and is not limited. However, when the signal quality of the source cell deteriorates, RLF may occur. If RLF occurs in the source cell, RRC connection disconnection will still occur even if the terminal device has MBB or eMBB capabilities. In one implementation, when the upper layer of the terminal device continuously receives the asynchronous signal sent by the physical layer several times (for example, continuously receives N310 asynchronous signals (out-of-sync) from the physical layer), the source can be determined RLF occurs in the cell.
  • the terminal device determines that the source cell has RLF or does not have MBB or eMBB capability, or the terminal device disconnects the RRC connection with the source cell, it can determine that the RRC connection with the source cell is disconnected.
  • the RRC connection between the terminal device and the source cell is disconnected, which means that there is no RRC connection between the terminal device and the source cell.
  • the terminal device needs to adopt a reasonable method to restore communication, which is a technical problem to be solved urgently. For example, if the terminal device still maintains an RRC connection with the source cell when the RACH-less handover fails, but the terminal device initiates an RRC re-establishment process, signaling overhead will be caused and the implementation complexity will be high. Therefore, the processing method of the terminal device is not very reasonable, which affects the user experience.
  • the present application provides a communication method to provide a reasonable recovery mechanism for the terminal device in the case of RACH-less handover failure.
  • "used to indicate” may include used for direct indication and used for indirect indication, and may also include explicit indication and implicit indication.
  • the information indicated by a certain piece of information is called information to be indicated.
  • the information to be indicated can be directly indicated, such as the information to be indicated or the information to be indicated. Index of the information to be indicated, etc.
  • the information to be indicated can also be indicated indirectly by indicating other information, where there is an association relationship between the other information and the information to be indicated. It is also possible to indicate only a part of the information to be indicated, and other parts of the information to be indicated are known or agreed in advance. For example, it is also possible to use a pre-arranged (for example, protocol stipulation) whether there is a certain cell to indicate the information to be indicated, thereby reducing the indication overhead to a certain extent.
  • protocol stipulation for example, protocol stipulation
  • the first, second, and various numerical numbers are only for easy distinction for description, and are not used to limit the scope of the embodiments of the present application. For example, distinguish different indication information, different time intervals, etc.
  • “pre-defined” or “pre-configured” can be realized by pre-saving corresponding codes, tables, or other methods that can be used to indicate relevant information in devices (for example, including terminal devices and network devices).
  • the specific implementation method is not limited.
  • "saving” may refer to saving in one or more memories.
  • the one or more memories may be provided separately, or integrated in an encoder or decoder, a processor, or a communication device.
  • the one or more memories may also be partly provided separately, and partly integrated in the decoder, processor, or communication device.
  • the type of the memory may be any form of storage medium, which is not limited in this application.
  • the “protocols” involved in the embodiments of the present application may refer to standard protocols in the communication field, for example, may include LTE protocol, NR protocol, and related protocols applied to future communication systems, which are not limited in this application.
  • At least one refers to one or more, and “multiple” refers to two or more.
  • And/or describes the association relationship of the associated objects, indicating that there can be three types of relationships, for example, A and/or B, which can mean: A alone exists, both A and B exist, and B exists alone, where A, B can be singular or plural.
  • the character “/” generally indicates that the associated objects are in an "or” relationship.
  • "The following at least one item (a)” or similar expressions refers to any combination of these items, including any combination of a single item (a) or plural items (a).
  • At least one of a, b, and c can mean: a, or, b, or, c, or, a and b, or, a and c, or, b and c, or, a , B, and c.
  • a, b, and c can be single or multiple.
  • the message names involved are all message names in the NR.
  • these message names are only examples for ease of understanding, and should not constitute any limitation to this application.
  • This application does not exclude the possibility of defining other message names in future agreements to replace the message names listed in this application to achieve the same or similar functions.
  • the message name in the NR is taken as an example to illustrate the embodiments of this application, which should not constitute any limitation to the scenarios to which the method provided in this application is applicable.
  • the method provided in this application can also be applied to the LTE system.
  • the terminal device shown in the following embodiments may be replaced with a component (such as a chip or a circuit) configured in the terminal device.
  • the network devices shown in the following embodiments can also be replaced with components (such as chips or circuits) configured in the network devices.
  • the embodiments shown below do not particularly limit the specific structure of the execution body of the method provided by the embodiments of the present application, as long as the program that records the code of the method provided by the embodiments of the present application can be provided according to the embodiments of the present application.
  • the execution subject of the method provided in the embodiment of the present application may be a terminal device or a network device, or a functional module in the terminal device or network device that can call and execute the program.
  • FIG. 2 is a schematic flowchart of a communication method 200 according to an embodiment of the present application, shown from the perspective of device interaction. As shown in FIG. 2, the method 200 may include step 210 to step 250. The steps in the method 200 are described in detail below.
  • step 210 the terminal device receives an RRC message, which instructs the terminal device to initiate RACH-less handover from the source cell to the target cell.
  • the RRC message can be sent by the source network device.
  • the RRC message may be a message used to instruct the terminal device to initiate RACH-less handover from the source cell to the target cell.
  • the message may carry indication information, which is used to instruct the terminal device to initiate the source cell RACH-less handover to the target cell.
  • the RRC message may be an RRC reconfiguration message carrying a reconfiguration with sync (reconfiguration with sync)
  • the message may be an RRC connection reconfiguration message carrying mobility control information (mobility control info) .
  • This application does not limit the specific name of the RRC message.
  • the indication information may, for example, explicitly instruct the terminal device to initiate RACH-less handover from the source cell to the target cell. For example, it is indicated by a certain predefined field in the RRC message. In this case, the indication information may be a certain predefined field in the RRC message.
  • the indication information may also implicitly instruct the terminal device to initiate RACH-less handover from the source cell to the target cell.
  • the above RRC message may include UL grant information for RACH-less handover.
  • the terminal device may determine to initiate the transfer from the source cell to the UL grant information for RACH-less handover. RACH-less handover of the target cell.
  • the indication information may be UL grant information in the RRC message.
  • the RRC message may include the parameters that the target network device configures for the terminal device and are required to access the target cell. For example, it contains the information of the target cell (such as the physical cell identifier (PCI) of the target cell and the frequency information corresponding to the target cell, the C-RNTI allocated by the target network device to the terminal device), and the information required to access the target cell RACH resource information (for example, dedicated RACH resources and/or public RACH resources), and UL grant information required for handover to the target cell through RACH-less handover.
  • PCI physical cell identifier
  • RACH resource information for example, dedicated RACH resources and/or public RACH resources
  • the terminal device uses the UL grant allocated by the target network device to the terminal device to send an RRC reconfiguration complete message to the target network device. In this way, the terminal device completes the RACH-less handover from the source cell to the target cell.
  • the UL grant allocated by the target network device to the terminal device may be the UL grant associated with the beam.
  • the handover message sent by the source network device to the terminal device includes UL grants respectively associated with one or more beams under the target cell, and the handover message may include a preset threshold, for example, recorded as the first Three preset thresholds.
  • the terminal device detects that there is a beam with a signal quality higher than the third preset threshold in the target cell, and the handover message contains the UL grant associated with the beam, the terminal device can use the UL grant associated with the beam to send to the target cell RRC reconfiguration complete message.
  • the physical downlink control channel (physic downlink control channel, PDCCH) sent by the target network device to the terminal device may include UL grant information.
  • the target network device may send a PDCCH to the terminal device through a certain beam, and the PDCCH includes UL grant information, that is, the UL grant information may be associated with the beam that transmits the PDCCH including the UL grant information.
  • the handover message may include a preset threshold, for example, the aforementioned third preset threshold.
  • the terminal device When the terminal device detects that there is a beam with a signal quality higher than the third preset threshold in the target cell, and the PDCCH sent on the beam contains UL grant information associated with the beam, the terminal device can use the beam associated with the beam
  • the UL grant sends an RRC reconfiguration complete message to the target cell.
  • the UL grant information described here is used to indicate the UL grant.
  • the UL grant may specifically include at least one of the following: time-frequency resources (such as PUSCH resources), MCS, NDI, time of initiating uplink transmission (such as subframes or slots), uplink scheduling interval, and so on. This application does not limit the specific content included in the UL grant for RACH-less handover.
  • the signaling/message used to carry UL grant information is not limited to the above list, and this application does not limit the specific signaling/message containing UL grant information.
  • step 220 the terminal device determines that the RACH-less handover fails.
  • the prerequisite for successful RACH-less handover of the terminal equipment from the source cell to the target cell is that there is a beam with a signal quality higher than the third preset threshold in the target cell, and the beam has an associated UL grant
  • the UL grant is allocated by the target network device to the terminal device, and may be included in the handover message sent by the source network device or in the PDCCH sent by the target network device.
  • the terminal device does not receive a beam with a signal quality higher than the third preset threshold from the target cell (or the terminal device finds that there is no beam with a signal quality higher than the third preset threshold in the target cell after measurement), or even if the signal is received
  • the terminal device does not allocate the UL grant associated with the beam, the RACH-less handover from the source cell to the target cell initiated by the terminal device fails.
  • the target network device pre-configures the UL grant, it gives one or more beams with poor quality (For example, the signal quality of these beams is lower than the third preset threshold) UL grant is pre-allocated.
  • the terminal device may fail to RACH-less handover because there is no beam with a signal quality higher than the third preset threshold and associated with a UL grant in the target cell.
  • the reason for the failure of the RACH-less handover from the source cell to the target cell initiated by the terminal device is not limited to the above.
  • Several possible scenarios of RACH-less handover failure are listed below.
  • the timer T304 represents the duration of the timer used by the terminal device when switching.
  • the foregoing RRC reconfiguration message may include relevant information of the timer T304, such as the effective duration of T304.
  • the timer T304 can start timing when the terminal device receives the RRC reconfiguration message. If the effective duration of T304 arrives, but the terminal device has not successfully accessed the target cell, it is considered that the handover has failed.
  • the T304 mechanism is also applicable to RACH-less handover, that is, the RRC reconfiguration message instructing the terminal device to perform RACH-less handover can include the effective duration of T304. After the terminal device receives the RRC message, it starts T304.
  • the terminal device has not successfully switched to the target cell (for example, the terminal device failed to send an RRC reconfiguration complete message to the target network device), it can be considered that the RACH-less handover initiated by the terminal device from the source cell to the target cell has failed.
  • the terminal device fails to send the RRC reconfiguration complete message to the target network device, for example, the terminal device does not send the RRC reconfiguration complete message, or the terminal device does not receive the RRC reconfiguration complete message although it has sent
  • the acknowledgement message (acknowledgement, ACK) fed back to the target network device.
  • the reason for the failure of the RACH-less handover is that there is no beam with a signal quality higher than the third preset threshold and associated with a UL grant in the target cell.
  • the failure reason value can be expressed as: HOF or RACH-less HOF or T304 timeout or there is no beam with signal quality higher than a certain preset threshold and associated with UL grant, which is not limited in this application.
  • the terminal device has determined that the signal quality is higher than the third preset threshold and is associated with the UL grant beam, but the terminal device has not successfully sent the RRC reconfiguration complete message. For example, if the number of retransmissions of the RRC reconfiguration complete message reaches the maximum and the RRC reconfiguration complete message cannot be successfully sent, it can be considered that the RACH-less handover from the source cell to the target cell initiated by the terminal device fails. Since the RRC reconfiguration complete message was not successfully sent, when the running time of the timer T304 reached, the terminal device still failed to complete the RACH-less handover.
  • the reason for the failure of RACH-less handover is that the number of retransmissions reaches the maximum.
  • the failure cause value can be expressed as HOF or RACH-less HOF, or the number of retransmissions reaches the maximum value, which is not limited in this application.
  • Timer T310 is a timer for terminal equipment to detect RLF.
  • the effective duration of T310 may be, for example, sent by the source network device to the terminal device through signaling in advance, or may be predefined, which is not limited in this application.
  • the terminal device starts the timer when a physical layer failure is detected. If the terminal device does not receive the RRC reconfiguration message sent by the source network device within the effective duration of the timer T310, it is considered that the RACH-less handover fails. In this case, the cause of RACH-less handover failure is RLF.
  • the failure reason value can be expressed as RLF, for example, which is not limited in this application.
  • the RRC reconfiguration message received by the terminal device from the source network device may be a handover message for instructing the terminal device to initiate RACH-less handover from the source cell to the target cell.
  • the RACH-less handover from the source cell to the target cell initiated by the terminal device is successful, but the signal quality of the target cell is unstable, and the terminal device quickly generates RLF in the target cell, resulting in the final failure of the RACH-less handover. If the terminal device accesses the source cell after RLF occurs in the target cell, in this case, the cause of RACH-less handover failure is premature handover; if the terminal device accesses the new cell after RLF occurs in the target cell In this case, the reason for the failure of RACH-less handover is handover to the wrong cell (for example, the target cell is not suitable). At this time, the failure cause value can be expressed as RLF or handover to the wrong cell, for example, which is not limited in this application.
  • the main reasons for the failure of the RACH-less handover from the source cell to the target cell initiated by the terminal device include: the target cell does not have a signal quality higher than the third preset threshold and is associated with a UL grant The beam, HOF (or RACH-less HOF or the number of retransmissions reaches the maximum) or RLF or handover to the wrong cell.
  • the terminal device communicates with a first network device, and the first network device is a network device to which the source cell belongs or a network device to which the target cell belongs or a network device to which the reestablished cell belongs, and the reestablished cell is a terminal device
  • the cell that attempts to access the network device to which the source cell belongs ie, the source network device
  • fails and/or the random access to the target cell fails.
  • the terminal device can communicate with the network device to which one of the source cell, target cell, and re-established cell belongs.
  • the terminal device may specifically implement communication with the first network device through one or more of fallback to the source cell, random access to the target cell, or RRC re-establishment, so as to resume normal communication of the terminal device.
  • the RRC connection may be established after the RACH-less handover fails, such as the RRC connection between the terminal device and the target cell or the RRC connection between the terminal device and the re-established cell; the RRC connection may also be established on the RACH-less. The less has existed before the handover and has not been disconnected due to the RACH-less handover. In other words, the RRC connection may be maintained before and after the RACH-less handover, such as the RRC connection between the terminal device and the source cell.
  • the re-established cell may refer to a cell accessed by initiating an RRC re-establishment procedure.
  • the terminal device may select a cell that meets a predetermined criterion from neighboring cells.
  • the predetermined criterion may be the cell selection S criterion.
  • the terminal device performs cell selection, regards a cell that meets the cell selection S criterion as a re-established cell, and initiates an RRC re-establishment procedure to the re-established cell to access the cell.
  • the re-established cell may be, for example, the source cell, the target cell, or other cells. This application does not limit this.
  • the re-established cell may be a cell that the terminal device requests to access when the terminal device fails to communicate with the source network device, or it may be the terminal device that fails to initiate random access with the target cell.
  • the cell requested for access may also be a cell that is accessed when the terminal device fails to attempt to communicate with the source network device and the random access initiated with the target cell fails. This application does not limit this.
  • the cells can be on the same site or different sites, which is not limited in this application.
  • the same station may refer to the same network device, for example, the same CU and the same DU, or the same CU but different DUs.
  • different stations may refer to different network devices, such as different CUs and different DUs. It should be understood that this application does not limit the specific form of the network device.
  • the terminal device may fall back to the source cell while maintaining an RRC connection with the source cell.
  • the "maintain RRC connection” mentioned here may mean that the RRC connection has existed before, for example, it has always existed before the terminal device performs RACH-less handover, and the terminal device can communicate with the source network device through the RRC connection. And after the RACH-less handover fails, the RRC connection is not disconnected, and the terminal device can still communicate with the source network device through the RRC connection.
  • the terminal device can determine whether the RRC connection with the source cell is disconnected by determining whether the source cell has RLF or whether the terminal device itself has MBB or eMBB capabilities. In the case that the RRC connection between the terminal device and the source cell is not disconnected, the terminal device can directly fall back to the source cell.
  • the aforementioned first network device is the network device to which the source cell belongs, that is, the source network device.
  • the terminal device falls back to the source cell, that is, the terminal device continues to communicate with the source network device through the connection with the source cell.
  • the terminal device can directly initiate a random access procedure to the target cell when the RACH-less handover fails.
  • the terminal device may send the random access preamble index to the target network device based on the RACH resource configured by the target network device in the RRC reconfiguration message. If the random access initiated by the terminal device to the target cell is successful, an RRC connection can be established between the terminal device and the target cell.
  • the foregoing first network device is the network device to which the target cell belongs, that is, the target network device.
  • the terminal device may initiate a random access procedure to the target cell when the RACH-less handover fails, but the random access fails.
  • the terminal device may further initiate RRC re-establishment to a cell meeting a predetermined criterion through cell selection.
  • the terminal device may directly initiate RRC re-establishment when the RACH-less handover fails and the RRC connection with the source cell is disconnected.
  • the terminal device can establish an RRC connection with the re-established cell.
  • the above-mentioned first network device is the network device to which the re-established cell belongs.
  • FIG. 2 is only an example, and the source network device and the first network device are shown as two different network devices.
  • the first network device and the source network device may be the same network device or different network devices.
  • the figure is only an example and should not constitute any limitation to the application.
  • the terminal device falls back to the source cell, the first network device and the source network device are the same network device; for another example, if the terminal device accesses the target cell through random access, but the target cell and the source cell are on the same site ,
  • the target network device and the source network device can be the same network device. That is, the first network device and the source network device may also be the same network device.
  • the network device to which the cell belongs and the source network device are re-established It can be the same network device. That is, the first network device and the source network device may also be the same network device.
  • FIG. 2 is only an example for ease of understanding and does not show various possible situations. Those skilled in the art can understand the relationship between the source network device and the first network device in different situations. Figure 2 is not shown one by one for the sake of brevity.
  • the communication method provided by the embodiments of the present application provides a variety of ways for the terminal device to resume communication when the terminal device fails the RACH-less handover from the source cell to the target cell.
  • the terminal device can implement communication with the network device by falling back to the source cell or randomly accessing the target cell.
  • the terminal device may also initiate RRC re-establishment to achieve communication with the network device. Therefore, after the RACH-less handover fails, the terminal device can try to restore the normal communication with the network device in a more reasonable manner to minimize the communication interruption time delay.
  • the fallback source cell fails or the random access to the target cell fails the RRC re-establishment process can still be used to restore normal communication with the network device.
  • the terminal device If the terminal device maintains an RRC connection with the source cell, it still resumes normal communication through a complicated RRC re-establishment process, or if the terminal device can access the target cell through a random access process, but through a complicated
  • the RRC re-establishment process to resume communication will on the one hand cause communication interruption to the user and affect the user experience; on the other hand, it will also cause the complexity of the terminal device implementation and increase the power consumption of the terminal device. This communication interruption and power consumption can be avoided or reduced. Therefore, the technical solution provided in this application provides a reasonable recovery mechanism for terminal devices that fail RACH-less handover, which is beneficial to improve user experience.
  • step 230 will be further described below with reference to FIGS. 3 to 8.
  • FIG. 3 to FIG. 8 schematically show the steps in which the terminal device determines that the RACH-less handover fails.
  • step 220 For the related description of this step, reference may be made to the related description of step 220 above. For the sake of brevity, it will not be repeated here.
  • the terminal device may prioritize fallback to the source cell or random access to the target cell after determining that the RACH-less handover fails.
  • the behavior of the terminal device can be pre-regulated.
  • priority is given to fall back to the source cell; or, in case of a RACH-less handover failure, priority is given to random access to the target cell.
  • the terminal device can decide subsequent actions (for example, fall back to the source cell or random access to the target cell or RRC re-establishment) through corresponding judgments.
  • Fig. 3 is a schematic flowchart of a communication method provided by an embodiment of the present application. The process shown in FIG. 3 may specifically include step 301 to step 306.
  • the terminal device determines whether there is an RRC connection with the source cell in step 301. Specifically, in step 301, the terminal device may determine whether an RLF occurs in the source cell or whether the RRC connection between the terminal device and the source cell is maintained.
  • the terminal device can determine whether the RRC connection between the terminal device and the source cell is disconnected by whether the source cell has RLF. If it is disconnected, it means that the RRC connection does not exist; if it is not disconnected, it means that the RRC connection does not exist. RRC connection exists. Or, the terminal device can determine whether there is an RRC connection between the terminal device and the source cell according to whether it has MBB or eMBB capabilities. If it can continue to be maintained, it means that the RRC connection exists; if it does not continue to be maintained, it means that the RRC connection exists. The connection does not exist.
  • step 301 can also be replaced by the terminal device determining whether to maintain an RRC connection with the source cell.
  • step 302 is executed, and the terminal device performs the operation of falling back to the source cell. If the terminal device successfully rolls back to the source cell by performing step 302, the terminal device can perform step 303 to communicate with the source network device; if the terminal device fails to roll back to the source cell by performing step 302, that is, the source cell is rolled back If it fails, the terminal device can perform step 304 to perform random access with the target cell.
  • the failure of the terminal device to fall back to the source cell may be caused by reasons such as heavy load on the source cell. If the terminal device fails to fall back to the source cell, it can resume communication by initiating random access to the target cell or initiating RRC re-establishment, which is not limited in this application.
  • the figure is only an example, showing the process of the terminal device performing random access with the target cell after the fallback source cell fails, but does not show the process of performing RRC re-establishment after the fallback source cell fails. But this should not constitute any limitation to this application. If the terminal device determines in step 301 that there is no RRC connection with the source cell, step 304 is directly executed, and the terminal device initiates a random access procedure to the target cell.
  • the type of random access initiated by the terminal device to the target cell may include: CFRA and/or CBRA.
  • the terminal equipment can complete random access only through CFRA or only through CBRA, or through CFRA first and then CBRA.
  • the terminal device may preferentially perform a random access procedure with the target cell through the CFRA resources. If the random access of the terminal device with the target cell through the CFRA resource is successful, the random access of the terminal device is successful this time.
  • step 305 may be performed to communicate with the target network device. If the terminal device fails to initiate random access to the target cell through CFRA resources, the terminal device can initiate random access to the target cell through CBRA resources. If the random access initiated by the terminal device to the target cell through the CBRA resource is successful, the random access of the terminal device is successful this time. When the terminal device accesses the target cell, step 305 may be executed to communicate with the target network device. If the terminal device fails to initiate random access to the target cell through the CBRA resource, the terminal device fails this random access.
  • the terminal device can initiate a random access procedure to the target cell through the CBRA resource. If the random access initiated by the terminal device to the target cell through the CBRA resource is successful, the random access of the terminal device is successful this time.
  • step 305 may be performed to communicate with the target network device. If the random access initiated by the terminal device to the target cell through the CBRA resource fails, the random access of the terminal device fails this time.
  • the terminal device can execute step 306 to initiate an RRC re-establishment procedure.
  • the terminal device may select a cell that meets a predetermined criterion from neighboring cells.
  • the preset condition may be the S criterion.
  • the terminal device performs cell selection and regards the cell satisfying the S criterion as the re Establish a cell and initiate an RRC re-establishment process to the cell.
  • an RRC connection is established between the terminal device and the re-established cell.
  • the terminal device can communicate with the network device to which the reestablished cell belongs.
  • FIG. 4 is a schematic flowchart of a communication method provided by another embodiment of the present application.
  • the process shown in FIG. 4 may specifically include step 401 to step 406.
  • the terminal device After determining that the RACH-less handover fails, the terminal device initiates a random access procedure to the target cell in step 401.
  • the type of random access initiated by the terminal device to the target cell may include CFRA and/or CBRA. Since the above step 303 has described the random access procedure in detail, for the sake of brevity, it will not be repeated here.
  • the terminal device can communicate with the target network device in step 402. If the terminal device fails to initiate random access to the target cell in step 401, the terminal device can have two options: fall back to the source cell or initiate RRC re-establishment.
  • the terminal device may prioritize fallback to the source cell.
  • Step 405 can communicate with the source network device; if the terminal device fails to roll back to the source cell by performing step 404, that is, the fallback to the source cell fails, then Step 406 can be executed to initiate RRC re-establishment.
  • the terminal device can perform step 406 to initiate an RRC re-establishment process.
  • the terminal device may communicate with the network device to which the re-established cell belongs after completing the RRC re-establishment procedure.
  • the terminal device may also further combine the signal quality of the source cell and the target cell (the signal quality may be evaluated by RSRP and/or RSRQ, for example) to determine whether to fall back to the source cell or randomly access the target cell.
  • the terminal device may preferentially select random access to the target cell when the signal quality of the target cell meets the preset condition (for the convenience of distinction and description, it is recorded as the first preset condition), and when the first In the case of preset conditions, priority is given to fall back to the source cell.
  • the terminal device may preferentially choose to fall back to the source cell when the signal quality of the source cell meets the preset condition (for the convenience of distinction and description, it is recorded as the second preset condition), and if the second In the case of preset conditions, random access to the target cell is preferred.
  • the preset condition for the convenience of distinction and description, it is recorded as the second preset condition
  • the first preset condition may be, for example, that there is a beam with a signal quality higher than a certain threshold in the target cell; or, the first preset condition may also be, for example, that the cell signal quality of the target cell is higher than a certain threshold. Or, the first preset condition may also be, for example, that the cell signal quality of the target cell is higher than the cell signal quality of the source cell by a certain threshold. For the sake of brevity, I will not list them all here.
  • the beam may be further associated with the RACH resource.
  • the first preset condition mentioned above is that there are beams with signal quality higher than a certain threshold in the target cell, which can be further extended to: the beams under the target cell allocated with RACH resources have high signal quality.
  • RACH resources may include CFRA resources and/or CBRA resources.
  • the target network device can allocate CFRA resources and CBRA resources to one or more beams under the target cell, or can allocate CBRA resources to one or more beams under the target cell, or can allocate CBRA resources to one or more beams under the target cell Beam allocation CFRA resources.
  • the specific resource type contained in the RACH resource is determined by the resource type pre-allocated by the target network device.
  • the CFRA resource pre-allocated by the target network device and the beam may have a one-to-one association relationship, or may be a one-to-many association relationship, which is not limited in this application.
  • the second preset condition may be, for example, that the cell signal quality of the source cell is higher than a certain threshold; the second preset condition may also be, for example, that the source cell has a beam with a signal quality higher than a certain threshold; Or, for example, the second preset condition may also be: the cell signal quality of the source cell is higher than the cell signal quality of the target cell by a certain threshold; or, the second preset condition may also be: The signal quality of the beam with the best signal quality is lower than the signal quality of the beam with the best signal quality in the source cell. For the sake of brevity, I will not list them all here.
  • the threshold contained therein may be an absolute value or a relative value.
  • the RRC reconfiguration message sent by the source network device to the terminal device carries the signal quality threshold of the corresponding beam, which is recorded as the first preset threshold for the convenience of distinction and description.
  • the first preset threshold can be used to determine the beam signal quality of the target cell. If the terminal device detects that there is a beam with a signal quality higher than the first preset threshold in the beam to which the target network device has pre-allocated RACH resources, that is, if the terminal device finds that there is a beam configured with RACH resources and the signal quality is higher than the first preset threshold in the target cell For a beam with a preset threshold, the terminal device preferentially selects random access to the target cell.
  • Fig. 5 shows the specific flow of this embodiment.
  • the process shown in FIG. 5 includes step 501 to step 509.
  • the terminal device After determining that the RACH-less handover fails, the terminal device determines in step 501 whether the target cell has a beam associated with CFRA resources and whose signal quality is higher than the first preset threshold.
  • the terminal device may determine whether there is a beam with a signal quality higher than the first preset threshold based on the received beam of the target cell. If it is determined that there is a beam with a signal quality higher than the first preset threshold, it can be further determined whether the beam is associated with CFRA resources. For example, the terminal device can follow the handover message (the handover message can include one or more beams with the target cell). The associated CFRA resource) determines whether the beam is allocated with the associated CFRA resource.
  • the terminal device first determines which beams are allocated CFRA resources.
  • the terminal device can determine which beams are allocated the CFRA resources associated with it according to the handover message (the handover message can contain the CFRA resources associated with one or more beams of the target cell), and determine which beams are associated with the CFRA resources Whether there is a beam with a signal quality higher than the first preset threshold.
  • the specific method for the terminal device to determine whether there is a beam associated with CFRA resources and the signal quality is higher than the first preset threshold in the target cell belongs to the internal implementation behavior of the terminal device, and this application does not limit the specific implementation manner of the terminal device.
  • step 502 is executed to perform CFRA with the target cell.
  • the terminal device may specifically perform CFRA with the target cell through beams with signal quality higher than the first preset threshold and associated CFRA resources. If the terminal device detects multiple beams with signal quality higher than the first preset threshold in the beams to which the target network device has pre-allocated CFRA resources, that is, there are multiple beams in the target cell, the signal quality of these beams is higher than The first preset threshold, and these beams are all associated with dedicated RACH resources.
  • the terminal device can select a beam from it and use its associated CRFA resource to perform CFRA with the target cell.
  • the beam selected by the terminal device for CFRA can be recorded as the first beam.
  • the first beam may be, for example, the beam with the best signal quality selected by the terminal equipment from multiple beams with signal quality higher than the first preset threshold and associated with CFRA resources, or it may be the terminal equipment detecting from the target cell.
  • the first beam whose signal quality is higher than the first preset threshold and is associated with CFRA resources can also be one of the multiple beams whose signal quality is higher than the first preset threshold and is associated with RACH resources. Beam. This application does not limit the specific determination method of the first beam.
  • the terminal device may perform step 503 to communicate with the target network device.
  • the terminal device may perform step 504 to determine whether there is a beam with a signal quality higher than the first preset threshold in the target cell. If the terminal device detects a beam with a signal quality higher than the first preset threshold from the target cell, the terminal device can perform CBRA with the target cell.
  • the resources used by the terminal device when performing CBRA are public RACH resources (ie, CBRA resources) rather than dedicated RACH resources (ie, CFRA resources). If the terminal device successfully performs CBRA with the target cell, that is, the random access initiated by the terminal device is successful, the terminal device may perform step 503 to communicate with the target network device.
  • the terminal device determines that there is no beam with a signal quality higher than the first preset threshold in the target cell, it can be considered that the terminal device has not found a suitable beam to perform random access with the target cell.
  • the terminal device does not find a suitable beam to perform random access with the target cell is also regarded as a case of random access failure.
  • the fact that the terminal device fails to find a suitable beam to perform random access with the target cell may mean that the terminal device does not find a beam with a signal quality higher than the first preset threshold to perform random access with the target cell based on the beam.
  • the case where the terminal device fails to find a suitable beam to perform random access with the target cell is classified as a random access failure, which is only a way of expression and should not constitute any limitation in this application.
  • the terminal device fails to find a suitable beam to perform random access with the target cell as not performing random access. In the following, for brevity, the description of the same or similar situations is omitted.
  • the terminal device may first determine whether there are beams associated with CFRA resources and with higher signal quality in the target cell. If the terminal device determines that there is a beam whose signal quality is higher than the first preset threshold and is associated with CFRA resources in the target cell, the terminal device determines the first beam and its associated CFRA resources, and performs random access with the target cell. Assuming that the first beam is beam 1, the CFRA resources associated with beam 1 include random access preamble sequence 1 and time-frequency resource 1, that is, the target network device allocates random access preamble sequence for beam 1 under the target cell 1 and time-frequency resource 1, then the terminal device can use the time-frequency resource 1 to send random access preamble sequence 1 to the target cell.
  • the target cell After receiving the random access preamble sequence 1, the target cell can use the first beam to The terminal device sends a random access response. After receiving the random access response, the terminal device may send an RRC reconfiguration complete message to the target network device. Thus, the terminal equipment can complete random access through CFRA. This round of random access is successful, and the terminal device can communicate with the target network device. The terminal device may further execute step 503.
  • the terminal device can determine whether the target cell has a beam with a signal quality higher than the first preset threshold (that is, determine The outgoing beam only needs to have signal quality higher than the first preset threshold and does not need to be associated with CFRA resources). If there is a beam with a signal quality higher than the first preset threshold in the target cell, the terminal device may perform step 505, that is, the terminal device may select a beam with a signal quality higher than the first preset threshold for CBRA.
  • the handover message may include CBRA resources (ie, common RACH resources).
  • the terminal device After the terminal device determines a beam with a signal quality higher than the first preset threshold, it may use the CBRA resources to conduct CBRA-based CBRA with the target cell.
  • the first beam thus determined is not the beam 1 described above, and for easy distinction, it is recorded as beam 2 for example.
  • the terminal device can perform CBRA with the target cell based on beam 2.
  • the specific process of CBRA can refer to the prior art. For the sake of brevity, no detailed description is provided here. If the terminal device CBRA succeeds, it can send an RRC reconfiguration complete message to the target network device. This round of random access is successful, and the terminal device can communicate with the target network device. If CBRA fails, it can be considered that the current round of random access initiated by the terminal device has failed.
  • the terminal device may perform step 506, and the terminal device determines whether there is an RRC connection with the source cell. Or, if the CBRA fails, the terminal device does not need to determine whether it still maintains an RRC connection with the source cell, and can directly execute step 509 to initiate RRC re-establishment.
  • the random access between the terminal device and the target cell fails. For example, it may only initiate CFRA and CFRA fails, or it may only initiate CBRA and CBRA fails, or it may also initiate CFRA and CBRA and both CFRA and CBRA fail. It may be that the terminal device cannot initiate random access with the target cell because the beam with the signal quality higher than the second preset threshold in the target cell is not detected.
  • the terminal device determines that there is no beam with a signal quality higher than the first preset threshold in the target cell, the terminal device can directly execute step 506, and the terminal device determines whether there is an RRC connection with the source cell.
  • the terminal device determines whether there is an RRC connection with the source cell. As mentioned above, the terminal device can determine whether the RRC connection between the terminal device and the source cell is disconnected by determining whether the source cell has RLF, whether the terminal device has MBB/eMBB capabilities, etc. If it is not disconnected, it indicates that there is an RRC connection between the terminal device and the source cell, and step 507 is executed to perform the operation of falling back to the source cell.
  • Step 508 If the terminal device successfully rolls back to the source cell by performing step 507, it can perform step 508 to communicate with the source network device; if the terminal device fails to roll back to the source cell by performing step 507, that is, the source cell fails to roll back, it can Step 509 is executed to initiate RRC re-establishment.
  • step 506 determines that the RRC connection with the source cell is disconnected in step 506, it means that there is no RRC connection between the terminal device and the source cell, and step 509 can be performed to initiate RRC re-establishment.
  • the terminal device can communicate with the network device to which the re-established cell belongs after establishing an RRC connection with the re-established cell.
  • the terminal device determines that there is no beam with a signal quality higher than the first preset threshold in the target cell, or, although there is a beam with a signal quality higher than the first preset threshold in the target cell, the terminal device communicates with the target cell. If the random access procedure fails, the terminal device can also directly perform step 509 instead of step 506 and step 507. For example, if the terminal device does not have MBB or eMBB capability, the terminal device does not need to determine whether it still maintains an RRC connection with the source cell, and can directly perform step 509 to initiate RRC re-establishment. In FIG. 5, for easy distinction and understanding, a dotted line shows the flow of the terminal device directly jumping from step 505 to step 509.
  • the RRC reconfiguration message sent by the source network device to the terminal device may carry the signal quality threshold, which is recorded as the second preset threshold for the convenience of distinction and description.
  • the second preset threshold can be used to determine the cell signal quality of the source cell. If the terminal device detects that the cell signal quality of the source cell is higher than the second preset threshold, the terminal device may choose to fall back to the source cell.
  • Fig. 6 shows the specific flow of this embodiment.
  • the process shown in FIG. 6 includes step 601 to step 606.
  • step 602 may be performed to determine whether there is an RRC connection with the source cell. If the terminal device determines that there is an RRC connection with the source cell in step 602, step 603 may be performed to perform the operation of falling back to the source cell.
  • step 602 is an optional step, that is, when the terminal device determines that the cell signal quality of the source cell is higher than the second preset threshold, step 603 may be directly executed.
  • FIG. 6 does not show the processes respectively executed by the terminal device in the case of the success or failure of the fallback source cell, but this should not constitute any limitation to this application.
  • the terminal device determines in step 602 that there is no RRC connection with the source cell, it can perform step 606 to initiate an RRC re-establishment procedure to establish an RRC connection with the re-established cell.
  • the terminal device may communicate with the network device to which the re-established cell belongs after completing the RRC re-establishment procedure.
  • step 604 may be performed to perform random access with the target cell. If the random access is successful, the terminal device executes step 605 to communicate with the target network device. If the random access fails, because the RRC re-establishment takes a long time and the implementation complexity is relatively high, the terminal device may still prioritize fallback to the source cell, so step 602 may be performed to determine whether there is an RRC connection with the source cell. After step 602 is executed, step 603 or step 606 can be selectively executed in the manner described above. For brevity, I won't repeat them here. It is understandable that if the terminal device fails to fall back to the source cell after the random access fails, the terminal device can still resume communication through RRC re-establishment at this time.
  • the specific process of the terminal device performing random access with the target cell in step 604 can refer to the related description of steps 501 to step 505 above, or it can be based on a process different from that shown in step 501 to step 505 in FIG. For example, only a part of steps from step 501 to step 505 are executed.
  • the random access between the terminal device and the target cell fails in step 604, it may be that the terminal device has not detected a beam with a signal quality higher than the first preset threshold in the target cell, or it may be that the terminal device has detected signal quality. A beam higher than the first preset threshold, but random access fails. This application does not limit the reason for the random access failure of the terminal device.
  • step 606 can also directly perform step 606, that is, directly initiate RRC re-establishment without performing step 602.
  • the signal quality of the source cell is poor, and the terminal device does not want to fall back to the source cell.
  • step 606 may also be performed directly. It should be understood that, in order to avoid confusion, the flow of the terminal device directly jumping from step 601 to step 606 is not shown in FIG. 6, but this should not constitute any limitation to this application.
  • FIG. 7 is a schematic flowchart of a communication method provided by another embodiment of the present application.
  • the process shown in FIG. 7 may specifically include step 701 to step 708.
  • the terminal device determines whether there is an RRC connection with the source cell in step 701.
  • the terminal device determines whether there is an RRC connection with the source cell in step 701. If the terminal device determines that there is an RRC connection with the source cell, it means that the RRC connection between the terminal device and the source cell is not disconnected, and the terminal device can perform step 702 to perform the operation of falling back to the source cell. If the terminal device successfully rolls back to the source cell by performing step 702, it can communicate with the source network device; if the terminal device fails to roll back to the source cell by performing step 702, it may consider performing random access with the target cell. The device may perform step 703 to determine whether there are beams with CFRA resources and signal quality higher than the first preset threshold in the target cell; or the terminal device may also perform step 708 to initiate RRC re-establishment. It should be understood that, in order to avoid confusion, FIG. 7 does not show the process executed by the terminal device when the fallback source cell succeeds or fails, but this should not constitute any limitation to this application.
  • the terminal device determines that there is no RRC connection with the source cell, it means that the RRC connection between the terminal device and the source cell has been disconnected, and the terminal device can perform step 703 to determine whether the target cell has associated CFRA resources and the signal quality is higher than the first preset Threshold beam.
  • step 704 may be performed to perform CFRA with the target cell. If the terminal device succeeds in CFRA with the target cell through step 704, step 705 can be performed to communicate with the target network device.
  • step 706 may be performed to determine whether the target cell has a beam with a signal quality higher than the first preset threshold. If it exists, the terminal device can perform step 707 to perform CBRA with the target cell. If the terminal device succeeds with the CBRA of the target cell through step 707, step 705 can be performed to communicate with the target network device.
  • the terminal device determines in step 706 that there is no beam with a signal quality higher than the first preset threshold in the target cell, or the CBRA with the target cell fails in step 707, it means that the random access between the terminal device and the target cell fails.
  • the terminal device can perform step 708 to initiate RRC re-establishment.
  • the terminal device can communicate with the network device to which the re-established cell belongs after establishing an RRC connection with the re-established cell.
  • step 703 to step 707 can refer to the related description of step 501 to step 505 above, and for the sake of brevity, it will not be repeated here.
  • the terminal device may directly perform step 708 to initiate RRC re-establishment, and skip steps 703 to 707.
  • FIG. 7 shows the flow of the terminal device directly jumping from step 701 to step 708 with a dotted line.
  • the terminal device may also not perform step 701 and directly try to perform random access with the target cell.
  • the terminal device can directly execute step 703.
  • step 703 For the specific process of random access between the terminal device and the target cell, refer to the process from step 703 to step 707 in FIG. 7, or it may be based on a process different from that shown in step 703 to 707 in FIG. 7, for example, only steps 703 to 707 are performed. Part of the steps in step 707. If the random access between the terminal device and the target cell fails, step 708 can be performed to initiate RRC re-establishment to establish an RRC connection with the re-established cell.
  • the terminal device may communicate with the network device to which the re-established cell belongs after completing the RRC re-establishment procedure.
  • the terminal device may even not perform steps 701, 703, and 706, and directly perform step 704 or 707, and may perform step 705 after successful random access, or perform step 708 after random access fails.
  • steps 701, 703, and 706, and directly perform step 704 or 707 may perform step 705 after successful random access, or perform step 708 after random access fails.
  • Figure 7 does not show this process.
  • FIG. 8 is a schematic flowchart of a communication method provided by another embodiment of the present application.
  • the process shown in FIG. 8 may specifically include step 801 to step 806.
  • the terminal device determines whether there is an RRC connection with the source cell in step 801. If the terminal device determines that there is no RRC connection with the source cell, step 804 may be performed to perform random access with the target cell. If the terminal device determines that there is an RRC connection with the source cell, step 802 may be performed to determine whether the cell signal quality of the source cell is higher than the second preset threshold.
  • step 803 may be performed to perform the operation of falling back to the source cell. If the terminal device successfully rolls back to the source cell by performing step 803, the terminal device can communicate with the source network device; if the terminal device fails to roll back to the source cell by performing step 803, the terminal device can perform step 804 to communicate with the target cell The cell performs random access, or, step 806 can also be performed to initiate RRC re-establishment. It should be understood that, in order to avoid confusion, FIG. 8 does not show the process performed by the terminal device when the fallback source cell succeeds or fails, but this should not constitute any limitation to this application.
  • step 804 may be performed to perform random access with the target cell.
  • step 703 to step 707 in FIG. 7 For the specific process of random access between the terminal device and the target cell, refer to the process from step 703 to step 707 in FIG. 7, or it may be based on a process different from that shown in step 703 to 707 in FIG. 7, for example, only steps 703 to 707 are performed. Part of the steps in step 707. For brevity, I won't repeat them here.
  • step 805 can be performed to communicate with the target network device. If the terminal device fails in random access to the target cell in step 804, step 806 may be performed to initiate RRC re-establishment to establish an RRC connection with the re-established cell. The terminal device may communicate with the network device to which the re-established cell belongs after completing the RRC re-establishment procedure.
  • the terminal device may not perform step 801 and directly perform step 802, and when the cell signal quality of the source cell is higher than the second preset threshold, perform step 803; the cell signal quality of the source cell is not higher than the first 2.
  • step 804 is executed. To avoid confusion in Figure 8, this process is not shown.
  • the terminal device may also directly initiate RRC re-establishment to establish an RRC connection with the re-established cell. To avoid confusion in Figure 8, this process is not shown.
  • the terminal device can recover the connection with the network device by one or more of the following methods: fall back to the source cell, randomly access to the target cell, and initiate RRC re-establishment. Communication.
  • the terminal device can record/store information about the RACH-less handover failure.
  • the terminal device may be, for example, a terminal device capable of recording/storing RACH-less handover failure related information.
  • the terminal device may further send RACH-less handover failure related information to the network device.
  • the terminal device may, for example, send the RACH-less handover failure related information to the above-mentioned first network device.
  • the information related to RACH-less handover failure may specifically include one or more of the following:
  • the cell identity of the target cell is the cell identity of the target cell
  • the cell identity of the cell that the terminal device accesses is the cell identity of the cell that the terminal device accesses
  • the reason value for the RACH-less handover failure includes: there is no beam, HOF or RLF whose signal quality is higher than the third preset threshold and associated with UL grant in the target cell;
  • the timing advance for RACH-less handover obtained in advance by the terminal equipment
  • the timing advance used by the terminal equipment for random access to the target cell The timing advance used by the terminal equipment for random access to the target cell
  • the cell identity may include a physical cell identity (PCI) and frequency information, and/or a cell global identity (CGI).
  • the frequency information may be, for example, an absolute radio frequency channel number (ARFCN) or other information that can be used to indicate a carrier frequency.
  • ARFCN absolute radio frequency channel number
  • the specific content contained in the frequency information can refer to the explanation of the downlink frequency information (FrequencyInfoDL) cell in the protocol TS38.331-f51. For the sake of brevity, no detailed description is given here.
  • the cell that the terminal device accesses specifically refers to the cell that ultimately serves the terminal device during the current round of RACH-less handover, or it can also be understood as the final establishment ( Maintain or exist) RRC connected cell.
  • the cell accessed by the terminal device may be the source cell, the target cell, or other re-established cells other than the source cell and the target cell. This application does not limit this.
  • the cell that the terminal device accesses is the source cell.
  • the cell identity of the cell accessed by the terminal device is also the cell identity corresponding to the source cell.
  • the cell that the terminal device accesses is the target cell.
  • the cell identity of the cell accessed by the terminal device is also the cell identity corresponding to the target cell.
  • the cell that the terminal device accesses is the re-established cell.
  • the re-established cell may be the source cell, the target cell, or other cells, which is not limited in this application.
  • the cell identity of the cell that the terminal device accesses is the cell identity corresponding to the re-established cell.
  • the terminal device may indicate the cell identity of the source cell, the cell identity of the target cell, and the cell identity of the accessed cell respectively, or may indicate only one or two of them. This application does not limit this.
  • the indication information of whether the RACH-less handover is successful can be indicated by a separate indicator bit, such as a binary bit value.
  • a separate indicator bit such as a binary bit value.
  • the indicator bit is "0" it means the RACH-less handover is successful, and when the indicator bit is " 1" indicates that the RACH-less handover failed.
  • a Boolean value or other forms may also be used to indicate whether the RACH-less handover is successful. This application does not limit the specific form of the information indicating whether the RACH-less handover is successful.
  • the terminal device can define a value for each failure reason, which is the reason value described here.
  • a cause value of "NoValidULgrant” means that there is no beam with a signal quality higher than the third preset threshold and associated UL grant in the target cell.
  • a cause value of "HOF” or "RACH-less HOF” means that the RACH-less handover failed.
  • a value of "RLF” indicates that a radio link failure has occurred.
  • whether the RACH-less handover is successful and the cause value of the RACH-less handover failure can be respectively represented by corresponding cells. As mentioned above, for the sake of brevity, I will not repeat them here.
  • the terminal device can indicate whether the RACH-less handover is successful and the reason value of the failure through the same indication information. For example, it is indicated by a two-digit binary bit value. When the indication information is "00", it indicates that the RACH-less handover is successful, and when the indication information is non-zero, it indicates that the RACH-less handover fails. For example, when the indication information is "01”, it means that the cause of failure is that there is no beam in the target cell whose signal quality is higher than the third preset threshold and is associated with UL grant. When the indication information is "10”, it means the cause of failure. The value is (RACH-less) handover failure. When the indication information is "11”, it means that the cause of the failure is the occurrence of a radio link failure.
  • the terminal device may obtain the TA used for RACH-less handover based on the RRC reconfiguration message, such as the RRC reconfiguration message described in step 210 above, in advance, that is, the RRC reconfiguration message used to indicate the handover may include RACH-less handover.
  • the timing advance of less handover When the terminal device switches to the target cell by means of RACH-less handover, the TA value that needs to be used is the TA of the RACH-less handover.
  • the TA obtained in advance by the terminal device for RACH-less handover is recorded as the first TA.
  • the source cell and the target cell co-site.
  • the TA corresponding to the target cell is equal to the TA corresponding to the source cell. That is, the first TA is the TA corresponding to the source cell.
  • the target cell is a small cell.
  • the TA corresponding to the target cell is 0. That is, the first TA is zero.
  • the information related to the RACH-less handover failure may also include the TA used by the terminal device to initiate random access to the target cell.
  • the TA used by the terminal device to initiate random access to the target cell is recorded as the second TA.
  • the second TA may include: the terminal device initiates the TA used by CFRA to the target cell, or the terminal device initiates the TA used by CBRA to the target cell, or the terminal device initiates the TA used by CFRA to the target cell and the terminal device initiates the use of CBRA to the target cell. TA.
  • the terminal device may not report the second TA. This application does not limit this.
  • the above-mentioned time information related to the RACH-less handover failure may also be different.
  • the time information related to the RACH-less handover failure may include, for example, one or more of the first time interval, the second time interval, and the third time interval.
  • the first time interval is from the moment when the terminal device receives the RRC message (for example, the RRC reconfiguration message used to instruct the terminal device to initiate RACH-less handover in the NR described in step 210 above) to the The time interval between the moments when the RACH-less handover fails.
  • the RRC message for example, the RRC reconfiguration message used to instruct the terminal device to initiate RACH-less handover in the NR described in step 210 above
  • the second time interval is the time interval from the moment when the RACH-less handover fails to the moment when the terminal device reverts to the source cell.
  • the terminal device may directly fall back to the source cell, or may initiate random access with the target cell and fall back to the source cell after the random access fails.
  • the time included in the second time interval varies depending on the behavior of the terminal device.
  • the second time interval is the time interval from the moment when the RACH-less handover fails to the moment when the terminal device falls back to the source cell .
  • the terminal device may determine whether there is an RRC connection with the source cell after the RACH-less handover fails, and fall back to the source cell if it is determined that there is an RRC connection. As in the embodiment described above in conjunction with FIG. 3. The terminal device falls back to the source cell when it is determined that there is an RRC connection, that is, the terminal device can continue to communicate with the source network device when it is determined that there is an RRC connection. Therefore, the terminal device may, for example, use the moment when it is determined that there is an RRC connection with the source cell as the moment when the terminal device falls back to the source cell.
  • the terminal device initiates random access to the target cell after the RACH-less handover fails and the random access fails, there may be the following three possibilities:
  • the second time interval may include: the time interval between the time when the RACH-less handover fails to the time when CFRA fails, and the time interval between the time when the CFRA fails to the time when the terminal device reverts to the source cell . If the terminal device fails to perform CFRA and then rolls back to the source cell, and the time interval between the moment CFRA fails and the moment when it rolls back to the source cell can be ignored, that is, the moment when CFRA fails can also be considered as the terminal device's return.
  • the second time interval may also be referred to as the time interval from the time when the RACH-less handover fails to the time when the CFRA fails.
  • the second time interval may include the time interval from the time when the RACH-less handover fails to the time when the CBRA fails, and the time interval from the time when the CBRA fails to the time when the terminal device reverts to the source cell. If the terminal device falls back to the source cell after failing to perform CBRA, the time interval between the moment when CBRA fails and the moment when it falls back to the source cell can be ignored, that is, the moment when CBRA fails can be considered as fall back to the source cell Therefore, the second time interval can also be considered as the time interval between the time when the RACH-less handover fails to the time when the CBRA fails.
  • the terminal device initiates CBRA after failing to initiate CFRA, and returns to the source cell after CBRA fails.
  • the second time interval may include: the time interval between the time when RACH-less handover fails to the time when CFRA fails, the time interval between the time when CFRA fails to the time when CBRA fails, and the time when CBRA fails The time interval to the moment when the terminal device retreats to the source cell.
  • the second time interval may also include the time interval between the time when the RACH-less handover fails to the time when the CFRA fails, and the time interval between the time when the CFRA fails to the time when the CBRA fails.
  • the second time interval may also include: the time interval between the time when the RACH-less handover fails to the time when the CBRA fails, and the time between the time when the CBRA fails to the time when the terminal device reverts to the source cell Time interval.
  • the radio frequency chain of the terminal device (The radio frequency chain, RF chain) can be changed from corresponding to the target network device to corresponding to the source network device. Therefore, in an implementation manner, the terminal device may determine the time to fall back to the source cell according to a change in the correspondence between the radio frequency chain and the network device.
  • the third time interval is the time interval from the moment when the terminal device retreats to the source cell to the moment when the terminal device reports the information about the RACH-less handover failure.
  • the time information related to the RACH-less handover failure may include, for example: the first time interval, the fourth time interval, and the fifth time interval One or more of.
  • the first time interval has been described in detail above, and is not repeated here for brevity.
  • the fourth time interval is the time interval from the moment when the RACH-less handover fails to the moment when the terminal device and the target cell are successfully randomly accessed.
  • the fourth time interval may be the time interval between the time when the RACH-less handover fails to the time when the CFRA succeeds.
  • the fourth time interval may be the time interval from the moment when the RACH-less handover fails to the moment when the CBRA succeeds.
  • the fourth time interval may include: the time interval between the time when the RACH-less handover fails to the time when CFRA fails, and the time interval between the time when CFRA fails to the time when CBRA succeeds.
  • the fifth time interval is the time interval from the moment when the terminal device succeeds in random access to the moment when the terminal device reports the information related to the RACH-less handover failure.
  • the moment when the terminal device succeeds in random access may be the moment when the CFRA succeeds or the moment when the CBRA succeeds.
  • the fifth time interval may refer to the time interval from the moment when CFRA is successful to the moment when information about RACH-less handover failure is reported.
  • the fifth time interval may refer to the time interval between the moment when CBRA is successful and the moment when information about RACH-less handover failure is reported. If the terminal device accesses the re-established cell through RRC re-establishment, the time information related to the RACH-less handover failure may include, for example, one or more of the first time interval, the sixth time interval, and the seventh time interval.
  • the first time interval has been described in detail above, and is not repeated here for brevity.
  • the sixth time interval is the time interval from the moment when the RACH-less handover fails to the moment when the terminal device initiates RRC re-establishment.
  • the terminal device may directly initiate RRC re-establishment, or it may initiate random access to the target cell but the random access fails before initiating RRC re-establishment. set up. Therefore, if the terminal device re-establishes through RRC after the RACH-less handover fails and accesses the re-established cell, there may be several possibilities:
  • the terminal device After the RACH-less handover fails, the terminal device directly initiates RRC re-establishment and accesses the re-established cell.
  • the sixth time interval may be the time interval from the moment when the RACH-less handover fails to the moment when the terminal device initiates RRC re-establishment.
  • the sixth time interval may include: the time interval from the time when the RACH-less handover fails to the time before the CFRA fails, and the time interval from the time when the CFRA fails to the time when the RRC re-establishment is initiated.
  • the sixth time interval may include: the time interval from the time when the RACH-less handover fails to the time before the CBRA fails, and the time interval from the time when the CBRA fails to the time when the RRC re-establishment is initiated.
  • the sixth time interval may include: the time interval from the time when RACH-less handover fails to the time before CFRA fails, the time interval from the time when CFRA fails to the time when CBRA fails, and the time from when CBRA fails to The time interval between the moments when RRC re-establishment is initiated.
  • the seventh time interval is the time interval from the moment when the terminal device initiates RRC re-establishment to the moment when the terminal device reports handover related failure information.
  • the time at which the RRC re-establishment is initiated may be replaced with the time at which the RRC re-establishment is completed, or in other words, the time at which the RRC re-establishment is completed.
  • the sixth time interval may refer to the time interval from the moment when the RACH-less handover fails to the moment when the RRC re-establishment is completed.
  • the sixth time interval may include: the time interval from the time when RACH-less handover fails to the time before CFRA fails, and from the time when CFRA fails to RRC re-establishment The time interval between the moments of completion.
  • the sixth time interval may include: the time interval from the time when RACH-less handover fails to the time before CBRA fails, and from the time when CBRA fails to RRC re-establishment The time interval between the moments of completion.
  • the sixth time interval may include: the time interval from the time when RACH-less handover fails to the time before CFRA fails, and from the time when CFRA fails to the time when CBRA fails.
  • the seventh time interval may refer to the time interval from the moment when the terminal device completes the RRC re-establishment to the moment when the terminal device reports the RACH-less handover failure related information.
  • the RACH-less handover failure related information may also include other information. This application does not limit this.
  • the RACH-less handover failure related information may also include indication information about whether the terminal device performs random access with the target cell after the RACH-less handover fails.
  • the indication information may be, for example, a binary bit value or a Boolean value or other representations. Form etc. This application does not limit the specific form of the instruction information.
  • the RACH-less handover failure related information may also include type information of random access between the terminal device and the target cell.
  • type information of the random access includes: only CFRA is executed, or only CBRA is executed, or CBRA is executed after CFRA is executed.
  • the RACH-less handover failure related information may also include information indicating whether the random access between the terminal device and the target cell is successful.
  • the RACH-less RACH-less handover failure related information may include the indication information of whether the CFRA between the terminal device and the target cell is successful, and/or the indication information of whether the CBRA between the terminal device and the target cell is successful.
  • the indication information may be a binary bit value or a Boolean value or other representation forms. This application does not limit this.
  • the RACH-less handover failure related information may also include the success of random access between the terminal device and the target cell ,
  • the identification information of the corresponding beam (or the beam selected during this successful random access, such as the first beam listed above).
  • the identification information of the beam may be, for example, SSB index or CSI-RS index.
  • the RACH-less handover failure related information may also include the terminal device and target
  • the corresponding beam for example, no matter which of the above three random access types, indicates the corresponding selected beam in each random access procedure where the failure occurs
  • the identification information of the beam can be SSB index or CSI-RS index.
  • the above method 200 further includes: step 240, sending RACH-less handover failure related information.
  • the first network device receives the RACH-less handover failure related information.
  • the RACH-less handover failure related information is carried in the RRC message.
  • the terminal device can actively send the RACH-less handover failure related information to the network device.
  • the terminal device can communicate with the first network device by falling back to the source cell, initiating random access with the target cell, or initiating RRC re-establishment. Therefore, the terminal device can actively send the RACH-less handover failure related information to the first network device.
  • the first network device may be the source network device. For example, the terminal device falls back to the source cell, or the re-established cell is the source cell.
  • the first network device may be the target network device.
  • the terminal device accesses the target cell through random access, or the re-established cell is the target cell.
  • the first network device may also be another network device.
  • the re-established cell is a cell other than the source cell and the target cell; or, for example, as the terminal device subsequently moves, the terminal device accesses other cells except the source cell and the target cell. This application does not limit this.
  • the terminal device may periodically send the RACH-less handover failure related information to the first network device; or, may also send the RACH-less handover failure related information to the first network device based on an event trigger. For example, once the terminal device accesses the first network device, it can send the RACH-less handover failure related information to the first network device.
  • the terminal device may, for example, send the RACH-less handover failure related information to the first network device through an RRC reconfiguration complete message or an RRC reestablishment complete message.
  • the terminal device may also send the RACH-less handover failure related information to the first network device through a user equipment information response (UE Information Response) message.
  • UE Information Response user equipment information response
  • the terminal device may also send the RACH-less handover failure related information to the first network device through other RRC messages or other forms of messages.
  • the terminal device may send the RACH-less handover failure related information through one or more signaling (such as RRC messages). This application does not limit this.
  • the terminal device may also send the RACH-less handover failure related information based on the request of the network device.
  • the method 200 further includes: step 250, the terminal device receives a request message, where the request message is used to request information about RACH-less handover failure.
  • the first network device sends the request message, and the request message is used to request information about the RACH-less handover failure.
  • the request message is an RRC message.
  • the request message may be a user equipment information request (UE Information Request) message, or other messages. This application does not limit this.
  • the terminal device After the terminal device normally communicates with the first network device, it may receive a request message from the first network device, where the request message is used to request information about the RACH-less handover failure.
  • the first network device may actively send the request message to the terminal device, or may send the request message to the terminal device based on a request from another network device.
  • the terminal device may send indication information to the first network device whether the terminal device has recorded/stored information related to the RACH-less handover failure.
  • the first network device may send the request message to the terminal device based on the indication information of whether the RACH-less handover related information is recorded/stored and reported by the terminal device.
  • the terminal device may indicate whether the RACH-less handover failure related information is recorded/stored through "HOF-InfoAvailabvle” or "RACH-less HOF-InfoAvailabvle” or other fields, and this application does not limit specific fields.
  • the indication information may use different values to indicate whether the RACH-less handover failure related information is recorded/stored. For example, when the value of the indication information is "TRUE”, it means that the terminal device has recorded/stored information about RACH-less handover failure; when the value of the indication information is "FALSE", it means that the terminal device has not recorded/stored RACH-less handover failure information. Less switch failure related information.
  • the indication information may be included in the RRC establishment complete message, or the RRC recovery complete message, or the RRC reestablishment complete message, or the RRC reconfiguration complete message, which is not limited in this application.
  • the operations performed by the first network device are also different.
  • the first network device is the source network device.
  • the source network device may actively send the request message to the terminal device to request information about the RACH-less handover failure.
  • the source network device may further send a release instruction to the target network device to instruct the target network device to release the UL grant for RACH-less handover, and/or for random Accessed RACH resources.
  • the release instruction for instructing the target network device to release the UL grant may correspond to the first release instruction in the following method 900
  • the release instruction for instructing the target network device to release RACH resources may correspond to the first release instruction in the following method 1000. 2. Release instructions.
  • the first network device is a target network device.
  • the target network device may actively send the request message to the terminal device to request information about RACH-less handover failure.
  • the target network device may release the UL grant for the RACH-less handover. Therefore, the information related to RACH-less handover failure is equivalent to implicitly indicating that the target network device releases the UL grant for RACH-less handover.
  • the first network device is a network device to which a re-established cell belongs, and the first network device is neither a source network device nor a target network device.
  • the first network device may actively send the request message to the terminal device to request information about RACH-less handover failure.
  • the first network device may receive a request message from another network device (such as a source network device), and forward the request message to the terminal device to request information about RACH-less handover failure.
  • the first network device may send the RACH-less switching failure related information to the target network device, or may also send the RACH-less switching failure related information To the source network device, and the source network device can forward the RACH-less handover failure related information to the target network device.
  • the target network device may release the UL grant for the RACH-less handover, and/or the RACH resource for random access. Therefore, the RACH-less handover failure related information is equivalent to implicitly instructing the target network device to release the UL grant for RACH-less handover, or implicitly instructing the target network device to release the RACH resources for random access.
  • the first network device may also send a release instruction to the target network device based on the analysis of the information related to the RACH-less handover failure to instruct the target network device to release the UL grant for RACH-less handover, and/or release RACH resources for random access.
  • the release instruction for instructing the target network device to release the UL grant may correspond to the first release instruction in the following method 900
  • the release instruction for instructing the target network device to release RACH resources may correspond to the first release instruction in the following method 1000. 2. Release instructions.
  • the release of the UL grant mentioned here may specifically include the release of the uplink resources scheduled by the UL grant and other information contained in the UL grant, such as MCS, NDI, and the time of initiating uplink transmission (such as subframe or slot). ), uplink scheduling interval, etc.
  • the target network device may also release the UE context and so on when it is determined that the terminal device is not connected to the target cell. This application does not limit the operations performed by the target network device after determining that the terminal device is not connected to the target cell.
  • the first network device When the first network device is not the target network device, or in other words, when the cell accessed by the terminal device is not the target cell, optionally, after the first network device receives the RACH-less handover failure related information from the terminal device, it may Part or all of the handover failure related information is forwarded to the target network device, and the target network device adjusts the handover related parameters.
  • the first network device When the first network device is not the source network device, or in other words, when the cell accessed by the terminal device is not the source cell, after the first network device receives the RACH-less handover failure related information from the terminal device, it can set the RACH- Some or all of the information related to less switch failure is forwarded to the source network device, and the source network device adjusts the switch related parameters.
  • the first network device When the first network device is not the target network device and the source network device, in other words, when the cell accessed by the terminal device is neither the source cell nor the target cell, optionally, the first network device receives the RACH from the terminal device -After less handover failure related information, part or all of the handover failure related information can be forwarded to the source network device, or part or all of the RACH-less handover failure related information can be forwarded to the target network device.
  • the network device and/or the target network device adjusts the relevant parameters of the handover.
  • the first network device may also adjust the handover related parameters according to the handover failure related information.
  • the source network device may also forward part or all of the information about the RACH-less handover failure to the target network device, so that the target network device can adjust the handover related parameters.
  • the first network device may also adjust the handover related parameters according to the RACH-less handover failure related information.
  • the target network device may also forward part or all of the information related to the RACH-less handover failure to the source network device, so that the source network device can adjust the handover related parameters.
  • the adjustment of the handover related parameters mentioned above may include, but is not limited to, for example: adjusting the allocation of UL grant (for example, the target network device allocates UL grant to beams with higher signal quality), adjusting the allocation of CFRA resources (for example, target The network equipment allocates CFRA resources to beams with higher signal quality), adjusts the signal quality threshold (the third preset threshold described above), and adjusts the effective duration of related timers (for example, adjusts the effective duration of T304) Wait.
  • adjusting the allocation of UL grant for example, the target network device allocates UL grant to beams with higher signal quality
  • CFRA resources for example, target The network equipment allocates CFRA resources to beams with higher signal quality
  • adjusts the signal quality threshold the third preset threshold described above
  • adjusts the effective duration of related timers for example, adjusts the effective duration of T304 Wait.
  • the network device (such as the source network device and/or the target network device) adjusts the relevant parameters of the handover, when the subsequent RACH-less handover is triggered, more reasonable parameters can be configured to make the handover performance better, thereby improving the RACH-less handover Success rate and reliability.
  • the communication method provided in the embodiments of the present application provides a variety of ways for the terminal device to resume communication when the terminal device fails in the RACH-less handover from the source cell to the target cell.
  • the terminal device can implement communication with the network device by falling back to the source cell or randomly accessing the target cell.
  • the terminal device may also initiate RRC re-establishment to achieve communication with the network device. Therefore, after the RACH-less handover fails, the terminal device can try to restore the normal communication with the network device in a more reasonable manner to minimize the communication interruption time delay.
  • the fallback source cell fails or the random access to the target cell fails the RRC re-establishment process can still be used to restore normal communication with the network device.
  • FIG. 9 and FIG. 10 show related operations after the RACH-less handover of the terminal device fails from the perspective of the network device.
  • FIG. 9 is a schematic flowchart of a communication method 900 provided by another embodiment of the present application. As shown in FIG. 9, the method 900 shown in FIG. 9 may include step 910 and step 920.
  • the target network device receives a first release instruction, which is used to instruct the target network device to release the UL grant, and the UL grant is used for the terminal device to switch from the source cell to the target cell through RACH-less handover.
  • the terminal device may communicate with the first network device by executing the method provided in the embodiments described above in conjunction with FIG. 2 to FIG. 8, for example.
  • the first network device may be the target network device, the source network device, or other network devices except the target network device and the source network device.
  • the terminal device may access the target cell and may also access other cells.
  • the other cell may be the source cell or a cell other than the source cell and the target cell.
  • the first release instruction may be received directly from the terminal device.
  • the target network device receives the first release instruction from the terminal device.
  • the first release indication may include, for example, the RACH-less handover failure related information described in the above embodiment, or may simply indicate whether the RACH-less handover is successful or not, or may also be the above-mentioned The reason value of the RACH-less handover failure mentioned above.
  • the first release instruction may be various possible forms of information sent by the terminal device that can be used to indicate the failure of the RACH-less handover, which is not limited in this application.
  • the first release indication may be included in the RRC reconfiguration complete message, or may be included in another existing or newly defined piece of signaling, which is not limited in this application.
  • the terminal device can implicitly indicate that the target network device uses the UL grant for the terminal device to switch from the source cell to the target cell through the RACH-less handover. Therefore, the target network device can release this part of the resource.
  • the first network device and the target network device shown in FIG. 9 are the same network device.
  • FIG. 9 is only for ease of understanding, and the first network device and the target network device are shown as different network devices, which should not constitute any limitation to this application.
  • the first release instruction may also be received from another network device.
  • the target network device can receive the data from the first network device
  • the first release instruction is shown in step 910b in the figure.
  • the first release instruction may explicitly or implicitly instruct the target network device to release the UL grant used by the terminal device to switch from the source cell to the target cell through the RACH-less handover.
  • the first network device may send the first release instruction based on the RACH-less handover failure related information reported by the terminal device, as shown in step 910c in the figure.
  • the first release indication may be the above-mentioned RACH-less handover failure related information, the indication information of whether the RACH-less handover is successful, or the reason value of the RACH-less handover failure, etc., which can be used to indicate the terminal Information about device RACH-less switch failure.
  • the first release instruction may also be information generated by the first network device and used to instruct the target network device to release the UL grant. This application does not limit the specific form of the first release instruction.
  • the target network device may release the UL grant required for RACH-less handover based on the received first release instruction, so as to use the UL grant scheduled uplink resources for other terminal devices or other scheduling scenarios. This helps to improve resource utilization.
  • the terminal device can also release the UE context and so on.
  • the first release instruction also carries the aforementioned handover failure related information.
  • the target network device can adjust the handover related parameters according to the handover failure related information reported by the terminal device. For example, adjust the allocation of UL grant (for example, the target network device allocates UL grant to beams with higher signal quality), adjust the allocation of CFRA resources (for example, the target network device allocates CFRA resources to beams with higher signal quality), and adjust the signal Quality threshold (such as the third preset threshold described above), adjustment of the effective duration of related timers (for example, adjustment of the effective duration of T304), etc.
  • the signal Quality threshold such as the third preset threshold described above
  • adjustment of the effective duration of related timers for example, adjustment of the effective duration of T304
  • the target network device can release the UL grant after determining that the RACH-less handover of the terminal device fails. That is, the UL grant that the terminal device will not use is released for the uplink transmission of other terminal devices. Since the target network device can release the uplink resources scheduled by the UL grant for other terminal devices or other scheduling scenarios, resource utilization can be improved.
  • FIG. 10 is a schematic flowchart of a communication method 1000 according to another embodiment of the present application. As shown in FIG. 10, the method 1000 shown in FIG. 10 may include step 1010 and step 1020.
  • the target network device receives a second release instruction, and the second release instruction is used to instruct the target network device to release RACH resources.
  • the RACH resources are resources used by the terminal device to initiate a random access procedure to the target cell.
  • the terminal device may communicate with the first network device by executing the method provided in the embodiments described above in conjunction with FIG. 2 to FIG. 8, for example.
  • the first network device may be the target network device, the source network device, or other network devices except the target network device and the source network device.
  • the terminal device may access the target cell, or may access other cells.
  • the other cell may be the source cell or a cell other than the source cell and the target cell.
  • the second release instruction may be received from another network device.
  • the target network device can receive the data from the first network device.
  • the second release instruction is shown in step 1010a in the figure.
  • the second release instruction may explicitly or implicitly instruct the target network device to release the RACH resources required by the terminal device to initiate random access to the target cell.
  • the first network device may generate and send the second release instruction based on the RACH-less handover failure related information reported by the terminal device, as shown in step 1010b in the figure. This application does not limit the specific form of the second release instruction.
  • the target network device may release the pre-allocated RACH resources required for random access to the target cell based on the received second release instruction, thereby helping to improve resource utilization.
  • the second release indication also carries a reason value for the RACH-less handover failure.
  • the target network device can adjust the handover related parameters according to the value of the cause of the RACH-less handover failure reported by the terminal device, such as adjusting the signal quality threshold, such as the first preset threshold or the second preset threshold described above, and many more.
  • the target network device can release the RACH resources required to access the target cell after determining that the terminal device has access to other cells other than the target cell. That is, the RACH resources that the terminal device will not use are released, thereby improving resource utilization.
  • the size of the sequence number of each process does not mean the order of execution.
  • the execution order of each process should be determined by its function and internal logic, and should not constitute any implementation process of the embodiments of this application. limited.
  • FIG. 11 is a schematic block diagram of a communication device 10 provided by an embodiment of the present application. As shown in FIG. 11, the communication device 10 may include a processing unit 11 and a transceiver unit 12.
  • the communication device 10 can implement the operations corresponding to the terminal device in the above method embodiments.
  • the communication device may be a terminal device, or a component configured in the terminal device, such as a chip or Circuit.
  • the terminal device 10 can implement the corresponding operations of the terminal device in the method embodiments shown in FIGS. 2 to 8.
  • the communication device 10 may include a unit for executing the method executed by the terminal device in the method embodiments shown in FIGS. 2 to 8.
  • each unit in the communication device 10 and other operations and/or functions described above are used to implement corresponding processes in the method embodiments shown in FIGS. 2 to 8 respectively.
  • the transceiver unit 12 may be used to receive an RRC message, which instructs the communication device 10 to initiate RACH-less handover from the source cell to the target cell; processing unit 11 It can be used to determine that the RACH-less handover fails; the transceiver unit 12 can also be used to communicate with the first network device.
  • the first network device is the network device to which the source cell belongs, the network device to which the target cell belongs, or the network device to which the re-established cell belongs
  • the re-established cell is a cell that meets predetermined criteria
  • the re-established cell is a terminal device trying to communicate with The cell to which access is requested after the communication of the network device to which the source cell belongs fails and/or the random access failure with the target cell.
  • the first network device is a network device to which the source cell belongs.
  • processing unit 11 is further configured to fall back to the source cell when it is determined that the communication device 10 has an RRC connection with the source cell.
  • the processing unit 11 is further configured to determine that there is no beam with a signal quality higher than a first preset threshold in the target cell.
  • the processing unit 11 is further configured to determine that the cell signal quality of the source cell is higher than a second preset threshold.
  • the processing unit 11 is further configured to initiate a random access procedure to the target cell, but the random access fails.
  • the processing unit 11 is further configured to determine that there is a beam with a signal quality higher than a first preset threshold in the target cell, or to determine that the cell signal quality of the source cell is not higher than a second preset threshold.
  • the first network device is a network device to which the target cell belongs.
  • the processing unit 11 is further configured to initiate a random access procedure to the target cell; the transceiver unit 12 is specifically configured to communicate with the network device to which the target cell belongs after the random access is successful.
  • the processing unit 11 is further configured to determine that the signal quality of the source cell is not higher than a second preset threshold.
  • the processing unit 11 is further configured to determine that a beam with a signal quality higher than a first preset threshold exists in the target cell; and is configured to initiate a random access procedure to the target cell based on the first beam and RACH resources, where the first wave number It is one of one or more beams in the target cell whose signal quality is higher than the first preset threshold.
  • the processing unit 11 is further configured to determine that the RRC connection between the communication device 10 and the source cell has been disconnected.
  • the first network device is a network device to which the re-established cell belongs.
  • the processing unit 11 is also used to initiate an RRC re-establishment procedure; the transceiver unit 12 is specifically used to communicate with the network device to which the re-established cell belongs.
  • the processing unit 11 is further configured to determine that the RRC connection between the communication device 10 and the source cell has been disconnected.
  • the processing unit 11 is further configured to determine that there is no beam with a signal quality higher than a first preset threshold in the target cell.
  • the processing unit 11 is also used to initiate a random access procedure to the target cell, but the random access fails.
  • the processing unit 11 is further configured to determine that there is a beam with a signal quality higher than a first preset threshold in the target cell before initiating a random access procedure to the target cell.
  • the processing unit 11 is further configured to initiate a random access procedure to the target cell when the cell signal quality of the source cell is not higher than a second preset threshold, but the random access fails; and to initiate an RRC reconfiguration. Establish a process.
  • the transceiver unit 12 is further configured to send RACH-less handover failure related information, and the RACH-less handover failure related information includes one or more of the following: the cell identity of the source cell; the cell identity of the target cell; the communication device 10 The cell identity of the cell to be accessed; the indication information of whether the RACH-less handover is successful; the value of the reason for the failure of the RACH-less handover; the timing advance obtained by the terminal equipment in advance for the RACH-less handover; the terminal equipment and the target cell Timing advance used for random access; and time information related to RACH-less handover failure; where the cell identity includes: PCI and frequency information, and/or, CGI; the reason value for RACH-less handover failure includes: target There is no beam, HOF, or RLF whose signal quality is higher than the third preset threshold and is associated with UL grant in the cell.
  • the RACH-less handover failure related information includes one or more of the following: the cell identity of the source cell; the cell identity of the target cell
  • the transceiver unit 12 is further configured to receive a request message, the request message being used to request information about RACH-less handover failure.
  • the communication device 10 may further include a storage unit, and the storage unit may be used to store instructions or data, and the processing unit may call the instructions or data stored in the storage unit to implement corresponding operations.
  • step 230 in the method 200 shown in FIG. 2 when the communication device 10 is used to implement the corresponding process in the method 200 in FIG. 2, Perform the steps in the embodiment shown in FIG. 3 to FIG. 9. For brevity, I won't repeat them here.
  • the communication device 10 can also implement corresponding operations in the terminal device in the above method 900 and method 1000.
  • the communication device 10 may include a unit for executing the method 900 in FIG. 9 or the method executed by the terminal device in the method 1000 in FIG. 10.
  • each unit in the communication device 10 and other operations and/or functions described above are used to implement the corresponding process of the method 900 in FIG. 9 or the method 1000 in FIG. 10, respectively.
  • the transceiving unit 12 in the communication device 10 may be implemented by a transceiver or a communication interface, for example, may correspond to the transceiver 2020 in the terminal device 3000 shown in FIG. 12.
  • the processing unit 11 in the communication device 10 may be implemented by at least one processor, for example, may correspond to the processor 2010 in the terminal device 3000 shown in FIG. 12.
  • the communication device 10 may correspond to the target network device in the above method embodiment, for example, it may be the target network device, or a component configured in the target network device, such as a chip or a circuit.
  • the communication device 10 can implement the corresponding operations of the target network device in the above method 900 or method 1000.
  • the communication device 10 may include a unit for executing the method 900 in FIG. 9 or the method executed by the target network device in the method 1000 in FIG. 10.
  • each unit in the communication device 10 and other operations and/or functions described above are used to implement the corresponding process of the method 900 in FIG. 9 or the method 1000 in FIG. 10, respectively.
  • the transceiver unit 12 may be used to receive a first release instruction, and the first release instruction is used to instruct the network equipment to which the target cell belongs to release the UL grant, and the UL grant It is used for the terminal device to switch from the source cell to the target cell through RACH-less handover; the processing unit 11 may be used to release the UL grant.
  • the transceiving unit 12 is specifically configured to receive a first release instruction from a first network device, which is the source cell or the network device to which the re-established cell belongs.
  • the transceiving unit 12 is specifically configured to receive indication information from the terminal device for indicating the failure of RACH-less handover, and the indication information is used to indicate that the terminal device has failed the RACH-less handover from the source cell to the target cell to indicate Release UL grant.
  • the transceiver unit 12 may be used to receive a second release instruction, which is used to instruct the network equipment to which the target cell belongs to release RACH resources, and the RACH resources are terminal
  • the device initiates the resources used by the random access procedure to the target cell; the processing unit 11 may be used to release the RACH resources.
  • the transceiving unit 12 is specifically configured to receive a second release instruction from a first network device, which is the source cell or the network device to which the re-established cell belongs.
  • the communication device 10 may further include a storage unit, which may be used to store instructions or data, and the processing unit may call the instructions or data stored in the storage unit to implement corresponding operations.
  • a storage unit which may be used to store instructions or data
  • the processing unit may call the instructions or data stored in the storage unit to implement corresponding operations.
  • the communication device 10 can also implement the corresponding operations of the target network device in the method embodiments shown in FIGS. 2 to 8 above.
  • the communication device 10 may include a unit for executing the method executed by the target network device in the method embodiments shown in FIGS. 2 to 8.
  • each unit in the communication device 10 and other operations and/or functions described above are used to implement the corresponding process of the method 200 in FIG. 2.
  • the transceiver unit 12 in the communication device 10 may be implemented by a transceiver or a communication interface, for example, may correspond to the transceiver 3300 in the network device 3000 shown in FIG. 13.
  • the processing unit 11 in the communication device 10 may be implemented by at least one processor, for example, may correspond to the processor 3100 in the network device 3000 shown in FIG. 13.
  • FIG. 12 is a schematic structural diagram of a terminal device 2000 provided by an embodiment of the present application.
  • the terminal device 2000 can be applied to the system shown in FIG. 1 to perform the functions of the terminal device in the foregoing method embodiment.
  • the terminal device 3000 includes a processor 2010 and a transceiver 2020.
  • the terminal device 3000 further includes a memory 2030.
  • the processor 2010, the transceiver 3002, and the memory 2030 can communicate with each other through internal connection paths to transfer control and/or data signals.
  • the memory 2030 is used for storing computer programs, and the processor 2010 is used for downloading from the memory 2030. Call and run the computer program to control the transceiver 2020 to send and receive signals.
  • the terminal device 3000 may further include an antenna 2040 for sending uplink data or uplink control signaling output by the transceiver 2020 through a wireless signal.
  • the aforementioned processor 2010 and the memory 2030 can be combined into a processing device, and the processor 2010 is configured to execute the program code stored in the memory 2030 to implement the aforementioned functions.
  • the memory 2030 may also be integrated in the processor 2010 or independent of the processor 2010.
  • the processor 2010 may correspond to the processing unit 11 in FIG. 11.
  • the aforementioned transceiver 2020 may correspond to the transceiver unit 12 in FIG. 11.
  • the transceiver 2020 may include a receiver (or called receiver, receiving circuit) and a transmitter (or called transmitter, transmitting circuit). Among them, the receiver is used to receive signals, and the transmitter is used to transmit signals.
  • the terminal device 2000 shown in FIG. 12 can implement various processes involving the terminal device in the method embodiments shown in FIGS. 2 to 10.
  • the operations and/or functions of each module in the terminal device 2000 are respectively for implementing the corresponding processes in the foregoing method embodiments.
  • the above-mentioned processor 2010 can be used to execute the actions described in the previous method embodiments implemented by the terminal device, and the transceiver 2020 can be used to execute the terminal device described in the previous method embodiments to send or receive from the network device action.
  • the transceiver 2020 can be used to execute the terminal device described in the previous method embodiments to send or receive from the network device action.
  • the aforementioned terminal device 2000 may further include a power supply 2050 for providing power to various devices or circuits in the terminal device.
  • the terminal device 3000 may also include one or more of the input unit 2060, the display unit 2070, the audio circuit 2080, the camera 2090, and the sensor 2100.
  • the audio circuit A speaker 2082, a microphone 2084, etc. may also be included.
  • FIG. 13 is a schematic structural diagram of a network device provided by an embodiment of the present application, for example, it may be a schematic structural diagram of a base station.
  • the base station 3000 can be applied to the system shown in FIG. 1 to perform the functions of the network device in the foregoing method embodiment.
  • the base station 3000 may include one or more radio frequency units, such as a remote radio unit (RRU) 3100 and one or more baseband units (BBU) (also known as distributed unit (DU) )) 3300.
  • RRU 3100 may be called a transceiver unit, which corresponds to the transceiver unit 12 in FIG. 11.
  • the transceiver unit 3100 may also be called a transceiver, a transceiver circuit, or a transceiver, etc., and it may include at least one antenna 3101 and a radio frequency unit 3102.
  • the transceiver unit 3100 may include a receiving unit and a transmitting unit, the receiving unit may correspond to a receiver (or receiver, receiving circuit), and the transmitting unit may correspond to a transmitter (or transmitter or transmitting circuit).
  • the RRU 3100 part is mainly used for receiving and sending radio frequency signals and converting radio frequency signals and baseband signals, for example, for sending instruction information to terminal equipment.
  • the 3300 part of the BBU is mainly used for baseband processing and control of the base station.
  • the RRU 3100 and the BBU 3300 may be physically set together, or may be physically separated, that is, a distributed base station.
  • the BBU 3300 is the control center of the base station, and may also be called a processing unit, which may correspond to the processing unit 11 in FIG. 11, and is mainly used to complete baseband processing functions, such as channel coding, multiplexing, modulation, and spreading.
  • the BBU processing unit
  • the BBU may be used to control the base station to execute the operation procedure of the network device in the foregoing method embodiment, for example, to generate the foregoing indication information.
  • the BBU 3300 may be composed of one or more single boards, and multiple single boards may jointly support a radio access network with a single access standard (such as an LTE network), or support different access standards. Wireless access network (such as LTE network, 5G network or other networks).
  • the BBU 3300 further includes a memory 3201 and a processor 3202.
  • the memory 3201 is used to store necessary instructions and data.
  • the processor 3202 is configured to control the base station to perform necessary actions, for example, to control the base station to execute the operation procedure of the network device in the foregoing method embodiment.
  • the memory 3201 and the processor 3202 may serve one or more single boards. In other words, the memory and the processor can be set separately on each board. It can also be that multiple boards share the same memory and processor. In addition, necessary circuits can be provided on each board.
  • the base station 3000 shown in FIG. 13 can implement each process involving the target network device in the method embodiments shown in FIG. 2 to FIG. 10.
  • the operations and/or functions of the various modules in the base station 3000 are used to implement the corresponding processes in the foregoing method embodiments.
  • the above-mentioned BBU 3300 can be used to perform the actions described in the previous method embodiments implemented by the network device, and the RRU 3100 can be used to perform the actions described in the previous method embodiments that the network device sends to or receives from the terminal device.
  • the RRU 3100 can be used to perform the actions described in the previous method embodiments that the network device sends to or receives from the terminal device.
  • the base station 3000 shown in FIG. 13 is only a possible architecture of the network device, and should not constitute any limitation in this application.
  • the method provided in this application can be applied to network devices of other architectures.
  • network equipment including CU, DU, and active antenna unit (AAU). This application does not limit the specific architecture of the network device.
  • An embodiment of the present application also provides a processing device, including a processor and an interface; the processor is configured to execute the method in any of the foregoing method embodiments.
  • the aforementioned processing device may be one or more chips.
  • the processing device may be a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), or a system on chip (SoC), or It is a central processor unit (CPU), it can also be a network processor (NP), it can also be a digital signal processing circuit (digital signal processor, DSP), or it can be a microcontroller (microcontroller unit). , MCU), it can also be a programmable logic device (PLD) or other integrated chips.
  • FPGA field programmable gate array
  • ASIC application specific integrated circuit
  • SoC system on chip
  • CPU central processor unit
  • NP network processor
  • DSP digital signal processing circuit
  • microcontroller unit microcontroller unit
  • MCU programmable logic device
  • PLD programmable logic device
  • the steps of the above method can be completed by hardware integrated logic circuits in the processor or instructions in the form of software.
  • the steps of the method disclosed in the embodiments of the present application may be directly embodied as being executed and completed by a hardware processor, or executed and completed by a combination of hardware and software modules in the processor.
  • the software module can be located in a mature storage medium in the field such as random access memory, flash memory, read-only memory, programmable read-only memory, or electrically erasable programmable memory, registers.
  • the storage medium is located in the memory, and the processor reads the information in the memory and completes the steps of the above method in combination with its hardware. To avoid repetition, it will not be described in detail here.
  • the processor in the embodiment of the present application may be an integrated circuit chip with signal processing capability.
  • the steps of the foregoing method embodiments can be completed by hardware integrated logic circuits in the processor or instructions in the form of software.
  • the above-mentioned processor may be a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components .
  • DSP digital signal processor
  • ASIC application specific integrated circuit
  • FPGA field programmable gate array
  • the methods, steps, and logical block diagrams disclosed in the embodiments of the present application can be implemented or executed.
  • the general-purpose processor may be a microprocessor or the processor may also be any conventional processor or the like.
  • the steps of the method disclosed in the embodiments of the present application may be directly embodied as being executed and completed by a hardware decoding processor, or executed and completed by a combination of hardware and software modules in the decoding processor.
  • the software module can be located in a mature storage medium in the field such as random access memory, flash memory, read-only memory, programmable read-only memory, or electrically erasable programmable memory, registers.
  • the storage medium is located in the memory, and the processor reads the information in the memory and completes the steps of the above method in combination with its hardware.
  • the memory in the embodiment of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memory.
  • the non-volatile memory can be read-only memory (ROM), programmable read-only memory (programmable ROM, PROM), erasable programmable read-only memory (erasable PROM, EPROM), and electronic Erase programmable read-only memory (electrically EPROM, EEPROM) or flash memory.
  • the volatile memory may be random access memory (RAM), which is used as an external cache.
  • RAM random access memory
  • static random access memory static random access memory
  • dynamic RAM dynamic random access memory
  • DRAM dynamic random access memory
  • SDRAM synchronous dynamic random access memory
  • double data rate synchronous dynamic random access memory double data rate SDRAM, DDR SDRAM
  • enhanced synchronous dynamic random access memory enhanced SDRAM, ESDRAM
  • serial link DRAM SLDRAM
  • direct rambus RAM direct rambus RAM
  • the present application also provides a computer program product.
  • the computer program product includes: computer program code, which when the computer program code runs on a computer, causes the computer to execute the steps shown in FIGS. 2 to 10 The method of any one of the embodiments is shown.
  • the present application also provides a computer-readable medium that stores program code, and when the program code runs on a computer, the computer executes the steps shown in FIGS. 2 to 10 The method of any one of the embodiments is shown.
  • the present application also provides a system, which includes the aforementioned one or more terminal devices and one or more network devices.
  • the network equipment in the above-mentioned device embodiments completely corresponds to the network equipment or terminal equipment in the terminal equipment and method embodiments, and the corresponding modules or units execute the corresponding steps.
  • the communication unit transmits the receiving or In the sending step, other steps except sending and receiving can be executed by the processing unit (processor).
  • the processing unit processor
  • component used in this specification are used to denote computer-related entities, hardware, firmware, a combination of hardware and software, software, or software in execution.
  • the component may be, but is not limited to, a process, a processor, an object, an executable file, an execution thread, a program, and/or a computer running on a processor.
  • the application running on the computing device and the computing device can be components.
  • One or more components may reside in processes and/or threads of execution, and components may be located on one computer and/or distributed among two or more computers.
  • these components can be executed from various computer readable media having various data structures stored thereon.
  • the component may be based on, for example, a signal having one or more data packets (such as data from two components interacting with another component in a local system, a distributed system, and/or a network, such as the Internet that interacts with other systems through signals) Communicate through local and/or remote processes.
  • a signal having one or more data packets (such as data from two components interacting with another component in a local system, a distributed system, and/or a network, such as the Internet that interacts with other systems through signals) Communicate through local and/or remote processes.
  • the disclosed system, device, and method may be implemented in other ways.
  • the device embodiments described above are only illustrative.
  • the division of the units is only a logical function division, and there may be other divisions in actual implementation, for example, multiple units or components can be combined or It can be integrated into another system, or some features can be ignored or not implemented.
  • the displayed or discussed mutual coupling or direct coupling or communication connection may be indirect coupling or communication connection through some interfaces, devices or units, and may be in electrical, mechanical or other forms.
  • the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.
  • each unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units may be integrated into one unit.
  • each functional unit may be implemented in whole or in part by software, hardware, firmware, or any combination thereof.
  • software When implemented by software, it can be implemented in the form of a computer program product in whole or in part.
  • the computer program product includes one or more computer instructions (programs).
  • programs When the computer program instructions (programs) are loaded and executed on the computer, the processes or functions described in the embodiments of the present application are generated in whole or in part.
  • the computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices.
  • the computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium.
  • the computer instructions may be transmitted from a website, computer, server, or data center. Transmission to another website, computer, server or data center via wired (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.).
  • 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 or a data center integrated with one or more available media.
  • the usable medium may be a magnetic medium, (for example, a floppy disk, a hard disk, and a magnetic tape), an optical medium (for example, a high-density digital video disc (digital video disc, DVD)), or a semiconductor medium (for example, a solid state disk, SSD)) etc.
  • a magnetic medium for example, a floppy disk, a hard disk, and a magnetic tape
  • an optical medium for example, a high-density digital video disc (digital video disc, DVD)
  • a semiconductor medium for example, a solid state disk, SSD
  • the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer readable storage medium.
  • the technical solution of this application essentially or the part that contributes to the existing technology or the part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including Several instructions are used to make a computer device (which may be a personal computer, a server, or a network device, etc.) execute all or part of the steps of the method described in each embodiment of the present application.
  • the aforementioned storage media include: U disk, mobile hard disk, read-only memory (read-only memory, ROM), random access memory (random access memory, RAM), magnetic disk or optical disk and other media that can store program code .

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

La présente invention concerne un procédé de communication et un appareil de communication. Le procédé comprend les étapes suivantes : un dispositif terminal reçoit un message RRC, le message RRC étant utilisé pour ordonner au dispositif terminal d'initier un transfert intercellulaire sans RACH, d'une cellule source à une cellule cible ; lorsqu'il est déterminé que le transfert intercellulaire sans RACH échoue, le dispositif terminal priorise la prise en considération du retour vers la cellule source ou la réalisation d'un accès aléatoire avec la cellule cible ; lorsque le retour vers la cellule source ou la réalisation d'un accès aléatoire avec la cellule cible échoue, utiliser le RRC pour rétablir et restaurer la communication avec un dispositif de réseau. Ainsi, la réponse est rapide une fois qu'un transfert intercellulaire sans RACH échoue, l'accès à une cellule se fait aussi rationnellement et rapidement que possible, une communication normale par un dispositif terminal est restaurée et l'expérience de l'utilisateur est améliorée.
PCT/CN2020/106162 2019-07-31 2020-07-31 Procédé de communication et appareil de communication WO2021018283A1 (fr)

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WO2023179736A1 (fr) * 2022-03-24 2023-09-28 华为技术有限公司 Procédé et appareil de communication
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CN115299125B (zh) * 2022-06-28 2023-10-10 北京小米移动软件有限公司 一种定时提前报告tar的触发方法、装置、设备及存储介质
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