WO2021134721A1 - 一种通信方法、装置以及系统 - Google Patents

一种通信方法、装置以及系统 Download PDF

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Publication number
WO2021134721A1
WO2021134721A1 PCT/CN2019/130979 CN2019130979W WO2021134721A1 WO 2021134721 A1 WO2021134721 A1 WO 2021134721A1 CN 2019130979 W CN2019130979 W CN 2019130979W WO 2021134721 A1 WO2021134721 A1 WO 2021134721A1
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WIPO (PCT)
Prior art keywords
terminal
user plane
downlink data
base station
gnb
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PCT/CN2019/130979
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English (en)
French (fr)
Inventor
王亚鑫
李岩
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华为技术有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Priority to PCT/CN2019/130979 priority Critical patent/WO2021134721A1/zh
Priority to CN201980101105.7A priority patent/CN114503781B/zh
Publication of WO2021134721A1 publication Critical patent/WO2021134721A1/zh

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    • 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
    • H04W76/00—Connection management
    • H04W76/10—Connection setup
    • H04W76/15—Setup of multiple wireless link connections

Definitions

  • the embodiments of the present application relate to the field of communication technologies, and in particular, to a communication method, device, and system.
  • Service handover is an important link in the communication between the terminal and the radio access network (RAN) equipment in the wireless communication system.
  • RAN radio access network
  • the handover process of the current mobile communication system usually includes three stages: handover preparation, handover execution, and handover completion.
  • the terminal still maintains the connection with the source RAN device, no additional time delay or interruption is generated, and the service is performed normally.
  • the source base station can send data packets of the terminal to the target base station through the forwarding tunnel between the source base station and the target base station.
  • the target base station Before the random access procedure between the terminal and the target base station is completed, the target base station temporarily buffers the received data packets of the terminal. The target base station will not send the data packet of the terminal to the terminal until the random access procedure between the terminal and the target base station is completed. Therefore, before the random access procedure between the terminal and the target base station is completed, the target base station does not send the data packet to the terminal, and the terminal's service is interrupted.
  • the time delay generated in this process can be called interrupt time delay.
  • the downlink data of the terminal is sequentially transmitted through a user plane function (UPF) network element -> source RAN device -> target RAN device -> terminal. That is, the downlink data of the terminal is transmitted through the forwarding tunnel between the source RAN device and the target RAN device.
  • the delay introduced by forwarding is called forwarding delay.
  • the downlink data of the terminal will be transmitted through the path of the UPF network element -> target RAN device -> terminal.
  • the generation of forwarding delay affects the user experience.
  • the embodiments of the present application provide a communication method, device, and system to solve the problem of forwarding delay in the handover process.
  • an embodiment of the present application provides a communication method, including: receiving, at the distributed processing node DU, downlink data from the first CU-UP through a user plane connection with the first centralized processing node CU-user plane UP During the packet process, the DU receives the downlink data packet from the second CU-UP through the user plane connection with the second CU-UP.
  • the first RLC entity included in the DU is associated with the second RLC entity included in the DU, the first RLC entity corresponds to the first CU-UP, and the second RLC entity corresponds to the second CU-UP.
  • the terminal switches from the first CU-UP to the second CU-UP.
  • the DU sends the downlink data packet from the first CU-UP to the terminal. In the case that the DU sends all the downlink data packets from the first CU-UP to the terminal, the DU sends the DU buffered downlink data packets from the second CU-UP to the terminal.
  • the embodiment of the present application provides a communication method.
  • this method there is a user plane connection between the DU and the first CU-UP and the second CU-UP, which can prevent the CU-UP of the terminal from being switched from the first CU-UP.
  • the downlink data packet of the terminal is forwarded between the first CU-UP and the second CU-UP, that is, there is no need to establish a connection between the first CU-UP and the second CU-UP.
  • the forwarding tunnel avoids the introduction of forwarding delay.
  • the DU since the first RLC entity is associated with the second RLC entity, and the first RLC entity corresponds to the first CU-UP, and the second RLC entity corresponds to the second CU-UP, it is convenient for the DU to check the information from the second CU-UP.
  • the downlink data packets are buffered. After all the downlink data packets of the first CU-UP are transmitted to the terminal, the DU starts to transmit the downlink data packets from the second CU-UP to the terminal, which not only ensures the low-latency handover of the CU-UP In addition, it can also avoid the problem of interruption of the terminal's business.
  • the DU is a DU that provides services for the terminal before the handover.
  • the DU is located in the service range of the first CU-UP and is located at the edge of the service range of the second CU-UP.
  • the DU is connected with the first CU-UP, but the DU can also establish a connection with the second CU-UP.
  • the DU is a DU that provides services for the terminal after the handover.
  • the DU is located in the service range of the second CU-UP and is located at the edge of the service range of the first CU-UP.
  • the DU is connected with the second CU-UP, but the DU can also establish a connection with the first CU-UP.
  • the method provided in the embodiment of the present application further includes: the DU receives a first request message including a first indication from the first device.
  • the DU associates the first RLC entity with the second RLC entity according to the first instruction. So that the DU determines to establish an association relationship between the first RLC entity corresponding to the first CU-UP and the second RLC entity corresponding to the second CU-UP.
  • the first indication is also used to indicate the user plane connection between the DU and the second CU-UP.
  • the method provided in this embodiment of the present application further includes: the DU establishes the DU and the second CU-UP according to the first indication.
  • User plane connection between the second CU-UP The establishment of a user plane connection between the DU and the second CU-UP facilitates subsequent DUs to receive downlink data packets from the second CU-UP.
  • the first request message further includes information of the second CU-UP.
  • the information of the second CU-UP may be the address information of the second CU-UP.
  • the method provided in the embodiment of the present application further includes: the DU sends to the terminal instructing the terminal to establish a user plane connection between the terminal and the second CU-UP, and maintains the connection between the terminal and the first CU-UP
  • the first configuration message can enable the terminal to establish a dual connection with the first CU-UP and the second CU-UP.
  • the method provided in the embodiment of the present application further includes: the DU receives the second indicating that the transmission of the downlink data packet transmitted on the user plane connection between the user plane network element and the first CU-UP is completed. Instructions. So that the DU determines that the user plane network element subsequently stops sending the downlink data packet to the first CU-UP.
  • the method provided in the embodiment of the present application further includes: in the case that the DU sends all the downlink data packets from the first CU-UP to the terminal, the DU sends the first report to the first device, The first report is used by the first device to trigger the first CU-UP to release the context of the terminal. So that the terminal completes the switch from the first CU-UP to the second CU-UP.
  • the first device is the CU-control plane CP of the first base station
  • the first base station is a base station that provides services for the terminal before the handover.
  • the first device is the CU-CP of the second base station
  • the second base station is a base station that provides services for the terminal after the handover.
  • the first CU-UP and the second CU-UP are connected to the same CU-CP, or the first CU-UP and the second CU-UP are connected to different CU-CPs.
  • an embodiment of the present application provides a communication method.
  • the method includes: a first device determines to switch a terminal from a first CU-UP to a second CU-UP.
  • the first device sends a first request message including the second indication to the DU.
  • the second indication indicates that the DU associates the first RLC entity of the DU with the second RLC entity of the DU, and establishes a user plane connection between the DU and the second CU-UP.
  • the first request message further includes information of the second CU-UP.
  • the method provided in the embodiment of the present application further includes: the first device receives a first report from the DU for the first device to trigger the first CU-UP to release the context of the terminal.
  • the DU is a DU that provides services for the terminal before the handover.
  • the DU is located in the service range of the first CU-UP and is located at the edge of the service range of the second CU-UP.
  • the DU is connected with the first CU-UP, but the DU can also establish a connection with the second CU-UP.
  • the DU is a DU that provides services for the terminal after the handover.
  • the DU is located in the service range of the second CU-UP and is located at the edge of the service range of the first CU-UP.
  • the DU is connected with the second CU-UP, but the DU can also establish a connection with the first CU-UP.
  • the DU is a DU that provides services for the terminal after the handover.
  • the method provided in the embodiment of the present application further includes: the first device switches the terminal from the first DU to the DU.
  • the first DU is a DU that provides services for the terminal before handover.
  • the first device is the centralized processing node CU-control plane CP of the first base station, and the first base station is the base station that the terminal accesses before handover.
  • the first device when the first device switches the terminal from the first DU to the DU, the first device sends a third instruction to the first CU-UP, and the third instruction instructs to switch to a different span this time. Switch between CU-UP.
  • the first device is the CU-CP of the second base station
  • the second base station is the base station accessed by the terminal after handover.
  • the first CU-UP and the second CU-UP are connected to the same CU-CP, or the first CU-UP and the second CU-UP are connected to different CU-CPs.
  • the first CU-UP and the second CU-UP are connected to the same CU-CP.
  • the first CU-UP and the second CU-UP are connected to different CU-CPs.
  • the embodiment of the present application provides The method may further include: the first device receives a second request message of the CU-CP from the first base station, and the second request message requests the terminal to switch the CU-UP. Specifically, the second request message requests to switch the terminal from the first CU-UP to the second CU-UP.
  • an embodiment of the present application provides a communication method.
  • the method includes: a terminal receives a downlink data packet from a first CU-UP sent by a DU, and sends all downlink data packets from the first CU-UP In the case of the terminal, the downlink data packet from the second CU-UP sent from the DU is received, and the terminal has a user plane connection with the first CU-UP and the second CU-UP.
  • the method provided in the embodiment of the present application may further include: the terminal receives the first configuration message from the DU.
  • the first configuration message instructs the terminal to establish a user plane connection between the terminal and the second CU-UP, and a first configuration message for maintaining the user plane connection between the terminal and the first CU-UP.
  • the first configuration message can enable the terminal to establish a dual connection with the first CU-UP and the second CU-UP.
  • an embodiment of the present application provides a communication device.
  • the communication device may be a DU or a chip applied to the DU.
  • the communication device includes a communication unit and a processing unit.
  • the communication unit executes the first aspect and any one of the communication methods in the optional design of the first aspect, the communication unit is used to perform transceiving operations, and the processing unit is used to perform other than transceiving operations. Other actions.
  • the communication unit is configured to receive the downlink data packet from the first CU-UP through the user plane connection with the first CU-UP, and also communicate with the second CU-UP.
  • the user plane connection between the CU-UP receives the downlink data packet from the second CU-UP.
  • the first RLC entity of the DU is associated with the second RLC entity of the DU.
  • the first RLC entity corresponds to the first CU-UP
  • the second RLC entity corresponds to the second CU-UP
  • the terminal switches from the first CU-UP to the second CU-UP.
  • the communication unit is also used to send the downlink data packet from the first CU-UP to the terminal.
  • the communication unit is further configured to send the downlink data packets from the second CU-UP buffered by the processing unit to the terminal.
  • the processing unit may be a processor, and the communication unit may be a communication interface.
  • the communication interface can be an input/output interface, a pin, or a circuit.
  • the processing unit executes the instructions stored in the storage unit, so that the DU implements the first aspect or a communication method described in any one of the possible implementation manners of the first aspect.
  • the storage unit may be a storage unit in the chip (for example, a register, a cache, etc.), or a storage unit in the DU located outside the chip (for example, a read-only memory, a random access memory, etc.).
  • an embodiment of the present application provides a communication device.
  • the communication device may be a first device or a chip applied to the first device.
  • the communication device includes a communication unit and a processing unit.
  • the communication unit is used to perform transceiving operations, and the processing unit is used to perform removal Actions other than sending and receiving operations.
  • the processing unit is configured to determine to switch the terminal from the first CU-UP to the second CU-UP.
  • the communication unit is configured to send the first request message including the second indication to the DU.
  • the second indication indicates that the DU associates the first RLC entity of the DU with the second RLC entity of the DU, and establishes a user plane connection between the DU and the second CU-UP.
  • the processing unit may be a processor, and the communication unit may be a communication interface.
  • the communication interface can be an input/output interface, a pin, or a circuit.
  • the processing unit executes the instructions stored in the storage unit, so that the first device implements the second aspect or a communication method described in any one of the possible implementation manners of the second aspect.
  • the storage unit may be a storage unit in the chip (for example, a register, a cache, etc.), or a storage unit (for example, a read-only memory, a random access memory, etc.) located outside the chip in the first device.
  • an embodiment of the present application provides a communication device.
  • the communication device may be a terminal or a chip applied to the terminal.
  • the communication device includes a communication unit and a processing unit.
  • the terminal executes the third aspect and any of the communication methods in the optional design of the third aspect, the communication unit is used to perform transceiving operations, and the processing unit is used to perform other than transceiving operations. Other actions.
  • the communication unit is configured to receive the downlink data packet from the first CU-UP sent by the DU, and send all the downlink data packets from the first CU-UP to the In the case of a communication device, it receives a downlink data packet from the second CU-UP sent from the DU, and the communication device has a user plane connection with both the first CU-UP and the second CU-UP.
  • the processing unit may be a processor, and the communication unit may be a communication interface.
  • the communication interface can be an input/output interface, a pin, or a circuit.
  • the processing unit executes the instructions stored in the storage unit, so that the terminal implements the third aspect or a communication method described in any one of the possible implementation manners of the third aspect.
  • the storage unit may be a storage unit in the chip (for example, a register, a cache, etc.), or a storage unit in the terminal located outside the chip (for example, a read-only memory, a random access memory, etc.).
  • the present application provides a DU including a processor that reads instructions stored in a memory to implement the above-mentioned first aspect and any one of the optional design methods in the first aspect.
  • the memory can be a memory inside the DU.
  • the present application provides a first device including a processor that reads instructions stored in a memory to implement the second aspect and any one of the optional design methods in the second aspect.
  • the memory may be a memory inside the first device.
  • the present application provides a terminal including a processor that reads instructions stored in a memory to implement the above-mentioned third aspect and any one of the optional design methods in the third aspect.
  • the memory may be an internal memory of the terminal.
  • the present application provides a terminal, including a communication interface and a processor connected to the communication interface. Through the communication interface and the processor, the terminal is used to execute the third aspect and any one of the optional designs of the third aspect. In the method.
  • the present application provides a first device, including a communication interface and a processor connected to the communication interface. Through the communication interface and the processor, the first device is used to execute any one of the second aspect and the second aspect described above.
  • An alternative design method including a communication interface and a processor connected to the communication interface.
  • the present application provides a DU, including a communication interface and a processor connected to the communication interface. Through the communication interface and the processor, the DU is used to execute the first aspect and any one of the first aspect. Method in design.
  • an embodiment of the present application provides a communication system, including the DU of any aspect of the foregoing fourth, seventh, and tenth aspects, as well as descriptions of any aspect of the sixth, ninth, and twelfth aspects Terminal.
  • the communication system described in the thirteenth aspect may further include the first device described in the fifth aspect, the eighth aspect, and the eleventh aspect.
  • this application provides a computer-readable storage medium, including computer-readable instructions.
  • the instructions run on a computer, the computer executes any one of the possible designs in any of the above-mentioned aspects of the first aspect. Methods.
  • this application provides a computer-readable storage medium, including computer-readable instructions.
  • the instructions run on a computer, the computer executes any one of the possible designs in any of the above-mentioned second aspects. Methods.
  • this application provides a computer-readable storage medium, including computer-readable instructions.
  • the instructions run on a computer, the computer executes any one of the possible designs in any aspect of the third aspect. Methods.
  • this application provides a computer program product, including a computer program, which when the program runs on a computer, causes the computer to execute any one of the possible design methods in any aspect of the first aspect.
  • this application provides a computer program product, including a computer program, which when the program runs on a computer, causes the computer to execute any one of the possible design methods in any aspect of the second aspect.
  • this application provides a computer program product, including a computer program, which when the program runs on a computer, causes the computer to execute any of the possible design methods in any aspect of the third aspect.
  • the present application provides a chip that is used in the DU.
  • the chip includes at least one processor and a communication interface, the communication interface is coupled to the at least one processor, and the processor is used to run a computer program or instruction to execute the first
  • the communication interface is used to communicate with other modules outside the chip.
  • the present application provides a chip that is applied to a first device.
  • the chip includes at least one processor and a communication interface, the communication interface is coupled to at least one processor, and the processor is used to run computer programs or instructions to To execute the second aspect or any possible implementation of the second aspect, the communication interface is used to communicate with other modules outside the chip.
  • the present application provides a chip that is used in a terminal.
  • the chip includes at least one processor and a communication interface, the communication interface is coupled to the at least one processor, and the processor is used to run a computer program or instruction to execute the first
  • the communication interface is used to communicate with other modules outside the chip.
  • the chip described above in this application may further include at least one memory, and instructions or computer programs are stored in the at least one memory.
  • an embodiment of the present application provides a communication device.
  • the communication device may be any one of a terminal, a first device, and a DU, or may be applied to any one of the terminal, the first device, and the DU. Chip.
  • the communication device has the function of implementing the method described in any one of the foregoing first aspect, second aspect, and third aspect. This function can be realized by hardware, or by hardware executing corresponding software.
  • the hardware or software includes one or more modules corresponding to the above-mentioned functions.
  • FIG. 1 is a schematic flowchart of a handover method provided by an embodiment of this application
  • FIG. 2 is an architecture of a communication system provided by an embodiment of this application.
  • FIG. 3 is a relationship between CP and DU provided by an embodiment of this application.
  • FIG. 4 is an architecture of another communication system provided by an embodiment of this application.
  • FIG. 5 is a schematic structural diagram of a communication device provided by an embodiment of this application.
  • FIG. 6 is a schematic flowchart of a communication method provided by an embodiment of this application.
  • FIG. 7 is a schematic diagram of a DU switching process provided by an embodiment of the application.
  • FIG. 8 is a schematic flowchart of another communication method provided by an embodiment of this application.
  • FIG. 9 is a schematic diagram of a specific implementation process of a communication method provided by an embodiment of this application.
  • FIG. 10 is a schematic diagram of path switching provided by an embodiment of the application.
  • FIG. 11 is a schematic diagram of a specific implementation process of another communication method provided by an embodiment of this application.
  • FIG. 12 is a schematic diagram of data path transmission according to an embodiment of this application.
  • FIG. 13 is a schematic structural diagram of a communication device provided by an embodiment of this application.
  • FIG. 14 is a schematic structural diagram of another communication device provided by an embodiment of this application.
  • FIG. 15 is a schematic structural diagram of a chip provided by an embodiment of the application.
  • Interruption delay When the terminal is handed over from the source base station to the target base station, the connection between the terminal and the source base station is disconnected during the handover phase, and the source base station can transfer to the target through the forwarding tunnel between the source base station and the target base station The base station sends the terminal's data packet. Before the random access procedure between the terminal and the target base station is completed, the target base station temporarily buffers the received data packets of the terminal. The target base station will not send the data packet of the terminal to the terminal until the random access procedure between the terminal and the target base station is completed. Therefore, before the random access procedure between the terminal and the target base station is completed, the target base station does not send the data packet to the terminal, so the service of the terminal is interrupted. Therefore, the time delay generated in this process can be called interrupt time delay.
  • the source base station sends the terminal's data packet to the target base station.
  • the so-called path switching refers to changing the downlink path between the terminal and the UPF network element from UPF network element ⁇ source base station ⁇ terminal to: UPF network element ⁇ target base station ⁇ terminal.
  • Step 101 The source base station sends a RAN usage data report to an access management network element (for example, an AMF network element), so that the AMF network element receives the RAN Usage data report from the source base station.
  • an access management network element for example, an AMF network element
  • Step 102 The target base station sends an N2 path switch request to the AMF network element, so that the AMF network element receives the N2 path switch request.
  • the N2 path switch request is used to request
  • Step 103 The AMF network element sends a PDU session update session management context request (PDU session_update SM context request) to the SMF network element, so that the SMF network element receives the PDU session update session management context request.
  • PDU session_update SM context request PDU session_update SM context request
  • Step 104 The SMF network element sends an N4 session modification request (N4 session modification request) to the UPF network element, so that the UPF network element receives the N4 session modification request.
  • the N4 session modification request is used to request to modify the N4 session.
  • Step 105 The UPF network element sends an N4 session modification response (N4 session modification response) to the SMF network element, so that the SMF network element receives the N4 session modification response.
  • N4 session modification response N4 session modification response
  • Step 106 The UPF network element sends an end marker to the source base station, so that the source base station receives the end marker.
  • the end marker is used to indicate that the UPF network element stops sending downlink data packets for the terminal to the source base station.
  • Step 107 The source base station sends an end marker to the target base station, so that the target base station receives the end marker.
  • the downlink path transmission between the terminal and the UPF network element becomes: UPF network element ⁇ target base station ⁇ terminal.
  • Step 108 The SMF network element sends a PDU session update session management context response (PDU session_update SM context response) to the AMF network element, so that the AMF network element receives the PDU session update session management context response.
  • PDU session_update SM context response PDU session_update SM context response
  • Step 109 The AMF network element sends an N2 path switching request response to the target base station to indicate that the N2 path switching is successful.
  • Step 110 The target base station sends a terminal context release request to the source base station, and the source base station releases the context of the terminal.
  • words such as “first” and “second” are used to distinguish the same items or similar items that have substantially the same function and effect.
  • the first base station and the second base station are only used to distinguish between different base stations, and the sequence of them is not limited.
  • words such as “first” and “second” do not limit the quantity and order of execution, and words such as “first” and “second” do not limit the difference.
  • 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 relationships, for example, A and/or B, which can mean: A alone exists, A and B exist at the same time, and B exists alone, where A, B can be singular or plural.
  • the character “/” generally indicates that the associated objects before and after 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 a plurality of items (a).
  • at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple .
  • FIG. 2 shows a communication system provided by an embodiment of the present application, and the communication system includes: a base station 1 and a terminal.
  • cloud radio access network cloud radio access network
  • C-RAN cloud radio access network
  • One possible way is to divide the protocol stack architecture and functions of traditional base stations into two parts, one part is called centralized The processing node (Centralized Unit, CU), and the other part is called the distributed processing node (Distributed Unit, DU), and the actual deployment of CU and DU is more flexible.
  • the processing node Centralized Unit, CU
  • the distributed processing node Distributed Unit, DU
  • the actual deployment of CU and DU is more flexible.
  • the network layout of the base station can be flexibly adjusted, which has good benefits for load balancing and maximum utilization of resources.
  • this architecture there is better support for solving tidal effects, deploying dual connectivity, edge computing, business offloading, and intelligent operation and maintenance.
  • base station 1 is split into CU1 and DU1 to DU3.
  • Multiple DUs (for example, DU1, DU2, and DU3) can be centrally controlled by one CU1.
  • the first interface may be an F1 interface.
  • CU and DU can be divided according to the protocol layer of the wireless network.
  • the packet data convergence protocol (PDCP) and the functions of the above protocol layers are set in the protocol layer below the CU and PDCP, such as radio link control (radio link).
  • Control, RLC radio link control
  • media access control layer and other functions are set in the DU.
  • This type of protocol layer division is just an example, it can also be divided in other protocol layers, for example, in the RLC layer, the functions of the RLC layer and above protocol layers are set in the CU, and the functions of the protocol layers below the RLC layer are set in the DU; Or, in a certain protocol layer, for example, part of the functions of the RLC layer and the functions of the protocol layer above the RLC layer are set in the CU, and the remaining functions of the RLC layer and the functions of the protocol layer below the RLC layer are set in the DU. In addition, it can also be divided in other ways, for example, by time delay. The functions that need to meet the time delay requirements for processing time are set in the DU, and the functions that do not need to meet the delay requirements are set in the CU.
  • control plane (CP) and user plane (UP) of the CU are separated and implemented in different entities.
  • the CU can be split into centralized processing The control plane of the node (CU Control Plane, CU-CP) and the user plane of the centralized processing node (CU User Plane, CU-UP).
  • CU1 is split into CU-CP1, CU-UP1 and CU-UP2.
  • CU-CP1 is connected to CU-UP1 and CU-UP2 through a second interface (for example, an E1 interface), respectively.
  • a second interface for example, an E1 interface
  • F1-C interface between CU-CP1 and DU1 to DU3.
  • Different DUs can be connected to different CU-UPs (for example, DU1 and CU-UP1 are connected through an F1-U interface, and DU3 and CU-UP2 are connected through an F1-U interface).
  • Different DUs can also be connected to the same CU-UP (for example, DU1 and CU-UP1 are connected through an F1-U interface, and DU2 and CU-UP1 are connected through an F1-U interface).
  • the F1-C interface is used for the control plane, and the F1-U interface is used for the user plane.
  • the F1-C interface is used to transmit the signaling between CU-CP and DU.
  • the F1-U interface is used to transmit data between CU-CP and DU.
  • the data generated by the CU can be sent to the terminal through the DU, or the data generated by the terminal can be sent to the CU through the DU.
  • the DU may directly pass the protocol layer encapsulation to the terminal or CU without analyzing the data.
  • the RRC or PDCP layer data will eventually be processed as physical layer (PHY) data and sent to the terminal, or converted from the received PHY layer data.
  • PHY physical layer
  • the RRC or PDCP layer data can also be considered to be sent by the DU.
  • the CU is divided into the access network equipment in the RAN.
  • the CU can also be divided into the access network equipment in the CN, which is not limited here.
  • the devices in the following embodiments of the present application may be located in terminals or access network equipment according to the functions they implement.
  • the access network device may be a CU node, or a DU node, or a RAN device including the functions of a CU node and a DU node.
  • FIG. 4 shows another communication system provided by an embodiment of the present application.
  • the communication system may further include a base station 2.
  • Base station 2 is the base station accessed by the terminal after handover.
  • the base station 2 and the base station 1 can be connected to the same access management network element, or can be connected to different access management network elements, which is not limited in the embodiment of the present application.
  • Fig. 4 illustrates the connection of base station 2 and base station 1 with the same access management network element as an example.
  • the base station 2 is split into CU2 and DU4, and CU2 is split into CU-CP2 and CU-UP3 as an example.
  • the base station 2 can be split into multiple CU2 and multiple DU4.
  • one CU2 and DU4 are taken as an example. It does not constitute a restriction on this application.
  • the terminals perform data transmission or signaling transmission with the network elements in the core network through the base stations they access.
  • Figures 2 and 4 take the network elements in the core network including user plane network elements and control plane network elements as examples.
  • the user plane network element refers to a device that can implement the user plane function of the core network device
  • the control plane network element refers to a device that can implement the control plane function of the core network device.
  • the control plane network element may be an access management network element.
  • the user plane network element and the control plane network element can be integrated in the same device, or can be set independently. In the embodiment of the present application, the independent setting of the user plane network element and the control plane network element is taken as an example for description.
  • base station 1 and base station 2 may be evolved Node Base Station (eNB) in the LTE system (may be referred to as LTE eNB).
  • the LTE eNB is connected to a 4G core network (for example, Evolved Packet Core (EPC)) through an S1 interface, and different LTE eNBs are connected through an X2 interface. That is, the base station 1 and the base station 2 in FIG. 4 are connected through an X2 interface. Among them, the X2 interface supports the direct transmission of data and signaling between base station 1 and base station 2.
  • EPC Evolved Packet Core
  • the X2 interface is also divided into two interfaces, for example, an X2-C interface and an X2-U interface.
  • the X2-C interface is used for the control plane
  • the X2-U interface is used for the user plane.
  • the X2-C interface is used to transmit signaling between base station 1 and base station 2.
  • the X2-U interface is used to transmit data between base station 1 and base station 2.
  • the entity corresponding to the access management network element in the 4G network may be a mobility management entity (Mobility Management Entity, MME), and the MME is connected to the base station 1 or the base station 2 through an S1-MME interface.
  • MME Mobility Management Entity
  • the network element or entity corresponding to the user plane network element can be the packet data network user plane ((PGW-User Plane, PGW-U) and the service gateway user plane (SGW-User Plane, SGW-U).
  • PGW-User Plane PGW-U
  • SGW-User Plane SGW-U
  • the SGW is responsible for the 4G network Processing equipment such as data packet routing and forwarding.
  • base station 1 and base station 2 can be the next generation node B (The Next Generation Node B) in the NR system.
  • the gNB is connected to the NG-Core network through the N2 interface, and different gNBs are connected through the Xn interface.
  • the base station 1 and the base station 2 are connected through the Xn interface.
  • Each gNB is connected to at least one terminal in the NR system.
  • the entity corresponding to the access management network element in the 5G network may be an access and mobility management function (Core Access and Mobility Management Function, AMF) network element, and the AMF network element is connected to the base station 1 or the base station 2 through the N2 interface.
  • the AMF network element is connected to the terminal through the N1 interface.
  • the network element or entity corresponding to the user plane network element may be a user plane function (UPF) network element).
  • UPF user plane function
  • AMF network element belongs to the core network network element, mainly responsible for the signaling processing part, such as: access control, mobility management, registration, de-registration, gateway selection and other functions.
  • the AMF network element provides services for the session in the terminal, it can also provide storage resources of the control plane for the session to store the session identifier, the SMF network element identifier associated with the session identifier, and so on.
  • UPF network element responsible for the forwarding and receiving of user data of the terminal.
  • User data can be received from the data network and transmitted to the terminal through the access network equipment.
  • the UPF network element can also receive user data from the terminal through the access network device, and forward it to the data network.
  • the transmission resources and scheduling functions that provide services for the terminal in the UPF network element are managed and controlled by the SMF network element.
  • the terminal can also be called user equipment (UE), access terminal, user unit, user station, mobile station, mobile station, remote station, remote terminal, mobile equipment, user terminal, terminal equipment, wireless communication equipment, user Agent or user device.
  • the terminal can be a station (STA) in a wireless local area network (WLAN), a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, and a wireless local loop (wireless local loop).
  • WLAN wireless local area network
  • SIP session initiation protocol
  • wireless local loop wireless local loop
  • next-generation communication systems such as , Terminal equipment in a fifth-generation (fifth-generation, 5G) communication network or terminals in a public land mobile network (PLMN) network that will evolve in the future.
  • 5G fifth-generation
  • PLMN public land mobile network
  • the terminal may also be a wearable device.
  • Wearable devices can also be called wearable smart devices. It is a general term for the application of 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 kind of 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.
  • Fig. 5 shows a schematic diagram of the hardware structure of a communication device in an embodiment of the present application.
  • the communication device includes a processor 51, a communication line 54 and at least one communication interface (in FIG. 5, the communication interface 53 is only used as an example for illustration).
  • the communication device may further include a memory 52.
  • the processor 51 may be a general-purpose central processing unit (central processing unit, CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more programs for controlling the execution of the program of this application. integrated circuit.
  • CPU central processing unit
  • ASIC application-specific integrated circuit
  • the communication line 54 may include a path to transmit information between the aforementioned components.
  • the communication interface 53 uses any device such as a transceiver to communicate with other devices or communication networks, such as Ethernet, radio access network (RAN), wireless local area networks (WLAN), etc. .
  • RAN radio access network
  • WLAN wireless local area networks
  • the memory 52 may be a read-only memory (ROM) or other types of static storage devices that can store static information and instructions, random access memory (RAM), or other types that can store information and instructions
  • the dynamic storage device can also be electrically erasable programmable read-only memory (EEPROM), compact disc read-only memory (CD-ROM) or other optical disk storage, optical disc storage (Including compact discs, laser discs, optical discs, digital versatile discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or can be used to carry or store desired program codes in the form of instructions or data structures and can be used by a computer Any other media accessed, but not limited to this.
  • the memory can exist independently and is connected to the processor through the communication line 54. The memory can also be integrated with the processor.
  • the memory 52 is used to store computer-executable instructions for executing the solution of the present application, and the processor 51 controls the execution.
  • the processor 51 is configured to execute computer-executable instructions stored in the memory 52, so as to implement a communication method provided in the following embodiments of the present application.
  • the computer-executable instructions in the embodiments of the present application may also be referred to as application program codes, which are not specifically limited in the embodiments of the present application.
  • the processor 51 may include one or more CPUs, such as CPU0 and CPU1 in FIG. 5.
  • the communication device may include multiple processors, such as the processor 51 and the processor 55 in FIG. 5.
  • processors can be a single-CPU (single-CPU) processor or a multi-core (multi-CPU) processor.
  • the processor here may refer to one or more devices, circuits, and/or processing cores for processing data (for example, computer program instructions).
  • the communication interface 53 may be replaced with a transceiver.
  • the base station is disassembled into CU-CP (mainly the control plane of the CU, including the RRC layer and the PDCP layer), CU-UP (mainly the user plane of the CU, the PDCP layer) and DU (mainly RLC layer, MAC layer and PHY layer that need real-time processing).
  • CU-CP mainly the control plane of the CU, including the RRC layer and the PDCP layer
  • CU-UP mainly the user plane of the CU, the PDCP layer
  • DU mainly RLC layer, MAC layer and PHY layer that need real-time processing.
  • the distributed deployment of DU compared with the distributed deployment of DU, the centralized deployment among multiple CU-UPs, one CU-CP can control multiple CU-UPs, and the multiple CU-UPs may be flexibly grouped. Distributed in different areas to provide services for DUs in different areas.
  • One CU-UP can be connected to multiple DUs, and one DU is connected to one CU-UP.
  • a base station can cover one or more cells.
  • One or more cells covered by a base station may mean that the CU of the base station covers one or more cells, or that the DU of the base station covers one or more cells. Therefore, the source base station accessed by the terminal can decide to switch the cell for the terminal according to the measurement report sent by the terminal.
  • the target cell determined by the source base station for the terminal handover may belong to the same base station as the source cell where the terminal is located. Of course, the target cell determined by the source base station for the terminal handover may belong to a different base station from the source cell where the terminal is located. The following will be described separately:
  • Scenario (1) handover under the same DU, that is, the terminal switches from cell a to cell b, and both cell a and cell b belong to cells within the coverage of the same DU.
  • both cell a and cell b belong to the cells covered by DU1 in FIG. 2.
  • Scenario (2) DU handover under the same CU-UP, that is, the terminal switches from cell 1 to cell 2. Both cell 1 and cell 2 belong to the cells covered by CU-UP1 as shown in Figure 2, but cell 1 It belongs to the coverage area of DU1, and the cell 2 belongs to the coverage area of DU2.
  • Scenario (3) DU handover under different CU-UPs under the same CU-CP, that is, the terminal switches from cell 3 to cell 4.
  • Cell 3 belongs to the cell covered by CU-UP1 as shown in Figure 2.
  • 4 belongs to a cell within the coverage area of CU-UP2 as shown in FIG. 2.
  • cell 3 belongs to the coverage area of DU2
  • cell 4 belongs to the coverage area of DU3.
  • Scenario (4) DU switching under different CU-CPs and different CU-UPs. That is, the terminal is handed over from cell 5 to cell 6.
  • Cell 5 belongs to the cell covered by CU-UP2 as shown in Figure 4
  • cell 6 belongs to the cell covered by CU-UP3 as shown in Figure 4.
  • the cell 5 belongs to the coverage area of DU3
  • cell 6 belongs to the coverage area of DU4.
  • scenario (1) and scenario (2) although the DU has changed, because the CU-UP has not changed, the UPF network element -> CU-UP link will not be adjusted.
  • scenario (1) is basically OK A 0ms handover is achieved.
  • scenario (2) Because the CU-UP does not switch, there is only the problem of service plane interruption during the execution of the RAN side handover. For a solution to the problem of how to avoid business interruption, refer to the solution of DU switching as described in FIG. 8.
  • the source RAN device In order to avoid interruption time delay, currently, after the source RAN device sends a handover command to the terminal, the source RAN device continues to maintain the connection with the terminal. In this solution, since the terminal reports a measurement report (measurement report), the handover process is triggered. Although the source RAN device still maintains the connection with the terminal, due to the signal strength, the connection may appear more frequently due to poor signal. Packet loss and error packets, so the source RAN device can copy and forward part of the data packet for the terminal to the target RAN device for transmission until the connection between the terminal and the target RAN device is successfully established, and the terminal releases the connection with the source RAN device.
  • the terminal needs to establish two protocol stack connections at the same time.
  • Each protocol stack includes a PDCP entity, a radio link control (RLC) entity, and a medium access control (MAC) entity from top to bottom.
  • the terminal needs to merge, sort and de-duplicate the data packets received in different PDCP entities.
  • the connection between the target RAN device and the UPF network element can be constructed first, and the connection between the source RAN device and the terminal can be maintained, and then the UPF network element sends the first connection to the source RAN device.
  • the source RAN device After receiving the first message, the source RAN device sends all the data packets received before the first message before starting the handover process.
  • the source RAN device sends the SN number related information of the bicast packet to the target RAN device through the second message.
  • the target RAN device After receiving the second message, the target RAN device generates PDCP according to the second message. Message and synchronize the SN number.
  • This solution does not use the method of establishing a forwarding tunnel between the Source RAN and the Target RAN for data transmission during the Path Switch process, thus effectively avoiding forwarding delay.
  • the connection between the target RAN device and the UPF network element needs to be constructed first, and the first message is sent, and the handover process is started after the Source RAN has sent all the data packets before the first message. The preparation time is too long. Added extra handover delay.
  • the UPF data bicasting method has been used for transmission throughout the entire Path Switch process, which has resulted in a lot of waste of transmission resources.
  • the terminal may need to receive data packets of the PDCP entities of the source RAN device and the target RAN device at the same time. Therefore, it is necessary to construct two PDCP entities and sequence and de-duplicate the received data packets.
  • the embodiments of the present application provide communication methods as shown in FIGS. 6-12.
  • the specific structure of the execution body of a communication method is not particularly limited in the embodiment of this application, as long as the program recorded with the code of a communication method of the embodiment of this application can be run according to this application.
  • Only one communication method of the application embodiment can be used for communication.
  • the execution subject of a communication method provided in an embodiment of the present application may be a functional module in the DU that can call and execute the program, or a communication device applied in the DU, such as a chip.
  • the execution subject of a communication method provided by an embodiment of the present application may be a functional module in the first device that can call and execute the program, or a communication device, such as a chip, applied to the first device. This application does not limit this.
  • the following embodiments are described with an example in which a communication method is executed by a DU and a first device.
  • FIG. 6 shows a communication method provided by an embodiment of the present application, and the method includes:
  • Step 601 While the DU receives the downlink data packet from the first CU-UP through the user plane connection with the first CU-user plane UP, the DU receives the downlink data packet from the first CU-UP through the user plane connection with the second CU-UP. Downlink data packet from the second CU-UP.
  • the first RLC entity of the DU is associated with the second RLC entity of the DU.
  • the first RLC entity corresponds to the first CU-UP
  • the second RLC entity corresponds to the second CU-UP
  • the DU Since the first RLC entity corresponding to the first CU-UP is associated with the second RLC entity corresponding to the second CU-UP, it is convenient for the DU to determine the second RLC entity corresponding to the second CU-UP to determine the second RLC entity corresponding to the first CU-UP. Whether the transmission of the first RLC entity corresponding to the UP is completed, and then it can be known when to start transmitting the downlink data packet buffered by the second RLC entity corresponding to the second CU-UP to the terminal.
  • first RLC entity and the second RLC entity belong to a DU, and the first RLC entity corresponds to the first CU-UP, and the second RLC entity corresponds to the second CU-UP.
  • the first CU-UP is a CU-UP that provides services for the terminal before the handover.
  • the second CU-UP is the CU-UP that provides services for the terminal after the handover.
  • the DU in the embodiment of the present application may be a DU that provides services for the terminal before handover.
  • the DU is a DU that provides services for the terminal after the handover.
  • the DU serving the terminal may not change.
  • the terminal switches between two cells in the same base station, that is, the first CU-UP and the second CU-UP belong to the same A base station.
  • the first CU-UP is CU-UP1
  • the second CU-UP is CU-UP2.
  • the DU may be DU2 connected to CU-UP1, or DU3 connected to CU-UP2, which is not limited in the embodiment of the present application.
  • DU2 is a DU that provides services for the terminal before handover.
  • DU3 is a DU that provides services for the terminal after the handover.
  • the terminal switches between two cells under the coverage of different base stations, that is, the first CU-UP and the second CU-UP belong to different Base station.
  • the first CU-UP is CU-UP2, which belongs to base station 1
  • the second CU-UP is CU-UP3, which belongs to base station 2.
  • the DU may be DU3 connected to CU-UP2, or DU4 connected to CU-UP3, which is not limited in the embodiment of the present application.
  • DU3 in FIG. 3 is a DU that provides services for the terminal before handover.
  • DU4 is a DU that provides services for the terminal after the handover.
  • the DU is a DU that provides services to the terminal before the handover or a DU that provides services to the terminal after the handover, it is before the DU releases the user plane connection (for example, the F1-U connection) with the first CU-UP If the DU also has a user plane connection with the second CU-UP, it can be considered that the DU is in a dual-connection state. At this time, the DU can not only receive downlink data packets from the first CU-UP, but also receive data packets from the first CU-UP. Two downstream data packets of CU-UP.
  • the first CU-UP and the second CU-UP may be connected to the same user plane network element that provides services for the terminal (for a scenario where the user plane network element does not change when the terminal is switched).
  • the first CU-UP and the second CU-UP can be connected to different user plane network elements that provide services for the terminal (for a scenario where the user plane network element changes when the terminal is switched).
  • the DU is a DU that provides services to the terminal before handover.
  • the DU is located in the service range of the first CU-UP and is located at the edge of the service range of the second CU-UP.
  • the DU is connected with the first CU-UP, but the DU can also establish a connection with the second CU-UP.
  • the DU is a DU that provides services to the terminal after the handover.
  • the DU is located in the service range of the second CU-UP and is located at the edge of the service range of the first CU-UP.
  • the DU is connected with the second CU-UP, but the DU can also establish a connection with the first CU-UP.
  • Step 602 The DU sends the downlink data packet from the first CU-UP to the terminal.
  • the terminal receives the downlink data packet from the first CU-UP.
  • the DU may send the downlink data packet from the first CU-UP to the terminal through the user plane connection with the terminal.
  • Step 603 When the DU sends all the downlink data packets from the first CU-UP to the terminal, the DU sends the downlink data packets buffered by the DU from the second CU-UP to the terminal, so that the terminal receives the downlink data packets from the second CU-UP. -UP downstream data packets.
  • the DU may first send the downlink data packet from the first CU-UP to the terminal. UP downlink data packets, and buffer the downlink data packets from the second CU-UP, until the DU sends all the downlink data packets from the first CU-UP to the terminal, the DU sends the DU buffered data from the second CU to the terminal. Downlink data packet of CU-UP.
  • the embodiment of the present application provides a communication method.
  • this method there is a user plane connection between the DU and the first CU-UP and the second CU-UP, which can prevent the CU-UP of the terminal from being switched from the first CU-UP.
  • the downlink data packet of the terminal is forwarded between the first CU-UP and the second CU-UP, that is, there is no need to establish a connection between the first CU-UP and the second CU-UP. Forwarding tunnel, therefore avoiding forwarding delay.
  • the DU since the first RLC entity is associated with the second RLC entity, and the first RLC entity corresponds to the first CU-UP, and the second RLC entity corresponds to the second CU-UP, it is convenient for the DU to check the information from the second CU-UP.
  • the downlink data packets are buffered. After all the downlink data packets of the first CU-UP are transmitted to the terminal, the DU starts to transmit the downlink data packets from the second CU-UP to the terminal, which not only ensures the low-latency handover of the CU-UP In addition, it can also avoid the problem of interruption of the terminal's business.
  • the method provided in the embodiment of the present application further includes: associating the DU with a first RLC entity corresponding to the first CU-UP and a second RLC entity corresponding to the second CU-UP , And establish a user plane connection between the DU and the second CU-UP.
  • step 701 to step 703 in FIG. 7 As shown, step 706, step 707, and step 710 can refer to the description of step 601 to step 603 above, which will not be repeated here.
  • an embodiment of the present application provides a communication method, which includes:
  • Step 701 The first device sends a first request message to the DU.
  • the DU receives the first request message from the first device.
  • the CU-CP directly determines the need to associate the first RLC entity corresponding to the first CU-UP and the first RLC entity corresponding to the second CU-UP The second RLC entity.
  • the first request message carries a first indication, where the first indication indicates that the DU associates a first RLC entity corresponding to the first CU-UP and a second RLC entity corresponding to the second CU-UP.
  • the first indication may explicitly indicate that the DU is associated with the first RLC entity corresponding to the first CU-UP and the second RLC entity corresponding to the second CU-UP.
  • the first indication may also implicitly indicate that the DU is associated with the first RLC entity corresponding to the first CU-UP and the second RLC entity corresponding to the second CU-UP.
  • the first instruction indicates that the DU maintains the user plane connection with the first CU-UP, and the DU establishes the user plane connection with the second CU-UP. In this way, the DU can determine that the first RLC entity corresponding to the first CU-UP and the second RLC entity corresponding to the second CU-UP also need to be associated.
  • the first request message may be a terminal context establishment request message. It is understandable that the first request message itself may have an indication that the DU is associated with a first RLC entity corresponding to the first CU-UP and a second RLC entity corresponding to the second CU-UP, and/or, instructing the DU to establish the DU and The meaning of the user plane connection of the second CU-UP. When the first request message itself has this meaning, the first indication can be omitted.
  • the embodiment of the present application takes the first indication carried in the first request message as an example. Of course, the first indication may also be sent to the DU separately, which is not limited in the embodiment of the present application.
  • the first device in the embodiment of the present application is a centralized processing node CU-control plane CP of the first base station, and the first base station is a base station that provides services for the terminal before handover.
  • the first base station is base station 1 shown in FIG. 2, and the first device is CU-CP1.
  • the first CU-UP and the second CU-UP are connected to the same centralized processing node CU-control plane CP.
  • the first CU-UP may be the CU-UP1 shown in FIG. 2 and the second CU-UP UP may be CU-UP2 shown in Figure 2.
  • the first device in the embodiment of the present application is a centralized processing node CU-control plane CP of a second base station
  • the second base station is a base station that provides services for the terminal after the handover.
  • the second base station may be base station 2 shown in FIG. 4, and the first device is CU-CP2.
  • the first CU-UP and the second CU-UP are connected to different centralized processing nodes CU-control plane CP.
  • the first CU-UP may be the CU-UP1 shown in FIG. 4, and the second CU-UP UP may be CU-UP3 shown in Figure 2.
  • the method may further include: the first device receives a handover request sent by the CU-CP from the first base station ,
  • the switching request is used to request the first device to trigger the CU-UP switching process.
  • the handover request should contain the context of the terminal, and the handover request is also used to request the establishment of a connection between the DU and the second CU-UP, and the first RLC entity corresponding to the first CU-UP and the second CU-UP The second RLC entity corresponding to the UP is associated. In this way, the implementation of the subsequent end marker (End Marker) mechanism can be facilitated.
  • End Marker End Marker
  • Step 702 The DU associates a first RLC entity corresponding to the first CU-UP and a second RLC entity corresponding to the second CU-UP according to the first instruction.
  • the first instruction also instructs the DU to establish a user plane connection between the DU and the second CU-UP.
  • the method provided in the embodiment of the present application may further include after step 701:
  • Step 703 The DU establishes a user plane connection between the DU and the second CU-UP according to the first instruction.
  • the first indication in the embodiments of this application may have the following meanings: 1.
  • the first indication indicates the establishment of a user plane connection between the DU and the second CU-UP, and the association of the first RLC entity corresponding to the first CU-UP and The second RLC entity corresponding to the second CU-UP.
  • the first instruction indicates the establishment of a user plane connection between the DU and the second CU-UP.
  • the DU may also determine that the first RLC entity corresponding to the first CU-UP needs to be associated with the first RLC entity and the second CU-UP.
  • the first indication indicates to associate the first RLC entity corresponding to the first CU-UP and the second RLC entity corresponding to the second CU-UP.
  • the DU may also determine to establish the DU and the second CU-UP. User plane connection between UPs.
  • an instruction to instruct the DU to establish a user plane connection between the DU and the second CU-UP, and to associate the first RLC entity corresponding to the first CU-UP and the second RLC entity corresponding to the second CU-UP It can also be a different indication.
  • the different instructions may be carried in the same message or in different messages, which is not limited in the embodiment of the present application.
  • the first request message in the embodiment of the present application may also carry the information of the second CU-UP.
  • the information of the second CU-UP may be the address of the second CU-UP or the identifier of the second CU-UP, which is not limited in the embodiment of the present application.
  • the information of the second CU-UP may be pre-configured in the first device, or may be obtained by the first device from the second CU-UP, which is not limited in the embodiment of the present application.
  • the method provided in the embodiment of the present application may further include:
  • Step 704 The DU sends a first configuration message to the terminal.
  • the terminal receives the first configuration message from the DU.
  • the first configuration message instructs the terminal to establish a user plane connection between the terminal and the second CU-UP, and maintain the user plane connection between the terminal and the first CU-UP.
  • the user plane connection between the terminal and the second CU-UP is used for the terminal to transmit uplink data packets to the second CU-UP.
  • the user plane connection between the terminal and the second CU-UP is established here, including the PHY layer and the MAC layer corresponding to the logical connection in the DU , The RLC layer entity, the PDCP entity in the CU-UP, and the PHY, MAC, RLC, and PDCP entities that should be connected in the terminal.
  • This user plane connection represents a logical connection with the granularity of a radio bearer, rather than a specific physical connection.
  • the first configuration message may be an RRC reconfiguration message (RRC Reconfiguration message).
  • Step 705 The terminal establishes a user plane connection with the second CU-UP, and maintains the user plane connection between the terminal and the first CU-UP.
  • the terminal may send a first configuration complete message (for example, an RRC Reconfiguration Complete message) to the DU to indicate that the terminal has Establish a user plane connection with the second CU-UP.
  • a first configuration complete message for example, an RRC Reconfiguration Complete message
  • the DU receives the RRC Reconfiguration Complete message, it can forward the RRC Reconfiguration Complete to the first device.
  • the method may further include:
  • Step 708 The DU receives a second instruction, which is used by the DU to determine that the transmission of the downlink data packet transmitted on the user plane connection between the user plane network element and the first CU-UP is complete.
  • the DU may receive the second indication from the first CU-UP.
  • the user plane network element when the CU-UP of the terminal is switched, first the user plane network element maintains the user plane connection with the first CU-UP, and passes between the user plane network element and the first CU-UP The user plane connection sends downlink data packets to the terminal. After that, during the CU-UP handover, on the one hand, the user plane network element continues to send to the terminal through the user plane connection between the user plane network element and the first CU-UP For downlink data packets, on the other hand, the user plane network element also establishes a user plane connection with the second CU-UP.
  • the user plane network element can stop the user plane connection between the user plane network element and the first CU-UP to the first CU -UP sends a downlink data packet for the terminal, and sends a second instruction to the first CU-CP, so that the first CU-UP receives the second instruction from the user plane network element.
  • Step 709 The DU determines, according to the second instruction, that the transmission of the downlink data packet transmitted on the user plane connection between the user plane network element and the first CU-UP has ended. That is, through the second instruction, the DU can determine that the subsequent user plane network element stops sending the downlink data packet to the first CU-UP on the user plane connection between the user plane network element and the first CU-UP. Subsequently, when the user plane network element still has a downlink data packet to send to the terminal, the user plane network element will send the downlink data packet to the second CU-UP through the user plane connection with the second CU-UP.
  • the user plane network element stops sending downlink data packets to the first CU-UP on the user plane connection between the user plane network element and the first CU-UP, for the DU, the following situations may still exist at the DU: Not all data packets from the first CU-UP are sent to the terminal, but the DU has received the downlink data packets from the second CU-UP. At this time, the DU can buffer the downlink data packets from the second CU-UP. Until the data packets from the first CU-UP are all sent to the terminal, then the downlink data packets from the second CU-UP are sent to the terminal, which can prevent the terminal from receiving the downlink data packets from the two CU-UPs at the same time and perform additional The merger process.
  • the terminal is to be switched to the second CU-UP, that is, the user plane network element has established a user plane connection with the second CU-UP, and the second CU-UP is also connected to the DU that provides services for the terminal.
  • the user plane connection is established, as shown in FIG. 7, the method provided in the embodiment of the present application may further include:
  • Step 711 When the DU sends all the downlink data packets from the first CU-UP to the terminal, the DU sends a first report to the first device, so that the first device receives the first report from the DU.
  • the first report is used by the first device to trigger the first CU-UP to release the context of the terminal.
  • Step 712 The first device triggers the first CU-UP to release the context of the terminal.
  • the first device if the first device is the CU-CP of the first base station, the first device sends a command to release the context of the terminal to the first CU-UP, so that the first CU-UP responds to the command to release the context of the terminal, and Command to release the context of the terminal.
  • the first device if the first device is the CU-CP of the second base station, the first device sends a command to release the context of the terminal to the CU-CP corresponding to the first CU-UP, so that the CU-CP corresponding to the first CU-UP
  • the command to release the context of the terminal is forwarded to the first CU-UP, and the subsequent first CU-UP responds to the command to release the context of the terminal and a command to release the context of the terminal.
  • the method provided in the embodiment of the present application may further include before step 701: the CU-CP of the first base station or the CU of the second base station -The CP switches the terminal from the DU that provided services for the terminal before the handover to the DU.
  • the DU handover process can refer to the description of FIG. 8 above.
  • Step 801 The terminal sends a measurement report to the source DU, so that the source DU receives the measurement report from the terminal.
  • the measurement report is used to reflect the signal power of the surrounding cells received by the terminal.
  • the downlink data packet transmission path of the terminal is shown in FIG. 8 as: CU ⁇ source DU ⁇ terminal.
  • the uplink data packet transmission path of the terminal is shown in Figure 8 as: terminal ⁇ source DU ⁇ CU.
  • Step 802 The source DU sends an uplink RRC message transfer (UL RRC message transfer) to the CU, so that the CU receives the uplink RRC message transfer from the source DU.
  • the uplink RRC message transmission includes a measurement report.
  • Step 803 The CU sends a terminal context setup request (UE context setup request) to the target DU, so that the target DU receives the terminal context setup request from the CU.
  • the terminal context establishment request is used to request the establishment of a terminal context (UE Context) on the DU side, which is mainly a configuration parameter related to the logical connection of the terminal, and is used to establish a MAC entity and an RLC entity.
  • the target DU is requested to feed back the port information used to establish the connection with the CU-UP.
  • Step 804 The target DU sends a terminal context setup response (UE context setup response) to the CU, so that the CU receives the terminal context setup response.
  • UE context setup response UE context setup response
  • Step 805 The CU sends a terminal context modification request (UE context modification request) to the source DU, so that the source DU receives the terminal context modification request from the CU.
  • UE context modification request UE context modification request
  • the terminal context modification request carries an RRC reconfiguration message.
  • the terminal context modification request includes a transmission action indicator (Transmission Action Indicator), which is used to instruct the source DU to continue to maintain the connection with the terminal.
  • Transmission Action Indicator Transmission Action Indicator
  • Step 806 The source DU sends an RRC reconfiguration message to the terminal, so that the terminal receives the RRC reconfiguration message from the source DU.
  • Step 807 The source DU sends a downlink data delivery status (downlink data delivery status) to the CU, so that the CU receives the downlink data delivery status from the source DU.
  • a downlink data delivery status downlink data delivery status
  • Step 808 The source DU sends a terminal context modification response (UE context modification response) to the CU, so that the CU receives the terminal context modification response from the source DU.
  • UE context modification response UE context modification response
  • Step 809 A random access procedure (random access procedure) is executed between the terminal and the target DU.
  • the target DU sends the downlink data transmission status to the CU, so that the CU receives the downlink data transmission status.
  • Step 810 The terminal sends an RRC reconfiguration complete message to the target DU, so that the target DU receives the RRC reconfiguration complete message from the terminal.
  • the CU sends the downlink data for the terminal to the target DU, so that the target DU receives the downlink data for the terminal from the CU.
  • Step 811 The target DU sends an uplink RRC message transmission to the CU, so that the CU receives the uplink RRC message transmission from the target DU.
  • the uplink RRC message transmission carries the RRC reconfiguration complete message of the terminal.
  • Step 812 The target DU sends downlink data for the terminal to the terminal, so that the terminal receives the downlink data for the terminal.
  • the uplink data can be sent to the CU through the target DU.
  • Step 813 The CU sends a terminal context release command (UE context release conmmand) to the source DU, so that the source DU receives the terminal context release command from the CU.
  • UE context release conmmand a terminal context release command
  • the source DU After receiving the terminal context release command, the source DU can release the terminal context of the terminal.
  • Step 814 After the source DU releases the terminal context, it can send a terminal context release response to the CU to indicate that the source DU successfully releases the terminal context. After the source DU releases the terminal context, it terminates the connection with the terminal.
  • the CU dual-broadcasts the downlink data stream to the source DU and the target DU, and the connection between the source DU and the terminal is interrupted until the connection between the terminal and the target DU is established. In this way, the Make Before Break handover of the DU is realized. Since the DU handover does not need to construct a forwarding tunnel, a 0ms handover can be achieved.
  • the CU-CP can switch the DU for the terminal first, and then switch the CU-UP for the terminal.
  • the CU-CP can switch the CU-UP first according to the service condition or load condition of the CU-UP, and then switch the DU when the terminal moves. That is, switch the CU-UP for the terminal first, and then switch the DU for the terminal.
  • the method provided in the embodiment of the present application may further include: the CU-CP of the first base station or the CU-CP of the second base station connects the terminal Switching from the DU to the target DU, the target DU is connected to the second CU-UP, and subsequently the target DU provides services for the terminal.
  • the method provided in the embodiment of the present application may further include: after the DU establishes an uplink channel with the second CU-UP according to the information of the second CU-UP, the DU sends the information of the DU to the first device , So that the first device receives the information from the DU.
  • the DU information can be used for the second CU-UP to establish a downlink channel with the DU.
  • the first device sends the DU information to the second CU-UP, so that the second CU-UP establishes a downlink channel with the DU according to the DU information.
  • the second CU-UP may feed back a response message to the first device to indicate that the establishment of the downlink channel is completed.
  • the DU establishes the uplink channel with the second CU-UP according to the information of the second CU-UP
  • the second CU-UP establishes the downlink channel with the DU according to the information of the DU
  • the user plane connection between CU-UP is established.
  • Figure 9 uses the same gNB-CU-CP control, a scenario where both gNB-DU and gNB-CU-UP are switched, and the DU serving the terminal after the handover is the target (Target) gNB-DU ,
  • the DU serving the terminal before handover is the source gNB-DU
  • the first CU-UP is the source gNB-CU-UP
  • the second CU-UP is the target gNB-CU-UP
  • the source gNB-CU-UP Taking the connection with the target gNB-CU-UP and the same gNB-CU-CP as an example, the handover method involved in the embodiment of the present application is described in detail, as shown in FIG. 9, the method includes:
  • Step 901 The gNB-CU-CP switches the terminal from the source gNB-DU to the target gNB-DU.
  • the downlink data packet from the UPF network element passes through the source gNB-DU.
  • the CU-UP is sent to the target gNB-DU, and then the target gNB-DU sends the downlink data packet from the UPF network element to the terminal.
  • the downlink signaling from the AMF network element is sent to the target gNB-DU through the gNB-CU-CP, and then the target gNB-DU sends the downlink signaling from the AMF network element to the terminal.
  • the terminal For uplink transmission (ie terminal ⁇ UPF network element/AMF network element), the terminal first sends the uplink data packet to the target gNB-DU, and the target gNB-DU sends the uplink data packet from the terminal to the source gNB-CU-UP UPF network element.
  • the terminal first sends the uplink signaling to the target gNB-DU, and the target gNB-DU sends the uplink signaling from the terminal to the AMF network element through the gNB-CU-CP.
  • step 901 For the specific implementation of step 901, reference may be made to the DU handover described in FIG. 8, which will not be repeated here.
  • the gNB-CU-CP sends an indication message to the source gNB-CU-UP.
  • the indication message indicates that this handover is a cross-gNB-CU-UP handover. (That is, the terminal switches the gNB-CU-UP).
  • the source gNB-CU-UP forwards the End Marker from the user plane network element to the target gNB-DU.
  • step 901 can be omitted.
  • Step 902 The gNB-CU-CP sends a bearer context setup request message to the target gNB-CU-UP, so that the target gNB-CU-UP receives the bearer context setup request message from the gNB-CU-CP.
  • the bearer context establishment request message instructs the target gNB-CU-UP to establish a user plane connection (for example, F1-U connection) with the target gNB-DU, and requests feedback from the target gNB-CU-UP to create the user Uplink (UL) interface information of the plane connection.
  • the uplink (UL) interface information here may be the information of the target gNB-CU-UP, which may correspond to the information of the second CU-UP in the foregoing embodiment.
  • Step 903 The target gNB-CU-UP sends a bearer context setup response message to the gNB-CU-CP, so that the gNB-CU-CP receives the bearer context setup response message from the target gNB-CU-UP.
  • the bearer context establishment response message carries the uplink interface information of the user plane connection.
  • Step 904 The gNB-CU-CP sends a terminal context setup request (UE context setup request) message to the target gNB-DU, so that the target gNB-DU receives the terminal context setup request message from the gNB-CU-CP.
  • UE context setup request UE context setup request
  • the terminal context establishment request message instructs the target gNB-DU to establish a user plane connection with the target gNB-CU-UP, and requests the target gNB-DU to feed back downlink (DL) interface information of the user plane connection.
  • the terminal context establishment request message instructs the target gNB-DU to associate the RLC entity 1 corresponding to the source gNB-CU-UP and the RLC entity 2 corresponding to the target gNB-CU-UP in the RLC entity corresponding to the source gNB-CU-UP. 1 Before receiving the End Marker (corresponding to the above-mentioned second instruction), buffer the downlink data packet sent by the target gNB-CU-UP to the target gNB-DU.
  • the terminal context establishment request message includes an RRC reconfiguration (reconfiguration) message.
  • the terminal context establishment request message includes the uplink interface information of the user plane connection.
  • Step 905 The target gNB-DU establishes an uplink channel with the target gNB-CU-UP.
  • Step 906 The target gNB-DU sends a terminal context establishment response message to the gNB-CU-CP, so that the gNB-CU-CP receives the terminal context establishment response message from the target gNB-DU.
  • the terminal context establishment response message includes the downlink interface information of the user plane connection.
  • the downlink interface information of the user plane connection may be the information of the target gNB-DU, corresponding to the information of the above DU.
  • the gNB-CU-CP can send the downlink interface information of the user plane connection to the target gNB-CU-UP, so that the target gNB-CU-UP can establish a downlink channel with the target gNB-DU. So far, the target gNB-DU The user plane connection with the target gNB-CU-UP is established.
  • Step 907 The target gNB-DU sends an RRC reconfiguration message to the terminal, so that the terminal receives the RRC reconfiguration message from the target gNB-DU.
  • the RRC reconfiguration message instructs the terminal to establish a user plane connection with the target gNB-CU-UP, and maintain the user plane connection between the terminal and the source gNB-CU-UP.
  • Step 908 The gNB-CU-CP sends a bearer context modification request message to the target gNB-CU-UP, so that the target gNB-CU-UP receives the bearer context modification request message from the gNB-CU-CP.
  • the bearer context modification request message includes the downlink interface information of the user plane connection fed back by the target gNB-DU.
  • the Bearer Context Modification Request message modifies the Bearer Context saved at gNB-CU-UP, including almost all Bearer Context-related parameters, such as security messages, session-related QoS Flow mapping relationships, QoS Flow establishment and deletion, port messages, etc. .
  • Bearer Context-related parameters such as security messages, session-related QoS Flow mapping relationships, QoS Flow establishment and deletion, port messages, etc.
  • port information is mainly to modify the port information.
  • Step 909 The target gNB-CU-UP feeds back a bearer context modification response message to the gNB-CU-CP, so that the gNB-CU-CP receives the bearer context modification response message.
  • the bearer context modification response message may indicate that the target gNB-CU-UP has successfully received the downlink interface information of the user plane connection fed back by the target gNB-DU, or the user plane connection between the target gNB-DU and the target gNB-CU-UP The establishment is complete.
  • Step 910 The establishment of the user plane connection between the terminal and the target gNB-CU-UP is completed, and an RRC reconfiguration complete (RRC Reconfiguration Complete) message is sent to the target gNB-DU.
  • RRC reconfiguration complete RRC Reconfiguration Complete
  • Step 911 The target gNB-DU sends an uplink RRC message transfer (UL RRC Message transfer) to the gNB-CU-CP, so that the gNB-CU-CP receives the uplink RRC message transfer from the target gNB-DU.
  • the uplink RRC message transmission carries the RRC Reconfiguration Complete message.
  • the terminal maintains the user plane connection with the source gNB-CU-UP and the target gNB-CU-UP at the same time, but only receives downlink data of one gNB-CU-UP at the same time.
  • the specific method is implemented by step 915 to step 917.
  • the uplink data is sent through the target gNB-CU-UP.
  • Step 912 The UPF network element maintains the connection with the source gNB-CU-UP, and establishes a connection path with the target gNB-CU-UP.
  • Step 913 After the UPF network element establishes a connection with the target gNB-CU-UP, it sends an End Marker (corresponding to the foregoing second instruction) to the source gNB-CU-UP.
  • Step 914 The UPF network element stops sending the downlink data packet for the terminal to the source gNB-CU-UP, and starts to send the downlink data packet for the terminal to the target gNB-CU-UP.
  • Step 915 Before receiving the End Marker, the target gNB-DU maintains transmission with the source gNB-CU-UP, and buffers the downlink data packets received from the target gNB-CU-UP.
  • Step 916 According to the instruction message sent by the gNB-CU-CP to the source gNB-CU-UP, the source gNB-CU-UP sends an End Marker to the target gNB-DU, so that the target gNB-DU receives the source gNB-CU-UP The End Marker.
  • Step 917 After receiving the End Marker, the target gNB-DU preferentially sends the terminal downlink data packets from the source gNB-CU-UP for the terminal, and waits for all the downlink data packets for the terminal from the source gNB-CU-UP to be sent to the terminal After the terminal, it starts to send the downlink data packet for the terminal from the target gNB-CU-UP to the terminal.
  • Step 918 After processing the downlink data packet from the source gNB-CU-UP for the terminal, the target gNB-DU sends an end instruction execution report (End Marker execution report) to the gNB-CU-CP (corresponding to the above first report) , So that the gNB-CU-CP receives the End Marker execution report from the target gNB-DU.
  • End Marker execution report the target gNB-DU can report the End Marker execution status to the gNB-CU-CP.
  • the target gNB-DU can receive downlink data packets for the terminal from the source gNB-CU-UP and the target gNB-CU-UP, it can be considered that the target gNB-DU is in a dual data connection state. Because the dual data connection is used to implement low-latency handover, it is necessary to notify the gNB-CU-CP to release resources after the handover is completed. The main function of this End Marker execution report is to report the handover execution status and notify the gNB-CU-CP to release resources.
  • Step 919 The gNB-CU-CP sends a bearer context release command to the source gNB-CU-UP, so that the source gNB-CU-UP receives the bearer context release command from the gNB-CU-CP.
  • the bearer context release instruction instructs the source gNB-CU-UP to release corresponding connections and resources.
  • the bearer context release instruction instructs the source gNB-CU-UP to send a message to the core network requesting the release of the connection and resources corresponding to the source gNB-CU-UP.
  • the specific bearer context release instruction instructs the source gNB-CU-UP to release the connection with the gNB-DU (the port used for the connection with the gNB-DU), and the released resource refers to the PDCP entity corresponding to the logical connection and the saved Bearer Context .
  • Step 920 The gNB-CU-CP sends an F1UE context release command to the target gNB-DU, so that the target gNB-DU receives the F1UE context release command. After that, the target gNB-DU releases related resources and connections between the target gNB-DU and the source gNB-CU-UP according to the F1 UE context release instruction.
  • Step 921 After releasing the corresponding resources, the source gNB-CU-UP feeds back a bearer context release complete message to the gNB-CU-CP, so that the gNB-CU-CP receives the bearer context release complete message.
  • the handover process is split into a gNB-DU handover process and a gNB-CU-UP process.
  • the terminal and the source gNB-CU-UP and The dual connection between the target gNB-CU-UP prevents the downlink user plane data from the UPF network element from being forwarded between the source gNB-CU-UP and the target gNB-CU-UP, and finally achieves the downlink user plane shown in Figure 10 Data transfer process. That is, the execution of the gNB-DU switching process can refer to the solution described in FIG.
  • FIG. 10 a schematic diagram of downlink user plane data transmission before the DU and CU-UP switching provided in this embodiment of the application, as shown in FIG. 10, the terminal's downlink user plane data before the terminal switches the DU and CU-UP
  • the transmission path is shown as line 1 in Figure 10, that is, the UPF network element first sends the downlink user plane data to the source gNB-CU-UP through the user plane connection with the source gNB-CU-UP, and then the source gNB -The CU-UP sends the downlink user plane data to the source gNB-DU through the user plane connection with the source gNB-DU. Finally, the source gNB-DU sends the downlink user plane data to the terminal through the user plane connection with the terminal.
  • the transmission path of the terminal's downlink user plane data is shown as line 2 in Figure 10, namely UPF
  • the network element first sends the downlink user plane data to the source gNB-CU-UP through the user plane connection with the source gNB-CU-UP, and then the source gNB-CU-UP passes through the user plane with the source gNB-DU.
  • the connection sends the downlink user plane data to the target gNB-DU.
  • the target gNB-DU sends downlink user plane data to the terminal through the user plane connection with the terminal.
  • the terminal's DU is switched from the source gNB-DU to the target gNB-DU
  • the terminal's gNB-CU-UP is switched from the source gNB-CU-UP to the target gNB-CU-UP
  • the terminal's downlink user plane data transmission The path is shown as line 3 in Figure 10, that is, the UPF network element first sends the downlink user plane data to the target gNB-CU-UP through the user plane connection with the target gNB-CU-UP, and then the target gNB-CU -UP sends downlink user plane data to the target gNB-DU through the user plane connection with the target gNB-DU. Finally, the target gNB-DU sends downlink user plane data to the terminal through the user plane connection with the terminal.
  • this application provides a schematic flow chart of another handover method.
  • the difference between this method and Figure 9 is that the source gNB-CU-UP is controlled by the source gNB-CU-CP, and the target gNB-CU-UP is controlled by the source gNB-CU-CP.
  • the target gNB-CU-CP is controlled, that is, the gNB-CU-UP to be switched is controlled by different gNB-CU-CPs.
  • the method includes:
  • Step 1101 is the same as step 901, and will not be repeated here.
  • the downlink data packet from the UPF network element passes through the source gNB-DU.
  • the CU-UP is sent to the target gNB-DU, and then the target gNB-DU sends the downlink data packet from the UPF network element to the terminal.
  • the downlink signaling from the AMF network element is sent to the target gNB-DU through the gNB-CU-CP, and then the target gNB-DU sends the downlink signaling from the AMF network element to the terminal.
  • the terminal For uplink transmission (ie terminal ⁇ UPF network element/AMF network element), the terminal first sends the uplink data packet to the target gNB-DU, and the target gNB-DU sends the uplink data packet from the terminal to the source gNB-CU-UP UPF network element.
  • the terminal first sends the uplink signaling to the target gNB-DU, and the target gNB-DU sends the uplink signaling from the terminal to the AMF network element through the gNB-CU-CP.
  • Step 1102 The source gNB-CU-CP sends a handover request to the target gNB-CU-CP, so that the target gNB-CU-CP receives the handover request from the source gNB-CU-CP.
  • the switching request is used to request to switch the gNB-CU-CP of the terminal from the source gNB-CU-CP to the target gNB-CU-CP.
  • the handover request triggers the handover procedure of gNB-CU-UP.
  • the handover request should include the terminal context related to the source gNB-CU-UP, which is used to associate the RLC entities of the two in the process of establishing the target gNB-CU-UP connection to facilitate the execution of the End Marker mechanism.
  • the gNB-CU-UP switching process is controlled and executed by Target gNB-CU-CP.
  • the signaling flow related to the source gNB-CU-UP is forwarded and fed back by the source gNB-CU-UP.
  • Other signaling processes are as shown in Figure 9. The scheme shown is the same.
  • the handover request requests that the terminal be switched to the target gNB-CU-CP. Only when the target gNB-CU-CP allows the handover and feeds back the Handover Acknowledge, the handover process can be triggered. Otherwise, the process is rejected, and the target gNB-CU-CP may need to be reselected.
  • Steps 1103 to 1122 are the same as steps 902 to 921, except that the steps executed by the source gNB-CU-CP in steps 902 to 921 are replaced by the target gNB-CU-CP.
  • the downlink data packet from the UPF network element passes through the target gNB-
  • the CU-UP is sent to the target gNB-DU, and then the target gNB-DU sends the downlink data packet from the UPF network element to the terminal.
  • the downlink signaling from the AMF network element is sent to the target gNB-DU through the target gNB-CU-CP, and then the target gNB-DU sends the downlink signaling from the AMF network element to the terminal.
  • the terminal For uplink transmission (ie terminal ⁇ UPF network element/AMF network element), the terminal first sends the uplink data packet to the target gNB-DU, and the target gNB-DU sends the uplink data packet from the terminal to the target gNB-CU-UP UPF network element.
  • the terminal first sends the uplink signaling to the target gNB-DU, and the target gNB-DU sends the uplink signaling from the terminal to the AMF network element through the target gNB-CU-CP.
  • Figure 12 shows the effect diagram of the program data plane described in Figure 9 or Figure 11.
  • the handover of gNB-CU-UP in the prior art is shown in the two sub-graphs in the upper half.
  • the source gNB- The forwarding tunnel between the CU-UP and the target gNB-CU-UP, and then the data stream is switched to the target gNB-CU-UP.
  • the entire PATHSwitch process there is always a forwarding delay in the sending of data plane messages.
  • the data plane processing process of this embodiment is shown in the two sub-figures in the following half.
  • the respective RLC entities of the CU-UP are associated, and the data packets of the target gNB-CU-UP are first buffered until the End Marker is received from the source gNB-CU-UP and the data packets on the path are sent, and then the target is sent.
  • the data packet on gNB-CU-UP, the transmission path switching is completed.
  • step 901 and step 1101 can be omitted.
  • each network element such as a DU, a first device, etc.
  • each network element includes a hardware structure and/or software module corresponding to each function.
  • the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a certain function is executed by hardware or computer software-driven hardware depends on the specific application and design constraint conditions of the technical solution. Professionals and technicians can use different methods for each specific application to implement the described functions, but such implementation should not be considered beyond the scope of this application.
  • the embodiment of the present application may divide the functional units according to the above method example DU and the first device.
  • each functional unit may be divided corresponding to each function, or two or more functions may be integrated into one processing unit.
  • the above-mentioned integrated unit can be implemented in the form of hardware or software functional unit. It should be noted that the division of units in the embodiments of the present application is illustrative, and is only a logical function division, and there may be other division methods in actual implementation.
  • FIG. 13 shows the communication device involved in the foregoing embodiment, and the communication device may include: a communication unit 102 and a processing unit 101.
  • the communication device is a DU or a chip applied in the DU.
  • the communication unit 102 is used to support the communication device to perform the receiving action performed by the DU in step 601 of FIG. 6 in the above-mentioned embodiment.
  • the communication unit 102 is further configured to support the communication device to perform the generating action performed by the DU in step 602 and the sending action performed by the DU in step 603 in FIG. 6.
  • the processing unit 101 is configured to support the communication device to perform the action of determining in step 603 of FIG. 6 that the communication unit sends all the downlink data packets from the first CU-UP to the terminal.
  • the communication unit 102 is further configured to support the communication device to execute the receiving action performed by the DU in step 701 in the foregoing embodiment.
  • the processing unit 101 is further configured to support the communication device to execute step 702, step 703, and step 709 in the foregoing embodiment.
  • the communication unit 102 is also used to support the communication device to perform step 704 in the above embodiment and the sending action performed by the DU in step 711.
  • the communication unit 102 is also used to support the communication device to perform the step 708 performed by the DU in the above embodiment. Receive action.
  • the communication unit is also used to support the communication device to implement the actions performed by the source DU in FIG. 8. If the DU is a DU that provides services for the terminal after the handover, the communication unit is also used to support the communication device to implement the actions performed by the target DU in FIG. 8.
  • the communication device is a first device, or a chip applied in the first device.
  • the processing unit 101 is configured to support the communication device to perform the determination of the association corresponding to the first CU-UP before the communication unit 102 executes the sending action performed by the first device in step 701 in the above embodiment
  • the communication unit 102 is configured to support the communication device to execute the sending action performed by the first device in step 701 in the foregoing embodiment.
  • the communication unit 102 is further configured to support the communication device to perform the receiving action performed by the first device in step 711 in the foregoing embodiment.
  • the processing unit 101 is further configured to support the communication device to execute step 712 in the foregoing embodiment.
  • the communication device is a terminal or a chip applied in the terminal.
  • the communication unit 102 is configured to support the communication device to perform step 602 in the foregoing embodiment and the receiving action performed by the terminal in step 603.
  • the communication unit 102 is also used to support the communication device to perform all the sending or receiving actions performed by the terminal in FIG. 8.
  • the communication unit is configured to support the communication device to perform the receiving action performed by the terminal in step 704.
  • the processing unit 101 is configured to support the communication device to perform step 705.
  • FIG. 14 shows a schematic diagram of a possible logical structure of the communication device involved in the foregoing embodiment.
  • the communication device includes: a processing module 112 and a communication module 113.
  • the processing module 112 is used to control and manage the actions of the communication device.
  • the processing module 112 is used to perform information/data processing steps on the communication device.
  • the communication module 113 is used to support the communication device to send or receive information/data.
  • the communication device may further include a storage module 111 for storing program codes and data that can be used by the communication device.
  • the communication device is a DU or a chip applied in the DU.
  • the communication module 113 is used to support the communication device to perform the receiving action performed by the DU in step 601 of FIG. 6 in the above-mentioned embodiment.
  • the communication module 113 is also used to support the communication device to perform the generating action performed by the DU in step 602 and the sending action performed by the DU in step 603 in FIG. 6.
  • the processing module 112 is configured to support the communication device to perform the action of determining in step 603 of FIG. 6 that the communication unit sends all the downlink data packets from the first CU-UP to the terminal.
  • the communication module 113 is further configured to support the communication device to execute the receiving action performed by the DU in step 701 in the foregoing embodiment.
  • the processing module 112 is also used to support the communication device to execute step 702, step 703, and step 709 in the foregoing embodiment.
  • the communication module 113 is also used to support the communication device to perform step 704 and the sending action performed by the DU in step 711 in the above-mentioned embodiment.
  • the communication module 113 is also used to support the communication device to perform the step 708 performed by the DU in the above-mentioned embodiment. Receive action.
  • the communication unit is also used to support the communication device to implement the actions performed by the source DU in FIG. 8. If the DU is a DU that provides services for the terminal after the handover, the communication unit is also used to support the communication device to implement the actions performed by the target DU in FIG. 8.
  • the communication device is a first device, or a chip applied in the first device.
  • the processing module 112 is configured to support the communication device to perform the determination of the association corresponding to the first CU-UP before the communication module 113 executes the sending action performed by the first device in step 701 in the above embodiment
  • the communication module 113 is configured to support the communication device to execute the sending action performed by the first device in step 701 in the foregoing embodiment.
  • the communication module 113 is also used to support the communication device to perform the receiving action performed by the first device in step 711 in the foregoing embodiment.
  • the processing module 112 is also used to support the communication device to execute step 712 in the foregoing embodiment.
  • the communication device is a terminal or a chip applied in the terminal.
  • the communication module 113 is configured to support the communication device to perform step 602 in the foregoing embodiment and the receiving action performed by the terminal in step 603.
  • the communication unit is also used to support the communication device to perform all the sending or receiving actions performed by the terminal in FIG. 8.
  • the communication unit is configured to support the communication device to perform the receiving action performed by the terminal in step 704.
  • the processing module 112 is configured to support the communication device to perform step 705.
  • the processing module 112 may be a processor or a controller, for example, a central processing unit, a general-purpose processor, a digital signal processor, an application specific integrated circuit, a field programmable gate array or other programmable logic devices, transistor logic devices, Hardware components or any combination thereof. It can implement or execute various exemplary logical blocks, modules, and circuits described in conjunction with the disclosure of this application.
  • the processor may also be a combination of computing functions, for example, a combination of one or more microprocessors, a combination of a digital signal processor and a microprocessor, and so on.
  • the communication module 113 may be a transceiver, a transceiver circuit, or a communication interface.
  • the storage module 111 may be a memory.
  • the processing module 112 is the processor 51 or the processor 55
  • the communication module 113 is the communication interface 53
  • the storage module 111 is the memory 52
  • the communication device involved in this application may be the communication device shown in FIG. 5.
  • the communication interface 53 is used to perform the receiving and sending steps of the DU, the first device, and the terminal in the embodiments shown in FIGS. 6-11.
  • the processor 51 or the processor 55 is configured to execute the processing steps of the DU, the first device, and the terminal in the embodiments shown in FIGS. 6-12.
  • FIG. 15 is a schematic diagram of the structure of a chip 150 provided by an embodiment of the present application.
  • the chip 150 includes one or more (including two) processors 1510 and a communication interface 1530.
  • the chip 150 further includes a memory 1540.
  • the memory 1540 may include a read-only memory and a random access memory, and provides operation instructions and data to the processor 1510.
  • a part of the memory 1540 may also include a non-volatile random access memory (NVRAM).
  • NVRAM non-volatile random access memory
  • the memory 1540 stores the following elements, execution modules or data structures, or their subsets, or their extended sets.
  • the corresponding operation is executed by calling the operation instruction stored in the memory 1540 (the operation instruction may be stored in the operating system).
  • One possible implementation is that the structures of the chips used by the DU, the terminal, and the first device are similar, and different devices can use different chips to realize their respective functions.
  • the processor 1510 controls processing operations of any one of the DU, the terminal, and the first device.
  • the processor 1510 may also be referred to as a central processing unit (CPU).
  • the memory 1540 may include a read-only memory and a random access memory, and provides instructions and data to the processor 1510. A part of the memory 1540 may also include NVRAM.
  • the memory 1540, the communication interface 1530, and the memory 1540 are coupled together by a bus system 1520, where the bus system 1520 may include a power bus, a control bus, and a status signal bus in addition to a data bus.
  • bus system 1520 may include a power bus, a control bus, and a status signal bus in addition to a data bus.
  • various buses are marked as the bus system 1520 in FIG. 15.
  • the methods disclosed in the foregoing embodiments of the present application may be applied to the processor 1510 or implemented by the processor 1510.
  • the processor 1510 may be an integrated circuit chip with signal processing capabilities. In the implementation process, the steps of the foregoing method can be completed by hardware integrated logic circuits in the processor 1510 or instructions in the form of software.
  • the above-mentioned processor 1510 may be a general-purpose processor, a digital signal processing (digital signal processing, DSP), an ASIC, an off-the-shelf programmable gate array (field-programmable gate array, FPGA) or other programmable logic devices, discrete gates or transistors. Logic devices, discrete hardware components.
  • 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 1540, and the processor 1510 reads the information in the memory 1540, and completes the steps of the foregoing method in combination with its hardware.
  • the communication interface 1530 is used to perform the receiving and sending steps of the DU, the terminal, and the first device in the embodiments shown in FIGS. 6-11.
  • the processor 1510 is configured to execute the processing steps of the DU, the terminal, and the first device in the embodiments shown in FIGS. 6-11.
  • the above transceiver unit may be a communication interface of the device for receiving signals from other devices.
  • the transceiver unit is a communication interface for the chip to receive signals or send signals from other chips or devices.
  • a computer-readable storage medium stores instructions. When the instructions are executed, the function of the DU in FIG. 6 or FIG. 8 is realized.
  • a computer-readable storage medium stores instructions. When the instructions are executed, the functions of the first device shown in FIG. 6 or FIG. 8 are realized.
  • a computer-readable storage medium is provided, and instructions are stored in the computer-readable storage medium.
  • the instructions are executed, the functions of the terminal as shown in FIG. 6 or FIG. 8 are realized.
  • a computer program product including instructions.
  • the computer program product includes instructions. When the instructions are executed, the function of the DU in FIG. 6 or FIG. 8 is realized.
  • a computer program product including instructions.
  • the computer program product includes instructions. When the instructions are executed, the functions of the first device as shown in FIG. 6 or FIG. 8 are realized.
  • a computer program product including instructions.
  • the computer program product includes instructions. When the instructions are executed, the functions of the terminal shown in FIG. 6 or FIG. 8 are realized.
  • a chip is provided.
  • the chip is used in a DU.
  • the chip includes at least one processor and a communication interface.
  • the communication interface is coupled to the at least one processor.
  • the processor is used to run instructions to implement the DU as shown in FIG. 6 or FIG. Function.
  • a chip is provided.
  • the chip is used in a first device.
  • the chip includes at least one processor and a communication interface.
  • the communication interface is coupled to the at least one processor.
  • the function of the first device in 8.
  • a chip is provided.
  • the chip is applied to a terminal.
  • the chip includes at least one processor and a communication interface.
  • the communication interface is coupled to the at least one processor. The function of the terminal.
  • the embodiment of the present application provides a communication system, which includes a terminal, a DU, and a CU-CP.
  • the terminal is used to perform the steps performed by the terminal in Figure 6 or Figure 8
  • the DU is used to perform the steps performed by the DU in Figure 6 or Figure 8
  • the first device is used to perform the first steps shown in Figure 6 or Figure 8.
  • the steps performed by the device there is a user plane connection between the DU and the first CU-UP and the second CU-UP.
  • the communication system may also include user plane network elements.
  • the user plane network element is used to send a second instruction to the first CU-UP.
  • the computer program product includes one or more computer programs or instructions.
  • the computer may be a general-purpose computer, a special-purpose computer, a computer network, network equipment, user equipment, or other programmable devices.
  • the computer program or instruction 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 program or instruction may be downloaded from a website, computer, The server or data center transmits to another website site, computer, server or data center through wired or wireless means.
  • 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 that integrates one or more available media.
  • the usable medium may be a magnetic medium, such as a floppy disk, a hard disk, and a magnetic tape; it may also be an optical medium, such as a digital video disc (digital video disc, DVD); and it may also be a semiconductor medium, such as a solid state drive (solid state drive). , SSD).

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Abstract

本申请实施例提供一种通信方法、装置以及系统，涉及通信技术领域，用以解决切换过程中的转发时延问题。该方法包括：在DU通过与第一CU-UP之间的用户面连接接收来自第一CU-UP的下行数据包的过程中，DU通过与第二CU-UP之间的用户面连接接收来自第二CU-UP的下行数据包。第一RLC实体和第二RLC实体关联，第一RLC实体与第一CU-UP对应，第二RLC实体与第二CU-UP对应。终端从第一CU-UP切换至第二CU-UP。DU向终端发送来自第一CU-UP的下行数据包；在将来自第一CU-UP的下行数据包全部发送至终端的情况下，DU向终端发送DU缓存的来自第二CU-UP的下行数据包。

Description

一种通信方法、装置以及系统 技术领域
本申请实施例涉及通信技术领域，尤其涉及一种通信方法、装置以及系统。
背景技术
业务切换是无线通信系统中终端与无线接入网(radio access network，RAN)设备之间通信的重要环节，当终端从源(Source)RAN设备的小区移动到目标(Target)RAN设备的小区时，源RAN设备和目标RAN设备之间将针对终端的业务数据发生切换。
基于通信网络对下行数据包的时延要求，例如第五代(the 5th generation，5G)通信系统的低时延高可靠连接(ultra-reliable and low latency communications，URLLC)场景，需要减小RAN设备在切换过程中下行数据包的时延。
目前移动通信系统的切换过程通常包含切换准备(handover preparation)，切换执行(handover execution)以及切换完成(handover completion)三个阶段。
其中，在切换准备阶段，终端仍保持与源RAN设备的连接，不会产生额外的时延或中断，业务正常执行。
源RAN设备在做好切换准备后，进入切换执行阶段。在此阶段中，源基站可以通过源基站和目标基站之间的转发隧道向目标基站发送终端的数据包。在终端与目标基站之间的随机接入流程未完成前，目标基站将收到的终端的数据包暂时缓存。直到终端与目标基站之间的随机接入流程完成后，目标基站才会将终端的数据包发送至终端。因此，在终端与目标基站之间的随机接入流程未完成前，目标基站并未将数据包发送给终端，终端的业务中断。可以将该过程中产生的时延称为中断时延。
之后，进入切换完成阶段，在此阶段中，需要执行路径切换(Path Switch)。在路径切换完成之前，终端的下行数据依次通过用户面功能(User plane function，UPF)网元->源RAN设备->目标RAN设备->终端的路径传输。也就是说，终端的下行数据通过在源RAN设备和目标RAN设备中间的转发隧道进行传输。由转发引入的时延称为转发时延。路径切换完成之后，才会通过UPF网元->目标RAN设备->终端的路径来传输终端的下行数据。
转发时延的产生影响了用户体验。
发明内容
本申请实施例提供一种通信方法、装置以及系统，用以解决切换过程中的转发时延问题。
为了解决上述技术问题，本申请实施例提供如下技术方案：
第一方面，本申请实施例提供一种通信方法，包括：在分布式处理节点DU通过与第一集中处理节点CU-用户面UP之间的用户面连接接收来自第一CU-UP的下行数据包的过程中，该DU通过与第二CU-UP之间的用户面连接接收来自第二CU-UP的下行数据包。该DU包括的第一RLC实体和该DU包括的第二RLC实体关联，第一RLC实体和第一CU-UP对应，第二RLC实体和第二CU-UP对应。终端从第一CU-UP 切换至第二CU-UP。DU向终端发送来自第一CU-UP的下行数据包。在DU将来自第一CU-UP的下行数据包全部发送至终端的情况下，DU向终端发送DU缓存的来自第二CU-UP的下行数据包。
本申请实施例提供一种通信方法，该方法中由于DU和第一CU-UP和第二CU-UP之间均具有用户面连接，这样可以避免终端的CU-UP从第一CU-UP切换到第二CU-UP的过程中，终端的下行数据包在第一CU-UP和第二CU-UP之间的转发，也即无需建立第一CU-UP和第二CU-UP之间的转发隧道，因此避免了转发时延的引入。此外，由于第一RLC实体和第二RLC实体关联，而第一RLC实体与第一CU-UP对应，第二RLC实体与第二CU-UP对应，这样便于DU对来自第二CU-UP的下行数据包进行缓存，在第一CU-UP的下行数据包全部传输给终端后，DU开始向终端传输来自第二CU-UP的下行数据包，这样不仅保证了CU-UP的低时延切换，此外还可以避免终端的业务面中断的问题。
在一种可能的实现方式中，DU为切换前为终端提供服务的DU。在这种情况下DU位于第一CU-UP的服务范围内，且位于第二CU-UP的服务范围边缘。该DU与第一CU-UP连接，但是该DU还可以与第二CU-UP建立连接。
在一种可能的实现方式中，DU为切换后为终端提供服务的DU。在这种情况下DU位于第二CU-UP的服务范围内，且位于第一CU-UP的服务范围边缘。该DU与第二CU-UP连接，但是该DU还可以与第一CU-UP建立连接。
在一种可能的实现方式中，本申请实施例提供的方法还包括：该DU接收来自第一设备的包括第一指示的第一请求消息。DU根据第一指示，关联第一RLC实体和第二RLC实体。以便于DU确定建立与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体之间的关联关系。
在一种可能的实现方式中，该第一指示还用于指示DU与第二CU-UP之间的用户面连接，本申请实施例提供的方法还包括：DU根据第一指示，建立DU与第二CU-UP之间的用户面连接。通过建立DU与第二CU-UP之间的用户面连接便于后续DU接收来自第二CU-UP的下行数据包。
在一种可能的实现方式中，该第一请求消息还包括第二CU-UP的信息。第二CU-UP的信息可以为第二CU-UP的地址信息。
在一种可能的实现方式中，本申请实施例提供的方法还包括：DU向终端发送指示终端建立终端与第二CU-UP之间的用户面连接，以及保持终端与第一CU-UP之间的用户面连接的第一配置消息。通过第一配置消息可以使得终端建立与第一CU-UP和第二CU-UP之间的双连接。
在一种可能的实现方式中，本申请实施例提供的方法还包括：DU接收指示在用户面网元和第一CU-UP之间的用户面连接上传输的下行数据包传输结束的第二指示。以便于DU确定用户面网元后续停止向第一CU-UP发送下行数据包。
在一种可能的实现方式中，本申请实施例提供的方法还包括：在DU将来自第一CU-UP的下行数据包全部发送至终端的情况下，DU向第一设备发送第一报告，该第一报告用于第一设备触发第一CU-UP释放终端的上下文。以便于终端完成从第一CU-UP到第二CU-UP的切换。
在一种可能的实现方式中，第一设备为第一基站的CU-控制面CP，第一基站为切换前为终端提供服务的基站。
在一种可能的实现方式中，第一设备为第二基站的CU-CP，第二基站为切换后为终端提供服务的基站。
在一种可能的实现方式中，第一CU-UP和第二CU-UP与相同的CU-CP连接，或者，第一CU-UP和第二CU-UP与不同的CU-CP连接。
第二方面，本申请实施例提供一种通信方法，该方法包括：第一设备确定将终端从第一CU-UP切换至第二CU-UP。第一设备向DU发送包括第二指示的第一请求消息。该第二指示指示DU关联该DU的第一RLC实体和该DU的第二RLC实体关联，以及建立DU与第二CU-UP之间的用户面连接。
在一种可能的实现方式中，第一请求消息还包括第二CU-UP的信息。
在一种可能的实现方式中，本申请实施例提供的方法还包括：第一设备接收来自DU的用于第一设备触发第一CU-UP释放终端的上下文的第一报告。
在一种可能的实现方式中，DU为切换前为终端提供服务的DU。在这种情况下DU位于第一CU-UP的服务范围内，且位于第二CU-UP的服务范围边缘。该DU与第一CU-UP连接，但是该DU还可以与第二CU-UP建立连接。
在一种可能的实现方式中，DU为切换后为终端提供服务的DU。在这种情况下DU位于第二CU-UP的服务范围内，且位于第一CU-UP的服务范围边缘。该DU与第二CU-UP连接，但是该DU还可以与第一CU-UP建立连接。
在一种可能的实现方式中，DU为切换后为终端提供服务的DU，本申请实施例提供的方法还包括：第一设备将终端从第一DU切换至该DU。第一DU为切换前为终端提供服务的DU。此时，第一设备为第一基站的集中处理节点CU-控制面CP，第一基站为终端切换前接入的基站。
在一种可能的实现方式中，第一设备将终端从第一DU切换至该DU过程中，第一设备向第一CU-UP发送第三指示，该第三指示指示本次切换为不同跨CU-UP之间的切换。
在一种可能的实现方式中，第一设备为第二基站的CU-CP，第二基站为终端切换后接入的基站。
在一种可能的实现方式中，第一CU-UP和第二CU-UP与相同的CU-CP连接，或者，第一CU-UP和第二CU-UP与不同的CU-CP连接。
在一种可能的实现方式中，第一CU-UP和第二CU-UP与相同的CU-CP连接。
在一种可能的实现方式中，第一CU-UP和第二CU-UP与不同的CU-CP连接。
在一种可能的实现方式中，第一CU-UP和第二CU-UP与不同的CU-CP连接的情况下，如果第一设备为第二基站的CU-CP，则本申请实施例提供的方法在还可以包括：第一设备接收来自第一基站的CU-CP的第二请求消息，该第二请求消息请求为终端切换CU-UP。具体的，第二请求消息请求将终端从第一CU-UP切换到第二CU-UP。
第三方面，本申请实施例提供一种通信方法，该方法包括：终端接收DU发送的来自第一CU-UP的下行数据包，以及在来自所述第一CU-UP的下行数据包全部发送至终端的情况下，接收来自DU发送的来自第二CU-UP的下行数据包，该终端与第一 CU-UP和第二CU-UP之间均具有用户面连接。
在一种可能的实现方式中，本申请实施例提供的方法还可以包括：终端接收来自DU的第一配置消息。该第一配置消息指示终端建立终端与第二CU-UP之间的用户面连接，以及保持终端与第一CU-UP之间的用户面连接的第一配置消息。通过第一配置消息可以使得终端建立与第一CU-UP和第二CU-UP之间的双连接。
第四方面，本申请实施例提供一种通信装置，该一种通信装置可以为DU，或者为应用于DU中的芯片。该通信装置包括通信单元和处理单元，当DU执行上述第一方面以及第一方面任意一种可选地设计中的通信方法时，通信单元用于执行收发操作，处理单元用于执行除收发操作以外的动作。例如，当DU执行第一方面的方法时，通信单元，用于通过与第一CU-UP之间的用户面连接接收来自第一CU-UP的下行数据包的过程中，还通过与第二CU-UP之间的用户面连接接收来自第二CU-UP的下行数据包。该DU的第一RLC实体和该DU的第二RLC实体关联。其中，第一RLC实体与第一CU-UP对应，第二RLC实体与第二CU-UP对应，终端从第一CU-UP切换至第二CU-UP。通信单元，还用于向终端发送来自第一CU-UP的下行数据包。在通信单元将来自第一CU-UP的下行数据包全部发送至终端的情况下，通信单元，还用于向终端发送处理单元缓存的来自第二CU-UP的下行数据包。
示例性的，当该通信装置是DU内的芯片或者芯片系统时，该处理单元可以是处理器，该通信单元可以是通信接口。例如通信接口可以为输入/输出接口、管脚或电路等。该处理单元执行存储单元所存储的指令，以使该DU实现第一方面或第一方面的任意一种可能的实现方式中描述的一种通信方法。该存储单元可以是该芯片内的存储单元(例如，寄存器、缓存等)，也可以是该DU内的位于该芯片外部的存储单元(例如，只读存储器、随机存取存储器等)。
第五方面，本申请实施例提供一种通信装置，该一种通信装置可以为第一设备，或者为应用于第一设备中的芯片。该通信装置包括通信单元和处理单元，当第一设备执行上述第二方面以及第二方面任意一种可选地设计中的通信方法时，通信单元用于执行收发操作，处理单元用于执行除收发操作以外的动作。例如，当第一设备执行第二方面的方法时，处理单元，用于确定将终端从第一CU-UP切换至第二CU-UP。通信单元，用于向DU发送包括第二指示的第一请求消息。该第二指示指示DU关联该DU的第一RLC实体和该DU的第二RLC实体，以及建立DU与第二CU-UP之间的用户面连接。
示例性的，当该通信装置是第一设备内的芯片或者芯片系统时，该处理单元可以是处理器，该通信单元可以是通信接口。例如通信接口可以为输入/输出接口、管脚或电路等。该处理单元执行存储单元所存储的指令，以使该第一设备实现第二方面或第二方面的任意一种可能的实现方式中描述的一种通信方法。该存储单元可以是该芯片内的存储单元(例如，寄存器、缓存等)，也可以是该第一设备内的位于该芯片外部的存储单元(例如，只读存储器、随机存取存储器等)。
第六方面，本申请实施例提供一种通信装置，该一种通信装置可以为终端，或者为应用于终端中的芯片。该通信装置包括通信单元和处理单元，当终端执行上述第三方面以及第三方面任意一种可选地设计中的通信方法时，通信单元用于执行收发操作， 处理单元用于执行除收发操作以外的动作。例如，当终端执行第三方面的方法时，通信单元，用于接收DU发送的来自第一CU-UP的下行数据包，以及在来自所述第一CU-UP的下行数据包全部发送至该通信装置的情况下，接收来自DU发送的来自第二CU-UP的下行数据包，该通信装置与第一CU-UP和第二CU-UP之间均具有用户面连接。
示例性的，当该通信装置是终端内的芯片或者芯片系统时，该处理单元可以是处理器，该通信单元可以是通信接口。例如通信接口可以为输入/输出接口、管脚或电路等。该处理单元执行存储单元所存储的指令，以使该终端实现第三方面或第三方面的任意一种可能的实现方式中描述的一种通信方法。该存储单元可以是该芯片内的存储单元(例如，寄存器、缓存等)，也可以是该终端内的位于该芯片外部的存储单元(例如，只读存储器、随机存取存储器等)。
第七方面，本申请提供了一种DU，包括处理器，该处理器读取存储器中存储的指令，以实现上述第一方面以及第一方面任意一种可选地设计中的方法。该存储器可以为DU内部的存储器。
第八方面，本申请提供了一种第一设备，包括处理器，该处理器读取存储器中存储的指令，以实现上述第二方面以及第二方面任意一种可选地设计中的方法。该存储器可以为第一设备内部的存储器。
第九方面，本申请提供了一种终端，包括处理器，该处理器读取存储器中存储的指令，以实现上述第三方面以及第三方面任意一种可选地设计中的方法。该存储器可以为终端内部的存储器。
第十方面，本申请提供了一种终端，包括通信接口以及与通信接口相连的处理器，通过通信接口和处理器，终端用于执行上述第三方面以及第三方面任意一种可选地设计中的方法。
第十一方面，本申请提供了一种第一设备，包括通信接口以及与通信接口相连的处理器，通过通信接口和处理器，第一设备用于执行上述第二方面以及第二方面任意一种可选地设计中的方法。
第十二方面，本申请提供了一种DU，包括通信接口以及与通信接口相连的处理器，通过通信接口和处理器，DU用于执行上述第一方面以及第一方面任意一种可选地设计中的方法。
第十三方面，本申请实施例提供一种通信系统，包括上述第四面、第七方面、第十方面任一方面的DU，以及第六方面、第九方面和第十二方面任意方面描述的终端。
在一种可能的实现方式中，第十三方面描述的通信系统还可以包括第五方面、第八方面以及第十一方面描述的第一设备。
第十四方面，本申请提供了一种计算机可读存储介质，包括计算机可读指令，当指令在计算机上运行时，使得计算机执行上述第一方面的任一方面中任一种可能的设计中的方法。
第十五方面，本申请提供了一种计算机可读存储介质，包括计算机可读指令，当指令在计算机上运行时，使得计算机执行上述第二方面的任一方面中任一种可能的设计中的方法。
第十六方面，本申请提供了一种计算机可读存储介质，包括计算机可读指令，当指令在计算机上运行时，使得计算机执行上述第三方面的任一方面中任一种可能的设计中的方法。
第十七方面，本申请提供了一种计算机程序产品，包括计算机程序，当程序在计算机上运行时，使得计算机执行上述第一方面的任一方面中任一种可能的设计中的方法。
第十八方面，本申请提供了一种计算机程序产品，包括计算机程序，当程序在计算机上运行时，使得计算机执行上述第二方面的任一方面中任一种可能的设计中的方法。
第十九方面，本申请提供了一种计算机程序产品，包括计算机程序，当程序在计算机上运行时，使得计算机执行上述第三方面的任一方面中任一种可能的设计中的方法。
第二十方面，本申请提供一种芯片，应用于DU中，该芯片包括至少一个处理器和通信接口，通信接口和至少一个处理器耦合，处理器用于运行计算机程序或指令，以执行第一方面或第一方面的任意可能的实现方式中的方法，通信接口用于与芯片之外的其它模块进行通信。
第二十一方面，本申请提供一种芯片，应用于第一设备中，该芯片包括至少一个处理器和通信接口，通信接口和至少一个处理器耦合，处理器用于运行计算机程序或指令，以执行第二方面或第二方面的任意可能的实现方式中的方法，通信接口用于与芯片之外的其它模块进行通信。
第二十二方面，本申请提供一种芯片，应用于终端中，该芯片包括至少一个处理器和通信接口，通信接口和至少一个处理器耦合，处理器用于运行计算机程序或指令，以执行第三方面或第三方面的任意可能的实现方式中的方法，通信接口用于与芯片之外的其它模块进行通信。
可选的，本申请中上述描述的芯片还可以包括至少一个存储器，该至少一个存储器中存储有指令或计算机程序。
第二十三方面，本申请实施例提供一种通信装置，该通信装置可以为终端、第一设备、DU中的任一个，也可以为应用于终端、第一设备、DU中的任一个中的芯片。该通信装置具有实现上述第一方面、第二方面、第三方面中任一个描述的方法的功能。该功能可以通过硬件实现，也可以通过硬件执行相应的软件实现。该硬件或软件包括一个或多个与上述功能相对应的模块。
附图说明
图1为本申请实施例提供的一种切换方法的流程示意图；
图2为本申请实施例提供的一种通信系统的架构；
图3为本申请实施例提供的一种CP和DU之间的关系；
图4为本申请实施例提供的另一种通信系统的架构；
图5为本申请实施例提供的一种通信设备的结构示意图；
图6为本申请实施例提供的一种通信方法的流程示意图；
图7为本申请实施例提供的一种DU切换的流程示意图；
图8为本申请实施例提供的另一种通信方法的流程示意图；
图9为本申请实施例提供的一种通信方法的具体实施流程示意图；
图10为本申请实施例提供的一种路径切换示意图；
图11为本申请实施例提供的另一种通信方法的具体实施流程示意图；
图12为本申请实施例提供的一种数据路径传输示意图；
图13为本申请实施例提供的一种通信装置的结构示意图；
图14为本申请实施例提供的另一种通信装置的结构示意图；
图15为本申请实施例提供的一种芯片的结构示意图。
具体实施方式
在介绍本申请实施例之前，首先对本申请实施例涉及到的相关名词作如下解释：
1)、中断时延：在终端从源基站切换至目标基站的过程中，终端在切换阶段与源基站之间的连接断开，源基站可以通过源基站和目标基站之间的转发隧道向目标基站发送终端的数据包。在终端与目标基站之间的随机接入流程未完成前，目标基站将收到的终端的数据包暂时缓存。直到终端与目标基站之间的随机接入流程完成后，目标基站才会将终端的数据包发送至终端。因此，在终端与目标基站之间的随机接入流程未完成前，目标基站并未将数据包发送给终端，因此终端的业务中断。因此，可以将该过程中产生的时延称为中断时延。
2)、转发时延：在切换完成阶段中，在路径切换完成前，由UPF网元向源基站发送终端的下行数据包，由源基站将终端的下行数据包转发给目标基站，因此，引入了转发时延。
在路径切换完成前，源基站向目标基站发送终端的数据包。所谓的路径切换即指将终端与UPF网元之间的下行路径从UPF网元→源基站→终端变为：UPF网元→目标基站→终端。
具体的路径切换流程可以参考图1中的描述，例如：
步骤101、源基站向接入管理网元(例如，AMF网元)发送RAN使用数据报告(Usage data report)，以使得AMF网元接收来自源基站的RAN Usage data report。
步骤102、目标基站向AMF网元发送N2路径切换请求，以使得AMF网元接收N2路径切换请求。
该N2路径切换请求用于请求
步骤103、AMF网元向SMF网元发送PDU会话更新会话管理上下文请求(PDU session_update SM context request)，以使得SMF网元接收PDU会话更新会话管理上下文请求。
步骤104、SMF网元向UPF网元发送N4会话修改请求(N4 session modification request)，以使得UPF网元接收N4会话修改请求。该N4会话修改请求用于请求修改N4会话。
步骤105、UPF网元向SMF网元发送N4会话修改响应(N4 session modification response)，以使得SMF网元接收N4会话修改响应。
步骤106、UPF网元向源基站发送end marker，以使得源基站接收end marker。该end marker用于表示UPF网元停止向源基站发送针对终端的下行数据包。
步骤107、源基站向目标基站发送end marker，以使得目标基站接收end marker。
之后，终端与UPF网元之间的下行路径传输变为：UPF网元→目标基站→终端。
步骤108、SMF网元向AMF网元发送PDU会话更新会话管理上下文响应(PDU session_update SM context response)，以使得AMF网元接收PDU会话更新会话管理上下文响应。
步骤109、AMF网元向目标基站发送N2路径切换请求响应，以表示N2路径切换成功。
步骤110、目标基站向源基站发送终端上下文释放请求，源基站释放终端的上下文。
为了便于清楚描述本申请实施例的技术方案，在本申请的实施例中，采用了“第一”、“第二”等字样对功能和作用基本相同的相同项或相似项进行区分。例如，第一基站和第二基站仅仅是为了区分不同的基站，并不对其先后顺序进行限定。本领域技术人员可以理解“第一”、“第二”等字样并不对数量和执行次序进行限定，并且“第一”、“第二”等字样也并不限定一定不同。
需要说明的是，本申请中，“示例性的”或者“例如”等词用于表示作例子、例证或说明。本申请中被描述为“示例性的”或者“例如”的任何实施例或设计方案不应被解释为比其他实施例或设计方案更优选或更具优势。确切而言，使用“示例性的”或者“例如”等词旨在以具体方式呈现相关概念。
本申请实施例描述的网络架构以及业务场景是为了更加清楚的说明本申请实施例的技术方案，并不构成对于本申请实施例提供的技术方案的限定，本领域普通技术人员可知，随着网络架构的演变和新业务场景的出现，本申请实施例提供的技术方案对于类似的技术问题，同样适用。
本申请中，“至少一个”是指一个或者多个，“多个”是指两个或两个以上。“和/或”，描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B的情况，其中A，B可以是单数或者复数。字符“/”一般表示前后关联对象是一种“或”的关系。“以下至少一项(个)”或其类似表达，是指的这些项中的任意组合，包括单项(个)或复数项(个)的任意组合。例如，a，b，或c中的至少一项(个)，可以表示：a，b，c，a-b，a-c，b-c，或a-b-c，其中a，b，c可以是单个，也可以是多个。
本申请实施例描述的系统架构以及业务场景是为了更加清楚的说明本申请实施例的技术方案，并不构成对于本申请实施例提供的技术方案的限定，本领域普通技术人员可知，随着网络架构的演变和新业务场景的出现，本申请实施例提供的技术方案对于类似的技术问题，同样适用。本申请实施例中以提供的方法应用于NR系统或5G网络中为例进行说明。
如图2所示，图2示出了本申请实施例提供的一种通信系统，该通信系统包括：基站1以及终端。
由于未来接入网可以采用云无线接入网(cloud radio access network，C-RAN)架构来实现，一种可能的方式是将传统基站的协议栈架构和功能分割为两部分，一部分称为集中处理节点(Centralized Unit，CU)，另一部分称为分布式处理节点(Distributed  Unit，DU)，而CU和DU的实际部署方式比较灵活。通过将基站拆分成CU和DU可以灵活地对基站布网进行调整，对负载均衡、资源最大化利用都有良好的收益。另外，该架构下，对于解决潮汐效应、部署双连接、边缘计算、业务分流以及智能化运维都有更好的支持。如图2所示，基站1被拆分为CU1和DU1～DU3。多个DU(例如，DU1、DU2以及DU3)可以由一个CU1集中控制。CU和DU之间具有第一接口。例如，第一接口可以为F1接口。
CU和DU可以根据无线网络的协议层划分，例如分组数据汇聚层协议(packet data convergence protocol，PDCP)及以上协议层的功能设置在CU，PDCP以下的协议层，例如无线链路控制(radio link control，RLC)和媒体接入控制层等的功能设置在DU。
这种协议层的划分仅仅是一种举例，还可以在其它协议层划分，例如在RLC层划分，将RLC层及以上协议层的功能设置在CU，RLC层以下协议层的功能设置在DU；或者，在某个协议层中划分，例如将RLC层的部分功能和RLC层以上的协议层的功能设置在CU，将RLC层的剩余功能和RLC层以下的协议层的功能设置在DU。此外，也可以按其它方式划分，例如按时延划分，将处理时间需要满足时延要求的功能设置在DU，不需要满足该时延要求的功能设置在CU。
对于集中处理节点，根据功能不同，CU的控制面(control plane，CP)和用户面(user plane，UP)分离，分成不同实体来实现，如图3所示，CU可以被拆分为集中处理节点的控制面(CU Control Plane，CU-CP)和集中处理节点的用户面(CU User Plane，CU-UP)。
例如，如图2所示，CU1被拆分为CU-CP1、CU-UP1和CU-UP2。CU-CP1分别通过第二接口(例如，E1接口)与CU-UP1和CU-UP2连接。在CU被拆分为CU-CP和CU-UP的情况下，CU-CP1与DU1～DU3之间具有F1-C接口。不同的DU可以与不同的CU-UP连接(例如，DU1与CU-UP1之间通过F1-U接口连接、DU3与CU-UP2之间通过F1-U接口连接)。不同的DU也可以与相同的CU-UP连接(例如，DU1与CU-UP1之间通过F1-U接口连接，DU2与CU-UP1之间通过F1-U接口连接)。
F1-C接口用于控制面，F1-U接口用于用户面。F1-C接口用于传输CU-CP和DU之间的信令。F1-U接口用于传输CU-CP和DU之间的数据。
在以上网络架构中，CU产生的数据可以通过DU发送给终端，或者终端产生的数据可以通过DU发送给CU。DU可以不对该数据进行解析而直接通过协议层封装后传给终端或CU。例如，RRC或PDCP层的数据最终会处理为物理层(physical layer，PHY)的数据发送给终端，或者，由接收到的PHY层的数据转变而来。在这种架构下，该RRC或PDCP层的数据，即也可以认为是由DU发送的。
在以上实施例中CU划分为RAN中接入网设备，此外，也可以将CU划分为CN中的接入网设备，在此不做限制。
本申请以下实施例中的装置，根据其实现的功能，可以位于终端或接入网设备。当采用以上CU-DU的结构时，接入网设备可以为CU节点、或DU节点、或包括CU节点和DU节点功能的RAN设备。
如图4所示，图4示出了本申请实施例提供的另一种通信系统，该通信系统与图2的区别在于：该通信系统还可以包括：基站2。基站2为终端切换后接入的基站。该 基站2和基站1可以与同一个接入管理网元连接，也可以与不同的接入管理网元连接，本申请实施例对此不作限定。图4以基站2和基站1与同一个接入管理网元连接为例进行说明。
在图4中，以基站2被拆分为CU2和DU4，CU2被拆分为CU-CP2和CU-UP3为例。当然，基站2可以被拆分为多个CU2以及多个DU4，在图4中以一个CU2和DU4为例。并不构成对本申请的限制。
在图2或图4所示的通信系统中，终端通过各自接入的基站与核心网中的网元进行数据传输或者信令传输。图2和图4以核心网中的网元包括用户面网元和控制面网元为例。其中，用户面网元表示能够实现核心网设备的用户面功能的设备，控制面网元表示能够实现核心网设备的控制面功能的设备。例如，控制面网元可以为接入管理网元。用户面网元与控制面网元可以集成在同一设备，也可以独立设置。本申请实施例以用户面网元与控制面网元独立设置为例进行说明。
若图2或图4所示的通信系统适用于4G网络中，则基站1和基站2可以为LTE系统中的演进式基站(evolved Node Base Station，eNB)(可以称为LTE eNB)。LTEeNB通过S1接口与4G核心网络(例如，分组核心网(Evolved Packet Core，EPC))连接，不同的LTE eNB之间通过X2接口连接。也即图4中基站1和基站2之间通过X2接口连接。其中，X2接口支持基站1和基站2之间的数据和信令的直接传输。
示例性的，X2接口也分为两个接口，例如，X2-C接口和X2-U接口。其中，X2-C接口用于控制面，X2-U接口用于用户面。X2-C接口用于传输基站1和基站2之间信令。X2-U接口用于传输基站1和基站2之间的数据。在4G网络中接入管理网元对应的实体可以为移动性管理实体(Mobility Management Entity，MME)，MME与基站1或基站2通过S1-MME接口连接。用户面网元对应的网元或实体可以为分组数据网用户面((PGW-User Plane，PGW-U)和服务网关用户面(SGW-User Plane，SGW-U)。SGW为4G网络中负责数据包的路由和转发等处理的设备。
若图2或图4所示的通信系统适用于5G网络或新空口(new radio，NR)系统中，则基站1和基站2可以为NR系统中的下一代节点B(The Next Generation Node B，gNB)。gNB通过N2接口与NG-Core网连接，不同的gNB之间通过Xn接口连接，例如，基站1和基站2之间通过Xn接口连接。每个gNB均与NR系统中的至少一个终端连接。
在5G网络中接入管理网元对应的实体可以为接入和移动性管理功能(Core Access and Mobility Management Function，AMF)网元，AMF网元与基站1或基站2通过N2接口连接。AMF网元通过N1接口与终端连接。用户面网元对应的网元或实体可以为用户面功能(User plane Function，UPF)网元)。
其中，AMF网元：属于核心网网元，主要负责信令处理部分，例如：接入控制、移动性管理、注册、去注册以及网关选择等功能。AMF网元为终端中的会话提供服务的情况下，还可以为该会话提供控制面的存储资源，以存储会话标识、与会话标识关联的SMF网元标识等。
UPF网元：负责终端的用户数据的转发和接收。可以从数据网络接收用户数据，通过接入网设备传输给终端。UPF网元还可以通过接入网设备从终端接收用户数据，转发到数据网络。UPF网元中为终端提供服务的传输资源和调度功能由SMF网元管理 控制。
当然，如图2和图4所示的系统中还可以根据需要存在其他网元，本申请在此不再赘述。
终端也可以称为用户设备(user equipment，UE)、接入终端、用户单元、用户站、移动站、移动台、远方站、远程终端、移动设备、用户终端、终端设备、无线通信设备、用户代理或用户装置。终端可以是无线局域网(wireless local area networks，WLAN)中的站点(station，STA)，可以是蜂窝电话、无绳电话、会话启动协议(session initiation protocol，SIP)电话、无线本地环路(wireless local loop，WLL)站、个人数字处理(personal digital assistant，PDA)设备、具有无线通信功能的手持设备、计算设备或连接到无线调制解调器的其它处理设备、车载设备、可穿戴设备以及下一代通信系统，例如，第五代(fifth-generation，5G)通信网络中的终端设备或者未来演进的公共陆地移动网络(public land mobile network，PLMN)网络中的终端等。
作为示例，在本申请实施例中，该终端还可以是可穿戴设备。可穿戴设备也可以称为穿戴式智能设备，是应用穿戴式技术对日常穿戴进行智能化设计、开发出可以穿戴的设备的总称，如眼镜、手套、手表、服饰及鞋等。可穿戴设备即直接穿在身上，或是整合到用户的衣服或配件的一种便携式设备。可穿戴设备不仅仅是一种硬件设备，更是通过软件支持以及数据交互、云端交互来实现强大的功能。广义穿戴式智能设备包括功能全、尺寸大、可不依赖智能手机实现完整或者部分的功能，例如：智能手表或智能眼镜等，以及只专注于某一类应用功能，需要和其它设备如智能手机配合使用，如各类进行体征监测的智能手环、智能首饰等。
如图5示，图5示出了本申请实施例中的一种通信设备的硬件结构示意图。本申请实施例中的DU、第一设备、终端的结构可以参考图5所示的结构。该通信设备包括处理器51，通信线路54以及至少一个通信接口(图5中仅是示例性的以包括通信接口53为例进行说明)。
可选的，该通信设备还可以包括存储器52。
处理器51可以是一个通用中央处理器(central processing unit，CPU)，微处理器，特定应用集成电路(application-specific integrated circuit，ASIC)，或一个或多个用于控制本申请方案程序执行的集成电路。
通信线路54可包括一通路，在上述组件之间传送信息。
通信接口53，使用任何收发器一类的装置，用于与其他设备或通信网络通信，如以太网，无线接入网(radio access network，RAN)，无线局域网(wireless local area networks，WLAN)等。
存储器52可以是只读存储器(read-only memory，ROM)或可存储静态信息和指令的其他类型的静态存储设备，随机存取存储器(random access memory，RAM)或者可存储信息和指令的其他类型的动态存储设备，也可以是电可擦可编程只读存储器(electrically erasable programmable read-only memory，EEPROM)、只读光盘(compact disc read-only memory，CD-ROM)或其他光盘存储、光碟存储(包括压缩光碟、激光碟、光碟、数字通用光碟、蓝光光碟等)、磁盘存储介质或者其他磁存储设备、或者能够用于携带或存储具有指令或数据结构形式的期望的程序代码并能够由计算机存取 的任何其他介质，但不限于此。存储器可以是独立存在，通过通信线路54与处理器相连接。存储器也可以和处理器集成在一起。
其中，存储器52用于存储执行本申请方案的计算机执行指令，并由处理器51来控制执行。处理器51用于执行存储器52中存储的计算机执行指令，从而实现本申请下述实施例提供的一种通信方法。
可选的，本申请实施例中的计算机执行指令也可以称之为应用程序代码，本申请实施例对此不作具体限定。
在具体实现中，作为一种实施例，处理器51可以包括一个或多个CPU，例如图5中的CPU0和CPU1。
在具体实现中，作为一种实施例，通信设备可以包括多个处理器，例如图5中的处理器51和处理器55。这些处理器中的每一个可以是一个单核(single-CPU)处理器，也可以是一个多核(multi-CPU)处理器。这里的处理器可以指一个或多个设备、电路、和/或用于处理数据(例如计算机程序指令)的处理核。
需要说明的是，当图5所示的通信设备为终端时，该通信接口53可以替换为收发器。
CU/DU分离架构下，基站被拆解为CU-CP(主要是CU的控制面，包含RRC层和PDCP层)、CU-UP(主要是CU的用户面，PDCP层)以及DU(主要是需要进行实时处理的RLC层、MAC层和PHY层)。其中，DU分布式部署，相对于DU采用分布式部署而言，多个CU-UP之间采用集中部署，一个CU-CP可控制多个CU-UP，该多个CU-UP可能灵活分组，分布在不同的区域为不同区域的DU提供服务。一个CU-UP可与多个DU连接，一个DU与一个CU-UP连接，为了系统灵活性，支持一个DU连接多个CU-UP。
如果一个基站可以覆盖一个或者多个小区。一个基站覆盖的一个或者多个小区可以指该基站的CU覆盖一个或者多个小区，也可以指该基站的DU覆盖一个或者多个小区。因此，终端接入的源基站可以根据终端发送的测量报告决定为终端切换小区。源基站决定为终端切换的目标小区可以与终端所在的源小区属于同一个基站，当然，源基站决定为终端切换的目标小区可以与终端所在的源小区属于不同的基站。以下将分别描述：
由于CU的CP和UP还可以分离，因此，同一个基站内的两个小区切换时包括如下场景：
场景(1)、相同DU下的切换，也即终端从小区a切换到小区b，小区a和小区b均属于同一个DU覆盖范围内的小区。例如，小区a和小区b均属于图2中DU1覆盖范围内的小区。
场景(2)、相同CU-UP下的DU切换，也即终端从小区1切换到小区2，小区1和小区2均属于如图2所示的CU-UP1覆盖范围内的小区，但是小区1属于DU1覆盖范围内，而小区2属于DU2覆盖范围内。
场景(3)、相同CU-CP下，不同CU-UP下的DU切换，也即终端从小区3切换到小区4，小区3属于如图2所示的CU-UP1覆盖范围内的小区，小区4属于如图2所示的CU-UP2覆盖范围内的小区，此外，小区3属于DU2覆盖范围内，而小区4属于DU3覆盖范围内。
由于CU的CP和UP还可以分离，因此，不同基站内的两个小区切换时包括如下场景：
场景(4)、不同CU-CP下，不同CU-UP下的DU切换。也即终端从小区5切换到小区6，小区5属于如图4所示的CU-UP2覆盖范围内的小区，小区6属于如图4所示的CU-UP3覆盖范围内的小区，此外，小区5属于DU3覆盖范围内，而小区6属于DU4覆盖范围内。
其中，场景(1)和场景(2)，虽然DU发生了变化，但是由于CU-UP未发生变化，因此UPF网元->CU-UP链路不进行调整，此外，场景(1)基本可以达成了0ms切换。场景(2)因为CU-UP不切换，仅存在RAN侧切换执行过程中产生的业务面中断的问题。关于如何避免业务面中断的问题的解决方案可以参考如图8所描述的DU切换的方案。
针对场景(3)和场景(4)，因为终端的CU-UP发生了切换，所以可能发生UPF网元->CU-UP链路的Path Switch，具体可能涉及到服务UPF网元的切换、I-UPF的插入与改变，在场景(3)和场景(4)中可能存在业务面中断和转发时延的技术问题。
为了避免中断时延，目前在源RAN设备向终端发送切换命令之后，源RAN设备继续保持与终端的连接。在该方案中由于终端上报一次测量报告(measurement report)即触发切换流程，尽管源RAN设备仍保持与终端的连接，但由于信号强弱的关系，该连接可能会因信号太差出现较多的丢包、错包，所以源RAN设备可以将针对终端的数据包部分复制转发到目标RAN设备进行传输，直到终端与目标RAN设备的连接成功建立，终端再释放与源RAN设备的连接。
但是，由于可能存在两路数据包同时传输的情况，而且可能传输的是相同的数据包，因此要求源RAN设备和目标RAN设备使用不同的分组数据汇聚协议(packet data convergence protocol，PDCP)实体，终端需要同时建立两个协议栈连接。每个协议栈由上至下依次包括PDCP实体、无线链路层控制(radio link control，RLC)实体和媒体接入控制(medium access control，MAC)实体)。终端需要对不同的PDCP实体中收到的数据包进行合并、排序和去重。
为了避免转发时延，目前可以在切换过程中，先构建目标RAN设备与UPF网元之间的连接，并保持源RAN设备与终端之间的连接，之后由UPF网元向源RAN设备发送第一消息，指示开始双播数据包。源RAN设备在接收到第一消息后，先发送完第一消息之前收到的所有数据包再开始切换流程。同时，源RAN设备在接收到第一消息后，将双播数据包的SN号相关信息通过第二消息发送给目标RAN设备，目标RAN设备接收到第二消息后，再根据第二消息生成PDCP报文并进行SN号的同步。该方案由于在Path Switch过程中未使用Source RAN和Target RAN之间建立转发隧道的方式进行数据传输，因此有效避免了转发时延。另外不需要对UPF进行改动。但是，需要先构建目标RAN设备与UPF网元之间的连接，并进行第一消息的发送，在Source RAN发送完所有第一消息之前的数据包之后才启动切换流程，准备时间过长，引入了额外的切换时延。此外，在整个Path Switch过程中一直采用了UPF数据双播的方式进行传输，产生了大量的传输资源浪费。在双播过程中终端可能需要同时接收源RAN设备和目标RAN设备的PDCP实体的数据包，因此需要构建两个PDCP实体并对接收 到的数据包进行排序和去重。
基于此，本申请实施例提供如图6～图12所示的通信方法。
在本申请实施例中，一种通信方法的执行主体的具体结构，本申请实施例并未特别限定，只要可以通过运行记录有本申请实施例的一种通信方法的代码的程序，以根据本申请实施例的一种通信方法进行通信即可。例如，本申请实施例提供的一种通信方法的执行主体可以是DU中能够调用程序并执行程序的功能模块，或者为应用于DU中的通信装置，例如，芯片。本申请实施例提供的一种通信方法的执行主体可以是第一设备中能够调用程序并执行程序的功能模块，或者为应用于第一设备中的通信装置，例如，芯片。本申请对此不进行限定。下述实施例以一种通信方法的执行主体为DU、第一设备为例进行描述。
需要指出的是，本申请各实施例之间可以相互借鉴或参考，例如，相同或相似的步骤，方法实施例、装置实施例或系统实施例之间，均可以相互参考，不予限制。
结合图2或图4所示的通信系统，如图6所示，图6示出了本申请实施例提供的一种通信方法，该方法包括：
步骤601、在DU通过与第一CU-用户面UP之间的用户面连接接收来自第一CU-UP的下行数据包的过程中，DU通过与第二CU-UP之间的用户面连接接收来自第二CU-UP的下行数据包。该DU的第一RLC实体和该DU的第二RLC实体关联。第一RLC实体与第一CU-UP对应，第二RLC实体与第二CU-UP对应，终端从第一CU-UP切换至第二CU-UP。
由于与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体关联，这样便于DU确定与第二CU-UP对应的第二RLC实体确定与第一CU-UP对应的第一RLC实体是否传输完成，进而可以知道何时开始向终端传输与第二CU-UP对应的第二RLC实体缓存的下行数据包。
应理解，第一RLC实体和第二RLC实体属于DU，且第一RLC实体与第一CU-UP对应，第二RLC实体与第二CU-UP对应。
在一种可能的实现中，第一CU-UP为切换前为终端提供服务的CU-UP。第二CU-UP为切换后为终端提供服务的CU-UP。
在一种可能的实现中，本申请实施例中DU可以为切换前为终端提供服务的DU。或者DU为切换后为终端提供服务的DU。
在一种可能的实现中，即使终端从第一CU-UP切换到第二CU-UP，但是为终端提供服务的DU可以不发生变化。
举例说明，以图6所示的方法适用于图2所示的系统为例，即终端在同一个基站内的两个小区之间切换，即第一CU-UP和第二CU-UP属于同一个基站。例如，第一CU-UP为CU-UP1，第二CU-UP为CU-UP2。此时，DU可以为与CU-UP1连接的DU2，也可以为与CU-UP2连接的DU3，本申请实施例对此不作限定。应理解，DU2为切换前为终端提供服务的DU。DU3为切换后为终端提供服务的DU。
举例说明，以图6所示的方法适用于图4所示的系统为例，即终端在不同基站覆盖下两个小区之间切换，即第一CU-UP和第二CU-UP属于不同的基站。例如，第一CU-UP为CU-UP2，属于基站1，第二CU-UP为CU-UP3，属于基站2。此时，DU可 以为与CU-UP2连接的DU3，也可以为与CU-UP3连接的DU4，本申请实施例对此不作限定。应理解，在图3中DU3为切换前为终端提供服务的DU。DU4为切换后为终端提供服务的DU。
可以理解的是，无论DU为切换前为终端提供服务的DU还是切换后为终端提供服务的DU，在DU释放与第一CU-UP之间的用户面连接(例如，F1-U连接)之前，如果该DU还与第二CU-UP之间具有用户面连接，则可以认为该DU处于双连接状态，此时DU不仅可以接收来自第一CU-UP的下行数据包，还可以接收来自第二CU-UP的下行数据包。该第一CU-UP和第二CU-UP可以与相同的为终端提供服务的用户面网元连接(针对终端发生切换时用户面网元不变的场景)。该第一CU-UP和第二CU-UP可以与不同的为终端提供服务的用户面网元连接(针对终端发生切换时用户面网元发生变化的场景)。
需要说明的是，如果DU为切换前为终端提供服务的DU。在这种情况下DU位于第一CU-UP的服务范围内，且位于第二CU-UP的服务范围边缘。该DU与第一CU-UP连接，但是该DU还可以与第二CU-UP建立连接。
如果DU为切换后为终端提供服务的DU。在这种情况下DU位于第二CU-UP的服务范围内，且位于第一CU-UP的服务范围边缘。该DU与第二CU-UP连接，但是该DU还可以与第一CU-UP建立连接。
步骤602、DU向终端发送来自第一CU-UP的下行数据包。相应的，终端接收来自第一CU-UP的下行数据包。
作为一种可能的实现方式，本申请实施例中DU可以通过与终端之间的用户面连接向终端发送来自第一CU-UP的下行数据包。
步骤603、在DU将来自第一CU-UP的下行数据包全部发送至终端的情况下，DU向终端发送DU缓存的来自第二CU-UP的下行数据包，以使得终端接收来自第二CU-UP的下行数据包。
可以理解的是，如果DU在接收到来自第一CU-UP的下行数据包的过程中，还接收到来自第二CU-UP的下行数据包，则DU可以先向终端发送来自第一CU-UP的下行数据包，并缓存来自第二CU-UP的下行数据包，直到DU将来自第一CU-UP的下行数据包全部发送至终端的情况下，DU向终端发送DU缓存的来自第二CU-UP的下行数据包。
本申请实施例提供一种通信方法，该方法中由于DU和第一CU-UP和第二CU-UP之间均具有用户面连接，这样可以避免终端的CU-UP从第一CU-UP切换到第二CU-UP的过程中，终端的下行数据包在第一CU-UP和第二CU-UP之间的转发，也即无需建立第一CU-UP和第二CU-UP之间的转发隧道，因此避免了转发时延。此外，由于第一RLC实体和第二RLC实体关联，而第一RLC实体与第一CU-UP对应，第二RLC实体与第二CU-UP对应，这样便于DU对来自第二CU-UP的下行数据包进行缓存，在第一CU-UP的下行数据包全部传输给终端后，DU开始向终端传输来自第二CU-UP的下行数据包，这样不仅保证了CU-UP的低时延切换，此外还可以避免终端的业务面中断的问题。
在一种可能的实施例中，本申请实施例提供的方法在步骤601之前还包括：DU 关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体，以及建立DU与第二CU-UP之间的用户面连接。
一种可能的实现，关于DU关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体的一种实现方式可以如图7中的步骤701～步骤703所示，其中，步骤706、步骤707以及步骤710可以对应参考上述步骤601-步骤603的描述，此处不再赘述。
如图7所示，本申请实施例提供一种通信方法，该方法包括：
步骤701、第一设备向DU发送第一请求消息。相应的，DU接收来自第一设备的第一请求消息。
如果第一CU-UP和第二CU-UP与相同的CU-CP连接，则由CU-CP直接确定需要关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体。
该第一请求消息中携带第一指示，其中，第一指示指示DU关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体。
可以理解的是，第一指示可以显式指示DU关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体。当然，第一指示也可以隐式指示DU关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体。例如，第一指示指示DU保持与第一CU-UP的用户面连接，DU建立与第二CU-UP的用户面连接。这样，DU可以确定还需要关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体。
示例性的，第一请求消息可以为终端上下文建立请求消息。可以理解的是，第一请求消息本身可以具有指示DU关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体，和/或，指示DU建立DU与第二CU-UP的用户面连接的含义。当第一请求消息本身具有该含义时，第一指示可以省略。本申请实施例以第一指示携带在第一请求消息中为例，当然该第一指示也可以单独发送给DU，本申请实施例对此不做限定。
作为一种可能的实现方式，本申请实施例中的第一设备为第一基站的集中处理节点CU-控制面CP，第一基站为切换前为终端提供服务的基站。例如，第一基站为图2所示的基站1，第一设备为CU-CP1。此时，第一CU-UP和第二CU-UP与相同的集中处理节点CU-控制面CP连接，此时，第一CU-UP可以为图2所示的CU-UP1，第二CU-UP可以为图2所示的CU-UP2。
作为一种可能的实现方式，本申请实施例中的第一设备为第二基站的集中处理节点CU-控制面CP，该第二基站为切换后为终端提供服务的基站。举例说明，第二基站可以为图4所示的基站2，第一设备为CU-CP2。此时，第一CU-UP和第二CU-UP与不同的集中处理节点CU-控制面CP连接，此时，第一CU-UP可以为图4所示的CU-UP1，第二CU-UP可以为图2所示的CU-UP3。
需要说明的是，如果第一设备为第二基站的CU-CP，则在第一设备执行步骤601之前，该方法还可以包括：第一设备接收来自第一基站的CU-CP发送的切换请求，该切换请求用于请求第一设备触发CU-UP的切换流程。该切换请求中应包含该终端的上下文，该切换请求还用于请求建立DU和第二CU-UP连接的过程中，将与第一CU-UP 对应的第一RLC实体和与第二CU-UP对应的第二RLC实体关联。这样，可以便于后续结束标记(End Marker)机制的执行。
步骤702、DU根据第一指示，关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体。
在一种可能的实现方式中，第一指示还指示DU建立该DU与第二CU-UP之间的用户面连接。相应的，本申请实施例提供的方法在步骤701之后还可以包括：
步骤703、DU根据第一指示，建立DU与第二CU-UP之间的用户面连接。
需要说明的是，步骤702和步骤703不分先后顺序。本申请实施例中第一指示可以具有如下含义：1、第一指示指示建立DU与第二CU-UP之间的用户面连接，以及关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体。2、第一指示指示建立DU与所述第二CU-UP之间的用户面连接，在这种情况下，DU还可以确定需要关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体。3、第一指示指示关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体，在这种情况下，DU还可以确定建立DU与第二CU-UP之间的用户面连接。
上述以指示DU建立DU与第二CU-UP之间的用户面连接，以及关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体为同一个指示为例，当然指示DU建立DU与第二CU-UP之间的用户面连接，以及关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体的指示也可以为不同的指示。该不同的指示可以携带在同一个消息中也可以携带在不同的消息中，本申请实施例对此不作限定。
在一种可能的实现方式中，本申请实施例中的第一请求消息中还可以携带第二CU-UP的信息。例如，第二CU-UP的信息可以为第二CU-UP的地址或者第二CU-UP的标识，本申请实施例对此不作限定。
示例性的，该第二CU-UP的信息可以预配置在第一设备中，也可以由第一设备从第二CU-UP处获取，本申请实施例对此不作限定。
在一种可能的实施例中，如图7所示，本申请实施例提供的方法还可以包括：
步骤704、DU向终端发送第一配置消息，相应的，终端接收来自DU的第一配置消息。
该第一配置消息指示终端建立终端与第二CU-UP之间的用户面连接，以及保持终端与第一CU-UP之间的用户面连接。
其中，终端与第二CU-UP之间的用户面连接用于终端向第二CU-UP传输上行数据包。
由于终端侧的协议栈需要与DU以及CU-UP的用户面连接保持一致，此处建立终端与第二CU-UP之间的用户面连接，包括DU中对应该逻辑连接的PHY层、MAC层、RLC层实体，以及CU-UP中的PDCP实体，还有终端中对应该连接的PHY、MAC、RLC、PDCP实体。这个用户面连接，表示无线承载(Radio Bearer)粒度的逻辑连接，而非具体的物理连接。
示例性的，第一配置消息可以为RRC重配置消息(RRC Reconfiguration消息)。
步骤705、终端建立与第二CU-UP之间的用户面连接，以及保持终端与第一CU-UP之间的用户面连接。
可选的，待终端建立与第二CU-UP之间的用户面连接之后，终端可以向DU发送第一配置完成消息(例如，RRC重配置完成(RRC Reconfiguration Complete)消息)，以表明终端已建立与第二CU-UP之间的用户面连接。待DU接收到RRC Reconfiguration Complete消息后，可以将该RRC Reconfiguration Complete转发给第一设备。
在一种可能的实施例中，为了使得DU知晓用户面网元和第一CU-UP之间的用户面连接上传输的下行数据包传输结束，如图7所示，本申请实施例提供的方法在步骤710之前还可以包括：
步骤708、DU接收第二指示，该第二指示用于DU确定在用户面网元和第一CU-UP之间的用户面连接上传输的下行数据包传输结束。
示例性的，DU可以接收来自第一CU-UP的第二指示。
需要说明的是，在终端的CU-UP发生切换的情况下，首先用户面网元保持与第一CU-UP之间的用户面连接，并通过用户面网元与第一CU-UP之间的用户面连接向终端发送下行数据包，之后，在CU-UP发生切换的过程中，一方面用户面网元继续通过用户面网元与第一CU-UP之间的用户面连接向终端发送下行数据包，另一方面，用户面网元还建立与第二CU-UP之间的用户面连接。待用户面网元与第二CU-UP之间的用户面连接建立完成后，用户面网元便可以停止在用户面网元与第一CU-UP之间的用户面连接上向第一CU-UP发送针对终端的下行数据包，并向第一CU-CP发送第二指示，以使得第一CU-UP接收来自用户面网元的第二指示。
步骤709、DU根据第二指示确定用户面网元和第一CU-UP之间的用户面连接上传输的下行数据包传输结束。也即通过第二指示，DU可以确定后续用户面网元停止在用户面网元和第一CU-UP之间的用户面连接上向第一CU-UP发送下行数据包。后续，待用户面网元处还具有向终端发送的下行数据包时，用户面网元将通过和第二CU-UP之间的用户面连接上向第二CU-UP发送下行数据包。虽然用户面网元停止在用户面网元和第一CU-UP之间的用户面连接上向第一CU-UP发送下行数据包，但是对于DU而言，DU处可能还会存在如下情况：来自第一CU-UP的数据包并未全部发送给终端，但DU已接收到来自第二CU-UP的下行数据包，这时DU可以将来自第二CU-UP的下行数据包缓存起来，直到来自第一CU-UP的数据包全部发送给终端之后再向终端发送来自第二CU-UP的下行数据包，这样可以避免终端同时接收到来自两个CU-UP的下行数据包并进行额外的合并处理。
在一种可能的实施例中，待终端切换到第二CU-UP，即用户面网元与第二CU-UP建立了用户面连接，且第二CU-UP也与为终端提供服务的DU建立了用户面连接，则如图7所示，本申请实施例提供的方法还可以包括：
步骤711、在DU将来自第一CU-UP的下行数据包全部发送至终端的情况下，DU向第一设备发送第一报告，以使得第一设备接收来自DU的第一报告。该第一报告用于第一设备触发第一CU-UP释放终端的上下文。
步骤712、第一设备触发第一CU-UP释放终端的上下文。
具体的，第一设备为第一基站的CU-CP，则第一设备向第一CU-UP发送释放终端的上下文的命令，以使得第一CU-UP响应于释放终端的上下文的命令，并释放终端的上下文的命令。
具体的，第一设备为第二基站的CU-CP，则第一设备向第一CU-UP对应的CU-CP发送释放终端的上下文的命令，以使得第一CU-UP对应的CU-CP将释放终端的上下文的命令转发给第一CU-UP，后续第一CU-UP响应于释放终端的上下文的命令，并释放终端的上下文的命令。
在一种可能的实现方式中，如果DU为切换后为终端提供服务的DU，则本申请实施例提供的方法在步骤701之前还可以包括：第一基站的CU-CP或第二基站的CU-CP将终端从切换前为终端提供服务的DU切换为该DU。具体的,DU切换过程可以参考上述图8的描述。
步骤801、终端向源DU发送测量报告，以使得源DU接收来自终端的测量报告。该测量报告用于反映终端接收周围小区的信号功率大小。具体的测量报告的内容可以参考现有技术中的描述，此处不再赘述。
可以理解的是，在未发生DU切换之前，终端的下行数据包传输路径如图8所示为：CU→源DU→终端。终端的上行数据包传输路径如图8所示为：终端→源DU→CU。
步骤802、源DU向CU发送上行RRC消息传输(UL RRC message transfer)，以使得CU接收来自源DU的上行RRC消息传输。其中，上行RRC消息传输中包括测量报告。
步骤803、CU向目标DU发送终端上下文建立请求(UE context setup request)，以使得目标DU接收来自CU的终端终端上下文建立请求。该终端上下文建立请求用于请求建立DU侧的终端上下文(UE Context)，主要是该终端逻辑连接相关的配置参数，用来建立MAC实体以及RLC实体等。另外请求目标DU反馈用来建立与CU-UP连接的端口信息。
步骤804、目标DU向CU发送终端上下文建立响应(UE context setup response)，以使得CU接收终端上下文建立响应。
步骤805、CU向源DU发送终端上下文修改请求(UE context modification request)，以使得源DU接收来自CU的终端上下文修改请求。
其中，终端上下文修改请求中携带RRC重配置消息。该终端上下文修改请求中包括传输动作指示(Transmission Action Indicator)，用于指示源DU继续维持与终端的连接。
步骤806、源DU向终端发送RRC重配置消息，以使得终端接收来自源DU的RRC重配置消息。
步骤807、源DU向CU发送下行数据传输状态(downlink data delivery status)，以使得CU接收来自源DU的下行数据传输状态。
步骤808、源DU向CU发送终端上下文修改响应(UE context modification response)，以使得CU接收来自源DU的终端上下文修改响应。
步骤809、终端与目标DU之间执行随机接入流程(random access procedure)。
关于终端与目标DU之间执行随机接入流程可以参考现有技术中的描述，此处不再赘述。
之后，目标DU向CU发送下行数据传输状态，以使得CU接收下行数据传输状态。
步骤810、终端向目标DU发送RRC重配置完成消息，以使得目标DU接收来自终端的RRC重配置完成消息。
在此过程中，CU向目标DU发送针对终端的下行数据，以使得目标DU接收来自CU的针对终端的下行数据。
步骤811、目标DU向CU发送上行RRC消息传输，以使得CU接收来自目标DU的上行RRC消息传输。该上行RRC消息传输中携带终端的RRC重配置完成消息。
步骤812、目标DU向终端发送针对终端的下行数据，以使得终端接收针对终端的下行数据。
在步骤812之后，后续终端存在上行数据时，可以通过目标DU向CU发送上行数据。
步骤813、CU向源DU发送终端上下文释放命令(UE context release conmmand)，以使得源DU接收来自CU的终端上下文释放命令。
在接收到终端上下文释放命令之后，源DU便可以释放该终端的终端上下文。
步骤814、源DU释放掉终端上下文之后，便可以向CU发送终端上下文释放响应，以表示源DU成功释放掉终端上下文。源DU释放掉终端上下文之后，便中断了与终端的连接。
由于在上述流程中，由CU双播下行数据流给源DU和目标DU，直到终端与目标DU的连接建立完成以后，再中断源DU与终端的连接。以此种方式，实现了DU的终止前建立(Make Before Break)切换，由于DU的切换无需构建转发隧道，因此可以达成0ms切换。
在为终端提供服务的DU和CU-UP均发生切换的情况下，一方面CU-CP可以先为终端切换DU，再为终端切换CU-UP。另一方面，CU-CP可以根据CU-UP的业务情况或负载情况先进行CU-UP的切换，再在终端发生移动的时候进行DU的切换。也即先为终端切换CU-UP，再为终端切换DU。
在一种可能的实现方式中，如果DU为切换前为终端提供服务的DU，则本申请实施例提供的方法还可以包括：第一基站的CU-CP或第二基站的CU-CP将终端从该DU切换为目标DU，该目标DU与第二CU-UP连接，且后续由目标DU为终端提供服务。
在一种可能的实施例中，本申请实施例提供的方法还可以包括：DU根据第二CU-UP的信息建立与第二CU-UP的上行通道后，DU向第一设备发送DU的信息，以使得第一设备接收来自DU的信息。该DU的信息可以用于第二CU-UP建立与DU的下行通道。之后，第一设备向第二CU-UP发送DU的信息，以使得第二CU-UP根据DU的信息建立与DU的下行通道。
可选的，待第二CU-UP根据DU的信息建立与DU的下行通道之后，第二CU-UP可以向第一设备反馈响应消息，用于表示下行通道建立完成。
可以理解的是，当DU根据第二CU-UP的信息建立与第二CU-UP的上行通道， 第二CU-UP根据DU的信息建立与DU的下行通道后，便可以认为DU和第二CU-UP之间的用户面连接建立完成。
如图9所示，图9以相同gNB-CU-CP控制下，gNB-DU与gNB-CU-UP均发生切换的场景，以切换后为终端提供服务的DU为目标(Target)gNB-DU，切换前为终端提供服务的DU为源(Source)gNB-DU，第一CU-UP为源gNB-CU-UP，第二CU-UP为目标gNB-CU-UP，源gNB-CU-UP和目标gNB-CU-UP与同一个gNB-CU-CP连接为例，详细描述，本申请实施例涉及到的切换方法，如图9所示，该方法包括：
步骤901、gNB-CU-CP将终端从将源gNB-DU切换为目标gNB-DU。
如图9所示，在将终端从源gNB-DU切换为目标gNB-DU之后，对于下行传输(即UPF网元/AMF网元→终端)，来自UPF网元的下行数据包经过源gNB-CU-UP发送至目标gNB-DU，然后由目标gNB-DU将来自UPF网元的下行数据包发送给终端。来自AMF网元的下行信令经过gNB-CU-CP发送至目标gNB-DU，然后由目标gNB-DU将来自AMF网元的下行信令发送给终端。对于上行传输(即终端→UPF网元/AMF网元)，终端先将上行数据包发送给目标gNB-DU，由目标gNB-DU将来自终端的上行数据包通过源gNB-CU-UP发送给UPF网元。终端先将上行信令发送给目标gNB-DU，由目标gNB-DU将来自终端的上行信令通过gNB-CU-CP发送给AMF网元。
关于步骤901的具体实现可以参考上述图8所描述的DU的切换，此处不再赘述。
其中，在gNB-CU-CP与源gNB-CU-UP的交互中，gNB-CU-CP向源gNB-CU-UP发送指示消息，该指示消息表示本次切换为跨gNB-CU-UP切换(即为终端切换gNB-CU-UP)，在后续的切换流程中，源gNB-CU-UP将来自用户面网元的End Marker转发至目标gNB-DU。
需要说明的是，如果终端的CU-UP从第一CU-UP切换为第二CU-UP，但是DU却未发生切换的情况下，则步骤901可以省略。
步骤902、gNB-CU-CP向目标gNB-CU-UP发送承载上下文建立请求(bearer context setup request)消息，以使得目标gNB-CU-UP接收来自gNB-CU-CP的承载上下文建立请求消息。
其中，该承载上下文建立请求消息指示目标gNB-CU-UP建立与目标gNB-DU之间的用户面连接(例如，F1-U连接)，以及请求目标gNB-CU-UP反馈用于创建该用户面连接的上行(uplink，UL)接口信息。此处的上行(uplink，UL)接口信息可以为目标gNB-CU-UP的信息，可以对应上述实施例中第二CU-UP的信息。
步骤903、目标gNB-CU-UP向gNB-CU-CP发送承载上下文建立响应(bearer context setup response)消息，以使得gNB-CU-CP接收来自目标gNB-CU-UP的承载上下文建立响应消息。
其中，承载上下文建立响应消息中携带用户面连接的上行接口信息。
步骤904、gNB-CU-CP向目标gNB-DU发送终端上下文建立请求(UE context setup request)消息，以使得目标gNB-DU接收来自gNB-CU-CP的终端上下文建立请求消息。
其中，终端上下文建立请求消息指示目标gNB-DU建立与目标gNB-CU-UP之间的用户面连接，并请求目标gNB-DU反馈用户面连接的下行(downlink，DL)接口信 息。该终端上下文建立请求消息指示目标gNB-DU关联与源gNB-CU-UP对应的RLC实体1和与目标gNB-CU-UP对应的RLC实体2，在与源gNB-CU-UP对应的RLC实体1接收到End Marker(对应上述第二指示)之前，缓存目标gNB-CU-UP向该目标gNB-DU发送的下行数据包。
可选的，该终端上下文建立请求消息中包含RRC重配置(reconfiguration)消息。可选的，该终端上下文建立请求消息中包含用户面连接的上行接口信息。
步骤905、目标gNB-DU建立与目标gNB-CU-UP之间的上行通道。
步骤906、目标gNB-DU向gNB-CU-CP发送终端上下文建立响应消息，以使得gNB-CU-CP接收来自目标gNB-DU的终端上下文建立响应消息。
其中，终端上下文建立响应消息中包括用户面连接的下行接口信息。该用户面连接的下行接口信息可以为目标gNB-DU的信息，对应上文DU的信息。
之后，gNB-CU-CP可以向目标gNB-CU-UP发送用户面连接的下行接口信息，以便于目标gNB-CU-UP建立与目标gNB-DU之间的下行通道，至此，目标gNB-DU与目标gNB-CU-UP之间的用户面连接建立完成。
步骤907、目标gNB-DU向终端发送RRC重配置消息，以使得终端接收来自目标gNB-DU的RRC重配置消息。
其中，RRC reconfiguration消息指示终端建立与目标gNB-CU-UP之间的用户面连接，并保持终端与源gNB-CU-UP之间的用户面连接。
步骤908、gNB-CU-CP向目标gNB-CU-UP发送承载上下文修改请求(bearer context modification request)消息，以使得目标gNB-CU-UP接收来自gNB-CU-CP的承载上下文修改请求消息。
其中，承载上下文修改请求消息中包含目标gNB-DU反馈的用户面连接的下行接口信息。该承载上下文修改请求消息对gNB-CU-UP处保存的Bearer Context进行修改，包括几乎所有与Bearer Context相关的参数，如安全消息、会话相关的QoS Flow映射关系、QoS Flow建立删除、端口消息等。此处主要是对端口信息进行修改。
步骤909、目标gNB-CU-UP向gNB-CU-CP反馈承载上下文修改响应(bearer context modification response)消息，以使得gNB-CU-CP接收承载上下文修改响应消息。
该承载上下文修改响应消息可以表示目标gNB-CU-UP已成功接收到目标gNB-DU反馈的用户面连接的下行接口信息，或者目标gNB-DU与目标gNB-CU-UP之间的用户面连接建立完成。
步骤910、终端与目标gNB-CU-UP的用户面连接建立完成，向目标gNB-DU发送RRC重配置完成(RRC Reconfiguration Complete)消息。
步骤911、目标gNB-DU向gNB-CU-CP发送上行RRC消息传输(UL RRC Message transfer)，以使得gNB-CU-CP接收来自目标gNB-DU的上行RRC消息传输。其中，上行RRC消息传输中携带RRC Reconfiguration Complete消息。
此时终端与源gNB-CU-UP和目标gNB-CU-UP同时保持用户面连接，但同一时间只接收一个gNB-CU-UP的下行数据，具体方法由步骤915-步骤917实现。同时上行数据通过目标gNB-CU-UP发送。
步骤912、UPF网元保持与源gNB-CU-UP连接，建立与目标gNB-CU-UP的连接路径。
步骤913、UPF网元建立与目标gNB-CU-UP之间的连接之后，向源gNB-CU-UP发送End Marker(对应上述第二指示)。
步骤914、UPF网元停止向源gNB-CU-UP发送针对终端的下行数据包，开始向目标gNB-CU-UP发送针对终端的下行数据包。
步骤915、目标gNB-DU在收到End Marker之前，保持与源gNB-CU-UP的传输，并缓存从目标gNB-CU-UP接收到的下行数据包。
步骤916、根据gNB-CU-CP向源gNB-CU-UP发送的指示消息，源gNB-CU-UP向目标gNB-DU发送End Marker，以使得目标gNB-DU接收来自源gNB-CU-UP的End Marker。
步骤917、目标gNB-DU收到End Marker之后，优先向终端发送来自源gNB-CU-UP的针对终端的下行数据包，待来自源gNB-CU-UP的针对终端的下行数据包全部发送给终端之后，再开始向终端发送来自目标gNB-CU-UP的针对终端的下行数据包。
步骤918、处理完来自源gNB-CU-UP的针对终端的下行数据包处理后，目标gNB-DU向gNB-CU-CP发送结束指示执行报告(End Marker execution report)(对应上述第一报告)，以使得gNB-CU-CP接收来自目标gNB-DU的End Marker execution report。通过该End Marker execution report，目标gNB-DU可以向gNB-CU-CP上报End Marker执行状况。
可以理解的是，由于目标gNB-DU可以接收到来自源gNB-CU-UP和目标gNB-CU-UP的针对终端的下行数据包，则可以认为目标gNB-DU处于双数据连接状态。因为采用双数据连接的方式实现低时延切换，所以需要切换完成后再通知gNB-CU-CP进行资源释放。此End Marker execution report的主要作用就是报告切换执行情况，通知gNB-CU-CP进行资源释放。
步骤919、gNB-CU-CP向源gNB-CU-UP发送承载上下文释放指令(bearer context release command)，以使得源gNB-CU-UP接收来自gNB-CU-CP的承载上下文释放指令。
其中，承载上下文释放指令指示源gNB-CU-UP释放相应的连接和资源。此外，承载上下文释放指令指示源gNB-CU-UP向核心网发送消息，请求释放源gNB-CU-UP相应的连接和资源。具体的承载上下文释放指令指示源gNB-CU-UP释放与gNB-DU之间的连接(与gNB-DU之间连接使用的端口)，释放的资源指逻辑连接对应的PDCP实体和保存的Bearer Context。
步骤920、gNB-CU-CP向目标gNB-DU发送F1UE上下文释放(context release)指令，以使得目标gNB-DU接收F1UE上下文释放指令。之后，目标gNB-DU根据F1 UE上下文释放指令释放目标gNB-DU与源gNB-CU-UP相关资源和连接。
步骤921、源gNB-CU-UP释放完相应资源后，向gNB-CU-CP反馈承载上下文释放完成(bearer context release complete)消息，以使得gNB-CU-CP接收承载上下文释放完成消息。
在图9所示的实施例中，将切换过程拆分为gNB-DU切换流程和gNB-CU-UP流 程，在gNB-CU-UP的切换流程中，通过终端与源gNB-CU-UP和目标gNB-CU-UP之间双连接的方式避免来自UPF网元的下行用户面数据在源gNB-CU-UP和目标gNB-CU-UP之间转发，最终达成图10所示的下行用户面数据传输流程。即gNB-DU切换流程执行可以参考图8所描述的方案，将下行用户面数据传输路径切换为UPF网元->源gNB-CU-UP->目标gNB-DU，未产生业务面中断。gNB-CU-UP切换流程中，通过终端与源gNB-CU-UP和目标gNB-CU-UP之间双连接的建立、目标gNB-DU缓存下行用户面数据以及End Marker处理机制保证了gNB-CU-UP的低时延切换，避免了转发时延。
参考图10，为本申请实施例提供的DU和CU-UP切换之前，下行用户面数据传输的示意图，如图10所示，在终端未切换DU和CU-UP之前，终端的下行用户面数据的传输路径如图10中的线条①所示，即UPF网元先将下行用户面数据通过与源gNB-CU-UP之间的用户面连接发送给源gNB-CU-UP，然后由源gNB-CU-UP通过与源gNB-DU之间的用户面连接将下行用户面数据发送给源gNB-DU。最后，源gNB-DU通过与终端之间的用户面连接将下行用户面数据发送给终端。
在终端的DU从源gNB-DU切换为目标gNB-DU，而gNB-CU-UP未发生变化的场景中，终端的下行用户面数据的传输路径如图10中的线条②所示，即UPF网元先将下行用户面数据通过与源gNB-CU-UP之间的用户面连接发送给源gNB-CU-UP，然后由源gNB-CU-UP通过与源gNB-DU之间的用户面连接将下行用户面数据发送给目标gNB-DU。最后，目标gNB-DU通过与终端之间的用户面连接将下行用户面数据发送给终端。
在终端的DU从源gNB-DU切换为目标gNB-DU，终端的gNB-CU-UP从源gNB-CU-UP切换为目标gNB-CU-UP的场景中，终端的下行用户面数据的传输路径如图10中的线条③所示，即UPF网元先将下行用户面数据通过与目标gNB-CU-UP之间的用户面连接发送给目标gNB-CU-UP，然后由目标gNB-CU-UP通过与目标gNB-DU之间的用户面连接将下行用户面数据发送给目标gNB-DU。最后，目标gNB-DU通过与终端之间的用户面连接将下行用户面数据发送给终端。
参考图11，为本申请提供的另一种切换方法的流程示意图，该方法与图9的区别在于：源gNB-CU-UP由源gNB-CU-CP控制，而目标gNB-CU-UP由目标gNB-CU-CP控制，即进行切换的gNB-CU-UP分别受不同的gNB-CU-CP控制。该方法包括：
步骤1101同步骤901，此处不再赘述。
如图11所示，在将终端从源gNB-DU切换为目标gNB-DU之后，对于下行传输(即UPF网元/AMF网元→终端)，来自UPF网元的下行数据包经过源gNB-CU-UP发送至目标gNB-DU，然后由目标gNB-DU将来自UPF网元的下行数据包发送给终端。来自AMF网元的下行信令经过gNB-CU-CP发送至目标gNB-DU，然后由目标gNB-DU将来自AMF网元的下行信令发送给终端。对于上行传输(即终端→UPF网元/AMF网元)，终端先将上行数据包发送给目标gNB-DU，由目标gNB-DU将来自终端的上行数据包通过源gNB-CU-UP发送给UPF网元。终端先将上行信令发送给目标gNB-DU，由目标gNB-DU将来自终端的上行信令通过gNB-CU-CP发送给AMF网元。
步骤1102、源gNB-CU-CP向目标gNB-CU-CP发送切换请求(handover request)， 以使得目标gNB-CU-CP接收来自源gNB-CU-CP的切换请求。该切换请求用于请求将终端的gNB-CU-CP从源gNB-CU-CP切换为目标gNB-CU-CP。该切换请求触发gNB-CU-UP的切换流程。该该切换请求中应包含源gNB-CU-UP相关的终端上下文，用于建立目标gNB-CU-UP连接的过程中，将两者的RLC实体关联，便于End Marker机制的执行。gNB-CU-UP切换流程由Target gNB-CU-CP控制执行，其中涉及到源gNB-CU-UP的信令流均由源gNB-CU-UP进行转发和反馈，其他信令流程与图9所示方案相同。切换请求请求将该终端切换到目标gNB-CU-CP，只有目标gNB-CU-CP允许切换，并反馈Handover Acknowledge，才能触发切换流程。否则该过程被拒绝(reject)，可能需要重新选择目标gNB-CU-CP。
步骤1103～步骤1122同步骤902～步骤921，区别在于，将步骤902～步骤921中由源gNB-CU-CP执行的步骤替换为由目标gNB-CU-CP执行即可。
具体的，在UPF网元与目标gNB-CU-UP之间建立用户面了解之后，对于下行传输(即UPF网元/AMF网元→终端)，来自UPF网元的下行数据包经过目标gNB-CU-UP发送至目标gNB-DU，然后由目标gNB-DU将来自UPF网元的下行数据包发送给终端。来自AMF网元的下行信令经过目标gNB-CU-CP发送至目标gNB-DU，然后由目标gNB-DU将来自AMF网元的下行信令发送给终端。对于上行传输(即终端→UPF网元/AMF网元)，终端先将上行数据包发送给目标gNB-DU，由目标gNB-DU将来自终端的上行数据包通过目标gNB-CU-UP发送给UPF网元。终端先将上行信令发送给目标gNB-DU，由目标gNB-DU将来自终端的上行信令通过目标gNB-CU-CP发送给AMF网元。
如图12所示，图12示出了图9或图11描述的方案数据面的效果图，现有技术对于gNB-CU-UP的切换如上半部分两个子图所示，先构建源gNB-CU-UP和目标gNB-CU-UP之间的转发隧道，再将数据流切换到目标gNB-CU-UP上。在整个PATHSwitch过程中，数据面消息的发送一直存在转发时延。而本实施例的数据面处理过程如下半部分两个子图所示，先创建目标gNB-CU-UP与gNB-DU之间的F1-U连接，并将源gNB-CU-UP和目标gNB-CU-UP各自的RLC实体进行关联，先对目标gNB-CU-UP的数据包进行缓存，直到从源gNB-CU-UP收到End Marker并发送完该路径上的数据包，再开始发送目标gNB-CU-UP上的数据包，传输路径切换完成。
应理解，图9或图11描述的方案以先为终端切换DU再为切换CU-UP为例进行描述。当为终端服务的DU不发生变化时，则步骤901和步骤1101可以省略。
上述主要从各个网元之间交互的角度对本申请实施例的方案进行了介绍。可以理解的是，各个网元，例如DU、第一设备等为了实现上述功能，其包括了执行各个功能相应的硬件结构和/或软件模块。本领域技术人员应该很容易意识到，结合本文中所公开的实施例描述的各示例的单元及算法步骤，本申请能够以硬件或硬件和计算机软件的结合形式来实现。某个功能究竟以硬件还是计算机软件驱动硬件的方式来执行，取决于技术方案的特定应用和设计约束条件。专业技术人员可以对每个特定的应用来使用不同方法来实现所描述的功能，但是这种实现不应认为超出本申请的范围。
本申请实施例可以根据上述方法示例DU、第一设备进行功能单元的划分，例如，可以对应各个功能划分各个功能单元，也可以将两个或两个以上的功能集成在一个处 理单元中。上述集成的单元既可以采用硬件的形式实现，也可以采用软件功能单元的形式实现。需要说明的是，本申请实施例中对单元的划分是示意性的，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式。
上面结合图6至图12，对本申请实施例的方法进行了说明，下面对本申请实施例提供的执行上述方法的通信装置进行描述。本领域技术人员可以理解，方法和装置可以相互结合和引用，本申请实施例提供的通信装置可以执行上述网络间互操作的方法中由DU、第一设备执行的步骤。
在采用集成的单元的情况下，图13示出了上述实施例中所涉及的通信装置，该通信装置可以包括：通信单元102和处理单元101。
一种示例，该通信装置为DU，或者为应用于DU中的芯片。在这种情况下，通信单元102用于支持该通信装置执行上述实施例的图6的步骤601中由DU执行的接收动作。通信单元102，还用于支持该通信装置执行图6的步骤602中由DU执行的发生动作以及步骤603中由DU执行的发送动作。处理单元101，用于支持该通信装置执行图6的步骤603中确定通信单元将来自第一CU-UP的下行数据包全部发送至终端的动作。
在一种可能的实施例中，通信单元102，还用于支持通信装置执行上述实施例中的步骤701中由DU执行的接收动作。处理单元101，还用于支持通信装置执行上述实施例中步骤702以及步骤703、步骤709。通信单元102还用于支持通信装置执行上述实施例中的步骤704、步骤711中由DU执行的发送动作、通信单元102还用于支持通信装置执行上述实施例中的步骤708中由DU执行的接收动作。
作为一种可能的实现方式，如果DU为切换前为终端提供服务的DU，即源DU，则通信单元，还用于支持通信装置实现图8中由源DU执行的动作。如果DU为切换后为终端提供服务的DU，则通信单元，还用于支持通信装置实现图8中由目标DU执行的动作。
另一种示例，该通信装置为第一设备，或者为应用于第一设备中的芯片。在这种情况下，处理单元101，用于在通信单元102执行上述实施例中的步骤701中由第一设备执行的发送动作之前，支持该通信装置执行确定关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体。通信单元102，用于支持该通信装置执行上述实施例中的步骤701中由第一设备执行的发送动作。
在一种可能的实现方式中，通信单元102，还用于支持该通信装置执行上述实施例中的步骤711中由第一设备执行的接收动作。处理单元101，还用于支持该通信装置执行上述实施例中的步骤712。
再一种示例，该通信装置为终端，或者为应用于终端中的芯片。通信单元102，用于支持该通信装置执行上述实施例中的步骤602以及步骤603中由终端执行的接收动作。
在一种可能的实现方式中，该通信单元102，还用于支持该通信装置执行图8中所有由终端执行的发送或接收的动作。通信单元，用于支持该通信装置执行步骤704中由终端执行的接收动作。
处理单元101，用于支持该通信装置执行步骤705。
在采用集成的单元的情况下，图14示出了上述实施例中所涉及的通信装置的一种可能的逻辑结构示意图。该通信装置包括：处理模块112和通信模块113。处理模块112用于对通信装置的动作进行控制管理，例如，处理模块112用于执行在通信装置进行信息/数据处理的步骤。通信模块113用于支持通信装置进行信息/数据发送或者接收的步骤。
在一种可能的实施例中，通信装置还可以包括存储模块111，用于存储通信装置可的程序代码和数据。
一种示例，该通信装置为DU，或者为应用于DU中的芯片。在这种情况下，通信模块113用于支持该通信装置执行上述实施例的图6的步骤601中由DU执行的接收动作。通信模块113，还用于支持该通信装置执行图6的步骤602中由DU执行的发生动作以及步骤603中由DU执行的发送动作。处理模块112，用于支持该通信装置执行图6的步骤603中确定通信单元将来自第一CU-UP的下行数据包全部发送至终端的动作。
在一种可能的实施例中，通信模块113，还用于支持通信装置执行上述实施例中的步骤701中由DU执行的接收动作。处理模块112，还用于支持通信装置执行上述实施例中步骤702以及步骤703、步骤709。通信模块113还用于支持通信装置执行上述实施例中的步骤704、步骤711中由DU执行的发送动作、通信模块113还用于支持通信装置执行上述实施例中的步骤708中由DU执行的接收动作。
作为一种可能的实现方式，如果DU为切换前为终端提供服务的DU，即源DU，则通信单元，还用于支持通信装置实现图8中由源DU执行的动作。如果DU为切换后为终端提供服务的DU，则通信单元，还用于支持通信装置实现图8中由目标DU执行的动作。
另一种示例，该通信装置为第一设备，或者为应用于第一设备中的芯片。在这种情况下，处理模块112，用于在通信模块113执行上述实施例中的步骤701中由第一设备执行的发送动作之前，支持该通信装置执行确定关联与第一CU-UP对应的第一RLC实体和与第二CU-UP对应的第二RLC实体。通信模块113，用于支持该通信装置执行上述实施例中的步骤701中由第一设备执行的发送动作。
在一种可能的实现方式中，通信模块113，还用于支持该通信装置执行上述实施例中的步骤711中由第一设备执行的接收动作。处理模块112，还用于支持该通信装置执行上述实施例中的步骤712。
再一种示例，该通信装置为终端，或者为应用于终端中的芯片。通信模块113，用于支持该通信装置执行上述实施例中的步骤602以及步骤603中由终端执行的接收动作。
在一种可能的实现方式中，该通信单元，还用于支持该通信装置执行图8中所有由终端执行的发送或接收的动作。通信单元，用于支持该通信装置执行步骤704中由终端执行的接收动作。
处理模块112，用于支持该通信装置执行步骤705。
其中，处理模块112可以是处理器或控制器，例如可以是中央处理器单元，通用处理器，数字信号处理器，专用集成电路，现场可编程门阵列或者其他可编程逻辑器 件、晶体管逻辑器件、硬件部件或者其任意组合。其可以实现或执行结合本申请公开内容所描述的各种示例性的逻辑方框，模块和电路。处理器也可以是实现计算功能的组合，例如包含一个或多个微处理器组合，数字信号处理器和微处理器的组合等等。通信模块113可以是收发器、收发电路或通信接口等。存储模块111可以是存储器。
当处理模块112为处理器51或处理器55，通信模块113为通信接口53时，存储模块111为存储器52时，本申请所涉及的通信装置可以为图5所示的通信设备。
一种可能的实现方式中，通信接口53用于执行图6-图11所示的实施例中的DU、第一设备、终端的接收和发送的步骤。处理器51或处理器55用于执行图6-图12所示的实施例中的DU、第一设备、终端的处理的步骤。
图15是本申请实施例提供的芯片150的结构示意图。芯片150包括一个或两个以上(包括两个)处理器1510和通信接口1530。
可选的，该芯片150还包括存储器1540，存储器1540可以包括只读存储器和随机存取存储器，并向处理器1510提供操作指令和数据。存储器1540的一部分还可以包括非易失性随机存取存储器(non-volatile random access memory，NVRAM)。
在一些实施方式中，存储器1540存储了如下的元素，执行模块或者数据结构，或者他们的子集，或者他们的扩展集。
在本申请实施例中，通过调用存储器1540存储的操作指令(该操作指令可存储在操作系统中)，执行相应的操作。
一种可能的实现方式中为：DU、终端、第一设备所用的芯片的结构类似，不同的装置可以使用不同的芯片以实现各自的功能。
处理器1510控制DU、终端、第一设备中任一个的处理操作，处理器1510还可以称为中央处理单元(central processing unit，CPU)。
存储器1540可以包括只读存储器和随机存取存储器，并向处理器1510提供指令和数据。存储器1540的一部分还可以包括NVRAM。例如应用中存储器1540、通信接口1530以及存储器1540通过总线系统1520耦合在一起，其中总线系统1520除包括数据总线之外，还可以包括电源总线、控制总线和状态信号总线等。但是为了清楚说明起见，在图15中将各种总线都标为总线系统1520。
上述本申请实施例揭示的方法可以应用于处理器1510中，或者由处理器1510实现。处理器1510可能是一种集成电路芯片，具有信号的处理能力。在实现过程中，上述方法的各步骤可以通过处理器1510中的硬件的集成逻辑电路或者软件形式的指令完成。上述的处理器1510可以是通用处理器、数字信号处理器(digital signal processing，DSP)、ASIC、现成可编程门阵列(field-programmable gate array，FPGA)或者其他可编程逻辑器件、分立门或者晶体管逻辑器件、分立硬件组件。可以实现或者执行本申请实施例中的公开的各方法、步骤及逻辑框图。通用处理器可以是微处理器或者该处理器也可以是任何常规的处理器等。结合本申请实施例所公开的方法的步骤可以直接体现为硬件译码处理器执行完成，或者用译码处理器中的硬件及软件模块组合执行完成。软件模块可以位于随机存储器，闪存、只读存储器，可编程只读存储器或者电可擦写可编程存储器、寄存器等本领域成熟的存储介质中。该存储介质位于存储器1540，处理器1510读取存储器1540中的信息，结合其硬件完成上述方法的步骤。
一种可能的实现方式中，通信接口1530用于执行图6-图11所示的实施例中的DU、终端、第一设备的接收和发送的步骤。处理器1510用于执行图6-图11所示的实施例中的DU、终端、第一设备的处理的步骤。
以上收发单元可以是该装置的一种通信接口，用于从其它装置接收信号。例如，当该装置以芯片的方式实现时，该收发单元是该芯片用于从其它芯片或装置接收信号或发送信号的通信接口。
一方面，提供一种计算机可读存储介质，计算机可读存储介质中存储有指令，当指令被运行时，实现如图6或图8中DU的功能。
一方面，提供一种计算机可读存储介质，计算机可读存储介质中存储有指令，当指令被运行时，实现如图6或图8中第一设备的功能。
一方面，提供一种计算机可读存储介质，计算机可读存储介质中存储有指令，当指令被运行时，实现如图6或图8中终端的功能。
一方面，提供一种包括指令的计算机程序产品，计算机程序产品中包括指令，当指令被运行时，实现如图6或图8中DU的功能。
又一方面，提供一种包括指令的计算机程序产品，计算机程序产品中包括指令，当指令被运行时，实现如图6或图8中第一设备的功能。
又一方面，提供一种包括指令的计算机程序产品，计算机程序产品中包括指令，当指令被运行时，实现如图6或图8中终端的功能。
一方面，提供一种芯片，该芯片应用于DU中，芯片包括至少一个处理器和通信接口，通信接口和至少一个处理器耦合，处理器用于运行指令，以实现如图6或图8中DU的功能。
又一方面，提供一种芯片，该芯片应用于第一设备中，芯片包括至少一个处理器和通信接口，通信接口和至少一个处理器耦合，处理器用于运行指令，以实现如图6或图8中第一设备的功能。
又一方面，提供一种芯片，该芯片应用于终端中，芯片包括至少一个处理器和通信接口，通信接口和至少一个处理器耦合，处理器用于运行指令，以实现如图6或图8中终端的功能。
本申请实施例提供一种通信系统，该通信系统包括：终端、DU以及CU-CP。其中，终端用于执行如图6或图8中由终端执行的步骤，DU用于执行图6或图8中由DU执行的步骤、第一设备用于执行如图6或图8中第一设备执行的步骤。其中，DU和第一CU-UP以及第二CU-UP之间具有用户面连接。
可选的，该通信系统还可以包括用户面网元。其中，用户面网元用于向第一CU-UP发送第二指示。
在上述实施例中，可以全部或部分地通过软件、硬件、固件或者其任意组合来实现。当使用软件实现时，可以全部或部分地以计算机程序产品的形式实现。所述计算机程序产品包括一个或多个计算机程序或指令。在计算机上加载和执行所述计算机程序或指令时，全部或部分地执行本申请实施例所述的流程或功能。所述计算机可以是通用计算机、专用计算机、计算机网络、网络设备、用户设备或者其它可编程装置。所述计算机程序或指令可以存储在计算机可读存储介质中，或者从一个计算机可读存 储介质向另一个计算机可读存储介质传输，例如，所述计算机程序或指令可以从一个网站站点、计算机、服务器或数据中心通过有线或无线方式向另一个网站站点、计算机、服务器或数据中心进行传输。所述计算机可读存储介质可以是计算机能够存取的任何可用介质或者是集成一个或多个可用介质的服务器、数据中心等数据存储设备。所述可用介质可以是磁性介质，例如，软盘、硬盘、磁带；也可以是光介质，例如，数字视频光盘(digital video disc，DVD)；还可以是半导体介质，例如，固态硬盘(solid state drive，SSD)。
尽管在此结合各实施例对本申请进行了描述，然而，在实施所要求保护的本申请过程中，本领域技术人员通过查看附图、公开内容、以及所附权利要求书，可理解并实现公开实施例的其他变化。在权利要求中，“包括”(comprising)一词不排除其他组成部分或步骤，“一”或“一个”不排除多个的情况。单个处理器或其他单元可以实现权利要求中列举的若干项功能。相互不同的从属权利要求中记载了某些措施，但这并不表示这些措施不能组合起来产生良好的效果。
尽管结合具体特征及其实施例对本申请进行了描述，显而易见的，在不脱离本申请的精神和范围的情况下，可对其进行各种修改和组合。相应地，本说明书和附图仅仅是所附权利要求所界定的本申请的示例性说明，且视为已覆盖本申请范围内的任意和所有修改、变化、组合或等同物。显然，本领域的技术人员可以对本申请进行各种改动和变型而不脱离本申请的精神和范围。这样，倘若本申请的这些修改和变型属于本申请权利要求及其等同技术的范围之内，则本申请也意图包括这些改动和变型在内。

Claims (24)

  1. 一种通信方法，其特征在于，包括：
    在分布式处理节点DU通过与第一集中处理节点CU-用户面UP之间的用户面连接接收来自所述第一CU-UP的下行数据包的过程中，所述DU通过与第二CU-UP之间的用户面连接接收来自所述第二CU-UP的下行数据包；所述DU包括的第一无线链路控制RLC实体与第二RLC实体关联，所述第一RLC实体与所述第一CU-UP对应，所述第二RLC实体与所述第二CU-UP对应；所述终端从所述第一CU-UP切换至所述第二CU-UP；
    所述DU向所述终端发送来自所述第一CU-UP的下行数据包；
    在所述DU将来自所述第一CU-UP的下行数据包全部发送至所述终端的情况下，所述DU向所述终端发送所述DU缓存的来自所述第二CU-UP的下行数据包。
  2. 根据权利要求1所述的方法，其特征在于，所述方法还包括：
    所述DU接收来自第一设备的第一请求消息，所述第一请求消息包括第一指示；
    所述DU根据所述第一指示，关联所述第一RLC实体和所述第二RLC实体。
  3. 根据权利要求2所述的方法，其特征在于，所述方法还包括：
    所述DU根据所述第一指示，建立所述DU与所述第二CU-UP之间的用户面连接。
  4. 根据权利要求2或3所述的方法，其特征在于，所述第一请求消息还包括所述第二CU-UP的信息。
  5. 根据权利要求1-4任一项所述的方法，其特征在于，所述方法还包括：
    所述DU向所述终端发送第一配置消息，所述第一配置消息指示所述终端建立所述终端与所述第二CU-UP之间的用户面连接，以及保持所述终端与所述第一CU-UP之间的用户面连接。
  6. 根据权利要求1-5任一项所述的方法，其特征在于，所述方法还包括：
    所述DU接收第二指示，所述第二指示指示在用户面网元和所述第一CU-UP之间的用户面连接上传输的下行数据包传输结束。
  7. 根据权利要求1-6任一项所述的方法，其特征在于，所述方法还包括：
    在所述DU将来自所述第一CU-UP的下行数据包全部发送至所述终端的情况下，所述DU向第一设备发送第一报告，所述第一报告用于所述第一设备触发所述第一CU-UP释放所述终端的上下文。
  8. 根据权利要求2或3或6或7所述的方法，其特征在于，所述第一设备为第一基站的集中处理节点CU-控制面CP，所述第一基站为切换前为所述终端提供服务的基站。
  9. 根据权利要求2或3或6或7所述的方法，其特征在于，所述第一设备为第二基站的集中处理节点CU-控制面CP，所述第二基站为切换后为所述终端提供服务的基站。
  10. 根据权利要求1-7任一项所述的方法，其特征在于，所述第一CU-UP和所述第二CU-UP与相同的集中处理节点CU-控制面CP连接，或者，所述第一CU-UP和所述第二CU-UP与不同的集中处理节点CU-控制面CP连接。
  11. 一种通信装置，其特征在于，包括：处理单元和通信单元，所述处理单元用 于执行除收发操作以外的动作，
    所述通信单元，用于在通过与第一集中处理节点CU-用户面UP之间的用户面连接接收来自所述第一CU-UP的下行数据包的过程中，还通过与第二CU-UP之间的用户面连接接收来自所述第二CU-UP的下行数据包；所述DU包括的第一无线链路控制RLC实体与第二RLC实体关联，所述第一RLC实体与所述第一CU-UP对应，所述第二RLC实体与所述第二CU-UP对应；所述终端从所述第一CU-UP切换至所述第二CU-UP；
    所述通信单元，还用于向所述终端发送来自所述第一CU-UP的下行数据包；
    在所述通信单元将来自所述第一CU-UP的下行数据包全部发送至所述终端的情况下，所述通信单元，还用于向所述终端发送所述处理单元缓存的来自所述第二CU-UP的下行数据包。
  12. 根据权利要求11所述的装置，其特征在于，所述通信单元，还用于接收来自第一设备的第一请求消息，所述第一请求消息包括第一指示；
    所述处理单元，还用于根据所述第一指示，关联所述第一RLC实体和所述第二RLC实体。
  13. 根据权利要求12所述的装置，其特征在于，所述处理单元，还用于根据所述第一指示，建立所述DU与所述第二CU-UP之间的用户面连接。
  14. 根据权利要求12或13所述的装置，其特征在于，所述第一请求消息还包括所述第二CU-UP的信息。
  15. 根据权利要求11-14任一项所述的装置，其特征在于，所述通信单元，还用于向所述终端发送第一配置消息，所述第一配置消息指示所述终端建立所述终端与所述第二CU-UP之间的用户面连接，以及保持所述终端与所述第一CU-UP之间的用户面连接。
  16. 根据权利要求11-15任一项所述的装置，其特征在于，所述通信单元，还用于接收第二指示，所述第二指示指示在用户面网元和所述第一CU-UP之间的用户面连接上传输的下行数据包传输结束。
  17. 根据权利要求11-16任一项所述的装置，其特征在于，在所述通信单元将来自所述第一CU-UP的下行数据包全部发送至所述终端的情况下，所述通信单元，还用于向第一设备发送第一报告，所述第一报告用于所述第一设备触发所述第一CU-UP释放所述终端的上下文。
  18. 根据权利要求12或13或16或17所述的装置，其特征在于，所述第一设备为第一基站的集中处理节点CU-控制面CP，所述第一基站为切换前为所述终端提供服务的基站。
  19. 根据权利要求12或13或16或17所述的装置，其特征在于，所述第一设备为第二基站的集中处理节点CU-控制面CP，所述第二基站为切换后为所述终端提供服务的基站。
  20. 根据权利要求11-17任一项所述的装置，其特征在于，所述第一CU-UP和所述第二CU-UP与相同的集中处理节点CU-控制面CP连接，或者，所述第一CU-UP和所述第二CU-UP与不同的集中处理节点CU-控制面CP连接。
  21. 一种计算机可读存储介质，其特征在于，所述可读存储介质中存储有指令，当所述指令被执行时，实现如权利要求1～10任一项所述的方法。
  22. 一种芯片，其特征在于，所述芯片包括处理器和通信接口，所述通信接口和所述处理器耦合，所述处理器用于运行计算机程序或指令，以实现如权利要求1～10任一项所述的方法，所述通信接口用于与所述芯片之外的其它模块进行通信。
  23. 一种通信装置，其特征在于，包括：处理器，其中，所述处理器用于运行存储器中存储的指令以执行如权利要求1～10任一项所述的方法。
  24. 一种通信系统，其特征在于，所述系统包括：分布式处理节点，用于执行如权利要求1-10中任意一项方法中的分布式处理节点的操作；
    终端，用于接收所述分布式处理节点发送的来自第一CU-UP的下行数据包，以及在来自所述第一CU-UP的下行数据包全部发送至所述终端的情况下，接收来自所述分布式处理节点发送的来自第二CU-UP的下行数据包。
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