CN111866971B

CN111866971B - Communication method and device

Info

Publication number: CN111866971B
Application number: CN201910383081.0A
Authority: CN
Inventors: 严乐; 张宏平; 曾清海; 耿婷婷
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2019-04-29
Filing date: 2019-05-09
Publication date: 2021-10-22
Anticipated expiration: 2039-05-09
Also published as: CN111866971A; WO2020221048A1

Abstract

A communication method and a communication device are used for solving the problem that a target base station in the prior art cannot timely send successfully received uplink data packets to a UPF (uplink packet forwarding) and causes data transmission delay. The method comprises the following steps: the source access network device receives a first message from the terminal device. Based on the first message, the source access network device sends a second message to the target access network device, wherein the second message carries a first sequence number, and the first sequence number is used for indicating the target access network device to send the uplink data packet of which the PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element.

Description

Communication method and device

This application claims priority from chinese patent office filed on 29/04/2019, application No. 201910357059.9, entitled "a method and apparatus for communication," the entire contents of which are incorporated herein by reference.

Technical Field

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

Background

In order to reduce the interruption delay of User Equipment (UE) during a moving process and implement 0ms handover interruption, a handover scheme based on a Dual Connectivity (DC) architecture is proposed. In the switching scheme based on the DC architecture, after the switching/role is changed, since data transmission is performed between the target base station and the UE subsequently, the source base station needs to send a Packet Data Convergence Protocol (PDCP) sequence number (service number, SN) PDCP SN value to the target base station, where the UL PDCP SN is used to indicate a PDCP SN of a first lost uplink packet. And after receiving the SN Status Transfer message, the target base station sends the uplink data packet which is successfully received from the UL PDCP SN to the UPF. However, there is currently no good solution for when the source base station sends the UL PDCP SN value to the target base station.

Disclosure of Invention

The application provides a communication method and a communication device, which are used for solving the problem that in the prior art, a target base station cannot timely send successfully received uplink data packets to a UPF (uplink packet forwarding) and the time delay of data transmission is caused.

In a first aspect, the present application provides a communication method, which may be applied to a source access device, or a chip set, or a functional module in the chip that performs the method, and so on. Taking the source access network device as an example, the method includes: the source access network device receives a first message from the terminal device. Based on the first message, the source access network device sends a second message to the target access network device, wherein the second message carries a first sequence number, and the first sequence number is used for indicating the target access network device to send the uplink data packet of which the PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element. Compared with the prior art, after receiving a Radio Resource Control (RRC) reconfiguration complete message sent by the UE, the target base station sends an indication message to the source base station, and after receiving the indication message, the source base station sends a serial number status transfer (SN status transfer) message to the target base station. Or, after receiving an end marker (end marker) sent by the UPF, the source base station sends an SN status transfer message to the target base station, in this embodiment of the present application, when the terminal device switches the uplink PDCP entity to correspond to the target access network device, the terminal device triggers the source access network device to send the first sequence number through the first message, so that the source access network device can send the first sequence number to the target access network device in time, and thus the target access network device can send, after receiving the first sequence number, an uplink data packet whose received PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element, thereby reducing uplink transmission delay in the switching process.

In one possible design, the first message may be a radio resource control Reconfiguration Complete (RRC Reconfiguration Complete) message; alternatively, the first message may also be an end marker message; alternatively, the first message may be a PDCP control protocol data unit (PDCP control PDU). Alternatively, the first message may be a physical layer message. Alternatively, the first message is a media access control element (MAC CE) message.

In one possible design, the second message may be an SN Status Transfer message. Alternatively, the second message may be a secondary node Reconfiguration Complete (SN Reconfiguration Complete) message.

In one possible design, the second message may further carry a second sequence number, where the second sequence number is used to instruct the target access network device to allocate a PDCP sequence number to the downlink data packet from the second sequence number. In the above design, the first sequence number and the second sequence number may be sent simultaneously through one message, so that signaling overhead may be reduced. And the above design has less changes to the 3GPP protocol.

In a possible design, the source access network device may also send a third message to the target access network device, where the third message carries a second sequence number, and the second sequence number is used to instruct the target access network device to allocate a PDCP sequence number to the downlink data packet from the second sequence number. In the above design, the first sequence number and the second sequence number may be sent through different messages, and the flexibility of sending the first sequence number and the second sequence number may be improved by decoupling and sending the first sequence number and the second sequence number.

In a possible design, the first message further carries a third sequence number, where the third sequence number is a maximum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using a key of the source access network device. In the design, the time for the source access network device to send the second message is indicated by carrying the third sequence number in the first message, so that the time delay of uplink data transmission in the switching process can be reduced.

In one possible design, the source access network device may send the second message to the target access network device after receiving all uplink data packets with the PDCP sequence number less than or equal to the third sequence number from the terminal device.

In a possible design, the first message may further carry a fourth sequence number, where the fourth sequence number is a minimum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using a key of the target access network device. In the design, the time for the source access network device to send the second message is indicated by carrying the fourth sequence number in the first message, so that the time delay of uplink data transmission in the switching process can be reduced.

In one possible design, the source access network device may send the second message to the target access network device after receiving all uplink data packets with the PDCP sequence number less than the fourth sequence number from the terminal device.

In a second aspect, the present application provides a communication method, which may be applied to a terminal device, or a chip set, or a functional module in a chip, etc. that performs the method. Taking a terminal device as an example, the method comprises the following steps: and the terminal equipment switches the uplink PDCP entity to correspond to the target access network equipment. The terminal device sends a first message to the source access network device, the first message is used for triggering the sending of a first sequence number from the source access network device to the target access network device, and the first sequence number is used for indicating the target access network device to send an uplink data packet of which the PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element. Compared with the prior art, after receiving the RRC reconfiguration completion message sent by the UE, the target base station sends the indication information to the source base station, and after receiving the indication information, the source base station sends an SN status transfer message to the target base station; or after receiving the end marker sent by the UPF, the source base station sends an SN status transfer message to the target base station, in this embodiment of the present application, when the terminal device switches the uplink PDCP entity to correspond to the target access network device, the terminal device triggers the source access network device to send the first sequence number through the first message, so that the source access network device can send the first sequence number to the target access network device in time, and the target access network device can perform uplink data transmission according to the first sequence number after receiving the first sequence number, thereby reducing the time delay of uplink transmission in the switching process.

In one possible design, the first message may be an RRC Reconfiguration Complete message; alternatively, the first message may also be an end marker message; alternatively, the first message may be a PDCP control PDU. Alternatively, the first message may be a physical layer message. Alternatively, the first message is a MAC CE message.

In a possible design, the first message further carries a second sequence number, where the second sequence number is a maximum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using a key of the source access network device. In the design, the time for the source access network device to send the second message is indicated by carrying the second sequence number in the first message, so that the time delay of uplink data transmission in the switching process can be reduced.

In a possible design, the first message may further carry a third sequence number, where the third sequence number is a minimum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using a key of the target access network device. In the design, the time for the source access network device to send the second message is indicated by carrying the third sequence number in the first message, so that the time delay of uplink data transmission in the switching process can be reduced.

In a third aspect, the present application provides a communication method, including: based on a first message from the terminal device, the source access network device sends a second message to the target access network device, wherein the second message carries a first sequence number, and the first sequence number is used for indicating the target access network device to send an uplink data packet of which the packet data convergence protocol PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element. And the target access network equipment sends the uplink data packet to the user plane functional network element based on the first sequence number. Compared with the prior art, after receiving the RRC reconfiguration completion message sent by the UE, the target base station sends the indication information to the source base station, and after receiving the indication information, the source base station sends an SN status transfer message to the target base station; or after receiving the end marker sent by the UPF, the source base station sends an SN status transfer message to the target base station, in this embodiment of the present application, when the terminal device switches the uplink PDCP entity to correspond to the target access network device, the terminal device triggers the source access network device to send the first sequence number through the first message, so that the source access network device can send the first sequence number to the target access network device in time, and the target access network device can perform uplink data transmission according to the first sequence number after receiving the first sequence number, thereby reducing the time delay of uplink transmission in the switching process.

In one possible design, the terminal device may switch the uplink PDCP entity to correspond to the target access network device and send the first message to the source access network device. In the design, the terminal device triggers the source access network device to send the first sequence number to the target access network device after switching the uplink PDCP entity to correspond to the target access network device, so that the target access network device can perform uplink data transmission to the UPF in time after the terminal device switches the uplink PDCP entity to correspond to the target access network device, and the terminal device does not need to receive the first sequence number after a period of time after switching the uplink PDCP entity to correspond to the target access network device, thereby reducing the time delay of uplink transmission in the switching process.

In one possible design, the second message may be an SN Status Transfer message. Alternatively, the second message may be an SN Reconfiguration Complete message.

In a fourth aspect, the present application provides a communication method, which may be applied to a source access device, or a chip, or a chipset, or a functional module in the chip that performs the method, and so on. Taking the source access network device as an example, the method includes: the source access network equipment sends a first message to the terminal equipment, wherein the first message is used for indicating the terminal equipment to carry out Radio Resource Control (RRC) reconfiguration. And the source access network equipment sends a second message to the target access network equipment, wherein the second message carries a first sequence number, and the first sequence number is used for indicating the target access network equipment to send the uplink data packet of which the packet data convergence protocol PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element. And the source access network equipment receives a third message from the target access network equipment or the user plane function network element. And the source access network equipment sends a fourth message to the target access network equipment based on the third message, wherein the fourth message carries a second sequence number, and the second sequence number is used for indicating the target access network equipment to distribute a PDCP sequence number for the downlink data packet from the second sequence number. In the embodiment of the application, the source access network device sends the first sequence number to the target access network device when instructing the terminal device to perform RRC reconfiguration, so that the target access network device can perform uplink data transmission to the UPF in time after the terminal device switches the uplink PDCP entity to correspond to the target access network device, and does not need to wait for a period of time to receive the first sequence number after the terminal device switches the uplink PDCP entity to correspond to the target access network device, thereby reducing uplink transmission delay in the switching process.

In one possible design, the second message may be sent earlier than the fourth message.

In one possible design, after the source access network device sends the second message to the target access network device, the source access network device may receive a first uplink data packet, where the first uplink data packet is a PDCP protocol data unit, PDCP PDU, from the terminal device, or the first uplink data packet is a PDCP PDU from the terminal device of the target access network device. The source access network device determines that the first uplink data packet is encrypted using a key of the source access network device. And the source access network equipment performs PDCP layer processing on the first uplink data packet to obtain a second uplink data packet, wherein the PDCP layer processing comprises decryption on the first uplink data packet. And when the PDCP sequence number of the second uplink data packet is greater than or equal to the first sequence number, the source access network equipment sends the second uplink data packet to the target access network equipment. When the target access network device receives the second message, the terminal device may not switch the uplink PDCP entity to correspond to the target access network device, so that the terminal device may still perform PDCP layer processing such as ciphering and the like by using the relevant parameters (such as the secret key of the source access network device) of the source access network device within a period of time after the target access network device receives the second message, and obtain the PDCP PDU. Through the design, the uplink data of the terminal equipment can be accurately transmitted to the UPF.

In one possible design, after the source access network device sends the second message to the target access network device, the source access network device receives a third uplink data packet, where the third uplink data packet is a PDCP PDU from the terminal device, or the third uplink data packet is a PDCP PDU from the terminal device of the target access network device. The source access network device determines that the third uplink data packet is encrypted using the key of the source access network device. And the source access network equipment performs PDCP layer processing on the third uplink data packet to obtain a fourth uplink data packet. And when the PDCP sequence number of the fourth uplink data packet is smaller than the first sequence number, the source access network equipment sends the fourth uplink data packet to the user plane functional network element. When the target access network device receives the second message, the terminal device may not switch the uplink PDCP entity to correspond to the target access network device, so that the terminal device may still perform PDCP layer processing such as ciphering and the like by using the relevant parameters (such as the secret key of the source access network device) of the source access network device within a period of time after the target access network device receives the second message, and obtain the PDCP PDU. Through the design, the uplink data of the terminal equipment can be accurately transmitted to the UPF.

In a possible design, if the third message is from the target access network device, the third message may be used to instruct the source access network device to send an SN Status Transfer message; alternatively, if the third message is from a user plane function network element, the third message may be an end marker message.

In a fifth aspect, the present application provides a communication method, which may be applied to a terminal device, or a chip set, or a functional module in a chip that performs the method, and so on. Taking a terminal device as an example, the method comprises the following steps: the terminal equipment receives a first message from the source access network equipment, wherein the first message is used for indicating the terminal equipment to carry out Radio Resource Control (RRC) reconfiguration. And the terminal equipment switches the uplink PDCP entity to correspond to the target access network equipment based on the reception of the first message.

In the embodiment of the application, the terminal device switches the uplink PDCP entity to correspond to the target access network device when receiving the first message instructing the terminal device to perform RRC reconfiguration, so that the terminal device can switch the uplink PDCP entity to correspond to the target access network device in time, thereby shortening a time interval between the time of switching the uplink PDCP entity and the time when the target access network device receives the first sequence number, and reducing uplink transmission delay in the switching process.

In a sixth aspect, the present application provides a communication method, including: the source access network equipment sends a first message to the terminal equipment, wherein the first message is used for indicating the terminal equipment to carry out Radio Resource Control (RRC) reconfiguration. And the terminal equipment switches the PDCP entity to correspond to the target access network equipment based on the reception of the first message. And the source access network equipment sends a second message to the target access network equipment, wherein the second message carries a first sequence number, and the first sequence number is used for indicating the target access network equipment to send the uplink data packet of which the PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element. In the embodiment of the application, the source access network device sends the first sequence number to the target access network device when instructing the terminal device to perform RRC reconfiguration, so that the target access network device can perform uplink data transmission to the UPF in time after the terminal device switches the uplink PDCP entity to correspond to the target access network device, and does not need to wait for a period of time to receive the first sequence number after the terminal device switches the uplink PDCP entity to correspond to the target access network device, thereby reducing uplink transmission delay in the switching process.

In one possible design, the target access network device or the user plane function network element may send a third message to the source access network device. And the source access network equipment sends a fourth message to the target access network equipment based on the third message, wherein the fourth message carries a second sequence number, and the second sequence number is used for indicating the target access network equipment to distribute a PDCP sequence number for the downlink data packet from the second sequence number. The time for the terminal device to switch the uplink PDCP entity is different from the time for the core network device such as the UPF or the AMF to switch the downlink transmission path to the target access network device, for example, the time for the terminal device to switch the uplink PDCP entity to the target access network device may be earlier than the time for the core network device to switch the downlink transmission path to the target access network device. And moreover, the uplink transmission time delay in the switching process can be reduced.

In a seventh aspect, the present application provides a communication method, including: and the source access network equipment sends a second message to the target access network equipment, wherein the second message carries a first sequence number, and the first sequence number is used for indicating the target access network equipment to send the uplink data packet of which the packet data convergence protocol PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element. And the target access network equipment or the user plane functional network element sends a third message to the source access network equipment. And the source access network equipment sends a fourth message to the target access network equipment based on the third message, wherein the fourth message carries a second sequence number, and the second sequence number is used for indicating the target access network equipment to distribute a PDCP sequence number for the downlink data packet from the second sequence number. Because the time for the terminal device to switch the uplink PDCP entity to the target access network device is different from the time for the core network devices such as the UPF and the AMF to switch the downlink transmission path to the target access network device, for example, the time for the terminal device to switch the uplink PDCP entity to the target access network device may be earlier than the time for the core network devices to switch the downlink transmission path to the target access network device. And moreover, the uplink transmission time delay in the switching process can be reduced.

In one possible design, before the source access network device sends the second message to the target access network device, the source access network device may send a first message to the terminal device, where the first message is used to instruct the terminal device to perform RRC reconfiguration. And the terminal equipment switches the uplink PDCP entity to correspond to the target access network equipment based on the reception of the first message. In the design, the terminal device switches the uplink PDCP entity to correspond to the target access network device when receiving the first message instructing the terminal device to perform RRC reconfiguration, so that the terminal device can switch the uplink PDCP entity to correspond to the target access network device in time, thereby shortening a time interval between the time of switching the uplink PDCP entity and the time when the target access network device receives the first sequence number, and reducing uplink transmission delay during the switching process.

In one possible design, after the source access network device sends the second message to the target access network device, the source access network device may receive a third uplink data packet, where the third uplink data packet is a PDCP PDU from the terminal device, or the third uplink data packet is a PDCP PDU from the terminal device of the target access network device. The source access network device determines that the third uplink data packet is encrypted using the key of the source access network device. And the source access network equipment performs PDCP layer processing on the third uplink data packet to obtain a fourth uplink data packet. And when the PDCP sequence number of the fourth uplink data packet is smaller than the first sequence number, the source access network equipment sends the fourth uplink data packet to the user plane functional network element. When the target access network device receives the second message, the terminal device may not switch the uplink PDCP entity to correspond to the target access network device, so that the terminal device may still perform PDCP layer processing such as ciphering and the like by using the relevant parameters (such as the secret key of the source access network device) of the source access network device within a period of time after the target access network device receives the second message, and obtain the PDCP PDU. Through the design, the uplink data of the terminal equipment can be accurately transmitted to the UPF.

In an eighth aspect, the present application provides a communication method, where the method may be applied to a source access device, or a chip, or a chipset, or a functional module in the chip that performs the method, and so on. Taking the source access network device as an example, the method includes: the source access network equipment sends a first message to the target access network equipment, wherein the first message carries a first sequence number, and the first sequence number is used for indicating the target access network equipment to send the uplink data packet of which the PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element. And the source access network equipment sends a second message to the terminal equipment, wherein the second message is used for indicating that an uplink PDCP entity of the terminal equipment is switched to correspond to the target access network equipment. In the embodiment of the application, after receiving an RRC reconfiguration message sent by a source access network device, a terminal device may not switch an uplink PDCP entity to correspond to a target access network device, but after the source access network device sends a first sequence number to the target access network device, under an instruction of the source access network device, the terminal device switches the uplink PDCP entity to correspond to the target access network device.

In one possible design, before the source access network device sends the first message to the target access network device, the source access network device may receive a third message from the target access network device, where the third message is used to instruct the source access network device to send an SN Status Transfer message; or, the source access network device receives a fourth message from the user plane function network element, where the fourth message is used to notify the source access network device that the user plane function network element does not send downlink data to the source access network device any more.

In one possible design, the first message further carries a second sequence number, where the second sequence number is used to instruct the target access network device to allocate a PDCP sequence number to the downlink data packet from the second sequence number. In the above design, the first sequence number and the second sequence number may be sent simultaneously through one message, so that signaling overhead may be reduced. And the above design has less changes to the 3GPP protocol.

In a ninth aspect, the present application provides a communication method, where the method may be applied to a target access network device, or a chip set, or a functional module in the chip that executes the method, and so on. Taking the target access network device as an example, the method includes: the target access network equipment receives a first message from the source access network equipment, wherein the first message carries a first sequence number, and the first sequence number is used for indicating the target access network equipment to send an uplink data packet of which the packet data convergence protocol PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element. And the target access network equipment sends a second message to the terminal equipment, wherein the second message is used for indicating that an uplink PDCP entity of the terminal equipment is switched to correspond to the target access network equipment. In the embodiment of the application, the terminal device may not switch the uplink PDCP entity to correspond to the target access network device after receiving the RRC reconfiguration message sent by the source access network device, but switch the uplink PDCP entity to correspond to the target access network device under the instruction of the target access network device after the source access network device sends the first sequence number to the target access network device.

In a tenth aspect, the present application provides a communication method, which may be applied to a terminal device, or a chip set, or a functional module in a chip, etc. for executing the method. Taking a terminal device as an example, the method comprises the following steps: the terminal equipment receives a first message from the source access network equipment, wherein the first message is used for indicating the terminal equipment to carry out Radio Resource Control (RRC) reconfiguration. And the terminal equipment sends a second message to the target access network equipment, wherein the second message is used for informing the target access network equipment that the terminal equipment completes RRC reconfiguration. And the terminal equipment receives a third message from the source access network equipment or the target access network equipment, wherein the third message is used for indicating the terminal equipment to switch the uplink PDCP entity to correspond to the target access network equipment. And the terminal equipment switches the uplink PDCP entity to correspond to the target access network equipment. In the embodiment of the application, after receiving the RRC reconfiguration message sent by the source access network device, the terminal device may not switch the uplink PDCP entity to correspond to the target access network device, but after the source access network device sends the first sequence number to the target access network device, switching the uplink PDCP entity to correspond to the target access network device under the instruction of the source access network device or the target access network device, in this way, the target access network device can transmit the uplink data to the UPF in time after the terminal device switches the uplink PDCP entity to correspond to the target access network device, therefore, after the terminal device switches the uplink PDCP entity to correspond to the target access network device, due to the fact that the target access network device does not receive the first sequence number and needs to wait for a period of time, the time delay of uplink transmission of the terminal device in the switching process can be further reduced.

In one possible design, the uplink PDCP entity may correspond to the source access network device before the terminal device receives the third message.

In an eleventh aspect, the present application provides a communication method, including: and the target access network equipment sends a third message to the source access network equipment based on the second message from the terminal equipment, wherein the third message is used for indicating the source access network equipment to send a sequence number state transmission SN Status Transfer message. And the source access network equipment sends a fourth message to the target access network equipment based on the third message, wherein the fourth message carries a first sequence number, and the first sequence number is used for indicating the target access network equipment to send the uplink data packet of which the packet data convergence protocol PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element. And the source access network equipment sends a fifth message to the terminal equipment, wherein the fifth message is used for indicating that an uplink PDCP entity of the terminal equipment is switched to correspond to the target access network equipment. In the embodiment of the application, the terminal device may not switch the uplink PDCP entity to correspond to the target access network device after receiving the RRC reconfiguration message sent by the source access network device, but switch the uplink PDCP entity to correspond to the target access network device under the instruction of the source access network device after the source access network device sends the first sequence number to the target access network device.

In one possible design, the terminal device may receive a first message from the source access network device, where the first message is used to instruct the terminal device to perform RRC reconfiguration. And the terminal equipment sends a second message to the target access network equipment, wherein the second message is used for informing the target access network equipment that the terminal equipment completes RRC reconfiguration.

In one possible design, the fourth message may further carry a second sequence number, where the second sequence number is used to instruct the target access network device to allocate a PDCP sequence number to the downlink data packet from the second sequence number. In the above design, the first sequence number and the second sequence number may be sent simultaneously through one message, so that signaling overhead may be reduced. And the above design has less changes to the 3GPP protocol.

In one possible design, the terminal device switches the uplink PDCP entity to correspond to the target access network device based on the fifth message. In the design, after the source access network device sends the first sequence number to the target access network device, the terminal device switches the uplink PDCP entity to correspond to the target access network device under the instruction of the source access network device.

In one possible design, the uplink PDCP entity may correspond to the source access network device before the terminal device receives the fifth message.

In a twelfth aspect, the present application provides a communication method, including: and the target access network equipment sends a third message to the source access network equipment based on the second message from the terminal equipment, wherein the third message is used for indicating the source access network equipment to send a sequence number state transmission SN Status Transfer message. And the source access network equipment sends a fourth message to the target access network equipment based on the third message, wherein the fourth message carries a first sequence number, and the first sequence number is used for indicating the target access network equipment to send the uplink data packet of which the packet data convergence protocol PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element. And the target access network equipment sends a fifth message to the terminal equipment based on the fourth message, wherein the fifth message is used for indicating that the uplink PDCP entity of the terminal equipment is switched to correspond to the target access network equipment. And the terminal equipment switches the uplink PDCP entity to correspond to the target access network equipment based on the fifth message. In the embodiment of the application, after receiving an RRC reconfiguration message sent by a source access network device, a terminal device may not switch an uplink PDCP entity to correspond to a target access network device, but after the source access network device sends a first sequence number to the target access network device, the target access network device instructs to switch the uplink PDCP entity to correspond to the target access network device.

In one possible design, the terminal device may receive a first message from the source access network device, where the first message is used to instruct the terminal device to perform radio resource control, RRC, reconfiguration. And the terminal equipment sends a second message to the target access network equipment, wherein the second message is used for informing the target access network equipment that the terminal equipment completes RRC reconfiguration.

In one possible design, the terminal device switches the uplink PDCP entity to correspond to the target access network device based on the fifth message. In the design, after the source access network device sends the first sequence number to the target access network device, the terminal device switches the uplink PDCP entity to correspond to the target access network device under the instruction of the target access network device.

In a thirteenth aspect, the present application provides a communication method, including: and the user plane function network element sends a third message to the source access network equipment. And the source access network equipment sends a fourth message to the target access network equipment based on the third message, wherein the fourth message carries a first sequence number, and the first sequence number is used for indicating the target access network equipment to send the uplink data packet of which the packet data convergence protocol PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element. And the source access network equipment sends a fifth message to the terminal equipment, wherein the fifth message is used for indicating that an uplink PDCP entity of the terminal equipment is switched to correspond to the target access network equipment. In the embodiment of the application, after receiving an RRC reconfiguration message sent by a source access network device, a terminal device may not switch an uplink PDCP entity to correspond to a target access network device, but after the source access network device sends a first sequence number to the target access network device, the terminal device switches the uplink PDCP entity to correspond to the target access network device under the instruction of the source access network device.

In a fourteenth aspect, the present application provides a communication method, including: and the user plane function network element sends a third message to the source access network equipment. And the source access network equipment sends a fourth message to the target access network equipment based on the third message, wherein the fourth message carries a first sequence number, and the first sequence number is used for indicating the target access network equipment to send the uplink data packet of which the packet data convergence protocol PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element. And the target access network equipment sends a fifth message to the terminal equipment, wherein the fifth message is used for indicating that an uplink PDCP entity of the terminal equipment is switched to correspond to the target access network equipment. In the embodiment of the application, after receiving an RRC reconfiguration message sent by a source access network device, a terminal device may not switch an uplink PDCP entity to correspond to a target access network device, but after the source access network device sends a first sequence number to the target access network device, the target access network device instructs to switch the uplink PDCP entity to correspond to the target access network device.

In a fifteenth aspect, the present application provides a communication apparatus, which may be an apparatus for a communication system, and may also be a chip or a chip set within an apparatus for a communication system, where the apparatus for a communication system may be an access network device or a terminal device. The apparatus may include a processing unit and a transceiver unit. When the apparatus is an apparatus for a communication system, the processing unit may be a processor, and the transceiving unit may be a transceiver; the apparatus may further include a storage unit, which may be a memory; the storage unit is configured to store instructions, and the processing unit executes the instructions stored by the storage unit to enable the access network device to perform the corresponding functions in the first aspect, the fourth aspect, the eighth aspect, or the ninth aspect, or to enable the terminal device to perform the corresponding functions in the second aspect, the fifth aspect, or the tenth aspect. When the apparatus is a chip or a chip set in an access network device, the processing unit may be a processor, and the transceiving unit may be an input/output interface, a pin, a circuit, or the like; the processing unit executes the instructions stored by the storage unit to cause the access network device to perform the corresponding functions in the first aspect, the fourth aspect, the eighth aspect, or the ninth aspect, or cause the terminal device to perform the corresponding functions in the second aspect, the fifth aspect, or the tenth aspect. The memory unit may be a memory unit (e.g., register, cache, etc.) within the chip or chipset, or a memory unit (e.g., read only memory, random access memory, etc.) external to the chip or chipset within a device for a communication system.

In a sixteenth aspect, the present application provides an access network device, including: a processor, a communication interface, and a memory. The communication interface is used for transmitting information, and/or messages, and/or data between the device and other devices. The communication interface may include a transceiver for communicating with terminal devices and/or an interface for communicating with core network devices or other access network devices. The memory is configured to store instructions, and when the apparatus is running, the processor executes the instructions stored in the memory to cause the apparatus to perform the communication method according to any one of the first aspect or the first aspect, or the communication method according to any one of the fourth aspect or the fourth aspect, or the communication method according to any one of the eighth aspect or the eighth aspect, or the communication method according to any one of the ninth aspect or the ninth aspect.

In a seventeenth aspect, the present application provides a terminal device, comprising: a processor, a transceiver, and a memory. The transceiver is used for transmitting information, and/or messages, and/or data between the device and other devices. The memory is configured to store instructions, and when the apparatus is running, the processor executes the instructions stored in the memory to cause the apparatus to perform the communication method according to any one of the second aspect or the second aspect, or the communication method according to any one of the fifth aspect or the fifth aspect, or the communication method according to any one of the tenth aspect or the tenth aspect, or the communication method according to any one of the sixth aspect or the sixth aspect.

In an eighteenth aspect, the present application also provides a computer-readable storage medium having stored therein instructions that, when executed, cause the method of the above-described aspects to be performed.

In a nineteenth aspect, the present application also provides a computer program product comprising instructions that, when executed, cause the method of the above aspects to be performed.

In a twentieth aspect, the present application provides a communication system including a source access network device and a target access network device. The source access network device is configured to send a second message to the target access network device based on a first message from the terminal device, where the second message carries a first sequence number, and the first sequence number is used to instruct the target access network device to send an uplink data packet with a PDCP sequence number greater than or equal to the first sequence number to the user plane functional network element. And the target access network equipment is used for sending the uplink data packet to the user plane functional network element based on the first sequence number from the source access network equipment.

In one possible design, the communication system may further include a terminal device. The terminal device is configured to switch the uplink PDCP entity to correspond to the target access network device, and send a first message to the source access network device.

In one possible design, the first message may be an RRC Reconfiguration Complete message; alternatively, the first message may also be an end marker message; alternatively, the first message may be a PDCP control PDU.

In one possible design, the second message may be an SN Status Transfer message.

In one possible design, the second message may further carry a second sequence number, where the second sequence number is used to instruct the target access network device to allocate a PDCP sequence number to the downlink data packet from the second sequence number.

In a possible design, the source access network device is further configured to send a third message to the target access network device, where the third message carries a second sequence number, and the second sequence number is used to instruct the target access network device to allocate a PDCP sequence number to the downlink data packet from the second sequence number.

In a possible design, the first message may further carry a third sequence number, where the third sequence number is a maximum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using a key of the source access network device.

In a possible design, when the source access network device sends the second message to the target access network device, the source access network device may specifically be configured to: and after receiving all uplink data packets of which the PDCP sequence numbers are less than or equal to the third sequence number from the terminal equipment, sending a second message to the target access network equipment.

In a possible design, the first message may further carry a fourth sequence number, where the fourth sequence number is a minimum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using a key of the target access network device.

In a possible design, when the source access network device sends the second message to the target access network device, the source access network device may specifically be configured to: and after receiving all uplink data packets of which the PDCP sequence numbers are smaller than the fourth sequence number from the terminal equipment, sending a second message to the target access network equipment.

Drawings

Fig. 1 is a flow chart of an architecture of a communication system provided in the present application;

fig. 2 is a schematic flow chart of an exemplary handover process provided herein;

fig. 3 is a schematic flow chart of a communication method provided in the present application;

fig. 4A is a schematic diagram of a user plane protocol stack architecture of a terminal device before handover of an uplink PDCP entity according to the present application;

fig. 4B is a schematic diagram of a user plane protocol stack architecture of a terminal device after handover of an uplink PDCP entity according to the present application;

fig. 5 is a schematic diagram of a handover process/role change process of a terminal device according to the present application;

fig. 6A is a schematic diagram of a user plane protocol stack architecture on a network side (a sending end) before a role provided by the present application is changed;

fig. 6B is a schematic diagram of a user plane protocol stack architecture of a network side (a sending end) after a role provided by the present application is changed;

fig. 6C is a schematic diagram of a handover process/role change process of another terminal device provided in the present application;

fig. 7 is a flow chart illustrating another communication method provided herein;

fig. 8 is a schematic diagram of a handover process/role change process of a terminal device according to the present application;

fig. 9 is a schematic diagram of a handover procedure/role change procedure of another terminal device provided in the present application;

fig. 10 is a flow chart illustrating another communication method provided herein;

fig. 11 is a schematic diagram of a handover process/role change process of a terminal device according to the present application;

fig. 12 is a schematic structural diagram of a communication device provided in the present application;

fig. 13 is a schematic structural diagram of an access network device provided in the present application;

fig. 14 is a schematic structural diagram of a terminal device provided in the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more clear, the present application will be further described in detail with reference to the accompanying drawings.

The handover method provided by the application can be applied to a communication system. The architecture of the communication system may be as shown in fig. 1, and includes at least two access network devices, a terminal device, and a core network device. The communication system according to the embodiment of the present application may be various types of communication systems, for example, Long Term Evolution (LTE), fifth generation (5G) communication systems, evolved UTRA (E-UTRAN), new radio technology (NR), and the like, or a hybrid architecture of multiple types of communication systems, such as a hybrid architecture of LTE and 5G.

The access network device may be a common base station (e.g., a Node B or an eNB), a new radio controller (NR controller), a enode B (gNB) in a 5G system, a Centralized network element (Centralized Unit), a new radio base station, a radio remote module, a micro base station, a relay (relay), a Distributed network element (Distributed Unit), a reception point (TRP), a Transmission Point (TP), or any other radio access device, but the embodiment of the present invention is not limited thereto.

A terminal device, also called a User Equipment (UE), is a device providing voice and/or data connectivity to a user, for example, a handheld device with wireless connection function, a vehicle-mounted device, and so on. Common terminals include, for example: the mobile phone includes a mobile phone, a tablet computer, a notebook computer, a palm computer, a Mobile Internet Device (MID), and a wearable device such as a smart watch, a smart bracelet, a pedometer, and the like.

The core network device may be a Mobility Management Entity (MME), a serving gateway, and the like in the LTE system, or may be an access and mobility management function (AMF), a User Plane Function (UPF), and the like in the 5G system.

The various numbers of the first, second, etc. mentioned in the embodiments of the present application are only used for the convenience of description and are not used to limit the scope of the embodiments of the present application, nor to indicate the sequence. "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. "at least one" means one or more. At least two means two or more. "at least one of," or similar expressions, refer to any combination of these items, including any combination of singular or plural items. For example, at least one (one ) of a, b, or c, may represent: a, b, c, a-b, a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple.

In order to improve user throughput, 3GPP introduces Dual Connectivity (DC) technology. DC, that is, two different base stations are supported to provide data transmission service for one UE at the same time, where a base station where a primary cell (PCell) is located is called a primary base station (master gbb, MgNB) or a primary node (MN), and another base station (i.e., a base station where a primary secondary cell (PSCell) is located) is called a secondary base station (secondary gbb, SgNB) or a secondary node (secondary node, SN), where the primary base station is a control plane anchor point, that is, the UE establishes Radio Resource Control (RRC) connection with the primary base station, and establishes control plane connection between the primary base station and a core network.

In a mobile communication system, as a UE moves, a network switches the UE from a source base station to a target base station for data transmission through a handover process, which is exemplified by an NR system, and a typical handover process is shown in fig. 2:

s201, the source base station (gNB) sends Measurement Control (Measurement Control) to the UE. Specifically, the source base station may send an RRC reconfiguration message including the measurement configuration information to the UE.

S202, the UE sends a Measurement report (Measurement Reports) to the source gNB. Specifically, the UE performs measurement according to the measurement configuration information sent by the source base station, and when a trigger condition of the measurement report is satisfied, the UE may send the measurement report to the source base station. The measurement report includes measurement information of a cell and/or measurement information of a beam, where the measurement information of the cell includes an identifier of the cell (e.g., a Physical Cell Identifier (PCI)), a signal quality of the cell (e.g., a Reference Signal Receiving Power (RSRP)) and/or a Reference Signal Receiving Quality (RSRQ)); the measurement information of a beam includes an identification of the beam (e.g., Synchronization Signal Block (SSB) index (index) or channel state information-reference signal (CSI-RS) index), and optionally includes a signal quality of the beam (e.g., RSRP and/or RSRQ).

S203, the source gNB makes switching decision according to the Measurement Reports sent by the UE. That is, the source gNB determines the target cell according to the Measurement Reports sent by the UE, and decides to switch the UE to the target gNB (i.e., the base station to which the target cell belongs).

S204, the source gNB sends a Handover Request message (Handover Request) to the target gNB. The handover request is used to inform the target gNB terminal device that it is ready to handover to the target gNB.

S205, the target gNB performs access Control (Admission Control), performs handover preparation according to the handover request message, and allocates relevant configuration required for the UE to handover to the target cell, for example, the target cell allocates a cell radio network temporary identifier (C-RNTI) for the UE, and a random access resource required for the UE to access the target cell.

S206, the target gNB sends a Handover Request acknowledgement (Handover Request Ack) to the source gNB.

S207, the source gNB sends a handover request message to the UE. Specifically, in the NR system, the handover message may be an RRC reconfiguration message carrying a reconfiguration withwithsync cell; in the LTE system, the handover message may be an RRC connection reconfiguration message carrying a MobilityControlInfo cell. The handover message includes related information required for the UE to access the target cell, for example, one or more of an identifier (e.g., PCI) of the target cell, frequency information of the target cell, C-RNTI allocated by the target cell to the UE, random access resource information required for the UE to access the target cell, and the like.

S208, the UE detaches from the source gNB and synchronizes to the target gNB. Namely, Detach from old cell, synchronize to new cell.

S209, the source gNB sends a Sequence Number (SN) Status Transfer (SN Status Transfer) message to the target gNB, where the SN Status Transfer message includes a Downlink (DL) Packet Data Convergence Protocol (PDCP) value and an Uplink (UL) PDCP SN value, where the DL PDCP SN value is used to indicate a starting sequence number value when the target base station performs PDCP SN assignment on a downlink packet to which no PDCP SN is assigned (i.e., the target base station assigns a PDCP SN to the downlink packet from the DL PDCP SN value), the UL PDCP SN is used to indicate a first SN of a lost uplink packet, and the SN Status Transfer message may also carry a receiving Status of an uplink packet that the UE needs to retransmit in the target cell.

S210, the source gNB forwards the buffered data packet to the target gNB. Specifically, the source base station may forward the out-of-order uplink data packets received from the UE (starting with the first out-of-order UL data packet and all other data packets (if any) subsequent to the first out-of-order packet) to the target base station; in addition, the source base station may forward the downlink data packet that has been sent to the UE but has not been successfully received by the UE, and the downlink data packet that is newly sent to the source base station by the UPF to the target base station.

S211, the UE performs a random access procedure with the target gNB.

S212, after the random access procedure is successful, the UE sends an RRC reconfiguration complete message to the target gNB, for indicating that the UE is successfully switched to the target base station.

S213, the target gNB sends a Path change Request message (Path Switch Request) to the AMF.

S214, the AMF sends a Modify Bearer Request message (Modify Bearer Request) to the UPF.

S215, the UPF performs downlink path switching.

S216, the UPF sends an end marker (end marker) message to the source gNB. end marker is used to inform the source gNB: the UPF no longer sends downstream data to the source gNB.

S217, the source gNB sends an end marker message to the target gNB.

S218, the UPF sends a Modify Bearer Response message (Modify Bearer Response) to the AMF. Step S216 may be performed before step S218, or may be performed after step S218, without limitation.

S219, the AMF sends a Path change Request acknowledge message (Path Switch Request ACK) to the target gNB.

S220, the target gNB sends a UE Context Release message (UE Context Release) to the source gNB, and the UE Context Release is used for indicating the source gNB to Release the Context of the UE.

S221, the source gNB releases at least one of context, radio resources, etc. of the UE.

In the above handover process, after the source base station sends the handover message to the UE (i.e., step S207), data transmission between the UE and the source base station is interrupted until the UE is successfully handed over to the target base station (i.e., step S211 or step S212), and the UE may perform data transmission with the target base station, that is, after the handover is successful, the UE may resume data transmission over the air interface. Therefore, there is an interruption delay during the handover (e.g., during the period from S207 to S212).

In order to reduce the interruption delay in the switching process, a switching scheme based on a DC architecture is proposed at present. In the switching scheme based on the DC framework, when the link quality of a source base station is good, an auxiliary node adding process is performed, namely, a target base station is added to be SN, after the SN is added, the source base station is MN, the target base station is SN, and UE can simultaneously perform data transmission with the source base station (namely MN) and the target base station (namely SN). When the link quality of the source base station is poor and/or the link quality of the target base station is good, the source base station makes a role switching judgment and instructs the UE to perform switching/role changing. Before the role is changed, the source base station is a main node, and the target base station is an auxiliary node. After the role is changed, the source base station becomes the auxiliary node, and the target base station becomes the main node. After the core network device switches the downlink transmission path to the target base station, the core network device subsequently does not send the DL data to the source base station any more, but sends the DL data to the target base station.

For Downlink (DL), before the role change, the source base station is the primary node (MN), the target base station is the secondary node, the source base station can perform DL packet offloading, i.e. the source base station is used as an anchor point (MN terminated split bearer) for data offloading, and the source base station performs DL packet encryption (assuming that the key used by the source base station encryption is K1). Before the role is changed, the UE may perform data transmission with the source base station and the target base station.

For DL, after the role is changed, the source base station becomes the secondary node and the target base station becomes the primary node (MN). The target base station may perform DL packet offloading, i.e. the target base station serves as an anchor (MN terminated split bearer) for data offloading, and perform DL packet encryption (assuming that the key used by the target base station encryption is K2). After the role is changed, the UE may continue to perform data transmission with the source base station and the target base station until the source base station is released. For example, when the link quality of the source base station is poor, the secondary node release process is performed, that is, the source base station is released, and after the SN release is completed, the UE can only perform data transmission with the target base station.

For Uplink (UL), the UE may maintain UL data transfer with the source base station and the target base station before or after the role change. Before the role is changed, a PDCP entity of the UE corresponds to a source base station, the UE encrypts a data packet using K1 (K1 is a key corresponding to the source base station), after receiving a UL Packet Data Convergence Protocol (PDCP) Protocol Data Unit (PDU) sent by the UE and a target base station (i.e., UL is sent by forking router), the UE sends UL PDCP PDUs to the source base station and the target base station respectively, the target base station forwards the UL PDCP PDUs received from the UE to the source base station, a PDCP layer (PDCP entity) of the source base station removes one or more PDCP headers, decrypts (using the key of the source base station), verifies integrity, reorders, discards duplicate packets, and decompresses headers (using a header decompression context of the source base station), and the source base station sends the processed UL PDCP SDUs to the UPF. After the role is changed, the PDCP entity of the UE corresponds to the target base station, the UE encrypts the data packet using K2 (K2 is a key corresponding to the target base station), after receiving the UL PDCP PDU from the UE and the source base station (i.e., UL performs split bearer transmission, the UE respectively sends the UL PDCP PDU to the source base station and the target base station, the source base station forwards the UL PDCP PDU received from the UE to the target base station), and the PDCP layer (PDCP entity) of the target base station performs one or more of PDCP layer processing such as PDCP header removal, PDCP header decryption (using the key of the target base station), integrity verification, reordering, duplicate packet discard, header decompression (using the header decompression context of the target base station) on the received PDCP PDU.

In the handover scheme based on the DC architecture, since the source base station may continue to perform data transmission with the UE after sending the handover message to the UE, the source base station may send the SN status transfer message to the target base station after a period of time after sending the handover message, for example, when the source base station does not perform DL packet offloading or ciphering any more, but the target base station performs DL packet offloading or ciphering, the source base station sends the SN status transfer message to the target base station.

There are two possible solutions for when the source base station sends an SN Status Transfer message to the target base station. As shown in fig. 5, one method is that, after receiving an RRC reconfiguration complete message sent by the UE, the target base station sends an indication message to the source base station, and after receiving the indication message, the source base station sends an SN status transfer message to the target base station. Or, another method is that the source base station sends an SN status transfer message to the target base station after receiving the end marker sent by the UPF.

For the UL, the target base station cannot transmit uplink data to the UPF until the target base station knows the UL PDCP SN (e.g., the PDCP SN of the first lost uplink packet of the source base station, or the PDCP SN of the first uplink packet that the source base station fails to successfully receive from the UE, or the PDCP SN of the first packet that needs to be sent by the target base station to the UPF), that is, the UL packet with the PDCP sequence number greater than or equal to the UL PDCP SN is sent to the UPF. However, the time when the UE switches the PDCP entity to the target base station is earlier than the time when the source base station informs the target base station of the UL PDCP SN value according to the above two methods. Therefore, after the UE switches the PDCP entity to correspond to the target base station, the target base station cannot acquire the UL PDCP SN value in time, so that the target base station cannot send the successfully received uplink data packet to the UPF in time, thereby causing a delay in data transmission.

Moreover, the time when the UE switches the PDCP entity to correspond to the target base station is not the same as the time when the UPF switches the downlink transmission link to the target base station, so it may be not appropriate to transmit the UL PDCP SN and the DL PDCP SN in the same message.

Based on this, embodiments of the present application provide a communication method and apparatus to solve the problem that a target base station cannot timely acquire an UL PDCP SN value, so that the target base station cannot timely send a successfully received uplink data packet to a UPF, thereby causing a time delay of data transmission. The method and the device are based on the same inventive concept, and because the principles of solving the problems of the method and the device are similar, the implementation of the device and the method can be mutually referred, and repeated parts are not repeated.

Hereinafter, some terms in the present application are explained to be understood by those skilled in the art.

Plural means two or more.

In the embodiment of the present application, an uplink PDCP entity of a terminal device corresponds to a source access network device, and may be understood as one or more of PDCP layer processes such as PDCP SN allocation, header compression (using a header compression context of the source access network), ciphering (using a key of the source access network), integrity protection, and PDCP header addition for an uplink data packet by the uplink PDCP entity of the terminal device using relevant parameters of the source access network device, or may be understood as an anchor point for uplink data transmission by the source access network device. Similarly, the uplink PDCP entity of the terminal device corresponds to the target access network device, and may be understood as one or more of PDCP layer processing such as PDCP SN allocation, header compression (using a header compression context of the target access network), ciphering (using a key of the target access network), integrity protection, and PDCP header addition for the uplink data packet by the uplink PDCP entity of the terminal device using the relevant parameters of the target access network device, or may also be understood as an anchor point for uplink data transmission by the target access network device.

In the embodiment of the present application, the header compression context may also be understood as a header decompression context, specifically, the header compression context is used when performing the header compression operation, and the header decompression context is used when performing the header decompression operation.

In the embodiment of the present application, switching, by the AMF, the downlink path to the target access network device may be understood as: the AMF releases the downlink transmission path with the source access network device and establishes the downlink transmission path with the target access network device, or may also be understood as an anchor point for transmitting downlink control information by the target access network device. The UPF switches the downlink bearer to the target access network device, which can be understood as: the UPF releases the downlink bearer transmission with the source access network device and performs downlink bearer transmission with the target access network device, or can be understood as that the target access network device is used as an anchor point for downlink user plane data transmission.

It should be understood that the naming of each message and information in the embodiment of the present application is only an exemplary illustration, and is not specifically limited to the naming of the message and information involved in the terminal device handover process, and in a specific implementation, each message and information may also be named as another, such as XX, and if XX can also implement the function of the message and information in the embodiment of the present application, XX may also be understood as the message and information in the embodiment of the present application.

In addition, it is to be understood that the terms first, second, etc. in the description of the present application are used for distinguishing between the descriptions and not necessarily for describing a sequential or chronological order.

The following takes the NR system as an example, and the communication method provided in the present application is specifically described with reference to the drawings. It should be understood that, in the embodiment of the present application, only the NR system is taken as an example for description, and a communication system is not particularly limited.

The first embodiment is as follows:

as shown in fig. 3, a communication method provided in an embodiment of the present application includes:

s301, based on the first message from the terminal device, the source access network device sends a second message to the target access network device, where the second message carries a first sequence number, and the first sequence number is used to instruct the target access network device to send an uplink data packet with a PDCP sequence number greater than or equal to the first sequence number to the user plane functional network element.

In some embodiments, the first message may be sent to the source access network device after the terminal device switches the uplink PDCP entity to correspond to the target access network device. That is, before step S301, the terminal device may switch the uplink PDCP entity to correspond to the target access network device, and send the first message to the source access network device.

Or, after determining that all transmitted uplink data packets before the uplink PDCP entity is switched to correspond to the target access network device are successfully received by the source base station, the terminal device transmits the first message to the source access network device. That is, before step S301, the terminal device has determined that uplink data packets transmitted by all UEs before switching the uplink PDCP entity to correspond to the target access network device are successfully received.

It should be noted that before the terminal device switches the uplink PDCP entity to correspond to the target access network device, the uplink PDCP entity of the terminal device corresponds to the source access network device, for example, taking a bearer as an example, before the uplink PDCP entity is switched, an architecture diagram of a user plane protocol station of the terminal device may be as shown in fig. 4A, and after the uplink PDCP entity is switched, an architecture diagram of a user plane protocol stack of the terminal device may be as shown in fig. 4B.

It should be noted that the PDCP entity is bearer granular, and different bearers correspond to different PDCP entities. The first sequence numbers are also of the bearer granularity, and different bearers carry the first sequence numbers corresponding to the respective bearers. If the UE performs multiple uplink bearer sending, the UE sends the first message to the source access network device after the terminal device switches the uplink PDCP entities corresponding to all bearers to correspond to the target access network device, or sends the first message to the source access network device after the terminal device determines that the uplink data packets sent on all bearers are successfully received by the source base station before the terminal device switches the uplink PDCP entities corresponding to all bearers to correspond to the target access network device.

Correspondingly, the first sequence numbers are also of the bearer granularity, and different bearer types carry the first sequence numbers corresponding to the respective bearer types. If the UE performs multiple uplink bearer sending, the first sequence number carried in the second message sent by the source access network device to the target access network device may include multiple first sequence numbers, and each first sequence number corresponds to a bearer one to one.

The first message may be used to instruct the source access network device to send a first sequence number. Illustratively, the first message may be a radio resource control Reconfiguration Complete (RRC Reconfiguration Complete) message. Alternatively, the first message may be an end marker (end marker) message. Alternatively, the first message may be a PDCP control protocol data unit (PDCP control PDU). The end marker may be an empty data packet, and is configured to instruct the source access network device to send the first sequence number, or instruct the terminal device to determine to switch the uplink PDCP entity to correspond to the target access network device.

In addition, the first message may also be a physical layer message, such as Uplink Control Information (UCI). Alternatively, the first message is a media access control element (MAC CE) message. In the method, because the UCI may not be processed by the layers 2 such as the MAC layer, the Radio Link Control (RLC) layer, the PDCP layer, and the like, and the MAC CE may not be processed by the layers 2 such as the RLC layer, the PDCP layer, and the like, the complexity and the processing time in processing the first message may be reduced, so that the speed of transmitting the first message may be increased, the source access network device may trigger the transmission of the first sequence number in time, and the time delay of uplink transmission in the handover process may be reduced.

As a possible implementation manner, the first message may further carry a third sequence number, where the third sequence number is a maximum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using the key of the source access network device, that is, a PDCP sequence number corresponding to a last uplink data packet encrypted by using the key of the source access network device. It should be noted that the third sequence numbers may be of a bearer granularity, and different bearers carry the respective corresponding third sequence numbers. When the terminal device performs multiple uplink bearer sending (for example, W uplink bearer sending is performed in total), if the first message is an RRC Reconfiguration Complete message, the third sequence number carried in the first message may include multiple (for example, W) sequence numbers, and each third sequence number corresponds to a bearer one to one; if the first message is a PDCP control PDU, the PDCP control PDU sent by the terminal device is of a bearer granularity, that is, corresponding to each uplink bearer, the terminal device sends one PDCP control PDU to the source access network device, where the PDCP control PDU includes a third sequence number corresponding to the uplink bearer, and after the source access network device receives the PDCP control PDUs corresponding to all bearers (e.g., the source access network device receives W PDCP control PDUs from the terminal device), the source access network device sends a second message to the target access network device. If the source access network device fails to successfully receive the PDCP control PDUs corresponding to all bearers (for example, the PDCP control PDUs for a certain bearer fail to be sent), one method is that after the target access network device receives an RRC reconfiguration complete message sent by the terminal device, the target access network device sends indication information to the source access network device, and after the source access network device receives the indication information, the source access network device sends a second message to the target access network device, where the second message carries the first sequence number. Or, another method is that after receiving the end marker sent by the UPF, the source access network device sends a second message to the target access network device, where the second message carries the first sequence number.

Further, when the source access network device sends the second message to the target access network device, corresponding to a certain uplink bearer, specifically: and after receiving all uplink data packets of which the PDCP sequence numbers are less than or equal to the third sequence number from the terminal equipment, sending a second message to the target access network equipment. For example, assuming that the third sequence number corresponding to a certain uplink bearer is 8, the source access network device may send the second message to the target access network device after receiving the uplink data packet with the PDCP sequence number of 0-8. When the terminal equipment sends a plurality of uplink bearers, because each bearer carries a third sequence number corresponding to each bearer, the source access network equipment sends a second message to the target access network equipment after receiving all uplink data packets of which the PDCP sequence numbers from the terminal equipment corresponding to each bearer are less than or equal to the third sequence number.

As another possible implementation, the first message may also carry a fourth sequence number, where the fourth sequence number is a minimum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using the key of the target access network device, that is, the PDCP sequence numbers respectively corresponding to the uplink data packets encrypted by using the key of the target access network device. It should be noted that the fourth sequence numbers may be of a bearer granularity, and different bearers carry the fourth sequence numbers corresponding to the respective bearers. When the terminal device performs multiple uplink bearer sending (for example, W uplink bearer sending is performed in total), if the first message is an RRC Reconfiguration Complete message, the fourth sequence number carried in the first message may include multiple (for example, W) sequence numbers, and each fourth sequence number corresponds to a bearer one to one; if the first message is a PDCP control PDU, the PDCP control PDU sent by the terminal device is of a bearer granularity, that is, corresponding to each uplink bearer, the terminal device sends one PDCP control PDU to the source access network device, where the PDCP control PDU includes a fourth sequence number corresponding to the uplink bearer, and after the source access network device receives the PDCP control PDUs corresponding to all bearers (e.g., the source access network device receives W PDCP control PDUs from the terminal device), the source access network device sends a second message to the target access network device. If the source access network device fails to successfully receive the PDCP control PDUs corresponding to all bearers (for example, the PDCP control PDUs for a certain bearer fail to be sent), one method is that after the target access network device receives an RRC reconfiguration complete message sent by the terminal device, the target access network device sends indication information to the source access network device, and after the source access network device receives the indication information, the source access network device sends a second message to the target access network device, where the second message carries the first sequence number. Or, another method is that after receiving the end marker sent by the UPF, the source access network device sends a second message to the target access network device, where the second message carries the first sequence number.

Further, when the source access network device sends the second message to the target access network device, corresponding to a certain uplink bearer, specifically: and after receiving all uplink data packets of which the PDCP sequence numbers are smaller than the fourth sequence number from the terminal equipment, sending a second message to the target access network equipment. For example, assuming that the fourth sequence number corresponding to a certain uplink bearer is 12, the source access network device may send the second message to the target access network device after receiving the uplink data packet with the PDCP sequence number of 0-11. When the terminal equipment sends a plurality of uplink bearers, because each bearer carries a corresponding fourth sequence number, the source access network equipment sends a second message to the target access network equipment after receiving all uplink data packets of which the PDCP sequence numbers from the terminal equipment and corresponding to the bearers are smaller than the fourth sequence number respectively.

In a specific implementation, the first message may not carry the third sequence number or the fourth sequence number.

Further, if the first message carries a third sequence number or a fourth sequence number, the source access network device may determine the first sequence number according to the third sequence number or the fourth sequence number, for example, the source access network device may use a value obtained by adding one to the third sequence number as the first sequence number, or may use the fourth sequence number as the first sequence number. Alternatively, the source access network device may also determine the first sequence number according to other manners, which is not limited herein.

If the first message does not carry the third sequence number or the fourth sequence number, the source access network device may use the currently recorded PDCP SN of the first missing uplink data packet as the first sequence number. Alternatively, the source access network device may determine a PDCP SN as the first sequence number and send the PDCP SN to the target access network device. The specific manner is not limited herein.

S302, the target access network device sends an uplink data packet to the user plane functional network element based on the first sequence number.

In a specific implementation, the first sequence number is of a bearer granularity. For a certain bearer, the target access network device may send an uplink data packet with a PDCP sequence number greater than or equal to the first sequence number to the user plane functional network element. For example, assuming that the first sequence number is 9, the target access network device may send an uplink data packet with a PDCP sequence number greater than or equal to 9 to the user plane function network element, that is, the target access network device sends a corresponding data packet to the user plane function network element starting from the uplink data packet with the PDCP sequence number of 9.

Illustratively, the second message may be an SN Status Transfer message. Alternatively, the second message may also be another Xn message or a newly defined Xn message, for example, the second message may be a secondary node Reconfiguration Complete (SN Reconfiguration Complete) message, and the like, which is not limited herein.

In some embodiments, the first sequence number and the second sequence number may be carried in a message for transmission. The second sequence number may be bearer granular. Therefore, for a certain downlink bearer, the second message may further carry a corresponding second sequence number, where the second sequence number is used to instruct the target access network device to allocate, for the downlink bearer, the PDCP sequence number to the downlink data packet from the second sequence number. That is, the second message may carry the first sequence numbers corresponding to the uplink bearers and the second sequence numbers corresponding to the downlink bearers, respectively.

In other embodiments, the first sequence number and the second sequence number may be sent in two messages, respectively. That is, the source access network device may also send a third message to the target access network device, where the third message carries the second sequence number, that is, the source access network device sends the first sequence number through the second message, and sends the second sequence number through the third message. Wherein the second message may be sent earlier than the third message. The third message may be an SN status transfer message, and the third message may be sent by the source gNB based on indication information from the target gNB, where the indication information is used to instruct the source gNB to send the SN status transfer message, or the third message may also be sent by the source gNB based on an end marker from the UPF. Specifically, the second sequence number may be transmitted as follows: after receiving the RRC reconfiguration complete message sent by the UE, the target gNB sends an indication message to the source gNB, and after receiving the indication message, the source gNB sends an SN status transfer message (i.e., a third message) to the target gNB, where the SN status transfer message carries the second sequence number. Or, after receiving the end marker sent by the UPF, the source gNB sends an SN status transfer message (i.e., a third message) to the target gNB, where the SN status transfer message carries the second sequence number.

Further, for a certain downlink bearer, the target access network device may process the downlink data packet according to the second sequence number after receiving the second sequence number. For example, assuming that the second sequence number is 5, when receiving downlink data sent by the UPF or downlink data which is forwarded by the source access network device and has not been assigned a PDCP sequence number and is from the UPF, the target access network device assigns a PDCP sequence number to the downlink data packet from 5.

In order to better understand the embodiment of the present application, the following describes in detail the communication method provided in the embodiment of the present application in conjunction with a handover scenario of a terminal device. It should be noted that, the terminal device may include, but is not limited to, the following steps S501 to S512 or steps S601 to S612 during the handover, and there may be other operation steps or some operation steps are not executed in the specific handover process, which is not described here.

As shown in fig. 5, the handover procedure/role change procedure of the terminal device may be as follows:

s501, configuring the target gNB into SN (target gNB is configured as SN).

In specific implementation, when the link quality of the source gNB is good, an auxiliary node adding process may be performed, that is, the target gNB is added as an SN, after the SN is added, the source gNB is an MN, the target gNB is an SN, and the UE may perform data transmission with the source gNB (i.e., MN) and the target gNB (i.e., SN) at the same time.

S502, the source gNB and the target gNB transmit data for the UE at the same time.

For DL data transmission, the UPF sends DL data to the source gNB, and the source base station may serve as an anchor point (MN terminated split bearer) for data offloading, that is, the source gNB performs one or more of PDCP layer processing such as PDCP SN allocation, header compression (using a header compression context of the source base station), ciphering (using a key of the source gNB), integrity protection, and adding a PDCP header to the DL data to obtain DL PDCP PDUs, and may directly send one DL PDCP PDU to the UE, and send one DL PDCP PDU to the secondary node (i.e., the target gNB) (e.g., send the DL PDCP PDU to the RLC layer of the target base station), and then the target gNB sends the DL data to the UE. After receiving the DL PDCP PDU sent by the source gNB or the DL PDCP PDU forwarded by the target gNB, the UE performs one or more of PDCP layer processing such as PDCP header removal, decryption (using a key of the source gNB), integrity verification, reordering, duplicate packet discarding, header decompression (using a header decompression context of the source base station) and the like using the relevant parameters of the source gNB.

For UL data transmission, the UE may perform one or more of PDCP layer processing such as PDCP SN allocation, header compression (using a header compression context of the source base station), integrity protection, ciphering (using a key of the source gNB), adding a PDCP header, and the like using relevant parameters of the source gNB, to obtain a UL PDCP PDU. Further, the UE may perform UL PDCP PDU shunting, where one path of UL PDCP PDU is directly sent to the source gNB; one path of UL PDCP PDU is sent to the target gNB, and the target gNB sends the UL PDCP PDU to the source gNB after receiving the UL PDCP PDU. After receiving the UL PDCP PDU, the source gNB performs one or more PDCP layer processes such as PDCP header removal, decryption (using a key of the source gNB), integrity verification, reordering, duplicate packet discarding, header decompression (using a header decompression context of the source base station), and the like, to obtain the UL PDCP SDU.

S503, the source gNB makes a role change decision (role change decision).

When the link quality of the source gNB becomes poor and the link quality of the target gNB becomes good, the source gNB makes a role switching decision. Before the role is changed, the source gNB is the master node, the target gNB is the slave node, the PDCP protocol layer (entity) on the network side is located in the source gNB, taking a downlink bearer as an example, and the user plane protocol stack architecture on the network side (sending end) is as shown in fig. 6A. After the role is changed, the source gNB becomes the secondary node, the target gNB becomes the primary node, the PDCP layer on the network side is located in the target gNB, and a user plane protocol stack architecture on the network side (the sending end) is shown in fig. 6B, taking a downlink bearer as an example.

S504, the source gNB sends a request message to the target gNB requesting Role switch (or Role change), for example, the request message may be a Role switch request (Role change request) message to indicate that the target gNB becomes MN and the source gNB becomes SN. Alternatively, the request message may reuse an existing handover request message. And are not limited.

S505, the target gNB sends a response message to the source gNB. For example, the response message may be a Role change response (Role change response) message. Alternatively, the response message may reuse an existing handover request acknowledge message. And are not limited.

S506, the source gNB sends an RRC Reconfiguration (RRC Reconfiguration) message to the UE to instruct the UE to perform role switching.

The RRC Reconfiguration message may be used to instruct the UE to change the source gNB into the secondary node and change the target gNB into the primary node, for example, instruct the UE to switch the uplink PDCP entity to correspond to the target gNB. Illustratively, the RRC reconfiguration message may include a reconfiguration withsync information element. Alternatively, the RRC reconfiguration message may include a MobilityControlInfo cell.

In specific implementation, after receiving the RRC reconfiguration message sent by the source gNB, the UE may switch the uplink PDCP entity to correspond to the target gNB. After the UE switches the uplink PDCP entity to correspond to the target gNB, one or more of PDCP layer processing such as PDCP SN allocation, header compression (using a header compression context of the target gNB), integrity protection, ciphering (using a key of the target gNB), and adding a PDCP header to the uplink data packet may be performed using the relevant parameters of the target gNB.

Taking a certain uplink bearer as an example, when an uplink PDCP entity of a terminal device (sending end) corresponds to a source gNB, a user plane protocol stack architecture is as shown in fig. 4A; when the uplink PDCP entity of the terminal device corresponds to the target gNB, the user plane protocol stack architecture is as shown in fig. 4B.

S507, the UE sends a first message to the source gNB.

The first message may be used to instruct the source access network device to send the first sequence number.

In addition, the first message may further carry a third sequence number or a fourth sequence number, where the third sequence number is a maximum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using the key of the source access network device, and the fourth sequence number is a minimum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using the key of the target access network device. Optionally, the third sequence number may be of bearer granularity, and the fourth sequence number may be of bearer granularity. When the terminal device sends multiple uplink bearers, the first message may carry the third sequence numbers corresponding to the respective uplink bearers, or the first message may carry the fourth sequence numbers corresponding to the respective uplink bearers. Optionally, the third sequence numbers corresponding to the uplink bearers may be the same or different, and the fourth sequence numbers corresponding to the uplink bearers may be the same or different.

After the UE switches the uplink PDCP entity to correspond to the target gNB, it may continue to perform uplink data transmission with the source gNB and the target gNB. The UE performs one or more of PDCP SN distribution, header compression (adopting a header compression context of a target base station), integrity protection, encryption (adopting a key of a target gNB), addition of PDCP header and other PDCP layer processing to obtain the UL PDCP PDU. Further, the UE may perform UL data packet offloading, where one path of UL data packets (UL PDCP PDU) is directly sent to the master node (i.e., target gNB); and the other path of UL data packet (UL PDCP PDU) is transmitted to the auxiliary node (namely the source gNB), and the source gNB transmits the other path of UL data to the target gNB after receiving the other path of UL data. After receiving the UL PDCP PDU, the target gNB performs one or more of PDCP layer processing such as PDCP header removal, decryption (using a key of the target gNB), integrity verification, reordering, duplicate packet discarding, header decompression (using a header decompression context of the target base station), and the like, to obtain the UL PDCP SDU.

In specific implementation, for a certain uplink bearer, if the first message carries the third sequence number, and for an uplink data packet whose PDCP sequence number is less than or equal to the third sequence number, the UE may perform one or more of PDCP SN allocation, header compression (using a header compression context of the source base station), integrity protection, ciphering (using a key of the source gNB), adding a PDCP header, and other PDCP layer processes by using the relevant parameters of the source gNB, so as to obtain an UL PDCP PDU. Further, the UE may perform UL PDCP PDU shunting, where one path of UL PDCP PDU is directly sent to the source gNB; and the other path of UL PDCP PDU is sent to the target gNB, and the target gNB sends the other path of UL PDCP PDU to the source gNB after receiving the other path of UL PDCP PDU. After receiving the UL PDCP PDU, the source gNB performs one or more PDCP layer processes such as PDCP header removal, decryption (using a key of the source gNB), integrity verification, reordering, duplicate packet discarding, header decompression (using a header decompression context of the source base station), and the like, to obtain the UL PDCP SDU.

In specific implementation, for a certain uplink bearer, if the first message carries the third sequence number, and for an uplink data packet with a PDCP sequence number greater than the third sequence number, the UE may perform one or more of PDCP layer processing such as PDCP SN allocation, header compression (using a header compression context of the target base station), integrity protection, ciphering (using a key of the target gbb), adding a PDCP header, and the like by using relevant parameters of the target gbb, to obtain a UL PDCP PDU. Further, the UE may perform UL PDCP PDU shunting, where one path of UL PDCP PDU is directly sent to the target gNB; and the other path of UL PDCP PDU is sent to the source gNB, and the source gNB sends the other path of UL PDCP PDU to the target gNB after receiving the other path of UL PDCP PDU. After receiving the UL PDCP PDU, the target gNB performs one or more of PDCP layer processing such as PDCP header removal, decryption (using a key of the target gNB), integrity verification, reordering, duplicate packet discarding, header decompression (using a header decompression context of the target base station), and the like, to obtain the UL PDCP SDU.

Or, in another implementation, for a certain uplink bearer, if the first message carries the fourth sequence number, and for an uplink data packet whose PDCP sequence number is smaller than the fourth sequence number, the UE may perform one or more of PDCP layer processing such as PDCP SN allocation, header compression (using a header compression context of the source base station), integrity protection, ciphering (using a key of the source gNB), adding a PDCP header, and the like by using the relevant parameters of the source gNB, to obtain an UL PDCP PDU. Further, the UE may perform UL PDCP PDU shunting, where one path of UL PDCP PDU is directly sent to the source gNB; and the other path of UL PDCP PDU is sent to the target gNB, and the target gNB sends the other path of UL PDCP PDU to the source gNB after receiving the other path of UL PDCP PDU. After receiving the UL PDCP PDU, the source gNB performs one or more PDCP layer processes such as PDCP header removal, decryption (using a key of the source gNB), integrity verification, reordering, duplicate packet discarding, header decompression (using a header decompression context of the source base station), and the like, to obtain the UL PDCP SDU.

Or, in another implementation, for a certain uplink bearer, if the first message carries the fourth sequence number, and for an uplink data packet whose PDCP sequence number is greater than or equal to the fourth sequence number, the UE may perform one or more of PDCP layer processing such as PDCP SN allocation, header compression (using a header compression context of the target base station), integrity protection, ciphering (using a key of the target gbb), adding a PDCP header, and the like by using the relevant parameter of the target gbb, to obtain an UL PDCP PDU. Further, the UE may perform UL PDCP PDU shunting, where one path of UL PDCP PDU is directly sent to the target gNB; and the other path of UL PDCP PDU is sent to the source gNB, and the source gNB sends the other path of UL PDCP PDU to the target gNB after receiving the other path of UL PDCP PDU. After receiving the UL PDCP PDU, the target gNB performs one or more of PDCP layer processing such as PDCP header removal, decryption (using a key of the target gNB), integrity verification, reordering, duplicate packet discarding, header decompression (using a header decompression context of the target base station), and the like, to obtain the UL PDCP SDU.

S508, the UE sends an RRC Reconfiguration Complete (RRC Reconfiguration Complete) message to the target gNB.

It should be noted that step S507 and step S508 are not in strict sequence, and S507 may be executed first and then S508 is executed, or S508 may be executed first and then S507, or S507 and S508 may be executed simultaneously, which is not specifically limited in this embodiment of the application.

S509, the source gNB sends a second message to the target gNB, where the second message carries the first sequence number.

Based on a first message sent by the UE, the source gNB sends a second message to the target gNB, wherein the second message carries the first sequence number. Optionally, the first sequence numbers are of a bearer granularity, and different bearer types respectively correspond to the first sequence numbers. If the UE performs multiple uplink bearer sending, the first sequence number carried in the second message sent by the source base station to the target base station may include multiple first sequence numbers, each first sequence number corresponds to a bearer one-to-one, and the first sequence numbers corresponding to different bearers may be the same or different.

In a specific implementation, for a certain uplink bearer, if the first message carries the third sequence number, the source gNB may send the second message to the target gNB after receiving all uplink data packets from the UE, where the PDCP sequence number of the uplink bearer is less than or equal to the third sequence number. Optionally, if the UE performs multiple uplink bearer sending, corresponding to each uplink bearer in the multiple uplink bearers, after the source base station can respectively receive all uplink data packets whose PDCP sequence number of each bearer is less than or equal to the third sequence number corresponding to the bearer, the source base station sends the second message to the target base station.

Or, for a certain uplink bearer, if the first message carries the fourth sequence number, the source gNB may send the second message to the target gNB after receiving all uplink data packets from the UE, where the PDCP sequence number of the uplink bearer is smaller than the fourth sequence number. Optionally, if the UE performs multiple uplink bearer sending, corresponding to each uplink bearer in the multiple uplink bearers, after the source base station can respectively receive all uplink data packets whose PDCP sequence numbers of the bearers are less than the fourth sequence number corresponding to the bearer, the source base station sends the second message to the target base station.

In addition, the second message may also carry a second sequence number, that is, the first sequence number and the second sequence number are carried in the same message (that is, the second message) for transmission. Or the first sequence number and the second sequence number may be carried in different messages to be sent, where the first sequence number is carried in the second message to be sent, the second sequence number may be carried in a third message to be sent, where the third message may be an SN status transfer message, and the third message may be sent by the source gNB based on indication information from the target gNB, where the indication information is used to instruct the source gNB to send the SN status transfer message, or the third message may also be sent by the source gNB based on an end marker from the UPF. Specifically, the second sequence number may be transmitted as follows: after receiving the RRC reconfiguration complete message sent by the UE, the target gNB sends an indication message to the source gNB, and after receiving the indication message, the source gNB sends an SN status transfer message (i.e., a third message) to the target gNB, where the SN status transfer message carries the second sequence number. Or, after receiving the end marker sent by the UPF, the source gNB sends an SN status transfer message (i.e., a third message) to the target gNB, where the SN status transfer message carries the second sequence number. Optionally, the first sequence number is of bearer granularity, and the second sequence number is of bearer granularity.

Correspondingly, after receiving the first sequence number corresponding to a certain uplink bearer, the target access network device may send an uplink data packet, which is received by the target access network device and whose PDCP sequence number of the bearer is greater than or equal to the first sequence number, to the user plane functional network element. Corresponding to a certain downlink bearer, after receiving the second sequence number corresponding to the bearer, the target access network device may allocate a PDCP SN to downlink data corresponding to the bearer.

S510, the target gNB sends a Path Switch Request (Path Switch Request) message to the AMF. The Path Switch Request message may be used to Request the AMF to Switch the downlink Path to the target gNB.

S511, the AMF sends a Modify Bearer Request (Modify Bearer Request) message to the UPF. The Modify Bearer Request message may be used to Request the UPF to switch to downlink Bearer transmission with the target gNB.

S512, the UPF sends an end marker (end marker) message to the source gNB. The end marker message is used to inform the source gNB: the UPF no longer sends downstream data to the source gNB.

S513, the UPF sends a Modify Bearer Response (Modify Bearer Response) message to the AMF.

It should be noted that step S512, step S511, and step S513 do not have a strict sequence, and step S511, step S512, and step S513 may be executed first; s511 and S512 may be performed simultaneously, and then S513 may be performed; or S511 may be performed first and then S512 and S513 may be performed simultaneously; or S511, then S513, and finally S512 may be executed, and the embodiment of the present application is not specifically limited herein.

S514, the AMF sends a Path Switch Request acknowledge (Path Switch Request ACK) message Path Switch Request acknowledge message (Path Switch Request ACK) to the target gNB.

Step S510 to step S514 are processes of switching the downlink transmission path from the source base station to the target base station by core network devices such as AMF, UPF, and the like. In this embodiment of the present application, a message and an execution sequence related to a process in which core network devices such as an AMF and a UPF switch a downlink transmission path from a source base station to a target base station are not limited, that is, the execution sequence of steps S510 to S514 is not strict, in a specific implementation, the execution sequence of steps S510 to S514 may be changed, and the message related to steps S510 to S514 may also be another message.

After the core network device completes the path change and bearer modification procedures, the source gNB and the target gNB may maintain downlink data transmission with the UE before the source gNB releases the context of the UE (or the source base station is released). Specifically, after the path change and bearer modification process is completed, the UPF may send data to the target gNB, the target gNB performs one or more of PDCP layer processing such as PDCP SN allocation, header compression (using a header compression context of the target base station), ciphering (using a key of the target gNB), integrity protection, and PDCP header addition to the DL data to obtain DL PDCP PDUs, and performs DL offloading, one DL PDCP PDU is directly sent to the UE, one DL PDCP PDU is sent to the secondary node (i.e., the source gNB), and then the source gNB sends the DL PDCP PDUs to the UE. After receiving the DL PDCP PDU sent by the target gNB or the DL PDCP PDU sent by the source gNB, the UE performs one or more of PDCP layer processing such as PDCP header removal, decryption (using a key of the target gNB), integrity verification, reordering, duplicate packet discard, header decompression (using a header decompression context of the target base station) and the like by using relevant parameters of the target gNB.

Until the source gNB (i.e., the SN after the role change) is released, the source gNB disconnects the RRC connection with the UE, and no DL/UL data transmission is performed between the UE and the source gNB.

As shown in fig. 6C, the switching process/role changing process of the terminal device may also be as follows:

step S601 to step S606, refer to step S501 to step S506 specifically, and are not repeated here.

S607, the UE sends an RRC Reconfiguration Complete message to the source gNB. S607 is similar to step S507, so step S607 may refer to the related description of S507. The RRC Reconfiguration Complete message in step S607 may correspond to the first message in step S507.

S608, the source gNB sends a fourth message to the target gNB, where the fourth message may be used to instruct the target gNB to: the UE has completed RRC reconfiguration.

Illustratively, the fourth message may be a secondary node Reconfiguration Complete (SN Reconfiguration Complete) message or other message to instruct the target base station to: and the UE completes the reconfiguration of the target base station. The specific message name is not specifically limited herein.

S609, the source gNB sends a second message to the target gNB, wherein the second message carries the first sequence number. S609 is similar to step S509, so that step S609 may refer to the related description of S509.

In addition, the second message may also carry a second sequence number, which may specifically refer to the related description in step S509 and is not described again.

In a specific implementation, after step S607 is executed, step S608 may not be executed, and step S609 may be directly executed. Or after step S607 is executed, step S608 may also be executed, and the fourth message of step S608 may implement the function of the second message, that is, the fourth message of step S608 may carry the first sequence number.

S610 to S614, refer to step S510 to step S514 specifically, and are not repeated here.

Compared with the prior art, after receiving the RRC reconfiguration completion message sent by the UE, the target base station sends the indication information to the source base station, and after receiving the indication information, the source base station sends an SN status transfer message to the target base station; or, after receiving the end marker sent by the UPF, the source base station sends an SN status transfer message to the target base station, in this embodiment of the present application, when the terminal device switches the uplink PDCP entity to correspond to the target access network device, the terminal device triggers the source access network device to send the first sequence number through the first message, so that the source access network device can send the first sequence number to the target access network device in time, and thus the target access network device can perform uplink data transmission according to the first sequence number after receiving the first sequence number (for example, the target access network device sends an uplink data packet with the received PDCP sequence number greater than or equal to the first sequence number to the user plane functional network element), thereby reducing uplink transmission delay in the switching process.

In addition, because the time for the terminal device to switch the uplink PDCP entity to the target access network device is different from the time for the core network device (e.g., UPF, AMF, etc.) to switch the downlink transmission path to the target access network device, for example, the time for the terminal device to switch the uplink PDCP entity to the target access network device may be earlier than the time for the core network device to switch the downlink transmission path to the target access network device.

Example two:

as shown in fig. 7, a communication method provided in an embodiment of the present application includes:

s701, the source access network equipment sends a second message to the target access network equipment, wherein the second message carries a first sequence number, and the first sequence number is used for indicating the target access network equipment to send the uplink data packet of which the packet data convergence protocol PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element.

Optionally, the first sequence numbers are of a bearer granularity, and different bearer types respectively correspond to the first sequence numbers. If the UE performs multiple uplink bearer sending, the first sequence number carried in the second message sent by the source base station to the target base station may include multiple first sequence numbers, and each first sequence number corresponds to a bearer one to one.

In some embodiments, when the target access network device receives the second message, the terminal device may not switch the uplink PDCP entity to correspond to the target access network device, so that the uplink PDCP entity may still correspond to the source access network device within a period of time after the target access network device receives the second message, that is, the terminal device may still perform one or more of PDCP layer processing such as PDCP SN allocation, header compression (using a header compression context of the source base station), integrity protection, ciphering (using a key of the source gbb), PDCP header addition, and the like using a relevant parameter of the source access network device and the like within a period of time after the target access network device receives the second message, and obtain the PDCP PDU. Further, the terminal device may perform UL data offloading, and one PDCP PDU is directly sent to the source gNB. And the other path of PDCP PDU is sent to the target gNB, and the target gNB sends the other path of PDCP PDU to the source gNB after receiving the other path of PDCP PDU. The source access network device may perform uplink data transmission through a 1-a 5 as follows:

a1, the source access network device receives a first uplink data packet, where the first uplink data packet is a PDCP PDU from the terminal device, or the first uplink data packet is a PDCP PDU from the terminal device of the target access network device. A2 is executed.

A2, the source access network device determines that the first upstream packet is encrypted using the key of the source access network device. A3 is executed.

A3, the source access network device performs one or more items of PDCP layer processing such as PDCP header removal, decryption (using the key of the source access network device for decryption), integrity verification, reordering, duplicate packet discarding, header decompression (using the header decompression context of the source access network device), and the like on the first uplink data packet, to obtain a second uplink data packet (i.e., PDCP SDU). Execute a4 or a 5.

A4, the source access network device sends the second uplink data packet to the target access network device when the PDCP sequence number of the second uplink data packet is greater than or equal to the first sequence number. And the target access network equipment sends the second uplink data packet to the UPF.

A5, the source access network device sends the second uplink data packet to the user plane function network element when the PDCP sequence number of the second uplink data packet is less than the first sequence number.

In a specific implementation, when the source access network device performs uplink data transmission, the source access network device may receive a plurality of first uplink data packets in a single transmission process. Further, the source access network device may determine that the plurality of first uplink data packets are encrypted using a key of the source access network device. And performing one or more items of PDCP layer processing such as PDCP header removal, decryption (using a key of the source access network device for decryption), integrity verification, reordering, duplicate packet discarding, header decompression (using a header decompression context of the source access network device), and the like on the plurality of first uplink data packets to obtain a plurality of second uplink data packets (i.e., PDCP SDUs). And the source access network equipment sends the second uplink data packet of which the PDCP sequence number is greater than or equal to the first sequence number in the second uplink data packets to the target access network equipment, the target access network equipment sends the second uplink data packet to the UPF, and the source access network equipment sends the second uplink data packet of which the PDCP sequence number is less than the first sequence number in the second uplink data packets to the user plane functional network element.

If the source access network device sends the first sequence number to the target access network device, assuming that the terminal device has not switched its uplink PDCP entity to the target access network device, a process of forwarding a packet may be required between the source access network device and the target access network device (see a 1-a 5). In order to reduce the time delay caused by data forwarding between the source access network device and the target access network device, in some embodiments, before the source access network device sends the second message to the target access network device, the source access network device may send a first message to the terminal device, where the first message is used to instruct the terminal device to perform radio resource control RRC reconfiguration (i.e., instruct the terminal device to perform role change). Correspondingly, the terminal device may switch the uplink PDCP entity to correspond to the target access network device based on the reception of the first message.

In the foregoing embodiment, the terminal device switches the uplink PDCP entity to correspond to the target access network device upon receiving the first message, so that data transmission delay caused by data forwarding between the source access network device and the target access network device can be reduced.

S702, the target access network device or the user plane functional network element sends a third message to the source access network device.

Illustratively, if the third message is from the target access network device, the third message is used to instruct the source access network device to send an SN Status Transfer message. Or, if the third message is from the user plane function network element, the third message is an end marker message.

And S703, the source access network device sends a fourth message to the target access network device based on the third message, wherein the fourth message carries a second sequence number, and the second sequence number is used for indicating the target access network device to distribute a PDCP sequence number for the downlink data packet from the second sequence number. Wherein the second message may be sent earlier than the fourth message.

In order to better understand the embodiment of the present application, the following describes in detail the communication method provided in the embodiment of the present application in conjunction with a handover scenario of a terminal device. It should be noted that the terminal device may include, but is not limited to, the following steps S801 to S812 during the handover, and other operation steps may be further included in the specific handover process, which is not described here.

As shown in fig. 8, the handover procedure/role change procedure of the terminal device may be as follows:

s801 to S806, refer to step S501 to step S506 specifically, and are not repeated here.

Alternatively, after step S806 is performed, step S807 may be performed.

S807, the UE switches the uplink PDCP entity to correspond to the target gNB.

After receiving the RRC reconfiguration message of S806, the UE may switch the uplink PDCP entity to correspond to the target gNB at a time that depends on the implementation of the UE, and once the UE receives the RRC reconfiguration message, the UE may switch the uplink PDCP entity to correspond to the target gNB, or after a period of time after receiving the RRC reconfiguration message, the UE may switch the uplink PDCP entity to correspond to the target gNB, which is not limited specifically.

S808, the source gNB sends a second message to the target gNB, wherein the second message carries the first sequence number. Optionally, the first sequence numbers are of a bearer granularity, and different bearer types respectively correspond to the first sequence numbers. The first sequence number carried in the second message may include a plurality of first sequence numbers, and each first sequence number corresponds to a bearer. Step S808 is similar to step S509, so step S808 may refer to the related description of step S509.

Since the UE may not have switched the uplink PDCP entity to correspond to the target gNB when the target gNB receives the second message, data forwarding between the source gNB and the target base station may be performed through a 1-a 5, and specific contents may refer to the above steps a 1-a 5, which is not repeated herein.

Accordingly, after receiving the first sequence number, the target gNB may send the uplink data packet with the PDCP sequence number greater than or equal to the first sequence number to the UPF. Specifically, for an uplink data packet with a PDCP sequence number greater than or equal to the first sequence number, if the uplink data packet is a PDCP SDU from the source gNB, the target gNB may directly send the uplink data packet to the UPF. If the uplink data packet is a PDCP PDU from the terminal device of the source gNB or the uplink data packet is a PDCP PDU from the UE, the target gNB may send the uplink data packet to the UPF after performing one or more PDCP layer processes such as PDCP header removal, decryption (decryption using a key of the target gNB), integrity verification, reordering, duplicate packet discarding, header decompression (header decompression using a header compression context of the target gNB), and the like on the uplink data packet.

S809, the UE sends an RRC Reconfiguration Complete message to the target gNB.

S810, the target gNB sends indication information (i.e. a third message) to the source gNB, where the indication information is used to instruct the source gNB to send an SN status transfer message.

S811, the source gNB sends an SN status transfer message (i.e., a fourth message) to the target gNB, the SN status transfer message carrying the second sequence number. Optionally, the second sequence numbers are of a bearer granularity, and different bearer second sequence numbers respectively correspond to the different bearer second sequence numbers. The second sequence number carried in the fourth message may include a plurality of second sequence numbers, and each second sequence number corresponds to a bearer.

S812 to S816, refer to step S510 to step S514 specifically, and are not described herein repeatedly.

As shown in fig. 9, the switching process/role changing process of the terminal device may also be as follows:

s901 to S909, refer to step S801 to step S809 specifically, and are not repeated here.

S910, the target gNB sends a Path Switch Request message to the AMF. The Path Switch Request message may be used to Request the AMF to Switch the downlink Path to the target gNB.

S911, the AMF sends a Modify Bearer Request message to the UPF. The Modify Bearer Request message may be used to Request the UPF to switch to downlink Bearer transmission with the target gNB.

S912, the UPF sends an end marker message (i.e., a third message) to the source gNB. The end marker message is used to inform the source gNB: the UPF no longer sends downstream data to the source gNB.

S913, the source gNB sends an SN status transfer message (i.e. a fourth message) to the target gNB, where the SN status transfer message carries the second sequence number.

S914, the UPF sends a Modify Bearer Response message to the AMF.

It should be noted that step S912, step S911 and step S914 do not have a strict sequence, and step S911, step S912 and step S914 may be executed first, and step S914 is executed last; or S911 may be performed first and then S912 and S914 may be performed simultaneously; or S911, then S914, and finally S912 may be executed, and the embodiment of the present application is not limited in this embodiment.

S915, the AMF sends a Path Switch Request ACK message to the target gNB.

Step S910 to step S915 are processes of switching the downlink transmission path from the source base station to the target base station by the core network device such as the AMF, the UPF, and the like. In this embodiment of the present application, a message and an execution sequence related to a process in which a core network device such as an AMF or an UPF switches a downlink transmission path from a source base station to a target base station are not limited, that is, the execution sequence of steps S910 to S915 is not strict, in a specific implementation, the execution sequence of steps S910 to S915 may be changed, and the message related to steps S910 to S915 may also be another message.

Compared with the prior art, after receiving the RRC reconfiguration completion message sent by the UE, the target base station sends the indication information to the source base station, and after receiving the indication information, the source base station sends an SN status transfer message to the target base station; or, after receiving the end marker sent by the UPF, the source base station sends an SN status transfer message to the target base station. Therefore, the target access network device can transmit uplink data to the UPF in time after the terminal device switches the uplink PDCP entity to correspond to the target access network device, and the terminal device does not need to wait for a period of time to receive the first sequence number after switching the uplink PDCP entity to correspond to the target access network device, so that the uplink transmission delay in the switching process can be reduced.

In addition, because the time for the terminal device to switch the uplink PDCP entity to the target access network device is different from the time for the core network device to switch the downlink transmission path to the target access network device, for example, the time for the terminal device to switch the uplink PDCP entity to the target access network device may be earlier than the time for the core network device to switch the downlink transmission path to the target access network device.

Example three:

as shown in fig. 10, a communication method provided in an embodiment of the present application includes:

s1001, the user plane functional network element sends a third message to the source access network device. The third message may be an end marker, and the end marker message is used to notify the source access network device to: the UPF no longer sends the downstream data to the source access network device.

S1002, the source access network device sends a fourth message to the target access network device based on the third message, wherein the fourth message carries a first sequence number, and the first sequence number is used for indicating the target access network device to send the uplink data packet of which the packet data convergence protocol PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element. The fourth message may be an SN Status Transfer message. Optionally, the first sequence numbers are of a bearer granularity, and different bearer types respectively correspond to the first sequence numbers. The first sequence number carried in the fourth message may include a plurality of first sequence numbers, and each first sequence number corresponds to a bearer. Step S1003 or S1004 is executed.

In addition, the fourth message may further carry a second sequence number, where the second sequence number is used to instruct the target access network device to allocate a PDCP sequence number to the downlink data packet from the second sequence number. Optionally, the second sequence numbers are of a bearer granularity, and different bearer second sequence numbers respectively correspond to the different bearer second sequence numbers. The second sequence number carried in the fourth message may include a plurality of second sequence numbers, and each second sequence number corresponds to a bearer.

S1003, the source access network device sends a fifth message to the terminal device, wherein the fifth message is used for indicating the terminal device to switch the uplink PDCP entity to correspond to the target access network device. Step S1003 and step SS1002 are not in strict sequence, and S1003 may be executed first and then S1002 is executed, or S1002 may be executed first and then S1003 is executed, or S1002 and S1003 are executed simultaneously, which is not specifically limited in this embodiment of the present application.

S1004, the target access network device sends a fifth message to the terminal device based on the fourth message, where the fifth message is used to instruct the terminal device to switch the uplink PDCP entity to correspond to the target access network device.

In a specific implementation, after step S1002 is executed, specifically, S1003 or S1004 may be determined based on a protocol or a setting of the system.

Illustratively, the fifth message may be a physical layer message, such as Downlink Control Information (DCI), or the fifth message may be a MAC CE, or the fifth message may be an RRC message.

In some embodiments, the terminal device may switch the uplink PDCP entity to correspond to the target access network device based on the fifth message. Before the terminal device receives the fifth message, the uplink PDCP entity may correspond to the source access network device. For example, for a certain uplink bearer, before the handover of the uplink PDCP entity corresponding to the bearer, the schematic diagram of the user plane protocol stack architecture of the terminal device may be as shown in fig. 4A, and after the handover of the uplink PDCP entity corresponding to the bearer, the schematic diagram of the user plane protocol stack architecture of the terminal device may be as shown in fig. 4B.

In order to better understand the embodiment of the present application, the following describes in detail the communication method provided in the embodiment of the present application in conjunction with a handover scenario of a terminal device. It should be noted that the terminal device may include, but is not limited to, the following steps S1101 to S1115 during the handover, and other operation steps may be further included in the specific handover process, which is not described here.

As shown in fig. 11, the handover procedure/role change procedure of the terminal device may be as follows:

s1101 to S1105, refer to step S501 to step S505 specifically, and are not repeated here.

S1106, the source gNB sends an RRC Reconfiguration (RRC Reconfiguration) message to the UE to instruct the UE to perform role switching.

In specific implementation, after the UE receives the RRC reconfiguration message sent by the source gNB, the uplink PDCP entity remains corresponding to the source gNB. The UE may perform one or more PDCP SN allocation, header compression (using a header compression context of the source base station), integrity protection, ciphering (using a key of the source base station), PDCP layer processing such as adding a PDCP header to the uplink data packet by using the relevant parameter of the source gNB, to obtain an UL PDCP PDU. Further, the UE may perform UL forking, and one path of UL PDCP PDU is directly sent to the source gNB; one path of UL PDCP PDU is sent to the target gNB, and the target gNB sends the UL PDCP PDU to the source gNB after receiving the UL PDCP PDU. And after receiving the UL PDCP PDU, the source gNB performs one or more items of PDCP layer processing such as PDCP packet header removal, decryption, integrity verification, reordering, repeated packet discarding, header decompression and the like to obtain the UL PDCP SDU. S1107 is executed.

S1107, the UE sends an RRC Reconfiguration Complete message to the target gNB. S1108 is performed.

S1108, the target gNB sends a Path Switch Request message to the AMF. The Path Switch Request message may be used to Request the AMF to Switch the downlink Path to the target gNB. S1109 is performed.

S1109, the AMF sends a Modify Bearer Request message to the UPF. The Modify Bearer Request message may be used to Request the UPF to switch to downlink Bearer transmission with the target gNB.

S1110, the UPF sends an end marker message to the source gNB. The end marker message is used to inform the source gNB: the UPF no longer sends downstream data to the source gNB. S1111 is executed.

S1111, the source gNB sends an SN Status Transfer message to the target gNB, wherein the SN Status Transfer message carries the first sequence number and the second sequence number. Alternatively, the source gNB may send the first sequence number and the second sequence number to the target gNB through other messages, which is not limited herein.

Optionally, the source base station may send the UL PDCP SDU whose UL PDCP SN is smaller than the first sequence number to the UPF, and send the UL PDCP SDU whose UL PDCP SN is greater than or equal to the first sequence number and/or the UL PDCP PDU whose UL PDCP SN is greater than or equal to the first sequence number to the UPF; after the target base station receives the first sequence number, the target base station may send the UL PDCP SDUs from the source base station to the UPF, and the target base station may perform PDCP layer processing on the UL PDCP PDUs from the UE and/or the source base station and send the processed UL PDCP SDUs to the UPF, that is, the target base station sends the UL PDCP SDUs with the UL PDCP SN greater than or equal to the first sequence number to the UPF.

Execute S1112a or execute S1112 b.

S1112a, the source gNB sends a fifth message to the UE. S1113 is performed.

S1112b, the target gNB sends a fifth message to the UE. S1113 is performed.

In a specific implementation, after the step S1111 is executed, specifically, the step S1112a or the step S1112b may be determined based on a protocol or a setting of the system.

S1113, the terminal device switches the uplink PDCP entity to correspond to the target gNB.

Step S1108 to step S1113 are processes in which core network devices such as AMF and UPF switch the downlink transmission path from the source base station to the target base station. In this embodiment of the present application, a message and an execution order involved in a process that a core network device such as an AMF and a UPF switches a downlink transmission path from a source base station to a target base station are not limited, that is, the execution order of steps S1108 to S1113 is not strict, in a specific implementation, the execution order of steps S1108 to S1113 may be changed, and the message involved in steps S1108 to S1113 may also be another message.

In specific implementation, after receiving the fifth message sent by the source gNB or the target base station, the UE switches the uplink PDCP entity to correspond to the target gNB. The UE may perform one or more PDCP layer processes, such as PDCP SN allocation, header compression (using a header compression context of the target base station), integrity protection, ciphering (using a key of the target base station), adding a PDCP header, and the like, using the relevant parameters of the target gNB, to obtain an UL PDCP PDU. Further, the UE may perform UL shunting, where one path of UL PDCP PDU is directly sent to the target gNB; and the other path of UL PDCP PDU is sent to the source gNB, and the source gNB sends the other path of UL PDCP PDU to the target gNB after receiving the other path of UL PDCP PDU. After receiving the UL PDCP PDU, the target gNB performs one or more of PDCP layer processing such as PDCP packet header removal, decryption, integrity verification, reordering, repeated packet discarding, header decompression and the like to obtain the UL PDCP SDU, and the target base station sends the UL PDCP SDU to the UPF.

S1114, the UPF sends a Modify Bearer Response (Modify Bearer Response) message to the AMF. S1115 is executed.

It should be noted that step S1109, step S1110 and step S1114 do not have a strict sequence, and step S1109 may be executed first, step S1110 may be executed later, and step S1114 may be executed last; or S1109 may be performed first and then S1110 and S1114 may be performed simultaneously; or S1109 may be executed first, then S1114 is executed, and finally S1110 is executed, which is not specifically limited in this embodiment of the application.

S1115, the AMF sends a Path Switch Request ACK message to the target gNB.

In this embodiment of the present application, after receiving an RRC reconfiguration message sent by a source access network device, a terminal device may not switch an uplink PDCP entity to correspond to a target access network device (that is, after receiving the RRC reconfiguration message sent by the source access network device, the terminal device may keep the uplink PDCP entity corresponding to the source access network device), but after the source access network device sends a first sequence number to the target access network device, the terminal device switches the uplink PDCP entity to correspond to the target access network device after receiving an instruction sent by the source access network device or the target access network device, and then the terminal device switches the uplink PDCP entity to correspond to the target access network device. By the method, the target access network equipment can transmit the uplink data to the UPF in time after the terminal equipment switches the uplink PDCP entity to correspond to the target access network equipment, so that the condition that the target access network equipment needs to wait for a period of time because the target access network equipment does not receive the first sequence number after the terminal equipment switches the uplink PDCP entity to correspond to the target access network equipment can be avoided, and the time delay of the uplink transmission of the terminal equipment in the switching process can be further reduced.

In the embodiment shown in fig. 11, after receiving the end marker message sent by the UPF (as in step S1110), the source gNB sends an SN Status Transfer message to the target gnnb (as in step S1111), optionally, in another embodiment, the source gNB sends the SN Status Transfer message to the target gnnb, or the target gNB triggers the source base station to send the SN Status Transfer message through indication information after receiving an RRC Reconfiguration Complete message from the UE, where the indication information (which is sent by the target base station) is used to instruct the source gNB to send the SN Status Transfer message to the target gNB. In these embodiments, the switching process of the terminal device is similar to that in fig. 11, and the specific process may refer to fig. 11, and the description of the similar process is omitted.

In the second and third embodiments of the present application, the terminal device switches the uplink PDCP entity to the relevant description corresponding to the target access network device, and the terminal device switches the uplink PDCP entity to the uplink data transmission process after corresponding to the target access network device, and the core network devices such as the UPF and the AMF complete the path change, the downlink data transmission process after the bearer modification process, and the like.

Based on the same inventive concept as the method embodiment, the embodiment of the present application provides a communication apparatus, which may have a structure as shown in fig. 12 and includes a transceiving unit 1201 and a processing unit 1202.

In a specific implementation manner, the communication apparatus may be specifically used to implement the method performed by the source access network device in the embodiments shown in fig. 3 to fig. 6C, and the apparatus may be the source access network device itself, or may be a chip or a chip set in the source access network device, or a part of a chip in the chip for performing the function of the related method. The transceiving unit 1201 is configured to transceive a message. A processing unit 1202, configured to control the transceiving unit 1201 to perform: receiving a first message from a terminal device; and sending a second message to the target access network equipment based on the first message, wherein the second message carries a first sequence number, and the first sequence number is used for indicating the target access network equipment to send the uplink data packet of which the packet data convergence protocol PDCP sequence number is greater than or equal to the first sequence number to the user plane functional network element.

Illustratively, the first message may be an RRC Reconfiguration Complete message; alternatively, the first message may be an end marker message; alternatively, the first message may be a PDCP control PDU.

Illustratively, the second message may be an SN Status Transfer message.

In a specific implementation, the second message may further carry a second sequence number, where the second sequence number is used to instruct the target access network device to allocate a PDCP sequence number to the downlink data packet from the second sequence number.

In an implementation manner, the processing unit 1202 is further configured to control the transceiver unit 1201 to send a third message to the target access network device, where the third message carries a second sequence number, and the second sequence number is used to instruct the target access network device to allocate a PDCP sequence number to the downlink data packet from the second sequence number.

For example, the first message may further carry a third sequence number, where the third sequence number is a maximum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using a key of the source access network device.

In an implementation manner, when the processing unit 1202 controls the transceiving unit 1201 to send the second message to the target access network device, specifically: after receiving all uplink data packets with the PDCP sequence number less than or equal to the third sequence number from the terminal device, the control transceiving unit 1201 sends a second message to the target access network device.

For example, the first message may further carry a fourth sequence number, where the fourth sequence number is a minimum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using a key of the target access network device.

In an implementation manner, when the processing unit 1202 controls the transceiving unit 1201 to send the second message to the target access network device, specifically: after receiving all uplink data packets with the PDCP sequence number smaller than the fourth sequence number from the terminal device, the control transceiving unit 1201 sends a second message to the target access network device.

In a specific implementation manner, the communication apparatus may be specifically used to implement the method performed by the terminal device in the embodiments shown in fig. 3 to fig. 6C, and the apparatus may be the terminal device itself, or may be a chip or a chip set in the terminal device or a part of the chip for performing the function of the related method. Wherein, the processing unit 1202 is configured to switch the PDCP entity to correspond to the target access network device. A transceiving unit 1201, configured to send a first message to a source access network device, where the first message is used to trigger sending of a first sequence number from the source access network device to a target access network device, and the first sequence number is used to instruct the target access network device to send an uplink data packet with a PDCP sequence number greater than or equal to the first sequence number to a user plane function network element.

For example, the first message may further carry a second sequence number, where the second sequence number is a maximum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using a key of the source access network device.

For example, the first message may further carry a third sequence number, where the third sequence number is a minimum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using a key of the target access network device.

The division of the modules in the embodiments of the present application is schematic, and only one logical function division is provided, and in actual implementation, there may be another division manner, and in addition, each functional module in each embodiment of the present application may be integrated in one processor, may also exist alone physically, or may also be integrated in one module by two or more modules. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. It is understood that the functions or implementations of the respective modules in the embodiments of the present application may further refer to the related description of the method embodiments.

Fig. 13 is a schematic structural diagram of an access network device (e.g., a source access network device or a target access network device), which may be a structural diagram of a base station, provided in an embodiment of the present application. As shown in fig. 13, the base station may be applied to the system shown in fig. 1, and performs the functions of the source access network device or the target access network device in the method embodiments described in fig. 3 to fig. 11. The base station 130 may include one or more Distributed Units (DUs) 1301 and one or more Centralized Units (CUs) 1302. The DU1301 may include at least one antenna 13011, at least one radio frequency unit 13012, at least one processor 13013 and at least one memory 13014. The DU1301 portion is mainly used for transceiving radio frequency signals, converting radio frequency signals and baseband signals, and partially processing baseband. CU1302 may comprise at least one processor 13022 and at least one memory 13021. The CU1302 and the DU1301 can communicate with each other through an interface, wherein a Control plane (Control Plan) interface can be Fs-C, such as F1-C, and a User plane (User Plan) interface can be Fs-U, such as F1-U.

The CU1302 section is mainly used for baseband processing, base station control, and the like. The DU1301 and the CU1302 may be physically located together or physically located separately, that is, distributed base stations. The CU1302 is a control center of the base station, and may also be referred to as a processing unit, and is mainly used for performing a baseband processing function. For example, the CU1302 may be configured to control the base station to perform the operation procedure related to the source access network device or the target access network device in the method embodiments described in fig. 3 to fig. 11.

Specifically, the baseband processing on the CU and the DU may be divided according to the protocol layers of the radio network, for example, the functions of the PDCP layer and the above protocol layers are set in the CU, and the functions of the protocol layers below the PDCP layer, for example, the functions of the RLC layer and the MAC layer, are set in the DU. For another example, a CU implements functions of an RRC and PDCP layer, and a DU implements functions of an RLC, MAC, and Physical (PHY) layer.

Further, optionally, the base station 130 may include one or more radio frequency units (RUs), one or more DUs, and one or more CUs. Wherein, a DU may include at least one processor 13013 and at least one memory 13014, an RU may include at least one antenna 13011 and at least one radio frequency unit 13012, and a CU may include at least one processor 13022 and at least one memory 13021.

In an example, the CU1302 may be formed by one or more boards, and the multiple boards may jointly support a radio access network with a single access indication (e.g., a 5G network), or may respectively support radio access networks with different access schemes (e.g., an LTE network, a 5G network, or other networks). The memory 13021 and processor 13022 may serve one or more boards. That is, the memory and processor may be provided separately on each board. Multiple boards may share the same memory and processor. In addition, each single board can be provided with necessary circuits. The DU1301 may be composed of one or more boards, where the boards may jointly support a radio access network with a single access instruction (e.g., a 5G network), and may also respectively support radio access networks with different access schemes (e.g., an LTE network, a 5G network, or other networks). The memory 13014 and processor 13013 may serve one or more boards. That is, the memory and processor may be provided separately on each board. Multiple boards may share the same memory and processor. In addition, each single board can be provided with necessary circuits.

Fig. 14 is a schematic structural diagram of a terminal device according to an embodiment of the present application. The terminal device may be adapted to the system shown in fig. 1, and performs the functions of the terminal device in the method embodiments described in fig. 3 to fig. 11. For convenience of explanation, fig. 14 shows only main components of the terminal device. As shown in fig. 14, the terminal device 140 includes a processor, a memory, a control circuit, an antenna, and an input-output means. The processor is mainly configured to process the communication protocol and the communication data, control the entire terminal device, execute a software program, and process data of the software program, for example, to support the terminal device to perform the actions described in the method embodiments of fig. 3 to 11. The memory is used primarily for storing software programs and data. The control circuit is mainly used for converting baseband signals and radio frequency signals and processing the radio frequency signals. The control circuit and the antenna together, which may also be called a transceiver, are mainly used for transceiving radio frequency signals in the form of electromagnetic waves. Input and output devices, such as touch screens, display screens, keyboards, etc., are used primarily for receiving data input by a user and for outputting data to the user.

When the terminal device is started, the processor can read the software program of the memory, interpret and execute the instruction of the software program, and process the data of the software program. When data needs to be sent wirelessly, the processor outputs a baseband signal to the radio frequency circuit after performing baseband processing on the data to be sent, and the radio frequency circuit performs radio frequency processing on the baseband signal and sends the radio frequency signal outwards in the form of electromagnetic waves through the antenna. When data is sent to the terminal equipment, the radio frequency circuit receives radio frequency signals through the antenna, converts the radio frequency signals into baseband signals and outputs the baseband signals to the processor, and the processor converts the baseband signals into the data and processes the data.

Those skilled in the art will appreciate that fig. 14 shows only one memory and one processor for ease of illustration. In an actual terminal device, there may be multiple processors and multiple memories. The memory may also be referred to as a storage medium or a storage device, etc. The memory may be a memory element on the same chip as the processor, that is, an on-chip memory element, or a separate memory element, which is not limited in this embodiment.

As an optional implementation manner, the terminal device may include a baseband processor and a central processing unit, where the baseband processor is mainly used to process a communication protocol and communication data, and the central processing unit is mainly used to control the whole terminal device, execute a software program, and process data of the software program. The processor of fig. 14 may integrate the functions of the baseband processor and the central processing unit, and those skilled in the art will understand that the baseband processor and the central processing unit may be independent processors, and are interconnected through a bus or the like. Those skilled in the art will appreciate that the terminal device may include a plurality of baseband processors to accommodate different network formats, the terminal device may include a plurality of central processors to enhance its processing capability, and various components of the terminal device may be connected by various buses. The baseband processor can also be expressed as a baseband processing circuit or a baseband processing chip. The central processing unit can also be expressed as a central processing circuit or a central processing chip. The function of processing the communication protocol and the communication data may be built in the processor, or may be stored in the memory in the form of a software program, and the processor executes the software program to realize the baseband processing function.

In the embodiment of the present application, an antenna and a control circuit having a transceiving function may be regarded as the transceiving unit 1401 of the terminal device 140, for example, for supporting the terminal device to perform a receiving function and a transmitting function. The processor 1402 having the processing function is regarded as the processing unit 1402 of the terminal device 140. As shown in fig. 14, the terminal device 140 includes a transceiving unit 1401 and a processing unit 1402. A transceiver unit may also be referred to as a transceiver, a transceiving device, etc. Alternatively, a device for implementing a receiving function in the transceiving unit 1401 may be regarded as a receiving unit, and a device for implementing a transmitting function in the transceiving unit 1401 may be regarded as a transmitting unit, that is, the transceiving unit 1401 includes a receiving unit and a transmitting unit, the receiving unit may also be referred to as a receiver, an input port, a receiving circuit, and the like, and the transmitting unit may be referred to as a transmitter, a transmitting circuit, and the like.

The processor 1402 may be configured to execute the instructions stored in the memory, so as to control the transceiver unit 1401 to receive and/or transmit signals, thereby implementing the functions of the terminal device in the above method embodiments. The processor 1402 also includes an interface to implement signal input/output functions. As an implementation manner, the function of the transceiving unit 1401 may be considered to be implemented by a transceiving circuit or a dedicated chip for transceiving.

The embodiment of the present invention further provides a computer-readable storage medium, which is used for storing computer software instructions required to be executed for executing the processor, and which contains a program required to be executed for executing the processor.

In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, cause the processes or functions described in accordance with the embodiments of the application to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored in a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, from one website site, computer, server, or data center to another website site, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device including one or more available media integrated servers, data centers, and the like. The usable medium may be a magnetic medium (e.g., floppy Disk, hard Disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., Solid State Disk (SSD)), among others.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.

Claims

1. A method of communication, comprising:

receiving a first message from a terminal device, wherein the first message is triggered after the terminal device switches an uplink Packet Data Convergence Protocol (PDCP) entity to correspond to a target access network device;

and sending a second message to the target access network equipment based on the first message, wherein the second message carries a first sequence number, and the first sequence number is used for indicating the target access network equipment to send an uplink data packet of which the packet data convergence protocol PDCP sequence number is greater than or equal to the first sequence number to a user plane functional network element.

2. The method of claim 1, wherein the first message is a radio resource control Reconfiguration Complete RRC Reconfiguration Complete message; or

The first message is an end marker message; or

The first message is a PDCP control protocol data unit PDCP control PDU.

3. The method of claim 1, wherein the second message is a sequence number Status Transfer (SN Status Transfer) message.

4. The method of claim 1, wherein the second message further carries a second sequence number, and the second sequence number is used to instruct the target access network device to assign a PDCP sequence number for the downlink data packet from the second sequence number.

5. The method of claim 1, wherein the method further comprises:

and sending a third message to the target access network equipment, wherein the third message carries a second sequence number, and the second sequence number is used for indicating the target access network equipment to distribute a PDCP sequence number for a downlink data packet from the second sequence number.

6. The method of any one of claims 1 to 5, wherein the first message further carries a third sequence number, and the third sequence number is a maximum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using a key of the source access network device.

7. The method of claim 6, wherein sending a second message to the target access network device comprises:

and after receiving all uplink data packets of which the PDCP sequence numbers are less than or equal to the third sequence number from the terminal equipment, sending the second message to the target access network equipment.

8. The method of any one of claims 1 to 5, wherein the first message further carries a fourth sequence number, and the fourth sequence number is a minimum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using the key of the target access network device.

9. The method of claim 8, wherein sending a second message to the target access network device comprises:

and after receiving all uplink data packets of which the PDCP sequence numbers are smaller than the fourth sequence number from the terminal equipment, sending the second message to the target access network equipment.

10. A method of communication, comprising:

switching an uplink packet data convergence protocol PDCP entity to correspond to the target access network equipment;

and sending a first message to a source access network device, where the first message is used to trigger sending of a first sequence number from the source access network device to the target access network device, and the first sequence number is used to instruct the target access network device to send an uplink data packet with a PDCP sequence number greater than or equal to the first sequence number to a user plane function network element.

11. The method of claim 10, wherein the first message is a radio resource control Reconfiguration Complete RRC Reconfiguration Complete message; or

The first message is an end marker message; or

The first message is a PDCP control protocol data unit PDCP control PDU.

12. The method of claim 10 or 11, wherein the first message further carries a second sequence number, and the second sequence number is a maximum value of PDCP sequence numbers respectively corresponding to the uplink data packets encrypted by using the key of the source access network device.

13. The method of claim 10 or 11, wherein the first message further carries a third sequence number, and the third sequence number is a minimum value of PDCP sequence numbers respectively corresponding to uplink data packets encrypted by using the key of the target access network device.

14. A method of communication, comprising:

based on a first message from a terminal device, a source access network device sends a second message to a target access network device, wherein the second message carries a first sequence number, the first sequence number is used for indicating the target access network device to send an uplink data packet of which the sequence number of a Packet Data Convergence Protocol (PDCP) is greater than or equal to the first sequence number to a user plane functional network element, and the first message is triggered after the terminal device switches an uplink PDCP entity to correspond to the target access network device;

and the target access network equipment sends an uplink data packet to the user plane functional network element based on the first sequence number.

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

the terminal equipment switches an uplink PDCP entity to correspond to the target access network equipment;

and the terminal equipment sends a first message to the source access network equipment.

16. The method of claim 15, wherein the first message is a radio resource control Reconfiguration Complete RRC Reconfiguration Complete message; or

The first message is an end marker message; or

The first message is a PDCP control protocol data unit PDCP control PDU.

17. The method of claim 14, wherein the second message is a sequence number Status Transfer (SN Status Transfer) message.

18. The method of claim 14, wherein the second message further carries a second sequence number, and wherein the second sequence number is used to instruct the target access network device to assign a PDCP sequence number for the downlink data packet from the second sequence number.

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

and the source access network equipment sends a third message to the target access network equipment, wherein the third message carries a second sequence number, and the second sequence number is used for indicating the target access network equipment to distribute a PDCP sequence number for a downlink data packet from the second sequence number.

20. The method according to any one of claims 14 to 19, wherein the first message further carries a third sequence number, and the third sequence number is a maximum value of PDCP sequence numbers respectively corresponding to uplink data packets ciphered using the key of the source access network device.

21. The method of claim 20, wherein the source access network device sending a second message to the target access network device, comprising:

and after receiving all uplink data packets of which the PDCP sequence number is less than or equal to the third sequence number from the terminal equipment, the source access network equipment sends the second message to the target access network equipment.

22. The method of any one of claims 14 to 19, wherein the first message further carries a fourth sequence number, and the fourth sequence number is a minimum value of PDCP sequence numbers respectively corresponding to uplink data packets ciphered using the key of the target access network device.

23. The method of claim 22, wherein the source access network device sending a second message to the target access network device, comprising:

and after receiving all uplink data packets with the PDCP sequence number smaller than the fourth sequence number from the terminal equipment, the source access network equipment sends the second message to the target access network equipment.

24. A communications apparatus, characterized in that the apparatus comprises means for implementing the method according to any one of claims 1-9; alternatively, the apparatus comprises means for implementing the method of any one of claims 10-13.

25. A communications apparatus, comprising a processor coupled with a memory;

the memory for storing programs or instructions;

the processor for executing the program or instructions to cause the apparatus to perform the method of any of claims 1-9; or for executing the program or instructions to cause the apparatus to perform the method of any of claims 10-13.

26. A computer-readable storage medium for storing a program or instructions which when executed perform the method of any one of claims 1-9; alternatively, the program or instructions, when executed, implement the method of any of claims 10-13.

27. A communication system, characterized in that the system comprises a source access network device and a target access network device;

the source access network device is configured to send a second message to the target access network device based on a first message from a terminal device, where the second message carries a first sequence number, the first sequence number is used to instruct the target access network device to send an uplink data packet with a packet data convergence protocol PDCP sequence number greater than or equal to the first sequence number to a user plane functional network element, and the first message is triggered after the terminal device switches an uplink packet data convergence protocol PDCP entity to correspond to the target access network device;

the target access network device is configured to send an uplink data packet to the user plane functional network element based on the first sequence number from the source access network device.