Data transmission method, access network device, terminal, and communications system

1. A communication system, comprising:

a first access network device that establishes a data radio bearer (DRB)-based tunnel and a session-based tunnel with a second access network device, wherein the DRB-based tunnel is used to transmit a Packet Data Convergence Protocol (PDCP) layer data packet from the second access network device to the first access network device, and the session-based tunnel is used to transmit a Service Data Adaptation Protocol (SDAP) layer data packet from the second access network device to the first access network device; and

the second access network device that forwards data packets to the first access network device via the DRB-based tunnel and the session-based tunnel; and

the first access network device is configured to:

map a PDCP layer data packet on a DRB of the second access network device to a first DRB which is corresponding to the DRB of the second access network device;

send the PDCP layer data packet to a terminal on the first DRB; and

after sending the PDCP layer data packet to the terminal on the first DRB, send to the terminal on the first DRB, a data packet received from a core network.

2. The communication system according to claim 1 , wherein a mapping relationship between a flow and the DRB of the second access network device is the same as a mapping relationship between the flow and the first DRB.

3. The communication system according to claim 1 , wherein the first DRB and the DRB of the second access network device have a same PDCP sequence number (SN) status and a same hyper frame number (HFN) status.

4. The communication system according to claim 2 , wherein the second access network device is configured to:

send the mapping relationship between the flow and the DRB of the second access network device to the first access network device.

5. The communication system according to claim 1 , wherein the first access network device is configured to:

receive data packets of a flow from the terminal on the first DRB and a second DRB; and

after receiving an end marker from the terminal on the first DRB, send one or more data packets of the flow received on the second DRB to the core network.

6. The communication system according to claim 1 , wherein:

the first access network device is a target access network device, and the second access network device is a source access network device; or

the first access network device is a master base station, and the second access network device is a secondary base station, both the master base station and the secondary base station connecting to a terminal; or

the first access network device is a secondary base station, and the second access network device is a master base station, both the master base station and the secondary base station connecting to a terminal.

7. A data transmission method, comprising:

establishing, by a first access network device, a data radio bearer (DRB)-based tunnel and a session-based tunnel with a second access network device;

forwarding, by the second access network device, data packets to the first access network device via the DRB-based tunnel and the session-based tunnel; and

receiving, by the first access network device, forwarded data packets from the second access network device via the DRB-based tunnel and the session-based tunnel; and

wherein the DRB-based tunnel is used to transmit a Packet Data Convergence Protocol (PDCP) layer data packet from the second access network device to the first access network device; and

wherein the session-based tunnel is used to transmit a Service Data Adaptation Protocol (SDAP) layer data packet from the second access network device to the first access network device, and the method further comprises:

mapping, by the first access network device, a PDCP layer data packet on a DRB of the second access network device to a first DRB which is corresponding to the DRB of the second access network device;

sending, by the first access network device, the PDCP layer data packet to a terminal on the first DRB; and

after sending the PDCP layer data packet to the terminal on the first DRB, sending, by the first access network device, to the terminal on the first DRB, a data packet received from a core network.

8. The method according to claim 7 , wherein a mapping relationship between a flow and the DRB of the second access network device is the same as a mapping relationship between the flow and the first DRB.

9. The method according to claim 7 , wherein the first DRB and the DRB of the second access network device have a same PDCP sequence number SN status and a same hyper frame number (HFN) status.

10. The method according to claim 8 , further comprising:

sending, by the second access network device, the mapping relationship between the flow and the DRB of the second access network device to the first access network device; and

receiving, by the first access network device, the mapping relationship between the flow and the DRB of the second access network device from the second access network device.

11. The method according to claim 7 , further comprising:

receiving, by the first access network device, data packets of a flow from the terminal on the first DRB and a second DRB; and

after receiving an end marker from the terminal on the first DRB, sending, by the first access network device, one or more data packets of the flow received on the second DRB to the core network.

12. A data transmission method, comprising:

establishing, by a first access network device, a data radio bearer (DRB)-based tunnel and a session-based tunnel with a second access network device; and

receiving, by the first access network device, forwarded data packets from the second access network device via the DRB-based tunnel and the session-based tunnel;

wherein the DRB-based tunnel is used by the first access network device to receive a Packet Data Convergence Protocol (PDCP) layer data packet from the second access network device; and

wherein the session-based tunnel is used by the first access network device to receive a Service Data Adaptation Protocol (SDAP) layer data packet from the second access network device and the method further comprises:

mapping, by the first access network device, a PDCP layer data packet on a DRB of the second access network device to a first DRB which is corresponding to the DRB of the second access network device;

sending, by the first access network device, the PDCP layer data packet to a terminal on the first DRB; and

after sending the PDCP layer data packet to the terminal on the first DRB, sending, by the first access network device, to the terminal on the first DRB, a data packet received from a core network.

13. The method according to claim 12 , wherein a mapping relationship between a flow and the DRB of the second access network device is the same as a mapping relationship between the flow and the first DRB.

14. The method according to claim 12 , wherein the first DRB and the DRB of the second access network device have a same PDCP sequence number SN status and a same hyper frame number (HFN) status.

15. The method according to claim 13 , further comprising:

receiving, by the first access network device, the mapping relationship between the flow and the DRB of the second access network device from the second access network device.

16. The method according to claim 12 , further comprising:

receiving, by the first access network device, data packets of a flow from the terminal on the first DRB and a second DRB; and

after receiving an end marker from the terminal on the first DRB, sending; by the first access network device, one or more data packets of the flow received on the second DRB to the core network.

17. A communication apparatus, comprising at least one processor coupled with a non-transitory storage medium storing instructions that, when executed by the at least one processor, cause an access network device to:

establish, a data radio bearer (DRB)-based tunnel and a session-based tunnel with a second access network device; and

receive, forwarded data packets from the second access network device via the DRB-based tunnel and the session-based tunnel;

wherein the DRB-based tunnel is used to receive a Packet Data Convergence Protocol (PDCP) layer data packet from the second access network device; and

wherein the session-based tunnel is used to receive a Service Data Adaptation Protocol (SDAP) layer data packet from the second access network device; and the instructions when executed by the at least one processor, further causing the access network device to:

map a PDCP layer data packet on a DRB of the second access network device to a first DRB which is corresponding to the DRB of the second access network device;

send the PDCP layer data packet to a terminal on the first DRB; and

after sending the PDCP layer data packet to the terminal on the first DRB, send to the terminal on the first DRB, a data packet received from a core network.

18. The communication apparatus according to claim 17 , wherein a mapping relationship between a flow and the DRB of the second access network device is the same as a mapping relationship between the flow and the first DRB.

19. The communication apparatus according to claim 17 , wherein the first DRB and the DRB of the second access network device have a same PDCP sequence number (SN) status and a same hyper frame number (HFN) status.

20. The communication apparatus according to claim 18 , the instructions when executed by the at least one processor, further causing the access network device to:

receive the mapping relationship between the flow and the DRB of the second access network device from the second access network device.

21. The communication apparatus according to claim 17 , the instructions when executed by the at least one processor, further causing the access network device to:

receive data packets of a flow from the terminal on the first DRB and a second DRB; and

after receiving an end marker from the terminal on the first DRB, send one or more data packets of the flow received on the second DRB to the core network.

22. The communication apparatus according to claim 17 , wherein:

the access network device is a target access network device, and the second access network device is a source access network device; or

the access network device is a master base station, and the second access network device is a secondary base station, both the master base station and the secondary base station connecting to a terminal; or

the access network device is a secondary base station, and the second access network device is a master base station, both the master base station and the secondary base station connecting to a terminal.