Enhanced make-before-break handover

Patent metadata

Field	Value
Publication number	US-10687263-B2
Application number	US-201916275214-A
Country	US
Kind code	B2
Filing date	Feb 13, 2019
Priority date	Feb 15, 2018
Publication date	Jun 16, 2020
Grant date	Jun 16, 2020

Abstract

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment concurrently communicates with a source base station (BS) and a target BS on a connection with the source BS and a connection with the target BS as part of a make-before-break (MBB) handover procedure; and performs a common packet data convergence protocol (PDCP) function for the connection with the source BS and the connection with the target BS before the connection with the source BS is released as part of the MBB handover procedure. Numerous other aspects are provided.

First claim

What is claimed is:

1. A method of wireless communication performed by a user equipment (UE), comprising:
communicating, as part of a make-before-break (MBB) handover procedure, with a source base station (BS) on a connection with the source BS and with a target BS on a connection with the target BS;
performing, before the connection with the source BS is released as part of the MBB handover procedure, a common packet data convergence protocol (PDCP) function for the connection with the source BS;
providing, to the source BS or the target BS, at least one indication based at least in part on a successful setup of the connection with the target BS; and
receiving, after a target cell of the target BS is added to a secondary cell group, one or more notifications to designate the target cell to a master cell group or to release a source cell of the source BS.

2. The method of claim 1 , wherein the common PDCP function is performed by a common PDCP entity of the UE, and wherein the common PDCP entity handles data of radio bearers associated with the connection with the source BS.

3. The method of claim 1 , wherein the common PDCP function comprises security key management for storing security keys of the source BS and using the security keys of the source BS.

4. The method of claim 1 , wherein the common PDCP function comprises ciphering, deciphering, integrity protection, or integrity verification for data units transmitted or received over the connection with the source BS.

5. The method of claim 4 , wherein, when a security key associated with the target BS is different from a security key associated with the source BS, the UE is configured to identify a security key to be used for ciphering, deciphering, integrity protection, or integrity verification based at least in part on at least one of:
a radio link control (RLC) entity from which an identifier for the security key to be used for ciphering, deciphering, integrity protection, or integrity verification is received,
an explicit bit in a packet data convergence protocol (PDCP) protocol data unit (PDU) header that indicates the security key to be used for ciphering, deciphering, integrity protection, or integrity verification, or
a unique identifier associated with a logical channel or a radio bearer.

6. The method of claim 1 , wherein the common PDCP function comprises PDCP sequence number (SN) continuity for radio link control (RLC) acknowledged mode and RLC unacknowledged mode data units that are transmitted on the connection with the source BS.

7. The method of claim 1 , wherein the common PDCP function comprises data unit reordering and duplicate discarding for one or more data units that are received on the connection with the source BS based at least in part on retransmission of unacknowledged data units or data unit duplication.

8. The method of claim 1 , wherein the common PDCP function comprises duplication for data units of a radio bearer via the source BS during the handover procedure.

9. The method of claim 1 , wherein the common PDCP function comprises link selection logic for switching an uplink (UL) signaling or user data transmission from a source protocol stack associated with the source BS to a target protocol stack associated with the target BS, or from the target protocol stack to the source protocol stack, based at least in part on link selection conditions or based at least in part on instructions received from the target BS or the source BS after the connection with the target BS is established.

10. The method of claim 1 , wherein the UE is configured to perform data transmission or reception for a radio bearer via the source BS while the UE is establishing the connection with the target BS or while sending or receiving data via the connection with the target BS.

11. The method of claim 1 , wherein the connection with the source BS and the connection with the target BS comprise respective data radio bearers and signaling radio bearers and are associated with respective physical layer, medium access control layer, or radio link control layer entities.

12. The method of claim 1 , further comprising:
adding the target cell to the secondary cell group based at least in part on a request received from the source BS; and
maintaining the source cell in the master cell group while establishing the connection with the target BS,
wherein the UE is configured to send uplink (UL) data to the target BS after the connection with the target BS is established.

13. The method of claim 12 , wherein the at least one indication is provided after the target cell is added to the secondary cell group.

14. The method of claim 12 , wherein the MBB handover procedure comprises a dual-connectivity based MBB handover procedure.

15. The method of claim 1 , further comprising:
receiving a master cell group serving cell identification field in a radio resource control (RRC) reconfiguration message indicating which configured cell group is the master cell group;
performing a role switch procedure to switch the master cell group to the target cell, wherein the connection with the source cell is maintained during the role switch procedure; and
releasing the connection with the source cell based at least in part on receiving the one or more notifications.

16. The method of claim 1 , wherein the MBB handover procedure is based at least in part on a radio resource control (RRC) reconfiguration message indicating that the UE is to perform the MBB handover procedure, and wherein the RRC reconfiguration message includes an indication of a handover type as an MBB handover or a dual connectivity based MBB handover based at least in part on a capability of the UE.

17. The method of claim 16 , further comprising:
signaling the capability of the UE to a network entity, wherein the capability is a simultaneous transmission and receiving capability.

18. The method of claim 17 , wherein the UE is to switch a data communication to the connection with the target BS as a primary connection after an RRC reconfiguration complete message is transmitted by the UE.

19. The method of claim 1 , further comprising:
releasing the connection with the source BS based at least in part on a message received from the source BS or the target BS.

20. The method of claim 1 , further comprising:
performing radio resource control signaling for the MBB handover procedure on a signaling radio bearer for the source BS before a signaling radio bearer for the target BS is established; and
performing radio resource control signaling for the MBB handover procedure on the signaling radio bearer for the source BS or the signaling radio bearer for the target BS after the signaling radio bearer for the target BS is established.

21. The method of claim 1 , wherein the common PDCP function comprises at least one of:
security key management,
ciphering or deciphering, or
integrity protection or verification, and wherein the common PDCP function is performed by respective PDCP entities corresponding to the connection with the source BS.

22. The method of claim 1 , wherein the source BS and the target BS are associated with a same centralized unit (CU) of a radio access network (RAN).

23. The method of claim 1 , wherein the source BS and the target BS are associated with a same radio access technology.

24. A method of wireless communication, comprising:
performing a role switch procedure from a source base station to a targ

Assignees

• Qualcomm Inc

Inventors

• Paladugu Karthika
• Horn Gavin Bernard
• Hande Prashanth Haridas
• Kubota Keiichi
• Kadiri Prasad Reddy
• Rico Alvarino Alberto
• Kitazoe Masato
• Phuyal Umesh
• Bhattacharjee Supratik

Classifications

• H04W12/0433

  Key management protocols · CPC title

• H04W36/08

  Reselecting an access point · CPC title

• H04W12/033

  of the user plane, e.g. user's traffic · CPC title

• H04W12/106

  Packet or message integrity · CPC title

• H04W76/27

  Transitions between radio resource control [RRC] states · CPC title