Method and apparatus for handover without interruption of transmission and reception of data in next-generation mobile communication system
The present disclosure relates to a communication method and system for converging a 5th-Generation (5G) communication system for supporting higher data rates beyond a 4th-Generation (4G) system with a technology for Internet of Things (IoT). The present disclosure may be applied to intelligent services based on the 5G communication technology and the IoT-related technology, such as smart home, smart building, smart city, smart car, connected car, health care, digital education, smart retail, security and safety services. A method of a terminal in a wireless communication system according to the disclosure includes receiving, from a first base station, a message including a command of handover from a first base station to a second base station through radio resource control (RRC) signaling; identifying the message includes information indicating dual protocol stack handover; and receiving data until a cell of the first base station is released.
1. A method performed by a terminal in a communication system, the method comprising:
receiving, from a first base station, a radio resource control (RRC) message indicating handover to a second base station, the RRC message including configuration information on a data radio bearer (DRB) for the handover using a dual protocol stack, wherein the DRB is associated with a radio link control (RLC)-acknowledged mode (AM) bearer or a RLC-unacknowledged mode (UM) bearer;
identifying a medium access control (MAC) entity associated with the second base station based on the RRC message;
identifying a RLC entity for the DRB associated with the second base station;
identifying a packet data convergence protocol (PDCP) entity for the DRB, the PDCP entity being associated with a RLC entity associated with the first base station and the RLC entity associated with the second base station; and
performing, at the PDCP entity, transmission of a PDCP service data unit (SDU) to the RLC entity associated with the second base station based on successful completion of a random access procedure with the second base station.
2. The method of claim 1 , wherein the performing comprises:
performing, at the PDCP entity for the DRB associated with the RLC-AM bearer, transmission of all of one or more PDCP SDUs from a first PDCP SDU in an ascending order of a counter value associated with a corresponding PDCP SDU to the RLC entity associated with the second base station, based on the successful completion of the random access procedure,
wherein a successful delivery of the first PDCP SDU has not been confirmed by the RLC entity associated with the first base station, and
wherein the one or more PDCP SDUs are already associated with PDCP sequence numbers (SNs).
3. The method of claim 2 , wherein the performing comprises:
performing, at the PDCP entity for the DRB associated with the RLC-AM bearer, a header compression of the one or more PDCP SDUs based on a robust header compression (ROHC) protocol;
performing, at the PDCP entity for the DRB associated with the RLC-AM bearer, an integrity protection and ciphering of the one or more PDCP SDUs based on security information for the second base station; and
submitting, at the PDCP entity for the DRB associated with the RLC-AM bearer, the one or more PDCP SDUs to the RLC entity associated with the second base station.
4. The method of claim 1 , wherein the performing comprises:
performing, at the PDCP entity for the DRB associated with the RLC-UM bearer, transmission of all of one or more PDCP service data units (SDUs) in an ascending order of a counter value associated with a corresponding PDCP SDU to the RLC entity associated with the second base station, based on the successful completion of the random access procedure,
wherein the one or more PDCP SDUs have been processed by the PDCP entity and have not yet been submitted to the RLC entity associated with the first base station.
5. The method of claim 4 , wherein the performing comprises:
performing, at the PDCP entity for the DRB associated with the RLC-UM bearer, a header compression of the one or more PDCP SDUs based on a robust header compression (ROHC) protocol;
performing, at the PDCP entity for the DRB associated with the RLC-UM bearer, an integrity protection and ciphering of the one or more PDCP SDUs based on security information for the second base station; and
submitting, at the PDCP entity for the DRB associated with the RLC-UM bearer, the one or more PDCP SDUs to the RLC entity associated with the second base station.
6. The method of claim 1 , further comprising:
in case that the PDCP entity is configured to transmit a PDCP status report, transmitting, at the PDCP entity, a PDCP status report to the first base station based on the successful completion of the random access procedure.
7. The method of claim 1 ,
wherein the PDCP entity is configured with separate security information for the first base station and the second base station, and
wherein a state variable used in the PDCP entity is not reset.
8. A terminal in a communication system, comprising:
a transceiver; and
a controller coupled with the transceiver and configured to:
receive, from a first base station, a radio resource control (RRC) message indicating handover to a second base station, the RRC message including configuration information on a data radio bearer (DRB) for the handover using a dual protocol stack, wherein the DRB is associated with a radio link control (RLC)-acknowledged mode (AM) bearer or a RLC-unacknowledged mode (UM) bearer,
identify a medium access control (MAC) entity associated with the second base station based on the RRC message,
identify a RLC entity for the DRB associated with the second base station,
identify a packet data convergence protocol (PDCP) entity for the DRB, the PDCP entity being associated with a RLC entity associated with the first base station and the RLC entity associated with the second base station, and
perform, at the PDCP entity, transmission of a PDCP service data unit (SDU) to the RLC entity associated with the second base station based on successful completion of a random access procedure with the second base station.
9. The terminal of claim 8 , wherein the controller is configured to:
perform, at the PDCP entity for the DRB associated with the RLC-AM bearer, transmission of all of one or more PDCP SDUs from a first PDCP SDU in an ascending order of a counter value associated with a corresponding PDCP SDU to the RLC entity associated with the second base station, based on the successful completion of the random access procedure,
wherein a successful delivery of the first PDCP SDU has not been confirmed by the RLC entity associated with the first base station, and
wherein the one or more PDCP SDUs are already associated with PDCP sequence numbers (SNs).
10. The terminal of claim 9 , wherein the controller is configured to:
perform, at the PDCP entity for the DRB associated with the RLC-AM bearer, a header compression of the one or more PDCP SDUs based on a robust header compression (ROHC) protocol,
perform, at the PDCP entity for the DRB associated with the RLC-AM bearer, an integrity protection and ciphering of the one or more PDCP SDUs based on security information for the second base station, and
submit, at the PDCP entity for the DRB associated with the RLC-AM bearer, the one or more PDCP SDUs to the RLC entity associated with the second base station.
11. The terminal of claim 8 , wherein the controller is configured to:
perform, at the PDCP entity for the DRB associated with the RLC-UM bearer, transmission of all of one or more PDCP service data units (SDUs) in an ascending order of a counter value associated with a corresponding PDCP SDU to the RLC entity associated with the second base station, based on the successful completion of the random access procedure,
wherein the one or more PDCP SDUs have been processed by the PDCP entity and have not yet been submitted to the RLC entity associated with the first base station.
12. The terminal of claim 11 , wherein the controller is configured to:
perform, at the PDCP entity for the DRB associated with the RLC-UM bearer, a header compression of the one or more PDCP SDUs based on a robust header compression (ROHC) protocol,
perform, at the PDCP entity for the DRB associated with the RLC-UM bearer, an integrity protection and ciphering of the one or more PDCP SDUs based on security information for the second base station, and
submit, at the PDCP entity for the DRB associated with the RLC-UM bearer, the one or more PDCP SDUs to the RLC entity associated with the second base station.
13. The terminal of claim 8 , wherein the controller is further configured to:
in case that the PDCP entity is configured to transmit a PDCP status report, transmit, at the PDCP entity, a PDCP status report to the first base station based on the successful completion of the random access procedure.
14. The terminal of claim 8 ,
wherein the PDCP entity is configured with separate security information for the first base station and the second base station, and
wherein a state variable used in the PDCP entity is not reset.