Handover method performed by user equipment, and user equipment

A User Equipment (UE), comprising:

• receiving circuitry configured to receive a first Radio Resource Control (RRC) message for an RRC configuration;
• and
• handover circuitry configured to apply the RRC configuration based on the first RRC message if an indication is configured for a Data Radio Bearer (DRB), wherein
• the application of the RRC configuration includes:
• establishing a Medium Access Control (MAC) entity for a target based station,
• for the DRB configured with the indication, establishing a Radio Link Control (RLC) entity for the target base station and reconfiguring a Packet Data Convergence Protocol (PDCP) entity to establish a security function, and
• for a Signal Radio Bearer (SRB), establishing a PDCP entity and establishing an RLC entity for the target base station,
• the indication indicates that the UE maintains a source base station communication and a target base station communication during handover for the DRB,
• the receiving circuitry is configured to receive a second RRC message including an instruction, and
• the handover circuitry is configured to perform a source base station release based on the instruction, wherein the source base station release includes:
• for the DRB configured with the indication, releasing an RLC entity for a source base station, releasing a security function for the source base station, and sending a PDCP status report to a base station.

A base station that communicates with a source base station for handover, the base station comprising:

• transmitting circuitry configured to transmit, to a user equipment (UE), a Radio Resource Control (RRC) message including an instruction, wherein
• the instruction causes the UE to perform a source base station release that includes:
• for a Data Radio Bearer (DRB) configured with an indication, releasing a Radio Link Control (RLC) entity for a source base station, releasing a security function for the source base station, and sending a Packet Data Convergence Protocol (PDCP) status report to a base station, and
• the indication indicates that the UE maintains a source base station communication and a target base station communication during the handover for the DRB.

A method performed by a User Equipment (UE), the method comprising:

• receiving a first Radio Resource Control (RRC) message for an RRC configuration;
• and
• applying the RRC configuration based on the first RRC message if an indication is configured for a Data Radio Bearer (DRB), wherein the application of the RRC configuration includes:
• establishing a Medium Access Control (MAC) entity for a target based station,
• for the DRB configured with the indication, establishing a Radio Link Control (RLC) entity for the target base station and reconfiguring a Packet Data Convergence Protocol (PDCP) entity to establish a security function, and
• for a Signal Radio Bearer (SRB), establishing a PDCP entity and establishing an RLC entity for the target base station, wherein
• the indication indicates that the UE maintains a source base station communication and a target base station communication during handover for the DRB,
• the method further comprising:
• receiving a second RRC message including an instruction;
• and
• performing a source base station release based on the instruction, wherein the source base station release includes:
• for the DRB configured with the indication, releasing an RLC entity for a source base station, releasing a security function for the source base station, and sending a PDCP status report to a base station.

A method performed by a base station that communicates with a source base station for handover, the method comprising:

• transmitting, to a user equipment (UE), a Radio Resource Control (RRC) message including an instruction,
• wherein the instruction causes the UE to perform a source base station release that includes:
• for a Data Radio Bearer (DRB) configured with an indication, releasing a Radio Link Control (RLC) entity for a source base station, releasing a security function for the source base station, and sending a Packet Data Convergence Protocol (PDCP) status report to a base station, and
• the indication indicates the UE maintains a source base station communication and a target base station communication during the handover for the DRB.