Method and device for handover without suspension of data transmission and reception in next generation mobile communication system

A method performed by a source base station in a wireless communication system, the method comprising:

• transmitting, to a terminal, a radio resource control (RRC) reconfiguration message indicating to the terminal to perform a handover to a target base station, the RRC reconfiguration message including bearer configuration information configuring a bearer for dual active protocol stacks;
• performing uplink data reception and downlink data transmission with the terminal until a random access procedure between the terminal and the target base station based on the RRC reconfiguration message is completed;
• and
• transmitting downlink data to the terminal after the random access procedure is completed,
• wherein a first medium access control (MAC) entity of the terminal for the source base station is not reset based on the RRC reconfiguration message,
• wherein a second MAC entity of the terminal for the target base station is generated based on the bearer configuration information,
• wherein the random access procedure is initiated through the second MAC entity, and
• wherein the uplink data reception from the terminal is stopped, after the random access procedure is completed.

A terminal for a wireless communication system, the terminal comprising:

• a transceiver configured to transmit and receive a signal;
• and
• a controller connected to the transceiver,
• wherein the controller is configured to:
• receive, from a source base station, a radio resource control (RRC) reconfiguration message indicating to the terminal to perform a handover to a target base station, the RRC reconfiguration message including bearer configuration information configuring a bearer for dual active protocol stacks,
• generate a second medium access control (MAC) entity for the target base station based on the bearer configuration information, while a first MAC entity for the source base station is not reset based on the RRC reconfiguration message,
• perform a random access procedure with the target base station through the second MAC entity based on the RRC reconfiguration message,
• perform uplink data transmission and downlink data reception with the source base station until the random access procedure is completed, and
• perform uplink data transmission and downlink data reception with the target base station, after the random access procedure is completed, while the downlink data reception from the source base station is maintained,
• wherein the uplink data transmission to the source base station is switched to the target base station, after the random access procedure is completed.

A source base station for a wireless communication system, the source base station comprising:

• a transceiver configured to transmit and receive a signal;
• and
• a controller connected to the transceiver,
• wherein the controller is configured to:
• transmit, to a terminal, a radio resource control (RRC) reconfiguration message indicating to the terminal to perform a handover to a target base station, the RRC reconfiguration message including bearer configuration information configuring a bearer for dual active protocol stacks,
• perform uplink data reception and downlink data transmission with the terminal until a random access procedure between the terminal and the target base station based on the RRC reconfiguration message is completed;
• and
• transmitting downlink data to the terminal after the random access procedure is completed,
• wherein a first medium access control (MAC) entity of the terminal for the source base station is not reset based on the RRC reconfiguration message,
• wherein a second MAC entity of the terminal for the target base station is generated based on the bearer configuration information,
• wherein the random access procedure is initiated through the second MAC entity, and
• wherein the uplink data reception from the terminal is stopped, after the random access procedure is completed.