Method and apparatus for minimizing interruption time of data transfer on handover in wireless communication network

A handover method of a base station controlling a target cell, the method comprising:

• receiving a sequence number status transfer message and information indicating whether a terminal supports a data transfer interruption time reduction function from a base station controlling a source cell;
• performing a random access procedure with the terminal;
• receiving a handover complete message from the terminal or transmitting a terminal (UE) context release message to the base station controlling the source cell before receiving an additional sequence number status transfer message;
• and
• receiving, from the base station controlling the source cell, as the additional sequence number status transfer message including information related to a data packet transmitted or received between the base station controlling the source cell and the terminal after receiving the sequence number status transfer message,
• wherein the terminal transmits or receives the data packet with the base station controlling the source cell and, simultaneously, perform the random access procedure with the base station controlling the target cell.

A handover method of a terminal being handed over from a source cell to a target cell, the method comprising:

• receiving a handover command from a base station controlling a source cell;
• performing, after receiving the handover command, a random access procedure with a base station controlling a target cell at the same time as transmitting or receiving a data packet with the base station controlling the source cell;
• and
• transmitting, after completing the random access procedure, a handover complete message to the base stations controlling the source and target cells,
• wherein an additional sequence number status transfer message is transmitted from the base station controlling the source cell to the base station controlling the target cell, the additional sequence number status transfer message including information related to a data packet transmitted or received between the base station controlling the source cell and the terminal after the base station controlling the source cell transmits a sequence number status transfer message.

A base station controlling a source cell for a handover, the base station comprising:

• a transceiver configured to transmit or receive signals with a terminal and a base station controlling a target cell;
• and
• a controller configured to control to:
• transmit a sequence number status transfer message and information indicating whether the terminal supports data transfer interruption time reduction function to the base station controlling the target cell,
• transmit or receive a data packet with the terminal,
• receive a handover complete message from the terminal or a terminal (UE) context release from the base station controlling the target cell, and
• transmit an additional sequence number status transfer message to the base station controlling the target cell after receiving the handover complete message or the terminal context release message including information related to data packets transmitted or received with the terminal after transmitting the sequence number status transfer message,
• wherein the terminal transmits or receives the data packet with the base station controlling the source cell and, simultaneously, performs a random access procedure with the base station controlling the target cell.

A base station controlling a target cell for a handover, the base station comprising:

• a transceiver configured to transmit or receive signals with a base station controlling a source cell and a terminal;
• and
• a controller configured to control to:
• receive a sequence number status transfer message and information indicating whether a terminal supports a data transfer interruption time reduction function from a base station controlling a source cell,
• perform a random access procedure with the terminal,
• receive a handover complete message from the terminal or transmitting a terminal (UE) context release message to the base station controlling the source cell before receiving an additional sequence number status transfer message, and
• receive from the base station controlling the source cell, the additional sequence number status transfer message including information related to a data packet transmitted or received between the base station controlling the source cell and the terminal after receiving the sequence number status transfer message,
• wherein the terminal transmits or receives the data packet with the base station controlling the source cell and, simultaneously, performs the random access procedure with the base station controlling the target cell.

A terminal being handed over from a source cell to a target cell, the terminal comprising;

• a transceiver configured to transmit or receive signals with a base station controlling a source cell and a base station controlling a target cell;
• and
• a controller configured to control to:
• receive a handover command from a base station controlling a source cell,
• perform, after receiving the handover command, a random access procedure with a base station controlling a target cell at the same time as transmitting or receiving a data packet with the base station controlling the source cell, and
• transmit, after completing the random access procedure, a handover complete message to the base stations controlling the source and target cells,
• wherein an additional sequence number status transfer message is transmitted from the base station controlling the source cell to the base station controlling the target cell, the additional sequence number status transfer message including information related to a data packet transmitted or received between the base station controlling the source cell and the terminal after the base station controlling the source cell transmits a sequence number status transfer message.