Method and apparatus for performing random access in a mobile communication system

A method by a terminal communicating with a master base station and a secondary base station, the method comprising:

• receiving, from a master base station, a request message for adding a cell of a secondary cell group that is controlled by a secondary base station, the request message including configuration information and dedicated parameter for a random access to the cell;
• applying the configuration information to add the cell;
• transmitting, to the master base station, a response message in response to the request message;
• and
• performing a random access procedure to the cell based on the dedicated parameter.

A method by a master base station communicating with the master base station and a secondary base station, the method comprising:

• transmitting, to a terminal, a request message for adding a cell of a secondary cell group that is controlled by a secondary base station, the request message including configuration information and dedicated parameter for a random access to the cell;
• receiving, from the terminal, a response message in response to the request message;
• and
• performing a random access procedure to the cell based on the dedicated parameter.

An apparatus by a terminal communicating with a master base station and a secondary base station, the apparatus comprising:

• a receiver configured to receive, from a master base station, a request message for adding a cell of a secondary cell group that is controlled by a secondary base station, the request message including configuration information and dedicated parameter for a random access to the cell;
• a transmitter configured to transmit, to the master base station, a response message in response to the request message;
• and
• a controller configured to:
• apply the configuration information to add the cell, and
• perform a random access procedure to the cell based on the dedicated parameter.

An apparatus by a master base station communicating with the master base station and a secondary base station, the apparatus comprising:

• a transmitter configured to transmit, to a terminal, a request message for adding a cell of a secondary cell group that is controlled by a secondary base station, the request message including configuration information and dedicated parameter for a random access to the cell;
• a receiver configured to receive, from the terminal, a response message in response to the request message;
• and
• a controller configured to perform a random access procedure to the cell based on the dedicated parameter.