Method and apparatus for allocating radio resource using random access procedure in a mobile communication system

A user equipment (UE) for performing a random access in a wireless communication system, the UE comprising:

• a transceiver configured to transmit or receive data;
• and
• a controller configured to:
• identify a path loss and a size of a message that the UE will transmit after a transmission of a preamble,
• select a preamble set from at least two preamble sets based on a first threshold and a second threshold, wherein a first preamble set is selected if the path loss is less than the first threshold and the size of the message is greater than the second threshold, and wherein a second preamble set is selected if the path loss is greater than or equal to the first threshold, or the size of the message is less than or equal to the second threshold,
• select a preamble from the selected preamble set,
• transmit, to a base station, the selected preamble,
• receive, from the base station, a random access response message including resource allocation information in response to the transmission of the selected preamble, and
• transmit, to the base station, a radio resource control message based on the resource allocation information.

A method for performing a random access by a user equipment (UE) in a wireless communication system, the method comprising:

• identifying a size of a message that the UE will transmit after a transmission of a preamble;
• selecting a preamble set from at least two preamble sets based on a first threshold and a second threshold, wherein a first preamble set is selected if a radio channel condition is greater than the first threshold and the size of the message is greater than the second threshold, and wherein a second preamble set is selected if the radio channel condition is less than or equal to the first threshold or the size of the message is less than or equal to the second threshold;
• selecting a preamble from the selected preamble set;
• transmitting, to a base station, the selected preamble;
• receiving, from the base station, a random access response message including resource allocation information in response to the transmission of the selected preamble;
• and
• transmitting, to the base station, a radio resource control message based on the resource allocation information.