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

1. A method for performing a random access in a wireless communication, comprising:

identifying a channel condition and a size of a message that a user equipment will transmit after a transmission of a preamble;

selecting a first preamble set from at least two preamble sets if the channel condition is greater than a first threshold and the size of the message is greater than a second threshold;

selecting a preamble from the selected first preamble set if the first preamble set is selected;

transmitting, to a base station, the selected preamble;

receiving, from the base station, a random access response (RAR) message including resource allocation information in response to the transmission of the selected preamble; and

transmitting, to the base station, the message based on the resource allocation information.

2. The method of claim 1 , further comprising:

selecting a second preamble set from the at least two preamble sets if the 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; and

selecting a preamble from the selected second preamble set if the second preamble set is selected.

3. The method of claim 1 , wherein the channel condition is determined by comparing a transmission power to a reception power for a downlink pilot channel.

4. The method of claim 1 , wherein the first threshold is associated with a maximum transmission power and a value in system information broadcasted by the base station.

5. The method of claim 1 , wherein the second threshold is configured by broadcasted system information.

6. The method of claim 1 , wherein the RAR message further includes at least one of a preamble identifier mapped to the transmitted selected preamble, uplink synchronization information, and resource information for a next uplink message transmission.

7. An apparatus for performing a random access in a wireless communication, comprising:

a transceiver configured to transmit or receive data; and

a controller configured to:

identify a channel condition and a size of a message that a user equipment will transmit after a transmission of a preamble;

select a first preamble set from at least two preamble sets if the channel condition is greater than a first threshold and the size of the message is greater than a second threshold;

select a preamble from the selected first preamble set if the first preamble set is selected;

transmit, to a base station, the selected preamble;

receive, from the base station, a random access response (RAR) message including resource allocation information in response to the transmission of the selected preamble; and

transmit, to the base station, the message based on the resource allocation information.

8. The apparatus of claim 7 , wherein the controller is further configured to select a second preamble set from the at least two preamble sets if the 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, and to select a preamble from the selected second preamble set if the second preamble set is selected.

9. The apparatus of claim 7 , wherein the channel condition is determined by comparing a transmission power to a reception power for a downlink pilot channel.

10. The apparatus of claim 7 , wherein the first threshold is associated with a maximum transmission power and a value in system information broadcasted by the base station.

11. The apparatus of claim 7 , wherein the second threshold is configured by broadcasted system information.

12. The apparatus of claim 7 , wherein the RAR message further includes at least one of a preamble identifier mapped to the transmitted selected preamble, uplink synchronization information, and resource information for a next uplink message transmission.