The present invention provides a method of selecting a random access preamble in a radio communication system operable at least on a physical layer and a medium access control layer. Random access preambles are divided into at least two groups, the groups depending on at least one of the following: radio conditions and a size of a message to be transmitted by user equipment. The method comprising: (a) the medium access control layer selecting one of the preamble groups; (b) the medium access control layer randomly selecting one random access preamble within the selected group; (c) the medium access control layer signalling the selected random access preamble to the physical layer; and (d) the physical layer generating and transmitting the generated random access preamble.