According to one embodiment, a method of requesting a random access connection between a mobile terminal and a base station includes: receiving, by the mobile terminal, information comprising at least one signature root sequence index, a cyclic shift parameter, and a number of signatures used for representing a boundary between a first signature set and a second signature set; preparing, by the mobile terminal, random access signatures according to the at least one signature root sequence index and the cyclic shift parameter, wherein at least one of the random access signatures is associated with the first signature set and the remaining of the random access signatures are associated with the second signature set; and selecting, by the mobile terminal, a random access preamble from the first signature set or the second signature set based on a message size and a radio condition.