The present invention relates to methods and apparatuses (radio base station and UE) for enabling a UE to perform a contention-based random access. According to embodiments of the present invention, a non-dedicated random access preamble identifier is determined by a radio base station and the determined preamble is transmitted in a message to the UE which selects a non-dedicated random access preamble based on the received preamble identifier and performs a contention-based random access using the selected preamble.