A unified two-stage network entry procedure is provided for OFDM multi-carrier wireless communications systems. During a first stage, a mobile station performs a common network entry procedure using a primary radio frequency carrier and then exchanges multi-carrier capability information with a base station. In one embodiment, the base station transmits a network entry allowance indicator to assist the mobile station in selecting the primary carrier. The network entry allowance indicator comprises information of preference of one or more available carriers. During a second stage, the mobile station enables multi-carrier transmission over multiple frequency channels if both the mobile station and the base station support multi-carrier capability. Before enabling multi-carrier transmission, the mobile station may optionally perform additional ranging by transmitting a ranging request for a secondary carrier. In one embodiment, the base station replies with a ranging response in response to the ranging request through the primary carrier.