Abstract: An uplink common physical channel (random access channel) frame structure with a separate preamble and data portion. The preamble is used by a base station to detect that a mobile station is attempting a random access request. The data portion of the channel includes user data, and pilot symbols that provide energy for channel estimation during reception of the data portion. A guard interval can be generated using a “filler” made up of dummy chips, predetermined symbols, and/or an unmodulated carrier, and inserted between the preamble and data portion of the frame, thus enabling a mobile station to maintain its power transmission and making it easier to implement such a guard interval in a WCDMA system.