Abstract: Methods and systems for acquiring service for a user terminal with a satellite communications system are provided wherein geographic information is received via an electromagnetic transmission at the user terminal defining a location of the user terminal. A control channel is selected corresponding to one of the spot beams covering the location of the user terminal using the geographic information. The user terminal acquires service from the satellite communications system over the control channel. The geographic information enables the user terminal to shorten the search time by searching those channels which correspond to the geographic region determined from the geographic information.

Abstract: A method for transmitting random access signals from a mobile unit to a satellite or other control station which requires the transmission of less information than in conventional terrestrial cellular or proposed mobile satellite systems. According to the method, the mobile unit acquires synchronization from the satellite and transmits reduced random access information to the satellite, and the satellite calculates time adjustment information for the mobile units based on the reduced random access information. The random access information is reduced by predetermining a slot number for each mobile unit, and by transmitting only the odd or even status of the frame number desired by the mobile unit.