A subscriber unit for communicating with a satellite communication system. This subscriber unit receives and transmits digital data from satellites of a satellite communication system. In addition, the subscriber unit self-determines its own position and transmits this position to the satellites of the satellite communication system. In this way, the satellite communication sytem knows the position of each subscriber unit so that communications may be established more efficiently. In addition, the position of the subscriber unit is automatically determined from the received GPS signals and reported to the satellite communication system for other uses such as asset management and search and rescue operations.