Abstract: To obtain service from a satellite communication system, a mobile subscriber unit must acquire a TDMA communication channel. Because the satellites move with respect to the surface of the earth, propagation delays and Doppler shift affect the timing and frequency of received signals. A mobile subscriber unit synchronizes to the frequency and timing windows of a satellite communication station by receiving frequency and timing corrections during channel acquisition. The satellite initially estimates correction factors during initial acquisition requests and further estimates correction factors from synchronization bursts from the subscriber unit.

Abstract: A communication system qualifies access to the services it provides to subscriber units based upon the locations of the subscriber units. Subscriber unit location data are routed through a satellite to a gateway where a home subscriber information manager for the subscriber unit resides. This home gateway selects a service control area and corresponding serving gateway to use in establishing calls to and from the subscriber unit. When an area of uncertainty for the subscriber unit's location overlies a boundary between service control areas, additional location data may be obtained to shrink the area of uncertainty. If the area still overlies a boundary, a serving gateway is selected based upon the current serving gateway, the home gateway, and the service control area where the center of the area of uncertainty resides.

Abstract: In a method and system for performing location determination using multi-beam satellites each beam of a multi-beam satellite transmits identification information which is received by a user terminal. This identification information either identifies the unique beam by enumeration or by geometrics. A user terminal processes multiple received signals from orbiting satellites. The user terminal maps the projected beam patterns of multiple received samples to determine an approximate self-location. The user terminal passively monitors its location and compares its current location with its previously reported location. When the user terminal has sufficiently roamed from its previously registered location, the user terminal performs an auto-registration to the system allowing for efficient routing of information.

Abstract: A network includes a system and a population of subscriber units. System satellites move in low earth orbits and form moving cells on the surface of the earth. A pattern of static areas that covers the service area of the system is defined in a map. The system discovers the static areas for the subscriber units. When an incoming call needs to be directed to a subscriber unit, the subscriber unit's static area is converted into identities of beams that form the cells that coincide with the static area. A ring signal is transmitted in only these cells. Subscriber units monitor area identification signals that identify the static areas coincident with the cells where the signals are transmitted. When the static area known by the system is not among the identified static areas, a subscriber unit engages in re-registration communications.