Abstract: A satellite communication system for delivering simplex messages to subscribers comprises multiple Message Origination Controllers (MOCs), one or more Message Termination Controllers (MTCs), satellites, and geographically-diverse communication units. Messages destined for particular communication units are transmitted to the one or more MTCs. The one or more MTCs then schedule delivery of the messages to communication units by employing a blocked timing structure for delivery of the messages. The one or more MTCs transmit the scheduled messages to satellites which broadcast the messages to communication units at the scheduled time. Communication units are assigned specific timing blocks during which they monitor radio signals for messages directed to them. During non-assigned timing blocks, communication units remain in a low-power state.

Abstract: In a satellite communication system, communication channels are dynamically assigned in real-time based on actual demand using a regionalized channel assignment and reuse scheme. The tradeoff between system capacity and channel interference:is optimized through the use of interlocking local regions. Satellite communication stations within a radio line-of-sight of each other make up each local region. The communication stations of a local region change as the communication stations move through orbital positions. Channel reuse rules are adapted to system load and demand for services. Each communication station establishes its local region and notifies the other communication stations within its local region whenever it assigns a communication channel to a subscriber unit. Channel assignments within each local region are maintained locally by the defining communication station.

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: 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.

Abstract: A cellular telecommunication system comprised of low-Earth orbiting satellites featuring allocation of communication channels among users in cells is disclosed. Each subscriber unit is programmed with an embedded class identifier. During periods when it is desirable to limit acquisition of a satellite to some restricted class or set of classes, such as periods of heavy use, the satellite broadcasts a list of inhibited class identifiers allowing only uninhibited classes access to the communication system. The method reduces thrashing by allowing access to users on a hierarchy class basis. The method uses both real time cell loading data and historical cell loading information based on previous experiences and can be programmed to limit access to emergency services in the case of natural disasters.

Abstract: Ongoing communications over radio links between communication stations and subscriber units may be unexpectedly broken. Where the communication stations include low-Earth orbit satellites, communication links are difficult to re-establish because of the timing differential and Doppler-frequency shift associated with the satellite's movement. The communication link is re-established by initially changing the modulation technique in an attempt to re-synchronize the communication station and the subscriber unit. If this fails, the subscriber unit performs an acquisition attempt on another antenna beam of the communication station. If this is not successful, the subscriber may perform an acquisition attempt on antenna beams of another communication station.