Abstract: A method of increasing satellite communication quality by using a MEO satellite constellation (12) and a LEO satellite constellation (14) in combination with a decision algorithm which selects the appropriate constellation to route a communication signal through. The decision algorithm can be embodied in three ways: gateway based (18), individual subscriber unit based (22) and satellite based (12, 14). The MEO constellation (12) and LEO (14) constellation may be cross-linked, allowing for switching of service between satellites, as needed, during a communication session.

Abstract: A method and apparatus for acquiring satellite signals and subscriber unit signals utilizes broadcast beams (205) and acquisition beams (215) projected from a satellite (20). The broadcast beams (205) and acquisition beams (215) form broadcast acquisition beam pairs that are swept within the footprint (50) of the satellite (20) on the surface of the earth. Broadcast bursts are transmitted by the satellite (20) in the broadcast beams (205), and acquisition bursts broadcast by subscriber units (30) are received by the satellite (20) in acquisition beams (215).

Abstract: Interoperability between terrestrial cellular systems and satellite based cellular systems allows handoffs between different cellular systems. A call in progress by a subscriber unit (101) over a terrestrial based cellular system (100) which includes a mobile switching center (MSC) (105a) and a plurality of base stations (103a-d) is handed off to a satellite based cellular system (1000) comprising a satellite network (100a, 1001b), a regional gateway (1007) and an interface gateway (1005). A call in progress by subscriber unit (101) over satellite based cellular system (1000) is also handed off to terrestrial based cellular system (100). A dual mode subscriber unit (400) provides switching functionality (409) to switch between transmit modes.

Abstract: In a communication system (10) having at least one control center (24) and multiple satellites (12), the satellites (12) operate according to tables (80), wherein each satellites table becomes obsolete at a known time referred to as the exhaustion time. The earliest exhaustion time of all satellites (12) is determined and sent to the satellites (12) in the form of a message or a time-tagged update table (150). When the earliest exhaustion time is reached without updating the satellite (12), the satellites (12) enter default operation at that earliest exhaustion time. The satellites (12) continue default operations until otherwise instructed by the control center (24).