Abstract: The present invention utilizes a dual polarization reception system (200) that utilizes the energy available in orthogonal polarizations to effectively increase link margin, thereby allowing for adequate signal quality reception in difficult environments. A co-polarized and a cross-polarized signal are separately downconverted and demultiplexed. The signals from each demultiplexed output are then sampled and weighted. The weighted samples for each polarity are combined in soft decision combining/decoding circuitry (255, 360), and this circuitry determines the most likely state of a received symbol's transmitted value.

Abstract: Due to the large up front cost in fielding a full capacity satellite constellation (100), it is desirable to have the ability to modify the constellation after deployment to add more capacity in a fashion that does not interrupt service, in order to satisfy a variable or growing market demand. In a satellite constellation including a plurality of orbital planes, each of the orbital planes precesses at a known rate. This invention employs deliberate dynamic manipulation of the orbital precession rates for different satellite planes to increase the separation distance between two adjacent planes. A new plane is then inserted between the two adjacent planes to increase the number of planes and increase the capacity. By continuing a gradual variation, a new orbital plane can be added periodically, e.g. once a year, and the variation can be stopped when no additional orbital planes are desired.

Abstract: A satellite communication system uses dual satellite coverage techniques to simulate the provision of full duplex communications in the system. Each subscriber (100) in the system communicates with two satellites (102, 104) that use complementary time division duplex (TDD) frame structures (50, 72) for communicating with the subscriber (100). In one embodiment, each satellite in the system performs a transition between a first TDD frame structure (50) and a second TDD frame structure (72) while travelling through a transition region (102) of an associated orbit (130). Preferably, the transition is performed gradually so that an abrupt reduction in system capacity is avoided. In another embodiment, individual orbital planes in the satellite system are dedicated for use with particular TDD frame structures. A subscriber thus communicates with one satellite in each of two planes during a connection.

Abstract: An aircraft based communication system (10) defining a wireless service area (20) is disclosed. The communication system (10) includes a communication gateway (30) connected to a terrestrial based communication network. A first aircraft (12) is located in proximity to the wireless service area (20). The first aircraft (12) communicates with the gateway (30) and communicates with at least one subscriber (24) located within the wireless service area (20). The first aircraft (12) transmits a first control signal (16) within the wireless service area (20). A second aircraft (14) is located in proximity to the wireless service area (20). The second aircraft (14) being operable for communicating with the gateway (30) and being operable for communicating with the subscriber (24) located within the wireless service area (20).

Abstract: A method and apparatus for soft decision propagation trades off system bandwidth in return for link margin. When signal quality on an uplink is low, a satellite (20) sends soft decision data, rather than hard decision data, to a gateway (40). When path diversity exists on the uplinks, and multiple satellites (20) receive the uplink, multiple versions of soft decision data are sent to the gateway (40). The gateway combines the soft decision data resulting from multiple uplink paths, thereby increasing the effective uplink signal to noise ratio.

Abstract: A multicast message is transmitted from an originating subscriber unit (110, FIG. 1) through a network of satellite communications nodes (120, 130, and 140) to a plurality of receiving subscriber units (150, 160, and 170). Each message is distributed through the network of satellite communications nodes (120, 130, and 140) and replicated at the node nearest to the receiving subscriber unit. Receiving subscriber units (150, 160, and 170) are mapped into geographic cells which allows a single multicast transmission to be transmitted from the satellite communications node to those subscriber units within the same geographic cell. Multicast groups and membership rules are established by the originating subscriber unit (110) through a service provider (180). A multicast session manager (185) manages the multicast session.

Abstract: A communications system (100) has at least one TDD platform pair (130, 200) operating synchronously using a Time Division Duplex (TDD) frame structure. A TDD platform pair (130, 200) has first communications platform (124) and second communications platform (126) that are coupled (135) together. First communications platform (124) transmits first data during a first frame and receives second data during a second frame. Second communications platform (126) receives third data during the first frame and transmits fourth data during the second frame. At least one TDDSU (110) receives the first data, transmits the second data, transmits the third data, and receive the fourth data. First communications platform (124) has a first coverage area, and the second communications platform (126) has a second coverage area. A dual coverage area exists where the first coverage region overlaps the second coverage region. At least one TDDSU (110) is located within the dual coverage region.

Abstract: In a communications system, an earth-based subscriber unit (40, FIG. 1) receives at least one communications beam (50, 60, FIG. 1) transmitted from one or more moving satellite communications nodes (10, 20). The earthbased subscriber unit evaluates which communications beam should be selected based on the power received (FIG. 2, 210), Doppler frequency shift (270), link quality, (290), interference level (300), and satellite and network specific parameters (310). By considering these factors, the earth-based subscriber unit selects the communications beam (50, 60) that will provide the optimum service and reduce the likelihood that an inter-satellite hand over of the call will be required while the call is in progress.

Abstract: In a code division multiplexed system, a subscriber unit (260, FIG. 1), which includes a pseudonoise code generator (70), is synchronized with the pseudonoise code generator (220) of a communications node (200). Synchronization between the pseudonoise code generators (70, 220) is achieved through measuring the time delay of a signal transmitted from the communications node (200) to the subscriber unit (260) and advancing the code generator of the subscriber unit in accordance with the time delay. This permits transmissions from the subscriber unit (260) to be received synchronously at the satellite. The synchronization is maintained through the periodic transmission from the communications node (200) to the subscriber unit (260) of a message which commands the subscriber unit (260) to adjust the timing of its pseudonoise code generator. The resulting synchronous code division multiplexed system offers increased capacity over conventional systems.

Abstract: A communications network is capable of using time division multiple access (TDMA) techniques, code division multiple access (CDMA) techniques, or a combination of both. A subscriber unit (30) makes a request for a traffic channel over a CDMA pilot channel or a TDMA broadcast channel. A satellite (20) or a base station (40) receives the request and determines whether to assign a TDMA or CDMA traffic channel. The downlink and uplink can have the same access scheme (e.g., TDMA) or different access schemes (e.g., TDMA on the uplink and CDMA on the downlink).

Abstract: In a satellite communications system (100), system capacity is improved using a satellite (110 and 120) that includes a main mission antenna (MMA) (310 FIG. 3), antenna subsystem (320), and controller (350). Antenna subsystem (320) comprises a beamformer and associated software to optimize the beam shape and cell position with respect to the satellite's location. In one example, beam optimization is performed using a location based on latitude. Satellite (110 and 120) determines its spatial position and determines its latitudinal location based on this position information. The satellite determines the number of cells, the cell sizes, and the beam steering angles required at this latitudinal location. In other cases, beam optimization is performed using a location based on latitude and longitude, system loading, and satellite health and status.

Abstract: With a constellation of low-earth orbiting satellites, instantaneous photographs of all large cities can be made available in real-time or near real-time. Those photographs can be downloaded to ground stations, and there photographically interpreted to determine traffic conditions. The use of high and low photographic resolution permit making distinctions between different causes of traffic conditions. A color-coded map may be generated showing all major roads and their current status, showing such conditions as light traffic, medium traffic, heavy traffic and traffic accidents or jams, for example. These color-coded maps or color-coded alphabetized lists of streets may be broadcast to subscribers (broadcast stations, companies or individuals). From the color-coded traffic report, the subscribers are updated about which routes to avoid and what the best detours are around the more congested areas.