Celsat America, Inc.

Other

Trw Limited

Atc Technologies, Inc.

David D Otten

David Glenn Duckworth

Robert L Sackheim

A hybrid satellite communications system provides communications, particularly Internet access, to computer users. The hybrid satellite communications system includes a satellite system and a terrestrial communications system. The satellite system includes two transceivers. The first transceiver receives and transmits a first set of signals received from the terrestrial communications system to a plurality of user units. In reverse fashion, the satellite systems second transceiver receives a second set of signals in a second frequency band from the user units and transmits those signals back to the terrestrial communications system. The first set of signals (downlink signals) are of much higher frequency than the second set of signals (uplink signals). Preferably, the first set of signals are relayed by a Direct Broadcast System (DBS) satellite in a frequency band between 12.2 GHz and 12.9 GHz, while the second set of signals are relayed by a Mobile Satellite System (MSS) satellite operating between 1.0 GHz and 3.0 Ghz, or relayed by a terrestrial node operating between 0.8 and 2.0 Ghz. The differences in frequency between the first set of signals and second set of signals is considered optimal for the transmission and receipt of communications between a computer user with the Internet. Moreover, the present invention is capable of using the present communications infrastructures dedicated to the satellite transmission of television via DBS satellites, satellite cellular communications via MSS satellites, and radio communications via terrestrial cellular systems.

Data communications systems and methods using different wireless links for inbound and outbound data

A hybrid satellite communications system provides communications, particularly Internet access, to computer users. The hybrid satellite communications system includes a satellite system and a terrestrial communications system. The satellite system includes two transceivers. The first transceiver receives and transmits a first set of signals received from the terrestrial communications system to a plurality of user units. In reverse fashion, the satellite systems second transceiver receives a second set of signals in a second frequency band from the user units and transmits those signals back to the terrestrial communications system. The first set of signals (downlink signals) are of much higher frequency than the second set of signals (uplink signals). Preferably, the first set of signals are relayed by a Direct Broadcast System (DBS) satellite in a frequency band between 12.2 GHz and 129 GHz, while the second set of signals are received and transmitted by a Mobile Satellite System (MSS) satellite operating between 1.0 GHz and 3.0 GHz. The differences in frequency between the first set of signals and second set of signals is considered optimal for the transmission and receipt of communications between a computer user with the Internet. Moreover, the present invention is capable of using the present communications infrastructure dedicated to the satellite transmission of television via DBS satellites and satellite cellular communications via MSS satellites.

Hybrid satellite communications system

Methods for operating a wireless communications system provided for reducing the use of the system by unauthorized users by establishing the geographical location of selected user, comparing this location with the known locations of authorized users and denying service to the selected user if the selected user's location does not correspond to the known location of authorized users. Seamless hand-over of a user between nodes of the communication system is effected by periodically recomputing a algorithm which determines a preferred node for communication with the user. When the algorithm indicates that another node is preferred, a call initiation handshake is established between the user and the preferred node, while still maintaining communication with the original node. Communication between the user and the first node is not interrupted until the user establishes a communication 'lock' with the second node. Passive intermodulation interference of signals transmitted and received by nodes of a multi-satellite node system is eliminated by using certain of the satellite nodes for transmit-only and other of the satellite nodes for receive-only operation. In another embodiment PIM interference is eliminated by time duplexing the signals transmitted and received by a satellite's antenna. PIM interference is also reduced by assigning unique portions of each transmitter subband and each receiver subband to each of the satellite nodes.

Position determination for reducing unauthorized use of a communication

A mobile communications system provides communications with mobile users in the interference zones of communications services having priority of use of the frequency band in which the mobile user operates. The frequency band has been previously allocated for use by the other services, such as fixed microwave service (FMS); however, by means of the invention, the mobile user is able to conduct communications operations on a subband or subbands in that frequency band. A position locating system determines the position of the mobile user and if the user is within an interference zone, the mobile user is assigned subbands for operation in the previously allocated frequency band that are outside the subbands of operation of the FMS. A memory accessible by the processor selecting the frequency band of operation of the mobile user includes descriptions of the transmit and receive interference zones of each FMS. The processor selects the frequency subband of operation of the mobile user based on its position relative to the interference zone or zones. The system may have surface and/or space nodes and a network controller that monitors the mobile user's position and controls the nodes and user to subbands. Mobile users are isolated from the fixed microwave sites either by continuous management of their frequency assignments by calculations and commands sent from the network controller to the mobile user or by computations by the mobile user's unit. The mobile system is frequency agile by operating in dynamically selectable frequency subbands.

System and method for mobile communications in coexistence with

Apparatus and a corresponding method for controlling the attitude of a space vehicle during operation of its propulsion engines, without gimbaling of the engines. Two engines are differentially throttled, one above and one below a nominal thrust setting of the engines, in response to an error signal indicative of the difference between an actual attitude angle and a desired attitude angle. Three or four engines can be used to control attitude about two orthogonal axes, or a greater number of engines can be used for redundancy.

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Redondo Beach, CA, United States of America

David D Otten