Abstract: An approach for providing message synchronization in a communication system is disclosed. Using a selected channel coding method (e.g., Golay coding), an encoder encodes a message for transmission over a communication channel. An interleaver applies a predetermined interleaving pattern to the encoded message. A mask pattern with a prescribed sequence of bits is applied to the interleaved message; the prescribed sequence is ordered to eliminate an all zeros bit pattern and an all ones bit pattern. A multiplexer multiplexes the masked message with data traffic over the communication channel. The masked message is segmented into multiple blocks of a fixed length. At the receiver side, the mask pattern is applied to the demultiplexed message. The message is de-interleaved and decoded to restore the original message.

Abstract: A satellite system includes a plurality of orbit slots having a first orbital and a second orbital slot. A first satellite occupies a first orbital slot and generates a first set of uniform beams. A second satellite located in a second orbital slot generates a second set of uniform beams. A tiling pattern on the face of the Earth has a plurality of cells, with each of the cells having a defined frequency for communication. The first set of beams and the second set of beams are generated according to parameters to avoid interference between them. The parameters may include satellite orbit separations, beam size, multiplicity of band reuse, and ground station received beamwidth.

Abstract: A method and apparatus for providing a virtual video on demand services is disclosed. The method and apparatus disclose the storing of a segment of the video program in advance for VOD viewing at a later time. When the subscriber selects VOD service, a pre-stored video segment is retrieved for presentation to the subscriber. Remaining video program segments simultaneously broadcast on a plurality of channels are recorded in parallel while the pre-stored video program segment is retrieved and presented to the user.

Abstract: General binary design criteria for PSK-modulated space-time codes are provided. For linear binary PSK (BPSK) codes and quadrature PSK (QPSK) codes, the rank (i.e., binary projections) of the unmodulated code words, as binary matrices over the binary field, is used as a design criterion. Fundamental code constructions for both quasi-static and time-varying channels are provided.

Abstract: A satellite communication system has a first deployment of a plurality of satellites deployed in a medium earth orbit and two later deployments of a plurality of satellites deployed in the medium earth orbit. The first deployment is spaced so that the second deployment may be easily deployed and interleaved into the first deployment. A ground terminal is used for communicating with the satellites in the first and second deployments.

Abstract: An optical communication terminal transmits data via an optical signal with a transmit mirror positioned to direct the optical signal. The optical communication terminal includes a processor configured to develop a control signal for a mirror controller to establish an optimal position of the transmit mirror. The optical communication terminal further includes a modulator coupled to the processor that modulates the optical signal in accordance with a position of the transmit mirror during transmission of the optical signal. The optimal position of the transmit mirror may be established by a scanning routine that adjusts the position of the transmit mirror to a plurality of predetermined offset positions during transmission of the optical signal. The intensity of the optical signal as received by a further optical communication terminal is then determined and provided via modulation of a further optical signal transmitted back to the first-named optical communication terminal.

Abstract: A VSAT communications outdoor unit for satellite communications has a saturated amplifier transmission circuit and a voltage detector. The voltage detector detects insufficient voltage to operate the transmission circuit. A signal generator connects and is responsive to a voltage detector output. The signal generator indicates with an external output that the transmitter is disabled. Preferably, the external output is separate from a link to the indoor unit. A switch for switching between the signal generator and an antenna pointing output responds to the voltage detector output.

Abstract: A satellite communications system having a fallback mode of operation, during which uplink signals are transmitted at a reduced data rate, is provided with a novel fallback mode ingress/egress mechanism utilizing a combination of a feedback-based fade detection scheme and fade detection based on parameters independent of the uplink signal transmission. The fallback mode ingress/egress mechanism is responsive to a satellite beacon signal independent of the uplink signals and to feedback signals produced by the satellite in response to the uplink signals, for requesting a satellite terminal to switch into the fallback mode when either the feedback signals indicate an increase in a fade level or in response to a first value of a selected parameter of the satellite beacon signal. The fallback mode ingress/egress mechanism requests the satellite terminal to switch out of the fallback mode in response to a second value of the satellite beacon signal parameter.

Abstract: A method of providing forward error correction for data services uses a parallel concatenated convolutional code which is a Turbo Code comprising a plurality of eight-state constituent encoders wherein a plurality of data block sizes are used in conjunction with said Turbo Code. A variation uses the method in a cellular radio system. Another variation uses the method in both forward and reverse likes of a cellular radio system.

Abstract: A system and method that provides satellite television users with a simple interface in which to choose from a variety of video images representing a different camera angle at a given event. The invention comprises a plurality of cameras positioned at a certain event, such as a sporting event. The video images from the cameras are broadcast to one or more satellites, which downlink the images to a central broadcast center. At the central broadcast center, information relating to the event is bundled with the video images and re-broadcast to a second set of satellites. The information and video images are then downlinked to multiple users situated within the satellite's footprint, to be viewed on their televisions.

Abstract: A radar surveillance system includes a plurality of satellites a plurality of medium earth orbit satellites to provide continuous, long dwell coverage of a region of interest. Each satellite has an antenna having a main reflector and a subreflector electromagnetically coupled to the main reflector. A phased array generates multiple electromagnetic beams positioned so the electromagnetic beams reflect from the subreflector onto said main reflector. The system may be used in determining slow moving targets using a combination of monopulse anomaly and target spectral width measurements. The system also performs synthetic aperture radar imagery and focussed area fast moving target detection using alternating slope linear frequency modulated pulses. The plurality of medium Earth orbit satellites include a self-contained communications system consisting of high bandwidth self-relay crosslinks, high bandwidth downlink, and direct broadcast downlinks for processed data.

Abstract: A method and apparatus for mitigating communications interference between satellite communications systems in different orbits is disclosed. The method comprises the steps of evaluating a geometrical relationship between a second ground station and the satellites in the second satellite constellation, and directing communications between the second ground station and the second satellite according to the evaluated geometrical relationship. In one embodiment communications are handed over from a first satellite to another satellite when the first satellite is no longer at the highest elevation angle of visible satellites. In another embodiment, handover occurs when the first satellite drops below a minimum elevation angle.

Abstract: A system and method for retransmitting data frames, which were inadequately received by a receiver, back to the receiver to increase receiver gain. Upon receiving a retransmission request from the receiver, the data transmitter retransmits a particular data frame to the receiver without transmitting a signaling message, and the receiver compares it to other data frames stored in a buffer. When a match is believed to exist, the receiver combines the retransmitted data frame with the matching data frame. Based on the result of a cyclic redundant code (CRC) check performed on the combined data frame, the receiver either provides the combined data frame to a higher layer in the receiver, or stores either the combined data frame, or the retransmitted and potentially matching data frame, in the buffer, depending on a confidence in the potential match, and sends another retransmission request to the transmitter to again retransmit the data frame and the above process is repeated.

Abstract: A method, apparatus, article of manufacture, and a memory structure for multicasting data in a cellular personal access communication system is disclosed. The method comprises the steps of allocating a multicast packet terminal identifier to a multicast group when a subscriber unit in a cell requests membership in the multicast group, receiving a multicast packet having a global multicast address, determining a cell identifier from a mapping of the global multicast address to at least one local multicast identifier and a cell identifier, and forwarding the multicast packet to the cell according to the cell identifier. The apparatus comprises a radio port controller unit having a packet data control unit coupled to a radio port configured to receive a multicast packet and a packet forwarding module. The packet data control unit includes an allocation module configured to allocate a local multicast identifier to a multicast group when a subscriber unit in a cell requests membership in the multicast group.

Abstract: A method and apparatus for providing an integrated presentation of existing media program services and secondary media program services is described. The method comprises the steps of accepting a election of a secondary media program transmitted on a secondary media program channel; accessing a mapping to determine a primary media program channel associated with the selected secondary media program channel; commanding a first tuner module to receive conditional access information associated with the primary media program channel from the primary service provider; evaluating the conditional access information to determine if a second tuner is authorized to receive the secondary media program channel; and commanding a second tuner module to receive the secondary media program if the second tuner is authorized to receive the secondary media program channel.

Abstract: A method and apparatus for performing satellite selection in a broadcast communication system is provided. In some embodiments, a controlling data stream broadcast on a first satellite over a broadcast channel is utilized to indicate that information signals such as a television program are being carried on the same channel on a different satellite. Remote receiving apparatus utilize the controlling data stream to locate the information signals by switching to the satellite identified in the controlling data stream.

Abstract: A system and method for optimizing random access control, and for optimizing transmission efficiency of data packets over reverse common channels between access terminals and a base station, in a wireless communications system. In the communications system, at least one of the access terminals is adapted to transmit at least a portion of an access data packet to the base station, and the base station is adapted to receive the portion of the access data packet and, in response, to transmit a message for receipt by the plurality of access terminals which indicates receipt of the access data packet portion by the base station and identifies the access terminal from which said access data packet portion is received. The message can control the other access terminals to refrain from transmitting an access data packet, while indicating receipt of the access data packet portion to the certain access terminal from which the access data packet portion had been transmitted.

Abstract: An approach for performing congestion avoidance in a switching communication system is disclosed. An input port of the switching communication system receives a bandwidth request from a source. The switching communication system includes a bandwidth control processor that examines the bandwidth request, and multiple output ports. The output ports communicate with various destination sites. A congestion avoidance logic within the switching communication system generates multiple clusters based upon a transmission constraint associated with the output ports; each of the clusters corresponds to a portion of the destination sites. The congestion avoidance logic determines a cluster threshold that corresponds to traffic load distribution among the critical clusters. Additionally, the congestion avoidance logic selectively grants the bandwidth request based upon the determined cluster threshold.

Abstract: A payload design for a multi-spot-beam satellite communication system includes a plurality of uplink spot beam receivers and downlink spot beam transmitters, and a broadcast transmitting subsystem capable of transmitting a broadcast beam to an entire system geographical service area. An input filter-switch-matrix (IFSM) controllably selects input IF signal bands for routing to an on-board digital signal processor-router (DSPR). The DSPR subsequently routes all received point-to-point and broadcast data packets to the appropriate downlink spot or broadcast transmitting subsystems for transmission thereof. The broadcast downlink allows broadcast transmissions to occur at the highest efficiency possible, while also allowing for flexible provision of surge capacity for point-to-point transmissions on previously exhausted spot beams by selective use of the broadcast beam for such point-to-point transmissions.

Abstract: A terrestrial communication system using satellite uplink and downlink frequencies is disclosed. A terrestrial cell site produces a signal at a satellite uplink frequency that is transmitted to a terrestrial user terminal. The terrestrial cell site receives a signal at a satellite downlink frequency that was transmitted by a terrestrial user terminal. The terrestrial cell site may include a signal nulling means in the direction of a satellite producing signals at the uplink and downlink frequencies.