Abstract: An approach for reliably communicating over a satellite in support of a communication service including, for example, as direct broadcast satellite and data service, is disclosed. An input message is encoded, yielding a structured Low Density Parity Check (LDPC) coded message. The coded message is modulated according to a high order modulation scheme that has a signal constellation representing more than two symbols per signaling point—e.g., 8-PSK (Phase Shift Keying) and 16-QAM (Quadrature Amplitude Modulation). The system includes a transmitter configured to propagate the modulated signal over the satellite. The above approach is particularly applicable to bandwidth constrained communication systems requiring high data rates.

Abstract: A system determines a voicing measure as a measure of the degree of signal periodicity and uses the determined voicing measure to quantize the spectral magnitude of the slowly evolving waveform (SEW) and the modeling of the SEW and rapidly evolving waveform (REW) phase spectra.

Abstract: A method and apparatus for determining star tracker misalignments is disclosed. The method comprises the steps of defining a defining a reference frame for the star tracker assembly according to a boresight of the primary star tracker and a boresight of a second star tracker wherein the boresight of the primary star tracker and a plane spanned by the boresight of the primary star tracker and the boresight of the second star tracker at least partially define a datum for the reference frame for the star tracker assembly; and determining the misalignment of the at least one star tracker as a rotation of the defined reference frame.

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.

Abstract: A first transmitting device is used to transmit a first signal on a first carrier frequency to a relay device. The relay device receives the signal by demodulating the first carrier frequency. Subsequently, the relay device retransmits the signal by modulating a second and/or a third carrier frequency. The signal is then recovered at one or more receiving devices by demodulating the second and/or third carrier frequencies. Further, a second transmitting device transmits a second signal on a fourth carrier frequency and the relay device retransmits the signal by modulating a fifth and/or a sixth carrier frequency. The signal is then recovered at one or more receiving devices by demodulating the fifth and/or sixth carrier frequencies. The transmitting and/or receiving devices are preferably voice terminals, such as a wireless telephones or data terminals, such as portable computers.

Abstract: An approach for generating a structured Low Density Parity Check (LDPC) codes is provided. Structure of the LDPC codes is provided by restricting a certain part of the parity check matrix to be lower triangular, hence enabling a very simple encoding method that does not require the generator matrix of the code. The approach can also exploit the unequal error protecting capability of LDPC codes on transmitted bits to provide extra error protection to more vulnerable bits of high order modulation constellations (such as 8-PSK (Phase Shift Keying)). Additionally, an efficient decoding scheme is described where both bit nodes and check nodes are partitioned into groups. The edge values associated with each of the group can be placed together in memory simultaneously for bit nodes groups and check nodes groups. This architecture allows the multiple edges to be fetched from memory at a single clock cycle.

Abstract: An apparatus for generating a modulated signal which includes a modulator operative for receiving a first signal and input data signals, and modulating the first signal in accordance with the input data signals so as to produce a modulated reference signal; a first frequency divider coupled to the modulator output, operative to reduce the frequency of the modulated reference signal by a predetermined factor; a signal generator operative to produce a second signal; a first mixer having a first input coupled to an output of the first frequency divider and a second input coupled to the output of the signal generator. The first mixer operates to frequency translate the modulated reference signal by an amount equal to the frequency of the second signal. In addition, the signal generator of the present invention contains a direct digital synthesizer coupled to a second phase lock loop which operates to up-convert the output signal of the DDS to the microwave region.

Abstract: A TDMA beacon for satellite system synchronization includes a beacon signal generator and a time division multiplexed switch. The beacon signal generator generates a beacon signal. The TDM switch is coupled to the beacon signal generator and receives the beacon signal. The TDM switch embeds the beacon signal with a data signal into a TDMA signal. The TDMA signal is then broadcast to a ground station where the beacon signal may be extracted from the TDMA signal and used to synchronize a terminal with the satellite system.

Abstract: A method and apparatus for transferring a data signal includes a transmitter having an encoder and a receiver having a decoder. The encoder includes a segment selector for identifying a signal segment from a group of speech, audio, video and graphic signals, each selected segment comprising a representation of an information quantity. The encoder includes a plurality of encoder libraries, one of the libraries containing a generic representation corresponding to the information quantity and a symbolic code corresponding to the object. The decoder has a second plurality of libraries corresponding to the plurality of encoder libraries, and one of the decoder libraries generates the information quantity as output in response to matching of the symbolic code transmitted from the encoder.

Abstract: A spacecraft emulation system that can emulate both the attitude control subsystem and the non-attitude control subsystem is integrated into a single compact unit. The unit includes an emulated spacecraft control processor for processing attitude control information and an emulated central command and telemetry unit for interfacing simulated spacecraft data. The inlet also includes a first simulation engine that is operative to simulate the spacecraft attitude control system and a second simulation engine that is operative to simulate the spacecraft power, thermal, propulsion and payload subsystems. Both the first and second simulation engines are connected to the emulated spacecraft control processor via a respective bus. A host computer provides the command data and receives the telemetry data from the emulated spacecraft control processor.

Abstract: A method, apparatus and computer program product for encoding data transmitted over a communications channel, including pre-loading an encoder dictionary with a set of character strings expected to appear in input data to be encoded; and encoding the input data with the set of expected character strings pre-loaded in the encoder dictionary. In another aspect, there is provided a method, apparatus and computer program product for decoding encoded data received over a communications channel, including pre-loading a decoder dictionary with a set of character strings expected to appear in the encoded data; and decoding the encoded data with the set of expected character strings pre-loaded in the decoder dictionary.

Abstract: An adaptive quadrature amplitude modulation (“QAM”) decoding system for use in, for example, high speed, bandwidth efficient QAM communication systems includes a circuit that adaptively adjusts gain and voltage bias and provides adaptive equalization feedback based on the same signal used to decode the QAM symbols.

Abstract: A method for estimating and compensating for a fading communications channel includes the steps of generating matched filter data from a received data burst, interpolating between reference symbols to generate a fading channel estimate from the matched filter data, applying a phase correction to the matched filter data from the fading channel estimate to recover free data from the matched filter data, and performing decision feedback on the free data to improve the fading channel estimate.

Abstract: A spacecraft protected by a coating comprises a spacecraft having an external surface, and a coating on the external surface of the spacecraft. The coating includes a binder that is an organic material or an inorganic material, and a plurality of pyroelectric pigment particles bound together by the binder. The coating initially includes a coating vehicle which is subsequently evaporated so that the coating is a solid. The coating has a thickness of from about 0.001 inch to about 0.020 inch where the binder is an organic material, and has a thickness of from about 0.001 inch to about 0.010 inch where the binder is an inorganic material.

Abstract: An apparatus for communicating with a communication network includes a processor, communication circuitry that interfaces with a communication network, and a bus connecting the processor to the communication circuitry. A port is connected to the bus, which communicates using an external communication protocol specified by a peripheral device. A memory, comprising a translator module that converts signals between the external communication protocol and an internal communication protocol operates such that communication signals transmitted to the port are converted from the internal communication protocol to the external communication protocol and signals received by the port are converted from the external communication protocol to the internal communication protocol.

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 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: An encoder, decoder, method of encoding, and method of decoding which preserves the turbo coder performance in the waterfall region, while improving upon performance in the error asymptote region, by applying a parser or other similar element to the input bit stream. The parser assigns input bits to a subset of constituent encoders in a pseudo-random fashion. The parsing strategy breaks up input sequences producing low Hamming weight error events, thereby improving the weight spectrum and asymptotic performance of the code, while not impacting waterfall region performance. The parser or other similar element may also strengthen the weight spectrum without adversely affecting convergence of a corresponding decoder.

Abstract: A combined interference cancellation communication system employing forward error code (FEC) decoding for high spectral efficiency satellite communications. The disclosed system enables efficient utilization of available bandwidth through overlapping adjacent channels. A receiver is used to receive a waveform having data information and noise information. A filter bank is coupled with the receiver to receive and filter waveform and output channel information received by the receiver. The channel information received includes a combination of data signals and adjacent channel interference signals. Soft-input and soft-output decoders are provided to receive the channel information in order to calculate an estimated interference value. Additionally, the soft-input and soft-output interference canceler is provided for receiving the output channel information and the estimated interference value calculated from the decoders in order to provide a relatively more accurate estimated data signal.

Abstract: A system in which a personal computer sends messages into a TCP/IP network using a conventional dial-up link and downloads data from the TCP/IP network using a high-speed one-way satellite link. A preferred embodiment uses a conventional SLIP provider to connect to the TCP/IP network and uses a commercial software TCP/IP package that has a standard driver interface. A spoofing protocol compensates for the long propagation delays inherent to satellite communication.