Abstract: A system and method of soft decision decoding is disclosed. An average signal magnitude is generated from a plurality of message bits. A scale factor is generated in accordance with the average signal magnitude, and soft decision bits are generated by processing the message bits using the scale factor. The scale factor and soft decision bits are transmitted and received across a communication link. The soft decision bits are rescaled using the scale factor and then rounded to the nearest integer value. The rounded values are then decoded. The soft decision bits are generated using a quantization having at least two bits, and soft decision bits are preferably rescaled using at least five bits.

Abstract: In a satellite communication system (20), a method (50) and system of locating terrestrial-based user terminals (UTs). A UT (23) is located by a two-tier estimation procedure. Under this procedure, an initial estimate of the UT location is performed based on absolute signal propagation delay and Doppler shift measured from a communication link between a satellite and the UT. A second, refined estimate of the UT location is then performed based on the results of the initial estimate. The second estimate can be a function of the absolute propagation delay and absolute Doppler, as well as differential delay and differential Doppler measured from transmissions from two or more satellites (21-22) to the UT (23).

Abstract: The present invention is embodied in a method an apparatus for reducing the number of leased E1 lines needed to backhaul communication traffic in a satellite communication situation. The present invention receives and decompressed a satellite signal. A copy of the compressed signal is then encoded into the least significant bits (LSBs) of the decompressed signal. The decompressed signal having the embedded information may be routed to an international PSTN network over leased communications lines. However, the compressed information is extracted from the decompressed signal and sent across the E1 lines, thereby conserving communication bandwidth and reducing the number of leased lines required. After passing through the E1 lines the information is decompressed and connected to the international PSTN network. Alternatively, the decompressed signal having the embedded information may be distributed to local PSTN networks, which interpret decompressed signals.

Abstract: The present invention is embodied in a method an apparatus for reducing the number of leased E1 lines needed to backhaul communication traffic in a satellite communication situation. The present invention receives and decompressed a satellite signal. A copy of the compressed signal is then encoded into the least significant bits (LSBs) of the decompressed signal. The decompressed signal having the embedded information may be routed to an international PSTN network over leased communications lines. However, the compressed information is extracted from the decompressed signal and sent across the E1 lines, thereby conserving communication bandwidth and reducing the number of leased lines required. After passing through the E1 lines the information is decompressed and connected to the international PSTN network. Alternatively, the decompressed signal having the embedded information may be distributed to local PSTN networks, which interpret decompressed signals.

Abstract: A method of channel estimation in a wireless communication system has steps of receiving a data burst comprising a plurality of portions of known data, and remaining data that is unknown; comparing reference data to each of the plurality of portions of known data and determining error for each of the portions of known data; averaging the determined error for predetermined ones of the portions of known data; and estimating error for at least a portion of the remaining data as a function of the determined error having been averaged.

Abstract: A method and apparatus for performing fractional minimum shift key modulation for a very small aperture terminal. A signal with a fractional modulation which appears to be frequency shift key is generated in the indoor unit. The outdoor unit employs a novel multiplication method to translate this signal to a minimum shift key modulated signal for satellite transmission.

Abstract: A frequency generation device for a satellite communication system composed of a central hub station and a number of remote units. The remote units contain a single synthesizer located in an indoor unit. In this invention, the indoor-located synthesizer is a direct digital synthesizer which modulates the baseband signal and conveys the modulated signal to an outdoor unit for communication between the remote unit and the central hub. In the outdoor unit, the signal is converted directly by a fixed number to a Ku band frequency and transmitted to the central hub.

Abstract: A remote ground terminal transmitter for transmitting a modulated data signal having a constant envelope amplitude. The remote ground terminal transmitter comprises a source of data signals, a modulator for providing a carrier signal, receiving a data signal from the source of data signals, and modulating the carrier signal with the received data signal so as to produce a constant envelope minimum shift key modulation signal. The transmitter further comprises a power amplifier which operates in the saturation mode to amplify the modulated carrier signal produced by the modulator to the desired power level.

Abstract: A mobile, satellite-based communication system includes a defined signaling arrangement developed from an analysis of factors including movement of the mobile terminals, movement of the satellite, beam discrepancies and duration of the call to the mobile terminal to set up a frame assignment plan for time division multiple access (TDMA) carriers and identifying permissible frame offset which can be accommodated throughout the entire transmission. As a result, timing and frequency references from a mobile to mobile command (MMC) may be provided from a reference source along with receive and transmit data communications without losing the command signals or the communication information and providing highly efficient use of each carriers time slots for receiving transmitting communication signals. Similarly, the signaling arrangement permits an efficient frame structure and a time slot assignment plan that does not require enhanced equipment at the mobile terminal.

Abstract: A remote ground terminal for transmitting a modulated data signal to a satellite. The remote ground terminal comprises a source of data signals, a demodulator for receiving a data signal and coupling the data signal to a transmitter, and for producing a power control signal during the period the data signal is present at an input of the demodulator. The power control signal is coupled to the transmitter and controls the operation of the transmitter such that the transmitter only receives power when the demodulator produces the power control signal. During the period the transmitter receives power, it functions to provide and modulate a carrier signal in accordance with the data signal received from the source of data signals.

Abstract: A method and system for using a low-cost, fixed output power radio in a multi-carrier communication system is disclosed herein. This system measures the output power of the multiple channel units within the system, obtains the current output power of the system, calculates a composite power and an expected power, compares the expected power and the current output power to calculate a gain adjustment value, and adjusting the output power of the system via the amplifier. The method for adjusting the power can also allow at least one of the carriers in the multi-carrier system to operate in a burst mode, and at least one of the remaining carriers to operate in a continuous mode during power measurement and gain adjustment steps.

Abstract: An apparatus for positioning a directional antenna of a remote ground terminal which transmits and receives signals to and from a satellite via the antenna. The apparatus includes a signal generator for producing a frequency variable reference signal having a variable duty cycle, and a controller which operates to analyze the signals received from the satellite and to vary the duty cycle of the reference signal in accordance with an identification tag forming part of the received signals. The apparatus further includes a detector which receives the reference signal and produces an antenna pointing signal having an average amplitude proportional to the duty cycle of the reference signal.

Abstract: A satellite communication system for providing maximum power output in a spread spectrum signal transmission is disclosed. Spectral shaping is provided at a satellite transmitter to shape a spread spectrum so that over a bandwidth of interest, the spectrum has a maximally flat characteristic. By maximizing the spectrum amplitude flatness, the required power density for a bandwidth limitation imposed to prevent interference with other communication facilities is maintained. In each earth station receiving the transmission from the satellite, a filtering is provided of the demodulated baseband satellite signal such that the spectrum is restored to its original shape. The filters on the receive side may be analog, having the same amplitude function as the transmit spectrum shaping filter, but having an inverse phase response. This insures a matched filter condition at transmitter and receiver, maximizing signal transfer. A programmable demodulator is provided to select a demodulation mode.