Hughes Electronics Corporation

Moe Rahnema

Mohammad Soleimani

Yezdi F Antia

A Roger Hammons, Jr

Anthony Robert Noerpel

Michael I Parr

David Alan Roos

Yash Vasavada

Zhen-Liang Shi

Ludong Wang

Jean-Aicard Fabien

Zheng-Liang Shi

A system and method employing an access terminal for maintaining discontinuous communications including a gateway receiver for receiving the discontinuous information, a radio frequency (RF) communication link via geosynchronous earth orbit satellite for conveying multiple communication channels using time division multiple access (TDMA), the access terminal initiating information communication with the receiver via at least one of the multiple communication channels. The access terminal further includes a memory for storing protocol processing information and a transmitter for establishing the radio frequency communication link to the receiver of the terrestrial gateway system. The access terminal memory provides for destroying of a signal pattern or protocol assigned to the access terminal by the gateway receiver or transmission of keep-alive bursts by the transmitter during periods of inactivity to maintain information communication with the receiver.

Signaling maintenance for discontinuous information communications

A message format and associated method for estimating the frequency and timing offset of a reference burst of a random access channel in a time-division multiple access communications system. A signal structure in which the continuous wave segment is split into two parts separated by some portion of the content of the random access channel burst is used to provide more precise frequency estimation. Iteration of separate frequency and timing estimation procedures is used to refine both estimates, as the individual estimation processes are more accurate when there is less error in the other parameter. Multiple hypothesis testing is used, in which more than one initial frequency estimate is carried through the iteration process, with thresholding to identify the best frequency offset. Reliable rejection of false ambiguities is achieved because the degradation in timing estimation, due to large frequency offsets, can be detected with thresholding.

Burst format and associated signal processing to improve frequency and timing estimation for random access channels

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.

Channel estimation in a fading channel

A method, and related apparatus, for coherently demodulating phase-modulated data which is coherently transmitted (i.e., without the use of differential encoding of the data) on Rician fading channels. The method uses phase unwrapping and phase interpolation, in conjunction with block phase estimation, to achieve a performance comparable with coherent detection of coherently transmitted data while reducing processing requirements.

Block phase estimator for the coherent detection of non-differentially

A data symbol timing recovery technique for determining an optimum symbol timing phase for use in digital communication systems using a burst mode digital communication format. The technique uses a nonlinear operation, e.g., squaring the magnitude of a down-converted baseband demodulated data burst. The squared signal is processed through a simple one pole IIR digital filter which extracts the symbol timing phase offset. The phase offset is scaled to the time domain and used to adjust the symbol timing of the next data burst. This technique is applicable to phase modulated data such as BPSK or QPSK modulated data. The technique was simulated using .pi./4 QPSK modulated data and provided improved and robust performance.

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Bethesda, MD, United States of America

Moe Rahnema