The Mitre Corporation

Other

John D Fite

Jerome Mark Shapiro

James P Dunyak

John W Betz

Paul Capozza

James L Rasmussen

The present invention relates to methods and systems for enhanced signal acquisition through cross-ambiguity function (CAF) interpolation. In one aspect, the present invention provides methods and systems for CAF interpolation. In an embodiment, a first CAF generated using a low input sampling rate (e.g., 1 sample/chip) is interpolated to generate a second CAF having a higher sample per chip rate. By lowering the initial input sampling rate, cost and complexity of initial synchronization processing can be significantly reduced at the receiver. In another aspect, coherent and non-coherent interpolation methods and systems are provided for time and frequency CAF interpolation. Low cost and low complexity implementations of these methods and systems are also provided with associated CAF peak detection methods and systems.

Interpolation processing for enhanced signal acquisition

Methods and systems of signal cancellation/separation for use in multi-signal communication environments are provided herein. Embodiments of the present invention use a feedback-optimized multi-signal multi-stage estimator with data-aided signal parameter estimation. Embodiments of the present invention require minimal information about the received signals and can be used to separate a desired signal from an interfering signal or two desired signals received on the same frequency. In the latter case, embodiments of the present invention effectively double the capacity of the communication system. Embodiments of the present invention are suitable for environments with intentional and/or unintentional jamming or interference. System embodiments of the present invention can be used as in-line solutions that can be inserted at different points in a receive chain.

Removal of matched waveform interference

Reduction of multiple access interference, in one example for asynchronous CDMA systems using long codes. In one aspect, parallel interference cancellation (PIC) implements a decoupled estimate, preferably non-linear and applied at chip intervals. According to another aspect, interference is cancelled using a technique that estimates bits for a symbol by interpolating signature waveforms for users to a common sampling lattice of the received data. According to another aspect, multi-stage, hybrid multi-stage, and reconfigurable recursive multi-stage multi-user detection architectures and corresponding processes are provided.

System and method for interference cancellation with multi-stage multi-user detection

Sub-symbol parallel interference cancellation

Signal processing architectures for direct acquisition of spread spectrum signals using long codes. Techniques are described for achieving a high of parallelism, employing code matched filter banks and other hardware sharing. In one embodiment, upper and lower sidebands are treated as two independent signals with identical spreading codes. Cross-correlators, in preferred embodiments, are comprised of a one or more banks of CMFs for computing parallel short-time correlations (STCs) of received signal samples and replica code sequence samples, and a means for calculating the cross-correlation values utilizing discrete-time Fourier analysis of the computed STCs. One or more intermediate quantizers may optionally be disposed between the bank of code matched filters and the cross-correlation calculation means for reducing word-sizes of the STCs prior to Fourier analysis. The techniques described may be used with BOC modulated signals or with any signal having at least two distinct sidebands.

System for direct acquisition of received signals

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Clifton, VA, United States of America

John D Fite