Raytheon Company

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Anthony Reid

A system for frame synchronization. Coarse synchronization is performed, in some embodiments, by using soft bit decisions to generate a list of candidate frame start positions, each with an associated estimated probability. The candidate frame start positions are then tested by decoding the frame data, and a frame start position for which a criterion of decoding success is met is selected. Fine synchronization is performed, in some embodiments, by using an encoded synchronization word in the encoded frame data. A first decoding pass is used to identify the position of the synchronization word. The start of the frame is inferred from the position of the synchronization word, and a second decoding pass, using the correct initial state, in the decoder, at the start of the encoded frame data, is performed.

System and method for frame synchronization

Concepts, systems and methods are provided herein for generating encoded binomial pulse position modulation (BPPM) signals having random, sparse sets of multiple pulses per channel usage interval for use in Free-Space Optical (FSO) communications. A data symbol can be modulated into a set of BPPM pulses for transmission over a FSO channel and a signal can be generated having the set of BPPM pulses over a predetermined time interval. The BPPM pulses can be encoded into one or more codewords based on a number of error correction bits to form a coded signal using the one or more codewords to represent the signal having the set of pulses for transmission over the free-space optical channel. The coded signal can be filtered and sampled to generate a set of samples. Position and amplitude data for the samples can be determined to reconstruct and decode the coded signal.

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Tucson, AZ, United States of America

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