Lockheed Martin Corporation

General Electric Company

John Bailey Anderson

John Anderson Fergus Ross

Nick Andrew Van Stralen

Richard Louis Zinser

Stephen Michael Hladik

Mark Lewis Grabb

Steven Robert Koch

A method is described for convolutionally encoding and decoding data (voice coded data), organized into (35-bit, 20 msec) frames, where the data is encoded by a finite-state data encoder (RSC coder ) for transmission over a data channel ( ). The RSC encoder avoids the need for termination bits associated with each N-bit frame of data, so that the number of bits associated with each encoded frame is reduced, and the throughput of the channel can be increased. The method according to the invention includes storing the first M bits of each frame. Once they are stored, they are loaded in parallel into the M stages of the encoder, thereby deleting residual states from the preceding frame. The remaining (N&minus;M) bits are then applied to the encoder, causing it to produce the convolutional code. After the last of the (N&minus;M) bits are encoded, the M stored bits are summed with feedback from the encoder, and reapplied to the encoder. The ending state of the encoder is thus equal to the starting state.

Method for tail-biting and decoding recursive systematic codes

A method for decoding (voice)data where the data is encoded by a finite-state data encoder ( ) for transmission over a data channel ( ), includes the step of procuring a table of joint statistics representing the probability of occurrence, in a frame of source data of each of the bits of the frame. The joint statistics may be determined ahead of time. The method includes the step of calculating intermediate gamma signals in response to the decoded data of the preceding frame and the joint statistics. The joint statistics source distribution signals represent the likelihood that, for a given logic level of the preceding bit, the &ldquo;current&rdquo; bit takes on a particular state; for uncorrelated bits, this value is 0.5. State probability signals and transition probability signals are generated from the gamma signals. The state probability and transition probability signals are processed to produce bit probability signals indicative of the probability that the current bit is in a given state, from which hard bit decisions can be made.

Channel decoder using vocoder joint statistics

A feedback control for a turbo decoder controls the feedback between component decoders by modifying updated a priori probabilities calculated by one component decoder and used as inputs to another component decoder during the decoding process, resulting in a significant performance advantage. A feedback control switch selects either previously estimated a posteriori probabilities, modifications of these values, or neutral values as a priori probabilities utilized by the next component decoder.

Turbo code decoder with controlled probability estimate feedback

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Lund, Sweden

John Bailey Anderson