High data rate maximum a posteriori decoder for segmented trellis code words
AssigneeGeneral Electric Company
InventorsStephen Michael Hladik, Nick Andrew Van Stralen, John Anderson Fergus Ross
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Abstract
In a communications system, a trellis code word is segmented by both the encoder and a segmented MAP decoder. The segmented MAP decoder operates on code word segments as if they were individual code words and takes advantage of knowing the state of the encoder at specified times to reduce decoding latency and required memory. In a turbo coding system, for example, coding gain is maintained by interleaving the information bits across the segments of a component code word.
Claims20
A method for encoding digital data into trellis code words, each code word comprising a predetermined number of information bits Icw, generated by a source, the method comprising the steps of:
- (a) setting a predetermined maximum number of information bits in a code word segment Iseg;
- (b) for each Icw information bits, shifting groups of the information bits generated by the source into an encoder, each group comprising Iseg information bits if there is no remainder of Icw/Iseg information bits, and if there is a remainder of Icw/Iseg information bits, each group except the last group comprising Iseg information bits with the last group comprising the remainder;
- and
- (c ) shifting a predetermined number of merge symbols into the encoder after each group of information bits shifted into the encoder in order to return the encoder to a predetermined known state.
A method for decoding a segmented trellis code word having merged trellis segments, the method comprising the steps of:
- determining a trellis code word segment length and the corresponding number of information bits therein;
- and
- decoding each respective segment upon receipt of the last symbol thereof by calculating maximum a posteriori probabilities associated with each trellis code word segment.
An encoder for encoding digital data into trellis code words, each code word comprising a predetermined number of information bits Icw, generated by a source, comprising:
- an index calculator for setting a predetermined maximum number of information bits in a code word segment Iseg;
- a shift register for shifting groups of the information bits generated by the source into an encoder, each group comprising Iseg information bits if there is no remainder of Icw/Iseg information bits, and if there is a remainder of Icw/Iseg information bits, each group except the last group comprising Iseg information bits with the last group comprising the remainder;
- the shift register shifting a predetermined number of merge symbols into the encoder after each group of information bits shifted into the encoder in order to return the encoder to a predetermined known state.
A decoder for decoding a segmented trellis code word having merged trellis segments comprising:
- an index counter for determining a trellis code word segment length and the corresponding number of information bits therein;
- and
- a segment decoder for decoding each respective segment upon receipt of the last symbol thereof by calculating maximum a posteriori probabilities associated with each trellis code word segment.
Dependencies are inferred from the claim text.