Turbo code: Difference between revisions

Revision as of 22:38, 26 July 2005

Revision as of 02:56, 27 July 2005

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This introduces a probabilistic aspect to the data-stream from the front end, but it conveys more information about each bit than just 0 or 1.

: For example, for each bit, the front end of a traditional wireless-receiver has to decide if an internal analog voltage is above or below a given threshold voltage level. For a turbo-code decoder, the front end would provide a integer measure of how far the internal voltage is from the given threshold.

: pokp[kp[okpokTo decode the ''m+n''-bit block of data, the decoder front-end creates a block of likelihood measures, with one likelihood measure for each bit in the data stream. There are two parallel decoders, one for each of the ''n/2''-bit parity sub-blocks. Both decoders use the sub-block of ''m'' likelihoods for the payload data. The decoder working on the second parity sub-block knows the permutation that the coder used for this sub-block.

: pokp[kp[okpokToTo decode the ''m+n''-bit block of data, the decoder front-end creates a block of likelihood measures, with one likelihood measure for each bit in the data stream. There are two parallel decoders, one for each of the ''n/2''-bit parity sub-blocks. Both decoders use the sub-block of ''m'' likelihoods for the payload data. The decoder working on the second parity sub-block knows the permutation that the coder used for this sub-block.

===Solving hypotheses to find bits===