Difference Metric Decoder for Interleaved Biphase Trellis Code
Original Publication Date: 1988-Dec-01
Included in the Prior Art Database: 2005-Feb-15
A simplified maximum likelihood decoding algorithm and digital implementation for the rate 1/2, interleaved biphase trellis code for an extended class IV partial-response (EPR4) channel is described. When used with the decoder, the code provides a coding gain of 4.8 dB over uncoded class IV partial-response, unnormalized for the rate loss. An EPR4 channel (1 - D2) can be viewed as a pair of interleaved dicode (1 - D) channels. The decoder achieves low hardware complexity and the capability of high speed operation by means of pipelined decoding of interleaved biphase-coded dicode sequences. The decoding algorithm for the biphase-coded dicode sequences requires only 2 states, and it is simplified by computing only a single difference survivor metric for each pair of dicode samples.