REDUCED-STATE SEQUENCE DETECTION WITH CONVOLUTIONAL-CODES

Reduced-state sequence detection (RSSD) reduces the state trellis of a channel code by forming the states into classes. States within a clas s are such that paths into the states lie further than a distance para meter d from each other. An RSSD decoder retains only one survivor per class at each trellis level. We apply RSSD to ordinary binary convolu tional codes. We first give a class-forming algorithm that finds the g reatest reduction. It turns out that no commonly tabulated good code b enefits from RSSD. However, RSSD is an effective way to repair weaker codes, such as Quick Look-In and RCPC codes. Finally, we show that RSS D cannot be more efficient than the M-algorithm.