Introduction

Abstract

There are two major error control techniques that are used for digital information transmission over noisy channels: convolutional codes and block codes. Although the block codes were discovered before the convolutional codes, efficient maximum likelihood decoding was first introduced for convolutional codes. Such a technique, also known as trellis or Viterbi decoding, has been under investigation since the early 1960’s. Significant progress has been achieved in this area and currently Viterbi decoders for convolutional codes are widely used in different communication systems, and are available in the information technology market in the form of application specific integrated circuits (ASIC), software packages for digital signal processors (DSP), etc.