Sequence-State Coding for Digital Transmission

1.1 General Binary information to be transmitted over a baseband digital system must typically be encoded into a sequence of symbols suitable for transmission through the channel. The structure of such codes is dominated by the set of requirements imposed by considerations such as channel characteristics and system operation. Several codes designed for baseband transmission have been discussed in the literature,1,2> 3 but the analysis of such coding has received little attention. This paper presents a systematic approach to the description and construction of codes for such application. The symbol sequence to be generated by the code is viewed as the output of a sequential machine with a set of permissible states derived from the imposed requirements. State-dependent codes, both of fixed and of variable length, are a direct result. Various properties of such codes are discussed, and two examples are presented. An advantage of using a sequence-state point of view is the ease with which it may be adapted to computer analyses, which are feasible due to the typically short word length of such codes (usually less 143