DESIGN AND EVALUATION OF A SOFT OUTPUT VITERBI ALGORITHM (SOVA) FOR USE IN A CONCATENATED CODING SCHEME

Focal designs of Digital Communication Systems have consisted of coding schemes of improved error performance and increased data transmission using the same number of bits.  In a Link 16 Digital Communication system, a Viterbi algorithm is implemented to minimize the transmission errors by computing the most likely state sequence of a soft decision input and then outputting it as a hard decision.  The Viterbi Algorithm attempts to minimize bit errors of the output by estimating the original input bits. This is accomplished by calculating the different input possibilities of a specific output symbol and then assigning a confidence level to those inputs that have a higher probability of actually having occurred. An extension of the classical Viterbi Algorithm is the Soft Output Viterbi Algorithm (SOVA), which attempts to minimize bit errors as well. The SOVA differs from the classical Algorithm in that it outputs soft decisions, rather than hard decisions

It is proposed that a concatenated coding scheme be designed utilizing a SOVA within a controlled Digital Communication System. Its overall performance will then be evaluated and compared to the performance of the classical Viterbi Algorithm.