Application of error modeling at the output of maximum likelihood decoder to concatenated coded 16 PSK

The authors study the performance of coded 16 PSK (phase shift keying) (inner code) concatenated with a Reed-Solomon (RS) code (outer code). The overall redundancy introduced by the codes is 33% (spectral efficiency 2.7 b/s/Hz), 10% for the outer code (transmitted at the expense of data rate), and 25% for the rate-3/4 convolutional code (transmitted by increasing the size of the alphabet from 8 to 16). Because the performance of the outer code is strongly influenced by the error characteristics of the inner decoder, which is based on the maximum likelihood principle, the errors that result from this type of decoding are modeled. This model is used to evaluate the performance of different RS codes. Particular attention is paid to the memory effect of the inner Viterbi decoder