Hybrid phase/data Viterbi demodulator for encoded CPESK modulation

The authors show that the Viterbi demodulator for correlative encoded CPFSK modulation is sensitive to carrier reference errors. They introduce a few extra phase states into the demodulation algorithm: The authors test the performance of their hybrid demodulation procedure, using an approximate analysis and a digital computer simulation which involves a simple vector structure and is based on orthogonal basis functions for the signal space under consideration. The demodulation algorithm result in a modest increase in the number of Viterbi decoder states and on increase in the number of receiver matched filters.