Performance of trellis-coded 8-DPSK modulation with co-channel interference in land mobile radio channels

The BER (bit error rate) performance of uncoded 4-DPSK (differential phase shift keying) and coded 8-DPSK (with 8 and 16 state codes) modulation schemes have been studied. A Rayleigh mobile channel and the presence of co-channel interferers have been assumed. BER calculations have been performed by means of computer simulation. In this simulation a Nyquist signaling and an ideal block interleaving process are assumed. Decoding of trellis codes with 8 and 16 states is performed by a soft Viterbi decoder. Results obtained for the uncoded 4-DPSK modulation scheme are considered as reference to determine the improvements introduced by the coding process. Remarkable coding gains can be attained for carrier to interference average power ratios greater than 20 dB. No significant improvements of the BER-performance seem to be obtained by increasing the number of states in the Ungerboeck codes