New Multilevel Continuous Phase Modulation Scheme

In this paper we present a four dimensional (4D) multilevel trellis coded continuous phase modulation (CPM) scheme. In order to use a coherent linear receiver the transmitted signal is pre-coded so that the information is in the received phase and not in the phase difference between the two consecutive phase samples. The receiver is composed of a simple quadrature demodulator, followed by a symbol-rate sampler and a Viterbi decoder matched to the code trellis. BER performance shows 1 dB improvement at the BER of 10-5.