Frequency-Domain Doubly-Iterative Equalization of Continuous Phase Modulation

In this paper, a doubly-iterative receiver with a soft-information-aided frequency-domain minimum mean square error (MMSE) equalizer is proposed for coded continuous phase modulation (CPM). Equalization in the frequency-domain provides low computational complexity in long multipath fading channel responses. The front-end equalizer is followed by the soft-input soft-output (SISO) CPM and channel decoders at the back-end. The receiver exploits double turbo processing by employing back-end demodulation/decoding iterations per each equalization iteration to improve the a priori information for the front-end equalizer. Such processing results in high bit-error rate (BER) performance with less number of equalization iterations, as also shown in the simulation results.