Sub-Optimum Detection of Coded Continuous Phase Modulation in Radio Channels

This paper presents a practical receiver for coded continuous phase modulation (CPM) intended for wireless communications in TDMA/FDMA modes. The coded CPM is interpreted as a single Markov chain. Usage of simultaneous complexity reduction techniques is proposed. Only two correlators (I and Q) are used as a front-end, both operating on over-sampling mode and projecting the received signal into a space of Walsh functions. Those metrics are fed to a reduced states sequence detector (RSSD) using the search algorithm, which is a generalised Viterbi decoding. A strong reduction in memory requirements is accomplished. The implications are studied for a known optimum concatenation: (8-ary; h=1/6) CPM with a rate 2/3 convolutional encoding.