Suboptimal symbol-by-symbol demodulation of continuous phase modulated signals using the Laurent decomposition

Symbol-by-symbol detection is often used in systems with interleaved coded modulation in order to provide the needed soft-decision metrics for the decoding of the outer code. The paper develops a suboptimal symbol-by-symbol detection method for the demodulation of continuous phase modulated (CPM) signals. The proposed algorithm offers a reduced-complexity symbol-by-symbol detection in which the numbers of matched filters and trellis states are appreciably reduced. The complexity reduction is achieved by approximating the CPM signal using the Laurent representation. A simulation study shows that the performance degradation relative to the optimal full complexity algorithm is small for a variety of CPM signals.