Optimal and suboptimal symbol-by-symbol demodulation of continuous phase modulated signals

In applications requiring soft-decision metrics, e.g., systems,vith interle aved coded modulation, symbol-by-symbol detection is preferred to sequence detection. This paper develops the optimum soft-output algorithm (OSA) for the demodulation of continuous phase modulated (CPM) signals, Since this op timum detector is computationally complex, a class of suboptimum symbol-by- symbol detectors, called the reduced state soft-output algorithm (RS-SOA) i s developed, By varying certain parameters, the RS-SOA offers an effective tradeoff between performance and complexity, as measured by arithmetic oper ation count and the number of integrators required. Additionally, some simp le complexity reduction schemes can be used in conjunction with the OSA and the RS-SOA, The properties of the OSA and the RS-SOA, and the various comp lexity reduction schemes are explored in an extensive simulation study.