The BICM Capacity of Coherent Continuous-Phase Frequency Shift Keying

Continuous-Phase Frequency Shift Keying (CPFSK) is an attractive modulation choice due its small spectral side-lobes and constant envelope. In order to improve the energy efficiency, CPFSK can be combined with a channel code. There is however a fundamental tradeoff between the energy efficiency of the coded system and its spectral efficiency, since coding gain typically occurs at the expense of bandwidth. In coded CPFSK, the power-bandwidth tradeoff is governed by the code rate r and the CPFSK parameters (the alphabet size M and the modulation index h). For CPFSK (and more generally for Continuous Phase Modulation (CPM)), signaling under bandwidth constraints involves a tradeoff between r and the modulation parameters.