Iterative Channel Estimation and Partially Coherent Demodulation of CPFSK in Time-Selective Fading Channels

When continuous-phase frequency-shift keying (CPFSK) is used over a fading channel, coherent demodulation can offer a significant performance gain over noncoherent demodulation. However, when the fading varies over a packet, pilot symbols must typically be inserted to help track the channel phase, thus reducing the data rate and energy efficiency. If the spacing between pilot symbols is greater than the channel coherence time, then the phase estimates for symbols that are far from the pilot symbols will be poor. In such scenarios, partially coherent demodulation can be utilized to properly demodulate symbols based on the quality of their phase estimates. In this paper, we apply iterative channel estimation, partially coherent demodulation in a system employing CPFSK modulation over a time-selective Rayleigh fading channel. We show that this approach can significantly improve the performance of CPFSK over schemes that use only noncoherent or coherent demodulation.