Coherent detection of interleaved trellis encoded CPFSK on shadowed mobile satellite channels

A receiver that utilizes trellis coded continuous phase frequency shift keying (CPFSK) with coherent detection and convolutional interleaving of the coded symbols for data transmission is presented. An earlier study considered decoding based solely on the code trellis. A new decoding algorithm that copes with the interleaving is presented and uses information from both the modulation trellis and the code trellis. The performance results are obtained by Monte Carlo simulation and are partially verified through analysis. The fading model is Rician, but the line-of-sight (LOS) component is subjected to a log-normal transformation that represents attenuations due to foliage which is referred to as shadowing. The system studied is not suitable for digital speech applications as the required interleaving depths lad to an unacceptable time delay