Performance of coherent and differential detection for trellis‐coded 8‐PSK over satellite flat rician fading channels

Abstract

AbstractTrellis‐coded 8‐PSK (TC‐8‐PSK) modulation is a power and bandwidth efficient modulation scheme which is finding increasing applications in terrestrial and satellite systems. In particular, TC‐8‐PSK is demonstrating attractive performances over die satellite mobile fading channel where it provides considerable coding gain with respect to uncoded QPSK with no bandwidth efficiency loss. In this paper die capabilities of a decision‐directed maximum‐likelihood coherent phase tracker are investigated for flat Rician fading channel. Open loop and steady‐state performances of die digital phase tracker are analytically determined and verified by means of computer simulations. By optimizing phase loop parameters in presence of Rician fading with respect to the mean time to lose lock, it is shown that, for typical satellite fading channels, die coherent decision‐directed phase tracker performs poorly. This is also true for feed forward decision‐feedback phase estimator. In these cases, the additional power loss required by differential detection of TC‐8‐PSK respect to coherent detection has been evaluated by means of computer simulations.