Analysis of coherent and differential detection for trellis-coded 8-PSK over satellite flat Rician fading channels

Trellis-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 the satellite mobile fading channel where it provides considerable coding gain with respect to uncoded QPSK with no bandwidth efficiency loss. In the paper the capabilities of a decision-directed maximum-likelihood coherent phase tracker are investigated for the flat Rician fading channel. By optimizing the phase loop parameters in the presence of Rician fading with respect to the mean time to lose lock, it is shown that, for typical satellite fading channels, the coherent decision-directed phase tracker performs poorly. This is also true for the feedforward decision-feedback phase estimator. In these cases, the additional power loss required by differential detection of TC-8-PSK with respect to coherent detection has been evaluated by means of computer simulations