How to obtain turbo gains in coherent and non-coherent orthogonal transmit diversity

We consider turbo detection for coherent and non-coherent orthogonal transmit diversity. The turbo iterations are done between a convolutional code and the diversity combiner. We show that due to the orthogonal structure of the space-time block codes, extrinsic information which enables turbo gains can only be obtained for special symbol mappings. Such optimized symbol mappings arc given for 8-PSK, 16-PSK and 16-QAM. Furthermore, we present a simple non-coherent soft-output detector for differential space-time block codes. Extrinsic information transfer ( EXIT) charts are used as a powerful tool for analysis and performance prediction of the turbo detector. We show that a turbo detector benefits from spatial diversity in terms of earlier convergence. For quasistatic fading, we introduce the x%-EXIT chart.