Differential space-time modulation in rapidly fading channels

Previously proposed differential modulation schemes for time-varying channels may not achieve the full transmit diversity and the maximum Doppler diversity simultaneously. Based on an existing basis expansion model, a new differential space-time code, which wisely combines interleaver/de-interleaver with traditonal space-time transmitting technique to overcome such limitation, .is presented. Two noncoherent differential decoders, named decision-feedback differential detector （DF-DD） and Viterbi-algorithmbased multiple-symbol-detection differential detector （ MSD-DD）, are also derived. We show that our design may recover data symbols with full antenna diversity and the maximum Doppler diversity at high signal-to-noise ratio. System performance is evaluated with simulations.     

An Efficient Differential Space-time Modulation Method Based on Amicable Orthogonal Design

The authors propose an amicable-orthogonal-design-based differential space-time block code (ADSTBC) for multiple antennas. Compared with the existing differential modulation designs, their scheme imposes no restrictions on underlying signal constellation, and therefore can improve the spectral efficiency by exploiting efficient modulation techniques such as QAM and APSK. They then derive a non-coherent maximum-likelihood decoder (MLD) for flat Rayleigh fading channels. The amicable orthogonal property of data matrices assures that MLD has very low bit error rate and linear decoding complexity. Particularly, in two special cases of ADSTBC, the simplified MLDs which can greatly reduce the implementation cost are derived.