Differential space-time block codes from amicable orthogonal designs

In this paper, we propose an amicable-orthogonal-design-based differential space-time block code (ADSTBC) for multiple antennas. Compared with the existing differential modulation designs, our scheme imposes no restrictions on underlying signal constellation, and therefore can improve the spectral efficiency by exploiting efficient modulation techniques such as QAM, APSK, etc. We then derive a non-coherent maximum-likelihood decoder (MLD) with linear complexity for flat Rayleigh fading channels. Particularly, when the QAM constellation is used in ADSTBC, MLD can be further simplified to independently detect the real and imaginary parts of each modulated data symbol, and accordingly the implement cost can be greatly reduced; moreover, the computational amount for detecting single modulated data symbol is kept constant in MLD while the order of the QAM constellation increases.