Orthogonally-distributed space-time block codes for relay channels

The direct application of orthogonal space-time block coding (OSTBC) for multiple input and multiple output (MIMO) systems to distributed cooperative relay networks makes the equivalent channel matrix for maximum likelihood (ML) detection lose its orthogonality. Hence, this paper proposes a new design that makes the channel matrix be orthogonally distributed (OD) for a suboptimal symbol-by-symbol detector (SBSD). Using ODSTBC, an asymptotic symbol error probability (SEP) formula with SBSD is derived, showing the optimal diversity gain function is achieved. In addition, two kinds of ODSTBC designs for the distributed relay networks are presented, which interestingly renders that SBSD is equivalent to the ML detector. Numerical results verify the diversity analysis and indicate competitive error performance to currently available orthogonal distributed STBC designs with much simpler complexity.