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Relaxed threaded space-time codes

It is well-known that diversity, despite being widely used as a design criterion, may not be enough to ensure good performance of a wireless system, because the diversity factor may "kick in" at unrealistically high values of SNR. This paper proposes a new class of layered space-time codes with a new design criterion that works well in moderate SNR's. Specifically, we propose to relax some of the constraints of threaded algebraic space-time (TAST) codes, leading to a class of codes with better error performance, which we call relaxed threaded space time (RTST) codes. We also propose a modified design criterion, the average union bound (AUB), which ensures good performance at medium SNR. For a 2 times 2 system operating at 6 b/s/Hz, improvements of more than 1.5 dB have been observed