Large-SNR Outage Analysis for the DF Relay Channel With Randomized Space-Time Block Coding
A simple half-duplex decode-and-forward relay channel is presented and analyzed. Relays access the common channel by means of a randomized linear-dispersion space-time block code which is flexible with respect to the number of relays and the coding rate. When the dimensions of the linear dispersion matrices grow large, but with constant ratio, the spectral efficiency of the system converges fast to a deterministic quantity. Simulation results show that this asymptotic value is an extremely good approximation of the finite reality, even for not so-large codes. Then, this asymptotic spectral efficiency is used to characterize the outage probability in the high-SNR regime.