Evaluation of average bit error probability for space-time coding based ona simpler exact evaluation of pairwise error probability

The moment generating function method previously proposed by the author for the analysis of uncoded and coded digital communication over fading channe ls using only a single transmitter is applied to provide a simple exact eva luation of the pairwise error probability (PEP) for space-time coded system s with multiple transmitters. In certain scenarios. the PEP (and therefore the approximation to the average bit error probability (BEP)) can be evalua ted in closed form. An example of such a closed-form evaluation is presente d for the 4-state space-time code described in the literature with both slo w (constant over the length of a codeword) and fast (constant over the dura tion of a symbol) Rayleigh fading. The method also has the additional advan tage of allowing for direct evaluation of the transfer function upper bound on average BEP for the latter case.