Optimal diversity vs multiplexing tradeoff for frequency selective MIMO channels

In this paper we derive the optimal diversity versus multiplexing tradeoff for a frequency selective i.i.d. Rayleigh MIMO channel. This tradeoff is shown to be better than the one of the frequency flat MIMO channel. Traditional approaches for frequency selective channels use OFDM techniques in order to exploit the diversity gain due to frequency selectivity. We show that although coding in OFDM over a sufficient subset of subcarriers allows to exploit full diversity as such (at fixed rate), such an approach leads to a suboptimal diversity vs multiplexing tradeoff