The distribution and percentiles of Foschini´s lower bound for channel capacity

Foschini gave a lower bound for the channel capacity of an N-transmit M-receive antenna system in a Rayleigh fading environment with independence at both transmitters and receivers. We show that this bound is approximately normal and that its distribution has a non-standard Edgeworth-type expansion. This allows one to obtain non-standard Cornish-Fisher expansions for its percentiles and so obtain its distribution and outage levels for given probabilities