Spectral efficiency limitations of maximum ratio transmission in the presence of channel estimation errors

In this paper, we study the effects of Gaussian channel estimation errors on the achievable spectral efficiency of multiple-input multiple-output (MIMO) systems employing the so-called maximum ratio transmission (MRT) scheme over independent and identically distributed (i.i.d.) Rayleigh fading channels. To that end, we derive the capacity statistics of this transmit-receive diversity scheme. These statistics are valid for arbitrary numbers of transmit and receive antennas and are expressed as a function of the degree of correlation between the actual MIMO channel and its estimated counterpart. Our analytical results are extremely valuable, as they first obviate the need for time-consuming Monte Carlo simulations, with which they are in complete agreement, and second allow to gather insightful information about the impact of estimation errors, which may arise as a result of an imperfect channel estimation process, on the spectral efficiency performance of MRT employed over i.i.d. MIMO Rayleigh fading channels.