On the Information Rate of Multiantenna Systems With Isotropic Unitary Input Signals in the Presence of Channel Estimation Errors

This correspondence focuses on the evaluation of the information rate conveyed by block-faded pilot-based multiple-input multiple-output (MIMO) systems when the input signals are isotropic-unitary (IU)-distributed and imperfect (e.g., error-affected) channel estimates are available at receiver and transmitter. Main contributions may be so summarized. First, we develop closed-form analytical formulas for the computation of the ergodic information rate conveyed by the considered MIMO systems equipped with a large number of transmit antennas. Second, we point out that no rate gain may be accomplished by shaping the transmitted streams on the basis of (possibly partial) channel state information (CSI) so that the feedback link becomes, indeed, useless when the system is block faded and fed by IU-distributed input signals. Third, we compare the obtained information rate with those supported by the corresponding MIMO systems fed by Gaussian-distributed input signals for various values of the mean-squared error (MSE) impairing the available MIMO channel estimates. So doing, we gain some insight about the operating conditions where actual implementation of a feedback link may be justified by the resulting improvement in the rate conveyed by the overall system