A Limited Feedback Scheme for Linear Dispersion Codes Over Correlated MIMO Channels

With partial channel state information (CSI) at the transmitter, the design of space-time codes for frequency flat, spatially correlated MIMO fading channels is considered. The focus of the paper is on the class of space-time block codes known as linear dispersion (LD) codes, introduced by Hassibi and Hochwald. For perfect CSI at the transmitter, the LD codes are optimized with respect to the instantaneous mutual information between the inputs to the space-time encoder and the output of the channel. An equivalent optimization problem is proposed and can that be solved by standard convex optimization algorithms. It is then conjectured that the LD codes obtained by maximizing the instantaneous mutual information converge to that obtained from maximizing the averaged mutual information in the large antenna asymptote. Based on the insights drawn from the conjecture, a limited feedback scheme for LD codes is proposed assuming a common codebook at the transmitter and receiver. The numerical result for a scattering environment suggests that the proposed feedback scheme achieves high performance at low complexity.