Asymptotic Capacity Analysis for Sparse Multipath Multiple-Input Multiple-Output Channels

This letter is concerned with the asymptotic capacity analysis for sparse multipath multiple-input multiple-output (MIMO) channels. On the basis of independent multipath assumption, we asymptotically analyze the impact of system sparsity on the eigenvalue performance and capacity of the channel, and derive the closed-form expressions for them. Moreover, the approximations of the asymptotic channel capacity at high signal-to-noise ratios (SNRs) and low SNRs have also been presented. Our results indicate that the channel capacity is a monotonic increasing function of channel sparsity. Compared with the rich scattering environments, there is a decrease of channel capacity in the sparse channels, and the decrease at high SNRs only depends on the channel sparsity. Numerical results show that the asymptotic results have good accuracy to predict the capacity of MIMO systems with limited number of antennas.