An Asymptotic Waterfilling Solution for AWGN MIMO System Channels

Exact waterfilling solutions for multiple-input multiple-output (MIMO) systems are usually obtained using computationally costly iterative processes. In addition, the cost increases with the number of inputs and outputs, i.e. the size of the MIMO channel matrix. Systems with large channel matrices require less expensive solutions. Fortunately, by modeling the channel matrix as a random matrix is possible to take advantage of its statistics. This paper proposes a waterfilling solution based on the asymptotic behavior of the singular values of the channel matrix. The solution can be applied to any channel matrix realization, without the need of updating the channel state information.