Power Control for MIMO Diversity Systems With Nonidentical Rayleigh Fading

We investigate the performance limits and associated power-allocation problems in a multiple-antenna diversity system with statistical channel information available at the transmitter. The channels are assumed to be independent and nonidentically distributed Rayleigh fading. By studying both ergodic mutual information and information outage, we derive two simple and near-optimal power-allocation schemes. Specifically, for ergodic information rate maximization in a system with multiple transmit antennas and a single receive antenna, the proposed power control only depends on the ratios between channel gains and is independent of the total transmit signal-to-noise ratio (SNR). Meanwhile, for information outage minimization in a system with an arbitrary number of transmit and receive antennas, the proposed power allocation follows the water-filling principle and pours more power into the transmit antenna with a larger geometric mean of channel gains.