Space-Time Water-Filling for Composite MIMO Fading Channels

We analyze the ergodic capacity and channel outage probability for a composite MIMO channel model, which includes both fast fading and shadowing effects. The ergodic capacity and exact channel outage probability with space-time water-filling can be evaluated through numerical integrations, which can be further simplified by using approximated empirical eigenvalue and maximal eigenvalue distribution of MIMO fading channels. We also compare the performance of space-time water-filling with spatial water-filling. For MIMO channels with small shadowing effects, spatial water-filling performs very close to space-time water-filling in terms of ergodic capacity. For MIMO channels with large shadowing effects, however, space-time water-filling achieves significantly higher capacity per antenna than spatial water-filling at low to moderate SNR regimes, but with a much higher channel outage probability. We show that the analytical capacity and outage probability results agree very well with those obtained from Monte Carlo simulations.