Water-filling capacity analysis in large MIMO systems

In this paper, we study a water-filling power allocation scheme in large M × N MIMO systems over flat Rayleigh fading channels. It is shown that when M = N with sufficiently large M, the channel capacity of the water-filling scheme almost converges to a constant regardless of channel randomness. Moreover, it is proved that for the water-filling scheme, the required channel information at the transmitter in large MIMO systems can be greatly reduced without capacity loss. When M ≫ N or M ≪ N, it is shown that allocating equal power on each eigenchannel is almost as optimal as water-filling power allocation scheme in channel capacity.