Opportunistic Power Allocation for Random Beamforming in MISO Broadcast Channels

This paper proposes the opportunistic power allocation (OPA) scheme for random beamforming with a limited feedback rate. Without the channel state information, the proposed scheme allocates different amounts of power to different beams. Various low-complexity search algorithms for the proposed OPA scheme are also proposed to find the optimal power allocation that maximizes the sum rate. Computer simulations show that the proposed OPA scheme significantly improves the sum rate, and the optimal power allocation is found with low complexity. In addition, it is shown that the number of beams should increase as the SNR increases in order to maximize the sum rate.