Feedback capacity sharing in MIMO broadcast channels

The capacity of feedback links is typically limited and shared by multiple users. So this paper studies the impacts on multiple input multiple output (MIMO) broadcast channel (BC) when limited feedback capacity is shared among multiple users. Our mathematical analysis proves that in the high signal-to-noise ration (SNR) region, allocating the whole feedback capacity to a single user is the optimal sharing strategy of limited feedback capacity. On the other hand, it is shown that the feedback capacity should be equally shared among users in the low SNR region to achieve the maximum sum capacity.