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In this paper, we study the minimum-mean-squared- error feedback precoder (MMSE-FBP) for the multiple-input multiple-output (MIMO) Gaussian broadcast channel (BC). It has recently been shown that MMSE-FBP can achieve higher sum capacity than zero-forcing and MMSE precoders, however, it still leaves a gap to the MIMO BC sum capacity. We propose two new schemes involving dynamic power allocation among users. These new schemes build on top of the MMSE-FBP structure and are able to achieve the MIMO BC sum capacity. We also discuss how our new schemes compare with an existing one and demonstrate how the transmitter and receivers can be simplified if the system is operating in mid to high SNR region.
Date of Conference: 27-30 Aug. 2007