On Limits of Wireless Communications in a Fading Environment when UsingMultiple Antennas
Wireless Personal Communications: An International Journal
On downlink beamforming with greedy user selection: performance analysis and a simple new algorithm
IEEE Transactions on Signal Processing - Part I
Zero-forcing methods for downlink spatial multiplexing in multiuser MIMO channels
IEEE Transactions on Signal Processing
Low complexity user selection algorithms for multiuser MIMO systems with block diagonalization
IEEE Transactions on Signal Processing
A transmit preprocessing technique for multiuser MIMO systems using a decomposition approach
IEEE Transactions on Wireless Communications
On the achievable throughput of a multiantenna Gaussian broadcast channel
IEEE Transactions on Information Theory
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This paper proposes a hierarchical feedback technique to solve the problem of massive feedback overhead in multiuser (MU-) multiple-input-multiple-output (MIMO) transmission, which is a serious obstacle to the application of MU-MIMO in real systems, especially with a joint operation of multiuser scheduling and precoding. Motivated by the observations that the multiuser scheduling phase dominates the feedback overhead and it is less sensitive to the accuracy of channel state information (CSI) than the precoding phase, the proposed technique adopts a two-stage feedback method to reduce the feedback overhead in the scheduling phase, meanwhile guarantee good performance of the precoding phase. In the scheduling phase, long-term CSI, such as mean and covariance channel matrixes, are used to reduce the overhead. In the precoding phase, on the other hand, more accurate short-term CSI is still used, since precoding is more sensitive to the CSI accuracy and also has less feedback overhead as only users selected in the scheduling phase are required to feed back their CSI. An angular information feedback technique is introduced to provide the long-term CSI for the transmitter in the scheduling phase, along with a low-complexity scheduling technique based on angular information. Simulation results have shown that the proposed hierarchical feedback technique can significantly reduce the feedback overhead of MU-MIMO transmission, while still achieve most of the performance gain.