Microwave Mobile Communications
Microwave Mobile Communications
Convex Optimization
Iterative multiuser uplink and downlink beamforming under SINR constraints
IEEE Transactions on Signal Processing
Experimental characterization of the MIMO wireless channel: data acquisition and analysis
IEEE Transactions on Wireless Communications
Space-time transmit precoding with imperfect feedback
IEEE Transactions on Information Theory
Sum capacity of the vector Gaussian broadcast channel and uplink-downlink duality
IEEE Transactions on Information Theory
Capacity and power allocation for fading MIMO channels with channel estimation error
IEEE Transactions on Information Theory
Capacity limits of MIMO channels
IEEE Journal on Selected Areas in Communications
A random beamforming technique in MIMO systems exploiting multiuser diversity
IEEE Journal on Selected Areas in Communications
On the trade-off between feedback and capacity in measured MU-MIMO channels
IEEE Transactions on Wireless Communications
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Both linear and nonlinear transmit precoding strategies based on accurate channel state information (CSI) can significantly increase available throughput in a multiuser wireless system. With propagation delay, infrequent channel updates, lag due to network layer overhead, and time-varying node position or environment characteristics, channel knowledge becomes outdated and CSI-based transmission schemes can experience severe performance degradation. This paper studies the performance of precoding techniques for the multiuser broadcast channel with outdated CSI at the transmitter. Traditional channel models as well as channel realizations measured by a wideband channel sounder are used in the analysis. With measured data from an outdoor urban environment, it is further shown the existence of stable subspaces upon which transmission is possible without any instantaneous CSI at the transmitter. Such transmissions allow for consistent performance curves at the cost of initial suboptimality compared to CSI-based schemes.