Predictive transmit beamforming for MIMO-OFDM in time-varying channels with limited feedback
IWCMC '07 Proceedings of the 2007 international conference on Wireless communications and mobile computing
Time-domain transmit beamforming for MIMO-OFDM systems with finite rate feedback
IEEE Transactions on Communications
Simplified maximum-likelihood precoder selection for limited feedback spatial multiplexing systems
GLOBECOM'09 Proceedings of the 28th IEEE conference on Global telecommunications
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Next-generation wireless systems are expected to leverage multiple-antenna, commonly called multiple-input multiple-output (MIMO), technology transmitting over broadband channels via orthogonal frequency-division multiplexing (OFDM). It is now well known that MIMO systems can obtain error rate and capacity improvements by adapting the transmitter to the current channel conditions. Linear spatial precoding is a popular technique for channel adaptation where the transmitted space-time signal for each subcarrier is multiplied by a precoding matrix before transmission. Spatial precoding is complicated, however, in OFDM because channel information is often only known for a small number of pilot tones. In this correspondence, we present a subspace interpolation method for designing spatial precoders for all subcarriers by using the precoders known on pilot tones. The nonpilot precoders are solutions to a weighted least-squares design on the Grassmann manifold. Simulation results show performance benefits over existing MIMO-OFDM techniques