MIMO transmission over a time-varying channel using SVD

The performance of a system using singular value decomposition (SVD) over the multiple-input multiple-output (MIMO) channel depends on the accuracy of the channel state information (CSI) at the transmitter and the receiver. Time division duplex (TDD) systems can provide easily the CSI at both ends of the wireless link, but the CSI is incorrect due to delay between estimation of the CSI and its use. Two new architectures are proposed to correct this impairment of the CSI, and allow transmission at a rate just one bit lower than the capacity of the channel at a FdT=0.038, corresponding to a speed of 2 m.s^-1 and the Hyperlan 2 standard (FdT is the product of the Doppler frequency and the time delay between estimation and usage of the CSI). The proposed systems are different hybrid combinations of the zero-forcing (ZF) and SVD methods. A key feature is the preprocessing (precoding) of the transmit data by an estimation of the unitary V matrix. Both architectures outperform simpler systems without processing at the transmitter.