Efficient Transmission Strategies Against Channel Time Variations in Multiuser MIMO Downlink Systems

Based on the analysis of the effect of the outdated channel state information (CSI) available at the transmitter (CSIT) on multiuser MIMO (MU-MIMO) downlink systems with block zero-forcing precoding (BZFP) method, two linear processing methods, BZFP at the transmitter with total MMSE decoding at the receiver (TBZF-RTMMSE) and BZFP at the transmitter with partial MMSE decoding at the receiver (TBZF- RPMMSE) are proposed. To fulfill them, a new pilot-sending and channel estimation architecture is introduced. Analysis and simulation results show that the two proposed methods can effectively reduce the impairment of the outdated CSIT and improve the system sum capacitv in the suitable time delav region of the CSIT.