The initial MU-MIMO technique has been submitted to solve the fundamental problems of multi-antenna diversity technique in cellular networks when use for packet scheduling systems. It has been proved that the Alamouti technique can degrade the performance of high speed packet access sytems because it can smoothing the peak of the user channel. We discuss the brief history of multiuser MIMO systems in the following sections based on the above motivation.
TxD with HSDPA
TxAA for multiuser transmission
PU2RC for MIMO