User-initiated Suboptial Multiuser Joint Transmit-Receive Diversity in An Asymmetric MIMO Fading Channel

In user-initiated multiuser joint transmit-receive diversity (JTRD), each user equipment (UE) determines its diversity weight vector based on its own multi-input multi-output (MIMO) channel matrix and transmits pilot precoded by its diversity weight vector. Then, the base station (BS) obtains the equivalent multiuser MIMO channel matrix (which is a concatenation of user side diversity weight vector matrix and multiuser MIMO channel) and determines its multiuser JTRD weight matrix. There are suboptimal and optimal multiuser JTRDs. In the former, each UE determines its JTRD weight vector based on its own MIMO channel matrix. In the latter case, each UE applies the singular value decomposition (SVD) to its MIMO channel and determines the largest eigen vector as its JTRD weight vector. We show that in a strongly asymmetric MIMO fading channel (i.e., the number of BS antennas is considerably larger than that of UE antennas), the suboptimal JTRD using the selection weight vector provides a slightly higher diversity gain than that using the maximal-ratio weight vector and that the transmission performance difference between the suboptimal and optimal multiuser JTRDs is small.