Multicarrier spread space-spectrum multiple access for the MIMO forward link transmission

We study our previously proposed space-time multiple access framework (see Ng, B.K. and Sousa, E., WCNC´02, 2002) for MIMO forward link transmission in a multipath-rich environment. The primary goal is to achieve high bandwidth efficiency employing multicarrier modulation, while the number of user-channels, rather than the individual´s data rate, is to be maximized. In the proposed framework, we focus on a single spreading period, in which the data from different users are multiplexed using space-time-frequency-diagonal (STFD) spreading sequences. It is shown that spectral efficiency of N users/Hz/sec can be achieved, where N is the number of transmit and receive antenna elements. Simulation results indicate that frequency diversity gain can be obtained with only linear-processing at the receiver.