Space-Time-Frequency Spreading and Coding for Multi-User MIMO-OFDM Systems

In this paper, we propose a multiple input multiple output, orthogonal frequency division multiplexing, code-division multiple-access (MIMO OFDM-CDMA) scheme. The main objective is to provide extra flexibility in user multiplexing, and offer better diversity/multi-user-multiplexing tradeoff. This is done by spreading on all the signal domains; i.e, space-time-frequency spreading is employed to transmit users´ signals. Our study and simulation results show that MIMO OFDM-CDMA is capable of flexible data rates and easy user multiplexing, while simultaneously suppressing the multi-user interfering signals. In addition, our scheme achieve a diversity gain significantly larger than that of the conventional 2-D CDMA OFDM scheme.