A high rate open-loop MIMO multi-user downlink transmission system

In this paper, we first propose a new class of full rate full diversity quasi-orthogonal space time block code (QO-STBC), namely QO-STBC with blind preceding (BP-QO-STBC). Based on this code, an open-loop MIMO multi-user downlink transmission scheme is derived. Presuming M blocks of BP-QO- STBC are transmitted from the access point simultaneously, thus achieving a multiplexing gain of M, we show that the broadcasted signal can be separated by any user with only m_R ges M receive antennas, which is much smaller than that required by conventional linear schemes. By exploiting the special structure of BP-QO-STBC, we derived two decoding algorithms with different complexities, namely an optimal maximum likelihood decoder which achieves the lowest decoding complexity known for all full rate full diversity QO-STBC, and a suboptimal linear decoder with even lower complexity. Thus a flexible tradeoff between complexity and performance is achieved. A comparison between the proposed scheme and Random Beamforming in terms of bit error rate is also shown via simulation and the results support our proposed scheme as a better practical candidate for high speed wireless network.