A Modified V-BLAST Scheme for Achieving The Maximum Possible Diversity Gain

This paper focuses on a modified Vertical-Bell Labs Layered Space-Time (V-BLAST) system, where different delay offsets are intentionally applied to the spatially multiplexed data streams. We consider a multiuser MIMO uplink environment, where each user carries M_t transmit antennas, but is allocated only one signature sequence. Compared with the conventional V-BLAST, the modified scheme gains advantage mainly in two aspects: firstly, it is able to recover the transmitted information from only one receive antenna, whereas the conventional V- BLAST requires that M_r ges M_t (M_r is the number of receive antenna); secondly, the modified system could achieve the maximum possible diversity gain M_r of V-BLAST at the cost of limited multiplexing gain, whereas the diversity gain is only M_r - M_t + 1 in conventional V-BLAST with ZF detector. The exact closed-form expression of bit error rate (BER) is derived for an M_t times M_r modified system with ZF strategy. And further explanation for the performance difference between the modified and conventional scheme is given from the spatial correlation point of view. Finally, we compare the performance of our proposed system with the conventional scheme by computer simulations which validate the analytical results.