Optimum zero-forcing detection of a Modified V-BLAST System with delay offsets

A modified Vertical-Bell Labs layered space-time (V-BLAST) system has been proposed in [1], where different delay offsets are intentionally applied to the spatially multiplexed data streams. Compared with the conventional synchronous V-BLAST system, the modified system can achieve M_r thorder diversity using zero-forcing(ZF) detection (where M_r is the number of receive antennas), therefore giving a reasonable tradeoff between complexity and performance. However, it is possible that there exist many detection algorithms under ZF criterion and we have no knowledge of whether the ZF detection algorithm used in [1] is the optimum among them. For this reason, this paper focus on how to find the optimum ZF detection of the modified V-BLAST systems. Both Analysis and simulation demonstrate that the optimum ZF detection is superior to the ZF detection algorithm used in [1], especially when the number of transmit antennas is large.