Lattice-reduction aided detection: spatial multiplexing versus quasi-orthogonal STBC

Recently, lattice-reduction (LR) aided detection has been proposed in combination with linear and non-linear spatial multiplexing (SM) schemes, like zero-forcing (ZF) and VBLAST, in order to improve the performance of wireless communications systems. The performance of the LR-ZF detector is parallel to the maximum-likelihood-detector with some penalty in power efficiency. In order to reduce this gap, one can employ non-linear schemes like VBLAST with higher complexity. Instead of non-linear schemes at the receiver, we apply linear schemes at the transmitter, namely quasi-orthogonal space-time block codes (QOSTBC), in order to close this gap and to achieve full diversity. We analyze the impact of SM and QOSTBC on the equivalent channel model. Furthermore, we compare both schemes in terms of error performance.