On effects of power reallocation and ordering in V-BLAST systems with adaptive modulation and antenna selection

The power reallocation effect and the ordering effect of interference cancellation (IC) of V-BLAST detectors are evaluated in two different systems, which are the V-BLAST system with antenna selection, and the V-BLAST system with both antenna selection and adaptive modulation. Power reallocation is introduced into the antenna selection process to keep a constant total transmit power. The performance of different IC ordering schemes, i.e. the optimal ordering scheme and the fixed ordering scheme, is compared in these systems through intensive simulations. The performance of optimal antenna selection schemes for both IC algorithms is also determined by searching all sets of transmit antennas extensively. It is shown that the performance of the optimal ordering scheme, in terms of throughput is superior to that of the fixed ordering scheme in the V-BLAST system with antenna selection, at the cost of heavy computational load. In the system with both antenna selection and adaptive modulation, the effect of the ordering is not consistent and the throughput of the optimal ordering scheme may sometimes even be worse than that of the fixed ordering scheme. Furthermore, when some optimal antenna selection scheme could be employed, the fixed ordering algorithm and the optimal ordering algorithm would have nearly the same performance.