Adaptive bit and power allocation algorithm in V-BLAST system

In the existing V-BLAST system with adaptive modulation, spectral efficiency decreases dramatically at lower SNR due to the invalid subchannnel which does not meet the target BER. To resolve this problem, a power reallocation algorithm is proposed in this paper. The post-detection SNR of the valid subchannel can be improved by reallocating the power quotas of the invalid channel to valid ones. Simulation results show that by means of the proposed method the spectral efficiency increases obviously, especially when the SNR is low.