Transmit Power Allocation for the V-BLAST Algorithm

Optimum power allocation for the V-BLAST algorithm, which is based on various criteria (average and instantaneous block and total error rates (BLER and TBER)), is considered. Closed-form solutions are derived for high-SNR case in a Rayleigh fading channel. They are shown to be robust to small variations in allocated power and average SNR. It is demonstrated that the optimization "on average" is only slightly worse than the instantaneous one, albeit the latter requires an instantaneous feedback and hence is of higher complexity. The generic upper-bound for the SNR gain of any power allocation technique is derived. The BLER and TBER optimization criteria result in the same performance. Power optimization (of unordered BLAST) and optimal ordering result in almost the same performance improvement at high SNR.