On Asymptotic BER Performance of the Optimal Spatial-Temporal Power Adaptation Scheme with Imperfect CSI

Conference: SCC 2013 - 9th International ITG Conference on Systems, Communication and Coding
01/21/2013 - 01/24/2013 at München, Deutschland

Proceedings: SCC 2013

Pages: 6Language: englishTyp: PDF

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Kuang, Quan (Institute of Telecommunications, University of Stuttgart, 70569 Stuttgart, Germany)
Leung, Shu-Hung (Department of Electronic Engineering, City University of Hong Kong, Kowloon, Hong Kong SAR)

This paper studies the asymptotic bit-error-rate (BER) performance of the joint spatio-temporal (S-T) power adaptation which has recently been proposed for beamforming space-time-coded multiantenna systems in the presence of imperfect channel state information at the transmitter (CSIT). We derive a closed-form asymptotic solution of the power adaptation, which is instrumental in characterizing the asymptotic BER performance. We show that with imperfect CSIT, the optimal S-T scheme gives exponential diversity gain in the low and medium SNR regions when the quality of CSIT is relatively good, but cannot increase the diversity order of the space-time-coded MIMO link at very high SNR. Compared to the previous design by treating imperfect CSIT as perfect to adjust the temporal power, the optimal S-T is more robust in retaining the exponential decrease in BER over a larger range of SNR. The results sharpen our understanding of the behavior of the optimal S-T strategy.