Performance of Adaptive Modulation with STBC and Imperfect Feedback Information over Rayleigh Fading Channel

Based on imperfect channel information feedback, the performance of space-time coded multi-antenna systems with adaptive modulation and feedback delay is investigated in Rayleigh fading channel, and the corresponding theoretical analysis for spectrum efficiency (SE) and bit error rate (BER) is presented. The fading gain value is partitioned into a number of regions by which the modulation is adapted in terms of the region the fading gain falls in. The fading gain switching thresholds for attaining maximum spectrum efficiency under a target BER and fixed power constraint are achieved. Based on these results, we derive the theoretical calculation formulae for the system spectrum efficiency and average BER in detail. As a result, the closed-form expressions for the spectrum efficiency and average BER are respectively obtained for perfect feedback. Besides, the system performance with delayed feedback information is analyzed, and the accurate and approximate BER expressions of the systems with imperfect feedback are derived, respectively. The obtained theoretical formulae will have more accuracy than the existing formulae. Simulation results show that the theoretical SE and BER are in good agreement with the corresponding simulated values, and the system has slight BER performance degradation for the normalized time delay less than 0.01.