Improve spectrum efficiency based on variable-power AMC and ARQ for OFDM systems

摘要

To improve spectrum efficiency (SE), the adaptive modulation and coding (AMC) and automatic repeat request (ARQ) scheme have been combined for OFDM systems. In this paper, we add variable power subject to power constraint in each AMC mode. We use KKT optimization algorithm to get the optimal transmit power and AMC mode boundaries. The numerical results show that the average SE is increased by about 0.3 bits/sec/Hz for OFDM systems with Nakagami fading with parameter m=2 when SNR is around 15dB and the retransmission is once.