Joint Optimization of Adaptive Modulation and Coding, Power Control and Packet Retransmission over Block Fading Channels

Adaptive modulation and coding (AMC) and automatic repeat request (ARQ) protocol are powerful techniques for improving the spectral efficiency (SE) or the error performance in wireless packet networks over fading channels. In this paper, we first consider a discrete-rate M-QAM based AMC scheme and propose a variable power transmission scheme for transmission of packets over block-fading wireless channels. Considering the error-correcting capability of the truncated-ARQ, which depends on the maximum number of retransmissions (N_r), we then optimize the AMC and power control schemes that guarantee the required packet loss rate (PLR) performance while satisfying an average transmit power constraint. Numerical results reveal that in wireless packet systems with limited packet length, the proposed link adaptation algorithm improves the system performance in terms of the SE and the PLR However, this improvement depends on the target PLR and N_r When the target PLR is sufficiently small, this improvement will be observed in terms of the SE for small N_p however, in the larger target PLR, the improvement will only be observed in terms of the achievable PLR.