Packet error rate-constrained optimized variable rate scheme for convolutionally coded M-QAM system

Link adaptation using adaptive modulation and coding (AMC) is a popular physical layer technique for efficient use of time-varying fading channel. In this paper, using a cross-layer approach, we analyze the spectral efficiency of a variable rate transmission scheme in a convolutionally-coded M-ary quadrature amplitude modulation (M-QAM) system under block fading situation. For imperfect channel state information (CSI), a closed form expression for packet error rate (PER) as a function of coded information rate is obtained. Transmission rate is determined in a way that maximizes the spectral efficiency while satisfying an average PER constraint. Hence the parameters in physical (PHY) and medium access control (MAC) layers are incorporated in our analysis.