Packet error rate-based adaptive rate optimisation with selective-repeat automatic repeat request for convolutionally-coded M-ary quadrature amplitude modulation systems

Link adaptation using adaptive modulation and coding (AMC) is a popular physical layer technique for efficient use of time-varying fading channels. Using a cross-layer approach, AMC and truncated automatic repeat request scheme at data link layer are jointly considered. For a convolutionally-coded M-ary quadrature amplitude modulation system under block fading channel condition, a variable rate transmission scheme that uses imperfect channel state information is derived. First, a closed-form expression for approximating packet error rate (PER) is found as a function of coded information rate. It is then shown that by solving an optimisation problem using this expression, optimum transmission rate can be determined in a way that maximises the spectral efficiency while satisfying an average PER constraint. Hence, the parameters in physical and medium access control layers are incorporated in the analysis.