Performance analysis of SNR threshold-setting strategies for adaptive modulation and coding under fading channels

Adaptive Modulation and Coding (AMC) is a popular technique that dynamically adapts the employed Modulation and Coding Scheme (MCS) to the instantaneous channel quality, typically expressed in terms of the instantaneous Signal-to-Noise Ratio (SNR). The optimum MCS is selected based on a set of SNR thresholds, which define the range of SNR values on which each MCS is employed. The calculation of the SNR thresholds is a key aspect in the design and performance of AMC. This work performs a detailed and rigorous analysis of SNR threshold setting strategies for AMC, not only considering conventional methods commonly used in the literature but also proposing new methods to attain specific performance targets in terms of error rate, delay and spectral/energy efficiency. Closed-form expressions for these performance metrics are analytically derived under Rayleigh fading and employed to comparatively assess the performance of the considered solutions. The obtained results demonstrate that the proposed SNR threshold setting methods provide significant improvements in terms of error rate, delay and spectral/energy efficiency with respect to traditional methods.