Cross-layer design of T-ARQ and adaptive modulation and coding in a spectrum sharing with cooperative relaying system

This study presents an analysis for a cross-layer design of a combined adaptive modulation and coding (AMC) with a truncated automatic repeat request (T-ARQ) scheme in an underlay spectrum sharing cognitive radio employing an amplify-and-forward cooperative relaying system. The considered AMC employs a coded M-ary quadrature amplitude modulation scheme combined with a T-ARQ to improve the performance of the secondary user (SU) system in the considered cognitive radio. To establish the performance analysis, the cumulative distribution function (CDF) of the end-to-end signal-to-noise-ratio at the receiver side of the SU system is derived. Then, using the derived CDF, closed-form expressions are derived for three important performance metrics: the average spectral efficiency, the average packet-error-rate, and the outage probability. To evaluate the performance of the considered system, numerical results obtained from the derived closed-form formulas are presented and compared. In addition, to verify the validity of the analysis, Monte-Carlo simulation results are also provided.