Cross-layer design of AMC and truncated HARQ using dynamic switching thresholds

In this paper, we develop a cross-layer design incorporating adaptive modulation coding (AMC) and truncated hybrid automatic repeat request (HARQ). We define different packet error rate (PER) constraints for each (re)transmission, thus adopting dynamic switching thresholds correspondingly to fully exploit the combining gain in HARQ protocols. Analytical expressions for performance metrics are derived, based on which both multidimensional and simplified single-dimensional optimization problems are proposed to maximize the average spectral efficiency. Numerical results are obtained for analysis and our design has shown considerable performance improvement compared with conventional switching thresholds. Moreover, the single-dimensional optimization approach implies a suitable tradeoff between throughput and complexity.