Cross-layer design and performance comparison of HARQ schemes with imperfect CSI in cooperative relay networks

we consider cross-layer design frameworks and performance comparison of HARQ schemes in cooperative relay networks with imperfect channel state information (CSI). Firstly, we propose a state transition models to analyze and calculate the HARQ average packet error rate (PER) and latency performance over Nakagami-m channel with imperfect CSI for relay networks; Secondly, By combing the adaptive modulation and coding (AMC) at the physical layer with hybrid automatic repeat request (HARQ) at data link layer, a cross-layer optimization model that maximizing the average spectral efficiency is formulated under average transmitting delay constraints, and an iteration algorithm for the cross-layer optimization model is designed. We compared the average packet error rate (PER) and spectral efficiency of three kinds of different HARQ protocols in our cross-layer optimization schemes. The numerical results show that our schemes can achieve maximumspectral efficiency. The cross-layer design with AMC and type-III HARQ provides a larger spectral efficiency and lower PER with cooperative relay than the other two HARQ protocols.