Abstract:

To improve spectral efficiency in cooperative relay system, a cross-layer optimization scheme is proposed, that combines adaptive modulation and coding (AMC) at physical layer with hybrid automatic repeat request (HARQ) at data link layer based on Nakagami-m fading channel. A state transition model is used to analyze and calculate the average packet error rate (PER) of cooperative relay system. To maximize the average spectral efficiency under the constraints of PER and transmission delay, the crosslayer optimization model by using iteration algorithm is solved, and the average PER and spectral efficiency of three types of HARQ protocol is compared. It is shown that the system performance of cooperative relay system is much better than that of non-cooperative relay system. In addition, the cross-layer design scheme combining type-III HARQ can achieve higher spectral efficiency and lower PER than type-I,II HARQ.

Key words: cross-layer design, cooperative relay, adaptive modulation and coding, hybrid automatic repeat request, Nakagami-m channel