Abstract
In this paper, a cross-layer scheme which uses joint queuing at the data link layer and orthogonal frequency division multiplexing (OFDM) adaptive modulation at the physical layer for two-hop multi-relay system is investigated. A finite state Markov chain for this scenario is proposed. Moreover, an amplify and forward (AF) cooperative system with finite-length queue at the data link layer is assumed. Finite-length buffer leads to lower delay quantities. We use relay selection scheme that improves the diversity gain in relay systems. Moreover, the packet loss rate is calculated. In order to minimize the packet loss rate, the optimized target packet error rate for adaptive modulation is obtained. The numerical results confirm the validity of using the proposed cross-layer scheme.