A Cross-Layer Relay Selection Algorithm for D2D Communication System

Device-to-Device (D2D) communication assisted with relay transmission could efficiently optimize the system performance when D2D users are too far away from each other. In this paper, considering the individual QoS requirements, we propose a cross-layer relay selection algorithm which combines channel state information (CSI) at physical layer with queue state information (QSI) of buffer for each relay node at data link layer. Then we deduce the relay selection rule based on the CSI and QSI. Our method could make up for the problem that traditional relay selection schemes fail to consider the limited buffer capacity of relays. Simulation results illustrate that the cross-layer relay selection strategy can obtain a substantial system throughput gain. Meanwhile the algorithm leads to a decrease in average transmission time delay and packet error probability compared with the traditional ones.