A reliable routing protocol against hotspots and burst for UASN-based fog systems

In Underwater Acoustic Sensor Network (UASN) based fog systems, the monitored messages are transmitted from the sensors deployed under the water to the surface sinks, which act as the fog nodes, for further processing. To ensure the reliability of the data transmission process, effective routing algorithms are necessary to reduce the packet loss rate as well as the transmission delay caused by potential traffic burst and hotspots. For this reason, a reliable routing protocol against hotspots and burst (RRAHB) is proposed in this paper. The fuzzy decision algorithm (FDA) for nodes path selecting is designed firstly. When the node chooses the next hop, the candidate nodes are evaluated by FDA. It eliminates the subjectivity of expert scoring and ensure fairness and effectiveness of the evaluated scores. But, FDA cannot solve the problems of hotspots and the load unbalance effectively, which are two important factors that cause data packets loss. Based on FDA, the random selection and hotspots avoidance mechanism are presented. The probability of the hotspots can be reduced by the random selection, and the hotspots effect is eliminated by the hotspots avoidance mechanism. In addition, in order to guarantee the network load balance, a priority-based traffic scheduling mechanism (PTSM) is proposed. It solves the traffic surge problem caused by emergency events and reduces the possibility of packets loss. The simulation results verify the effectiveness of RRAHB in the network with dynamic topology. Compared with the traditional routing algorithm, it has great advantages in improving network reliability and enhancing network performance.