A Delay-Guaranteed Geographic Routing Protocol with Hole Avoidance in WSNs

Wireless sensor networks (WSNs) are used in many mission-critical applications, such as target tracking on a battlefield, emergency alarms, and disaster detection. In such applications, QoS provisioning in the timeliness domain is indispensable. Moreover, because of the diversity of sensory data, QoS provisioning should support not only one but multiple levels of end-to-end delay constraints. As a result of several characteristicssuch as the limitations on the energy supply, available storage and computational capacity of the sensor nodes, guaranteeing timely delivery in WSNs is a challenging problem. To overcome these limitations, several lightweight and stateless QoS-based geographic routing protocols have been proposed. The existing protocols work well in networks without routing holes (i.e., regions with no working sensors). However, with the occurrence of routing holes, they suffer from the so-called local minimum phenomenon and traffic congestion around the hole boundary. In this paper, we consider the presence of routing holes and propose a delay-guaranteed geographic routing protocol called DEHA that can support multiple end-to-end delay levels. The main idea is to achieve early awareness of the presence of a routing hole and then to utilize this awareness in determining a routing path that can avoid the hole. Simulation results show that our protocol outperforms the existing protocols in terms of several performance metrics, including packet delivery ratio, energy efficiency, and load balancing.