FAST-DTN: Farther-Aim-Shorter-Try disruption tolerant network for building monitoring applications

Wireless sensor network in building monitoring system (WSN-BMS) requires high reliability at scale. However, the performance of WSN-BMS is usually deteriorated by a unidirectional link and dynamic nature of wireless links in the building. Potential-based Entropy Adaptive Routing (PEAR) protocol uses DTN approach to attain reliability and scalability over intermittently-connected wireless network, but this approach resulted unacceptable high delivery latency. In this paper, we point out the problems leading to large delivery latency and propose FAST (Farther-Aim-Shorter-Try) forwarding scheme for PEAR in WSN-BMS. FAST modifies the current next-hop selection scheme to avoid the unidirectional links and combines DTN approach with traditional routing schemes, i.e. link quality metric and retransmission, to decrease delivery latency. We implemented FAST to PEAR and evaluated its performance on WiFi-based UTMesh testbed with 16 node-floor scenario and 33 node-multistory scenario. The experiment results show that FAST outperformed PEAR regarding delivery latency. FAST decreased 65.28% and 83.5% of median delivery latency compared to PEAR in floor and multistory scenario respectively.