Program

Interference-Aware Real-Time Flow Scheduling for Wireless Sensor Networks

Abstract

With the emergence of wireless sensor networks an enabling communication technology for distributed real-time systems, we face the critical challenge of meeting the end-to-end deadlines of real-time flows. This paper presents Real-time Flow Scheduling (RFS), a novel conflict-free real-time transmission scheduling approach for periodic real-time flows in wireless sensor networks. In contrast to existing transmission scheduling algorithms that ignore interference between transmissions or prevent spatial reuse within a same channel, RFS supports spatial reuse through a novel interference-aware transmission scheduling. While recent work on conflict-free transmission scheduling focused on specialized communication patterns such as queries and converge cast, RFS is designed for peer-to-peer real-time flows with arbitrary inter-flow interference. Moreover, RFS features several novel contributions that makes it particularly suitable for distributed real-time systems: RFS provides a real-time schedulability analysis that accounts for interference between real-time flows. Second, RFS improves reliability by incorporating retransmissions in a flexible scheduling scheme. Finally, RFS enhances scalability by dividing the network into neighborhoods and provides real-time performance for flows crossing multiple neighborhoods through a novel application of Release Guard. RFS was evaluated through simulations based on the traces collected from an indoor sensor network testbed. Compared with a traditional TDMA protocol, RFS reduces flow latencies by up to two orders of magnitude, while improving the real-time capacity by as much as 3.5 times.