A Low Duty-cycle Low Latency MAC Protocol for Wireless Sensor Networks 1

Abstract. This paper presents Tone-Propagated MAC (TP-MAC), a novel MAC protocol for Wireless Sensor Networks (WSN)s, specially suited for early warning and tracking applications, where the traffic generated by sensor nodes (mainly alert messages) is sporadic but has stringent latency requirements. This protocol aims to maximize energy-efficiency while minimizing latency in source-to-sink and sink-to-source communication. This difficult objective is achieved integrating scheduled channel polling (i.e. synchronized low power listening) with rapid fast path establishment based on the propagation of short wake-up tones. An analytical model was used to compare TP-MAC with SCP-MAC. The results show that TP-MAC is able to achieve better target latencies even when its duty-cycle is lower during periods of inactivity. The results also show that the advantage of using TP-MAC increases with the hop-distance between source and sink