Efficient and reliable MAC-layer broadcast for IEEE 802.15.4 Wireless Sensor Networks

IEEE 802.15.4 represents a widely used MAC-layer standard for Wireless Sensor Networks. In multihop topologies, the protocol exploits a cluster-tree and organizes the transmissions by alternating sleeping and active periods in a superframe delimited by beacons. In this paper, we propose a new Contention Broadcast Only Period to limit beacon collisions and to reduce bandwidth wastage due to variable beacon durations. We adopt a CSMA-approach during the Contention Broadcast Only Period to efficiently deliver both beacon and broadcast packets. We also propose to use broadcast sequence numbers for a reliable MAC-layer broadcast delivery, for both cluster-tree and radio neighbors. Simulations with realistic conditions prove the relevance of this approach. We increase energy savings by reducing idle listening, and improve the MAC-layer broadcast reliability for both radio and cluster-tree delivery.