Energy efficient broadcast protocols for asynchronous duty-cycled wireless sensor networks

In asynchronous duty-cycled wireless sensor networks (WSNs), each node has its own sleep schedule that is independent of the schedules of neighboring nodes. Since each node follows its own independent sleep schedule, the probability that a node’s neighbors will wake up concurrently is quite low. For this reason, each single hop broadcast must be completed through multiple unicast transmissions, and the sender node must remain awake until all of its neighboring nodes have received the broadcast packet. In this paper, we present two energy efficient broadcast protocols, namely Broadcast Progress-based Efficient Multihop Broadcast (BPEMB) protocol and Tree-based Efficient Multihop Broadcast (TEMB) protocol, for asynchronous duty-cycled WSNs. In both of the proposed protocols, the decision of whether to transmit the broadcast packet is based on the link quality information and without any forwarder’s guidance list. The redundant transmissions and collisions are avoided effectively with cooperation among the neighbors, so that the node with the best link quality to the receiver node takes responsibility to forward the packet to the receiver node. With this approach, nodes that are not involved in transmitting the broadcast packet can go to sleep and save their energy. In the BPEMB protocol, the forwarding decision of transmitting the broadcast packet is also influenced by the broadcast progress information, which is piggybacked in the broadcast packet. Through extensive simulations, we demonstrate that the proposed protocols can significantly improve the broadcast efficiency through reducing the energy consumption and minimizing the broadcast latency. The evaluation results also show that both the BPEMB and TEMB protocols can substantially reduce the collisions and redundant transmissions in asynchronous duty-cycled WSNs.