Cross-layer opportunistic forwarding to reduce patterned synchronization effect in highly resource constrained WSNs

Abstract

In duty-cycled wireless sensor networks, senders suffer from long delays while waiting in awaken state for receivers to wakeup for packet transmissions. It results in unnecessary energy usages and lower network lifetime. Opportunistic packet forwarding schemes have been proposed to reduce such delays where the selection of next hop forwarder is performed opportunistically without waiting for a particular neighbor to wakeup. Even under the opportunistic nature of such schemes, the duty-cycle patterns of neighboring nodes can require a sender to be synchronized with a particular receiver so that it is always selected as the next hop forwarder. This effect, which is called as patterned synchronization effect in this paper, leads to unnecessary drain of energy in packet forwarder nodes reducing their lifetime. We therefore propose a new opportunistic forwarding scheme which is able to identify the occurrence of patterned synchronization effect and resolves it by dynamically adjusting duty-cycle ratio of nodes in a self-organized manner. Using extensive simulations, we show that our scheme significantly improves network lifetime and power utilization of the network while maintaining an acceptable packet transmission delay at the senders.