ART: an asymmetric and reliable transport mechanism for wireless sensor networks

Many applications developed for wireless sensor networks (WSNs) demand for Reliable communication service, since majority of these applications are event-critical applications. There has been a vast body of knowledge on reliable data transfer in wireless networks; however, many of those solutions are not applicable to WSNs due to the fact that they address the problem by offering per message transport reliability. However, densely deployed sensor nodes can generate many redundant messages that essentially indicate the same event from the area of interest, this message-level reliability usually poses significantly high and unnecessary communication costs. In this paper, we address the problem of reliable data transferring by first defining event reliability and query reliability to match the unique characteristics of WSNs. Unlike other studies on transport protocols for WSN, we consider event delivery in conjunction with query delivery. For the purpose, we propose an energy-aware sensor classification algorithm to construct a network topology that is composed of sensors in providing desired level of event and query reliability. Using such an approach, reliability is granted in the sense that critical event reports are received by the sink and queries are received by a small subset of sensors that can monitor the entire sensing field. We analyze our approach by taking asymmetric traffic characteristics into account and incorporating a distributed congestion control mechanism. We evaluate the performance of the proposed approach through an ns-2 based simulation and show that significant savings on communication costs are attainable while achieving event and query reliability.