A Low Latency MAC Scheme for Event-Driven Wireless Sensor Networks
In this paper, we present a low latency media access control scheme which we call LLMAC (Low Latency MAC) for event-driven wireless sensor networks (WSN). In this kind of WSN, sensors do not regularly send data to the sink. They send a burst data only whe
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Laboratoire d’Informatique de l’Université de Franche Comté, France 2 Laboratoire d’Automatique de Besançon, France {le, guyennet, felea}@lifc.univ-fcomte.fr [email protected]
Abstract. In this paper, we present a low latency media access control scheme which we call LLMAC (Low Latency MAC) for event-driven wireless sensor networks (WSN). In this kind of WSN, sensors do not regularly send data to the sink. They send a burst data only when there is an event in the monitoring area. It takes time for this burst data to arrive to the sink. Normally, these events are critical and we hope to obtain the information on the event in the shortest delay. Hence, the latency is considered to be a crucial requirement in event-driven WSN contrary to the traditional wireless networks where the fairness is the most important requirement. Our proposal LLMAC makes a trade-off between fairness and latency in order to offer a shorter latency transmission when certain events happen. The performance evaluation shows that our proposal reduces the latency in comparison to existing MAC protocols.
1 Introduction Wireless sensor network is a very hot research topic tendency in distributed systems. A WSN is a network composed of hundreds to thousands of communicating sensors deployed on an area in order to collect environment events. WSN have a wide range of domain application: industry, medical, military, civilization etc. Generally, there are three models of WSN: continuous, on-demand and event-driven. In continuous WSN, sensors send data periodically to the sink. There are always sensors in the network which initiate the communication. In the on-demand WSN model, sensors send data only when they receive a request from the access point. Without request, sensors sense information and store it in their local memory. In the context of this paper, we are interested in the last model: event-driven WSN. In this model, the sensors send data only when certain events occur. For example, a wireless sensor network is deployed on a machine in a factory to detect abnormal symptoms of the machine. Sensors can sense the temperature, the vibration or the humidity of the machine. Normally, when the machine works well, sensors stay silent. When there is a problem in the machine, this problem will produce environment change: an increase in temperature, humidity of the machine or the machine vibrates faster. This ambient information can be detected by sensors and they will activate many camera or sound H. Zhang et al. (Eds.): MSN 2007, LNCS 4864, pp. 291–301, 2007. © Springer-Verlag Berlin Heidelberg 2007
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sensors to take pictures or record sounds and immediately report an event, composed of many packets, to the sink via multi-hop transmission. In traditional wireless networks, every node is fair in term of channel access. They have the same role in the network. The transmission objective is that when a node has a data to send, it can win the channel in the shortest delay. Hence, almost every existing MAC protocol wants to gua
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