WSNdeploymentQualityAnalysis - ERSOY LAYOUT 10/31/07 1:56...

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IEEE Network • November/December 2007 48 0890-8044/07/$20.00 © 2007 IEEE wireless sensor network (WSN) comprises small low-cost sensors with limited computational and communication power. The objective is to sense the environment and communicate the informa- tion to a data collection center. Many areas of employment are envisaged for WSNs ranging from the monitoring of endan- gered animals populations to military surveillance. In this article we concentrate on surveillance WSNs (SWSNs) whose duty is intrusion detection in applications such as border surveillance against penetration by hostile elements and perimeter protection. Sensors are deployed to a region; they wake up, organize themselves as a network, and start sensing the area for intrusion. When a sensor detects an intru- sion, the event is communicated to the sink node so that an appropriate action is taken. SWSNs are designed such that the intrusion detection probability is maximized while maintaining a long network lifetime. Such performance constraints affect the quality of sensor deployment, for the assessment of which we need meaningful measures. It is hard to define a metric that is independent of the type and variety of sensors, number of sensors deployed, deployment scheme, and characteristics of the target and environment. For example, detectability in a geography that is harsh and nonuniform in shape will be lower than that in a plain for fixed number of sensors. The network lifetime is directly related to the energy resources of the sensors and can be extended by energy-aware protocols. The detection performance of the SWSN can be further improved by using data/decision fusion techniques. The SWSN must be able to adapt to changing network and environment conditions. Because intrusions are usually detect- ed by several sensors, highly reliable intrusion information can be derived by means of cooperation among the sensor nodes. This necessitates time synchronization in order to meet the required accuracy in the network by increasing the probability of intrusion detection while keeping the false alarm rate at a reasonable level. Network failure, partial or whole, may not only be due to power exhaustion of the sensor nodes. A group of sensors may be intentionally destroyed, leading to area failures in an SWSN that must be studied along with the failure distribution of power-deprived sensors. An example of area failure is the effective elimination of sensor nodes through the presence of strong jamming. What must be done in terms of sensor deployment once an area failure occurs is an open research topic. Since sensor failures are common, fault tolerance of the network should be investigated because loss of individual sen- sors or a group of sensors should not hamper the task accom- plishment of the network.
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This note was uploaded on 10/27/2009 for the course CSE 824 taught by Professor Xiao during the Fall '08 term at Michigan State University.

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WSNdeploymentQualityAnalysis - ERSOY LAYOUT 10/31/07 1:56...

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