INDEX1. INTRODUCTION 11.1 Deployment of wireless sensors 21.2 Wireless sensor and actor networks 31.3 Physical architecture of WSANs 31.4 Difference between WSNS and WS 41.5 Requirement of WSNs 52. Wireless ad hoc network 53. Current problems and solutions 63.1 Problem of key management for the future 94. Advantages, Disadvantages and applications of WSNs 105. Conclusion 116. References 12List of figuresFigure 1 Working principle of WSNs 1Figure 1.3 The physical architecture of WSANs 4Figure 1.3.1 (a) Automated vs (b) Semi -automated 4Figure 3 (a) Example coverage problem: Detection ranges are unit disks 7Figure 3 (b) Detection ranges are non-unit disks 7Figure 3.1 (a) the coverage problem with irregular detection region (a) Coverage levels of irregular sub-regions (b) Polygon approx. of the detection region of the Si sensor (c) Covered segments of the Si sensor 8Figure 3.1.1 Security requirements for WSNs 9Figure 3.1.2 Common key distribution schemes for WSNs 9Figure 4 Applications 11IntroductionWireless sensor networkThe rapid progress of Integrated MEMS (micro-sensing technologies) and wireless communication technologies have made wireless sensor networks possible. Such an environment may have many inexpensive wireless nodes; each node is capable of collecting, storing and processing environmental data, and communicating with neighboring nodes. These sensors were connected by wires in the past, but today...... middle of paper ...... in Wireless Sensor Networks: Current proposal and Future Development, IEEE Xplore, Hong Kong, October 2007.5) Jeremy Eric Elson, “Time Synchronization in Wireless sensor Networks”, University of California, USA: ANSII Std 239-18, 2003.6) Michele Zorzi, “Wireless sensors and networks: recent trends and research issues”, University of Padua , Italy, IEEE communications society, Poland, April 28-30, 2008.7) CHI-FU HUANG and YU-CHEE TSENG, “Mobile Network and Application”, the Coverage Problem in a Wireless Sensor Network, National Chiao-Tung University, Taiwan, Netherlands, IEEE Senior Member, 2005, article. 5.8) Ian F. Akyildiz, Ismail H. Kasimoglu, “Ad Hoc Networks”, Wireless sensor and Actor Networks: Research Challenges, Georgia Institute of Technology, United States, May 2004.9) Salvatore La Malfa, “Wireless Sensor Networks”, IEEE Xplorer, 2010.