INDEX1. INTRODUCTION 11.1 Deployment of wireless sensors 21.2 Sensor networks and wireless actors 31.3 The physical architecture of WSANs 31.4 Difference between WSNS and WS 41.5 Requirements of WSNs 52. Ad hoc wireless network 53. Current problems and solution 63.1 Key management problem for the future 94. Advantages, Disadvantages and Applications of WSNs 105. Conclusion 116. References 12 List of Figures Figure 1 Working principle of WSNs 1 Figure 1.3 The physical architecture of WSNs 4 Figure 1.3.1 (a) Automated Vs (b) Semi- automated 4 Figure 3 (a) Example of coverage problem: The detection distances are unit disks 7Figure 3 (b) The detection distances are non-unit disks 7Figure 3.1(a) the coverage problem with irregular detection regions(a) Coverage levels of irregular sub-regions(b) Polygon approx. of the sensor Yes sensing region (c) Covered segments of the sensor Yes 8Figure 3.1.1 Security requirements for WSN 9Figure 3.1.2 Common key distribution schemes for WSN 9Figure 4 Applications 11IntroductionWireless sensor networkThe rapid progress of integrated MEMS micro-sensing) and wireless communication has made wireless sensor networks possible. Such an environment may have many inexpensive wireless nodes; each node is able to collect, store and process environmental data and communicate with neighboring nodes. In the past these sensors were connected with wires, but today… middle of paper… in Wireless Sensor Networks: Current Proposition 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 Sensor and network: Recent trends and Research Issues'', University of Padua, Italy, IEEE Communication Society, Poland, 28-30 April 2008.7) CHI-FU HUANG and YU-CHEE TSENG, “Mobile Network and Application”, the cover Problem in a Wireless Sensor Network, National Chiao-Tung University, Taiwan, Netherlands, senior member of the IEEE, 2005, Sec. 5.8) Ian F. Akyildiz, Ismail H. Kasimoglu, “Ad Hoc Networks'', Wireless sensor and actor network: Research Challenges, Georgia Institute of Technology, USA, May-2004.9) Salvatore La Malfa, “Wireless Sensor Networks”, IEEE Xplore, 2010.