隨著無線感測網路（Wireless Sensor Networks）的應用日漸廣泛，如何利用有限的資源提高感測網路的覆蓋率成為一項重要的議題。近來有許多針對這項議題的改進方法，它們也能夠達到相當高的覆蓋率。然而這些方法均假設感測器的感測範圍為一個完美的圓形，並利用這假設來估算感測網路的覆蓋率。但這個假設並不完全適用於所有的狀況，如果在一般的環境裡，會產生許多無法預知的未覆蓋區域，進而影響整個感測網路的效能。
　本篇論文分析了隱藏在這項假設之後的影響，並提出一個預測的演算法來評估這些未覆蓋區域的位置。這個演算法主要利用各感測器感測範圍的交點，透過這些交點的特性，再劃分為許多不同的群組，配合有效的過濾機制決定出最有可能包含這些未覆蓋區域的群組。使用者能夠根據評估的結果來決定哪些區域需要額外的感測器支援，以提升整個網路的覆蓋率。

In wireless sensor networks, the coverage ratio of sensing field often determines the performance
and efficiency of the whole network. Therefore, coverage is taken as an important issue for related researches. Many mechanisms have been proposed to enhance the coverage ratio and most of them can achieve excellent coverage ratio with limited resource. These mechanisms typically assume that the sensing range of a node is a perfect circle with a fixed radius. However, the assumption may not be true for all sensing environments and it will result in unexpected coverage holes in practical. This thesis restricts the assumption and analyzes the effects hidden behind it. Besides the analysis, the thesis also presents an Irregular Coverage Prediction (ICP) method to solve the issue. The ICP uses the property of intersection points between active sensors to determine which areas
may encounter coverage holes when the assumption is revoked. Assistant sensors can thus be deployed to remove the potential holes. The simulation results show that the ICP is efficient for improving the coverage ratio with sensing irregularity.

[1] M. Tubaishat and S. Madria, “Sensor Networks: An Overview,” IEEE Potentials Magazine, vol. 22, pp. 20–23, Apr. 2003.
[2] H. Karl and A. Willig, “A Short Survey of Wireless Sensor Networks.” TKN Technical Report TKN-03-018, Technical University Berlin, Oct. 2003.
[3] M. Kuorilehto, M. Hannikainen, and T. D. Hamalainen, “A Survey of Application Distribution in Wireless Sensor Networks,” Journal on Wireless Communications and Networking, vol. 5, pp. 774–788, May 2005.
[4] D. J. Cook, G. M. Youngblood, E. O. Heierman, K. Gopalratnam, S. Rao, A. Litvin, and F. Khawaja, “MavHome: An Agent-Based Smart Home,” Proceedings of the First IEEE International Conference on Pervasive Computing and Communications (PerCom), pp. 521–524, Mar. 2003.
[5] C. Chong and S. Kumar, “Sensor Networks: Evolution, Opportunities, and Challenges,” Proceedings of the IEEE, vol. 91, no. 8, pp. 1247–1256, Aug. 2003.
[6] D. Estrin, R. Govindan, J. Heidemann, and S. Kumar, “Next Century Challenges: Scalable Coordination in Sensor Networks,” Proceedings of the ACM/IEEE International Conference on Mobile Computing and Networking, pp. 263–270, Aug. 1999.
[7] G. Xing, C. L. Pless, and R. Q. Huang, “Impact of Sensing Coverage on Greedy Geographic Routing Algorithms,” IEEE Transactions on Parallel and Distributed Systems, vol. 17, no. 4, pp. 348–360, Apr. 2006.
[8] C. F. Huang and Y. C. Tseng, “The Coverage Problem in a Wireless Sensor Network,” Wireless Sensor Networks and Applications Workshop (WSNA), pp. 115–121, Apr. 2003.
[9] H. Bai, X. Chen, Y. C. Ho, and X. Guan, “Percentage Coverage Configuration in Wireless Sensor Networks,” International Workshop on Bioinformatics at Nankin (ISPA), pp. 780–791, Nov. 2005.
[10] R. Ghrist and A. Muhammad, “Coverage and Hole Detection in Sensor Networks via Homology,” Proceedings of the Fourth International Symposium on Information Processing in Sensor Networks (ISPN), pp. 254–260, Apr. 2005.
[11] J. Jiang and W. Dou, “A Coverage Preserving Density Control Algorithm for Wireless Sensor Networks,” 3rd International Conference on AD-HOC Networks and Wireless (ADHOC-NOW), pp. 42–55, July 2004.
[12] H. Zhang and J. C. Hou, “Maintaining Sensing Coverage and Connectivity in Large Sensor Networks,” Ad Hoc and Sensor Wireless Networks, vol. 1, no. 2, pp. 89–123, Mar. 2005.
[13] A. Sekhar, B. S. Manoj, and C. S. R. Murthy, “Dynamic Coverage Maintenance Algorithms for Sensor Networks with Limited Mobility,” Third IEEE International Conference on Pervasive Computing and Communications (PerCom), pp. 51–60, Mar. 2005.
[14] G. Wang, G. Cao, and T. LaPorta, “A Bidding Protocol for Deploying Mobile Sensors,” 11th IEEE International Conference on Network Protocol (ICNP), pp. 315–325, Nov. 2003.
[15] A. Ghosh, “Estimating Coverage Holes and Enhancing Coverage in Mixed Sensor Networks,” 29th Annual IEEE International Conference on Local Computer Networks (LCN), pp. 68–76, Nov. 2004.
[16] N. Ahmed, S. S. Kanhere, and S. Jha, “The Holes Problem in Wireless Sensor Networks: A Survey,” Mobile Computing and Communication Review, vol. 9, no. 2, pp. 4–18, Apr. 2005.
[17] X. Wang, G. Xing, Y. Zhang, C. Lu, R. Pless, and C. Gill, “Integrated Coverage and Connectivity Configuration in Wireless Sensor Networks,” ACM Conference on Embedded Networked Sensor Systems (SenSys), pp. 28–39, Nov. 2003.
[18] D. Tian and N. D. Georganas, “A Coverage Preserving Node Scheduling Scheme for Large Wireless Sensor Networks,” Proceedings of the First ACM International Workshop on Wireless Sensor Networks and Applications (WSNA), pp. 32–41, Sept. 2002.
[19] A. Cerpa, N. Busek, and D. Estrin, “A Tool for Simple Connectivity Assessment in Lossy Environments.” Technical Report 0021 UCLA Center for Embedded Network Sensing (CENS), University of California at Los Angeles, Sept. 2003.
[20] D. Ganesan, B. Krishnamachari, A. Woo, D. Culler, D. Estrin, and S. Wicker, “Complex Behavior at Scale: An Experimental Study of Low-Power Wireless Sensor Networks.” Technical Report CSD-TR 02-0013, University of California at Los Angeles, Feb. 2002.
[21] A. Woo, T. Tong, and D. Culler, “Taming the Underlying Challenges of Reliable Multihop Routing in Sensor Networks,” The ACM Conference on Embedded Networked Sensor Systems (SenSys), pp. 14–27, Nov. 2003.
[22] Y. J. Zhao and R. Govindan, “Understanding Packet Delivery Performance in Dense Wireless Sensor Network,” The ACM Conference on Embedded Networked Sensor Systems (SenSys), pp. 1–13, Nov. 2003.
[23] G. Zhou, T. He, S. Krishnamurthy, and J. A. Stankovic, “Impact of Radio Irregularity on Wireless Sensor Networks,” ACM Proceedings of International Conference on Mobile Systems, Applications, and Services (MobiSys), pp. 125–138, June 2004.
[24] The Network Simulator - ns-2. URL http://www.isi.edu/nsnam/ns/.
[25] S. Meguerdichian, F. Koushanfar, G. Qu, and M. Potkonjak, “Exposure in Wireless Ad-Hoc Sensor Network,” The ACM Conference on Mobile Computing and Networking (MobiCom), pp. 139–150, July 2001.