在無線感測網路許多應用當中，經常需要多重覆蓋移動的目標。藉由選取一組感測器去多重覆蓋移動目標的所有預測區域，則將能夠達成多重覆蓋移動目標。比起配備多個指向性感測元件而成的指向性感測器，可轉動式指向性感測器成本更為低廉，並且每個感測器擁有更多可選擇的轉動方向。因此，可轉動式指向性感測器更適用於覆蓋預測區域。然而，轉動延遲對於可轉動式指向性感測器而言，是不可忽視的。所以，這篇論文針對可轉動式指向性感測器設計了一個預先轉動機制，以用於有多重覆蓋需求的移動目標。在移動目標到達之前，所提出的機制考量轉動延遲以去分配轉動角度給所選擇可轉動式感測器。經由模擬結果驗證了該機制能夠在長時間內達成多重覆蓋移動目標與其多重覆蓋的需求。並且，當可轉動式指向性感測器擁有較高轉動速度時，其表現更勝於多方向式指向性感測器。

Multiple coverage for a mobile target is needed for many applications in wireless sensor networks. By selecting a set of sensors to totally multi-cover the prediction region
of a mobile target, it is able to multi-cover the mobile target. Compare with directional sensors with several sectors, rotating directional sensors are cheaper and the number of selectable orientations per node is more. Thus, it is suitable for using rotating directional sensors to cover the prediction region. However, the delay for rotating orientation of rotating directional sensors is not neglectable. Therefore, a pre-orientation mechanism
is designed for rotating directional sensors to cover mobile targets with multi-coverage requirement in this thesis. Under the consideration of delay constraints, the proposed mechanism assigns a set of rotating directional sensors to rotate their orientations before targets arrive. Simulation results show that the proposed mechanism covers targets for long period and also achieves coverage requirement. In addition, the performance is even better than multi-sectors directional sensors when rotation speed is high.

[1] I. F. Akyildiz, W. Su, Y. Sankarasubramaniam, and E. Cayirci, “A Survey on Sensor Networks,” IEEE Communications Magazine, vol. 40, no. 8, pp. 102–114, August 2002.
[2] Y. Cai, W. Lou, and M. Li, “Cover Set Problem in Directional Sensor Networks,” in IEEE Future Generation Communication and Networking (FGCN), Decemtber 2007, pp. 274–278.
[3] J. Li, R. C. Wang, H. P. Huang, and L. J. Sun, “Voronoi Based Area Coverage Optimization for Directional Sensor Networks,” in 2nd International Symposium on Electronic Commerce and Security (ISECS), May 2009, pp. 488–493.

[4] C. Huang and Y. Tseng, “A Survey of Solutions to the Coverage Problems in Wireless Sensor Networks,” Journal of Internet Technology, vol. 6, no. 1, pp. 1–8, March 2005.
[5] M. Cardei and J. Wu, “Energy-Efficient Coverage Problems in Wireless Ad-hoc Sensor Networks,” Computer Communications, vol. 29, no. 4, pp. 413–420, Febrary 2006.
[6] S. Yang, F. Dai, M. Cardei, J. Wu, and F. Patterson, “On Connected Multiple Point Coverage in Wireless Sensor Networks,” International Journal of Wireless Information Networks, vol. 13, no. 4, pp. 289–301, October 2006.
[7] M. Cardei, M. T. Thai, Y. Li, and W. Wu, “Energy-Efficient Target Coverage in Wireless Sensor Networks,” in Proceedings of 24th Annual Joint Conference of the IEEE Computer and Communications Societies (INFOCOM), March 2005, pp. 1976–1984.
[8] H. E. Kuo and K. F. Ssu, “Using Target-View Clustering Algorithm to Solve Target Multi-Coverage Problem in Directional Sensor Networks,” in Proceedings of the International Conference on Mobile Computing and Ubiquitous Networking, June 2008, pp. 100–107.
[9] G. Fusco and H. Gupta, “Selection and Orientation of Directional Sensors for Coverage Maximization,” in 6th Annual IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks(SECON), June 2009, pp. 1–9.
[10] X. Han, X. Cao, E. Lloyd, and C. C. Shen, “Deploying Directional Sensor Networks with Guaranteed Connectivity and Coverage,” in 5th Annual IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks (SECON), June 2008, pp. 153–160.
[11] J. Hong, J. Cao, Y. Zeng, S. Lu, D. Chen, and Z. Li, “A Location-Free Prediction-Based Sleep Scheduling Protocol for Object Tracking in Sensor Networks,” in 17th IEEE International Conference on Network Protocols(ICNP), October 2009, pp. 63–72.
[12] G. Fusco and H. Gupta, “Placement and Orientation of Rotating Directional Sensors,” in 7th Annual IEEE Communications Society Conference on Sensor Mesh and Ad Hoc Communications and Networks (SECON), June 2010, pp. 1–9.
[13] V. Sadaphal and B. Jain, “Tracking Mobile Target Using Selected Sensors,” in First International Communication Systems and Networks and Workshops, January 2009, pp. 1–10.