近年可充電無線感測網路(Wireless Rechargeable Sensor Networks, WRSNs)頻繁的出現在文獻中，主要是研究利用適時的充電來延長整體感測網路的壽命。由於無線充電車(wireless charging vehicle)行走及充電都需要花費時間，在過去有許多研究中，是不能完全保證每個節點都能適時充電而存活。若重要的代傳節點上有死亡節點，將會導致其子節點無法將感測資訊和充電資訊回傳至基地台，喪失原本感測的目的，且最終會因能源耗盡而死亡。
本論文針對此議題提出動態優先權充電(Dynamic Priority Charging)，利用感測器回傳的剩餘能源和該節點在網路的重要性，來判斷是否為充電車此趟的充電依據，以提高網路生命週期。模擬結果顯示所提出的方法比一般的貪婪充電法較能延長網路的使用壽命。

In recent years, wireless rechargeable sensor networks (WRSNs) has become a popular research issue as it can prolong the lifetime of the entire sensor network by recharging nodes appropriately. Due to the limited capacity of recharging vehicles and it takes time to move around to charge sensor nodes, the system cannot guarantee that every node can be alive and transmitting data back to sink. If a relay node depletes its energy, all child nodes would not be able to transmit sensor data back. Eventually all child nodes will be running out of energy. 
This paper proposed a dynamic priority charging (DPC) scheme that utilizes the information of remaining energy and topological importance to calculate the node priority in charging sensor nodes. Simulation results confirm the superiority of our scheme against the widely known greedy method.

目錄
第1章	緒論	1
1.1	前言	1
1.2	研究動機 2
1.3	研究方法	3
1.4	論文架構	4
第2章	背景知識與相關研究	5
2.1 	Single-Hop Energy Transfer	5
2.2	Multi-Hop Energy Transfer	6
2.3 	網路相連性	7
第3章	動態優先權充電	10
3.1	集聚係數	10
3.2	代傳資料	12
3.3	權重值與充電挑選	14
3.4 	權重分析	17
第4章 網路效能模擬	22
4.1 	實驗場景及參數設定	22
4.2 	貪婪充電	23
4.3 	實驗結果及分析	23
第5章	結論	28
參考文獻	29
附錄 31
圖目錄
圖 1：傳輸路徑	1
圖 2：封包傳輸	3
圖 3： Betweenness centrality以節點i為例	9
圖 4：傳輸路徑	11
圖 5：尾端節點	12
圖 6：過於密集的網路	13
圖 7：距基地台較近之感測器	13
圖 8：Relay factor	14
圖 9：低電量之CC	16
圖 10：感測器存活時間	18
圖 11：充電車平均行走距離	19
圖 12：充電車尋訪次數	20
圖 13：感測器平均電量	21
圖 14：貪婪充電(一)門檻40%之電量比較圖	24
圖 15：充電車尋訪次數	25
圖 16：貪婪充電(一)門檻80%之電量比較圖	26
圖 17：與貪婪充電(一)平均電量比較	27
圖 18：與貪婪充電(二)平均電量比較	27
表目錄
表1：權重分析模擬參數設定。	17
表2：實驗的模擬參數設定。	22

[1]J.-S. Liu, S.-Y. Wu, and K.-M. Chiu, “Path planning of a data mule in wireless sensor network using an improved implementation of clustering-based genetic algorithm,” IEEE Symposium on Computational Intelligence in Control and Automation, pp. 30-37, Apr. 2013.
[2]A. B. Nacef, S.-M. Senoucik, Y. Ghamri-Doudane, and A.-L. Beylot, “A Cooperative Low Power Mac Protocol for Wireless Sensor Networks,” IEEE International Conference on Communications, pp. 1-6, Jun. 2011.
[3]Y. Cai, K. Xu, Y. Mo, B. Wang, and M. Zhou, "Improving WLAN throughput via reactive jamming in the presence of hidden terminals," IEEE Wireless Communications and Networking Conference, pp. 1085-1090, Apr. 2013.
[4]Y. Shi, L. Xie, Y.T. Hou, and H.D. Sherali, “On renewable sensor networks with wireless energy transfer, ” in IEEE INFOCOM, pp. 1350-1358, Apr. 2011.
[5]S. Guo, C. Wang, and Y. Yang, “Mobile data gathering with Wireless Energy Replenishment in rechargeable sensor networks, ” IEEE INFOCOM , pp. 1932-1940, Apr. 2013.
[6]M. Zhao, J. Li, and Y. Yang, “A Framework of Joint Mobile Energy Replenishment and Data Gathering in Wireless Rechargeable Sensor Networks, ”  IEEE Transactions on Mobile Computing, pp. 2689-2705, Feb. 2014.
[7]K. Li, H. Luan, and C.C. Shen, “Qi-ferry: Energy-constrained wireless charging in wireless sensor networks, ” IEEE Wireless Communications and Networking Conference, pp.2515-2520, Apr. 2012.
[8]C. Wang, J. Li, F. Ye, and Y. Yang, “Recharging schedules for wireless sensor networks with vehicle movement costs and capacity constraints,” IEEE International Conference on Sensing, Communication, and Networking, pp.468-476, Jun. 2014.
[9]L. Xie, Y. Shi, Y.T. Hou, W. Lou, H.D. Sherali, and S.F. Midkiff, “On renewable sensor networks with wireless energy transfer: The multi-node case,” IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks, pp. 10-18, Jun 2012.
[10]M.K. Watfa, H. Al-Hassanieh, , Salmen, S. “The road to immortal sensor nodes,”   International Conference on Intelligent Sensors, Sensor Networks and Information Processing, pp. 523-528, Dec. 2008.
[11]T. Rault, A. Bouabdallah, Y. Challal, “Multi-hop wireless charging optimization in low-power networks, ” IEEE Global Communications Conference, pp. 462-467, Dec. 2013.