因為在無線感測器網路之中通常感測器是以電池做為電源，且電池之充電或置換並不容易，所以能量管理就成為無線感測器網路之一關鍵議題。在本篇論文中，我們研究無線感測器網路之效能，其中感測器節點可切換成為睡眠模式以節省能量。但是，處於睡眠模式之感測器將失去一些處理功能，且因此自來源點至目標節點之封包延遲會增加，且成功送達率會降低。換句話說，封包延遲，能量消耗，與成功送達率之間之折衷必須列入考慮。另外，如眾所知，無線鏈結較其之有線對等物會造成更多之通道引發錯誤。假設感測器只收集非即時性資料，且因此發生錯誤之封包將重傳至成功為止。重傳可增加封包之可靠性，但必須付出延遲增加與能量消耗增加之代價。我們推導所研究之系統之解析模型，且以疊代方式計算感興趣之效能指標。感興趣之效能指標包含平均延遲，平均能量消耗，與平均成功送達率。我們研究作用/睡眠轉移速率，流量負載，與錯誤率對於該等效能指標之影響。最後，但並非最不重要，我們以電腦模擬來驗證解析結果之正確性，其中電腦模擬程式是以C語言自行撰寫。

Since in wireless sensor networks usually sensors are battery-based and batteries are not easy to be recharged or replaced, energy management becomes a critical issue in wireless sensor networks. In this work, we study the performance of wireless sensor networks, where the sensor nodes may switch into sleep mode to save energy. However, sensors in sleep mode lose some of their processing capability, and thus the packet delay form source node to the sink increases and throughput decreases. In other words, the tradeoff among packet delay, energy consumption, and throughput must be taken into account. Furthermore, as is well known, wireless link causes more channel-induced errors in transmissions than its wireline counterpart. Assume that sensors collect only non-real-time data, and thus packets in errors are retransmitted until successful. Retransmissions increase the reliability of packets at the expense of increased delay and energy consumption. We derive an analytical model for the studied system and compute the performance metrics of interest iteratively. The performance metrics of interest include average delay, average energy consumption, and average throughput. We study the effect of active/sleep transition rates, traffic load, and error rate on those performance metrics. Last but not least, we validate our analytical results through simulation, where the simulation is written in C language.

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