現今科技發展出各式各樣的無線裝置，提供手持裝置更多元化的使用服務，以及監控周遭電器的各項狀態改變，讓人們能更便利更智慧化的生活。在無線感測網路中的感測器大部分皆為受限制型裝置，近幾年的研究學者們提出將IPv6嵌入至受限型裝置，進而發展出受限型應用層協議 (CoAP，Constrained Application Protocol) ，使得受限型裝置能更容易的聯接上物聯網。然而當受限型裝置間的訊息傳送頻繁時，遽增的耗電量，將使電量受限制的無線裝置難以負荷，因此，節省耗電量將是無線裝置互相通訊的首要關注問題。
　　我假設情境為客戶端們各自指定接收訊息的週期，我企圖使用Minimum Period (p_min) 和Maximum Period (p_max) 作為指定週期的參數，客戶端將這兩個參數放入訊息中，便能達到指定週期的效果。在滿足客戶端服務品質 (Quality of Service) 需求的同時，也會確保客戶端和服務器端的連結關係依然存在且能獲得最新的資源狀態訊息。
　　我將使用分群演算法對客戶端們進行分組，將週期過短和週期過長的客戶端分開，進而避免週期短的客戶端大幅降低最大週期的情形。也使用代理伺服器的緩存機制加上Max-Age選擇演算法設置每一則通知在緩存中的更新頻率，使客戶端能取得最新的通知，並確認客戶端與服務器端的連線狀態。接著使用合併演算法，將緩存中有效且同一接收端的通知進行合併，以減少客戶端接收通知的次數。
　　本篇論文將提出在滿足所有CoAP客戶端的服務品質 (Quality of Service) 需求下，使用分群演算法、緩存機制、Max-Age選擇演算法以及合併演算法，降低代理伺服器的傳輸次數和降低客戶端的訊息接收數量，減少服務器端回應訊息的傳輸次數。於是，得以分別減少客戶端和代理伺服器間的訊息數量以及代理伺服器和服務器端間的訊息數量，進而達成降低整體架構的能量消耗。

Nowadays, we make a broad varieties of wireless devices by new technology, which providing handheld devices with multiple variations of services, such as monitoring the state changes of the electrical appliances. The electrical appliances have a greater diversity of functions. Consequently, people life becomes more convenient and intelligent. Most of the sensors in the wireless sensor network are constrained devices. In recent year, researcher have proposed to integrate IPv6 into constrained devices, and subsequently developed a constrained application protocol (CoAP). So that a constrained device can be more easily connected to realize Internet of things. However, when the message transmissions between constrained devices are frequent, the increased power consumption will make micro-wireless devices infeasible for high loads. Therefore, saving power is the primary concern of wireless devices to communicate with each other.
　　In this thesis, clients specify the period of receiving messages and inform the proxy, which allows clients to avoid excessive information, and therefore saves energy consumption. Clients confirm the connections with the proxy and the proxy maintains connections with servers. The Minimum Period (p_min) and Maximum Period (p_max), which satisfy the quality of service requirements of clients are used as the parameters of the specified periods. Clients will append these two parameters into their request messages and send them to the proxy.
　　Grouping algorithm groups clients by splitting clients of long periods and short periods, for avoiding situations where short-cycle clients drastically let down the maximum periods of the high-cycle groups. Next, the cache mechanism of proxy and the Max-Age selection algorithm to set the frequency at which each notification is updated in the cache ensure the clients receiving the latest notifications and the client-server connections. The merge algorithm combines notifications from the cache that are valid and have the same receiving end, to further reduce the number of times the client getting notifications.
　　This thesis will propose scheme to decrease the energy consumption of the overall structure by which all CoAP clients’ quality of service (QoS) requirement are satisfied. To use grouping algorithm, caching mechanism, Max-Age selection algorithm and merge algorithm substantially reduce the number of proxy transmissions, the number of messages received by the clients, and the number of server response messages. As a result, the number of messages between the clients and proxy, the number of messages between the proxy and the server, and the energy consumption of the overall architecture are greatly decreased.

第一章 導論+1
1.1 前言+1
1.2 研究動機+2
1.3 論文架構+3
第二章 相關背景與研究+4
2.1 物聯網(Internet of Things)+4
2.2 無線感測網路(Wireless Sensor Network)+8
2.3 CoAP (Constrained Application Protocol)+11
2.3.1 觀察資源(Observing Resources)+14
2.3.2 代理伺服器(Proxying)+17
2.3.3 緩存(Caching)+19
2.4 相關論文+21
第三章 研究方法+24
3.1 系統架構+24
3.2 客戶端分群+28
3.3 設定Max-Age+38
3.4 合併機制+40
第四章 效能分析+43
4.1模擬環境與參數設定+43
4.2模擬結果與效能分析+46
第五章 結論+84
參考文獻+85

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