近身網路中雙無線多模路由器省電及交叉備援機制

Abstract

中文摘要 長期以來節能都是近身網路研究中一個重要的議題。在近身網路架構中的個人無線路由器，相對於感測器而言其電池存續時間較短，所以延長無線路由器的存續時間就成為關鍵。而因為近年行動裝置的普及，同時擁有手機和平板的使用者日增，常攜帶行動電源以免手機電量用盡的情況也趨於平常，所以本研究假想將來行動電源也可以連網，則一個使用者可以同時擁有兩個連網裝置。因此我們提出一個新的近身網路架構，在一個近身網路中存在兩個無線路由器，形成雙無線路由器的近身網路架構，其中一台為主要路由器，另一台為備用路由器。 為了延長整個網路壽命，我們設計了兩種機制。第一為備援機制，當任何一個路由器電量耗盡時，另一個路由器需要取代它的工作，作為網路對外的閘道，如此可以延長一個路由器的存續時間。第二為無線卸載機制，因為使用者可能會穿戴傳輸量較大的感測器如穿戴式錄影機，因此我們把傳輸量大的感測器卸載到備用路由器上，以減少主要路由器接收動作。又因Wi-Fi上傳大量資料較行動網路省電，因此無線卸載機制也讓備用路由器可以在有Wi-Fi情況下上傳大量的影音資料而達到省電的目的。 本研究利用網路模擬軟體Castalia驗證雙路由器設計機制的正確性，並且使用電力監測器量測Android行動裝置的背景耗電及藍芽、3G、4G、Wi-Fi介面的耗電情況，並參考相關文獻數據，建立耗電模型，並藉此模型預測雙無線路由器網路的存續時間。最後則考慮多種情境進行試算，推估出雙無線路由器的架構配合本研究設計機制可以有效延長整體網路的壽命。

Abstract Power saving is always a crucial issue in wireless body area network (BAN) research. In the architecture of a body area network, there often exits a type of devices called the personal router. Comparing with the sensors in the BAN, a personal router usually has less battery life. Therefore, it is essential to improve the battery life of personal routers in related research. Since mobile devices have become popular in recent years, there are more and more users equipped with both smart phone and tablet. Moreover, the use of the mobile power bank for preventing smart phone from out of energy also becomes common. Therefore, we assume that mobile power bank will evolve to a new device able to interconnect the internet and BAN in the future, and a user could have two or more networking devices. Therefore, we propose a novel BAN architecture which includes two wireless personal routers: one is the main router, and the other is used for battery backup. In order to extend the battery life of BAN, we design two instrumental mechanisms. The first is the backup mechanism which is started when one of two routers is in low energy. The second design is an offload mechanism which will offload large volume transmissions from certain sensor devices, such as Video Recorder(s). Moreover, through the offload mechanism a backup router can upload a large number of data packets via the Wi-Fi interface, which consumes much less energy than that when is upload through the 3G interface. We employ a network simulator called Castalia to verify the correctness of all designed algorithms in our mechanism. We also use power monitor to measure the power consumption of different wireless interfaces and background usage in there personal routers. Through those measurement results, we develop an energy consumption model which can predict the life time of our dual-router BAN. Finally, we employ several usage scenarios to calculate the expected life time of BAN, and then the effectiveness of our dual-router BAN architecture in extending network life time is validated.