為了減少行動應用程式資料下載時間以及攤平行動應用程式流量之決策理論預先下載演算法

Abstract

由於科技的日新月異，智慧型的行動裝置結合行動上網的功能產生了五花八門的應用，導致行動網路流量大增，使得原本的硬體架構已經不敷使用，因為頻寬不足而導致資料下載速度緩慢一直都是行動上網使用者所抱怨的。 傳統的解決辦法從硬體層面下手，增建基地台以增加頻寬，但這方法成本高而且費時，不符合經濟效益。所以我們換個方式從軟體層面下手，試著減少頻寬需求、善用現有資源。我們未更動原有的行動網路架構，在智慧型手機上加上一個有快取功能的行動應用程式代理伺服器，除了快取可以減少不必要的流量之外，本篇論文的貢獻是在代理伺服器上加入了預先下載功能，根據使用者的使用紀錄以及應用程式的更新紀錄，使用決策理論決定當行動應用程式代理伺服器收到應用程式資料更新通知時，是否應該預先下載這次更新的資料。藉由預先下載的方式善用現有頻寬資源來減少使用者等待行動應用程式資料下載的時間，以減少使用者對資料下載速度緩慢的抱怨。 最後以模擬實驗驗證我們系統在不同情境下的行為。實驗結果告訴我們，我們的行動應用程式代理伺服器配上預先下載機制不但可以有效減低反應時間，提升使用者滿意度，電信公司也可以提升資源使用率，不需一直增建基地台，藉此減少硬體成本開銷。

With the state-of-the-art technology of the mobile network and mobile devices, the demand of mobile network traffic is increasing rapidly. However, the current infrastructure can barely satisfy all the demand of the exploding network traffic. The users always complain about their slow network speed and insufficient bandwidth. The traditional solution is to establish new base stations, which is a costly and time-consuming approach. Therefore, we have proposed a new software approach: a mobile application proxy with a cache on the mobile device, which can reduce unnecessary bandwidth demands and utilize available bandwidth efficiently. In this research, we add the prefetch mechanism on the proxy. A prefetch decision algorithm, based on decision theory, is proposed to make informed decision about whether the proxy should prefetch the updated content of the mobile applications, depending on user’s use pattern and application’s update pattern. As a result, user waiting time for data downloading can be reduced by prefetching the updated content and, consequently, the user’s complaints can be diminished. Finally, simulations are conducted to test our algorithm’s behavior in different situations. The simulation results show that our system with prefetch mechanism can reduce application’s response time effectively and utilize available bandwidth efficiently so that operators can increase their customers’ satisfaction and reduce their hardware cost for establishing new base stations.