無線資料存取使用快取機制的分析

Abstract

無線資料傳輸的頻寛相當有限，因為許多應用服務的資料存取都具有temporal locality的特性，所以把快取機制應用在無線終端設備(wireless terminal)上，能有效地縮短資料存取的時間。本論文以名片系統作為應用，探討無線終端設備的快取效能。我們主要考慮least recently used快取取代演算法和二種強制一致性(strongly consistent)演算法，分別為poll-each-read和callback。本論文並使用數學分析推導資料的有效快取命中率(effective hit ratio)，並用此結果來驗證我們的模擬結果。我們也在論文中探討資料存取率和資料更新分佈如何影響無線終端設備的快取效能。

In wireless data transmission, the capacity of wireless link is typically limited. Since many applications exhibit temporal locality for data access, the cache mechanism can be built in a wireless terminal to effectively reduce the data access time. This thesis studies the cache performance of the wireless terminal by considering a business card application. We investigate the least recently used replacement policy and two strongly consistent data access algorithms called poll-each-read and callback. An analytic model is proposed to derive the effective hit ratio of data access, which is used to validate against simulation experiments. Our study reports how the data access rate and the data update distribution affect the cache performance in a wireless terminal.