行動版網路相簿之預先擷取方法

Abstract

網路相簿服務允許使用者利用網路上傳照片與檢視其他使用者的網路相簿。藉由行動寬頻網路，使用者可以在任何地方即時地享用網路相簿的內容。在行動版網路相簿中的使用者體驗(user experience) 會被網路傳輸延遲所影響，因為網路傳輸延遲決定了使用者檢視圖片是否需要等待。針對這個議題，我們提出一個預先擷取圖片的機制來增強檢視行動版網路相簿上的使用者體驗。我們採用一種類似TCP滑動視窗的協議 (緩衝區大小為N) ，而當使用者設備裡的滑動視窗緩衝區滿載時，預先擷取會暫停。緩衝區的大小N影響了預先擷取的效能。當N值越大，則使用者體驗越佳。然而，一個大的N值代表著很多張圖片會被預先傳輸到手機。如果它們沒有被使用者觀看,傳輸這些圖片的網路資源則造成浪費。本論文進行效能分析來選擇最小的N值 (最佳的N值) 以達成預期的使用者體驗。

A web album service allows a user to publish photo albums on the web and view albums of other users. Through broadband mobile telecom, users can enjoy watching contents of web albums at any place in real time. User experience on mobile web album is affected by the transmission delay of mobile network, which determines whether the user needs to wait to view the images. We propose a prefetching mechanism that enhances user experience on accessing mobile web albums. A TCP-like sliding window protocol (of size N) is exercised, and when the buffer for the sliding window at the user equipment (UE) is full, prefetching is suspended. The buffer size N affects the prefetching performance. The larger the N value, the better the user experience. However, a large N value means that many images will be prefetched. If they are not actually viewed by the user, the network resources for transmitting these images are wasted. This paper proposes both analytic and simulation models to select the smallest N (the optimal N value) so that the expected user experience can be achieved.