透過802.11b WLAN來增進GPRS的傳輸速率

Abstract

近來由於網路的普及, 許多使用者需要隨時隨地的使用網路資源. 舉例來說, 使用者可能剛好在戶外卻突然要收發一個緊急的email.當人們遠離他們的辦公室或是家裡時, 可以利用廣域的GPRS網路來持續的使用網路. 然而一個GPRS頻道所提供的頻寬卻是非常的低. 除了GPRS網路, 3G網路也可以提供廣域的服務和更高的頻寬. 但是不幸的, 在發表本篇論文時, 市場上還沒有3G的產品.

在本篇論文中, 我們提出了一個方法可以增加GPRS使用者的檔案傳輸速率. 我們的方法是利用多條的GPRS頻道來平行下載檔案. 使用網路服務的使用者除了利用自己的GPRS頻道下載資料外, 同時間也利用其他鄰近的GPRS頻道來幫助下載. 當鄰近的GPRS頻道收到資料封包後, 這些鄰近的GPRS頻道會利用802.11b 無線網路來傳送收到的資料封包給要求網路服務的那一位使用者.

我們設計並實作出上述的方法. 且我們的系統並不需要GPRS業者的任何支援. 我們量測了此系統再真實世界的表現. 實驗結果顯示在同時有四個GPRS頻道平行下載情況中, 我們的系統可以達到約原本傳輸速率的2.7倍. 為了量測我們系統在更複雜的拓撲和移動的情形下之表現. 我們使用NCTUns2.0模擬器, 模擬並量測系統的表現.

Recently the Internet becomes more and more popular. Users may need Internet access everywhere. For example, one may need to browse a web page or want to send/receive emails outdoors. To remain connected to the Internet, people may use wide-area GPRS networks when they are away from their home and office networks. A GPRS channel, however, provides very little bandwidth. Excepting a GPRS network, a 3G network is another choice that provides much higher bandwidth. Unfortunately, a 3G network has not put to market yet.

In this paper, we propose a scheme to increase the file transfer throughput for a GPRS user. Our approach is to transfer a requested file over multiple GPRS channels in parallel. The requesting user uses one’s channel and those of one’s neighbors for the transfer. When receiving packets from their GPRS channels, these neighbors forward them to the requesting user through a mobile ad-hoc network (MANET) using IEEE 802.11 (b) WLAN interfaces.

We have designed and implemented our scheme. Our scheme can be deployed for a real-world GPRS network without any support from it. We have evaluated the performance of our scheme on a real-world GPRS network. Our experimental results show that our scheme achieves about 2.7X speedup over 4 GPRS channels. To further evaluate our scheme with a much complicated topology, we have simulated our scheme and evaluated the performance of it on network simulator NCTUns2.0.