WiMAX 系統中 TCP 傳輸之耗電評估

Abstract

為了解決行動裝置的耗電問題，寬頻無線存取系統(Broadband Wireless Access, BWA)通常會提供省電機制以減少網路閒置時的耗電。其中IEEE 802.16e提供數種適合不同應用服務的省電類別(Power Saving Class)來降低耗能。在這個研究中，我們針對WiMAX網路上的TCP傳輸，進行耗電方面的研究。首先觀察WiMAX的媒體存取層在進行TCP傳輸時的額外耗電行為，再者對於一個長期處於傳輸的TCP連線的網路裝置，例如FTP，分析討論在閒置等待TCP封包時的額外耗電。在本研究中我們透過實際的量測取得耗電參數與模型，結合網路分析器 NS2，來評估和分析TCP傳輸在WiMAX系統中的耗電情形。實驗結果顯示在高延遲的傳輸環境下，使用第二型態省電類別並採取代理伺服器，會比傳統的方法好50%的省電效益。

Broadband Wireless Access (BWA) system usually provides power saving mechanisms to save the energy consumption of a mobile device during idle. IEEE 802.16e suggests several Power Saving Classes for different type of applications to minimize the power consumption. In this work, we investigate the energy consumption of TCP transmission over WiMAX. First, we evaluate the extra energy consumption introduced by WiMAX MAC in transmitting TCP packets. Then, we consider a long TCP session such as FTP, and evaluate the power consumption of the WiMAX interface when the interface waits for incoming TCP packets. We conduct a number of experiments in a real WiMAX test-bed and obtain the power consumption parameters and models of a WiMAX interface. These power consumption parameters are further fed into network simulator 2 (NS2) to evaluate the power consumption of WiMAX in transmitting TCP packets. Experimental and simulation results demonstrate that by applying sleep class type II and proxy server in BS can outperform traditional always-on approach by 50% in terms of energy efficiency.