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標題: 無線區域網路 802.11b及載波回復迴路之研究
A Study of Wireless LAN 802.11b and Carrier Recovery Loop
作者: 黃逸群
Huang, Yi-Chun
關鍵字: wireless LAN;無線區域網路;802.11.b;802.11;frequency offset;carrier recovery loop;loop filter;802.11.b;802.11;頻率偏移;載波回復迴路;迴路濾波器
出版社: 電機工程學系
近年來隨著科技的發展,人類對資訊的需求已邁入了無線通訊的時代。許多無線通訊系統陸續被提出,無線區域網路IEEE 802.11便是其中之一。在本論文中我們將介紹802.11b中的通道模型、展頻技術以及調變技術等。但仍然有許多因素嚴重干擾無線網路系統的通訊品質,包括通道雜訊、通道衰減、以及頻率偏移及相位偏移等等…。論文中也針對載波回復迴路做討論,載波回復迴路已被廣泛的應用在解決送器及接收器之間的頻率偏移及相位偏移的問題。

In recent years, with technology progress, data transmission used wireless interface has become popular. The IEEE 802.11 standard for wireless LAN was proposed for this propose. In this thesis, we introduce channel model, modulation formats, spread spectrum techniques and modulation techniques for 802.11.b. The wireless network systems would be degraded by numerous factors including channel fading, channel noise, frequency offset, and phase offset… etc. We discuss the carrier recovery loop to resolve the problem of frequency offset and phase offset between transmitter and receiver in this thesis.
The frequency offset is converged and compensated by the carrier recovery loop, but the residual phase error can't be recovered. A new structure and algorithm are proposed for carrier recovery. The algorithms use the information of received signal to compensate the frequency offset and residual phase error without using the loop filter and NCO (Numerically Controlled Oscillator). In other words, the recovered signal is on the I and Q correctly. Compare with traditional carrier recovery loop, the new structure have the advantage of easy to implement and a shorter convergent time.
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