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標題: 在IEEE802.11a下之OFDM系統之效能分析
Performance Analysis of OFDM System Based on IEEE 802.11a
作者: 何堂源
Ho, Tarng-Yuan
關鍵字: Performance Analysis of OFDM System;OFDM系統之效能分析
出版社: 電機工程學系
摘 要
無線區域網路標準IEEE802.11a採用正交分頻多工(Orthogonal Frequency Division Multiplexing, OFDM)的技術,可以抵抗通道環境之多重路徑的效應,同時能提供高頻譜效益,高速傳輸。無線區域網路之應用日益普及,實際之資料速率並未臻802.11a所訂定之54Mbps(最佳約為24Mbps),此問題已經漸漸浮現,然而廣受關注的是受到哪些主要效應或因素所限制與如何改進其傳輸效能,此為本論文研究之重要課題。
本論文之目的在研討適用於IEEE 802.11a規格的OFDM系統架構與探討其設計議題(design issues),例如,多徑通道衰落,訊框起始時序誤差,峰值功率截切,高斯雜訊等通道效應影響之下,分析位元錯誤率(BER)之性能降低,並且分析評比系統效能。同時提出OFDM系統之發射與接收系統之模型,然後以所設計之軟體model透過電腦模擬出OFDM系統在這些通道效應之下的BER退化特性,並以此model實際傳輸檔案來探討與分析BER與SNR之變化趨勢。模擬結果顯示我們所建立之model可以得到正確的功能.

Orthogonal frequency division multiplexing (OFDM) is the chosen modulation technique for IEEE802.11a of Wireless Local Area Network communications. Using the OFDM can provide larger data rates with sufficient robustness to radio channel impairments, which can also provide a high spectral effency. Besides, WLAN application is popular worldwide, some issues are gradually appeared before our eyes, that is, real data rate, in fact, can not reach to 54Mbps specified in 802.11a specification (optimized 24Mbps).
The objective of this thesis is to study an OFDM sysem architecture, and probe into the design issues, such as multi-path channel fading, peak power clipping, frame starting timing error, AWGN, and how they cause the distortion and how to compensate the system performance. Meanwhile, an OFDM system model of transmitter and receiver is constructed. Simulation was conducted under the multi-path fading channel model. The system characteristics of BER degradation verus channel effects was also studied. Finally, a set of files was sent for test by using this 802.11a OFDM model. The simulation results show that the model we have built was functioned correctly.
Appears in Collections:電機工程學系所

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