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研究生:黃文佐
研究生(外文):Wen-Tso Huang
論文名稱:正交分頻多工為基礎的IEEE802.11a無線區域網路之性能研究
論文名稱(外文):Performance Evaluation of the IEEE 802.11a OFDM-based Wireless Local Area Network
指導教授:王蒞君
指導教授(外文):Li-Chun Wang
學位類別:碩士
校院名稱:國立交通大學
系所名稱:電信工程系
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2002
畢業學年度:90
語文別:中文
論文頁數:135
中文關鍵詞:正交分頻多工無線區域網路
外文關鍵詞:OFDMWLAN
相關次數:
  • 被引用被引用:4
  • 點閱點閱:419
  • 評分評分:
  • 下載下載:81
  • 收藏至我的研究室書目清單書目收藏:3
無線區域網路IEEE 802.11a根據不同的通道品質提供6 Mb/s ~ 54 Mb/s的資料傳輸速率供使用者選擇﹔然而,在文獻中去探討各種資料傳輸速率的涵蓋範圍之研究並不多見。於是,本論文針對IEEE 802.11a 的標準,進行實體層(Physical layer)部分之模擬,得到各種資料速率在雷利(Rayleigh)以及萊斯(Rician)的衰減通道下,位元錯誤率(BER)對訊號雜訊比(SNR)的關係圖,再利用這些模擬結果,進行連線預算分析(Link budget Analysis),求得有效的傳輸距離。結果發現,在室內NLOS環境下,傳送功率為23 dBm,IEEE 802.11a傳輸距離為7公尺(54 Mb/s)~62公尺(6 Mb/s)。另外我們亦發現加入非線性放大器之後,IEEE 802.11a的系統涵蓋範圍大幅縮小成2.8 公尺~ 39.5公尺。另外,考慮非線性放大器的影響,且改用soft-decision Viterbi Decoder,系統涵蓋範圍小幅增加至3.3 公尺~ 47.7公尺。
另外,利用TDD(Time Division Duplex)系統通道可逆性(Channel reciprocity)的優點,吾人提出一種”Adaptive Channel Pre-compensation”方法,專門應用在TDD模式下,以相位調變為主的QPSK-OFDM系統,比起傳統的接收端補償方式,我們提出的方法不需要複雜的通道估測演算法就能得到不錯的效能增益。另外,我們提出的技術也比現存的通道預補償方法優異,因為不會有error floor出現。在一個簡單的例子裡,用我們的方法可達到 的BER,然而用Witrisal [28]的方法,則BER會因非線性放大器的影響而限制在 。
The IEEE 802.11a Wireless Local Area Network (WLAN) provides several data rates from 6 Mb/s to 54 Mb/s according to different channel quality. However, few studies about the coverage area for various data rates have appeared in the literature. The aim of this thesis is to simulate the physical layer performance of the IEEE 802.11a system and to obtain the BER performance for various data rates in Rayleigh and Rician fading channel. By incorporating the physical layer simulation results into the link budget analysis, we then calculate the effective coverage area of the IEEE 802.11a system for different service rates. Based upon our simulation results, for transmission power of 23 dBm and under a non-light-of sight channel, the indoor coverage range for 54 Mb/s is 7 meters and that for 6 Mb/s is 62 meters. With the nonlinear effects of power amplifier, our simulation results show that the transmitter has a range of 2.8 meters and 39.5 meters for data rates 54 Mb/s and 6 Mb/s, respectively. Soft decision Viterbi decoder can improve the range area to 3.3 meters for 54 Mb/s and 47.7 meters for 6 Mb/s when taking the nonlinearity of power amplifier into account.
Secondly, we have proposed an “Adaptive Channel Pre-compensation Method” for a TDD QPSK-OFDM system. By taking advantage of channel reciprocity of the TDD system, we avoid using complex channel estimation algorithms in the receiver. We demonstrate that the proposed pre-compensation method can still outperform the conventional post-compensation method by 1 dB of SNR. Furthermore, we show that the proposed pre-compensation method does not exhibit error floor phenomenon as other approaches. In a typical example, our approach can achieve a BER less than , while the conventional technique in [28] will be bounded by an error floor of due to the nonlinear effects of power amplifier.
第一章、 緒論……………………………………………………………… 1
1.1 簡介……………………………………………………………………1
1.2 研究動機………………………………………………………………4
1.3 章節概要………………………………………………………………5
第二章、 背景資料………………………………………………………… 6
2.1 OFDM簡介………………………………………………………………6
2.1.1單載波與多載波系統………………………………………………6
2.1.2 OFDM架構………………………………………………………… 8
2.1.3 Guard Interval和Cyclic Prefix………………………………9
2.2 OFDM PAPR的問題……………………………………………………13
2.3 OFDM在無線區域網路上的應用…………………………………… 16
2.3.1 IEEE 802.11a和HIPERLAN/2之MAC…………………………… 17
2.3.2 IEEE 802.11a和HIPERLAN/2之實體層…………………………18
第三章、 WLAN IEEE 802.11a系統涵蓋範圍之研究…………………… 20
3.1 IEEE 802.11a系統描述…………………………………………… 20
3.1.1 IEEE 802.11a傳送端架構………………………………………20
3.1.2 IEEE 802.11a接收端架構………………………………………32
3.2無線通道模型…………………………………………………………37
3.2.1 Multipath Channel Profile………………………………… 37
3.2.2路徑衰減模型…………………………………………………… 38
3.3位元錯誤率之性能……………………………………………………39
3.3.1 NLOS情況下之位元錯誤率………………………………………42
3.3.2 LOS情況下之位元錯誤率……………………………………… 44
3.4連線預算分析…………………………………………………………46
3.5討論……………………………………………………………………51
第四章、 非線性放大器對IEEE 802.11a系統的影響……………………52
4.1非線性功率放大器的特性……………………………………………52
4.2非線性對OFDM的影響…………………………………………………55
4.3模擬參數………………………………………………………………57
4.4模擬結果………………………………………………………………58
4.4.1 非線性放大器的影響……………………………………………59
4.4.2 非線性放大器在NLOS情況下之位元錯誤率……………………66
4.4.3 非線性放大器在LOS情況下之位元錯誤率…………………… 66
4.5連線預算分析…………………………………………………………69
4.6討論……………………………………………………………………74
第五章、 Soft Decision Viterbi解碼器的影響……………………….75
5.1動機……………………………………………………………………75
5.2 Soft Decision Algorithm…………………………………………76
5.3模擬結果………………………………………………………………82
5.3.1 不同量化層次(Quantization Level)的影響…………………83
5.3.2 Soft Decision Viterbi解碼器之性能………………………83
5.4連線預算分析…………………………………………………………90
5.5討論……………………………………………………………………94
第六章、 TDD OFDM系統的通道預補償評估………………………………95
6.1動機……………………………………………………………………95
6.2 OFDM通道預補償模型……………………………………………… 96
6.3 Proposed Method for Channel Pre-Compensation……………101
6.4模擬條件…………………………………………………………… 103
6.5模擬結果………………………………………………………… …107
6.6討論……………………………………………………………… …108
第七章、 結論和未來研究方向………………………………………… 109
7.1結論………………………………………………………………… 109
7.2未來研究方向……………………………………………………… 111
參考文獻……………………………………………………………………113
附錄…………………………………………………………………………116
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