OFDM技術應用於LMDS系統在時變通道模型下之效能評估

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姓名

陳宜德(Yi-De Chen) 查詢紙本館藏

畢業系所

電機工程學系

論文名稱

OFDM技術應用於LMDS系統在時變通道模型下之效能評估
(Performance evaluation of an OFDM-based LMDS using time-variant channel models)

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摘要(中)

LMDS (Local Multi-point Distribution Service) 有釵h好處，例如：能提供寬頻的服務、架構建立較簡單、硬體設備花費較少等；而OFDM (Orthogonal Frequency Division Multiplexing) 對於ISI (Inter-symbol Interference) 、多路徑傳輸衰減有較大的抵抗能力。因此，本篇論文嘗試將兩者合併並加以模擬分析。
本篇論文首先設計傳送和接收端的模組，其中實體層的參數是參照IEEE 802.16所提供的標準[8]。通道模型是採用1999年在新加坡以LMDS為架構所測量而得的模型[6]，再加上兩種通道預測方法去模擬比較其效能。
論文中的模擬結果顯示： (1) 在LMDS的環境裡，OFDM對於多路徑傳輸衰減的抵抗力較傳統PSK、QAM的系統強。 (2) OFDM技術應用於LMDS系統，加上通道預測確實可以再提高其效能。

摘要(英)

Local multipoint distribution service (LMDS) has three advantages: 1) large bandwidth 2) lower installation cost 3) ease of deployment [6]. Orthogonal frequency division multiplexing (OFDM) can solve some questions in communication systems, for example: inter-symbol interference, multi-path fading and so on.
This thesis combines the OFDM technique with the LMDS system to simulate the OFDM-based LMDS system under the time-variant channel, which modeled by the measurement in Singapore [6]. And we use the two channel estimation methods, which one is linear interpolation method; the other is a novel method proposed in [3], to combat the interference of multi-path components.
The simulation results show that 1) the performance of the OFDM system is better than of the traditional modulation systems in multi-path channel in LMDS environment 2) the channel estimation using pilot sub-carriers can improve the performance in the OFDM system.

關鍵字(中)

★ OFDM
★ LMDS

關鍵字(英)

★ LMDS
★ OFDM

論文目次

Abstract I
Contents II
List of Figures IV
List of Tables VII
Chapter 1 Introduction 1
1.1 Motivation and Objective 1
1.2 Structure of the Thesis 2
Chapter 2 Basic Principles of OFDM 4
2.1 Introduction to OFDM 4
2.2 Generation of Sub-carriers using the IFFT 5
2.3 Guard Interval 8
2.4 Choice of OFDM Parameters 9
2.5 Channel Estimation 12
Chapter 3 Transceiver Implementation 16
3.1 An OFDM-based LMDS System 16
3.2 An OFDM-based 802.16 BWA PHY Layer 17
3.3 Wide-band Channel Model 19
3.3.1 AWGN Channel 20
3.3.2 Multi-path Fading Channel 22
3.3.3 Frequency-Selective Fading Channel 29
3.4 Transmitter and Receiver Model 30
3.5 Receiver Model with Channel Estimation 34
Chapter 4 Simulation Results 39
4.1 Simulation of the OFDM System 39
4.2 Simulation of the OFDM System with Channel Estimation 53
Chapter 5 Conclusions 59
References 62

參考文獻

[1]. Richard van Nee, Ramjee Prasad, “OFDM for Wireless Multimedia Communications”
[2]. Blahut, R. E., “Fast Algorithms for Digital Signal Processing”, Reading, MA: Addison-Wesley, 1985
[3]. Yuping Zhao and Aiping Huang, “A Novel Channel Estimation Method for OFDM Mobile Communication Systems Based on Pilot Signals and Transform-Domain Processing”, Vehicular Technology Conference, IEEE, 1997
[4]. J.Rinne and M. Renfors, “Channel estimation in OFDM systems utilizing pilots”, Espoo, Finland, 1996
[5]. http://grouper.ieee.org/groups/802/16/
[6]. K. V. Ravi and P. Soma, “Analysis and modeling of local multipoint distribution service (LMDS) channel”, Global Telecommunications Conference, IEEE, 1999
[7]. K. V. Ravi, D. Guo and K. L. Cheah, “Performance Evaluation of an OFDM-based LMDS using Measured Channel Models”, Wireless Communications and Networking Conference, IEEE, 2000
[8]. Naftali Chayat, “Proposal for an OFDM-based 802.16 BWA Air Interface Physical Layer”, IEEE 802.16 Broadband Wireless Access Working Group, 1999
[9]. Bernard Sklar, “Digital Communications Fundamentals and Applications”
[10]. K. V. Ravi, P. Soma, “Field Measurements and Channel Models for LMDS System Design”, CWC Technical Report, 1998
[11]. J. D. Parsons, “The Mobile Radio Propagation Channel”
[12]. Jay Klein, “PHY Layer proposal for BWA”, IEEE 802.16 Broadband Wireless Access Working Group, 2000
[13]. Aiping Huang and Yuping Zhao, “Estimating Channel Response from Pilot Sub-carrier Pairs for OFDM System”, Circuits and Systems conference, IEEE, 1997
[14]. J. Schoukens and J. Renneboog, “Modeling the noise influence on the Fourier coefficients after a discrete Fourier transform”, IEEE, 1986
[15]. S. Farahvash and M.Kavehrad. “Assessment of Cochannel Interference in Fixed Wireless Cellular Systems”, Radio and Wireless Conference, IEEE, 1999
[16]. Jean Armstrong, “Analysis of New and Existing Methods of Reducing Inter-carrier Interference Due to Carrier Frequency Offset OFDM”, Communications Journal, IEEE, 1999
[17]. Baoguo Yang, “Channel Estimation for OFDM Transmission in Multi-path Fading Channels Based on Parametric Channel Modeling”, Communications Journal, IEEE, 2001
[18]. Thomas keller and Lajos Hanzo, “Adaptive Modulation Techniques for Duplex OFDM Transmission”, Vehicular Technology Journal, IEEE, 2000

指導教授

蔡木金(Mu-King Tsay)

審核日期

2002-6-13

推文