| 摘要(英) |
In wireless cellular systems, co-channel interference is the limiting factor to system performance. Fixed wireless systems such as Local Multipoint Distribution Service (LMDS) is no exception to this rule. In LMDS, because the downlink is usually higher capacity and the narrow beam of subscriber’s antenna is an interference-limiting factor, the downlink interference is more serious. Consequently, improve of co-channel interference on the downlink direction of LMDS is the subject of this thesis.
In OFDM systems, data is transmitted simultaneously on parallel sub-carriers, each occupying a small fraction of the available bandwidth. The basic principle of OFDM is to split a high-rate data into a number of lower rate system. Multi-user OFDM is a promising new modulation technique for wireless communications. It includes many of the advantages of broadcast OFDM that is used for Digital Audio Broadcasting (DAB) and for Digital Video Broadcasting (DVB) in Europe and Australia. OFDM was selected for these systems primarily because of its high spectral efficiency and multi-path tolerance.
OFDM/FDMA is one of the multi-user OFDM multiple access. In OFDM/FDMA, the number of sub-carriers for a specific user can be varied, according to the required data rate. In the simplest OFDM/FDMA system, each user occupy fixed group of sub-carriers. We consider parts of the sub-carrier be used. Then we can improve system by using sub-carriers allocation. In this thesis, we proposed a simple sub-carriers allocation method compared to the convention and random OFDM/FDMA. |
| 論文目次 |
LIST OF CONTENTS
Abstract………………………….……………………Ⅰ
Contents…………………………….……...…………Ⅴ
List of Figures……………………….………..………Ⅶ
List of Tables………………………….……………....Ⅷ
Chapter 1 Introduction…………………...…...……………...1
1.1 Research background…………………...……………………..……...1
1.2 Research motivation………………………...……………………..…2
1.3 Structure of Thesis…………………………...…………………….....2
Chapter 2 LMDS Networks……………………….………….4
2.1 Background of LMDS………………………………………………..4
2.2 FCC Band Plan……………………………………….……………....5
2.3 LMDS Cellular Architecture……………………………………..…..8
2.3.1 Configuration…………………………………………………...…..8
2.3.2 Cell planning…………………………………………………….....9
2.4 Downlink Capacity Estimation……………………………………...10
2.4.1 Propagation Path Loss…………………………………………….10
2.4.2 Inter-Cell Interference…………………………………………….12
2.4.3 Rotated Base station………………………………………………13
2.5 Link Budget Calculation………………………….………………....16
Chapter3 OFDM Applications..……………………………..17
3.1 Introduction of OFDM………...……………………………………17
3.2 Basic Principles of OFDM……………………………….…………18
3.2.1 Generation of Sub-carriers Using the IFFT.………………………18
3.2.2 Guard Interval……………………………………………………..22
2.2.3 choice of OFDM parameters……………………………………...24
3.3 Multi-user OFDM…………………………………………………...26
3.4 Staggered Sub-carriers Allocation Method………………………….29
Chapter4 Numerical Simulation………………...………….34
4.1 Performance Estimation Results…………………………………….34
4.2 Discussions………………………………………………………….41
Chapter5 Conclusions……………………………………….42
References…………………………………………………….44
List of Figures
Figure 2-2-1 LMDS Band Allocation…………………………………….7
Figure 2-2-2 LMDS Band Allocation…………………………………….7
Figure 2-3-1 Definition of the Configuration……………….……………9
Figure 2-3-2 Cell Layout for LMDS………………………...………….10
Figure 2-4-1The log-normal probability density function………………12
Figure 2-4-2 Inter-cell interference with typical architecture…………...14
Figure 2-4-3 Rotated Base Station………………………………………14
Figure 2-4-4 Rotated base station architecture………………………….15
Figure 2-4-5 Inter-cell interference with rotated base station…………..15
Figure 3-2-1. OFDM modulator……………………………….……...20
Figure 3-2-2 Spectrum of OFDM……………………………….…….21
Figure 3-2-3 Spectrum of traditional FDM……………………………..21
Figure 3-2-4 OFDM symbol with cyclic extension……………………..23
Figure 3-2-5. Example of an OFDM signal……………………………..23
Figure 3-3-1. OFDM time and frequency grid………………………….27
Figure 3-3-2. Sub-carrier allocation in conventional OFDM/FDMA…..28
Figure 3-4-2. Order of sub-carrier for the SSA method………………...33
Figure 4-1 Outage probability vs. system load, BS1……………………35
Figure 4-2 Outage probability vs. system load, BS2……………………35
Figure 4-3 Outage probability vs. system load, BS3……………………36
Figure 4-4. bits/carrier vs. system load, BS1…………………………..37
Figure 4-5. bits/carrier vs. system load, BS2…………………………..37
Figure 4-6. bits/carrier vs. system load, BS7…………………………..38
Figure 4-7. outage probability vs. system load, with or without RL…..39
Figure 4-8. outage probability vs. system load, rotated BS……………..39
Figure 4-9. bits/carrier vs. system load, rotated BS……………………..40
Figure 4-10. outage probability vs. system load, with or without RL…..40
List of Tables
Table 2-1 Parameters, Formula and Calculations for LMDS……..……………………………………...….16
Table 4-1. Threshold levels for different modulation schemes………....31 |
| 參考文獻 |
[1]. Gray, D.A.; “A broadband wireless access system at 28 GHz”, Wireless Communications Conference, 1997, Proceedings, 11-13 Aug. 1997 Page(s): 1 -7
[2]. Parsons J. D., “The Mobile Radio Propagation Channel”, John Wiley & Sons, 1998.
[3]. W.C.Y Lee, “Mobile Communication Engineering”, McFraw-Hill, 1982.
[4]. Chang-Hoon Lee; Boo-Young Chung; Su-Hee Lee, “Dynamic Modulation Scheme in Consideration of Cell Interference for LMDS.” Communication Technology Proceedings, 1998.
[5]. Richard van Nee, Ramjee Prasad, “OFDM for Wireless Multimedia Communications”
[6]. Lawrey, E; “Multiuser OFDM”, Signal Processing and Its Applications, 1999. ISSPA '99. Proceedings of the Fifth International Symposium on , Volume: 2 , 22-25 Aug. 1999 Page(s): 761 -764 vol.2
[7]. Hsuan-Jung Su; Geraniotis, E; “A distributed power allocation algorithm with adaptive modulation for multi-cell OFDM systems”, Spread Spectrum Techniques and Applications, 1998. Proceedings., 1998 IEEE 5th International Symposium on , Volume: 2 , 2-4 Sept. 1998 Page(s): 474 -478 vol.2
[8]. Proakis, J., “Digital Communications,” McGraw-Hill Series in Electrical and Computer Engineering, 3rd Edition, 1995.
[9]. Leke, A.; Cioffi, J.M.; “A maximum rate loading algorithm for discrete multitone modulation systems”, Global Telecommunications Conference, 1997. GLOBECOM '97., IEEE , Volume: 3 , 3-8 Nov. 1997 Page(s): 1514 -1518 vol.3
[10]. Fong, T.K.; Henry, P.S.; Leung, K.K.; Xiaoxin Qiu; Shankaranarayanan, N.K.; “Radio resource allocation in fixed broadband wireless networks”, Communications, IEEE Transactions on , Volume: 46 Issue: 6 , June 1998 Page(s): 806 –818
[11]. Mu-King Tsay; “Twisted sector cell on local multipoint distribution service“, Microwave Conference, 2001. APMC 2001. 2001 Asia-Pacific , 3-6 Dec. 2001 Page(s): 601 -604 vol.2
[12]. Alen, T.C.H.; Madhukumar, A.S.; Chin, F.; “Capacity enhancement of a multi-user OFDM system using dynamic frequency allocation”, Wireless Communications and Networking, 2003. WCNC 2003. 2003 IEEE , Volume: 3 , 16-20 March 2003 Page(s): 1866 -1870 |
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