臺灣博碩士論文加值系統

在具移動性的通訊環境中，通道的變化量與都卜勒效應對訊號造成的影響是需要克服的難題。本文探討了兩種不同的通道估測方法：首先在IEEE 802.11p的規格下對車車通道環境做了分析，設計有效益的指標訊號來準確的估測通道變化量。此外，我們利用期望最大化的演算結合低密度同位元檢查碼解碼作循環式的通道資訊更新，在不同的正規化都卜勒環境中作模擬實驗，經過多次數的更新動作後可達到不錯的效能

The channel variation and Doppler Effect should be solved in a mobile communication environment. Two methods of channel estimation have been proposed from two facts in this thesis. First, an efficient channel tracking method is proposed to estimate the channel variation in the vehicle to vehicle communication environment under the IEEE 802.11p standard. Second, we proposed an iterative method which joints channel estimation and LDPC decoding by using Expectation Maximization (EM) and Sum-Product Algorithm (SPA). In our simulation that based on normalized Doppler environment, we can obtain good system performance after several iteration.

書頁名 i
中文摘要 ii
英文摘要 iii
誌謝 iv
目錄 v
表目錄 vii
圖目錄 viii
第一章 序論 1
1.1 引言 1
1.2研究動機與目的 1
1.3 本篇論文架構 2
第二章 IEEE 802.11p 系統與通道估測 3
2.1 OFDM技術簡介 3
2.1.1 OFDM訊號分析 3
2.1.2 OFDM符元架構 4
2.1.3 OFDM 載波頻率偏移及取樣時間偏移 5
2.1.4 都卜勒效應 5
2.2 IEEE 802.11p系統簡介 6
2.2.1 IEEE 802.11p 規格介紹 7
2.2.2 DSRC系統效能要求 8
2.3 通道設計 8
2.3.1多路徑通道特性 9
2.3.2 DSRC VTV通道模型 10
2.3.3 通道設計的方法 12
2.4 通道估測方法及介紹 14
2.4.1估測通道中指標訊號數量與位置設計原理 15
2.4.2系統指標信號介紹 18
第三章 DSRC VTV 估測通道方法與效能 22
3.1 DSRC VTV 通道估測改良 22
3.2 在802.11p下 VTV的通道模擬 25
第四章 結合EM與LDPC在其他系統的通道估測 30
4.1 LDPC介紹 30
4.1.1 LDPC編碼及Factor graph 31
4.1.2 LDPC解碼演算法 32
4.2 EM演算法介紹 37
4.3結合EM與LDPC循環通道估測法 39
4.4移動環境系統與改善方法 42
4.4.1鄰近載波降低方法介紹 42
4.4.2移動環境系統與通道參數設定 44
4.5 結合EM與LDPC在移動環境系統的模擬結果 46
第五章 結論與未來展望 57
參考文獻 58

[1] IEEE Draft Std P802.11p/D1.0, February 2006 , Part 11: Wireless LAN Medium Access Control（MAC） and Physical Layer（PHY） specifications, Wireless Access in Vehicular Environments（WAVE）.
[2] R. Negi and J. Cioffi, “Pilot tone selection for channel estimation in a mobile OFDM system”, IEEE Trans. Consumer Electron., vol. 44, pp. 1122–1128, Aug. 1998.
[3] Part11:Wireless LAN, Medium Access Control (MAC) and Physical Layer (PHY) Specification :High-Speed Physical Layer Extension in the 2.4GHz Band. supplement to IEEE 802.11 Standard，Sept.1999.
[4] K.Kim,H.Kim,H.Park, “An efficient channel tracking method for OFDM based high mobility wireless multimedia system ,”LNCS 3768 pp. 235-245,2005.
[5] Yasamin ostofi ,D.Cox, “ICI Mitigation for Pilot-Aided OFDM Mobile System”, IEEE Trans. on Wireless communication ,vol4,2,MARCH 2005.
[6] R.G. Gallager, “Low Density Parity Check codes,” IRE Trans. Inform. Theory, vol.IT-8,pp.21-28,Jan.1962.
[7] H.Futaki and T.Ohtuski, “Low –density parity-check(LDPC) coded OFDM systems ,”IEEE ICC,pp.1696-1670,2002.
[8]D.J.C MacKay ,S.T. Wilson, and M.C. Davey, “Comparsion of constructions of irregular Gallager codes,”Proc. 36th Allerton Conf. Communication, control, and Computing, Sept. 1998
[9] Xiaoqiang Ma, H.Kobayashi, S.C.Scheartz,“EM-based channel estimate -on algorithm for OFDM,”EURASIP journal ,2004:10,1460-1477.
[10] A.W.Eckford, S.Rogers, “The factor Graph EM algorithm :application for LDPC codes,”
[11] Xiaowei Jin, Andrew W.Eckford and Thomas. E. Fuja, “Analysis of joint channel estimation and LDPC decoding on block fading channels.ISITA 2004 Oct.
[12] H.Niu, M.Shen, J.A.Ritcey, H.Liu, “A factor graph approach to iterative channel estimation and LDPC decoding over fading channel ,”IEEE Tran -s. vol.4 Jul 2005.
[13] D.Huang, K.B.Letaief, “Carrier frequency offset estimation for OFDM system using null subcarrier. IEEE Trans vol 54 No.5 MAY 2006.
[14] X.Dai, “carrier frequency offect estimation for OFDM/SDMA system using consecutive pilots,” IEEE Proc-Commun. Vol.152 No5. Oct,2005.
[15] P.Liu, B.Li, Z.Lu,F.Gong, “A new frequency Synchronization scheme for OFDM,” IEEE, Manuscript received May 18,2004.
[16] Bruce McNair, Leonard, J. Cimini, JR., and Nelson Sollenber , “A robust timing and frequency offset estimation scheme for OFDM system, ”Vehicular Technology conference,1999 IEEE 49th.
[17] IEEE Std 802.11a-1999, Part 11: Wireless LAN Medium Access Control（MAC） and Physical Layer（PHY） specifications: High Speed Physical Layer in the 5GHz Band.
[18] J. I. Smith, “A computer generated multipath fading simulation for mobile radio,” IEEE Trans. Veh. Technol.
[19] Jakes.W.C,Ed microwave mobile communications,Wiley,1974.
[20] Douglas C. Montgomery, George C. Runger, “Applied statistics and probability for engineers,” John Wiley Sons, New York, 1999.
[21] Jonathan H.Manton, “Optimum training sequences and pilot tones for OFDM system,” IEEE Comm. Letters ,vol.5 no.5,Apr 2001.
[22] Heung-Gyoon Ryu and Kyoung-Jae Youn, “A new PAPR reduction scheme: SPW (sub-block phase weighting),” IEEE Transactions on Consumer Electronics, Vol. 48, No. I, FEBRUARY 2002.
[23] Dov Wulich, “Definition of Efficient PAPR in OFDM,” IEEE communication letters,vol.9,no.9,September 2005.
[24] Frank Dellaert, “The expectation maximization algorithm ,”.Feb 2002.
[25] Shu Lin,D.J.Costello, “Error control coding,” second edition,2004.
[26] K.Fu, Achilleas, “Performance analysis of LDPC codes for time selective complex fading channels,” Global Telecommunications conference, 2002.
[27]David J. Young, “The generation of correlated rayleigh random variates by inverse discrete fourier transform,” IEEE transactions on communications, vol.48 no.7,July 2000.