面向数据分组传输的OFDM时频同步系统研究
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摘要
本文研究OFDM分组传输系统的符号同步与频偏估计算法。在分析信道特性和总结已有算法的基础上，对一种基于前导的定时同步算法在多径信道下出现较大定时误判的缺点做了改进。同时针对利用循环前缀的非数据辅助类估计算法在多径信道下定时估计不准确、频偏估计范围受限的缺点，提出使用改进型循环前缀相关估计来获得更准确的粗定时估计；利用OFDM分组传输系统载波结构上的特点进行整数频偏估计；利用有限的导频信号进行信道延迟估计从而获得准确的符号同步。结合几点改进提出了一种面向分组传输的无前导时频同步体系，并给出了信道估计算法以及载波和抽样频率的跟踪算法。随后使用MATLAB仿真验证了算法性能并提出了进一步研究的方向。这种同步方案适合于分组传输中的快速同步，具有复杂度低，数据利用率高的优点。
This paper investigated the timing and frequency offset estimation algorithm of OFDM burst transmission systems. An improvement to Minn's preamble based synchronization method is proposed to overcome the severe timing error in multipath environments. A new frame and frequency synchronization scheme without using preamble is presented for burst transmission. Based on modified OFDM cyclic prefix, the new method can achieve a more reliable coarse timing. The integer frequency offset, which cannot be acquired in cyclic prefix based algorithm, is achieved through post-FFT virtual sub-carriers. Channel delay estimation via pilot sub-carriers is used to provide accurate frame synchronization in multipath channels. Besides, the channel estimation method, carrier frequency and sampling clock offset tracking algorithms are also discussed in this paper. It is demonstrated through simulation that this scheme can provide a robust synchronization for OFDM burst transmission systems in Reyleigh fading channel with low comp
lexity and high data rate. Finally the further research direction is suggested.
This paper investigated the timing and frequency offset estimation algorithm of OFDM burst transmission systems. An improvement to Minn's preamble based synchronization method is proposed to overcome the severe timing error in multipath environments. A new frame and frequency synchronization scheme without using preamble is presented for burst transmission. Based on modified OFDM cyclic prefix, the new method can achieve a more reliable coarse timing. The integer frequency offset, which cannot be acquired in cyclic prefix based algorithm, is achieved through post-FFT virtual sub-carriers. Channel delay estimation via pilot sub-carriers is used to provide accurate frame synchronization in multipath channels. Besides, the channel estimation method, carrier frequency and sampling clock offset tracking algorithms are also discussed in this paper. It is demonstrated through simulation that this scheme can provide a robust synchronization for OFDM burst transmission systems in Reyleigh fading channel with low comp
lexity and high data rate. Finally the further research direction is suggested.
引文
1 Alister Burr. Modulation and coding for wireless communications．电子工业出版社，2003．2
2 Juha Heiskala, John Terry，杨晓春等译．OFDM无线局域网．电子工业出版社，2003．3
3 王世一．数字信号处理．北京：北京理工大学出版社．1997．11
4 Michael Speth, Stefan A. Fechtel, etc. Optimum receiver design for wireless broad-band systems using OFDM—Part Ⅰ. IEEE Trans. Comm, VOL. 47, NO. 11, November 1999, 1668-1677
5 佟学俭，罗涛，OFDM移动通信技术原理与应用．北京：人民邮电出版社，2003．6
6 Paul H. Moose. A technique for orthogonal frequency division multiplexing frequency offset correction. IEEE Transaction on Communication. Vol. 42, No. 10, 1994,2908-2914
7 王亚莉等．一种适用于瑞利衰落信道的有效OFDM时频同步体制．通信学报．Vol．24．2003．1
8 IEEE 802.11a, "Wireless LAN Medium Access Control(MAC) and Physical Layer (PHY) specifications: High-speed Physical Layer in the 5GHz Band",IEEE Std 802.11a-2001 Amd
9 T. Pollet, P. Spruyt and etc, "The BER performance of OFDM systems using non-synchronized sampling" in Proc. IEEE Globecom, San Francisco, CA, VOL 1, Nov, 1994, pp 253-257
10 樊凌涛，梁天明，陈健，OFDM技术在高速数据传输中的进展．无线电通信技术，2002年第28卷第四期
11 王立宁等，MATLAB与通信仿真．北京：人民邮电出版社，2000．1
12 Theodore S. Rappaport，无线通信原理与应用．电子工业出版社，1998．9
13 J. G Prokis，数字通信．电子工业出版社，2001．4
14 滕勇，罗涛，乐光新，5G Hz无线局域网信道特性与信道模型．无线通信技术，2002年第四期
15 Chun Loo and Norman Secord. Computer models for fading channels with application to digital transmission. IEEE Trans. vehicular Technology, Vol. 40, Nov, 1991
16 Octavia Adina Dobre and Djuradj Budimir, The modeling of a flat Rayleigh fading mobile radio channel. 10~(th) Mediterranean Electrotechnical Conference, MEleCon 2000, Vol. I, 2000
17 Lei-Lei Lock, Xiangming Kong and Richard J. Barton. Simulation of time-varying, frequency-selective multipath fading channels for spread-spectrum waveforms. IEEE, 1999
18 钱学荣，宽带移动OFDM系统的盲信道估计及信号检测．南京邮电学院博士研究生学位论文，TN911．10293，2003．10
19 J-J-Van de Beek, M. Sandell. ML estimation of timing and frequency offset in multicarrier systems. IEEE Trans. Signal Processing, vol. 45, pp. 1800-1895, July 1997
20 J-J-Van de Beek, M. Sandell, etc. Low complex frame synchroniztion in OFDM systems. Pro IEEE int. Conf. Universal Personal Communication, Toronto
Canada. Vol27-29. September, 1995, 982-986
21 Kenkich Takahashi Takashiko Saba. Anovel symbol synchronization Algorithm with reduced Influence of ISI for OFDM systems. Telecommunication Conference 2001, Globecom, 2001
22 T.M. Schmidl D.C. Cox. Robust frequency and timing synchronization for OFDM. IEEE Transaction on Communication. Vol. 45. No. 12,1997, 1613-1621
23 T.M. Schmidl D.C. Cox. Low-overhead, low complexity [Burst] synchronization for OFDM. IEEE International Conference on Communications. Vol. 3.1996.1301-1306
24 M. Morelli and U. Mengali, An improved frequency offset estimator for OFDM systems, IEEE Comm. Letter, vol. 4, pp. 75-77, Mar. 1999
25 Hlaing Minn, Vijay K. Bhargava etc., A robust timing and frequency synchronization for OFDM systems, IEEE Trans. Wireless Comm., vol. 2, No. 4, July 2003. pp. 822-838
26 徐磊，董在望．一种基于保护间隔的数字音频广播系统载波同步方法．电声技术．No．10，2002，59-62
27 周一青 胡爱群．利用训练帧进行OFDM系统同步的新算法．通信学报，Vol．22，No．4，2001，13-18
28 Byungjoon Park, Hyunsoo Cheon, Changeon Kang, Daesik Hong. A novel timing estimation method for OFDM systems. IEEE Communications Letters. Vol. 7. No. 5,2003
29 H. Liu and U. Tureli, A high efficiency carrier estimator for OFDM communications, IEEE Comm. Letters, vol. 2, pp. 104-106, April 1998
30 U. Tureli, D. Kivanc, and H. Liu, Experimental and analytical studies on a high-resolution OFDM carrier frequency offset estimator, IEEE Trans. Vehicular Technology, vol. 50, pp. 629-643, March 2001
31 U. Tureli, H. Liu, and M. Zoltowski, OFDM blind carrier offset estimation: ESPRIT, IEEE Trans. Communications, vol. 48, pp. 1459-1461, Sep, 2000
32 Helmut Boelcskei, Blind estimation of symbol timing and carrier frequency offset in wireless OFDM systems, IEEE Trans. Communications, vol. 49, No. 6, June 2001, pp. 988-999
33 Biao Chen and Hao Wang, Maximum likelihood estimation of OFDM carrier frequency offset, IEEE Signal Processing Letters, vol. 9, No. 4, pp. 123-126, Apr 2002
34 R. Roy, A. Paulraj etc., ESPRIT-A subspace rotation approach to estimation of Parameters of cisoids in Noise, IEEE Trans. Acoustics, Speech and Signal Processing, Vol. ASSP 34, No. 5, Oct 1986
35 Baoguo Yang, Khaled Ben Letaief etc., Timing recovery for OFDM transmission, IEEE Journal on Selected areas in Comm., vol. 18, No. 11, Nov 2000, pp. 2278-2291
36 Shao Huaizong, Peng Qicong, Li Yubai, Blind channel estimation using aid of Pseudo-Pilot-Symbols for OFDM system．电子科技大学学报，vol．31，N0．6，Dec，2002
37 艾渤，葛建华，赵妍妮，高清晰度数字电视中的符号定时检测算法．华中科技大学学报(自然科学版)．Vol．31，No．1，Jan，2003
38 冯爱刚等，正交频分复用码分多址系统盲自适应频率同步算法，西安交通大学学报．Vol．36，No．8，Aug．2002
39 Navid Lashkarian and Sayfe Kiaei, Class of cyclic-based estimators for frequency-offset estimation of OFDM systems. IEEE Trans. On Comm. Vol. 48, No. 12,
Dec, 2000
40 M. Speth F. Classen and H. Meyr, Frame synchronization of OFDM systems in frequency selective fading channels, Proc. IEEE Int. Conf. Vehicular Technology, 1997, pp. 1807-1811
41 Dusan Matic, Nicolas Petrochilos, A. Trindade, OFDM synchronization based on the phase rotaion of sub-carriers. VTC IEEE, 2000, pp. 1260-1264
42 Samir Kapoor, Daniel J, Marchok, Yih-Fang Huang. Pilot assited Synchronization for wireless OFDM systems over fast time varying fading channels. VTC IEEE, 1998,2077-2080
43 Yu Song, Sumit Roy, L.A. Alkers, Joint blind estimation of channel and data symbols in OFDM. VTC IEEE, 2000, 46-50
44 Meng-Han Hsieh and Che-Ho Wei, A low-complexity frame synchronization and frequency offset compensation scheme fOR OFDM systems over fading channels, IEEE Trans. On Vehicular Technology, Vol. 48, No. 5, Sep, 1999
45 Byungjoon Park etc., A blind OFDM synchronization algorithm based on cyclic correlation, IEEE Signal Processing Letters, Vol. 11, No. 2, Feb, 2004
46 张贤达．现代信号处理—2版．北京：清华大学出版社，2002
47 李熠，李式巨．无线局域网环境中OFDM系统频偏综合估计．电路与系统学报，2002年6月，第7卷第2期
48 Michael Speth, Stefan Fechtel, etc. Optimum receiver design for OFDM-based broadband transmission-Part Ⅱ: A case study. IEEE Transactions on communications, Vol. 49, No. 4, April, 2001
49 Wen Lei, Jianhua Lu, A new pilot assisted frequency synchronization for wireless OFDM systems. IEEE 2003, 0-7803-7663-3/03, ICASSP 2003
50 Ma Zhangyong, Zhao Chunming, etc. A novel OFDM time and frequency synchronization algorithm. Proceedings of ICCT2003, IEEE 2003, 1114—1118
51 邝育军，乐光新．OFDM系统信道估计中的插值算法性能分析．北京邮电大学学报，2003年3月，第26卷第1期
52 张继东，郑宝玉．基于导频的OFDM信道估计及其研究进展．通信学报，2003年11月，第24卷第11期
53 Ove. E, Sandell. M, Jaap J. etc. OFDM channel estimation by singular value decomposition. IEEE Transaction on communication, 1998, 46(7)-931-939
54 Shou Yin Liu, Jong Wha Chong. A study of joint tracking algorithm of carrier frequency offset and sampling clock offset for OFDM-based WLANs. IEEE 2002, 0-7803-7547-5
55 王文博，郑侃．宽带无线通信OFDM技术．人民邮电出版社，2003．11
2 Juha Heiskala, John Terry，杨晓春等译．OFDM无线局域网．电子工业出版社，2003．3
3 王世一．数字信号处理．北京：北京理工大学出版社．1997．11
4 Michael Speth, Stefan A. Fechtel, etc. Optimum receiver design for wireless broad-band systems using OFDM—Part Ⅰ. IEEE Trans. Comm, VOL. 47, NO. 11, November 1999, 1668-1677
5 佟学俭，罗涛，OFDM移动通信技术原理与应用．北京：人民邮电出版社，2003．6
6 Paul H. Moose. A technique for orthogonal frequency division multiplexing frequency offset correction. IEEE Transaction on Communication. Vol. 42, No. 10, 1994,2908-2914
7 王亚莉等．一种适用于瑞利衰落信道的有效OFDM时频同步体制．通信学报．Vol．24．2003．1
8 IEEE 802.11a, "Wireless LAN Medium Access Control(MAC) and Physical Layer (PHY) specifications: High-speed Physical Layer in the 5GHz Band",IEEE Std 802.11a-2001 Amd
9 T. Pollet, P. Spruyt and etc, "The BER performance of OFDM systems using non-synchronized sampling" in Proc. IEEE Globecom, San Francisco, CA, VOL 1, Nov, 1994, pp 253-257
10 樊凌涛，梁天明，陈健，OFDM技术在高速数据传输中的进展．无线电通信技术，2002年第28卷第四期
11 王立宁等，MATLAB与通信仿真．北京：人民邮电出版社，2000．1
12 Theodore S. Rappaport，无线通信原理与应用．电子工业出版社，1998．9
13 J. G Prokis，数字通信．电子工业出版社，2001．4
14 滕勇，罗涛，乐光新，5G Hz无线局域网信道特性与信道模型．无线通信技术，2002年第四期
15 Chun Loo and Norman Secord. Computer models for fading channels with application to digital transmission. IEEE Trans. vehicular Technology, Vol. 40, Nov, 1991
16 Octavia Adina Dobre and Djuradj Budimir, The modeling of a flat Rayleigh fading mobile radio channel. 10~(th) Mediterranean Electrotechnical Conference, MEleCon 2000, Vol. I, 2000
17 Lei-Lei Lock, Xiangming Kong and Richard J. Barton. Simulation of time-varying, frequency-selective multipath fading channels for spread-spectrum waveforms. IEEE, 1999
18 钱学荣，宽带移动OFDM系统的盲信道估计及信号检测．南京邮电学院博士研究生学位论文，TN911．10293，2003．10
19 J-J-Van de Beek, M. Sandell. ML estimation of timing and frequency offset in multicarrier systems. IEEE Trans. Signal Processing, vol. 45, pp. 1800-1895, July 1997
20 J-J-Van de Beek, M. Sandell, etc. Low complex frame synchroniztion in OFDM systems. Pro IEEE int. Conf. Universal Personal Communication, Toronto
Canada. Vol27-29. September, 1995, 982-986
21 Kenkich Takahashi Takashiko Saba. Anovel symbol synchronization Algorithm with reduced Influence of ISI for OFDM systems. Telecommunication Conference 2001, Globecom, 2001
22 T.M. Schmidl D.C. Cox. Robust frequency and timing synchronization for OFDM. IEEE Transaction on Communication. Vol. 45. No. 12,1997, 1613-1621
23 T.M. Schmidl D.C. Cox. Low-overhead, low complexity [Burst] synchronization for OFDM. IEEE International Conference on Communications. Vol. 3.1996.1301-1306
24 M. Morelli and U. Mengali, An improved frequency offset estimator for OFDM systems, IEEE Comm. Letter, vol. 4, pp. 75-77, Mar. 1999
25 Hlaing Minn, Vijay K. Bhargava etc., A robust timing and frequency synchronization for OFDM systems, IEEE Trans. Wireless Comm., vol. 2, No. 4, July 2003. pp. 822-838
26 徐磊，董在望．一种基于保护间隔的数字音频广播系统载波同步方法．电声技术．No．10，2002，59-62
27 周一青 胡爱群．利用训练帧进行OFDM系统同步的新算法．通信学报，Vol．22，No．4，2001，13-18
28 Byungjoon Park, Hyunsoo Cheon, Changeon Kang, Daesik Hong. A novel timing estimation method for OFDM systems. IEEE Communications Letters. Vol. 7. No. 5,2003
29 H. Liu and U. Tureli, A high efficiency carrier estimator for OFDM communications, IEEE Comm. Letters, vol. 2, pp. 104-106, April 1998
30 U. Tureli, D. Kivanc, and H. Liu, Experimental and analytical studies on a high-resolution OFDM carrier frequency offset estimator, IEEE Trans. Vehicular Technology, vol. 50, pp. 629-643, March 2001
31 U. Tureli, H. Liu, and M. Zoltowski, OFDM blind carrier offset estimation: ESPRIT, IEEE Trans. Communications, vol. 48, pp. 1459-1461, Sep, 2000
32 Helmut Boelcskei, Blind estimation of symbol timing and carrier frequency offset in wireless OFDM systems, IEEE Trans. Communications, vol. 49, No. 6, June 2001, pp. 988-999
33 Biao Chen and Hao Wang, Maximum likelihood estimation of OFDM carrier frequency offset, IEEE Signal Processing Letters, vol. 9, No. 4, pp. 123-126, Apr 2002
34 R. Roy, A. Paulraj etc., ESPRIT-A subspace rotation approach to estimation of Parameters of cisoids in Noise, IEEE Trans. Acoustics, Speech and Signal Processing, Vol. ASSP 34, No. 5, Oct 1986
35 Baoguo Yang, Khaled Ben Letaief etc., Timing recovery for OFDM transmission, IEEE Journal on Selected areas in Comm., vol. 18, No. 11, Nov 2000, pp. 2278-2291
36 Shao Huaizong, Peng Qicong, Li Yubai, Blind channel estimation using aid of Pseudo-Pilot-Symbols for OFDM system．电子科技大学学报，vol．31，N0．6，Dec，2002
37 艾渤，葛建华，赵妍妮，高清晰度数字电视中的符号定时检测算法．华中科技大学学报(自然科学版)．Vol．31，No．1，Jan，2003
38 冯爱刚等，正交频分复用码分多址系统盲自适应频率同步算法，西安交通大学学报．Vol．36，No．8，Aug．2002
39 Navid Lashkarian and Sayfe Kiaei, Class of cyclic-based estimators for frequency-offset estimation of OFDM systems. IEEE Trans. On Comm. Vol. 48, No. 12,
Dec, 2000
40 M. Speth F. Classen and H. Meyr, Frame synchronization of OFDM systems in frequency selective fading channels, Proc. IEEE Int. Conf. Vehicular Technology, 1997, pp. 1807-1811
41 Dusan Matic, Nicolas Petrochilos, A. Trindade, OFDM synchronization based on the phase rotaion of sub-carriers. VTC IEEE, 2000, pp. 1260-1264
42 Samir Kapoor, Daniel J, Marchok, Yih-Fang Huang. Pilot assited Synchronization for wireless OFDM systems over fast time varying fading channels. VTC IEEE, 1998,2077-2080
43 Yu Song, Sumit Roy, L.A. Alkers, Joint blind estimation of channel and data symbols in OFDM. VTC IEEE, 2000, 46-50
44 Meng-Han Hsieh and Che-Ho Wei, A low-complexity frame synchronization and frequency offset compensation scheme fOR OFDM systems over fading channels, IEEE Trans. On Vehicular Technology, Vol. 48, No. 5, Sep, 1999
45 Byungjoon Park etc., A blind OFDM synchronization algorithm based on cyclic correlation, IEEE Signal Processing Letters, Vol. 11, No. 2, Feb, 2004
46 张贤达．现代信号处理—2版．北京：清华大学出版社，2002
47 李熠，李式巨．无线局域网环境中OFDM系统频偏综合估计．电路与系统学报，2002年6月，第7卷第2期
48 Michael Speth, Stefan Fechtel, etc. Optimum receiver design for OFDM-based broadband transmission-Part Ⅱ: A case study. IEEE Transactions on communications, Vol. 49, No. 4, April, 2001
49 Wen Lei, Jianhua Lu, A new pilot assisted frequency synchronization for wireless OFDM systems. IEEE 2003, 0-7803-7663-3/03, ICASSP 2003
50 Ma Zhangyong, Zhao Chunming, etc. A novel OFDM time and frequency synchronization algorithm. Proceedings of ICCT2003, IEEE 2003, 1114—1118
51 邝育军，乐光新．OFDM系统信道估计中的插值算法性能分析．北京邮电大学学报，2003年3月，第26卷第1期
52 张继东，郑宝玉．基于导频的OFDM信道估计及其研究进展．通信学报，2003年11月，第24卷第11期
53 Ove. E, Sandell. M, Jaap J. etc. OFDM channel estimation by singular value decomposition. IEEE Transaction on communication, 1998, 46(7)-931-939
54 Shou Yin Liu, Jong Wha Chong. A study of joint tracking algorithm of carrier frequency offset and sampling clock offset for OFDM-based WLANs. IEEE 2002, 0-7803-7547-5
55 王文博，郑侃．宽带无线通信OFDM技术．人民邮电出版社，2003．11