室内可见光通信中OFDM同步问题的研究
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摘要
可见光通信是一种新型的无线光通信技术,由于其自身的优点和广阔的应用前景而受到关注。将OFDM技术应用到可见光通信中,可以进一步提高系统的传输速率以及抗多径干扰能力,而解决可见光OFDM通信系统的同步问题,对于系统的实现有着重要意义。
本文主要针对室内可见光OFDM通信系统进行了研究。首先通过对可见光信道的分析,给出了系统的信道模型;并结合可见光OFDM系统的原理,讨论了循环前缀长度、多普勒频移对系统的影响以及LED的非线性失真等问题;针对可见光通信只能使用单极OFDM信号的特点,引用了非对称削减OFDM的方法,并比较了不同调制方法的误码率性能和带宽利用率。
最后,本文重点研究了室内可见光OFDM系统的同步问题。分析了与射频OFDM在同步问题上的不同点,即系统只需要进行符号定时同步和采样时钟同步。在Park算法基础上,使用一种改进算法作为系统定时同步的解决方案:使用一种简单的基于导频序列的最大似然估计法进行采样时钟频偏估计,并采用内插环路作为频偏补偿电路,以实现系统的采样时钟同步。仿真结果表明,所采用的同步算法在室内可见光条件下可以准确地实现符号定时同步和采样时钟同步。
Visible light communication is a new type of wireless optical communication technology, because of its own advantages and wide application prospects attention. We introduce OFDM technology into the visible light communication, which can further improve the system transmission rate and the ability of anti-multipath interference, and to solve the synchronization of visible light OFDM system is very important for the realization of the system.
This thesis mainly focuses on indoor visible-light OFDM communication system. First, we analysis the indoor optical channel, given the channel model; then gives the principle of visible light OFDM system model and discuss the system in a number of practical issues, such as the cyclic prefix length, the impact of Doppler frequency shift and the LED non-linear distortion; for visible light communication can only use the characteristics of a unipolar OFDM signals, we introduce the Asymmetrically Clipped OFDM, and compare the error-rate performance and bandwidth utilization for difference modulation.
Finally, the thesis focuses on the synchronization issues of OFDM for indoor visible light communication system. Analyzes difference between the RF-OFDM and VLC-OFDM on synchronization, which is the system requires timing synchronization and sampling clock synchronization, but no need for carrier frequency synchronization. Based on the Park algorithm, we improved a new algorithm as the system timing synchronization solution; and use of a simple the maximum likelihood sequence estimation method based on pilot for the sampling clock frequency offset estimation, using interpolation loop as the frequency deviation compensation circuitry to achieve the sampling clock synchronization. The simulation results show that, the synchronization algorithm we proposed can accurately achieve timing synchronization and sampling clock synchronization for indoor visible light communication system.
本文主要针对室内可见光OFDM通信系统进行了研究。首先通过对可见光信道的分析,给出了系统的信道模型;并结合可见光OFDM系统的原理,讨论了循环前缀长度、多普勒频移对系统的影响以及LED的非线性失真等问题;针对可见光通信只能使用单极OFDM信号的特点,引用了非对称削减OFDM的方法,并比较了不同调制方法的误码率性能和带宽利用率。
最后,本文重点研究了室内可见光OFDM系统的同步问题。分析了与射频OFDM在同步问题上的不同点,即系统只需要进行符号定时同步和采样时钟同步。在Park算法基础上,使用一种改进算法作为系统定时同步的解决方案:使用一种简单的基于导频序列的最大似然估计法进行采样时钟频偏估计,并采用内插环路作为频偏补偿电路,以实现系统的采样时钟同步。仿真结果表明,所采用的同步算法在室内可见光条件下可以准确地实现符号定时同步和采样时钟同步。
Visible light communication is a new type of wireless optical communication technology, because of its own advantages and wide application prospects attention. We introduce OFDM technology into the visible light communication, which can further improve the system transmission rate and the ability of anti-multipath interference, and to solve the synchronization of visible light OFDM system is very important for the realization of the system.
This thesis mainly focuses on indoor visible-light OFDM communication system. First, we analysis the indoor optical channel, given the channel model; then gives the principle of visible light OFDM system model and discuss the system in a number of practical issues, such as the cyclic prefix length, the impact of Doppler frequency shift and the LED non-linear distortion; for visible light communication can only use the characteristics of a unipolar OFDM signals, we introduce the Asymmetrically Clipped OFDM, and compare the error-rate performance and bandwidth utilization for difference modulation.
Finally, the thesis focuses on the synchronization issues of OFDM for indoor visible light communication system. Analyzes difference between the RF-OFDM and VLC-OFDM on synchronization, which is the system requires timing synchronization and sampling clock synchronization, but no need for carrier frequency synchronization. Based on the Park algorithm, we improved a new algorithm as the system timing synchronization solution; and use of a simple the maximum likelihood sequence estimation method based on pilot for the sampling clock frequency offset estimation, using interpolation loop as the frequency deviation compensation circuitry to achieve the sampling clock synchronization. The simulation results show that, the synchronization algorithm we proposed can accurately achieve timing synchronization and sampling clock synchronization for indoor visible light communication system.
引文
[1]Y.Tanaka,S.Haruyama,M.Nakagawa.Wireless optical transmissions with white colored LED for wireless home links.The 11th IEEE International Symposium,2000:1325-1329
[2]Y.Tanaka,T.Komine,S.Haruyama et al.Indoor visible communication utilizing plural white LEDs as lighting.The 12th IEEE Interrntional Symposium on.2001:F81-F85
[3]K.Fan,T.Komine,Y.Tanaka,et al.The Effect of Reflection on Indoor Visible Light Communication System utilizing White LEDs.The 5th Int.Symposium Wireless Personal Multimedia Communication,September 2002:611-615.
[4]胡国永,陈长缨,陈振强白光LED照明光源用作室内无线通信研究.无线光通信.2006:46-48
[5]Tanaka,T.Komine,S.Haruyama,et al.Indoor visible light data transmission system utilizing white LED lights.IEICE Trans on Communications.2003:2440-2454.
[6]T.Komine,M.Nakagawa.Fundamental Analysis for Visible Light Communication System using LED Lights.IEEE Trans.on Consumer Electron,2004:100-107.
[7]T.Komine,L.J.Hwan,S.Haruyama.Adaptive equalization for indoor visible-light wireless communication systems.Asia-Pacific Conf.on Communication,2005:294-298.
[8]O.Gonzalez,S.Rodriguez,R.Perez-Jimenez et al.Error analysis of the simulated impulse response on indoor wireless optical channels using a Monte Carlo-based retracing algorithm.IEEE,2005:124-130.
[9]H.Elgala,R.Mesleh,H.Haas et al,OFDM Visible Light Wireless Communication Based on White LEDs.IEEE Symposium Wireless Pervasive Computing.2007:2185-2189
[10]S.K.Hashemil,Z.Ghassemlooy,L.Chao,and D.Benched,Orthogonal Frequency Division Multiplexing for Indoor Optical Wireless Communications using Visible Light LEDs.Communication Systems,Networks and Digital Signal Processing,2008.CNSDSP 6th International Symposium on Volume,Issue,25-25 July 2008 Page(s):174-178
[11]Elgala.H;Mesleh.R,Haas.H,Indoor broadcasting via white LEDs and OFDM;IEEE Transactions on Volume 55,Issue August 2009 Page(s):1127-1134Digital Object Identifier 10.1109/TCE.2009.5277966
[12]Tanaka,T.Komine,S.Haruyama,etal.Indoor visible light data transmission system utilizing white LED lights.IEICE Trans on Communications.2003:2440-2454
[13]S.R.Saunders.Antenna and Propagation for Wireless Communication Systems,John Wiley & Sons,1999.
[14]胡国永,陈振强,陈长缨 基于LED的可见光无线通信关键技术研究,2007.5
[15]丁德强,柯熙政,李建勋VLC系统的光源布局设计与仿真研究,光电工程,2007:131-134
[16]X.Ning,R.Winston,and J.O' Gallagher,Dielectric totally internally reflecting concentrators,Applied Optics,vol.26,no.2,pp.300-305,1987.
[17]J.R.Barry,J.M.Kahn,W.J.Krause,et al.Simulation of multipath impulse response for indoor wireless optical channels.IEEE.1993:367-379
[18]Madeira A J C.Valdes R T,Oliveira Duarte de A M,Optical interference Produced by artificial Light[J],Wireless Networks,1997,3(2):131-140
[19]The International Commission on Illumination(CIE).CIE 1931 Standard Colorimetric Observer.
[20]Kim Y H,Song L,Kim H G,Chang T,etal.Performance analysis of a coded OFDM system in time-varying multipath Raleigh fading channels[J].IEEE Transactions on Vehicular Technology,1999,48(5):1610-1615
[21]B.R.Mendoza,S.Rodriguez,R.Perez-Jaime,et al Considerations on the design of sectored receivers for wireless optical channels using a Monte-Carlo-based ray-tracing algorithm.ITE.2007:226-232
[22]J.Armstrong,OFDM for Optical Communications,Journal of Volume 27,Issue 3,Feb.1,2009 Page(s):189-204 Digital Object Identifier 10.1109/JLT.2008.2010061
[24]J.Armstrong and B.J.C.Schmidt,"Comparison of asymmetrically clipped optical OFDM and DC-biased optical OFDM in AWGN," IEEE Communication.Lett.vol.12,pp.343-345,2008.
[23]J.Armstrong and A.J.Lowery,"Power efficient optical OFDM," Electron.Lett,vol.42,pp.370-371,2006.
[25]K.R.Panta and J.Armstrong,"Effects of clipping on the error performance of OFDM in frequency selective fading channels,IEEE Trans.Wireless Communication vol.3,pp.668-71,2004.
[26]J.M.Kahn and J.R.Barry.Wireless infrared communications.IEEE.1997:265-298
[27]方向红OFDM通信系统的符号和频率同步算法研究 东南大学2006.3
[28]Shuang Tian,Kusha Panta,Himal A.Suraweera,A Novel Timing Synchronization Method for ACO-OFDM-Based Optical Wireless Communications,IEEE Transactions on wireless communication,VOL.7,NO.12,DECEMBER 2008
[29]Timothy M Schmidl,Donald C Cox.Robust Frequency and Timing Synchronization for OFDM[J].IEEE Transactions on Communications,1997,45(12):1613-1621
[30]Minn H M,Letaief K B.A Robust Timing and Frequency Synchronization for OFDM Systems[J].IEEE Transactions on Wireless Communications,2003,2(4):822-839
[31]Park B,Cheon H Kang C,et al,A Novel Timing Estimation Method for OFDM Systems[J].IEEE communications Letters,2003,7(5):239-241
[32]刘冬彦 基于OFDM的室内可见光通信系统研究 硕士研究生论文 长春理工大学 2009
[33]崔小准,胡光锐,陈豪采样频率误差对OFDM系统的影响和估计方法 上海交通大学学报第37卷第10期2003年10月
[34]刘海义,OFDM无线通信系统中的同步技术研究 北京邮电大学硕士研究生论文,2006.3
[35]Keon Woo Kang,Jaemin Ann,Hwang Lee.Decision directed maximum likelihood estimation of OFDM frame synchronization offset[J].Electronics Letters,1994,30(12):2153-2154.
[36]王毅军 OFDM解调中的同步的研究与载波偏差估计仿真实现,电子科技大学 2006.5
[37]宋月伟 数字电视地面广播系统采样时钟恢复算法研究与实现 西安电子科技大学 2009.1
[38]魏承功 基于白光LED的室内可见光通信系统研究 长春理工大学硕士学位论文 2008.4
[39]云文岳室内可见光通信系统调制与解调技术研究 长春理工大学硕士学位论文 2008.4
[40]Moose P H.A technique for orthogonal frequency division multiplexing frequency offset correction[J].IEEE Transactions on Communication s,1994,42(10):2908-2914.
[2]Y.Tanaka,T.Komine,S.Haruyama et al.Indoor visible communication utilizing plural white LEDs as lighting.The 12th IEEE Interrntional Symposium on.2001:F81-F85
[3]K.Fan,T.Komine,Y.Tanaka,et al.The Effect of Reflection on Indoor Visible Light Communication System utilizing White LEDs.The 5th Int.Symposium Wireless Personal Multimedia Communication,September 2002:611-615.
[4]胡国永,陈长缨,陈振强白光LED照明光源用作室内无线通信研究.无线光通信.2006:46-48
[5]Tanaka,T.Komine,S.Haruyama,et al.Indoor visible light data transmission system utilizing white LED lights.IEICE Trans on Communications.2003:2440-2454.
[6]T.Komine,M.Nakagawa.Fundamental Analysis for Visible Light Communication System using LED Lights.IEEE Trans.on Consumer Electron,2004:100-107.
[7]T.Komine,L.J.Hwan,S.Haruyama.Adaptive equalization for indoor visible-light wireless communication systems.Asia-Pacific Conf.on Communication,2005:294-298.
[8]O.Gonzalez,S.Rodriguez,R.Perez-Jimenez et al.Error analysis of the simulated impulse response on indoor wireless optical channels using a Monte Carlo-based retracing algorithm.IEEE,2005:124-130.
[9]H.Elgala,R.Mesleh,H.Haas et al,OFDM Visible Light Wireless Communication Based on White LEDs.IEEE Symposium Wireless Pervasive Computing.2007:2185-2189
[10]S.K.Hashemil,Z.Ghassemlooy,L.Chao,and D.Benched,Orthogonal Frequency Division Multiplexing for Indoor Optical Wireless Communications using Visible Light LEDs.Communication Systems,Networks and Digital Signal Processing,2008.CNSDSP 6th International Symposium on Volume,Issue,25-25 July 2008 Page(s):174-178
[11]Elgala.H;Mesleh.R,Haas.H,Indoor broadcasting via white LEDs and OFDM;IEEE Transactions on Volume 55,Issue August 2009 Page(s):1127-1134Digital Object Identifier 10.1109/TCE.2009.5277966
[12]Tanaka,T.Komine,S.Haruyama,etal.Indoor visible light data transmission system utilizing white LED lights.IEICE Trans on Communications.2003:2440-2454
[13]S.R.Saunders.Antenna and Propagation for Wireless Communication Systems,John Wiley & Sons,1999.
[14]胡国永,陈振强,陈长缨 基于LED的可见光无线通信关键技术研究,2007.5
[15]丁德强,柯熙政,李建勋VLC系统的光源布局设计与仿真研究,光电工程,2007:131-134
[16]X.Ning,R.Winston,and J.O' Gallagher,Dielectric totally internally reflecting concentrators,Applied Optics,vol.26,no.2,pp.300-305,1987.
[17]J.R.Barry,J.M.Kahn,W.J.Krause,et al.Simulation of multipath impulse response for indoor wireless optical channels.IEEE.1993:367-379
[18]Madeira A J C.Valdes R T,Oliveira Duarte de A M,Optical interference Produced by artificial Light[J],Wireless Networks,1997,3(2):131-140
[19]The International Commission on Illumination(CIE).CIE 1931 Standard Colorimetric Observer.
[20]Kim Y H,Song L,Kim H G,Chang T,etal.Performance analysis of a coded OFDM system in time-varying multipath Raleigh fading channels[J].IEEE Transactions on Vehicular Technology,1999,48(5):1610-1615
[21]B.R.Mendoza,S.Rodriguez,R.Perez-Jaime,et al Considerations on the design of sectored receivers for wireless optical channels using a Monte-Carlo-based ray-tracing algorithm.ITE.2007:226-232
[22]J.Armstrong,OFDM for Optical Communications,Journal of Volume 27,Issue 3,Feb.1,2009 Page(s):189-204 Digital Object Identifier 10.1109/JLT.2008.2010061
[24]J.Armstrong and B.J.C.Schmidt,"Comparison of asymmetrically clipped optical OFDM and DC-biased optical OFDM in AWGN," IEEE Communication.Lett.vol.12,pp.343-345,2008.
[23]J.Armstrong and A.J.Lowery,"Power efficient optical OFDM," Electron.Lett,vol.42,pp.370-371,2006.
[25]K.R.Panta and J.Armstrong,"Effects of clipping on the error performance of OFDM in frequency selective fading channels,IEEE Trans.Wireless Communication vol.3,pp.668-71,2004.
[26]J.M.Kahn and J.R.Barry.Wireless infrared communications.IEEE.1997:265-298
[27]方向红OFDM通信系统的符号和频率同步算法研究 东南大学2006.3
[28]Shuang Tian,Kusha Panta,Himal A.Suraweera,A Novel Timing Synchronization Method for ACO-OFDM-Based Optical Wireless Communications,IEEE Transactions on wireless communication,VOL.7,NO.12,DECEMBER 2008
[29]Timothy M Schmidl,Donald C Cox.Robust Frequency and Timing Synchronization for OFDM[J].IEEE Transactions on Communications,1997,45(12):1613-1621
[30]Minn H M,Letaief K B.A Robust Timing and Frequency Synchronization for OFDM Systems[J].IEEE Transactions on Wireless Communications,2003,2(4):822-839
[31]Park B,Cheon H Kang C,et al,A Novel Timing Estimation Method for OFDM Systems[J].IEEE communications Letters,2003,7(5):239-241
[32]刘冬彦 基于OFDM的室内可见光通信系统研究 硕士研究生论文 长春理工大学 2009
[33]崔小准,胡光锐,陈豪采样频率误差对OFDM系统的影响和估计方法 上海交通大学学报第37卷第10期2003年10月
[34]刘海义,OFDM无线通信系统中的同步技术研究 北京邮电大学硕士研究生论文,2006.3
[35]Keon Woo Kang,Jaemin Ann,Hwang Lee.Decision directed maximum likelihood estimation of OFDM frame synchronization offset[J].Electronics Letters,1994,30(12):2153-2154.
[36]王毅军 OFDM解调中的同步的研究与载波偏差估计仿真实现,电子科技大学 2006.5
[37]宋月伟 数字电视地面广播系统采样时钟恢复算法研究与实现 西安电子科技大学 2009.1
[38]魏承功 基于白光LED的室内可见光通信系统研究 长春理工大学硕士学位论文 2008.4
[39]云文岳室内可见光通信系统调制与解调技术研究 长春理工大学硕士学位论文 2008.4
[40]Moose P H.A technique for orthogonal frequency division multiplexing frequency offset correction[J].IEEE Transactions on Communication s,1994,42(10):2908-2914.