相干光FBMC/OQAM系统的信道和载波频率偏移联合估计及补偿方法研究
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摘要
色散和激光器频率偏移能够对使用交错正交幅度调制格式的相干光滤波器组多载波(CO-FBMC/OQAM)系统产生严重影响。针对这个问题,重点研究了该系统的基于训练序列的信道和载波频率偏移联合估计及补偿方法。详细分析了CO-FBMC/OQAM系统的信道传输模型,对训练序列的结构进行了设计和优化,抑制了固有虚部干扰(IMI)的影响。为了消除信道噪声对估计过程的干扰,提出了基于不同帧之间频域平均的估计方法。该方法将实值导频的交叉关联函数在不同帧之间进行频域平均,取其相位后获得载波频率偏移估计值。信道响应也在不同帧之间进行频域平均后得到最终估计值。搭建了CO-FBMC/OQAM系统的数值仿真平台,并研究了激光器频率偏移不同时,经过1500km标准单模光纤传输后系统的误差幅度矢量和误码率。数值仿真结果表明:不管是在背靠背场景下,还是在1500km光纤传输后,该方法都能够抑制色散和激光器频率偏移的影响,有效提升系统的传输性能。
Chromatic dispersion and laser frequency offset have serious impact on coherent optical filter bank multicarrier systems with offset quadrature amplitude modulation(CO-FBMC/OQAM system).Preamble-based joint estimation and correction algorithm of channel and carrier frequency offset(CFO)in CO-FBMC/OQAM system is investigated.The channel transmission model of CO-FBMC/OQAM system is theoretically elaborated,and the preamble structure is deliberately designed and optimized to suppress the impact of inherent imaginary interference(IMI).In order to reduce the noise impact,an estimation method based on inter-frame averaging is proposed.In this method,the cross-correlation function within multiple frames is averaged and the laser frequency offset according to the phase of this average is estimated.Finally,we get the final channel response by averaging channel estimation results within multiple frames.The error amplitude vector and error rate of the system are numerically demonstrated through 1500 km standard single-mode fiber transmission with different CFO values.The results show that the proposed method can suppress the influence of chromatic dispersion and laser frequency offset,and significantly enhance transmission performance in the back-to-back scenario or after 1500 km optical fiber transmission.
Chromatic dispersion and laser frequency offset have serious impact on coherent optical filter bank multicarrier systems with offset quadrature amplitude modulation(CO-FBMC/OQAM system).Preamble-based joint estimation and correction algorithm of channel and carrier frequency offset(CFO)in CO-FBMC/OQAM system is investigated.The channel transmission model of CO-FBMC/OQAM system is theoretically elaborated,and the preamble structure is deliberately designed and optimized to suppress the impact of inherent imaginary interference(IMI).In order to reduce the noise impact,an estimation method based on inter-frame averaging is proposed.In this method,the cross-correlation function within multiple frames is averaged and the laser frequency offset according to the phase of this average is estimated.Finally,we get the final channel response by averaging channel estimation results within multiple frames.The error amplitude vector and error rate of the system are numerically demonstrated through 1500 km standard single-mode fiber transmission with different CFO values.The results show that the proposed method can suppress the influence of chromatic dispersion and laser frequency offset,and significantly enhance transmission performance in the back-to-back scenario or after 1500 km optical fiber transmission.
引文
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[4]Zhao Y,He R,Chen H,et al.Experimental performance evaluation of software defined networking(SDN)based data communication networks for large scale flexi-grid optical networks[J].Optics Express,2014,22(8):9538-9547.
[5]Liu J F,Wang S Y,Zeng X Y,et al.PAPRreduction in optical OFDM systems based on swarm intelligence algorithms[J].Acta Optica Sinica,2017,37(1):0106006.刘剑飞,王少影,曾祥烨,等.基于群智能算法的光OFDM系统PAPR抑制[J].光学学报,2017,37(1):0106006.
[6]Yu J,Huang M L,Zou Y Z,et al.Phase noise cancellation for coherent optical OFDM system based on polarization diversity[J].Acta Optica Sinica,2016,36(8):0806001.余骏,黄鸣柳,邹垚昭,等.偏振分集相干光OFDM通信系统中的相位噪声消除[J].光学学报,2016,36(8):0806001.
[7]Farhang-Boroujeny B,Kempter R.Multicarrier communication techniques for spectrum sensing and communication in cognitive radios[J].IEEECommunications Magazine,2008,46(4):80-85.
[8]Farhang-Boroujeny B.OFDM versus filter bank multicarrier[J].IEEE Signal Processing Magazine,2011,28(3):92-112.
[9]Li C,Yang Q.Optical OFDM/OQAM for the future fiber-optics communications[J].Procedia Engineering,2016,140:99-106.
[10]Chang R W.Synthesis of band-limited orthogonal signals for multichannel data transmission[J].Bell System Technical Journal,1966,45(10):1775-1796.
[11]Saltzberg B.Performance of an efficient parallel data transmission system[J].IEEE Transactions on Communication Technology,1967,15(6):805-811.
[12]Bellanger M.Efficiency of filter bank multicarrier techniques in burst radio transmission[C].Global Telecommunications Conference,2010:11743960.
[13]Du J,Signell S.Novel preamble-based channel estimation for OFDM/OQAM systems[C].IEEE International Conference on Communications,2009:10814964.
[14]Cheng G,Xiao Y,Li S,et al.Joint frequency offset and channel estimation for OFDM/OQAM systems[J].IEICE Transactions on Communications,2012,95(5):1848-1851.
[15]Liu X,Buchali F.Intra-symbol frequency-domain averaging based channel estimation for coherent optical OFDM[J].Optics Express,2008,16(26):21944-21957.
[16]Kofidis E,Katselis D,Rontogiannis A,et al.Preamble-based channel estimation in OFDM/OQAMsystems:a review[J].Signal Processing,2013,93(7):2038-2054.
[17]Zhao J.Channel estimation in DFT-based offset-QAMOFDM systems[J].Optics Express,2014,22(21):25651-25662.
[18]Fang X,Xu Y,Chen Z,et al.Frequency-domain channel estimation for polarization-division-multiplexed CO-OFDM/OQAM systems[J].Journal of Lightwave Technology,2015,33(13):2743-2750.
[19]Fang X,Xu Y,Chen Z,et al.Time-domain least square channel estimation for polarization-divisionmultiplexed CO-OFDM/OQAM systems[J].Journal of Lightwave Technology,2016,34(3):891-900.
[20]Zhang L,Xiao S,Bi M,et al.Channel estimation algorithm for interference suppression in IMDD-OQAM-OFDM transmission systems[J].Optics Communications,2016,364:129-133.
[21]Zhou X,Long K,Li R,et al.A simple and efficient frequency offset estimation algorithm for high-speed coherent optical OFDM systems[J].Optics Express,2012,20(7):7350-7361.
[22]Fan S H,Yu J,Qian D,et al.A fast and efficient frequency offset correction technique for coherent optical orthogonal frequency division multiplexing[J].Journal of Lightwave Technology,2011,29(13):1997-2004.
[23]Buchali F,Dischler R,Mayrock M,et al.Improved frequency offset correction in coherent optical OFDMsystems[C].34th European Conference on Optical Communication,2008:10426275.
[24]Bellanger M,Le Ruyet D,Roviras D,et al.FBMCphysical layer:aprimer[J].PHYDYAS,2010,25(4):7-10.
[25]Mattera D,Tanda M.Blind symbol timing and CFOestimation for OFDM/OQAM systems[J].IEEETransactions on Wireless Communications,2013,12(1):268-277.
[26]Jansen S L,Morita I,Schenk T C W,et al.Coherent optical 25.8-Gb/s OFDM transmission over 4160-km SSMF[J].Journal of Lightwave Technology,2008,26(1):6-15.
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[28]Cho J,Xie C,Winzer P J.Analysis of soft-decision FEC on non-AWGN channels[J].Optics Express,2012,20(7):7915-7928.