FSO-WOFDM系统的实验研究

Oct.2018FSO-WOFDM系统的实验研究柯熙政，张棋雯(西安理工大学自动化与信息工程学院，陕西西安710048)摘要院在无线光正交频分复用(FSO-OFDM)系统中，因需要加入循环前缀而消耗近20%的带宽，降低了数据传输效率。为了进一步减少带宽损耗，改善系统性能，采用小波包变换代替FSO-OFDM中的傅里叶变换，设计了一种基于小波变换的无线光正交频分复用(FSO-WOFDM)系统。该系统无需加入循环前缀，利用小波基函数的正交性来抑制子载波间的干扰。根据FSO-WOFDM系统原理，研究了信道估计方法、湍流强度、小波基对FSO-WOFDM系统误码率的影响，对比分析了FSO-WOFDM与FSO-OFDM的系统性能，并通过实验验证了FSO-WOFDM系统的可行性及其优良的抗混合噪声干扰能力。关键词院无线光通信；离散小波包变换；正交频分复用；Mallat算法中图分类号院TN929.12文献标志码院ADOI院10.3788/IRLA201847.1022003ExperimentalstudyonFSO-WOFDMsystem

KeXizheng,ZhangQiwen(FacultyofAutomationandInformationEngineering,Xi忆anUniversityofTechnology,Xi忆an710048,China)

Abstract:Inthefreespaceopticalorthogonalfrequencydivisionmultiplexing(FSO-OFDM)system,nearly20%ofthebandwidthisconsumedduetoaddacyclicprefix,thedatatransmissionefficiencyisreduced.Inordertofurtherreducethebandwidthlossandimprovethesystemperformance,awaveletpackettransformwasusedinsteadoftheFouriertransforminFSO-OFDM,freespaceopticalorthogonalfrequencydivisionmultiplexingsystembasedonwavelettransform(FSO-WOFDM)wasdesigned.Thesystemdidn忆tneedtoaddacyclicprefix,andtheorthogonalityofthewaveletbasisfunctionswasusedtosuppressinter-carrierinterference.AccordingtotheprincipleofFSO-WOFDMsystem,theeffectsofchannelestimationmethod,turbulenceintensityandwaveletbasedonthebiterrorrateofFSO-WOFDMsystemwerestudied.ThesystemperformanceofFSO-WOFDMandFSO-OFDMwascomparedandanalyzed.TheexperimentverifiesthefeasibilityofFSO-WOFDMsystemanditsexcellentabilitytoresistmixednoise.Keywords:freespaceoptical;discretewaveletpackettransform;OFDM;Mallatalgorithm收稿日期院2018-05-05曰基金项目院作者简介院修订日期院2018-06-03(61377080袁60977054)曰袁袁袁(2017ZDCXL-GY-06-01)遥Email:xzke@263.net

(1962-)袁1022003-1

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第10期www.irla.cn第47卷0引言袁尧袁袁遥[1]

袁袁遥曰袁袁袁1FSO-WOFDM袁遥遥袁尧袁曰1OFDM遥(FSO-OFDM)袁袁(FSO-WOFDM)OFDM[2]

(WOFDM)WOFDMOhtsuki[3]OFDM遥2001[5]

袁B.G.Negash[6]

遥2001袁M.J.Manglani遥2003袁袁Omoaki遥2006FSO-O.Gonzalez[4]遥20092012GhaithWOFDM尧袁1FSO-WOFDM袁MariusOlteanWOFDM2MallatFig.1SystemofFSO-WOFDM

FSO-WOFDM[10]

N

N遥袁VolkanKumbasarOFDM[7]

WOFDM遥2014袁Alaa袁袁[8]

袁Nlog2N

遥[9]

袁(AWGN)log2遥2015袁OFDM遥2016WOFDMChafiiMMeyerOFDM遥FSO-OFDMWOFDM遥FSO-OFDMFSO-WOFDMFSO-OFDMFSO-WOFDM遥FSO-WOFDM袁FSO-OFDM1FSO-WOFDM的基本理论FSO-WOFDM(IDWT/DWT)/遥袁/袁FSO-OFDM2FSO-WOFDMFig.2ModulationanddemodulationprocessofFSO-WOFDM

2仿真分析2.1大气湍流信道模型遥2I(IFFT/FFT)遥1022003-2

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第10期www.irla.cn第47卷[11]

院OFDM掖I2业-掖I业2=掖I2业=I掖I业2掖I业22

10-2(1)2

10-4曰QAM1610-3袁FSO-WOFDM袁FSO-OFDMFSO-WOFDM遥院I曰掖业袁遥12I袁[12]

袁FSO-WOFDMf(I)=院2II姨2仔袁2Iexp-袁曰L蓸(lnI+2遥院I2I/2)2

2I蔀FSO-OFDM遥(2)=1.23Cn窑32

k7/6L11/6遥遥k(t)[13]

遥袁袁k袁遥曰Cn2

袁袁[12]曰Gamma-Gamma[14]遥FSO-WOFDMy(t)s(t)n(t)3Fig.3Noisemodel

2.2不同调制方式下FSO-WOFDM系统性能1281袁袁遥2I袁遥FSO-OFDM袁db44FSO-OFDMFSO-WOFDMFSO-WOFDMFig.4ComparisonofBERofFSO-OFDMandFSO-WOFDM

withdifferentmodulationmethods

1000bitBPSK尧QPSK尧4=0.1遥遥5袁FSO-WOFDM遥2I袁QAM-1610-7袁4FSO-OFDMFSO-WOFDM袁FSO-OFDM遥SNR=20袁BPSK尧QPSK袁QAM16FSO-OFDMFSO-WOFDMFSO-OFDMSNR=12dB袁BPSK曰QPSK=0.1袁FSO-OFDM曰10-6袁FSO-WOFDMFSO-WOFDMFSO-1022003-3

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第10期www.irla.cn第47卷5(a)遥袁5袁遥袁遥FSO-WOFDM7袁遥袁遥袁袁5(b)FSO-WOFDMFSO-OFDM袁FSO-WOFDM2.4不同湍流强度下FSO-WOFDM系统的性能袁7遥FSO-WOFDMSNR=12dB10-6曰BPSK10-7袁FSO-WOFDMWOFDMQPSK5FSO-OFDMconstellation

FSO-WOFDMFig.5FSO-OFDMandFSO-WOFDMdemodulatedsignal

10-3遥FSO-WOFDM遥10-4袁FSO-2.3FSO-WOFDM系统的信道估计6遥袁遥遥遥LS6袁尧LS7FSO-WOFDMFig.7BiterrorrateofFSO-WOFDMunderdifferentturbulence

intensities

遥袁DFTOFDM(LS)尧(LMMSE)FSO-WOFDMLMMSEFSO-WOFDMFSO-WOFDMLMMSEFSO-WOFDM890.32I

FSO-WOFDM遥SNR=20袁2I

=0.1=0.30.1袁FSO-OFDM遥袁8尧FSO-WOFDM9袁院2I6FSO-WOFDMFig.6FSO-WOFDMerrorratecurveunderdifferentchannel

estimationmethods

8SNR=20,constellationwhenSNR=20,

2I2I=0.1FSO-OFDMFSO-WOFDM袁LS尧LMMSE袁袁WOFDMFig.8FSO-OFDMandFSO-WOFDMdemodulatedsignal

=0.1

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第10期www.irla.cn第47卷遥袁袁8尧(b)9遥(a)(b)(a)遥ICI袁遥遥FSO-WOFDMSNRFSO-OFDM袁FSO-WOFDM3实验分析3.1实验装置袁FSO-WOFDMQPSK遥袁袁遥128遥遥袁850nm袁1150m遥DG5102FSO-WOFDM9SNR=20袁2I=0.3

2I=0.3FSO-OFDMFSO-WOFDMFig.9FSO-OFDMandFSO-WOFDMdemodulatedsignal

constellationwhenSNR=20,

LQA8502.5不同小波基的FSO-WOFDM系统的性能遥FSO-WOFDM袁10遥遥袁袁NDaubechies遥FSO-袁FSO-10遥袁曰袁袁Daubechies(dbN)WOFDMSNR=12dB袁WOFDMdb210-3曰FSO-WOFDM10-5遥Daubechiesdb1211袁FSO-WOFDMFig.11Modulesofexperimentaldevice

3.2实验验证12遥12袁FSO-WOFDM10dbNFSO-WOFDMFig.10BiterrorratecurvesofFSO-WOFDMsystemswith

differentdbN

12N袁袁1022003-5

Fig.12Modulatedsignalwaveformoftransmitter

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第10期www.irla.cn第47卷袁13遥遥袁FSO-OFDMFSO-WOFDM遥袁袁FSO-WOFDMFSO-OFDM遥FSO-WOFDM4结论13Fig.13Samplingsignalwaveformofreceiver

袁袁遥遥袁袁20%FSO-WOFDMFSO-WOFDMFSO-OFDM袁遥袁袁遥1414袁袁FSO-WOFDMWOFDM100bit袁遥袁FSO-WOFDM4.7伊10-5遥2.3伊10-4曰1000bitFSO-WOFDMFSO-OFDM遥FSO-OFDM参考文献院[1]

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