水下无线光通信系统参数对LDPC码性能的影响
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摘要
随着海洋资源的探索,无线光通信在海洋中的应用越来越广泛,但是由于海水对光信号的吸收和散射,导致传输距离增加时接收功率快速衰减,从而限制了无线光在海水中的传输。文中通过研究无线光在海水中的传输特性,建立无线光海水信道传输模型;并在该模型研究基础上,建立水下无线光通信实验仿真系统,研究在低密度奇偶检验码的条件下,系统结构对系统性能和无线光信号在海水中传输距离的影响。结果表明,相同条件下LDPC编码系统可提高4.5 dB编码增益和2 m的传输距离;同时增加光信号发射功率、光学接收半径和减小光源发散角都可降低系统误码率和提高光信号传输距离,并且系统结构参数的改变和对应系统性能以及传输距离的改变不是线性关系。
With the exploration of marine resources, the application of wireless optical communication in the ocean becomes more and more extensive. However, due to the absorption and scattering of optical signals by seawater, the receiving power is rapidly attenuated when the transmission distance increases, thereby limiting the transmission of wireless optical signals in seawater. By exploring the transmission characteristics of wireless light in seawater, a wireless optical seawater channel transmission model is established. Based on the research of this model, an underwater wireless optical communication experiment simulation system is constructed, thus to explore the influence of system structure on the system performance and the transmission distance of wireless optical signals in seawater under LDPC(low density parity check code) condition. The experiment results indicate that the LDPC coding system can increase the coding gain of 4.5 dB and the transmission distance of 2 m under the same conditions. At the same time, by increasing the optical signal transmission power and optical receiving radius, and reducing the divergence angle of the light source, the system error rate can be reduced, the optical signal transmission distance be increased, while the change of the system structural parameters and corresponding system performance and the change of the transmission distance are not linear.
With the exploration of marine resources, the application of wireless optical communication in the ocean becomes more and more extensive. However, due to the absorption and scattering of optical signals by seawater, the receiving power is rapidly attenuated when the transmission distance increases, thereby limiting the transmission of wireless optical signals in seawater. By exploring the transmission characteristics of wireless light in seawater, a wireless optical seawater channel transmission model is established. Based on the research of this model, an underwater wireless optical communication experiment simulation system is constructed, thus to explore the influence of system structure on the system performance and the transmission distance of wireless optical signals in seawater under LDPC(low density parity check code) condition. The experiment results indicate that the LDPC coding system can increase the coding gain of 4.5 dB and the transmission distance of 2 m under the same conditions. At the same time, by increasing the optical signal transmission power and optical receiving radius, and reducing the divergence angle of the light source, the system error rate can be reduced, the optical signal transmission distance be increased, while the change of the system structural parameters and corresponding system performance and the change of the transmission distance are not linear.
引文
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[2]Oubei H M,Duran J R,Janjua B,et al.4.8 Gbit/s16-QAM-OFDM Transmission Based on Compact450-Nm Laser for Underwater Wireless Optical Communication[J].Optics Express,2015,23(18):23302-9.
[3]Kaushal H,Kaddoum G.Underwater Optical Wireless Communication[J].IEEE Access,2016,4(1):1518-1547.
[4]Oubei H M,Duráan JoséR,Janjua B,et al.Wireless Optical Transmission of 450 nm,3.2 Gbit/s 16-QAM-OFDM Signals over 6.6 m Underwater Channel[C]//Lasers&Electro-optics.[s.l.]:IEEE,2016.
[5]Ao J,Liang J,Ma C,et al.Optimization of LDPC Codes for PIN-Based OOK FSO Communication Systems[J].IEEEPhotonics Technology Letters,2017,29(9):727-730.
[6]Zhang D,Qin H,Wu J,et al.Received Response based Heuristic LDPC Code for Short-range Nonline-of-sight Ultraviolet Communication[J].Optics Express,2017,25(5):5018.
[7]Everett J.Forward-error Correction Coding for Underwater Free-space Ptical Communication[D].Raleigh,NCUSA:North Carolina State Univ.,2009.
[8]Li T,Zhou H,Sun L.The Study of Ldpc Code Applied to Underwater Laser Communication[C]//Conference on Lasers&Electro Optics&the Pacific Rim Conference on Lasers&Electro-optics.America:IEEE,2009.
[9]Alkhasraji J,Tsimenidis C.Coded OFDM over Short Range Underwater Optical Wireless Channels Using LED[C]//OCEANS-2017-Aberdeen.[s.l.]:Aberdeen,2017.
[10]Zeng Z,Fu S,Zhang H,et al.A Survey of Underwater Optical Wireless Communications[J].IEEE Communications Surveys&Tutorials,2017,19(1):204-238.
[11]Simpson J A.5 Mbps optical Wireless Communication with Error Correction Coding for Underwater Sensor Nodes[C]//OCEANS 2010 MTS/IEEE SEATTLESeattle,WA:[s.n.],2010:6-9.
[12]Cox W C,Simpson J A,Domizioli C P,et al.An Underwater Optical Communication System Implementing ReedSolomon Channel Coding.OCEANS 2008.Quebec City,QC,Canada:[s.n.],2008:1-6.
[13]Jose R,Pe A.Analysis of Hard Decision and Soft Decision Decoding Algorithms of LDPC Codes in AWGN[C]//2015IEEE International Advance Computing Conference(IACC).Banglore:[s.n.],2015:430-435.