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Crosstalk And Suppression Method Research Of OAM-multiplexed Communicatoin System In The Model Of Atmospheric Turbulence

Posted on:2016-12-31Degree:MasterType:Thesis
Country:ChinaCandidate:G L WangFull Text:PDF
GTID:2308330473960886Subject:Electronic and communication engineering
Abstract/Summary:PDF Full Text Request
Like other degrees of freedom, such as frequency, time, orthogonal code pieces, orbital angular momentum(OAM) mode provides a new degree of freedom for multiplexing. The OAM-multiplexed communication system greatly increases both the channel capacity and spectral efficiency by exploiting the orthogonality phenomenon among different OAM modes. However, the OAM-multiplexed communication system in free space is inevitably influenced by atmospheric turbulence(AT),and the crosstalk produced by AT seriously damage the performance of the communication system. Therefore, the research on the crosstalk caused by AT and the mitigation method promises important theoretical significance and reference value. The main research works are as follows.(1) The thesis focuses on the influence on OAM-multiplexed system caused by AT with Kolmogorov atmospheric turbulence model and the corresponding mitigation method. First of all, the thesis analyzes the influence of AT with Kolmogorov model atmospheric turbulence on the OAM-multiplexed system, and discuss the effect on the light density distribution and bit error rate performance. Subsequently, a mitigation scheme based on Multiple-Input Multiple-Output(MIMO) equalization is given to mitigate the crosstalk. The results show that AT with Kolmogorov atmospheric turbulence destroys light phase and intensity, and increases bit error rate of the system; MIMO equalization method can effectively mitigate the crosstalk on the OAM-multiplexed system. System enjoys lower bit error rate, and it performance was improved. On the other hand, different equalization algorithm has different effects on the OAM-multiplexed system. In the condition of weak and medium atmospheric turbulence(2 1410nC??),Recursive Least Squares(RLS) equalization algorithm which requires training sequences can improve the system performance by making bit error rate decline 1 to 3 orders of magnitude; Constant Module Algorithm(CMA) blind equalization algorithm which does not require a training sequence only can make bit error rate decline 0.5 to 1 orders of magnitude; Improved RLS-CMA semi-blind equalization algorithm which requires only half of the training sequence of RLS algorithm makes bit error rate decline 1 to 3 orders of magnitude, just as RLS does.(2)The thesis also focuses on the influence on OAM-multiplexed system caused by AT with non-Kolmogorov atmospheric turbulence and the corresponding mitigation method. First of all, the thesis analyzes the influence of AT with non-Kolmogorov atmospheric turbulence model on the OAM-multiplexed system, mainly from the aberration which caused by AT with non-Kolmogorov atmospheric turbulence model, influence on the probability distribution of OAM photons, the effect on the light density distribution, and bit error rate performance. On this basis, a mitigation scheme based on MIMO equalization is given to mitigate the crosstalk. The numerical simulation results show that Zernike wavefront tilt aberration, astigmatism aberration and coma aberration caused by AT with non-Kolmogorov atmospheric turbulence model have changed the OAM photons probability distribution; AT with non-Kolmogorov atmospheric turbulence model destroyed light phase and intensity, and increases bit error rate of the system; On the other hand, MIMO equalization method can effectively mitigate the crosstalk on the OAM-multiplexed system. In the condition of weak and medium atmospheric turbulence(2 1410nC??), RLS-CMA equalization algorithm can improve the bit error rate performance to 1 to 2 orders of magnitude in comparison with the system without MIMO equalization method.
Keywords/Search Tags:OAM-multiplexed communication, atmospheric turbulence, MIMO equalization, Kolmogorov atmospheric turbulence model, non-Kolmogorov atmospheric turbulence model
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