Performance Analysis Of Multi-carrier FTN Optical Wireless Communication System

With the rapid development of the Internet,modern communication systems increasingly demand high-speed,efficient,and stable wireless transmission technologies.Optical Wireless Communication(OWC)and Fast-than-Nyquist(FTN)techniques are two promising research directions with broad application prospects.OWC utilizes light as a wireless transmission medium,offering advantages such as high spectral efficiency,no interference,and no frequency allocation issues.However,in complex turbulent atmospheric conditions,the optical signal is susceptible to fluctuations in light intensity,beam drift,and other factors.The combination of multicarrier FTN technology is employed to better address the effects of complex turbulent atmospheres.Specifically,the intervals between multiple carriers and symbols are compressed to increase system capacity and spectral efficiency.Moreover,compressed signals can result in poor bit error rate performance,high computational complexity,and high Peak-to-Average Ratio(PAPR),presenting significant challenges to receiver demodulation.To tackle these issues,the primary objectives of this paper are as follows:(1)Introduces the multi-carrier modulation system represented by Filter Bank Multi-Carrier(FBMC).The basic theory,technical characteristics,and system model of the FBMC system based on Fourier Transform(FT)are elaborated in detail,and it is explained that this system has significant advantages over traditional Orthogonal Frequency Division Multiplexing(OFDM)systems in terms of spectral efficiency and power spectral density.(2)The basic principle of Offset Quadrature Amplitude Modulation(OQAM)and the implementation method of FTN were introduced in detail.Based on the Direct Current-biased Optical FBMC(DCO-FBMC)system,time frequency two-dimensional FTN technology is introduced to realize the model construction of FTN-DCOFBMC/OQAM system.Monte Carlo simulations are used to analyze the bit error performance,spectral efficiency,computational complexity,and PAPR of the model under strong,moderate,and weak atmospheric turbulence channels.The results show that the proposed model has stronger adaptability in turbulent channels compared to DCO-OFDM with Quadrature Amplitude Modulation(DCO-OFDM/QAM)system.Additionally,the introduction of FTN technology has brought the system’s spectral efficiency to a new height,but its computational complexity and PAPR still need to be improved.(3)To address these issues,Wavelet Transform(WT)technology is used instead of the FT technology,and the advantages of Discrete Wavelet Transform(DWT)in BER performance,computational complexity,and PAPR are explained in detail.Then,in order to find a better optical modulation scheme,Monte Carlo simulation are used to compare the performance of three systems: FTN-PAM-DWT based on Pulse Amplitude Modulation(PAM),FTN-DWT with Pulse Position Modulation(PPM)joint QAM,and FBMC/OQAM-DWT.The results demonstrate that the FTN-PPM-QAM-DWT system performs well at high time-frequency compression rates,while the FBMC/OQAMDWT system has better robustness.