Research On The Non-uniform Quantization Scheme In Analog Optical And Wireless Transmission System Based On UFMC

Recently,with the popularization of 5G technology in the commercial and civil fields,the continuous expansion and development of mobile network access application scenarios,and the scale of various access devices growing year by year,higher requirements have been put forward for the bearer of radio access network(RAN).In the face of the requirements of large bandwidth,high speed and high frequency spectral efficiency,Intensity Modulation Direct Detection(IMDD)based on multi carrier modulation technology has been one of the current mainstream solutions in the short distance optical fiber transmission system.Among them,IMDD technology is considered to be the preferred solution for the current short distance high-speed optical transmission system due to its low cost and simple implementation;In the multi carrier modulation technology,the Universal Filter Multi Carrier(UFMC)technology has become a strong candidate in the current 5G because of its high spectral efficiency,small out of band radiation,strong time frequency offset resistance and other characteristics.IMDD optical transmission system based on UFMC is one of the current research focuses.However,in this system,the high bit accuracy Analog to Digital Converter/Digital to Analog Converter(ADC/DAC)requirements brought by the Peak to Average Power Ratio(PAPR)brought by the multi carrier modulation technology have increased the cost and power consumption of the system to a certain extent.Therefore,quantization technologies are studied in this paper,focusing on the non-uniform quantization scheme for the waveform distribution characteristics of UFMC signals,to achieve a high-performance,low-cost multicarrier modulation optical transmission system.The main research contents of this paper are as follows:Firstly,the optical fiber bearer wireless transmission system based on IMDD is introduced,and the advantages and disadvantages of the commonly used multicarrier modulation technology are described.By analyzing the research status of quantization technology in the existing multicarrier based IMDD optical transmission system at home and abroad,the research significance of nonuniform quantization algorithm based on IMDD-UFMC optical transmission system in this paper is summarized.Then,the generation and reception of UFMC signal and the transmission process of optical UFMC signal in IMDD transmission system are summarized.Through the simulation software,the optical transmission system simulation experiment platform based on IMDD-UFMC is built.Taking uniform quantization as an example,the principle of quantization is expounded and the formula of quantization noise is analyzed.At the same time,the formula of quantization noise based on nonuniform quantization is deduced.Finally,the influence of data precision and amplitude limiting technology based on Inverse Fast Fourier transform/Fast Fourier transform(IFFT/FFT)on the performance of multi carrier system is analyzed.Consequently,a companding quantization scheme based on Fast Statistical Estimation(FSE)applied to IMDD-UFMC optical transmission system is proposed whose process is equivalent to nonuniform quantization and the optimal mapping relationship in a companding scheme is analyzed.The optimal mapping relationship based on Gaussian distribution signal source is derived theoretically,and the feasibility of the scheme is verified on the simulation platform.The results show that the companding quantization scheme based on the optimal mapping function achieves almost the same quantization performance as the non-uniform quantization scheme using complex machine learning algorithm under the condition of ensuring lower implementation complexity and computational complexity.Finally,a vector non-uniform quantization scheme based on two-dimensional K-means clustering and Gaussian Mixture Model(GMM)clustering is proposed.By combining with "rate distortion theory",the theoretical basis,definition and characteristics of vector quantization technology are described.At the same time,aiming at the key problem of vector quantization codebook design,two schemes based on K-means and GMM are designed.The feasibility of the two schemes is verified by theory and simulation experiment platform.The results show that the performance of twodimensional vector quantization scheme is better than that of one-dimensional scalar quantization scheme under the same quantization bit resolution.