Optimization Of Multi-carrier Waveforms Based On Nonlinear Distortion

With the commercialization of the fifth generation(5G)technology,the performance of orthogonal frequency division multiplexing(OFDM)system is widely used in various evolving communication scenarios.Multipath fading,shadow fading and atmospheric fading still exist in 5g microcellular communication design,which bring new challenges to the amplifier efficiency in OFDM system.However,due to the peak to average power(PAPR)characteristic of OFDM,nonlinear distortion seriously restricts the performance of OFDM waveform.With the research of multi carrier waveform and its related linearization technology under nonlinear distortion,the industry proposes the nonlinear amplifier model and OFDM waveform improvement suitable for different scenarios.In this paper,the waveform performance,waveform analysis and waveform improvement based on nonlinear distortion are studied,and the modeling method of high power amplifier(HPA)is explored.The models of high power amplifier(HPA),the parameters and nonlinear distortion of multi carrier,and the improvement of low PAPR waveform are studied.The details are as follows:Firstly,based on the input-output relationship of amplitude and frequency,the classical HPA nonlinear model is introduced,and the amplifier model conversion based on parameter fitting is explored.Considering the scenarios of the high-frequency multi subcarrier under different amplifiers,the correlation between transmission distortion index and transmission waveform index is analyzed.At the same time,the correlation between transmission distortion index and transmission waveform index under different modulation is discussed.Secondly,based on the research of the high orbit satellite amplifier and group delay fitting,the performance of single carrier and multi carrier in the real high orbit satellite channel is measured.In view of the disadvantage of the poor resistance of multi carrier signal to group delay distortion,the performance of the multi carrier under amplifier can be effectively improved by combining index modulation(IM)and noise remapping.Finally,in order to optimize the performance of constant envelope OFDM(CE-OFDM)waveform the pre-processing algorithm and IM are used,which can effectively alleviate the phase jumps and low transmission efficiency.In order to solve the problem of the gap between the performance of phase demodulation and maximum likelihood demodulation,this paper proposes an iterative detection algorithm at the receiver according to the property of phase modulation,which effectively improves the potential of CE-OFDM system.