| With the development of emerging technologies,earth shaking changes have taken place in the field of mobile communication.As 5g becomes commercially available,6G research advances steadily,and the communication rate is rising.At the same time,the working frequency band of the communication network is also rising to meet the growing demand for communication rate.Therefore,millimeter wave and even terahertz wave will become an important transmission means in the future mobile communication network.However,on the one hand,the large bandwidth and high rate improve the accuracy requirements of digital to analog converter / analog to digital converter(DAC / ADC).The high power consumption and high cost problems caused by high bit DAC / ADC increase the cost and complexity of the system to a certain extent.On the other hand,when faced with multi-user access scenarios,especially when 5g communication adopts MIMO technology on a large scale,a large number of communication terminals bring a large amount of computing data,and high-precision DAC / ADC will further aggravate the difficulty and complexity of digital signal processing(DSP)at the receiver.It can be seen that the high bit DAC / ADC seriously limits the application of photonics-assisted millimeter-wave / terahertz communication system.Therefore,how to minimize the number of quantization bits on the premise of ensuring the quantization performance of photonics-assisted millimeter-wave / terahertz communication system has become a research hotspot in this field.This paper studies the ADC quantization technology schemes in a variety of photonics-assisted millimeter-wave / terahertz communication systems.The main work and innovations are as follows:1.Three kinds of photonics-assisted millimeter-wave / terahertz communication systems and their key technologies are analyzed and designed.The research focuses on the key technologies of photonics-assisted millimeter-wave communication system based on direct detection,photonicsassisted terahertz communication system based on direct detection and photonics-assisted terahertz communication system based on coherent detection,including signal transmission and reception,signal modulation technology,DSP technology and so on.Based on the three systems,the quantization performance of various quantization schemes is studied.2.According to the signal distribution characteristics in photonics-assisted millimeter-wave /terahertz communication system,a low bit non-uniform scalar quantization scheme is proposed.It includes non-uniform quantization based on K-means clustering and non-uniform quantization based on GMM clustering.The two schemes can adaptively adjust the quantization interval according to the distribution of signal points,so as to improve the signal quantization performance and reduce the quantization noise.The results show that the non-uniform quantization scheme can effectively improve the signal-to-noise ratio of the receiver and reduce the bit error rate.Finally,by analyzing the principle of non-uniform quantization scheme,the advantages and disadvantages of different schemes are summarized and compared.3.In order to further improve the quantization performance and reduce the quantization noise,two vector quantization schemes are proposed: vector quantization based on K-means clustering and vector quantization based on GMM.Vector quantization maps the signal to be quantized to twodimensional space through vector compression,and reduces the number of quantization points to improve the quantization efficiency.In the case of low quantization bits,vector quantization can further improve the quantization performance compared with non-uniform scalar quantization.Through three kinds of photonics-assisted millimeter-wave / terahertz communication systems,the effectiveness and reliability of vector quantization are verified.Experiments and simulations show that the scheme can effectively improve the quantization performance of the system. |
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