基于Flip-OFDM的光无线通信系统优化设计

发布时间：2018-05-26 20:27

本文选题：可见光通信 + 翻转正交频分复用　；参考：《东南大学》2017年硕士论文

【摘要】：近年来,可见光通信(visible light communication,VLC)作为一门新兴的无线光通信技术正被越来越多的学者所关注。该技术采用强度调制/直接检测(intensity modulation and direct detection,IM/DD)方式对光源强度进行调制以传输信号,因此需确保发送信号为正实数。而翻转正交频分复用(flipped orthogonal frequency division multiplexing,Flip-OFDM)技术,作为一种适用于IM/DD的单极性OFDM技术具有着硬件复杂度较低和功率效率高等优势,在现阶段中正被广泛关注与研究。因此,本文将基于Flip-OFDM可见光通信系统对相关技术展开研究与改进。首先,对可见光通信系统进行了整体概述,并阐述了本文研究Flip-OFDM可见光通信系统的意义与价值。接着,简述了分集合并技术的基本原理,并基于时域和频域分集合并技术提出了一种新型Flip-OFDM接收机技术。该技术充分利用接收到的正负子帧信息对原系统通信性能进行优化。仿真表明,本章所提出的新型接收机,尤其是频域分集合并接收机,在加性白高斯噪声(additive white Gaussian noise,AWGN)信道和非视距(non-line-of-sight,NLOS)信道中与常规接收机、新型阈值接收机相比,误比特率(bit error ratio,BER)性能均显著提高。此外,与迭代接收机相比,频域分集合并接收机大大简化了原有接收机的计算复杂度。然后,基于预编码器与均衡器的自适应联合优化技术提出了新型预编码Flip-OFDM系统,并通过限定发送信号功率来降低最大峰值平均功率比(peak to average power ratio,PAPR)出现的概率。此外,本文将预编码系统与Flip-OFDM接收机技术相结合,在充分利用接收信号功率的同时进一步对系统性能进行优化。仿真结果表明,新型预编码Flip-OFDM系统,尤其是与接收机技术结合后的新技术,在AWGN信道和NLOS信道中BER性能均显著提高。其中,本文所提出的PE-Scale预编码系统的频域接收机技术在NLOS信道中相对性能最优。最后,基于双边削波与PE-Scale预编码系统提出了新型削波PE预编码Flip-OFDM系统,进一步解决高PAPR问题。其中,双边削波技术的引入会对原有通信系统的BER性能产生不利影响,因此在新系统的预编码器设计中融入了削波信息以减小削波引起的性能损失。仿真结果表明,与其他系统相比,在NLOS信道中削波PE预编码Flip-OFDM系统因削波产生的性能损失最少。此外,将各削波预编码系统与接收机技术相结合,在NLOS信道中新型削波PE预编码系统的频域接收机技术综合性能最优。
[Abstract]:In recent years, as a new wireless optical communication technology, visible light communication has been paid more and more attention by more and more scholars. The intensity modulation / direct detection of intensity modulation and direct detection / IM-DDD is used to modulate the intensity of the light source to transmit the signal, so it is necessary to ensure that the transmitted signal is a positive real number. As a unipolar OFDM technology suitable for IM/DD, flipped orthogonal frequency division multiplexing Flip-OFDM technology has the advantages of low hardware complexity and high power efficiency. Therefore, this paper will research and improve the related technologies based on Flip-OFDM visible light communication system. Firstly, the paper gives a general overview of the visible light communication system, and expounds the significance and value of the study of Flip-OFDM visible light communication system in this paper. Then, the basic principle of diversity combining technology is briefly introduced, and a new Flip-OFDM receiver technology is proposed based on time-domain and frequency-domain diversity combining techniques. This technique optimizes the communication performance of the original system by using the received positive and negative subframe information. Simulation results show that the new receiver proposed in this chapter, especially the frequency-domain diversity combining receiver, is compared with the conventional receiver and the new threshold receiver in additive white Gaussian noise (AWGN) channel and non-line-of-sight (non-line-of-sight) channel. The bit error rate (BER) of bit error ratio per) was improved significantly. In addition, compared with the iterative receiver, the frequency domain diversity combining receiver greatly simplifies the computational complexity of the original receiver. Then, a novel precoding Flip-OFDM system is proposed based on the adaptive joint optimization technique of precoder and equalizer, and the probability of peak to average power ratio is reduced by limiting the transmitted signal power. In addition, the precoding system is combined with Flip-OFDM receiver technology to optimize the system performance while making full use of the received signal power. The simulation results show that the performance of the new precoding Flip-OFDM system, especially the new one combined with the receiver technology, is significantly improved in both AWGN and NLOS channels. Among them, the frequency domain receiver technique of PE-Scale precoding system proposed in this paper has the best relative performance in NLOS channel. Finally, based on the bilateral clipping and PE-Scale precoding system, a new clipping PE precoding Flip-OFDM system is proposed to solve the problem of high PAPR. The introduction of bilateral clipping technology will adversely affect the BER performance of the original communication system, so the clipping information is incorporated into the design of the new system precoder to reduce the performance loss caused by clipping. The simulation results show that, compared with other systems, clipping PE precoding Flip-OFDM system has the least performance loss due to clipping in NLOS channel. In addition, combining each clipping precoding system with receiver technology, the comprehensive performance of the new clipped PE precoding system in frequency domain is optimized in NLOS channel.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1

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