基于分数傅里叶变换的OFDM系统的PAPR和ICI研究

发布时间：2018-06-18 03:25

本文选题：分数傅里叶变换 + OFDM系统　；参考：《哈尔滨工业大学》2014年硕士论文

【摘要】：随着人们生活质量的提高，人们对于通信业务的要求也不再仅仅局限于通话业务和文字传输业务，对于视频传输业务的要求就在不断的增高。4G技术的出现满足了人们这方面的需求，相比于3G技术，它拥有更快的下载速率。OFDM技术是4G的主要技术，更高的速率意味着OFDM系统需要更多的子载波数，更多的子载波数意味着OFDM系统会有更高的峰均功率比和子载波间干扰，而这两个问题正是制约OFDM系统发展的两个非常重要的问题。本文就是针对OFDM系统的这两个问题进行深入的研究。首先，介绍了分数傅里叶变换理论的发展历史和目前的理论应用，以及介绍了分数傅里叶变换的定义、基本性质、常用信号的分数傅里叶变换的表达式，尤其重点介绍了分数傅里叶变换与傅里叶变换的关系，，介绍了FRFT-OFDM系统，对于该系统进行了简单的介绍，论证了FRFT-OFDM系统子载波之间的正交性，对其信号的形式给出了定义。其次，介绍了OFDM系统的峰均功率比产生的原因、峰均功率比的定义以及利用CCDF曲线从概率的角度对峰均功率比进行描述；对于传统的OFDM系统降低峰均功率比的方法，如限幅类技术、概率类技术、编码类技术等技术进行了说明，以及每种技术的优缺点和这些技术之间的联合互补，并把FRFT-OFDM系统的峰均功率比和传统的OFDM系统的峰均功率比相比较，说明了FRFT-OFDM系统低峰均功率比的原因并且给出了理论的推导和随着分数傅里叶变换角度的变换峰均功率比的变化状况，把FRFT-OFDM系统和传统SLM技术和限幅类技术相结合来进一步降低系统的峰均功率比。最后，对于传统的OFDM系统由于载波频率偏移产生的子载波间干扰进行了分析，按照系统的流程对于子载波间干扰的表达式进行了推导。对于BPSK调制的OFDM系统的由于子载波间干扰的误码率的性能的下降进行了分析，说明了误码率随着载波频率偏移的变化情况，并把传统的OFDM系统扩展为FRFT-OFDM系统，重复上述过程再进行分析。由于FRFT-OFDM系统的阶次可选择性，当出现相同的载波频率偏移时，FRFT-OFDM系统相比于传统的OFDM系统拥有较小的子载波间干扰以及较好的误码率性能。
[Abstract]:With the improvement of people's quality of life, people's requirements for communication services are no longer confined to telephone services and text transmission services. The requirement of video transmission service is increasing. 4G technology meets the demand of people in this respect. Compared with 3G technology, it has faster download rate. OFDM technology is the main technology of 4G. Higher rate means that OFDM systems need more subcarriers, and more subcarriers mean higher peak-to-average power ratio (PAPR) and inter-carrier interference (ISI). These two problems are two very important problems restricting the development of OFDM system. This paper focuses on the two problems of OFDM system. First of all, the history and application of fractional Fourier transform theory are introduced, and the definition, basic properties and expression of fractional Fourier transform of signal are introduced. Especially, the relationship between fractional Fourier transform and Fourier transform is introduced, FRFT-OFDM system is introduced, the orthogonality between sub-carriers of FRFT-OFDM system is discussed, and its signal form is defined. Secondly, the causes of PAPR in OFDM system are introduced, the definition of PAPR and the PAPR are described by CCDF curve from the point of view of probability. For example, limiting technology, probability class technology, coding technology and so on, and the advantages and disadvantages of each technology and the joint complementation between these technologies, The PAPR of FRFT-OFDM system is compared with that of traditional OFDM system. The reason of low peak-to-average power ratio (PAPR) in FRFT-OFDM system is explained, and the theoretical derivation and the change of PAPR with fractional Fourier transform angle are given. The FRFT-OFDM system is combined with the traditional SLM technique and the amplitude limiting technology to further reduce the peak-to-average power ratio (PAPR) of the system. Finally, the intercarrier interference caused by carrier frequency offset in traditional OFDM system is analyzed, and the expression of inter-carrier interference is deduced according to the system flow. The BER performance of BPSK modulated OFDM system due to inter-carrier interference (ISI) is analyzed. The change of BER with carrier frequency offset is explained, and the traditional OFDM system is extended to FRFT-OFDM system. Repeat the above process and then analyze it. Because of the order selectivity of FRFT-OFDM system, when the same carrier frequency offset occurs, the FRFT-OFDM system has smaller inter-carrier interference and better bit error rate performance than the traditional OFDM system.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.53

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