【作者】 甘君心；

【导师】 唐碧华；

【作者基本信息】 北京邮电大学 ， 电子科学与技术， 2013， 硕士

【摘要】 OFDM是一种特殊的多载波传输技术,能够有效的对抗多径衰落,并以很高的频谱利用率来实现数据传输的高效性。但是,目前在OFDM系统中,还有很多的关键问题没有得到很好的解决,例如高峰均功率比、频偏敏感等,这在一定程度上制约了OFDM技术的广泛应用。本文主要就OFDM系统中如何降低峰均功率比进行研究。本文首先讨论了该课题的研究背景,对OFDM的系统进行了介绍,讨论了OFDM系统的基本原理,并对OFDM技术的发展和现状做了简要描述,通过阐述OFDM系统的优缺点,说明了对系统中峰均比问题研究的必要性。通过完成对降低峰均比技术的研究现状进行介绍和分析对比,本文主要针对概率类技术中性能较好的PTS技术进行研究和改进。在原有的降PAPR的PTS算法的基础上,针对PTS算法复杂度过高的问题,提出了一种结合多种群遗传的改进PTS算法。该算法通过结合仿生学,大大提高了搜索最优相位序列的效率,从而降低了系统的复杂度。同时针对传统的遗传算法具有早熟的和收敛速度过慢的问题,采用各个种群取不同的控制参数,同时采用可变的交叉概率和变异概率,避免早熟和收敛过慢的现象。运用Matlab软件完成了相关的仿真验证,与同类型的算法进行了对比,结果证明了该改进算法在同等的计算复杂度下有更优越的降低峰均比性能。最后,针对原始PTS算法需要发送边带信息的问题,研究并提出了一种改进型无边带信息传输PTS算法,该算法基于导频音的理论,且复杂度较低。改进算法通过在原算法的基础上进一步完成接收到的导频音虚部和实部之和的计算,使得发送端所使用的最优序列能够完美的在接收端得被估计出来。通过Matlab软件完成仿真,证明了改进的算法能够以少量的BER性能为代价,换来较高的峰均比抑制能力。更多还原

【Abstract】 OFDM is a special kind of multicarrier transmission technology which is effective against multipath fading, and it has high frequency spectrum utilization ratio to achieve data transmission efficiency. But now, in the OFDM system, there are still a lot of key problems which have not got a good solution, such as peak power ratio, frequency deviation sensitivity and so on. To a certain extent this restrict the application range of OFDM technology. This paper mainly discusses the problem of how to reduce PAPR in OFDM system.First of all, this paper introduces the research background of the chosen topic. The OFDM system is introduced, the development features and the present situation of the technology are described. Then the paper makes a brief description on the advantages and disadvantages of OFDM system, illustrating the necessity of the research on PAPR reduction.Secondly, this paper introduces the basic principle of OFDM system in detail, including the OFDM system realization model, subcarrier modulation and the realization of the DFT, protect interval and cycle prefix paper, and the peak of OFDM system than the average power to carry on the detailed description, then introduces the PAPR of pressing method which is divided into three categories, including signal preliminary distortion technology, coding class technology and probability class methods.According to the improved GA-PTS algorithm to reduce PAPR algorithm and algorithm based on the thought, using Matlab software of the corresponding simulation program, set up corresponding simulation parameters, the corresponding simulation, get the corresponding simulation results. According to the improved GA-PTS algorithm to reduce PAPR of simulation results, the corresponding simulation contrast, through the original PTS algorithm and improved GA-PTS algorithm simulation results contrast with the improved GA, found PTS algorithm can effectively reduce PAPR.Finally, when using the original PTS algorithm, according to the problem of the necessity for sending sideband information, the paper puts forward a PTS algorithm which based on the pilot tone of modified low complexity endless information transmission. Based on the original algorithm, the new algorithm can estimate the phase factort of the sender through further calculating the sum of the received pilot tone’s real part and the imaginary part under conditions of expanding phase factors, resulting in the stronger ability to reduce PAPR. At the same time, the new algorithm won’t significantly influence the system BER performance, and won’t significantly increase the complexity of the system, so that the ability of the improved method to reduce PAPR is stronger than the old one.At last the paper makes a simulation of the proposed algorithm, and the results have proved that the proposed algorithm has better performance than the existing algorithm.更多还原