论文标题:基于混沌训练序列的OFDM系统同步算法研究
论文作者
论文导师 孙克辉,论文学位 硕士,论文专业 物理电子学
论文单位 中南大学,点击次数 112,论文页数 83页File Size4063K
论文网 http://www.lw23.com/lunwen_56243667/
OFDM;; chaos training sequence;; timing synchronization;; frequency offset estimation;; bit error rate
正交频分复用(OFDM)因具有抗频率选择性衰落、频谱效率高和抗窄带干扰的优点，是通讯技术研究中的热点。本文采用理论分析和计算机仿真相结合的研究方法，研究了OFDM系统同步技术，在训练序列产生、定时同步、频偏估计、以及系统设计仿真与算法性能分析等方面做了较为深入的研究。 分析和比较了四种伪随机序列的平衡性、游程性、相关特性及在OFDM系统中的峰均比特性，得出了采用混沌序列作为OFDM系统同步训练序列的可行性结论。由于混沌序列具有高度保密性等优势，研究混沌序列在OFDM系统中的应用具有重要意义。 提出了一种基于混沌训练序列的系统定时同步新算法。该算法训练符号结构简单，带宽资源消耗少；消除了定时测度存在模糊平顶和多尖峰的现象，同步精度高；对频率偏差具有较强的鲁棒性，可抗多径干扰；在时域内一次性完成，降低了频偏估计的实现难度；可适用于各种子载波数目的系统。 提出了一种新的系统频偏估计算法。新算法采用与定时同步新算法完全相同的训练符号，消除了定时和频偏估计采用不同训练符号而引起的传输效率下降的现象；克服了以往算法的高复杂性和低精度的缺陷，抗多径干扰能力强；频偏估计在时域内完成，加快了频率补偿速度；频率估计范围广。 设计了完整的OFDM传输系统。在不同信道环境下，对采用同步新算法的传输系统进行仿真研究。分析表明，该系统具有性能稳定、适用性强、误码率低和易于实现等特点。
Due to its frequency-selective fading channels resistance, highfrequency available rate and anti-narrow-band performance, OFDMbecomes a hot topic in communication technology. In this paper,theoretical analysis and computer simulation are adopted to study thesynchronization technology of OFDM system, including the generation oftraining sequence, timing synchronization, frequency offset estimation,system design and algorithm analysis. According to the analysis and comparison of the balance, run-length,correlation and peak-to-average ratio (in OFDM systems) from 4different pseudo random sequence, the feasibility of taking chaoticsequences as the training sequences is proved. Besides, the high securityof chaotic sequences ensures the great importance of their application. A new algorithm of system time synchronization by trainingsequence is proposed. Only one training sequence is needed whichensures the simple construction and low spending. It can conquer theambiguous flat top and multi-peaks, and has a high precision. Thesynchronization algorithm shows a strong robust of carrierfrequency-offset as well as anti multi-path interference. Timingsynchronization is accomplished in time domain in one time whichdecreases the difficulty of frequency-offset estimation, and it is suitablenot only for small sub carrier systems, but also for systems with a greatdeal sub carriers. A new algorithm of frequency-offset estimation is proposed. Thetraining sequence is same as the one used in timing synchronization, andeliminates the decline of transmission efficiency caused by differentsequences. It moves the high complexity and low precision. The proposedfrequency-offset estimation scheme is finished in time domain, whichexpedites speed of frequency compensation. The frequency estimationdomain is extended. An OFDM transmission system is designed, and system simulations are conduced with different channels mode. Simulation results show thatthe system has many features, such as stability, strong robust, low biterror rate and easy realization.
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