电力线通信系统中同步技术的研究

发布时间：2018-07-02 14:59

本文选题：电力线通信 + 扩频　；参考：《电子科技大学》2015年硕士论文

【摘要】：电力线通信(Power line communication,PLC)技术使用电力线作为传输媒介进行数据传输,具有投资少、用户多、布线安装简单、覆盖范围广等特有的优势在智能电网中已得到广泛运用,但是由于电力线传输环境复杂,高噪声、高衰减和多径特性等因素使得电力线通信的传输质量大大降低,本文重点对电力线通信系统中的同步算法进行研究与改进。首先,本文研究了电力线信道的特点,给出了本文使用的电力线信道的仿真模型,接着分析了几种常见的电力线载波通信的传输方式,通过分析各自的优缺点,给出了本论文选择直接扩频通信的理由,接着介绍了扩频通信的理论基础和系统结构,并设计了电力线扩频系统的帧结构。然后,本文在深入研究直接扩频通信同步理论的基础上,提出了一种新颖的基于线性调频Chirp信号的定时同步算法,具体而言,主要工作及创新点如下:研究了直接扩频系统中传统的定时同步算法,这类算法都是依据伪随机序列的自相关特性,在接收端通过寻找相关峰值点来获得同步,这种算法的不足之处在于同步时间过长,同步精度不高。接着研究了基于Chirp信号脉冲压缩特性的同步方法,该算法使用Chirp信号作为训练序列,在接收端对接收信号进行匹配滤波可得到一个很尖锐的窄脉冲,由此获得同步。接着研究了基于Chirp信号分数阶傅里叶变换(Fractional Fourier Transform,FRFT)的同步算法,由于Chirp信号的FRFT在最优分数域上产生“能量汇聚”,根据能量汇聚点位置的偏移量确定定时同步的位置,该算法在零频偏环境下定时同步精度高,但频偏存在时算法性能大大降低。根据普通的FRFT法会受频偏的影响,提出了改进的FRFT法,设计了新的训练序列结构,利用首尾相接的两个Chirp信号作为同步头。分别对接收信号做最优分数域上的分数阶傅里叶变换可得到两个能量汇聚点,由这两个能量汇聚点的偏移量计算出定时同步的位置,该位置已消除掉频偏的影响,定时同步准确度高。最后,本文就提出的改进FRFT算法在DSP(TMS320C6455)上进行了代码转换和验证,分析了DSP实现和matlab仿真的性能差异,结果表明改进算法的硬件实现是有效的。
[Abstract]:Power line communication (PLC) technology has been widely used in smart grid because of its advantages such as less investment, more users, simple wiring, wide coverage and so on, which uses power line as a transmission medium for data transmission. However, due to the complexity of power line transmission environment, high noise, high attenuation and multipath characteristics, the transmission quality of power line communication is greatly reduced. This paper focuses on the research and improvement of synchronization algorithm in power line communication system. Firstly, this paper studies the characteristics of power line channel, gives the simulation model of power line channel used in this paper, then analyzes several common transmission modes of power line carrier communication, and analyzes their advantages and disadvantages. The reason for choosing direct spread spectrum communication in this paper is given. Then, the theoretical basis and system structure of spread spectrum communication are introduced, and the frame structure of power line spread spectrum system is designed. Then, on the basis of deeply studying the synchronization theory of direct spread spectrum communication, this paper proposes a novel timing synchronization algorithm based on linear frequency modulation (LFM) Chirp signal. The main work and innovations are as follows: the traditional timing synchronization algorithms in direct spread spectrum systems are studied. These algorithms are based on the autocorrelation characteristics of pseudorandom sequences and can be synchronized at the receiving end by finding correlation peak points. The shortcoming of this algorithm is that the synchronization time is too long and the precision of synchronization is not high. Then the synchronization method based on the pulse compression characteristic of Chirp signal is studied. The algorithm uses Chirp signal as training sequence and matches the received signal to obtain a very sharp narrow pulse at the receiving end. Then, the synchronization algorithm based on Fractional Fourier transform (FRFT) of Chirp signal is studied. Because the FRFT of Chirp signal produces "energy convergence" in the optimal fractional domain, the position of timing synchronization is determined according to the offset of the position of energy convergent point. The algorithm has high precision of timing synchronization in zero-frequency offset environment, but the performance of the algorithm is greatly reduced when frequency offset exists. According to the influence of frequency offset on the common FRFT method, an improved FRFT method is proposed, and a new training sequence structure is designed. Two Chirp signals are used as synchronization heads. Two energy convergent points can be obtained by using fractional Fourier transform in the optimal fractional domain respectively. The position of timing synchronization is calculated from the offset of these two energy convergent points, and the influence of frequency drop is eliminated. Timing synchronization accuracy is high. Finally, the improved FRFT algorithm is implemented on DSP (TMS320C6455) for code conversion and verification, and the performance difference between DSP implementation and matlab simulation is analyzed. The results show that the hardware implementation of the improved algorithm is effective.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM73

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