【作者】 杨明；

【导师】 宋正勋；

【作者基本信息】 长春理工大学 ， 信息与通信工程， 2010， 硕士

【摘要】 可见光通信是一种新型的无线光通信技术,由于其自身的优点和广阔的应用前景而受到关注。将OFDM技术应用到可见光通信中,可以进一步提高系统的传输速率以及抗多径干扰能力,而解决可见光OFDM通信系统的同步问题,对于系统的实现有着重要意义。本文主要针对室内可见光OFDM通信系统进行了研究。首先通过对可见光信道的分析,给出了系统的信道模型;并结合可见光OFDM系统的原理,讨论了循环前缀长度、多普勒频移对系统的影响以及LED的非线性失真等问题;针对可见光通信只能使用单极OFDM信号的特点,引用了非对称削减OFDM的方法,并比较了不同调制方法的误码率性能和带宽利用率。最后,本文重点研究了室内可见光OFDM系统的同步问题。分析了与射频OFDM在同步问题上的不同点,即系统只需要进行符号定时同步和采样时钟同步。在Park算法基础上,使用一种改进算法作为系统定时同步的解决方案:使用一种简单的基于导频序列的最大似然估计法进行采样时钟频偏估计,并采用内插环路作为频偏补偿电路,以实现系统的采样时钟同步。仿真结果表明,所采用的同步算法在室内可见光条件下可以准确地实现符号定时同步和采样时钟同步。更多还原

【Abstract】 Visible light communication is a new type of wireless optical communication technology, because of its own advantages and wide application prospects attention. We introduce OFDM technology into the visible light communication, which can further improve the system transmission rate and the ability of anti-multipath interference, and to solve the synchronization of visible light OFDM system is very important for the realization of the system.This thesis mainly focuses on indoor visible-light OFDM communication system. First, we analysis the indoor optical channel, given the channel model; then gives the principle of visible light OFDM system model and discuss the system in a number of practical issues, such as the cyclic prefix length, the impact of Doppler frequency shift and the LED non-linear distortion; for visible light communication can only use the characteristics of a unipolar OFDM signals, we introduce the Asymmetrically Clipped OFDM, and compare the error-rate performance and bandwidth utilization for difference modulation.Finally, the thesis focuses on the synchronization issues of OFDM for indoor visible light communication system. Analyzes difference between the RF-OFDM and VLC-OFDM on synchronization, which is the system requires timing synchronization and sampling clock synchronization, but no need for carrier frequency synchronization. Based on the Park algorithm, we improved a new algorithm as the system timing synchronization solution; and use of a simple the maximum likelihood sequence estimation method based on pilot for the sampling clock frequency offset estimation, using interpolation loop as the frequency deviation compensation circuitry to achieve the sampling clock synchronization. The simulation results show that, the synchronization algorithm we proposed can accurately achieve timing synchronization and sampling clock synchronization for indoor visible light communication system.更多还原