LED-to-LED可见光通信技术研究

发布时间：2018-05-15 22:27

本文选题：可见光通信 + 纠错码　；参考：《哈尔滨理工大学》2017年硕士论文

【摘要】：可见光通信VLC(Visible Light Communication)是使用LED(Light Emitting Diodes)作为数据的传输装置进行网络通信。LED具有体积小、重量轻、寿命长、亮度高等诸多优点,此外,LED通信具有绿色环保、无电磁干扰、信息安全、频谱无需申请等优点,使得世界各国纷纷关注并进行相关研究。LED-to-LED可见光通信是一个基于TCP/IP协议的点对点通信平台,使用一个发光二极管实现数据的发送与接收,LED通过其天然特性将数据以光信号的形式发送出去,LED利用其感光特性将光信号转为电压信号实现数据的接收。由于微观上发送数据与接收数据不是同时进行的,所以LED-to-LED通信平台的两端只需一个LED即可同时实现发送端与接收端功能。根据大量实验发现在可见光通信中存在随机误码问题,该问题由环境中光线干扰、光信号衰减等因素导致,并且随机误码具有发生概率高、误码位数低且误码位置和时间点不可预期等特点,高发生率无疑增加了重传次数,降低了传输效率。针对该问题本文提出了一种将低密度奇偶校验码纠错码(Low Density Parity Check Code,LDPC)与RS(Reed Solomon)纠错码进行级联的混合编码方案,RS码具有很强的处理突发错误的能力,LDPC码具有接近香农极限的良好性能,该混合编码能够有效降低甚至避免随机误码问题,进而提高通信传输效率。由于可见光通信中使用的光元器件的物理性质限制,在高速数据传输过程中,常见的光通信LED很难实现信号的高频转换,并且接收端接收信号失真较严重,这无疑限制了高负载率的可见光数据传输。针对可见光通信负载率低的问题,根据现有编码方法的性能对比分析,本文提出了一种使用OOK(On-Off Keying)和FSK(Frequency Shift Keying)混合编码的编码方式,有效的解决了目前传输负载量低的问题。此外,由于FSK相对于OOK有更好的抗干扰能力的特点,本文还提出了一种粗粒度载波传输的辅助传输方式,FSK编码数据由于其具有较好的传输正确率的优点作为粗粒度载波数据,传输概要数据,而OOK由于其具有单位时间传输数据量高的优点作为细粒度基波数据,传输详细数据。根据接收端实际精度需求来解决重传问题,如果粗粒度数据能够满足数据需求那么无须进行细粒度数据重传,进而降低了重传次数。可见光通信具有广阔的应用领域,但目前人们的研究焦点仍然停留在参数性能上面,对其应用领域的考虑缺乏研究。针对可见光通信的功能应用问题,本文提出了一种兼具照明功能的可见光通信方案(Brighten Visible Light Communication,Brighten VLC),该方案能够使得LED始终处于常亮状态,不受可见光通信设备所处运行状态的影响,该方案使得可见光通信能够很好的实现通信兼具照明功能,丰富了VLC的应用领域。
[Abstract]:Visible light communication (VLC(Visible Light) is a network communication device using LED(Light Emitting Diodes as a data transmission device. It has many advantages, such as small volume, light weight, long life, high brightness and so on. In addition, VLC(Visible Light communication has green environmental protection, no electromagnetic interference, and information security. The spectrum does not need to be applied for, which makes the countries all over the world pay close attention to and research. LED-to-LED visible light communication is a peer-to-peer communication platform based on TCP/IP protocol. Using a light-emitting diode (LED) to transmit and receive the data, the LED transmits the data in the form of light signal through its natural characteristics. The LED converts the light signal into the voltage signal to realize the data receiving by using its photosensitive characteristics. Since sending and receiving data are not carried out at the same time microscopically, the function of sending and receiving can be realized by only one LED at both ends of LED-to-LED communication platform. Based on a large number of experiments, it is found that there is a random error code problem in visible light communication, which is caused by light interference and optical signal attenuation in the environment, and the random error code has a high probability of occurrence. Because of the low number of bit errors and the unpredictable error position and time point, the high incidence rate increases the number of retransmissions and reduces the transmission efficiency. To solve this problem, this paper presents a hybrid scheme for concatenation of low Density Parity Check code and RS(Reed code. RS codes have a strong ability to deal with burst errors. LDPCcodes are close to Shannon. The excellent performance of the limit, The hybrid coding can effectively reduce or even avoid the random error problem and improve the transmission efficiency. Due to the limitation of the physical properties of the optical components used in visible light communication, it is difficult for the LED to realize the high frequency signal conversion in the process of high-speed data transmission, and the distortion of the received signal at the receiving end is serious. This undoubtedly limits the transmission of visible light data at high load rates. Aiming at the problem of low load rate of visible light communication, according to the performance comparison and analysis of the existing coding methods, this paper proposes a hybrid coding method using OOK(On-Off Keying and FSK(Frequency Shift Keying, which effectively solves the problem of low transmission load at present. In addition, because FSK has better anti-jamming ability than OOK, a coarse-grained carrier transmission auxiliary transmission method is proposed in this paper, which is coarse-grained carrier data as coarse-grained carrier data because of its good transmission accuracy. OOK transmits detailed data as fine grained fundamental data because of its advantages of high data volume per unit time. To solve the retransmission problem according to the actual precision requirement of the receiver, if the coarse-grained data can meet the data requirement, then the fine-grained data retransmission is not necessary, thus reducing the retransmission times. Visible light communication has a wide range of applications, but at present, the research focus is still focused on the performance of the parameters. Aiming at the functional application of visible light communication, this paper presents a new visible light communication scheme, Brighten Visible Light Communication and Brighten VLC, which can make LED always be in a normal state without being affected by the operating state of the visible light communication device. This scheme enables visible light communication to achieve both lighting functions and enriches the application field of VLC.
【学位授予单位】：哈尔滨理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1

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