自由空间光通信语音传输系统中编解码技术研究

发布时间：2018-04-12 20:45

本文选题：自由空间光通信 + 可编程逻辑器件　；参考：《重庆大学》2016年硕士论文

【摘要】：光通信可分为有线光通信和无线光通信,两者存在各自的优缺点。自由空间光通信是无线光通信的一个分支,它兼备了有线光通信和无线光通信的优势,不但具有传输速率高、频带宽、保密性好等优点,而且还不需要预先铺设通信链路、安装灵活方便,因而受到了广泛的关注和研究。本文基于自由空间光通信和语音编解码算法理论,利用可编程逻辑器件、激光器、声光调制器和光电倍增管等设备搭建了无线光语音通信系统平台。本文对自由空间光通信的相关理论、语音信号数字化过程以及语音编解码算法的分类进行分析介绍,确定选择波形编解码中的A率和ADPCM编解码算法作为本通信系统的研究目标。在编解码算法确定后,对通信系统的整体框架进行拟定,并对系统中关键器件的工作原理进行介绍,做出对比分析和选择。最终选择波长为637nm的半导体激光器为激光光源,PMT为光电探测器,声光调制器为外调制器来实现语音通信系统的搭建。为了保证通信系统工作的正常进行,对语音通信系统的发射端和接收端的相关编解码程序模块进行编译和仿真,分析各个子模块的功能是否正常实现。同时对系统的关键器件如激光光源、声光调制器等进行测试。测试结果表明激光器可以接受低于5MHz的外调制和低于30MHz的内调制。同时对声光调制器在输入不同类型、幅值以及频率的调制信号时进行测试,结果表明需要对调制器输入幅值大于2.4V的TTL方波信号来实现数字调制。基于以上的设计与选择,本文首先使用波形编解码算法中较为简单的A率编解码算法进行系统的搭建与测试,并在A率编解码算法实现的基础上进行了ADPCM编解码算法的设计与验证,并成功搭建通信系统平台,在室内进行了多次实验,由人工接收解码后的信号来进行判定,经过多次测试,得到MOS值在4.0左右,能够将信息不失真地传达,基本上实现了正常的语音通信。最后,对全文做出总结,针对本文的实验结果和未来可做的改进工作做进一步分析。
[Abstract]:Optical communication can be divided into wired optical communication and optical wireless communication, both have their own advantages and disadvantages. Free space optical communication is a branch of optical wireless communication, it is both wired and optical communications and optical wireless communication, not only has high transmission rate, wide bandwidth, good security, but also not prior to the laying of the communication link, flexible and convenient installation, which has received extensive attention and research. In this paper, free space optical communication and speech codec algorithm based on the theory of the use of programmable logic devices, laser, acousto-optic modulator and photomultipliers, and other equipment to build optical wireless voice communication system platform. This paper on free space theory optical communication, digital speech signal classification and speech codec algorithm are introduced to determine the choice of waveform codec rate in A and ADPCM decoding algorithm for the communication system. Study on the target system. The codec algorithm is determined, the overall framework of the communication system was proposed, and the working principle of the key components of the system are introduced, and make a comparative analysis. Finally 637nm diode laser as the laser source, PMT photodetector, acousto-optic modulator for external modulator to achieve build a voice communication system. In order to ensure the normal operation of the communication system, the related series of voice communication system for transmitting and receiving end of the decoding program module was compiled and simulated, the analysis of each module function is normal. At the same time the system of key devices such as laser source, acousto-optic modulator is tested. The test results show that the laser can accept less than 5MHz and lower than the internal external modulation 30MHz modulation. At the same time for different types of input in the acousto-optic modulator, amplitude and frequency To test the modulation signal, the results indicate the need for more than 2.4V of TTL amplitude modulator input square wave signal to realize digital modulation. Design and selection based on the above, this paper use waveform codec algorithm in a relatively simple A rate codec algorithm to build and test system, and the design and verification of ADPCM codec algorithm on the basis of A rate codec algorithm realization, and successfully build communication platform, a number of experiments performed in the laboratory, by artificial signal receiving decoded to determine, after repeated testing, the value of MOS at around 4, will be able to convey information without distortion, basically realizes the normal speech communication at last, make a summary of this thesis, further analysis on the experiment results and improvement work to do in the future.

【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN929.1

【参考文献】