【作者】 徐东镪；

【导师】 肖沙里；

【作者基本信息】 重庆大学 ， 仪器科学与技术， 2008， 硕士

【摘要】 紫外光通信是基于大气散射和吸收的无线光通信技术。分子(颗粒)的强吸收作用使得在近地面太阳光没有紫外光波段,属于日盲区,减少了对紫外发射光源的干扰。紫外光通信以紫外日盲区的光谱为载波,信息电信号调制加载在紫外光上,通信系统的发射端和接收端通过初定位和调整,然后以自由空间和大气为信道来传输信息。紫外光通信与其他传统的通信方式相比更加隐秘,需要的发射功率大大降低,在通信范围以外很难被截收,非常适用于短距离、窄带宽、能量受限的无人监管小型的地面传感系统中。由于在受到雨、雪、雾、云和湍流等的影响时,大气传输信道受限并且不稳定,紫外信号衰减严重,产生随机错误甚至突发错误,从而影响紫外通信质量。为了提高紫外信道的传输特性,就必须采用信道编码技术。本文在研究紫外光大气传输模型的基础上,提出了基于紫外光传输信道的卷积码和Viterbi译码的FPGA设计方法,本文的主要研究内容和工作有如下几个方面:①回顾了紫外光通信发展的历程,紫外光通信的潜在应用,相比常规通信的优势以及紫外光通信的缺点,由此引入信道编码技术,介绍了目前流行的信道编码技术并重点研究了卷积码和Viterbi译码。②重点研究了紫外光大气传输特性,同时结合实际情况,引入非直视单散射信道模型。并用数学方法分析了非直视单散射信道Luettgen模型。分析了三种不同的非直视单对单传输系统模式,给出了系统性能指标参数,并从不同角度对模型进行仿真和计算,并得出相应结论。③采用VHDL语言设计了Viterbi译码器,采用八电平量化软判决和并行结构,提高了译码速度,引入信息存储和管理对传统的寄存器交换法进行改进。对Viterbi译码器各个模块进行了分析和仿真,并在QUARTUSII软件上进行了下载验证。本文所提出的基于紫外光大气传输信道的(2,1,7)Viterbi译码器,电路设计简单,采用VHDL语言编写,下载到FPGA芯片上,完全可以满足正常紫外光通信的需要。随着对紫外光通信的研究和发展,特别是大容量信道,将采用更为复杂的译码。更多还原

【Abstract】 UV communication is a new wireless optical communication based on atmosphere absorption and scattering. There is no uv in sunlight near the ground for the strong absorption of molecule(particle), called Solar-blind, which reduces the interference to the optics source. UV commuincation takes UV in solar-blind section as carrier that modulated and loaded by the information electrical signal. The communication system transmits the signal through the free space and atmosphere channel, positioned and adjusted in the transmitter and receiver. UV communication is more confidential and much lower transmission power and more difficult to capture compared with the conventional communication. With such attractive features, UV communication can be employed in short distance,narrowband, power restricted and unattended sensor network on the ground.The atmosphere propagation channel becomes restricted and unstable when affected by the rain, snow, frog, cloud and onflow weather. There will be random errors or even burst errors due to UV signal attenuation, which affects the communicaion quality. To improve UV propagation characteristics, it must employ the channel coding technology. The paper proposes a FPGA designed method of convolutional code and Viterbi decoder based on research of the UV propagation channel module. The main research and work are as follows:①Review the UV communication history briefly, the potential applicaions, the advantages and disadvantages compared with the conventional communication, presents the popular channel coding technology, focus on the convolutional code and Viterbi decode.②Make a significant research on the UV propagation characteristics, present non-line-of-sight single scattering channel module,analyse the Luettgen module using mathematics methods and three different single to single NLOS transmission system modules, present the system performance parameters.Simulate, calculate and summarize the module through varied degrees.③Design the Viterbi decoder in VHDL language, employ eight-voltage quantum soft decision and parallel structure, improve the decode speed,present information storage and management to ameliorate the traditional register exchange method. Analyse and simulate Viterbi modules, download and validate on QUARTUSII. The paper presents a (2,1,7)Viterbi decoder based on the UV propagation channel, the circuit is simple which is pragrammed in VHDL language and downloads on the FPGA chip. It can meet the common UV communication. With the research and development of UV communication especially large capacity channel, it needs to employ more complicated decoder.更多还原