【作者】 王海；

【导师】 曾桂根；

【作者基本信息】 南京邮电大学 ， 电子与通信工程， 2012， 硕士

【摘要】 认知无线电(Cognitive Radio, CR)具有感知周围无线电环境的能力,能提高频谱的利用率和通信系统的容量。正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)技术是一种被高度认可的、能够有效提高频谱资源利用率的通信技术。将OFDM调制解调技术应用到认知无线电的次用户通信中、并在FPGA下进行方案设计与实现,是当前认知无线电技术发展的必然选择。本论文在FPGA硬件平台下研究并实现了OFDM解调器的详细实现方案。本文首先介绍了课题背景及认知无线电和OFDM技术的研究动态及应用现状,详细阐述了OFDM调制解调的基本原理及接收端解调系统中符号同步、载波同步及信道均衡等关键技术的原理。根据项目的实际要求对物理层主要参数、帧结构以及整个OFDM接收端解调方案进行了设计。其次重点分析了ADC采样、正交解调、低通滤波、符号同步、载波同步、速率转换、FFT解调、信道均衡、剩余相位跟踪及解扰和QAM逆映射各模块在FPGA上实现的相关算法、结构框图及处理流程,并使用VHDL语言在Altera公司的FPGA开发板上实现了OFDM解调系统。通过对最终搭建好的认知无线电验证平台进行实际测试,结果表明：本文设计并实现的OFDM解调器能够很好的完成接收端的数据解调,其功能和指标均能满足项目要求。论文最后主要介绍了本课题中遇到的几种FPGA常用设计思想,对课题开发中遇到的实际问题进行了说明,并给出了一些常用的解决方法。更多还原

【Abstract】 Cognitive Radio has the ability of sensing the surrounding radio environment and improving the spectrum utilization and communication capacity. Orthogonal frequency division multiplexing is a highly recognized communications technology to improve the utilization of spectrum effectively. It is inevitable for the cognitive radio technology to use OFDM modulation and demodulation technology in secondary user communications, design and put it into practice with FPGA. This paper gives the design and implementation of OFDM demodulation with FPGA hardware platform.First, this paper gives the background of the subject, research trends and application status of cognitive radio and OFDM technology. It elaborates the basic principle of OFDM modulation and demodulation, as well as the key technical principles, including symbol synchronization, carrier synchronization and channel equalization and so on, that used in demodulation system of receiver. The main parameters and frame structure of the physical layer, as well as the entire OFDM receiver demodulator program has been designed according to the actual requirements of the project.Second, this paper emphasizes the algorithm, block diagram and processes of modules implemented on FPGA, including ADC sampling, quadrature demodulator, low pass filtering, frame synchronization, carrier synchronization, conversion rate, the FFT demodulation, channel equalization, the remaining phase tracking and descrambling, and QAM inverse mapping. The OFDM demodulation system was built in Altera FPGA board with VHDL language. The application project worked on the cognitive radio verification platform shows that the OFDM demodulation designed in this paper could accomplish the data demodulation in the receiver, while the functions and indicators are able to meet the project requirements.Finally, this paper gives a introduction to several common FPGA design ideas that used in the subject, descrips the practical problems encountered in the development of this subject, and gives some commonly used methods to solve them.更多还原