【作者】 翟卫松；

【导师】 杨守义；

【作者基本信息】 郑州大学 ， 信号与信息处理， 2010， 硕士

【摘要】 认知无线电(Cognitive Radio, CR)技术能够感知到无线通信环境中的“频谱空洞”,并且能够通过一定的方式充分利用这些频谱来提高频谱的利用效率。随着无线通信技术的发展、用户需求不断的增加,该技术解决了无线频谱资源紧张的局面。它是一种智能的无线通信系统,具有认知和重新配置能力,能够动态地改变认知用户的配置参数,不会对正在工作的授权用户造成干扰的情况下,合理利用空闲频谱进行通信。正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)技术具有较高的频谱利用效率和较强的抗多径干扰能力,并且可以实现高速的数据传输,成为了4G通信的热点候选方案。另外,OFDM技术可以通过频率的组合或裁剪实现良好的频谱资源控制能力,并可以有效的利用频谱进行数据传输,这些都满足了实现认知无线电的技术要求。OFDM技术和认知无线电的结合可以缓解当前无线频谱资源紧张和分配不均的局面,实现无线频谱资源的合理分配和充分利用。文章首先介绍了OFDM技术基本原理及其相关的技术知识；阐述了认知无线电的基本原理以及与OFDM技术相结合的优势；分析了自适应OFDM系统在认知无线电条件下提高频谱效率,最大化系统容量的性能；之后,又分析了零前缀OFDM系统的性能,并对NC-OFDM系统进行了仿真分析。最后,着重研究了所提出的基于认知无线电的预编码无循环前缀OFDM(无CP OFDM)系统。基于通过认知无线电技术感知到的无线频谱状态信息,控制OFDM用户实时地改变系统通信配置参数,包括调制方式、编码方式、频率及带宽和发射功率等,从而在数据传输时避免对授权用户造成干扰。另外,将这些配置参数预编码成伪随机序列与OFDM符号数据一起发送。这样可以省去专门用于传输通信配置参数的控制信令,从而提高了频谱利用效率,减小了传输功率,增加了系统容量。更多还原

【Abstract】 Cognitive radio technology can aware the "spectrum hole" in wireless communication environment; and makes full use of the spectrum through a certain way to increase spectrum utilization efficiency. The technology solves the tense situation of radio spectrum resources as wireless communication technology development and the users demand increasing. As an intelligent wireless communication system it has the ability of cognition and reconfigure. It can rationally communicate using free spectrum with dynamic changing secondary users’ configuration parameters, and doesn’t cause interference to the working authorized users.OFDM technology has high spectral efficiency and the ability of anti-multipath interference. It may achieve high speed data transmission as a hot candidate for 4G communication. In addition, OFDM technology achieves well control of spectrum resources through combination or cutting frequency, and effectively uses spectrum for data transmission, that meets the requirements of cognitive radio. The combination of OFDM and cognitive radio technology not only eases the situation of current short supply radio spectrum and uneven distribution, but also achieves rational allocation and fully utilizing of radio spectrum.This paper first introduces the basic principle of OFDM technology and its related technical knowledge, and describes the basic principles of cognitive radio technology and the advantages combined with OFDM. In cognitive radio conditions, adaptive OFDM system can improve spectrum efficiency and maximize its system capacity. Then we analyses the system performance of ZP-OFDM and make simulation analysis of NC-OFDM system. In the last, it focuses on the precoded OFDM system without CP based on cognitive radio. Cognitive radio makes the user of OFDM real-time change communication configuration parameters including modulation, coding, frequency, bandwidth and transmission power etc according the perceived status of wireless spectrum, so as to avoid interference to the authorized users in data transmission. The system makes these configuration parameters precoded into a pseudo-random sequence and transmits it with OFDM symbols. In this way, the system eliminates the specific control signaling for the transmission of communication configuration parameters, also improves the spectrum utilization efficiency and reduces the transmission power to increase system capacity.更多还原