【作者】 刘晏昌；

【导师】 肖扬；

【作者基本信息】 北京交通大学 ， 人机交互工程， 2010， 硕士

【摘要】 无线通信技术在人们日常生活中的应用越来越广泛,但是有限的频谱资源和较低的频谱资源利用率,导致频谱资源匮乏这一问题也日益严重。瑞典Joseph Mitola博士于1999年提出的认知无线电(Cognitive Radio, CR)系统为解决频谱资源不足、实现频谱动态管理以及提高频谱利用率开创了崭新的局面,对认知无线电网络的研究已经成为国内外无线通信技术的热点。其中,认知无线电网络的媒体访问控制层(Medium Access Control, MAC)协议的作用是根据服务质量(Quality of Service, QoS)要求和用户配置来协调、控制网络中各节点共享无线资源从而实现通信资源的最优化使用。作为一种MAC层接入控制协议,载波侦听多路访问／冲突避免(Carrier Sense Multiple Access with Collision Avoid, CSMA/CA)协议已经成功应用在IEEE802.11无线局域网络(Wireless Local Area Network, WLAN)中。但是由于认知无线电网络中各节点可利用频谱资源存在着动态性和差异性,所以认知无线电网络MAC层必须实现动态频谱接入和动态频谱共享。这导致IEEE802.11无线局域网络的接入控制协议不能直接应用在认知无线电网络系统中,必须对其做出相应的改进,以使其能适应认知环境。因此本论文的研究思路就是在IEEE802.11无线局域网络的接入控制方法研究分析的基础上循序渐进地对认知无线电网络MAC层进行深入研究。本论文首先分析研究了IEEE802.11无线局域网的接入控制方法,详细地对分布式协调接入控制方法进行建模分析,提出改进后的接入控制优化方案；并在此基础上,提出CSMA/CA为适应认知无线电网络环境而做出的改进方案；然后,进一步对认知无线电网络MAC层基于频谱池策略的频谱分配算法建立模型并对其性能进行定量分析；最后,结合干扰温度机制得出一种频谱资源管理方案。更多还原

【Abstract】 The wireless communication technology has been widely used in daily life, but the limited spectrum resources and low utilization of the spectrum resources make the lack of spectrum more and more serious. Cognitive Radio (CR) was proposed by Joseph Mitola in 1999, which was based on the conception of Software Radio and enhanced it. The CR Network has a cognitive process that can perceive current network conditions, and then plan, decide and act on those conditions and the network can learn from these adaptations and use them to make future decisions, all while taking into account end-to-end goals, which can increase the utilization of the spectrum resources and the prime user in the CR Network cannot be disturbed.The IEEE802.22 standard promises to be the first practical implementation of Cognitive Radio technology. It is based on dynamic spectrum sensing and opportunistic access of the bands that are not currently in use by TV transmitters. The distinctive and most critical requirement for the IEEE802.22 air interface is the flexibility and adaptability. This stems from the fact that IEEE802.22 operates in a spectrum where incumbents (such as wireless microphones) may appear and disappear arbitrarily and where the collocated operation of multiple networks will be commonplace, as IEEE802.22 operates under license exempt regulatory model. This requirement has a direct impact on the various dynamic spectrum access (DSA) and dynamic spectrum sharing (DSS) mechanisms present at the PHY and the Medium Access Control (MAC) layers, which will be discussed in detail in this paper.The MAC protocol in the wireless communication coordinates and controls the access process to the medium. The Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA), as a MAC protocol, has been widely used in Wireless Local Area Network (WLAN). Different from the MAC of IEEE802.11, the application of CR technology suffers the uncertain spectrum and frequency width, which can not ensure the access of mobile users to be valid. To solve the problem, in this paper, we first analysis the CSMA/CA mechanism in IEEE802.11 in detail, and then we modify the CSMA/CA mechanism in order to make it suit the CR environments, in which the spectrum can be effectively used. In addition, we make some proposals for the spectrum sharing and the spectrum management based on the conception of spectrum pooling and interfere temperature.更多还原