【作者】 赵梦欣；

【导师】 程文青；

【作者基本信息】 华中科技大学 ， 通信与信息系统， 2007， 硕士

【摘要】 随着人们对无线通信需求的迅猛增长,频谱资源变得越来越紧张;另一方面,目前频谱利用率却十分低下:大部分频点不能充分使用,而某些热点频率又超负荷运行。为了解决频谱资源匮乏以及频谱利用率低下的问题,人们提出了认知无线电的概念。认知无线电网络是目前认知无线电研究的主要对象,其工作原理可以概述为:认知节点主动感知无线电频谱资源的状态,伺机选择最合适的频段接入,以自组织形式进行数据传输。本文在全面分析了认知无线电演化,认知无线电网络体系架构,网络路由策略研究现状基础上,对认知无线电网络的若干特性及由此带来的路由关键问题进行了详细的讨论,包括多频段通信差异,控制频段的选择问题,动态变化的可用频段对选路的影响以及节点间感知的可用频段不一致性与相似性,指出认知无线电网络中一条好的路由应具有低冲突及干扰、低频段切换和低跳数三种特性。综合以上几点,本文提出了一个新的认知无线电网络的选路指标—期望路由时延EPD,设计并仿真实现了认知无线电网络路由协议。协议使用频谱监控管理器监视管理节点感知的各个频段,使用协作方式初始化节点的立足频段;在媒体接入控制层使用探测包实时测量计算各个频段接收率;在选路时,协议为每条候选路由计期望路由时延并选出期望路由时延最小的路由传递数据。仿真结果表明,本协议在网络部署时,能尽量降低潜在传输冲突及干扰;在数据传输时,能综合考虑冲突干扰,频段切换时延及跳数,选择具有路由时延小、吞吐量高及分发率稳定的路由传输数据。更多还原

【Abstract】 Along with the rapidly increasing requirement of wireless communications, the frequency resources become more and more precious. On the other hand, the current frequency utilization ratio is regrettably low: some hot bands are excessively overloaded while most bands are not fully used. In order to resolve the radio frequency rarity problem and enhance frequency utilization, the CR(Cognitive Radio) technology is brought forward. The CRN (Cognitive Radio Network) is the main topic of the Cognitive Radio research and its working principle can be summarized as cognitive nodes actively sense radio spectrums, opportunistically select and access the best fitted spectrum, schedule data communication in the form of Ad Hoc.Based on the comprehensive analysis of CR evolution, CRN architecture and the current research on its routing, this paper discusses several CRN characteristics and key routing problems lead by those characteristics, including multi-band communication differences, control band selection problem, influence of dynamic available bands and features of non-identical and partly consistent available band sensed by nodes, and points out that a good route in CRN should have three features: low conflicts and interferences, low spectrum switches, and low hops.The author presents a new routing metric Expected Path Delay, EPD for CRN, designs and implements a CRN routing protocol in simulation platform. The protocol uses spectrum monitor & manager to monitor and manage every bands sensed and initializes foothold band in collaboration with neighbors. It also uses probe packets in the media access control layer to compute real-time reception ratio of a band. In route selection, the protocol calculates every candidate route’s EPD and picks up the one that has the smallest EPD. The simulation shows that the proposed protocol can greatly decrease the potential transmission conflicts and interferences in the stage of network deployment and can select low path delay, high throughput and steady delivery ratio routes through joint consideration of conflicts and interferences, spectrum switch delay and hops.更多还原