【作者】 张冰玉；

【导师】 郑宝玉；

【作者基本信息】 南京邮电大学 ， 信号与信息处理， 2011， 硕士

【摘要】 认知无线电是一种解决频谱稀缺的有效途径,作为下一代网络发展中的关键技术正受到越来越多的关注,而频谱感知作为认知无线电网络中的重要技术近年来也成为了研究的热点。协作频谱感知是在单用户频谱感知技术上发展起来的,通过利用认知无线电用户的分集作用提高感知的准确度和灵敏度。本文在总结了现有各种协作频谱感知方法的基础上,着重研究了以下问题:首先,重点研究了采用双门限能量检测的协作频谱感知,分析了一种“β-比”融合准则,以提高系统感知准确度。理论推导并仿真了感知信道(sensing channel)为AWGN信道或Rayleigh衰落信道,汇报信道(reporting channel)理想或非理想时的系统性能参数,并与采用“与”规则和“或”规则融合时的情况做了比较,得出结论:“β-比”融合准则在提高系统感知准确度和降低传输开销方面都具有较明显的优势。其次,本文还针对协作频谱感知中存在的异步问题,构建了一种基于异步分布式融合的协作频谱感知模型,推导了此模型在似然比准则下的最优融合方案,并分析了一种不需要主用户先验信息的次优方案——最大后验概率(MAP)估计-K秩规则融合方案。分别对采用这两种方案时的系统性能进行了理论分析和仿真,仿真结果显示两种方案都能有效提高频谱感知的可靠性。更多还原

【Abstract】 Cognitive radio (CR), an innovative technology to mitigate the spectrum scarcity problem, is being paid on increasingly attention as a key technology in the next-generation wireless network. And spectrum sensing, one of the most important issues in CR networks, has become a hot research topic in recent years. Cooperative spectrum sensing can improve the inference accuracy and sensitivity by using diversity of CR users. This thesis summarizes existing cooperative spectrum sensing schemes, and then focuses on the following two issues:First, and then cooperative spectrum sensing using double threshold energy detection is investigated. A fusion rule called‘β-ratio’rule is analyzed for improving the accuracy of sensing. The performance parameters of the sensing system whose sensing channel is AWGN channel or Rayleigh fading channel, and reporting channel is perfect or imperfect are derived and then simulated, which are compared with those of a system based on‘and’fusion rule or‘or’fusion rule. The conclusion is that‘β-ratio’rule has quite obvious superiority both on improving sensing accuracy and reducing transmission overheads.Second, a cooperative spectrum sensing model is proposed based on asynchronous distributed fusion. An optimal fusion rule is derived, and a suboptimal scheme, maximum posteriori probability (MAP) estimate-K-rank fusion scheme is analyzed, which does not require prior knowledge of primary user. The probabilities of system by using these two schemes are theoretically analyzed and then simulated respectively. Simulation results show that both of them could improve spectrum sensing reliability effectively.更多还原