文档介绍：摘要
认知无线电CR(Cognitive Radio)作为一种革命性智能频谱共享技术,以不干扰授权业务为前提,允许非授权业务利用频段传输信号,可显著提高频谱的使用率,是解决目前频谱资源紧张的有效手段,并逐渐成为了当今通信界的研究热点。避免干扰主用户PU(Primary User)的正常通信是认知无线电最重要的限制,而频谱感知则为这一目标提供保障。为了提高频谱感知的性能,认知无线电网络中的大量节点可以被用来进行协同频谱感知,协同频谱感知可以有效地克服单节点频谱感知的局限性。
本文首先分析研究了常用的频谱感知技术,尤其是能量检测技术。在无线信道中信号会受到多径衰落、阴影的影响,将导致频谱检测性能急剧下降。为了解决这个问题,多个认知用户可以通过协同感知提高检测性能。本文研究了当今热门协同频谱检测算法和协同感知中的数据融合问题,随着参与协同检测的认知用户数目的增大,频谱检测检测性能逐渐增强。但频谱检测差错概率并不随着认知用户数目的增大而继续增大,而是趋于平缓。相反过多的认知用户参与协同检测会使整个认知无线电网络的感知时间过长,即灵敏度降低。同时也会造成巨大的系统开销。
本文提出了一种新的基于可信度的协同检测算法。在满足目标错误概率的条件下,只选择可信度较高的一些认知用户参与协同频谱检测。仿真结果表明当认知用户中存在恶意节点或者故障节点时,该算法同传统算法相比较,频谱检测性能更好,具有更强的健壮性。
关键词:认知无线电;频谱检测;能量检测;协同频谱检测
Abstract
Cognitive radio (CR) technique is considered as one of the solutions of current spectrum resource scarcity. The core idea of cognitive radio is to exploit the licensed but underutilized spectrum, in order to improve the spectrum efficiency. In cognitive radio systems, avoiding interference to primary users is the most important constraint. And spectrum sensing is the key technique to achieve this goal. In order to improve the performance of spectrum sensing, cooperative spectrum sensing is proposed, which can recover the limits of spectrum sensing by only one node.
In this dissertation, we first give an overview of some well-known spectrum sensing techniques, especially energy detection. However, in wireless channels, signals often suffer from shadowing and fading, which may lead to a very poor sensing performance. In order to solve this problem, cooperative spectrum sensing has been studied to improve the spectrum sensing performance. This dissertation focuses on the well-known cooperative spectrum sensing techniques and the optimal fusion rule for cooperative spectrum sensing. The sensing performance is improved as the number of secondary users for cooperative sensing increases. However, there exists an error floor where the decrease of the probability of error is minor and too many cooperative users will make the whole sensing