基于两步式融合重构的压缩频谱检测方法

在宽带频谱检测技术中,针对传统分布式压缩感知方法(DCS)数据传输量大、能耗高的问题,提出了一种基于两步式融合重构的压缩频谱检测(TS-CSS)方法.该方法的数据重构过程分为先支撑集信息融合,后信号联合重构两步,通过支撑集信息融合获得的先验信息可指导信号的联合重构.仿真结果表明,联合重构时随机选择50％的用户参与,即可获得与传统DCS接近甚至更优的频谱检测性能,因而,该方法能够有效地降低系统数据传输量,节省频谱检测耗能.     

Blind Spectrum Sensing Algorithms for Cognitive Radio Networks

In a cognitive radio network, the spectrum that is allocated to primary users can be used by secondary users if the spectrum is not being used by the primary user at the current time and location. The only consideration is that the secondary users have to vacate the channel within a certain amount of time whenever the primary user becomes active. Thus, the cognitive radio faces the difficult challenge of detecting (sensing) the presence of the primary user, particularly in a low signal-to-noise ratio region, since the signal of the primary user might be severely attenuated due to multipath and shadowing before reaching the secondary user. In this paper, a blind sensing algorithm is derived, which is based on oversampling the received signal or by employing multiple receive antennas. The proposed method combines linear prediction and QR decomposition of the received signal matrix. Then, two signal statistics are computed from the oversampled received signal. The ratio of these two statistics is an indicator of the presence/absence of the primary signal in the received signal. Our algorithm does not require the knowledge of the signal or of the noise power. Moreover, the proposed detection algorithm in this paper is blind in the sense that it does not require information about the multipath channel distortions the primary signal has undergone on its way to reaching the secondary user. Simulations have shown that our algorithm performs much better than the commonly used energy detector, which usually suffers from the noise uncertainty problem.      

一种认知无线网络中的协作感知优化方法

认知无线电技术能够显著提高频谱资源的利用率,因此越来越受到学术界的关注。频谱感知是认知无线电的基础,一方面它要求能够快速找到可用频谱,另一方面当授权用户返回时又要求能够快速释放信道避免干扰。提出了一种认知无线网络中多用户协作感知分级方法,并通过数学推导给出最优的分级策略。仿真结果表明,采用所提出的协作频谱感知方法,能够提高认知无线网络的吞吐量。     

一种适用于认知无线电系统的盲感知算法

频谱感知是认知无线电中最具挑战的问题之一。提出一种基于信号协方差矩阵特征值的盲感知算法,仿真显示这种方法有较好的检测性能,适用于认知无线电系统中授权用户的检测。     

一种新的认知无线电频谱感知方法

认知无线电是一种用于提高无线电通信频谱利用率的新的智能技术。首先简述了认知无线电的背景和概念,然后针对认知无线电频谱感知的能力,对比分析了现有的三种频谱检测方法：匹配滤波器法、能量检查法和循环平稳特征检测法,在对其进行研究的基础上,提出一种将能量检测法和循环平稳特征检测法相结合的双门限检测法,通过仿真验证了该方法的有效性和优越性。     

认知无线电的频谱感知算法研究

频谱感知技术、频谱共享技术、频谱管理技术是当前认知无线电的三大核心技术,而频谱感知技术是实现后续的频谱共享和频谱管理的前提。因此主要对当前认知无线电频谱感知技术的基础理论、算法模型以及频谱感知的具体算法做了详尽的分类,并利用Matlab仿真平台对主要的频谱感知算法进行了仿真,并根据仿真结果,比较了各个算法的性能优劣性,可为认知无线电用户的算法选择提供参考,同时也为认知无线电后续的频谱共享和频谱管理工作奠定一定基础。     

Ad Hoc认知网络中基于梯度算法的协作压缩频谱感知方法

ad hoc认知网络(CRAHNs)比起传统ad hoc网络有很多优势,如分布式多跳结构及动态变化的网络拓扑等。频谱感知是认知无线电技术的基础,采用压缩感知方法以低于奈奎斯特采样率的速率来获得较好的重构信号,同时可减轻数字处理设备的压力。本文使用多跳模型,每个认知用户感知的频谱不仅包括主用户的主频谱,也包括认知用户自身收到其他认知用户干扰的更新频谱。由于具有动态特性的ad hoc网络缺少融合中心,所以本文中提出一种基于梯度的分布式协作感知算法。该算法基于能量检测,具有可靠的感知性能和较少的能量消耗,并能快速收敛。仿真实验验证了算法的有效性。      

感知无线电中的高效频谱侦测方案

感知无线电是一种能有效提高频谱利用率的先进技术,他能在主用户没有使用频谱的时候发现并使用"频谱空洞".近来有研究结果表明,在衰落和阴影效应影响下频谱侦测的结果会有大幅度下降.为了削弱衰落和阴影效应的影响联合侦测诞生了,传统的联合侦测方式在每个用户所受衰落不同的情况下不能有效的工作.文章提出一种加权联合侦测来提高联合侦测性能.由大量分析和仿真结果可以表明加权联合侦测能大幅度提高侦测性能.     

Spectrum Sensing Framework for Cognitive Radio Networks

Spectrum sensing feature of cognitive radio devices represents a cornerstone characteristic facilitating real-time and accurate spectrum occupancy measurements in cognitive radio networks. It practically enables the cognitive radio devices to detect vacant spectrum holes and use them for their communication purposes. There are numerous spectrum sensing methods proposed in the literature ranging from local based ones to cooperative strategies among several devices increasing the confidence level of the detected spectrum. This paper gives a general spectrum sensing framework for cognitive radio networks, classifies and explores different spectrum sensing techniques and approaches and shows practical examples, from authors’ own experience, of realized spectrum sensing engines and strategies along with some obtained results.     

一种新的认知无线电频谱感知算法

频谱感知是认知无线电的关键技术之一,通过检测授权用户信号的有无来发现频谱空穴,以提高频谱利用率。基于接收信号的统计协方差理论,提出一种新的认知无线电频谱感知算法,无需信号的先验信息,且计算复杂度较低。仿真分析了该算法,结果表明其在低信噪比环境下,较传统能量检测法有更好的感知性能。     

认知无线电的频谱感知技术研究

认知无线电技术接入灵活,能够大大提高频谱的利用率,被认为是当前解决频带使用拥挤的最佳方案。认知无线电是一种可以感知周围通信环境来改变发射机在特定的参数上实时改变的智能通信系统。它采用动态频谱管理来提高频谱利用率,高可靠性的频谱感知是实现频谱共享的关键技术,对频谱感知技术的匹配滤波器检测、能量检测、静态循环特征检测和合作检测等进行了讨论,并分析了各种方法的特点和性能。     

认知无线电频谱感知估计时延的随机规划优化算法

为了提高认知无线电网络的频谱利用率,该文提出对认知无线网络频谱感知估计时间进行优化。如果频谱感知时间较长,一方面对信道参数的估计更准确,会减小对授权用户的干扰并提高认知用户的吞吐量;另一方面,数据传输时间相应缩短,使系统吞吐量减小,这时存在一个最优的感知时间使得系统吞吐量最大。该文认为子频段的信道状态信息服从指数分布,故提出随机规划的方法,对认知无线网络频谱感知估计时间进行优化运算。计算机仿真结果表明,该算法是切实有效的,具有一定的工程应用价值。     

认知无线电网络中基于压缩感知的有限反馈

提出一种基于压缩感知技术的认知无线电网络中的有限反馈协议,反馈带宽仅与感知接收机个数的对数呈线性增长。在二种信道误差模型下,采用压缩感知重建算法（LASSO算法）,仿真分析系统的重建性能,结果表明在信道信息不完美的情况下,能够保持较好的重建性能,同时还表明通过适当增加反馈带宽可换取系统对差错容忍程度的大幅提高。     

认知无线电协作频谱感知技术综述

频谱感知是实现认知无线电功能的前提条件,也是认知无线电领域的一个研究热点.近年来人们提出了很多种频谱感知方法,尤其协作感知技术日益受到关注.综述了协作频谱感知技术的最新研究进展,先描述典型的认知无线电协作频谱感知模型,然后讨论了协作感知中信息融合及性能分析等关键问题,最后指出了协作感知的研究挑战和发展趋势.     

认知无线电的合作频谱检测分析

认知用户需要持续快速地检测主用户的出现,对基于认知无线电的合作频谱检测机制进行了分析。在理想的两用户网络中,认知用户采用合作机制可以提高系统的平均侦测时间。在多认知用户网络中,参与合作的用户越多,单个认知用户对主用户的侦测概率越高。对于多用户网络,还考虑了整体的实现。     

认知无线电系统中频谱感知方法的研究

由于无线通信技术的飞速发展，因此无线资源频谱日趋紧张．而另一方面现有无线通信网络采用的固定频谱分配策略导致许多已分配的频段在大多数情况下未能被充分利用。认知无线电技术的出现为提高频谱利用率提供了一条新的思路．认知无线电的一个重要要求就是能够动态的感知并接入频段，这就需要人们能够感知出空闲频段。论文主要介绍了认知无线电系统中的频谱感知方法，并运用能量检测法对对OFDM信号进行了仿真分析．     

Replacement of Spectrum Sensing in Cognitive Radio

Two major challenges exist in the development and deployment of cognitive radio networks: spectrum sensing and hidden terminal problem. In this research, we consider a network structure where the spectrum sensing task is separated from the unlicensed users (secondary users). The service provider for the secondary users needs to place sensing devices within the networks of licensed users (primary users). These sensing devices sense the primary users? activity. The sensing devices also decide whether to admit a secondary user?s transmission. A new cognitive cycle is proposed accordingly. The proposed protocol is analyzed using the theory of Lamé curve. The problem of optimally locating sensing devices and the properties of the proposed system are studied for single-user case and multi-user case. For the case without a separate control channel, a lowtemperature handshake technique is proposed for handshakes between the secondary users and the sensing devices. The other advantage of the proposed scheme is from the business model point of view: the expensive sensing devices will be implemented by the cognitive radio service provider, instead of being built in the secondary user devices which are usually consumer products demanding low cost.     

协作频谱感知在认知网络中的应用

认知无线电能够灵敏感知周围环境的变化,通过频谱感知功能发现频谱空洞,使得认知无线电能够与周围通信环境相适应。在认知无线电网络中,认知用户（次用户）必须连续地监控频谱,检测主用户是否存在。如果主用户存在,次用户必须尽快地退出该频段,从而不影响主用户。在文中采用一种协作机制,即两用户进行协作频谱感知,从而提高主用户的检测率,减少了检测时间,并且得到捷变增益。我们用Matlab给出仿真结果。     

Cooperative Spectrum Sensing Techniques in Cognitive Radio

Cognitive radio has become an effective theory to solve the inefficiency of the spectrum usage. One of the main requirements of cognitive radio systems is the ability to reliably detect the spectrum hole. Previous works on the problem of detection for cognitive radio have suggested the necessity of user cooperation to enable the detection at the low signal-to-noise ratios experienced in practical situations. This paper introduces energy sensing and the cooperative sensing techniques: AND model, OR model, counting model, double threshold model, likelihood ratio model, linear cooperation model and DWCS model. It is proved that significant cooperative gain can be achieved by the proposed models in reducing interference and improving spectrum usage.     

认知无线电网络的一种协作频谱感知方案

认知无线电技术能够让非授权用户利用已经分配给授权用户的频段.为了不对首要用户的工作造成干扰,认知用户需要对频谱进行不间断的监测来判断首要用户是否存在.因此,频谱的感知是认知无线电技术的关键.协作频谱感知能够充分的利用网络资源,提高网络中的认知用户的检测概率.文中笔者简单地介绍了一种协作频谱感知的方案.仿真结果表明,通过该方法能够提高网络中认知用户的检测概率,提高网络的检测灵敏度.