基于最小误检概率的最优感知用户数目优化算法

频谱感知是认知无线电系统的关键技术之一,协作频谱感知能够提高频谱感知性能。首先定义了修正后的误检概率,然后以能量检测为基础,推导了在不同判决门限下为使误检概率达到最小的最优感知用户数目,并根据最优感知用户数目进行协作频谱感知。仿真结果表明,与传统的K秩准则相比,文章所提算法能够有效提高感知性能。     

多信道认知无线电频谱感知时间和门限联合分配

为提高多信道认知无线电的吞吐量,提出采用交替方向优化联合分配次用户的频谱感知时间和子信道感知门限.基于"先听后传"的次用户帧结构,建立了感知时间和门限的优化分配模型.该模型在保证满足主用户通信需求和子信道频谱感知性能的前提下,最大化次用户各子信道的吞吐量总和.联合优化算法通过交替优化感知时间和门限能够获得模型的最优解.仿真结果表明:存在最优的感知时间和门限最大化次用户的吞吐量,并且相比之前的方案,联合分配能够提高次用户的吞吐量.     

基于阈值优化的频谱感知算法

协方差绝对值（Covariance Absolute Value,CAV）感知算法使用固定阈值和固定虚警概率的频谱感知策略,无法保证在任何时候都能使频谱感知性能达到最优。提高频谱感知性能包括降低对主用户的干扰概率并提高空闲频谱的利用率,即最大限度地降低漏检概率与虚警概率。为此,本文对协方差绝对值感知算法进行改进,提出了不同信噪比下自适应阈值的优化方法使频谱感知误差（漏检概率与虚警概率的代数和）达到最小。实验结果表明,本文算法有效降低了频谱感知误差,提高了检测概率,特别是在信噪比较低的情况下性能改善较为明显。     

认知无线电网络中压缩协作频谱感知

低频谱利用率条件下的信道状态向量具有稀疏性,为降低认知无线电网络中各个认知用户的频谱感知冗余,基于压缩感知技术提出了一种低复杂度的协作频谱感知方法. 仿真结果表明,通过稀疏观测矩阵提高了单个认知用户感知过程的速度和效率;在融合中心对观测数据进行重构过程中使用因子图迭代算法,大幅降低了计算难度;同时可以根据认知网络中的频率使用情况,自适应调整认知用户的感知点数,确保整个网络的高效感知.     

认知无线电网络中合作频谱感知参数优化

为提高频谱感知的效率,提出了一种在资源受限的认知无线电网络中合作频谱感知参数优化算法,在保证对授权用户的干扰不超过指定门限时,对信道利用效率与系统资源利用效率进行选择性加权,使认知无线电网络的感知效率最大化. 针对不同使用特征的授权信道,该算法均可求解出相应的最优感知参数组合. 仿真结果表明,在避免干扰授权用户的前提下,最优感知参数组合系统能最大化感知效率.     

同时收发的认知干扰机频谱感知

为了增强复杂电磁环境中同时收发认知电子战干扰机的作战能力,基于一般能量检测算法,提出一种改进的认知干扰机频谱感知算法,推导出该算法对作战目标信号感知的虚警概率和检测概率的理论表达式.仿真结果表明:所提频谱感知算法能够有效地降低自干扰对同时收发认知干扰接收机性能的影响,提升认知干扰机对作战目标的电磁频谱感知能力.     

认知无线电网络的检查协作频谱感知技术

在认知无线电中,协作频谱感知通常被用来提高感知性能。但当用户个数较多时,控制信道带宽的限制和感知时延会影响协作感知的性能。作者提出采用检查协作频谱感知可以有效避免这些问题。检查协作频谱感知通过减少认知用户上报基站的感知信息,降低通信负荷和感知时延,从而提高系统的敏感性。通过最大化频谱利用率可以得到最优的不发送概率,从而在感知时延和接入频谱机会的错失上得到折衷。通过分析及仿真结果可以看出,检查协作感知与传统协作感知相比,有效提高了系统的敏感性。通过最优的不发送概率可以确定最佳的感知门限进行感知。     

基于无速率编码的认知无线电系统能量分配算法

针对目前广泛应用的认知无线电技术,研究最大化认知系统能量利用率的问题.全局计入信道特性和系统本身特性对能量利用率的影响,利用无速率编码对网络动态环境的自适应能力以对抗主用户不可预知的出现,研究基于无速率编码的多信道认知无线电系统的能量分配算法.通过引入周期频谱感知模型,提出的能量分配算法根据信道和系统特性分配从用户的感知能量和传输能量,利用系统门限约束干扰概率以保护主用户通信.仿真结果表明,对应不同的信道或系统特性,提出的算法均能够显著降低能耗,提高能量利用率.     

基于时域-空域联合的认知无线电频谱感知算法

为提高认知无线电系统中频谱感知的性能和检测概率,提出了一种时域-空域联合的频谱感知算法。该算法利用主用户信号时域与空域的特性,通过空域感知对主用户定位,利用主用户的定位信息时域感知选择认知用户进而提高检测概率。仿真结果表明,该算法的检测性能优于时域或空域感知。     

认知无线电自适应频谱感知时间分配机制

为最大化频谱利用率,根据主用户使用信道的频率和次级用户的数据传输需求推导得到最优次级用户数据传输时间.在毫秒级频谱空洞场景下,基于部分可观测马尔可夫决策过程提出一种自适应频谱感知时间分配机制.该机制根据前一时段的信念状态和能量感知结果判断在当前时段内的最优行为.仿真结果表明,该机制能够根据不同主用户和次级用户的冲突概率需求最大化频谱利用率.     

Optimization of sensing time and cooperative user allocation for OR-rule cooperative spectrum sensing in cognitive radio network

In order to improve the throughput of cognitive radio(CR), optimization of sensing time and cooperative user allocation for OR-rule cooperative spectrum sensing was investigated in a CR network that includes multiple users and one fusion center. The frame structure of cooperative spectrum sensing was divided into multiple transmission time slots and one sensing time slot consisting of local energy detection and cooperative overhead. An optimization problem was formulated to maximize the throughput of CR network, subject to the constraints of both false alarm probability and detection probability. A joint optimization algorithm of sensing time and number of users was proposed to solve this optimization problem with low time complexity. An allocation algorithm of cooperative users was proposed to preferentially allocate the users to the channels with high utilization probability. The simulation results show that the significant improvement on the throughput can be achieved through the proposed joint optimization and allocation algorithms.     

删余协作频谱感知性能分析及优化

提出了一种新的基于删余的协作频谱感知方法,通过减少实际发送的本地决策值数来节约控制信道带宽,降低检测性能对认知用户数的依赖; 分析了这种删余协作频谱感知在感知信道和报告信道均存在衰落下的性能,它可以有效解决报告信道衰落所带来的尾感知问题,降低了虚警率; 提出了进一步优化算法,算法在确保主用户受到足够保护的前提下,通过寻找最优的次用户数和相应的检测门限使次用户的接入机会最大化．仿真结果与理论分析相一致．     

A novel weighed cooperative bandwidth spectrum sensing for spectrum occupancy of cognitive radio network

In cognitive radio network(CRN), a secondary user(SU) may utilize the spectrum resource of the primary user(PU) and avoid causing harmful interference to the primary network(PN) via spectrum sensing. In the traditional time spectrum sensing, the SU cannot detect the PU's presence during its transmission, thus increasing interference to the PN. In this work, a novel weighed cooperative bandwidth spectrum sensing method is proposed, which allows multiple SUs to use part of the bandwidth to perform cooperative spectrum sensing throughout the whole frame in order to detect the PU's reappearance in time. The SU's spectrum efficiency is maximized by jointly optimizing sensing bandwidth proportion, number of cooperative SUs and detection probability, subject to the constraints on the SU's interference and the false alarm probability. Simulation results show significant decrease on the interference and improvement on the spectrum efficiency using the proposed weighed cooperative bandwidth spectrum sensing method.     

Cooperative detection algorithm of spectrum holes in cognitive radio

To improve the detection performance of sensing users for primary users in the cognitive radio, an optimal cooperative detection algorithm for many sensing users is proposed. In this paper, optimal decision thresholds of each sensing user are discussed. Theoretical analysis and simulation results indicate that the detection probability of optimal decision threshold rules is better than that of determined threshold rules when the false alarm of the fusion center is constant. The proposed optimal cooperative detection algorithm improves the detection performance of primary users as the attendees grow. The 2 dB gain of detection probability can be obtained when a new sensing user joins in, and there is a 17 dB improvement when the accumulation number increases from 1 to 50.     

Joint optimization of cooperative sensing and transmission in energy-efficiency cognitive radio

Aiming at the low energy utilization caused by the sensing energy consumption of cognitive radio (CR), we propose to improve the energy efficiency (EE) of multi-channel CR by jointly optimizing cooperative spectrum sensing and transmission resources. Setting optimizing parameters such as cooperative spectrum sensing time, sensing threshold, transmission bandwidth and power, etc., the optimization model for maximizing EE is built based on the periodic cooperative spectrum sensing. The proposed non-convex optimization model is effectively resolved by a combined algorithm of the interior method and Dinkelbach's optimization. Simulation results show that when the detection probability is 0.6, compared with the traditional maximizing spectrum efficiency model, the transmission rate of the maximizing energy efficiency model increases by 100bit/(s·Hz^-1) under unit energy. The proposed model decreases the sensing power consumption and improves the energy utilization effectively.     

判决相关条件下联合频谱检测的性能分析

为了改善认知无线电中感知用户(未授权)对主用户弱信号的检测性能,采用多个感知用户合作的联合最优门限判决算法.在考虑参与联合检测的各感知用户判决门限具有相关性的条件下,通过理论分析和软件仿真,表明联合检测算法随着参与检测用户数目的增加,能够改善对主用户弱信号的检测性能.在融合中心虚警概率恒定的条件下,与给定各判决门限和系统融合准则的算法相比较,联合最优门限判决算法性能更好.但因各感知用户判决门限具有相关性,系统检测性能比各感知用户判决独立条件下有一定损失.     

分布式协作频谱感知的信誉模型

协作感知技术能大大提高认知无线电网络中的频谱感知效果,但也会产生一些安全隐患,如频谱感知数据伪造攻击。针对单个恶意次用户发起的连续性频谱感知数据伪造攻击和若干个恶意次用户发起的非连续性频谱感知数据伪造攻击,设计并实现了一种分布式协作频谱感知的信誉模型。仿真实验表明,该模型能有效地识别恶意次用户和抵御频谱感知数据伪造攻击。同时,该模型还具有较小的虚警率、丢失率和较好的容错能力。     

认知无线电中自适应分步合并协作频谱感知算法

在等增益合并协作频谱感知基础上,提出了一种新的频谱感知算法．根据认知用户接收信噪比的变化,通过自动调整参与协作频谱感知的认知用户数,以减少认知无线电网络中的数据开销．推导了瑞利衰落信道下采用此算法时,认知用户通过控制信道发送到中心控制器的平均数据量的计算公式．理论分析和仿真结果表明,和等增益合并协作频谱感知算法相比,在保证频谱检测性能的前提下,该算法减少了认知用户通过控制信道到中心控制器的平均数据开销．