Energy Efficiency in Cognitive Radio Network Using Cooperative Spectrum Sensing

Wireless Personal Communications - In this paper, we consider an optimization of number of secondary users (SUs) in a cooperative spectrum sensing by maximizing the energy efficiency of the...     

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.     

衰落信道下基于簇的协作频谱感知分析

在分布式协作频谱感知网络中,认知用户向融合中心上报本地检测的信道是带宽受限的,并且受各种衰落的影响。分析了衰落信道下认知用户通过"与"规则进行融合的协作感知策略,提出了认知用户间为Nakagami信道时基于簇理论的协作感知方案,推导得出了2种方法的检测概率和归一化平均感知比特数。仿真结果表明,基于簇理论的协作感知通过牺牲一定的信令开销得到较好的感知性能。     

基于信噪比加权的协作频谱感知方法

认知无线电中协作频谱感知技术能显著提高频谱感知性能,但传统协作频谱感知算法大多采用等权重进行数据融合,未考虑在实际通信环境中感知用户的信噪比差异。针对这种情况,提出了一种基于信噪比加权的协作感知方法,根据信噪比影响因子的不同,给感知用户本地判决结果分配不同的权重,并在此基础上对影响因子定义做了改进,减小了信噪比极值对感知性能的影响。仿真结果表明,在AWGN信道非衰落环境中,基于信噪比加权的协作感知比传统协作感知性能要好,改进后的加权感知方法对感知性能又有进一步的改善。     

认知无线电合作频谱感知算法研究

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频谱感知的方法,尤其是合作频谱感知算法日益受到人们的关注。综述了合作频谱感知技术的最新研究进展,从简单的线性信息融合算法到复杂的非线性感知算法,以及多天线合作感知等算法,通过仿真比较各种方法的检测性能,并展望未来频谱感知所面临的挑战和发展趋势。     

Fault-Tolerant Cooperative Spectrum Sensing Scheme for Cognitive Radio Networks

In order to solve the uncertainty resulting from shadowing effect and resist the attack from malicious cognitive radio (CR) users, we propose a fault-tolerant cooperative spectrum sensing scheme for CR networks, where an energy detection-based local spectrum sensing is performed at each CR user, a coefficient is used to weight each CR user’s sensing result, a linear weighted fusion process is performed at the fusion center (FC) to combine received sensing results. For a fault-tolerant cooperative spectrum sensing scheme, the most important issue is to distinguish whether the CR user is reliable or not. In this paper, a reputation-based cooperative mechanism is presented to alleviate the influence of the unreliable sensing results from CR users suffering shadowing and the false sensing data from malicious CR users on the detection result at the FC. In proposed fault-tolerant cooperative scheme, each cooperative CR user has a reputation degree which is initialized and adjusted by the FC and used to weight the sensing result from the corresponding user in the fusion process at the FC. And then, two reputation degree adjusting methods are presented to manage the reputation degree of each CR user. Simulation results show that the proposed scheme can not only weaken the harmful influence caused by malicious CR users, but also alleviate the corrupted detection problem resulting from destructive channel condition between the primary transmitter and the CR user. Moreover, the detection performance of the fault-tolerant cooperative scheme, which has a feasible computational complexity and needs no instantaneous SNRs, is close to that of the optimal scheme.     

Secondary Spectrum Access in Cognitive Radio Networks Using Rateless Codes over Rayleigh Fading Channels

In this paper, we propose secondary relaying schemes in cognitive spectrum leasing. In the proposed protocols, a primary transmitter uses rateless code to transmit its data to a primary receiver. In the secondary network, \(M\) secondary transmitters are ready to help the primary transmitter forward the data to a primary receiver so that they can find opportunities to transmit their data. For performance evaluation, we derive the average outage probability, the average number of encoded packets transmitted by the primary transmitter, the average number of remaining time slots for secondary network and the average capacity of the secondary network over Rayleigh fading channels. Various Monte-Carlo simulations are presented to verify the derivations.     

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。     

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.     

Soft Combination Schemes for Cooperative Spectrum Sensing in Cognitive Radio Networks

This paper investigates linear soft combination schemes for cooperative spectrum sensing in cognitive radio networks. We propose two weight-setting strategies under different basic optimality criteria to improve the overall sensing performance in the network. The corresponding optimal weights are derived, which are determined by the noise power levels and the received primary user signal energies of multiple cooperative secondary users in the network. However, to obtain the instantaneous measurement of these noise power levels and primary user signal energies with high accuracy is extremely challenging. It can even be infeasible in practical implementations under a low signal-to-noise ratio regime. We therefore propose reference data matrices to scavenge the indispensable information of primary user signal energies and noise power levels for setting the proposed combining weights adaptively by keeping records of the most recent spectrum observations. Analyses and simulation results demonstrate that the proposed linear soft combination schemes outperform the conventional maximal ratio combination and equal gain combination schemes and yield significant performance improvements in spectrum sensing.     

一种优化的认知无线电频谱感知策略

协作频谱感知技术可以有效地避免频谱感知过程中的隐终端问题,降低感知用户对主用户的干扰。但是随着协作感知中感知用户数目的增加,感知中的通信量也会增加。相对于传统的协作感知单门限判决法,双门限判决法可以在对感知性能影响很小的情况下,降低协作感知过程中的通信量。在传统的双门限感知技术的基础上,提出了一种基于权重的双门限协作算法。仿真结果表明,在保证较小的感知通信量下,相对于传统的双门限判决,提出的算法可以提高系统的感知性能。     

Adaptively Controlled Cooperative Spectrum Sensing Using OR Fusion Rule for Throughput Maximization in Cognitive Radio

Utilization of wireless spectrum resources should be improved with the great increase of using wireless services. Cognitive radio (CR) has been proposed to overcome the problem of inefficient use of spectrum holes. Spectrum sensing is the most important functional block, which is used to estimate the spectrum holes in the CR system. Cooperative spectrum sensing improves the detection performance and minimizes miss-detection of the primary user. The objective of this paper is to achieve the maximum throughput for all values signal-to-noise ratio (SNR). Cooperative spectrum sensing with fixed sensing time does not provide efficient throughput performance for all values of SNR. In this paper, we propose an adaptively controlled cooperative spectrum sensing scheme using OR fusion rule for throughput maximization in CR system. The proposed scheme estimates the required optimal sensing time for each value of the SNR to achieve the maximum throughput. Simulation results of the proposed scheme demonstrate that it maximizes the achieved throughput for all values of SNR and minimizes the probability of false alarm.

     

基于滤波器组的认知无线电频谱检测

认知无线电的首要任务是动态、可靠地检测无线电频谱环境。因此,每个认知无线电终端必须具有频谱检测的功能。文章在简述认知无线电频谱检测技术的基础上,提出了基于滤波器组的频谱检测方案,详细描述了多相滤波器组的设计方法和功率谱估计算法,并在加性高斯白噪声环境下进行了仿真。仿真结果表明,在恰当设置判决门限的情况下基于滤波器组的认知无线电频谱检测具有良好的性能。     

Reputation-Based Hierarchically Cooperative Spectrum Sensing Scheme in Cognitive Radio Networks

Cooperative spectrum sensing in cog- nitive radio is investigated to improve the det- ection performance of Primary User （PU）. Meanwhile, cluster-based hierarchical coop- eration is introduced for reducing the overhead as well as maintaining a certain level of sens- ing performance. However, in existing hierar- chically cooperative spectrum sensing algo- rithms, the robustness problem of the system is seldom considered. In this paper, we pro- pose a reputation-based hierarchically coop- erative spectrum sensing scheme in Cognitive Radio Networks （CRNs）. Before spectrum sensing, clusters are grouped based on the location correlation coefficients of Secondary Users （SUs）. In the proposed scheme, there are two levels of cooperation, the first one is performed within a cluster and the second one is carried out among clusters. With the reputa- tion mechanism and modified MAJORITY rule in the second level cooperation, the pro- posed scheme can not only relieve the influ- ence of the shadowing, but also eliminate the impact of the PU emulation attack on a rela- tively large scale. Simulation results show that, in the scenarios with deep-shadowing or mul- tiple attacked SUs, our proposed scheme ach- ieves a better tradeoff between the system robustness and the energy saving compared with those conventionally cooperative sensing schemes.     

A Robust Cooperative Spectrum Sensing Scheme in Cognitive Radio Systems

Performance of cluster-based cooperative spectrum sensing is more greatly improved than that of the traditional cooperative spectrum sensing.However,the style of clusters is not pointed out on traditional cluster-based method.In view of all the fading in the cooperative spectrum sensing,space diversity,and selective diversity,a robust cooperative spectrum sensing scheme based on clusters is proposed.Simulation results show that the detection performance of this new scheme is more close to that of the ideal cluster-based cooperative spectrum sensing scheme,and the excellent performance with higher reliability is gained relative to the actual cluster-based cooperative spectrum sensing scheme.Finally,the number of users in a cluster of the proposed scheme is discussed.The two users in a cluster are not the optimal solution to the overall implementation of cognitive radio.     

Review of Robust Cooperative Spectrum Sensing Techniques for Cognitive Radio Networks

Cognitive radio networks sense spectrum occupancy and manage themselves to operate in unused bands without disturbing licensed users. The detection capability of a radio system can be enhanced if the sensing process is performed jointly by a group of nodes so that the effects of wireless fading and shadowing can be minimized. However, taking a collaborative approach poses new security threats to the system as nodes can report false sensing data to reach a wrong decision. This paper makes a review of secure cooperative spectrum sensing in cognitive radio networks. The main objective of these protocols is to provide an accurate resolution about the availability of some spectrum channels, ensuring the contribution from incapable users as well as malicious ones is discarded. Issues, advantages and disadvantages of such protocols are investigated and summarized.     

Cooperative Spectrum Sensing with Adaptive Node Selection for Cognitive Radio Networks

In cooperative spectrum sensing, secondary users can cooperate based on their local sensing observations so as to detect primary signals in a more reliable manner. However, because of the low strength of received primary signals, observations from some secondary users may contribute little to global decisions at the fusion center. To reduce energy consumption and sensing overhead, cooperation is recommended only with a subset of nodes receiving high-strength primary signals. This paper proposes a selection probability based cooperative spectrum sensing scheme that exploits historical observations to exclude nodes receiving low-strength primary signals. The selection probability is maintained based on local sensing information and global decisions. Simulation results demonstrate that the proposed scheme can exploit location advantages and shows almost the same detection performance as cooperative spectrum sensing with accurate node selection.