Detecting anomalous spectrum usage in dynamic spectrum access networks

Dynamic spectrum access has been proposed as a means to share scarce radio resources, and requires devices to follow protocols that access spectrum resources in a proper, disciplined manner. For a cognitive radio network to achieve this goal, spectrum policies and the ability to enforce them are necessary. Detection of an unauthorized (anomalous) usage is one of the critical issues in spectrum etiquette enforcement. In this paper, we present a network structure for dynamic spectrum access and formulate the anomalous usage detection problem using statistical significance testing. The detection problem investigated considers two cases, namely, the authorized (primary) transmitter is (i) mobile and (ii) fixed. We propose a detection scheme for each case by exploiting the spatial pattern of received signal energy across a network of sensors. Analytical models are formulated when the distribution of the energy measurements is given and, due to the intractability of the general problem, we present an algorithm using machine learning techniques to solve the general case when the statistics of the energy measurements are unknown. Our simulation results show that our approaches can effectively detect unauthorized spectrum usage with a detection probability above 0.9 while keeping the false alarm rate less than 0.1 when only one unauthorized radio is present, and the detection probability is even higher for more unauthorized radios.     

Molecular-based concepts in PV towards full spectrum utilization

Molecular-based concepts offer the potential of low materials and processing costs in photovoltaics (PV), which is especially interesting if high efficiencies can be obtained. To accomplish high efficiencies, a better utilization of the solar spectrum is of high importance. The concept of two-photon absorption in dye-sensitized solar cells and full spectrum aspects of luminescent flat plates concentrators are discussed in this paper. The two-photon dye cell can be compared to a tandem solar cell on the molecular level. The luminescent concentrator offers the potential to employ full spectrum utilization in combination with static concentration of both direct and diffuse light.     

Dynamic spectrum access — concepts and future architectures

New trends and developments in radio technology are enhancing the future capabilities of devices to access electromagnetic spectrum using the full range of dimensions associated with the spectrum. This increased capability, together with current developments towards liberalisation of spectrum management regulations, are opening up opportunities to exploit an emerging paradigm in wireless communications and networking known as dynamic spectrum access (DSA). The key characteristic of DSA networks is their ability to exploit knowledge of their electromagnetic environment to adapt their operation and access to spectrum. Their key promise is that they open the possibility of highly efficient (re)use of spectrum. This paper introduces the main concepts behind DSA, reviews the proposed architectures for future DSA systems, and outlines some of the key research challenges associated with this new paradigm. Particular emphasis will be given to autonomous cognitive radio DSA.     

新型的使用访问控制模型

对传统访问控制模型进行了扩展，提出了一种新的访问控制模型——使用控制模型UCON(usage control)。这种模型包含授权、证书和条件组成成分，能解决作为访问结果而对主体客体属性进行更新的问题，以及在访问过程中对访问权限延续和即时回收的问题。同时对该模型的核心模型进行了形式化描述和定义。     

New concepts in early failure modelling

The problem of early failure modelling has been discussed comprehensively. Present models have been discussed and new models are suggested. A drawback of failure rate not being finite at t = 0 for some of the present models is eliminated in the suggested models.     

Optimum number of secondary users in collaborative spectrum sensing considering resources usage efficiency

The optimum number of secondary users in collaborative spectrum sensing is derived for lognormal shadowing channels, static additive white Gaussian noise channels and Rayleigh fading channels, when the efficiency of resources usage is considered in the system design. By weighting the detection performance and the usage efficiency in a target function that is maximized with respect to the number of secondary users, it is shown that the optimum number of secondary users decreases when the weighting coefficient of the usage efficiency increases, the sample correlation increases, or the SNR increases.     

无线电频谱利用面临的问题、机遇与对策

针对日益严重的无线电频谱资源利用问题,重新审视了频谱概念和频谱稀缺性问题.分析表明,只要采用合适的频谱管理策略和高效频谱利用技术,频谱资源可以满足无线电业务高速增长的需求.结束频谱资源紧缺局面的根本途径是开发高效频谱利用技术,而多无线电系统动态频谱分配与共享技术最具潜力.同时,无线电频谱政策必须作相应的调整,使之适应技术发展和市场业务需求,充分发挥高效频谱利用技术的潜力.通过对多无线电系统动态频谱分配与共享技术的分析,结合国际频谱政策变化特点和改革实践,给出了我国频谱政策改革的几点建议.     

New media adoption and usage among Flemish youngsters

This article presents a study on the adoption and usage of new media among a representative sample of Flemish youngsters. Some major findings include the dominant role of computers and Internet in the media behavior of these youngsters, challenging traditional media such as TV and radio. However, the supposed popularity of mobile applications and gaming among youngsters was not universally present in our sample, which led us to look for different profiles within the data. Based on the adoption of new media technology and devices, the studied sample could be divided into four distinct profiles by means of a latent class analysis.     

New antimultipath technique for spread spectrum receivers

The adaptive RAKE filter can be used in spread spectrum systems to combine the separate signal energies received due to multipath propagation effects. However, shorter length coding schemes are often subject to significant autocorrelation sidelobes, which when incorporated into the RAKE scheme cause further interference. A new approach to combining these signal energies is made possible using the adaptive multipath cancellation receiver and the improved RAKE filter is shown to avoid the sidelobe interference experienced with nonideal autocorrelation functions.<>     

New concepts of worst-case delay and yield estimation in asynchronous VLSI circuits

Estimation of asynchronous circuit performances, such as speed, is one of the major reasons that still keeps that design style undeservedly unpopular. A simple logic simulator would be very useful in overcoming this problem if it is used for evaluating the worst-case delays in the paths of an asynchronous circuit using. In this paper a method for timing analysis of the asynchronous circuits using a VHDL simulator is presented. It is capable to deal with both non-sequential and sequential asynchronous circuit. An appropriate extension of the standard logic simulation process enables all worst-case delays for all paths in a digital circuit to be obtained with only one run of the simulation. High levels of accuracy are achieved using extensive gate modelling while statistical analysis of the results was also used to evaluate part of the parametric yield loss related to the delay. Due to the lack of asynchronous benchmark circuits, the method is verified on a set of asynchronous circuit selected by the authors.     

European view of automated VHF/UHF radio systems—Marine spectrum usage alternatives and trends

The current situation for VHF/UHF marine communications in Europe is outlined, and the expectations for increased automation of that service are presented within the framework of the historical and regional factors which have shaped the current system. The degree of automation now employed, types and number of channels available, and services provided, are described for the different regions of Europe, and in specific instances, compared to U.S. practices. Estimates are given for the additional radio spectrum required to support automated service through the turn of the century. The radio bands which offer the best prospects for support of this growth are discussed in terms of their relative availability and advantages for the marine user.     

New assignments in the submillimeter emission spectrum of the stratosphere

New line assignments in the spectrum of the stratospheric submillimeter emission, measured with unapodized resolution of 0.0033 cm^?1, have been made. Positive evidence for the presence of symmetric and asymmetric ozone isotopes, water vapour excited to the (010) level, and HCN is given.     

New coalition formation game for spectrum sharing in cognitive radio networks

In cognitive radio networks, Secondary Users (SUs) can access the spectrum simultaneously with the Primary Users (PUs) in underlay mode. In this case, interference caused to the licensed users has to be effectively controlled. The SUs have to make spectrum access decisions in order to enhance their quality of service, but without causing harmful interference to the coexisting PUs. In this paper, we propose a cooperative spectrum decision, which enables the SUs to share the spectrum with the PUs more efficiently. Our approach is based on a new coalitional game in which the coalition value is a function of the SUs' spectral efficiencies, the inter‐SUs interference, and the interference caused to the PUs. By applying new Enter and Leave rules, we obtain a stable coalition structure. Simulation results show that the SUs' spectral efficiencies are considerably increased and that the interference caused to the coexisting PU is reduced by about 7.5% as compared to an opportunistic spectrum access scheme. Moreover, the proposed coalitional game results in a more balanced spectrum sharing in the network. Copyright © 2014 John Wiley & Sons, Ltd.     

基于信任簇的协作压缩频谱感知新算法

频谱感知是实施认知无线电CR的关键问题。一些恶意用户篡改数据,降低了频谱感知性能。为此,提出面向恶意用户环境的基于信任簇的压缩频谱感知TCCSS算法。先利用最大似然ML估计簇离主级用户的距离,并与预设的门限值比较,寻找到信任簇。然后,依据信任簇提供的信息,使用压缩频谱感知算法对信道状态进行检测。仿真结果表明,提出的TCCSS算法能够有效地应对恶意用户的环境,准确地检测恶意用户,同时保持高的频谱检测率。     

New family of bipolar sequences and its correlation spectrum

Based on a class of bipolar sequences with two-values autocorrelation functions, a new family of bipolar sequences is constructed and its correlation spectrum is calculated. It is shown that the new family is optimal with respect to Welch‘s bound and is different from the small set of Kasami sequences, while both of them have the same correlation properties.     

分子谱线参数测量新方法

介绍了一种利用F-P腔透射峰宽度测量分子谱线参数的新方法,论文从多光束干涉叠加原理出发,推导出有样品气体吸收的F-P腔的透过率函数,F-P腔的透过率是样品气体吸收线型的函数,随着样品吸收的增加,F-P腔透射条纹宽度增加.实验测量得到的谱线强度与HITRAN2004数据库数据、谱线宽度与理论计算结果很好地一致.     

新的二维谱估计方法——参数加权法

提出了一种新的二维MUSIC方法。由于同时利用了矩阵的特征值和特征向量,其搜索(或求根)过程由2个一维过程组成,避开了二维谱峰搜索且无需配对。通过分析,证明该方法不存在兼并问题,阵元利用率较高。理论分析和仿真结果表明算法的有效性。     

新型电光逻辑门的设计及计算机图形光谱

光逻辑门是未来全光网络中光信息处理的核心元件,它可以实现高速光包交换,全光地址识别,数据编码,奇偶校验,信号再生等功能。采用微环谐振器设计了一种新型的电光逻辑门,结构通过三个非对称微环组成,分析耦合区的传输矩阵方程得出加载电压信号的变化能够实现微环折射率的变化,利用光强的逻辑开关特性可以实现光门逻辑。计算机仿真验证了工作波长1 600 nm时,实现的高电平50.7 V定义为逻辑1,低电平0 V定义为逻辑0,通过光强变化得出了6位逻辑运算;整个系统的响应时间理论上得到了1.8 ps,运算速率可达近200 Gbit/s。逻辑的双稳态分析中得出:微环发生最大谐振值时对应的控制波长等于微环未发生形变前的谐振波长和偏移量之和;调制可以通过微环谐振波长实现控制。这一研究对于未来全光通信的实现具有一定的意义。