A selection scheme for optimum number of cooperative secondary users in spectrum sensing

An optimization scheme for choosing the optimum number of secondary users in cooperative spectrum sensing based on the cyclostationary feature detection with Neyman-Pearson criterion is proposed in this paper. The optimal soft combination test statistic for the cooperative spectrum sensing based on cyclostationary feature detection is derived according to the generalized likelihood ratio test and its corresponding detection performance is deduced. A target function, considering two important parameters as the resource use efficiency and the number of samples employed by each cooperative secondary user in the system design, is constructed to obtain the optimum number of cooperative secondary users. It can be found that the selection scheme is to make a tradeoff between the system complexity of the cognitive radio network and the global sensing performance of the cooperative spectrum sensing.     

认知无线电带宽频谱感知性能分析及优化

为了降低认知无线电中主用户受到的干扰,根据主用户状态的变化,通过将通信带宽分为感知频带和传输频带,建立了次用户在整个帧周期内进行带宽频谱感知的模型.该模型中,次用户在每个帧使用部分带宽进行频谱感知,其余的带宽传输数据.在限制主用户受到的干扰和次用户虚警概率的基础上,通过联合优化感知带宽比和检测概率,最大化次用户的频谱效率.使用MATLAB软件仿真模型的干扰概率和频谱效率,结果表明:相比传统的时间频谱感知,当虚警概率为0.5时,带宽频谱感知能够使主用户受到干扰的概率降低30%;当干扰概率为0.2时,带宽频谱感知能够使次用户的频谱效率提高0.3 (bit/s)/Hz.      

Reputation-based collaborative spectrum sensing scheme in cognitive radio networks

Collaborative spectrum sensing is proposed to improve the detection performance in cognitive radio (CR) networks. However, most of the current collaborative sensing schemes are vulnerable to the interference of the malicious secondary users (SUs). In this paper we propose a reputation-based collaborative spectrum sensing scheme to improve the security of cooperative sensing by mitigating the impacts of misbehaviors. The fusion center calculates the reputation rating of each SU according to their history reports to weight their sensing results in the proposed scheme. We analyze and evaluate the performance of the proposed scheme and its advantages over previous schemes in expansibility and integrity. Simulation results show that the proposed scheme can minimize the harmful influence from malicious SUs.     

An improved cyclostationary feature detection based on the selection of optimal parameter in cognitive radios

Spectrum sensing is an important part of cognitive radio systems to find spectrum hole for transmission which enables cognitive radio systems coexist with the authorized radio systems without harmful interference. In this paper, an improved cyclostationary feature detection method is proposed to reduce computational complexity without loss of good performance based on the optimal parameter selection strategy for choosing detection parameters of cyclic frequency and lag. Taking binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) signals as examples, the theoretical analyses are presented for choosing the optimal parameters. Simulation results are given to certify the correctness of the proposed parameter selection strategy and show the performance of the proposed method.     

Cyclostationary property based spectrum sensing algorithms for primary detection in cognitive radio systems

To implement the primary signal without interference in cognitive radio systems, cognitive radios can detect the presence of the primary user in low SNR. Currently, energy detector is the most common way of spectrum sensing because of its low computational complexity. However, performance of the method will be possibly degraded due to the uncertainty noise. This paper illustrates the benefits of one-order and two-order cyclostationary properties of primary user’s signals in time domain. These feature detection techniques in time domain possess the advantages of simple structure and low computational complexity comparing with spectral feature detection methods. Furthermore, performance of the one-order and two-order feature detection is studied and the analytical results are given. Our analysis and numerical results show that the sensing performance of the one-order feature detection is improved significantly comparing with conventional energy detector since it is robust to noise. Meanwhile, numerical results show that the two-order feature detection technique is better than the one-order feature detection. However, this benefit comes at the cost of hardware burdens and power consumption due to the additional multiplying algorithm.     

MIMO双向中继网络的预编码设计与功控策略

为加强MIMO双向中继系统的空间复用增益,研究一种低复杂度的发送和接收预编码矩阵.利用子空间对齐方法,将双向MIMO信道分解为多路单入单出（SISO）的子信道形式,使得两个源用户能够使用网络编码获取更好的空间复用增益.同时通过矩阵计算和转化,给出了一种优化的功率分配方案.在确定优化矩阵后,该方案能够为每个子信道独立地进行优化功率分配,并且能够得到各节点间优化功率分配的闭合表达式,从而将算法复杂度从O（n3）降低为O（n）.仿真结果表明,在典型场景下,所提方案在具有更低复杂度的优势下,系统性能接近优化的梯度下降迭代方案,优于传统单纯前向放大转发方式（AF） ,有2.99 bit/（sHz）的性能增益.      

一种新的循环谱统计量频谱感知算法

为了提高认知无线电中感知用户对授权用户（主用户）的检测概率,提出一种新的基于循环谱统计量的主用户信号检测算法．该算法利用循环谱离散频域平滑方法,对信号的循环谱在循环频率处建立合理的检测统计量,然后求解得到对应不同虚警概率的判决门限,以使感知用户能检测信噪比更低的授权用户信号．该算法具有检测结构简单,易实现的特点．仿真结果表明,在高斯白噪声信道中,虚警概率为0．1,频域平滑累积次数为255,在信噪比为-16dB的条件下,与Dandawate-Giannakis（DG）方法相比,本文算法的检测概率提高23％．     

地铁中压环网供电系统可靠性评估方法

地铁中压环网供电系统起电能分配及传输作用,结构复杂且设备繁多,分析地铁中压环网供电系统可靠性具有重要意义. 本文通过分析地铁中压环网供电系统的拓扑结构和运行方式,采用分区的思想对中压环网供电系统进行区域化、模块化处理,简化复杂系统并提出系统“最小基本单元”的概念,建立系统可靠性评估通用性模型,并运用序贯Monte Carlo法计算中压环网供电系统可靠性评估指标. 通过算例分析可知,在不考虑系统设备磨损的情况下,当抽样次数为50 000次时,求得某条地铁中压环网供电系统稳态可用度为99.996%,验证了通用性模型的可行性.      

CAN现场总线运行故障调试和分析

CAN总线以其高可靠性、长传输距离和低成本而具有巨大的应用潜力。但在网络的构建过程中或现场调试时，可能影响网络安全运行的因素较多，使CAN总线的应用受到限制。章从网络拓扑，终端电阻的匹配、CAN波形的选择、抗干扰和接地保护等几个对网络安全运行和通信质量有严重影响的关键方面来阐述网络的维护和故障的分析诊断。     

基于CAN总线的船舶分油机控制系统

介绍以CAN总线为基础的船舶分油机控制系统的组成、软件结构与设计.此系统采用软PLC（KingACT）与组态软件（KingVIEW）的无缝连接,利用OPC方式采集iCAN总线模块的数据,实现了分油机控制过程的可靠性和实时性.     

基于小波变换的频谱检测算法分析

文章分析了认知无线电频谱检测中匹配滤波检测、能量检测、周期平稳过程特征检测的性能,指出了噪声对各自检测性能的影响,给出了一种基于小波变换的信号频谱检测算法,着重对含噪2FSK、2PSK信号进行分离仿真。仿真结果表明,该算法可以有效地进行信号的成分分离,降低了噪声的频谱检测的影响。     

轨道交通中异构智融车载网络发展综述

从蜂窝无线接入技术、非蜂窝无线接入技术、异构智融车载网络接入技术三方面，分析了国内外轨道交通车载网络的研究现状；针对非蜂窝无线接入技术和蜂窝无线接入技术的问题，阐述了协同利用轨道交通周边异构无线资源进行网络融合、协同通信的优越性；从网络模型、网络架构两方面论述了异构智融车载网络的融合方案；结合智能轨道交通业务需求，从可靠性和资源利用率两方面对现有的异构智融车载网络研究进行了系统性的归类梳理；从人工智能、安全性和云边结合三方面提出未来异构智融车载网络的发展趋势。研究结果表明:异构智融车载网络可靠性分为网络架构的可靠性和数据传输的可靠性，其中在网络架构可靠性方面，主要研究了通过冗余网络架构、车云传输架构、软件定义网络构架和智慧协同网络架构4种方式提升可靠性，在数据传输可靠性方面，主要研究了通过多路径传输、网络编码和切换算法降低传输过程中的丢包率；异构智融车载网络资源利用率分为无线接入的资源利用率和链路调度的资源利用率，其中在无线接入资源利用率方面，主要通过信道状态预测、频谱划分、频移补偿3种方式增加网络吞吐量，提高资源利用率，在链路调度的资源利用率方面，主要通过调度算法、接收缓存算法和拥塞控制算法来减少异构链路对数据传输的影响，降低数据重传次数，提高网络资源利用率。      

插电式纯电动汽车上下电控制策略研究与设计

针对纯电动汽车动力系统结构,定义了基于CAN通讯的整车控制网络。以整车安全性为主要参考量,研究设计了电动汽车上电控制策略和下电控制策略。基于MotoTron快速开发平台,使用Simulink/Stateflow进行策略开发,通过MotoHawk建立产品级ECU与控制策略之间的连接。结果表明:此上下电控制策略提高了纯电动汽车的系统效率和安全性,是一种合理有效的能量优化策略。     

Trade-off in optimizing energy consumption and end user quality of experience in radio access network

To reduce network access latency, network traffic volume and server load, caching capacity has been proposed as a component of evolved Node B (eNodeB) in the ratio access network (RAN). These eNodeB caches reduce transport energy consumption but lead to additional energy cost by equipping every eNodeB with caching capacity. Existing researches focus on how to minimize total energy consumption, but often ignore the trade-off between energy efficiency and end user quality of experience, which may lead to undesired network performance degradation. In this paper, for the first time, we build an energy model to formulate the problem of minimizing total energy consumption at eNodeB caches by taking a trade-off between energy efficiency and end user quality of experience. Through coordinating all the eNodeB caches in the same RAN, the proposed model can take a good balance between caching energy and transport energy consumption while also guarantee end user quality of experience. The experimental results demonstrate the effectiveness of the proposed model. Compared with the existing works, our proposal significantly reduces the energy consumption by approximately 17% while keeps superior end user quality of experience performance.     

Price-based power control algorithm in cognitive radio networks based on monotone optimization

This paper considers a price-based power control problem in the cognitive radio networks(CRNs).The primary user(PU) can admit secondary users(SUs) to access if their interference powers are all under the interference power constraint. In order to access the spectrum, the SUs need to pay for their interference power.The PU first decides the price for each SU to maximize its revenue. Then, each SU controls its transmit power to maximize its revenue based on a non-cooperative game. The interaction between the PU and the SUs is modeled as a Stackelberg game. Using the backward induction, a revenue function of the PU is expressed as a non-convex function of the transmit power of the SUs. To find the optimal price for the PU, we rewrite the revenue maximization problem of the PU as a monotone optimization by variable substitution. Based on the monotone optimization, a novel price-based power control algorithm is proposed. Simulation results show the convergence and the effectiveness of the proposed algorithm compared to the non-uniform pricing algorithm.     

基于模拟首部的FlexRay车载适配器设计

FlexRay总线以其高带宽、时间触发机制、高可靠性和灵活性的优势,在汽车控制总线中应用越来越广泛,FlexRay总线与车上传统总线CAN及LIN总线之间的信息交互成为迫切需要解决的问题.本文针对此提出一种基于模拟首部添加的适配器,用于FlexRay总线与其他总线之间信息传递,根据FlexRay总线及其他车用总线的特点,设计了专门的模拟首部格式,将模拟首部和有效数据封装在FlexRay数据帧中,以车用混合动力系统为目标,搭建了实验平台,验证了适配器的功能与传输效果.本文所述的方法降低了中间网络适配器软件处理的复杂度,同时减少了系统时延.     

基于CAN总线的综合船桥模拟实验系统的设计

综合船桥模拟实验系统将综合船桥系统硬件设备与传统的船舶操纵模拟器进行有机结合.提出一种基于CAN总线实现综合船桥导航设备互联的优化网络结构并应用于综合船桥模拟实验系统,利用该CAN总线网络能够实现各导航设备与船舶操纵模拟器之间的信息共享与交互,使得系统具有高度整合性和可靠性.从系统可靠性理论分析了该总线网络的优化方案可行性.     

基于拟不可积哈密顿理论的桥梁动力可靠度计算

为提高铁路桥梁动力可靠度计算的效率,考虑结构非线性,基于振型空间,导出了铁路桥梁动能和势能的表达式,进而根据拟Hamilton系统理论确定铁路混凝土桥梁的广义动量、广义速度、Hamilton函数及拟Hamilton系统方程.只考虑横向位移和扭转位移,导出了铁路混凝土桥梁的拟不可积Hamilton系统方程,得到条件可靠度函数应满足的后向Kolmogorov方程及其定量边界、初值条件,并用中心差分法求解该方程.以实际铁路桥梁为算例,用上述方程求解其在列车荷载作用下的动力可靠度.研究结果表明:非线性桥梁结构的动力可靠度和概率密度峰值随桥梁初始能量增大而减小,随桥梁临界能量增大而增大;不同跨度桥梁的分析结果与实际情况相符,说明基于拟不可积Hamilton系统理论计算铁路桥梁的非线性动力可靠度是可行的.      

面向路基监测的WSN分簇自适应加权融合算法

部署在铁路路基监测区域内的无线传感器网络（WSN）,由于节点能量和带宽等资源的限制,要求数据的采集、处理、传输满足低能耗、高效率和高可靠性. 本文提出面向智能监测的无线传感器网络分簇部署策略,在感兴趣的区域内部署尽量多的节点,并根据数量类型、环境特征等因素将网络以簇为单位进行划分. 以簇为单位,采用自适应加权数据融合处理技术,将采集的地温数据按照精度分别乘以权重值再进行平均值处理,有利于降低数据冗余度,提高数据准确度和采集效率. 仿真性能分析表明,该方法可以显著提高数据传输效率,降低网络能耗,延长网络生命周期.     

ATIS 环境下随机动态路网行程时间可靠性0

为评价随机动态道路网络系统在ATIS 环境下的行程时间可靠性,将出行者群 体划分为装载和未装载信息接收设备两类,并假设他们均遵循随机动态用户最优原则 (SDUO)进行动态路径选择,运用动态均衡理论建立了基于路径的混合SDUO 不动点模 型,并证明该模型至少存在一个不动点.使用离散随机变量序列描述需求的随机动态变 化,基于Monte Carlo 模拟和对角化相继平均算法(MSA),提出了ATIS 环境下随机动态路 网的行程时间可靠性评价方法.随后通过算例验证了可靠性评价方法的可行性. 数值结果 表明：OD 行程时间可靠性随出发时段动态变化,且在动态情形下,扩大ATIS 市场占有率 并不能进一步提高可靠性,反而可能会导致可靠性下降.