Dynamic Update Scheme of Spectrum Information Based on Spectrum Opportunity Incentive in the Database-Assisted Dynamic Spectrum Management

To solve the problem of delayed update of spectrum information(SI) in the database assisted dynamic spectrum management(DB-DSM), this paper studies a novel dynamic update scheme of SI in DB-DSM. Firstly, a dynamic update mechanism of SI based on spectrum opportunity incentive is established, in which spectrum users are encouraged to actively assist the database to update SI in real time. Secondly, the information update contribution(IUC) of spectrum opportunity is defined to describe the cost of accessing spectrum opportunity for heterogeneous spectrum users, and the profit of SI update obtained by the database from spectrum allocation. The process that the database determines the IUC of spectrum opportunity and spectrum user selects spectrum opportunity is mapped to a Hotelling model. Thirdly, the process of determining the IUC of spectrum opportunities is further modelled as a Stackelberg game by establishing multiple virtual spectrum resource providers(VSRPs) in the database. It is proved that there is a Nash Equilibrium in the game of determining the IUC of spectrum opportunities by VSRPs. Finally, an algorithm of determining the IUC based on a genetic algorithm is designed to achieve the optimal IUC. The-oretical analysis and simulation results show that the proposed method can quickly find the optimal solution of the IUC, and ensure that the spectrum resource provider can obtain the optimal profit of SI update.

Age of Information for Short-Packet Covert Communication with Time Modulated Retrodirective Array

In this paper,the covert age of information(CAoI),which characterizes the timeliness and covertness performance of communication,is first investigated in the short-packet covert communication with time modulated retrodirective array(TMRDA).Specifically,the TMRDA is designed to maximize the antenna gain in the target direction while the side lobe is sufficiently suppressed.On this basis,the covertness constraint and CAoI are derived in closed form.To facilitate the covert transmission design,the transmit power and block-length are jointly optimized to minimize the CAoI,which demonstrates the trade-off between covertness and timelessness.Our results illustrate that there exists an optimal block-length that yields the minimum CAoI,and the presented optimization results can achieve enhanced performance compared with the fixed block-length case.Additionally,we observe that smaller beam pointing error at Bob leads to improvements in CAoI.

认知物联网短包通信中双向中继系统的信息年龄分析

未来认知物联网(IoT)将存在大量用于监控的时间敏感类短包信息。针对认知物联网短包通信场景,该文分析了认知次用户对在双向中继短包通信系统中的信息新鲜度。该文采用信息年龄(AoI)作为衡量信息新鲜度的性能指标。根据短包通信理论,该文推导出系统的误包率和平均峰值AoI(PAoI)表达式,并得出了系统在高信噪比情况下的表达式。在此基础上,考虑认知物联网短包通信中频谱检测性能的非理想,采用交替迭代优化算法对感知包长和传输包长进行联合优化以最小化PAoI加权和。仿真结果验证了理论分析的正确性。该研究发现,对于双向中继系统次用户对的PAoI加权和,感知包长和传输包长存在折中关系,该文所采用的交替迭代优化算法能够有效提升系统PAoI性能。

计及柔性直流装置的交直流配电网保护控制研究

交直流混合配电网可更好地接纳分布式电源和直流负荷,缓解城市电网站点走廊有限与负荷密度高的矛盾,已成为现代城市配电网的一个重要发展趋势。接入柔性环网控制装置后,配网由单端电源供电网络变为多端电源供电网络,其可靠性面临新的挑战。通过对交直流混合配电系统的故障特点进行总结,分析接入柔性直流控制装置后柔直侧及系统侧的保护影响,提出基于时序配合的智能装置协同控制架构。利用柔性电力电子器件的快速响应特性,设计柔性直流控制装置与交流保护控制装置配合的保护控制策略。在GOOSE有向节点及快速通信机制的作用下,运用保护控制协同策略进行故障定位及隔离,有效地增强了含柔性互联装置的交直流混合配电网可靠性,具有工程实用价值。

适用于配电物联网的低压智能终端自适应接入方法

配电物联网是泛在电力物联网的重要组成部分,打造配电物联网生态系统是提高配电网运行效率、优化企业经营绩效、实现发展成果共享的一项重要举措。针对未来配电物联网面临海量低压智能终端的接入导致安装调试运维工作量增加的问题,文中首先提出借鉴物联网模型、IEC61850以及IEC 61968等标准,建立一套适用于配电物联网的模型体系,并应用以消息队列遥测传输(MQTT)协议和受限应用协议(CoAP)为代表的物联网通信协议,促使设备之间的通信标准化,实现终端数据模型高效传输。接着,从低压智能终端首次接入、功能升级以及因故退出等3个方面论述了自适应接入实现流程。最后,通过实验测试并结合工程应用,验证了文中所提方法的有效性。

面向泛在电力物联网的边缘节点感知自适应数据处理方法

泛在电力物联网(UEP-IoT)背景下,采用数据中心集中处理的传统云计算运行方式难以适应急剧扩大的数据规模,且存在对电力数据中心计算能力要求较高的缺点。针对上述问题,在构建基于边缘计算的泛在电力物联网数据处理架构的基础上,提出一种新的感知自适应数据处理方法。首先,通过设计基于计数bloom滤波器的边缘节点数据类型自适应感知机制,从而自动识别泛在电力物联网数据类别与对应字段。其次,设计了一种包含了通用可移植的文件尾(EOF)识别插件以及数据副本管理系统的边缘节点感知自适应处理方法,最终实现了泛在电力物联网数据的有效收集。仿真结果表明,对于相同的数据集,所提方法对辨识数据类别的正确率提升了1.3%以上;与传统数据副本管理方法相比,所提就地管理与集群管理相结合的副本管理方法对数据集的处理平均时间下降了33.33%,表明所提方法能够有效提升对海量UEP-Io T数据的处理性能。

基于分布智能控制的供电恢复方案研究

分布式馈线自动化(FA)系统关于故障定位与隔离方面的研究日趋成熟,而在供电恢复方面略显不足。为了进一步提升分布式FA系统的供电恢复能力,解决因故障点位置不同而导致供电恢复困难的问题,提出了一种可用于多联络、多分支配电网的供电恢复方案,通过建立负荷评估模型和待恢复区拓扑模型,由代理终端负责通过单联络开关、单联络开关切负荷完成供电恢复的工作,实现了非故障区域的供电恢复,并通过实时数字仿真仪(RTDS)验证了控制策略及其算法的有效性。

认知无线电非正交多址接入随机网络物理层安全性能分析

该文针对干扰源以及窃听节点均随机分布的通信场景,分析了认知无线电启发式非正交多址接入(CRNOMA)网络中次用户通信对的安全通信性能。采用随机几何理论,将窃听节点和干扰节点建模为服从特定分布的齐次泊松点过程(PPP)。首先,在保证主用户通信对通信可靠性的前提下,得到了发端设定的功率分配系数,进一步得到了次用户通信对的连接中断概率和安全中断概率的闭式表达式。随后,得到了功率分配系数随主用户可靠性能约束的变化规律。最后,研究了次用户对的中断概率随着窃听节点密度、发端发送功率的变化情况,结果表明干扰信号的增强在降低网络可靠性能的同时,换来了安全性能的提高。仿真结果验证了理论分析的正确性。

配电网络模型二次校核方法

随着用户对配电网供电可靠性的要求越来越高,传统故障处理模式已无法满足用户需求,以智能分布式馈线自动化为代表的新技术逐渐兴起。为了解决智能分布式馈线自动化系统与主站之间存在拓扑不统一、不准确的问题,文中提出拓扑模型的二次校核方案,通过分析拓扑类型、拓扑变更原因和拓扑更新方式,论述了拓扑校核的必要性,介绍了一次校核对象、方案及其缺陷。在此基础上,搭建二次校核的总体框架,设计灵活的校核模式并提供相应的算法,开发出具备二次校核功能的校核系统,以辅助模型维护人员的校核工作。

多缓存容量场景下的D2D内容缓存布设优化方案

在终端直传(D2D)缓存网络中,用户有限且各异的缓存能力是制约缓存效率的一个关键参数,然而现有文献大多考虑不同用户具有相同的缓存能力,针对这一不足有必要进行用户具有不同缓存容量下的D2D内容缓存布设方案优化。首先,鉴于用户终端的移动性和随机分布特性,利用随机几何理论将网络中不同缓存容量的用户节点建模为相互独立的齐次泊松点过程;其次,考虑本地卸载和邻近D2D链路卸载两种内容卸载方式,推导得到网络缓存命中率;最后,将最大化缓存命中率作为优化目标函数,提出了基于坐标梯度的联合缓存布设(JCP)算法,从而得到多用户多缓存容量场景下的内容缓存布设方案。仿真结果表明,与现有的缓存布设方案相比,由JCP得到的缓存布设方案可以有效提高缓存命中率。

低压配电台区拓扑辨识及校核方法

为了提升低压配电区域的自动化水平,解决当前配电自动化主站系统中关于低压配电台区拓扑关系不完整和连通混乱等问题,提出一种关于低压配电台区拓扑辨识及其校核方法,通过采用相电压过零点调制法,自动识别低压配电台区拓扑模型,由智能配变终端将该模型上传至主站,并与由地理信息系统(geographic information system, GIS)或者生产管理系统(production management system, PMS)导入主站内部的模型进行校核,以提升模型的准确性。经过现场测试,验证了所提方法的可行性。

基于小波-树突状网络的配电网单相接地故障辨识方法

单相接地故障是智能配电网中最为常见的一种故障,但当接地过渡电阻较高时单相接地故障稳态特征不明显,难以与正常扰动进行区分,故障辨识的准确率受到较大影响。针对上述情况,文章采用小波分析法对故障信号进行三级分解,得到不同的高频成分,构建特征向量,并采用树突状神经网络对故障特征向量进行分类和识别。在MATLAB/Simulink中建立仿真模型,测试结果表明,运用该方法能够对单相接地高阻故障和正常扰动进行准确快速分类,其收敛速度和分类准确率均优于一般的智能算法。同时在信号存在噪声的情况下,该方法仍然具有较高的准确率。

A COLLABORATIVE SPECTRUM SENSING SCHEME USING FUZZY COMPREHENSIVE EVALUATION IN COGNITIVE RADIO

Cognitive Radio(CR) is a promising technology to solve the challenging spectrum scarcity problem.However, to implement CR, spectrum sensing is the groundwork and the precondition.In this paper, a collaborative spectrum sensing scheme using fuzzy comprehensive evaluation is proposed.The final sensing decision of the proposed scheme is based on the combination of distributed sensing results of different Secondary Users(SUs).To improve the reliability of the sensing decision, the combination procedure takes into account the credibility of each SU, which is evaluated using fuzzy comprehensive evaluation.The effect of the presence of malicious SUs and malfunctioning SUs on the performance of the proposed scheme is also investigated.The efficiency of the scheme is validated through analysis and simulation.

CRAM(?)R-RAO BOUND FOR BLIND CHANNEL ESTIMATION IN COMPLEX-VALUED CHANNEL

Compared with the traditional channel estimation methods, blind channel estimation methods can increase the bandwidth efficiency of the systems, but their precision is low and they converge slowly. In this paper, the Cramér-Rao Bound （CRB） for blind channel estimation in complex-valued Single-Input Multiple- Output （SIMO） channel is derived. In the simulations, the correctness of the CRB is validated and some channel estimation methods are evaluated by using the CRB.

Nakagami-m信道的TSR非可信中继网络安全性能分析

针对中继可能窃听转发的私密信号,研究了Nakagami-m信道中时间切换中继协议的非可信中继网络安全传输性能,该网络中源节点与目的节点均配置了多根天线,而能量受限的非可信中继仅有一根天线。为分析网络的安全传输,考虑了两种安全传输方案,即发送天线选择/最大比合并方案和最大比传输/最大比合并方案。为研究非可信中继网络的安全性和可靠性,依次推导出两种方案安全中断概率、连接中断概率、安全吞吐量的闭式表达式,并分析了高信噪比下安全吞吐量的渐进性能。利用蒙特卡洛仿真验证了理论分析的正确性,仿真结果揭示了信噪比、发送功率分配因子、时间切换系数、天线数对安全吞吐量的影响。

Impacts of feedback delay and estimation error on secrecy performance of MISO single eavesdropper cognitive radio networks

Due to the broadcast nature of wireless transmission medium,security threats may hinder propagation of cognitive radio systems for commercial and military data application. This paper sets a channel error analytical framework and studies the joint impact of estimation errors and feedback delay on secrecy performance in cognitive radio networks. Under the assumption that system applies beamforming and jamming scheme,a multi-antenna cognitive base station( CBS) sends confidential signals to a secondary user( SU) in the presence of M primary users( PUs) and an eavesdropper. Assuming only imperfect channel state information( CSI) about the receivers is available,secrecy rate,outage probability,secrecy throughput are deduced to obtain a closed-form expression. It is shown that while the transmit power increases,secrecy throughput would reach to a constant. Simulation results show that feedback delay adversely impacts on secrecy rate,connection outage probability and secrecy throughput,while estimation error causes more impact on secrecy outage probability. Furthermore,the secrecy rate could increase progressively with the transmit power only if there exists no feedback delay.

端到端通信中基于时间转换能量采集的计算迁移方案

在端到端(D2D)通信网络中,为提高移动云计算的有效性,提出了一种基于时间转换能量采集的计算迁移方案。首先,一个流量受限的智能移动终端把其需要迁移的计算任务通过D2D通信以射频信号的形式发送给一个能量受限的智能移动终端,后者利用时间转换方案对接收信号进行能量采集。然后,能量受限终端会为流量受限终端中继任务到云端服务器付出额外的流量消耗。最后,所提的方案被建模为一个最小化终端能量与流量消耗的非凸优化问题,通过优化能量受限终端的时间转换因子、采集能量分配因子以及流量受限终端的传输功率,最终获得了最优方案。仿真结果表明,相比于非协作方案,所提方案通过互惠协作进行计算迁移能有效地减少终端的匮乏资源开销。

Outage performance of OFDM-based selective decode-and-forward cooperative networks over Weibull fading channels

The outage performance of OFDM-based decode-and-forward cooperative networks is studied. The channels are modeled as independent Weibull distributed coefficients. A closed-form expression for the outage probability is obtained for three selective relaying schemes in the Weibull fading channels and a derived optimum power allocation method based on the closed form expressions of outage probability debases the outage probability. Monte Carlo simulations verify the analytical results.

Performance analysis and code recognition for dual N-ary orthogonal hybrid modulation systems

A dual N-ary orthogonal hybrid modulation system is introduced in this paper, which can increase the data rate greatly compared with conventional N-ary orthogonal spread spectrum system, so it can be used for high rate data communication. Then, three code recognition algorithms are presented for dual N-ary orthogonal hybrid modulation system and the analytic bit error rate （BER） performance of the system in additive white Gaussian noise （AWGN） and fiat Rayleigh fading channel is derived. Finally, the computer simulation of the system with three code recognition algorithms is performed, which shows that the simplified maximum a posteriori （MAP） algorithm is the best for the system with a compromise between the performance and the complexity.

Saturation throughput analysis of the cooperative MAC with opportunistic Relaying for Ad Hoc Networks

In this paper, the system saturation throughput of the cooperative MAC with opportunistic relaying for ad hoc networks is evaluated by exploiting the proposed analytical model based on the Markov chain model of DCF. Both of the cooperative scheme and opportunistic relaying are considered into the analytical model. Simulations are also performed to validate the proposed analytical model. Simulation results show that the cooperative MAC with opportunistic relaying can significantly improve the system performance. Furthermore, we also reveal the impact of the opportunistic relaying on the performance from the MAC layer perspectives.