软判决协作频谱感知的最优判决门限(英文)

为了获得认知无线电系统更高的频谱利用效率,基于最小总错误概率准则推导了软判决协作频谱感知最优判决门限的闭合表达式,并且分析了各种频谱感知参数对最优判决门限的影响.理论分析表明,所提出的最优门限可以获得虚警概率和漏检概率2种性能指标的折中.从仿真结果可以看出,平均信噪比和软判决方案对最优判决门限影响较大,而样本数量对最优的判决门限几乎无影响.对于MRC和MDC两种软判决方案,随着协作用户数量的增加,最优判决门限值随之增加并且趋近于某一极限值.而对于EGC软判决方案,协作用户数对其最优门限值影响很小.     

基于LUC密码体制的分类多秘密共享方案

提出一种基于LUC公钥体制的分类多秘密共享方案,该方案使用各用户的私钥作为各自的秘密份额,秘密分发者不需要进行秘密份额的分配,整个系统不需要维护安全的信道,每个子组共享一个秘密,全体参与者共享一个总秘密,所有类型的秘密之和构成核心秘密,该方案能够有效地保管多个秘密,并且实现了对多个秘密的分类管理,其安全性是基于LUC密码体制与Sham ir门限秘密方案的安全性.     

Reputation-based linear cooperation for spectrum sensing in cognitive radio networks

We propose a reputation-based cooperative spectrum sensing scheme in cognitive radio （CR） networks to solve the uncertainty resulting from the multipath fading and shadowing effect. In the proposed scheme, each cooperative CR user has a reputation degree that is initialized and adjusted by the central controller, and used to weight the sensing result from the corre- sponding CR user in the linear fusion process at the central controller. A simple method for adjusting the reputation degree of CR users is also presented. We analyzed and evaluated the detection performance of the reputation-based cooperative spectrum sensing scheme. Simulation results showed that our proposed scheme alleviates the problem of corrupted detection resulting from destructive channel conditions between the primary transmitter and the CR user. The performance of our proposed scheme was improved compared to the average-based linear cooperation scheme, and was similar to that of the optimal linear cooperation scheme with feasible computational complexity. Moreover, our proposed scheme does not require knowledge of channel statistics.     

SFBC-OFDM系统中基于自适应训练机制的迭代接收机

研究了在空频块码正交频分复用(SFBC-OFDM)无线通信系统中适用于多径衰落信道下的迭代接收机的设计,导出了一种迭代的联合信道估计与符号检测的算法.在提出的算法中,信道估计器交替地工作于2种模式.在训练阶段,采用基于DFT的估计器估计出信道状态信息,并且采用所提出的算法估计出噪声方差和信道响应的互相关矩阵.在数据传输模式下,迭代地获得发送数据和信道状态信息.为了抑制由于符号检测中误判引起的错误传播,提出了一种简单的错误传播判定准则,并使用了一种自适应的训练机制来抑制误差传播.仿真结果显示,与传统的迭代算法相比,所提出的算法能够提供更好的误码性能,且节约了系统开销.     

一种新的无线视频传输帧内刷新策略

首先分析了无线信道突发性出错和二阶Markov无线信道模型. 根据该模型和视频编码器的编码方式推导了突发性出错引起的帧内编码和帧间编码的信道失真. 然后提出了一种新的速率失真率(R-D)框架内的帧内刷新策略. 该策略一方面对无线视频传输系统的容错性能和编码效率进行了优化, 另一方面可有效阻止帧间错误传播, 减小信道失真. 在不同传输信道中的仿真结果验证了该策略在无线视频传输容错方面的性能改进.     

Energy-efficient distributed lifetime optimizing scheme for wireless sensor networks

In this paper, a sensing model for the coverage analysis of wireless sensor networks is provided. Using this model and Monte Carlo method, the ratio of private range to sensing range required to obtain the desired coverage can be derived considering the scale of deployment area and the number of sensor nodes. Base on the coverage analysis, an energy-efficient distributed node scheduling scheme is proposed to prolong the network lifetime while maintaining the desired sensing coverage, which does not need the geographic or neighbor information of nodes. The proposed scheme can also handle uneven distribution, and it is robust against node failures. Theoretical and simulation results demonstrate its efficiency and usefulness.     

Non-interactive identity-based threshold signature scheme without random oracles

A （t, n） threshold signature scheme distributes the secret key and hence the signing ability to n players in a way that any set of t＋ 1 or more honest players can collaborate to sign, while any set of t players cannot. In this paper we propose an identity-based threshold signature （IBTHS） scheme from bilinear pairings. The signing phase of our scheme is non-interactive, meaning that the signing players do not need to talk to each other. We prove our scheme secure （i.e., unforgeable and robust） in the standard model （i.e., without random oracles）. No earlier proposed IBTHS scheme achieved even one of the features of being non-interactive （in the signing phase） and secure in the standard model.     

Compressed sensing-based multiuser cooperative networks

To avoid interference, compressed sensing is introduced into multiuser cooperative network. A cooperative compressed sensing and amplify-and-forward(CCS-AF)scheme is proposed, and it is proved that the channel capacity increases compared with the traditional cooperative scheme by considering the CCS-AF transmission matrix as the measurement matrix. Moreover, a new power allocation algorithm among the relays is proposed to improve the channel capacity. Numerical results validate the effectiveness of the proposed scheme.     

基于图像处理的工件检测

研究了基于图像处理的工件轮廓检测技术的流程及算法,通过图像滤波、图像增强、阈值分割、边缘检测、边缘定位和参数测量及拟合等一系列算法,可以测出被检测工件是否符合要求及其误差范围。     

应用于无线传感网频率合成器的0.5V低电压鉴频鉴相器设计

基于0.13μm CMOS技术设计了一个应用于无线传感网频率合成器、电源电压为0.5 V的鉴频鉴相器.它的功能是比较输入信号的频率和相位差,并输出一个与该差值成比例的电压.因电源电压是0.5 V,所以该电路采用低阈值晶体管.为了增大相位误差的检测范围和提高最大工作频率,该电路采用了脉冲锁存的结构.当输入信号频率为2 M...     

一种基于椭圆曲线的物联网双向身份认证协议

身份认证是物联网安全可信的第一道防线,是保障感知网络稳定运行的基石。基于感知节点的安全性需求及有限的计算能力,提出一种基于椭圆曲线的双向身份认证协议。该方案能够认证通信感知节点双方身份的真实性,加解密所需密钥信息量少,且不存在密钥协商问题。为解决认证延迟和能量消耗问题,实现簇头节点对同一群组内感知节点的批身份认证,对可疑节点基于二分搜索技术实现身份追踪,快速定位可疑节点位置,及时甄别不可信节点。安全性分析表明,该机制具有正确性、匿名性、不可抵抗性,可有效阻止恶意节点窃取及篡改感知数据。     

论言语交际容错机制对网络文字交流的调控

网络文字交流中存在编码语义所指错误而解码无误的现象,是因为编码错误在解码者的容错阈之内,是言语交际的容错机制在起调控作用.解码者调动容错机制为编码错误纠错的频率,取决于两个方面,一是解码者自身的容错阈大小,二是编码者在解码者心目中的语言文字素养高低.网络文字交流中的“编码拟误”现象,是具有一定的语用价值的修辞现象.这类“编码拟误”的语言形式能否流行开来,成为网络上约定俗成的“网络语言”,取决于能否被纳入大多数人的容错阈.     

已知签名者的指定验证者门限代理签名方案

将指定验证者的签名引入到门限代理签名方案中,综合了两种方案的优点,基于离散对数,构造了一个已知签名者的指定验证者门限代理签名方案．该方案可以有效地限制代理终止时间与代理消息的范围,指定验证者可以确定代理签名群中实际签名者的身份,验证签名时,无须传送验证参数,节省了通信成本．     

A new solution to wireless sensor network density control problem

1 Introduction a At present, the research work on wireless sensor networks is based on the assumption that the energy of a sensor node is provided by the battery and can not be regenerated. The lifetime of the node is limited and ephemeral. Hence research…     

An adaptive joint source and channel coding scheme for H.264 video multicasting over wireless LAN

INTRODUCTION Video multicasting over wireless local area net- work (WLAN) (IEEE Standard 802.11, 1997) enables the distribution of live or pre-recorded programs to many receivers efficiently. An example application is to redistribute TV programs or location-specific in- formation in hot spots such as airport. Users can watch their favorite TV programs on mobile devices while browsing the Internet. For enterprise applica- tions, an example is multicasting video of a lecture or trainin…     

无线802.11网络中自适应调整载波侦听阈值算法研究

近年来,随着基于802.11协议的无线网络的广泛的应用,提高网络的吞吐率,成为亟待解决的问题。现有的算法以提高空间重用为目的,调整载波侦听阈值和速率或发送功率和速率。这些算法在一定程度上提高了网络总的吞吐率,但也都存在一定的弊端。     

基于包含度理论的双阈值视频镜头边界检测算法

在视频镜头边界检测中,由于人眼视觉具备的主观性和视频帧图像结构与边界的不确定性,比较适合采用模糊理论,本文基于模糊集中的包含度理论提出双阈值化的视频镜头边界检测方法：首先基于包含度公式定义视频镜头边界检测函数,然后利用包含度理论提出视频边界镜头渐变和突变的通用检测算法,最后提出双阈值优化选取办法,实验结果表明本文方法具有较好的检测渐变和突变镜头能力。     

言语交际容错阈与语言文字规范化

言语交际中存在编码语义所指错误而解码无误的现象,是因为编码错误在容错阈之内;容错阈的大小既与解码者的语言素质高与低有关,也与编码错误的显与隐、广与狭有关;当一种编码错误非常广泛,已进入"全民容错阈"时,应该就是被语言文字规范化"容错"的对象。     

在线/离线门限短签名

对在线/离线签名方案进行研究,提出一种新的基于身份(id-based)的在线/离线短签名方案,并且把它用在在线/离线门限签名上.该签名的有效性在于产生的签名长度非常短,适合于在网络上快速传输。     

OFDM系统改进的迭代联合信道估计与符号检测算法

在正交频分复用 (OFDM)无线通信系统中 ,系统的吞吐量和数据速率受到导频因素的制约 ,这种情况在高速移动环境下尤为明显 .本文提出了一种改进的迭代联合信道估计与符号检测算法 ,以提高系统的吞吐量和数据速率 .首先降低导频功率来提高系统的吞吐量 ,然后在一个OFDM符号内 ,通过迭代进行的信道估计与符号检测来提高系统的误码率 .每个OFDM符号的初始信道估计值取自上一个OFDM符号的信道估计 ,从而该算法能有效地跟踪衰落信道的变化 ,因此导频的数目可以大大降低 .仿真结果显示 ,与传统的迭代算法相比 ,本文提出的算法能提供更好的误码性能 .