Group-based user pairing for virtual MIMO in LTE

A user pairing method is proposed to improve the throughput gain of virtual multiple input multiple output (virtual MIMO) in 3G long-term evolution (LTE).The approach taken in this study separated the user pairing into four steps 1) the users are divided into two groups according to their signal-to-noise ratio (SNR), and different user pairing metrics are proposed for each group; 2) the scheduler chooses a user for transmitting by a given rule; 3) the scheduler searches the pairing candidate for the selected user in each group; 4) the scheduler chooses the final pairing user from the co-group and crossover-group candidates by using a marginal utility function, to balance fairness and efficiency.The method can improve the throughput of users with high SNR, and guarantee fairness for users with low SNR, so it can be used in 3G LTE systems.The article provides both theoretical analysis and simulation results to support the idea.     

Cuprate Superconducting Characteristics on the Doping Scale. A Multiband Approach

Some results on the doping dependence of cuprate superconductivity characteristics by an multiband approach are presented. A nonmonotonic dependence of the critical coherence length agrees with the experiment. Periodic spatial structures of T _c , etc. are expected at underdoping by Leggett noncritical mode fluctuations. The paired carrier effective mass diminishes moderately with doping. The inverse plane penetration depth shows a dependence with a maximum dominated by the supercarrier density. For the latter, the isotope effect is predicted and calculated. It is decisive for the isotope effect in the superfluid stiffness. This work was supported by the Estonian Science Foundation Grant No. 6540.     

An Effective Interaction Approach to Anisotropic Superconductors Beyond the Weak Coupling Theory—An Origin of the d-wave Symmetry in High-T c Cuprate

We propose an effective interaction approach to superconducting systems which is adapted to periodic systems and intermediate net coupling between charge carriers by phonon mediated and Coulomb repulsive interactions. A coupling function of effective interaction is given for homogeneous field beyond the weak coupling approximation by using a generalized intermediate coupling method. Adequate kernel for the periodic systems is also reduced to that coupling function in homogeneous field and the Fourier coefficients relevant to the Bloch function. Within the present approach we discuss the symmetry of the superconducting gap in cuprate under the assumption that a nonbonding band filled by 2p_σ electrons exists in an undoped system and that doped holes occupy orbitals in this band. Those orbitals are represented by linear combinations of p _x and p _y functions. It is argued, in the tetragonal limit, that the symmetry of the gap function is d-wave-like on account of the products of orbital functions in combination of singlet spin-pair in the kernel.     

Online pairing of VoIP conversations

This paper answers the following question; given a multiplicity of evolving 1-way conversations, can a machine or an algorithm discern the conversational pairs in an online fashion, without understanding the content of the communications? Our analysis indicates that this is possible, and can be achieved just by exploiting the temporal dynamics inherent in a conversation. We also show that our findings are applicable for anonymous and encrypted conversations over VoIP networks. We achieve this by exploiting the aperiodic inter-departure time of VoIP packets, hence trivializing each VoIP stream into a binary time-series, indicating the voice activity of each stream. We propose effective techniques that progressively pair conversing parties with high accuracy and in a limited amount of time. Our findings are verified empirically on a dataset consisting of 1,000 conversations. We obtain very high pairing accuracy that reaches 97% after 5 min of voice conversations. Using a modeling approach we also demonstrate analytically that our result can be extended over an unlimited number of conversations.     

联合子载波抑制与配对的双向DF-PLNC OFDM中继

子载波抑制(SS)技术已被证明能够显著提高正交频分复用(OFDM)系统的误码率性能,因此引起了学术界的广泛关注。在双向OFDM中继网络(TWRN)中,由于两个源节点与中继之间的链路具有独立性,直接应用子载波抑制技术会造成两条链路的活跃子载波具有非对称性,从而导致大量子载波在中继节点无法实现网络编码。提出了一种联合子载波抑制与子载波配对(SP)的双向译码转发(DF)-物理层网络编码(PLNC)OFDM中继系统。该方法对中继两端链路的非对称活跃子载波进行配对,在配对的子载波上发送物理层网络编码信息。仿真结果表明,该方法显著改善了误码率性能,消除了原有的误码平台并且提高了系统的吞吐量性能。     

标准模型下2种基于身份的环签名的安全性分析

环签名是一种保护签名者隐私的密码学原语。一个安全环签名方案必须满足无条件匿名性、不可伪造性等安全属性。文章对标准模型下2种基于身份的环签名方案的安全性进行详细分析,发现它们无法满足环签名的不可伪造性要求,并给出相应的攻击方法。     

Jacobi交上的配对计算

目前已知的配对计算都是在椭圆曲线的平面模型下实现的,比如Weierstrass型曲线、Ed-wards曲线和Jacobi四次曲线。本文第一次讨论空间曲线上配对的具体计算。密码学中所关心的空间曲线主要是三维空间中的二次曲面的交,它与Edwards曲线、Jacobi四次型都有极其紧密的联系,因而研究二次曲面交上的算术与配对将促进我们对Edwards曲线、Jacobi四次曲线上的相关特性的理解。为了讨论的简洁,我们将主要分析Jacobi交,但我们的结果基本上可以类推到其他的二次曲面交上去。我们分析了Jacobi交上的几何特性,构造了Jacobi交上的有效可计算同态,并在此基础上给出了Jacobi交上配对的具体计算。     

基于视频的夜间车辆检测与跟踪

在道路交通管理中基于视频的车辆检测技术发挥了越来越重要的作用。针对夜间交通视频图像中由于照明度低和光线反射干扰导致运动目标提取困难等问题,提出一种建立矩形框来标志车辆的夜间车辆检测与跟踪的方法。通过对图像进行预处理,提取可能为车灯的亮点,建立连通区域。利用两车灯之间的水平位置,两车灯的面积应该是相近或几乎相等以及两者之间的距离应该小于设定的阈值来进行车灯配对。车灯配对成功之后,适当放大配对车灯的连线长度,得到车头宽度。进而根据车头长宽比关系得到车头区域,再通过规则集来定义多种情况下矩形框保存车辆信息的基本原则。车辆的统计跟踪通过基于邻域的方法来实现。经过实验表明,该方法能很好地适用于夜间车辆的检测,并且能满足夜间检测的要求,具备一定的稳定性和准确率。     

一种高效的基于身份的部分盲签名方案*

提出了一个新的基于身份的部分盲签名方案,证明了所提方案的完整性、部分盲性和不可伪造性,并比较了所提方案与现有方案的计算代价,比较结果显示所提方案是目前效率较高的基于身份的部分盲签名方案。     

基于双线性映射的多重签名方案

双线性映射作为一种构建密码体制的新工具,在密码学领域中引起了普遍的关注.基于双线性映射提出两种新的多重签名方案,由于多重签名方案是以双线性对为工具构造的,所以密钥长度和签名长度比用其它方法构造的签名要短,该方案的实现是高效的.在CDH和DLP问题的安全假设下,这两种方案是安全的.