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.     

基于身份的安全组播密钥协商

如何有效地进行密钥管理是安全组播的难点。在Wang等人所做工作的基础上，提出了一个新的基于身份的密钥协商方案，分析了子组之间的通信过程，以及组成员动态变化时密钥的更新过程，结果表明该方案满足密钥协商安全性要求，且在降低计算和通信代价方面取得了较好的效果。     

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.     

可公开验证的高效聚合签密方案

聚合签名能够把多个不同用户对不同消息所产生的不同签名聚合成一个签名,大幅度地提高验证的效率.聚合签密不仅能实现聚合,同时还提供机密性与认证性.本文利用双线性对构造了一个新的基于身份的聚合签密方案,并基于BDH和CDH问题,证明了方案的机密性和不可伪造性.此外,方案还满足可公开验证性,与同类方案相比具有更高的安全性,且运算量更小,效率更高.     

高效安全的无证书混合签密方案

对两种新提出的无证书混合签密方案进行密码学分析,指出它们各自存在的正确性和安全性缺陷,进而提出一种更加安全和高效的无证书混合签密方案。通过引入vBNN-IBS签名算法,从而避免使用幂指数运算,进一步降低新方案的计算开销。在随机预言机模型下,新方案被证明是安全的,满足不可伪造性和机密性。对比分析表明,新方案在确保强安全性的同时具有更低的计算开销。     

协同OFDM系统联合中继选择、子载波配对和功率分配算法

研究了协同OFDM系统中的资源分配问题,提出了一种联合中继选择、子载波配对和功率分配的算法.首先在假定等功率分配的情况下,对中继节点进行选择并对子载波进行配对,然后在此基础上对选定的子载波对进行功率分配.分析结果显示所提算法是一种计算复杂度比较低,且系统容量接近最优容量的算法.     

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.     

基于虚拟MIMO的TD-LTE终端省电机制

介绍了无线资源管理上行链路中的虚拟MIMO技术,分析了该技术几种常用的用户配对方案的优缺点,最后重点分析了虚拟MIMO技术在TD-LTE系统中用来提高能量有效性的可能,并提出了基于虚拟MIMO的TDLTE终端省电机制的构想。     

基于身份代理权可撤销的代理签名

代理签名体制中代理签名权的撤销问题至关重要,SONG等人提出一种可撤销代理权的代理签名方案。提出了一种新的基于身份的可撤销代理权的代理签名方案,原始签名者在发现代理签名者不诚实时,可以通过可信中心TA及时有效地撤销代理签名者的代理签名权,且在该方案中将用户个人信息作为身份标识,大大减少了密钥的存储和管理开销。