Cooperative beamforming design for physical-layer security of multi-hop MIMO communications在多跳MIMO通信系统下的基于物理层安全的协作波束赋形设计

The security issue is critically important for wireless communications, especially for multi-hop communications. In this paper, we propose a cooperative secrecy beamforming scheme for a multi-hop MIMO communication network, in which there is a single-antenna source, multiple multi-antenna relays and a singleantenna destination. Moreover, two types of eavesdroppers exist in the network, one of which has known channel state information (CSI), while the other not. To achieve security communications, in our work null-space beamforming and artificial noise beamforming are jointly optimized to improve the secrecy rate of the multi-hop network. In nature, the joint optimization is nonconvex and challenging. Exploiting its structure, the considered optimization problem is decoupled into a series of subproblems that can be efficiently solved based on convex optimization theory. Finally, some numerical experiment results are provided to assess the performance of the proposed secrecy beamforming design.     

一种浮标通信天线的波束赋形设计

海洋浮标是一种现代化的海洋观测设施,它具有全天候、全天时稳定可靠地采集海洋环境资料的能力,并利用通信卫星把数据发送到陆地上的数据处理中心.卫星通信一般采用地球同步轨道上的静止卫星来实现,本文重点研究地球同步通信卫星作为浮标通信卫星时的天线赋形波束设计.     

一种精确控制旁瓣的自适应波束形成算法

提出了一种精确控制旁瓣和抑制干扰的自适应波束形成算法。它是通常的最小方差无畸变（MVDR）波束形成算法的改进形式，使阵列输出信号功率最小的同时，保持目标信号方向的无失真响应，并且严格保证旁瓣低于某一给定值，抑制干扰。在仿真过程中，充分应用了二阶锥规划（second—order cone programming）算法，并与MVDR波束形成算法进行比较，验证了方法的正确性，同时研究了该算法的稳健性。     

一种自适应波束赋形的大规模MIMO信道估计方法

大量研究结果表明大规模多输入多输出(Massive MIMO)信道表现出一种稀疏结构特性。利用这个特性开发了一种全新的信道估计算法,它能够自适应波束赋形,并且联合优化稀疏矢量和矩阵函数的方法。该算法关键部分是随机优化基于连续常量的结构模型,并且与基本的去噪优化方案交替使用以找到稀疏特征信道。仿真结果表明,与基于傅里叶变换的普通稀疏信道估计方法进行比较,这种改进型的稀疏信道估计方法不但能够允许适当减少导频数量,且至少改善20 d B以上的信道估计误差。     

一种基于移动边缘计算与波束赋形的任务分配算法

本文主要关注通信技术中两项较为热门的研究,分别是移动边缘计算(MEC)和天线波束赋形。MEC技术将信息一部分处理从云端移动到网络的边缘节点完成,混合波束赋形技术能通过码本控制波束相位,形成高增益的定向窄波束,以此获取更小的发射功率。本文针对MEC部分建立了一个马尔科夫链模型来模拟信息决策分配的过程,然后加入波束赋形的天线模型,将MEC算法的任务分配时延和能耗,与天线模型中的时延和能耗结合起来,并通过这个模型计算数学表达式,来得到能使得时延和能耗都较低的任务分配方案。     

小功率开关电源芯片VIPER12A的应用——一种节能开关电源的设计

目前开关电源大量使用于各种电器设备中。且开关电源直接接在市电电网上,电源设备与电网之间有着双向的电磁干扰影响,对于较高频率的开关电源在设计中都需要考虑电磁兼容问题。用VIPER12A芯片设计的开关电源具有节能特性,而且电磁兼容性较强,外围电路也很简单。一、芯片VIPER12A简介芯片VIPER12A是意法半导体有限公司于2002年出的单片小功率开关电源。具有固定60kHz的开关频率,芯片的电源电压范围很宽(9V-38V);具有电流控制型PWM调制器;具有滞     

用PMM8713和SI-7300A构成的一种步进电机功率驱动电路

给出了PMM8713和SI-7300A的结构框图及主要技术指标，并用它们构成了一种步进电机功率驱动电路。     

A QoE-based jointly subcarrier and power allocation for multiuser multiservice networks在多业务多用户网络场景下的基于QoE的联合子载波和功率资源分配

Quality of experience (QoE) is widely applied to reflect user’s satisfaction of the network service, which exactly conforms to the user-centric concept in 5G. In this paper, we propose a QoE-based subcarrier and power allocation algorithm for the downlink transmission of a multiuser multiservice system. For the subcarrier allocation algorithm, the rate proportional fairness factor is defined to ensure the fairness between users. Based on different QoE models of three services, i.e., file down (FD), video streaming and voice over internet protocol (VOIP), a multi-objective optimization method is exploited to allocate the power resource by minimizing the total power consumption and maximizing the mean opinion score (MOS) value of users simultaneously. Simulation results indicate that the proposed algorithm has less power consumption and higher QoE performance than the traditional proportional fairness (PF) algorithm. In addition, the proposed algorithm can achieve nearly the same fairness performance as the PF algorithm. Moreover, when the number of subcarriers becomes larger, the power assumption will be less but with little influence on both the QoE and fairness performances.     

A novel unsupervised method for new word extraction一种新颖的非监督新词抽取方法

New words could benefit many NLP tasks such as sentence chunking and sentiment analysis. However, automatic new word extraction is a challenging task because new words usually have no fixed language pattern, and even appear with the new meanings of existing words. To tackle these problems, this paper proposes a novel method to extract new words. It not only considers domain specificity, but also combines with multiple statistical language knowledge. First, we perform a filtering algorithm to obtain a candidate list of new words. Then, we employ the statistical language knowledge to extract the top ranked new words. Experimental results show that our proposed method is able to extract a large number of new words both in Chinese and English corpus, and notably outperforms the state-of-the-art methods. Moreover, we also demonstrate our method increases the accuracy of Chinese word segmentation by 10% on corpus containing new words.     

A multipath resource updating approach for distributed controllers in software-defined network软件定义网络中一种分布式控制器间的多路径资源更新方法

Finding effective ways to collect the usage of network resources in all kinds of applications to ensure a distributed control plane has become a key requirement to improve the controller’s decision making performance. This paper explores an efficient way in combining dynamic NetView sharing of distributed controllers with the behavior of intra-service resource announcements and processing requirements that occur in distributed controllers, and proposes a rapid multipathing distribution mechanism. Firstly, we establish a resource collecting model and prove that the prisoner’s dilemma problem exists in the distributed resource collecting process in the Software-defined Network (SDN). Secondly, we present a bypass path selection algorithm and a diffluence algorithm based on Q-learning to settle the above dilemma. At last, simulation results are given to prove that the proposed approach is competent to improve the resource collecting efficiency by the mechanism of self-adaptive path transmission ratio of our approach, which can ensure high utilization of the total network we set up.