我国移动电话网络的演变

移动通信以其灵活、便捷的特点符合现代社会人们对通信的要求,成为20世纪80年代中期以来发展最为迅速的通信方式,它经历了从模拟调制技术到数字调制技术的发展过程。现在我国已经出现了5种移动电话网共存的局面,它们是A、B、C、D、G网。这5种网各有不同的通话范围和业务功能。其中A网和B网采用FDMA频分复用多址方式、TACS体制;C网采用CDMA码分复用多址方式;D、G网采用TDMA时分复用多址方式、GSM体制。A网和B网是模拟网,C、D、G网是数字网。A网和B网属于第1代移动通信系统,C、D、G网属于第2代移动通信系统。 A网和B…     

漫谈"双频"

在电视广告上经常听见双频手机这个名词,什么是双频呢,它有哪些优点?且听我慢慢道来。首先来了解一下手机的网络。常用的G网——GSM900移动电话网,是频率为900MHz的数字蜂窝移动通信系统,除此还有D网——DCS1800移动电话网,     

手机＋PDA＋INTERNET＝未来的趋势—通讯市场回顾

我国自1987年开始开通移动电话业务以来,到现在主要有五种移动电话网共存,这五种网各有不同的通话范围和不同的业务功能。用户选择配备移动电话手机时,需要对现有的五种网有所了解。我国的五种移动电话网又被称为A、B、C、D、G网,其中A网和B网是模拟网(已经进入消失阶段,大都已经转入了GSM网),C、D、G网是数字网。     

协同异构蜂窝层叠网络中的终端直通通信技术

终端到终端(device-to-device,D2D)的直通通信实现了联合蜂窝和移动自组网的无缝操作,大幅提高了系统频谱效率和网络容量.介绍了D2D局域网的理论概念和在实践中的应用挑战;并着重论述了跨层资源管理在解决D2D通信中于扰避免问题的重要性,给出了一个无线资源管理实例.数据结果显示,所提出的算法性能接近穷举搜索最优算法,并具有相对较低的复杂度.目前,D2D通信技术表现出能够获得系统高容量和充分利用无线资源的巨大潜力.     

移动电话中的G网和D网

1．关于G网和DN的名称由来G网是指GSM－900移动电话网，是频率为900MHz的数字式蜂窝移动通信系统。总的讲来，数字移动电话要比模拟移动电话的频谱利用率高，通话质量也要好一些。GSM的英文原义是GlobeSystemforMobilCommunication，直译为全球移动通信系统。所以把"中国电信"GSM的中文名字叫做"全球通"。D网指DCS－1800移动电话网，是频率为1800MHz的数字式蜂窝移动通信系统，DCS的英文原义为DigitalCommunicationSystem，即数字通信系统。由于DCS－1800和GSM－900在网络结构、语音编码、调制技术、信令规程等方面均相同。…     

金鹏WAP网关助力中国移动

近日,金鹏KC-WISEWAP网关平台顺利接入了内蒙古移动的移动数据通信网络,用于企业移动办公自动化系统。2003年,金鹏KC-WISEWAP网关曾成功应用于广西联通cdma20001X网络的移动办公自动化系统。金鹏WAP网关助力中国移动@刘静     

异构网中移动鲁棒性优化技术仿真研究

文章通过大量的仿真验证找出异构网场景中具体的移动鲁棒性问题,进而有针对性地给出解决方案。仿真中通过同构网和异构网场景中的移动鲁棒性性能比较,发现异构网场景中移动性参数应根据切换的对象不同,进行相应的参数匹配;仿真中通过异构网场景中设置不同的参数配置发现,在选择合适的移动性参数时应综合考虑移动鲁棒性性能和系统开销。     

移动自组网路由恢复算法的研究

移动自组网是由一组带有无线收发装置的移动终端组成的自治通信系统.煤矿井下移动自组网可应用于矿井的监控管理系统、数据采集系统或者应急通信系统.移动自组网的路由方案主要包括表驱动(Proactive)和按需驱动(Reactive)两种,AODV是一种代表性的按需驱动算法.文中介绍了利用辅助路径基于AODV的一种矿井移动自组网的路由恢复算法,给出了辅助路由算法的性能测评方案.     

移动互联网Web网关的设计

文章首先结合目前限制移动互联网业务发展和用户体验提升的因素,分析了建设Web网关的必要性;然后提出一套切实可行的移动互联网Web网关设计方案,深入阐述了Web网关的系统架构、内部各模块的功能、外部接口和业务处理流程,对运营商今后的Web网关建设部署有一定的指导意义。     

G&C双模移动通信系统

项目简介:项目所属科学技术领域、主要内容、特点及应用推广情况:技术领域:G&C移动通信系统的应用领域是在移动通信运营行业。其主要目的是综合利用GSM和CDMA两网的资源,做到两网的优势互补,满足移动运营商向用户提供不同制式网络漫游的需求。主要内容:G&C双模移动通信系统是一个能够支持CD-MA、GSM两种制式移动网络之间用户互相漫游的一个全新的技术和系统。系统满足以下几方面的市场需求:GSM用户可以根据需要选择CDMA网或GSM网的服务,即GSM用户可以使用CDMA网络的数据业务和语音业务;CDMA用户可以根据需要选择GSM网或CD…     

电力系统无功补偿技术发展现状

本文阐述了电网中进行无功功率补偿的重要性,概述了国内外无功补偿技术的研究现状,重点介绍SVC装置发展应用情况,提出了基于可变电抗的静止无功补偿装置的拓扑结构,该结构可实现功率的无级调节,在实际应用中可提高配电网的运行效率,降低系统损耗,亦可用于调压、调功控制及谐波治理等场合.     

Energy-efficient resource allocation model for device-to-device communication in 5G wireless personal area networks

In general, there are several many devices that can overload the network and reduce performance. Devices can minimize interference and optimize bandwidth usage by using directional antennas and by avoiding overlapping communication ranges. In addition, devices need to carefully manage their use of resources, such as bandwidth and energy. Bandwidth is limited in wireless personal area networks (WPANs), so devices need to carefully select which data to send and receive. In this paper, an intelligent performance analysis of energy-efficient resource optimization model has been proposed for device-to-device (D2D) communication in fifth-generation (5G) WPAN. The proposed energy-efficient resource allocation in D2D communication is important because it helps reduce energy consumption and extend the lifespan of devices that are communicating with each other. By allocating resources in an efficient manner, communication between two devices can be optimized for maximum efficiency. This helps reduce the amount of energy needed to power the communication, as well as the amount of energy needed to power the device that is communicating with another device. Additionally, efficient resource allocation helps reduce the overall cost of communication, as the use of fewer resources results in a lower overall cost. The proposed efficient resource allocation helps reduce the environmental impact of communication, as less energy is used for communication. The proposed energy-efficient resource allocation model (EERAM) has reached 92.97% of energy allocation, 88.72% of power allocation, 87.79% of bandwidth allocation, 87.93% of spectrum allocation, 88.43% of channel allocation, 25.47% of end-to-end delay, 94.33% of network data speed, and 90.99% of network throughput.     

New Look on Device to Device NOMA Systems: with and Without Wireless Power Transfer Modes

In this paper, device to device (D2D) network is studied to support transmission in close distance among group of two users. Such two users benefit from new technique of multiple access, namely non-orthogonal multiple access. Two modes of D2D are considered, such as direct and relay links. Energy harvesting and design of multiple antennas have main impacts on system performance. We derive the closed-form expressions of outage probability for two devices in many scenarios. The Decode and Forward relaying scheme is adopted in this study. To ensure the quality of service (QoS) for the devices, suitable mode can be decided based on specific demand. We compare system performance by varying main parameters such as power allocation factors or transmit signal to noise ratio. Numerical results are performed to verify the effectiveness of the proposed D2D transmission strategies.

     

D2D网络中基于立即可解网络编码的时延最小化重传方案

该文针对D2D无线网络中多终端并发协作重传冲突避免问题,提出一种基于立即可解网络编码的时延最小化重传方案。在重传阶段,充分利用D2D无线网络终端协作传输数据的优势,结合各终端数据包接收状态,综合考虑时延的影响因素,选取单次重传时延增量较小的数据包生成编码包,最小化重传时延。同时,构建终端冲突图,在图中搜索极大独立集,根据各终端的编码包权重值,选择最大加权独立集中的终端作为并发协作重传终端,从而降低重传次数。仿真结果表明,所提方案能够进一步改善D2D无线网络的重传效率。     

探讨电力电子设备对配电系统继电保护的影响

随着我国电网技术的不断发展,种类广泛的电子电力设备因其具有快速反应特征的显著优点逐渐被引入配电系统中,从而大大的提高了配电系统运行过程中的可行性.然而,电力电子设备在给配电系统带来可行性的同时,也给配电系统和继电保护系统带来了降低电网安全稳定性的不利影响,从而给配电系统和继电保护系统带来了不可忽视的安全隐患问题.本文对电力电子设备对配电系统继电保护的影响进行探究分析.     

Progressive meshes transmission over a wired-to-wireless network

The evolution of mobile network and the popularization of mobile devices; the demand for multimedia services and 3D graphics applications on limited resource devices is more contemporary. Most of the works on multimedia transmission are focused on bit errors and packet losses due to the fading channel environment of a wireless network. Error resilient multimedia is significant research topic which can be adapted to the different conditions in a wireless environment. The current solutions in transmission of multimedia across different networks include some type of transcoder where the source is partially or fully decoded, and re-encoded to suit the network conditions. This paper introduces a flexible progressive coding framework for 3D meshes, which can be adapted to the different conditions imposed by wired and wireless channels at the bitstream level. By avoiding the computationally complex steps of transcoding between networks, could deteriorate decoded model quality. The framework also allows refined degradation of model quality when the network conditions are poor due to congestion or deep fades. Xiaonan Luo, male, born in Feb. 1963 in Jiangxi Province, China, Ph. D., completed his post-doctorate training in Mar. 1995. He is a professor and Ph. D. advisor of the School of Information Science and Technology, and the Chairman of Computer Application Institute of Sun Yat-sen University. His current interests are in mobile graphics transmission and 3D geometric simulation methods. He enjoys the government special allowance granted by the State Council of China. He won the National Science & Technology Progress Prize awarded by the Ministry of Science and Technology of China and the National Natural Science Funds granted by the National Nature Science Foundation of China. Guifeng Zheng, male, born in Jan. 1977 in Guangdong Province, China, Ph. D., received his Ph.D. degree from Sun Yat-sen University in 2005. He is currently an research assistant in the Computer Application Institute of Sun Yat-sen University. His research interests span the areas of wireless networks and mobile graphics computing.     

Precoding and power allocation algorithms for device-to-device communication in massive MIMO networks

Device-to-device communication (D2D) and massive multiple input multiple output (MIMO) systems are two emerging technologies that are being considered to improve the performance of next generation wireless cellular systems. In D2D, two mobile nodes communicate directly without traversing the base station (BS). Consequently, interference management, coordination, and/or cancellation techniques have to be adopted to target the problem of mutual interference between the D2D devices and the BS (or the normal mobiles nodes connected to the BS). In this paper, we investigate the problem of BS precoder design and D2D devices power allocation in the downlink of a single-cell network assuming existence of D2D devices as well as massive MIMO at the BS. We propose algorithms to maximize the sum of the achievable data rates of the D2D pairs while maintaining quality of service constraints on the cellular user equipment, which communicate normally with the BS. We also propose two algorithms for the precoding problem; the first is based on semi-definite programming while the second is based on gradient descent algorithms. Moreover, we investigate two solutions for the power allocation problem; the first solves an approximate convex optimization problem iteratively while the second is a suboptimal, but far less complex, heuristic. Finally, we propose a technique to apply the mentioned solutions when only partial channel state information is available at the BS. Simulation results show that the proposed solutions are superior to the conventional precoding and power allocation schemes.     

Analysis and Modeling of Hybrid Planar-Type Electromagnetic-Bandgap Structures and Feasibility Study on Power Distribution Network Applications

A unified 1D analysis model of hybrid planar-type electromagnetic-bandgap (EBG) structures is developed. Based on the analysis results, three types of hybrid design methods to reduce the cutoff frequency of the EBG structures are discussed, and design equations for their noise suppression bandwidths are derived. In order to simulate switching noise characteristics of the hybrid planar-type EBG structures, 2D circuit level models are developed and experimentally verified. With the developed circuit-level models and CMOS active switching devices, feasibility studies on the power distribution network design using the hybrid EBG structures are conducted. The hybrid EBG structure with series lumped chip inductors shows efficient noise suppression characteristics in both the frequency and time domains; however, it has potential limitations because of its generation of higher switching noise voltages depending on power supply connection configurations.     

Blind mask template attacks on masked cryptographic algorithm

Masking is a countermeasure against differential power analysis (DPA) attacks on cryptographic devices by using random masks to randomize the leaked power of sensitive information.Template attacks (TA) against cryptographic devices with masking countermeasure by far require attackers have knowledge of masks at the profiling phase.This requirement not only increase the prerequisite of template attacking,but also lead to some sort of difference between the experimental encryption codes of the profiling device and the codes of commercial cryptographic devices,which might degrade performance in real world attacking.Blind mask template attack directly learns templates for the combination of no mask intermediate values without the need of knowing the masks of training power traces,and then uses these templates to attack masked cryptographic devices.Both traditional Gaussian distribution and neural network were adopted as the templates in experiments.Experimental results verified the feasibility of this new approach.The success rate of neural network based blind mask template attacking against masked cryptographic devices is very close to that of traditional template attacks against cryptographic devices without masking countermeasure.     

集中直流远供系统在分布式基站的应用探讨

随着“无缝网络”建设和光纤拉远技术的发展,分布式基站已成为了网络建设的主要形式。传统的电源保障模式已无法满足远端有源通信设备的供电需求。本文以中国移动企标的电压范围（225V～380V可调）为标准,通过对集中直流远供系统在工程实践中的应用总结,就系统在分布式基站的应用方面进行探讨。