MPLS支持移动IP技术研究

移动IP是一种在全球Internet上为移动节点提供移动功能的方案。同时,鉴于MPLS是一种基于三层边缘路由、二层核心标签交换的技术,可以较大程度地提高分组的转发速度,业界对扩展MPLS功能使其支持移动性产生了极大的兴趣。文章主要讨论MPLS支持移动IP的技术细节。     

网络电话应用中对H．323的移动扩展

网络电话实现了基于IP的双向、实时的传输。H．323就是其标准，它允许IP与基于电路交换的电话的互通，但是对于移动的IP主机却是不支持的。文章中探讨了对于H．323的在移动主机方面的扩展，使网络电话服务得以对移动IP主机支持。文章中提出的方法结合了蜂窝电话系统和移动IP机制的特点，实现了语音的实时传输对主机的支持。本方法的关键在于在会议中动态加入、退出过程中的复杂的管理功能。本方法可以看做是对基于H．323的网络电话系统的一个附加功能。     

IPv6如何与移动通信相结合?

IPv6与移动通信的结合点地址容量的扩展IPv6把IP地址的大小从32位增至128位,可以支持更多的地址层次,更大数量的节点,以及更简单的地址自动配置。IPv6支持邻居发现(NeighborDiscovery,ND)和地址自动配置(Autoconfiguration)技术,以上两项技术可以分配给大量的无线移动终端固定的全球IP地址,从而避免了NAT-PT带来的不足和限制,使各种移动终端快速,方便地接入到移动通信网络中,使“时时在线”成为可能,使开展各种端到端的应用和业务,诸如游戏、话音、多媒体信息、聊天等成为可能,而这些业务不需要服务器的支持。地址结构层次化IPv6采…     

基于卫星移动通信的网络移动研究

文中研究了利用卫星移动通信支持网络移动的必要性,提出了利用卫星移动通信网扩展地面IP网覆盖范围的设想和实现方案,分析了该方案的特点及需要解决的关键技术问题,重点分析了卫星移动信道对TCP/IP协议的影响及网络移动过程中的连接和路由选择问题,卫星移动信道误码率、往返时延、变化率、信道不对称性及信道频繁通断对TCP/IP协议工作效率的影响,以及提供网络移动应解决的双重隧道问题。     

CDMA2000 分组域核心网移动IP技术

移动IP技术为CDMA2000 系统中的一种基本接入技术.分析了移动IP技术网络架构,介绍了移动IP网络部署下的几种关键技术.为了使只支持简单IP的终端使用移动IP业务,引入了代理移动IP技术.内容计费业务作为一种灵活的计费方式,同样也可以应用在CDMA2000分组网络中.     

移动IP安全性分析与研究

随着Internet的迅猛发展及便携终端的日益普及,要求网络具有移动计算支持能力;同时,Internet中的通信会受到各种攻击,移动IP的引入则使安全问题更为突出。本文侧重分析了移动IP中的安全问题并讨论了移动IP如何穿越防火墙技术。     

浅析移动IPv6的基本原理及其扩展技术

移动通信和因特网的发展带给我们新机遇和新业务的同时,也带来了新的技术难题,传统的TCP/IP协议不支持主机的移动。移动IP技术正是为解决此问题而产生的一种新技术。本文首先了解了移动IPv4的功能实体和工作原理,介绍了移动IPv6操作原理并将其与移动IPv4比较。最后介绍了针对移动IPv6存在的问题而提出的三种扩展技术。     

一种新的移动IP与GPRS的融合方案

IETF制定的移动IPV4标准是一种在基于IP的网络上提供通用移动功能的方案，它可以使终端在不改变其IP地址的前提下，通过不同的接入网接入基于IP的网络。为了使GPRS系统也支持移动IPV4功能，3GPP提出了一种解决方案。该方案的主要缺陷是对现有GPRS规范改动较大，且改变了GGSN的功能定位，不利于系统的平滑升级，本文提出了一种新的实用的移动IPV4与GPRS的融合方案，特点是在不改变GPRS体系结构和移动IP结构框架的基础上，通过改进GPRS相关参数的配置以及SGSN选择GGSN的算法，实现移动IPV4与GPRS的融合，测试表明，通过该方案，使GPRS不仅可以支持标准IP业务，而且也支持移动IP业务。     

无线回传IP化上演双管齐奏

多制式支持、多业务传送、易扩展、高可靠性和可用性等是3G移动网络的建设目标。网络IP化是实现这些目标的有效途径。移动网络的IP化分为核心网和接入网两大块。目前。运营商已经开始全面实施核心网的IP化,并取得了很好的成果,业界逐渐将关注重心转移到接入网的IP化工作。 EPON和电信级以太网是目前备受关注的两种面向未来的基站IP化无线回传方案。     

基于AARP协议的移动IP算法及其性能分析

基于RFC2002的移动因特网协议(Mobile Internet Protocol,MIP),解决了因特网协议(Internet Protocol,IP)不支持节点跨子网漫游的问题,但要求移动节点必须具备动态修改路由表的功能;而在实际中广泛应用的操作系统,特别是Windows9x/Me等系统不支持对路由表的动态改变,这严重制约了移动IP的应用与推广.本文提出了主动ARP(Active ARP,AARP)协议,并在此基础上设计了一种新的移动IP算法.实验和分析表明,该算法在不引起性能下降的同时,克服了以往移动IP算法难以在Windows等系统上实现的缺点,极大扩展了移动IP的应用范围,并且易于实现、兼容性强、便于用户使用.同时,虽然该协议主要是针对Windows系统设计的,但也适用于其他许多操作系统.     

Steady state analysis of P-MIP mobility management

Paging extensions for Mobile IP (P-MIP) was proposed to avoid unnecessary registration signaling overhead of Mobile IP (MIP) and there is a tradeoff between registration and paging signaling based on the probability that a mobile node (MN) is in active or idle state. This probability varies from MN to MN and changes even for a given MN as time goes by. It is, however, assumed to be a fixed value in P-MIP for simplicity. In this letter, the steady-state probability of active and idle states is derived using a semi-Markov chain approach and the performance of P-MIP is compared with MIP based on session-to-mobility ratio.     

P-MIP: Paging Extensions for Mobile IP

As the number of Mobile IP users grows, so will the signalling overhead associated with Internet mobility management in the core IP network. This presents a significant challenge to Mobile IP as the number of mobile devices scale-up. In cellular networks, registration and paging techniques are used to minimize the signalling overhead and optimize the mobility management performance. Currently, Mobile IP supports registration but not paging. In this paper, we argue that Mobile IP should be extended to support paging to improve the scalability of the protocol to handle large populations of mobile devices. To address this, we introduce P-MIP, a set of simple paging extensions for Mobile IP, and discuss the construction of paging areas, movement detection, registration, paging and data handling. We present analysis and simulation results for Mobile IP with and without paging extensions, and show that P-MIP can scale well supporting large numbers of mobile devices with reduced signalling under a wide variety of system conditions.     

Combinatorial Mobile IP: A New Efficient Mobility Management Using Minimized Paging and Local Registration in Mobile IP Environments

Combinatorial Mobile IP, a new mobility management scheme for Mobile IP, is proposed and analyzed. We present how to adopt mobility management schemes on cellular networks and adapt them in Mobile IP without disrupting the nature of the Internet. We apply widely used mobility management schemes such as hierarchical architecture and paging in cellular networks to Mobile IP. We restrict paging to the area that has to be paged using local registrations. In this way, we show that the total signaling costs of Combinatorial Mobile IP are reduced compared to other micro-mobility protocols such as Mobile IP Regional Registration and P-MIP. Random walk on a connected graph is used to analyze the performance of Combinatorial Mobile IP.     

Identification of the source of an interferer by comparison with known carriers using a single satellite

We describe a method for identifying the source of a satellite interferer using a single satellite. The technique relies on the fact that the strength of a carrier signal measured at the downlink station varies with time due to a number of factors, and we use a quantum‐inspired algorithm to compute a “signature” for a signal, which captures part of the pattern of variation that is a characteristic of the uplink antenna. We define a distance measure to numerically quantify the degree of similarity between two signatures, and by computing the distances between the signature for an interfering carrier and the signatures of the known carriers being relayed by the same satellite at the same time, we can identify the antenna that the interferer originated from, if a known carrier is being relayed from it. As a proof of concept, we evaluate the performance of the technique using a simple statistical model applied to measured carrier data.     

DSP在捷联惯性制导技术中的应用

捷联惯性制导系统由于没有稳定的平台而需要通过大量的数学运算建立数学平台 ,因此制导对计算装置的性能要求很高。DSP芯片的出现为这种需要大量实时计算的制导系统提供了方便的应用方案。文中介绍了一种用DSP芯片设计的捷联惯性制导系统 ,给出了整个系统的电路和程序设计方法     

A quad-rotor system for driving and flying missions by tilting mechanism of rotors: From design to control

This article presents the hybrid design and control of a quad-rotor system called Flymobile. Flymobile is a combined system of a mobile robot and a quad-rotor system aimed to perform both flying and driving tasks. Flymobile performs flying tasks in the same way as conventional quad-rotor systems while the tilting mechanism of each rotor allows Flymobile to navigate in its terrain for a driving task. The body frame with rotors is implemented by a calibration process through a test-bed equipped with a force sensor. The triangular wheel frame is designed to mimic motions of a mobile robot with three passive wheels. Sensor data of a gyro and an accelerometer are filtered and used for controlling the attitude of the system. Focusing on a practical approach of implementing a hybrid system, a non model-based approach is applied to control Flymobile. Experimental studies are demonstrated to show the feasibility of performing both driving and flying missions.     

Optical and electrical characteristics of GaN vertical light emitting diode with current block layer

A GaN vertical light emitting diode(LED)with a current block layer(CBL)was investigated.Vertical LEDs without a CBL,with a non-ohmic contact CBL and with a silicon dioxide CBL were fabricated.Optical and electrical tests were carried out.The results show that the light output power of vertical LEDs with a non-ohmic contact CBL and with a silicon dioxide CBL are 40.6%and 60.7%higher than that of vertical LEDs without a CBL at 350 mA,respectively.The efficiencies of vertical LEDs without a CBL,with a non-ohmic contact CBL and with a silicon dioxide CBL drop to 72%,78%and 85.5%of their maximum efficiency at 350 mA,respectively. Moreover,vertical LEDs with a non-ohmic contact CBL have relatively superior anti-electrostatic ability.     

Virtual impedance control for a regional dynamic voltage restorer

A dynamic voltage restorer (DVR) can be installed in a middle-voltage (MV) power grid, to concurrently protect a cluster of sensitive loads from voltage sags. To further improve its efficiency and reduce the difficulty in its implementation, a novel control strategy for operating such a DVR as a virtual impedance in series with sensitive loads is proposed in this paper. In addition to its usual function of compensating for voltage sags, such a DVR can also operate as a virtual inductance, to function as a fault current limiter (FCL) during a downstream fault, or a virtual capacitance, to function as a series compensator (SC) to compensate the voltage loss along the feeder line during heavy load. Based on a dual-loop control design, strategies for operating a DVR as a series virtual inductance and a virtual capacitance are proposed, and methods for tuning the parameter values and a stability analysis of the whole system are presented. The feasibility and effectiveness of the proposed method are verified by simulations using the PSCAD software, and experimental results obtained using a prototype DVR are presented.     

一种安全的纠错网络编码

该文利用消息空间的所有子空间上的一种度量,给出了一种安全的纠错网络编码。首先,此度量下的最小距离译码法可以纠正一定维数的错误。另外,在此编码方法下,当攻击者能窃听到的信道数目小于网络的最大流时,攻击者得不到关于信源的任何信息。最后,当攻击者能窃听网络中所有信道时,本文通过让信源和信宿共享一个随机数生成器和一个秘钥,进一步给出了能防此类强攻击者的安全纠错网络编码。     

多路径环境下电信流量模型研究

在下一代通信网络中,一个终端可同时拥有多个网络接口,在一对源、目的终端间存在多条可用路径。这为网络通信提供了一种全新的思路,即利用多条路径并发进行数据传输。针对多路径传输出现的问题,文章为多路径传输建立了流量模型,分析了多路径传输流媒体的优势,提出了＂流体带宽＂和＂流体调度＂的概念,并引入网络流理论计算了多路径环境下的目标流量。