轻载移动通信网的随机接入方式

本文着眼于移动通信IP化的发展趋势，尤其是未来移动Internet随机接入的特点，提出了双发随机接入方式，导出了该方式接入成功率和信道负载间的关系式。理论分析和实验结果表明，这种方式适用于移动网络中的轻载小区，能节省无线频率资源，还能大幅提高抗御信道劣化的能力。     

对3G移动通信随机接入方式的改进

本文介绍了3G移动通信(WCDMA)的随机接入过程以及存在的不足,给出了改进思路,建立了数学模型,提出了基站调控的slotted-ALOHA随机接入方式,并与现行的WCDMA随机接入方式进行了计算机仿真对比,结果表明该方式能使随机接入噪声强度大幅降低,接入时延和吞吐率指标显著改善.     

Internet的ISDN接入方式

Ｉｎｔｅｒｎｅｔ的ＩＳＤＮ接入方式上海市电话局李安民Ｉｎｔｅｒｎｅｔ（因特网）是全球信息高速公路的一个重要组成部分，全世界已有近亿台计算机通过Ｉｎｔｅｒｎｅｔ联系在一起，Ｉｎｔｅｒｎｅｔ在提供信息服务，实现全球信息共享、信息互访以及信息传递方面起到了...     

高速度Internet接入方式

本文主要对几种高速率的Ｉｎｔｅｒｎｅｔ接入方式的原理和工作方式作了介绍。     

TD-SCDMA随机接入信道的分析

给出了TD-SCDMA(时分双工同步码分多址)系统中一种新的随机接入方案,对该方案进行了理论分析 和计算机仿真,得到了随机接入信道吞吐率和时延公式,并将其数值计算结果与计算机仿真结果以及原方案计算 机仿真结果进行了对比。     

Internet及其接入方式

本文概述Ｉｎｔｅｒｎｅｔ的体系结构和网络组织；着重介绍Ｉｎｔｅｒｎｅｔ的接入方式、接入设备、软件接入工具，接入提供者提供的接入业务；以及中国Ｉｎｔｅｒｎｅｔ－ＣＨＩＮＡＮＥＴ的网络组织，接入方式及其业务。     

ALOHA应用于TD-SCDMA的随机接入过程

分析了TD-SCDMA系统物理层过程中的随机接入过程和ALOHA算法的应用。随机接入过程作为无线通信系统中的一个关键性过程,其在UpPCH公共信道上产生的碰撞问题将直接影响用户接入的成功和无线资源的利用。在系统级仿真软件OPNET中对用户和基站分别进行建模,并在基站侧对在同一时隙接入的用户强度以及由此产生的碰撞进行了仿真分析,得出:当用户的接入强度很大时,碰撞的概率比较大。应用ALOHA算法于具有竞争冲突特性的上行同步信道,经仿真后得出结论,ALOHA算法的应用可以减少碰撞的影响。     

移动自组网接入Internet的自适应技术研究

在移动自组网接入Internet的过程中,为适应节点高速移动导致网络拓扑频繁更新的特性,在混合式路由发现中引入自适应机制,从网关通告跳数的合理范围、广播风暴的避免、各节点和网关负载的动态变化等方面进行自适应性优化。以AODV路由协议为基础,改进网关发现算法的自适应机制,在NS2平台进行仿真,实现移动自组网与有线网络的互联,且其接入性能有一定程度优化。     

多级业务CDMA随机接入技术研究

针对卫星通信系统的特点,研究了结合CDMA和随机接入协议的扩频随机接入方式。在卫星通信的传播时延较长和短数据通信为主的情况下,这种接入技术能根据分组数据等业务的不同需求,实现满足多优先级业务的接入。理论分析和仿真结果表明,这种接入技术可以提高系统的综合性能。     

一种拨号接入Internet的技术方案

本文分析了拨号接入Ｉｎｅｔｎｅｔ方式的优点，核心技术和软件要求，介绍了北方电讯Ｒａｐｐｏｒｔ拨号接入交换机系列ＤＳ８Ｅ／８Ｔ、ＤＳ１１２和ＤＳ６７０的功能和应用。     

移动无线互联网接入中视频编码率控制策略

建立了用于移动无线互联网接入的视频编码转换模型,提出了自适应运动矢量估值方法.将编码转换码率控制分为图像层控制和宏块层两级,首先在总体上对每帧图像的编码比特数进行预分配,然后采用小波变换系数来表征图像特征,为帧内不同特征的宏块选用不同的量化因子,提出了一种新的码率控制策略.模拟实验表明:该方法在视频图像质量没有明显失真的前提下,提高了视频编码转换速度;编码转换输出码流和编码转换缓冲区占用量较稳定,重建图像的信噪比得到了明显的改善.     

面向大规模物联网的随机接入:现状、挑战与机遇

在传统通信系统中,随机接入是终端与网络之间建立无线链路的必经过程,只有在随机接入完成之后,终端与网络之间才能正常进行数据传输.聚焦大规模节点物联网,首先阐述了大规模物联网随机接入的基本特征,分析了传统授权随机接入(RA)方法对于大规模物联网应用的局限性;然后从系统模型、协议框架、算法流程、系统性能等多个角度,讨论免授权...     

An approximate analysis of TDMA out-of-slot random access protocols for microcellular mobile communications

In this paper, out-of-slot random access protocols for voice services that operate in microcellular environment are studied and simulated. The bearer service is assumed to be structured as time division multiple access/frequency division multiple access/frequency division duplex (TDMA/ FDMA/FDD). According to a stratification of information flow ascall, talkspurt, andpacket, the protocols are implemented at the talkspurt level. During a call, talkspurts generate a stream of packets. Each talkspurt has to reserve a voice time slot with a special control packet sent in a dedicate control slot (out of slot signaling). After a successful access, a voice slot is assigned for the duration of the talkspurt. This work concentrates on the out of slot random access method. When a transition from the idle state to the active state occurs, a voice terminal starts generating a talkspurt. Access for a voice slotV is then initiated via a dedicated control slotC. The time spent in gaining aV slot depends on the kind of random access protocol used in theC slots. Once the access reservation phase is successful, the talkspurt starts the second phase of information transmission in a freeV slot. If allV slots are occupied by other talkspurts, the new talkspurt is queued until aV slot becomes free. If the sum of the access and queueing times exceeds a thresh-old, a portion of the talkspurt is clipped. In our work we define an analytical model to evaluate the percentage of clipped voice packets. Simulations validate the analytical model.The second version of this work was rewritten while the author was a visiting scholar at WINLABThe IS-54 standard itself has the TDMA/FDMA structure. The ETDMA enhancement appears to be very much like what is described in this paper.     

一种适用于LAN及中高速Internet接入的PON系统

一种适用于高速计算机通信的共享接入的新型PON系统,将使多个ONU公平共享一条高速宽带通道,从而提供经济有效的中高速Internet接入。     

A new solution for assigning cryptographic keys to control access in mobile agent environments

A mobile agent is a technological promising product. It is an executive program that can migrate from host to host, performing tasks autonomously. However, in an open environment, the mobile agent has many potential threats. Security becomes a critical issue for the mobile agent. Recently, Volker and Mehradad have constructed a mobile agent structure and designed a key assignment strategy to prevent the sensitive data to from being accessed by an unauthorized host. However, their scheme requires a larger agent size and a higher computational cost. In this paper, we shall propose an efficient key assignment scheme to enhance the performance of Volker and Mehradad's scheme. Only few computations and a fixed and small storage are required in our proposed scheme. Furthermore, our scheme can achieve the dynamic key management efficiently. It can also be implemented simply and practically. Copyright © 2006 John Wiley & Sons, Ltd.     

一种基于CoMP的随机接入方案

提出了一种新的基于协作多点传输和接收（CoMP）技术的多发随机接入流程,并根据 随机接入的目的和业务类型设计了接入优先级,在此基础上设计了一种新的随机接入方案, 对 不同类型的随机接入请求提供不同的接入机制,以保证边缘用户的接入性能和满足不同业务 的QoS需求。仿真结果表明,与LTE标准随机接入方案相比,该方案对系统整体接入性能略有 提高,且大大提高了边缘高优先级用户的接入性能。     

移动Ad Hoc网络基于IPv6的Internet接入技术研究

针对实现移动用户无线上网的需求，通过对移动AdHoc网络的体系结构和路由技术的研究，以及对移动IPv6协议的工作原理及其与IPv4特性的比较分析，提出了AdHoc网络基于IPv6的Intemet接入方法，并对其地址自动配置、路由发现、网关发现、协议转换和分组转换等关键技术进行了分析，同时针对这两种技术相结合存在的广播和多跳问题提出了改进方法，并对今后的工作进行了展望。     

A survey of current architectures for connecting wireless mobile ad hoc networks to the Internet

Connecting wired and wireless networks, and particularly mobile wireless ad hoc networks (MANETs) and the global Internet, is attractive in real‐world scenarios due to its usefulness and praticality. Because of the various architectural mismatches between the Internet and MANETs with regard to their communication topology, routing protocols, and operation, it is necessary to introduce a hybrid interface capable of connecting to the Internet using Mobile IP protocol and to MANETs owing to an ad hoc routing protocol. Specifically, the approaches available in the literature have introduced updated versions of Mobile IP agents or access points at the edge of the Internet to help MANET nodes get multi‐hop wireless Internet access. The main differences in the existing approaches concern the type of ad hoc routing protocol as well as the switching algorithm used by MANET nodes to change their current Mobile IP agents based on specific switching criteria. This paper surveys a variety of approaches to providing multi‐hop wireless Internet access to MANET nodes. Copyright © 2006 John Wiley & Sons, Ltd.     

卫星物联网混合随机接入技术

在卫星物联网(IoT)场景中,随着终端数量不断增加,频谱资源日益紧张。传统的随机接入技术频谱利用率较低,使得传统随机接入协议不适用于未来卫星IoT的高并发业务需求。同时,卫星通信链路长,开放性强,难以保证特种终端信号的安全性。对此,本文提出一种适用于卫星IoT的混合随机接入方案。该方案引入重叠传输的容量提升与安全性优势,利用扩频码对瞬时功率谱密度的控制能力,构造功率域非正交接入条件,并通过接收端的迭代分离实现稳健接收。对本文所提方案的吞吐量性能进行闭式解推导分析与计算机仿真,结果表明,与传统的随机接入协议相比,所提方案可提高系统吞吐量。同时,相较于常用信号隐藏方法,所提方法利用常规接入数据包的功率优势,强化了波形隐藏效果,提升了特种信息接入的安全性。