平流层通信技术在军事通信中的应用

由于平流层通信平台具有高度稳定、长时间驻空、准静止、可承载一定规模有效载荷等特点。与卫星通信和地面蜂窝系统相比,平流层通信系统具有费用低、部署快速、地面设备少、使用灵活、通信质量好等特点,其应用在军事中是一个新的突破,已经引起越来越多国家的重视。     

平流层通信技术在军事通信中的应用

由于平流层通信平台具有高度稳定、长时间驻空、准静止、可承载一定规模有效载荷等特点.与卫星通信和地面蜂窝系统相比,平流层通信系统具有费用低、部署快速、地面设备少、使用灵活、通信质量好等特点,其应用在军事中是一个新的突破,已经引起越来越多国家的重视.     

WiMAX在宽带无线城市中的应用

WiMAX是基于IEEE802．16标准的无线宽带接入技术,可为固定、移动、便携形式的通信终端提供更为便捷的宽带无线接入。与wi—Fi等无线通信技术相比,WiMAX具有更强的抗干扰性,更高的带宽利用率,因此,在无线城市建设中WiMAX、3G和WiFi三者的技术结合会创造出一个完美的宽带无线网络,实现数字化生活。     

宽带卫星通信系统编址方案研究

基于星上路由交换技术的宽带卫星通信系统一直是未来移动通信系统的重要组成部分。其中星上路由交换技术成为移动通信领域研究的热点之一。本文在深入分析宽带卫星通信网络的框架结构的基础上,提出了一套用于星上高速数据交换的编址方案,并以此为基础设计了星上交换系统依据数据流的地址域所进行的数据处理流程。     

智能天线在无线宽带系统中的应用分析

从智能天线原理入手,结合实际应用中的复杂度、使用成本等因素,重点介绍了智能天线在McWiLL系统中的应用,并详细分析了它的优势和存在的问题.     

宽带卫星通信与互联网

一、卫星通信的发展、现状及动力几十年来,卫星通信一直在与地面通信齐头并进地发展。由于受技术进步、经济全球化、市场竞争、互联网发展等因素的影响,卫星通信的产业格局和服务形式正在发生结构性的变化。这些变化主要表现在以下几个方面:Hughes、Jilat、Loral、Lockheed MaKin等传统卫星及地面设备制造商纷纷从上游制造行业进入到下游运营服务行业;Intelsat、Panamsat等传统卫星转发器租赁公司从基本的转发器业务扩展到网络服务业务;     

宽带卫星通信数字信道化技术研究

自从《国家中长期科学和技术发展规划纲要(2006-2020年)》提出以后,航天事业越来越对国家发展起着重要作用。十一五以来,数字信道化卫星有效载荷技术不断革新,且取得显著改观,不仅如此,它还对我国未来移动卫星通信系统中卫星的有效载荷设计的发展影响深远。     

Wi-Fi技术在宽带无线城市建设中的应用

无线保真（WirelessFidelity,Wi-Fi）宽带无线接入技术的应用代表了宽带接入技术的一种新的不可忽视的发展趋势。该技术由于有着自身的优点,受到了通信运营商和我国各级政府信息化建设部门的青睐,成为宽带无线城市建设的主要技术。本文介绍了Wi-Fi技术在国内无线城市建设中的主要应用领域,可以为各级政府信息化决策部门在进行无线宽带城市建设规划时提供参考。     

宽带城域网中的新一代宽带无线接入技术——LMDS

1.引言当前,随着国际电信市场的迅速发展,目前各国的核心网络建设均初具规模,基本可满足当前通信的需求。而突出的矛盾体现在接入网方面,即用户与核心网络的连接部分。这一问题是通信向宽带、智能、个人化发展的关键。随着网络经济的迅速崛起和因特网的快速发展,人们对于数据业务、语音、数据、图像等多媒体通信的需求日益增强,传统的铜线、电缆,已完全不能满足传输的要求,更新成本又     

宽带LEO星座卫星通信系统业务量仿真分析

由于小卫星技术的快速发展,以及低轨卫星(LEO)相比传统的地球同步轨道卫星(GEO)具有低时延、低传播损耗等优点,宽带LEO星座卫星通信系统逐渐成为当前卫星通信领域的发展热点之一。目前,世界许多国家和卫星通信公司都在制定宽带LEO星座卫星通信系统方案。针对中国的现实条件,为建造一个合理的宽带LEO星座卫星通信系统,研究一个高效的组网方案,需要分析系统的业务量需求。对此构建了系统的位置业务模型与一日变化模型,提出了业务量仿真的方法,利用STK和MATLAB仿真软件,模拟了宽带LEO星座卫星通信系统单颗卫星与单个轨道面内的相对业务量,相关成果对建设我国自主的宽带LEO星座卫星通信系统具有一定的参考与指导意义。     

Routing in broadband communication networks using neural computations

This paper will briefly review some of the published work on applying Artificial Neural Networks (ANN) to routing in Asynchronous Transfer Mode (ATM) networks and critically appraise some of the conclusions which have been drawn from these studies. The paper will go on to explain the design and implementation of a simulation of a neural network array superimposed on a simulated ATM network. The results of routing experiments, which were compared with decisions made using Shortest Path First (SPF) routing, will be discussed and the need for appropriate comparison metrics explained. The paper will end with a review of what needs to be considered when the applicability of ANNs to ATM network control is being assessed and the required functionality of simulation tools which allow these assessments to be made.     

卫星通信和物联网技术在水文数据传输中的应用

当前水文数据监测通信主要是靠4G公众网络的方式,在偏远的山区或应急监测时,往往4G网络不能全覆盖,造成水文监测数据无法及时传输。为解决水文监测中通信能力的不足,实现水文监测数据的自动化,利用卫星通信、物联网等新技术,在4G通信方式上增加备份通信链路,保证水文数据传输通道的畅通。     

Windows CE系统中卫星通信的实现

介绍了Windows CE系统下嵌入式设备与卫星信号接收机之间进行通信的一般方法，详细设计了一个实用的多线程实时通信解决方案，并以GPS系统的通信格式为例实现了一种提取其定位信息的方法。实验证明，该方法在PDA上能够实时、正确地获取GPS的定位信息，从而证明该方案是可行的、正确的。     

Scheduling support for multicasting sessions in broadband communication networks

Multimedia applications require support from the underlying broadband network at the end-to-end communication level. Multicasting is an important paradigm of end-to-end communication. The root node of a multicasting session is responsible for controlling the session including monitoring, maintenance, and the implementation of the multicasting protocol. The job that controls the multicasting session executes as a group of tasks at the root node of a multicasting tree. The scheduling scheme at the root node should give support to a multicasting session by improving the completion time of the jobs controlling the multicasting session, hence increasing throughput and the probability of admitting new multicast sessions into the system. In this paper, we model the tasks that carry out the multicasting session monitoring and maintenance as a fork-join job executing on a multiprocessor system. We assume that an executing task blocks for device I/O as a part of the activities associated with sending and receiving data packets. We develop two analytic models for scheduling a session control job on a multiprocessor system. The first model allows incoming job tasks to multiplex processors with existing tasks of another multicasting session, while the other model schedules a task of the incoming job to an idle processor. We assume that the overhead of rescheduling a task to another processor is large. We compare the performance of both models and show the range of conditions under which a model outperforms the other. We point out how the results can be used in the design of an adaptive scheduler that uses both models to improve throughput and consequently the probability of admitting new multicast sessions.     

Throughput of a satellite channel communication

Summary The throughput of a satellite channel communication is depending upon the link protocol. It is well known that the classical HDLC protocol is inadequate when applied to satellite links instead of short terrestrial links. Several modifications have been proposed to overcome this problem. The present paper gives an analysis and evaluation of a new class of protocols called Virtual Subchannel schemes which splits the satellite link into several components; these subchannels are assigned for transmission in cyclic order and are controlled independently of each other by the classical HDLC procedure.     

Monitoring northern mixed prairie health using broadband satellite imagery

The mixed prairie in Canada is characterized by its low to medium green vegetation cover, high amount of non‐photosynthetic materials, and ground level biological crust. It has proven to be a challenge for the application of remotely sensed data in extracting biophysical variables for the purpose of monitoring grassland health. Therefore, this study was conducted to evaluate the efficiency of broadband‐based reflectance and vegetation indices in extracting ground canopy information. The study area was Grasslands National Park (GNP) Canada and the surrounding pastures, which represent the northern mixed prairie. Fieldwork was conducted from late June to early July 2005. Biophysical variables—canopy height, cover, biomass, and species composition—were collected for 31 sites. Two satellite images, one SPOT 4 image on 22 June 2005, and one Landsat 5 TM image on 14 July 2005, were collected for the corresponding time period. Results show that the spectral curve of the grass canopy was similar to that of the bare soil with lower reflectance at each band. Consequently, commonly used vegetation indices were not necessarily better than reflectance when it comes to single wavelength regions at extracting biophysical information. Reflectance, NDVI, ATSAVI, and two new coined cover indices were good at extracting biophysical information.     

Decentralized control in packet switched satellite communication

The model introduced by Schoute [1] is analyzed using a minimum principle for decentralized stochastic control [2]. For certain values of the input message ratespand numberNof transmitting stations, simple open-loop strategies are shown to be person-by-person optimal. The true optimal control is shown to be open loop forN = 2.     

DVB-RCS卫星系统无线资源管理体系架构

基于DVB-RCS（Digital Video Broadcasting and Return Channel via Satellite）卫星无线接入技术标准的宽带卫星通信技术已成为目前研究的热点。现有的DVB-RCS标准以物理层规范为主,其中的无线资源管理技术等重要的宽带无线接入功能的定义缺乏系统性,缺少具有可实现性的无线资源管理体系的描述,尚不能构成一个较完整的卫星宽带无线接入体系结构。针对宽带卫星通信的无线资源管理技术,提出一种基于DVB-RCS的宽带卫星无线资源管理体系结构,给出其主要功能模块设计及关键技术分析,并就可能的实现方法和进一步研究方向进行讨论。