通信卫星切换控制技术研究及仿真

提出了一种通信卫星全球通信切换控制方案,与传统的单纯依靠地面信关站控制的方案相比,该方案不需要在全球范围内设置信关站,只需在内陆设置一个信关站就可以控制整个卫星群。用户的切换过程将由卫星星上处理和信关控制子系统协调完成,从而明显减少了切换时延和信令开销。在此基础上用opnet搭建了星座卫星系统仿真平台,在平台上实现了该方案。实验结果充分证实了该方案的可行性。     

LEO卫星IP网中的低延时切换

提出了一种由覆盖全球的无星际链路的低轨(LEO)星座构成卫星IP网,首次提出了一种按信关站来划分网络的策略,并着重讨论了卫星IP网中的星间切换技术,提出用邻站广播技术来实现低延时切换的策略。仿真结果表明,本文提出的策略能大大减少信令交换量和降低切换延时,有效保障了卫星网中实时多媒体业务的QoS。     

星座卫星系统安全防护体系建设的几点建议

1 星座系统和安全防护 1．1 星座系统安全肪护规划 星座通信系统信道组成如图1所示。星座通信系统的用户分为境内和境外用户。星座通信系统在主权领域内设置有信关站,卫星覆盖范围内有信关站时不做星上交换,采用透明转发方式,信息经由地面网络传送至对方所在信关站,再传给对方用户终端。若覆盖范围内没有信关站,则采用星际路由或存储转发的方式进行信息转发。     

VSAT数据网与地面分组网互连的流量控制技术实现

本文采用X.25网络互连协议,提出了实现基于HDLC收据链路规程的VSAT卫星数据网与地面分组数据网网络互连信关的流量控制技本实现的具体方法以及网络互连信关分组层虚电路呼入/呼出实现方案、给出了采用文献[1]的流量控制算法和X.25协议实现网络互连信关流量控制及虚电路呼入/呼出业务的硬件配置及软件包运行实例。     

卫星移动通信系统无线接入网模拟实现

根据我国卫星移动通信系统的发展趋势,借鉴地面移动网络管理与运维技术思路,开展卫星移动通信系统网络管理与运维技术的研究很有必要。信关站无线接入网模拟技术实现卫星移动通信系统模拟信关站无线接入部分的协议处理功能,包括业务和信令。无线接入部分主要包括模拟物理层、模拟RLC/MAC层和模拟无线资源控制RRC层,完成终端的接入和无线资源管理过程。实现的协议栈模拟软件参考GMR-1 3 G系统框架展开研制,能够有效地模拟载波、时隙和信道的分配过程,且能够与模拟核心网设备交互,是卫星移动通信验证测试系统的重要组成部分。     

嵌入式安全Web网关系统的硬件研究与设计

针对传统嵌入式Internet方案占用空间大、成本高、安全性差、功能单一等不足,设计了嵌入式安全Web网关系统的硬件结构,分别对嵌入式Web网关系统的主控模块、CAN总线通信模块和智能断路器的CAN通信接口进行了设计。设计中采用32位ARM7TDMI网络专用处理器,内部集成以太网控制器,提供高性能、高可靠、低成本的硬件平台。设计的硬件结构具有可靠性、稳定性和合理性,保证了整个Web网关系统的运行质量。     

TES网络系统

TES网络系统是休斯公司结合中国实际情况研制开发的一种VSAT通信网络，基于卫星的以全数字话音传输为主、兼具中低速数据通信的网状网，系统结构见图1。TES系统由许多节点（或称远端站Remote）和一个网络控制系统（NCS）组成。网络控制系统NCS提供网络管理与控制，是整个网络的核心，可位于任一TES节点。节点有两种类型：TES远端站及TES网关。TES网关支持多条信道进入公共网。TES系统支持网络内任意两个远端站间直接进行话音、同步及异步数据通信。远端站间直接传输话音和数据，因此卫星传输延时最小。系统中话音电路采用按需…     

地面分组网利用MF-TDMA卫星网组网的网关研究

卫星通信网络因其在各种突发事件中表现出的应急通信保障能力等独特优势受到越来越广泛的关注。其中MF-TDMA卫星通信网因为支持综合业务接入、能够实现大小终端同网工作、可以针对不同的应用需求进行灵活设计等诸多优点而成为目前国内外卫星应用、发展及研究的热点。利用有线、微波中继等进行组网的地面分组网络如何高效便捷地利用MF-TDMA卫星通信网络进行组网已经成为当前混合组网的热点之一。通过对地面分组网络和MF-TDMA卫星网络的简单介绍,提出了实现MF-TDMA卫星网在地面网中的应用方案并进行了一些分析,针对通信网关方案进行了较为详细的介绍,可以作为相关工程设计的参考。     

同步轨道卫星移动通信的网络内部通信

完善的网络内部通信是通信系统向用户提供及时的,高质量的通信服务的重要保证。同步轨道卫星移动通信的网络内部通信是卫星网的节点之间的信息传送,网络节点之间的内部通信链路构筑了网络内部通信。它可为整个卫星风提供同步服务,即保障卫星网点节点在统一的时间基准和频率基准下同步工作,还可在节点间传送资源管理,网络管理信息和完成信关站之间的信令传送。     

基于XML技术的WSN网关系统的设计与实现

为了完成Internet与WSN之间的互联,扩展WSN数据服务,提出一种基于XML技术的WSN网关系统的设计和实现方案。基于S3C2440低功耗嵌入式处理器设计并实现了具有以太网,USB等扩展接口的网关硬件平台。利用XML技术和XML-RPC技术,设计了＂用户配置,按需解析＂的网关中间件。利用Flash动态网页和Web Service服务提供实时动态数据表现。网关系统有效地将数据解析与应用表现分离,实现了＂一网关多用途＂的功能,大大地简化了网关系统的配置、部署,提高了网关系统的重复利用性。     

Emulation platform for inter-domain protocols validation of integrated space-terrestrial network

The inter-domain routing protocol is a key factor in the rapid integration of various satellite systems and heterogeneous networks in integrated space-terrestrial network (ISTN).However,the wide difference between network topologies of space and terrestrial networks may present significant challenges to the deployment of existing inter-domain protocols.To test the performance of these protocols,an emulation platform for ISTN was designed to efficiently emulate the dynamic and large-scale space network and the existing terrestrial networks using virtual network technology.Extensive experiments demonstrate that,with the expansion of the scale of space network and the scale of terrestrial Internet’s routing table,the integration efficiency between space and terrestrial networks becomes very low.     

Critical issues of onboard switching in DVB-S/RCS broadband satellite networks

The next generation of broadband satellite networks is challenged to accommodate multimedia services while concurrently integrating with terrestrial IP networks. With IP applications dominating the Internet, carrying IP traffic over the satellite has been under intensive study. Originally developed to bring digital television home through satellites, the DVB-S and DVB-RCS standards empower interactive satellite communications with economical standardized satellite terminals. Furthermore, onboard switching technology is increasingly gaining attention, due to optimized bandwidth usage, fully meshed network topology through one satellite hop, and quality of service guarantee. This article investigates the onboard switching technologies in DVB-S/DVB-RCS broadband satellite networks. Aside from the network system infrastructure and switch hardware architecture, the QoS mechanisms supported by the switch onboard the satellite are discussed in depth.     

Spectrum allocation method for cognitive satellite network based on service priorities

By using spectrum allocation technology of cognitive radio into integrated satellite and terrestrial networks,the satellite communication network can share spectrum with the terrestrial network and improve utilization efficiency of frequency spectrum in the satellite communication system.Firstly,a spectrum resource sharing model in integrated satellite and terrestrial networks was introduced,and the scenery that cognitive satellite downlinks use the vacant spectrum of terrestrial network was analyzed.Then,the interference and signal model was analyzed.Finally,considering different priority types of satellite terrestrial terminals,a spectrum allocation scheme based on priority was proposed,which could ensure the total throughput in satellite downlink communication and increase the throughput of high-priority terrestrial terminals.     

一种适用于星地网络的流量负载均衡算法

在星地网络的背景下,为了降低由于地面网络链路负载过高导致的传播时延,提出了一种适用于星地网络的负载均衡算法。算法基于网络的链路容量设置一个链路资源利用率作为阈值,当发现路径出现过载的时候分成两步进行路径的预规划：第一步,运用蚁群算法为链路过载的数据流选择其他的路径,以满足地面网内部的负载均衡;第二步,如果仍出现链路超阈值的情况,通过卸载延迟容忍数据流来执行地面与卫星网络之间的负载均衡。仿真结果表明,设定自适应的过载阈值可以有效降低链路的拥塞,与现有算法相比该算法不仅可以更加均匀地分配地面网络中的流量,而且借助卫星网络使地面网络的平均时延降低了18.3%,提高了网络的服务质量。     

Survivability and scalability of space networks: a survey

Survivability and scalability are key terms for any network. The challenge is greater in space networks than in terrestrial networks. Satellites have various uses, some notable uses are communication, observation, meteorology, navigation etc. In future satellites will aid terrestrial users by providing Internet connectivity. With proliferation of Internet users, demand for satellite services will increase and soon we will suffer from bandwidth limitation. Hence, the scalability and survivability of space networks are very important issues to ensure smooth connectivity to all the users both mobile and immobile. Since, most of the existing works on network survivability and scalability are focused on terrestrial networks. We have categorized the existing works on survivability and scalability of terrestrial networks. In addition, we have performed a comprehensive survey on the popular products available in the market for network survivability and scalability. Finally, we have listed the major issues and challenges of space networks that needs to be considered before applying network scalability and survivability solutions on them. This work can help network engineers to select suitable solutions for space networks considering the available choices and challenges listed in this paper.     

低中轨道双层卫星光网络的分时切换半实物仿真演示系统

为精确模拟验证低中轨道（LEO／MEO）双层卫星光网络及其关键技术,按1：30的比例设计了分时切换双层卫星光网络半实物实验演示系统。系统包括计算机仿真环境和硬件平台两部分,通过SITL模块互联而成。软件部分由虚拟网络组成,实现灵活、可扩展的配置;硬件平台由1个圆形往复转台、6个伺服机构、6个无线激光通信终端和6组自动追...     

S-WiMAX: adaptation of IEEE 802.16e for mobile satellite services - [WiMAX update]

Mobile satellite services are attracting renewed attention stemming from the FCC ancillary terrestrial component ruling that allows satellite spectrum to be used for integrated terrestrial services in the footprint of the satellite. This attention is focused on the development of dual-mode satellite-terrestrial devices to facilitate hybrid satellite-terrestrial networks intended by the ATC order. The satellite component in these dual-mode devices is best adapted from the air interface chosen for the ATC to optimize form factor, especially for small hand-held devices, mobility management, power efficiency, and a common core network functionality. With the advent of WiMAX as a viable 4G technology, satellite adaptation of WiMAX has been considered for the satellite services coupled with WiMAX ATC. The main considerations for satellite adaptation of WiMAX, relative to its terrestrial counterpart, are reduced link margin and longer transmission delays ? both absolute delay from the center of a spot beam to the satellite and differential delay between the beam edge and the beam center to the satellite. These considerations suggest adaptation of the subchannelization schemes, the frame synchronization methods, and the ranging process in WiMAX to make it operable over satellite, while keeping the general framework of the WiMAX protocol stack intact, thereby facilitating the incorporation of S-WiMAX into a common baseband processor with terrestrial WiMAX; this allows S-WiMAX to be added to terrestrial WiMAX devices with minimal cost and formfactor impact. Methods for these adaptations are considered here.     

基于ARM＋ZigBee的通用网络测控系统硬件设计

根据当前网络化测控需求,采用了ARM920T核的微处理器S3C2440,ZigBee无线SoC芯片CC2430F128相结合的硬件设计方案,设计了一种基于ARM和ZigBee的通用网络化测控系统硬件平台,详细阐明了系统各模块的硬件设计。实际应用表明,系统硬件平台网络性能好、通用性强且成本较低。     

A new satellite communication system integrated into publicswitched networks-DYANET

A system concept of a common alternative routing system is proposed for reducing total network costs by integrating satellite communications into public-switched networks, where satellite systems carry overflow traffic from terrestrial systems through common satellite channels. This concept has been realized by a satellite communication system called DYANET (dynamic channel assigning and routing satellite aided digital networks), which provides trunk circuits in combination with terrestrial systems. The key technologies developed for DYANET are a centralized network control system and a transponder hopping demand assignment TDMA (time-division multiple-access) system, to assure single-hop connection and to use satellite channel efficiently. The authors describe the system concept and configuration, the network control system, and the results of its commercial use     

Optimized handover and resource management: an 802.21‐based scheme to optimize handover and resource management in hybrid satellite‐terrestrial networks

Satellite communications can provide fourth generation (4G) networks with large‐scale coverage. However, their integration to 4G is challenging because satellite networks have not been designed with handover in mind. The setup of satellite links takes time, and so, handovers must be anticipated long before. This paper proposes a generic scheme based on the Institute of Electrical and Electronics Engineers 802.21 standard to optimize handover and resource management in hybrid satellite‐terrestrial networks. Our solution, namely optimized handover and resource management (OHRM), uses the terrestrial interface to prepare handover, which greatly speeds up the establishment of the satellite link. We propose two mechanisms to minimize the waste of bandwidth due to wrong handover predictions. First, we leverage the support of 802.21 in the terrestrial access network to shorten the path of the signaling messages towards the satellite resource manager. Second, we cancel the restoration of the satellite resources when the terrestrial link rolls back. We use OHRM to interconnect a digital video broadcasting and a wireless 4G terrestrial network. However for the simulation tool, we use a WiMAX as the terrestrial technology to illustrate the schemes. The simulation results show that OHRM minimizes the handover delay and the signaling overhead in the terrestrial and satellite networks. Copyright © 2013 John Wiley & Sons, Ltd.