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本文主要介绍了我国卫星移动通信的发展现状及市场需求，针对当前国内外具体情况，提出了发展我国国内，国际卫星移动通信业务的合理建议。文章认为国内移动通信业务应采取先租星过渡，然后再建设自主运营，功能完备的卫星移动系统的方针；国外业务则采取慎重选择加入国际性系统的策略。 相似文献
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Performance evaluation of an improved PRMA protocol for low earth orbit mobile communication systems
Enrico Del Re Romano Fantacci Giovanni Giambene Sergio Walter 《International Journal of Satellite Communications and Networking》1997,15(6):281-291
Future mobile communication systems will be characterized by the interworking of several networks that will be integrated into a unique system. The satellite component and the terrestrial one will use as far as possible the same protocols. This work is concerned with Medium Access Control (MAC) protocols. In particular, Packet Reservation Multiple Access (PRMA) has been considered as a good candidate for terrestrial cellular systems, since it allows high multiplexing gains, dynamic PRMA carrier allocation to cells, easy management of integrated voice and data traffic and a near-transparent behaviour with respect to user mobility. The main aim of this preliminary work is to investigate the suitability of the PRMA protocol for application to Low Earth Orbit Mobile Satellite Systems (LEO-MSSs). Moreover, we have proposed a novel version of the PRMA protocol, named PRMA with Hindering States (PRMA-HS), that is particularly suitable for application in LEO systems. This new technique has shown very promising results in terms of both packet dropping probability and throughput. © 1997 John Wiley & Sons, Ltd. 相似文献
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本文讨论典型中、低轨道卫星通信系统网络结构和ＬＥＯ／ＭＥＯ／ＧＥＯ系统性能对比方法，亦展望了其存在问题及发展前景。 相似文献
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Jonathan P. Castro 《International Journal of Satellite Communications and Networking》1994,12(1):71-75
This article presents an overview of the concept of a multiple purpose global satellite network. It identifies some of the main needs of telecommunication services today, and projects the potential of future demands. It also describes the great possibilities of economic expansion and mass participation in the growth and prosperity of a nation, if basic telecommunication services are accessible on a global scale. The study suggests that the rapid recovery of capital investments on universal satellite networks lies in developing regions through cost-effective service diversification. 相似文献
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LEO/MEO卫星通信系统发展展望 总被引：3，自引：0，他引：3
本简述了LEO/MEO卫星通信系统的主要特点,并介绍了几个典型的LEO/MEO卫星通信系统,如Iridium、Globalstar、ICO、Teledesic、Skybridge系统。还从星座、频率、星上处理及星际链路、无线技术、网络技术等方面讨论了LEO/MEO卫星通信系统的发展趋势和研究热点。 相似文献
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面向２１世纪的现代卫星移动通信（下）陈如明（邮电部外事司北京１００８０４）３．３ＭＥＯ－Ｏｄｙｓｓｅｙ系统Ｏｄｙｓｓｅｙ（奥德赛）系统是由美国ＴＲＷＩｎｃ。公司开发的ＭＥＯ系统，于１９９１年５月２８日向美国ＦＣＣ提出了使用许可证申请。它由１２颗星组成... 相似文献
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Raúl Chvez Santiago Valeri Ya. Kontorovitch Mauricio Lara Barrn 《International Journal of Satellite Communications and Networking》2003,21(6):547-560
Computing interference is very important in satellite networks design in order to assure the electromagnetic compatibility (EMC) with other radiocommunication systems. There are different methods to compute interference in geostationary (GEO) satellite systems including conventional methods using link budget equations and alternate methods such as increase in noise temperature. However, computing interference in low earth orbit (LEO) systems represents a different problem. Due to the special characteristics of this kind of orbits, the elevation angle at any site changes continuously over time, meaning a time dependent change of the propagation path length between an interfering transmitter and an interfered‐with receiver, and of the discrimination provided by the transmitting and/or the receiving antenna. Thus, conventional interference prediction methods developed for fixed links must be adapted to the case of LEO systems. To overcome this problem a mathematical model that characterizes the path length variations by an average value obtained from the probability density function of the varying distance between an interfering transmitter and an interfered‐ with receiver is proposed in this paper. This average path length enables the use of conventional link budget methods to reduce the computation time for the evaluation of interference in LEO satellite environments. Two practical examples show the possible applications of the proposed model. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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信息高速公路中卫星无缝隙覆盖综合业务发展的技术问题与解决途径（下）陈如明（邮电部电信总局北京１００８０４）４一些主要技术问题与可能的解决途径在明确了未来ＳＤＨ／ＡＴＭ卫星网络与地面网络无缝隙覆盖综合的基本网络结构考虑后，下面进一步讨论欲实施其相应互操... 相似文献
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Jos Mauro P. Fortes Jorge E. Amores Maldonado 《International Journal of Satellite Communications and Networking》2002,20(1):15-27
Until 1997, the power flux density (pfd) limits applicable to fixed satellite service (FSS) satellite transmitters to protect fixed service (FS) receivers operating in the same frequency band were those in Article 21 of the radio regulations. They were developed assuming that potentially interfering satellites in the FSS would only operate in the GSO. The need to revise these limits to allow for the protection of FS receivers from interference generated by non‐geostationary satellites has led to several studies, most of them based on the non‐realistic assumption that every visible satellite in a NGSO constellation produces the maximum allowed pfd level at the FS receive station location. To provide a quantitative indication of how pessimistic this assumption is, this paper considers a more realistic model in which the pfd entries reaching a given FS receiver location are characterized by statistically independent random variables. The probability density functions of these random variables depend on the operational characteristics of the NGSO network. The obtained results have also shown the need to consider some of the operational characteristics of NGSO satellite networks when evaluating the interference produced by their satellites. If these operational characteristics are not taken into account in the calculations, higher values of interference, that do not reflect the real interference environment, are obtained. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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首先分别分析了GEO层、MEO层、LEO层卫星的优缺点，接着简述了LEO＆MEO双层卫星网络的特点及对路由算法的要求，然后对已有的卫星网络路由算法进行简要分析，最后提出了一套适合LEO＆MEO双层卫星网络的动态路由技术。在拓扑快照DT-DVTR路由算法和MLSR的基础上，设计了动态路由算法，该路由算法采用了主动路由和按需路由相结合的方式，使得路由查找时间短、效率高。 相似文献
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P. Loreti M. Luglio R. Kapoor J. Stepanek M. Gerla F. Vatalaro M. A. Vazquez‐Castro 《International Journal of Satellite Communications and Networking》2004,22(6):587-610
Satellites offer a promising alternative for mobile access to the Internet by both pedestrians, and more importantly, from vehicles. As such, satellites provide an essential complement to the cellular radio (UMTS) infrastructure in sparsely populated areas where high bandwidth UMTS cells cannot be economically deployed. In this paper, we analyse various mobile Internet applications in representative urban scenarios for two LEO constellations (one with polar orbits and the other with inclined orbits), as well as for some simple GEO configurations. To this end, we develop a satellite channel propagation model that includes shadowing from surrounding building skylines based on actual data in a built‐up area. Using these tools, we analyse various Internet applications and the performance of various TCP schemes in different topologies. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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卫星通信在信息高速公路中的地位与作用 总被引：1，自引：1，他引：0
本文从信息高速公路的无缝隙网络构成及个人用户驱动的基本特征出发，论述了卫星通信在未来全球／区域／国家信息高速公路中的独特地位与作用；进而较详细地讨论了涉及未来信息高速公路的卫星通信的基本发展态势及一些值得引起注意和必须深入研究的重要技术问题和规则、政策问题。 相似文献
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QoS Handover Management in LEO/MEO Satellite Systems 总被引：4，自引：0，他引：4
Low Earth Orbit (LEO) satellite networks are foreseen to complement terrestrial networks in future global mobile networks.
Although space segment topology of a LEO network is characterized by periodic variations, connections of mobile stations (MSs)
to the satellite backbone network alter stochastically. As a result the quality of service delivered to users may degrade.
Different procedures have been proposed either as part of a resource allocation mechanism or as part of an end-to-end routing
protocol to manage transitions of MSs from one satellite to another (handover). All of these techniques are based on the prioritization
of requested handovers to ease network operation and therefore enhance provision of service. This paper proposes a new handover
procedure that exploits all geometric characteristics of a satellite-to-MS connection to provide an equable handover in systems
incorporating onboard processing satellites. Its performance is evaluated by simulations for a variety of satellite constellations
to prove its general applicability.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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陈如明 《电信工程技术与标准化》2000,(5):5-10
本文论述了当前全球无线通信发展中的六大新走势,即市场走势规模化,网络走势全球化,业务走势数据化,技术走势宽带化,接入走势普遍化以及知识走势经济化。 相似文献
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Emilio Matricciani Simone P. Selva 《International Journal of Satellite Communications and Networking》2002,20(3):167-185
Based on experimental data, we have reported a method to scale the cumulative time, TF,T(A), a given attenuation, A (dB), is exceeded in a MEO satellite system in fixed terminals, to the time, TM,T(A), A is exceeded in mobile terminals. Zigzag routes and ring roads simulated city patterns; straight routes simulated freeways. In all cases, TM,T(A) can be expressed as TM,T(A)=ξTF,T(A) with a probability scaling factor ξ independent of A. Although the satellite systems have been simulated at 19.77 GHz, the results concerning ξ can be considered frequency‐independent. We have used a very large number of rain‐rate maps of storms randomly observed in 1991–1992 by a meteorological radar in Northern Italy. The speed of vehicles was modelled as a lognormal random variable. We found: (a) in zigzag routes TM,T(A)<TF,T(A), i.e. ξ<1, with results depending on vehicle speed modelling and starting conditions; (b) in ring roads there is no difference between fixed and mobile systems (ξ≈1); (c) in straight freeways TM,T(A)?TF,T(A) (ξ?1) and TM,T(A) can change significantly in different straight lines and in opposite directions (anisotropy and asymmetry) for medium–large attenuation. When compared with zigzag routes or ring roads, the performance in straight freeways is the most optimistic. The numerical values of ξ applicable to a MEO satellite system are not significantly different from those applicable to a GEO satellite system working in the same conditions. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献