共查询到19条相似文献,搜索用时 304 毫秒
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在临时或应急卫星通信应用中,较多地采用了车载卫星站或便携式卫星站的方式在现场建立通信传输链路。在现场,通过一辆(台)或数辆(台)卫星车或便携式卫星站,将现场各类图像、数据、话音、指挥调度或移动基站的信号传送到远端,建立卫星双向(或单向)链路,以实现现场信息传送、指挥调度建立或现场通信保障等。非固定地球站在卫星通信传输的运行操作中的必须关注站址的选择、通信系统的性能掌控、卫星资源(频率)申请、上星的许可,并做好非固定地球站在运行中的卫星通信链路质量管控,确保本站和相应卫星的通信运行质量。 相似文献
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地球同步轨道(GEO)卫星通信系统具有通信时延长的特点,适用于GEO卫星长期演进(LTE)通信的资源调度算法非常重要。为提升星上资源分配的高效性,基于可变最大加权时延优先(M-LWDF)算法,提出了一种综合考虑媒体接入控制(MAC)层参数和应用层参数的跨层调度算法。该算法在MAC层从数学角度推导,提出权重更大的时延判决因子及在应用层根据业务优先级不同引入Q因子。仿真结果表明,与M-LWDF算法相比,不同业务情况下,跨层资源调度算法减小了通信时延,提高了系统吞吐量,但公平性能略有下降并增加了复杂度。 相似文献
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集群通信在指挥调度及抢险救灾中发挥中重要作用,目前地面集群通信网络的覆盖范围有限,在处理有些紧急事件时可能会超出网络覆盖。依托通信对距离不敏感的卫星移动通信,在GMR-1标准基础上实现组呼呼叫业务功能,可以扩大集群通信的覆盖面积。对空闲模式下组呼通知过程进行了研究,对处于空闲模式下的移动台使用简化的NCH监听机制做了概述,最后提出了组呼通知信道的配置方法,计算得到NCH信道可以支持的话务量,与现有的GSM网络通信的相比具有更高的寻呼效率、可以承栽更大的用户数量。 相似文献
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自2002年提出转型以来,中国卫通以保障国家卫星通信广播安全、服务国民经济和社会发展为已任,确立了以卫星广播通信、指挥调度通信、应急通信、调度指挥通信和卫星导航定位通信等特殊领域的通信及农村通信、海上通信等特殊区域的通信为主导,以小容量、广覆盖、机动化的网络结构为支撑,专注发展特色业务、提供特色服务的企业发展思路,并以此发展思路为指导,加快业务创新步伐,加大结构调整力度,强化市场开拓,大力培育新经济增长点,坚定不移地走有卫星通信广播特色的发展之路,形成了卫星通信广播电视、数字集群应急通信和卫星导航定位综合信息… 相似文献
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集群通信系统是多个用户或部门群体共用一组无线电信道,并动态地使用这些信道的专用移动通信系统,主要用于指挥调度通信。文章首先简要介绍了TETRA系统中移动台(MS)侧MAC层基本工作原理,然后详细阐述了移动台接收下行突发到逻辑信道映射方案的实现。 相似文献
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卫星集群应急通信系统 总被引:2,自引:0,他引:2
卫星通信以其独特的特点,在许多场合中具有重要的应用价值。在指挥调度、应急救灾等场合中一般使用地面集群通信,但是其信号覆盖范围有限,集群通信组网受频率资源限制比较大。将具有覆盖面积大、受地理条件限制小以及通信频带宽等特点的卫星通信系统与地面集群通信系统结合组网,形成天地一体化的通信网络。 相似文献
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Radio resource management across multiple protocol layers in satellite networks: a tutorial overview
Paolo Barsocchi Nedo Celandroni Franco Davoli Erina Ferro Giovanni Giambene Francisco Javier Gonzlez Castao Alberto Gotta Jose Ignacio Moreno Petia Todorova 《International Journal of Satellite Communications and Networking》2005,23(5):265-305
Satellite transmissions have an important role in telephone communications, television broadcasting, computer communications, maritime navigation, and military command and control. Moreover, in many situations they may be the only possible communication set‐up. Trends in telecommunications indicate that four major growth market/service areas are messaging and navigation services (wireless and satellite), mobility services (wireless and satellite), video delivery services (cable and satellite), and interactive multimedia services (fibre/cable, satellite). When using geostationary satellites (GEO), the long propagation delay may have great impact, given the end‐to‐end delay user's requirements of relevant applications; moreover, atmospheric conditions may seriously affect data transmission. Since satellite bandwidth is a relatively scarce resource compared to the terrestrial one (e.g. in optical transport networks), and the environment is harsher, resource management of the radio segment plays an important role in the system's efficiency and economy. The radio resource management (RMM) entity is responsible for the utilization of the air interface resources, and covers power control, handover, admission control, congestion control, bandwidth allocation, and packet scheduling. RRM functions are crucial for the best possible utilization of the capacity. RRM functions can be implemented in different ways, thus having an impact on the overall system efficiency. This tutorial aims to provide an overview of satellite transmission aspects at various OSI layers, with emphasis on the MAC layer; some cross‐layer solutions for bandwidth allocation are also indicated. Far from being an exhaustive survey (mainly due to the extensive nature of the subject), it offers the readers an extensive bibliography, which could be used for further research on specific aspects. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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Satellite antennas 总被引:1,自引:0,他引:1
Communication satellites have evolved from a radio relay in space to encompass other applications such as processing and meteorology. The demand for high capacity communication satellites has led in the past two decades to the development of multibeam antennas, a landmark in satellite antenna technology. Satellite antennas are classified into three categories according to function: communication; tracking, telemetry, and command (TT and C); and special satellite antennas. While the application of shaped beam antennas has been developed to its fullest extent as in INTELSAT VI and VII, an active monolithic microwave integrated circuit (MMIC) phased array will play an important role in future satellite antenna technology. Examples of each state-of-the-art satellite antenna technology and the process of space qualification are presented briefly 相似文献
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Athanasios D. Panagopoulos George E. Chatzarakis 《Journal of Infrared, Millimeter and Terahertz Waves》2007,28(2):169-179
Satellite communication networks play an important role in the “digital divide” problem, by offering broadband services everywhere in the world. The ever increasing demand for multimedia services has led to the use of Ku, Ka and V band in modern satellite communication networks. In these frequency bands, rain attenuation is the most dominant propagation fading mechanism. Moreover, interference due to propagation phenomena deteriorates the performance of the satellite links and should be taken into account for the reliable design of satellite communication networks. In this paper, an analytical physical mathematical propagation model is presented for the prediction of channel capacity statistics of a dual-polarized interfered broadband satellite link. Rain attenuation spatial inhomogeneity is incorporated in the analysis with the employment of correlated slant paths. The obtained numerical results show the significance of these effects to channel capacity estimation. Finally, the proposed model may be used towards the optimum utilization of the satellite channel capacity by means of adaptive fade mitigation schemes. 相似文献
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Using traffic prediction and estimation of provider revenue for a joint GEO satellite MAC/CAC scheme
Polychronis Koutsakis 《Wireless Networks》2011,17(3):797-815
Satellite networks present an attractive solution in providing worldwide access to the present and future generation multimedia
communication services. However, the burstiness of multimedia traffic and the long propagation delays in Geostationary (GEO)
satellite systems call for an efficient Medium Access Control (MAC) protocol and an equally efficient Call Admission Control
(CAC) scheme, in order to provide acceptable Quality of Service (QoS) to multimedia users. This paper proposes a fair and
dynamic CAC and MAC framework, named Fair Predictive Resource Reservation Access (FPRRA), which is based on accurate videoconference
traffic prediction and makes decisions after taking into account the provider revenue. The framework’s performance is evaluated
in comparison to other efficient schemes from the literature. 相似文献
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探讨解决互联网到国际移动卫星C系统的通信协议转换问题。采用的方法是通过互联网的Telnet协议来仿真PSDN网络的X.25协议,通过2种协议的转换来实现互联网和卫星C系统的信息交互,并保持了原有用户直接使用X.25连接的访问习惯和指令集。采用X.25协议的单进程模式并结合虚拟多条电路方式对应互联网的多个Socket链接,该方法使得系统支持并发用户访问,并且提高访问速度和通信的稳定性。 相似文献
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在卫星通信系统中,卫星是一个很重要的环节,卫星转发器的参数在一定程度上决定着整个系统的性能.转发式卫星导航系统是一个导航通信一体化的系统,通信系统中的微小卫星终端由于其发射天线波束宽,从邻星干扰方面考虑,远区卫星还处在微小卫星终端的主瓣内,因此发射功率受到了限制,是一个很明显的上行功率受限的系统.为了缓解对发射终端的压力,文中对卫星转发器的增益表减档对整个通信系统的性能影响进行了分析,得到的结果显示,在转发器增益衰减档减小时,整个系统的性能可以得到提高,试验结果也表明,对于微小卫星终端系统,卫星转发器的增益档设置在2dB左右比较适宜. 相似文献