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低轨(Low Earth Orbit, LEO)卫星互联网相较于地面网络有更大的网络覆盖范围与更强的网络稳定性,有利于实现全球立体无缝网络覆盖,是未来6G网络重要的发展趋势。低轨卫星相较于中高轨卫星具有更高的运行速度,因此,低轨卫星信号具有更大的多普勒频移和动态特性,而低轨卫星信号的高精度捕获与跟踪是低轨卫星通信的基础。随着相控阵天线在低轨卫星和卫星终端上的推广应用,多波束和跳波束技术也为信号的捕获与跟踪带来挑战。从低轨卫星信号互联网的信号特点出发,提出了信号捕获与跟踪过程中的技术挑战,重点阐述了现有捕获与跟踪方法的基本原理与适用范围,探讨了低轨卫星网络中信号捕获与跟踪技术的未来发展方向。 相似文献
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随着大规模低轨卫星星座的全面部署,对天基测控服务模式提出了新的挑战。分析了低轨卫星星座在常态运行、应急使用以及智能化应用中的测控需求;构建了新型天基测控服务系统,设计了前返向实时跟踪波束和全域静态波束组合应用的天基测控资源保障模式。提出了基于地面运管中心统一调度的天基测控服务模式,给出了即时计划驱动和“返向全时分发+前向业务驱动”两种典型模式下的系统工作流程,归纳总结了所述服务模式产生的效益。详细梳理了与所述服务模式相适配的卫星终端设计要求,明确了不同模式下的卫星终端工作状态。可用于指导后续对低轨卫星星座天基测控服务的工程化应用。 相似文献
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针对静止轨道(Geostationary Earth Orbit, GEO)卫星系统和低轨道(Low Earth Orbit, LEO)卫星系统频率共享时存在的干扰问题,本文基于低轨分布式卫星编队提出了一种鲁棒自适应波束成形算法,从空间域功率隔离角度解决了高低轨卫星通信系统上行链路共用频谱时GEO用户对于LEO卫星共线干扰问题。算法中综合考虑卫星通信系统长传播时延导致的阵列导向矢量存在一定误差,在基于线性约束最小方差(LCMV)准则的自适应波束成形器中设计了考虑系统最恶劣误差情况的鲁棒性约束,并采用泰勒级数逼近法求解波束成形器加权矢量。仿真结果表明本文的鲁棒波束成形算法在卫星通信环境下适应度较高,能够有效地缓解高低轨卫星通信系统频率共享带来的同频干扰问题。 相似文献
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近年来,国家在卫星体系建设方面投入了大量的人力、财力和物力资源,卫星系统的发展也取得了一系列的成果。低轨卫星是卫星系统的重要组成部分,而且由于低轨卫星具有许多其他卫星不具备的特点而引起了广泛的关注。文章围绕低轨卫星在信号处理方面所需的关键技术进行研究,试图为改进低轨卫星的运行做出一定的努力。 相似文献
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本文采用偏置馈源口径场技术从理论上分析了偏置波束场型和增益,研究和计算了慧形象差影响所引起的增益损失。研制出的双波束馈源系统,可用于任意前馈卫星站的改造;3m双波束卫星接收天线增益高、副瓣低、噪声小。 相似文献
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GPS-based navigation and attitude determination of LEO satellites is presently considered as an alternative to the conventional systems which utilize earth sensors and magnetometers. The onboard GPS receiver determines the orbit position of the LEO satellite by the conventional system of linearized navigation equations, requiring the simultaneous reception of ranging signals from four GPS satellites by a single antenna. For attitude determination, pairs of antennae, suitably mounted on the satellite and feeding a common receiver, form several interferometric baselines. The baselines vectors, defined in a given coordinate system, determine the attitude of the satellite. For each baseline and each GPS satellite, the difference in phase of the received signal carriers is measured. The differencing operation eliminates the receiver clock bias. Solutions for the baseline vectors can be obtained with signals received from only three GPS satellites. If the coverage of a receive antenna is restricted to less than the hemisphere it will not have four GPS satellites in view all the time. It is demonstrated that a GPS pseudolite transmitter located on earth supplements the system, which then provides a usable geometric dilution of precision (GDOP) for position determination and an improved position dilution of precision (PDOP) for attitude determination. Pseudolites can be co-located with the gateways which provide access to the public switched telephone networks (PSTNs) for the LEO communication satellites. 相似文献
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It is an effective method to broadcast the augmentation information of satellite navigation system using GEO technology. However, it becomes difficult to receive GEO signal in some special situation, for example in cities or canyons, in which the signal will be sheltered by big buildings or mountains. In order to solve this problem, an Internet based broadcast network has been proposed to utilize the infrastructure of the Internet to broadcast the augmentation information of satellite navigation system, which is based on application layer multicast protocols. In this paper, a topology and position aware overlay network construction protocol is proposed to build the network for augmentation information of satellite navigation system. Simulation results show that the new algorithm is able to achieve better performance in terms of delay, depth and degree utilization. 相似文献
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Abbas Jamalipour Masaaki Katayama Takaya Yamazato Akira Ogawa 《International Journal of Wireless Information Networks》1996,3(1):29-39
It has been shown in our previous studies that the geographical traffic nonuniformity considerably affects the performance of the low earth orbit satellite communications systems. In this paper, a new scheme for improving the throughput characteristics of these systems at nonuniform traffic distribution is proposed. In this method, some parts of the users under the satellite which is flying over the area with high traffic load are assigned to its neighbor satellites with lower transmitting power levels. It is shown that the method equalizes the traffic loads of the satellites to some degree and, hence, can improve the throughput characteristics of the system. 相似文献
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Francesco Delli Priscoli Flavio Muratore 《International Journal of Satellite Communications and Networking》1994,12(1):13-24
The integration between cellular networks and satellite systems is a very promising issue, since it permits the immediate provision of the radio services offered by the cellular networks to areas lacking in terrestrial facilities. In this paper the viability of a full integration between the GSM cellular network and a satellite system is dealt with. The L-band land mobile payload has been assumed as a reference; nevertheless the presented results can be extended to other payloads. The basic requirement of full integration is that the insertion of the satellite system does not entail any modification of the already existing GSM network. The integration analysis has been carried out by examining both the link feasibility and the network architecture. As far as link feasibility is concerned, the analysis is performed by means of an ad hoc simulation tool developed at CSELT (Turin). The simulation results are displayed for GSM speech channels at both full-rate (TCH/FS) and half-rate (TCH/HS). Such results are used in order to compute the satellite link budgets and the satellite system capacity. The characteristics of the satellite propagation channel, of the satellite-compatible mobile station and of the reference payload are explained as well. As far as the network architecture is concerned, the paper identifies the most promising satellite system configuration and the satellite system counterpart of the GSM functional areas (cell, location area, MSC area). Moreover, the problems and the relevant solutions related to the extension of the main GSM procedures (e.g. call set-up, cell selection/reselection, handover) to the integrated network are dealt with. This paper is based upon the work performed by the authors in the framework of the European Space Agency (ESA) study: ‘Assessment of a public mobile satellite system compatible with the GSM cellular network’, Telespazio (Rome) is the prime contractor of this study. The opinions herewith reported are not necessarily those of ESA. 相似文献
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Efficient dynamic authentication for mobile satellite communication systems without verification table 下载免费PDF全文
The mobile satellite system is an important wireless communication system widely used nowadays. The issue of protecting the transmission security in low‐earth‐orbit satellite networks thus becomes more and more critical. It is known that several authentication schemes for satellite communication systems have been proposed to deal with the issue. However, previous protocols either employ complicated public key computation or have to maintain a verification table. In this paper, the author will introduce a new dynamic authentication protocol for mobile satellite communication systems without using a verification table. The comparison results will also show that the proposed scheme has lower computational costs. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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王存良 《太赫兹科学与电子信息学报》2012,10(4):421-425
为了对地面某一区域在未来某一时段连续覆盖,需要对在轨卫星变轨,并计算变轨后的卫星轨道参数。基于在轨卫星部分轨道参数(椭圆轨道a,i,e,圆轨道a,i)和t时刻星下点的位置坐标及卫星的地面高度,计算卫星的6个轨道参数,从而得到t时刻对星下点位置为中心的区域覆盖所需要的卫星轨道参数。利用t时刻卫星在J2000.0平天球坐标系3个坐标轴的位置与速度分量计算其卫星轨道参数。用STK卫星工具箱软件6.0高精确度轨道产生器仿真,输入所得的t时刻卫星轨道参数,运行STK 6.0得到的星下点位置与事先设置的星下点相距6.63 m,完全满足卫星对地面覆盖的需要。欲对该区域在t时刻以后的一段时间连续覆盖,所需要的卫星轨道参数可按共地面轨迹计算;通过STK 6.0高精确度轨道产生器对计算得到的卫星轨道参数进行仿真,验证了计算结果的正确性。 相似文献
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卫星应急通信指挥平台设计是一项复杂的系统设计工作,需要设计人员掌握和运用多种设计方法。本文概括性地归纳了卫星应急通信指挥平台设计的一般性方法论,分析了卫星应急通信指挥平台设计的基本原则、主要特征、性质分类,总结了设计过程中运用的传统设计方法和现代设计方法,包括模型设计法、常规设计法、系统设计法和可靠性设计法等4种主要设计方法,为设计人员进行卫星应急通信指挥平台设计提供了理论指导。 相似文献