基于OpenGL的卫星在轨运行可视化仿真系统设计与实现

针对如何构建一个卫星在轨运行可视化平台的现实问题,设计出一种基于OpenGL的卫星运行可视化仿真系统;介绍了该仿真系统的逻辑结构和网络结构,采用ADO技术实现了对卫星运行数据库的访问,利用3DS MAX构造了卫星模型和地球模型,实现了卫星在轨运行、覆盖效果、通信链路情况的可视化;实践证明,该仿真系统能够实时仿真卫星在轨运行的全过程,为卫星在轨实时管理提供了辅助决策支持平台;同时,该系统为航天部队网络化练兵提供了虚拟训练平台;对构建信息化条件下的虚拟战场仿真系统具有一定的借鉴意义。     

On the performance of UNB for machine‐to‐machine low earth orbit (LEO) satellite communications

Ultra narrow band (UNB) is a widely used technology for machine‐to‐machine and low‐power wide‐area communications. Its properties, long range with small RF power, make it naturally attractive for satellite communications but also draw new challenges compared with terrestrial systems where this technology is already deployed. Indeed, the main advantage of UNB signals, their small bandwidth, makes them more sensitive to frequency drifts that are particularly present in the case of LEO satellite systems. It also implies the use of a random access method in which the carrier frequency is a parameter unknown by the receiver. In this paper, we propose a general semianalytical model to evaluate the performance of a terrestrial or satellite system using UNB technology, taking into account the multiuser interference and the frequency drift. This model is then used to assess the performance (packet loss ratio and throughput) on the return link medium access control (MAC) of a representative LEO satellite system. With our model, we analyze the effect of frequency drift on the system performance. This paper also proposes to investigate more deeply the multiuser interference modeling in order to estimate accurately the performances of a UNB system in terms of bit error rate (BER). We propose a semianalytical approach to study the interference in presence of arbitrary power imbalance that includes the effect of frequency offset and frequency drift and applicable for any linear modulation and any pulse‐shaping filter. The expression of the multiuser interference is established in the general case. We then propose a methodology to compare this exact model to the Gaussian interference approximation (mainly used through the central limit theorem) in order to assess its accuracy.     

基于虚拟卫星的隧道内卫星导航信号增强方法

针对现有卫星导航接收机在隧道内无法有效定位的问题,提出了基于虚拟卫星的隧道内卫星导航信号增强方法。通过建立信号传播模型,在隧道两端模拟位于隧道延长方向的低仰角卫星的导航信号,发出后在隧道内接收解算,实现定位。同时,使用信号时延控制方法对伪距误差进行预补偿。经过硬件系统的实验分析,验证了其在隧道内的定位能力,仿真实验结果表明系统定位精度满足大部分隧道需求。     

无线网络技术在卫星通信中的应用研究

无线网络技术是一种新型网络通信技术,从网络节点出发,实现信息存储转发和编码处理,实现对网络无线传输的优化。首先,文章介绍了无线网络技术的优势;其次,分析了无线网络技术对于卫星通信的作用;最后,重点探究了无线网络技术在卫星通信技术领域中的应用。     

Modeling of UAV/RPAS data traffic in space,air, and ground networks

Remotely piloted air systems (RPASs) are increasingly used for data transmission in the space-air-ground integrated networks (SAGINs). That is why it is important to know the possibilities and ways of integrating existing space, air and terrestrial networks for effective interaction with RPASs. This paper studies the issues of ensuring the required quality of service during heavy traffic in SAGIN and the choice of the necessary data transmission modes for this. Models of communication channels were created, including line-of-sight transmission (Model 1), public terrestrial network (PTN) (Model 2), low-orbit satellite transmission (Model 3) and PTN plus satellite transmission (Model 4). The relationships between models' performance and traffic parameters, channel bandwidths, bit errors, lost packets and models' topology were investigated using NetCracker Professional 4.1 software. The dependencies of the average utilization on the transaction size and the time between transactions with different statistical distribution laws were analyzed. The effect of different bandwidths was investigated. The influence of the bit error rate and the probability of packet fail chance on the channel performance was studied. The traffic characteristics in all models were compared.     

Preparation of a CubeSat LEO radio wave propagation campaign at Q and W bands

Due to the congestion of the spectrum and the need for wider bandwidths, ultrahigh throughput satellites (UHTSs) are moving towards the use of higher frequency bands (Q/V and W bands). These frequencies are however severely impaired by atmospheric phenomena causing attenuation, scintillation and depolarization and compromising the quality of service (QoS). In order to study the Earth-space link, several experimental campaigns have been performed up to the Q band with geostationary (GEO) satellites. This paper introduces a new propagation experiment that will extend the characterization of the Earth-space channel up to the W band and low Earth orbits (LEOs).     

卫星扩频通信中一种简化的窄带干扰抑制方法

针对卫星扩频通信中的强窄带干扰，提出了一种基于频域处理的窄带干扰抑制技术。该技术采用了简化的自适应方法估计接收信号中噪声的功率，确定窄带干扰与噪声之间的阂值。通过降低高于阈值的干扰谱线的幅度同时保持这些谱线的相位信息，降低了处理后信号中的干扰能量，使接收信号信噪比大大提高。该窄带干扰抑制算法的复杂度比较小，硬件实现占用的资源较少。     

GPS的发展趋势与市场状况

作为一个出色的军民两用技术,GPS全球定位系统近年来获得了飞速的发展,文章介绍了当前军事和民用GPS应用产品的技术发展状况和趋势及国内外GPS市场的情况。     

卫星跳频调制解调器同步设计

研究了基于DSP实现的卫星跳频调制解调器的实现方案,介绍了系统的基本组成结构和调制解调原理,着重探讨了解调的同步算法的选取。卫星跳频通信的同步包括频率估计、位同步和跳频同步等多方面。首先讨论了频率同步,针对卫星通信频差较大的特点,采用了两个阶段的前馈式频率同步,分别完成对频差的粗略估计和精确估计,并对其同步性能做出了具体分析。位同步选用了数字锁相环法以忍受小的剩余频差。最后简单介绍了基于跳频同步的跳频信号的拼接。