Meteor scatter: an overview

The phenomenon of radio propagation using meteor trails is reviewed. Underdense and overdense propagation mechanisms are described. The multipath and fading profile of the meteor channel is examined. Mechanisms other than meteor trails that are commonly observed on meteor links and can change the characteristics of the meteor communication channel are considered. These include sporadic-E propagation, auroral scatter, ionospheric scatter, diffraction, line-of-sight propagation, and tropospheric scatter     

基于速率自适应流星余迹通信设计

针对随机突发并且接收信号多数以指数衰减的流星余迹信道来说,研究链路自适应技术以达到充分利用流星余迹信道资源就显得尤为重要。深入研究了流星余迹突发通信的传播机理和信道的随机特性,从理论上经过分析计算证明了采用自适应变速率技术可以显著改善和提高流星突发通信性能,在此研究基础上提出了基于流星余迹动态信道估计的流星余迹自适应变速率通信技术解决方案。     

流星余迹通信信道统计特性及模型仿真

流星余迹通信不同于传统的通信,它是低速率通信,具有突发、不连续以及不定时的特性。流星余迹通信的复杂性要求有必要对其通信信道进行研究。可用流星率、占空比、平均持续期、等待时间和通信通过量是影响流星余迹通信信道性能的重要参数。根据偶发流星日心空间和地心空间的几何关系,得到了流星突发通信信道参数预测模型;并对流星通信链路观测的数据进行统计分析,得到流星余迹通信信道的各参数,预测结果和通信链路观测结果比较一致,为流星通信系统的建立提供了技术支持。     

流星余迹信道建模与仿真分析

为检验流星余迹通信设备及软件在实战化环境中的应用效能,针对流星余迹通信信道规律复杂、实测代价高等问题,建立流星余迹信道仿真模型。通过对典型数学模型的深入研究,以欠密类流星余迹和过密类流星余迹信道模型为基础,融入了欠密类流星簇和多径信道两种特殊类型,按照概率论原理,建立了流星余迹信道混合模型,并结合流星余迹到达间隔模型,利用C++实现了流星余迹信道混合模型的仿真。该模型可生成包含单颗欠密类、单颗过密类、欠密类流星簇和多径信道等多种类型的复杂信道。仿真结果表明,所产生的流星余迹信道特征与实际信道基本相符,验证了该模型的可用性和合理性。     

流星余迹反射信号特性研究

通过对采集到的流星余迹反射信号样本的分析和研究,总结出了反射信号的基本特征和分布规律,分析了不同类型反射信号的形成机理,指出了非流星余迹反射信号是流星余迹通信研究中不可缺少的内容。对如何充分利用非流星余迹反射信号给出了抗衰落措施以及协议设计要注意的问题,最后提出了流星余迹通信系统工程设计的新思路。     

链路自适应技术在流星余迹通信中的应用

流星余迹通信具有其他通信系统无法比拟的优点,如:大跨距、抗干扰、低截获概率特性和抗毁性等特点,使得这种通信方式的应用范围越来越广泛,尤其是支援短波通信及用作卫星通信的替补手段。但是流星余迹信道又是一种典型的突发信道,通信容量小和实时性差。为了最大限度地利用短暂的流星余迹信道,人们设计了链路自适应技术。此技术能够根据信道状况自动调整发射机和接收机的参数,使得流星余迹信道资源得到最大限度的利用。     

流星余迹通信信道季节变化模型与仿真

流星余迹通信不同于传统的通信,它是低速率通信,具有突发、不连续、不定时的特性。因此,流星余迹通信的复杂性要求有必要对其通信信道进行建模。根据流星轨道分布的特点,推导出轨道-辐射的转换,得到流星分布和通信链路的关系,建立了流星余迹通信信道季节变化预测模型,并将预测模型应用于流星余迹通信链路。预测的结果和中纬度雷达观测结果比较一致,为建立流星余迹通信系统提供了技术支持。     

基于DSP的流星信道模拟器设计

讨论了流星突发通信欠密类余迹的信道特性及其模型。以TMS320VC5509 DSP为核心设计了流星信道模拟器系统，并给出模拟器在实验室流星突发通信自适应变速率系统设计中的测试应用。     

流星突发信道的Matlab模拟

流星余迹信道是一种典型的突发无线超视距信道,对流星突发通信系统的设计方案,使用模拟信道进行分析比较,有着简易、经济的优势。基于公认的流星突发信道的数学模型,通过合理假设,推导出适合建立计算机模型的数学表达式,由此编写Matlab程序,选取典型信道参数,实现了对流星突发信道的计算机模拟。     

Radio propagation by reflection from meteor trails

This paper is a survey of those characteristics of meteors, and of meteor propagation, which are important to the understanding and use of meteor ionization insofar as it provides a means of radio transmission. The subjects discussed include the utility of meteor bursts for intermittent radio communication, physical properties of meteors and meteor trails, reflection properties of individual trails, short-term statistical characteristics of received signals, and long-term statistical characteristics of received signals.     

An Estimate of the Capacity of the Meteor Burst Channel

An estimate of the capacity of the meteor burst communication channel is given. The model takes into account both overdense and underdense trails as well as the effects of wind-induced trail warping.     

流星余迹极低信噪比通信技术

根据流星余迹信道特性,在频域信号处理的基础上提出利用迭代的信号处理方法对极低信噪比条件下的流星余迹通信系统进行信号检测,讨论了实现步骤,并在SPW环境下进行仿真、比较,仿真结果验证了此算法的可行性.     

流星突发通信中的变速率编码方案研究

流星突发通信是一种利用流星余迹进行通信的短时、突发通信方式。如何在较短通信时间内尽可能多的实现数据的可靠传输,始终是研究者关注的问题。传统的固定速率编码方案无法很好地适应信道变化,因此提出变速率编码以提高系统性能。通过对两种方案研究,对变速率编码算法进行了改进。仿真结果表明,改进后的变速率编码方案可明显改善系统性能。     

A Physical Meteor-Burst Propagation Model and Some Significant Results for Communication System Design

This paper describes a meteor-burst communication model based on physical models and astronomical observations of meteor orbits and flux. It compares model results to experimental results and uses them to illuminate this complex propagation medium and to show how "hot spots" of meteor activity vary in position and relative importance with the fundamental meteor-burst link parameters. It also presents antenna and other meteor-burst link design considerations with emphasis on military systems.     

Meteor burst communications. I. Meteor burst propagation

Meteor burst communication systems are introduced with emphasis placed on the unusual propagation mode which they employ. The origin of meteors and their trails is reviewed and the trail characteristics relevant to communication systems described. The restriction on scattering geometries for viable transmission paths is explained and the related footprint and hot-spot properties of meteor burst systems outlined. Meteor burst transmission loss is formulated in the conventional way as a modified bistatic radar equation and the origins of the modifying factor qualitatively explained. Meteor burst equipment, operating principles and applications are also briefly discussed. Finally, important quantities for assessing the performance of meteor burst systems are defined and typical values quoted     

Channel Capacity Statistics of an Interfered Broadband Satellite Link

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.     

Modelling the land mobile satellite channel: a review

The use of satellite systems in the implementation of third-generation mobile communication systems obviously involves a propagation environment for the signal different from that in the conventional terrestrial first- and second-generation systems. The propagation conditions and phenomena met with are embraced by the expression `land mobile satellite (LMS) channel'. This paper reviews the studies of the LMS channel reported in the literature. The various models are classified and compared in such a way that their similarities and differences are apparent     

MBC中的Ⅰ型HARQ改进方案

在流星突发通信中,为确保数据有效可靠地传输,通常采用前向纠错与自动重传请求相结合的方法,即HARQ。传统I型HARQ效率较低,难以满足大数据量通信。为了有效利用流星信道,建立了流星突发通信模型,提出了一种基于分集合并的Ⅰ型HARQ方案,推导出了有效信噪比公式,讨论了信噪比改善系数和最大重传次数,并进行了仿真。仿真结果表明,该方案可有效提高可靠性,增加吞吐量。     

基于TPC-RS的自适应编码流星余迹通信系统

 针对流星余迹通信系统原理及信道特点,研究了基于自适应编码机制的流星余迹通信系统．根据流星余迹信道能量随时间呈指数变化的规律,在系统误比特率的约束条件下,通过实时估计出的流星信号接收信噪比,动态地改变系统TPC-RS编码的码率冗余,实现信息速率的自适应变化,有效提高了流星余迹信道的利用率．仿真结果和分析表明,在相同信道条件下,采用自适应编码较固定编码传输效率在误比特率为2×10^-4时可获得3.68dB系统增益,数据通过量提高了一倍,验证了该方案的有效性和可行性．     

海上VHF/UHF频段信道环境及其空时频率选择性

已有的针对海上VHF/UHF(Very High Frequency/Vltra High Frquency)频段信道环境的研究,在电波传播特性和底噪特性方面缺少试验数据支撑.本文在VHF/UHF频段上做了一系列海上通信试验,基于试验数据,分析了传统电波传播模型对海上视距、超视距、视距超视距临界等传播路径的适用性.同时本文提出了空时二维海上频率选择性信道分析方法,从空间、时间二维视角下定量描述了海上无线信道演变现象,对空时频率迁移和空时频率衰变的概念做了定义.结论可用于海上电波传播建模和异常现象分析.