SATELLITE-ENHANCED PERSONAL COMMUNICATIONS EXPERIMENTS

Users of future generation wireless information services will have diverse needs for voice, data, and potentially even video communications in a wide variety of circumstances. For users in dense, inner-city areas, low power personal communications services (PCS) technology should be ideal. Vehicular-based users travelling at high speeds will need high-power cellular technology. For users in remote or inaccessible locations, or for applications that are broadcast over a wide geographic area, a satellite technology would be the best choice. Packet data networks provide an excellent solution for users requiring occasional small messages, whereas circuit switched networks provide more economical solutions for larger messages. To provide ubiquitous personal communications service, it is necessary to capitalize on the strength of each wireless technology and network to create one seamless internetwork including both current and future wired and wireless networks. As an initial step in exploring the opportunities afforded by the merging of satellite and terrestrial networks, Bellcore and JPL conducted several experiments. These experiments utilized Bellcore's experimental personal communications system (including several messaging applications with adaptations to wireless networks), NASA's advanced communications technology satellite (ACTS), JPL's ACTS mobile terminal, and various commercial data networks (such as the wireline Internet and the RAM wireless packet data network). Looking at loss of bits, packets and higher layer blocks (over the satellite-terrestrial internetworks with mobile and stationary users under various conditions) our initial results indicate that the communication channel can vary dramatically, even within a single network. We show that these conditions necessitate powerful and adaptive protocols if we are to achieve a seamless internetworking of satellite and terrestrial networks.     

Land mobile satellite channel measurements and modeling

This paper, tutorial in nature, describes the effort of many investigators who have and still are conducting channel measurements and modeling for land mobile satellite communications. Various channel measurement results, ranging from ultrahigh frequency to Ka-band, are given. Many statistical channel models and simplified models that have been developed are referred to. Some of the models are applicable to geostationary and nongeostationary communications satellites. A statistical model developed by Loo (1985) is described in detail, as well as its extension to modeling land mobile satellite communications at Ka-band. This was accomplished by including a Gaussian probability density function to account for weather conditions. Also, practical computer-generated statistical channel models are given. These computer models should facilitate the estimation of performance of satellite communications systems     

个人通信的研究发展和面临的新挑战

本文应国家“863”计划通信技术主题的个人通信高技术研究发展,特别是无线接入技术、CDMA通信技术、第三代移动通信技术、高空平台移动通信方式和第二代移动通信新技术的突出研究成果,和在个人通信发展中的作用和地位进行论述,并对21世纪我国个人通信面临的新挑战和发展策略进行讨论。     

NATIONAL SECURITY/EMERGENCY PREPAREDNESS AND DISASTER RECOVERY COMMUNICATIONS VIA ACTS

During the period from early 1993 to 1994, the U.S. National Communication System (NCS), a government agency, sponsored the development and execution of several fixed and mobile experiments using the advanced communications technology satellite (ACTS). The purpose of these experiments was to evaluate the feasibility of integrating an ACTS-like communications system into national security/emergency preparedness (NS/EP) operational scenarios. These experiments focused on clear and secure voice communications in both the fixed and mobile environment. For the mobile experiments, the focus was on the performance of both clear and secure voice in the land-mobile satellite communications channel. For the fixed experiments, the focus was on the use of a T1 terminal for restoration of communication services in the event of a disaster and for remote user communications. The results of these experiments are described in this paper.     

Optical Communications in Space – a Challenge for Europe

The successful test of a laser communication link between an ESA data-relay satellite and an Earth observation satellite marks a milestone in the development of optical space communications. It is the right moment to look back on more than 20 years of R & D effort in Europe. The paper gives an overview of the optical space communication activities at the European Space Agency (ESA), which have started in summer 1977, when ESA placed the first technology study contract in the domain of intersatellite optical links, and reports on the most recent European systems andhardware technology efforts aimed at the development of small and compact laser terminals for global mobile communication systems and satellite-based data networks.     

蓬勃发展的中国公众卫星通信

本文通过详细的统计数字，介绍了我国公众卫星通信发展现状及新的一年规划，剖析了国内其它卫星系统如移动卫星通信，农村卫星通信和ＶＡＳＴ的发展，并对我国２０００年前卫星通信的发展规划和策略进行了探讨。     

A FREQUENCY OFFSET ESTIMATION AND COMPENSATION ALGORITHM FOR K/Ka-BAND COMMUNICATIONS

This paper presents a new open-loop technique for estimating and correcting Doppler frequency shift in K/Ka-band communication systems with special reference to the advanced communications technology satellite (ACTS) mobile terminal (AMT) modem, which utilizes square-wave pulse-shaped, binary differential phase shift-keyed (DPSK) modulation. The novelty of this estimation scheme is that it exploits the Doppler-induced phase shift over a fraction of a symbol interval to provide an estimate of the Doppler offset, without requiring symbol synchronization. Furthermore, by utilizing time-differential detection (delay-and-multiply), the proposed technique can tolerate much larger frequency offsets than existing open- or closed-loop techniques. Analytical results are provided for the variance of the above estimator and the error probability performance of the AMT is evaluated in the presence of the Doppler correction. Practical design considerations are also discussed, including a method for modifying the front end, digital bandlimiting filter in such a way that Doppler bias effects in the new estimator are eliminated. Simulation results reveal that, in general, performance improves with increasing data rates, i.e., the new frequency offset estimation/compensation algorithm induces a degradation from ideal of approximately 1 dB at a 6 dB energy per data symbol (bit) and a 2⋅4 kbps data rate. However, there is no appreciable degradation when the data rate is increased to 9⋅6 or 19⋅2 kbps.     

机载Ku、Ka频段卫星通信系统综述

叙述了Ku频段和Ka频段机载卫星通信系统的国内外发展现状,列举了几个典型的卫星通信系统技术指标,并简述了研制机载卫星通信系统应注意的事项和技术途径,其中包括选择天线系统形式,合理分配系统指标,消除多普勒效应的影响等。     

Inmarsat expands its horizons

The International Maritime Satellite Organization (INMARSAT) is the world's only commercial satellite system providing mobile communications. This article describes the system and the services which are provided through it to the worldwide shipping and offshore industries. It provides some background on the establishment of the system and why maritime nations looked to satellites as the way to effect a dramatic improvement in maritime communications. The article discusses some of the research and development now being carried out which is expected to lead to the provision of new services, including aeronautical communications via satellite. Also mentioned is the role to be played by INMARSAT in the Future Global Maritime Distress and Safety System, now being developed by the International Maritime Organization for introduction in 1990. New services, such as these, and greatly expanded capacity are to be provided by INMARSAT in its second generation system, consisting of a new series of satellites for launch from 1988.     

Improving satellite services with cooperative communications

This paper proposes new transmission schemes for the delivery of satellite services. In the proposed scenarios, mobile terminals are allowed to forward the signal received from the satellite. This scheme provides spatial diversity just like MIMO transmission schemes. Moreover, the coverage area is extended because masked terminals have an additional opportunity to get the service from neighboring terminals. We use the paradigm of cooperative communications to compare the advantages and limitations of several scenarios in hybrid terrestrial/satellite systems. In particular, we study the following basic transmission scheme: in a first time slot, the satellite sends its signal and, in a second time slot, mobile terrestrial terminals are relaying the satellite signal. An analysis framework is proposed and applied to this cooperation scenario at the destination terminal. The framework is modeling the cooperation process and clearly separates the control part from the data user part. The paper outlines the importance of the control part by evaluating the relay selection policy on a basic hybrid satellite/ad hoc system. Copyright © 2011 John Wiley & Sons, Ltd.     

宽带移动卫星通信信道模型研究

从多径衰落、阴影效应和多普勒效应三个方面研究宽带移动卫星通信信道的频率色散特性和多普勒功率谱非对称特性。基于WSSUS模型提出宽带移动卫星通信信道的统计模型。采用蒙特卡洛仿真方法对农村地区和城市地区两种信道的冲激响应和误码率特性进行仿真。仿真结果表明该信道模型能够真实反映宽带移动卫星通信信道的特性,对卫星通信系统关键技术设计具有参考价值。     

ACTS AERONAUTICAL EXPERIMENTS

This paper discusses a series of aeronautical experiments that utilize the advanced communication technology satellite (ACTS). As part of the ongoing effort to investigate commercial applications of ACTS technologies, NASA's Jet Propulsion Laboratory and various industry/government partners have developed a series of experiments that utilize the ACTS mobile terminal (AMT)¹ and the broadband aeronautical terminal¹ to investigate aeronautical uses of the ACTS. This paper discusses these experiments including the experiment configurations, technologies, results and future implications.     

COMETS experiments for advanced mobile satellite communications and advanced satellite broadcasting

The Communications and Broadcasting Engineering Test Satellite (COMETS) was developed to evaluate Ka‐band (31/21GHz) and millimetre‐wave (47/44 GHz) advanced mobile satellite communications systems, 21GHz advanced satellite broadcasting systems, and S‐band and Ka‐band inter‐orbit satellite communications systems. COMETS was launched because it was to become the new ‘bridge’ toward advanced satellite communications technologies in the next century, but the launch on 21 February 1998 regretfully failed due to premature shut down of the second stage engine of the H‐II launch rocket. After this accident, the initial low elliptic orbit of COMETS was improved by the apogee engine to a larger elliptic orbit with an apogee altitude of 17711km, a perigee altitude of 473 km, an inclination of 30.1°, and an orbital period of 319 min. Original and modified COMETS experimental plans, countermeasures in earth stations for the orbiting satellite, as well as an overview of the COMETS satellite and ground terminals are presented. Copyright © 2000 John Wiley & Sons, Ltd.     

DISA comes through [C4I architecture]

The development of a command, control, communications, computers, and intelligence (C4I) architecture for the central command (CENTCOM) theater of operations during Operations Desert Shield and Desert Storm is described. CENTCOM C4I merged commercial and military communications systems into a fully integrated network. It employed tactical ground mobile forces (GMF) satellite systems, line-of-sight (LOS) radio systems, unit-level circuit switches (ULCS), and the primary interfaces to strategic systems, the TRI-TAC switching centers, automatic circuit (TTC-39A) and automatic message (TYC-39) switchboards. By the end of the ground war, the CENTCOM strategic network considered of over 100 defense satellite communication system (DSCS) satellite links, nine T-1 systems, over 300, DSN trunks, 26 AUTODIN circuits, and numerous dedicated-user, point-to-point, and data circuits     

卫星移动通信系统的发展思考

本文回顾了现代中低轨道卫星移动通信系统的发展历程、在发展过程中存在的问题,全面分析了各行业、部门对卫星移动通信系统的使用需求,并展望未来发展前景,提出了未来卫星全球人个移动通信系统的发展策略。     

Single and multiple satellite visibility statistics of first-generation non-GEO constellations for personal communications

The first generation of global satellite systems for personal and mobile communications is preparing to start commercial services. Service quality and availability are paramount to the user's acceptance of the service. For satellite systems, service quality and availability build up from satellite visibility, propagation conditions and equipment availability. This paper discusses the impact of elevation angle on visibility and propagation, that of azimuth separation between visible satellites, and compares multiple visibility statistics of all first-generation non-geostationary communications systems, namely Iridium, Globalstar, ICO, Ellipso and ECCO. © 1998 John Wiley & Sons, Ltd.     

ANALYSIS OF A RAIN COMPENSATION ALGORITHM FOR K/Ka-BAND COMMUNICATIONS

A rain compensation algorithm (RCA) has been developed for use in the advanced communications technology satellite (ACTS) mobile terminal (AMT) system. The basic goal of the RCA is to control the transmitted data rates (9·6, 4·8 or 2·4 kbps) in the forward and return links so that a 3 dB link margin is maintained at the highest possible transmitted data rate. In this paper, analyses of both theoretical and practical issues relating to the RCA are presented. In addition, sample simulations of a one-dimensional version of the RCA at the MT are presented which illustrate typical RCA performance using both simulated and recorded pilot fade field data. It is found that with suitable post-processing, the RCA can provide reasonable (conservative) data rate estimates without making excessive data rate changes, i.e., data rate change fluctuations. It is anticipated that the results presented here will not only be useful for the eventual operation of the RCA, but more generally will be useful in the design and operation of other rain compensation techniques for K/Ka-band communication systems.     

全球星低轨移动卫星系统及其应用

低轨移动卫星通信的发展给实现通信的全球化和个人化带来了更多的机会和选择。不同系统的不同设计思路带来了系统之间的差异,同时也决定了其在通信市场中的位置。本文介绍全球星低轨移动卫星通信系统的设计思想、技术体系和终端设备以及目前的实施情况。     

Ka频段卫星通信系统降雨衰减分析

Ka频段卫星通信因其具有可提供的带宽大(3.5GHz)、通信容量大、波束窄、终端尺寸小,轨道平面内可容纳的卫星多和抗干扰能力强等优势成为未来卫星通信的必然趋势。Ka频段卫星通信面临的一个巨大挑战在于它受气象因素的影响大,这一度使研究人员认为Ka频段卫星通信是不可能实现的。降雨、闪烁、大气吸收等因素都会导致Ka频段地空链路信道质量的恶化。根据Ka频段卫星通信的特点,分析了降雨衰减的特性,提出了几种抗雨衰的办法。     

未来中国4G开放移动通信终端和网络接入架构

This paper relates to an advanced open mobile communication system and method of integrating the mobile communications, wireless access systems and wired communications into one common platform architecture for China＇s 4th generation mobile communications, supporting costeffective broadband voice, data and video services in wireless, mobile and wired environment with one single integrated mobile terminal device. The paper includes new architecture in the integrated mobile device and converged network access, and minimum modification in the existing mobile telecommunication infrastructures. This paper introduces the long-term evolution strategy for China＇s TDD system platform towards China＇s future 4G mobile communications.