Global mobile N-ISDN satellite communication system

The paper presents the recent situation of the research and development on global multimedia mobile satellite communications system using non-geo type satellite constellations. This system is called Next-generation LEO system (NeLS). NeLS research center has carried out the key technology development of the satellite constellation system, which would provide a global mobile satellite service with broadband handheld terminals. The paper presents the development results of key technologies including the digital beam forming (DBF) satellite antenna, optical inter-satellite link system, on-board switching system.

This paper presents a satellite communication system that realizes high speed access lines for multimedia communications. At first, this paper considers the characteristics of multimedia traffic and satellite communications. Based on this consideration, this paper proposes a global multimedia satellite communication system using a geostationary multibeam communication satellite. This system employs an asymmetric satellite channel configuration and ATM cell-based signal multiplexing. This paper also analyzes satellite channel access schemes for the system by simulation and presents necessity the combined use of contention type and conflict free type access schemes to match the traffic patterns of the customers. Lastly, it presents a multibeam satellite configuration for this system.

From the moment the air/aero/aerial objects appeared the necessity of monitoring for them arose and were solved using different tools, such as radio communications, radio direction finding, radar and others. With the advent of global satellite navigation, the massive introduction of navigation equipment began in almost all areas of human activity and especially in mobile (moving) objects (cars, aircraft, ships, etc.). This allowed aircraft crews to accurately determine their coordinates in real time under any weather conditions. However, the organization of uninterrupted data transmission to ground control centers remained problematic. In this regard, aircraft monitoring systems were primarily installed on military and civil aircraft, while the other categories and types of aircraft were equipped only with communication systems. Thus, currently, there is the lack of navigation devices allowing flight monitoring and communication in small aviation. As a result, in case of emergency landing of small aircraft, it takes a lot of time and effort to find its location, therefore providing emergency assistance to passengers and crew is not possible. This problem can be solved by the system for determining the location of small aircraft using technologies of global navigation satellite systems and mobile satellite communications. This system includes devices for registering the location of the observed object, transmitting data via mobile cellular and satellite communications, processing, storage and displaying of data. The proposed system, by continuously recording and transmitting aircraft location data to the ground control center, helps minimize time and narrow the search area of the aircraft that made an emergency landing.

A study of next-generation LEO system for global multimedia mobile satellite communications

In little more than two decades, communications satellite technology has gone from being revolutionary to commonplace, from an idea to world wide service. In both industrialized and developing countries, economic and social progress depends on improved telecommunications. Like other means of transport, telephones, computers, satellites and fiber optic cables and their proper interfaces are essential for moving commercial goods and services. Benefits of satellite communications should in the 1990's be extended to users in all parts of the world through the use of smaller, inexpensive and less sophisticated Earth stations for two way (voice and data), and one way (video, data) use. While earlier satellite systems have been designed and implemented using C and S band communications with satellites in geostationary orbits (GEO), K band communications using VSATs (Very Small Aperture Terminals) have enabled the communications across areas of the US and the world where extensive telecommunications networks did not exist and/or were not affordable. In addition, several systems have been proposed (being built) to provide for the global communication of the mobile users using clusters of smaller, less complex satellites in low Earth orbit (LEG) and medium Earth orbit (MEO). Mobile satellite systems are the future of the satellite communications technology applications. In this presentation, we will briefly summarize the status for satellite communications and then present a comparison of the enabling mobile satellite communications technologies and mobile satellite systems currently being developed. We will also review applications of these systems in public and commercial areas in this presentation. >

Experiments on mobile satellite communications are being carried out to determine if they are technically feasible for future domestic satellite services in the Experimental Mobile Satellite System project, which uses Engineering Test Satellite-V. Experimental ISDN (integrated services digital network) basic-rate communications services have also been offered for marine vehicles. The authors describe the configuration of an experimental system for maritime ISDN satellite communications, and the characteristics of ISDN basic-rate interface connections for the digital telephones, G4 facsimiles, and color video-phone terminals of terrestrial ISDN services. This experiment provided much information for designing future mobile satellite communications systems. Moreover, it indicates that forward error correction in a mobile satellite link with poor transmission quality is very effective at improving the communication quality of mobile satellite systems. >

The National Aeronautics and Space Administration (NASA) and the National Science Foundation (NSF) commissioned a panel of scientists and engineers in 1997 to benchmark the global status of commercial communications satellite technology, markets and regulatory and policy issues. After visiting or interviewing over 60 manufacturing, R&D laboratory, service provider and government institutions in North and South America, Europe and Asia, the review panel concluded as follows: 7.3cm\begin{itemize} \item Many European and Asian governments are increasing their satellite communications R&D programs and supporting demonstrations and space marketing efforts, relative to the US. \item The US is currently the leader in new technology and its insertion into commercial satellite systems, but ambitious foreign efforts threaten this position. \item Global commercial satellite communications is a large and rapidly growing business. \item New technology is being inserted into satellites at an increasingly rapid pace with an increasing number of international participants. \item Aerospace communications companies, worldwide, are consolidating their efforts and are expanding into the end user service business. \item The ‘Direct‐to‐End User’ mass consumer satellite service industry has the potential to be quite large and is changing the way satellites are manufactured and deployed and is creating a potentially large satellite terminal industry. \item Satellite manufacturing is increasingly becoming a design, assembly and test operation with parts and sub‐systems obtained from global suppliers. \end{itemize} 7.3cm \begin{itemize} \item This increased use of satellites for communications services is creating a shortage of spectrum and orbital slots and is resulting in spectrum utilization conflicts with terrestrial wireless service providers. \item Future development of commercial satellite communications is dependent on the resolution of key regulatory, trade, spectrum, inter‐operability and standards issues and government leadership is vitally needed. \item There are opportunities for international cooperation to facilitate the development of satellites technologies, systems, standards and protocols. \end{itemize} There is concern that unless several issues are addressed, particularly an increase in long term oriented R&D and trade and regulatory issues, the US may experience a deterioration of its leading position in the manufacture of satellites for global service providers and the initiation of new services, much in the way that it lost its leading position in the launch of commercial satellites.

RF and microwave switching elements using silicon CMOS technology are being investigated and show promise as an alternative to the traditional PIN diode and GaAs MESFET devices. Silicon CMOS RF switching elements are attractive because of their potential application in all-silicon monolithic CMOS solutions for completely integrated baseband and RF functions in low cost wireless, mobile satellite and personal communications systems. Initial results of an SPDT switch show 1 dB insertioni loss and 44 dB isolation at 200 MHz on a developmental device with switch performance characterized to 2.0 GHz.

A highly innovative global broadband mobile communication system concept

Recently, engineers have focused on developing mobile satellite communications systems using GEO, MEO and LEO satellites. We are now studying an on-board antenna for future S-band mobile satellite communications using hand-held terminals. This antenna is carried on a GEO satellite, and consists of a large deployable mesh reflector and a primary feed using an active phased array. It has the advantage of beam forming flexibility. For example, when its radiation pattern changes due to an amplifier problem, we can obtain the desired pattern by adjusting the only excitation phase of the array feed. We first present the satellite antenna's configuration, then describe pattern correction by adjusting the excitation phase of the array feed.

Communication satellites have a much longer propagation delay than terrestrial communication networks such as cellular or WiFi. In addition, as the carrier frequency moves up, mobile satellite communications show worse performances than the conventional fixed satellite communications. The mobile satellite service (MSS) has not been actively pursued with long latency at high-frequency bands for future applications. In this paper, the adverse impact of long propagation delay in the conventional satellite system is investigated with various user mobility and Doppler-shifted carrier frequency. The satellite network is modeled as a basic delayed feedback channel system and the communication performance is analyzed under delayed channel state information (CSI) for assessing the system feasibility in mobile conditions. The results of performance analysis are provided at high-frequency bands with high-speed user movement, specifically on the outage probability and the channel capacity exploiting three types of channel models: conventional land mobile satellite (LMS) channel models of E. Lutz and C. Loo, and Nakagami fading model. In the circumstance with various user speeds, system performances are evaluated with different propagation delays in the LMS channel models and for line-of-sight (LOS) components in the Nakagami fading. In addition, the conventional models are compared depending on different altitudes for geostationary orbit (GEO), medium earth orbit (MEO), and low earth orbit (LEO) satellites, as well as high-altitude platforms (HAP).

This paper discusses the effectiveness and/or usefulness of the inter-satellite link (ISL) in a global gigabit satellite communications system, in terms of technology and applications. In order to make such a discussion easy, first, work statement of this study is discussed. Second, a gigabit information space corridor is assumed to be a satellite communications infrastructure that a satellite constellation having a orbit of 15,500 km altitude on the equatorial plane is linked up via a gigabit (approximately 10 Gbps) ISL to provide a continuous communications and global connection as a competitive communications system with a terrestrial optical fiber cable system. Third, tile effectiveness of the ISL for the gigabit information space corridor in the global area is discussed. Finally, the technical aspect of ISL and its related technology are discussed and traded-off briefly. this system as Space Information Super Corridor on an Equatorial Orbit (SISCEO). Third,

The subject addressed here is a design of an antimultipath facling used in Time-Division Multiple Access (TDMA) operation. The feature of this modem is an effective execution of fast burst acquisition and adaptive equalization by all digital signal processing. This modem mainly consists of a data memory and phase rotation circuit, an incoherent correlator, an adaptive equalizer and a frame synchronizer. Detailed acquisition algorithm using the incoherent correlator a n d the adaptive equalizer is described and perforn~ances are assessed by computer simulation and sorne hardware experimentation. This modem is capable of executing fast acquisition and stable demodulation in the presence of a large f requency offset in s e v e r e mult ipath fad ing environment.

Satellite communication technology has become a research hotspot in today's society because of its important significance to the development of modern society. However, the realization of satellite communication is a big project with high difficulty and high cost. Therefore, it is necessary to use computer software to model the satellite communication system and further understand the satellite communication scenarios and communication links. Based on the basic theory of LEO communication satellite, this paper uses STK software to complete the modeling of traditional satellite communication system, and realizes the visual simulation of LEO satellite communication. Finally, through the analysis of the simulation process and simulation results, the connection rate of normal communication between ground stations is calculated.

We calculate the availability of circuit service to a user in a mobile satellite communication system. The availability, i.e., the percentage of time the user can expect to communicate reliably using the communication system is a function of the power available to the user and the channel (Rician or Rayleigh fading) encountered by the user. In a mobile satellite communication system, the channel is a function of user position, the number of satellites visible to the user, and their positions. Using a simulation of the constellation orbits and an associated channel model, we calculate the availability provided by various proposed mobile satellite communication systems that use LEO and MEO satellites. A conclusion of this paper is that the visibility of multiple satellites is imperative for high availability.