ISDN terminal connection experiment for mobile satellite communications

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.

This paper presents a dual band Band Pass Filter (BPF) operating at both the downlink and uplink frequency bands for Ku-band satellite applications. The commonly used frequency band in mobile communications satellites is the Ku-band. These mobile satellite systems help connect remote regions, vehicles, ships, people and aircraft to other parts of the world and/or other mobile or stationary communications units, in addition to serving as navigation systems. The structure of the proposed filter is based on parallel coupled microstrip lines and four sections are used. Tuning the two operational bands can be achieved using two open-circuited stubs at the first and last sections of the parallel coupled microstrip lines. The proposed filter is adjusted to operate at 12.54 GHz and 14.14 GHz for downlink and uplink bands, respectively. The proposed dual band BPF is fabricated, measured, and good agreement is obtained between simulated and measured results.

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. >

Current and planned global mobile satellite systems (MSSs) are aimed mainly at serving voice, facsimile and low-bit-rate data services with rates of up to about 4.8 kbit/s. In the multimedia communication era, however, this channel rate, regardless of the use of GEO or LEO satellites, is too low to realize comfortable mobile computing for operations such as Internet access, e-mail, remote LAN access, image transmission, and videophone. This paper proposes a global mobile N-ISDN satellite communication (GMISC) system: a GEO satellite communication system offering the ISDN basic rate up to 144 kbit/s (2B+D) with notebook size user terminals and vehicular terminals to provide a comfortable nomadic communication environment. It also discusses satellite channel control techniques for the proposed GMISC system. It is clear that a layered satellite channel control scheme consisting of a master satellite channel controller and plural local satellite channel controllers that assign shared satellite channels within a country, is suitable for the proposed system.

A double-layered constellation for a future global satellite communications network connected by optical intersatellite links has been proposed. The constellation consists of lower layer satellites for mobile and personal satellite communications, and upper layer satellites for large- capacity fixed satellite communications and feeder links. Optical inter-satellite links, which can perform high-capacity communications with small terminals, are used for all intersatellite data transmission. Although a polar orbit constellation offers the merit of simpleness in network configurations, the inclined orbit constellation offers the potential for reducing the required number of satellites, improving link properties, and enhancing the coverage in middle and low latitudes, by selecting the most adequate inclination of the orbits. The optical inter- satellite link properties, coverage properties, and required number of satellites are evaluated for constellations using inclined orbits, and then compared with those of a polar orbit constellation. Three constellation types in each layer achieving continuous double coverage are assumed. For each constellation, the relations between these properties and the inclination of the orbits are examined. The basic parameters of optical inter-satellite links on satellite constellations using inclined orbits are also shown.

[Abstract] This paper proposes dynamic bandwidth/channel access technique using FFT based block signal transmission for future broadband mobile satellite communication systems, which is to supplement next generation terrestrial mobile networks. One of the key issues for next generation mobile satellite communication systems is flexible and scalable access technique in terms of data rate and traffic type, to accommodate various satellite users. OFDMA is a technique to meet the above-mentioned requirements, however it needs large output backoff at HPA. To solve this problem, this paper proposes a new bandwidth/channel access technique using FFT based block signal transmission. The proposed technique uses single carrier modulation suitable for small output backoff operation in HPA, keeping flexibility and scalability as OFDMA has. This paper describes basic principle of the proposed dynamic bandwidth/channel access technique and preliminary performance evaluation results by computer simulation.

A concept for a future advanced mobile satellite communications system using a geostationary satellite is described. In the satellite of this system, a multiple spotbeam antenna, onboard beam interconnection, and millimeter-wave and Ka-band components are required. The configuration of the payloads of Japan's COMETS (Communications and Broadcasting Engineering Test Satellite) for advanced mobile satellite communication experiments is also described. The transponder has an IF filter bank and a SCPC/TDM (signal-carrier-per-channel/time-dimension multiplexing) regenerative modem for beam interconnection. >

Mobile satellite communication is becoming a crucial component for broadcast and broadband coverage in professional, commercial, military and emergency scenarios. Mobile devices and network control center (NCC) are the basic components of Low-Earth-Orbit (LEO) satellites which communicate with each other with the help of gateways. The communication between these components needs high security. The various existing protocols for the environment of mobile satellite communication are insecure against numerous attacks and can be easily attacked by an adversary. So, there is an indispensable requirement of a reliable protocol which can offer efficient and secure communication for mobile satellite system. Therefore, a robust key agreement authentication scheme for mobile satellite environment is proposed in this article. The proposed protocol is developed according to the major security demands in the satellite communication networks. Our protocol provides mutual-authentication, session-key agreement and correct notion of user anonymity. The performance analysis for evaluation shows that the storage, communication and computation cost of the proposed protocol is less than many of existing protocols. Moreover, our protocol offers additional security features than that are available in the existing protocols. Hence, our protocol offers a secure authentication and key agreement for mobile satellite systems.

Racal Instruments Limited has been involved in the development and manufacture of test equipment for digital radio communications systems since the inception of the Global System for Mobile communications (GSM) in the late 1980s. Involvement in satellite mobile communication systems began with the development of production and service test equipment for the American Mobile Satellite Corporation (AMSC) system in 1992. Racal Instruments has also been involved in the development of test equipment for the Asia Cellular Satellite System (ACeS). This paper discusses the experience of Racal Instruments Limited in developing test equipment for testing dual mode satellite mobile terminals particularly for the ACeS system. The topics covered include: (1) the test equipment requirements of the dual mode handset developers; (2) specific issues faced by test equipment developers; (3) how Racal Instruments Limited has responded to the requirements and issues; and (4) how test equipment may evolve to meet future requirements. (5 pages)

A multibeam digital beamforming (DBF) antenna, developed for a future mobile satellite communications system, is mounted on a vehicle for a receiving experiment in a mobile environment using a satellite signal in the L band. The multibeam is formed by 2-dimensional FFT signal processing. Automatic acquisition and tracking of an arriving signal are achieved by selecting a maximum beam out of the multiple beams in real-time.

An increase in the size of on‐board antenna reflectors is a key technology in providing economical services by miniaturized portable equipment in future mobile satellite communication systems. In practice, a mesh antenna can be used as the on‐board antenna. However, since the reflector surface of this antenna is supported by the cable and the mesh, and its size is larger, the surface is subject to larger thermal deformation in orbit than is the solid antenna reflector. Conventional compensation methods such as passive thermal control or rotation of the antenna reflector cannot maintain the required antenna performances. Various methods have been reported to compensate for the deterioration of antenna performance by thermal deformation.This paper describes a static shape control system for a 10‐m diameter antenna which actively compensates for the deformation by using a shape‐measuring sensor and shape‐compensation actuator. The configuration of the sensor and the experimental results by a functional model are described to confirm the design validity. The shape‐compensation method by the actuator was confirmed to be useful in achieving a required surface accuracy.

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).

The performance of TCP degrades considerably on land-mobile satellite communication channels because of the long propagation delays and frequent correlated packet losses. In order to improve TCP performance on such channels, several techniques have been proposed including the use of link layer automatic repeat request (ARQ) protocols. This paper extends previous work by examining in greater detail the interactions between TCP and link layer ARQ protocols. We present a link layer selective repeat ARQ protocol that is specifically designed for particular mobile satellite communication systems. The performance of TCP with this link layer ARQ protocol is evaluated using a flexible test environment which is integrated with the Linux TCP/IP stack.

This paper reviews the demand for mobile satellite communications and radiodetermination services from the maritime, aviation, and land mobile communities. It briefly examines existing alternatives and the factors that are affecting the growth and development of mobile satellite communications, with particular reference to INMARSAT. Future mobile earth station standards and services are described as are the key technological developments and challenges, which need to be met before mobile satellite services-on aircraft, the smallest of vessels, and land vehicles-become widely available at significantly lower costs than today. The authors are cautiously optimistic that the 1990's will see a rapid growth of mobile satellite services, but such growth will depend in large part on the resolution of certain institutional and technical problems, particularly relating to the limited mobile satellite spectrum available at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</tex> -band.

The role of satellite communications in networks that provide new services, such as frame relay and multimedia, is investigated. Both passive and active (onboard switching, processing) satellite systems are considered. Novel techniques are developed for each system to demonstrate, via detailed analysis, how the communications bandwidth agility of multipoint/broadcast satellite channels, and the switchability of spot beams, makes it feasible to provide these new services via satellite in a resource-efficient manner. The current worldwide revolution in the telecommunications environment has led to significant changes in the generation and transmission of information. The coupling of local and global communications networks can make information, databases, and processing power available virtually everywhere. The essential infrastructure for this connectivity depends on the integrated services digital network (ISDN). Well-specified standards will initiate a worldwide movement toward the implementation of ISDN, and the 1990s are likely to be the decisive era for establishing the foundation for this new communications architecture. ISDN standards for interfaces, signaling procedures, service definitions, and other operational and architectural features will provide a common framework for developing satellite network configurations that can offer a range of new and enhanced services. The key elements of such communications systems will be the communications bandwidth agility of multipointlbroadcast satellite channels, global coverage, and the deployment of very small aperture terminals and mobile satellite terminals (VSATs and MSATs). These factors will play a crucial role in the cost-effective realization of ISDN; intelligent network deployment; the future public land mobile telecommunications system (FTLMTS); and ultimately, the universal personal telecommunications (UPT) service. There is a distinct paradigm shift in the way these telecommunications networks are evolving. The next generation, which will incorporate frame relay, broadband ISDN