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.     

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.     

ACTS MOBILE TERMINALS

The development of the advanced communications technology satellite (ACTS) mobile terminal (AMT) and its follow-on, the broadband aeronautical terminal (BAT), have provided an excellent testbed for the evaluation of K- and Ka-band mobile satellite communications systems. Such systems have proved viable for many different commercial and government applications. Combining emerging satellite communications technologies such as ACTS' highly focused spotbeams with the smaller, higher-gain K- and Ka-band antenna technology, results in system designs that can support significantly higher throughput capacity than today's current commercial systems. An overview of both of these terminals is presented in this paper.     

A satellite-tracking K- and Ka-band mobile vehicleantenna system

This paper describes the development of the K- and K_a-band, satellite-tracking mobile-vehicular antenna system for NASA's ACTS Mobile Terminal (AMT) project. ACTS is NASA's Advanced Communications Technology Satellite, which will be launched into its geostationary orbit in September 1993. The AMT task will make the first experimental use of the satellite soon after the satellite is operational, to demonstrate mobile communications via the satellite from a van on the road. The AMT antenna system consists of a mechanically steered small reflector antenna that uses a shared aperture for both frequency bands and fits under a radome of 23 cm diameter and 10 cm height, and an antenna controller that tracks the satellite as the vehicle moves about. The RF and mechanical characteristics of the antenna and the antenna tracking control system are discussed. Laboratory measurements of the antenna performance are presented     

European third-generation mobile systems

Vast importance is being placed in Europe on the development of third-generation mobile telecommunications systems, since it is expected that mobile and personal communications will become a key driver for growth and innovation in the next millenium as well as being a necessary building block of the wireless information society. Significant progress has been made since 1988 by a number of European Union funded R&D projects working toward the development of future generations of mobile communication concepts, systems, and networks. The ACTS (Advanced Communications Technologies and Services) program will offer, in the period 1995-1998, service providers, communications operators, and equipment manufacturers greater opportunities to master and trial mobile and personal communications services and technologies. From the user's perspective the ACTS program will strive to ensure that current mobile services are extended to include multimedia and broadband services, that access to services are made without regard to the underlying networks, and that convenient, lightweight, compact, and power-efficient terminals adapt automatically to whatever air-interface parameters are appropriate to the user's location and desired services     

Present Trends in High-Speed and Broad-Band Communications Services in Japan

This paper describes present trends in high-speed and broad-band communications services in Japan. It gives an overview of video, high-speed digital leased circuit and satellite digital communications services, and gives examples of their applications. Recent trends in telecommunication services and technology are described, including video conferencing services presently available in more than ten cities throughout Japan, as well as a video response system which is about to be put into service. It also describes the present status of Japan's cable television (CATV) system and discusses its future development. Finally, NTT's plans for high-speed and broad-band communications service in the future are previewed.     

Fusion of digital television,broadband Internet and mobile communications—Part II: Future service scenarios

This is the second part of the tutorial paper following the previous tutorial paper describing enabling technologies in digital video broadcasting (DVB) system. The paper presents the current and future operational scenarios for DVB via satellite (DVB‐S) system. Review of the current state‐of‐the‐art technologies consisting of integration of broadband Internet and mobile communications and integration of broadband Internet and DVB are given. The future operational scenarios emphasize the fusion of DVB systems with other technologies in terms of network fusion and terminal fusion. For satellite service scenarios, it also takes into consideration mobility management and standard quality‐of‐service mechanism issues, such as integrated services and differentiated services. Several research directions for providing seamless services regardless of network, access technology and terminal in the fusion network are also highlighted in this paper. Copyright © 2007 John Wiley & Sons, Ltd.     

Satellite Scenarios and Technology for the 1990's

Commercial satellite communications continues to undergo changes arising not only from advancing technology but also from new service offerings and regulatory activities. As the communications industry grows more competitive, future directions in satellite communications will become more economically than technologically motivated. This paper addresses the future of satellite communications, emphasizing fixed satellite services but also covering maritime mobile and broadcast satellite services. Following a brief recapping of the past, current services are discussed and future services are projected for the above service categories. A projection is made of the economics of satellite communications systems using gateway and varying degrees of distribution of earth stations, for both INTELSAT VI and future multibeam satellites and the TAT-8 fiber-optic undersea cable. After a brief allusion to systems design considerations, the anticipated technology projections towards the year 2000 for satellite communication services (including satellite antennas, transmitters and receivers, and on-board interconnection subsystems) are presented in some detail. Finally, it is concluded that satellite communications will have a major role in this epoch, and widespread use of low-cost customer premise earth station may justify more sophisticated and more expensive spacecraft.     

On Attaining Lower Sidelobes and New Antenna Envelopes for Better Orbit Spectrum Utilization in Satellite Broadcasting

The orbit spectrum is a natural resource for satellite communications which must be utilized efficiently in order to meet the rapid growth in demand for communication capacity 1,2 and which may become very crowded in the near future. Efficient allocation of this resource has been approached from many different aspects, such as technical, operational, practical and economic. Different methods of improving this utilization efficiency have been proposed, such as reducing the inhomogenity among satellites and defining limitations on system parameters. This report focuses the discussion on a simple method: improving the antenna patterns used in satellite systems, on both the satellite antennas and the ground station antennas. Only broadcasting applications are considered. The discussion includes how the antenna envelope can be improved, how this improvement can be interpreted in terms of orbit spectrum utilization efficiency, and whether this improved envelope is actually realizable and feasible, considering practical aspects.     

Millimeter wave personal radio using an advanced communication satellite

THIS PAPER describes a millimeter-wave personal radio system using a communications satellite. It focuses on the development of a 50/40-GHz-band earth station. First, the trends of future satellite services are discussed. Satellite communications will be ready for personal utilization, namely the personalization of satellite communications, in the near future. The idea of a personal radio using a satellite and an example of an advanced communications satellite are introduced. The communications system and access method are also discussed and an FDMA system is recommended. Second, a small earth station for the millimeter-wave personal radio is proposed which has a 30-cm-diameter antenna, a transmission rate of 64 kb/s for wide applications, direct FSK modulation in the RF stage, the local signal fed from the transmit system, and link availability of 99%.     

Advanced Communications Technology Satellite (ACTS): four-yearsystem performance

The Advanced Communications Technology Satellite (ACTS) was conceived at the National Aeronautics and Space Administration (NASA) in the late 1970s as a follow-on program to ATS and CTS to continue NASA's long history of satellite communications projects. The ACTS project set the stage for the C-band satellites that started the industry, and later the ACTS project established the use of Ku-band for video distribution and direct-to-home broadcasting. ACTS, launched in September 1993 from the Space Shuttle, created a revolution in satellite system architecture by using digital communications techniques employing key technologies such as a fast hopping multibeam antenna, an on-board baseband processor, a wide-band microwave switch matrix, adaptive rain fade compensation, and the use of 900 MHz transponders operating at Ka-band frequencies. This paper describes the lessons learned in each of the key ACTS technology areas, as well as in propagation investigations     

ADVANCED COMMUNICATIONS TECHNOLOGY SATELLITE (ACTS): DESIGN AND ON-ORBIT PERFORMANCE MEASUREMENTS

The advanced communications technology satellite (ACTS), developed and built by Lockheed Martin Astro Space for the NASA Lewis Research Center, was launched in September 1993 on the Shuttle STS 51 mission. ACTS is a digital experimental communications test bed that incorporates gigahertz bandwidth transponders operating at Ka band, hopping spot beams, on-board storage and switching and dynamic rain fade compensation. This paper describes the ACTS enabling technologies, the design of the communications payload, the constraints imposed on the spacecraft bus, and the measurements conducted to verify the performance of the system in orbit.     

Ka-band propagation measurements: an opportunity with the AdvancedCommunications Technology Satellite (ACTS)

The Advanced Communications Technology Satellite (ACTS) was conceived at the National Aeronautics and Space Administration (NASA) as a follow on program to its long history in satellite communications projects that have reduced the risk of developing new technologies that fall outside the sponsorship capability of the private sector. To counter the foreign challenge that developed in the late 1970's to the once insuperable US lead in this field, ACTS was developed to maintain the US preeminence. Launched in September 1993 from the space shuttle, key technologies on ACTS include a multibeam antenna, a baseband processor, a 900 MHz wideband microwave switch matrix, adaptive rain fade compensation techniques, and the use of Ka-band frequencies. Since this is the United States' first effort in using Ka-band for satellite communications, beacons are incorporated on the satellite, which provide an opportunity for propagation measurements. NASA is sponsoring a network of propagation experimenters using these beacons and receive-only terminals identical in design. This paper provides some history that leads to the eventual development of ACTS. Also, a system overview of the spacecraft is provided for those less familiar with it     

Personal communications by satellite

Personal communications (PC) refers to two-way voice (and possibly data) communications to a small hand-held unit, capable of being carried by a person and used in various locations. PC via satellite refers to the case where this hand-held unit communicates directly with a satellite to provide the duplex voice (or data) service. Both geosynchronous earth orbit (GEO) and low earth orbit (LEO) satellites have been considered to provide this service. GEO and LEO satellite systems must compete with existing mobile cellular radio systems both in meeting performance requirements and service costs, if they are to be a significant supplier of PC services. GEO and LEO systems each have unique advantages and disadvantages when used to provide a PC service. While these general characteristics are identified in Section 1 of the paper, a more quantitative comparison is needed. This quantitative comparison is made by comparing a GEO PC satellite system, operating at EHF (K_a-band) frequencies with a LEO system operating at UHF (L-band) frequencies, including service costs for both systems. The two systems used in the comparison are examples of realistic GEO and LEO system designs for PC service, and although it is not exhaustive, the comparison points out some of the key differences between GEO and LEO systems that affect service performance and cost.     

Satellite telenets: A techno-economic assessment of major trends for the future

This paper reviews the historical trends in the development of new communications satellite technology and the technical and economic forces that will drive a new revolution in wide-band communications services in the 1980s and 1990s. The following key technical and service aspects of the new satellite telenets of the 1980s and 1990s will be addressed: new digital services, new antenna designs, intersatellite links, on-board signal processing and regeneration, and new architectural and servicing concepts for long-lived satellites. The possibility of non-Clarke orbit communications satellites in the 21st century will also be reviewed. Competitive technical and economic trends in other forms of telecommunications technologies will also be explored, in order to establish some economic and service "figures of merit" for the future. This analysis reveals some exciting and unexpected aspects about the new satellite telenets of the late-twentieth and early-twenty- first centuries. If messages are beamed to and from communications satellites by laser, there would be room for so many channels that every person on Earth could have his own, just as he has his own telephone number. He could reach everyone on Earth with no trouble, transmitting sight as well as sound... It is not unlikely that a good beginning toward laser satellite communications may be made by the end of the century... If so, it will represent a remarkable advance, considering that at the beginning of the century, mankind was still tied to the wire. (Isaac Asimov, Science Past, Science Present. New York: Ace Books, 1975.) If you're willing to spend enough money on advanced electronics you can virtually guarantee they can be made to not work.--One of Augustine's Laws. ("Augustine's Laws and major systems development programs, pt. 2," Aeronautics and Astronautics, p. 49, Jan. 1981.)     

Digital video broadcasting over satellite (DVB‐S): a system for broadcasting and contribution applications

The general system concepts for digital television transmission and broadcasting by satellite, developed within the European digital video broadcasting (DVB) Project and standardized by ETSI are described. The system (EN 300 421) is designed to provide direct‐to‐home (DTH) multi‐programme TV services in the BSS and FSS bands and is addressed to consumer integrated receiver decoders (IRDs), as well as collective antenna systems (SMATV) and cable television head‐end stations, with a likelihood of remodulation. The system operational modes have been extended in 1998 (EN 301 210) to cover also ‘contribution’ applications by satellite, such as conveying vision and sound material between TV studios, or from remote locations directly to the broadcaster's premises through light and portable up‐link terminal digital satellite news gathering (DSNG). The exploitation of the multiplex flexibility allows the use of the transmission capacity for a variety of TV service configurations. The use of flexible and advanced error protection techniques, based on the concatenation of Reed‐Solomon and convolutional codes (with Viterbi decoding), allows optimum adaptation to different satellite transponder characteristics, i.e. bandwidth and power, providing high service quality and availability with small receiving antennas (DTH applications) or transmitting terminals (DSNG applications). Copyright © 2000 John Wiley & Sons, Ltd.