Experimental advanced mobile satellite communications system in MM-wave and Ka-band using Japan's COMETS

The National Space Development Agency of Japan (NASDA) plans to launch the Communications and Broadcasting Engineering Test Satellite (COMETS) by an H-II launch vehicle in summer of 1997, which was rescheduled from the original planing date of launching in February of 1997. The COMETS project has progressed through the critical design phase and the design follow-up phase. The system Critical Design Review (CDR) was held in April of 1995. Almost all the flight components have been already assembled, integrated and tested, and it is now in the stage of mission and bus system integration test phase. From the beginning of 1996, the satellite Proto-Flight Test (PFT) will be conducted in NASDA Tsukuba Space Center. This paper describes the characteristics of COMETS spacecraft, the development-test using the satellite system engineering models, and the key components of the flight hardware.

Mission Profile of Advanced Satellite Broadcasting System on Communications and Broadcasting Engineering Test Satellite (COMETS)

[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.

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. >

Wireless communications are expected to take place in increasingly complicated scenarios, such as dense urban, forest, tunnel, and other cluttered environments. A key emerging challenge is to understand the physics and characteristics of wave propagation in these environments, which is critical for the analysis, design, and application of advanced mobile and wireless communication systems. In this paper, we present a full-wave field-based computational methodology for radio wave propagation in complex urban environments. Both transmitting/receiving antennas and propagation environments are modeled by first-principles calculations. A system-level, large scene analysis is enabled by the scalable, ultraparallel algorithms on the emerging high-performance computing platforms. The proposed computational framework is verified and validated with semianalytical models and representative measurements.

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.

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.

Wide-band digital indoor and future mobile communication systems are being developed in the quasi-millimeter and millimeter wave frequency bands. In such high-speed systems, the degradation of transmission quality by multipath fading constitutes a limiting barrier. Multipath fading, which results from reflection, refraction and scattering of radio waves by buildings and other structures, gives rise to more than one path reaching the receiver and produces a distorted version of the transmitted signal. In mobile and indoor communication systems it cannot be eliminated, therefore the multipath channel must be well characterized in order to reduce its effect in the design of such systems. The objective of this research is to study the multipath fading and delay spread effects due to buildings in an urban propagation channel. In particular, the effects of the building materials, shapes and number of buildings on multipath fading are being studied.

Reviews the European Union Research programs in the area of personal mobile telecommunication systems and their position in the context of European telecommunications research and development. The ACTS program call for proposals was launched in 1994, and proposals are to be submitted by March 1995. This program will provide a unique opportunity for organizations to participate in, and influence, the development of future global third-generation advanced personal mobile communications systems. It is hoped that projects will be actively supported by telecommunications operators, equipment manufacturers, service providers, research institutes, universities and leading-edge users. The participation of users reflects the policy that ACTS projects must be user-driven to ensure that the research and development program benefits directly the application of the technology, and ensures that the projects are responsive to user requirements. By their very nature, mobile communications markets are global, which implies that different world regions need to cooperate, particularly in the area of standards development and frequency allocations, to ensure the widespread availability of advanced and affordable wireless services and applications. National and regional borders must be transcended, interconnection of networks, and interoperability of services and applications must he encouraged, all with the objective of ensuring, through the convergence of the telecommunications, computer and audio-visual industries, the enhancement of the quality of life in the mobile information age.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper presents the design of a compact planar inverted-F antenna (PIFA) suitable for mobile handset applications. The prototype of the proposed antenna designs to satisfy specific bandwidth specifications of present-day mobile cellular communication systems, including the global system for mobile communication (GSM; 890-960 MHz), the digital communication system (DCS; 1710-1880 MHz), the personal communication system (PCS; 1850- 1990 MHz), and the universal mobile telecommunication system (UMTS; 1920- 2170 MHz). Therefore, it could be applicable for the existing and future mobile communication systems. Design details and experimental results are also presented and discussed.

Mobile communication systems rely on radiofrequency waves to operate. Given the popularity and ubiquity of mobile communication devices as well as network densification, the level of Electromagnetic Field (EMF) exposure to the public is expected to rise significantly over the next few years. Although there is no clear evidence linking short-term exposure to EMF emission from wireless communication systems with adverse health effects, the International Agency for Research on Cancer (IARC) has concluded that EMF radiation is possibly carcinogenic. To cope with the concerns of the general public, the European Environmental Agency has recommended non-technical precautionary approaches to minimize exposure to EMF emissions. Rather than relying on these non-technical approaches, EMF, latency, network resilience and connection density, alongside traditional criteria such as spectral efficiency and energy efficiency are expected to take centre stage in the development of 5G systems. This book focuses on innovative EMF exposure research for future generations of mobile and wireless communications. This timely publication highlights the novel work done on reducing EMF emissions in future mobile communication systems and how to develop smart integrated technical solutions.

Mobile communication has increasingly become a part of daily life. Tourism industry, as all other industries, has been affected by the advances in mobile communication. Because almost all definitions of tourism are based on travelling from one place to another for various purposes, the term ‘mobile’ is used as synonym for the words portable and moving. In this context, mobility is in the nature of tourism. Mobile communication, although currently not at the desired stage, will have a growing role in tourism. In today’s world, airlines, travel agencies, tour operators and hospitality businesses develop mobile applications and new business processes that take advantage of mobile technologies. This chapter attempts to reveal the relationship between mobile communication and applications in tourism.

Beyond the reminder: The next steps in pharmacist-driven, mHealth patient engagement

A highly innovative global broadband mobile communication system concept