Shingo Ohmori

The future generations of mobile communications based on broadband access technologies

The forthcoming mobile communication systems are expected to provide a wide variety of services, from high-quality voice to high-definition videos, through high data rate wireless channels anywhere in the world. The high data rate requires broad frequency bands, and sufficient broadband can be achieved in higher frequency bands such as microwave, Ka-band, and millimeter-wave. Broadband wireless channels have to be connected to broadband fixed networks such as the Internet and local area networks. The future-generation systems will include not only cellular phones, but also many new types of communication systems such as broadband wireless access systems, millimeter-wave LANs, intelligent transport systems, and high altitude stratospheric platform station systems. Key to the future generations of mobile communications are multimedia communications, wireless access to broadband fixed networks, and seamless roaming among different systems. This article discusses future-generation mobile communication systems.

A novel broadband all-wireless access network using stratospheric platforms

This paper proposes a novel broadband access network using a number of stratospheric platforms. This is a new wireless infrastructure, and consists of wireless access links between the platform and terminals in the Ka-band and a mesh-like network using optical inter-platform links. One platform covers a 40 km/spl times/40 km area with 64 beams of an onboard multi-beam antenna. Thus, the cell size is almost as same as that of current cellular systems. This network can provide 25 Mbps to more than 156 Mbps access links and a flexible wireless ATM network to subscribers.

Experiments on aeronautical satellite communications using ETS-V satellite

The worlds first aeronautical satellite communication experiments, conducted at L-band frequencies using a commercial aircraft, are described. An airborne antenna with electronically steerable beam and communication equipment was installed in a B-747F freighter flying over transoceanic flight routes. The satellite used in these experiments is the Engineering Test Satellite-Five (ETS-V). During the test period, various experiments, such as antenna pattern measurements, transmission performances, and voice quality evaluation were conducted. As the airborne antenna is the key component for the aeronautical satellite communication system, emphasis has been placed on antenna characteristics. Its performance is found to be closely related to the fading characteristics in low-elevation areas and to transmission error performance. >

The Future Generations of Mobile Communications Based on Broadband Access Methods

The forthcoming mobile communication systems are expected to provide much variety of services from high quality voice to high definition videos through high data rate wireless channels at anywhere in the world. High data rate requires broad frequency bands, and sufficient broadband can be achieved in higher frequency bands such as microwave, Ka-band and millimeter-wave. Broadband wireless channels have to be connected to broadband fixed networks such as the Internet and local area networks. The future generation systems will include not only cellular phones, but also many new types of communication systems such as broadband wireless access systems, millimeter-wave LAN, intelligent transport systems (ITS) and high altitude stratospheric platform station (HAPS) systems. The key words in the future generations of mobile communications are “multimedia communications”, “wireless access to broadband fixed networks” and “seamless roaming among different systems”. This article discusses the future generations mobile communication systems.

Radio communication technologies for vehicle information systems

Publisher Summary This chapter introduces the intelligent transportation systems (ITS) from a standpoint of radio communication technologies for information and communications for transportation systems. An integration method of wireless multiple services in ITS that is based on common frequency band radio on fiber (CFB-ROF) technique is proposed. The CFB-ROF will become a key technique for mobile multimedia communications in ITS. An inter-vehicle communication system (IVC) system was prepared to investigate the behavior of propagation characteristics comprehensively. Various services of the ITS-driving information, drivers assistant information, and vehicle control data can be provided for vehicles by using both the road-vehicle communication (RVC) and the IVC systems. Moreover, automotive radar systems have already been practically used for collision avoidance. The chapter also introduces the present research and development of the optical and millimeter-wave devices, which make it possible to downsize the RVC system and the automotive radar system.

Communications and radio determination system using two geostationary satellites. I. System and experiments

We developed two types of hybrid terminals that can provide both satellite communication and position determination services in one system. One terminal uses the single channel per carrier (SCPC) technique and the other uses the spread spectrum (SS) technique. To evaluate the performance of the two systems, we carried out experiments in Japan and in the Pacific Ocean using two geostationary satellites, ETS-V (150/spl deg/E) and Inmarsat (180/spl deg/E). The ranging accuracy between the mobile terminals and the base station via the satellites was found to be about 200 m using the SCPC system and about 10 m using the SS system. The measured positioning accuracy was about 1 km in the SCPC system and about 600 m in the SS system when experiments were carried out near Japan. The experimental results show that the positioning errors were mainly caused by the orbital determination errors of the two satellites. Presented here are the configurations and features of the SCPC and SS terminals, the experimental system, and the experimental results. >

Planar radiating oscillator using butterfly-shaped patch element and spatial power-combining array

A planar radiating oscillator using a butterfly-shaped patch element is described. To obtain an injection-locking range that can be changed and low cross-polarization, we used a butterfly-shaped patch. The patch element was able to change the injection-locking range while maintaining low cross-polarization, and two types of patch were compared. As one application, we designed and fabricated 1x2, 2x1 and 2x2 spatial power-combining arrays by using radiative mutual coupling. The 2x2 array was successfully operated with a single-bias supply without using a 3-D (three-dimensional) Fabry-Perot cavity. An equivalent isotropic radiated power of 2.5 W was measured at X-band.

Antenne à réseau à commande de phase pour les communications avec des mobiles

Un systeme d’antenne incluant des elements rayonnants et un modele de poursuite est considere comme un point clef dans la technologie des systemes de communication avec des mobiles. Le reseau a commande de phase a ete longtemps considere comme le meilleur candidat du fait de ses nombreuses proprietes attractives telle que sa compacite, sa vitesse de poursuite, etsonfaible coutpoten-tiel. D’un autre cote, ilpresente des inconvenients, comme I’erreur de pointage, les pertes dans les lignes d’alimentation et l’elevation du niveau de bruit dans les bandes de reception. Des reseaux a commande de phase ont deja ete utilises en communication par satellite, et d’autres sont en cours de developpement. Cet article presente les performances de bases ainsi que quelques exemples de reseaux destines au service mobile par satellite.An antenna system including antenna elements and a tracking method is considered a key technology in mobile communication systems. A phased array antenna has been considered the most favorite candidate because of many attractive characteristics such as a low and compact profile, high-speed tracking and potentially low cost performance for vehicle antennas in mobile communications. On the other hand, it has several such disadvantages as beam steering error, loss in feed lines and an increase of noise level in a receiving frequency band. Some of phased array antennas have already been used in satellite communications, and some of them are under development. This paper overviewed basic performance and some examples of phased array antennas for especially satellite mobile communications.RésuméUn système d’antenne incluant des éléments rayonnants et un modèle de poursuite est considéré comme un point clef dans la technologie des systèmes de communication avec des mobiles. Le réseau a commande de phase a été longtemps considéré comme le meilleur candidat du fait de ses nombreuses propriétés attractives telle que sa compacité, sa vitesse de poursuite, etsonfaible coûtpoten-tiel. D’un autre côté, ilprésente des inconvénients, comme I’erreur de pointage, les pertes dans les lignes d’alimentation et l’élévation du niveau de bruit dans les bandes de réception. Des réseaux à commande de phase ont déjà été utilisés en communication par satellite, et d’autres sont en cours de développement. Cet article présente les performances de bases ainsi que quelques exemples de réseaux destinés au service mobile par satellite.