Site: Communications Research Laboratory
Ministry of Post and Telecommunications
Koganei, Tokyo 184, Japan
Date Visited: June 3, 1997
WTEC: A. Mac Rae (report author), K. Bhasin, C. Bostian, W. Brandon, R. DePaula, N. Helm, C. Mahle, S. Townes
The Ministry of Posts and Telecommunications (MPT) is a government agency that funds the Communications Research Laboratory (CRL). It is a national institute with the charter to do advanced and fundamental research on information and communications, environmental science and materials science. Its goal is to be a Center of Excellence in research fields of telecommunications, information sciences, radio science and radio applications. It has established high standards for its research by hiring excellent people and exchanging people with other institutions. It encourages its staff to publicize its results by publishing their results in highly regarded journals and presenting papers at international meetings.
Many of the research programs supported by CRL involve satellites. The CRL research program is as follows:
This research includes investigations into the use of satellites for interconnection of terrestrial facilities in a multimedia network.
This research includes satellite broadcasting, mobile satellite communications, intersatellite communications and space optical communications. The activities include research on low-earth-orbiting satellite communications systems, satellite cluster systems and high data rate satellite communications systems.
This satellite work includes investigations into the safety of man in space, the Japanese Mars mission and research on the upper atmosphere.
Satellites are used to detect and measure global rainfall.
Satellites are used for very long baseline interferometry and laser ranging.
CRL has nine principal facilities in Japan. The headquarters are located at Koganei and it contains people investigating space communications, terrestrial wireline and cellular communications, broadband communications and communications sciences, with many of the people having skills in rf technologies. It operates an antenna facility in Kashima, where most of the satellite communications measurements are made. Kashima contains numerous antennas, including a large steerable 34 meter diameter. This facility is located northeast of Tokyo and is reached by a two hour bus ride.
Ten per cent of the CRL budget, 2 billion Yen (~ $18 million), is spent on space communications R&D and this represents a 10% increase over the 1996 budget. This budget includes funds for the research facilities but does not include the cost of the construction of experimental satellites.
The technical program for the day was divided into two parallel sessions, requiring the WTEC team to split into two groups, one covering mobile satellite communications, the other high data rate and optical satellite communications
Most of this meeting addressed two advanced experimental communications satellites, ETS-VIII and COMETS.
ETS-VIII (Engineering Test Satellite) is in the design stage and is expected to be a 3,000 kg dry mass GEO satellite that will be used primarily for studies of multimedia mobile communications between the base station and handheld terminals, mobile receivers in cars and trucks, and portable stations such as laptops as well as for studies of digital audio broadcasting. It will use a newly developed 3 ton class bus and is scheduled for launch in 2002 onboard an H-IIA launch vehicle. It will be located at 146º East, and will be used to test an S-band handheld telephone system, mobile packet data, and audio broadcasting communications services. Special features include an on-board 1,000 channel telephone circuit switch and a 1 Mbps on-board packet switch.
COMETS (Communications Engineering Test Satellite) is an experimental GEO satellite that will be used to test out new communications and broadcasting technologies, such as mobile communications and high definition TV (HDTV) and is scheduled for launch in early 1998.
Most of this discussion focused on a proposal for a Ka-band "Gigabit Satellite," which CRL would like to launch in 2002. The purpose of this satellite is to investigate high speed global multimedia applications, with seamless connectivity with the terrestrial network. Three classes of service are being considered: gigabit (1.2-1.5 Gbps) using a 200 watt, 0.5-1.2 meter OD terminal, very high data rate (155 - 820 Mbps) using a 100 watt 1.2 -2.3 meter OD terminal, and broadband multimedia (1.5-155 Mbps). The satellite will feature five scanning spot beams. Direct radiating active phased array and active phase array fed imaging reflector technologies are being considered. The gigabit and very high data rate links will use SS/TDMA and the broadband multimedia will use SCPC/TDMA (up) and TDM/TDMA (down), with onboard ATM switching. Optical (not rf) ISL will be used. CRL is expected to work with Mitsubishi on the K/Ka-band antennas and SSPAs, NEC or Mitsubishi for the ATM switch, NEC for the digital modems and Toshiba for the analog modems.
A discussion followed on CRL's free space optical communications program. CRL was responsible for the optical package on the ETS-VI satellite. While this satellite did not reach its planned GEO orbit, researchers in Japan and the U.S. (JPL) were able to use the optical payload for space-ground link communications studies at 1 Mbps. The next phase of this program is OICETS, which will demonstrate a 50 Mbps LEO to GEO link. The "Gigabit Satellite" mentioned above will use two types of ISL. The first will function at 0.8 microns, with wavelength division multiplexing, and intensity modulation with direct detection, to obtain four 300 Mbps channels. The second type will use two channels of 1.2 Gbps DPSK at 1.54 microns wavelength. This higher speed system is the precursor to future 10 Gbps experiments, envisioned for 2006. These higher speed links will also be part of the laser communications demonstrations for the Japanese Experimental Module aboard the International Space Station. CRL is recognized in Japan as the center of excellence in advanced technologies for optical communications and remote sensing. To support this effort, they are studying "light wavefront control technologies," which include lasers, detectors, high speed modulation/demodulation, propagation, superconductivity for optical devices, and lightwave/radiowave conversion.
CRL is a world renowned institution devoted to fundamental and advanced research on satellite communications. Its primary focus is on mobile and high data rate multimedia satellites, optical communications technology, and satellite/terrestrial communications systems experiments. It uses metrics as a measure of the interaction of its research staff with the global satellite research community, encouraging the publication of the results of their work in refereed journals and the presentation of talks at international conferences. It works closely with Japanese industry to optimize the technology transfer process.