| Research Abstract |
For the aspects of a new minimum cost, high reliability system strategy for the Hokkaido Integrated Telecommunication (HIT) network, system designs and propagation experiments for site diversity and satellite diversity characteristics were examined.
[1] HIT Network system design for emergency use.
Three aspects of a new system strategy for the Hokkaido Integrated Telecommunication (HIT) network are examined, i.e., (1) network construction by using MS Windows 2000 Server, (2) A packet communication ultra small aperture terminal (PC-USAT) system, which contains a method for overcoming the satellite links rain attenuation discontinuities, (3) An optimum rain margin technique and the 14/12 GHz band rain, snow attenuation and satellite diversity (Sat.D) experiments.
[2] Sat.D experiments using plural satellites
The possibilities of the satellite diversity (Sat.D) system for VSAT earth station in snowing climates are examined by using plural satellites. Six satellite down-link signals are measur
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ed in experiments, i.e., JCSAT-1, JCSAT-3 and Broadcasting Satellite (BS) etc. and diversity gains are obtained by the Sat.D simulation program. From the obtained Sat.D results for snowing attenuation in snowing climates, it becomes clear that the Sat.D would be utilized effectively for the VSAT system, rather than conventional site diversity (SD) system.
[3] Site diversity experiments using JCSAT transponder
As for the system design of the HIT network, it must first overcome rain attenuation discontinuity of satellite links. To resolve some of these problems, site diversity (SD) is another candidate. To clarify the SD characteristics for introduction possibility, SD experiments were continued for medium distance earth stations
[4] Propagation characteristics and satellite-diversity (Sat.D) characteristics of mobile broadcast geostationary satellite system
This study deals with the urban propagation characteristics and satellite-diversity (Sat.D) characteristics of mobile broadcast geostationary satellite system by using the GPS (Global Positioning System) signals. For designing digital broadcast from geostationary satellite, it must be clarified the shadowing characteristics by urban building, electrical light poles and trees etc. Southern orbital arc GPS satellite signals with elevation angle between 40〜50 degrees data are used for propagation characteristics, rather than actual geostationary satellite, e.g., the N-STAR.This new measuring method has several merits, i.e., low measuring equipment cost, easy data accumulation (i.e., satellite position, receiver position ard height, received signal levels etc.). A receiving system on a vehicle measured signals fades caused by shadowing building etc. As a result, west to east urban roads are heavily attenuated.
Furthermore, to overcome this attenuation, the Sat.D characteristics are processed from measured data. From processing results, more than 90 % satellite visibility percentage can be achieved in urban city by selecting two diversity satellites with separation angles more than about 45 degrees. Less
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