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A new national R&D project on novel communication systems using a number of high altitude large airships(stratospheric platform). The pla t form will be used as base station and switching center for various types of communication systems. The goal of the national project is to develop key technology for stratospheric platform system in several years and to demonstrate it using airship in stratosphere . [1] This paper describes various ap plications and network system design of IMT2000 mobile communications system using stratospheric plat form (SPF) and plan of mission flight tests 2002. INTRODUCTION Research on the use of stratospheric platforms (SPFs) for wireless communication is being con ducted in Japan jointly by the Ministry of Education , Culture, Sports, Science and Technology (MEXT) and the Ministry of Public Management, Home Affairs, Posts and Telecommunications (MPMHAPT). An SPF is an unmanned airship kept at a stratospheric altitude and used for radio communications, broadcasting, earth observation, and monitoring. [1] The requirements for an SPF are station-keeping efficiency, long period undisturbed operation , [mission payload and power supply capability], mission recovery (reuse), and stratospheric environment-friendly. Therefore an unmanned large airship type is the most promising candidate . The Telecommunications Advancement Organization of Japan ( TAO) [2] and The Communication * Researcher, Yokosuka Stratospheric Platform Research Center, TAO of Japan, Yokosuka, Japan † General Manager, Yokosuka Stratospheric Platform Research Center, TAO of Japan, Yokosuka, Japan ‡ Head, Research Planning Office, Communications Research Laboratory, Japan § Group Leader, Senior Researcher, Communications Research Laboratory, Yokosuka, Japan ¶ Executive Director Business Operation Division NEC TOSHIBA Space Systems, Ltd . Research Laboratory (CRL) are research ing and developing a radio communications system and a broadcast ing system that use SPFs. In this article we will describe characteristics and various applications and network system designs for mobile communications (IMT2000 system) that use SPFs. We also describe the flight tests planned for 2002. Experiments and demonstrations will be conducted using a helicopter flying 3 km high. Finally, we describe a stratospheric communication experiment planned for 2002 that will use a so lar-powered stratospheric plane, the “Pathfinder Plus”, and be conducted in cooperation with NASA. R&D SCHEDULE & PROGRESS (1998-2004) (1) 1998: Conceptual design of mobile communications systems using SPFs (2) 1999: Basic design of mobile communications systems using experimental airship (3) 2000: Design and manufacture of on -board mobile communications system for preliminary experiment (4) 2001: Design and manufacture of IMT2000 base station system for preliminary exp eriment (5) 2002: 1) Preliminary experiment using helicopter 2) Stratospheric communication experiment us ing solar-powered stratospheric plane deve loped by NASA (6) 2003: Design and manufacture of IMT2000 test system for low-altitude position-controlled airship test (7) 2004: Low-altitude position-controlled airship test The R&D schedule for the mobile communic ation system using SPFs is shown in t able 1. [2] 20th AIAA International Communication Satellite Systems Conference and Exhibit 12-15 May 2002, Montreal, Quebec, Canada AIAA 2002-2002 Copyright © 2002 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. American Institute of Aeronautics and Astronautics 2 In 2000 and 2001, we designed and manufa ctured the on-board communication equipment and the ground communication equipment. In 2002, pre liminary experiments and demonstrations will be conducted using a helicopter fly ing 3 km high. The original plan called for the use of a stratospheric position-controlled airship. However, airship development has been delayed, so a helicopter will be used instead. The IMT2000 system uses the 2-GHz band, which was newly allocated at the WRC2000. A stratospheric communication experiment planned for May and June 2002 will use a solar -powered stratospheric plane, the “Pathfinder Plus”, developed by NASA. [3] CHARACTERISTICS OF MOBILE COMMUNICATIONS SYSTEM USING SPFS Mobile communications systems using SPFs have the follo wing characteristics. (1) The wide coverage area of the airships a llows for an economical communications system. (2) The high elevation angle and line-o f-site transmission minimize propagation loss and significantly reduce multi-path fading. (3) The propagation loss and delay are less than with a sate llite system. (4) The service area can be flexibly set. Moreover an IMT2000 system using the 2-GHz band can operate with a low elevation angle. An SPF flying 20 km high can cover a 200km service area with a 10-degree elevation angle (EL). (Fig. 1) For example , the entire country of Canada could be covered by 360 SPFs . (Fig. 2) If te rrestrial IMT2000 base stations were used, 463,129 of them would be needed. (Assuming each base station (BS), coverage area has a 2.5-km radius.) In other words one SPF can cover the same area as 1300 terrestrial BSs. [4] Using SPFs is thus an efficient way to services rural areas, particularly mountain and forest areas . They are effective in urban areas because the e ffects of blocking by buildings and multi-path fading are low due to the high elevation angle and line-o f-site transmission. Therefore, a network system using SPFs has lower propagation loss than terrestrial systems. For example, the propagat ion loss of an IMT2000 terrestrial system using the 2-GHz band is in proportion to the 4 power of the distance. That of an SPF system is in proportion to the square of the distance. (The 100-km propagation loss of an SPF system is the same as the several-km loss of a terrestrial system.) Therefore, (In terms of propagation loss) terrestrial IMT2000 terminal equipment can be used for SPF mobile communication system. And the propagation distance is much shorte r than that of satellite communication, the propagation loss of the SPF system (130dB) is 30 d B lower than that of LEO (low earth orbit) systems (160 dB) and 60 d B lower than that of GEO (geo-stationary earth orbit) systems (190 d B). Fig. 2 Example service areas for Canada (EL=10 deg) A L T : 2 0 k m E L : 1 0 S P F : 3 6 2 Fig. 1 Coverage area with EL of 10 deg 200 km (656,000 ft) 5 km (16,400 ft) Altitude 20 km (65,600 ft) Terrestrial Base Station SPF |
