School on Digital Radio Communications for Research and Training in Developing CountriesThe Abdus Salam International Centre for Theoretical Physics ICTP Trieste (Italy) 9 - 28 February 2004
Emerging stratospheric radio Prof. Dr. R. Struzak
Former Vice-Chairman, Radio Regulations Board, [email protected]
Note: These are preliminary notes, intended only for distribution among the participants. Beware of misprints!
Aim
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• The 1st lecture dealt with the future of telecommunications
• Following lectures were devoted to telecom. technologies that have worked
• In this lecture, we shall discuss emerging technologies of satellite radio, which may work, according to some predictions
About predictions…
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• Many predictions made in the past have proved to be dramatically wrong ...even when made by experts with impeccable credentials...
• “Prediction is difficult - especially of the future” (Storm Petersen, Danish humorist)
Example: Radio
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“Radio has no future”
– Lord Kelvin (famous physicists, 1897)• 1896: Marconi - 1st transmission at 1.6 km distance
Outline
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• Introduction• What is the stratosphere?• How does work satellite radio?• What are major projects?• Short movies on recent tests • Discussion
Access to Information
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= Key Problem of Humanity• Report Of The UN
Secretary General, 2000 • G8 Okinawa Charter on
Global Information Society, 2000
• World Summit on Information Society (WSIS) 2003, 2005
http://www.un.org/millennium/sg/report/full.htmhttp://www.itu.int/wsis
http://www.un.org/millennium/sg/report/full.htmhttp://www.itu.int/wsis
Quest for new technologies
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• The existing access technologies are impractical in many situations
• >96% of computers connected to Internet were used by 15% of the world’s population… what about the rest?
• Hope in Radio Access
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Radio Wavescarry information 300’000 km/s to fixed & mobile users
• Ubiquitous - accessible at any place, any time…* • Deployment cost & time• Fixed and mobile uses… • Free, no right-of-way- no deployment/ installation/ maintenance… • Indestructible - no theft, snow, wind, flood, earthquake, tornado, trees…• No cable production/ transport/ warehousing…
*Over the Earth’s surface
The first experiment …
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Flight zone:2 km diameter circle, 21 km altitude
Coverage zone:500 km horizon
Powering antenna80 m diameter
Power beam:5.8 GHz, 500 kW
Control & contents signals
Earth surface
On 17 Sept. 1987, the Canadian Stationary High Altitude Relay Platform (SHARP) makes history by flying for twenty minutes, powered by microwaves (An official flight takes place on October 7)
10 years passed…
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• The SHARP project was abandoned. • Some (limited) research continued, but
real “explosion” took place after 1997…• Today, a number of governmental and
non-governmental organizations are involved– China, Germany, Hungary, Indonesia, Italy,
Japan, Korea, Slovenia, Spain, Switzerland, UK, USA…
What happened in 1997?
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• HAPS recognized by the ITU Radio Regulations Board as a new category of radio stations
This decision has removed obstacles/ uncertainties in financing the development of that new technology
WRC Geneva 1997
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• The decision of RRB has been confirmed by consensus of all ITU Member Countries at the World Radiocommunication Conference (WRC) Geneva 1997
WRC Istanbul 2000
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• allocated frequency bands near 20 GHz for HAPS and
• made appropriate provisions in the international treaty (Radio Regulations)
The ITU Radiocommunication Assembly and World Radiocommunication Conference Istanbul 2000:
3 categories of radio
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• Classic: Terrestrial radio– You were exposed to that technology during
the whole School • Modern: Satellite radio: GEO, MEO, LEO
– See my paper “Satellite industries at the turn of the century” (+references) just distributed
• Emerging: Stratospheric radio
IMT-2000: flexible, multifunctional
Satellite
Macrocell Microcell
UrbanIn-Building
Picocell
Global
Suburban
Basic TerminalPDA Terminal
Audio/Visual Terminal
HAPS
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Launch of GEO satellites
Source: ESA - (Ariane 5)
Satellites avoid radiation belts
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2 3 4 5 6 7
Cosmic rays, Solar wind
GEO
LEO
MEO
150-1500 km 5000-10000 km
Geomagnetic field
35’784 km
Geomagnetic axis Concentration of radiation (10’000x, James Van Allen, 1958)
Launch of LEO satellites
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Low-Earth-Orbit Constellations
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Sky Station International
2100 Cells
Urban
Sub-Urban
Rural
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Altitude of radio stations
• Satellite– GEO Geostationary Orbit Satellites, alt. 35’784 km
– MEO Medium-Earth Orbiting Satellites, alt. 5’000-10’000 km
– LEO Low-Earth Orbiting Satellites, alt. 150-1’500 km
• Stratospheric, alt. 15-30 km
• Terrestrial, alt. 10-300m (+ terrain height,
Stratospheric radio family
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– HALE: High Altitude Long Endurance– HAPS: High Altitude Platform Station– SHARP: Stationary High Altitude Relay
Platform – SPR: Stratospheric Platform Radio – “Stratospheric Satellite” – All at the altitude 15 – 30 km
Why 15-30 km?
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0
20
40
60
80
100
120
0 10 20 30 40 50 60 70
Wind speed, m/s
Alti
tude
, km
Tropopause
Mesopause
Stratopause
Stratosphere
Line-Of-Sight (LOS) area
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A ( ) ( ) 22sin RhRhRd −+=+= α
Shadowed area of theEarth’s surface
tangent cone
h Max LOS celld
B
RO
α
RsinαP
( )
⎟⎠⎞
⎜⎝⎛
+=
−=
hRhR
RareaLOS
2
2
2
cos12_
π
απ
Rcosα
∞→→
→→
hifRareaLOShifareaLOS
2_0 0_
2π
2
1sin ,cos ⎟⎠⎞
⎜⎝⎛
+−=
+=
hRR
hRR αα
Simplifications
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• Ideal smooth, spherical, earth• Zero elevation angle above horizon• No refraction in the atmosphere
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1
10
100
1000
10000
100000
1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05
Altitude, km
Max
. Foo
tprin
t Dia
met
er, k
m
Earth diameter
Terrestrial HAPS LEO MEO GEO
Minimum elevationangle (= 0) 15 deg.
45 deg.
Signal latency restrict interactive applications
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0.1
1
10
100
10001.
E-01
1.E
+00
1.E
+01
1.E
+02
1.E
+03
1.E
+04
1.E
+05
Altitude, km
Late
ncy,
ms
The time required for a signal to travel from one point on a network to another.
STR
LEO
GEO
MEO
More power for higher altitudes
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1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
1.E
-02
1.E
-01
1.E
+00
1.E
+01
1.E
+02
1.E
+03
1.E
+04
1.E
+05
Altitude, km
Rela
tive
tran
sm. l
oss
Power limits for hand-held radio
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Head
Radio
Intended radiation
Unintended power
Radio waves interact with living tissue
Limits: 2.7mW/cm2 (6min.) or 8W/kg (for any gram of tissue)
Source: J. Lin: Wireless communication radiation and its biological effects, Global Communications Interactive 1998
2 categories
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• Aerodyne: – A heavier-than-air aircraft deriving lift from
motion.• Aerostat:
– A balloon or dirigible, deriving its lift from the buoyancy of surrounding air rather than from aerodynamic motion.
Aerodyne powering
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• Periodical refueling – Combustion engine (Gasoline)– Thermoelectric nuclear engine
• Capturing energy from the earth• Capturing solar energy + fuel cells
Proteus
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http://www.dfrc.nasa.gov/Newsroom/FactSheets/FS-069-DFRC.html
http://www.dfrc.nasa.gov/Newsroom/FactSheets/FS-069-DFRC.html
Predator
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Helios
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Helios: semi-transparent wings
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Sad news
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• On June 26, 2003, the Helios unmanned solar-electric powered aircraft was lost in the Pacific Ocean on the Hawaiian island of Kauai, 29 minutes after takeoff during a test flight.
• The intent of the flight was to checkout the operation in the stratosphere of a new fuel cell system developed for overnight flight operation, prior to demonstrating the world’s first multi-day fuel cell flight in the stratosphere.
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太 陽 電 池
船 側プ ロ ペ ラ
船 尾プ ロ ペ ラ
カ テ ナ リカ － テ ン
Ｈ ｅ ガ ス 嚢
再 生 型 燃 料 電 池
Ｘ 形 状安 定 尾 翼
NAL-SPATMarch 99
成 層 圏 プ ラ ッ ト フ ォ － ム 飛 行 船 シ ス テ ム の 概 念
Solar Cells
Side
Propeller
Regenerative Fuel Cells
Helium Gas Bag
CatenaryCurtain
BackPropeller
X-shaped Tail
Assembly
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Stratolite
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• Stratolite (stratospheric pseudo-satellite) -- The augmented navigation system (satellite + ground station + HAP)
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“Stratospheric satellites”
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Model of Fully-Pressurized Balloons In Flight. Picture courtesy of NASA.
•“Super-pressure" balloons at 115,000 feet, powered by solar array. •Can carry remote sensing or telecom. payloads up to 2 tons, roughly the size and weight of a small truck. •Can be steered and directed to group themselves, fly over, and monitor disaster areas, with a trajectory control, according to the company
StratoSat ™
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• Constellations of StratoSatplatforms would circle the Earth at an altitude of 35 km for 3 to 10 years. They would augment and complement many satellite measurements, and possibly even replace some of them.
• The keys are (a) affordable, long-duration balloon systems, (b) balloon flight path control capability, (c) constellation geometry management, and (d) a global communications infrastructure.
StratoSatTM 2
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• Projected life: 3-10 years. • The projected life-cycle cost < $400,000/ unit • Would be a low-cost alternative to aircraft and space
satellite communications platforms, costing 10 to 100 times less
• A constellation of 400 Stratospheric Satellites is projected to cover most of the northern hemisphere. Cost: < $160 million (less than the cost of most space satellites including launch), + < $10 million per year of operations costs
• http://www.gaerospace.com/ (June 2002).
http://www.gaerospace.com/
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• 10 march 2001 Super pressure balloon test flight. Picture courtesy of NASA
What we have learned
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• HAPS technology is a way to keep antenna at stratospheric heights (~20 km) at relatively low cost
• Multiple applications– Fixed/mobile broadband data & multimedia– Direct broadcasting video/audio on demand– Non-telecom applications
• Environmental observations; Navigational systems; Military
• Complement to terrestrial & satellite systems – may change dramatically the telecom. business model
Comparison
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System Terrestrial HAPS SatelliteLifetime Up to 15y ? Up to 15 yCapacity High High LowCoverage Land Rather land Land & SeaFade margin High Medium LowIndoor reception
Possible ? Not possible
Remarks Easy maintenanceWell proven technology
Easy maintenanceTechnology not provenUnresolved power problems
High launching costsWell proven technology
References
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• See the references in my paper “Mobile telecommunications via stratosphere” (+references) just distributed
–
Any questions?
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Thank you for your attention
Copyright note
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• Copyright © 2004 Ryszard Struzak. All rights are reserved. • These materials and any part of them may not be published,
copied to or issued from another Web server without the author'swritten permission.
• These materials may be used freely for individual study, research, and education in not-for-profit applications.
• If you cite these materials, please credit the author • If you have comments or suggestions, you may send these
directly to the author at [email protected].
mailto:[email protected]
Emerging stratospheric radioAimAbout predictions…Example: RadioOutlineAccess to InformationQuest for new technologiesRadio Wavescarry information 300’000 km/s to fixed & mobile usersThe first experiment …10 years passed…What happened in 1997?WRC Geneva 1997WRC Istanbul 20003 categories of radioIMT-2000: flexible, multifunctionalSatellites avoid radiation beltsLow-Earth-Orbit ConstellationsSky Station InternationalAltitude of radio stationsStratospheric radio familyWhy 15-30 km?SimplificationsSignal latency restrict interactive applicationsMore power for higher altitudesPower limits for hand-held radio2 categoriesAerodyne poweringProteusPredatorHeliosHelios: semi-transparent wingsSad newsStratolite“Stratospheric satellites”StratoSat ™StratoSatTM 2What we have learnedComparisonReferencesAny questions?
