High Altitude Platform
As the demand grows for communication services,
wireless solutions are becoming increasingly
important. Wireless offers
Solution to the ‘last mile’ problem.
Essential for mobile services and cellular
Capacity for broadband services and
High bandwidth service provision
To provide bandwidth to a large number of users,
frequency reuse strategy must be adopted
The neighboring cells have
different frequency of
Base Station operation.
At the center Frequency reuse depends
Signal to interference
plus noise ratio
Fig 1: Cellular frequency reuse concept.
Limitations of existing system
No proper LOS propagation Solution : Use of very tall
base stations mast
No microcellular structure
Sea Coverage not possible
High Free space path loss
Solution : Use of geostationary
Lengthy propagation delay systems but at low
High Altitude Platform
HALE : High Altitude Long Endurance
HAAP : High Altitude Aeronautical Platform
Solar-powered aerial platforms, capable of long endurance
on-station up to several months or more.
operating in a quasi-stationary position at altitudes up to
Hap technologies are
Situated at altitude of 17 – 22 km (up to 70000 ft)
Mission Duration Up to Few Years
Airship Enabling Technology
Light weight solar cells
(<400 gm per square meter)
Reliable and efficient fuel cells
Plastic laminated materials
Resilient to UV
Helium leak proof
Aircrafts are like man made aero plane.
They fly in roughly circular path.
Can be manned or unmanned.
Fig. 1 Fig. 2
Piloted Aircraft Pilot less Aircraft
Working in three Solar powered
8 hours shifts.
Wind Speed Profile
Altitude selection for HAP
Should be above
commercial air traffic
Air should be mild with
low wind speed
Altitude around 20 km.
Wind speed, m/s
(depend on season and location)
D=2R.[ arccos( R.cos(Φ) / (R+h) ) -Φ]
R=Earth Radius(6378 km.),
Φ=Minimum Elevation Angle (h)
For Φ=15°, D=152 km.
For Φ=0°, D=1033 km. Diameter
(values at h = 21 km)
alternative backhaul via
satellite for remote areas
Inter HAP link
local backhaul links to base
stations for less remote areas
Fiber Network 60 – 400 km Fiber Network
General Communication Scenario
Broadband Wireless Access (BWA)
Principle application as broadband fixed wireless
access or simply BWA.
Can provide potentially very high data rates to the
Offers 600 MHz of bandwidth.
for downlink 47.2 – 47.5 GHz
for uplink 47.9 – 48.2 GHz
Footprint Diameter = 60 km
Number of cells = 121
Nominal ground diameter = 5 km
Downlink HAP power = 1W/cell
Deployment of mobile cellular services
One Base station on HAP can serve a wide
area with a wide beam width antenna
Alternatively, for smaller cells directional
antennas can be used
Elimination of much ground station
Number of inter linked HAPs deployed to
cover an entire area.
Inter-HAP links may be accomplished at
high EHF frequencies or using optical links.
Emergency services and Disaster relief
Traffic monitoring and control
Comparison with Terrestrial/Satellite
Terrestrial HAPs Satellite System
Height over 5 to 250 m Up to 22 km 500 – 36000 km
Lifetime 15 years < 5years 15 years
Capacity High Medium Low
Coverage Land and Global Global
Station < 1km Up to 200 km > 500 km
Cell Size (Dia) .1 - 1 km 1 - 10 km 50 km
Maximum Tx. 30 Mbps 25 - 155 Mbps < 2 Mbps
Advantages of HAP
Larger area coverage
Flexibility to respond larger area traffic.
Platform and Payload upgrading
Some Issues and Challenges
• System level requirement
• Designs of cellular type structure
• Frequency planning of different spot beam layouts
• Propagation and diversity
• Consideration of rainfall and scattering statistics
• Modulation and coding
• Platform Station Keeping
• Propellers and thrusters technique
• Payload power
• Sufficient power required for continuous coverage especially
Some Current and Proposed Programs
• For communications and monitoring
• Integrated Network of some 10
airships to cover Japan
• 150 m class airship
• Communications payload of 800 kg.
Some Existing Platforms: Aircrafts
The novelty of HAP communications calls for
some new concepts and researches in terms of
delivery of services and the platforms themselves
present some challenges and potential problems.
But A combination of ‘technology push’
from the providers of platforms and ‘applications
pull’ from the demand for enhanced
communications may provide significant
developments in HAPs for communication service
delivery in the near future