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High Altitude Platform
      Wireless Communication
 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
       rapid deployment
       High bandwidth service provision
                    Cellular Concept
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
                                             upon factors—
                                                 Local propagation
                                                 Signal to interference
                                                 plus noise ratio

                Fig 1: Cellular frequency reuse concept.
    Limitations of existing system
 Terrestrial systems
    No proper LOS propagation    Solution : Use of very tall
                                             base stations mast
    No microcellular structure
    Sea Coverage not possible
 Satellite systems
    High Free space path loss
                                  Solution : Use of geostationary
    Lengthy propagation delay               systems but at low
    Low Capacity
                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
  some 22km
 Hap technologies are
   – Airship
   – Aircraft
         Airships Technology
Situated at altitude of 17 – 22 km (up to 70000 ft)

  Solar Powered
  Unmanned
  Helium Filled
  Semi Rigid
  Very Large(150m)
  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
      Strong
      Helium leak proof
      Aircraft Technology
 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

                             Height, km.
commercial air traffic
Air should be mild with
low wind speed

  Altitude around 20 km.
                                           Wind speed, m/s
                                 (depend on season and location)
              Footprint Diameter
D=2R.[ arccos( R.cos(Φ) / (R+h) ) -Φ]
D=Footprint Diameter
R=Earth Radius(6378 km.),
Φ=Minimum Elevation Angle                           (h)

h=Altitude                                Φ
   For Φ=15°, D=152 km.
                                              Earth Radius
   For Φ=0°, D=1033 km.        Diameter
   (values at h = 21 km)
         Communication Applications
                     alternative backhaul via
                     satellite for remote areas

                                                                 Inter HAP link
local backhaul links to base
stations for less remote areas
                                           User Traffic


     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
Experimental Parameters:
Footprint Diameter = 60 km
                                       Data Rates
Number of cells = 121
Nominal ground diameter = 5 km
                                        60 Mbps
Downlink HAP power = 1W/cell
                   3G/2G Application
 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

                    HAP Networks
 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.
            Other Applications
 Emergency services and Disaster relief
 Oil/gas/mineral exploration
 Positioning System
 Remote Sensing
      Flood detection
      Seismic monitoring
      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
ground level
Lifetime          15 years      < 5years       15 years
Capacity          High          Medium         Low
Coverage          Land and      Global         Global
                  shore only
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.
   Low cost
   Incremental Deployment
   Rapid Deployment
   Platform and Payload upgrading
   Environment friendliness
  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
       in night
 Some Current and Proposed Programs

               • For communications and monitoring
               • Integrated Network of some 10
                 airships to cover Japan
  Sky Net

               • 150 m class airship
               • Communications payload of 800 kg.

 Sky Station
Some Existing Platforms: Aircrafts

                            Global Hawk

  Halo(Proteus 9)


                           Military UAV
 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