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					     Ultra-High-Speed Wireless Ad-Hoc Networks using
                 Free-Space-Optics (FSO)




       Shiv Kalyanaraman, Murat Yuksel, Partha Dutta
                   shivkuma@ecse.rpi.edu
                                   : “shiv rpi”

Rensselaer Polytechnic Institute                  Shivkumar Kalyanaraman
                                    1
           Motivations: Free-Space-Optical (FSO) Ad-
           Hoc Networks: Mobile or Fixed Multi-Hop




                     Application: Mixed RF/FSO Ad-Hoc Networks
                            (Military Application)
Rensselaer Polytechnic Institute                    Shivkumar Kalyanaraman
                                       2
        Bringing Optical Communications and Ad Hoc
                  Networking Together…


               Free-Space-Optical                                    Ad Hoc
              Communications (FSO)                                  Networking

  High bandwidth                                                               Mobile communication
  Low power                                                                    Auto-configuration
  Directional


                                          Free-Space-Optical
                                           Ad Hoc Networks

                                   Spatial reuse and angular diversity in nodes
                                   Low power and secure
                                   Electronic auto-alignment
                                   Optical auto-configuration (switching, routing)




Rensselaer Polytechnic Institute                                               Shivkumar Kalyanaraman
                                                         3
                        Current Commercial FSO




 Point-to-Point Links in dense metros, competing with “wires”
 and “leased lines”
 Issue: How to achieve link reliability/availability despite weather
Rensselaer Polytechnic Institute                 Shivkumar Kalyanaraman
                                   4
             Ad-Hoc/Meshed Optical Wireless:
                        Why?
     Positive points:
            High-brightness LEDs (HBLEDs) are very low cost and highly reliable
             components
                35-65 cents a piece, and $2-$5 per transreceiver package + upto 10 years
                  lifetime
            Very low power consumption (100 microwatts for 10-100 Mbps!)
                Even lower power for 1-10 Mbps
                4-5 orders of magnitude improvement in energy/bit compared to RF
            Directional => Huge spatial reuse => multiple parallel channels for huge
             bandwidth increases due to spectral efficiency
            More Secure: Highly directional + small size & weight => low probability of
             interception (LPI)
     Issues:
            Need line-of-sight (LOS); and alignment of LOS & network auto-configuration
            Need to deal with weather & temporary obstacles, alignment loss
        Challenge: leverage huge benefits while tackling problems.
Rensselaer Polytechnic Institute                                  Shivkumar Kalyanaraman
                                              5
                                   Optical Wireless: Commodity
                                           components
  LEDs…

                                                VCSELs…




                                                               IrDAs…
                             Lasers…




   Many FSO components are very low cost and available
                  for mass production.
Rensselaer Polytechnic Institute                          Shivkumar Kalyanaraman
                                            6
                   Spatial Re-use: 2D FSO Arrays: 1-100Gbps
                                    Backhaul

                    Node 1                                                                    Node 2




                                                           D
                                   D/N




                    Node 1                                             …                      Node 2




                                         Repeater 1       Repeater 2       Repeater N-1




                  1cm2 LED/PIN => 1000 pairs in 1ft x 1ft square structure
                     100 Gbps aggregate bandwidth (= 1000 x 100 Mbps)



Rensselaer Polytechnic Institute                                                   Shivkumar Kalyanaraman
                                                      7
                Aggregate Capacity in 2-d Arrays:
                Interference vs Density vs Distance
  Interference Error vs.               Bandwidth-Volume Product
     Packaging Density




Rensselaer Polytechnic Institute                Shivkumar Kalyanaraman
                                   8
                Auto-Alignment: 3D Spherical FSO
                           Structures
                                                                               LED

                                                                               Micro Mirror
                                                                               PhotoDetector




                          Spherical Antenna     Cluster of FSO Components Optical Transmitter/Receiver Unit




                                                          LOS




                                    Step1: LOS Detection Through the use of Spherical FSO Antenna Array




                       Step2: Links Set-Up by Bundling LOS’ through Mirror adjustments for each LED-Photodetector Units
Rensselaer Polytechnic Institute                                                                  Shivkumar Kalyanaraman
                                                                   9
                      Initial Ad-Hoc FSO Prototypes




Rensselaer Polytechnic Institute           Shivkumar Kalyanaraman
                                   10
                              Initial Ad-Hoc FSO Prototypes (contd)


                        Received Light Intensity
                             from the moving
                         70        train.
                         60
Light Intensity (lux)




                         50
                                                                                                                         Misaligned                                       Aligned
                         40
                                                                                                                                                                       Duration of Alignment (%)
                         30
                         20
                         10
                          0
                                                                                                                                         100
                              0
                                  11
                                       17
                                            23
                                                 33




                                                                    65
                                                                         72
                                                                              79




                                                                                                 105
                                                                                                       112
                                                                                                             121
                                                                                                                   128
                                                      40.5
                                                             51.5




                                                                                   88.5
                                                                                          97.5




                                            Angular Position of the Train (degree)                                                        50



                                                                                           Very dense packaging                            0
                                                                                                                                           0                                                                                 0

                                                                                           and high mobility are                                 10
                                                                                                                                                        20                                                       40
                                                                                                                                                                                                                       20


                                                                                                        feasible.                                              30
                                                                                                                                                                                                   80
                                                                                                                                                                                                          60

                                                                                                                                                                        40                 100
                                                                                                                                                                               50   120                 Circuit Delay (milliseconds)

                         Rensselaer Polytechnic Institute                                                                                                Shivkumar Kalyanaraman
                                                                                                                                      Angular Speed (degrees/second)



                                                                                                                         11
                                   Initial FSO Prototypes
                                                Inside of the sphere          Photo-detector
                                                 is coated w/ mirror



    Integrating ball to increase
   angle of reception – inside is
        coated with mirror.




Rensselaer Polytechnic Institute                                   Shivkumar Kalyanaraman
                                           12
      Audio Transmission on FSO Link using low cost
      LED’s and Photo Diodes: Two Channel Mixing




  a) Two transmitters on different                     b) Single receiver and circuit for both
  channels                                             the channels

Rensselaer Polytechnic Institute
                                   Indoor FSO ad-hoc networks Shivkumar Kalyanaraman
                                                  13
  Indoor Ad-Hoc FSO: Music App (contd)




Rensselaer Polytechnic Institute        Shivkumar Kalyanaraman
                                   14
  Hybrids: 3D Auto-Alignment with 2D Arrays




Rensselaer Polytechnic Institute        Shivkumar Kalyanaraman
                                   15
      Auto-configuration: Location tracking and
                    management
      Location tracking: (optional integration w/ GPS)
          Use highly granular spherical FSO antennas (e.g. hundreds of
           transceivers)  can detect angle of arrival
         Use time of flight or signal strength  can detect distance
         Unlike RF, no need for triangulation: sense of direction is available.
      Allows easy integration with Community Wireless Networks (CWNs)
         Organic network growth




                                                           - angle of arrival


Rensselaer Polytechnic Institute                                Shivkumar Kalyanaraman
                                           16
     Emerging Apps: Broadband Sensor Networks:
         Eg: Mobile/Fixed Camera Networks
    More than 10,000
     public and private
     cameras in
     Manhattan, 2.5
     million in the UK!
    Subways, airports,
     battlefields,
     factory floors,
     highways…



          Thousands of un-supervised and moving cameras w/o centralized
           processing or control
             Key: Mix of Low Power AND High Speed AND Ad-Hoc/Unsupervised

    Rensselaer Polytechnic Institute                  Shivkumar Kalyanaraman
                                       17
              SUMMARY: Ultra-Broadband
             Wireless: puzzle falling in place…
      (1) Infinite Spectrum in Thin Air!
         Key: use unlicensed spectrum or larger licensed bands


      (2) Multi-hop architecture w/ Base-Station Interfaces
         Wireless is fundamentally cheap for shorter distances, smaller coverage
         Organic architecture: auto-conf, self-management (10+ years of research in ad-hoc
           networks), community wireless
         IP/geographic routing, fully distributed traffic engineering mechanisms
         Technology neutral, extensible, modular: 802.11x, 802.16x, FSO
         (2a) Multi-hop Free-space-optics (FSO) using ultra-low-cost components for
           100 Gbps+ capabilities

      Key: Broadband CWNs & ad-hoc FSO complementary to ongoing advances in
       FTTH, DSL/Cable, WiMax, 3G rollouts.
         Open Problems in upgrading the network and transport layers to leverage raw, but
          distributed bandwidth, and tolerate higher bursty losses (weather related)
Rensselaer Polytechnic Institute                               Shivkumar Kalyanaraman
                                            18
                                   Thanks!
                         Student Heroes:
      Jayasri Akella, sri@networks.ecse.rpi.edu
      Dr. Murat Yuksel (post-doc): yuksem@ecse.rpi.edu
      Chang Liu, c.liu@ee.unimelb.edu.au
      David Partyka, partyd@rpi.edu
      Sujatha Sridharan
      Bow-Nan Cheng: chengb@rpi.edu (CWN project)


                                     : “shiv rpi”
Rensselaer Polytechnic Institute                    Shivkumar Kalyanaraman
                                      19

				
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