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1 1040 Henry Nsma May 2008 V3
1 1040 Henry Nsma May 2008 V3
1 1040 Henry Nsma May 2008 V3
1 1040 Henry Nsma May 2008 V3
1 1040 Henry Nsma May 2008 V3
1 1040 Henry Nsma May 2008 V3
1 1040 Henry Nsma May 2008 V3
1 1040 Henry Nsma May 2008 V3
1 1040 Henry Nsma May 2008 V3
1 1040 Henry Nsma May 2008 V3
1 1040 Henry Nsma May 2008 V3
1 1040 Henry Nsma May 2008 V3
1 1040 Henry Nsma May 2008 V3
1 1040 Henry Nsma May 2008 V3
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1 1040 Henry Nsma May 2008 V3

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  • 1. UHF TV White Space --A New Challenge for Spectrum Managers Annual Meeting, National Spectrum Managers Association Arlington, VA May 20-21, 2008 Paul Henry AT&T Labs – Research Middletown, NJ [email_address]
  • 2. Underutilized Spectrum Can ‘white space’ spectrum be successfully managed ?
  • 3. UHF TV Whitespace
    • May 2004: FCC proposes to allow unlicensed use of TV whitespace
      • Primarily UHF ~500-700 MHz (chan 21-51) -- Desirable propagation characteristics
      • Must protect TV and wireless microphone
      • Smart (cognitive) radio may be needed
    Channel 54 in the Eastern US (graphic courtesy of Shared Spectrum Co. from a contribution to IEEE 802.18 SG1) Unlicensed operation Allowed Not allowed
    • Nov 2004: IEEE802.22 formed to explore WRAN (~33 km nominal range)
    • Oct 2006: FCC allows low-power fixed use; regulations TBD
    • Continues inquiry re portable use; regulations 1H08 3Q08
    • Dec 2007: OFCOM (UK) Report
    • 112 MHz to be allocated for unlicensed use after Digital Switchover (2012)
    • Feb 2009: US DTV transition (2012 in UK)
  • 4. Available Spectrum (after Digital TV transition in Feb 2009) *6 MHz/channel
  • 5. Wireless Residential Multimedia Networking Broadband Access Media & Communications Server White space (cog radio) modem PDA Remote
    • Capability
      • 19Mbps per 6 MHz TV channel
      • Multimedia with QoS (incl HDTV), Internet, VoIP
      • Portability
    • Modest power: ~10mW
    • Technical challenge: protect incumbent users
    Typ path loss ~75dB
  • 6. Protecting TV Users
    • Keep white space devices
    • outside of TV service area.
    • Geolocation -- GPS
      • Authoritative database – central control
      • Unreliable indoors
      • Increased device cost
    • Spectrum sensing
      • White space users scan for vacant channels
      • Hidden-node problem
    • What is ‘radius of destruction’ for white space device?
    TV Service Area Residential white space network
  • 7. Radius of Destruction
    • To avoid interference to DTV:
    • Air path loss > Pt – DTV tolerance – penetration loss + TV antenna gain
    • = +10dBm + 104 – 10 + 8 = 112 dB
    • Propagation loss (Longley-Rice model): 112 dB implies R d ~ 2 km
        • Faster decay than inverse-square
    • Note: Outdoor WRAN (802.22): 4 watt transmitter implies Rd ~ 15 km!
    • Must inhibit transmission whenever within ~2 km of ‘viewable’ DTV signal
        • Can white space device ‘sniff’ for TV signal and then make reliable decision?
    TV transmitter White space device DTV receiver sensitivity: -84 dBm DTV Interference tolerance: -104 dBm R d
  • 8. Spectrum Sensing --The Hidden Node Problem TV transmitter DTV sensitivity -84dBm White space device Shadow
    • Device sensitivity margin = shadow fading + penetration loss + antenna gain difference
      • Shadow fading in 90% of locations < 15dB*
      • Typical penetration loss ~10dB**
      • Antenna gain difference ~ 8dB*
      •  Required device margin ~ 15 + 10 + 8 = 33 dB (~ 90% successful detection)
    •  Device sensitivity = -84 dBm -33 dB = -117 dBm
    • Demonstrated device sensitivity: -115 to -120 dBm
    • *R.A.O’Connor, IEEE Trans Broadcasting , Sept 2001
    • **M.A.Sturza, Working Paper #16 , New America Foundation, Jan. 2007
    DTV spectrum
  • 9. Wireless Microphone
    • Low power (working range < 100m)
    • No standard signature like DTV; therefore very hard to detect
    • Solution – Easily recognized beacon; protective bubble
    • Problems
        • Abuse of protection
        • Unlicensed users (e.g. schools, churches); squatters’ rights
    WSD Mic Rcvr Protective Bubble Beacon
  • 10. Field of Battle Opposed Cox communications Nat Assn Broadcasters NFL NASCAR ● ● ● In Favor Dell Google Microsoft Philips ● ● ● FCC Docket ET 04-186
    • Radio science lost in political shouting match
    • FCC labs conducting independent evaluation
    Mobility UVerse
  • 11. FCC Field Tests
    • Initial tests summer 2007
    • DTV detection: Philips -115dBm; Microsoft device failed
    • Wireless mic detection (no beacon): Many false positives
    • Technology not good enough for definitive field tests
    • Recent activity
    • Google laboratory: -120dBm sensitivity
    • Ongoing tests: Philips, Microsoft, Motorola, Adaptrum
    • No abatement of political posturing
  • 12. Breaking the Logjam --Motorola and Google Proposals
    • Goal: Get past the squabbles over spectrum sensing
    • Dec. ’07: In FCC filing Motorola proposes 2 classes of white space devices
        • <10mW (e.g. WLAN): spectrum sensing only
        • >10mW (e.g. 802.22 WRAN): Geolocation with spectrum sensing backup
        • Minimal public reaction
    • March ’08: Google proposes geolocation for all white space operation
        • Calls press conference
          • “ WiFi on steroids”
          • “ Gigabit rates”
        • Lots of headlines – Mission Accomplished
        • Probably consistent with Google’s aspirations,
        • but unacceptable to proponents of bluetooth-like applications
    • Intense lobbying continues
  • 13. Takeaways
    • UHF TV white space
          • Opportunity to use sparsely occupied, attractive spectrum
    • Must protect digital TV and wireless microphone
          • Technologies: Spectrum sensing, geolocation, beacon
          • Protection achievable in lab setting; field tests to come
    • Intense political posturing; logjam at FCC
    • DTV transition Feb 2009 less than a year away; stay tuned…..
  • 14. Thank you!

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