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1 1040 Henry Nsma May 2008 V3


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1 1040 Henry Nsma May 2008 V3

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