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UHF TV White Space --A New Challenge for Spectrum Managers

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 psh@research.att.com. Underutilized Spectrum.

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UHF TV White Space --A New Challenge for Spectrum Managers

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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 psh@research.att.com

  2. Underutilized Spectrum Can ‘white space’ spectrum be successfully managed ?

  3. 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) UHF TV Whitespace Unlicensed operation Allowed Not allowed • 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)

  4. Available Spectrum (after Digital TV transition in Feb 2009) *6 MHz/channel

  5. Wireless Residential Multimedia Networking Typ path loss ~75dB White space (cog radio) modem Broadband Access Media & Communications Server 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

  6. Protecting TV Users Residential white space network • 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

  7. Radius of Destruction DTV receiver sensitivity: -84 dBm DTV Interference tolerance: -104 dBm • 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 Rd ~ 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? Rd TV transmitter White space device

  8. Spectrum Sensing --The Hidden Node Problem DTV sensitivity -84dBm Shadow DTV spectrum TV transmitter White space device • 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

  9. Beacon Protective Bubble 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

  10. Mobility UVerse 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

  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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