1. © 2008 AT&T Knowledge Ventures. All rights reserved. AT&T and the AT&T logo are trademarks of AT&T Knowledge Ventures. 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. © 2008 AT&T Knowledge Ventures. All rights reserved. Underutilized Spectrum Can white space spectrum be successfully managed ?

3. © 2008 AT&T Knowledge Ventures. All rights reserved. UHF TV Whitespace Channel 54 in the Eastern US (graphic courtesy of Shared Spectrum Co. from a contribution to IEEE 802.18 SG1) 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 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. © 2008 AT&T Knowledge Ventures. All rights reserved. Available Spectrum (after Digital TV transition in Feb 2009) *6 MHz/channel

5. © 2008 AT&T Knowledge Ventures. All rights reserved. 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. © 2008 AT&T Knowledge Ventures. All rights reserved. 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? Protecting TV Users TV Service Area Residential white space network

7. © 2008 AT&T Knowledge Ventures. All rights reserved. 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 RdRd

8. © 2008 AT&T Knowledge Ventures. All rights reserved. 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.OConnor, IEEE Trans Broadcasting, Sept 2001 **M.A.Sturza, Working Paper #16, New America Foundation, Jan. 2007 DTV spectrum

9. © 2008 AT&T Knowledge Ventures. All rights reserved. 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. © 2008 AT&T Knowledge Ventures. All rights reserved. Field of Battle Opposed Cox communications Nat Assn Broadcasters NFL NASCAR In Favor Dell Google Microsoft Philips FCC Docket ET 04-186 Mobility UVerse Radio science lost in political shouting match FCC labs conducting independent evaluation

11. © 2008 AT&T Knowledge Ventures. All rights reserved. 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. © 2008 AT&T Knowledge Ventures. All rights reserved. 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 Googles aspirations, but unacceptable to proponents of bluetooth-like applications Intense lobbying continues

13. © 2008 AT&T Knowledge Ventures. All rights reserved. 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…..

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