© 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

© 2008 AT&T Knowledge Ventures. All rights reserved. Underutilized Spectrum Can white space spectrum be successfully managed ?

© 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 SG1) May 2004: FCC proposes to allow unlicensed use of TV whitespace Primarily UHF ~ 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: IEEE 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)

© 2008 AT&T Knowledge Ventures. All rights reserved. Available Spectrum (after Digital TV transition in Feb 2009) *6 MHz/channel

© 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

© 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

© 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 – = 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

© 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 ~ = 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 DTV spectrum

© 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

© 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 Mobility UVerse Radio science lost in political shouting match FCC labs conducting independent evaluation

© 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

© 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 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

© 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…..

© 2008 AT&T Knowledge Ventures. All rights reserved. Thank you!