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Cognitive Use of TV Whitespace
Regulatory and Market Implications
John Chapin William Lehr
MIT RLE MIT CSAIL
jchapin@mit.edu wlehr@mit.edu
First IBBT-MIT Joint Workshop on Cognitive Radio
Standardization and Markets 11 May 2009
Claude E. Shannon Communication and Network Group Communications Futures Program
Computer Science and Artificial Intelligence Laboratory
Massachusetts Institute of Technology
2. Outline
TV whitespace in the USA
Policy analysis of the TVBD approach
Technical and market analysis
Copyright © 2009 John Chapin and William Lehr, MIT 2
3. What / Where are the TV White Spaces?
VHF & Lower UHF Bands
More (> 70 MHz) in smaller markets
Not much in urban markets
New Orleans
San Francisco
Washington DC
Minneapolis
St Louis
Boston
Copyright © 2009 John Chapin and William Lehr, MIT Slide by: Peter Tenhula, SDRF 3
4. FCC proposal: unlicensed secondary access to TV spectrum
Primary users in the US
– High-power television
– Low-power television repeaters, relays
– Public safety land-mobile radio channels 14-20 in some big cities
– Wireless microphones only 1 out of 400 are legal users
Cognitive radio methods to protect primary users
– Secondary user determines own location
– Query central database to determine potentially available channels
– Listen for primary users in specific channel
Secondary device requirements
– Check central database every day
– Detect primary users at -114 dBm
• approximately -15 dB signal to noise ratio
– Max transmit power 4 W if fixed, 100 mW if portable
Copyright © 2009 John Chapin and William Lehr, MIT 4
5. TV whitespace status in the USA
Rules adopted November 2008, published February 2009
Unknown when the rules will take effect, if at all
– 17 petitions for reconsideration
– 3 lawsuits
• National Association of Broadcasters
• Association for Maximum Service Television
• Coaltion of wireless microphone users (ESPN, sports leagues, theaters)
– New Obama government with new priorities
In this talk, “TVBD” means the FCC’s current proposal
Copyright © 2009 John Chapin and William Lehr, MIT 5
6. Outline
TV whitespace in the USA
Policy analysis of the TVBD approach
Technical and market analysis
Copyright © 2009 John Chapin and William Lehr, MIT 6
7. Potential goals for TV whitespace policy
Maximize productive use of spectrum
– Technical efficiency amount of data transmitted
– Economic benefit value of economic surplus generated
– Social value number of people served or needs met
Provide low-cost spectrum access
– Promote services for underserved populations
– Promote innovative business models
– Enhance competition for existing services
Establish viability of cognitive radio for spectrum sharing
– Make it easier to share other bands in the future
Copyright © 2009 John Chapin and William Lehr, MIT 7
8. Goal: Maximize productive use of TV broadcast spectrum
TVBD proposal is one approach...
– TVBD = non-cooperative unlicensed secondary use of TV spectrum
... out of many possible policy options
– Market-oriented mechanisms
– Non-market mechanisms
Cognitive Radio can be used to support any of the policy options
Copyright © 2009 John Chapin and William Lehr, MIT 8
9. Market-oriented mechanisms
Make licenses more technically and service neutral
Establish property rights
– Coasian: allow compensation for interference
– Secondary market for transmission licenses
Example: Qualcomm MediaFLO in UHF chan 55 (716-722 MHz)
Cognitive radio can support these market mechanisms
– When deploying new systems, use CR to avoid interference
– Cooperative secondary use
• Contract between licensee and secondary users
• CR enables licensee to retain some transmission rights
• e.g. CPC broadcasts availability, terms and conditions
Copyright © 2009 John Chapin and William Lehr, MIT 9
10. Non-market mechanisms
Regulator allows unlicensed secondary use
– “TVBD” approach
– Non-cooperative: existing licensees do not have control
Regulator reallocates existing licenses
– FCC reserved some UHF channels for for public safety broadband
Regulator allocates new secondary use licenses
– TVBD proposal reserves 2 channels nationwide for wireless microphones
– De facto this is a license for (currently illegal) wireless microphone users
Cognitive Radio can support these non-market mechanisms
– Eg. use CR to avoid interference during reallocation transition
Copyright © 2009 John Chapin and William Lehr, MIT 10
11. Evaluation of TVBD approach against policy goals
Maximize productive use of spectrum
– Much more spectrum usage than current situation
– Likely less efficient than fully liberalized market
– Possible tragedy of the anticommons
• Many unlicensed users make it difficult to reallocate band in the future
Provide low-cost spectrum access
– Unclear whether services being discussed are viable (next slides)
– Nevertheless, high potential for innovative uses
Establish viability of non-cooperative spectrum sharing
– Excellent opportunity to demonstrate success
– Not a good model for some other major sharing opportunities
• Government bands
Copyright © 2009 John Chapin and William Lehr, MIT 11
12. Outline
TV whitespace in the USA
Policy analysis of the TVBD approach
Technical and market analysis
Copyright © 2009 John Chapin and William Lehr, MIT 12
13. Key technical issues for the TVBD approach
TV band spectrum has long range propagation
– Unlike 2.4 GHz, 5 GHz, and 60 GHz which are short range
– Possible tragedy of the commons
Unlicensed users must coordinate quiet times for sensing
Important class of primary users are receive-only (TV receivers)
– Hidden node problem reduces utility of spectrum sensing
– Lack of receiver standards
– Digital television picture quality “cliff”
For all of these reasons, spectrum access etiquette for TVBDs is
expected to evolve significantly
Copyright © 2009 John Chapin and William Lehr, MIT 13
14. Market analysis
All applications: uncertain payoff makes investment challenging
– Regulatory risk
– Potential congestion
Low-cost internet access
– Free spectrum & long range reduce infrastructure cost for rural coverage
– Google claims TVwhitespace could increase its profits by 20-30%
– Risk: not enough spectrum available for true broadband in populated areas
• Brown/Sicker DYSPAN 2007 paper: 80 MHz needed
Home consumer electronics interconnect
– Must use multiple TV channels to achieve 1 Gbps (uncompressed HD video)
– Risk: Competition from 2.4 GHz 802.11n and 60 GHz unlicensed
Niche networks
– Exploit low entry cost to meet specialized needs, e.g. sensor networks
– Risk: High device cost due to low volume outweighs benefits of low entry cost
Copyright © 2009 John Chapin and William Lehr, MIT 14
15. Opinion of the authors
With low cost spectrum, innovative applications will develop
Spectrum sharing is essential for future growth of radio services
TV whitespace is an important first step to establish viability
Copyright © 2009 John Chapin and William Lehr, MIT 15
16. Key takeaway points
FCC TVBD is one out of many ways to use CR in the TV band
Cognitive Radio techniques can also support market mechanisms
for increasing productive use of the spectrum
Many technical questions face the TVBD approach
Methods for primary user protection will evolve over time
Viable applications are unknown
Copyright © 2009 John Chapin and William Lehr, MIT 16
17. Next steps
Upcoming SDRF workshop
– June 16, 2009
Dearborn, Michigan, USA
“Spectrum Access by TV Band Devices”
http://www.sdrforum.org
Stay tuned to see what happens to TVBD in the USA
– FCC will respond to petitions for reconsideration
– Then lawsuits will be argued
Thank you!
– John Chapin William Lehr
jchapin@mit.edu wlehr@mit.edu
Copyright © 2009 John Chapin and William Lehr, MIT 17
18. BACKUP SLIDES
Copyright © 2009 John Chapin and William Lehr, MIT 18
19. Managing certification risk for TV Band Devices
Many subsystems must work correctly to protect primary users
– location mechanism (GPS or other)
– sensor receiver
– processing of sensor signals
– network connection to database (including security against attackers)
– device attestation
– processing of database response
– clock
Policy implications
– Likelihood of problems in the field
• Cannot afford to test to 100% guarantee level
– Solution: make it easy recall to misbehaving devices
FCC: DB can alter available channel list based on make/model
Open issue: how to more easily determine source of interference
Copyright © 2009 John Chapin and William Lehr, MIT 19