An Analysis of Unlicensed Device Operation in Licensed

An Analysis of Unlicensed Device Operation in Licensed Broadcast Service Bands It’s about harmful interference Timothy X Brown Interdisciplinary Telecommunications Electrical and Computer Engineering University of Colorado IEEE Symposium on New Frontiers in Dynamic Spectrum Access Networks November 9, 2005 Baltimore CU-Boulder

One Strategy for Dynamic Spectrum Access l The spectrum is fully allocated. l Point measurements show: l l Over 75% is “vacant” no usage at all over a month Over 90% of spectrum goes unused on average Rural areas - even more Strategy: Use “white spaces”, avoid licensed users 2

Channel Avoidance Strategies l Locate Unlicensed Device, check Database l Detect Licensed Devices l Licensed Device Beacons All can avoid interference and provide useful bandwidth 3

Locate Unlicensed Device l Do not need accurate position l l l As long as can bound error 100 km OK in rural areas GPS is only one way White space TV Channels Potential conflict: Can not use LA U RE RI Buffalo, SD LA No conflict: Can use LB New York, NY LB Distance (km) 4

Check Database How often? Licensed Users How often? Database Unlicensed Users Internet? l Proactive Database l l Licensed user schedules in advance (e. g. 48 hrs) Unlicensed user only needs to check once/48 hrs 5

Detect Licensed Devices l Hidden Terminal Problem Licensed TX Licensed RX Hill Unlicensed TX l Networked Detection l l Unlicensed RX Much more reliable Detection ≠ Reception 6

Licensed Device Beacons l Receiver Beacons Transmitter Beacons l Area Beacons: l l Require Constant Monitoring Combine best of Database and Beacons Licensed Users Database Unlicensed Users 7

Evaluating Methods Requires Avoids Interference Constant Internet Positioning Standard BW Monitoring Connection Method Database X X Detecting Transmitters X X Transmitter Beacons X X Receiver Beacons X X Area Beacons X X X o X X Any of these methods is technically feasible. 8

Enter Economics: Who Pays? Cost Burden is on Method Unlicensed Licensed Devices Transmitter Database X Detecting Transmitters X Transmitter Beacons X Receiver Beacons X Area Beacons Licensed Receiver X X 9

Enter Politics: Nobody will pay for this unless there is a clear regulatory model for defining the allowed interactions between licensed and unlicensed devices. The key to this interaction is the definition of harmful interference. 10

Do we need a Harmful Interference framework? Licensed Service Providers FCC 04 -186 NPRM Unlicensed Operation in the TV Broadcast Bands Regulator Unlicensed Device Manufacturers These rules will degrade my service! What do we have to do to certify equipment? Any unlicensed use can interfere This will create more problems then it will solve Court rulings can render my equipment obsolete For UWB set power limits extremely low With the proper framework, today’s radios can do better. 11

A Harmful Interference Framework: The Idea l Define interference up front: l l l How it is measured By who What levels constitute “harmful” What to do if it is harmful Define so that: l l l Licensed users have sufficient protection Unlicensed users/manufacturers have assurances Regulators solve problem once a priori 12

Measurement Scenario Evaluation Licensed Receivers Model Unlicensed Rules Unlicensed Transmitter Model Remedy 13

Conclusion l Channel avoidance is key to the success of unlicensed devices l Many approaches possible. Area beacons most promising. l A proactive approach to harmful interference is needed to enable meaningful unlicensed communication in licensed bands 20