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The Radio Environment MapSami Lunnamo
Presentation outline
REM
Definitions
Requirements
Challenges
Design
Location and
mobility
Database
WS availability
Layered REM
REM - Definitions• Geolocation service• And more
• Centralized database• Radio environment data
• Predictions of spectrum opportunities• Cognition cycle
REM – Definitions - Analogy
REM
- Location (x, y, z)- Geographical
location- Radio spectrum
profile
Tourist map of Beijing, source: http://images.chinatravel.com/city/beijing/beijing-city-map-large.jpg
REM – Requirements• Normal CR requirements• Safety• Efficiency
• Centralized service• Availability• Reliability• Throughput• Latency• Security
REM – Challenges – Signal overhead• Communication between REM and CR• Amount of relevant data• Quality of connection
• Balance between overhead and benefits of REM
REM
Clipart from bestclipartblog.com
REM – Challenges - Validity• REM is collection of data• How long will any data be valid?
• Information exchange between layers of REM
REM – Challenges – Spectrum opportunities• Ability to detect and predict spectrum opportunity
• Model-driven scheme to calculate opportunities• Loss-ratio can be close to 0%
Hey, I have data I’d like to
send
REM
Nope, no free bands here Bands
REM – Challenges - Locations• Determining a location is error-prone and expensive
• Could CRs use base station location as substitute for knowing own location accurately?
• Mobile CRs
• One-off events and wireless microphones
REM – Challenges - Bootstrapping• New client
• Connecting with REM through base station
• Chicken-and-egg
REM – Design – Spectrum opportunities• Model-driven schemes vs. Data-driven schemes
• Longley-Rice (L-R) with terrain data• Climactic effects, soil conductivity, permettivity, Earth’s curvature
and surface refractivity• 8% spectrum opportunity loss and even less false positives
• In practice, no one model is sufficient alone
REM – Design - Location• Different channels open in different areas• If using base station location, REM would have to use channels
that are open and available in every part of the coverage area• 80% spectrum opportunity loss• Location granularity• 4km = 80% loss• 800m = ~0% additional loss
• Bootstrapping beacon• Data of available channels
REM – Design - Mobility• Mobile CRs location is constantly changing
• CR might travel to an area where it uses a channel in use by PU • Old data about spectrum availability
• Protection range for channels
• Polling frequency for spectrum updates• 96 km/h, 60sec, 1.6km = 20% loss• 96 km/h, 30sec, 800m = 0% loss
REM – Design – Database• What kind of data should the database contain?
• TV transmitter data• Tower locations, antenna heights, transmit powers…
• Client data• Locations, IDs, channels, transmit powers…
• Cache
REM – Design – Layered REM• Distributing and decentralizing
• Layers• REM SA and REM Managers
• Subsidiarity• Data stored and analysed in least centralized node possible• National – regional – local
• Proportionality• Data with shorter life span needs to be readily available• REM SA and manager within quick reach
REM - Summary• Geolocation service• Analysis and historical data of spectrum opportunities• Can detect and use ~92% of all spectrum opportunities in area• No false positives
• Accommodates mobile CRs• Mobility doesn’t cause breach of safety requirement
• Layered architecture gives robustness and eliminates overhead
• Uses broadcast beacons to bootstrap new clients