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Cognitive Radio. Jeff Reed (540) 231 2972 James Neel (540) 230-6012 CERDEC February 5, 2008 . Jeffrey H. Reed. Director, Wireless @ Virginia Tech

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cognitive radio

Cognitive Radio

Jeff Reed

(540) 231 2972

James Neel



February 5, 2008

 Cognitive Radio Technologies, 2008

jeffrey h reed
Jeffrey H. Reed
  • Director, Wireless @ Virginia Tech
  • Willis G. WorcesterProfessor, Deputy Director, Mobile and Portable Radio Research Group (MPRG)
  • Authored book, Software Radio: A Modern Approach to Radio Engineering
  • IEEE Fellow for Software Radio, Communications Signal Processing and Education
  • Industry Achievement Award from the SDR Forum
  • Highly published. Co-authored – 2 books, edited – 7 books.
  • Previous and Ongoing CR projects from
    • ETRI, ONR, ARO, Tektronix
  • Email:

 Cognitive Radio Technologies, 2008

james neel
James Neel
  • President, Cognitive Radio Technologies, LLC
  • PhD, Virginia Tech 2006
  • Textbook chapters on:
    • Cognitive Network Analysis in
    • Data Converters in Software Radio: A Modern Approach to Radio Engineering
    • SDR Case Studies in Software Radio: A Modern Approach to Radio Engineering
    • UWB Simulation Methodologies in An Introduction to Ultra Wideband Communication Systems
  • SDR Forum Paper Awards for 2002, 2004 papers on analyzing/designing cognitive radio networks
  • Email:

 Cognitive Radio Technologies, 2008

presentation overview
Presentation Overview
  • (22) Introductory Material
    • Definitions, applications
  • (76) Implementation Issues
    • Architectures, sensing, classification, decisions
  • (39) Networking Issues
    • Problems and different approaches to mitigate those problems
  • (14) Ongoing Efforts
    • Commercial, University, Military
  • (19) Conclusions

 Cognitive Radio Technologies, 2008

what is a cognitive radio

What is a Cognitive Radio?

Concepts, Definitions

 Cognitive Radio Technologies, 2008

cognitive radio basic idea
Cognitive Radio: Basic Idea
  • Software radios permit network or user to control the operation of a software radio
  • Cognitive radios enhance the control process by adding
    • Intelligent, autonomous control of the radio
    • An ability to sense the environment
    • Goal driven operation
    • Processes for learning about environmental parameters
    • Awareness of its environment
      • Signals
      • Channels
    • Awareness of capabilities of the radio
    • An ability to negotiate waveforms with other radios

Waveform Software

Software Arch


Control Plane


Board APIs

Board package

(RF, processors)

 Cognitive Radio Technologies, 2008

cognitive radio capability matrix
Cognitive Radio Capability Matrix

 Cognitive Radio Technologies, 2008

why so many definitions
Why So Many Definitions?
  • People want cognitive radio to be something completely different
    • Wary of setting the hype bar too low
    • Cognitive radio evolves existing capabilities
    • Like software radio, benefit comes from the paradigm shift in designing radios
  • Focus lost on implementation
    • Wary of setting the hype bar too high
    • Cognitive is a very value-laden term in the AI community
    • Will the radio be conscious?
  • Too much focus on applications
    • Core capability: radio adapts in response changing operating conditions based on observations and/or experience
    • Conceptually, cognitive radio is a magic box

 Cognitive Radio Technologies, 2008

conceptual operation
OODA Loop: (continuously)

Observe outside world

Orient to infer meaning of observations

Adjust waveform as needed to achieve goal

Implement processes needed to change waveform

Other processes: (as needed)

Adjust goals (Plan)

Learn about the outside world, needs of user,…

Conceptual Operation

Cognition cycle


Infer from Context


Infer from Radio Model

Establish Priority



Select Alternate


Parse Stimuli










User Driven


Generate “Best”






Allocate Resources

Initiate Processes

Negotiate Protocols

 Cognitive Radio Technologies, 2008

typical cognitive radio applications

Typical Cognitive Radio Applications

What does cognitive radio enable?

 Cognitive Radio Technologies, 2008

bandwidth isn t scarce it s underutilized
Bandwidth isn’t scarce, it’s underutilized

Measurements averaged over six locations:

  • Riverbend Park, Great Falls, VA,
  • Tysons Corner, VA,
  • NSF Roof, Arlington, VA,
  • New York City, NY
  • NRAO, Greenbank, WV,
  • SSC Roof, Vienna, VA

~25% occupancy at peak

 Cognitive Radio Technologies, 2008

Modified from Figure 1 in Published August 15, 2005 M. McHenry in “NSF Spectrum Occupancy Measurements Project Summary”, Aug 15, 2005. Available online:

conceptual example of opportunistic spectrum utilization



Primary Signals


Opportunistic Signals

Conceptual example of opportunistic spectrum utilization

 Cognitive Radio Technologies, 2008

cognitive radio permits the deployment of cheaper radios
RF components are expensive

Cheaper analog implies more

spurs and out-of-band emissions

Processing is cheap and getting cheaper

Cognitive radios will adapt around spurs (just another interference source) or teach the radio to reduce the spurs

Better radios results in still more available spectrum as the need arises.

Likely able to exploit SDR

Cognitive radio permits the deployment of cheaper radios

 Cognitive Radio Technologies, 2008

improved link reliability
Improved Link Reliability
  • Cognitive radio is aware of areas with a bad signal
  • Can learn the location of the bad signal
    • Has “insight”
  • Radio takes action to compensate for loss of signal
    • Actions available:
      • Power, bandwidth, coding, channel, form an ad-hoc network
    • Radio learns best course of action from situation

Signal Quality




  • Can aid cellular system
    • Inform system & other radios of identified gaps

 Cognitive Radio Technologies, 2008

automated interoperability
Automated Interoperability
  • Basic SDR idea
    • Use a SDR as a gateway to translate between different radios
  • Problems
    • Which devices are present?
    • Which links to support?
    • With SDR some network administrator must answer these questions
  • Basic CR idea
    • Let the cognitive radio observe and learn from its environment in an automated fashion.

 Cognitive Radio Technologies, 2008

spectrum trading
Spectrum Trading
  • Underutilized spectrum can be sold to support a high demand service
    • Currently done in Britain
    • Permitted in US among public safety users
  • Currently has a very long time scale (months)
  • Faster spectrum trading could permit for significant increases in available bandwidth
    • How to recognize need and availability of additional spectrum?
    • Environment + context awareness + memory

 Cognitive Radio Technologies, 2008

collaborative radio
Collaborative Radio
  • A radio that leverages the services of other radios to further its goals or the goals of the networks.
  • Cognitive radio enables the collaboration process
    • Identify potential collaborators
    • Implies observations processes
  • Classes of collaboration
    • Distributed processing
    • Distributed sensing

 Cognitive Radio Technologies, 2008

cooperative antenna arrays

Leverage other radios to effect an antenna array


Extended vehicular coverage

Backbone comm. for mesh networks

Range extension with cheaper devices


Timing, mobility



Cooperative Antenna Arrays

Cooperative MIMO

Second Hop

First Hop

First Hop

First Hop

First Hop

First Hop

First Hop

Relay cluster

Relay cluster

Relay cluster

Relay cluster

Relay cluster

Relay cluster

Destination Cluster

Source Cluster

Source Cluster

Source Cluster

Source Cluster

Source Cluster

Source Cluster

Transmit Diversity


 Cognitive Radio Technologies, 2008


other opportunities for collaborative radio 1 3
Distributed processing

Exploit different capabilities on different devices

Maybe even for waveform processing

Bring extra computational power to bear on critical problems

Useful for most collaborative problems

Collaborative sensing

Extend detection range by including observations of other radios

Hidden node mitigation

Improve estimation statistics by incorporating more independent observations

Immediate applicability in 802.22, likely useful in future adaptive standards

Other Opportunities for Collaborative Radio (1/3)

 Cognitive Radio Technologies, 2008

other opportunities for collaborative radio 2 3
Improved localization

Application of collaborative sensing


Friend finders

Reduced contention MACs

Collaborative scheduling algorithms to reduce collisions

Perhaps of most value to 802.11

Some scheduling included in 802.11e

Other Opportunities for Collaborative Radio (2/3)

 Cognitive Radio Technologies, 2008

other opportunities for collaborative radio 3 3
Distributed mapping

Gather information relevant to specific locations from mobiles and arrange into useful maps

Coverage maps

Collect and integrate signal strength information from mobiles

If holes are identified and fixed, should be a service differentiator

Congestion maps

Density of mobiles should correlate with traffic (as in automobile) congestion

Customers may be willing to pay for real time traffic information

Theft detection

Devices can learn which other devices they tend to operate in proximity of and unexpected combinations could serve as a security flag (like flagging unexpected uses of credit cards)


Car components that expect to see certain mobiles in the car

Laptops that expect to operate with specific mobiles nearby

Other Opportunities for Collaborative Radio (3/3)

 Cognitive Radio Technologies, 2008

Cognitive radio evolves the software radio concept to permit intelligent autonomous adaptation of radio parameters

Significant variation in definitions of “cognitive radio”

Question of how “cognitive” the radio is

Numerous new applications enabled

Opportunistic spectrum utilization, collaborative radio, link reliability, advanced network structures

Differing implementation approaches

Many applications implementable with simple algorithms

Greater flexibility achievable with a cognitive engine approach

Many objectives will require development of a cognitive language

In a network, adaptations of cognitive radios interact

Interaction can be mitigated with policy, punishment, cost adjustments, centralization or potential games

Commercial implementations starting to appear

802.22, 802.11h,y, 802.16h

And may have been around for a while (cordless phones with DFS)


 Cognitive Radio Technologies, 2008