Industry Perspective on Cognitive Radio

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Industry Perspective on Cognitive Radio
Samir SolimanVP of TechnologyQUALCOMM
IncorporatedJune 3, 2004
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Presentation Outline

• What is cognitive radio?
• What do we mean by spectral efficiency?
• How do operators keep improving spectral
  efficiency?
• What are the cognitive radio technical
  challenges?
• What are the take-away points?

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What is Cognitive Radio?

• Cognitive radio means different things to
  different people
• Catchy name and there is more hype than
  substance at this point
• Noble way to increase spectral efficiency but
  will it work?
• Is it a hole filling or underlay solution?
• Is it implicit that cognitive radio must be a
  software defined radio?

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What do we mean by spectral efficiency?

• Measured in bits/sec/Hz/cell
• Is single type of service or more homogenous
  services more spectrally efficient?
• Is opening the licensed spectrum to unlicensed
  users a wise choice?
• Is pilling up users without careful assignment a
  good strategy for increasing spectral efficiency?
• What is the cumulative effect of a very large
  number of cognitive radio users?
• What is the impact of cognitive radio,
  interference temperature, receiver standards, and
  UWB on spectral efficiency?

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How do operators keep improving spectral
efficiency?

• Spectral efficiency through increase internal
  efficiency
• Base station antenna diversity 3 dB
• Multiple antenna can even do better
• Adaptive power control 30 dB
• Soft handoff 3-4 dB
• Adaptive coding/modulation 9 dB
• Mobile receive diversity 2-3 dB
• Self policing to control out of band interference

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What are the technical challenges?

• Protection criteria (distances)?
• Protection assumptions?
• What is the minimum desired (incumbent) signal
  level?
• How do we get the channel captured back when
  needed by licensed (incumbent) service?
• Out-of-band emissions?
• How to achieve a pre-specified spectral
  efficiency?
• Does cognitive radio provide QoS guarantee?

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What are the technical challenges? (cont.)

• How can a licensed user determine that an
  interference is the result of cognitive radio and
  not another source?
• Do we need a standard for cognitive radio
  implementation?
• What is the cumulative effect of a very large
  number of cognitive radio users?

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What are the technical challenges? (cont.)

• How does anyone enforce the rules?
• Who has economic incentive to enforce these
  rules?
• Once the floodgates open, how do you ever close
  them again if there is a problem? 

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Potential Interference Scenarios

• Cellular Mode
• Idle state
• Connected state
• Broadcast Mode
• Marginal coverage case
• Strong coverage case

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Cellular Mode

• Idle state
• Mobile station is monitoring BTS
• Unlicensed device cannot hear BTS
• Unlicensed device will cause harmful interference
  to mobile station

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Conclusions

• Top 4 take-away messages
• Technology shows promise, we have to wait though
  until the technology is proven and fielded
• Rigorous field testing must be conducted to
  validate the results of sharing studies
• We should experiment with cognitive radio in the
  unlicensed band first
• Define and agree on what constitutes harmful
  interference to licensed users