Cognitive Radio Networks (CRN)
Speaker:You-Min Lin
Advisor: Dr. Kai-Wei Ke
Date: 2011/04/25
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Outline
 Introduction
 Basic cognitive cycle
 MAC Layer Design
 Applications
 Conclusions and Future
 Reference
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What is Cognitive Radio(CR)
 Mitola’s definition (1999):
 Software radio that is aware of its environment and its
capabilities
 Alters its physical layer behavior
 Capable of following complex adaptation strategies
 “A radio or system that senses, and is aware of, its operation
environment and can dynamically and autonomously adjust its
radio operating parameters accordingly”
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What is Cognitive Radio(CR)
 A “Cognitive Radio” is a radio that can change its transmitter
parameters based on interaction with the environment in
which it operates (FCC’2005)
 Capability to use or share the spectrum in an opportunistic
manner
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What is Cognitive Radio Networks (CRN)
 Primary Network
 Primary User (or Licensed User)
 Secondary Networks (or Unlicensed Network)
 Secondary User (or Unlicensed User)
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Cognitive Radio Networks (CRN)
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TV White Space
 Digital TV Broadcasting systems have freed up channels used
in the analog TV frequency bands. These vacated channels are
called “TV white space”.
 The economic potential for the TV white spaces was
estimated at $100 billion.
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Spectrum utility (1/3)
 Spectrum Scarcity
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Spectrum utility (2/3)
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Spectrum utility (3/3)
 3kHz~300GHz
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Spectrum hole
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Worldwide Regulatory Agencies
 FCC in the US, Office of Communications (Ofcom) in the
UK and Electronic Communication Committee (ECC) of
CEPT in Europe.
 On February 17, 2009, the FCC released the final rules for
“Unlicensed Operation in the TV Broadcast Bands”
 http://edocket.access.gpo.gov/2009/pdf/E9-3279.pdf
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FCC “Unlicensed Operation in the TV
Broadcast Bands” (1/3)
 TV Band Devices (TVBDs) can only operate on channels that are
not adjacent to an incumbent TV signal in any channel between 2
and 51 except 3,4 and 37
 TVBDs are divided into two categories:
 Fixed
 Higher power (< 4W)
 Must have a geolocation capability, capability to retrieve list of available
channel from an authorized database, and a spectrum sensing capability.
 Personal/portable (channels 21-51(except 37)
 a maximum of 100mW on non-adjacent channel and 40mW on adjacent
channels
 and are further divided into 2 types: Mode I and Mode II.
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FCC “Unlicensed Operation in the TV
Broadcast Bands” (2/3)
 Sensing is a mandatory function for all TVBDs.
 A channel must be sensed for 30 seconds before determining
if it is available for use by a TVBD.
 Once Operation has started on a channel, sensing must be
done at least once every 60 seconds and if a wireless
microphone is detected the channel must be vacated within 2
seconds.
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FCC “Unlicensed Operation in the TV
Broadcast Bands” (3/3)
 Geolocation means must be present in all fixed and Mode II
device (+/- 50 meters)
 Safe harbor channels for wireless microphone usage are
defined in the 13 major metropolitan market to be the first
available channel on either side of Channel 37.TVBDs cannot
operate on these channels.
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Some Fun
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Some Fun
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Some Fun
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Basic cognitive cycle
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Main functions
 Spectrum sensing
 Detecting unused spectrum
 Spectrum management
 Capturing the best available spectrum
 Spectrum mobility
 Maintaining seamless communication during the spectrum transition
 Spectrum sharing
 Providing fair spectrum scheduling method
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MAC Layer Design
 The basic building blocks for MAC
 Beaconing protocols and channel access protocols.
 Multi-device beaconing
 Single-device beaconing can lead to the potential interference
between adjacent networks.
 Channel reservation access
 To achieve high protocol efficiency and strict QoS provisioning.
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MAC Structure and Beaconing
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Single-device beaconing
 Client A and C becomes hidden terminal to each other. As a
result, the channel reservation and QP scheduled for client A
and C will be disrupted.
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Multi-device beaconing
 Beaconing Client A and C devices exchange channel
reservation information and QP schedule across network A
and B periodically. Therefore, collision on channel
reservation and QP is minimized.
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Channel selection
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Applications (1/2)
 Robust delivery of High Definition Video inside home and
across multiple walls.
 The benefit of TVWS:
 Better propagation characteristics and therefore increased range
and robustness, in comparison to higher frequencies.
 The ability to operate at lower power-levels for a given range
would result in better energy efficiencies.
 Additional spectrum in the TVWS helps deal with overcrowding
of ISM bands.
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Applications (2/2)
 Robust coverage inside buildings and across campuses for wireless data
applications
 Enhanced range for municipality, community and rural Internet access.
 Enhanced coverage for smart service and remote machine-to-machine
and RFID deployments.
 New interactive applications for TV broadcasters, such as weather and
news updates, upcoming program previews, interactive advertisements
and games and web access.
 Enhanced range, robustness and quality for emergency-response and
public service communication networks.
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Conclusions and Future
 Fundamental research
 Implementation
 Government
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Reference
 [1] S. Haykin, “Cognitive radio: Brain-empowered wireless
communications”, IEEE Journal on Selected Areas in
Communications, pp. 201-220, 2005.
 [2] Ecma 392, ”MAC and PHY for Operation in TV White Space ”,
Dec.2009.
 [3] Carlos Cordeiro, Kiran Challapali, and Dagnachew Birru,
“IEEE 802.22: An Introduction To The First Wireless Standard
Based On Cognitive Radios,” JOURNAL OF
COMMUNICATIONS, VOL. 1, NO. 1, APRIL 2006.
 [4] I. F. Akyildiz et al., “NeXt Generation/Dynamic Spectrum
Access/Cognitive Radio Wireless Networks: A Survey,” Comp.
Networks J., vol. 50, Sept. 2006, pp. 2127–59
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