Cognitive Radio Network (IEEE 802.22 WRAN)

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Cognitive Radio Networks
NetSim v9
Network Simulation/Emulation Platform
(IEEE 802.22- WRAN)
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What is Cognitive Radio

• Cognitive radio is a wireless communication
  system which is aware of the environment and its
  changes and can adapt its transmission parameters
  accordingly.
• Cognitive Capability The ability to sense the
  unused spectrum at a specific time and location.
• Reconfigurability The ability to receive and
  transmit at different frequency band enables the
  cognitive radio to reconfigure its parameters and
  select the best band.
• This operates in 54 MHz to 862 MHz band.

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Why Cognitive Radio?

• Inefficient spectrum utilization
• - Current wireless networks are regulated by
  fixed spectrum assignment policy.
• -According to Federal Communication Commission,
  temporal and geographical variations in the
  utilization of the assigned spectrum ranges from
  15 to 85.
• - Cognitive radio network is a new paradigm
  that provides the capability to share or use the
  spectrum in an opportunistic manner.

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Components

• Primary network
• Primary users
• Primary users have the license to operate in
  certain spectrum bands
• Primary base station
• Controls the access of primary users to spectrum
• Secondary network
• Secondary users
• Secondary users have no licensed bands assigned
  to them.
• Secondary base-station
• A fixed infrastructure component with cognitive
  radio capabilities and provides single hop
  connection to secondary users.

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Spectrum Hole
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Functionalities of a CRN

• Spectrum sensing Cognitive radio user has the
  ability to sense the unused spectrum at any time
  and location.
• Spectrum management Based on the availability
  of the spectrum and other policies, CR user
  allocates the best available spectrum band.
  Allocation of a channel not only depends on
  spectrum availability but also depends on
  internal and external policies.

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Functionalities of a CRN(Cont..)

• Spectrum mobility CR user shall vacate the
  spectrum in the presence of any primary user and
  move to next best available spectrum band. If the
  specific portion of the spectrum is needed by a
  licensed user, the communication needs be
  continued in another vacant portion.
• Spectrum sharing CR network has to provide a
  fair and optimal spectrum allocation method among
  multiple CR users. Since there are multiple
  secondary users trying to access the spectrum,
  their access should be coordinated to avoid
  colliding in overlapping portions of the spectrum

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Interference
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Cognitive Radio Cycle
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Super Frame Structure
The first frame shall be constituted of a
superframe preamble, a frame preamble, Superframe
Control header (SCH), the rest of the first frame
including its frame header and data payload. At
the beginning of every superframe, the BS shall
transmit the superframe preamble and the SCH on
the operating channel. In order to associate
with a base station, a CPE must receive the SCH
to establish communication with the BS. During
each MAC frame, the BS shall manage the upstream
and downstream operations, which may include
ordinary data communication, measurement
activities, coexistence procedures, and so on.
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Frame Structure
A frame is comprised of two parts a downstream
(DS) subframe and an upstream (US) subframe. The
boundary between the DS and US subframes shall be
adaptive to adjust to the downstream and upstream
relative capacity. The upstream subframe may
contain scheduled upstream PHY PDUs, each
transmitted from different CPEs for their
upstream traffic. The FCH specifies the burst
profile and the length of either the DS-MAP, if
transmitted, or the US-MAP. If neither, the
DS-MAP nor the US-MAP is transmitted, the value
shall be set to zero.
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Typical Cognitive Radio Applications
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Thank you
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