Cognitive Radio Network

(IEEE 802.22- WRAN)

Visit : www.tetcos.com

NetSim v9NetSim v9Network Simulation/Emulation Platform

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.


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.Visit : www.tetcos.com


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.


Spectrum Hole


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.


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 spectrumVisit : www.tetcos.com

Interference


Cognitive Radio Cycle


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.

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.


Typical Cognitive Radio Applications



Date post:	26-Jan-2017
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Cognitive Radio Network

Technology