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8/2/2019 Cognitive Radio1
http://slidepdf.com/reader/full/cognitive-radio1 1/21
Cognitive Radio: Next
Generation CommunicationSystem
ByV.ALAGU ABINAYA
11MCO02
8/2/2019 Cognitive Radio1
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Evolution of Communication
Systems
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Software Defined Radio
Software Defined Radio as a basic platform on
which to build a Cognitive Radio
Cognitive Radio can provide the spectral
awareness technology to support FCC
initiatives in Spectral Use
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Definition of SDR Software defined radios -evolutionary process from
purely hardware-based equipment to fully software-based equipment.
1. Hardware driven radios- Transmit frequencies, modulation type
and other radio frequency (RF) parameters are determinedby hardware and cannot be changed without hardware changes.
2. Digital radios - A digital radio performs part of the signal processing
or transmission digitally, but is not programmable in the field
3. Software Defined Radios- All functions, modes and applications
can be configured and reconfigured by software SDR Forum-
- waveform properties, cryptography and applications, is re-
programmable, and may be upgraded in the field with new
capabilities
- Importance of Standards (APIs)*Notice of Proposed Rule Making (NPRM) 8/12/00
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COGNITIVE RADIO
Two-way radio
Automatically changes its transmission or reception
parameters
communicates efficiently, avoiding interference withlicensed or licensed exempt users.
Monitoring of several factors in the external and internal
radio environment
-radio frequency spectrum, user behaviour andnetwork state
FCC ±Federal Communication Commission
³A software defined radio with a cognitive engine brain".
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Cognitive Radio Means ´Smartµ
and ´AlertIt knows where it is
It knows what services areavailable, for example, it canidentify then use empty spectrumto communicate more efficiently
It knows what services interestthe user, and knows how to findthem
It knows the current degree of needs and future likelihood of needs of its user
Learns and recognizes usagepatterns from the user
Applies ³Model BasedReasoning´ about user needs,local content, environmentalcontext
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Need for Cognitive Radio Radio spectrum is a scarce resource and is regulated
Spectrum usage is one of the key issues in
communication system challenges
The spectrum efficiency can be improved with idea of
dynamic spectrum allocation.
Cognitive radio network - on effective spectrum
utilization
-allocates to primary user or licensed user
-user is not utilizing ,secondary user can claim
without interfering to primary user
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What is needed for a CR ?
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Cognitive Radio Evolution
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How Cognitive radio works?
Cognitive radio
-Spectrum sensing
-Spectrum management
-Spectrum mobility
-Spectrum sharing
awareness of changes in its environment
response to these changes adapts - operatingcharacteristics
- improve its performance or to minimize a loss in
performance
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How Does a Cognitive Radio Get So Smart?
ExternalIntelligence
Sources
Mitola, ³Cognitive Radio for Flexible Mobile Multimedia Communications´, IEEE Mobile Multimedia Conference, 1999, pp3-10
OrientEstablish Priority
PlanNormal
Generate Alternatives(Program Generation)
Evaluate Alternatives
Register to Current Time
Decide
Alternate Resources
Initiate Process(es)(Isochronism Is Key)
Act
Learn
Save GlobalStates
Set DisplaySend a Message
ObserveReceive a Message
Read Buttons
Outside
World
New
States
The Cognition Cycle
Prior
States
Pre-process
Parse
Immediate
Urgent
Infer on Context Hierarchy
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Spectrum Sensing Dynamic spectrum allocation
Cognitive radio networks
± scans the entire spectral band for the
presence/absence of primary users Performed either locally
- secondary user
- collectively by a group
Contd«
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Spectrum Sensing
Transmitter detection- capability to determine if a signal
from a primary transmitter is locally present in a certain
spectrum.
There are several approaches-Matched filter detection
-Energy detection
-Cyclostationary feature detection
Cooperative detection- information from multipleCognitive radio users are incorporated for primary user
detection.
Interference based detection
Contd«
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Spectrum Management Spectrum Management - capturing the best available
spectrum to meet user communication requirements
Decide on the best spectrum band -Quality of service
These management functions can be classified
± spectrum analysis
± spectrum decision
Practical implementation of functions
- very complex and multifaceted issue in itself.
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Spectrum Mobilit y
Spectrum Mobility- when a user exchanges its
frequency of operation
- use the spectrum in a dynamic manner withthe best available frequency band
- maintaining seamless communication
requirements with better spectrum.
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Spectrum Sharing
Spectrum Sharing provides the fair
spectrum scheduling method
O
ne of the major challenges is spectrumsharing.
It can be regarded to be similar to generic
media access control MAC problems in
existing systems
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The future of CR
The unlicensed band in range of wireless
devices and services
FCC - consider opening further bands forunlicensed use.
Exploits the inefficiently utilized licensed
bands without causing interference to
incumbent users
Unlicensed radios to operate in the TV
broadcast bands and also TV services.