Cognitive Radio: Next
Generation Communication
System
By
V.ALAGU ABINAYA
11MCO02
Evolution of Communication
Systems
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
Definition of SDR
• Software defined radios -evolutionary process from
purely hardware-based equipment to fully softwarebased equipment.
1. Hardware driven radios- Transmit frequencies, modulation type
and other radio frequency (RF) parameters are determined
by 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 reprogrammable, and may be upgraded in the field with new
capabilities
- Importance of Standards
(APIs)
*Notice of Proposed
Rule Making (NPRM) 8/12/00
Cognitive Radio
Spectrum Allocation
COGNITIVE RADIO
• Two-way radio
• Automatically changes its transmission or reception
parameters
• communicates efficiently, avoiding interference with
licensed or licensed exempt users.
• Monitoring of several factors in the external and internal
radio environment
-radio frequency spectrum, user behaviour and
network state
• FCC –Federal Communication Commission
“A software defined radio with a cognitive engine brain".
Cognitive Radio Means “Smart”
and “Alert
•It knows where it is
•It knows what services are
available, for example, it can
identify then use empty spectrum
to communicate more efficiently
•It knows what services interest
the user, and knows how to find
them
•It knows the current degree of
needs and future likelihood of
needs of its user
•Learns and recognizes usage
patterns from the user
•Applies
“Model
Based
Reasoning” about user needs,
local
content,
environmental
context
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
What is needed for a CR ?
Cognitive Radio Evolution
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 - operating
characteristics
- improve its performance or to minimize a loss in
performance
How Does a Cognitive Radio Get
So Smart?
External
Intelligence
Sources
Orient
Establish Priority
Infer on Context Hierarchy
Plan
Pre-process
Immediate
Urgent
Parse
Learn
Observe
Receive a Message
New
States
Read Buttons
Outside
World
Normal
Save Global
States
Prior
States
Act
Send a Message
Set Display
Generate Alternatives
(Program Generation)
Evaluate Alternatives
Register to Current Time
Decide
Alternate Resources
Initiate Process(es)
(Isochronism Is Key)
The Cognition Cycle
Mitola, “Cognitive Radio for Flexible Mobile Multimedia Communications”, IEEE Mobile Multimedia Conference, 1999, pp3-10
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…
Contd…
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 multiple
Cognitive radio users are incorporated for primary user
detection.
• Interference based detection
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.
Spectrum Mobility
• Spectrum Mobility- when a user exchanges its
frequency of operation
- use the spectrum in a dynamic manner with
the best available frequency band
- maintaining seamless communication
requirements with better spectrum.
Spectrum Sharing
• Spectrum Sharing – provides the fair
spectrum scheduling method
• One of the major challenges is spectrum
sharing.
• It can be regarded to be similar to generic
media access control MAC problems in
existing systems
The future of CR
• The unlicensed band in range of wireless
devices and services
• FCC - consider opening further bands for
unlicensed 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.