By:
Gamal El Din Fathy Amin
Ahmed Ossama El Fiky
Supervised By: Dr Tarek El Naffouri
Outline
 Introduction.
 Why Cognitive Radio?
 Issues.
 Benefits.
 Applications.
 Challenges.
 Our Approach.
 Proposed Protocol.
Introduction
 CR  Intelligent Wireless Technology.
 a radio that is aware of its surroundings and adapts
intelligentlyIntelligence Searching the spectrum.
 Cognitive radio requirements
 co-exists with legacy wireless systems
 uses their spectrum resources
 does not interfere with them
Introduction
 Embedded intelligence to determine optimal transmission
and vary communication parameters (bandwidth, center
frequency, QoS) based on primary users’ behavior
 Defining new concepts:
 Spectrum sharing.
 Adaptive parameters.
Why CR?
 Recent measurements by the FCC in the US show 70%
of the allocated spectrum is not utilized. (Spectrum
scarcity)
Why CR?
 Bandwidth is expensive and good frequencies are
taken
 Unlicensed bands – biggest innovations in spectrum
efficiency.
 Spectrum utilization.
Applications
 Band sharing, emergency services, broadband wireless
services, multi-media networking
 Non-time sensitive services, such as downloading
could be most appropriate.
Cont. Application
 Cellular operator
 Local KAUST free mobile network.
 Sensing is limited of the operator’s band.
Challenges
 Hidden tunnel  Cooperative Spectrum Sensing
 Controlling CRs to ensure they have the same spectrum picture.
 Spectrum sharing
 Could add lots of interference.
 Scarcer resources.
 A lot of control communications (increase throughput)
Our Approach.
What is Compressive Sensing?
 Mathematical tool that can help in reducing the
number of measurements to solve a system given it is
sparse.
Cont. What is Compressive
Sensing?
•N equations is needed to solve this system.
•M=N.
Cont. What is Compressive
Sensing?
•S = number of nonzero elements in U.
•S<<N
•m = α S log (n/S) & S<<m<<N
Control Channels On Cognitive
radio.
 Handles the control communication between Cognitive
base station (CBS) and Cognitive Radios (CR).
 Ex. spectrum sensing information.
 Share scarce resources.
 Collision Happens.
 Collision Resolving Algorithms Should Be Applied.
 The channel is given to the strongest connection users:
 Support Higher rates.
 Increase throughput.
Control Channels On Cognitive
radio.
Reservation
•Increase Throughput:
•Increase the frame length.
•Decrease Reservation Time
Data
Control Channels On Cognitive
radio.
Reservation
Data
Apply Compressive Sensing to
Optimize the number of slots.
Reservation
Data
Compressive Sensing Protocol
 CBS has fixed reservation slots=m.
 CBS sends a beacon with a threshold level L.
• CRs compare their channel gain a with L.
• If a>L Strong Connection CR (SCR)
• Otherwise, Weak connection (WCR)
Cont. Compressive Sensing
Protocol
 WCR go to sleep mode.
 Saves Battery.
 Eliminate WCRs that can cause slow rates and
interference.
 SCR multiplies 1 by random sequence of length m +1
&-1 and reply on all slots.
Cont. Compressive Sensing
Protocol
• CBS receives the replies and form the
system of independent equations.
 CBS then knows SCRs.
 It reserves the channel randomly to any of SCRs.
Cont. Compressive Sensing
Protocol
 CBS senses the spectrum and send the spectrum
information to SCRs.
 SCRs sense spectrum and compare with CBS.
 If SCRs agree it remains silent and apply the decision.
 If SCRs object they reply back.
 CBS base a new decision on the amount of objection to
its decision.
Cont. Compressive Sensing
Protocol
 Advantages:
 Shared control channels are used.
 Limit collision by limiting the number of users.
 decrease reservation time and increase data time.
 Strong connection users only use channel.
Questions
Control Channels On Cognitive
radio
 Traditional way N users send their ID and Channel
gain G to reserve the channel.
Apply Compressive Sensing to
decrease
reservation
Time
 If N is limited to s users need to send s<<N,
compressive sensing can be used.
 m reservation slots is used each of one bit.
The goal
 Increase throughput.
 Give channels to strong connection users.
 They support high rates.
 Limit the activity of weak connection users.