By: Gamal El Din Fathy AminAhmed Ossama El Fiky

Supervised By: Dr Tarek El Naffouri

OutlineIntroduction.Why Cognitive Radio?

Issues.Benefits.

Applications.Challenges.Our Approach.

Proposed Protocol.

IntroductionCR 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

IntroductionEmbedded 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. ApplicationCellular operator

Local KAUST free mobile network.

Sensing is limited of the operator’s band.

ChallengesHidden 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.

Mathematical tool that can help in reducing the number of measurements to solve a system given it is sparse.

What is Compressive Sensing?

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.

DataReservation

•Increase Throughput:•Increase the frame length.•Decrease Reservation Time

DataReservation

Control Channels On Cognitive radio.

Apply Compressive Sensing to Optimize the number of slots.

DataReservation

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 then knows SCRs.It reserves the channel randomly to any of SCRs.

• CBS receives the replies and form the system of independent equations.

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 radioTraditional way N users send their ID and

Channel gain G to reserve the channel.

Apply Compressive Sensing to decrease reservation TimeIf 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 goalIncrease throughput.Give channels to strong connection users.

They support high rates.

Limit the activity of weak connection users.