Pres Cmpe 300 Project

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Utility Based Scheduling inCognitive Radio Networks

Term ProjectCmpE-300 Analysis of Algorithms

Spring 2009Computer Engineering,Boazii University, Istanbul

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Outline

Wireless networks FDMA, TDMA, CDMA

Dynamic Spectrum Access

Cognitive Radio Networks

Problem Formulation

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Cellular Networks

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Cellular Networks

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Cellular Networks

MSC: Mobile Switching Center

How do different mobile stationscommunicate simultaneously with the BS?

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Frequency Division MultipleAccess (FDMA)

Each mobile device tunesto a frequency band

Analogous to peopletalking in different rooms

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Frequency Division MultipleAccess (FDMA)

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Time Division Multiple Access

(TDMA) Each mobile device transmits data in a different time slot

Analogous to people talking one by one

GSM: Combination of FDMA and TDMA 25 MHz bandwidth divided into 124 carrier

frequencies of 200 KHz bandwidth Each carrier frequency divided into 8 time slots

using TDMA

3G licenses: Type-A: 40 MHz, Turkcell Type-B: 35 MHz, Vodafone Type-C: 30 MHz, Avea

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Time Division Multiple Access(TDMA)

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Code Division Multiple Access(CDMA)

Analogous to people talking indifferent languages

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Dynamic Spectrum Access

(DSA) PROBLEM : Underutilized spectrum

resources due to fixed assignmentstrategy

IDEA : Utilizing white spaces in thespectrum without disturbing licensedusers [1]

CHALLENGE : Sensing the environment,

detecting white spaces white spaces frequently change

by time and space Changing radio parameters on the

fly

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Frequency Allocation Charts In Turkey:

http://www.tk.gov.tr/Duzenlemeler/teknik/marfl/_marfl1.asp

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White Space Concept

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Cognitive Radio (CR) Concept

Initially proposed by Mitola [2]

Next step evolution of Software Defined

Radio (SDR)

Cognitive Radio (CR): Intelligent devicesthat can [2]: Sense and autonomously reason

about their environment Adapt their communication

parameters accordingly Realize DSA concept

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Terminology Primary User (PU):

Licensed user Has exclusive rights for the

spectrum

Secondary User (SU): Unlicensed user Opportunistically utilizes the white

spaces Has to vacate the spectrum band

as soon as a PU appears Also called cognitive user

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IEEE 802.22 Network Architecture

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Research Problem totalNetworkUtility : Total number of SUs that are

satisfied in terms of throughput

Maximize (totalNetworkUtility)

subject to

No interference is imposed on the PUs

Reliable communication with the CBS is achievedNo collisions occur among the SUs

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Research Problem Terminology N: Total number of SUs

F: Total number of frequencies

T: Total number of time slots

Uif = Maximum number of packets that can be transmitted by user i to theCBS using frequency f

(in a time slot)

t i = Throughput (data rate) of SU i

g(t i )=The level of satisfaction of SU i from throughput t i

t imin = Minimum throughput required by SU i

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t timeslot in f frequencywithtransmitsiuser if X ift


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Problem Formulation

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totalNetworkUtility

Each SU is assigned at least 1 time slot

At most 1 user isassigned a certaintime slot and frequency pair

Throughput of SU i


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Problem Formulation

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Problem Formulation

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References

[1] Akyildiz, I., W. Lee, M. Vuran, and S. Mohanty, NeXtgeneration/dynamic spectrum access/cognitive radiowireless networks: A survey , Computer Networks, Vol.50, No. 13, pp. 2127-2159, 2006.

[2] Mitola, J., Cognitive Radio: AnIntegrated Agent Architecture for

Software Defined Radio, Doctor of

Technology, Royal Institute of Technology(KTH), Stockholm, Sweden, 2000.

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Questions?

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Pres Cmpe 300 Project

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