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A Conservative ApproachA Conservative Approachfor Transmission infor Transmission in

Cognitive RadiosCognitive RadiosPresented by: Syed Ahmed Faran

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Contents of PaperContents of Papery I nterference considerationy Filteringy

Channel codingy Modulationy Transmission Algorithm

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Why Consider Transmission?

Why Consider Transmission?

y The transmission parameters determinethe capabilities of a radio.

y Transmission schemes vary dependingupon the bandwidth efficiency, powerrequirements and BER performance.

y Efficient techniques can lead to a robustsystem design.

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The Cognitive EnvironmentThe Cognitive Environmenty The cognitive radios form a cognitive

network.y The cognitive radios use their intelligence

to render the spectrum resource in anefficient manner.

y The cognitive network has variables

designs.

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The Secondary UserThe Secondary Usery The cognitive radio accesses the spectrum

as secondary user (SU).y Primary user (PU) should not suffer from

performance degradation.

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Accessing the Channel:Accessing the Channel:

InterferenceInterferencey The SU can gain access to the channel in

two ways.i) Underlay approachii) Opportunistic approach

y I nterference caused by both methods isdifferent to the PU.

y

The point is to keep the interference lowto the PU.

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G aussian FilteringG aussian Filteringy G aussian filtering is

used to cater for outof band interference.

y The G aussian filterused has BT productof 0.3 and 0.5.

I mg ref: http://www.aero.org/publications/crosslink/winter2002/images/03_03.gif

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Channel CodingChannel Codingy G aussian filtering introduces I S I . Tradeoff!y Robust channel coding techniques are

used cater for this interference.y Turbo codes and convolutional codes with

rates 1/2 and 1/3 are used.y Decision of using a coding technique

depends upon channel condition.

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M odulationM odulationy Modulation techniques are used that

provide low power to signal componentsleaving given frequency band.

y MSK, 2-MSK, 16-QAM and 64-QAM areused.

y G aussian filtering is not used with 16-QAM

and 64-QAM.

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TransmissionTransmission

AlgorithmAlgorithm

The access mode is decided first.I nterference is modeled differently.Transmission parameters adjusted

based on the access mode used.G aussian filter used if interference

in environment.Channel coding and modulation

adjusted accordingly.

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Conservativeness?Conservativeness?y I nterference to the PU is considered prior

to maximization of the throughput for SU.y The SU is a less privileged user.y The bandwidth requirement of 2-MSK

signal is almost same as 16-QAM.Why use it then?

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Transmission ParametersTransmission Parameters

Opportunistic Access Underlay Access

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RefrencesRefrencesy S. Haykin, Cognitive radio: Brain-empowered wireless communications, IEEE J. Select. Areas Commun .,

vol. 23, no. 2, pp. 201220, Feb. 2005.y FCC, Spectrum policy task force report, FCC 02-155, Nov. 2002.y J. Mitola, Cognitive Radio, Ph.D. dissertation, Royal I nstitute of Technology (KTH), Stockholm, Sweden,

2000.y I . F. Akyildiz, W. Y. Lee, M. C. Vuran, and S. Mohanty, Next generation/ dynamic spectrum

access/cognitive radio wireless networks: a survey, E lsevier Computer Networks Journal , 50:21272159,September 2006.

y

Sudhir Srinivasa and Syed Ali Jafar, The throughput potential of cognitive radio: a theoretical perspective, IEEE Commun magizine , May 2007.y X . Hong, C.- X . Wang, and J. Thompson, I nterference modeling of cognitive radio networks, in P roc. IEEE

Veh. Technol. Conf ., pp. 1851-1855, May 2008.y Y. Fei et al., I nterference effect evaluation of cognitive radio by using statistical method, IEEE

I nternational symposium on microwave, antenna, propogation and EM C technologies for wirelesscommunication , pp. 858-861, Dec. 2009.

y M. Pursley and T. Royster, Low-complexity adaptive transmission for cognitive radios in dynamic spectrumaccess networks, IEEE J. Select Areas Commun , vol. 26, no. 1, pp. 8394, Jan. 2008.

y Y. Zhang, F. Zhang. W. He, Adaptive transmission in cognitive radio networks, CCDC 09, pp. 1951-1953,2009.

y S. Misra, S. G eirhofer, and L. Tong, "Optimal adaptive transmission for a cognitive radio with sensing,"IEEE I CASS P , pp. 2797-2800, 2008..

y X . Li, J. Chen, F. Ng, "Secure transmission power of cognitive radios for dynamic spectrum accessapplications," in P roc. 42nd Annual C I SS , pp. 213-218, Mar. 2008..

y A.A. Eltholth et al ., Performance of multi-amplitude minimum shift keying with orthogonal frequencydivision multiplexing The I nt. Conf. on computer as a tool EURO C O N , pp. 1057-1060, 2007.

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Thank You!Thank You!

QUEST I ONS?

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