بررسي روش هاي طيف سنجي همكارانه مبتني بر ادغام اطلاعات

چكيده انگليسي :

A study on methods for cooperative spectrum sensing based on data decision fusion in cognitive radio Mahboobeh Mohammadi Eshkaftaki ma mohammadi@ec iut ac ir Date of Submission 2013 01 22 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Ali M Doost Hoseini alimdh@cc iut ac irAbstractThe increasing demands for spectrum resources the limited available spectrum and the inefficiencyin the spectrum allocation necessitate a new communication paradigm to exploit the existingwireless spectrum opportunistically Cognitive radio CR has been proposed in recent years topromote the spectrum utilization by exploiting the existence of spectrum holes i e channels notused by any primary licensed users The CR nodes must constantly sense the spectrum in order todetect the presence of the Primary Radio PR nodes and use the spectrum holes without causingharmful interference to the PRs Cooperative spectrum sensing in which different CRs interact with each other has been proposedas an alternative and efficient solution to the problems posed by multipath fading shadowing andhidden node problem in single node spectrum sensing methods It also improves the probability offalse alarm and the probability of miss detection which are achieved via the exploitation of spatialdiversity among the CRs This thesis investigates the problem of cooperative spectrum sensing in cognitive radiosconsidering the radiation pattern of the primary transmitter In other words we assume that theprimary transmitter is equipped with a directional antenna whose beam angle is to be estimated We also assume that additional information regarding the approximate location of the primarytransmitter as well as the distribution of the receivers is available Spectrum sensing is donethrough sensing and reporting channels To take advantage of cooperation CR nodes need acommon reporting channel to transmit their local observations decisions to a common receiverknown as the Fusion Center When the number of secondary nodes increases the reporting channelwill be impaired Cluster based cooperative spectrum sensing which divides nodes into differentgroups with the same fading tries to overcome this problem Upon a spectrum sensing request aninitial primary transmitter presence is assessed through the nodes that received higher energies Knowing the locations of these nodes we use two well defined fitness functions and geneticalgorithm optimization to approximate the area of primary radiation as a sector In later stages spectrum sensing will be performed via the nodes in this sector named optimum detection cluster Thus in addition to the improvement in detecting licensed users the cost for deploying numerousunnecessary nodes is reduced Deployment of directional antennas by secondary users enablesthem to communicate with the corresponding receivers outside the primary radiation sector increasing the hole utilization factor considerably Simulation results show the performance of ourproposed method in comparison with conventional methods Keywords Cooperative spectrum sensing Clustering Data fusion Genetic algorithm

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