بهبود توام تصميمات محلي و مركزي در طيف سنجي همكارانه مبتني بر سانسور داده در درايوي شناختگر

چكيده انگليسي :

Joint local and central decisions improvement in Censor based cooperative spectrum sensing Ensieh Berenjkoub e berenjkoob@ec iut ac ir Date of Submission 6 15 2010 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor M Modarres Hashemi modarres@cc iut ac irAbstract Nowadays in addition to some sensitive situations such as military and disaster applications wireless communication has become a part of the human life This has led to increase the demandfor spectrum while almost the entire part of the spectrum over which the communication can bepracticed more effectively has been assigned to users and spectrum scarcity is becoming a majorchallenge now On the other hand it has been observed that the assigned spectrum is used in aninefficient way so that a huge part of it remains unused most of the time These two observationslead to the dynamic spectrum allocation and sharing ideas and cognitive radio is proposed to bringthese ideas to reality The idea of Cognitive radio was first proposed in 1999 Since then several definitions areintroduced for the term cognitive radio all of whom are common in two specifications theability of environment cognition and the ability of reconfiguration of operating status Cognitiveradio acting as a secondary user tries to find the spectrum holes channels assigned to primaryusers being idle in specific times and locations through spectrum sensing It is necessary toperform the sensing accurately and fast in order not to lose opportunities as well as not to causeinterference for primary users After that the cognitive radio chooses one of the idle channels andsets its communication parameters accordingly Several schemes have been proposed for spectrumsensing including cooperative approaches in which several radios cooperate to sense the spectrum One method of cooperation is the centralized one with hard decision in which cooperating nodesprovide their local decisions for a fusion center to combine them and make the final decision aboutthe idelity in a specific band In addition because of a probable communication rate constraint inthe control channel between the fusion center and nodes a censoring scheme can be used In thisscheme each node sends its decisions to the center only if it is informative In this research after reviewing existing works in cooperative spectrum sensing area an optimaldecision rule in the center and an optimal censoring strategy in nodes based on Neyman Pearsoncriterion are proposed To do so first an optimal decision strategy in the center is investigated Then an optimal censoring strategy in nodes is obtained Finally the joint optimization isperformed on the above two strategies and an algorithm is proposed In addition based on anothercriterion the problem is resolved and it is shown that the same algorithm can be adopted for thisproblem Comparing the proposed method with some other existing methods shows that theproposed method has much better performance Key Words cognitive radio cooperative spectrum sensing censoring optimization

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بهبود توام تصميمات محلي و مركزي در طيف سنجي همكارانه مبتني بر سانسور داده در درايوي شناختگر

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