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چكيده انگليسي :

012 Bounded Delay Transmission of Different Traffic Classes in Wireless Sensor Networks Narjes Torabi Narges Torabi@ec iut ac ir Date of Submission April 11 2009 Department of Electical and computer engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Masoud Reza Hashemi hashemim@cc iut ac irAbstractA hybrid sensor network can be utilized to transfer multiple traffics with diverse delay and loss requirements To satisfy the worst case delay and loss requirements the network has to service each category of trafficaccording to its characteristics and quality of service QoS requirements So we consider a hybrid sensornetwork that is responsible for carrying burst traffics taking place for a short period of time as in event driven sensor networks and low rate traffics occurring periodically as in time driven networks The main problem in these networks appears when the critical events happen These events intrinsically areburst traffics So probably they can bring about local congestion in the zone that they occur Existence ofpackets belonging to other applications can intensify this congestion As a result the quality of the radiochannel is affected traffic services degrade and packets are delayed and dropped regardless of their priority So we need an algorithm to decrease the probability of congestion Also in the presence of congestion itshould hinder low priority data from making the situation worse In the thesis we introduce a simple algorithm for sensor nodes that satisfies the service requirements ofdifferent kinds of traffics By using this algorithm packets with the same priority generated after an event aredelivered to the sink with bounded and almost equal delays The algorithm combines a specific time framingpattern to prevent congestion with a medium access scheduling method This method assigns timeslotsproportional to the importance and QoS requirements of the traffic to differentiate between the traffics Theproposed algorithm adapts medium access scheduling proportional to the importance and QoS requirements ofthe traffic in each node So the access pattern is dynamic and changes proportional to the mix of traffic at eachtime Besides our algorithm schedules the transmission of packets through a specific framing pattern to reducethe probability of congestion This framing strategy is used to decrease congestion which is the main obstacleto satisfy QoS Simulation results shows that this algorithm provides a bounded delay framework fordelivering different kinds of traffics and each traffic category experience delays proportional to its sensitivityto delay This algorithm is tested on OPNET for various scenarios The results approve that each traffic gets serviceaccording to its priority Simulation results verify that packet delays are proportional to the priority of thepackets such that higher priority packets experience less delay than lower priority packets In addition thismethod effectively resolves congestion Because of these features this approach can meet the QoSrequirements These extensive simulation results approve the effectiveness of this method for satisfying QoSrequirements in sensor networks Key words Wireless Sensor Networks Quality of Service Bounded Delay Congestion Framing Startegy

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