شناسايي توزيع شده وقوع دو رخداد همزمان با قابليت تحمل خرابي ر شبكه هاي سنسوري بي سيم

چكيده انگليسي :

49 Fault Tolerant and Distributed Detection of Two Simultaneous Events in Wireless Sensor Network Mina Moradi kordmahalleh m moradikordmahale@ec iut ac ir Date of Submission 2011 09 13 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Persian Supervisors J Ghaisari ghaisari@cc iut ac ir Javad Askari j askari@cc iut ac ir Abstract A Wireless Sensor Network WSN is composed of a large number of distributedtiny sensor nodes which report data from an environmental phenomenon Each sensor nodeconsists of measurement devices computational resources a communications component and afinite power source Typically the sensor nodes are densely deployed prone to failure and limitedin power In centralized data processing all of the sensor nodes data s and their geographylocations are sent to a central processor But because of requirements in communication bandwidthusage reducing reliability increasing and cost decreasing in WSN application employing of thisstructure is not suitable As a result a distributed data processing scheme is considered in WSNapplications In this scheme some local processing is done on each sensor nodes then onlycondensed information sent to central processors Event region detection and faulty sensorrecognition are two major research issues in WSN In this thesis a distributed processing scheme isproposed to detect two simultaneous events in WSN area This procedure consists of twoprocessing layers local detection layer and final detection layer This detection procedure isdesigned based on hypothesis tests and Bayesian detection criteria By applying three hypothesisincluding normal first event and second event the risk function in the Bayesian detection criteriais defined based on the priori probability of each hypothesis and probability of each option may behappened in decision making Then decision rules are obtained via minimization of the riskfunction In chapter 4 a fault tolerant algorithm is proposed to improve the precision of detectionof two events in presence of sensor fault By proposing all the sensor faults that may be occurred indecision making layers and in occurrence of specific probability of sensors fault computation ofthe optimal thresholds used in first layer of decision making will be attainable By using anumerical method the optimal values of thresholds are calculated such that the overall riskfunction is minimized Sensor networks are usually deployed in uncontrolled and harshenvironments and observations are associated with noises by excessive variance which may corruptthe observations Since the probability of sensor fault not been determined before detection of twoevents it is necessary to recognize the faulty sensors On the next step of this thesis improveddistributed fault detection has been employed to recognize the sensor nodes which have a noisewith excessive variance Therefore the error probability of the two events detection is reduced byelimination of faulty nodes decisions in the second processing layer To show the accuracy andefficiency of the proposed methods numerical examples are presented in all chapters and thesimulation results are compared Keywords Two Simultaneous events detection Distributed data processing Wireless SensorNetwork Bayesian criteria Fault tolerant Improved distributed fault detection

مرادي كردمحله، مينا

شناسايي توزيع شده وقوع دو رخداد همزمان با قابليت تحمل خرابي ر شبكه هاي سنسوري بي سيم

پردازش توزيع شده داده ها , معيار شناسايي بيزين