1. By:SHAGUFTA YASMIN 2SD12SCS11

2. Topics for discussion Introduction Sensor network Architecture of sensor network. Applications of sensor network. Challenges of sensor network. Cuts in sensor networks. Detection of cuts. Distributed cut detection algorithm. Conclusion. Future aspects. References. 3. Sensor Network: It is a group of specialized transducers with a communication infrastructure intended to monitor and record conditions at diverse location, it may be temperature, pressure humidity wind direction and speed etc It consists of multiple detection station called nodes, which is small, lightweight and portable. 4. Contd 5. Contd 6. Architecture of WSNs Transducer generates electrical signals. Microcomputer processes and storesSensor output. Transceiver receives thecommands from centralcomputer, transmits datato that computer. Power from battery. 7. Applications Industrial monitoring. Machine health monitoring. Data logging. Industrial sense and control applications. Automated and smart homes. monitoring the activities performed in a smart home is achieved using wireless sensors embedded within everyday objects forming a sensor network. Medical device monitoring. 8. Contd Monitoring of weather conditions. Air traffic control. Robot control. Air pollution monitoring. Forest fire detection. Natural disaster prevention. 9. Challenges One of the challenge in the successful use of WSNscome from limited energy of the individual sensornodes. WSNs consist of large number of small, low costsensor nodes distributed over large area. WSNs have emerged as a promising new technologyto monitor large regions. Node failure is expected to be quite common. this istrue for sensor networks deployed in harsh anddangerous fields such as forest fire monitoring and indefense applications. 10. Cuts in sensor networks WSNs can get separated into multiple connectedcomponents due to failure of some of its nodes, whichis called cut. So here we consider the problem of detecting cuts. Two nodes are said to be disconnected if there is nopath between them. 11. Contd 12. Contd In the figure, filled circles represents active nodes andunfilled circles represent failed node. Solid lines represents the edges, and dashed linesrepresent the edges that existed before the failure ofnode. the hole in (d) is indistinguishable from the cut in (b)to nodes that lie outside the region R 13. Detection of cuts Nodes that detect the occurrence and approximate thelocations of the cuts can then alert the source node or basestation. If the node were able to detect the occurrence of cut it couldsimply wait for the network to be repaired and eventuallyreconnected, which saves on-board energy of multiple nodesand prolongs their lives. The ability to detect cuts by both the disconnected node andsource node will lead to increase in the operational lifetimeof the network as a whole. 14. Distributed cut detection algorithm This algorithm allows each node to detectDOS(Disconnection frOm Source) events and subset of nodeto detect CCOS(connected but cut occurred somewhere)events. The algorithm is distributed and asynchronous. It involves only local communication between neighboringnodes and is robust to temporary communication failurebetween node pairs. A key component of the DCD algorithm is a distributediterative computational step through which the nodescompute their electrical potentials. 15. Distributed cut DetectionDefinition and problem statement Time is measured with a discrete counter k=,., -1,0,1,2,.. We model the sensor network as a time varying graph( ) = ( (k )(k)), whose node set V(k) represents thesensor nodes active at time k and the edge set ( )consist of pairs of nodes (u,v) such that nodes u and v candirectly exchange the message between each other attime k. By an active nodes we mean a nodes that has not failedpermanently . 16. Contid All graphs considered here are undirected i.e (i,j)=(j,i). The neighbors of node i is the set of nodes connected to ii.e. = { |( , ) }.The numbers of neighbors of i, | |, is called itsdegree, which is denoted by di.A path from i to j is sequence of edges connecting i and j. A graph is called connected if there is a path between everypair of nodes. A component Gc of the graph is maximal connected subgraph of G. 17. Contid A cut is formally defined as the increase of thenumber of components of a graph due to the failure ofsubset of nodes. The number of the cuts associated with a cut event isthe increase in the number of components after theevent. 18. Contid The problem we seek to address is two fold First we want to enable every node to detect if it isdisconnected from source. Second we want to enable nodes that lie close to the cutsbut are still connected to the source. 19. Contid The DCD algorithm is based on the following electricalanalogy.Imagine the wireless sensor network as an electrical circuitwhere the current is injected at the source node andextracted out of a common fictitious node that is connectedto every node of sensor network.Each edge is replaced by the 1 resistor.When a cut separates certain nodes from source node, thepotential of each of those nodes becomes 0, since there is nocurrent injection into their components.The potential is computed by an iterative scheme which onlyrequires periodic communication among the neighboringnodes. 20. ContidDOS detection When node u is disconnected from the source, we say that adisconnected from source event has occurred for u. The algorithm allows each node to detect DOS events. The nodes use the computed potentials to detect if DOSevent have occurred . The approach here is if the state is close to 0 then the node isdisconnected from the source , otherwise not. 21. Contid DOS detection part consist of steady state detection, normalized state computation and connection/separation detection. 22. ContidCCOS detection When a cut occurs in the network that does not separate anode u from the source node, connected but a cut occurredsomewhere (CCOS) event has occurred for u. Detection of CCOS events by the nodes close to a cut, andapproximate location of cut means location of one or moreactive nodes that lie at the boundary of cut and that areconnected to source. 23. Contid To detect the CCOS event the algorithm uses the factthat the potential of nodes that are connected tosource node changes after the cut and also using probemessages. Probe messages that are initiated by the certain nodesthat encounter failed neighbors, and are forwardedfrom one node to another node in a way that if shortpath exist around a hole created by node failures, themessage will reach initiating nodes. 24. Contid Each probe message contains the followinginformation:A unique source IDSource node ID SDestination node,path traversed, andangle traversed by probe message. 25. Conclusion The DCD algorithm we propose here enables everynode of a wireless sensor network to detectdisconnected from source event if they occur. Second it enables the subset of nodes that experiencesCCOS event to detect them and estimate theapproximate location of the cut in the form of a list ofactive nodes that lie at the boundary of the cut/hole. 26. Future Aspect Application of DCD algorithm to detect the node separation and reconnection to the source in mobile networks. 27. references http:// www.liveieeeprojects.com http://www.ijsrp.org/research-paper-1212/ijsrp-p1203.pd http://www.faculty.cs.tamu.edu/stoleru/papers/prabir12cut.pdf - United States www.cs.ucsb.edu/~suri/psdir/sentinel.pdf www.slideshare.net/.../cut-detection-in-wireless-sensor-networks http://en.wikipedia.org/wiki/Wireless_sensor_network 28. 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