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Relay Sensor Placement in Wireless Sensor Networks

Relay Sensor Placement in Wireless Sensor Networks. Xiuzhen Cheng, Dign-Zhu Du, Lusheng Wang, and Baogang Xu (ACM WINET 2004) Presented by Taehee Kim. Table of Contents. Related Work Problem Definition Relay sensor placement problem SMT-MSP

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Relay Sensor Placement in Wireless Sensor Networks

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  1. RelaySensorPlacementinWirelessSensorNetworks XiuzhenCheng,Dign-ZhuDu,LushengWang,andBaogangXu (ACMWINET2004) PresentedbyTaeheeKim

  2. TableofContents • RelatedWork • ProblemDefinition • Relaysensorplacementproblem • SMT-MSP • SteinertreeproblemwithminimumnumberofSteinerpointsandboundededge-length • Twoapproximatealgorithms • Ratio3algorithmforSTP-MSP • 2.5-approximatealgorithmofSTP-MSP • Conclusion

  3. RelatedWork • WirelessSensorNetworks • isAdhocmultihopsystems • Haskeyissues:Connectivity,performance,lifetime,andcost • RelatedWork • Focusontopologycontrolbyminimizingthemaximumtransmitpower[8,14]orminimizingtotaltransmitpower[3,18]tomaintainglobaltopology.

  4. ProblemDefinition • Relaysensorplacementproblem: Givenasetofdutysensors(requiredsensors)intheplane, placeminimumnumberofrelaysensorstomaintainglobalconnectivity suchthatthetransmissionrangeofeachsensorisatmostR,whereRisaconstant.

  5. ProblemDefinition • Relaysensorplacementproblem • ismodeledbySteinerMinimumTreewithMinimumnumberofSteinerPointsandboundededgelength(SMT-MSP) • Theyproposetwoapproximatealgorithms, • aratio3and2.5-approximatealgorithmofSMT-MSP • BecauseSMT-MSPisaNP-hard • Assumption: • Sensorsarefixedandtheirplacementsarepre-determinedina2-dimensionalplane

  6. SMT-MSP • SMT-MSP • Findatreeinterconnectingagivensetofnterminalpoints andaminimumnumberofSteinerpoints suchthattheEuclideanlengthofeachedgeisnomorethanagivenpositiveconstant

  7. SMT-MSP • SMT-MSPheuristic • Step1.ComputeaminimumspanningtreeT Step2.DivideeachedgeinTintosmallpiecesoflengthatmostRusingtheminimumnumberofSteinerpoints Step3.OutputthefinaltreeasTA • Worst-caseperformanceratioof4[2]

  8. Ratio3algorithmforSTP-MSP • 3-approximateAlgorithmforSTP-MSP • hasPerformanceratioatmost3 • hasO(n3)runningtime • Input:AsetPofnterminals,apositiveconstantR • Output:ASteinertreeTAinwhicheachedgehaslengthatmostR

  9. Ratio3algorithmforSTP-MSP • Ratio3algorithm

  10. 2.5-approximatealgorithmforSTP-MSP • 2.5-approximateAlgorithm • isarandomizedalgorithmwithPerformanceratioatmost2.5 • ASteinertreefornterminalsisak-restrictedSteinertreeifeachfullcomponentspansatmostkterminals • H3(V,F,W):aweighted3-hypergraph,where • V=P • F={(a,b)|a∈Vandb∈V} ∪{(a,b,c)|a∈V,b∈Vandc∈V} • w(e)=thesmallestnumberofSteinerpointstoformanoptimalsolutionoftheSTP-MSPproblemontheterminalsine

  11. 2.5-approximatealgorithmforSTP-MSP

  12. Randomizedalgorithm[12]

  13. Conclusion • ComputerelaysensorstomaintainglobalconnectivityinWSNswhentransmissionrangeofallsensorsarerestricted • Futurework • istheoptimalrelaysensorplacementfork-connectivity,wherek>1,toimprovefaulttoleranceinsensornetworks • isarelaysensorplacementwiththedesigntradeoffbetweentransmitpowerpersensorandthenumberofsensorsinthenetworkfortopologycontrol

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