在無線傳感器網路(WSAN)中，當感測器(sensor)偵測到事件發生時，傳感器(actor)必須即時提供服務來處理事件。因此傳感器的佈建方式對於無線傳感器網路的效能有非常大的影響。在許多可能的情況下，傳感器會毀損，或是正忙於處理事件，因此無法繼續覆蓋原本的感測器，這時原本被傳感器覆蓋的感測器就無法即時將資料傳給傳感器。基於這個情況，我們需要將傳感器重新佈建。在這篇論文中，我們研究傳感器重新佈建的方法來達到最多感測器的覆蓋以及達到能減少最多沒被覆蓋感測器到最近有被覆蓋的感測器的距離。我們證明了這兩個問題的困難度都是NP-完全，並證明使用貪婪演算法來處理這兩個問題得到的答案與最佳解的比值都小於2。實驗也顯示出使用貪婪演算法可以達到夠好的效能，也佐證了我們的分析。

Inawirelesssensor-actornetwork,anactorusuallyhastoprovideservicesassoonastheactorreceivestheeventsignalsfromthesensors.Therefore,theperformanceofawirelesssensor-actornetworkdependsontheactordeployment.Inmanycircum-stances,actorsmayfailorgoouttodealwithevents,andthus,thesensorscoveredbythemissingactorscouldbeunreachableintime.Thisintroducesthenecessityofactorredeployment.Inthispaper,westudytheproblemsofredeployingactorstomaximizethenumberofsensorsabletobecoveredbyactorsandtomaximizethedecreaseoftheresidualdistancesofsensors,respectively.BothproblemsareshowntobeNP-complete.Additionally,weprovethatthegreedyalgorithmforeachprob-lemhasanapproximationratioof2.Simulationsshowthatthegreedyalgorithmforeachproblemperformswell.Keywords:wirelesssensor-actornetwork,coverage

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