Connected Sensor Cover Self-Organization of Sensor Networks for Efficient Query Execution(6)

1.R Q?(S i1∪S i2∪...S i m)

2.the subgraph induced by M in CG is connected,where

CG is the communication graph of the sensor network.

In other words,any sensor I i

j

in the connected sensor cover can communicate with any other sensor I i

k

in the cover,possibly through other sensors in the selected set M.

A set of sensors that satis?es only the?rst condition is called a sensor cover for Q in the network.2 Connected Sensor Coverage Problem:Given a sensor network and a query over the network,the connected sensor coverage problem is to?nd the smallest connected sensor cover.

The connected sensor coverage problem is NP-hard as the less general problem of covering points using line segments is known to be NP-hard[16].Constructing a minimum con-nected sensor cover for a query in a sensor network enables the query to be computed by involving a minimum num-ber of sensors without compromising on the accuracy of the query result.

2.3A Note on Sensing Regions

The sensing region associated with a sensor signi?es an area for which the sensor can take the full responsibility for sensing a given physical phenomenon within a desired con?-dence.The real semantics of a sensing region is application speci?c.For example,for target detection/tracking applica-tions,the sensing region is a region around the sensor within which the sensor can detect a target with a pre-determined minimum con?dence.In such applications,the sensing re-gion for a sensor could be modeled as a circular region of radius d around itself,where d is the distance beyond which a target cannot be detected within a given con?dence.In some other applications,sensing regions are de?ned in terms of the resolution of the application queries or the correlation of the sensed data.For example,consider an application

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