What is k-Coverage

In this chapter, we study duty-cycling to achieve both k-coverage and connectivity in highly dense deployed wireless sensor networks, where each location in a convex sensor field (or simply field) is covered by at least k active sensors while maintaining connectivity between all active sensors. Indeed, the limited battery power of the sensors and the difficulty of replacing and/or recharging batteries on the sensors in hostile environments require that the sensors be deployed with high density in order to extend the network lifetime. Also, the sensed data originated from source sensors (or simply sources) should be able to reach a central gathering node, called the sink, for further analysis and processing. Thus, network connectivity should be guaranteed so sources can be connected to the sink via multiple communication paths. Finally, wireless sensor networks suffer from scarce energy resources. A more practical deployment strategy requires that all the sensors be duty-cycled to save energy. With duty-cycling, sensors can be turned on or off according to some scheduling protocol, thus reducing the number of active sensors required for k-coverage and helping all sensors deplete their energy as slowly and uniformly as possible. We also extend our discussion to connected k-coverage with mobile sensors as well as connected k-coverage in a three-dimensional deployment area. Furthermore, we discuss the applicability of our protocols to heterogeneous wireless sensor networks.