Preserving coverage for wireless sensor networks of nodes with various sensing ranges

In wireless sensor networks (WSN), preserving sensing coverage with energy constraint is a basic issue drawing increasing attentions. However, most of the existing methods require global time synchronization with significant costs in energy consumption etc, or uniform sensing ranges of all nodes, which may have limitations in applications. In this paper, we develop a state switching scheme without global time synchronization. Based on the scheme, a grid based coverage preserving protocol (GBCPP) is proposed for the sensor nodes with different sensing ranges. Simulation and testing results in comparisons with the existing coverage preserving protocols show that the GBCPP scheme outperforms the other existing methods.