Reliable relay node placement in wireless sensor network

To enhance the structure of networks, some costly but more powerful relay nodes are usually placed in wireless sensor networks. These nodes can prolong network lifetime and preserve connectivity of networks. So it makes sense to place relay nodes to guarantee the connectivity and reliability of wireless sensor networks. In this paper, we focus on the reliable relay node placement problem. We take set-cover based iterative actions to deal with the problem of placing minimum number of relay nodes to achieve connectivity and reliability, and then propose algorithms for two typical networks: single-tiered network and two-tiered network, respectively. We prove that the performance ratio of our algorithm for single-tiered network is no worse than (1+[(radic2D-2r)/2R])(lnn-lnlnn+thetas(1)), and performance ratio of our algorithm is no worse than (1+[radic2D/2R])(lnn-lnlnn+thetas(1)) for two-tiered network, where n is the number of initial sensor nodes, D is the size of the square sensing field, constants R > r > 0 are the communication radius of relay node and sensor node. At last, we carry out some experiments to show the nicer performance of our algorithm.