Relay node placement techniques in wireless sensor networks

Relay node placement is one of the critical need of wireless sensor networks when connectivity, lifetime, fault tolerance like factors are desired in the network. In this study, we review the present relay node placement techniques and provide an overall view of this study by summarizing previous achievements. We categorize the placement strategies into four broad categories, namely, approximation, algorithms, heuristics, meta-heuristics based techniques. A taxonomy is presented to enlist the present techniques. The paper also emphasizes on the research challenges and gives an idea of potential future scope in this research domain.