Improved time synchronization in ML-MAC for WSN using relay nodes

Time synchronization among nodes is an essential requirement in many wireless sensor network (WSN) applications. In unsynchronized network the local time in the subnet varies due to clock drift resulting in skew in the network that causes more energy consumption, packet loss and message delay. For synchronization of network we have deployed relay nodes (RNs) in a set of candidate locations in the network to satisfy specific requirements, such as connectivity, coverage.We validate the effectiveness of our relay nodes placement strategy through numerical results to show that the RNs placed by our algorithms harvest more energy on average than those placed by the algorithms unaware of energy harvesting. Simulation results show that improved time synchronized multi-layer MAC (ML-MAC) using relay nodes outperforms the existing unsynchronized as well as ML-MAC scheme for network lifetime, packets dropped, reduced message delay and improving the synchronization accuracy at individual nodes.