The weighted average based clock synchronisation protocols for wireless sensor networks (WSNs), viz., energy efficient and fault-tolerant clock synchronisation (EFCS) protocol, weighted average based internal clock synchronisation (WICS) protocol, and weighted average based external clock synchronisation (WECS) protocol, have several fault-tolerant properties including automatic interchangeability among these protocols, but a major problem with these protocols is that their synchronisation accuracy is not very high. In this paper, we propose a generic technique to improve the synchronisation accuracy in these three protocols. We also give a proof that the synchronisation error in the EFCS protocol is bounded. The improved protocols also make use of estimated drift rate to provide an accurate reading of time at any instant, and the logical time provided by these protocols is monotonic. The simulation and experimental studies clearly show that the average synchronisation error in the improved protocols is much less than that in the original protocols
