In recent years, an increasing number of applications appeared that demand the fusion of information from multiple locations. These are typically such sensor networks, which are spatially distributed, and act according to the available information. In many cases, these systems have real-time requirements to comply with, which makes it essential to know precisely the timing and causality relations.
In wireless networks firstly the IEEE~1588 standard has been developed for the Ethernet, which helps us to synchronise the clocks of the devices with accuracy under microseconds. Nevertheless the building of the wireless infrastructure is not always possible or remunerative, for this reason wireless time synchronization procedures became very important. In case of sensor networks the wireless communication is usually desirable, moreover for the large occuring distances there is a demand for the long-range but low power solutions. The
wireless networks present time synchronisation protocols for a multifarious challenges. One problem that many devices have to send a message through a single channel, so the choice of the communication protocol is not trivial.