Investigations on packet delay variations over the wireless channel

The increasing presence of wireless communication in factories has encouraged the introduction of novel applications on the factory floor. Highly accurate clock synchronization of wireless devices is necessary for timely communication between these devices and in some cases such as time-based localization, a major pre-requisite. One critical factor affecting synchronization performance is propagation delay variations suffered by a packet when it moves from its source to the destination. In this preliminary study, a set of measurements have been carried out to find out the extent of these variations. A highly accurate timestamping unit is used to detect the departure and arrival of a packet on the wireless channel, as the timestamping unit undergoes relative motion in an office environment. The results indicate that propagation delay variations are less affected by mobility than by reflections of signals from surrounding surfaces and objects. Future work will investigate whether the above observation is correct by employing higher speed mobility.