Title: Location Service In Wireless Sensor-Actuator Networks

Abstract

Wireless Sensor-Actuator Networks (WSAN), where there are several resource-rich and potentially mobile actuators in addition to the static sensors, is a variant of Wireless Sensor Networks. Due to the limited power supply of sensors, energy conservation is always the prime objective of any protocols designed for WSAN. To save sensors' energy, sensors are organized with periodic active and sleep activities. In addition, connected dominating set (CDS) is constructed among the active sensors to further reduce the number of the sensors.

In WSAN, sensors need to report their sensing data to the actuators regularly. At the beginning, by limited flooding, every sensor can know the position of the nearest actuator. The problem addressed here is how to report the new positions of the actuators to sensors from CDS with minimal total number of messages so that routing to the actuators still has good hop count? Quorum-based location update scheme is a good candidate to solve the problem, where actuators report their new positions to their CDS neighbors whenever a link is broken or created; after certain number of such link changes, actuators forward their new positions to all nodes located in its ‘column’, that is, to the north and south of their current location with certain 'thickness' of reporting. In the meanwhile, after receiving the update message, sensors in CDS check whether the forwarding neighbor from CDS, for selected routing, for old position and new position of the actuator is the same or different. If it is different, and if this actuator is still the closest one (in terms of known hop count distance), then retransmit its new position. Receiving sensors from CDS will do the same.