Location Based Sleep Scheduling for Target Tracking Applications in Smart Space Environments

This paper describes LocMAC, a new location aware power saving MAC layer for target tracking applications in smart space environments. Target tracking applications focus on providing proximity based local services to mobile users within a fixed deployment of wireless nodes. Conventional wireless sensor MAC layers increase the lifespans of battery powered wireless nodes by scheduling sleep periods for the entire network, which are either of fixed length, or vary based upon current network metrics. LocMAC bases its sleep schedule on the relative physical location of network nodes and allows target tracking service to be guaranteed. It propagates user location updates, and uses this knowledge to perform ´location based sleep scheduling´ (LBSS). LBSS describes the use of wireless node and network target positions to maximise the potential sleep periods. Adding knowledge of user mobility allows those nodes which will not be required by the network application to sleep for longer periods of time, waking up just in time to service network user requirements. The paper describes the operation of LocMAC and compares its performance against existing sleep scheduling MAC protocols through analysis and simulations of typical application scenarios. The results show that LocMAC performs significantly better for target tracking applications and is particularly appropriate for use in future Smart Spaces.