An Energy Efficient Middleware Architecture for Processing Spatial Alarms on Mobile Clients

Time based alarms are used by many on a daily basis. Spatial alarms extend the very same idea to location based triggers, which are fired whenever a mobile user enters the spatial region of the location alarms. Spatial alarms provide critical capabilities for many mobile location based applications ranging from personal assistants, inventory tracking to industrial safety warning systems. In this paper we present a middleware architecture for energy efficient processing of spatial alarms on mobile clients, while maintaining low computation and storage costs. Our approach to spatial alarms provides two systematic methods for minimizing energy consumption on mobile clients. First, we introduce the concept of safe distance to reduce the number of unnecessary mobile client wakeups for spatial alarm evaluation, enabling mobile clients to sleep for longer intervals of time in the presence of active spatial alarms. We show that our safe distance techniques can significantly minimize the energy consumption on mobile clients compared to periodic wakeups while preserving the accuracy and timeliness of spatial alarms. Second, we develop a suite of techniques for minimizing the number of location triggers to be checked for spatial alarm evaluation upon each wakeup. This further reduces the computation cost and energy expenditure on mobile clients. We evaluate the scalability and energy-efficiency of our approach using a road network simulator. Our spatial alarms middleware architecture offers significant improvements on battery lifetime of mobile clients, while maintaining high quality of spatial alarm services, especially compared to the conventional approach of periodic wakeup and checking all alarms upon wakeup.