Scheduling at the Edge for Assisting Cloud Real-Time Systems

We study edge server support for multiple periodic real-time applications located in different clouds. The edge communicates both with sensor devices over wireless sensor networks and with applications over Internet type networks. The edge caches sensor data and can respond to multiple applications with different timing requirements to the data. The purpose of caching is to reduce the number of multiple direct accesses to the sensor since sensor communication is very energy expensive. However, the data will then age in the cache and eventually become stale for some application. A push update method and the concept of age of information is used to schedule data updates to the applications. An aging model for periodic updates is derived. We propose that the scheduling should take into account periodic sensor updates, the differences in the periodic application updates, the aging in the cache and communication variance. By numerical analysis we study the number of deadline misses for two different scheduling policies with respect to different periods.