Smart Decision Fog Computing Layer in Energy-Efficient Multi-hop Temperature Monitoring System using Wireless Sensor Network

Smart decision layer, as Fog Computing layer in WSN is presented and discussed. Working WSN sleep state mode analysis is presented in multi-hop temperature monitoring system using wireless sensor network in environmental monitoring scenario. The monitoring system consists of wireless sensor nodes, called motes. In laboratory experiment are used SunSPOT motes, invented by Sun Microsystems, now manufactured by Oracle. Temperature analyzing application is presented, forwarding measured data in a multi-hop way to the network host. Desktop computer plays here a role of temperature measurements database. Link-Quality Routing Protocol (LQRP) is used, which is based on Ad-hoc On-Demand Distance Vector (AODV), which is reactive routing protocol. All gathered measurements, all data are sent to the base-station node, which is a special WSN node, directly connected via USB to the computer. Experiments were conducted taking into consideration especially SunSPOTs’ processor board parameters sleep state modes. Their processor board is turned into different sleep modes for different periods of time. A comparison of sleep mode time periods in total time of running an application is discussed. Periods of sleep states are different depending on how long is turned on the utility thread sleep. The experiment’s results show, that there is a need to build smart decision layer as fog computing layer for WSN. It should be done in order to manage in a better way environmental monitoring with usage of different kind of sensors, especially to better manage transferring big portions of data from sensors to the Cloud data storage. Sensors, which build WSN, should be distributed over specific areas, as well as fog computing devices should be able to communicate with sensors in order to transfer only relevant data to the Cloud.