Interoperability among Sub-GHz Technologies for Metallic Assets Tracking and Monitoring

This paper focuses on a prototype of an Internet of Things (IoT) system for the tracking and monitoring of intermodal containers throughout their whole shipment which may include heterogeneous methods (e.g., road transport and sea transport). The system accounts for a couple of devices for each container. The former is a sensor node placed on the inner surface of the container and it is in charge of monitoring the state of the shipped goods by sampling endo-container environmental parameters (i.e., temperature, moisture and air pressure). Such measurements are wirelessly sent outside the container by exploiting the Amplitude Shift Keying (ASK) modulation over a 433 MHz carrier. The other device is mounted on the outer surface of the container just above the inside one. This receives the data broadcast from the sensor node and forwards such information to a cloud service by making use of Sigfox technology. In so doing, a twofold scope is achieved: remote monitoring of goods since each Sigfox packet carries the aforementioned air related parameters and tracking of the containers. Indeed, Sigfox gateways also collect metadata of the received packets (e.g., timestamp, Received Signal Strength Indicator (RSSI)) on which trilateration algorithms and probabilistic calculations are applied by Sigfox cloud. Tests results proved the system capability of integrating different Sub-GHz technologies within the same application along with its effectiveness in retrieving any sort of measured data from sealed containers or from analogous metallic assets.