WSN–IoT-Based Mobile Environmental Monitoring System for Smart Cities

In smart cities, reliable environmental information is essential for decision-making. Environmental monitoring using fixed stations presents limitations in spatial coverage. This work presents an environmental monitoring system for precipitation, PM2.5, PM10, CO2, global irradiance, temperature, barometric pressure, and wind speed, based on an Edge, Fog, and Cloud architecture. The system consists of a mobile sensor node that integrates the sensors and performs spatially resolved measurements, and a fixed sink node that forwards the data to an IoT broker and a database. In addition, a web application was developed for MQTT message visualization, geospatial queries, and measurement download. The nodes were developed using an iterative and incremental methodology based on agile principles, pragmatic programming, and a Bottom-Up strategy. The nodes incorporate spatial segmentation, intermediate storage, automatic retransmission, integrity verification, and flow control mechanisms. Laboratory and real-world tests confirmed TRL 6. Metrological performance evaluation using independent validation showed reduced RMSE for four of six variables, with the greatest improvement for PM2.5. CO2 measurements had a coefficient of variation below 1.3%, and the rain gauge a previously determined relative error of 8.5%. These results demonstrate the feasibility of the system for extending the spatial coverage of urban environmental monitoring through mobile sensing.