Real-time air pollution monitoring systems using wireless sensor networks connected in a cloud-computing, wrapped up web services

Air pollution continues to grow at an alarming rate, decreasing the quality of life around the world. As part of preventive measures, this paper presents the design and implementation of a secure and low-cost real-time air pollution monitoring system. In such sense, a three-layer architecture system was implemented. The first layer contains sensors connected to an Arduino platform towards the data processing node (Raspberry’s Pi), which through a wireless network sends messages, using the Message Queuing Telemetry Transport (MQTT) protocol. As a failback method, strings are stored within the data processing nodes within flat files, and sent via SSH File Transfer Protocol (SFTP) as a restore operation in case the MQTT message protocol fails. The application layer consists of a server published in the cloud infrastructure having an MQTT Broker service, which performs the gateway functions of the messages sent from the sensor layer. Information is then published within a control panel using the NODE-RED service, which allowed to draw communication flows and the use of the received information and its posterior storage in a No SQL database named “MongoDB”. Furthermore, a RESTFUL WEB service was shared in order to transmit the information for a posterior analysis. The client layer can be accessed from a Web browser, a PC or smartphone. The results demonstrate that the proposed message architecture is able to translate JSON strings sent by the Arduino-based sensor Nodes and the Raspberry Pi gateway node, information about several types of air contaminants have been effectively visualized using web services.