MQTT for IoT-based Applications in Smart Cities

Abstract

This research presents a study on the use of the MQTT communications protocol for the Internet of Things in Smart City applications. A network model is proposed and a typical practical scenario is developed based on MQTT protocol, that cope with the requirements of some Smart City applications, mainly those which use event-based messages. Many market-available embedded electronic systems were employed for this scenario including the inexpensive Wi-Fi platform ESP8266, Arduino, Raspberry, in addition to some sensors and actuators. The network model is chosen based on the TCP/IP model, and the application layer is totally depending on the MQTT protocol that employs JavaScript Object Notation (JSON) to solve the problem of interoperability. To evaluate the protocol for small-to-medium, IoT-based, business applications of Smart Cities, some available free Open Source Software (OSS) of MQTT servers and clients were compared and tested against latency over the cloud. The protocol shows good results for cloud-based, small-to-medium business applications that depend on event-based message-oriented communication paradigms. Since the protocol defines three levels of quality of service (QoS), the simulations and the tests were conducted for QoS type zero (QoS0) to get the best results.