Comparison of two lightweight protocols for smartphone-based sensing

Smartphones are equipped with numerous sensors and have become sophisticated sensing platforms. However, several sensing applications running on a smartphone can degrade the device performance. This can be overcome by using lightweight application protocols which improve the smartphone performance in terms of bandwidth consumption, battery lifetime and communication latency. This work focuses on two emerging application protocols: the Message Queuing Telemetry Transport (MQTT) and the Constrained Application Protocol (CoAP). Although both protocols have been designed for highly constrained environments such as sensors, they are also appropriate to be adopted in smartphone applications. We provide a qualitative and quantitative comparison between MQTT and CoAP when used as smartphone application protocols and we give preliminary indications on the application scenarios in which either protocol should be adopted. While MQTT has already been adopted in smartphone applications, CoAP is relatively new and has up to now mainly been considered for sensors and actuators. Our comparison shows that CoAP can be a valid alternative to MQTT for certain application scenarios.