TOWARDS A HYBRID MQTT-COAP PROTOCOL FOR DATA COMMUNICATIONS IN WIRELESS SENSOR NETWORKS

Abstract

Wireless Sensor Networks (WSNs) consist of sensor nodes and gateways which are resource constrained devices. Lightweight communication protocols for WSNs are emerging for Machine to Machine (M2M) communications and thusthere isalways going to bea possible conflict ofinterest onwhich protocol isbest suited for any particular application. The architecture of these emerging protocols is mainly categorized into the publish-subscribe architecture and the request-response architecture. Although there are other protocols for data communication in WSNs, the two protocols of interest inthis study are the Message Queuing Telemetry Transport (MQTT) protocol based onthe publish-subscribe architecture and the Constrained Application protocol (CoAP) based onthe request- response architecture. Studies have shown that the performance of these different protocols are dependent on different network conditions and they have complimentary advantages and disadvantages. MQTT messages experience lower delays than CoAP for lower packet loss and higher delays than CoAP for higher packet loss. MQTT is also considered very scalable since message subscribers do not need to know about the publishers and vice-versa as opposed to CoAP where the client has to explicitly know the server address to be able to make requests. In this paper we propose a hybrid MQTT-CoAP protocol technique for data communication in wireless sensor networks that harnesses the advantages of both MQTT and CoAP protocol.