MQTT Protocol Extension for Real Time Location based Service

This paper introduces an extension of the MQTT protocol to reduce communication overhead in real-time location-based service system where mobile MQTT clients move and change their administrative district location frequently. The MQTT protocol was extended to handle UNSUBSCRIBE and SUBSCRIBE processing with a single step and the LBS server was revised to handle the extended protocol. Instead of directly processing SUBSCRIBE and UNSUBSCRIBE, mobile clients need to send their GPS location to the LBS server. LBS Server communicate with MQTT Broker to using extended protocol on behalf of each client. In an environment where large number of clients frequently move, the extended MQTT protocol can drastically reduce the number of messages between MQTT Broker and clients. This is mainly because clients do not need to issue SUBSCRIBE and UNSUBSCRIBE request to MQTT Broker. In addition, in contrast to our previous study where clients receive new administrative area name after sending its GPS location to LBS server, in this research, using extended MQTT protocol, mobile clients do not need to receive new administrative name even though they move across different district areas and as a result, the number of message exchanges can also be reduced. The LBS system applying the extended MQTT protocol can be used as a real-time location-based information service for large-scale mobile devices, such as real-time pedestrian population and vehicle traffic analysis, and location-based message delivery.