Semantic data exchange between collaborative robots in fog environment: Can CoAP be a choice?

The transition of Internet from human-centric exchanges to the Internet of Things has posed several interesting challenges regarding the communication model and data exchange pattern. The emergence of edge/fog computing as a compute model has further highlighted the need of a uniform model to cater to the inherent heterogeneity of participating devices. In several domains, the devices may range from standard compute and communication devices to gateways/switches, as well as robots/drones and other types of autonomous entities. In scenarios like disaster management, warehouse automation, surveillance etc. use of robots/drones/AGVs/UAVs is steadily increasing in order to minimise potentially hazardous human intervention. Optimality of data exchange and further processing is a desired feature in such scenarios, especially in outdoor disaster situations where availability of the back-end cloud infrastructure can not be guaranteed. In this paper, we demonstrate a real life robotic data exchange model based on Resource Description Framework (RDF). We further perform a comparative analysis of network performance between TCP in Robot Operating System (ROS) and block-wise extension to Constrained Application Layer Protocol (CoAP) for bidirectional exchange of such RDF data in a disaster situation where robotic entities accomplish search and rescue missions in collaboration with fog devices. The causal analysis presented in this paper puts a stepping stone for potential future enhancement of CoAP.