Using RELOAD and CoAP for wide area sensor and actuator networking

In this article, we propose a new architecture for wide area sensor and actuator networking. The architecture is based on combining two protocols being standardized by the Internet Engineering Task Force, REsource LOcation And Discovery (RELOAD) and Constrained Application Protocol (CoAP). To integrate CoAP and RELOAD, we introduce a CoAP application usage for RELOAD. The architecture provides a decentralized peer-to-peer rendezvous service for CoAP nodes in Wireless Sensor Networks (WSNs). Our architecture also enables a peer-to-peer federation of geographically distributed WSNs. This is supported by proxy nodes that are part of the WSN but also connect to a RELOAD overlay network via cellular Internet access. Due to the use of RELOAD, the system does not need to rely on centralized services such as DNS service discovery (DNS-SD) or central resource directories to discover sensors and resources. Other features of the architecture include integration to web, self-organization, scalability, and robustness. We evaluate the proposed architecture through simulations and real-life measurements, and compare its performance to a traditional client/server architecture.