IMPLEMENTING HOME GATEWAY USING THE COAP PROTOCOL

Abstract

This project aims at creating a home gateway / resource directory using the Constrained Application Protocol (CoAP) that would list as well provide various services to interact with the various sensors and actuators available in the household. CoAP is an alternative to Hypertext Transfer Protocol (HTTP) for interconnected objects, exploiting a binary data representation and a subset of HTTP methods (GET, PUT, POST, DELETE). It follows the Representational State Transfer (REST) paradigm for making data and resources accessible. CoAP uses User Datagram Protocol (UDP) for transport, as Transmission Control Protocol (TCP) is considered too resource-consuming. It is not feasible to interact with such constrained devices, since at a particular time these nodes may be in a sleeping state, be a part of disperse networks or networks with inefficient multicasting capability. Therefore in order to interact and observe multiple devices at a time it is required that a gateway be created which acts as a single point destination to which a client needs to connect and be able to communicate with the various smart devices in the household. The Resource Directory supports various services like register, maintain, lookup and remove resource description. Here we focus on implementing these interfaces using Java that could be used in Android platform. Also, to provide useful information from the data captured from the sensors using CoAP protocol we have enhanced the gateway with a SPARQL endpoint which offers a uniform interface to access resources and its observation data in the domestic network, as well as retrieve data using SPARQL queries. Additional services have been created which provide observation data based on the time and location criteria. In addition we have added the support of group management by which resources having a similar feature can create and join a group, as well as enable the client to interact with the group member resources by a single command. This has been achieved by creating a proxy resource on which the external client sends a request.