RESTful Web services in Wireless Sensor Networks

Premi Accenture al millor projecte de fi de carrera d’Enginyeria de Telecomunicació en Serveis Telemàtics (curs 2011-2012) English: Wireless Sensor Networks (WSNs) have become very popular in recent years. A WSN consists of distributed autonomous sensors to monitor physical or environmental conditions and to cooperatively send their data through the network to a main location. A WSN facilitates the creation of low-cost networks that can be used for multiple applications when the use of wires is impractical and expensive. Examples of these applications are home and building automation, asset management and logistics or health care automation. The main objective of this work is to investigate and propose a solution to enable Web services in WSNs. To accomplish this task, a research to choose the Web architectural style that fits best with WSNs has been done. Discussions show that the REST architectural style seems to be the one which is more suitable for WSNs. The next step is to choose an appropriate application layer protocol. In this sense, the CoAP protocol has been used to enable Web services in constrained networks. In this work, a CoAP implementation for the TinyOS operating system is proposed and developed. The most popular application protocol used in the Internet is HTTP. In order to integrate the proposed solution with the Internet, some translation between CoAP and HTTP is needed. In this work, a hardware and software proxy-based solution to connect CoAP resources with the actual Internet is proposed and developed. This solution also enables extra services that are interesting in WSNs. Finally, a performance evaluation is done in order evaluate the proposed implementation. Results show that using CoAP in constrained devices in WSNs improves the overall latency in comparison with using HTTP/1.0 in constrained nodes. A comparison between using a CoAP client to access CoAP resources and using a HTTP client using the proposed proxy solution has been done. Results show that using the proxy solution adds low extra latency, thus providing a good solution when using a CoAP client is not possible. Castellano: Las redes de sensores inalámbricas se han vuelto muy populares durante los últimos años. Están formadas por sensores autónomos que están distribuidos para monitorizar las condiciones físicas y ambientales y transferir de forma colaborativa sus datos a través de una red hasta un punto central. Estas redes facilitan la creación e implantación de redes