Efficient group communication based on Web services for reliable control in wireless automation

The ongoing demand for more energy efficiency within commercial buildings and homes is a driving motivation for using IT and IP technologies within underlying building automation systems (BAS). Building data and access to automation systems should be made available within internal and external IT systems enabling visionary cloud computing based interaction scenarios. Web services and service-oriented architectures are a promising approach to provide such a communication infrastructure. Communication protocols like CoAP and EXI enable Web service communication on embedded devices but are currently limited to a client-server interaction model with unicast based message exchange. Several existing building automation systems use a group communication approach to exchange process data, which allows to create basic control scenarios without the need of a central control unit. This group communication model for process data is strongly tied to the application layer services and information models of the according BAS. This paper presents a group communication model for CoAP and EXI based Web services, contributes further details on the implementation and provides an evaluation compared to client-server based interaction scenarios.