Hierarchical concept for IP-based resilient communication in building automation

In building automation, IP-based communication is commonly used. However, availability and reliability recently gained importance in this domain since even safety critical applications (e.g., fire alarm systems) are integrated in building automation networks. Usually, IP-based communication systems, as they are used in functional buildings, do not provide redundancy mechanisms. However, redundancy and deterministic behavior is crucial for a reliable communication system. For different reasons, building automation networks facilitate standard network technologies and components. Nevertheless, such networks are required to be flexible and scalable ranging from small buildings up to areas of buildings by additionally being efficient regarding communication overhead. This paper presents a new hierarchical system concept which provides a homogeneous communication infrastructure to the automation devices. The concept is based on physical Ethernet-ring topologies which represent the bottom level. However, the design and selection of such protocols is out of scope. The rings are connected by a special kind of Router in a redundant way which represents the next level. To establish a connection between dislocated network segments, a reliable backbone communication mechanism is introduced, that can be seen as top level of the hierarchy. In contrast to other technologies, this concept can be statically configured and does not need dynamic reconfiguration in case of a fault. It tolerates one single fault per ring and provides deterministic and local fault handling. The concept is theoretically analyzed; a proof-of-concept shows the feasibility.