Multi-Hop Real-Time Communication over Switched Ethernet Technology

Sammanfattning: Switched Ethernet technology has been introduced to be exploited in real-time communication systems due to its features such as its high throughput and wide availability, hence being a cost-effective solution. Many real-time switched Ethernet protocols have been developed, preserving the profits of traditional Ethernet technology, to overcome the limitations imposed by using commercially available (COTS) switches. These limitations mainly originate from the non-deterministic behavior of the Ethernet switches inherent in the use of FIFO queues and a limited number of priority levels. In our research we focus on two particular real-time communication technologies, one based on COTS Ethernet switches named the FTT-SE architecture and the other using a modified Ethernet switch called the HaRTES architecture. Both architectures are based on a master-slave technique supporting different and temporally isolated traffic types including real-time periodic, real-time sporadic and non-real-time traffic. Also, they provide mechanisms implementing adaptivity as a response to the requirements imposed by dynamic real-time applications. Nevertheless, the two mentioned architectures were originally developed for a simple network consisting of a single switch, and they were lacking support for multi-hop communication. In industrial applications, multi-hop communication is essential as the networks comprise a high number of nodes, that is far beyond the capability of a single switch. In this thesis, we study the challenges of building multi-hop communication using the FTT-SE and the HaRTES architectures. We propose different architectures to provide multi-hop communication while preserving the key characteristics of the single-switch architecture such as timeliness guarantee, resource efficiency, adaptivity and dynamicity. We develop a response time analysis for each proposed architecture and we compare them to assess their corresponding benefits and limitations. Further, we develop a simulation tool to evaluate the solutions.