QoS and robustness of priority-based MAC protocols for the in-car power line communication

Communication demands of electronic devices are rising in almost every area of life including modern vehicles. In the past, growing in-car communication demands were countered with an increasing number of deployed bus systems, thus increasing complexity and weight of the wiring harness. A promising technology to counteract these effects is Power Line Communication (PLC). With PLC the cabling is reduced to the minimum as existing power lines are used for communication. Besides the physical layer, the Medium Access Control (MAC) layer has to meet automotive requirements, too. As a result of our previous research, a priority-based MAC for in-car PLC is considered most promising. Unique message IDs are used as priorities, thus collisions are avoided. The priority ordering is crucial for guaranteeing worst case response times for functions and applications with strict Quality of Service (QoS) requirements. In this paper, a worst case response time calculation for the analysis of our priority-based PLC MAC protocol is given. The analysis builds upon available Controller Area Network (CAN) schedulability analyses. In addition, we introduce a new definition of robustness and provide an extended algorithm determining the priority ordering with highest robustness. The reservation and assignment of priorities is discussed, having flexibility for future changes in the traffic mix in mind.