Sensitivity Analysis on Flexray Dynamic Segment Design Parameters

The Flexray protocol is rapidly emerging as the next generation in-vehicle communication protocol that will accommodate safety critical, high bandwidth and real time requirements coming from the burgeoning increase of automotive electronic content. The Flexray protocol provides a globally synchronized time base and has provisions for a Time Division Multiple Access (TDMA) based transmit model (static segment) and a priority based transmit model (dynamic segment). The challenging aspect about Flexray is leveraging its degree of flexibility. Just configuring the dynamic segment alone involves ten protocol level parameters, each of which has significant affect on various key performance metrics such as the message transmission latency, number of message overwrites and bus utilization. This paper presents results from sensitivity analysis for these key parameters relative to the various performance metrics. The results seem to indicate that the assumed notion of message priority as being the main driver that affects transmission latency is far from accurate. Also, the results clearly indicate that one of the in-built protocol constraints has a major detrimental effect on the performance metrics. This paper proposes the removal of this constraint and indicates the degree of performance improvement that can be achieved without the constraint. Finally, a brief discussion on the conclusions of this study and future work will be provided.