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MOST Network and System

MOST and AVB: Two Candidates for Infotainment Networks

25. April 2013, 16:30 Uhr | Günter Dannhäuser, Dr. Walter Franz und Prof. Dr. Wolfgang Rosenstiel

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Fortsetzung des Artikels von Teil 2

Differences between both technologies

Both technologies are essentially independent of baseband physical layers. MOST150 INIC interconnects the FOT using LVDS interfaces, whereas Ethernet MACs connect to Ethernet PHY units with Media Independent Interface variants. Otherwise, choice of a physical layer, whether on optical media, electrical over twisted pairs or coax, is to a large extent independent of the approach taken on the data link layer.

Whereas MOST has been designed and developed for automotive use and automotive qualification, for AVB a lot of experience needs to be gained regarding automotive use of the standards and realisation of automotive requirements. This ranges from the API level to service discovery and control mechanisms, wake-up strategies and times to power consumption, just to name a few. AVB generation 2, which is being standardised now, will address some crucial issues, including the handling of high frequency/low volume data such as sensor data and further minimization of latency by preemption of packets [8–10]. AVB standards were written to flexibly support comparatively dynamic networks and to provide interoperability between brands of different manufacturers. The in-car situation is a lot more static, with plenty of opportunities to keep oversizing, redundancy, start-up times and thus power consumption and costs down. Pre-configuration for the startup phase and beginning to reduce complexity right at design time are examples for that. A strip-down of AVB protocols and techniques is imperative for automotive usage. Yet, an appropriate form of cooperation for standardisation of such a tailored AVB automotive profile needs to be found that fits into the landscape of the IEEE and other groups concerned.

Both MOSTnG and AVB can be considered technologically feasible concepts, sufficient to meet the demands of next generation infotainment networks. MOST has a big bonus in confidence and maturity and is better adapted for automotive use. Development of MOSTnG could further on be directly influenced and tailored via the MOST Cooperation, in line with OEM demands, quickly and pragmatically.

There is a great deal of work to do for automotive use of AVB. Although its standardisation enables flexible usage that results in a prolific supplier and market situation, the standardisation processes are challenging, with lots of voices from non-automotive interest groups in manifold international committees and working groups.

With these points in mind, at present it is very difficult to identify clear decisive factors on a technical level for one approach or the other. Regarding market size and heterogeneity on each side, especially in the long term, AVB is an option that needs to be seriously considered, at least. As for automotive usage, primarily in the infotainment domain, AVB needs to be evaluated and its performance needs to be compared to the MOST system.