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MOST and Ethernet

John Day

John Day

Posted Nov 7, 2012

It might seem as if it’s taken MOST (Media Oriented Systems Transport), the automotive multimedia and infotainment standard, a long time to catch on, and there are some who suggest that it’s time has already passed, now that Ethernet is the Next Big Thing in automotive networking. But that’s relative if not downright wrong, according to Henry Muyshondt, Technical Liaison of the MOST Cooperation.

The MOST Cooperation, which is responsible for refining and standardizing the technology, includes 16 automakers and 65 suppliers. German automakers pioneered the technology, and the Volkswagen Group now plans to deploy MOST across all of its brands, but Muyshondt says MOST is becoming ubiquitous, currently deployed in more than 120 vehicle models. Toyota, Hyundai, Kia, and GM are among its supporters. Toyota was instrumental in developing the MOST50 (50 megabits/second) electrical physical layer, and GM is using MOST in the Cadillac ATS and XTS. “MOST is growing steadily, and relatively fast,” Muyshondt says, adding that hundreds of millions of MOST nodes are on the road, ranging from two or three in lower-end vehicles and 15 or more in luxury cars.

As cars gain more electronics content an efficient, cost-effective network becomes increasingly important for tying all of the vehicle’s electronic functions and devices together and MOST was designed from the ground up for just that purpose. It uses bandwidth efficiently and has low processing overhead.

The latest generation of MOST, MOST150 (150 megabits/second) , includes a dedicated Ethernet channel that operates like an IEEE 802.x network to support connected services and general Internet access.

Muyshondt notes that Internet protocol is in widespread use and says there are times when it’s beneficial for use in cars, but he adds, “It has no guaranteed form of delivery, isn’t deterministic, and is not acceptable for control applications. And latency can be high. That’s not a problem for email, or loading a web page, but for streaming audio or video – continuous flow between two points that are well-defined and in close proximity, it’s better to use a different mechanism.” Like MOST, which uses all of its bandwidth for data transfer. “Data just flows without addressing information in a defined timeframe, with short latency and high determinism.”

MOST Cooperation, MOST, MOST150, Cadillac XTS, Ethernet, Cadillac ATS, MOST50, IEEE 802.x, Toyota, Kia, GM, Volkswagen Group, Hyundai

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John DayJohn Day recently launched John Day’s Automotive Electronics News ( to provide news and feature coverage of the automotive electronics industry. Earlier he wrote for Auto Electronics magazine, Auto E-lectronics, EE Times, and other business and engineering publications. Visit John Day

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