http://intelematicstoday.com/2010/02/22/telematics-maybe-the-business-case-isnt-the-problem/

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It has been a while since we’ve run into each other at an automotive event. I remember when we first met before either MOST or 1394 were in any vehicle almost a decade ago. At the time, 1394 was already an established consumer technology. Since then, MOST has been adopted in over 73 vehicle models with tens of millions of nodes on the road. It is included in the car models of most of the 16 car makers who are a part of the MOST Cooperation to develop this technology. In fact, every single vehicle factory outfitted with a high-speed digital multimedia network on the road today uses MOST. No longer just for high-end European luxury cars, MOST is rapidly making its way to mid-range vehicles with such key design wins as Toyota and Hyundai/Kia. Today, there is not a single car on the road that uses 1394 as a standard multimedia backbone. The car industry made its choice a long time ago.

I agree with your points about why a network is required. That is why the car industry decided to come together to develop MOST in the first place. The automotive industry has very unique requirements in terms of quality and reliability so it is not easy to just take a consumer grade chip and use it in a car. Most devices brought into the automotive market have to be specifically designed and built for that environment, which means even semiconductor suppliers of technologies like USB and Ethernet need to have special versions for the car industry. There is only one semiconductor company that I see actively promoting an automotive 1394 chip and it happens to implement video functions. There are others that provide consumer products, but few that are willing to take on the rigors of providing automotive grade components. You can’t just do some additional stress tests and say an IC is automotive grade. It takes a lot of effort to have parts with close to zero defects per million. You also have to commit to providing the same unchanged part for over a decade. Typical consumer products have their lifetime measured in months. There is a fallacy in thinking that because a semiconductor product is available in large volume for commercial applications the equivalent automotive version will be less expensive than another product designed specifically for the automotive market.

In terms of bandwidth, many of the original adopters of MOST have been so satisfied with the initial version that they are already moving to MOST150. The MOST Cooperation has been showing a system that includes 3 HD audio and video streams running concurrently with 18 (yes, 18) standard definition streams in parallel with an Ethernet connection, all over a single plastic optical fiber link. MOST has also been shown carrying Blu-ray content. Compressed material read directly from a Blu-ray disc has a maximum data rate of around 48 Mbps so you don’t need gigabits of bandwidth to deal with it. With intelligent codecs you can reduce the bandwidth even further. MOST was the first network technology to be approved by the DVD Content Control Association (DVD-CCA) to transport DVD content protected with DTCP. Back in 2003 the DVD-CCA even created a special automotive environment to address the needs of the automotive industry.

A lot is said about raw network bandwidth numbers. In reality, there is a balance between the cost of the physical layer needed to transport higher bandwidth and the cost of compressing/decompressing data to reduce the required bandwidth. Car makers have made these trade-offs and they are developing MOST to keep pace with their real requirements, rather than just going for the maximum possible bit rate. A couple of years ago, at the Automotive LAN Seminar in Tokyo there was a presentation about 1394 cabling. I believe that was the last time I saw you. The cable had 9 conductors in it, including 3 or so that were associated with shielding to control EMI issues. MOST uses a single strand of plastic fiber or a single twisted pair wire (with or without shielding) for the same connection. Silicon is becoming cheaper and cheaper. With the proliferation of video codecs in many different consumer devices the price of technology has come down so much, that even adding an extra chip to a system may be cheaper than having to add all the components required to control the issues that arise as you try to transmit high speed data over long distances.

MOST supports synchronous, isochronous and asynchronous data transmission. MOST150 also has a dedicated Ethernet channel that presents itself as a standard Ethernet MAC so data applications can use it with little change. It provides an automotive-grade Ethernet infrastructure that uses the same link as the MOST system, further reducing system costs. I do agree with you that Ethernet is not optimized for continuous A/V streaming, but it is still a useful interface to attach to the data infrastructure at service bays and other services from outside the vehicle.

In terms of backward compatibility, MOST150 uses the same wiring harness of MOST25. No changes in the connectors or plastic optical fiber are required to run at the higher data rate. In addition, the Intelligent Network Interface Controller (INIC) architecture separates the physical layer from the software layers so that little effort is needed to move from one speed grade to another. INIC’s provide the same logical interface to the network to the different speed grades. Several automotive microcontroller suppliers, such as TI, Renesas, NEC and others, are even building a new high-speed serial inter-IC interface called MediaLB that was pioneered by these INICs. It was necessary to find a way to efficiently get the video data in and out of the network interface at high speed but without using an excessive number of pins that would make board design cumbersome.

MOST is the de-facto standard for high bandwidth automotive multimedia networking. There is not really a competition between MOST and 1394 anymore. Even Ethernet is getting more attention at car makers than 1394 is though it is not designed to efficiently carry streaming data, as you point out in your article.

I hope to run into you again soon so we can have more conversations about this topic – maybe in Hawaii!

Aloha,
Henry Muyshondt