In-vehicle networking today and tomorrow

It has always been a particular strength of MOST to not shoot for the highest bitrates technically possible, but rather find the appropriate 'sweet spot', as discussed previously. Instead, the development of new functions and features, speed grades and physical layers has always been driven by the MOST Cooperation, collecting the real market requirements of a broad community. In fig.3 the driving functions for Most25, Most150 and also the future generation are shown.

The absolute speed grade for the future generation of MOST is not entirely determined yet. The same applied for MOST150 at the time: It was clear that a bandwidth of more than 100 Mbit/s would be required, but the exact bandwidth was determined by other parameters, e.g. the strong requirement of keeping the POF and the connector system identical to MOST25.

Technically, the feasibility of implementing a speed grade in the range of 5-10 Gbit/s for a next generation has been investigated already. As discussed previously, the even more interesting question is: What does the automotive market really need? Why would people like to transport data at such high speed and which data shall be transported at all?

And, even more importantly, what is the appropriate physical medium and what is the overall system cost, including an automotive grade Network Interface Controller, physical medium and connector system? Solutions are being developed for POF, PCS and Coax Physical Layer, with each offering certain advantages but also trade-offs. For instance, staying with POF and boosting up the bandwidth to the 1 Gbit/s range by smart modulation techniques may be a very interesting option, allowing to keep the advantage of handling a very well known optical cable and connection system, taking full advantage of the MOST150 volumes in the market.

Another question is, what will be the appropriate time line to introduce a next generation to the market, given the fact that MOST150 is just about to be launched in production this year? Some boundary conditions are crystal clear already:

One fact is that the bit rate will be beyond 1Gbit/s. Both the optical and electrical physical layer will be available, and most importantly, MOST will stay a synchronous network providing a payload efficiency of nearly 100%, with the ability to seamlessly transport IP packet data.

In order to serve the Driver Assist market, relevant parameters will be considered to fulfill the functional safety requirements according to ISO26262. Other open items, such as appropriate interfaces to the application processor and of course overall system cost are being considered before the product and system concept can be finalized.