In-vehicle networking today and tomorrow

A major strength of the MOST technology consists of carefully balancing technological possibilities, real market requirements and economic considerations. From that perspective, it is extremely important to show a clear cost-down roadmap parallel to technological advancements. Several different aspects need to be addresses, including data transport capacity (bitrate), physical media and topology options. As there will be an increasingly strong tie between infotainment/telematics and Driver Assist, requirements from both areas need to be fulfilled.

At the MOST Forum 2010, a prototype version of a Multiport-INIC for MOST150 was presented. The OS81111 implements a two port architecture which enables prototype design for alternative network topologies.

In a very elegant way, several topology options can be realized, included ring (key to allow for the absolute minimum number of connections in a network), daisy chain and a star. Obviously, in such a 'pseudo-ring' architecture, the bandwidth is shared between the different branches in the event that a star topology is implemented.

Within the last year, technology has advanced and the requirements have become more defined. To meet these needs, a true multiport INIC chip is being developed by SMSC, eliminating the bandwidth sharing of the prototype:

With this chip, each branch will provide the full 150 Mbit/s data transport capacity. In addition to the well established MediaLB 6 pin interface providing 300 Mbit/s bandwidth, a standard high speed interface offering minimum 1.2 Gbit/s speed is implemented. The interface will match to state-of-the art interfaces used by powerful media processors used in multimedia or driver assist processing units.

The different branches themselves will run on MOST150, with the add-on option that each branch can be hot plugged or cut off without impacting data communication within the rest of the system. Of course, each branch may again consist of a ring itself, or a daisy chain, in case the Dual-Port INIC is used. With such an architecture, those use cases which require a true star architecture, e.g. coming from the driver assist domain, are addressed, while at the same time maintaining the principal advantages of MOST, including the synchronicity and the low latency of the network.