MOST and AVB: Two Candidates for Next-Gen Automotive Infotainment Networks: Page 2 of 6

June 05, 2013 //By Günter Dannhäuser, Dr. Walter Franz, Prof. Dr. Wolfgang Rosenstiel
MOST and AVB: Two Candidates for Next-Gen Automotive Infotainment Networks
MOST150 is the prevalent networking technology for the coming years in automotive infotainment. Although MOST150 is only at the beginning of mass deployment, pre-development of the next generation has already started. With IEEE802.1 AVB, another concept has entered the discussion about the successor to MOST150. AVB needs to be considered, appropriately evaluated and compared with current and evolving MOST concepts.
from current systems. Concept proposals, on the other hand, are the technical basis for the time being. They are a flexible matter and therefore often deliver only weak arguments for hard technical decisions.

MOST as a synchronous system has the advantage of inherently providing maximum Quality of Service, since collisions or priority conflicts principally do not occur. Delay is minimal and, moreover, it is deterministic and predictable, thus enabling application-level synchronization with simple fixed delay elements. On top of this, MOST150 offers isochronous and packet channels, including a transparently usable Ethernet channel. In the short term, the MOST Multiport INIC concept as presented earlier [7] already answers the most frequently raised objections against classic MOST systems by enabling flexible, mixed topologies and different speed grades on the same net. A MOST successor, preliminarily called “MOSTnG”, will further improve on this, key points being error detection/correction and bridging between network clusters, which may run at different speed grades over various, even mixed physical layers.

With the introduction of AVB standards, Ethernet as a packet-switched networking technology responds to the lack of guarantees and determinism with a synchronized network layer, enabling time-synchronized low-latency streaming services. The standards cover precise clock synchronization, traffic classes with bounded latency, partitioning of bandwidth, stream reservation, traffic prioritization and data link layer transport protocol. Layering of this synchronized network then looks very similar to synchronous MOST (Figure 1). However, application level synchronization is a question not in the scope of AVB standards so far and thus must be taken into account by application developers.

Figure 1: ISO/OSI model layering for synchronized audio/video streaming on MOST and on AVB

Regarding automotive infotainment systems, a crucial feature is the seamless integration of audio/video (A/V) interfaces in the network interface controllers. A/V streams should be directly transferred to corresponding A/V interfaces, thus unloading the host processor from handling A/V tasks. The MOST150 INIC already integrates various interfaces such as MediaLB,

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