MOST and AVB: Two Candidates for Next-Gen Automotive Infotainment Networks: Page 3 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.
TSI, SPI, I2C and I2S, benefitting from its synchronous network layer transport. AVB-enabled Ethernet NICs can, in principle, provide similar interfaces by separating AVB streams from other traffic on the Data Link Layer, taking care that the AV streams do not burden the host processor. However, such functions are not found in today's NIC implementations (Figure 2).

Figure 2: Integration of host and physical layer hardware interfaces in MOST and Ethernet AVB.

Both technologies are essentially independent of baseband physical layers. MOST150 INIC interconnects the FOT using LVDS interfaces, whereas Ethernet MACs connect to Ethernet PHY units with Media Independent Interface variants (also Figure 2). Otherwise, choice of a physical layer, whether on optical media, electrical over twisted pairs or coax, is to a large extent independent of the approach taken on the data link layer.

Whereas MOST has been designed and developed for automotive use and automotive qualification, for AVB a lot of experience needs to be gained regarding automotive use of the standards and realization of automotive requirements. This goes from the API level to service-discovery and control mechanisms, to wake-up-strategies and -times, to power consumption, just to name a few. AVB generation 2, which is only in standardization now, will address some crucial issues, including the handling of high frequency/low volume data such as sensor data and further minimization of latency by preemption of packets [8-10]. AVB standards were written to flexibly support comparatively dynamic networks and to provide interoperability between brands of different manufacturers. The situation in-car is a lot more static, with plenty of opportunity to keep oversizing, redundancy, start-up times and thus power consumption and costs down. Pre-configuration for the startup phase and beginning to reduce complexity right at design time are examples for that. A strip-down of AVB protocols and techniques is imperative for automotive usage. Yet an appropriate form of cooperation for standardization of such a tailored AVB automotive profile needs to

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