MOST and Ethernet: Payload efficiency and network considerations

Since MOST was originally designed for automotive infotainment, it is using the available bandwidth in an optimal way for all kinds of media streaming and is, in this respect, superior to Ethernet and other physical layers. However, MOST is designed as a bus system that shares the available bandwidth, rather than a switched network that multiplies the available bandwidth.

Another upcoming topic is the communication between the ADAS and Infotainment domain. With MOST, there is no simple layer 2 bridging, as is the case with Ethernet by simply connecting the ADAS unit and Infotainment Head Unit.

An alternative approach is to implement an efficient MOST/Ethernet Gateway, maintaining the main advantages of Ethernet (higher total network bandwidth, highly scalable, flexible) and MOST (highly efficient media streaming). Due to the IEEE 802.1AS protocol, Ethernet AVB simplifies the implementation of such a MOST/Ethernet Gateway, since it allows maintain the synchronous MOST timing on the Ethernet side.

Furthermore, a media source on the Ethernet side can stream synchronously using MOST as reference clock. A demonstrator system, which was built up in line with the SEIS project, was successfully used to validate this MOST/Ethernet AVB Gateway concept.

Figure 1 illustrates that bandwidth requirements keep rising. Both technologies have the capability to address the bandwidth needs of the future using alternative system architecture approaches. The suggestion is to use Ethernet for applications that will need high bandwidth, like the different kinds of video streaming. Furthermore, the transformation to an IP-based common network layer, as targeted by the SEIS project, can be supported by an efficient MOST/Ethernet Gateway realization.

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2. Bruckmeier, Dr. Robert. Freescale Technology Forum. [Online] 23. June 2010. http://http://www.freescale.com/files/ftf_2010/Americas/WBNR_FTF10_AUT_F0558.pdf.

3. IEEE, Inc. Audio Video Bridging Task Group. IEEE Standard 802.1 edition. [Online] October 2010.

4. IEEE, Inc. Forwarding and Queuing Enhancements for Time-Sensitive Streams. IEEE802.1Qav/D7.0 edition. [Online] October 2009.

5. IEEE, Inc. Stream Reservation Protocol. IEEE 802.1Qat/D6.1 edition. [Online] June 2010.

6. IEEE, Inc. Timing and Synchronization for Time-Sensitive Applications in Bridged Local Area Networks. IEEEP802.1AS/D7.5 edition. [Online] October 2010.

7. IEEE, Inc. Layer 2 Transport Protocol Working Group for Time-Sensitve Streams. IEEE 1722/D2.5 edition. [Online] September 2010.

8. IEEE, Inc. Standard for Layer 3 Transport 2 Protocol for Time Sensitive 3 Applications in Local Area Networks. IEEE 1733/D6.0 edition. [Online] October 2009.

9. SMSC. OS8110 Data Sheet. s.l. : SMSC, Oct. 2010.

10. Schöpp, Harald. Elektronik automotive . Special Issue MOST. 2010, Bd. S2, March 2010.

About the Authors:
Josef Nöbauer is team leader at Continental and an expert for the cross divisional usage of automotive network technologies like MOST, Ethernet, FlexRay. He is coordinating Continental's activities around the introduction of Ethernet as automotive bus system.

Continental Automotive GmbH, Siemensstrasse 12, 93055 Regensburg, Tel: +49-941/790-8684, josef.noebauer@continental-corporation.com.

Helge Zinner is currently working towards the Ph.D. degree at the Institute for Communication Networks, University Ilmenau (Germany) and at Continental. He has been with Continental as a development engineer for infotainment systems since 2004.

Continental Automotive GmbH, Siemensstrasse 12, 93055 Regensburg, Tel: +49-941/790-90327, helge.zinner@continental-corporation.com.

Article published in Elektronik automotive, Special Edition MOST, April 2011, http://www.elektroniknet.de.

This article originally appeared on EE Times Europe.

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