The MOST Cooperation, the organization through which the leading automotive multimedia network Media Oriented Systems Transport (MOST) is standardized, has created MOST Specification Rev. 3.0 for the next generation infotainment backbone. It is a complete overhaul of the specification structure offering several new features. While the specification is independent of speed grade, it can already work with the newly defined MOST150 physical layer. Thus it enables the use of higher bandwidth of 150 Mbps, an isochronous transport mechanism to support extensive video applications, as well as an Ethernet channel for efficient transport of IP-based packet data.
MOST Specification Rev. 3.0 provides the specification for audio and video signals to be transported with high bandwidth efficiency and without any overhead for addressing, collision detection/recovery or broadcast. This way it offers capacity that packet-switched networks can only achieve with much higher gross bandwidth. Consequently multiple high-definition (HD) video streams and multi-channel surround sound with premium quality of service can be transmitted, while simultaneously moving high loads of packet data around.
MOST Specification Rev. 3.0 – The Multi-Channel Network
MOST Specification Rev. 3.0 adds Ethernet and isochronous channels to the well known channels for synchronous, packet and control data channels of previous specification versions. The Ethernet channel can transport unmodified Ethernet frames according to IEEE 802.3. This permits software stacks and applications from the consumer and IT domain, where the speed of innovation is much faster, to be seamlessly migrated into the car. TCP/IP stacks or protocols utilizing TCP/IP can communicate via MOST without any modification. Thus, the new generation of MOST provides the automotive-ready physical layer for Ethernet in the car. In addition, MOST Specification Rev. 3.0 offers an isochronous channel to support streams which are not synchronized to the MOST frame rate. A typical use-case is the transport of MPEG streams over a MOST network, since MPEG streams generally use variable bit-rate. This new MOST feature enables extensive video applications. MOST Specification Rev. 3.0 also adds significant enhancements to the control channel (which is used for real-time control of devices) by doubling the bandwidth compared to MOST25.
Lessons Learned from Compliance Verification
MOST Specification Rev. 3.0 incorporates several “lessons learned” mainly driven by the experience of MOST Cooperation´s Compliance Verification Program. Emphasis has been put on clear specification points where conformance can be easily verified during compliance testing.
Diagnosability has been optimized by an overhaul of Ring Break Diagnosis behavior as well as Detection of Sudden Signal-Off. The robustness of the procedures has been verified during the early phase of the specification by using Failure Mode Effects Analysis (FMEA) as well as reference implementations through virtual prototypes. For example, to verify Ring Break Diagnosis behavior the functional and timing behavior was modeled and executed in over 100,000 test sets that use well-known methods from System-on-Chip (SoC)-Verification. These measures help to simplify risk assessment and increase confidence in the readiness to apply the new technology.
The development of MOST Specification Rev. 3.0 has been accompanied by a cost/benefit analysis that led, on the one hand, to several innovations and on the other to a high level of backward compatibility. Existing applications can easily be reused in the new network just by modifying their network interfaces. MOST Specification Rev. 3.0 supports the new MOST150 Physical Layer with a bandwidth of 150 Mbps that allows carmakers to continue to use POF and LEDs as light sources. They can continue to use their established optical wire harness and assembly processes. This makes the transition to higher bandwidth networking a smooth evolution and leads to a high acceptance.
About MOST Technology
MOST (Media Oriented Systems Transport) is a multimedia networking technology optimized for use in cars and other applications. It enables the transport of high Quality of Service audio and video together with packet data and real-time control over a single transmission medium. MOST can use plastic optical fiber or electrical unshielded or shielded twisted pair wire physical layers, that meet automotive environmental requirements. Today MOST is used in over 55 car models as the communication backbone for their information and entertainment equipment.
About MOST Cooperation
The MOST Cooperation is the organization through which MOST Technology is standardized and refined so that it continues to stay abreast of the latest industry requirements. Today it consists of 16 international carmakers and more than 75 key component suppliers. They have joined together to work with the MOST Technology and to contribute to its innovation. The MOST Cooperation is prepared to embrace efforts to further develop and standardize the technology for other industries and to establish the corresponding work structures. The MOST Cooperation was founded in 1998 to standardize MOST Technology as a global standard for multimedia networking. Audi, BMW, Daimler, Harman/Becker and SMSC are its core partners and constitute its Steering Committee.