From the start back in 1998, Media Oriented Systems Transport (MOST) technology was designed as a multimedia backbone for the transfer of infotainment data in the car. 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. Over the course of time, MOST has turned into one of the major standards for automotive infotainment networking, implemented in as many as 100 car models. Now the challenge is to keep pace with the ever-evolving and expanding variety of entertainment applications across the consumer industry. Consumers live a digital lifestyle with their entertainment systems always on hand, whether at home, in the office, or in the car.
As more people spend more time on the road, use of their entertainment electronics in the car becomes essential. It’s no surprise, then, that the amount of new applications for the car continues to climb. Information and assistance functions now include sate
llite navigation systems with traffic news, status updates of the car’s condition, distance controls, cameras, lane-changing systems, Car2X, and so on.
MOST expands to five major fields of in-car use cases (Fig. 1). It meets the requirements for traditional areas of entertainment and information, and for the new domains of mobile connectivity, connected services, and driver assistance.
The latest generation of MOST technology—MOST150—supports next-gen automotive infotainment features and devices such as head units, rear-seat entertainment, amplifiers, TV tuners, and video displays. Moreover, it handles new features like Internet access devices, iPods, cameras, and video-processing units, among many others. MOST150 is currently ready for implementation; in fact, various auto makers are already working on first series projects.
Modern Network Architecture
Of course, fuel economy is an issue at the forefront of the automotive industry. To that end, the MOST Cooperation developed a low-weight optical physical layer for MOST150 that saves on fuel. It’s also non-susceptible to any kind of EMI potentially arising from hybrid or electrical engines in modern cars.
Continuously increasing software complexity sometimes makes it difficult to maintain system stability, particularly when system components are being simultaneously developed by several different Tier-1 companies. Therefore, a standardized software protocol stack becomes as important as the ability to offer a powerful data pipe for non-standardized software applications that only focus on the IP protocol as common denominator. As a result, the powerful MOST protocol stack can be applied (in total or in parts) even on a pure software level in applications where there’s no physical network, as the so-called “Virtual MOST.”
Safety Through Driver Assistance
Driver-assistance systems are about to conquer the market. The latest studies forecast these systems to grow from the 9 million in 2005 to 62 million units in 2013.
In current and future vehicles, driver-assistance functions are starting to complete and extend the feature set of traditional infotainment systems (Fig. 2). Along with information features such as navigation systems, traffic information, and function warnings, the number of vehicles with driver-assistance features like camera systems, distance controls, or lane-departure warnings will rapidly increase.
In the safety-critical application domain, communication faults can lead to crashes that may ultimately cause damage or injuries. Some of the latest studies show that MOST may offer a solution for these types of applications.
On behalf of the MOST Cooperation, TUEV Nord/IFM investigated the measures that must be taken in order to fulfill the requirements of the forthcoming ISO 26262 safety standard for the automotive industry, which also respects necessary requirements of current standards (e.g., IEC 61508). As a solution, it proposes an architecture with a safety layer as the basis for safety-related applications.
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The safety layer offers dependable transmission of safety-related application data over a MOST network, providing the necessary protection of critical data. It offers safe virtual communication services on top of the MOST application layer as defined in the MOST Specification Rev. 3.0.
To attain a high degree of failure detection, engineers often use specific safety codes that are embedded into the payload. The safety layer introduces the safety codes on the sender side, and the codes are analyzed on the receiver side. This way, the receiver’s safety layer can reliably detect several failures in the incoming transmissions and execute a suitable reaction (e.g., indicate the error to the application).
New Requirements Demand Appropriate Network Infrastructure
Driver-assistance systems will have interfaces to many different clusters of automotive electric/electronic systems. Taking into account the complexity of the applications and the different areas of the car that must exchange information, it becomes obvious that an appropriate network infrastructure is crucial for system efficiency. Also, from a functional standpoint, driver-assistance functions start to expand the functional range of classical information systems.
On top of the relative complexity of the infrastructure (sensors, network, and computing units), these systems can be expensive. Moreover, the technical specifications of such an infrastructure for different applications overlap considerably. Therefore, an appropriate network has to combine high speed and bandwidth with high safety.
None of today’s existing car networks (CAN, LIN, FlexRay, MOST) fulfill these needs completely, As a result, the MOST Cooperation is working on additional topology options like a new physical layer along with protocol improvements. Eventually, implementing MOST as a sensor network might be the first step toward leading MOST from the infotainment-only world to driver-assistance applications.
Harald Schoepp, vice president of marketing for the Automotive Information Systems division at SMSC, is a founding member of the MOST Cooperation and representative of SMSC in the Steering Committee. He holds a Diploma (Masters Degree) in electrical engineering (Karlsruhe, Germany). E-mail: [email protected].