[Design View / Design Solution]
Get The MOST Out Of Your Automotive Communications
The MOST network protocol for cars offers support for music, video, telecom, and anything else engineers can imagine.
T he clamor for more digital connectivity in vehicles has car designers scrambling to implement systems that efficiently distribute audio, video, and other content. These requirements have led to the design of a future-proof system and networking architecture that can cope with the different development time frames in the consumer and the automotive worlds.
While existing implementations focused on audio, Media Oriented Systems Transport (MOST) now provides distributed network protocols for multimedia high-definition (HD) audio/video networking. MOST also supports Digital Transmission Content Protection (DTCP), required by content owners for the secure movement of video over distributed networks.
MOST offers more than the physical connection between devices. It also provides the software infrastructure to manage the complexity of multiple devices communicating with each other. As telephones, navigation systems, portable media devices, and infotainment systems are integrated to provide a rich entertainment experience, they need to communicate so they don’t overwhelm the user with the details of moving audio and video to multiple stations in the car.
Via MOST, designers can tame this complexity by moving all audio, video, and necessary control signals over a single cable, using either plastic optical fiber (POF) or unshielded twisted-pair (UTP) wires.
MOST Technology is the result of the collaboration among members of the MOST Cooperation, which consists of 16 carmakers and more than 75 suppliers working to establish and refine a common standard for the evolving requirements of automotive multimedia networking. Through this work, MOST has become the de facto standard in the automotive industry for transporting high-bandwidth audio, video, and control information between various vehicle subsystems.
Its quality of service (QoS) makes it a prime transport for applications that stream content to provide consumers with high-quality information, video, and sound. MOST is used in over 58 vehicle models from more than 16 vehicle brands from around the world. The technology started in Europe but has now expanded into Asia, with Toyota, Hyundai, Kia, and SsangYong recently introducing several models.
The traditional way of connecting analog signals between various components and using controllerarea networking (CAN) to control communications isn’t viable in the long run. That’s because too many devices would have to be connected with each other. If several of the connections involved surroundsound, for example, each link between devices would need six or more wires just for the audio signals alone.
Car designers can significantly reduce the complexity of the wiring harness by using MOST, which uses a ring structure (Fig. 1). Figure 2 shows an actual example of one vehicle manufacturer going from a traditional analog-based system to using MOST.
CONSUMER, AUTO ELECTRONICS CONVERGE MOST helps car companies connect to the consumer world. It allows the network backbone in the car to comply with the robustness and reliability requirements of the automotive industry and provides a pipeline for moving audio and video. The long design cycles of a car make it difficult to quickly adapt to the latest consumer trends, though.
With the standardized interfaces of MOST, car companies can maintain their infotainment backbone on their own time schedules and only need to develop a single customized gateway device to connect to the latest consumer electronics. It would even be possible to make such a gateway an accessory that could be upgraded over time. Other consumer- and computer- oriented technologies, such as Ethernet and USB, are relevant to the car.
Ethernet’s wide proliferation, high bandwidth, and the optimized communication of bursts or packets of information make it an excellent connectivity solution between the outside world and the automobile. The protocol can connect an external Ethernet-based infrastructure to a vehicle and move large amounts of diagnostic information between the two, such as downloading software into the vehicle when the car is in a repair bay.
Many vehicles rely on embedded Ethernet products. The non-PCI architecture is well suited for the automobile since it obviates the need for a full personal- computer infrastructure. Instead, it provides simple interfaces to the typical microcontrollers used inside the car while taking advantage of the vast computing power that exists outside of the vehicle.
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