Part 1 of this series discussed development of automotive connectivity systems that bridge the benefits of Ethernet, USB, and Media Oriented Systems Transport (MOST) to deliver fast and efficient data; and how rapid evolution of consumer electronics has to be resolved with longer automotive design cycles.
Consumers today have embraced a digital lifestyle that includes having their entertainment content with them at all time, whether in the home, at work, or in the car. The significant amount of time people spend commuting in their vehicles presents the challenge of integrating the car into their digital lifestyles.
Designers of new vehicles have to contend with many different interfaces to connect to the external world, but the devices that enable this digital connectivity need to interact smoothly to ensure drivers are not distracted. In order to seamlessly move large amounts of audio, video, and control information to, from, and between devices, the car needs to have a flexible and powerful communications backbone.
Media Oriented Systems Transport (MOST®) has become the de-facto standard in the automotive industry for transporting high-bandwidth audio, video, and control information between various vehicle subsystems. There are now approximately 45 car models on the road equipped with the technology and just about all European luxury brands and a few mid-range ones are using MOST in current production vehicles or designing it into future car platforms. MOST is also expanding in Asia, with Hyundai and another major Asian carmaker stating they will integrate MOST into 2008 models.
Why a network?
In the 1970s, many automobiles, even high-end cars, used a separate amplifier and radio. Over the years, audio products such as cassette and CD players were added. Telephones and navigation systems followed, and now video and Internet access are becoming mainstream in mini-vans, SUVs, and luxury sedans. New cars already include a dozen or more devices that need to interact with the driver and passengers over a limited number of visual and audio interfaces. This technology acts as the foundation for users to be able to access telematics and information services in the car.
As the number of devices consumers desire in a car increases, the need for compatibility becomes more important. As a result, the number of connections required to control the system rises exponentially (see below) and it becomes necessary to network the components, rather than simply establishing more links between them.
The high-speed MOST network can provide current automobiles with the infrastructure for the orderly interaction and coordination among the various subsystems. MOST was designed by the automotive industry specifically to meet the rugged environmental requirements of in-vehicle applications with a reliable technology designed to efficiently move large amounts of streaming and packetized information along with the necessary control data.
Current MOST implementations use plastic optical fiber (POF) due to its low weight, low cost, and electromagnetic interference advantages. However, MOST's object orientation makes it easy to use other media such as copper wiring or glass fiber and, in fact, an electrical physical layer has already been standardized by the MOST Cooperation (see Sidebar on the next page).
The increasing automotive electronics features and applications being deployed result in an increased bandwidth requirement, increased electromagnetic emissions, and increased weight and volume for the necessary cabling. MOST technology was developed specifically to address these issues.
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The figure above shows a comparison of two real production system implementations from a European OEM. This typical application has a human-machine interface (HMI) controlling a CD player, a radio, and a telephone. The first vehicle system (left) uses conventional copper cables that were replaced in a newer model with a MOST network. Benefits of this change included:
The total length of the connections was reduced, specifically because some devices close to each other didn't have to be connected back to a central unit.
There are also fewer cables because each fiber optic link only requires one physical fiber.
The system is significantly less susceptible to electromagnetic interference.
Reduced component count results in increased reliability, lower weight, and lower space requirements.
Because the system is synchronous, electromagnetic emissions were more easily controlled because they appeared at known frequencies and can be directly addressed.
This implementation used a conventional radio but due to the modular design of MOST, it would be easy to include a satellite radio or rear-seat entertainment system in place or in addition to any of the components shown.