IAN FERGUSON, QuickLogic

When I was a child (back in the ’70s), a long car journey was interminable, but times are a changing for the next class of car-bound children.

Vehicles now come with networks capable of transferring video, audio, and data content to passengers. I’m referring to the networks that allow users to access content available on a home network from the Internet or subscription services. The arrival of 3G networks will remove most of the technical barriers halting the vision of “on demand” services. The bigger issue is whether there’s a compelling demand from end users to encourage service providers to build up systems needed to deliver the content.

There are some significant challenges that the support of this functionality places on the system designer. These issues can be placed into four categories:

• These new applications demand an order of magnitude higher bandwidth than was previously available in established car networks like controller area network (CAN) and local interconnect network (LIN).

• Care needs to be taken to distribute video and audio content in a manner acceptable to the user. Delays in audio or incorrectly displayed pixels on a video screen won’t be tolerated.

• As content is distributed in digital form, the designer must worry about protecting the content.

• There’s a need to ensure that the network is secure from viruses that may inadvertently be introduced by connecting a consumer peripheral.

As is customary with emerging system challenges in the embedded market, a number of technologies have emerged that are vying to become the dominant solution. There are four main technologies under consideration. CAN is the incumbent technology. New versions of CAN have increased the available bandwidth. However, the protocol wasn’t designed to support such a high quality of service. Consumer companies are rallying behind Firewire (IEEE 1394) to become a player in the automotive market. But automakers seem to be behind Multimedia Oriented Systems Transport (MOST). The suppliers like the weight and low-cost nature of the plastic-fiber implementation of this technology, and it’s already shipping in some vehicles from BMW, Mercedes, and Audi. From the technical side, the protocol was designed from the ground up to support the needs of multimedia traffic. The bus provides synchronous channels that offer guaranteed bandwidth.

The wild card is wireless technology. For a number of reasons, the automotive segment is relatively slow to adopt new standards. Although the simplified installation, maintenance, and cost advantages that Ultra Wideband (UWB) technology seems to provide, and the fact that technically it seems suited for delivering high data rates across short distances in noisy environments, the lack of a definitive single standard scares the OEMs and will prevent its deployment. The longer that multiple standards exist, the greater the installed base for MOST technology grows.

Connection to the MOST network is typically achieved using an intelligent network interface controller (iNIC) that implements the PHT and majority of MAC functionality. Embedded subsystems connect to the iNIC through a three-pin serial bus known as the media local bus (MediaLB) that supports all the MOST network data types. The network must include connection points that let end users connect appliances purchased independent of the vehicle. The most likely scenario is that there will be more than one specific network. One “trusted” network will support the equipment that’s fully validated prior to shipping the vehicle. The second “untrusted” network will let users connect consumer appliances. A gateway would provide controlled access between these two worlds.

Most of today’s rear-seat infotainment platforms use an analog connection to move data from the entertainment source to the display. The move to a completely digital domain raises huge concerns from the content providers, particularly video content. The content providers are concerned about ensuring their video technology is viewed only by authorized subscribers. That forces designers to follow certain standards to guarantee content is not copied. Digital transmission content protection (DTCP) is the standard that the platform uses to securely transfer information. There are two primary elements of the solution. The first is authentication, whereby the two devices connected by the MOST network ring communicate between themselves to ensure the receiving device is authorized to receive the content. Second, once the connection’s validity is established, the receiving device decodes the incoming stream. For the MOST network, an encryption scheme known as M6 is used. With other networking standards, alternative encryption schemes such as AES are mandated.

Portable Design June, 2005