MOST ups bandwidth to 150 Mbps

  • 03-Jul-2008 06:04 EDT
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The new 150-Mbps fiber-optic transceiver from Melexis is the first component for the latest MOST protocol network.

In Frankfurt, Germany, the MOST Cooperation presented the third generation of its optical multimedia network protocol called MOST (Media Oriented System Transport). At 150-Mbps bandwidth, the new infotainment backbone offers the muscle for in-vehicle digital video streaming including HDTV.

It also incorporates an additional channel for ethernet communication that “would make standard internet protocol applications in the vehicle very well possible,” said Christian Thiel, Administrator of the MOST Cooperation.

While MOST was, in effect, a European standard that was basically limited to luxury sedans when it was defined in 1998, it has proliferated into the middle segment. According to Thiel, 56 cars now have a MOST network on board. In Europe, the multimedia standard spans such diverse vehicle types as the BMW 7 Series (the first production application in 2001), the compact BMW 1 Series, and the Mini. In addition, it can be found on five Audi series, practically all Mercedes-Benz classes, Citroën C8, Mitsubishi Colt, Jaguar XF and XK, several Porsche models, and seven Volvo models.

In 2007, Toyota first adopted the MOST standard for its Japanese market models Mark X ZiO and Crown. At the beginning of 2008, Hyundai (Genesis sedan) and Kia (Mohave SUV) introduced MOST networks “and another Asian vehicle manufacturer will soon follow,” said Thiel.

“After 10 years of refining and optimization, MOST is the de facto automotive-grade infotainment network standard,” claimed Thiel.

It comes as no surprise then that he perceives neither ethernet nor IDB1394 as an alternative. “If you look at the roughly 3800 pages of specification we have accumulated, including the latest specification, Rev. 3.0, you know what level of maturity and detail optimization MOST has reached. MOST is synonymous with high-quality audio and video service,” Thiel added.

Carsten Kellner, Team Leader of Vector Tools for Networks and Distributed Systems, agrees: “Probably the biggest strength of MOST is that it is automotive driven.”

On its path to a truly global standard, the initial cost level proved to be a hindrance, so pushing costs down is one of the main aims of the MOST Cooperation and its 94 members—16 vehicle manufacturers and 78 suppliers.

 “The growing number of applications means that there is a scale effect in both cost driver areas: step index fiber and IC development,” explained Harald Schöpp, Director–System Development, Harman/Becker Automotive Systems. “In total, we have already reached a third to a quarter of the first MOST series application cost levels.”

The most significant cost reduction stems from the optic transceiver field that still accounts for up to two-thirds of a MOST node’s cost. Migrating to the new 150-Mbit protocol is simple and cost efficient, said Schöpp, as the existing POF (polymer optical fiber) based network infrastructure can also be used for the high bandwidth.

The new generation has the potential to overcome what is sometimes perceived as a downside of MOST technology—an alleged lack of bandwidth. At 25 Mbps, the first generation was tailored for digital-audio signals at a time when no one considered digital video streaming. The second generation of the protocol had 50 Mbps. This double density version was, among other things, tailored for use with shielded or unshielded twisted pair (STP/UTP) cabling. The new protocol version is said to offer all the bandwidth digital-video streaming requires.

“MOST is based on a synchronous data transfer mechanism that is ideal for audio service,” said Matthias Stümpfle, Head of System Architecture and Platforms, Daimler AG. “However, new use cases such as an isochronous video service can be added to this base function with comparatively little effort. To us, that is the current attraction of the MOST solution.”

Still, 150 Mbps may not be the end of the line. Robert Reiter, System Architect at BMW for Information and Communication Systems, explains: “Permanent progress in the LED field means that the opto-electric coupling keeps getting faster. The current limit is around 200 Mbps.”

Melexis, a General Motors networking component supplier, presented the first component for the new MOST generation at Frankfurt. The highly compact MLX75605 surface-mount transceiver embeds a 650-nm light source and driver IC (integrated circuit). It is based on the recently published 0.9 version of the physical layer specification. After the 1.0 version is published, “that is when series production of our new transceiver can start,” said Piet de Pauw, Chairman of the Opto Division of Melexis.

A demonstrator application served to underpin the crucial role of bandwidth. It networks three HDTV streams and 18 video channels within a single MOST ring and displays the signals on 21 screens. “With this 150-Mbps application, we are using roughly two-thirds of the bandwith. The rest is reserved for ethernet packet data communication via MOST. So we are now offering automotive-grade ethernet,” said Thiel.

Following the maxim that seeing is believing, the demonstrator may help to overcome the prejudice that in-vehicle video streaming requires 1 GB. “Often MOST is compared to the Firewire S800 standard, but if you consider the big amount of S800 overhead, MOST 150 has the same performance,” said de Pauw.

“You can use a MOST network with close to 100% of efficiency,” Thiel added.

The protocol also offers a flexible use of the bandwidth. “In most cases, the allocation of channels is done dynamically within the MOST network controller according to the instantaneous requirements,” said Reiter.

Accepting the importance of the aftermarket, the third-generation MOST has an auxiliary I/O interface. This consumer port can be used to integrate compatible aftermarket and consumer systems such as MP3 players.

For the future, the MOST Cooperation is also reviewing the possibilities to use the protocol for transmitting noninfotainment video signals. This could possibly open the door for a whole new area of applications such as camera-based driver-assistance functions requiring fast video transfer.

“The borders between infotainment and assistance functions may become more fluid,” said Schöpp. “So we are looking into what our technology has to offer for that.”

The MOST Cooperation will be showing its latest technology highlights at the Convergence Exhibition from October 20 to 22 in Detroit.

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