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01/05/2012
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Mark Fletcher takes a look at MOST and discovers how it is helping car companies keep pace with ever-changing consumer demands, while also evolving to counter competition.
 The automotive industry has its work cut out, if it is to keep pace with the connected consumer. As more and more disparate media sources come online, to which the consumers want instant and mobile access, car companies need to adopt hardware and software that will not only cope with the increase in data volume, but also integrate into existing systems and infrastructure.
It wasn't all that long ago that in-car infotainment comprised a 1 DIN radio/cassette deck that quite happily relayed its audio signal across a very basic analogue circuit. It wasn't complicated and had absolutely no need to interact with other services within the car. Since then, the influx of media formats, data variants and solutions has been almost exponential; creating all manner of hardware and integration issues for the automotive designers.
Interconnected
Cars are now the embodiment of a sophisticated, integrated, cross-platform audiovisual (A/V) system – often far more complex than even the most advanced installations you will find in the home – where audio, video and data all need to be interconnected. And with true, real-time information being the key to successful driver interaction – not just with infotainment devices, but also with onboard safety, video and sensor systems – the use of a robust and fit-for-purpose network is paramount to ensure the efficacy of all these new avenues of information delivery.
With infotainment companies constantly trying to outdo each other with the next, greatest USP – unique selling point – a common hardware platform is just not feasible. Instead, the most efficient and cost-effective way to allow these companies to continue down their own, individual hardware development routes is to give them the means to connect with each other, using a standard hardware and software interface. It is this digital interoperability that is the key to allowing car manufacturers to incorporate systems comprising modules from different vendors.
Sophisticated control systems
Unlike the 'not invented here' problems that Ethernet faces (discussed in the last issue), MOST – Media Oriented Systems Transport – has the advantage that it was developed from the ground up by leading players in the automotive industry. Its design allows it to provide a low-overhead, low-cost interface for the simplest of devices, such as microphones and speakers. At the same time, more intelligent devices can automatically determine the features and functions provided by all other devices on the network and establish sophisticated control mechanisms to take away distractions from the driver of the car, as different subsystems try to communicate information.
MOST not only defines the physical interconnection between devices, but also specifies and standardises an embedded communication protocol and software framework that simplifies the development of complete systems and applications to distribute and manage multimedia content.
Automotive Design spoke to Harald Schöpp, founding member and steering committee member of the MOST Cooperation, about the history and future of MOST. Setting the scene, he explains: "There was an early analogue solution for infotainment distribution, but it was cumbersome, used big cables and suffered from EMC issues. What was needed was an EMC-robust digital solution. This led to the development of the first iteration of MOST by a group of companies comprising BMW, Daimler, SMSC, Harman and Audi. The technology was, from the outset, based on fibre optics, which offered perfect EMC immunity, while also offering the necessary bandwidth and a reduction in weight. The first MOST network, optimised for audio and control, appeared in the BMW 7 series in 2001."
Automotive optimised
From the very beginning, MOST was optimised for the automotive environment, catering for temperature extremes (-40°C to 95°C) and the harsh electromagnetic conditions. It was also optimised for real-time synchronous data, unlike other solutions, including Ethernet, which are packet based.
Schöpp continues: "Ethernet can be optimised for other purposes, as we have seen with the AVB variant used in the broadcast industry and being looked at for automotive. But it is still a modified standard, much like the early attempts to use USB in cars."
Originally optimised for infotainment solutions, the latest generation of MOST (150) has been developed, after a significant independent study, to merge infotainment with driver assist capabilities.
With this new, faster format, MOST is now attempting to wrestle back the market share gained by Ethernet, which was, at the time, able to offer faster data rates.
When quizzed about the demands of the major car companies, Schöpp explains: "With infotainment today, I think the functions and features that can usefully be added are starting to reach saturation.
"After 10 to 15 years of creating 'driver distractions', we are now seeing huge growth in driver assist features. If you look at the requirements regarding data, driver assist relies on all kinds of sensors that have low data rates.
Ultra fast future
"What are now driving the challenge are low-cost, high performance cameras, which can use data rates up to 2GBit/s. This is a lot of data, but as we know from the consumer industry, there are ways of compressing the data, maybe down to 50MBit/s. But it is still huge, compared to radar/ultrasonic data.
"Cameras for reversing or lane assist require an appropriate network, due to the speeds involved," he continues. "You need to react and process this data in real time. Latency, or rather the lack of it, is important – it must be as low as possible.
"With multiple sensors, cameras and radars, it is very obvious that they need to be in synch with each other, with the correct timeframes. It is here where MOST excels, with its low-latency, synchronous data transport."
The next generation of MOST is already defined and looking set to offer data rates in excess of 1GBit per second. "The launch date is still being determined," Schöpp elaborates. "We are looking very carefully at cost versus performance. When MOST 25 was first developed, it hit a sweet spot, in terms of cost and performance; and we are looking to achieve the same for the next generation."
A network's physical medium is also very important. Although optical is very good, when it comes to data rate and EMC resilience, not all car companies like deploying it – for manufacturing reasons.
And that is why current and future versions of MOST are also available on electrical cable.
Recognising the foothold that Ethernet has in the industry, Schöpp explains that it is possible to connect the two. "Earlier generations needed protocol translators, but MOST 150 can do it seamlessly. All you need is an appropriate Ethernet driver; it is completely transparent." When pressed on the coexistence between Ethernet and MOST, Schöpp believes there is certainly a valid case, particularly with regards to diagnostics and the interface with a garage's PC-based systems.
Quick switch
We also sought the views of Rick Kreifeldt, vice president, at Harman's corporate technology division. "Harman started on analogue, then moved very quickly into digital, as we saw the need to not only have point-to-point communication, but also a bus system," he comments. "We started developing an optical solution and, from that, went into the development of MOST as a founding member. We started with simple audio and control, and then went into imagery and video. Now, thanks to a native Ethernet channel on the MOST architecture, we can handle the transport of IP data.
Restrictions and options
"At the time of MOST's conception more than 15 years ago, we were investigating many different options, including USB and Firewire, but found many restrictions to do with cost and the transportation of audio. We needed a synchronous solution, as memory was expensive at the time, so buffering was a real cost issue. A synchronous network would bypass the need for buffering and the associated memory requirements.
"MOST has partners in compliance, development, test and frameworks, and the cooperation was able to develop it from scratch," he explains. "We really tried to find out what was needed at the time and discovered that the major drivers revolved around the need for synchronous data transport and EMC resilience."
Harman isn't ignoring Ethernet. It helped drive standardisation of AVB in the IEEE and was a founding member of the Avnu Alliance. It considers Ethernet AVB to be suited, not just for audio/video transport as the future converged backbone, but for many other real-time data transport needs in the vehicle.
Like Schöpp, Kreifeldt believes that MOST and Ethernet will coexist, at least in the near term, as car makers transition their architectures. Acknowledging that many OEMs have a deep legacy in MOST, Harman will fully support existing MOST customers and solutions, as dictated by OEMs' architectural roadmaps.
Looking towards the future a little, Kreifeldt adds: "The connectivity of mobile devices and mobile networks will become more and more important, adding functionality to the existing in-car systems. There has been a lot of research over the last few years, one area of which has been the exploitation of 'The Cloud' to offer personalised services to drivers. For the moment, looking at 4G data rates, existing networks are capable. But, in the future, there will be more cloud connectivity and Gigabit Ethernet is already defined. MOST needs to play catch-up to keep pace."
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Author
Mark Fletcher
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