Ethernet And MOST Go Head To Head For In-Car Network Solutions
The modern car has become yet another 'node' in the modern consumer's connected lifestyle. Traditional CANBus solutions are not up to the rigours of intensive data transfer and handling, and for this reason the automotive industry has been investigating alternatives. Some based on tried and trusted technology, others based on bespoke, industry specific hardware and protocols, as Mark Fletcher discovers.Acco
This connected lifestyle is already putting strain on network infrastructure in the home and office, so imagine what it is going to do to the car. As well as the obligatory e-mail and internet, the car's network also has to handle in-car audio, video and telemetry data, attaching priorities and routing information depending on what sort of information it is, who needs to see or hear it, where they need to see or hear it and how they need to see or hear it. As you can imagine it all gets a little complicated and a bit busy.
When it comes to in-car electronics, one of the biggest 'data hogs' that has led to a reappraisal of in-car networks is video. According to recent research, video-based systems, which were at around five million in 2006, are set to reach 30 million by 2015 — an astonishing growth rate that has certainly helped to fuel the impetus towards a more data-capable infrastructure. Add this to the fact that the number of network nodes within a vehicle is also expected to rise to an average of 35 per vehicle in Europe and all of a sudden we have a dire need for an in-car network that can not only handle significantly elevated amounts of data, but also one that can do it a lot quicker than the in-car networks in use today.
On top of media and audio-visual components, there is also the desire to network in-car sensors and components, so that the driver can see just about everything happening with their car that is driving the adoption of alternative networks, due to the current bottlenecks in CANBus. It is fair to say that CANBus will live alongside any alternative networks for the time being — with both doing what they are good at — but extra copper means extra weight and there is also the need to interact with each other across certain systems, which requires the use of additional (and potentially expensive) silicon solutions and software. The network interoperability seen in the industrial and manufacturing arena will almost certainly filter down to the automotive industry and it may be that we will see single-architecture networks; but not until the technical and the industry's 'not invented here' barriers have been breached; this is unlikely to happen any time soon.
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Heading down the tried and tested route, many leading OEMs and Tier Ones are taking a long hard look at Ethernet, with a few of them already incorporating variants into certain models since 2008. Considering the pace of change within the automotive industry — and its tag as an early adopter — it is surprising to see that the industry has only recently begun to appreciate the benefits of Ethernet; a 40-year old technology.
According to Dr Hans-Gerd Krekels, Director for Technology Strategy & Core Electronics/Portfolio Director for Integrated Electronics at TRW: The issue that might have fettered Ethernet's uptake a little earlier was the ‘not invented here’ ethos that has held so many good developments back. Regarding infotainment, the discussion started some years ago as it was quickly realised that CAN could not offer sufficient performance for data transmission. However, in safety systems we are now seeing an additional demand.”
With CAN and FlexRay, he continues, we have two buses that are effective and safe, but now the industry (specifically BMW) is pushing Ethernet to get 360° sensing, so you need a sensor bus capable of very high and very fast data rates. Other networks such as MOST can handle this, but you would be continuing with a proprietary standard rather than an open one such as Ethernet.
Peter Schönenberg, responsible for E/E architecture and processes at BMW, adds to this: The important point regarding Ethernet is that we are building a scalable switched network, which goes beyond the era of standard automotive bus systems. Ethernet provides a uniform, simple, scalable solution at the level of physical topology, yet enabling point-to-point connections by protocol.
Krekels mentioned MOST, or Media Oriented Systems Transport, arguably Ethernet's biggest rival. Unlike the ‘not invented here’ problems that Ethernet faces, MOST 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.
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. Even now the next generation of MOST is already defined and is looking set to offer data rates in excess of 1Gbit/s.
Coupled to this internal delivery of information, the car companies also have to deal with sharing certain telemetry-based data streams with other vehicles and roadside data points as the idea of the intelligent highway evolves. Indeed, organisations such as the Car 2 Car Communication Consortium already comprise a collection of like-minded manufacturers and Tier Ones who have come together with the laudable aim of improving safety via real time traffic-condition reporting.
Tests have already been conducted between telematic services delivered from road side units to and between intelligent vehicles via an exclusively allocated ITS frequency band for Europe (5.875 to 5.905GHz). Further applications of the technology include real-time, accurate information about traffic jams, route recommendations and information about approaching emergency vehicles to ensure their efficient passage through urban areas and green light optimum speed advisory which can provide a signal phase and timing alert, facilitating steady traffic flow and avoiding abrupt speed changes which cause high emissions.
It is still not abundantly clear which network will come out as the winner in this rather protracted race. Ethernet has the advantage of longevity, robustness and economies of scale, but is afflicted by its development outside of the industry. MOST on the other hand is the industry's own baby and ticks all the right boxes. Whatever the case, it is unlikely that the consumer will see any real difference relating to their experiences of both networks. After all, as long as they can see photos of the cat from Mum, e-mails from Dad and download the latest tracks from the cloud, the network this all travels across becomes, to them at least, largely irrelevant.