Alternative standard to MOST and Ethernet provides long life cycles along with performance, security, flexibility, and economy
By Max Bassler and Bill Rose, 1394 Trade Association; Ricardo Wong, Nissan; and Mike Gardner, Molex
In today's economy—where R&D investments are difficult to justify and long life cycles for electronic technologies are mandated—the 1394 Automotive network standard offers an improved solution for in-vehicle electronic applications. Whether the platform is an entry-level or a luxury model, this same technology can be shared and is expandable, even at the dealer level.
1394 Automotive technology was developed by automakers, Tier 1, and component companies with baseline requirements for today's automobile; and it meets the requirements expected over the next 10 years. In addition, several proven automotive harnessing systems are specified for maximum flexibility, and all are interoperable with multiple sources for cost-effective implementation.
The 1394 Trade Association (1394TA), AMI-C, and IDB Forum have spent eight years developing and proving out the networking technology. The 1394TA leads the effort with proposed device compliance testing and extensions to the standard. The results will be new and innovative automotive entertainment systems, as illustrated below.
1394 Automotive enables a reliable, sophisticated rear seat audio and video entertainment system. (Photo: Nissan)
The developers of the 1394 standard know the competition, with technologies such as MOST and Ethernet for networking, and feel they offer an improved long-term solution. For example, applications such as navigation (VGA quality), multiple HD quality video and audio content, camera systems for driver assistance—and enough bandwidth to add more—are provided for with 1394 Automotive.
Comparison: 1394 Auto, MOST, and Ethernet
1394 Auto provides the following building blocks for networking, which MOST or Ethernet do not offer all of or often lesser performance:
Reliability
Cost
Aggregate maximum bandwidth and expansion
Media Access Control
Isochronous capabilities
Reverse/legacy compatibility and scalability
Media choice (harness flexibility)
Flexible topology (Star, Rings, Tree, etc.)
Silicon cost
IP license fees
Silicon industry support
Synergy with other control technologies
Synergy with broad consumer technologies
Auto device discovery and configuration protocols
Tested and available software
The 1394 Auto standard defines data rates as fast as 800 Mbps (called S800 or FireWire 800) today. Because 1394 is backward compatible, the Auto Standard supports any 1394 devices operating at S100, S400, and S800 seamlessly and simultaneously. The next generation of silicon for S1600 and S3200 (1.6 Gb/second and 3.2 Gb/second) is defined and will ship in 2009. These too will be fully backward compatible to 1394 Auto Standard that exists today.
MOST
First-generation MOST25 operates at 22.5-Mb/second, maximum. The MOST group has also defined a 150Mb/second version called MOST150, a non-backward compatible spec completed in the spring of 2008. Major harnessing changes may be required when MOST transitions to higher speeds.
A single MOST25 network will not support all of the A/V traffic that automakers envision, and the next-generation MOST150 technology will lack needed performance and backward compatibility. There will be no economy of scale with older MOST products that can't be carried forward to new designs.
Ethernet
Ethernet brings the same advantages and disadvantages to the auto that it does to home video-centric networks. Ethernet is a "best-effort"system and therefore lacks the quality of service guaranteed by 1394. There is also no IT department to reboot your automobile entertainment system when it freezes. Such support is not needed with 1394 Auto, which automatically resets by design when any devices are changed.
Infrastructure
There are also different media choices—copper or optical fiber. MOST was defined from the start based on optical media. The first 1394-centric automotive spec also specified fiber; IDB-1394 has been fiber based since initial publication. But with advances in signaling and silicon technology resolving the EMI and EMC challenges of copper, automakers and Tier 1 suppliers can mix and match fiber and copper using 1394,whatever their preference or experience. The newest 1394 Automotive S800 is based on copper interconnects, and three different automotive-proven systems have been specified.
1394 Auto is flexible, allowing for bus, star, ring, daisy chain, tree, and other topologies. The topologies can be mixed and matched using 1394 Auto in a ring for fail-safe operation that will survive any single cable or device fault.
