One concern related to automotive Ethernet efforts is power management. "Ethernet will need to adopt a methodology similar to partial networking, which is available in CAN bus today," Hank said. When a variety of ECUs are attached to an Ethernet backbone, not everything needs to be powered on all the time. "You should be able to shut down part of the network in order to save energy. A rear-view camera, for example, should be powered off when a car is moving forward."
The fact that "the Ethernet is not time triggered" is another concern. Hank wrote in an NXP whitepaper published on our site in March: "Ethernet has not been developed for TDMA networking, and one topic that still needs to be addressed for automotive systems is a suitable solution to achieve the required real-time performance and Quality of Service."
The AVnu Alliance's audio/video bridging (AVB) task group already includes measures to ensure the timely delivery of media streams. As Hank explained in the whitepaper (written for the Automotive AVB Gen2 Work Group), latency time improvements are a major target for this group.
First applications for Time-Triggered Ethernet took place in Avionic systems with highest safety level requirements. Defined in SAE AS6802 and different to Audio/Video Bridging, TTEthernet is based on a distributed clock-synchronization algorithm that finally results in an exact schedule with deterministic behavior.
Although the integration of both AVB and TTEthernet is possible, further investigations are needed to allow its use in automotive applications where multimedia streams, real-time control data as well as diagnostic information and software updates will be transmitted on the same network..
The goal is to shorten latency in automotive Ethernet and make it closer to that of FlexRay.
Does the emerging Gigabit Ethernet for automotive applications mean that the currently de facto 100Mbit/s BroadR-Reach automotive Ethernet will be eventually replaced? Not really. Hank told us that, aside from higher-resolution uncompressed video, and more powerful and complex processing applications, Gigabit will be overkill in data paths for radar information or audio, for example. There will be costs associated with Gigabit Ethernet, so carmakers will limit its use to applications that absolutely require more bandwidth muscle.
When asked where Ethernet switches will be placed inside a car and how many will be needed, Hank said, "It is still an ongoing debate, as we work on the concept." Presumably, one could design one big switch box and place it at a central location in a car. But carmakers are more likely to opt for smaller, delocalized switches. "I think they want more flexibility."
NXP is fully on board with BroadR-Reach-based automotive Ethernet. Stephan Rave, the company's product marketing manager responsible for advanced networks, told us its first BroadR-Reach phy chips are sampling now.
Hank said that, though the BroadR-Reach draft specification is very close to being final, "the Open Alliance SIG will still need to finalize the spec, so that all the changes are made clear and every chip is developed based on the clear spec." The next step for the Open Alliance SIG is to establish a compliance test, so that OEMs will be assured of interoperability.