Requirement of 100Mbps/1Gbps bandwidth on automotive applications
I know that ADAS, infotainment systems require high bandwidth due to audio and video, but do they really require such a high bandwidth?


Let's talk about infotainment first:

I personally don't even consider 1Gb/s a high bandwidth, let alone 100Mb/s. 

Also, this is the year 2016. 1Gb Ethernet has been cheaply available for 2 decades now. Using something older for development definitely sounds like you'd be investing R&amp;D time into already obsolete standards. It's a no-brainer, from a commercial aspect, to make sure the systems you build will be able to deal with the current communication standards.

So, let's assume that you're building a non-shitty entertainment system for your car, again, with the background that the system you're building should be reusable next year, which means that there are two 1920x1080 screens for the back, and one such display in the center console. You do the math – it doesn't take a lot of uncompressed (or only slightly-compressed) video to fill 100Mb/s.

Assume you want to let your user plug in his smart phone to copy a movie that he downloaded to your entertainment system. USB2 is faster than fast ethernet. USB3 is faster than 1GigE.

In any case, you won't find anyone doing anything slower than 100Mb/s over ethernet these days – since the cables are the same as for 100Mb/s, and there's virtually no "video-capable" controllers that can only do 10Mb/s, it doesn't make any sense. 1Gb/s does need twice as many cable as 100Mb/s, but seeing that it'd be kind of limiting to use 100Mb/s when you can have 1Gb/s, I'd assume that you'd usually prefer to directly go for 1Gb/s if your central media processor can do that.



Autonomous driving: As soon as latency, number of streams, resolutions, uncompressed video data, a lot of systems trying to communicate with each other get involved, there's simply no way 100Mb/s can cut it. In fact, with just one 1024x768x24bit video stream with 25fps, you use up half of 1Gb/s. 

There's no discussing that. Also, autonomous driving systems are expensive for different reasons than the let's say 1€ per device that you could save by using 100Mb/s instead of 1Gb/s ethernet, so why would anyone even consider using anything short of gigabit ethernet?