Replacing USB3 with slim Power-over-Ethernet, too crazy?

Question

I'm not an expert in USB3 implementation details, but it seems to be a nightmare, even if you can afford to buy the spec. Meanwhile, power-over-ethernet has existed for a while. It seems like all we would need is slightly different connectors to fit into slim devices like phones, and PoE capable cables could fill the data-and-charging roles of USB3, with less weird proprietary nonsense, almost none except for the connector itself, which could conceivably (definitely in my fantasy world) be an open-source design. The software and most of the other hardware pretty much already exists, right? Connecting your phone to your computer is just networking, like plugging in an Ethernet adapter.I'm sure it can't actually be as simple as just CADing up some new connectors, but is there a reason besides inertia this couldn't be done and be effective? Say, by a startup willing to abandon a bit of precedent to get a less-proprietary connector?

theamk · Accepted Answer

Using ethernet for the data part will need new specifications because Ethernet defines so little. For example, right now, I can plug in any random USB keyboard or camera into my computer and it'd just work in under a second, no special drivers needed. With Ethernet, someone needs to define a spec -- I don't know of any standardized "input device over ethernet" protocols for example.
Additionally, ethernet transport is pretty basic -- for example, there are no specs for Ethernet hubs which provide "device present" signal, or which can forward "sleep mode" state to/from devices as USB does.
The power delivery part will need to be reworked. Plain standardized POE promises 15W, while USB3 can get up to 240W. Plus 48V is pretty high and needs high-voltage converters, which will be hard to do in portable devices.
The PHY will need to be updated -- the copper-based ones rely on transformers for safety, but those are pretty big and hard to fit into portable devices. Also, I am not sure how power-efficient Ethernet cards are, but I bet they draw more power than USB ones. All this error correction logic to support long distances cannot be free.
So it's not like Ethernet-based stack will have less "weird proprietary nonsense". Once you get it to provide feature parity to current USB, it would be as complex, if not more.

detaro · Answer

Some counter-points:ad-hoc networking (addressing, names, ...) is kind of a pain still, especially cross-platform.Affordable Ethernet is slow compared to modern USB-standards.For many things USB does there isn't one "that's the equivalent networking protocol".Modern USB does a lot of alternate stuff over the same connector, which makes it a lot more complicated, but also useful.All that means it seems unlikely for this to happen and a bigger hurdle than "abandaon a bit of precedent". Given computers already have Ethernet today: how many peripherals with USB do you see where there is just one Ethernet-based option somewhere on the market, and what does that cost in comparison? What's needed to adopt them?To take some examples: we have storage devices with Ethernet. We have cameras with Ethernet. How do they fare with USB-based ones in your comparison?