Understanding power lan - from a tech point of view, why does it get slower

Question

I do use power lan at my home. I found out that every few weeks, the connection speed drops. My internet has usually a download of 3.5 mb/s. It drops to a 0.55 mb/s.

It's an easy fix, plug the pwer lan out. Plug it back in. Back to 3.5 mb/s. Fascinating, if I don't replug them, the slow speed holds up for weeks. I do assume indefinitely. But I never tested it more than 3 weeks.

But I wonder how. I can understand that in a router, sometimes a single device cannot be allowed in the internet, due to various pointer mistakes or an overfull array.

But in a power lan device, what can cause a slowing. Not a complete connection out. Just slowing it down. I am really interested on a technical explanation.

Cheers

EDIT: Oh, almost forgot. I am also very happy about answer like look at this and that electrical phenomina in wikipedia. I think I lack the right search terms. Slowing in power lan doesn't really help me. So, just referencing to the right physical phenomina would be great. My own best guess is electric noise. But I couldn't confirm it so far.

Answer 1

Powerline is notoriously fincky about line noise. One of the ways it deals with a less than perfect connection is to slow down to try to actually get data through. Error correction and retransmissions reduce transmission speeds. Same thing happens with ethernet and crappy cables, or wireless (and essentially, homeplug is 'radio' with power cables as media rather than air)

It dosen't help that most homeplug management software is terrible and dosen't give you much data

This answer talks about a better third party tool that gives you insight over SNR and actual speed. Keep an eye on this to see if line noise is increased at the time things slow down.

As for noise? Big AC motors are noisy, as are switch mode power supplies. When I was troubleshooting my connection I realised that I had disconnections when my washing machine was running, and moving the plug to a further switch helped. I eventually upgraded to a AV500 and better (from AV200). Newer generations reject noise much better.

I also tend to favour the units that have built in line filtering (line filter -> power strip -> PC, so all the nearby switch mode noise is filtered out. I pondered actually getting a line filter for the washing machine, but inbetween network reconfiguration, the inability to find a UK style plug in line filter cheap, and upgrades, I never did it.

Answer 2

If there is noise on the electrical line then the powerline adapters will reduce their speed, they will not send on some frequencies or they will not use a frequency at every time slot. Of course if the noise vanishes then the adapters should return to full speed. In case of firmware programming errors the adapters might fail to return to maximum speed possible.

You should ask the vendor if there is an update available. I have already seen connection instabilities on powerline adapters which went away after updating to the latest powerline firmware.