PSA: USB 3.0 can interfere with the 2.4GHz band

[alkemyst]

This has been coming up in my circle for friends and colleagues lately and will probably be more prevalent as more and more USB 3.0 hubs and devices become popular.

Apple reports it even:
http://support.apple.com/kb/ht5172

Whitepaper on USB 3.0 interference
http://www.usb.org/developers/whitepapers/327216.pdf


Just an FYI

 

[Zargon]

LOL

if they are buying fancy USB3 stuff they should move to 5ghz N

/troll hat



man I bet that was fun to troubleshoot prior to stuff getting published on it

 

[alkemyst]

even with the information out there unless you actually break out the tools to show interference, who is going to think a USB hub is a culprit

 

[CubanlB]

From the summary of the Intel document,

"The noise generated due to the USB 3.0 data spectrum can have an impact on radio receivers whose antenna is placed close to a USB 3.0 device and/or USB 3.0 connector. The noise is a broadband noise that cannot be filtered out, since it falls within the band of operation of the wireless device (2.4–2.5GHz). The noise degrades the signal-to-noise ratio that the wireless receiver sees and limits its sensitivity. This then reduces the operating wireless range of the device."

I think this would mostly be an issue for usb wifi adapters/mouse adapters. Antenna placement far from the radiating usb3 ports/cables. I would like to know how much noise it is radiating at a meter or so just to make sure the interference is localized to a client.

 

[Railgun]

In short, 99% of people won't have an issue.

 

[Mushkins]

From the summary of the Intel document,

"The noise generated due to the USB 3.0 data spectrum can have an impact on radio receivers whose antenna is placed close to a USB 3.0 device and/or USB 3.0 connector. The noise is a broadband noise that cannot be filtered out, since it falls within the band of operation of the wireless device (2.4–2.5GHz). The noise degrades the signal-to-noise ratio that the wireless receiver sees and limits its sensitivity. This then reduces the operating wireless range of the device."

I think this would mostly be an issue for usb wifi adapters/mouse adapters. Antenna placement far from the radiating usb3 ports/cables. I would like to know how much noise it is radiating at a meter or so just to make sure the interference is localized to a client.

Pretty much this. Don't plug your old wifi dongle in next to a usb 3.0 device, and keep your laptop a few feet away from your old b/g router (which you need to do anyway to get a decent signal).

Kind of a non-issue, considering how totally saturated 2.4Ghz already is and how many other things cause larger amounts of interference.

 

[alkemyst]

It's really not a non-issue regardless if it's a rare one.

 

[JackMDS]

It might be an issue since thousands of Users have Desktop with Wireless PCI and Antenna in the back of the Desktop/Tower.

I.e., the Wireless Antenna and the USB3 in the back of the BOX are few Incas apart, and usually stuck together mask between the back of the box and the wall.

As far as Laptop concern. One does not even know the layout inside and close or apart are the internal Antenna and the USB3 circuitry, and the peripherals used with Laptops are very close to its hardware too.

 

[azazel1024]

Correct. It very much can be an issue. First off, you have lots of setups with things like a blue tooth USB2 dongle in a port next to a USB3 device, which can mess it up (per the white paper).

Also if your antennas are near an active USB3 port. I've seen/heard of at least one or two routers where using the USB3 port DOES cause problems with 2.4GHz, fortunately (I think) the couple I've seen that do cause interference have an option in the router firmware to downgrade the USB port to 2.0. You'd think they'd just shield the port better though...

More than a few inches away though, I agree, it is basically a non-issue.

 

[CubanlB]

I didn't mean to suggest that it couldn't cause issues. I mostly am ambivalent because there are lots of devices that interfere with 2.4 that have a much greater impact on a large number of clients. A video device running on 2.4 that has a large mW output can just destroy a 2.4 ghz 802.11 network.

Tracking down the cause is much harder in that scenario because it affects so many clients. If the issue is localized to a client it should be pretty easy to diagnose.

 

[RadiclDreamer]

Thanks for posting, I've sent to my team. Would not have thought about USB causing interference.

 

[skace]

Nevermind, it was a failing Xfinity X1 box that was the root cause. Although I did move my USB hub away from my router moving forward.

 

[azazel1024]

How in the heck are you getting that much interference? I haven't played with USB3 induced interference very much, but my USB3 hub for my desktop sits about 6ft from my router. Zero interference when it is plugged in, unplugged or actively transfering data. I've used USB3 storage plugged in to my router and even when actively in use, no apparently 2.4GHz interference. I even ran my USB3 hub, USB3 card reader AND USB3 harddrive on 2m male to female extensions so they could sit right next to my router. No apparent 2.4GHz interference.

I could try something more elaborate, but maybe short of wrapping USB cables around the antennas for my router, I am not seeing any interference. I can't imagine all of those devices or the cabling are shielded (though I suppose I just hit the jackpot). Granted, I was checking transfers with my laptop maybe 20ft away through a single wall. Possibly if I was REALLY far away, the interference being generated would be enough to have a noticable impact on 2.4GHz. However, my microwave located almost directly above where I was testing my laptop (about 12ft above it) when turned on, cuts my 2.4GHz speed by about 10%. Sticking my laptop on my stove top right below my microwave, turning the microwave on cuts my 2.4GHz speed by about 30-40%. My old cordless phone that was on 2.4GHz (now have a DECT phone) if I put the handset within a foot or two of my laptop would also typically cut about 5-10% off my 2.4GHz speeds if it was in use.

I wouldn't consider it the gods' truth, but from what I can find, USB3 signaling seems to be at somewhere between 50-70mw. Since a good chunk of that power is obviously getting to the host/client and not radiated as EM, you are maybe talking 1-10mw of radiated EM. Which is on the order of 1/10th to 1/100th as strong as a typical wifi router/chipset. Assuming there is even that much (seems to be alot less than that).

Intel was finding a rise in noise floor of about 30dB in the worst case scenario at a few inches distance. At 5ft you should expect the noise floor to go up maybe 2-5dB at most. That should have zero impact except maybe at extreme range between the router and client.