B5-Lite - broken or massive interference?

Hi all, we’ve been deploying Mimosa products in dense urban areas with pretty good success. This one is something I’ve never seen before.

The link is roughly 100meters/300ft, we are using a pair of B5-Lite that have worked well on much longer links.

The buildings are the same height and on the same street. It’s a busy downtown road of a big city neighborhood.

Side A of the link see mostrly free spectrum with very low background noise.

Side B though, just 300ft away, sees a TON of background noise, something I’ve never seen before, even in links deployed between high rise buildings or long shots of 20miles in that same city.
On Site B there is a bunch of Cell Tower equipment, I’m thinking if that’s the background noise I’m seeing but… on basically mostly every channel???

Check the two screenshots.



We’ll try tomorrow to replace them and see what’s up.

Any thoughts?

here an updated screenshot… it’s incredible, never seen something like this

Never seen that with any of my equipment. Does rebooting at change the overall pattern there or does the picture stay pretty much the same?

What MCS are you able to negociate up to? Maybe the radio is fine, but there is some sort of software bug. Or have you changed out the radio already?

Hi William, thanks for taking the time to write here.

No changes through reboots, and the impacted radio could negotiate around 500mbits upload and 8 to 29mbits download.

My guys went on site, replaced the radio and got the same result. I tested the radio they brought back in the lab and it’s working fine.

We then soon realized that it’s an old building with wooden roof converted to multi-tenant business offices and there are probably a lot of WiFi APs from the office units below blasting through the roof.
We moved it temporarily to a different location and the situation improved, but still with some consistent background noise.
I’m still puzzled by the signal power of the interfering devices but from the picture you can count something like about 6-7 WiFi APs that are blasting full power and used the whole spectrum basically…

We also verified the cell radio equipment on that roof and it’s just, as I suspected, cell radio freq from 800Mhz to 2.5Ghz.

We’ll try to see tomorrow when we move the pole to the new location.

Otherwise I’ll have to consider moving to a different spectrum.

24 GHz would probably not have those issues.

You might try wrapping the B5-Lite in aluminum foil (not the front) and putting a pretty large base of aluminum foil on the ground around it. (5x5 might work, I would go for 10x10) As a cheaper solution to your noise issue. (note, I will bet Mimosa would not recommend this as a solution)

60 GHz would be a pretty good solution as well… Though Mimosa doesn’t make one, yet…

Yeah, 60GHz is what I had in mind. For 300feet with a 1ft I guess that would be solid as a rock.

We’ll try the aluminum just for the sake of it and see how it goes.

Please post a picture of the noise. Could be educational.

We are using 60Ghz for a number of short links. The longest is 350m. All of them are at least 500Mbps.

Thanks Roy.

@William, we haven’t been yet on the roof. I decided to send the guys out once when we have the new 60GHz dishes we ordered and do the aluminum test before replacing them.
I’ll post our findings, but I’m a bit skeptic since I’d expect such device to be already shielded from such interference coming from the sides and behind.
Anyways, will let you know.

There is shielding…however it’s not meant to stop screaming loud radios.

Aluminum foil might work as a test, and if so that’s good news – The problem you’ll have though is that if the suspected AP’s in the building below are running full power, then my past experience shows that you’ll really want to get something just below your radio instead of the ground below it.

You need to reflect/deflect the offenders quite solidly.

This is a battle we fight all the time — consumer devices being set to max power because they think it’s like a speaker – higher is better — and when you make them wide-channel to increase bandwidth, you just take out a larger portion of the band, also screaming loud at full power…

Tin is a similar solution, and even aluminum flashing would be ok and it’s quite “bendable” when compared to foil.

Since it appears you’re moving to 60ghz, then as @William5 suggested, it would be a good educational/informational report.

Things get REALLY interesting when you have what’s called “intermod” interference… Mixing of 2 (or more) completely unrelated frequencies that come out on yours! RF is fun, but can sure be a supreme challenge at times when you least expect it.