Multiple B5 issues

#1

Hello, I have two issues. The first is, upon reboot, both of my B5 radios report a different altitude every time. I believe that may be causing the second issue, but I’m not sure. My second problem… my link is only ~800ft yet [from the Access Point’s dashboard], the RX has a way lower PHY and MAC throughput than the TX. I have tried re-aiming, checking the cables, proper grounding, making sure the spectrum I’m on is clear, I’m even running beta firmware (1.5.2 beta1) and nothing has seemed to have fixed this. I usually see a high (20% or more) PER when the throughput drops down. I have contacted support multiple times about this issue and a solution has never been found. It is getting frustrating as I have a great SNR, around 30-40 dB, but on the Access Point end of the link, the signal strength keeps jumping around. I’m starting to regret making this purchase even though I’ve heard excellent things about Mimosa.

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#2

I’m not sure about the altitude, maybe you have GPS issues / interference.

On the SNR side, what is your RSSI level? have you tried to back off on the power? We don’t have enough B5’s to know for sure but years back, I now some radios being too loud could cause an issue. Dialing back the power reduced the issue.

800’ isn’t very far, so I’d expect this to be flawless. We’ve gone further with both 24 GHz and 60 GHz with success.

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#3

Sorry I missed your post @Jim, this is right up my alley.

Would you mind posting your Dashboard, Channel & Power and Location pages from each side of the link?

I have a whole slew of questions, sorry if they sound stupid, but sometimes my idiocy helps in diagnostics.

How much different altitude? A few dozen feet is within GPS’s error margin.
Do the actual GPS Coordinates change?

How often do you reboot your B5?

How much does the signal strength move? Like is it < 1dB or >1dB, if greater what is it? Is it one chain or multiple chains that are changing.

You wouldn’t happen to have a picture of what the link looks like? Like from the AP to Client or Vice Versa. Or maybe a Google Maps picture?

On that train of thought, I am guessing that there are not any link obstructions otherwise we may have found the source of your problem, but might there be some large metal structures along the path or metal roofs? If so, approximately where are they in relation to the link?

Have you ever used Mimosa’s Link Planner tool? If so, what does Link Planner say you should be getting as far as signal strength?

Would this link have happened to have replaced another link? If so what did it replace and what were the signal characteristics you saw there?

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#4

So just an update for everyone and to answer questions:

RSSI was around -50dBm, and I did try backing off power. According to my phone GPS, one location is 422’ and the other is 427’, however the Mimosa would be anywhere between 400’ and 500’. I did not reboot my B5 except for when these issues started occurring. The signal would jump around +/- 10dB, and it would usually be the last 3 chains that would either drop out or jump around. The link is rooftop to rooftop with only a trailer park being between the buildings. I did use the link planner and it seemed to think I should be getting around -39dBm or so.

After working with Mimosa’s support multiple times, they all seemed to agree that the 5GHz spectrum around here may be too crowded. I find that odd because one direction was always 1733Mbps while the other usually settled out at around 175Mbps. I had also tried changing channels and widths, with the same issue always happening - an imbalance of the UL/DL speed.

I ended up returning the B5s and purchasing 24GHz radios instead. Lo and behold - it took me 5 minutes on either end of the link to align and have a -37 dBm signal strength and max throughput.

Still makes me wonder if I had a bad radio to begin with, or the spectrum was truly that rough (we do have a local company that provides internet to other businesses via 5GHz UBNT links).

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