ePMP 3000 Poor Uplink performance


We’ve been swapping some towers from 1k AP’s with KP Performance sectors to 3k AP’s with the 4x4 sector from Cambium.

What we have seen is we went from good uplink performance with less than 5% uplink retransmission, to horrible uplink performance with retrans above 30-50%. An AP that was happily moving 10-15 Mbps on a 20mhz channel before on 1k is only moving 1-2 Mbps on 3k after the upgrade. Same channels, same GPS sync settings, but different sector antenna.

We have adjusted downtilt and while those customers close to the tower have improved, those far away have gotten worse downlink signal unless we do mechanical uptilt.

Anyway, have others seen horrible uplink performance on their 3k AP’s when upgrading from 1k? I have a ticket open and will be working with Cambium but wanted opinions from others.

First check “Subscriber Module Target Receive Level” epmp3000 at default have 40dBi vs epmp1000 60dBi…
Therefore all SMs transmit at full power and disrupt the opposite sector direction.

Yes I did catch that during the configuration and they’re all set to -60 just like the 1k’s were. So that isn’t the problem for us.

And what firmware are you running on AP and SMs?

4.5.6 on AP’s and 4.4.3 and 4.5.6 mix on SM’s. Elevate, Force 200, some Force 300.

I’m trying to convey that the only thing we changed was the AP and sector. Otherwise same channels and SM’s.

Please make sure you have no 4.4.x on SMs while AP is running 4.5.x already. Anyway, I’d recommend latest official beta 4.6.rc35 to be put on AP + all SMs asap. You changed N sector for AC. It is different chipset and you can expect different behavior if versions between AP and SMs do not match.


I can upgrade them to 4.5.5 and 4.5.6 with the STA firmware we’re approved for but we already did this on one tower and the uplink retransmission remains.

We don’t run Beta firmware on production towers though so I won’t be putting on 4.6.

Is there a way to tell if the dynamic filter is defective or something that could cause this after swapping hardware for the same channels?

IMHO, I wouldn’t set the target to -60 anymore.
For my 2c,-- the chain signals will be worse on a 3000 vs a 1000 if the overall target is -60 on both. I’m not complaining about the 3000’s at all – its just the way 4x4 works.

The reason is: A -60 target on a 2x2 system will be ideally comprised of a -63 + -63, which add up to -60. On a 4x4 system, if you have the target set to -60, it will (if things are perfectly balanced) be made up of -66 + -66 + -66 + -66 (which add up to a -60). So setting the target the same, will result in LOWER UPLINK powers.

Plus - of course - on a 2x2 ePMP1000/2000, that -60 might not really be a -63 + -63… maybe the chains will be a -62 & -66, but the point remains… in a 4x4 system, that -60 target 'might theoretically; be made up of -66 -66 -66 -66 (adding up to -60), but the chains will probably be something like -66 -71 -65 -73, and still add up to -60. On average, the chains will be -3 db lower if you use the same target.

SO - on a 2x2 system, the chains will need to be 3dB stronger in order to add up to the -60, and the AP will tell the SM’s to turn them up by that 3dB. On a 4x4 system, each chain will be turned down 3dB weaker, in order to add up to that same -60. SO - DON’T USE -60 AS YOUR TARGET.

SO SO - for us, we have our target on 1000/2000’s set to -59, and on 3000’s we set it to -56 – and that get’s each chain of each SM associated at the same signal strength.

Now - you may be having other issues for other reasons of course, but for starters - if you only set your overall ‘target’ at -60, then a 4x4 3000AP will tell it’s SM’s to turn themselves down 3dB quieter than a 2x2 1000/2000 will - and that won’t help your situation. IMHO, I’d try -55 and see what results that gives as a starting point, and work from there.

We’re seeing the same issue with F300 SM’s. Regardless of AP, we have a mix of 2000 and 3000 AP’s. All firmware is at 4.4.3 or 4.5. AP and SM’s are always on the same firmware.

We upgraded everyone to 4.5.5 or 4.5.6 and some sectors that were doing 10+ Mbps on the uplink on 20mhz channel are still struggling to do 1-2 Mbps for the WHOLE AP.

This is the same channels, same SM’s. Just upgrading from 1k to 3k AP’s and new sectors.

Customers are asking us to downgrade the towers back to 1k because it worked better even though frame utilization was at 100% at peak times. This is not a good image for our company to “upgrade” but performance for our customers is actually worse.

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Agree, this has been a major pain for us, as well.

You should be able to squeeze much more out of those 1k AP’s than 10-15 in a favorable RF environment. Are you in a real RF congested area? We have 1k AP’s that get to around 70 on a 20 MHZ channel. In all honesty you should really give the newest 4.6 RC35 a shot. I understand that you don’t want to run a beta in a production environment, but its better than crappy service for your customers. We have AP’s getting to over 120 on 20MHZ and there looks to be room leftover.

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I’m only talking about 10-15 Mbps on the uplink side for our 1k AP’s. Upgrading them to 3k with the 4x4 sector we’re only seeing 1-3 Mbps TOTAL for the AP. This is unusable for our customers. I don’t know what to do and I’m just looking for a straight answer from Cambium what it could be. In cnMaestro, uplink retransmission was under 5% on uplink for 1k AP’s and now it’s 30-50% or higher on 3k using the SAME Channels.

Man your complaint is a bit hard to follow, you list Uplink and total and flop on what you are specifying. I can tell you are frustrated, and we have been there with this 3k line. I’d still recommend upgrading to the beta firmware. You’re at 6 days on this post, so that’s at least 6 days your customers have had unusable service. You’re left with a few simple options that vary from quick to time consuming. Test out the beta firmware as suggested, that is the quick path. OR Swap out AP and sector. The other option is to open a real support ticket with Cambium at this link https://www.cambiumnetworks.com/support/contact-support/

You’re not understanding. I’m clearly stating what we’re seeing. This isn’t one AP we swapped. We swapped four AP’s on three different towers and each and every one results in uplink retransmission spiking using the same channels. And each AP went from 10+ Mbps uplink throughput to much lower overall. So unless we have 12 bad AP’s, there is something going on.

Thank you for clarifying, the above is what threw me off Uplink/Upload is the issue on the new firmware. Ok

My best advice is to upgrade to the newest beta. If not you are 100% wasting your time. We have over 100 3K’s deployed and have suffered miserable Uplink on and off the whole time we’ve used them. The only real fix so far has been the 4.6 RC35. We have worked with support, and directly with some of the engineers and none of that did us any good. The uplink issue was very hit and miss for us, and there was no reason we could find aside from a firmware issue. We got to the point of considering ripping down all the 3K line gear and moving to UBNT.

Again, the best thing you can do right now is upgrade to the 4.6 RC35 on at least 1 AP and see if it gives you any relief like it did for ours. If not, swap back to the 1000’s

How many AP’s do you have deployed on 4.6 and have you seen good results?


Cambium, can you confirm any known uplink issues and if the 4.6 firmware will help with uplink issues many of us are seeing?

We have deployed it on 10 AP’s so far and their SM’s. We would have done more, but we wanted to test a small group first. We have seen great results so far. Customers that have had open trouble tickets on these AP’s have reported their service is greatly improved. We plan on putting this firmware out on our AP’s with complaints/issues that are still remaining next week.

Also good luck getting a confirmation on the Uplink issues. They are intermittent. Some folks have zero issues, and others have posted their frustrations here.


From the internal testing we see UL improvement on 4.6 firmware for sectors with high SMs number.
Beside that variable TDD ratio feature is introduced in 4.6. That gives you ability to switch from standard 75/25 to 65/35 improving UL and not affecting DL much.
There were no critical issues reported on 4.6 so far.
(BSA disconnects on E3K have been reported and that is under investigation now)

Thank you.

If I was to place one of my problem AP’s to 65/35, would I need to place all of my AP’s on that level of synchronization or can I leave them on 75/25?