ePMP / Firmware Version questions

Hey Everyone,

I thought I might request some advice from some larger operators of ePMP, we have a site with 10 ePMP APs all across the 5Ghz band. Each AP having 20-25 users on it, we are starting to see some fairly poor performance on downlinks for a number of the APs. I suspect noise may be at the root of the issue, but what I'm not sure is if this noise is self interference. The way our tower is placed we *do not* get back to back sectors and cannot use then for noise reduction. We do use the RF-Elements horn product, and that gives us the ability to add this number of sectors to the tower.

Up until last night we had all the sectors in flex mode, as an experiment I switched them to 75/25 5MS frames with a 6 Mile Max Distance. What I hope to get from you here is an idea of what you have done in a dense AP deployment to optimize your network.

My second question comes down to Firmware versions. We have always been hesitant to change firmware as it seems we always find a show stopping bug. We are currently on and would like to make the jump to the 3.x. Can anyone who operates 500+ SMs (110's, 180's, and 200's) chime in and let me know what version they have found to be most stable?


gps snyc is always good to use.  the horns have good characteristics, but you can still get noise without GPS.   

we've got sectors as deep as 50 subs with good performance using snyc and RF planning + sector tiliting. 

Flex mode has its perks, but in dense situations, flex can and will cause more harm than good.   snyc will reduce your retries, allow you to run weaker signals at better modulations etc etc.    provided you've got outside noise handled.  

GPS nearly eliminates self interference when implemented correctly. 

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Hey Chris,

Do you care to go into detail (outside what cambium published) into a properly implemented GPS sync setup with ePMP?

You definitely want to be using GPS sync... for a start, just turn it on and make sure the distance, ratio and frame size settings match on all the APs - that alone should get you a huge reduction in self interference.

If you're not doing any frequency re-use, that would be pretty much all you need to do. If you want to get into running multiple APs on the same channel, it gets a little more complicated. For frequency re-use to work, you don't necessarily need to have the sectors back to back (especially since you're using horns), as long as the SMs from one AP can't see the other AP on the same channel (and the AP can't see the SMs on the other AP), it'll work fine.

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cambiums publication is actually spot on.  

we generally will use ABAB on the first tower, and CDCD on the next. 

with you have 10 horns on the same tower, you'd likely want to impliment 5 freqencies.     so ABCDE 

your 0 degree and 180 degree sectors share a freq, then your 30 degree and 210 degree share a freq and so forth. remeber to mark one front, and one back. and down the road when your sync the next tower, if it hears a channel "a" AP, and its marked front, you'll need to mark that one as back.     an AP marked as back can hear any number of "front" APs but you don't want to like front or back APs on the same channel to hear each other.  that won't be an issue with the horns as long as your tilting them below horizon or staying out of beam width. 

if they are on diffrent channels, the front and back mark doesn't matter.  you'll just want to use the same cycle.  IE 75/25 on all of them.    also keep 5 mhz gaurd band between APs. 

How about on the firmware front. Do you ensure all APs and SMs are on the exact same version. What version do you currently use, and trust? We as mentioned before are on, and are running a full mix of SM models.

we are still mostly on  

all CPEs that are fielded are on  towers that would benefit from 3.x enhancements have them, but i'm usually show to roll major releases across the network.  its not that i don't trust cambiums releases, if there isn't something there we need, we don't upgrade (and of course security concerns)    

I do have 2 towers that we used the elivate on, and we are keeping those sites to the latest firmware as our network trial, and i'm pleased with the results overall.    once 2.4 ghz elivate is here, i've got a few more sites we will run that release.

we will probably remain mostly until full ipv6 support is out or unless another enhancement or security patch is out that i feel pertains to us. otherwise i'll keep watching those CPE uptimes climb :) we've had plenty get past 100 day session times. 

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I try to always upgrade the SMs along with the APs, but all the new SMs we've been deploying have been on 3.2.x for awhile, so we have quite a few APs with mixed versions, and I haven't seen any issues with that.

I am in the process of moving everything to 3.2.2 (probably around 50% so far... I don't want to do everything at once, in case we do run into issues), and it has been working well.

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Are you running 3.2.2 on GPS Sync too? Can you confrim you use 110's, 200's and 180's?