Nearby towers, how to sync together to minimize interference

We still haven't deployed many of the Cambium 2.4Ghz sectors just yet, but I had a question. How would I setup the GPS synchronization on two towers that are around 8 miles apart, if they in fact see each other? Can this be possible? The plan is to run 3 120° channels to minimize the upfront cost of the AP's, and we don't have many SM's on our current sectors anyway. I know I can't run ABAB, so as of now I'm running ABC channels. How would I properly set this up on nearby towers to minimize any self interference?

All settings that affect frame timing (AP mode, max range, Up/Down ratio [maybe max reg?]) have to be the same, and sync has to be reliable and not internally generated.  Once that is achieved the APs should (at least mostly) not see each other, regardless of channel.  The idea is that all the APs transmit during the same chunk of time (determined by the sync pulse) so they don't 'hear' each other.  But that's only part of the special sauce.

Apart from the sync working to protect the APs from seeing each other, you need to try to ensure no client sees two APs on the same channel on two different towers, at least not without a huge difference in strength.  For example, a customer with an SM mounted way up a tree that can see both towers nice and clear, one behind the other, will see all APs facing it transmitting at the same time, so any where channels overlap will likely not be usable for that client with a possible SNR of 0-10dB...

The first part is easy, the second part is mostly dependant on local geography.

And don't forget the usefulness of downtilt at the AP - with towers 8 miles apart you can probably downtilt enough at both to greatly reduce the signal that will be seen by clients at/beyond the other tower.  (depending on coverage needs and geography that may not be possible though)  Interfering signal at -90 is surmountable, -70 probably not...

In short, sync makes it all possible, but it's not the only factor in whether it actually works on the ground.



I was told by Cambium that the max distance setting on the ePMP radios does not affect their SYNC abilities like it does on the PMP450 APs.  I am under the understanding though that the rest of the setting sneed to be the same on ePMP for APs to sync properly (timeslots / AP Mode).  I was told onm the ePMP always set the max distance to the max distance of the farthest client (add a bit to ensure no issues).

The ePMP 2000 should operate the exact same way correcty?

I'd like confirmation please....

Hello carullos,

The information you have is correct. And yes, ePMP2000 operates in the same way.