Frequency Reuse Questions

I have a question on Frequency Reuse. I have (all 2.4ghz) 3 epmp sectors currently up and running and still have one sector of a UBNT Rocket m2 and I need to change out yet. so 4 sectors total I have 2 of my epmp sectors back to back they are about 8 ft apart. The 3rd epmp is back to back with the rocket M2, which I still have to change out the rocket yet but have not had time. I am going to use elevate on this sector for clients I think in a month or so. Anyway I want to be sure I have my Frequency Reuse settings correct. AP1 and AP3 epmp are back to back. AP1 settings are Frequency Reuse = Back Sector and AP3 Frequency Reuse settings are Frequency Reuse=Front of sector (or should this be off) Both are set to the same channel, power output, frame rate and antenna.

Also is there anyway to tell if gps sync is working correctly? My GPS area is showing this. 





Yes, AP1 as "Front" and AP3 as "Back" is the correct setting. The other settings that need to match are:

1. Frame Ratio

2. Frame Size

3, Tx Power

4. Subscriber Module Target Recieve Level

3 & 4 are key to even up the self interference/noise levels in the system. 

Last but not the least, please ensure you are using sector antennae with a good F/B ratio, i.e. > 30 dB. The Cambium sector antennae provide you that. 




to add to Sriram comment, 

if you can figure out your actual noise floor, you can push your target power as weak as you can to hold your max desired uplink mcs.   if you have no noise at all to deal with (in rural settings it seems we are our own worst enemies with noise) you can push your target rssi to 65 ot 66 so your able to use much weaker RSSIs much more effectively.   

my personal home connection is a 2.4 ghz force200, my rssi would not work at all on UBNT, and as you can see, is just fine with epmp thanks to GPS and a few of the extra knobs.      the AP group i'm attached to uses -66 at its target uplink power, the cpes are that loud are hitting mcs 14 15 for uplink and the downlink.   if i had been using the default target power of -60, and my uplink is -77, my cir would only be 13db.   enough to work, but only mcs 9 or 10 effectively. moving to -66, i'm not at 20db CIR and can hold MCS 12 no problem.         if you've got noise to deal with you may need to increase your target RSSI.    in really noise areas we've had to move up to -55 to keep them running well. 

attached are screen shots of my wireless stats and speedtest.       this connection is a 10mhz wide channel, and 14 other subs on the AP runing 75/25 ratio with gps reuse on the opposite panel.   not quite peak time yet, but its 7 pm and getting busy.

welcome to cambium!    


So I went to do a spectrum analyse  this morning to see if anything changed from my ubnt spectrum scans and now my ap is stuck in that mode and I have about 10 clients on it that can not connect. I change the settings in the readio area to AP and it just sits there at applying and the reboot button lights up and everytime I reboot it is back in spectrum mode. Could us some help as soon as possible does cambuim have a call in line. ? Firmware 3.4.1

Will it reboot via ssh?

I am still having troubles getting my requency reuse working correctly. I have updated the firmware to 3.2.2 on all ap's, I have the latest gps firmware on all them. Here is what is happening and config

I have 2 ap's back to back they are about 10ft apart,

I am trying to use a 10mhz channel (2452)

My transmit power is at -21 my antenna gain is at -15 and target receive is at -60

Ratio is 75/25 using 5ms frames  on both AP's

AP 1 has frequency reuse ticked as front

AP 2 has frequency reuse ticked as back

Sync Source is GPS and hold off time is 30 on both

When I try to use this config  with 2452 as the frequency on both ap's the clients can barely talk and throughput is horrible if I move one ap to a different frequency like 2407 the sectors run much much better but shouldnt I be able to use 2452 on both ap's with these sync settings and not have a issue? 

Did your set your tx power to -21 or 21 ?

Could ypu post a screen cap of your stayys wireless page and performances pages ? Your gps settings sound correct. Also what antennas are you using ?

My transmit power I have no option to choose  if it is at -  it is only up down controls to change the power, I am aslo using cambuim 90 degree sectors as recommended. 

Here is a image of what I have. 

what are your wireless downlink quality indicators look like?

these are at the AP, under status, and then wireless

from the CPEs what does your uplink quality look like ?  (these are found on the main page) 

on the CPEs under status and wireless, can it hear both of the APs within 30db of each other?     

if it hears both APs, and they are less than 30db apart, it will have a negative effect on throughput.  the more similar the RSSI, the poorer the performance would be. 

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I do have 3 clients that are very close to the tower that can hear the other ap's farely well. For instance one client is connected at -58 but can hear the other synced ap at -68 according to the wireless  monitoring page. The other 2 clients are similar in hearing the ap's

10 db difference isn’t going to work, mcs9 gonna be hard to hold

Tilting your sectors forward should improve your cinr so you’ll be in good shape. If you can share your antennas asl and cpes asl plus your distances to your cpes i can help you calculate your tilt. Ill need to kmow the asl of your fuetherst sub and distance too


What if I took the hot cpe's and moved them to a sector pointed away from them the 3 hot cpe's can see another sector at around -74 


Well, as a little test I took the 3 very hot radios off the sectors and connected them to the adjacent sector, there link now is at around -67 or so and the frequency reuse appears to be working I have tested a fewe clients and before I could barely pass traffic and now I can wireless speedtest to about 28mb There is barely traffic on the ap's right now so I am going to double check it in the morning. 

The CPE's are all Force 200 2,4's and the AP antennas are all cambuim epmp antenna's . The fartherest link is 6miles out. Is that what you are looking for. 

@pgator17 wrote:

The CPE's are all Force 200 2,4's and the AP antennas are all cambuim epmp antenna's . The furthest link is 6miles out. Is that what you are looking for. 

part of it,


to properly calculate sector tilt, in each sector you need to know the nearest CPEs distance from the tower, and the antennas height above sea level  (above ground level is a dynamic value), the furtherst CPE and its height above sea level and finally the APs height above sea level 



this information can be used to calculate the angle down to the nearest subscriber, and the furthered.  then you'll want to tilt the sectors as far forward as possible so the furthest CPE can still get your signal without issue, this will direct the majority of your signal field to your mid range cpes and your near side cpes will get a large push if they are currently out of angel.   that can take your 10db separations and move it to 20db or more depending how far out of angel they are.