Hi,
In SM PMP450 Radio Parameters, What does it mean the following information (in bold)
" (target power [31 dBm] exceeded maximum) "
We remark this kind of information in SM which are bad quality of modulation.
Find in attached file a screnshot.
The AP will tell the SM to turn up it's power to reach the desired receive level set in the AP. If the level is above what the SM can transmit at, you will see this message.
Are there any guides as to what levels we should set as the target?
I typically use the following for each band:
-65 for PMP450 3.65
-60 for PMP450 5
-55 for PMP450 2.4
-50 for PMP450 900
Thanks Eric, greatly appreciated. Do you have any insight as to the underpinnings on raising/lower this value- such as what happens to the overall noise floor? Assume would also depend on what channel reuse scenarios are in place.
Hoping for a little more insight as to what the overall tradeoffs are when adjusting this value, as Cambium's documentation only states that "This value represents the transmitted and received power (combined power) perceived on the SM" - which is apparent, but wanting to see what the tolerances and ramifications are.
The values I've selected represent trial and error over time across my network.
The 3.65ghz one is -65, because if you set it to a stronger, like -60dBm, you might have an LBT event because of the amount of energy hitting the AP. ALSO, the 3.65 band is generally the most quiet of all the bands listed, so there's a better chance of having a higher SnR, because the noise floor is so low.
The 5ghz is -60, because the noise floor typically isn't as bad as 2.4, or 900.
The 2.4ghz is -55 because typically the noise floor is poor, and we want all the SM's to connect with the highest SnR possible, and thus have a better chance at achieving a higher level modulation on the uplink. The maximum uplink power for SM is 22dBm, so it's very rare that you'd run into a situation, even using back to back frequency reuse, where you'd be blasting too much energy at a tower, and thus effecting the opposing AP in a back to back setting.
The 900mhz is -50 because typically the noise floor is incredibly bad, and again, we want all the SM's to connect with the highest SnR, and thus have a better chance at achieving a higher level modulation on the uplink. You might want to fine tune this, or possibly back off to -55 or -60 if you're running a back to back frequency reuse configuration, and you have clients that are very close to the AP, using the maximum output power of 25dBm.
I ended up using -60 for both 3.6 and 900.
It's a balancing act between higher uplink modulations for customers with strong signals and reducing self-interference impacting weaker signals. I ended up finding a few customers with strong signals, and adjusting the value until I found one that just barely allowed them to use 256 QAM.
I have a quetion about target rssi.
When playing with the levels whether it is lower or higher, I see when I set at -70 I get lower SNR.
If I set it to -50, I see -20 or lower SNR. Maybe I am doing this wrong but the question is, do you adjust the Target based on what SNR you are seeing from the SMs?
Thanks
The target should be set so that SMs adjust themselves to get to the best modulation possible. You probably want to keep it as high as your network can tolerate. If you don't get to an RSL of around -60 or so, you may not be in the highest modulation.
However, if you set it to something like -50, the SM will drive very high Tx Power when it doesn't really need to, causing unnecessary interference for the rest of your network.
You really shouldn't need to modify this much once you have a comfortable number for your network.
It should definitely NOT be something that you're changing on a per SM or per sector basis.
