First the background..
RB433ah
XR5

Occasionally I have this sector's noise floor go from -94 to -83 or lower, when it does that it drops customers from the normal 21 to maybe 13 or so. When I see this I will disable the sector and enable it after 3 seconds and it will fix it. I use the dude to monitor clients but only have notifications setup on 3 or 4 people, if they don't lose signal then I don't know about the sectors noise floor dropping. My question, is there a script I could put in place that If it drops below -90 the sector disables and enables??

In the Wireless -> Advanced tab you can set the noise floor manually if you wish, this however, may or may not cause problems (though loosing customers completely is a big problem!)

Or alternatively, you can disable periodic calibration, which can have affect the noise floor.

-Brad

Thanks for your response Brad, I don't have Periodic Calibration enabled on any of my sectors, as far as the noise floor threshold, that won't really stop it from going below that will it? I'm really looking for something automatic that if the noise floor drops below say -90 it either sends me an alert or disables/enables the sector to correct it.

When it happens it just happens out of nowhere, I was looking at a sector earlier today everything was fine, I jump on it a few hrs later and it's at -84, disable/enable and it goes back up to -93 and all customers are back up and running fine.

For monitoring, you can set up "The Dude"

and have graphs of the noise floor from each wireless card, and set up an E-mail alert when/if it happens.

If you set the noise floor manually, it will not dynamically calibrate it, and prevent you from having the noise floor drop low. You may want to really investigate the root cause of the problem, and

perhaps not just treat the symptoms. Do you have other equipment near your main antenna site? have you performed some spectral scans in the vicinity with some other equipment? that might be a

place to start looking, and you might be able to band-aid the problem by setting the noise floor manually, that way the AP will never change it. if you set it to -93, the ap will assume the noise floor

is -93 and treat all signals below -93 as noise. It will eliminate the AP from setting a noise floor anything lower (-83 for example!)

i'm sure you can also write a script for that as well. but not my forte, and might not necessarily be recommended.

-Brad

If you set the noise floor manually, it will not dynamically calibrate it, and prevent you from having the noise floor drop low. You may want to really investigate the root cause of the problem, and

perhaps not just treat the symptoms. Do you have other equipment near your main antenna site? have you performed some spectral scans in the vicinity with some other equipment? that might be a

place to start looking, and you might be able to band-aid the problem by setting the noise floor manually, that way the AP will never change it. if you set it to -93, the ap will assume the noise floor

is -93 and treat all signals below -93 as noise. It will eliminate the AP from setting a noise floor anything lower (-83 for example!)

i'm sure you can also write a script for that as well. but not my forte, and might not necessarily be recommended.

-Brad

Brad, you seem to have a good idea on how the noise floor setting works...

I have an CPE running v5.4 associated to an rb433AH v.5.4 with NV2 enabled.
The signals from and to this client are -63 to -65dBm and relative stable.
According the ´Status´ in the client the Noise Floor (in default setting) is -107dBm.
Resulting in a S/N of 43/44dB

But unit is still very regularly disconnecting and re-connecting. This of most probably caused by interferences of other tdma protocol AP's in the region.

I am trying to find a way to tackle these disconnects. I tried and know most of the ins and outs of the other settings but would like to focus now on 'Noise Floor Threshold´ setting and possibly the combination of setting the Periodic Calibration.

I am a bit confused in what the manual NFT can be since when the fill-in window is opened in winbox is shows 127! (NO minus???)
So I am wondering if the level I would like to set has to be in positive or negative number?
I would think negative, like -75 in this particular case. But is this right? (I would still have a N/S of 12 dB?)

Is my understanding that if I set NFT at lets say -75 it means that radio will disregard any signal weaker then -75? (Thus interfering signal with -76 or -80 would be disregarded?)

Is this the way it works?

And what is the "Periodic Calibration" setting influencing on the NFT?

rgds.
Rudy

Well... To attempt to answer your question, which is a pretty good one... you have to delve deep into the atheros driver and how things work. I'll admit it is much beyond my comprehensive powers.

But these settings are supposedly all related to the Adaptive Noise Immunity (ANI) features of Atheros chipsets. Adaptive Noise Immunity is not just an "on/off"

feature of the chipset, but rather, a complete SET of commands that set various parameters on the reciever chipsets demodulator to raise or lower reciever

sensitivity as necessary.... Here are the main parameters in the ANI command set.

noise immunity (variable parameter)
spur immunity (variable parameter only used w/ OFDM )
firstep level (variable parameter)
OFDM weak signal detection (On or Off)
CCK weak signal detection (On or Off)

Factors that go into the adaptive noise immunity algorithm are:

Client or AP RSSI
OFDM and CCK error rates.

Based on these values, and the algorithm used, the chipset can either raise or lower immunity (any of the 5 parameters individually) at defined intervals. It

is also possible for the alogorithm to look at the time spent sending/receiving and make a decision based on errors / time.

It is also possible to not necessarily use all these functions together, and just use certain ones, so how ANI works is highly dependent on how these

features are implemented into the drivers. Now this would be a question for Mikrotik directly, as there seems to be absolutely no information about it.

So, i guess in conclusion... A proper Adaptive Noise Immunity implementation should theoretically make your wlan chipset have lower hardware error rates in

a noiser enviornment... While setting just the noise floor is just a hack way of setting a fixed static noise floor threshold. (Or enabling periodic calibration

which is also something else entirely.) These parameters can be set statically to any real value, or they can be set dynamically with driver algorithms...

highly dependent on how its implemented!

and by the way, your explanation of noise floor is how i understand it currently. You set the NFT using a NEGATIVE number. I don't understand what types

(if any) of applications a positive number can be used for.


Ok, so by no means is what i've written above anything conclusive on ANI, it is just a very brief clip of what i understand it to be. I have absolutely no idea

how far in depth Mikrotik has implemented the parameters of Adaptive Noise Immunity. It could be that they just turn OFDM and CCK weak signal detection

registers on or off based on RSSI beacons, or have a full blown automated implementation of ANI. i honestly don't know.

And if anyone else has input, or has corrections please please let me know.

Edit: After a little more research i've updated some things written here, and have more things to talk about with regards to Periodic Calibration... i'm

determined to really figure this all out.

-Brad