I have two nanostation M2's set up 1/3 mile apart on channel -2 @ 5MHz bandwidth. I have the distance on both set to .6mi (minimum setting). They are the only two nodes in the area.
Admittedly there are roofs of houses and trees in the signal path. Most of the time I see 100% LQ and around 10Mbps.
One station's signal/noise chart is rock solid while the other has sudden jumps in both signal and noise. These are the respecive charts for the same 48 hour period:
Is this normal? My only guess is that the receive amplifier is switching to a higher gain, maybe in reaction to a signal drop-out...
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Nanostation M2 Signal/Noise
Fri, 11/18/2016 - 19:21
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KD2EVR
Nanostation M2 Signal/Noise
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This can occur when there is interference. The firmware has this "Ambient Noise Immunity" control system working to minimize the data error rates. Any obvious sources of interference? Turning on an old microwave oven at those times :) ?
See https://wiki.freebsd.org/dev/ath_hal%284%29/AutomaticNoiseImmunity
Joe AE6XE
I already determined that 5MHz on channel -2 gives a usable signal while 20MHz on Ch 1 barely works.
Starting to see a pattern. We installed our first semi-permanent node this Saturday high atop the local firehouse. It was another Nanostation M2 pointed towards the two original nodes which were now both pointed to the new one, everything within about a 1/2 mile. All was well with good signal strength and -95dBm noise at all stations, the two original ones no longer seeing each other.
Later on I fired up a fourth nanostation on the dash of my car and drove around a bit. Some time after that, I noticed that the new station's noise level had jumped up to -85dBm and it was having trouble connecting with the more distant station. At some point I rebooted the firehouse node and everything went back to "normal". Is it possible that the weak/varying signal from the mobile node was the trigger of the corruption?
Seems like it is kicking up to a higher gain to try to pull in a weak signal which raises the noise level which turns the good signals into marginal ones to it never goes back so normal...
It's difficult to determine from the SNR chart what combination of these things are taking place. What we have found is this logic can get stuck at times. I put in some code in 3.16.1.0 to kick the logic and reset (to trigger calibrations in the driver). But just like the root-cause challenge, it is difficult to know what is noise and what is a legitimate signal.
All it takes to trigger a reset of this logic is to do a wifi scan (a channel change triggers this) and you should be able to avoid doing a reboot. But if the environment stays the same and the 'interference' still exists, we'll find our self back in the same boat. Best to engineer to not have weak signals live that end up being interpreted as noise.
We've not done very much testing with this ANI logic turned off. The one time I tried it, the situation was worse--doesn't do these receiver optimizations. Maybe something to add "ANI on/off' toggle to get more data and operating choices.
Joe AE6XE