I have a Motorola 900Mhz Canopy AP that normally holds about 25 subscribers, in the densely packed pine tree forest of East Texas. Normally these customers have no problems, whether 1.2 miles or 8, they lock on and stay connected. About 4 weeks ago, amid all of the torrential rain, the AP started logging more than half of it’s subscribers falling off for about 5 minutes, then all that hadn’t connected to it’s sister APs connected right back up for an hour and ten minutes before falling off again. As we were dealing with the high winds and flooding I didn’t notice it until we had a clear day, about a week and a half ago.
None of the other APs on this tower are experiencing this problem, and I’ve rebooted every SM and anything else attached to the tower, to clear out anything that might have been introduced.
I am 99% positive that it’s interference from outside of our system, but I have done spectrum analysis with the AP in SM mode, as well as from a couple of spots nearby during the dropout periods, and I haven’t seen anything conclusive. As it only happens for 5 minutes every 1:10 in a heavily wooded area, it’s proving difficult to track anything down.
The timing is like clockwork, regardless of what I do to our network or the devices, it drops a significant number of our clients off every time. Neither distance nor signal strength appears to prevent it, though our less than fantastic signal customers do tend to have higher reregister counts.
So, I was wondering if anyone has experienced anything like this before, or has any idea as to what may be causing it. Any help, or questions to clarify would be really appreciated.
Thanks,
Jeff Williams
Network Admin
ESA Wireless
Longview, TX
it most def. sounds like a freq. issue. do you have your AP’s timed together? When youre running a spectrum test is there another freq that you could move to for trouble shooting?
vince wrote: it most def. sounds like a freq. issue. do you have your AP's timed together? When youre running a spectrum test is there another freq that you could move to for trouble shooting?
Yeah, that was my first thought, too, but I switched up to the more polluted 924 channel (I'm running at 906) and along with some of the expected reregisters, like clockwork, the subscribers dropped off at the 1:15 mark.
Yes, all of my aps are synced to GPS and it's not losing sync, minimum 8 tracked satellites, etc.
Thanks,
Jeff Williams
Network Admin
ESA Wireless
Longview, TX
Could be a SCADA system near-by reporting in to the master controller?
Swap the AP yet?
amd phreak wrote: Could be a SCADA system near-by reporting in to the master controller?
I'm almost positive this is the problem, I just wanted to get some feedback on this. I'm not sure about how I would go about tracking it down due to the short time span I have to work in.
amd phreak wrote: Swap the AP yet?
This would be a last ditch effort, after swapping out everyones subscriber module, as the AP is not on an easily accessible tower and this particular AP is the worst of the 6.
Vince -
After your comment on switching to a new frequency, I went back and tried 924 again, and it seems to have sidestepped the problem. I'm no longer seeing the complete dropoffs. However this is not a good solution for us, as 924 is incredibly polluted around here (the SCADA systems, et. al.) Can you explain how you arrived at this suggestion and why it would only be affecting the 906 channel?
Thanks,
Jeff Williams
Network Admin
ESA Wireless
Longview, TX
The scada system could be a spread spectrum system. It’d trash the spectrum all over. Or…it could be a frequency hopper. Many different types.
The rains and flooding could have damaged the transmitter or antenna on one of the SCADA radios causing it to shift freq or to give off spurious emmisions. You might need a real spectrum analyzer to find it. Being that it happens at the same intervals sounds like SCADA to me.