I have a client I just installed (4625SM) that is only 0.14 miles from the tower. It can hear its AP (North AP) at -52 but it can also hear the opposite AP (frequency reuse) at -72 so only a 20db SNR.
Where this SM should by signal get a DS11 signal the RX rates are unstable so I have it capped at DS8. While an issue this is minor but possibly expected. Is the AP front or back setting supposed to help with this?
Anyway the bigger issue is that this SM caused the UL rates of the SMs on the opposite AP (South AP) to become unstable. Some worse than others. What is odd is that some clients with better signals at the South AP are affected more than clients with worse signals at the AP.
I have the North AP set to -60 on the SM receive target signal like Cambium says as I am using 30db as the front-to-back of the OEM 4x4 Antennas.
I had to turn down this particular SM to a TX power of 0 which gave it a -64db signal at the AP to lessen the effects, but the South AP SMs TX rates are still lower than before this client came online. What is odd is that other clients on the North AP with -60db signals to the North AP did not seem to cause any issues with the South AP clients. It was not until I brought this close SM online. I even have another SM on the norht AP at .33 miles and it does not cause any issues for the South SMs.
Is this expected behaviour? Could the South AP be getting multi-path signals greater than the North AP SM signal minus 30db from this SM?
Honestly it makes me regret putting this client online as they are now affecting a dozen other clients who have been good until now.
These are the South AP SM TX rates to the AP. Yellow line represents when the new client on the North AP came online.
I will also mention that the North and South AP are not directly front to back. The are offset. One is mounted to a pole on the NE corner of a grain elevator catwalk and the South is on the SW corner pole. The are probably separated east to west by around 10-12ft and from north to south by around 6-8ft.
Would have preferred to use the 4616 SM for this one but they are not available yet.
I also guess I could try the Asymetric Channel width of the recent beta FW to offset the UL frequencies of the North and South AP to use 40mhz on opposite ends of the 80mhz channel, but I want to see if we can resolve this issue as it is first, if it can be resolved.
I did exactly that with one AP and that had a clear benefit on a few SM’s. Most of them were already working OK and not having any problems in the first place, but a couple SMs were not ideal with more retries than we’d like - and moving that AP 80Mhz down / 40Mhz up seemed to smarten them all right up.
Of course, the overall possible upload bandwidth is also halved, which can introduce it’s own problems, but in this case, we had ample bandwidth surplus upload, so this was a positive where we tried that feature out.
If I cannot find a resolution for this I will give it a try, but I hope someone from Cambium could chime in and let me know if this is expected behaviour based on my description of the issue and setup.
I tried doing the asymmetric channel with north AP on lower 40mhz and south AP on upper 40mhz and noticed very little improvement for my issue in this thread. Some but not much.
I then turned it off and it caused the DL rates for many clients to become 2-3 MCS lower and get stuck. I needed to reboot the SMs to fix it.
I am going to probably downgrade back to 5.9.2 as just the act of upgrading to 5.10RC35 (no changes) caused rate instability for almost all the clients.
