Hi team,
We have a 2x v3000 PTP links deployed. One link generally has a large amount of traffic transiting at any given time, up to >1Gbps and usually never less than 100Mbps, and it operates at MCS-12 at all times. This link is running software version 1.3.1.
The second link has a much smaller amount of traffic, up to ~50Mbps but is generally utilizing ~1Mbps-10Mbps at any given time. We’ve recently upgraded this link from 1.3.1 to 1.4 in an attempt to solve the following.
I understand that when the link session is idle the radios will fallback to MCS-9 (or any highest MCS achieved below MCS-9) but we see strange modulation variability on this link. After a reboot, the radios will happily operate at MCS-12 for a number of days and then drop to a much lower, “random”, MCS rate. We have even seen this link gradually step itself all the way down to MCS-2 over a 3 month period:
In the most recent example, the link dropped from MCS-12 to MCS-9/MCS-6. This MCS drop oddly coincided with the RSSI and SNR improving. This doesn’t seem like “idle session” behavior and I believe the link should be capable of maintaining MCS-12 consistently given it’s overall wireless link metrics actually out performs our other deployment, and there is generally always some amount of traffic occurring. Packet Error ratios are also no better or worse than our other deployment as well. Radio metrics below, after a reboot was performed on 19-11.
Are we potentially missing or misunderstanding radio behavior here? Is there a way to manually disable the link adaptation feature for troubleshooting purposes? We monitor and alarm on our backhaul links if capacity drops below a certain threshold.
