So we use two of the CPE510s as a wireless point to point bridge from our fourth floor office near the window to the top of a parking garage about 130 meters away (which is not far at all for these things), with a pretty clear line of sight. One side is configured with the AP Client Router mode and the other as an Access Point. They both have latest firmware. For over a year it was working fine but in the last few weeks we noticed these intermittent periods of high latency across the link. Normally pings have a latency of 2 to 5ms but they can now go as high as 1600ms sometimes. I notice it tends to be worse in the morning as people start coming into the office but can occur at different times throughout the day; usually in the evening and late afternoon its better. We're not sending a lot of data over the link either.

I tweaked various features to no avail. Our wired network up to the wireless device has basically no latency, so it's definitely something about the TP Link. I'm thinking the only variable that may have changed is that more people moved into the building and there is more interference from other networks on the same frequency ranges or channels in the 5Ghz range. However, it is set to auto, so it's supposed to find and move to the best available channel with the lowest noise and interference. Spectrum Analysis indicates fairly even spread for the most part. I've also used the Survey feature and found there are up to 82 other networks and the 5805 range seems the least crowded, and what the auto setting seems to choose the vast majority of the time. I even manually set it to that for a while, but it doesn't make a difference.

The SNR is consistently rather low, from 18 to 24 usually.

MAXtream is enabled, for what it's worth, but I'm not sure it really matters in this case. Short GI wouldn't help in this situation either, I take it.

Results of the survey:

How should this be interpreted in terms of the SNR from other devices SSIDs? As I said the 5.8 range has the least others on it, but how should I take into account the strength of the noise? Higher figures (less negative) are stronger and will cause more interference, right?

On the link inside the building next to the window:

On the other end on the parking garage:

The advanced settings are the same on both sides:

Noticed the CCQ isn't ideal either, so there is some retransmission.

I was also worried there might have been a degradation in the hardware capabilities from running it at max dB for a while, so replaced both devices with identical fresh ones we had as a backup and configured the same way, but we still had the same problem.

Also did a port mirror on the Cisco switch in our network to get some traffic for analysis on Wireshark, but am somewhat new to all this so I'm not fully sure what I should be looking for in this situation. Or even if that would be particularly useful for this.

Any ideas at what to look at or tweak? Much appreciated.