Thanks for the update, always great to get more results from the field.
If the sector utilisation was really ‘capped’ I would expect both that and your throughput graphs to have a flattening at the top. We don’t see this and the system seems to meet the peak demand.
To explain the rise early in the morning sector utilisation, without any subsequent increase in the day despite the increase in throughput, I propose the following may happen.
During the night there is just the slow background traffic mainly covered by SU-MIMO. In the morning as a few more users come on line there is more demand, which will initially be met by SU-MIMO (this will increase the sector Utilisation). During the day as more load is placed on the AP it will switch over to using MU-MIMO groups more and more often. This may actually decrease the sector utilisation figure as the MU-MIMO operation is so much more efficient than the SU-MIMO it is replacing. This leads to the, not immediately obvious, conclusion that the sector utilisation can be lower during the peak throughput times (e.g. 8 or 9PM in your data). I think you still have a significant overhead available on this sector.
If you also managed to collect the SU-MIMO utilisation and MU-MIMO utilisation then we could corroborate this.
You could also look at the MU-MIMO multiplexing gain, which should increase to a peak in the busy time.
Finally, you could also collect your original 450 DL frame utilisation for comparison – as that is where this thread started. This should confirm the MU-MIMO usage increasing as the frame utilisation gets large (the frame utilisation may seem to plateau but the actual throughput and sector utilisation should not).
Thanks again for taking the time to share some real world performance data with the community.