This was first fixed by LOS 16 with their stock kernel. The fix is also in Derp 3.0 kernel ("Rebased over CAF Pie kernel (LA.UM.7.2.r1)"), which can be used with custom ROMs like RR and PE. This kernel can not be used with MIUI, but MIUI did not have this problem, so that does not matter.So it looks like it was changes/fixes to the WiFi driver in CAF that had to be merged into the kernel. Other custom kernels which also include those fixes would very likely also fix the problem.-----------------------------------------------------------------------This is the continuation of the discussion from this thread: https://forum.xda-developers.com/red...3804473/page85 I have a problem, together with a few other guys (discussed at LOS, RR and AOSiP threads) and that is WiFi idle drain on custom ROMs.I tried various Oreo ROMs (LOS, AospEx, AOSiP, PE) and various kernels (stock, NoName, Derp) and various firmwares (9.5.6.0, 9.5.11.0, 9.5.17.0, 8.7.5 and even 8.8.16 non-arb) and always have 3%/hour battery drain on WiFi, while I have only 0.5%/hour on LTE.There was no problem during my 2 weeks on MIUI global stable 9.5.13.0 and 9.5.17.0.There are apparently 2 settings that can affect WiFi power saving on clients: DTIM and UAPSD. On my Unifi APs, DTIM was at 1 (default) und UAPSD is off. I tried with 3 and on, but it did not change anything.This is all while the device is in deep sleep.Until now, I only had the drain at home (5 GHz, only tested once with 2.4 GHz). At work or in a hotel, everything was OK. But all other devices do not have that problem on my home WiFi and neither did this phone running MIUI.For example, LOS 15.1 with same apps and same WiFi causes no such drain on Note 4/Mido.