ASUS RT-AC66U loses MIMO and slows down on 5 GHz band

[theveterans]

I bought the ASUS RT-AC66U 2 weeks ago to take advantage of my laptop's AC WiFi adapter. I used it as a 5 GHz AP Mode. I'm at the room with the router in line of sight and I'm 99% always connected at 866 Mbps. However, earlier today I noticed that my laptop only connects to 433 Mbps. At this point, no ping spikes or lag happens while streaming radio and Silverlight videos but throughput went drastically from 45 - 55 MB/s (866 Mbps) to 20 MB/s (433 Mbps).

Then I turned off the router and turned it on again and my connection went up from 433 to 585 - 780 Mbps. However, it's still not at optimum whereas I've 99% of time held a 866 Mbps connection prior to this "reducing speed after a some time"

My last resort was to reboot through the router page. It worked and I'm back at 866 Mbps stable. RSSI is around -35 dbm as well.

My 2.4 GHz is turned off and the only thing I changed in the 5 GHz settings is to disable WMM ASPD and change TX power to 140ms. I'm running the 3.0.0.4.374_5517 stock firmware.

I've searched for online reviews and discovered similar issues but my case isn't as dramatic as theirs.

Do you guys ever experience this issue? Right now I'm 50% considering for replacement AC66U if this happens again after 2 weeks.

 

[RMerlin]

Since your speed seem to be cutting in half, make sure it's not your router downgrading to 20 MHz due to the presence of interference. Check your wireless surroundings using a tool such as Inssider to ensure your router is set to a channel that is free from interference.

 

[theveterans]

Thanks for reply!

The router is on auto channel and using Inssider it finds channel 36 - 48 free from co-channel and overlapping channels. That's one factor why I get stable 866 Mbps when in line of sight with the router. It's still odd to me that the router would just slow down like that though it's very warm to touch but not hot enough to tingle my palm. I would guess that the surface temp of the chipset is around 60 degrees Celsius but it should still be within operating limits. I've seen reviews of this router running hot but it shouldn't be overheating after only 2 weeks of use.

Hopefully this is just a minor glitch and it won't arise again for months

 

[theveterans]

It seems like no one has this issue. I just hope the router doesn't end up like on this review: http://www.amazon.com/review/RTKTCD0EE10BG/ref=cm_cr_pr_viewpnt#RTKTCD0EE10BG

Mine was manufactured on 2014 according to the side of the router box so I'm hoping it's better built than the 2013 even though the H/W version is still A1.

Since the reboot, my laptop still connects at 866 Mbps for 13 hours straight (left it running when I went to work). Throughput is still in top shape and connection speed doesn't even decrease at all. This is my first ASUS router and I chose this router due to being cheaper than Netgear R6300 v2 at the time of purchase. I'm not really a poweruser myself so I'm keeping the stock firmware since it has a lot of features for a stock firmware except it needs the Merlin FW to get the "beamforming +" feature that Netgear R6300 uses.