2018 15" MBP + Synology rt2600AC = super-slow 802.11ac. 13Mpbs, MCS=0

I've tried SmartConnect both on and off before, it made no difference. Same behavior observed on the dedicated _5G SSID.

I tried setting 5Ghz to just 20/40 and it had the effect that the MBP would no longer even connect at 5Ghz! It would only connect to the 2.4 at 200-300Mbps, which is fine for 2.4. When I bumped it back to 20/40/80 or 20/40/80/160 or even 80+80, the MBP would connect at 5Ghz again, always at 80Mhz. At one point it seemed reliable on the 80+80 setting, the MBP spending a good couple of hours pushing files around at MCS 8/9 at 1066/1300 Mbps with decent real transfer speeds. But then it fell off a cliff again. As always, resetting the 5Ghz band by manually moving the channel or changing the width would fix it for 15-30 minutes.

Did a factory restore on the router. Set it back up again, sticking close to the defaults, and it seemed fine for about an hour. Then it did it again. Bah. Disconnected 2600 & reconnected the trusty old TC as the sole router+AP. Zero issues the rest of the evening, as it has been the past 4+ years; rock-solid 5Ghz @ 866-1300Mbps from the normal workspaces in my home.

I've spent 3 weeks fighting with this thing. I'm done. Synology has ignored my support tickets. There's either some strange defect in the router/firmware, there's some defect in my 2018 MBP's Wifi, or there's some unknown source of interference in my home that only affects Synology 5Ghz + 2018 MBP connections. I don't know which it is, but of those three, the easiest option is to just return the Synology. Today's the last day of my return window so that's what it shall be.

Guess I'll plow on with the TC! Just hope the darn thing never dies, lol!

Good advice on the Ubiquity gear. I've heard good things. The Ampli-Fi series of mesh routers was my next choice if the Synology didn't work out, which I believe are by Ubiquity. I may give those a shot....

Yes, running the latest/greatest SRM 1.2-7742 Update 5. In my ~1 month of ownership I've learned quite a bit about Synology Firmware SNAFU's from browsing their boards. It's quite troubling.

Apple does recommend using MU-MIMO, so I've left that on. I believe the TC had that too. But I had the same thought last week, disabled, made no difference.

Agreed on the 40mhz trial and the factory reset. Hadn't tried that yet. I'm up for trying anything just to see what kind of affect it has. Though if the solution is no 80mhz then the Syno will get returned as then the TC remains the better option since it's done 5/80 reliability for years.

Good ideas guys, I appreciate it!

I hope it works for you. I didn't notice any improvement with disabling MU-MIMO. I messed with DTIM, lowering from 4 *seemed* to help a little, but didn't resolve the problem

I found another thread that has interesting information... https://discussions.apple.com/thread/8531525

Check out the latest stuff, especially if you have an Apple Watch. Apparently a few have had success in disabling the "unlock with Apple Watch" functionality on their MBP's. Something about the type of wifi connection used for that may be flaky on the new chipsets.

Meanwhile, this Unifi gear has been flawless. My home network & wifi has never been as fast and reliable.

I forgot to mention it, but the "MCS Index: 0" reported in that software above appears to be a bug. It always reports that for any 5Ghz connection on my 2018 MBP. MCS Indexes I'm reporting above are from the OSX Wifi Diagnostics.

Here's a screen grab from right now showing what I mean (with the MBP operating perfectly against the RT @ 1300Mpbs).

The MCS Index in the OSX diagnostics report 0 or 1 when the slow connection is happening.

I have tried channels all over the spectrum, manually setting the TC & RT away from eachother, even forcing them to overlap to see if it's worse. From the lower 36/54 groups to the higher 132 and even the DFS's. Changing the channel disconnects Wifi, which does usually temporarily resolve the issue. But it always returns. I've not observed any difference in length of "good" connection.

The software I'm using doesn't generate a spectral analysis, sorry. My environment is a small-town subdivision. I can see other faint 2.4's, as above. 99% of the time nothing shows up on 5Ghz. Above is a rare 1% time where a whiff of that "Bookend-5G" shows up, but it's very faint. Doesn't seem relevant to speed drop-outs, as above, it's rocking 1300 and that one is fainly visible.

I've had WiFi routers for well over a decade in my current home, relying on 5Ghz since I bought the TC, 4+ years ago. I've never had any issues with the TC doing this. I briefly tried other routers (Google WiFi, Orbi) last year when thinking about upgrading and none exhibited the same behavior. Nothing in my household that I'm aware of has changed in terms of interference-generating things. No new microwaves, DECT phones, satellite, etc. And no other devices seem to be acting strangely either (though none are tasked with moving as much data across WiFi as my MBP).

Great points, thanks for the detail on the Tx. I wasn't aware of that. I figured it was actual bandwidth. I knew MCS was an indication of potential quality/bandwidth.

I've been trying to pay very close attention to what's going on in the household with the drop offs. As far as I know, nothing interesting is happening. And like today, the MBP is sitting at home in an empty house, yet when I just remoted in it's showing slow speeds again. It almost seems like there's some sort of power-saving feature that's idling-down the connection when not needed but not able to resume again when demand is there. I've tried resetting PRAM and SMC, no affect.

Just weird because my other Apple OSX machines, a 2011 Macbook Air, 2011 MacMini, and 2014 Macbook Pro all seem fine with 5Ghz when literally sitting right next to the 2018 on the same table. And the MBP seems perfectly fine with other AP's. And sometimes my MBP is fine for hours on end with the Synology. Then it'll degrade and sometimes it won't regain speed until I do a full reboot of MBP or the Synology. One or the other bounces it back up. Occasionally I've seen it come back on it's own, but it's very rare (or I don't have enough patience...).

Only other thing I see is that when it's slow, the Synology diagnostics show the MBP's connection as "Marginal", the lowest of its three designations with a 100-200Mbps connection speed that doesn't jive with the MBP. So it "knows" the MBP is struggling. Upon reboot the same info bounces back to "Good" or "Excellent", showing the high 866+Mbps connection.

Very interesting, especially the 802.11n 20Mhz No SGI Data Rate column. 13, 26, 39, 52 - I've seen the OSX TX Rate bounce around on those exact numbers when it's stuck in the super-slow mode. Sort of suggests the MBP + Syn connection is somehow "stuck" on 802.11n in just that 20Mhz slot, rather than 802.11ac 80Mhz like indicated.

Yeah, no scale on the X axis, sorry. Full scale above is about 30 minutes. Sometimes it will drop within seconds, other times it will stay up for hours. I purposefully left the MBP on all night, idle, and the connection was still 1300 mbps this morning. I remoted into home around 10am and it had fallen to 13Mpbs. Recycled my Wifi and it returned at 1300. Still at 1300 now. It almost seems like *using* the network is what pushes it into slow mode. Very often it seems to fail just as I'm starting to move some big file across my network or some big Time Machine delta. Have your buddy try moving files around your network, see if that causes it.

Interesting idea on the antenna. I'll give that a shot.

No word from Synology yet...