Wifi slow on Macbook Pro

Hold down the Option key while you click on the Wi-Fi icon on the menubar to open up the tools for investigating and fixing Wi-Fi issues

First is "Open Wireless diagnostics", which opens the wireless diagnostics Assistant, but does not proceed.

There are about eight different things you can do from here, but the top-level is to choose Diagnostics off the Window menu, or simply click continue, to do a quick check for Gross misconfiguration or operating problems. Your Admin password will be required. If any recommendations are shown, you should consider then seriously.

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The usual way we do this with ONE Router and No boosters is the set the Router to "automatic" channel selection. Then when the Router powers up, it listens momentarily to what is already on the air, and adjusts to the least-busy channel.

it is not an accident that every debugging procedure starts with "cycle the power to your Router."

The next level we can use is to use the SCAN tool in Wireless Diagnostics to look around at what is visible over the air around the Mac. This has the advantage of showing what is seen at the Mac, which may be slightly different than what is seen at the Router(s).

this is what it looks like:

(drag and drop on Preview to see larger, or make your own)

Click on the channel column to sort by channel. This tells you the nominal channel in use, but every channel also spreads up and down the channel numbers, depending in its channel width. For example, channel 36 at 80 MHz wide spreads to engulf everything up to channel 48. You may need to look up the spectrum spread with some tables, available online. Or post back here and readers can look those up for you.

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Your initial measurements show there is a problem, but can not really help diagnose what that problem really is.

Option WiFi numbers (shown in the last pane) are much more useful.

Using the modulation technique showing, 802.11ax 80 MHz wide on channel 149, with two working antennas, your throughput should be 2x 340 for a Transmit rate of 680, where at the moment yours is 216. Also, your noise number is a bit higher than expected, and it's on a logarithmic scale, so subtle differences from expected turn out to be HUGE.

My conclusion is that you have one of:

• a disconnected antenna wire

• another Router using your channel or an adjacent channel. (80 MHz wide on channel 149 uses ALL channels from 144 to 161, inclusive. A neighbor's or your own Wi-FI Access Point on one those nearby channel will clobber BOTH.

(How to detect in next posting)

The screenshot posted said they had made a 802.11ax connection. If the Router can only do 802.11ac, it is usually reflected in the Option-Wi-Fi parameters as an 802.11ac connection.

I had a connection that was dithering between two speeds, and if you caught it at just the wrong instant, it showed the higher MCS index with the lower Transmit Rate.

There is definitely something not right, but we need to hear from the original Author about anything more they might have learned, or any more assistance needed.

for complex troubleshooting, third-party App WiFi Explorer, can draw a Spectrum diagram, which can be extremely helpful. That Utility is available at the Mac App store, is inexpensive, and has a three day free trial.

these folks are getting NOTHING done.

one more thing:

RSSI of -45 suggests you may be quite close to your Router or Access Point. Consider connecting using an Ethernet cable.

A speed of 216 Mbps doesn't correspond to an MCS index of 8 on any of the MCS HE, HE ODFM or HE ODFMA tables. Usually corresponds to MCS 2, 7 or 9 depending on the number of spatial streams and other factors.

Suggests something isn't working quite right.

Although, I suppose it's possible that 802.11ax at 80 MHz bandwidth is just the highest standard the wireless card supports, but it had to fall back to 802.11ac because of something in the wireless access point or the AP negotiation - 216 Mbps is a valid speed for MCS 8 under 802.11ac with 40 MHz bandwidth.

Yeah, there are a few possible causes - MCS index reported is wrong; channel bonding failed but the wifi adapter isn't reflecting it in the reported info; real world HW or wifi interference issues that are causing the connection to fall back to 216 Mbps even if the MCS index says it should be higher...probably three or four other possibilities, too.