Client data rate statistics for wireless not accounting for channel width?

[karlosterlund]

While investigating WLAN issues and enjoying the new capabilites of the dashboard I noticed something.

"Terrible data rates!!!" I thought at first but upon closer inspection this seems like a miscalculation.

Clicking the info-button shows:

"This graph shows data rates used as a percentage of the maximum data rate that this client supports."

So if my device supports 80 MHz channels and can do 2 spatial streams it's max data rate is 867 Mbps. The client info in the dashboard confirms this

BUT if I'm using 20 MHz channels on this AP (which I should, and am), the maximum data rate for this client is 173 Mbps.

Looking at the statistics from the client: 18% of 867 Mbps is 156 Mbps. That would be the second best data rate for a 2SS client on a 20 MHz channel. Shouldn't the chart show 90% instead of 18% if the data rate is 156 out of 173 Mbps?

[PhilipDAth]

I think you are correct.

[GIdenJoe]

Lol, that's a silly mistake.

Even the cheaper Mobility Express AP's do it better in that regard:

[Dunky]

So if I have a client showing this:

with a channel width of 160MHz:

is the low Data Rate that that s being shown something I should be concerned about, or is the information in the dashboard wrong?

[GIdenJoe]

You shouldn't worry about it.

The major problem with this metric is that it always uses the clients max supported bitrate which is highly dependent on the channel width.  However if your Wi-Fi is designed around 20 or 40 MHz and your client supports 160 MHz then you'll have 12.5 to 25% of your max bitrate all the time if you have a good signal.

I think Meraki should consider removing this metric or perhaps try to use the channel width of the largest portion of AP's in the network and put that at 100% but I'm not sure if there are too many variables to make a metric like that work.

To explain: If an AP is running a BSSID at 40 MHz and the client has support for Wi-Fi 5 MCS 9 with 2 spatial streams then the maximum bitrate achievable would be 400 Mbps then that number would have to be set at 100%.  Only then would the metric be fair because if you have good coverage those clients should vary between 400 and 270 Mbps IMHO.  If you have bad coverage or an issue then you could see the client drop to below 100Mbps and THAT would be a problem to show on that metric.

[Dunky]

Thank you for the reply.

I can see on the MR36 datasheet:

20 and 40 MHz channels (802.11n); 20, 40, and 80 MHz channels (802.11ac Wave 2); 20,
40 and 80 MHz channels (802.11ax)

So I guess it like people say, the graph is very misleading.