Wi-Fi 6E Channel Scanning

[The_Roo]

When I go into the dashboard to configure 6E, I get the opportunity to set the channel width to 20, 40, 80 MHz, etc but the default is 80MHz wide and the PSC are only every 4th channel. That's fine if I'm using 80MHz channels, my AP will scan the PSCs, find one or more of the (in the UK, 6) 80MHz channels associated with the PSC channels and associate with the most appropriate one.

Now let's say I have a congested high-density environment. Meraki gives me the 20 MHz (24 x 20MHz channels) choice on the dashboard and says "Recommended for High Density deployments and environments expected to encounter DFS events. More unique channels available, reducing chance of interference".

The client device can only scan on the PSCs, so the client will scan on channels 7, 23, 39, 55, 71 and 87, but if the AP is running a manually-set 20MHz channel that is not one of those (for example 25), how will the client find it?

I know (I THINK I know...) that out-of-band RNR is mandatory and wonder if there is some sort of connection, but I can't find it documented anywhere.

Thanks for any insights

Roo

[GIdenJoe · Accepted solution]

While PSC is a possible used method of finding AP's broadcasting an SSID on 6 GHz it is not the only method.

Most if not all clients should have support for a method where the AP is sending any SSID on the 2.4 or 5 GHz it will also contain an information element containing reduced neighbor report containing operating channel and a short SSID field and some more fields.  This is enough for the client to start probing on the 6 GHz band and find it's SSID.

[mlefebvre]

Seconded, the RNR will do the heavy lifting for you here, but are you actually seeing congestion in your WiFi 6E spectrum already or is this more of a theoretical question? I know the UK has only deployed a subset of 6E spectrum that the US and Canada have, but this would still come as surprising to me that you would have a use case for downgrading to 20 MHz channels on 6E already and I would love to know if that is indeed the case and a little bit more of the environment you operate in.

[GIdenJoe]

If you are doing a design on 6 GHz in Europe 40 or even 20 MHz is considered normal.  Since if you use 80 MHz channels you only have room for 6 AP's within each other's range.
So if you are purist and don't want any OBSS above -86 dBm you may very well need the extra channels.

[Paccers]

Recommend watching Wes Purvis's presentation from WLPC earlier in the year who covers 6 GHz discovery methods, RNR specifically as well.