Auto WiFi mode - can the channels change while running?

[sirwifi]

How does the Auto WiFi mode work? Does it scan and pick the "best" channels at boot time and then that's it or does it periodically scan and switch channels even after boot (during normal runtime) and the channels may change depending on whether new neighbor APs come and go?

 

[sfx2000]

Most AP's that support DFS - they'll initialize on a non-DFS channel first, and then scan into the DFS band on a scheduled basis - looking for the signature energy pulses that might prohibit use on given channels, and if things are good, they'll make the jump over...

The challenge is that some clients may not support DFS channels - that's a vendor decision based on cost (DFS testing is extra cost that some vendors may not want to bear as it's long and involved, much longer time is needed there compared to other Regulatory type approvals)...

 

[sirwifi]

That's for the 5Ghz band. Can the channel change in the 2.4Ghz band also?

And in particular, have you seen Merlin firmware do channel hopping during normal operation? RT-AC68U is my hardware.

 

[sfx2000]

That's for the 5Ghz band. Can the channel change in the 2.4Ghz band also?

And in particular, have you seen Merlin firmware do channel hopping during normal operation? RT-AC68U is my hardware.

I have not seen an Asus device hop - it is possible with some chipsets, but many only do the initial channel activity scan on boot...

(I have directly observed some Broadcom, along with Atheros and Marvell, dynamically jump channels - but these were not associated with ASUS OUI's (MAC addresses) in war driving logs).

 

[sirwifi]

Sounds marginally useful to only do it on boot. How often do people reboot their APs?

 

[sfx2000]

Sounds marginally useful to only do it on boot. How often do people reboot their APs?

The more recent chipsets do have the capability to do better - depends on how the OEM configures them, as it's much more than just drivers - but it does exist...

 

[RMerlin]

I have not seen an Asus device hop - it is possible with some chipsets, but many only do the initial channel activity scan on boot...

(I have directly observed some Broadcom, along with Atheros and Marvell, dynamically jump channels - but these were not associated with ASUS OUI's (MAC addresses) in war driving logs).

Asus does use the Broadcom acsd daemon, however I have no idea what policy they are applying to it.

 

[sfx2000]

Asus does use the Broadcom acsd daemon, however I have no idea what policy they are applying to it.

That gets into blackbox Broadcom stuff with the driver - I'd have to go and look at what inputs go in - right now, if I recall, either the channel is explicitly defined or not (if not, it's auto) - and in Auto, it's all inside the firmware on the WiFi chip's RTOS to make decisions based on RSSI (CINR) and other thresholds (Bit Errors on Rx Side, Retransmissions on Tx side, etc...) - now whether this is real-time (in-situ) or run time (on init), that's firmware most likely, and that's part of the driver...

 

[RMerlin]

That gets into blackbox Broadcom stuff with the driver - I'd have to go and look at what inputs go in - right now, if I recall, either the channel is explicitly defined or not (if not, it's auto) - and in Auto, it's all inside the firmware on the WiFi chip's RTOS to make decisions based on RSSI (CINR) and other thresholds (Bit Errors on Rx Side, Retransmissions on Tx side, etc...) - now whether this is real-time (in-situ) or run time (on init), that's firmware most likely, and that's part of the driver...

The acsd daemon is kept running, so it must not be doing something just at boot time.

 

[sfx2000]

The acsd daemon is kept running, so it must not be doing something just at boot time.

ascd is a blob, but if one looks at the header files, all the signs are there, and it doesn't look like it's 5GHz only...

My gut says yes - as it is monitoring the channel, and you can see dynamic updates in the QBSS stanza inside the beacon frame - but the engineer in me says "prove it", which I can't right now, as I don't have easy access to an Asus RT series, and I'm not going to "test" against someone else's router