Wireless Access

Super Contributor II

ARM and VHT80 mode

Hi All,


I'm looking for an explanation as to how VHT80 mode works with ARM and channel planning.


I have a large network of AP-225 and i can see all the AP's with a-VHT mode channels allocated to channels that are within the VHT80 group assignments from Airwave and the BSS Table however i'd like to understand how the AP consumes channels when a VHT 80 client tries to connect?


For example.


If i have an AP on channel 44 in a-VHT mode servicing 802.11n clients and then a client connects to that AP using VHT80 ,will the AP switch channels to consume all 36-48 block? What happens to the n clients, are they shifted to the edge channels or do they continue to use 44 as the centre channel?


How is this represented in the ap bss table?




Re: ARM and VHT80 mode


If the 802.11ac detects a 802.11n device It uses a protection mechanism similar to the way 802.11g/a to communicate to older 802.11b it sends RTS/CTS (so the devices know how long the device will have the medium) on each of the 20 MHz channel (instead of using 80 MHz bonded channel) 


802.11n device will use the primary channel and if the device is able to support 40 Mhz then will use the next secondary channel : CH - or CH +


The 802.11ac will still use the same OFDM channel planning setup as the 802.11n and are able to switch between 40 / 20 Mhz per packet basis




Thank you

Victor Fabian
Lead Mobility Architect @WEI
Super Contributor II

Re: ARM and VHT80 mode

so how does the controller allocate the VHT80 channel?


with HT40 i recall it used to specify the channel and the +or - eg 36+ but in VHT mode it doesn't appear to do this for VHT80?

Re: ARM and VHT80 mode


if you run the following command you will be able to tell :


show ap active 

 test-225-12              Feldberg-106  0            AP:HT:1/3/21         0            AP:VHT:48E/15/21     225      Ada


show ap arm rf-summary ap-name


VHT Channel Summary
channel_group 80MHz_intf_index
------------- ----------------
149-161 41
36-48 94

Interface Name :wifi0
Current ARM Assignment :48E/15




Thank you

Victor Fabian
Lead Mobility Architect @WEI
Search Airheads
Showing results for 
Search instead for 
Did you mean: