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[STDS-802-11-TGBE] CID 11120,11439 in 1344r2

Hi Guarang, Laurent,

 

Regarding the resolution on CID11120 and CID11439, there are two technical issues:

 

  1. (1st )Switch to DFS channel(encounter Radar)à(2nd )Switch to the second DFS channel: When the affiliated AP switches to first DFS channel and perform CAC, the affiliated AP shall set the disabled Link indication in RNR element to prevent legacy STA/ associated non-AP MLD/unassociated non-AP MLD probing that AP, the affiliated AP may switch to the second DFS channel when it encounters radar signal. In this scenario, the non-AP MLD can know when the affected AP starts beaconing via the updated Expected duration field in TID-To-Link Mapping element on the disabled link. The proposal to have the second Max channel switch Time signaling will confuse the non-AP MLD as two Timer appears in one Beacon/probe response frame.

 

  1. (1st )Switch to DFS channel(encounter Radar)à(2nd )Switch to the non-DFS channel: the non-AP MLD also can know the updated Beacon time via the updated Expected duration field in TID-To-Link Mapping element on the disabled link. And the affected AP will reduce the expected start Beaconing timer in such case. e.g. the affected AP expects to start beaconing after 1 mins when it’s stay in the DFS channel, and it will start Beacon immediately after switching to a non-DFS channel.

 

In summary, seems it’s not necessary to set a Max Channel Switch Time element again when the affected AP is on DFS channel, as the signaling can be obtained via the signaling in TID-To-Link Mapping element , please correct me if I make any mistake.

 

 

(#11120, #11439) NOTE - The reporting AP might increase the value carried in the Switch Time field of the Max Channel Switch Time element if the affected AP performs a second channel switch between the target time of a first channel switch and the time at which the affected AP will start beaconing on the new channel corresponding to the first channel switch

 

 

11120

35.3.11

436.12

It would be more helpful if CSA or CSA-like information was sent on non-switching affiliated APs until the switching AP was live on a channel since then, if the switching AP was hunting for a radar-free DFS channel and failing and failing before  ultimately succeeding, then the non-switching affiliated APs could report the latest target operating class, channel and expected start time on the new target operating class and channel. Also, newly arriving clients can see the existence of the switching AP mid-switch.

Especially if an AP advertises a large Max Channel Switch Time with its CSA,  once that has counted down to zero (start of switch), allow non-switching affiliated APs to advertise a new CSA for the AP. By reducing the Max Channel Switch Time to zero with the CSA Channel Switch Count equal to zero, the non-switching AP can identify when the switching AP will restart operations on the new channel (i.e., the end of the switch). Also, if the target operating class/channel of the switching AP changes, or the time of the end of the switch changes, then allow the non-switching affiliated APs to report this too. Note that the ultimate operating class/channel might be the starting operating class and channel if the AP couldn't find a DFS channel free of radar.

 Revised – agree with the commenter. Channel change is handled by the RNR rules. Max Channel Switch time can also be transmitted on the other link and can be changed if there is a need for a second channel change for instance. As such all is sort of supported right now, but needs clarification. Add a note to clarify this. Apply the changes marked as #11120 in this document.

11439

35.3.11

437.32

The value carried in the Switch Time field may need to be updated if the affected AP cannot start Beaconing in the new channel. This can happen when the affected AP detects a new radar on the new channel before it can start Beaconing.

Add the following note - 'NOTE - The reporting AP might increase the value carried in the Switch Time field of the Max Channel Switch Time element if the affected AP performs a second channel switch between the target time of a first channel switch and the time at which the affected AP will start beaconing on the new channel corresponding to the first channel switch'.

 

 

 

 

Thanks

 

Best Regards

 

Jay Yang

 

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