Controller Based WLANs

About "AP Scanning Optimization" feature in 6.4.3

by ‎06-10-2015 05:04 AM - edited ‎06-10-2015 05:04 AM
Q:

About "AP Scanning  Optimization"  in 6.4.3



A:

The feature enables APs to effectively visit and monitor channels. By increasing the frequency of channel visits, the AP is able to gather the required data on time and input this information to the client match algorithm.

 

i. Unconventional Scan

ii. Group Scanning

 

Unconventional Scan

  • Unconventional scans will only be done in all-reg and rare scan-modes, and would be no longer done if scan-mode is set to reg-domain.
  • Unconventional scan means the direction is away from the paired channel.  Ex. 40+, 44-, 48+, 52-, …
  • Before Optimization ,Unconventional scans are interspersed with conventional scans, such that both are done before moving on to the next channel. 

             Ex. 36+, 40-, 40+, 44+, 44-, 48-, 48+, 52+, 52-, 56-,..

  • After Optimization Unconventional scans will only be done in all-reg and rare scan-modes,and would be no longer done if scan-mode is set to reg-domain 
  • Scans are now run separately at a lower priority (lower frequency than All-reg, but higher frequency than Rare) which allows us to cycle through the conventional scans faster).

 

Group  Scanning:

 

  • Channel group scanning leverages the fact that the radio can hear 20/40MHz frames on sub-channels when it does an 80MHz wide scan. Because of this, scanning can be optimized by putting channels into scan groups, which will be visited sequentially, each time selecting a new primary channel. This allows us to cycle through the list of channels faster, so that the delay between visits to a channel (group) is much smaller. 

 

  • A single 36E scan allows us to hear:

80MHz wide frames in the 36-48 channel width
40MHz wide frames in the 36+/40- channel width
40MHz wide frames in the 44+/48- channel width
20MHz wide frames on 36, 40, 44 and 48

 

CLI config:

Scan Mode in AP mode
(config) #rf arm-profile default
 
Scan Mode in AM mode
(config) #rf am-scan-profile default

Group Scan output:
 #show ap arm scan-times ap-name ap225-sk

 

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