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Spirent TestCenter: WiFi - Why channel width column is not updating under Wireless Client Result view?


Why the channel Width column under IEEE 802.11 Client Results  is NOT updating as expected when changing port bandwidth from 20MHz to 40MHz and backwards? Instead it get stuck in 20MHz

When associating a device while the port is in 20MHz the Channel Width column is updated to 20MHz as expected, however, if you set the port to 40MHz instead (By going to the Wifi port > General Tab > Under Channel Bandwidth section) and associate the devices again, the Channel Width column remains in 20MHz instead of 40MHz, also, if you create a streamblock from the WiFi port to the Ethernet port, the Channel Width column remains in 20MHz:
  • 5.14
  • WiFi
  • Channel Width
  • IEEE 802.11 Client Results
  • Channel Bandwidth

The Channel Width is only meaningful when running traffic (Downstream traffic - From eth port to Wifi Client) – without downstream traffic all control/mgmt frames are set in 20Mhz, this is WAD (working as design), as per IEEE 80211 spec (Even for 40Mhz/80Mhz AP), the primary channel for control/mgmt is only 20Mhz.

Tested, and after downstream traffic flows (when the AP is transmitting traffic), the Channel Width changes to 40MHz as expected:
The screenshot shows both streams (Down/UP) sending traffic, however all the traffic we need to update the Channel Width column accurate is Downstream traffic.

  • Sometimes you can make this field updating to the correct value by just "Clearing Counters" once.

Product : WiFi,Spirent TestCenter,WiFi