What is the difference between Channel Estimation types and L-LTF Enabled in RFmx WLAN

Updated May 16, 2023

Reported In

Software

  • RFmx WLAN

Issue Details

When you used the channel estimation feature to improve the EVM performance in RFmx WLAN , you will see below setting panel:



MicrosoftTeams-image (29).png



Check the help document , you can find below information about the types, like below picture:

MicrosoftTeams-image (30).png


You can see the channel estimation also used the LTFs , why did NI add the L-LTF enabled feature ?
 

Solution

First , the LTFs is not including the L-LTF. The LTFs are meaning for EHT-LTF , HE-LTF , VHT-LTF,HT-LTF , so we can think the LTFs as x-LTF; The spec only defined the channel estimation using the "LTFs" , which are no including the L-LTF; To enable the L-LTF for channel estimation , you can get a good improvement on EVM , but it is out of specs.  
For example, the frame structure show as below for 802.11be :

MicrosoftTeams-image (31).png


EHT-LTF and Data part are using for channel estimation in specs , the L-LTF can be used for channel estimation as one optional solution;
 

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