What is the purpose of having “Data” or “LTF” in Channel Estimation?

Actual devices need to perform real-time channel estimation. They rapidly estimate the channel (using LTF) and then demodulate the data.

With test equipment we do not need to do real-time data demod. We post-process the capture. After receiving the RF burst we demodulate the data to perform measurements like EVM. During this post-processing we can apply a different type of channel estimation (which removes some of the DUT errors) to provide a better EVM results. Wi-Fi test standard is not specific, so this is user selectable and – you can choose to apply these corrections or not. There is no “standard method” so the chipset vendors are able to implement their own proprietary methods.