How does CableIQ measure ACR-F?
The measurement is done in the time domain by looking at the amount of reflected FEXT which comes from the end of link, where all the FEXT piles up. There is a low power DSP chip in the remote adapter which enables CableIQ to take advantage of time domain measurement techniques.
ACR-F is an important parameter for ensuring successful transmission of 1000BASE-T.
For further information on how CableIQ works, click here

If you are required to provide ACR-F as part of a certification test, this is done using the DTX CableAnalyzer.