Equalizer Properties (DOCSIS 4.0 Downstream)

The Equalizer properties are used to configure and apply equalizer filtering to the measurement. The VSA uses an equalizer to correct for linear impairments in the signal path, such as multi-path and fading.

The Equalizer properties allow you to select what subcarrier data is included to initialize, or "train", the equalizer:

Parameter	Description
Equalizer Smoothing:	When enabled, a smoothing filter is applied to the equalizer channel frequency response. Use the editable field to the right to set the smoothing filter width. The field becomes active when this setting is enabled. Default: 5 Subcarriers
Training
	Preamble and Pilots: The OFDM equalizer is initialized ("trained") using the Continuous Pilots, Scattered Pilots, and PLC. The advantage of Preamble and Pilots is that it is not affected by incorrect symbol decisions in the data (which can happen at lower SNR or or higher modulation orders).
	Preamble, Pilots, and Data: The OFDM equalizer is trained using the data subcarriers as well as pilots and PLC. The advantage of Preamble, Pilots, and Data is that it usually gives a more accurate estimate of the channel response, resulting in lower EVM.
Average Mode	Selects the averaging method used to determine the equalizer filter coefficients across multiple symbols:
	Equal Weight: Equalizer averaging calculated using the Equal Weight method. Signal impairments other than additive white gaussian noise may make Equal Weight work better than Least Squares.
	Least Squares Equalizer training calculated using the Least Squares method. If the only signal impairment is additive white gaussian noise, Least Squares should result in the best estimate of channel response, and therefore the lowest EVM for the measurement.

Associated Trace Data Results

Ch Frequency Response