Pilot Tracking (802.11n/ac/ax/be)
When demodulating an OFDM Orthogonal Frequency Division Multiplexing: OFDM employs multiple overlapping radio frequency carriers, each operating at a carefully chosen frequency that is Orthogonal to the others, to produce a transmission scheme that supports higher bit rates due to parallel channel operation. OFDM is an alternative tranmission scheme to DSSS and FHSS. burst, the equalizer response computed from the burst preamble is used to correct many imperfections in the OFDM signal. Because the equalizer response is not perfect, pilot tracking is used to correct for imperfections in the equalizer response and for imperfections that change over the length of the burst.
In each OFDM symbol, a set of the subcarriers are dedicated to pilot signals in order to make the coherent detection robust against frequency offsets and phase noise.
Pilot subcarriers transmit with a known data sequence. This information is used to determine the difference, or error, between an ideal signal and the actual received signal. Because the data is complex, the VSA calculates phase, amplitude, and timing error data. The error data can then be used to correct both pilot and data subcarrier imperfections, producing a more accurate demodulation.
Pilot Tracking is controlled by the pilot tracking check boxes located in the Advanced tab of the 802.11n/ac/ax/be Demod Properties dialog box.
- Track Amplitude: When selected, the average pilot amplitude will be used to scale the expected amplitudes of the rest of the subcarriers. The Common Pilot Error trace will show the amplitude tracking in the magnitude portion of the trace. The default value is off.
- Track Phase: When selected, the selection determines which subcarrier types will have phase error correction applied. The Common Pilot Error trace will show the phase tracking in the phase portion of the trace. The default value is on.
- Track Timing: When selected, the average slope of the phase of the pilots will be used to remove timing errors from symbol to symbol. The default value is off.
- Tracking Mode: Determines where the Pilot Tracking occurs.
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