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Wireless & Mobility · Intermediate

Subcarrier

A narrow frequency component of an OFDM channel carrying data, pilot, or null signals.

Definition

OFDM channels contain data subcarriers, pilot subcarriers for tracking, and null subcarriers at the DC and edges. 802.11a/g/n/ac use 312.5 kHz spacing, while 802.11ax and 802.11be use 78.125 kHz, giving four times as many subcarriers. 802.11ax groups subcarriers (tones) into resource units.

Example

An 802.11ax 20 MHz channel has 256 subcarriers.

Exam tip

Wi-Fi 6 quadrupled subcarriers per channel, which lengthened symbol time to 12.8 microseconds.

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