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Wireless & Mobility · Foundational

Orthogonal Frequency-Division Multiplexing (OFDM)

Multicarrier modulation splitting a channel into many orthogonal subcarriers transmitted in parallel.

Definition

OFDM divides a channel into closely spaced subcarriers that do not interfere because they are mathematically orthogonal. Each subcarrier carries a low-rate stream, making the signal resistant to multipath. It is used by 802.11a/g/n/ac/ax/be, LTE, and 5G NR.

Example

An 802.11a 20 MHz channel has 64 subcarriers spaced 312.5 kHz, 48 for data and 4 pilots.

Exam tip

OFDM serves one station at a time per transmission; OFDMA serves several.

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