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Wireless & Mobility · Intermediate

Quadrature Amplitude Modulation (QAM)

Modulation that varies both amplitude and phase to encode multiple bits per symbol.

Definition

QAM places symbols at points on a constellation diagram defined by amplitude and phase. Wi-Fi uses 16-QAM, 64-QAM, 256-QAM (802.11ac), 1024-QAM (802.11ax), and 4096-QAM (802.11be). Bits per symbol equal log2 of the constellation size.

Example

64-QAM carries 6 bits per symbol.

Exam tip

Each QAM step up needs several dB more SNR.

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