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Wireless & Mobility · Intermediate

Modulation and Coding Scheme (MCS)

An index combining modulation type and coding rate that determines a PHY data rate.

Definition

802.11n defined MCS 0-76 including spatial streams, while 802.11ac/ax/be use MCS 0-9, 0-11, and 0-13 per spatial stream. Actual data rate also depends on channel width, guard interval, and spatial streams. Radios dynamically select MCS based on conditions (rate adaptation).

Example

802.11ax MCS 11 is 1024-QAM 5/6.

Exam tip

Know that MCS 8/9 = 256-QAM (ac), 10/11 = 1024-QAM (ax), 12/13 = 4096-QAM (be).

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