QPSK (Quadrature, Quadriphase, or Quaternary Phase-Shift Keying)

A modulation technique

that achieves dibit transmission by defining four phase shifts separated by 90 degrees (0°, 90°, 180°, and 270°). IEEE 802.11a (Wi-Fi5) wireless LAN (WLAN) standards call for binary phase-shift keying (BPSK) at 6 Mbps and QPSK at 12 Mbps. IEEE 802.11b (Wi-Fi) calls for BPSK at 1 Mbps and QPSK at 2 Mbps.

Bluetooth specifies BPSK for use in the 868 and 915 MHz bands, and QPSK for use in the 2.4 GHz band.

µ/4 differential quaternary phase shift keying (µ/4 DQPSK) can be viewed as the superposition of two QPSK constellations offset by 45 degrees relative to each other. See also 802.11a, 802.11b, Bluetooth, BPSK, modulation, phase, PSK, µ/4 DQPSK, and WLAN.

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