In QPSK (Quadrature Phase Shift Keying), the symbol refers to the phase shift of the carrier signal, which represents data. Each symbol in QPSK encodes two bits of information by shifting the phase of the carrier signal by one of four distinct values: 0°, 90°, 180°, or 270°. These four phase shifts correspond to different combinations of the two bits.

### What is QPSK?

QPSK (Quadrature Phase Shift Keying) is a modulation scheme that conveys data by varying the phase of the carrier signal. It encodes two bits per symbol by shifting the carrier signal’s phase among four distinct values. This allows for efficient data transmission with good performance in terms of bandwidth and noise resilience.

A QPSK signal appears as a series of phase shifts on the carrier waveform. The signal alternates between four distinct phase angles (0°, 90°, 180°, and 270°), creating a constellation diagram where each point represents one of the four possible phase states. This results in a signal that varies in phase to encode different bits of data.

In computer networks, QPSK (Quadrature Phase Shift Keying) is used for its efficient data transmission capabilities. It allows for the encoding of multiple bits per symbol, enhancing the overall data rate while maintaining robustness against noise and interference. QPSK is particularly useful in wireless communication and satellite systems where bandwidth efficiency is crucial.