Quadrature Phase-Shift Keying (QPSK) is a digital modulation technique used in communication systems to transmit data efficiently. It encodes information by varying the phase of a carrier wave, allowing four distinct phase shifts: 0°, 90°, 180°, and 270°. Each phase shift represents two bits of data, enabling QPSK to transmit twice the amount of information compared to simpler methods like Binary Phase-Shift Keying (BPSK). QPSK is widely used in various applications, including satellite communications, Wi-Fi, and cellular networks. Its ability to maintain a robust signal in noisy environments makes it a popular choice for high-speed data transmission. By utilizing phase shifts, QPSK optimizes bandwidth usage while minimizing errors in data reception.