Quadrature Phase Shift Keying is a form of Phase Shift Keying in which two bits are modulated at once, selecting one of four possible carrier phase shifts in 0, 90, 180, or 270 degrees-Quadrature Phase Shift Keying is a form of Phase Shift Keying in which two bits are modulated at once, selecting one of four possible carrier phase shifts　in 0, 90, 180, or 270 degrees