Additional data transmission with rotated QPSK constellation

A quadrature phase-shift keying (QPSK) modulation scheme is proposed to improve the data rate using the rotated constellation. The additional data is not physically transmitted to improve the spectral efficiency, but it can be detected in the receiver through the rotated phases of constellations. In this Letter, the performance of the proposed transmission scheme is verified by simulation and mathematical analysis with the majority detection rule as the lower bound.