Half-symbol-rate-carrier PSK modulation for bandwidth-efficient high-speed data communications

This paper proposes new quadrature phase-shift-keying (QPSK) modulation techniques for high-speed data communication systems that use two orthogonal half-symbol-rate-carrier (HSRC) signals by which channel bandwidth requirements are reduced compared to that of the conventional non-return-to-zero (NRZ) modulation. The simulation results show the HSRC-QPSK has almost the same bit-error-rate (BER) performance with reduced signal bandwidth compared to that of the NRZ modulation. This paper also analyzes the performance of the recently proposed HSRC offset-QPSK (HSRC-OQPSK), which improves spectral efficiency by reducing the side lobes of the signal spectrum. In addition, HSRC minimum-shift-keying (HSRC-MSK) modulation is also introduced. The performances and the simulation results of the proposed modulation techniques are studied and compared with those of the conventional ones.