SP-QPSK - A NEW MODULATION TECHNIQUE FOR SATELLITE AND LAND-MOBILE DIGITAL BROADCASTING

A new Modulation technique, “SP-QPSK” (sinusoidal shaped π/4-QPSK) suitable for land-mobile and satellite digital broadcasting systems applications is introduced. In digital data and/or sound broadcasting systems, which may have a relatively low bit rate transmission requirement, the residual phase noise introduced by the Doppler shift of moving vehicles presents a high bit error floor in coherently demodulated systems. To avoid this problem, non-coherent detection methods may have to be employed. Even though these systems require a higher C/N than their theoretical coherent counterparts in stationary AWGN environments, the overall performance of non-coherent systems is frequently superior in a mobile radio environment. In addition, to satisfy the high power and spectral efficiency requirements of emerging digital broadcast systems, nonlinear, saturated amplifiers may become essential subsystems. We introduce a new modulation technique, SP-QPSK, which combines the advantages of the IJF-OQPSK narrowband satellite systems and of the π/4-QPSK systems which have been adopted as the second generation land-mobile cellular standards, i.e., the US digital cellular standard. The performance of our new generation of SP-QPSK systems is investigated by computer simulations and experimentally. Digital signal processing implementation techniques have been used in the experimental prototype design. We demonstrate that nonlinearly amplified SP-QPSK has a 10dB lower out-of-band radiated power than conventional QPSK and it is suitable for differential and discriminator detection. Improved performance and simplified (non-coherent hardware) receivers could lead to novel digital broadcasting applications of this powerful modulation technique. © 1990 IEEE