BER improvement of multilevel CPM in the mobile radio environment

An attractive modulation scheme, named accelerated phase-quaternary continu ous phase modulation CPM (AP-QCPM), is proposed for digital mobile radio ap plications. As AP-QCPM is a constant envelope modulation scheme, it is well suited to nonlinear power amplifier use in the mobile equipment and the ha ndheld equipment of wireless LAN applications. Error performance of multile vel low-deviation frequency-shift keying (FSK) is severely degraded in the Rayleigh fading channel. On the other hand, degradation of phase-shift keyi ng (PSK) remains within a moderate amount. The paper is an attempt to clari fy what kind of modification could be added to the conventional four-level FSK to achieve an error probability comparable with the QDPSK in the Raylei gh fading channel. Error probability of the proposed scheme and the power s pectral characteristics are obtained to reveal critical values of the modif ication parameter. The analytical results are confirmed by the hardware sim ulation at 900 MHz.