A novel modulation technique for spectral efficiency enhancement of ternary precoded Continuous Phase Modulation

Abstract

Due to spectral finiteness and energy limitations, there is an undiminished attractiveness of Continuous Phase Modulations (CPMs), where Shaped Offset QPSK (SOQPSK) is a particularly well suited example in this class of single carrier and constant envelope waveforms to tackle these restrictions. A broad variety of wireless communication systems, such as deep-space, Unmanned Aerial Vehicle (UAV) and telemetry links are applications that benefit from the properties of these modulations. Based on an analysis of SOQPSK's binary to ternary precoder rules and their effect on the signal's spectrum, a new precoding technique is derived in this paper, to incorporate into the modulated signal more than one bit per symbol. The result is Constrained Ternary Precoded CPM (CTP-CPM), a novel modulation technique with a 25% increase in spectral efficiency compared to SOQPSK, usable to enlarge the data rate without spectrum modification, or to decrease the required radio frequency bandwidth for a given data rate.