A Novel Modulation Method for Multicarrier Systems

Quadrature-Quadrature Phase Shift Keying (Q PSK) was proposed by D. Saha
and T. G. Birdsall [1] to increase the spectral efficiency in comparison to Quadra- ture Phase
Shift Keying (QPSK) and Minimum Shift Keying (MSK). For band- limited Q2PSK some examples for
transmit and receive filters were shown but no explicit design rules were given. In this work
these design rules are derived. The filters are, in principle, a low-pass and a band-pass filter
overlapping with root-Nyquist slopes. The band-pass filter can be replaced by a low-pass filter
and Vestigial Sideband (VSB) Modulation. While having solved the problem of how to design
bandlimited Q2PSK is scientifically quite satisfactory, the spectrum efficiency remains the same as
in bandlimited QPSK (2bit/(s·Hz)). However, extending these ideas to Multicarrier (MC) systems
leads to two systems: One is based on Offset Quadrature Amplitude Modulation (OQAM) and has
been known for a long time. The other one is a VSB-MC system. The latter system is shown to have
improved performance properties compared with OQAM-MC and OFDM.