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.