Digital signal processing for extended phase-shift keying (EPSK)-a new modulation scheme

Extended Phase-Shift Keying (EPSK) is a new digital phase modulation scheme that extends standard Phase-Shift Keying (PSK) to allow for phase shifts that exceed the traditional 2π limit. The new modulation can be applied to binary (BPSK), quadrature (QPSK), and m-nary PSK allowing the addition of symbols without requiring a decrease in the distance between symbols. The optimum bit-error rate BER for a band-limited PSK modulated system with typical practical constraints is shown to occur for a modulation factor of approximately 1.25, meaning that EPSK with phase-shifts of approximately 2.5π are required to achieve this optimum. We show that the hardware for both the modulator and demodulator can be very simple for this optimized EPSK, but to achieve the full benefit of EPSK it is necessary to develop a digital signal processor that removes the effects of “clicks” that occur under the conditions of low signal-to-noise ratio. Design of a high-quality Click Removal Signal Processor (CRSP) turns out to be the most critical issue for the practical implementation of EPSK