Noncoherent detection of FQPSK signals using MLDD

Feher-patented quadrature phase shift keying (FQPSK) is the most spectrally efficient modulation technique and robust to the nonlinear distortion caused by nonlinear amplifier. For the simple receiver structure, noncoherent detection is preferred to coherent detection. In this paper, we propose noncoherent detection using maximum likelihood differential detection (MLDD) by inspecting the phase transition patterns of FQPSK signals according to input bit sequences. The proposed method can reduce complexity of receiver by using one sample per one bit duration. Simulation results show that the proposed method has no performance degradation compared to other noncoherent detection methods which use more samples per bit duration. It is also shown in simulation that the proposed method is robust to sampling timing error.