Performance of the FQPSK modulation over TWDP fading channels

The performance computation for deep space communication systems was studied. The systems adopt the Feher quadrature phase shift keying (FQPSK) modulation and the TWDP (two-wave with diffuse power) fading channel because the TWDP fading channel model can express different fadings according to different parameters so it is suitable for complex electromagnetic deep-space communication, and the FQPSK modulation is widely used in deep-space communication systems due to its constant envelope and high spectrum efficiency characteristics. To simplify the computation of system performance, the closed-form BER of the FQPSK modulation in a TWDP fading was derived and the correctness of the derivation was verified by simulation. Based on the software platform of deep-space communication systems, the performances of the FQPSK modulation under different TWDP fading parameters were simulated, and the results show that the FQPSK modulation can suitably be applied to deep space communication systems for its better features in comparison with other QPSK modulations, which is important to actual system design.