Bit Error Rate of FQAM Transmission in Fast Fading Channel

Frequency and quadrature amplitude modulation (FQAM) is a combination of frequency shift keying and quadrature amplitude modulation. This modulation scheme is considered as a possible candidate for the use in future mobile networks. In the paper, FQAM reception in a flat fast fading channel is considered with two practical techniques: pilot-based reception with channel state information estimation, and differential transmission with noncoherent reception. Approximate analytical formulas for uncoded bit error probability are derived for the case of Rayleigh flat fast fading channel. It is shown that under fast fading both schemes demonstrate error floor depending on the Doppler spread of the channel, but pilot-based scheme allows additional control by tuning the pilot spacing. Recommendations about practical use of two schemes are given. Theoretical estimations demonstrate good agreement with simulation results.