Multicarrier demultiplexing and demodulation for an MDR frequency hopped satcom system: simulation analysis

This paper presents a multicarrier demodulator (MCD) for FDM systems, which is based on the fast Fourier transform (FFT) technique. We show that, without pulse shaping, user´s synchronization errors and Doppler shifts imply the use of weighting functions or guard time on the received symbols. Both techniques, evaluated through computer simulations, lead to a loss in SNR and spectral efficiency. The next step is to study a possible coherent QPSK mode in order to oppose these losses. Because of the small number of symbols per hop, coherent demodulation is not an easy task. We present a demodulation technique, based on a feedback principle, that shows little loss compared to the theoretical QPSK performance and resists high enough Doppler values