Quasi-Orthogonal Time Division Multiplexing and Its Applications under Rayleigh Fading Channels

Based on the principle that inserting N-l equally spaced zeros between each pair of samples is equivalent to sampling the original signal at rate of N times the Nyquist sampling rate. The representation of the quasi-orthogonal time division multiplexing (QOTDM) signal in both time and frequency domain was investigated for QOTDM system. The spectrum of QOTDM signal is the overlapping spectrum of each parallel signal which is rotated a certain angle in phase. Comparisons between QOTDM and orthogonal frequency division multiplexing (OFDM) was made in terms of bit error rate (BER) in Rayleigh fading channels. Simulation results indicate that the proposed QOTDM system does not have an error floor as OFDM does, and QOTDM is more robust against Rayleigh fading in high signal-to-noise ratio (SNR) region (larger than 14 dB) compared with OFDM.