Space-frequency-Doppler coded OFDM over the time-varying Doppler fading channels
In this paper, space-frequency-Doppler coded OFDM (SFDO-OFDM) scheme over the time-varying Doppler fading channels via the time-frequency duality is proposed. Based on the basis expansion model (BEM) and the time-frequency duality, through the circulant matrix diagonalized processing, the nonlinear time-varying Doppler fading channel is dually converted to the virtual frequency-selective linear channels. With OFDM module, subgrouping the subcarriers in OFDM through the block matrix method and fatherly general complex orthogonal coding (GCOD) on each corresponding block subcarriers, SFDO-OFDM codes for the general multiple input multiple output (MIMO) is thus constructed. And concatenating it with the signal constellation precoding, full maximum diversity gains including the inherent Doppler fading are achieved. Theoretical analysis and corroborating simulation results demonstrate that, comparing with existing Doppler coding alternatives, the proposed scheme can effectively and robustly combat the Doppler fading with high bandwidth efficiency and even lower bit error ratio (BER).
sfdo-ofdm time-frequency duality bem block matrix linearly conversion full diversity gains