Frequency Domain Iterative Combining-Equalization for HF High Data Rate Transmission Systems

In high frequency high data rate transmission (HF-HDRT) systems, the intersymbol interference and deep fading of ionosphere channel seriously hindered the improvement of data transmission rate. In order to solve these problems, a novel frequency domain iterative combining-equalization (FD-ICE) algorithm based on minimum mean square error (MMSE) criterion is proposed, which can realize diversity combining and equalization simultaneously, and iteratively exchange log-likelihood ratio values between soft-input soft-output (SISO) decoder and SISO combining-equalizer. Moreover, a simplified method fast frequency domain iterative combining-equalization (FFD-ICE) with low performance loss is given. Simulation results show that the proposed FD-ICE algorithm can provide a much better performance especially when more antennas are used and the low-complexity FFD-ICE algorithm can achieve an excellent trade off between complexity and performance. Both of the FD-ICE and the simplified FFD-ICE algorithm converge faster than the conventional iterative equalization.