Improved Frequency-Domain Channel Estimation for Fast Time-Varying MIMO-SCFDE Channels

A frequency-domain channel estimation method is proposed for time-varying multiple-input multiple output (MIMO) single-carrier frequency-domain equalization (SC-FDE). The proposed method uses frequency-domain interpolation to obtain channel frequency responses of data blocks from estimated responses of two adjacent pilot blocks. It takes the channel temporal-spatial correlation into account to achieve minimum mean squared error (MMSE) estimation, thus improving the accuracy and effectiveness in high Doppler scenarios. The simulation results of the bit error rate (BER) performances show that the proposed method works well for fast time-varying channels with Doppler spread as high as 300 Hz while maintaining over 70% data efficiency

Robust frequency-domain turbo equalization for multiple-input multiple-output (MIMO) wireless communications

This dissertation investigates single carrier frequency-domain equalization (SC-FDE) with multiple-input multiple-output (MIMO) channels for radio frequency (RF) and underwater acoustic (UWA) wireless communications. It consists of five papers, selected from a total of 13 publications. Each paper focuses on a specific technical challenge of the SC-FDE MIMO system. The first paper proposes an improved frequency-domain channel estimation method based on interpolation to track fast time-varying fading channels using a small amount of training symbols in a large data block. The second paper addresses the carrier frequency offset (CFO) problem using a new group-wise phase estimation and compensation algorithm to combat phase distortion caused by CFOs, rather than to explicitly estimate the CFOs. The third paper incorporates layered frequency-domain equalization with the phase correction algorithm to combat the fast phase rotation in coherent communications. In the fourth paper, the frequency-domain equalization combined with the turbo principle and soft successive interference cancelation (SSIC) is proposed to further improve the bit error rate (BER) performance of UWA communications. In the fifth paper, a bandwidth-efficient SC-FDE scheme incorporating decision-directed channel estimation is proposed for UWA MIMO communication systems. The proposed algorithms are tested by extensive computer simulations and real ocean experiment data. The results demonstrate significant performance improvements in four aspects: improved channel tracking, reduced BER, reduced computational complexity, and enhanced data efficiency --Abstract, page iv