Low Complexity Adaptive Turbo Space-Frequency Equalization for Single-Carrier Multiple-Input Multiple-Output Systems

By combining single-carrier (SC) frequency domain equalization (FDE) and Turbo equalization, we propose a minimum mean square error (MMSE) based block-wise low complexity Turbo space-frequency equalization (TSFE) structure, which offers a tremendous complexity reduction over the symbol-wise TSFE and Turbo time-domain equalization (TTDE) structures. With a moderate code rate, the proposed SC TSFE significantly outperforms its Turbo OFDM (TOFDM) counterpart, at a comparable complexity. Besides, TSFE based on the least-mean-square structured channel estimation (LMS-SCE) provides a performance close to the case with perfect channel state information (CSI), at a high convergence rate.