Vikram Subramanian
Independent Researcher
India
ABSTRACT
This manuscript investigates channel estimation techniques for MIMO-OFDM systems in the pre-5G era (up to 2015), providing a comprehensive survey of pilot-based, blind, and semi-blind methods, together with a simulation-based statistical comparison. A novel semi-blind algorithm combining minimum mean-square error (MMSE) estimation with subspace tracking is proposed. Simulation results demonstrate that the proposed method yields a 25 % reduction in mean-square error (MSE) at 20 dB SNR compared to conventional MMSE. Key contributions include (1) a detailed taxonomy of estimation methods, (2) design of pilot patterns optimized for high Doppler spreads, (3) development of a low-complexity subspace-based estimator, and (4) a statistical analysis comparing performance across typical 4×4 MIMO channels. Results inform design guidelines for robust channel estimation in high-mobility environments.
Keywords
Channel estimation, MIMO-OFDM, MMSE, subspace methods, pilot design
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