Improved EM-based H-infinity Channel Estimator for MIMO-OFDM Systems

In this paper, an H-infinity channel estimator, adopting simplified objective function, is introduced to multiple-input multiple-output with orthogonal frequency division multiplexing (MIMO-OFDM) systems. Next, the matrices inversions and multiplications are reduced by using the expectation maximum (EM) algorithm. Finally, the performance degradation due to the carrier frequency offset (CFO)) is improved by using the equivalent signal model (ESM). Simulation experiments show that the proposed H-infinity estimator has almost the same performance as the MAP estimator and EM-based H-infinity estimator has obviously improvement over least square (LS) estimator with good convergence. Furthermore, EM-based H-infinity estimator based on ESM could obtain remarkable improvement under frequency mismatch circumstance.