Low-complexity H-infinity channel estimator for MIMO-OFDM systems

Although maximum a posteriori probability (MAP) channel estimator has an optimal performance for MIMO-OFDM systems, its high complexity could be in the order of O(K
³
), where K is the number of subcarriers. So, in this paper, we introduce an H-infinity estimator which has good performance, but with much less complexity. Next, lots of matrices inversions and multiplications are reduced by the iterative expectation maximization (EM) algorithm. It is shown that the proposed EM-based H-infinity estimator has obviously improvement over optimal least square (LS) estimator with good convergence and the H-infinity estimator has almost the same performance as optimal MAP estimator with much less complexity.