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Improved H-infinity channel estimator based on EM for MIMO-OFDM systems
Authors:Peng Xu  Jin kuan Wang  Feng Qi
Affiliation:1. Engineering Optimization and Smart Antenna Institute, Northeastern University, Shenyang 110004, P. R. China
2. Electrical Engineering Department(ESAT)-Telecommunications Microwaves(TELEMIC),Katholieke Universiteit Leuven(K. U. Leuven), Leuven 3001, Belgium
Abstract:H-infinity estimator is generally implemented in timevariant state-space models,but it leads to high complexity when the model is used for multiple input multiple output with orthogonal frequency division multiplexing (MIMO-OFDM) systems.Thus,an H-infinity estimator over time-invariant system models is proposed,which modifies the Krein space accordingly.In order to avoid the large matrix inversion and multiplication required in each OFDM symbol from different transmit antennas,expectation maximization (EM) is developed to reduce the high computational load.Joint estimation over multiple OFDM symbols is used to resist the high pilot overhead generated by the increasing number of transmit antennas.Finally,the performance of the proposed estimator is enhanced via an angle-domain process.Through performance analysis and simulation experiments,it is indicated that the proposed algorithm has a better mean square error (MSE) and bit error rate (BER) performance than the optimal least square (LS) estimator.Joint estimation over multiple OFDM symbols can not only reduce the pilot overhead but also promote the channel performance.What is more,an obvious improvement can be obtained by using the angle-domain filter.
Keywords:multiple input multiple output (MIMO)  orthogonal frequency division multiplexing (OFDM)  channel estimation  Hinfinity  expectation maximization (EM)  angle domain
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