Joint Decision-Directed Channel and Noise-Variance Estimation for MIMO OFDM/SDMA Systems Based on Expectation-Conditional Maximization

A joint channel impulse response (CIR) and noise-variance estimation scheme is proposed for multiuser multiple-input-multiple-output (MIMO) orthogonal frequency-division multiplexing/space-division multiple access (OFDM/SDMA) systems, which is based on the expectation-conditional maximization (ECM) algorithm. Multiple users communicating over fading channels exhibiting a range of different characteristics are considered in this paper. Channel estimation becomes quite challenging in this scenario since an increased number of independent transmitter-receiver links having different statistical characteristics have to be simultaneously estimated for each subcarrier. To cope with this scenario, we design an ECM-based joint CIR and noise-variance estimator for multiuser MIMO OFDM/SDMA systems, which is capable of simultaneously estimating diverse CIRs and noise variance. Furthermore, we propose a forward error code (FEC)-aided decision-directed channel estimation scheme based on the ECM algorithm, which further improves the ECM algorithm by exploiting the error correction capability of an FEC decoder for iteratively exchanging information between the decoder and the ECM algorithm.

[1]  Marc Moonen,et al.  Optimal training design for MIMO OFDM systems in mobile wireless channels , 2003, IEEE Trans. Signal Process..

[2]  Yongzhe Xie,et al.  Two EM-type channel estimation algorithms for OFDM with transmitter diversity , 2002, 2002 IEEE International Conference on Acoustics, Speech, and Signal Processing.

[3]  Jie Gao,et al.  Low-Complexity Map Channel Estimation for Mobile MIMO-OFDM Systems , 2008, IEEE Transactions on Wireless Communications.

[4]  Geoffrey Ye Li,et al.  Simplified channel estimation for OFDM systems with multiple transmit antennas , 2002, IEEE Trans. Wirel. Commun..

[5]  Geoffrey Ye Li,et al.  MIMO-OFDM for wireless communications: signal detection with enhanced channel estimation , 2002, IEEE Trans. Commun..

[6]  Lajos Hanzo,et al.  OFDM and MC-CDMA for Broadband Multi-User Communications, WLANs and Broadcasting , 2003 .

[7]  S. Kay.  Fundamentals of statistical signal processing: estimation theory , 1993 .

[8]  Vijay K. Bhargava,et al.  A reduced complexity channel estimation for OFDM systems with transmit diversity in mobile wireless channels , 2002, IEEE Trans. Commun..

[9]  Lajos Hanzo,et al.  An Optimized-Hierarchy-Aided Approximate Log-MAP Detector for MIMO Systems , 2007, IEEE Transactions on Wireless Communications.

[10]  Lajos Hanzo,et al.  Multiuser MIMO-OFDM for Next-Generation Wireless Systems , 2007, Proceedings of the IEEE.

[11]  X. Dai.  Pilot-aided OFDM/SDMA channel estimation with unknown timing offset , 2006 .

[12]  D. Rubin,et al.  Maximum likelihood from incomplete data via the EM - algorithm plus discussions on the paper , 1977 .

[13]  Xiao-Li Meng,et al.  Maximum likelihood estimation via the ECM algorithm: A general framework , 1993 .

[14]  Geoffrey Ye Li,et al.  Optimum training symbol design for MIMO OFDM in correlated fading channels , 2006, IEEE Transactions on Wireless Communications.

[15]  Jinho Choi.  An EM based Joint Data Detection and Channel Estimation Incorporating with Initial Channel Estimate , 2008, IEEE Communications Letters.

[16]  Lajos Hanzo,et al.  Parallel-interference-cancellation-assisted decision-directed channel estimation for OFDM systems using multiple transmit antennas , 2005, IEEE Transactions on Wireless Communications.

[17]  Alberto Morello,et al.  CD3-OFDM: a novel demodulation scheme for fixed and mobile receivers , 1996, IEEE Trans. Commun..

[18]  Hugo De Man,et al.  A combined OFDM/SDMA approach , 2000, IEEE Journal on Selected Areas in Communications.

[19]  Lajos Hanzo,et al.  Iterative Joint Channel Estimation and Multi-User Detection for Multiple-Antenna Aided OFDM Systems , 2007, IEEE Transactions on Wireless Communications.

[20]  Luc Vandendorpe,et al.  Comparison of EM-Based Algorithms for MIMO Channel Estimation , 2007, IEEE Transactions on Communications.

[21]  Sirikiat Lek Ariyavisitakul,et al.  Channel estimation for OFDM systems with transmitter diversity in mobile wireless channels , 1999, IEEE J. Sel. Areas Commun..