GLOBECOM'09 Proceedings of the 28th IEEE conference on Global telecommunications
MIMO OFDM over underwater acoustic channels
Asilomar'09 Proceedings of the 43rd Asilomar conference on Signals, systems and computers
SAGE Algorithm for Semi-Blind Channel Estimation and Symbol Detection for STBC MIMO OFDM Systems
Wireless Personal Communications: An International Journal
| Hi-index | 0.01 |
This paper presents a reduced-complexity maximum a posteriori probability (MAP) channel estimator with iterative data detection for orthogonal frequency division multiplexing (OFDM) systems over mobile multiple-input multiple- output channels. The optimal MAP estimator needs to invert an NNT x NNT data-dependent matrix each in OFDM symbol interval, where N is the number of subcarriers and NT is the number of transmit antennas. We derive an expectation maximization (EM) algorithm with low-rank approximation to avoid inverting large-size matrices, and thus drastically reduce the receiver complexity. In the iterative process, channel parameters are initially obtained by a least square (LS) estimator for temporary symbol decisions. Then, inter-carrier interference (ICI) due to fast fading is approximated and canceled. Finally, the temporary symbol decisions and the ICI-canceled received signals are processed by the EM-based MAP estimator to refine the channel state information for improved detection. The proposed scheme achieves about 2 dB gain over the LS scheme in channels with medium to high normalized Doppler shifts.