Channel Estimation In High-rate WLAN System Based On MIMO-OFDM

As a combination of OFDM with space-time coding technique, MIMO-OFDM can not only effectively enhance the transmission rate and capacity of the wireless communication system but also effectively combat multipath fading and ISI, so MIMO-OFDM is adopted in IEEE802.11n, the new generation standard of high-rate WLAN. The channel state information (CSI) is crucial for an optimal detector at the receiver especially in MIMO-OFDM systems, so the contents of this dissertation are concentrated on the channel estimation approaches in the new generation WLAN system. After a brief introduction of wireless fading channels and the MIMO-OFDM technique, the approaches of channel estimation in high-rate WLAN systems, including ones in time-domain and in frequency-domain, are investigated with emphasis. Firstly the time-domain LS channel estimation is investigated and improved, and several simplified algorithms and a complete channel estimating and tracking scheme in time-domain are presented. Then several channel estimation approaches in frequency-domain, as well as an iterative joint channel estimation and signal detection method, are presented and improved respectively, next an effective channel estimating and tracking scheme in frequency-domain is proposed. Finally, simulation results confirmed the validity and feasibility of these channel estimation approaches.