An EM based semi-blind channel estimation algorithm designed for OFDM systems

OFDM systems traditionally perform channel coefficients relying on known training sequences. However in wireless systems, performance and mobility can be further enhanced either by operating semi-blind channel estimation refinement or variation tracking between reference symbols. In this paper, we propose a semi-blind expectation-maximization (EM) based estimation method which takes into account OFDM specificities. Indeed, a new EM cost function is introduced accounting for the fact that the channel impulse response is shorter than the cyclic prefix duration. Simulation results using the new algorithm yields a 2 dB SNR improvement compared to classical training sequences based channel estimation in the context of 5 GHz OFDM WLAN (IEEE 802.11a and HIPERLAN/2).