Blind carrier frequency offset and channel estimation using ICA in QAM-OFDM systems

In this paper we propose a blind estimation of fading coefficients without using the pilot symbols in QAM-OFDM systems subjected to carrier frequency offset (CFO), where the phases of the fading coefficients are within ±7r/4. First, under a frequency selective fading channel, the inter-carrier interference (ICI) due to CFO is formulated in the framework of independent component analysis (ICA). Then the permutation and scale uncertainty inherent in ICA is resolved and CFO is estimated. Next, based on the CFO estimation results, the fading coefficients are estimated by use of the fact that symbol constellation at each sub-carrier is stretched/shrunk and rotated according to the value of its fading coefficient. Then, the unknown transmitted symbols are restored by use of the coefficient estimates. Finally, the validity of the proposed approach is confirmed from several simulations for 16QAM-OFDM.