Takaaki Ishibashi

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.

Studies on Estimation of the Sources Number in Blind Source Separation Problems

ICA (Independent Component Analysis) can separate unknown source signals from their mixture signals without information on the transfer functions, provided that the sources are statistically independent. When the number of the source signals is equal to that of the observed signals, the original sources can be recovered except for indeterminacy of scale and permutation. However, the number of the sources is unknown in a real environment. In this paper, we propose an estimation method for the number of the sources based on the joint distribution of the observed signals under two-sensor configuration. From several simulation results, it is found that the number of the sources is coincident to that of peaks in the histogram of the distribution