Independent component analysis based semi-blind equalization for multiuser-CoMP OFDM systems with low-complexity estimation of multiple CFOs

We propose a low-complexity carrier frequency offset (CFO) estimation method and an independent component analysis (ICA) based semi-blind equalization structure for multiuser and coordinated multi-point (CoMP) OFDM systems. A group of orthogonal sequences is employed to enable separation and simultaneous estimation of multiple CFOs, dividing the multi-dimensional search into series of low-complexity mono-dimensional searches. The ICA is used for equalization, with a small number of pilot symbols employed for ambiguity elimination in the ICA equalized signals. The proposed semi-blind equalization structure slightly outperforms the previous precoding aided scheme, with a lower complexity. It also provides a almost same BER performance to the case of zero forcing (ZF) and minimum mean square error (MMSE) based equalization with perfect CSI and no CFO at the receiver.