Joint source separation and offset estimation for asynchronous ofdm systems using subspace fitting

An asynchronous multi-user cyclic prefix (CP) transmission system, such as OFDM is considered where the receiver is offset in time by an unknown value with respect to the desired user. The user signals are transmitted with superimposed training and an antenna array is used in the receiver to compute the offset and perform space-time (ST) source separation using subspace fitting. Smoothing is used to improve on the offset estimate and alternating projections are used to improve the beamformer weights to cancel the interference. Simulation results indicate that the blind source separation scheme converges to a reference scheme, where the receiver is synchronized to the desired user and has complete knowledge of its signal.