Non-stationary multiple-antenna interference cancellation for unsynchronized OFDM systems with distributed training

Adaptive interference cancellation is addressed in an asynchronous orthogonal frequency-division multiplexing (OFDM) system with a frame containing a number of temporally distributed pilot symbols, e.g., as in the IEEE 802.16-2004 standard. A non-stationary symbol-by-symbol switching technique is proposed that is based on banks of the second-order statistics semi-blind solutions with on-line algorithm selection using a higher-order statistics criterion. Three banks of algorithms are formulated and analyzed by means of comparison to the conventional stationary pilot- based solution and to the non-asymptotic maximum-likelihood benchmark especially developed for assessment of the proposed interference cancellation algorithms. Their efficiency is compared to the conventional stationary solutions by means of simulations in a WiMAX (Worldwide Interoperability for Microwave Access) environment.