Efficient spatial covariance estimation for asynchronous co-channel interference suppression in MIMO-OFDM systems

We present algorithms to suppress the asynchronous co-channel interference (CCI) in MIMO OFDM systems. The key challenge is that the cyclic prefix of the interference signal does not line up with that of the intended signal due to the asynchronous transmission in WLAN. Therefore, the orthogonality across the tones of the interference signal is destroyed and the conventional frequency domain minimum mean square error (MMSE) cancelation techniques that employ the interference channel response per tone can not work effectively. To suppress the asynchronous interference, we design an efficient estimator for the spatial covariance matrix of the interference using Cholesky decomposition and low-pass smoothing. Both a MMSE and a maximum a posteriori (MAP) receiver are derived based on the estimated interference statistics. Simulation results demonstrate the effectivity of our solution.