Doubly-selective channel estimation with unknown interference in OFDM systems

In orthogonal frequency division multiplexing-based spectrum sharing networks, due to inefficient coordination or imperfect spectrum sensing, the signals from femtocells or secondary users appear as interference in a subset of subcarriers of the primary systems. For pilot-based doubly-selective channel estimation, the embedded pilots in pilot subcarriers would inevitably be harmed by the unpredictable interference. This unsolved issue is considered and proposed is a variational expectation maximisation-based method to iteratively learn the distribution of thermal noise plus interference, and refine doubly-selective channel estimates. Simulations demonstrated the superiority of the proposed approach over existing algorithms without considering interference mitigation.