Oblique projection based equalization for OFDM in presence of in-device coexistence interference

One of the biggest challenges in the modern System On Chips (SOCs) is the interference due to the coexistence of multiple communication systems and standards. Due to this, multiple radios operate simultaneously in adjacent or overlapping radio frequency spectra and in close physical proximity to each other. In such a scenario, estimation of the received data in the presence of interference due to the adjacent communication system(s) becomes a challenging problem. This interference cannot always be assumed to be completely uncorrelated (orthogonal) to the data of interest. Hence the normally used Least Squares and Minimum Mean Squared Error (MMSE) Estimators based on orthogonal projections cannot be used for equalization to estimate the data of interest. In this paper, we discuss how oblique projection operators can be used to mitigate the effects of interference due to an adjacent communication system on the OFDM system of interest. A novel scheme is proposed to cancel the interference using oblique pseudo inverses. Numerical and simulation results show that the proposed scheme provides significant performance improvement and also better diversity order.