Mitigation of Pulsed Interference in OFDM Based Systems

In order to enhance spectral efficiency an orthogonal frequency-division multiplexing (OFDM) based system is operated in a frequency band already in use by a licensed system. When transmitting an OFDM signal in the spectral gaps left by the licensed system, the OFDM system is exposed to severe interference, in the considered example characterised by short but strong Gaussian shaped pulses. Well-known approaches for mitigating the impact of pulsed interference are pulse blanking or clipping. As these techniques have not been applied to OFDM systems with this type of interference so far, the optimal thresholds for both techniques are determined. Simulations in a realistic interference scenario in the L-band show, that with clipping or pulse blanking based on the optimal threshold the impact of interference can be reduced considerably. The remaining gap to the interference-free case can be partly explained by the fact that not only the interference signal but also the desired OFDM signal is affected by pulse blanking or clipping.