Gerd Kilian

Window Design for Non-Orthogonal Interference Reduction in OFDM Receivers

For conventional orthogonal frequency-division multiplexing (OFDM) systems, the guard interval is disregarded in the receiver and rectangular shaped windows are used implicitly due to the discrete Fourier transform (DFT). We consider a Nyquist-shaped window in the receiver, so that the transmit signal does not need to be modified, and optimize the window shape in order to suppress interference from non-orthogonal single carrier interferer signals. For the window coefficients, a closed form solution is derived. This type of interference usually occurs in OFDM radio systems like digital radio mondiale (DRM) that are operating in low frequency bands. (Disturbance is given for instance by harmonics of switched-mode power supplies)

Reduction of Non-Orthogonal Interference in OFDM Receivers by Optimized Windowing

For conventional orthogonal frequencydivision multiplexing (OFDM) systems, the guard interval is disregarded in the receiver and rectangular shaped windows are used implicitly due to the discrete Fourier transform (DFT). We consider a Nyquistshaped window in the receiver, so that the transmit signal does not need to be modified, and optimize the window shape in order to suppress interference from non-orthogonal single carrier interferer signals. For the window coefficients, a closed form solution is derived. This type of interference occurs for example in OFDM radio systems like Digital Radio Mondiale (DRM) that are operating in low frequency bands. (Disturbance is given for instance by harmonics of switched-mode power supplies.) Further for multiple interferers, the receiver with optimized window outperforms the conventional receiver.

Single Carrier Interference Cancellation for Digital Radio Mondiale (DRM)

We consider cancellation of a single carrier interferer for the digital radio mondiale (DRM) system. The interferer is fully described by its frequency, amplitude, and phase. These parameters can be estimated in a maximum-likelihood sense using the pilot symbols in the orthogonal frequency division multiplexing (OFDM) signal. Subsequently, the interference may be reconstructed and subtracted from the received signal. Alternatively, the knowledge of the interferer frequency may be exploited for the design of a notch filter, nulling out the interference. Results show that the reconstruction and substraction method outperforms the notch filtering approach only if an accurate estimate of the interferer frequency is available. Otherwise, notch filtering has better performance