Narrowband interference mitigation for SDR based DAB/DAB+ receivers

In this paper, different narrowband interference (NBI) cancellation procedures in Orthogonal Frequency Division Multiplexing (OFDM) based systems are analyzed with respect to Software Defined Radio (SDR) applications. Besides the well-known methods for narrowband interferer detection within an OFDM signal, an appropriate notch filter structure is necessary to compensate the influence of the interferer and to get the lowest bit-error-rate (BER) for a given signal to noise ratio (SNR). Especially in systems with differentially modulated subcarriers, the influence of a nonlinear phase response caused by Infinite Impulse Response (IIR) filters is investigated and compared to Finite Impulse Response (FIR) filters with a linear phase behaviour. Besides these well-known NBI cancellation methods also alternative and computationally efficiently notch filter structures via allpass realization are discussed. In order to demonstrate the performance of appropriate notch filters in OFDM applications with differentially modulated subcarriers, all simulations are applied to the Digital Audio Broadcasting (DAB/DAB+) system.