A method of signal processing according to one of several embodiments includes estimating a deterministic component of a received signal. The estimating is based on an estimated response of a transmission channel. Based on the estimated deterministic component, a non-deterministic component of the received signal is estimated. Based on corrupted portions of the estimated non-deterministic component, a noise estimate is obtained, and the received signal is compensated based on the noise estimate. A method according to another embodiment includes replacing received samples at corrupted locations with values from a calculated model.

Systems, methods, and apparatus for impulse noise mitigation

In this paper, an algorithm for mitigating impulsive interference in OFDM based systems is presented. It improves the conventional blanking nonlinearity approach for interference mitigation, which typically distorts the entire received signal, by combining the blanked and the original signal. The algorithm uses a Neyman-Pearson like testing procedure to detect interference at individual sub-carriers. Provided interference is detected, the blanked and the original received signals are then optimally combined such as to maximize the signal-to-interference-and-noise ratio. The algorithm does not require any prior knowledge about the impulsive interference and only marginally increases computational complexity as compared to the conventional blanking nonlinearity approach. Numerical results demonstrate the superior performance of the proposed scheme.

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Mitigation of Impulsive Frequency-Selective Interference in OFDM Based Systems

Impulse noise is prevalent in urban and indoor radio channels where OFDM system is deployed. In this paper we propose a novel impulse noise cancellation algorithm for OFDM channel estimation under impulse noise. The algorithm first calculates the frequency domain difference on pilot subcarriers between the received signal and the recovered signal from least square channel estimate. Then the difference is used to estimate a sufficient statistics of the impulse components of time domain noise. Finally the impact of the impulsive noise components on the original channel estimation is cancelled to produce a new channel estimate. Simulation results show that our algorithm can improves OFDM channel estimation performance significantly under impulse noise environments.

OFDM Channel Estimation with Impulse Noise Cancellation

In this paper, we introduce advancements of the conventional blanking nonlinearity (BN) for orthogonal frequency-division multiplexing (OFDM)-based systems, which is referred to in the following as advanced BN. Blanking is a common measure for mitigating impulsive interference that often occurs in wireless communication systems. Although the BN removes impulsive interference reliably, it possesses various drawbacks for OFDM-based systems. In particular, the choice of the blanking threshold (BT), to decide whether a received sample is blanked, is a critical issue. We present an algorithm for determining the optimal BT to maximize the signal-to-noise-and-interference ratio (SINR) after blanking. Another drawback is that the entire received signal is discarded during a blanking interval, despite the fact that only a fraction of the spectrum of the OFDM signal might be affected by interference. We show how blanking can be limited to subcarriers that are actually affected by interference. Further, we show how these measures can be combined and how a priori information obtained in an iterative loop can be incorporated into the proposed scheme. Simulation results incorporating realistic channel and interference models demonstrate the effectiveness of the proposed scheme.

Advanced Blanking Nonlinearity for Mitigating Impulsive Interference in OFDM Systems

The application of a blanking nonlinearity to cope with impulsive interference is a common approach in OFDM systems. The choice of the amplitude threshold to decide whether a received sample is blanked, heavily affects the performance of the entire transmission. As a matter of fact, the perfect blanking threshold strongly depends on the characteristics of the interference. In previous publications this perfect threshold has been derived, given knowledge about the interference statistics. In general, however, no reliable information about the interference statistics is known at the receiver side. In this paper a practical method for calculating an adaptive blanking threshold to maximize the signal-to-interference-and-noise ratio after the blanking nonlinearity is proposed. The calculation is based on the distribution of the amplitude of the received signal at the OFDM receiver. Simulation results show only a negligible performance degradation when comparing the proposed method to the case where the theoretically derived perfect threshold is applied for blanking.

/pdf/adaptive-threshold-optimization-for-a-blanking-nonlinearity-57o5zedwmo.pdf

Adaptive threshold optimization for a blanking nonlinearity in OFDM receivers

Impulse noise is a significant problem in some OFDM applications, including digital television broadcasting. In this paper, we study a novel decision directed impulse mitigation algorithm, both analytically and with simulations for the DVB-T parameters. In this algorithm, the noise component in each received input sample is estimated based on preliminary decisions on the transmitted data. When the estimate is large enough to indicate that impulse noise is present in the sample, the estimated noise component is subtracted from the input sample before final demodulation. This technique has been shown to be extremely effective in flat fading channels. In this paper, its application in frequency selective fading channels is analyzed. The optimum weighting factors for combining noise estimates from subcarriers subject to different fading are calculated. Simulation results are presented for Rayleigh and Ricean channels which show that the technique can reduce the error rates due to impulsive noise by an order of magnitude.

H.A. Suraweera

Papers

Decision directed impulse noise mitigation for OFDM in frequency selective fading channels [DVB-T example]