Deep Clipping for Impulsive Noise Mitigation in OFDM-Based Power-Line Communications

Exponential demand for broadband applications has elicited renewed interest in characterizing noise in power line communication (PLC) networks for optimal error performance analysis. PLC is economical and ubiquitous, however due to multipath phenomena and nonstationary impulsive noise, the PLC channel is very harsh to signal transmission. Recent studies reveal that PLC noise is cyclostationary and modelling its characteristic should exploit the spectral and temporal redundancy. In addition, preliminary research shows that PLC noise exhibits self-similarity and can be predicted by fractal theory. In modelling noise employing fractal theory, the Hausdorff dimension (D) needs to be approximated. D is related to Hurst parameter (H), which is a measure of self-similarity. Hence, it is important to estimate H for accurate noise prediction using fractal theory. H parameter estimators assume stationarity in time series data. Therefore, preprocessing is required for the case of PLC noise before estimating H to make it stationary as periodicity and nonstatioanrity affects the H estimators. In this study, we remove the periodicity hidden in the PLC noise obtained from measurement campaign within several university offices, workshops and laboratories. Then long-range dependence is estimated from this pre-processed noise data by employing three estimation algorithms: R/S (rescaled adjusted range) method, aggregated variance method and absolute values of aggregated series method. Results from the said estimation methods though not the same, show that the Hurst parameters obtained from various noise measurements are greater than 0.5, implying presence of self-similarity with long-term memory. Results from this study will find valuable applications in PLC noise modelling using fractal and chaos theory and in error performance analysis in both narrowband and broadband PLC systems.

Impulsive noise is one of the main channel impairments in orthogonal frequency division multiplexing (OFDM)-based power line communications (PLC). Clipping nonlinearites such as conventional clipping, blanking, joint blanking/clipping, and deep clipping have been proposed to mitigate the impulsive noise. However, OFDM systems result in high peak amplitude after inverse discrete Fourier transform (IDFT) at the transmitter, which leads to large peak-to-average power ratio (PAPR). High peak amplitude can be falsely clipped by the impulsive noise clipper at the receiver leading to poor system performance. In this paper we propose a joint peak amplitude clipping and impulsive noise clipping nonlinearities to improve the bit error rate (BER) performance.

Impulse noise in power line communication (PLC) channel seriously degrades the performance of Multiple-Input Multiple-Output (MIMO) system. To remedy this problem, a MIMO detection meth ...

Mitigating impulsive noise in airborne PLC: Introducing the S-SAMP-PV algorithm for MIMO OFDM systems

Power Lines Communication (PLC) deals with the transmission of data through the use of power lines. It is one emerging infrastructure for the home area network of Smart Grid (SG). There are two types of additive noise significantly affects the performance of PLC systems, namely background noise and impulsive noise. And the noise effects of both background noise and impulsive noise are taken from Bernoulli-Gaussian Process. The log-normal distribution has been used to model the PLC channel. As power lines are not designed for data communication. Because of signal attenuation and Electromagnetic Compatibility (EMC) regulations, the PLC link has low coverage and capacity To mitigate the EMC issue, the concept of Cognitive Radio (C.R.) is used in PLC. In this paper, receiver diversity scheme namely L-channel Selection Combining (SC) and Maximal Ratio Combining (MRC) is used for improving the Signal to Noise Ratio (SNR) to improve overall the reliability system. The system performance is evaluated in terms of Outage Probability for SC and MRC.

In this paper, burst impulse noise is measured and a practical burst impulse noise model is proposed. The noise presented on power-line system is generated by start or stop of relay and motor. The parameters of noise model were derived from measurements of the mains voltages by using data acquisition card and a digital signal processing program. Using the measured parameters, the burst impulse noise model is established. The simulation shows that the results of proposed model are very akin to actual power line noise, it helps researcher to work independent of power line voltage in complex working environment.

Many IN mitigation techniques have been proposed to mitigate impulsive noise (IN) over powerlines, the most common of which is the blanking technique. The conventional way to implement this technique however requires prior knowledge about the IN characteristics to identify the optimal blanking threshold (OBT). When such knowledge cannot be obtained the performance deteriorates rapidly. To alleviate this, a look-up table (LUT) based algorithm with uniform quantization is deployed to utilize estimates of the peak to average power ratio at the receiver to determine the OBT. In this paper, we investigate the impact of quantization bits on the system performance as well as the performance loss due to the impact of IN on the side information. Two aspects of the achievable performance are considered namely, output signal-to-noise ratio (SNR) and symbol error rate under various IN scenarios. The results reveal that a 5 bit LUT is sufficient to achieve a gain of up to 3dB SNR improvement relative to the conventional blanking method. Furthermore, it will be shown that the loss due to the practical impact of IN on the side information is insignificant.

Power line communications (PLC) and visible light communications (VLC) are two emerging communication technologies which have several similarities. Among them, the advantage related to cost effectiveness is considered as strong research motivation. These two technologies are also characterized by the fact that each one of them barely form a complete communication system without the need of other supporting technologies. In this paper, based on the positive aspect of VLC technology, we exploit the Hermitian symmetry to design an hybrid system combining PLC and VLC technologies using orthogonal frequency division multiplexing (OFDM). A DC biased optical OFDM (DCO-OFDM), employed in VLC, is investigated when combined with PSK-OFDM (used in PLC). In the hybrid PLC-VLC system proposed in this paper, we exploit the inherent clipping feature of DCO-OFDM to combat impulsive noise found in the PLC channel, where the optimal combination of the DC bias level for optical communication, DC and impulse noise clipping threshold, T <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> are investigated through simulations. We also exploit the fact that both DCO-OFDM and PSK-OFDM employ the FFT, to simplify the system.

Ergodic chaotic parameter modulation (ECPM) has recently been proposed as a viable modulation technique for power-line communications (PLC) due to its robustness to multipath conditions and low complexity in receiver design. While performance of ECPM has been found to be satisfactory in limited noise conditions, performance issues for other hostile challenges in the power-line environment, such as narrowband and impulsive noise, have not been extensively studied for this technique. Numerous studies have been performed on direct-sequence spread-spectrum (DSSS) modulation used in a wireless channel. The technique has been found to be well suited for a mobile environment due to its resistance to multipath fading and inherent narrowband interference suppression capability. For this study, PLC performance is investigated for both the DSSS and ECPM receiver for PLC. A signal-to-noise ratio (SNR) analysis is presented which investigates the noise-limiting properties of the power-line channel. This work provides a detailed insight to communication system performance in a power-line environment that includes the presence of significant narrowband and impulsive noise. It is concluded that while DSSS significantly outperforms ECPM in terms of bit-error rate for a Gaussian white noise-limited channel, the performance of the two techniques is similar for low SNR communication dominated by narrowband or impulsive noise. While the implementation of DSSS is more complex, ECPM is found to be less robust to low-frequency interference

Powerline communication technology is a promising communication platform for smart grid and has nowadays become an attractive alternative for data transmission in the home. Impulsive noise (IN) over such channels, however, remains the main factor responsible for degrading communication signals. Many techniques for mitigating IN have been reported in the literature the most common of which is preceding the OFDM receiver with blanking, clipping or hybrid (combined blanking-clipping) nonlinear preprocessors. In this paper, we propose to enhance the capability of these techniques by preprocessing the signal at the transmitter. A closed-form analytical expression for the probability of IN detection error is derived and the problem of blanking/clipping threshold selection is also considered. The results reveal that the proposed is able to minimize the probability of IN detection error significantly and can provide up to 3dB SNR improvement relative to the conventional techniques.

Power line communication (PLC) utilizes power lines for the purpose of electronic data transmission. The performance of a PLC system is significantly affected by the additive and multiplicative power line noises; the additive noises are of two types, namely background noise and impulsive noise. Whereas, the multiplicative PLC noise leads to fading in the received signal strength. In this paper, we evaluate the performance of a PLC system over log-normal fading channel under Nakagami-m distributed additive background noise assuming binary phase shift keying modulation scheme. The analysis involving log-normal fading is very complicated. Hence we use a novel gamma approximation to log-normal distribution for our analysis. We evaluate the probability density function of the decision variable. A closed-form expression of the analytical average bit error rate of the considered system is derived. We also compute the diversity order of the considered PLC system. The validity of the derived analytical expressions is closely verified by the simulation results.

Broadband communications for indoor power-line networks with impulsive noise using orthogonal frequency division multiplexing (OFDM) is considered. From earlier investigations, it is known that this channel suffers from multipath fading and frequency selectivity along with man-made impulsive bursty noise. Nevertheless, the calculated channel capacity limit promises very high data rates over this channel. Enhancement techniques, such as coding can help an OFDM system to tackle impulsive noise burst. In this paper, the bit error rate (BER) performance of the OFDM system under impulsive noise and frequency fading is theoretically analyzed and closed form expression for the performance is derived. Two different impulsive noise environment models are studied and it is confirmed that both models represent the same environment. Furthermore, a theoretical upper bound on the performance of coded OFDM system is obtained, given perfect interleaving. The effect of the interleaver length on coding performance is also studied. Simulations show that the upper bound is quite tight for the case of employing a longer interleaver. The effect of interleaver size on the system performance is studied, as well

Orthogonal frequency division multiplexing (OFDM) is adopted in most wireless communication systems, and the performance of OFDM is affected by impulse noise (IN). Better channel estimation (CE) performance is required to detect the channel information on the receiving side. The OFDM system is considered with the number of subcarriers carrying the data and pilot symbols. In the OFDM modulator, the symbols of the frequency domain are transformed into the signals of the time domain using inverse discrete Fourier transformation (IDFT). Effective impulsive noise mitigation is crucial for improving the effectiveness of OFDM communication systems, and it improves the signal-to-noise ratio (SNR) at the receiver. A cyclic prefix is then appended before transmission through the channel. In the receiver noise, the effect of IN is mitigated jointly with CE using the Bayesian matching pursuit (BMP) and Moth-flame algorithm (MFA). In this approach, the IN and channel information is considered as a sparse vector. Here, the data symbols used are considered an unknown parameter. The approach incorporating all subcarriers has a lower mean square error (MSE) of IN estimate for impulsive noise reduction. The MFA algorithm is used to optimize the sensor matrix in BMP. The sparsity of the channel and the impulse response are observed in the time domain to represent the channel and IN together. It exactly recovers the sparse signal for finding the convex objectives of the sparse minimizer, and the sparse solution is obtained with fixed point updates. The proposed BMP algorithm improves the CE by explicitly considering the existence of IN. The BMP is a greedy algorithm that selects the most correlated residuals at each column. Under mutual incoherence, it recovers the signal with a higher probability. The simulated outcomes proved that the proposed CE and noise mitigation model achieved better performance based on the bit error rate (BER), throughput and MSE.

A weighted fractional Fourier transform (WFRFT) scheme is proposed for the orthogonal frequency division multiplexing (OFDM) system to combat impulsive noise (IN) in substation communications. According to the central limit theorem, the analytic expression of the real-valued IN probability density function (PDF) after WFRFT is derived and for ease of calculation, the closed form expression of the approximate PDF is also put forward. The PDF of IN shows that WFRFT makes IN more concentrated to the small amplitudes in the fractional Fourier transform domain than in the frequency domain at the receiver. As a result, the WFRFT scheme achieves a better bit error rate (BER) performance than the conventional OFDM system. In addition, the proposed scheme is also compatible with other existing IN mitigation techniques, such as dynamic peak-based threshold estimation-lookup table (DPTE-LUT) blanking. Simulation results have verified that the derived analytic and closed form PDF expressions of IN after WFRFT and the advantage of the proposed scheme over the counterpart OFDM system in the IN channels at high SNR with and without the DPTE-LUT blanking.

Additive asynchronous and cyclostationary impulsive noise limits\ncommunication performance in OFDM powerline communication (PLC) systems.\nConventional OFDM receivers assume additive white Gaussian noise and hence\nexperience degradation in communication performance in impulsive noise.\nAlternate designs assume a parametric statistical model of impulsive noise and\nuse the model parameters in mitigating impulsive noise. These receivers require\noverhead in training and parameter estimation, and degrade due to model and\nparameter mismatch, especially in highly dynamic environments. In this paper,\nwe model impulsive noise as a sparse vector in the time domain without any\nother assumptions, and apply sparse Bayesian learning methods for estimation\nand mitigation without training. We propose three iterative algorithms with\ndifferent complexity vs. performance trade-offs: (1) we utilize the noise\nprojection onto null and pilot tones to estimate and subtract the noise\nimpulses; (2) we add the information in the data tones to perform joint noise\nestimation and OFDM detection; (3) we embed our algorithm into a decision\nfeedback structure to further enhance the performance of coded systems. When\ncompared to conventional OFDM PLC receivers, the proposed receivers achieve SNR\ngains of up to 9 dB in coded and 10 dB in uncoded systems in the presence of\nimpulsive noise.\n