Impulsive noise mitigation scheme that combines nulling and time sample replacement

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

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.

In this work, an efficient interleaving process is proposed for orthogonal frequency division multiplexing (OFDM) systems over impulsive noise channels. Unlike the conventional OFDM systems where the interleaving process is implemented before the inverse discrete Fourier transform (IDFT), the proposed scheme is based on performing the interleaving process post the IDFT. The aim of this process is to average the effect of the impulsive noise burst over a large number of OFDM symbols, which can reduce its impact on the bit error rate (BER) significantly. For the system and channel models considered in the work, simulation results have confirmed that the proposed system can effectively reduce the BER degradation due to the impulsive noise to about 1 dB as compared to the impulsive noise-free case.

This paper presents an evaluation of data transmission through M-QAM (Quadrature Amplitude Modulation) and OFDM (Orthogonal Frequency Division Multiplexing) systems under the influence of Gaussian and impulsive noise on channel PLC (Power Line Communication). The goal is the comparative analysis of symbol error probability in cases: only M-QAM modulation and M-QAM/OFDM systems in the presence of Gaussian and impulsive noise. The results obtained show that the value of the symbol error probability increases when data transmission is performed only with M-QAM modulation and decreases when data transmission is performed by the M-QAM system/OFDM.

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.

This paper reports on findings on the analysis of the fast Fourier transform (FFT) hybrid power line communication (PLC) - visible light communication (VLC) system (PLC- VLC) based on ACO-OFDM in impulsive noise, when the perfect nulling technique is utilized to combat noise in the system. In this work, we develop theoretical expressions that describe the error floors realized in the system due to perfect nulling. Perfect nulling refers to a noise mitigation technique that perfectly identifies impulsive noise locations in a string of data samples and clips them to zero, leading to an error floor at a high Signal to Noise (SNR) ratio. Thus, the principal contribution of this paper is to analyze and derive theoretical Bit Error Rate (BER) expressions for the error floor achieved by a BPSK OFDM signal in the FFT hybrid PLC-VLC system based on asymmetrically clipped optical - orthogonal frequency division multiplexing (ACO-OFDM), in a channel corrupted with Added White Gaussian Noise (AWGN) and impulsive noise. The derived theoretical BER results will be compared to the error floors obtained through simulations.

In this paper, we consider out-of-band radiations caused by high sidelobes in orthogonal frequency division multiplexing (OFDM) system. Suppression of sidelobes in OFDM system allows higher spectral efficiency and less interference with existing legacy systems in OFDM based overlay system. We combine different sidelobe suppression techniques to suppress the sidelobes in OFDM system. The multiple-choice sequence (MCS) is combined with cancellation carriers (CCs) and also MCS is combined with subcarrier weighting (SW) technique. MCS is applied prior to CCs or SW techniques. Simulation results show that combining MCS with CCs and MCS with SW techniques the sidelobes in OFDM system can be significantly reduced, which allow a successful co-existance between OFDM overlay system and an existing legacy system.

Performance improvement of a power line communication system is presented here considering the noise as a cyclostationary non-white Gaussian random process. Performance of a power line communication system is severely deteriorated by fading and multipath effect. The impulsive noise has been considered time variant, has short duration, random occurrence with a high power spectral density (PSD). It causes bit error in the signal. Using orthogonal frequency division multiplexing (OFDM) technique, the effect of impulsive noise and fading can be improved greatly. An analytic approach is presented to evaluate the performance of a power line communication link in the presence of the above limitations. The simulation results show that there is deterioration in system BER due to time and frequency dependence of noise and the degradation is found to be significant at higher bit rates and bandwidth. The system suffers penalty in receiver sensitivity due to non-white nature of the noise process. In this paper, an analytical approach using diversity reception is carried out to examine the performance improvement of a power line channel in fading and impulsive noise. The system bit error rate (BER) is compared numerically for both binary phase shift keying (BPSK) and OFDM system. The BER results show that there is significant improvement in OFDM. Also the performance is remarkably upgraded using diversity reception.

Broadband low-voltage power line communication (PLC) has many advantages including less investment cost, construction speed, and convenient access. Since the orthogonal frequency division multiplexing (OFDM) technology has strong anti-jamming and anti-frequency selective fading characteristics naturally it becomes a better low voltage power line communication solution. We proposed an OFDM channel estimation method based on compressed sensing (CS) technique according to the channel characteristics of low-voltage power lines. CS algorithm in OFDM system was discussed and an orthogonal matching pursuit (OMP) algorithm was applied to reconstruct the PLC channel information. The simulation results showed that the communication channel estimation method based on CS technique was feasible in PLC system, and the validity of information transmission in OFDM systems can be enhanced.

Orthogonal frequency division multiplexing (OFDM) system has been widely used for the high speed digital communication area and it is very promising for the next generation communication standard because of high data rate capability. However, OFDM system has inherent serious problem of high peak-to-average power ratio (PAPR) that makes the OFDM signal be distorted in the nonlinear HPA (high power amplifier). In this paper, CI (carrier interferometry)-OFDM system is considered to overcome this problem and is newly analyzed in the selective fading and narrow-band interference channel. CI-OFDM system distributes each parallel data to all sub-carriers in differently phase-rotated form. So, PAPR becomes lowered and it shows the frequency diversity effects. BER (bit error rate) performance is analyzed in the selective fading and narrow-band interference environment. From the simulation results, it is confirmed that CI-OFDM system calms down the high PAPR problem and CI-OFDM system is more robust than the ordinary OFDM system in the selective fading and narrow-band interference channel.

In this paper, an integrated Orthogonal Frequency Division Multiplexing (OFDM) system is developed to improve Bit Error Rate (BER) performance of communication systems in order to meet the requirements of advanced communication systems like long term evaluation advanced (LTE –A). The proposed OFDM system consists of channel estimation using comb type pilot arrangement and convolution encoder with the best known Coding Bounds and Maximum A Posteriori (MAP) decoder. Using pilot symbols, the channel quality is estimated. The BER performance of OFDM system is improved using pilot carriers, channel estimation schemes and MAP decoder at the best known coding bounds. The system performance is analyzed with recursive systematic and non-systematic convolution codes, ML and MAP decoders. From the results, it is evident that the proposed OFDM system with channel estimation and MAP decoder at the best known coding bounds improves the system performance significantly.

Orthogonal frequency division multiplexing (OFDM) systems suffer from high sidelobes level. In some applications, as cognitive radios, this phenomenon can be a serious matter. This paper proposes Minimum shift keying (MSK)-OFDM to address this problem. The proposed method is an OFDM system using MSK modulation in each subcarrier. The corresponding transmitter and receiver are introduced. The method doesn't entail great changes in the main parts of OFDM. Like OFDM systems, the transceiver can be implemented using DFT/IDFT. Simulation results show great reduction in out of band radiation in comparison with conventional OFDM.

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.

In this paper, an algorithm that estimates the parameters of impulse noise (IN) is proposed in power line communication. The Peak to Average Power Ratio (PAPR) of the Orthogonal Frequency Division Multiplexing (OFDM) symbol sent by the transmitter is reduced by the selective mapping (SLM) technology. In addition, the peak value of each OFDM symbol is sent with a separate control channel. At receiver, the frequency characteristics of IN is calculated using the received peak value and the OFDM symbol. The noise used for simulation comes from actual measurement. Results from simulations show that the proposed algorithm can estimate the IN well under different IN environments, and the obtained parameters are very valuable for mitigating IN in power line communication.

ABSTRACTWhile inter-symbol interference is not of concern, inter-carrier interference that is caused by carrier frequency offset (CFO) is more concerned in orthogonal frequency division multiplexing (OFDM) systems. The estimation of channel impulse response (CIR) is another important parameter of interest in the system. Recently, a number of approaches for the joint estimation of CFO and CIR in OFDM systems have been proposed in the literature, and most of them are traditional maximum-likelihood-based approaches. In this paper, we propose a number of mixture cost-reference particle filtering (CRPF) approaches for joint estimation of CIR and CFO, and a couple of them can be applied without the knowledge of both state and measurement noise statistics. Conventional least mean squares algorithm or recursive least squares algorithm is jointly employed with recently developed CRPF for nonlinear and multiple parameters estimation in OFDM systems. The computer simulation results show that mixture CRPFs are more robust against particle impoverishment (PI) problem than standard mixture particle filtering (PF) and mixture regularized PF (RPF) approaches although RPF was particularly developed to tackle the PI problem. In this paper, we investigate a number of mixture PF approaches including ones that do not need the information of noise statistics for the joint estimation of CFO and channel in OFDM systems.