Narrowband Interference Signals Research Articles

Research on interference and noise reduction technology of solar radio observation system

The dynamic spectrum of solar radio burst is a very important tool to study the characteristics of solar radio burst. However, due to the influence of the instruments noise of the solar radio telescope, external interference, the change of ambient temperature, absorption of clouds and so on, the sensitivity of the observation system will be reduced. In particular, the weak solar radio burst signal is easily submerged by various interference signals. In order to improve the sensitivity of solar radio telescope to observe solar radio burst signals and remove narrow-band interference signals, a spectrum data processing algorithm of spectral subtraction method based on entropy and energy threshold values (SSM-EE) is proposed in this article. There are multiple processing steps of SSM-EE. The first step is to improve the signal-to-noise ratio (SNR) through accumulating and averaging the spectrum data. The second step is to eliminate narrowband interference. The spectral kurtosis algorithm is used to calculate the spectral kurtosis of the narrowband interference signal, and then whether to smooth it is determined according to whether it is greater than the threshold. The third step is to establish a noise model. Calculating the power spectrum entropy and energy entropy of each frame of the processed spectrum data, judge whether it is a noise signal by judging the relationship between the power spectrum entropy and energy entropy and the corresponding threshold. The update model for noise floor is used to obtain the real-time noise floor data. The last step is to eliminate the background noise through spectral subtraction. The new spectrum data are obtained by subtraction method between the original spectrum data and the noise floor data. After a large number of data simulation and verification of the actual observation data, it shows that the method proposed in this article has good practical value.

A miniaturized microstrip antenna with tunable double band-notched characteristics for UWB applications

This paper proposes the step-by-step design procedure for obtaining independent dual band-notch performance, which provides a valuable method for designing tunable dual band-notched UWB antenna. The proposed antenna consists of the semicircle ring-like radiating patch with an elliptical-shaped slot and double split ring resonators on the top surface of the substrate and defected ground structure (DGS) on the bottom surface of the substrate. The operating frequencies ranged from 1.3 to 11.6 GHz (S11 < − 10 dB). By loading varactor diodes at the gap of the resonators structure and changing the varactor diode’s reverse bias voltage(0–30 V), a wider band-notched tuning range from 2.47–4.19 to 4.32–5.96 GHz can be achieved, which covers the whole WiMAX band and WLAN band. The experimental results agree well with the simulated results. The notched gain at notched frequency points is about − 5.3 dBi and − 5 dBi, demonstrating that the narrow-band interference signal could be efficiently suppressed. The security of UWB communication systems can be further enhanced. Meanwhile, the selection of varactor diode and DC bias circuit are fully considered. Hence, the accuracy of the experiment results and antenna operating performance have been improved. Furthermore, the proposed antenna only has an electrical size of 0.26λ*0.19λ at 1.3 GHz. Compared to the related reported antennas, the proposed antenna has achieved a simpler structure, low profile, compact size, tunable dual band-notched characteristics, extensive independent tunable range, and good band-notched performance simultaneously, to the best of our knowledge. The proposed antenna is believed to have a valuable prospect in UWB communication, Wireless Body Area Network, Industry Science Medicine, mobile communication applications, etc.

NBI Suppression Method for SAR Based on Sparse Segmentation Search

In remote sensing research, narrowband interference (NBI) suppression in synthetic aperture radar (SAR) is an urgent problem. Recently, many methods on NBI suppression are proposed via sparse recovery. In these methods, the optimal regularization constants are always hard to choose. Moreover, the number of NBI signals, equaling to the sparsity of the sparse vector, may change at different pulses, and the suppression performance might be reduced due to the regularization constants which control the sparsity of the sparse vector, are fixed. In this letter, aiming at these problems, a NBI suppression method for SAR based on sparse segmentation search (SSS) is proposed. Firstly, we build a non-convex optimization model without the regularization constant. Then the adaptive linear enhancer (ALE) is used to convert the non-convex model to a convex one. Finally, we solve this convex model and suppress NBI signals. The real-world SAR data experiments illustrate the effectiveness of the proposed method.

Suppression Method of Partial Discharge Interferences Based on Singular Value Decomposition and Improved Empirical Mode Decomposition

Partial discharge detection is an important means of insulation diagnosis of electrical equipment. To effectively suppress the periodic narrowband and white noise interferences in the process of partial discharge detection, a partial discharge interference suppression method based on singular value decomposition (SVD) and improved empirical mode decomposition (IEMD) is proposed in this paper. First, the partial discharge signal with periodic narrowband interference and white noise interference x(t) is decomposed by SVD. According to the distribution characteristics of single values of periodic narrowband interference signals, the singular value corresponding to periodic narrowband interference is set to zero, and the signal is reconstructed to eliminate the periodic narrowband interference in x(t). IEMD is then performed on x(t). Intrinsic mode function (IMF) is obtained by EMD, and based on the improved 3σ criterion, the obtained IMF components are statistically processed and reconstructed to suppress the influence of white noise interference. The methods proposed in this paper, SVD and SVD + EMD, are applied to process the partial discharge simulation signal and partial discharge measurement signal, respectively. We calculated the signal-to-noise ratio, normalized correlation coefficient, and mean square error of the three methods, respectively, and the results show that the proposed method suppresses the periodic narrowband and white noise interference signals in partial discharge more effectively than the other two methods.

Robust Estimation of Arrival Time of Complex Noisy Partial Discharge Pulse in Power Cables Based on Adaptive Variational Mode Decomposition

Periodic narrowband signals and white noise are the main interferences in online detection and localization of cable partial discharge (PD), however, existing research has always focused on the white noise suppression only, which is not in line with the actual scene. A novel de-noising method for effectively extracting random PD pulse from complex and strong interferences is proposed in this paper and applied to PD localization. Firstly, an improved adaptive variational mode decomposition (AVMD) is used to decompose periodic narrowband interference, white noise, and PD signal into different intrinsic mode. According to the characteristic that the power of intrinsic mode component of periodic narrowband interference in the discrete Fourier transformation (DFT) power spectrum is much larger than that of PD and white noise, the periodic narrowband is removed out. In order to effectively filter out white noise, a scale adaptive wavelet packet decomposition method based on correlation coefficient is proposed, which decomposes the signal into high, middle, and low-frequency components. The components with low frequency, small amplitude are removed out as the white noise interference according to the threshold method, and the residual is the de-noising PD signal. Experimental results show that the proposed method can robustly suppress the interference of periodic narrowband signal and white noise, and effectively preserve the essential characteristics of the real PD signal. In the multi-sensor travelling wave based localization system of cable PD source using time-varying kurtosis, accurate estimation of first arrival time of PD pulse can be achieved by the de-noising results.

Performance of UWB communication systems in presence of perfect/imperfect power control MAI and IEEE802.11a interference

This paper evaluates the bit error rate performance of Impulse Radio-Ultra-Wideband (IR-UWB) communication system under the impact of both multiple access and narrowband interferences operating. The Narrowband Interference (NBI) signal is modelled as the IEEE802.11a orthogonal frequency division multiplexing-based wireless local area network signal, which can be approximated by the sum of independent asynchronous tone interferers with arbitrary frequencies. Multiple Access Interference (MAI) is assumed a zero mean Gaussian process, where it has been investigated in both perfect and imperfect power control scenarios. The bit error rate performance is evaluated in three different channel models: ideal channel model (additive white Gaussian noise channel), Nakagami-m multipath fading channel model and the IEEE802.15.3a UWB channel model. It will be shown that the performance of a UWB system is severely degraded due to the presence of both types of interference, yet the NBI has more impact on the performance of UWB communication systems compared to the multiple access one.

Dual Notched Band Quad-Element MIMO Antenna With Multitone Interference Suppression for IR-UWB Wireless Applications

Ultrawideband (UWB) signals are extremely power limited due to the severe power spectral density constraints obligated by the Federal Communications Committee. Therefore, the design of radiation efficient antennas for UWB signaling is a challenging step in the design and development of impulse radio UWB (IR-UWB) communication systems, especially when these signals coexist with previously standardized narrowband (NB) wireless services. In this paper, a dual-band-notched quad-element UWB multiple-input multiple-output (MIMO) antenna design is presented. The proposed design is capable of suppressing NB interference (NBI). The NBI suppression capability of the proposed design is tested both experimentally and through simulations. Moreover, the experimentally measured spectral characteristics of the proposed design are employed in simulating the bit error rate (BER) performance of IR-UWB systems, considering the biphase modulation (BPM) scheme. Both experimental and simulation results show that the proposed design is capable of improving the BER performance of BPM-modulated IR-UWB systems in an NBI environment by suppressing the NBI signals located at six different frequencies within the bandwidth of the two band notches of the proposed design, while introducing a negligible distortion to the IR-UWB signaling waveforms.

Block sparse representation and suppression of narrow-band interference signals for quadrature compressive sampling radar

Abstract The suppression of narrow-band interference (NBI) has received wide attention with Nyquist-sampling data. However, the developed techniques cannot be directly integrated into sub-Nyquist radar systems. In this paper, we study the NBI suppression for quadrature compressive sampling (QuadCS) radar having sub-Nyquist sampling rate. With slow time-varying property of the NBI envelope, we first define a short-time sinusoidal (STS) dictionary to represent the NBI signals and reveal that QuadCS NBI signals are not only sparse but also block sparse. Then we find that for sparse targets, QuadCS radar outputs a combined sparse signal consisting of sparse targets and block sparse NBI signals. Considering this structure and inherent property of the NBI signals, we finally develop a sparse reconstruction method for estimating both the target signals and the NBI signals. The proposed method is a cascade of the block sparse reconstruction and the sparse reconstruction with data-driven stopping conditions and therefore, it works without any a priori information on the sparsity and noise level. Computer simulations show that the STS dictionary approximates the NBI signals well and the cascade reconstruction derives high accurate estimation of the target signals with strong suppression of the NBI signals.

Sparsity-Based Joint NBI and Impulse Noise Mitigation in Hybrid PLC-Wireless Transmissions

We propose a new sparsity-aware framework to model and mitigate the joint effects of narrow-band interference (NBI) and impulsive noise (IN) in hybrid powerline and unlicensed wireless communication systems. The proposed mitigation techniques, based on the principles of compressive sensing, exploit the inherent (non-contiguous or contiguous) sparse structures of NBI and IN in the frequency and time domains, respectively. For the non-contiguous NBI and IN, we develop a multi-level orthogonal matching pursuit recovery algorithm that exploits prior knowledge about the sparsity level at each receive antenna and powerline to further reduce computational complexity without performance loss. In addition, for the non-contiguous asynchronous NBI scenario, we investigate the application of time-domain windowing to enhance the NBI’s sparsity and, hence, improve the NBI mitigation performance. For the contiguous NBI and IN scenario, we estimate the NBI and IN signals by modeling their burstiness as block-sparse vectors with and without prior knowledge of the bursts’ boundaries. Moreover, we show how to exploit the spatial correlations of the NBI and IN across the receive antennas and powerlines to convert a non-contiguous NBI and IN problem to a block-sparse estimation problem with much lower complexity. Furthermore, we investigate a Bayesian linear minimum mean square error-based approach for estimating both non-contiguous and contiguous NBI and IN based on their second-order statistics to further improve the estimation performance. Finally, our numerical results illustrate the superiority of the joint processing of our proposed NBI and IN sparsity-based mitigation techniques compared to separate processing of the wireless and powerline received signals.

Narrow-Band Interference Mitigation Using Compressive Sensing for AF-OFDM Systems

We investigate narrow-band-interference (NBI) mitigation for single and multiple relay amplify-and-forward (AF) orthogonal-frequency-division-multiplexing (OFDM) cooperative communication systems. Based on the channel gains between the interferer, destination, and relay nodes, three copies or more of the NBI signal are received at the destination node, in addition to the desired signal. NBI degrades the performance of AF-OFDM systems, which motivates the need for NBI mitigation techniques. NBI is a sparse signal in the frequency-domain (FD); hence, a compressive sensing framework can be used to estimate NBI and cancel it before detecting the transmitted signal. However, frequency-grid-mismatch destroys the sparsity of NBI in the FD at the receiver. Therefore, we propose a structured-dictionary-mismatch formulation to estimate the frequency-grid-mismatch and recover NBI in the FD. While convex optimization techniques can be used to recover NBI, their computational complexity is high. Therefore, we apply a block-orthogonal-matching-pursuit greedy algorithm to reduce the computational complexity of NBI recovery, where the sensing matrix is rearranged to have sparse blocks. Simulation results demonstrate the advantages of our proposed approach.

Performance Analysis of Optimum Combining Technique in OFDM Based Full Duplex Multiantenna DF Relay Network with Narrowband Interference

In this paper, optimum combining technique is applied to minimize the effect of Narrowband Interference (NBI) in Orthogonal Frequency Division Multiplexing based full duplex relay network. The NBI signal is assumed to be quasi-static over the duration of a transmitted signal. Multiple antennas are employed at Decode and Forward relay and destination nodes. The Probability Density Function of Signal to Interference Ratio at relay and destination nodes is derived using Hotelling's T2 distribution. Analytical expression for the end-to-end outage probability of the proposed network is derived using the hypergeometric functions. As the weight vector of the optimal combiner is determined using the statistics of the interference channels, the performance of the proposed network becomes better than the network with maximal ratio combining.

Narrow Band Interference Elimination based on Compressed Sensing in UWB Energy Detector

&lt;p&gt;Wireless communication applications with large signal bandwidth are developed tremendously in recent times. Due to large bandwidth the wide band communication causes huge power consumption and signal deterioration after addition of narrow band interference (NBI). The ultra wide band (UWB) energy detector, which is highly robust against NBI signal is presented. Compressed sensing is implemented to reduce the power consumption at the analog to digital converter with approximated message passing reconstruction. In addition to this, digital notch is employed to eliminate the NBI affected measurements from compressed version of the received signal before applying it to the energy detector. To analyze the efficiency of the detector, the energy detection and bit error probability of the detector in the absence of NBI and after mitigating NBI is compared. The simulation results are the evidence of effectiveness of the presented energy detector.&lt;/p&gt;&lt;p&gt; &lt;/p&gt;

DS-UWB pulse design in IEEE802.15.3a multipath fading channel for cognitive radio applications

This paper presents a novel spectrum shaping technique in direct sequence ultra-wideband (DS-UWB) communication systems. This proposed pulse introduces spectral nulls to limit the interference impact of high power coexisting narrowband signals and to elevate the applications of cognitive radio. The idea depends on the addition and subtraction of several UWB Gaussian derivative pulses in order to design a new pulse that has spectral null at the operating frequency of the narrowband interference (NBI) signal. The use of the Gaussian derivative ensures that the UWB spectrum mask established by the Federal Communications Commission (FCC) is met. The NBI signals are modelled as either the wireless local area network (WLAN) IEEE802.11n which operates in the 5 GHz frequency band or multi tone signals. The power spectral density of the proposed transmitted UWB pulse is derived analytically. The bit error rate performance of the proposed pulse is derived in the multi-path IEEE802.15.3a UWB fading channel models and validated with simulations. Results show that the impact of either the IEEE802.11n interference signal or the multi tone interference signals can be effectively suppressed by transmitting and matched filtering the new pulse with a single or multiple spectral nulls at the interference operating frequencies.

A New Method for Suppressing Periodic Narrowband Interference Based on the Chaotic van der Pol Oscillator

The chaotic van der Pol oscillator is a powerful tool for detecting defects in electric systems by using online partial discharge (PD) monitoring. This paper focuses on realizing weak PD signal detection in the strong periodic narrowband interference by using high sensitivity to the periodic narrowband interference signals and immunity to white noise and PD signals of chaotic systems. A new approach to removing the periodic narrowband interference by using a van der Pol chaotic oscillator is described by analyzing the motion characteristic of the chaotic oscillator on the basis of the van der Pol equation. Furthermore, the Floquet index for measuring the amplitude of periodic narrowband signals is redefined. The denoising signal processed by the chaotic van der Pol oscillators is further processed by wavelet analysis. Finally, the denoising results verify that the periodic narrowband and white noise interference can be removed efficiently by combining the theory of the chaotic van der Pol oscillator and wavelet analysis.

Narrowband Interference Mitigation Based on Compressive Sensing for OFDM Systems

A narrowband interference (NBI) estimation and mitigation method based on compressive sensing (CS) for communication systems with repeated training sequences is investigated in this letter. The proposed CS-based differential measuring method is performed through the differential operation on the inter-block-interference-free regions of the received adjacent training sequences. The sparse NBI signal can be accurately recovered from a time-domain measurement vector of small size under the CS framework, without requiring channel information or dedicated resources. Theoretical analysis and simulation results show that the proposed method is robust to NBI under multi-path fading channels.

Training Sequence Design for NBI Mitigation in Compressive Sensing UWB Systems

Ultra wideband (UWB) is a promising technology in delivering high data rate for short range wireless communication systems. Because of their large bandwidth, UWB signals may encounter some problems especially with high sampling rate requirements. Moreover, coherence existence with other narrowband systems is a major concern which needs to be addressed through proper mechanisms. The problem becomes so complex if multiple users exist. Since narrowband interference (NBI) signals have sparse representation in the discrete cosine transform (DCT) domain, they can be estimated and suppressed using Compressive Sensing (CS). CS also has the ability to reduce the high sampling rate requirements. For training based NBI mitigation with CS, three groups of pilot symbols are used to estimate the NBI signal subspace, the UWB signal subspace, and to provide information about the channel. In this paper, the distribution of pilot symbols among the three groups is investigated in the presence of strong NBI. The investigation is based on the bit error rate performance and throughput. The influence of each pilot symbols group is studied. The performance is also evaluated in the presence of multiuser interference in addition to the NBI. Simulation results show that the size of the third group of pilot symbols which is used to estimate the channel is the most dominant one.

Analysis on the Performance of Anti-Narrowband Interference of GNSS Receiver in Time Domain

Starting from the actual demand for eliminating narrowband interference signals common in GNSS receiver, this brief has described basic principles of adaptive filter first based on LMS algorithm, and then analyzed the performance of anti-narrowband interference receiver with bilateral interpolation filter based on above principles. Finally, simulation results shows that compared with that without interference suppression processing, when JSR is 35dB, the Eb/N0 can improve by 5dB by this method; and when compared with theoretical values without interference, the Eb/N0 deteriorates by 1dB. With the increase of interference strength, the interference suppression effect by this method is more significant.

Interference and multipath mitigation utilising a two‐stage beamformer for global navigation satellite systems applications

The performance of location-based services provided by global navigation satellite systems is compromised by interference and multipath propagations. Although time/frequency interference suppression methods have been widely studied in the literature, they fail to cope with wideband interference signals. Instead, techniques utilising several antenna elements can be employed to mitigate both narrowband and broadband interference signals. However, the performance of beamforming techniques utilising antenna arrays severely degrades in dealing with correlated and coherent multipath components which cause signal cancellation phenomenon and temporal correlation matrix rank deficiency. This study proposes a two-stage beamformer to jointly deal with interference and multipath signals. In the first stage, before the despreading process, by applying the subspace method, the interference subspace is estimated and used as a constraint for the optimisation problem in the next stage. In the second stage, a modified version of the minimum power distortionless response beamformer employing several overlapping sub-arrays called the minimum difference output power method is utilised to mitigate the correlated multipath components. The proposed beamformer can deal with the signal cancellation phenomenon and temporal correlation matrix rank deficiency. Several simulation examples and a real data test are provided to illustrate the effectiveness of the proposed beamformer. Results show that the proposed method is able to put deep nulls in the direction of the narrowband and wideband interference signals, and significantly reduces the multipath-induced time of the arrival error.

Analysis and Mitigation of the Narrowband Interference Impact on IR‐UWB Communication Systems

The impact of narrowband interference signals on impulse radio ultrawideband (UWB) communication systems has been investigated. A closed form expression for the bit error rate performance of UWB communication system in a Log‐normal flat fading channel under such impact is evaluated. The actual UWB channel model is known as a multipath fading channel; however flat fading channel model can be considered with some of the UWB wireless applications such as UWB wireless sensor networks which are characterized by size and energy constraints. Thus, a simple and low‐cost one‐finger Rake receiver can be used with such wireless systems. It was proven that UWB systems unavoidably suffer from the interference caused by the coexisting systems due to the restraint on their transmission power levels. To this end, we propose an interference canceller scheme which is capable of suppressing the impact of such interference and enhancing the performance of UWB communication systems. The interference canceller scheme performance is also investigated in various scenarios of operation such as the presence of multiple narrowband interference signals, symbol timing error, and a comparison with a notch filter‐based case.

Multiple narrowband interference suppression for UWB communication systems in Nakagami fading channels

This paper investigates the performance of ultra-wideband (UWB) communication systems in the presence of multiple in-band narrowband interference signals in a Nakagami-m frequency selective fading channel. The UWB systems have a restraint on their transmission power levels in order to control its interference to other in-band operating services; however UWB systems unavoidably suffer from the interference caused by the coexisting systems such as the IEEE802.11a signal, making it extremely difficult to maintain adequate signal-to-noise-and interference ratio (SNIR) levels. In order to mitigate the impact of such strong interference the paper proposes a suppression technique which introduces spectral nulls at the operating frequencies of the narrowband interference (NBI) signals. The bit error rate performance of the proposed scheme is derived in a Nakagami multi-path frequency selective fading channel and validated with simulation. The results show that with the use of such proposed technique the NBI impact can be effectively suppressed leading to an improvement to the bit error rate performance of the UWB communication systems. A comparison with a notch filter-based case is also presented where it will be shown that the proposed technique out performs a perfectly tuned notch filter.