Narrowband Interference Rejection Research Articles

Research of the efficiency of Kravchenko weighting functions and combinations based on them in the problem of narrow band interference rejection

The influence of weight functions (WFs) of preliminary weighting on the quality of narrowband interference rejection based on direct and inverse discrete Fourier transforms has been studied. Classical and modern WFs are considered: Kravchenko, Kravchenko–Dolph–Chebyshev, Kravchenko–Gauss, Kravchenko–Bernstein–Rogozinsky. Quantitative estimates of efficiency were obtained – the coefficients of interference suppression and signal transmission, as well as their product – the total efficiency coefficient. Graphic examples of the behavior of the total efficiency coefficient depending on the interference frequency are shown. Estimates of the indicated quality indicators are presented when a fixed number of frequency samples are removed from the spectrum. The families of dependences of the probabilities of correctly performing a search for a spread spectrum signal on the “interference/signal” ratio when using modern WFs to weigh the implementations of an additive mixture of signal, interference and noise are presented. The significant advantage of modern WFs formed through combinations with Kravchenko functions in the problem of interference rejection has been demonstrated and confirmed.

Adaptive orientational beamforming techniques for narrowband interference rejection

In this paper, the adaptive theory of the orientational beamforming (OBF) system is investigated. Three adaptive OBF algorithms, namely the orientational maximum signal-to-interference-plus-noise ratio (O-MSINR), the orientational linearly constrained minimum variance (O-LCMV), and the orientational generalized sidelobe canceller (O-GSC) algorithms, are proposed to reject narrowband interferences (NBIs) and recover the desired ultra-wideband (UWB) signal in the OBF system. They are developed by applying adaptive techniques in conventional directional beamforming systems to the OBF system, taking into account the similarities and differences between the OBF system and the conventional beamforming system. These algorithms are constructed on the orientation dimension, and orientational constraints instead of directional constraints are used to guarantee an orientational gain. Therefore, they are independent of signal directions. This perfectly solves the problem when an NBI has the same direction as the desired UWB signal, which current adaptive beamforming algorithms cannot handle. If all the NBIs have the same center frequency, the three algorithms work effectively regardless of the number of NBIs. If all the NBIs have different center frequencies, the O-LCMV and O-GSC algorithms outperform the O-MSINR algorithm. Simulation results show that the proposed algorithms significantly reduce the bit error rates as compared with the original OBF system.

Experimental study of the efficiency of narrowband interference rejection using a square-law filter in wireless engine monitoring systems

Experimental study of the efficiency of narrowband interference rejection using a square-law filter in wireless engine monitoring systems

Eigen Domain Interference Rejection Combining Algorithm for MIMO Systems

In this letter, we investigate an eigen domain interference rejection combining (E-IRC) algorithm for multiple-input–multiple-output (MIMO) systems suffering from narrowband interference (NBI). The received signals are transformed into the eigen domain, which is obtained by eigenvalue decomposition of the time domain autocorrelation matrix of the NBI, and the interference is rejected in the eigen domain via multiple antennas. V-BLAST and Alamouti schemes are considered in this letter. For the V-BLAST scheme, the E-IRC algorithm is an extension of the one for SIMO system. For the Alamouti scheme, we redesign the transmission codeword, which can preserve the orthogonality in the eigen domain, and propose an NBI rejection algorithm based on the spatial whitening filter.

Wireless Image Transmission Based on Cognitive Radio for Robotic Communication

Wireless communication plays a vital role in robotic communication. The robots can communicate using any of the wireless standards like Bluetooth, Zigbee, Wi-fi, etc. based on the application. Many applications involve wireless transmission of images from the robots to the access point. The images can be transmitted at a particular frequency based on the wireless standard. However, interference is a major issue in wireless communication. In order to overcome interference and to make use of white space spectrum, cognitive radio is used. Hence in this paper, wireless image transmission based on cognitive radio is proposed for robotic communication. The paper proposes an efficient design of orthogonal frequency division multiplexing (OFDM) based cognitive radio to transmit and receive grayscale images over an AWGN channel. OFDM technologies are particularly well suited to cognitive radio applications because of the ease to which signals can be adapted to channel conditions and capacity requirements. The narrowband interference rejection is facilitated by suitable subcarrier allocation. The whole system has been designed and analyzed using SystemVue software.

A High Efficient Baseband GNSS Signal Narrow Band Anti-Jamming Approach in Frequency Domain

In order to reduce the burden of the calculation and the low frequency resolution of the tradition GNSS signal intermediate narrow band anti-jamming method, it introduces a high efficient approach of narrow band interference rejection based on baseband GNSS signal processing. After digital down conversion to baseband and down sampling to a low rate, the interference is removed in frequency domain. According to the theoretical analysis and simulation, it claims that the method can reduce the calculation and increase the detection resolution in frequency domain which will realize a high efficient interference rejection.

Perfect symbol recovery and NBI suppression in MIMO‐OFDM systems

It is shown that by exploiting the degrees of freedom arising from the use of multiple antennas and/or insertion of virtual carriers in multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems, perfect symbol recovery and complete narrowband interference (NBI) cancellation can be achieved in the absence of noise by means of constrained minimum mean-output-energy linear filtering. Moreover, a nonlinear iterative scheme is proposed to improve NBI rejection in realistic operative conditions.

Adaptive median threshold algorithm used in FDIS of DSSS receivers

For direct sequence spread spectrum (DSSS) receivers, the capability of rejecting narrow-band interference can be significantly improved by a process of frequency-domain interference suppression (FDIS). The key issue of this process is how to determine a threshold to eliminate interference in the frequency domain, which has been extensively studied. However, these previous methods are tedious or very complex. A simple and efficient algorithm based on medians is proposed. The elimination threshold is only related to the median by a scale factor, which can be obtained by the numerical analysis. Simulation results show that the algorithm provides excellent narrow-band interference suppression while only slightly degrading the signal-to-noise ratio (SNR). A one-pass algorithm using logarithmic segmentation is further derived to estimate medians with low computational complexity. Finally, the FDIS is implemented in a field programmable gate array (FPGA) of Xilinx. Experiments are carried out by connecting the FDIS FPGA to a DSSS receiver, and the results show that the receiver has an effective countermeasure for a 60 dB interference-to-signal ratio (ISR).

Spectral shaping of spreading sequences as a mean to address the trade-off between narrowband and multi-access interferences in UWB systems

This paper presents a way to cope with the need of simultaneously rejecting narrowband interference and multi-access interference in a UWB system based on direct-sequence CDMA. With this aim in mind, we rely on a closed-form expression of the system bit error probability in presence of both effects. By means of such a formula, we evaluate the effect of spectrum shaping techniques applied to the spreading sequences. The availability of a certain number of degrees of freedom in deciding the spectral profile allows us to cope with different configurations depending on the relative interfering power but also on the relative position of the signal center frequency and the narrowband interferer.

A Kind of Cascade Anti-Jam Method for GPS Receiver

The anti-jam technique of GPS is researched in the paper, a cascade anti-jam method is proposed, and it eliminates narrowband interference (NBI) in transform domain, and suppress the residual interferences with array processing method which utilizing Matrix decomposition.A spectrum slicing method is proposed as the frequency excision algorithm for NBI rejection in transform domain. After NBI elimination, the decomposition of matrix based on improved Jacobi algorithm which reduce computation is discussed. Simulation indicates that when wideband interference exists, narrowband interference can be detected and eliminated using the proposed method. Through simulation, it is tested that in multiple jam environment, the method has a better anti-jam capability then space-time adaptive processing (STAP) anti-jam method.

Integrated Planar Monopole Antenna With Microstrip Resonators Having Band-Notched Characteristics

Novel integrated planar monopole antennas with various microstrip resonators are presented. The proposed integrated antennas consist of wideband planar monopole antennas and electromagnetically coupled microstrip resonators producing band-notched characteristics. Various types of microstrip resonators such as open-circuited line resonator, short-circuited line resonator, closed-loop resonator and open-loop resonator are described. The proposed designs are suitable for wideband antennas with narrowband interferer rejection characteristic or multi-band antennas.

Robust Narrowband Interference Rejection for Power-Line Communication Systems Using IS-OFDM

In this paper, two narrowband-interference (NBI) rejection methods are formulated for power-line orthogonal frequency-division multiplexing (OFDM) communications. The inherent NBI suppression capability of the OFDM system is improved upon through the application of a spreading sequence (i.e., IS-OFDM) and further improved through the utilization of NBI filtering implemented at the OFDM receiver. A block least-mean-square (BLMS) algorithm, called cyclic prefix BLMS (CP-BLMS), is constructed for time-domain NBI filtering and a corresponding fast BLMS (FBLMS) algorithm, called linear FBLMS (LFBLMS), is also presented which performs the NBI filtering in the frequency domain. The fast implementation reduces the computational burden of the additional filtering process for a large number of subcarriers without impact on filter performance. Both simulation and theoretical analysis demonstrate the bit-error rate improvement of the proposed approaches compared to previous methods. Numerical results from theoretical analysis also illustrate the speed advantage of the LFBLMS algorithm.

Tunable band‐notched ultra wideband planar monopole antenna

AbstractA new tunable band‐notched ultra wideband planar monopole antenna is presented. The proposed antenna consists of a wideband planar monopole antenna, band‐notched resonating stubs, and varactor diodes. To generate the tunable band‐notched characteristic, we applied a short‐circuited quarter‐wavelength stub with a varactor diode to the wideband planar monopole antenna. We show the mechanism for notch characteristic using surface current distribution. This new approach is suitable for designing wideband antenna with narrow band interferer rejection characteristic. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2829–2832, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24744

Time-hopping spread-spectrum system for wireless optical communications

This paper describes an optical wireless system based on time-hopping spread-spectrum techniques, as a first approach, at infrared wavelengths. It can be used either for low-speed sensor interconnections or as a return channel in a visible light communications system. The main advantage of this scheme is an improvement in the narrowband interference rejection capability and the number of simultaneous users supported, compared with other wireless optical standards. Moreover, a wide analysis is carried out about the mutual interference between time-hopping spread-spectrum systems and other infrared ones. Finally, some conclusions are drawn about some design parameters of the time-hopping system in order to allow its compatibility with preexisting optical devices.

간섭제거기를 갖는 이중전송률 MC/MC-CDMA 시스템의 성능분석

In this thesis, Multi-code/Multi-carrier CDMA(MC/MC CDMA) system which is combination of Multi-code CDMA and Multi-carrier CDMA is analyzed. This system is suitable fur multi-rate services that use multi-codes and high data rate transmission that employ multi-carriers. In addition, the MC/MC CDMA system is robust against frequency selective fading, is good for narrowband interference rejection, and has higher spectral efficiency. In this paper, The users are assigned OVSF codes as a spreading code according to their data rates and divides the active users having different representative code split into a number of groups for effective cancellation. At the receiver, The code grouping interference canceller performs cancellation between the groups. The proposed receiver does not require any information about interference users, such as code, data and amplitude, and has relatively low complexity. The results show the large improvement in performance that can be attained by cancellation scheme.

Wide-Band Planar Monopole Antenna With Triple Band-Notched Slots

A new quad-band planar monopole antenna is presented. The proposed antenna consists of a wide-band planar monopole antenna and the triple band-notched slots. In order to generate quad-band characteristic, we insert three kinds of slots in the interior of the radiating element, such as connected three U-shaped slots, unconnected triple ∏-shaped slots and combination of double ∏-shaped slots and -shaped slot. This new approach is suitable for creating wide-band antenna with narrow-band interferer rejection.

Narrow-band interference suppression in Time-Division-Duplex CDMA systems using preprocessing techniques

This letter presents two preprocessing techniques for narrow-band interference (NBI) rejection in Time-Division-Duplex (TDD) CDMA systems. In the proposed methods, at the transmitter, by using Karhaunen-Loeve Transform and Discrete Fourier Transform, the transmitted power is set to zero in the directions of the eigenvectors that will be severely contaminated by NBI; and therefore less part of the transmitted energy will be polluted by NBI in channel. The processing is transferred from receiver to transmitter, and thus the complexity of the receiver is significantly reduced. It is assumed that channel state information can be estimated at the transmitter because in symmetric TDD systems each receiver in turn also acts as a transmitter.

Anti-Interference Receiver Structures for Direct Sequence Spread Spectrum Signals

Conventional narrowband interference (NBI) rejection algorithms often assumed perfect pseudo-noise (PN) code synchronization. The functions of NBI rejection and code tracking are performed separately and independently by an adaptive filter and a code tracking loop, respectively. This paper presents two new receiver structures for direct sequence spread spectrum (DS/SS) systems, one operates in coherent mode and the other operates in noncoherent mode. Both receivers are designed to suppress NBI and minimize tracking jitter. Numerical results show that the proposed coherent receiver performs as good as the conventional receiver that uses an LMS NBI rejection filter with zero tracking jitter. The noncoherent receiver, when compared with the coherent one, suffers less than 3dB degradation for bit error probability smaller than 10-3.

NARROW-BAND INTERFERENCE SUPPRESSION IN CDMA SPREAD-SPECTRUM COMMUNICATION SYSTEMS USING PRE-PROCESSING BASED TECHNIQUES IN TRANSFORM-DOMAIN

In this paper, we present two pre-processing based techniques in unitary transform-domain for narrow-band interference rejection in CDMA communication systems. In our techniques, by using Karhaunen-Loeve Transform (KLT) and Discrete Fourier Transform (DFT), at the transmitter, eigenvectors occupied by NBI are determined; then the energy ofthe transmitted signal is set to zero into the direction ofthose determined vectors. Hence, any information is not deleted by NBI through channel. As a result after applying these transforms, a major part of the processing would be shifted to the transmitter, and thus complexity ofreceiver is reduced. Our simulation results show that the proposed methods improve the performance of the CDMA communication systems in the presence ofnarrow-band interference.

OFDM Interference Suppression for DS/SS Systems Using Complex FIR Filter

In this paper, the performance of narrow band interference (NBI) rejection scheme for direct sequence spread spectrum (DS/SS) is analyzed. A 2-tapped complex FIR filter is used for filtering a chip code to suppress NBI. In this system, the spectrum of transmitted signal has a null at an arbitrary frequency. By choosing filter coefficients, the authors place this null at NBI center frequency to mitigate the effect of NBI. In this paper, an OFDM signal is considered as NBI. The performance of this scheme is theoretically analyzed by introducing Queueing model, and validated via simulation.