Interference Mitigation Techniques Research Articles

An observational investigation of very low frequency radio emissions originating from meteors

This study presents results from five months of meteor observations that included simultaneous and nearby very low frequency (VLF) wave detections. We explore the plausibility of VLF emissions from meteors resulting in the documented phenomena of simultaneous optical and audio signatures with meteor events. Most previous attempts to observe VLF emissions from meteors have been limited in duration and/or in area covered during observations. With the extended duration and an observational network of three cameras and two VLF receivers across Colorado, an exhaustive approach was taken to detect meteor VLF emissions. The ∼650 events collected were closely inspected for any signs of emissions, with an emphasis on brighter meteors and fireballs. The VLF data was filtered using interference mitigation techniques to eliminate spurious signals that could obscure the VLF signals of interest. By comparing the VLF spectral content at the time of meteors and during control times, we search for very small changes in the signal that would be statistically correlated with meteor observation times. Despite these efforts, no VLF emissions have been detected that cannot be attributed to other sources. Most commonly, lightning-generated sferics coincident with the time of meteor events lead to false attributions to meteors.

УСУНЕННЯ ЗАВАД У ДИНАМІЧНИХ СПЕКТРАХ ЗА НАЯВНОСТІ ПОТУЖНОГО СИГНАЛУ ЧАСТИНА 1. ПОТУЖНІ ШИРОКОСМУГОВІ ІМПУЛЬСИ ТА ЛІНІЙНО ЧАСТОТНО-МОДУЛЬОВАНІ ЗАВАДИ

Subject and Purpose. The writers aim at developing and testing a new method of interference mitigation, proceeding from the example of radio emissions from Jupiter. Its effectiveness is compared with the results of other workers, equally relating to the case of a significant overlapping, within the time-frequency window under analysis, of the areas occupied by the useful signal and the interference. Methods and Methodology. The analysis has revealed several fundamental limitations associated with the use of standard statis- tical methods for identifying sources of interference. A new approach is proposed that allows separating useful signals from inter- ference in the time-frequency plane. It is based on the idea of transferring the statistical analysis from the space of signal amplitudes to such of linear patterns which are formed by maximal readings while the spectrograms are being scanned in time, frequency or otherwise. Results. Methods of statistical data processing have been suggested which allow analysis of signals of a variety of power lev- els against the background of interference of comparable intensity. This enables a detailed analysis of the time-frequency patterns demonstrated by signals with a broad range of parameter variations. The algorithms developed demonstrate stability against changes in the interference background conditions that may be caused either by human activity or by natural factors, such as, e.g. ionospheric perturbations, changes in the frontend frequency response of a receiver resulting from a changed antenna beam orientation, or else from Faraday’s polarization plane rotation in the radio emission being received. Conclusions. The necessity of creating new interference mitigation techniques is stipulated both by worsening of the general level of interference at radio frequencies, and by the growth of complexity in the sporadically emerging time-frequency patterns that result from the improved time and frequency resolutions in the course of signal reception. A significant progress has been achieved, owing exclusively to the fundamental modifications of the signal processing algorithms that are based on varying the direction of analysis in the time-frequency plane.

A Systematic Review of Interference Mitigation Techniques in Current and Future UAV-Assisted Wireless Networks

A Systematic Review of Interference Mitigation Techniques in Current and Future UAV-Assisted Wireless Networks

Measures for attenuation of interference at the level of design of the measuring device of spacecraft

When developing temperature control interface modules used as part of spacecraft onboard equipment, it is important to correctly substantiate the set of measures to ensure their noise immunity, taken at the design levels of the measuring system, measuring device and temperature control interface module. Such a justification involves an assessment of the effectiveness of possible interference mitigation techniques at each design level. The article is devoted to the consideration of interference mitigation measures at the design level of the measuring device, which should be taken to ensure the required noise immunity of the temperature control interface module in combination with measures taken at other design levels. It is shown that in order to ensure the required noise immunity of temperature control interface modules, it is necessary at the design level of the measuring device to provide for measures to mitigate interference in the power supply module, the central instrument module and inter-module interfaces, as well as measures to eliminate gross measurement errors (misses) when processing digital data in the central instrument module. In the power supply module, it is possible to attenuate interference by introducing differential and common mode filters at the input and switching filters at the output. In the central instrument module and inter-module interfaces of the secondary power buses, noise mitigation is possible by dividing the common power bus into analog and digital buses and combining them at an equipotential point. In the central instrument module, it is possible to eliminate misses by using various statistical methods for processing digital data.

Probabilistic Modeling of Multicamera Interference for Time-of-Flight Sensors.

The behavior of multicamera interference in 3D images (e.g., depth maps), which is based on infrared (IR) light, is not well understood. In 3D images, when multicamera interference is present, there is an increase in the amount of zero-value pixels, resulting in a loss of depth information. In this work, we demonstrate a framework for synthetically generating direct and indirect multicamera interference using a combination of a probabilistic model and ray tracing. Our mathematical model predicts the locations and probabilities of zero-value pixels in depth maps that contain multicamera interference. Our model accurately predicts where depth information may be lost in a depth map when multicamera interference is present. We compare the proposed synthetic 3D interference images with controlled 3D interference images captured in our laboratory. The proposed framework achieves an average root mean square error (RMSE) of 0.0625, an average peak signal-to-noise ratio (PSNR) of 24.1277 dB, and an average structural similarity index measure (SSIM) of 0.9007 for predicting direct multicamera interference, and an average RMSE of 0.0312, an average PSNR of 26.2280 dB, and an average SSIM of 0.9064 for predicting indirect multicamera interference. The proposed framework can be used to develop and test interference mitigation techniques that will be crucial for the successful proliferation of these devices.

Novel EBBDSA based Resource Allocation Technique for Interference Mitigation in 5G Heterogeneous Network

Telecom operators have applied the cell association and load balancing technique with femtocell (HeNB) in urban dense 5G Heterogeneous networks (HetNets) for reducing loads of macrocells (MeNBs) and improving the total capacity. However, this deployment creates an interference scenario; mainly, the problem occurs severely from the users of the connected and autonomous vehicle in MeNBs coverage to HeNBs coverage. The main reason is that deploying HeNBs in MeNBs applies the co-subchannels by HeNB and MeNB, leading to severe cross-tier interference (CSI) in the OFDMA subcarrier. Due to this CSI occurrence, the spectral efficiency, Signal to Interference Noise Ratio (SINR), and system outages affect severely. As a result, the MeNB User Equipment (MUEs) and HeNB User Equipment (HUEs) suffer from service disruption, and the entire system’s performance degrades. This challenge has attracted the attention of many researchers and the telecom industries. As a result, several interferences controlling methods such as enhanced frequency allocation strategies, power management, control technique, resource scheduling, spectrum sharing, and Cognitive Radio (CR) techniques have been suggested for 5G communications. However, the study suggests that downlink interference is still challenging in dense urban zones, especially in multilevel and high-rise complex buildings. This paper proposes the EBBDSA-CSI technique where a novel Evolutionary Biogeography-based Dynamic Subcarrier Allocation (EBBDSA) algorithm is introduced for reducing the cross-tier Subcarriers interference (CSI) issues in MeNB and HeNB. The system-level simulation results suggest that the proposed algorithm reduces the system outage to 88.1%, and total spectral efficiency achieves 83.6% compared to the existing techniques.

Low-Complexity Wideband Interference Mitigation for UWB ToA Estimation.

Reliable time of arrival (ToA) estimation in dense multipath (DM) environments is a difficult task, especially when strong interference is present. The increasing number of multiple services in a shared spectrum comes with the demand for interference mitigation techniques. Multiple receiver elements, even in low-energy devices, allow for interference mitigation by processing coherent signals, but computational complexity has to be kept at a minimum. We propose a low-complexity, linearly constrained minimum variance (LCMV) interference mitigation approach in combination with a detection-based ToA estimator. The performance of the method within a realistic multipath and interference environment is evaluated based on measurements and simulations. A statistical analysis of the ToA estimation error is provided in terms of the mean absolute error (MAE), and the results are compared to those of a band-stop filter-based interference blocking approach. While the focus is on receivers with only two elements, an extension to multiple elements is discussed as well. Results show that the influence of strong interference can be drastically reduced, even when the interference bandwidth exceeds 60% of the signal bandwidth. Moreover, the algorithm is robust to uncertainties in the angle of arrival (AoA) of the desired signal. Based on these results, the proposed mitigation method is well suited when the interference bandwidth is large and when computational power is a critical resource.

Metaheuristic for Optimal Dynamic K-Coloring Application on Band Sharing for Automotive Radars

The number of vehicles equipped with radars on the road has been increasing for years and is expected to reach 50% of cars by 2030. This rapid rise in radars will likely increase the risk of harmful interference, especially since radar specifications from standardization bodies (e.g., ETSI) provide requirements in terms of maximum transmit power but do no mandate specific radar waveform parameters nor channel access scheme policies. Techniques for interference mitigation are thus becoming very important to ensure the long-term correct operation of radars and upper-layer ADAS systems that depend on them in this complex environment. In our previous work, we have shown that organizing the radar band into time-frequency resources that do not interfere with each other vastly reduces the amount of interference by facilitating band sharing. In this paper, a metaheuristic is presented to find the optimal resource sharing between radars, knowing their relative positions and thereby the line-of-sight and non-line-of-sight interference risks during a realistic scenario. The metaheuristic aims at optimally minimizing interference while minimizing the number of resource changes that radars have to make. It is a centralized approach where everything about the system is known (e.g., the past and future positions of the vehicles). This and the high computational load induce that this algorithm is not meant to be used in real-time. However, the metaheuristic approach can be extremely useful for finding near optimal solutions in simulations, allowing for the extraction of efficient patterns, or as data generation for machine learning.

Multi-layered Multi-Constellation Global Navigation Satellite System Interference Mitigation

<h3>Abstract</h3> Several layers of defense can be implemented in a global navigation satellite system (GNSS) receiver to improve its performance in the presence of interference. These layers include the use of pre-correlation mitigation techniques, post-correlation quality indicators to screen measurements, and fault detection and exclusion (FDE) at the position solution level. This paper provides a characterization of the interactions between these layers of interference mitigation and a measurement quality check. Data collected in the presence of increasing levels of jamming were processed using different interference mitigation techniques, including robust interference mitigation (RIM) and the adaptive notch filter (ANF). A software defined radio (SDR) approach was adopted and measurements were generated by considering five interference-mitigation techniques. Position solutions were then computed using a forward-backward approach for receiver autonomous integrity monitoring (RAIM). Signals from GPS, Galileo, and Beidou were processed and both single and dual-constellation solutions were analyzed. The analysis revealed that interference mitigation allows the receiver to track a larger number of signals even in the presence of high levels of jamming power. This increased measurement availability was then effectively exploited by RAIM techniques to provide more reliable solutions. Measurements from several constellations further improved the reliable availability of the position solutions.

Interference Compression and Mitigation for Automotive FMCW Radar Systems

Millimeter-wave (mm-wave) frequency-modu- lated continuous wave (FMCW) radars are increasingly being deployed for scenario perception in various applications. It is expected that the mutual interference between such radars will soon become a significant problem. Therefore, to maintain the reliability of the radar measurements, there must be procedures in place to mitigate this interference. This article proposes a novel interference mitigation technique that utilizes the pulse compression principle for interference compression and mitigation. The interference in the received time-domain signal is compressed using an estimated matched filter. Afterward, the compressed interference is discarded, and the signal is repaired in the pulse-compressed domain using an autoregressive (AR) model. Since the interference spans fewer samples after compression, the signal can be restored more accurately in the compressed domain. Real outdoor measurements show that the interference is effectively suppressed down to the noise floor using the proposed scheme. A signal to interference and noise ratio (SINR) gain of approximately 14 dB was achieved in the experimental data, supporting this study. Moreover, the results indicate that this method is also applicable to situations where multiple interference sources are present.

Design and performance evaluation of successive interference cancellation based Slotted Aloha MAC protocol

As a result of densification, the performance of the wireless networks has become highly interference-limited and energy inefficient. To overcome this problem, interference mitigation techniques such as Successive Interference Cancellation (SIC) can be used to decode multiple packets simultaneously at the receiver. In this context, we analyze a SIC-based Slotted Aloha (SIC-SA) Medium Access Control (MAC) protocol for wireless networks. We derive expressions for packets decoding probability and optimal transmission probability of the nodes of the SIC-SA MAC protocol. Our derivation is based on the order statistics of Independent and Identical/non-Identical exponentially distributed received-signal-powers from the nodes under the Rayleigh channel condition. Throughput, delay, and energy efficiency of the SIC-SA MAC protocol have been derived and validated against simulation. The effect of path loss exponent, SINR threshold, and the number of nodes on the performance of SIC-SA have been studied. The performance of SIC-SA in a network of nodes distributed randomly according to the Poisson Point Process has been analyzed. Extension of our analysis to Power Domain Non-Orthogonal Multiple Access (NOMA) has been demonstrated. We also analyzed the impact of imperfect estimation of channel state information and imperfect SIC at the receiver. Results show an improvement in performance metrics of SIC-SA over the traditional Slotted Aloha.

Comparative Analysis of Deterministic and Random Modulations Based on Mathematical Models of Transmission Errors in Series Communication

In many papers, random modulation of power electronic converters is described as an electromagnetic interference (EMI) mitigation technique, which contributes to the assurance of electromagnetic compatibility (EMC) of systems consisting of power electronic converters and serial transmission-based control and measuring devices. However, experimental results as well as theoretical analyses of physical phenomenon suggest that the EMI reduction is ostensible and results from the measuring procedure adopted in standards. This article presents the first known approach to compare the influence of deterministic and random modulation of transmission errors rate in serial communication systems. The comparison is based on the especially developed mathematical models, which are validated experimentally, using a simple setup with a dc/dc converter injecting a noise into the USB/RS232 converter representing a serial transmission scheme. The comparison reveals that for the studied switching frequency range from 10 kHz to 1 MHz, on average, there is no significant difference between random and deterministic modulations with respect to the probability of error rate in serial communication systems. Thus, in such systems, random modulation should not be considered as a valid EMC-assuring technique.

Interference Challenges and Management in B5G Network Design: A Comprehensive Review

Beyond Fifth Generation (B5G) networks are expected to be the most efficient cellular wireless networks with greater capacity, lower latency, and higher speed than the current networks. Key enabling technologies, such as millimeter-wave (mm-wave), beamforming, Massive Multiple-Input Multiple-Output (M-MIMO), Device-to-Device (D2D), Relay Node (RN), and Heterogeneous Networks (HetNets) are essential to enable the new network to keep growing. In the forthcoming wireless networks with massive random deployment, frequency re-use strategies and multiple low power nodes, severe interference issues will impact the system. Consequently, interference management represents the main challenge for future wireless networks, commonly referred to as B5G. This paper provides an overview of the interference issues relating to the B5G networks from the perspective of HetNets, D2D, Ultra-Dense Networks (UDNs), and Unmanned Aerial Vehicles (UAVs). Furthermore, the existing interference mitigation techniques are discussed by reviewing the latest relevant studies with a focus on their methods, advantages, limitations, and future directions. Moreover, the open issues and future directions to reduce the effects of interference are also presented. The findings of this work can act as a guide to better understand the current and developing methodologies to mitigate the interference issues in B5G networks.

Simulating Spectral Kurtosis Mitigation against Realistic Radio Frequency Interference Signals

We investigate the effectiveness of the statistical radio frequency interference (RFI) mitigation technique spectral kurtosis () in the face of simulated realistic RFI signals. estimates the kurtosis of a collection of M power values in a single channel and provides a detection metric that is able to discern between human-made RFI and incoherent astronomical signals of interest. We test the ability of to flag signals with various representative modulation types, data rates, duty cycles, and carrier frequencies. We flag with various accumulation lengths M and implement multiscale , which combines information from adjacent time-frequency bins to mitigate weaknesses in single-scale . We find that signals with significant sidelobe emission from high data rates are harder to flag, as well as signals with a 50% effective duty cycle and weak signal-to-noise ratios. Multiscale with at least one extra channel can detect both the center channel and sideband interference, flagging greater than 90% as long as the bin channel width is wider in frequency than the RFI.

Interference management in backhaul constrained 5G HetNets through coordinated multipoint

The inter-cell interference (ICI) is a major bottleneck that harshly impairs the cell-edge performance in the cellular networks. In heterogeneous networks (HetNets), time domain enhanced inter-cell interference coordination (TD-eICIC) is a promising and well recognized cell-coordination technique to cope with the inter-tier cell interference. However, this scheme incurs significant loss in the allocated spectrum resources caused by blanked or reduced power subframes. The coordinated multipoint (CoMP) is a spectrally efficient and dynamic coordination approach to improve the performance of cell-edge users. In this article, first we provide a brief overview of conventional interference mitigation techniques in the heterogeneous networks. Next, application of CoMP on top of conventional TD-eICIC is investigated to diminish the pitfalls of TD-eICIC. Primarily, we propose a simplified but efficient multi-tier adaptive cell-coordination approach by combining features of joint transmission CoMP (JT-CoMP) and TD-eICIC to provide a pragmatic solution in the dynamically varying mobile environments. Finally, a hypothetical HetNet-CoMP paradigm is propounded that can effectually alleviate the interference in the backhaul-constrained densed fifth generation (5G) and beyond networks where multiple HetNet co-exist in the neighborhood. The analytical expressions and evaluation results validate the improvements achieved by the proposed methods in the network performance in terms of cell-edge user throughput and spectral efficiency performance metrics.

GAE and OBE Enhanced Interference Mitigation Techniques in LDACS

Interference mitigation in L-band digital aeronautic communication systems from legacy users is vital due to stringent safety requirements and steady-state increase in air traffic. This paper proposes an L-band digital aeronautic communication systems receiver prototype that employs nonlinear operations to reduce the interference from the prime interference contributor distance measuring equipment. The knowledge of genie-aided estimator and optimum Bayesian estimator is utilized to propose improved and low complexity nonlinear devices, such as a genie-aided estimator enhanced pulse peak attenuator, genie-aided estimator enhanced pulse peak limiter, joint genie-aided estimator enhanced pulse peak attenuator, joint genie-aided estimator enhanced pulse peak limiter, optimum Bayesian estimator enhanced pulse peak attenuator, optimum Bayesian estimator enhanced pulse peak limiter, joint optimum Bayesian estimator enhanced pulse peak attenuator and joint optimum Bayesian estimator enhanced pulse peak limiter. The performance of the proposed methods is compared with the classical pulse blanking in terms of the received bit error rate for different signal-to-noise ratios. The proposed genie-aided estimator enhanced methods exhibited SNR saving in the range of 2 to 2.5 dB at a bit error rate of 10−1. At the same BER, the proposed optimum Bayesian estimator enhanced methods achieved SNR saving in the range of 2.5 to 3 dB.

Enhanced Interference Management for 6G in-X Subnetworks

Short-range low-power 6th generation (6G) in-X subnetworks are proposed as a viable radio concept for supporting extreme communication requirements in emerging applications such as wireless control of robotic arms and control of critical on-body devices, e.g. wireless heart pacemaker. For these applications, ultra-high reliability (e.g., above 6 nines) with sub-ms latency must be guaranteed at all spatio-temporal instants. To meet these requirements, radio systems that are robust against fading and interference are crucial. In this paper, we present a comprehensive investigation on technology enablers and techniques for interference mitigation in 6G in-X subnetworks. We present several techniques including blind-repetition with pseudo-random frequency hopping and environment-aware mechanisms for interference management via dynamic channel allocation. We further propose two novel enhancements viz: (1) repetition order adaptation involving real-time selection of the number of repetitions based on current channel conditions; and (2) anticipatory packet duplication in which each subnetwork duplicates its transmission on a secondary channel group whenever it detects the presence of a potentially harmful neighbouring subnetwork. We perform extensive simulations in an industrial factory environment with mobile in-X subnetworks using models and parameters defined by the 3rd Generation Partnership Project (3GPP). Results show that in-X subnetworks requires large bandwidth (≥ 1 GHz), up to 2 packet repetitions and environment-aware interference coordination in order to support packet loss rate below 10-6 with a latency < 100μs. The number of repetitions can however be reduced for systems with survival time greater than the cycle time. The proposed enhancements also result in up to ×104 packet loss rate reduction for systems with survival time above 2 cycle times.

Low Complexity Interference Mitigation Technique in IRCI-Free SAR Imaging Algorithms

Inter range cell interference (IRCI)-free synthetic aperture radar (SAR) imaging algorithms experience antenna-based interference which severely degrades the SAR image. In this letter, we propose a low complexity interference mitigation technique based on array processing for IRCI-free SAR imaging algorithms. A low complexity array processing is proposed, by designing a linear array with a limited number of fully controllable elements. The complex weight of array elements is optimized for the desired array pattern with constraints on close-in sidelobe levels (SLL). The proposed methodology reduces the desired two-way SLL to 40.5 dB by using only 18 fully controllable elements out of 100 array elements. The state-of-the-art improved-gray wolf optimization (I-GWO) is used for optimization and is shown to be computationally more efficient than some well-known optimization algorithms. Finally, simulated SAR images validate the effectiveness of the proposed technique.

Inter-Radar Interference Analysis Based on L and S Band Propagation Models and Radar Beam-Scanning Scenarios

This paper presents an overview and novel method on inter-radar interference analysis based on propagation models and radar beam-scanning scenarios. Many studies on radar interference have provided proper methodologies and recommendations for system safety, coexistence, and higher spectrum utilization. However, the propagation models and radar beam-scanning scenarios have not given detail consideration because they usually focus on the proposed interference mitigation techniques. This paper provides a statistical interference analysis method to understand selection of propagation model and various beam-scanning scenarios on the radar interference. The time, duration, probability of the worst-case interference and expected performance degradation is presented statistically. From the simulation result, the maximum gain alignment under 1 degree between two radar occurs with 1.82 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> probability in an example scenario. The proposed simulation and analysis method can help to derive radar operational parameters for interference mitigation and efficient spectrum utilization.

Exploring the alternatives to the conventional interference mitigation schemes for 5G wireless cellular communication network

SummaryThe manifold increase in the number of cellular wireless network consumers has presented a monumental challenge to upgrade the current infrastructure for imparting superior throughput and good quality of service. End‐users of the network will want super high‐speed data with very low latency, as well as secure and with a lower packet data drop rate. Joint coordination between various network resources such as that of a dense heterogeneous network is crucial for achieving the above demands. It is also inevitable that such a dense arrangement of small cells or macro cells or other network equipment will be challenged by different forms of interference apart from being costly and less mobile. Beamforming is among the most advanced technology that is available up to date which has shown good results at handling interference and at guiding transmitted data to the desired end‐user. It is quite useful but also struggles from certain factors when deployed in a dense network. A thorough review of recent works of literature is detailed in the current paper with a focus placed on two major fields, which are interference mitigation techniques and gainful interference exploitation techniques. Some highly advanced interference mitigation techniques which are either developed or under development with their merits have been proposed. Most of these techniques use machine learning and artificial intelligence‐based methods to ensure the best quality of service (QoS) to every individual connected to the network. However some research works focused on negating away any kind of interference present in a signal, some focused on harnessing interference for optimizing the power of transmitted signals.