Interference Reduction Techniques Research Articles

Adaptive Spatial Scheduling for Event Traffic in LoRaWAN Networks.

Low-Power Wide-Area Networks constitute a leading, emerging Internet-of-Things technology, with important applications in environmental and industrial monitoring and disaster prevention and management. In such sensor networks, external detectable events can trigger synchronized alarm report transmissions. In LoRaWANs, and more generally in networks with a random access-based medium access algorithm, this can lead to a cascade of frame collisions, temporarily resulting in degraded performance and diminished system operational capacity, despite LoRaWANs' physical layer interference and collision reduction techniques. In this paper, a novel scheduling algorithm is proposed that can increase system reliability in the case of such events. The new adaptive spatial scheduling algorithm is based on learning automata, as well as previous developments in scheduling over LoRaWANs, and it leverages network feedback information and traffic spatial correlation to increase network performance while maintaining high reliability. The proposed algorithm is investigated via an extensive simulation under a variety of network conditions and compared with a previously proposed scheduler for event-triggered traffic. The results show a decrease of up to 30% in average frame delay compared to the previous approach and an order of magnitude lower delay compared to the baseline algorithm. These findings highlight the importance of using spatial information in adaptive schemes for improving network performance, especially in location-sensitive applications.

Inter-Carrier Interference Reduction Technique for Backscattered OFDM

Inter-Carrier Interference Reduction Technique for Backscattered OFDM

In band full duplex (IBFD) technology for next generation wireless networks: A survey in cellular networks

Next-Generation (NextG) wireless communication networks with their widespread applications require high data rates, seamless connectivity and high quality of service (QoS). To cope up with an unprecedented rise of data hungry applications, users demand more spectral resources imposing a limitation on available wireless spectrum. One of the potential solutions to address the spectrum scarce issue is to incorporate in band full duplex (IBFD) or full duplex (FD) paradigm in next generation networks including 5G new radio (NR). Recently, FD has gained the research interest in cellular networks for its potential to double the wireless link capacity and enhancing spectral efficiency (SE). In half duplex (HD) cellular networks, base stations (BSs) can either perform uplink (UL) or downlink (DL) transmission at a particular time instant leading to reduced throughput levels. Due to the advancement in the self interference reduction (SIR) techniques, full duplex base stations (FD-BSs) can be employed to allow simultaneous UL and DL transmissions at the same time-frequency resources as compared to its HD counterpart. It ideally achieves twice the throughput without any additional complexity at user-equipment(UE). This paper covers a detailed survey on FD cellular networks. A series of SIR approaches, UE-UE mitigation techniques are summarized. Various existing MAC protocols and antenna architectures for FD cellular networks are outlined. An overview of security aspects for FD in cellular networks is also presented. Lastly, various open issues and possible research directions are brought up for FD cellular networks.

A Survey of Techniques for Reducing Interference in Real-Time Applications on Multicore Platforms

This survey reviews the scientific literature on techniques for reducing interference in real-time multicore systems, focusing on the approaches proposed between 2015 and 2020. It also presents proposals that use interference reduction techniques without considering the predictability issue. The survey highlights interference sources and categorizes proposals from the perspective of the shared resource. It covers techniques for reducing contentions in main memory, cache memory, a memory bus, and the integration of interference effects into schedulability analysis. Every section contains an overview of each proposal and an assessment of its advantages and disadvantages.

Analysing the Impact of Mutual Interference in Body Area Networks

The development of electronics and short-range communications gave rise to smart healthcare systems known as body area networks (BAN), to record the vital signs of patients for diagnosis. However, these systems may be located in dense areas, where several networks operate next to each other. Hence, interference occurs, which can adversely affect their proper functioning. Before proceeding with interference reduction or avoidance techniques, it is very important to first analyze this problem under different contexts and scenarios, to better understand it. The aim of this paper is to study the impact of inter-ban interference in body area networks on overall energy consumption, under two different contexts: when the inter-ban distance is varying, and when the amount of nodes in surrounding BANs increases. For this purpose, the two following scenarios are considered: In the first scenario, the distance between two adjacent BANs is decreasing from 6 to 2 m, and the overall energy consumption of the BAN of interest is evaluated. On the other hand, the second scenario highlights the impact of the amount of nodes in an interfering BAN on the overall energy consumption. Simulations were conducted using Castalia 3.3 software. The obtained results showed that when two BANs are located next to each other, if the distance between them becomes smaller, or the amount of nodes in the interfering BAN exceeds that of the reference one, the energy consumption of the BAN of interest will increase, due to the highly experienced interference levels, especially at high data rates.

Power Line Interference Reduction Technique with a Current-Reused Current-Feedback Instrumentation Amplifier for ECG Recording

This paper presents a power line interference (PLI) reduction technique with a current-reused current-feedback instrumentation amplifier (CFIA) for electrocardiogram (ECG) recording. In a portable two-electrode ECG monitoring application, the presence of undesired PLI may severely corrupt the quality of ECG recording. Since PLI can be over a few volts, the input signal including the ECG signal can exceed the supply or ground level by an electrostatic discharge (ESD) diode in input/output (I/O) pad. To prevent this problem, this paper presents a continuous-time input common-mode current feedback loop that can limit displacement current from a capacitive coupling between the human body and a power line. The continuous-time input common-mode current feedback loop can clamp an input common-mode voltage to the saturation region of the input transistor of the current-reused CFIA. After the clamping procedure, the clamped input signal is amplified by the current-reused CFIA. The proposed circuit was designed using a 0.18-μm bipolar-complementary metal semiconductor–double-diffused metal oxide semiconductor (BCDMOS) process with an active area of 1.8 mm2. The total power consumption is 18 μW with 1.8 V. The input-referred noise and noise efficiency factor (NEF) of the current-reused CFIA is 2.68 μVRMS and 4.28 with 107 Hz, respectively.

Analysis of 64 channels based IS-OWC system using different intereference reduction techniques

Abstract Optical wireless communication in space is attracting great consideration due to high speed, high capacity, no EMI, high security, and wide bandwidth. OWC has edge over microwave communication because in laser based communication, relay feature saves the time of the system. In this paper, different interference reduction techniques in wavelength division multiplexing based inter-satellite optical wireless system are presented at different data rates 10, 20, and 40 Gbps. Hybrid multiplexing using wide division multiplexing and time division multiplexing is proposed first and second technique proposed is polarization interleaving in IsOWC systems. Dense channel spacing system with diverse modulations is investigated further such as Chirped, differential phase shift keying, and alternate mark inversion (AMI). Q factor is the performance evaluation parameters for different distances.

Analysis and comparison of different cooperative cellular networks

SummaryThis paper addresses cochannel interference (CCI) in mobile networks. So enhancements of network performance by decreasing CCI are assessed using four diverse interference reduction techniques. These techniques signify traditional sectored fractional frequency reuse (FFR), sectored FFR with beamforming (BF), relay‐assisted (R‐A) sectored FFR, and R‐A sectored FFR with BF technique. Additionally, each BF cooperative technique applies the vertical BF, three‐dimensional (3D) BF, and horizontal BF. Consequently, sectored FFR with BF contains three cases. These cases indicate sectored FFR applies horizontal BF, sectored FFR deploys vertical BF, and sectored FFR uses 3D BF. Furthermore, there are three different arrangements of applying BF in R‐A sectored FFR with BF. These arrangements signify that relay station (RS) employs BF only, base station (BS) uses BF only, and both RS and BS apply BF. Therefore, each arrangement consists of three different cases according to the applied BF technique. Consequently, nine dissimilar cases are considered. Also, a comparison of all cases in different techniques is introduced to enhance the network performance. Analytical treatments are conducted. As a result, closed‐form expressions (CFEs) for worst cases cell‐center user's (CCU's) signal‐to‐interference ratio (SIR), cell‐edge user's (CEU's) SIR, and inner radius (IR) are implemented. These closed forms are used to complete the comparison of all techniques using numerous performance evaluation metrics. The results show, that as unpredicted, the performance of R‐A sectored FFR is close to that of R‐A sectored FFR BF in low SIR threshold and high path‐loss exponent (PLE) ranges. Therefore, R‐A sectored FFR is preferred to be used from the perspectives of network cost and power consumption. Furthermore, vertical BF shows performance close to that of 3D BF in low PLE range. Consequently, using vertical BF is preferable with regard to the energy preservation and network budget. Moreover, it is noticed that BS that applies BF arrangement outperforms other arrangements when vertical or horizontal BF technique is applied. Additionally, the arrangement of both RS and BS that apply BF is superior to the other arrangements when 3D BF is used. But, as expected, it does worse than the others if the other BF techniques are applied. The work results achieve much higher CEU SIR enhancement. Therefore, the probability of outage is decreased. Then, rate of served users by the network is heightened. Accordingly, the total network cost is reduced. So this study advances the network performance while maintaining lower network cost.

NISP: An NFC to I2C Sensing Platform With Supply Interference Reduction for Flexible RFID Sensor Applications

This paper presents a fully passive 13.56MHz Radio Frequency Identification (RFID) to I2C platform integrated circuit (IC), which has been optimized to reduce supply interference, for RFID sensor applications. In order to reduce the supply interference, this paper proposes a methodology to analyze the power supply rejection (PSR) for the power path. The PSR of the power path is effectively optimized by modifying the low-dropout regulator (LDO) topology. In order to support various highprecision I2C sensors and eliminate the micro-controller, an I2C master is integrated on-chip directly. This minimizes the complexity of the overall system. This design utilizes an internal volatile memory to exchange the communication information between RFID and I2C. Therefore the RFID and I2C communication operate independently, so that both communications can maintain maximum compatibility and flexibility. The chip is fabricated in a standard $0.35-\mu \text{m}$ CMOS technology and mounted to a tuned RFID transponder coil on an FR4 PCB substrate. Measurements show that the ripple reduction of this proposed LDO reaches 26 dB from 400 Hz to 25MHz in the worst case. During the communication, the ripple of the supply voltage V DDA reaches a maximum 44 mV, while the input ripple of the unregulated DC voltage V DCA reaches maximum 892 mV. A multi-sensor Bosch BME280 is tested with and without supply interference reduction. The result shows that the sensor’s resolution improves 6.4 times with the proposed supply interference reduction technique. The RFID to I2C platform IC was employed in a demonstrator for wireless real-time measurement of temperature, humidity, and pressure using two commercially available sensor ICs and two RFID readers.

Exploiting the Fast Spectral Roll-Off of CPM Sidelobes to Improve Bandwidth Efficiency in Satellite Communications

Simple and efficient carrier-overlapping and interference-reduction techniques are addressed for frequency-division multiplexing–continuous phase modulation (FDM–CPM) schemes. CPM carriers are densely multiplexed (packed) in the frequency-domain, without leaving any guard bands, thus allowing frequency content in adjacent bands to overlap, so as to enhance the bandwidth efficiency. The intentional adjacent channel interference, introduced by carrier-overlapping during transmission, is combated at the receiver front-end using simple interference-reduction filters that are designed to exploit the fast roll-off of CPM spectral sidelobes. The receiver back-end is governed by a serially concatenated CPM iterative demodulation/decoding detector. Numerically optimal carrier-packing ratios are determined with respect to information-theoretic bounds. The presented method does not require cooperation among users, and is extended to QAM and PSK schemes as well. Bit error rate analyses show that the proposed non-cooperative receiver design facilitates bandwidth and energy-efficient communication for both the nonlinear and linear satellite channels, without resorting to multiuser detectors, and becomes an attractive solution when cooperation may not be feasible among users that are geographically spread-out.

Design and Experimental Measurement of EMI Reduction Techniques for Integrated Switching DC/DC Converters

This paper presents the design and verification of electromagnetic interference (EMI) reduction techniques for switching dc/dc converters. A 48-V dc/dc converter for electric/hybrid cars is considered as an application case study. An EMI filter with a very low inductor value is designed to reduce the overvoltage issues. The proposed design procedure takes into account the converter impedance and the cable model in order to avoid the state-of-the-art tendency of oversizing the filter components. Thus, the filter implementation is simplified and its EMI reduction capability is kept unaltered. Measurements of near EM field in anechoic room show that, using a low switching frequency for the dc/dc converter, the EMI problem is shifted from radiated to conducted emissions. A SKIP-mode modulation technique is implemented to control the converter output and also to reduce the conducted EMI, as shown by CAD simulations and experimental measurements. In addition, a soft-start technique, which reduces by three times the currents' spikes, is integrated into the dc/dc converter to minimize the EMI at the car's starting.

Inter-cell Interference Mitigation through Flexible Resource Reuse, LP-OFDM and Coordination techniques for LTE Advanced in Dense Urban Area

<p><em>The inter-cell interference problem is a key issue in LTE Advanced system especially in dense urban environments. This paper present a new inter-cell interference reduction technique for LTE Advanced downlink system in dense urban area based on a new coordination algorithm with the use of linear precoding OFDM, coordination between cells and power management techniques. The objective of our new technique is to improve cell edge and centre capacity in LTE Advanced downlink system. For this purpose, we prove with real time simulations using Matlab that the S.F.R and P.F.R scheme with our algorithm is a good candidate to enhance the average cell capacity and edge user experience, without sacrificing the average cell throughput.</em><br /><strong></strong></p>

FPGA-based RF interference reduction techniques for simultaneous PET–MRI

The combination of positron emission tomography (PET) and magnetic resonance imaging (MRI) as a multi-modal imaging technique is considered very promising and powerful with regard to in vivo disease progression examination, therapy response monitoring and drug development. However, PET–MRI system design enabling simultaneous operation with unaffected intrinsic performance of both modalities is challenging. As one of the major issues, both the PET detectors and the MRI radio-frequency (RF) subsystem are exposed to electromagnetic (EM) interference, which may lead to PET and MRI signal-to-noise ratio (SNR) deteriorations. Early digitization of electronic PET signals within the MRI bore helps to preserve PET SNR, but occurs at the expense of increased amount of PET electronics inside the MRI and associated RF field emissions. This raises the likelihood of PET-related MRI interference by coupling into the MRI RF coil unwanted spurious signals considered as RF noise, as it degrades MRI SNR and results in MR image artefacts. RF shielding of PET detectors is a commonly used technique to reduce PET-related RF interferences, but can introduce eddy-current-related MRI disturbances and hinder the highest system integration. In this paper, we present RF interference reduction methods which rely on EM field coupling–decoupling principles of RF receive coils rather than suppressing emitted fields. By modifying clock frequencies and changing clock phase relations of digital circuits, the resulting RF field emission is optimised with regard to a lower field coupling into the MRI RF coil, thereby increasing the RF silence of PET detectors. Our methods are demonstrated by performing FPGA-based clock frequency and phase shifting of digital silicon photo-multipliers (dSiPMs) used in the PET modules of our MR-compatible Hyperion IID PET insert. We present simulations and magnetic-field map scans visualising the impact of altered clock phase pattern on the spatial RF field distribution, followed by MRI noise and SNR scans performed with an operating PET module using different clock frequencies and phase patterns. The methods were implemented via firmware design changes without any hardware modifications. This introduces new means of flexibility by enabling adaptive RF interference reduction optimisations in the field, e.g. when using a PET insert with different MRI systems or when different MRI RF coil types are to be operated with the same PET detector.

Spectral and Energy Efficiency Trade-offs in Cellular Networks

This paper presents a simple and effective method to study the spectral and energy efficiency (SE-EE) trade-off in cellular networks, an issue that has attracted significant recent interest in the wireless community. The proposed theoretical framework is based on an optimal radio resource allocation of transmit power and bandwidth for the downlink direction, applicable for an orthogonal cellular network. The analysis is initially focused on a single cell scenario, for which in addition to the solution of the main SE-EE optimization problem, it is proved that a traffic repartition scheme can also be adopted as a way to simplify this approach. By exploiting this interesting result along with properties of stochastic geometry, this work is extended to a more challenging multicell environment, where interference is shown to play an essential role and for this reason several interference reduction techniques are investigated. Special attention is also given to the case of low signal-to-noise ratio (SNR) and a way to evaluate the upper bound on EE in this regime is provided. This methodology leads to tractable analytical results under certain common channel properties, and thus allows the study of various models without the need for demanding system-level simulations.

Dynamic channel gain parameter based resource allocation strategy for cellular system

Future mobile communication systems will be designed to support a wide range of data rates with complex quality of service matrix. The demand of higher bandwidth and data rates has been increased substantially during recent years. In order to achieve efficient resource utilization in all sorts of deployment scenarios and QoS requirements. Several interference reduction techniques have been suggested in past and proved to be effective in reducing the interference to some extent and thereby increase system capacity. Till now the research was done only on to control intracellular interference but in this paper it is discussed about the intracellular interference. However, in a highly loaded system, the problem of intercellular interference remains an important issue. In this paper, the intercellular interference problem of scheduling process is to be overcome by introducing a new and efficient resource allocation strategy called weight Matrix (WM) and with dynamic channel gain parameter. The proposed algorithm is to evaluate the existing resource allocation for performance evaluation. In this paper we increase system throughput and decrease the packet loss and we analyze the communication period. Finally we show how the throughput is increased compared to fixed algorithm. Also we show how the packet loss is decreased compared to fixed algorithm. This work considered single carrier but it can further be extended with multicarrier systems and also it can be extended to priority queuing and also we can give power ratings to users.

Performance Enhancement of LTE through Interference Reduction Techniques

Long Term Evolution (LTE) is the standard for wireless communication of high speed data and mobile terminal. Among the current emerging technologies like LTE based on orthogonal frequency division multiple access (OFDMA) technique, it found to be more attractive for high speed wireless communication. However co-channel interference (CCI) from the neighbouring cells is one of the limiting factors that degrade the LTE system. Fractional frequency reuse (FFR) technique is proposed to overcome the same as it is suitable for idealized cellular layout since power is not considered in this scheme. In this paper FFR is generalized and sub band allocation among user is made in optimal manner which increases the performance of the system.

Comparisons of Receive Array Interference Reduction Techniques Under Erroneous Generalized Transmit Beamforming

This paper studies generalized single-stream transmit beamforming employing receive array co-channel interference reduction algorithms under slow and flat fading multiuser wireless systems. The impact of imperfect prediction of channel state information for the desired user spatially uncorrelated transmit channels on the effectiveness of transmit beamforming for different interference reduction techniques is investigated. The case of over-loaded receive array with closely-spaced elements is considered, wherein it can be configured to null specified interfering sources. Both dominant interference reduction and adaptive interference reduction techniques for statistically ordered and unordered interferers powers, respectively, are thoroughly studied. The effect of outdated statistical ordering of the interferers powers on the efficiency of dominant interference reduction is studied and then compared against the adaptive interference reduction. For the system models described above, new analytical formulations for the statistics of combined signal-to-interference-plus-noise ratio are presented, from which results for conventional maximum ratio transmission and single-antenna best transmit selection can be directly deduced as limiting cases. These results are then utilized to obtain quantitative measures for various performance metrics. They are also used to compare the achieved performance of various configuration models under consideration.

Non-Linear Companding Transform aided MIMO-OFDM Systems

In this paper a new non-linear companding transform (NCT) technique based on inverse hyperbolic cosine function is proposed and implemented along with new Intercarrier interference reduction technique to improve the performance of Multi Input and Multi Output Orthogonal Frequency Division Multiplexing (MIMO-OFDM) system in terms of Peak-to-Average Power Ratio (PAPR) and Inter Carrier Interference (ICI). An effective trade-off between the PAPR and Bit Error Rate (BER) performance is achieved by introducing an inflection point and variable companding parameters in the companding function, such that it enables more design flexibility and freedom in companding form. As per theoretical study, a desired PAPR threshold can be achieved by proposed technique, since it introduces the companding distortion as small as possible with appropriate selection of the companding parameters. And new ICI cancellation scheme maintains orthogonality among subcarriers of OFDM symbol, since it decreases the Carrier to Interference Ratio (CIR). The analytical expressions regarding the achievable PAPR reduction transform gain G, signal attenuation factor and CIR expression are derived. Simulation results demonstrate this combination together substantially improves performance of the MIMO-OFDM system. Keywords: MIMO-OFDM, PAPR, ICI, non-linear companding transform (NCT), CIR, high power amplifiers (HPA).

Performance Comparison of SER and SNR using different states of PSK in presence of various noises

To enhance the data rates of next generation wireless communication operating in frequency selective fading environments, the combination of orthogonal frequency division multiplexing (OFDM) and multiple input multiple output (MIMO) is proved to produce improved results. To analyze this combination, various changes in baseband signal processing are required which includes time and frequency synchronization, channel estimation and diversity gain. In this paper, a noise interference reduction technique for the improvement of high data rate in traditional space time coding technique (STTC) has been proposed. These codes generate the points of the constellation with the same probability. Therefore, the systematic search for good codes can be reduced to in this class. Finally, the performance of proposed techniques 2-state, 4-state and 16-state codes is evaluated by simulation and described by the Symbol Error Rate (SER) over fast Rayleigh fading channels with AWGN floor. Reduced noise based estimation schemes are widely favored as their implementation is relatively simple and most current wireless standards already provide for their use. Training sequences for multiple transmit antennas require properties of zero (or very low) cross correlation between sequences transmitted from different transmit antennas. Keywords: STTC; Symbol Error Rate; Signal to Noise Ratio; Orthogonal frequency division multiplexing.

Protocols for acoustic devices on cabled ocean observatories

Cabled ocean observatories offer an unprecedented opportunity for marine acoustic devices. With continuous power and high bandwidth, long-term broadband measurements from both passive and active systems are possible over a wide range of oceanographic environments. In particular, the cabled ocean observatories VENUS and NEPTUNE operated by Ocean Networks Canada offer a unique set of possibilities for acoustic research, ranging from littoral to mid-ocean ridge installations. Since 2006 fiber optic telecommunication cables have provided high power and up to GB data rates from nine distributed observatory Nodes across marine provinces, which include fjords, tidal straits, river deltas, continental shelves, slopes and rises, abyssal plains, and spreading margins. Experience from passive hydrophones as well as both mono- and bi-static active systems including echo-sounders, sonars, and many acoustic Doppler current devices will be discussed. This paper will review our experiences, provide examples, and propose protocols, or at least our suggested best practices, for many active and passive acoustic devices, including calibration, configuration, interference reduction techniques, bandwidth considerations, data handling, and data analysis and delivery methods.