Maximum Allowable Interference Research Articles

Establishing hemolysis, icterus, and lipemia interference limits for body fluid chemistry analytes measured on the Roche cobas instrument.

The aims of this study were to (1) establish the maximum allowable interference limits for hemolysis, lipemia, and icterus for chemistry analytes tested in body fluid samples and (2) assess the effectiveness of serial dilution to mitigate spectral interferences. Residual body fluids from clinically ordered testing were mixed (<10% by volume) with stock solutions of interferent (spiked) and compared with a control spiked with an equal volume of 0.9% saline. The analytes were measured on the Roche cobas c501 instrument. Difference and percentage difference were calculated and compared with allowable total error limits. A subset of samples were serially diluted with 0.9% saline. Mean (SD) difference and percentage difference were calculated. The interference thresholds were lower than the package insert for lactate dehydrogenase, cholesterol, triglycerides, and total protein for hemolysis; amylase, cholesterol, and total protein for icterus; and albumin for lipemia. Only cholesterol and triglyceride results returned to baseline upon dilution of icteric samples. Interference thresholds in body fluids were lower than blood for 6 analytes. Diluting interferences that surpass these limits does not produce reliable results that are comparable to the baseline results before spiking in the interferent.

Significance of Anisotropic Thermal Expansion in High Speed Electric Machines Employing NdFeB Permanent Magnets

Many high speed applications employ a surface permanent magnet (PM) machine topology with a retaining sleeve due to its robustness and ability to achieve high overall peripheral speeds as well as efficiencies. One often overlooked feature in the mechanical design of such machines, which has not achieved sufficient attention to date is the anisotropic thermal expansion of rare earth magnets, the degree of which varies for different magnet technologies. This paper investigates the effects of the aforementioned on the mechanical design of a high speed PM spindle machine with NdFeB magnets. The maximum allowable interference is found to be limited by the working temperature of the magnets while the minimum required interference is increased due to their anisotropic thermal expansion. Based on this, appropriate conditions are formulated to integrate a Neodymium Iron Boron (NdFeB) PM in high speed rotors. These modifications considering the shaft together with the magnet anisotropic thermal expansion are included in a proposed rotor design and validated using simulations in ANSYS mechanical environment.

Stress-Strain State of Disperse-Hardened Aluminum Joint Tube Under Internal Pressure

The paper presents research into the stress-strain state of an interference-fit connected tube made of dispersehardened aluminum alloy and subjected to the uniform internal pressure. The contact pressure and interference are determined to enhance the elastic resistance limit of the joint tube compared to a one-piece tube. It is shown that with increasing temperature and distance between strengthening particles at the same volume fraction, the maximum allowable interference decreases. In the case of small thickness, the elastic resistance limit of the inner tube increases linearly with the interference growth. The increase in the contact pressure at a comparable thickness of the outer and the inner tubes causes the higher stresses in the outer tube wall and contributes to its plastic deformation.

Data Dissemination in IoT Using a Cognitive UAV

In this paper, we consider a cognitive unmanned aerial vehicle (UAV) to disseminate data to a group of Internet of Things (IoT) devices. The cognitive UAV shares the wireless spectrums of primary users (PUs) where it accesses the spectrums opportunistically when the corresponding channels are available. The UAV predicts the OFF periods of the PU, then it decides the number of consecutive transmission slots to be used for data transmission. To protect the PUs from harmful interference, the number of slots used for transmission should not exceed a certain threshold, i.e., maximum allowable interfering slots. We formulate our problem mathematically, where the objective is to maximize the minimum bits received by the IoT devices. The formulated problem is in a form of mixed integer non-linear program (MINLP). Therefore, we propose a successive convex approximation-based algorithm to solve this problem after approximating it to a convex problem. We show that the algorithm converges to a Karush–Kuhn–Tucker (KKT) point. In the simulation, we examine how the OFF period model of the PUs, maximum number of transmission slots, maximum allowable interference threshold affect the maximum minimum bits received by the IoT devices.

Using Bender’s Decomposition for Optimal Power Control and Routing in Multihop D2D Cellular Systems

In this paper, multihop device-to-device (D2D) communications for cell coverage extension are studied. An in-band underlay D2D mode is considered, and the aim is to satisfy the signal-to-noise-ratio requirements for pre-allocated resource blocks (RBs) on the downlink connections, the signal-to-interference-plus-noise-ratio requirements on pre-allocated RBs for every D2D sidelink connection, and a maximum allowable interference at the base station receiver on all uplink RBs. Power control and routing are performed to minimize the expended user equipment energy in the system while meeting these requirements. An optimization problem is formulated that turns out to be a mixed-integer nonlinear program, which is solved using the generalized Benders decomposition (GBD). The GBD breaks down the formulation into a master sub-problem, an auxiliary sub-problem, and a feasibility sub-problem. In this paper, we focus on finding efficient solution methods for the relaxed version of the master sub-problem that is responsible for generating lower bounds on the optimal objective function. Also, an efficient solution technique for the feasibility sub-problem is proposed. Furthermore, a benchmark disjoint scheme for the same problem is proposed, which performs routing and power control separately. The simulations are conducted to compare the performance of both schemes, which show the superiority of joint routing and power control scheme.

Multi-Beam UAV Communication in Cellular Uplink: Cooperative Interference Cancellation and Sum-Rate Maximization

Integrating unmanned aerial vehicles (UAVs) into the cellular network as new aerial users is a promising solution to meet their ever-increasing communication demands in a plethora of applications. Due to the high UAV altitude, the channels between UAVs and the ground base stations (GBSs) are dominated by the strong line-of-sight (LoS) links, thus severe interference may be generated to/from the GBSs in the uplink/downlink, which renders the interference management with coexisting terrestrial and aerial users a more challenging problem to solve. In this paper, we study the uplink communication from a multi-antenna UAV to a set of GBSs in its signal coverage region. Among these GBSs, we denote available GBSs as the ones that do not serve any terrestrial users at the assigned resource block (RB) of the UAV, and occupied GBSs as the rest that are serving their respectively associated terrestrial users in the same RB. We propose a new cooperative interference cancellation strategy for the multi-beam UAV uplink communication, which aims to eliminate the co-channel interference at each of the occupied GBSs and in the meanwhile maximize the sum-rate to the available GBSs. Specifically, the multi-antenna UAV sends multiple data streams to selected available GBSs, which in turn forward their decoded data streams to their backhaul-connected occupied GBSs for interference cancellation. To draw useful insights, the maximum degrees-of-freedom (DoF) achievable by the multi-beam UAV communication for sum-rate maximization in the high signal-to-noise ratio (SNR) regime is first characterized, subject to the stringent constraint that all the occupied GBSs do not suffer from any interference in the UAV's uplink transmission. Then, based on the DoF-optimal design, the achievable sum-rate at finite SNR is maximized, subject to given maximum allowable interference power constraints at each occupied GBS.

Distributed Power Control Algorithm in Orthogonal Frequency Division Multiple Cognitive Radio Systems for Fading Channel

In order to guarantee the quality of service (QoS) for primary users (PUs) and secondary users (SUs) in fading channel, a distributed power control algorithm is proposed based on convex optimization theory in underlay OFDM cognitive radio networks (CRNs). Our purpose obtains the maximum transmit data rate of each SU at all subcarriers under three constraints of the maximum allowable transmission power, the minimum signal to interference plus ratio (SINR) of each SU and the maximum allowable interference generated from SUs to PU at each subcarrier. Simulation results show that the performance of the proposed algorithms (m2) are superior to the geometric programming algorithm (m1) in fading channel environment.

Drone-Aided Communication as a Key Enabler for 5G and Resilient Public Safety Networks

Wireless networks comprising unmanned aerial vehicles can offer limited connectivity in a cost-effective manner to disaster-struck regions where terrestrial infrastructure might have been damaged. While these drones offer advantages such as rapid deployment to far-flung areas, their operations may be rendered ineffective by the absence of an adequate energy management strategy. This article considers the multi-faceted applications of these platforms and the challenges thereof in the networks of the future. In addition to providing an overview of the work done by researchers in determining the features of the air-to-ground channel, the article explores the use of drones in fields as diverse as military surveillance and network rehabilitation for disaster-struck areas. It also presents a case study that envisages a scenario in which drones operate alongside conventional wireless infrastructure, thereby allowing a greater number of users to establish a line-of-sight link for communication. This study investigates a power allocation strategy for the microwave base station and the small base stations operating at 28 GHz frequency band. The self-adaptive power control strategy for drones is dependent on the maximum allowable interference threshold and minimum data rate requirements. This study highlights the importance of incorporating the drones in the multi-tier heterogeneous network to extend the network coverage and capacity.

Robust Power Allocation for OFDM-Based Cognitive Radio Networks: A Switched Affine Based Control Approach

In this paper, we investigate the robust power allocation issue in orthogonal frequency division multiplexing-based cognitive radio networks (CRNs) with unavoidable uncertainties (channel perturbations and variable environment). In this case, to control the performance degradation due to the uncertainties, we maximize the data rate of secondary users (SUs) by considering maximum allowable interference constraints and total power budget of SUs. To solve this problem, we design a controller for a switched affine system with state constraint. This system is based on a distributed projected dynamic system in accordance with the classical distributed convex optimization model for the power allocation and dynamic property of the Nash equilibrium. The robust controller design is on the basis of Lyapunov stability theory and linear matrix inequality to better realize the original power allocation from the control perspective. To the best of our knowledge, we are the first to solve the aforementioned problem by this kind of approach under the control frame, which is more practical for the realization in CRNs. Simulation results are provided to show the validation of the effectiveness of this approach in comparison with iterative water filling algorithm and the worst-case method.

Performance Analysis and Power Allocation for Underlay Cognitive MIMO Relaying Networks with Transmit Antenna Selection Under Antenna Correlation

In this paper, we examine transmit antenna selection with receiver maximal ratio combining (TAS/MRC), and selection combining (TAS/SC) in underlay multiple-input multiple-output cognitive relay networks with decode-and-forward relaying protocol, considering optimal and suboptimal cases. The considered secondary user (SU) network consists of a source, a relay and a destination each equipped with multiple correlated antennas. On the other hand, the primary network is composed of L primary users (PU) destinations, each of which is equipped with multiple correlated antennas. The SU transmission power is limited to the minimum between the maximum allowable power for transmission and the maximum interference power allowed by the PU network. In the analysis, all the channel coefficients between the PU and SU networks and between the SU nodes are assumed to follow independent and identically distributed (i.i.d.) Rayleigh fading distribution. Hence, new exact closed-form expressions are derived to study the outage performance of the considered CRN system. Moreover, for the high SNR values, simple asymptotic expressions for the outage probability are obtained to get more insights on the characterization of the achievable diversity orders and coding gains. The impact of antenna correlation on the system outage probability is investigated for special correlation cases. To enhance SU network performance, a power allocation optimization problem is formulated to minimize the SU asymptotic outage probability by optimally distributing the SU power budget between the SU source and SU relay under the constraints of total allowable SU transmission power and maximum allowable PU interference limit. The derived analytical formulas herein are supported by numerical and simulation results to clarify the main contributions. The results show that although the antenna correlation harms the system coding gain, the considered system can still achieve a full diversity order. Also, The results show that although the outage performance of optimal case outperforms the suboptimal case, the optimal case is more complicated compared to the suboptimal one. Moreover, the optimal power allocation solutions enhance the system outage performance compared to equal distribution model.

MIMO Cognitive Relay Networks With Correlated Antennas Over Rayleigh Fading Channels

In this paper, we examine orthogonal space–time block coding with receiver maximal ratio combining (OSTBC/MRC) and selection combining (OSTBC/SC) in multiple-input–multiple-output (MIMO) decode-and-forward (DF) relay networks with underlay spectrum sharing, considering optimal and suboptimal cases. The secondary network under consideration is equipped with multiple correlated antennas at the source, the relay, and the destination. On the other hand, the primary network is composed of $L$ primary users (PUs), each of which is equipped with multiple correlated antennas. For the considered underlay spectrum sharing, the transmit power condition is related by an interference limit on the primary network and the maximum transmission power in the secondary network. In particular, new exact expressions for the outage probability of the adopted system models are obtained. Moreover, simple asymptotic expressions for the outage probability are provided to enable the characterization of the achievable diversity orders and coding gains. To enhance the secondary network performance, optimal power allocation (PA) between the secondary source and the secondary relay is obtained based on the asymptotic outage probability under the constraints of total allowable transmit power at the secondary user (SU) and maximum allowable interference power limit at the PU. The derived analytical formulas herein are supported by numerical results to clarify the main contributions.

Design and implementation of spectrum sensing for cognitive radios with a frequency-hopping primary system

In this work, spectrum sensing for cognitive radios is considered in the presence of multiple Primary Users (PU) using frequency-hopping communication over a set of frequency bands. The detection performance of the Fast Fourier Transform (FFT) Average Ratio (FAR) algorithm is obtained in closed-form, for a given FFT size and number of PUs. The effective throughput of the Secondary Users (SU) is formulated as an optimization problem with a constraint on the maximum allowable interference on the primary network. Given the hopping period of the PUs, the sensing duration that maximizes the SU throughput is derived. The results are validated using Monte Carlo simulations. Further, an implementation of the FAR algorithm on the Lyrtech (now, Nutaq) small form factor software defined radio development platform is presented, and the performance recorded through the hardware is observed to corroborate well with that obtained through simulations, allowing for implementation losses.

A Comparative Performance Analysis of Interweave and Underlay Multi-Antenna Cognitive Radio Networks

In this paper, an analytical performance study for multi-antenna Cognitive Radio (CR) systems is presented. The two most popular CR approaches, namely, the interweave and underlay system designs, are considered and based on the derived analytical framework, a throughput-based comparison of these two system designs is presented. The system parameters are selected such that a quality of service (QoS) constraint on primary communication, is satisfied. Closed form expressions for the outage probability at the Primary User (PU), as well as expressions for the ergodic rate of the Secondary User (SU) are derived, for both system designs. The derived expressions are functions of key design parameters, such as the sensing time and the detection threshold in the case of interweave CR, and the maximum allowable interference power received by the PU, in the case of underlay CR. Based on the derived expressions, for interweave CR, the sensing parameters, i.e., sensing time and energy detection threshold, are optimized such as to maximize the secondary system rate. By comparing the throughput performance for both system designs, the existence of specific regimes (in terms of primary activity, number of transmit and receive antennas as well as the outage probability of the PU), where one CR approach outperforms the other, is highlighted.

Outage Analysis of Dual-hop Cognitive Networks with Relay Selection over Nakagami-m Fading Environment

AbstractIn this paper, we investigate the outage performance of decode-and-forward cognitive relay networks for Nakagami-m fading channels, with considering both best relay selection and interference constraints. Focusing on the relay selection and making use of the underlay cognitive approach, an exact closed-form outage probability expression is derived in an independent, non-identical distributed Nakagami-m environment. The closed-form outage probability provides an efficient means to evaluate the effects of the maximum allowable interference power, number of cognitive relays, and channel conditions between the primary user and cognitive users. Finally, we present numerical results to validate the theory analysis. Moreover, from the simulation results, we obtain that the system can obtain the full diversity.

VHF/UHF 대역에서 지리정보와 임의 안테나 패턴을 갖는 무선시스템의 간섭분석 연구

ITU-R 권고 P.1546의 전파전파 예측, 지리정보시스템, 신호-간섭(S-I) 평면에 기반하여 최소커플링손실을 적용한 무선시스템 간의 간섭분석 방법을 제시하며, 또한 임의의 안테나 패턴에 대해 간섭원과 피해 수신기 간의 방위각 및 앙각을 산출하는 국부좌표계를 도출하였다. 제시된 알고리즘의 확인을 위해 지도상의 면적 <TEX>$80{\times}60[km^2]$</TEX> 갖는 실제 육지-바다 혼합지역의 지리정보를 취하였다. 가정한 주파수에 대해 지도상에 위치한 고정무선시스템 및 레이더의 전계강도와 경로윤곽 및 최대허용간섭레벨을 갖는 보호비를 산출하였으며, 간섭원의 방위각 및 앙각의 변화에 대해 피해 수신기의 간섭전력을 계산하였다. VHF 및 UHF 대역에서 개발된 간섭분석 방법론은 상용 또는 군용 무선시스템 간의 상호 운용성 및 양립성 평가에 실제로 적용될 수 있을 것으로 여겨진다. By using the radio propagation prediction of Rec. ITU-R P.1546, geographic information system, and S-I plane, we presented the methodology of interference analysis based on the minimum coupling loss, and also suggested the local coordinate system for calculating azimuth and elevation angles between the victim receiver and the interferer for an arbitrary antenna pattern. To check the presented algorithm, the map with the land-sea mixed area was taken for the given area of <TEX>$80{\times}60[km^2]$</TEX> as real geography information. Field strength, path profile, and protection ratio with maximum allowable interference level have been illustrated for radar and fixed wireless system for the assumed frequency. In addition interference power of the victim receiver was calculated asa function of azimuth and elevation angles of the interferer. The developed methodology of interference analysis in the VHF and UHF bands can be actually applied to assess interoperability as well as compatibility in the civil or military applications.

An Analytical Approach to Study the Intraoperative Fractures of Femoral Shaft During Total Hip Arthroplasty

An analytical approach which is popular in micromechanical studies has been extended to the solution for the interference fit problem of the femoral stem in cementless total hip arthroplasty (THA). The multiple inhomogeneity problem of THA in transverse plane, including an elliptical stem, a cortical wall, and a cancellous layer interface, was formulated using the equivalent inclusion method (EIM) to obtain the induced interference elastic fields. Results indicated a maximum interference fit of about 210 μm before bone fracture, predicted based on the Drucker-Prager criterion for a partially reamed section. The cancellous layer had a significant effect on reducing the hoop stresses in the cortical wall; the maximum press fit increased to as high as 480 μm for a 2 mm thick cancellous. The increase of the thickness and the mechanical quality, i.e., stiffness and strength, of the cortical wall also increased the maximum interference fit before fracture significantly. No considerable effect was found for the implant material on the maximum allowable interference fit. It was concluded that while larger interference fits could be adapted for younger patients, care must be taken when dealing with the elderly and those suffering from osteoporosis. A conservative reaming procedure is beneficial for such patients; however, in order to ensure sufficient primary stability without risking bone fracture, a preoperative analysis might be necessary.

Outage Probability of Single-Carrier Cooperative Spectrum Sharing Systems with Decode-and-Forward Relaying and Selection Combining

For cyclic prefixed single-carrier (CP-SC) spectrum sharing relaying systems, a two-hop decode-and-forward (DF) relaying protocol with a direct link and selection combining are employed in the secondary user relay network. For this cooperative CP-SC spectrum sharing system, the end-to-end signal-to-noise ratio (e2e-SNR) is first derived, and then the outage probability performance of the secondary user relaying system is investigated. Having derived an asymptotic expression for the cumulative distribution function of the e2e-SNR, the asymptotic outage diversity is obtained under a limited maximum transmit power at the secondary source and relay while satisfying the maximum allowable interference at the primary user. Notably, when the maximum allowable interference is independent of a limited transmission power, an outage probability floor is observed. Moreover, under the assumption of an unlimited transmit power at the secondary nodes, the asymptotic outage diversity is derived as a function of the interference. It can be seen that the same outage diversity gain can be achieved as in the non-spectrum-sharing CP-SC relaying system. Analytically derived asymptotic outage diversity gains for limited and unlimited transmission power cases are verified by Monte Carlo simulations.

Adaptive resource allocation for cognitive radio networks with multiple primary networks

Abstract In this article, adaptive resource allocation (ARA) is investigated for multiple primary networks based-cognitive radio networks under a more practical system model, where the bandwidth of each secondary user is assumed to be limited and the maximum allowable interference for each primary network is different. We first formulate the ARA as a constrained optimization problem with the objective function of maximizing the proportional fairness-based ergodic sum capacity. The multiple constraints optimization problem is NP-hard and therefore, we propose a scheme to decompose the optimization problem into two unconstrained optimization problems by designing alternative objective functions and penalty functions. Then, a suboptimal heuristic solution framework based on particle swarm optimization is proposed to solve the unconstrained optimization problems. Computation simulations are carried out and the results show that the proposed scheme outperforms traditional ARA schemes.

Uso Eficiente da Órbita de Satélites Geoestácionarios: Otimização das Posições Orbitais

This work is related to the efficient use of the geostationary satellite orbit. It presents and describes an optimization model which chooses the best orbital position for each satellite so that the length of the used orbital arc is minimized. A mathematical model considering aspects such as interference and geometry details (satellite orbital position, earth station positions, boresights of the antennas, etc) is proposed. The model is used in the definition of a constrained optimization problem in which the objective function is defined as the length of the used orbital arc. Constraints imposed by propagation aspects (minimum elevation angles) and by the maximum allowable interference levels (aggregate and single-entry) are considered. The model is applied to specific situations involving real data, leading to the minimization of the used orbital arc.