System Performance Metrics Research Articles

Hardware impairments aware full-duplex non-orthogonal multiple access networks over Nakagami-m channels

Non-orthogonal multiple access (NOMA) and full-duplex (FD) relaying communications are promising candidates for 5G cellular networks. In this paper, by exploiting the impact of hardware impairment, we study FD NOMA communications with a downlink scheme. In a group of two users, we find that the target rates and power allocation strategies are main factors affecting the system performance metric. We derive the closed-form formula of outage probability for two users. As main contribution, numerical results are considered to illustrate the performance of the FD NOMA. We also study the base station (BS) can adjust its transmit signal to noise ratio (SNR) to achieve relevant outage probability in several scenarios.

Asymptotic analysis of aperture averaged exponentiated Weibull distribution with diversity technique for FSO communication

Closed-form statistics are highly desirable in wireless communication while analyzing system performance. Nevertheless, at a few instances, the mathematical intricacy introduced by the probability density function (PDF) limits the analysis of the system. In this context, asymptotic analysis has been entertained in wireless communication to obtain the approximate closed-form statistics of the system performance metrics under high-power regime. With this motivation, the asymptotic framework for exponentiated Weibull (EW) distribution has been presented. First, the origin PDF for EW distribution is proposed. Later, the earlier derived result is utilized in obtaining asymptotic results for the average bit error rate (BER). In addition, we also provide a mathematical framework with maximal ratio combining and selection combining diversity over the average BER. In addition, aperture averaging technique is also implemented over the aforesaid asymptotic results for further improvements in system performance. The results of the asymptotic analysis have been validated using the Monte–Carlo simulation.

Accountability and Collaboration for Intergovernmental Performance Management: Communicating Goals through the HUD Grantmaking Process

This paper presents an exploratory case study of a performance-based intergovernmental grant program, U.S. Department of Housing and Urban Development's (HUD) homeless assistance grants to local Continuums of Care (CoC). The goal is to illuminate the mechanisms by which a federal agency may communicate its priority goals to local grant recipients and seek to promote local actions that further those goals. The mixed-methods case study finds that meeting HUD performance targets does not lead to larger awards in the competitive grant process, casting doubt on the strength of incentives provided by the competitive grants. Nevertheless, the grant making process plays an important role in communicating federal priorities. The system performance metrics emphasized in the grant process coupled with targeted technical assistance appear to promote a focus on performance at the local level and play a role in system reform and capacity building.

A novel approach for low mutual coupling and ultra-compact Two Port MIMO antenna development for UWB wireless application

In this paper, a novel MIMO antenna operating in the UWB frequency band is presented. The proposed new antenna shape is derived from the conventional circular ring patch antenna having a partial ground plane. An array of three Quad-G Shaped Metamaterial structures was used between the antenna elements of the two-port MIMO antenna to expand the bandwidth in the lower frequency band of UWB application (below 5.567 GHz) and reduce the mutual coupling in such expanded band. The proposed MIMO antenna operates over a bandwidth of 8GHz from 4 GHz to 12 GHz. Over the entire bandwidth, the mutual coupling between antenna elements is less than -19.0 dB with an inter-element separation (sep) of λ/6 mm. The overall optimized dimensions of the proposed antenna are 0.34λ×0.22λ×0.021λ for a free-space wavelength, λ, calculated at 4GHz. The radiation pattern of the proposed MIMO antenna was analyzed using the Combined Results Technique (CRT) integrated into the CST microwave studio. The obtained peak radiation efficiency and gain are 83.0% and 5.57 dB respectively. The MIMO Performance metrics such as envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), Mean Effective Gain (MEG), Total Active reflection Coefficient (TARC), and multiplexing efficiency are evaluated and compared to the standard values. The proposed antenna was compared to other antennas in the literature. It has been found that the key benefit of the present method was observed in achieving the highly miniaturized overall antenna dimension having good MIMO system performance metrics and better radiation characteristics. The proposed antenna was fabricated and measured. The measured and simulated values are found to be in good agreement.

IMPLEMENTATION OF RANGE-BASED AND RANGE-FREE 3D INDOOR LOCALIZATION IN MULTI-STORY BUILDING BASED ON RSSI

The real-life indoor localization implementation in a multi-story building is reasonably necessary. Multi-floor shopping centers, airports, residential areas, especially in the big cities, apply positioning schemes to ease visitors or inhabitants. However, most indoor localization researches still emphasize 2D-indoor localization, and the multi-story indoor localization implementations are still limited. One of the challenges of 3D-indoor localization implementation is the shadowing effect caused by signal propagation obstructed by objects in the room, the walls, and floors between rooms. Some researchers conducted the 3D-indoor localization to consider the elevation property of the position estimation scenario. However, there are still very few experimental results in an actual multi-story building as the authors' concerns. This paper proposes the measurement campaign of a 3D-indoor localization system in the actual multi-story building by applying the range-based and range-free method based on the Wireless-Fidelity (Wi-Fi). This research is essential since Wi-Fi is available in almost all smart devices and is installed almost in every corner globally. Compared to other approaches, we propose a relatively simple Wi-Fi-based indoor 3D localization utilizing the specific parameter, received signal strength indicator (RSSI), in a static indoor lobbies environment. Despite some of its advantages, the RSSI parameter has a disadvantage in signal fluctuation over time. In our approach, we tried to solve this issue by applying the min-max algorithm to improve the known trilateration method as the range-based method. We implemented the min-max to observe how far the range-based can still give acceptable positioning results in an actual multi-story building. On the other hand, we used the RSSI values for the range-free method to construct the fingerprint database and employed the machine-learning (ML)-based pattern matching algorithm, the random forest algorithm. We expect to solve the shadowing problem with this radio fingerprint method and to achieve minimal errors. We conducted the measurement campaign using the low-cost Wi-Fi module, the ESP-8266, to generate the RSSI. We placed three ESP-8266 nodes on each floor of a two-floor building as the access points (APs) and an ESP-8266 as a target node or a station (STA). We emphasized two performance metrics to evaluate our proposed system performance: the location estimation accuracy observed as the mean square error (MSE) and the precision shown as the standard deviation (Std Dev). The results show that the fingerprint technique yielded the MSE of 0.9m and Std Dev of 0.69 m, while the min-max method resulted in the performance of MSE of 1.79 m and Std Dev of 0.89 m. These results show that the fingerprint technique still gave better accuracy and precision in the same measurement campaign than the min-max. However, the min-max results are also acceptable since the whole multi-floor building has more than 4 m in elevation. The indoor localization system for multi-story buildings can be applied using both the fingerprint and the min-max in a relatively static environment by observing our system performance metric

Experimentally validated x-ray image simulations of 50 μm x-ray PIV tracer particles

We evaluate Beer–Lambert (BL) ray-tracing and Monte Carlo N-Particle (MCNP) photon tracking simulations for prediction and comparison of x-ray imaging system performance. These simulation tools can aid the methodical design of laboratory-scale x-ray particle image velocimetry (XPIV) experiments and tracer particles by predicting image quality. Particle image signal-to-noise ratio (SNR) is used as the metric of system performance. Simulated and experiment data of hollow, silver-coated, glass sphere tracer particles (AGSF-33) are compared. As predicted by the simulations, the AGSF-33 particles are visible with a SNR greater than unity in 100 ms exposure time images, demonstrating their potential as x-ray PIV or particle tracking velocimetry (XPTV) tracers. The BL approach predicts the image contrast, is computationally inexpensive, and enables the exploration of a vast parameter space for system design. MCNP simulations, on the other hand, predict experiment images slightly more accurately, but are more than an order of magnitude more computationally expensive than BL simulations. For most practical XPIV system design applications, the higher computational expense of MCNP is likely not justified by the modest accuracy improvement compared to BL.

Considering the κ − µ fading channels adopted in multiple antennas downlink non-orthogonal multiple access

Massive connectivity and effective spectrum usage have become more important as the use of wireless communication devices and networks has grown dramatically. The approach of non-orthogonal multiple access (NOMA) is advocated as a viable solution for meeting consumers’ current needs. The signals are overlaid with various power levels for each user in a NOMA-assisted system, and then broadcast to the receiver. SIC (successive interference cancellation) is used by the receiver to discriminate and get the needed signal. Until far, most studies have concentrated on SIC with ideal features, with only a handful focusing on SIC with imperfect qualities (ipSIC). While the perfect SIC (pSIC) represents the ideal condition of no data loss and no external sounds, the ipSIC represents data transfer in a real-time context. In this research, we will assess the system performance metrics of the investigated NOMA system in the presence of ipSIC and compare them to the performance of the same user’s pSIC. We define channels as κ−µ fading distributions, which is more essential. For two destinations, we construct accurate outage probability formulas. Meanwhile, Monte-Carlo simulations are run to ensure that the mathematical expressions derived are genuine.

Applying empirical method for performance metrics measurement of a nuclear security system

A nuclear security system is often developed based on a particular framework. In our case, a nuclear security system is developed based on the big data analytics framework with the purpose of integrating all nuclear security systems within a nuclear facility. Nuclear security can be defined as the prevention and detection of, and response to, theft, sabotage, unauthorized access, illegal transfer, or other malicious acts involving nuclear material, other radioactive substances, or their associated facilities. Whereas, big data analytics is denoted as a new way of collecting, analyzing large amounts of data, finding the appropriate patterns to support decision making, hence improving the action taken in solving the problems. The system-based evaluations methodology is widely used to measure the performance metrics of nuclear security systems. However, the system-based evaluation methodology consumes time and demands a lot of effort because in applying the methodology, a complete nuclear security system that is based on the particular framework needs to be designed, developed, and implemented in the nuclear facilities environment before the performance metrics could be measured. In this paper, we present an empirical method of measuring the performance metrics by utilizing the Rasch Measurement Model. The methodology is formulated to reduce the time and efforts in measuring the performance metrics of a nuclear system that is developed based on a framework…

MAFLD/NAFLD Biopsy-Free Scoring Systems for Hepatic Steatosis, NASH, and Fibrosis Diagnosis.

Metabolic dysfunction-associated fatty liver disease (MAFLD), formerly known as nonalcoholic fatty liver disease, is the most prevalent liver disorder worldwide. Historically, its diagnosis required biopsy, even though the procedure has a variable degree of error. Therefore, new non-invasive strategies are needed. Consequently, this article presents a thorough review of biopsy-free scoring systems proposed for the diagnosis of MAFLD. Similarly, it compares the severity of the disease, ranging from hepatic steatosis (HS) and nonalcoholic steatohepatitis (NASH) to fibrosis, by contrasting the corresponding serum markers, clinical associations, and performance metrics of these biopsy-free scoring systems. In this regard, defining MAFLD in conjunction with non-invasive tests can accurately identify patients with fatty liver at risk of fibrosis and its complications. Nonetheless, several biopsy-free scoring systems have been assessed only in certain cohorts; thus, further validation studies in different populations are required, with adjustment for variables, such as body mass index (BMI), clinical settings, concomitant diseases, and ethnic backgrounds. Hence, comprehensive studies on the effects of age, morbid obesity, and prevalence of MAFLD and advanced fibrosis in the target population are required. Nevertheless, the current clinical practice is urged to incorporate biopsy-free scoring systems that demonstrate adequate performance metrics for the accurate detection of patients with MAFLD and underlying conditions or those with contraindications of biopsy.

Performance analysis and optimisation of Bernoulli serial production lines with dynamic real-time bottleneck identification and mitigation

With the rapid advances of Industry 4.0 technologies, developing rigorous, model-based algorithms for production system performance metrics calculation, control, and optimization has become a critical task to inject intelligence into the smart manufacturing practice, thus facilitating automated decision-making on the factory floor. This paper is intended to contribute to this area. Specifically, we consider serial production lines with finite buffers and machines following the Bernoulli reliability model. In addition, we assume that one can dynamically control the allocation of a shared workforce via real-time production bottleneck identification and mitigation. We first derive formulas to calculate the performance metrics of two-machine systems. Then, we extend the results to multi-machine cases by developing an aggregation-based analytical algorithm, whose accuracy is verified using numerical experiments. Based on this performance evaluation method, we study the optimization of the control policy. In particular, a space reduction technique is applied that decomposes the system into several sub three-machine lines and search algorithms are proposed to identify a good-quality control policy in the reduced policy space. Numerical experiments are used to demonstrate the efficacy of the optimized policy. An illustrative example is given to provide insights into the structure and operation of an effective control policy.

Downstream variations of air-gap membrane distillation and comparative study with direct contact membrane distillation: A modelling approach

Air-Gap Membrane Distillation (AGMD) promises to reduce heat loss in membrane distillation. Most AGMD models are one-dimensional and do not consider the downstream variations. In addition, a linear function of vapour pressure is used, which either relies on experimentally determined parameters or a simplified mass transfer resistance to model the water permeate flux. This study introduces a new, improved model that simultaneously considers both heat and mass transfer in the AGMD process by coupling the continuity, momentum, and energy equations. A novel precise logarithmic function of vapour pressure was derived to model the water permeate flux, independent of experimentally determined parameters. By varying the inlet temperature, Reynolds number, inlet concentration, and air-gap thickness, the performance of AGMD was evaluated. The results revealed that our model improved the water flux prediction from more than 10% to less than 4% deviation from experimental results. Among the operating conditions, only increasing the Reynolds number improved all the system performance metrics, including higher water flux and lower temperature and concentration polarisation effects. Results were compared with Direct Contact Membrane Distillation (DCMD) outcomes and showed that unlike AGMD, DCMD suffers from a substantial decrease in water flux along the module. For DCMD, the exit water flux value decreased by 50% in comparison with the inlet value, while the water flux decreased by only 2% for AGMD, using a 1 mm air gap thickness.

On the Design of FSO-Based Satellite Systems Using Incremental Redundancy Hybrid ARQ Protocols With Rate Adaptation

This paper presents a cross-layer design of error-control protocols with rate adaptation for free-space optical (FSO) burst transmission in satellite communication systems. While the prior works mostly focused on the design of error-control protocols for terrestrial-based FSO communications, using either hybrid automatic repeat request (HARQ) based stop-and-wait mechanism or pure sliding window ARQ, we instead propose a design of HARQ-based sliding window mechanism for the high data-rate and long-distance of FSO-based satellite systems. In particular, we model and analyze the performance of low-earth orbit (LEO) satellite-to-ground FSO systems over atmospheric turbulence channels when truncated incremental redundancy (IR) HARQ protocols, which combine the rate-compatible punctured convolutional (RCPC) codes and sliding window ARQ, are employed. For this purpose, the time-varying behavior of atmospheric turbulence channels is first captured by a finite-state Markov chain. Then, the channel model is used to develop the burst loss model to analytically derive the system performance metrics, including throughput, energy efficiency, and average frame delay. The results quantitatively demonstrate the impact of atmospheric turbulence and pointing error on the system performance and support the optimal selection of parameters. Additionally, the effectiveness of the proposed system is numerically confirmed. Monte Carlo simulations are also performed to validate the accuracy of theoretical derivations.

Joint Design of Improved Spectrum and Energy Efficiency With Backscatter NOMA for IoT

To develop emerging transmission techniques for potential applications of Internet of Things (IoT), the system performance analysis of a cognitive radio (CR)-enabled ambient backscatter (AmBC) system will be studied in this paper with functionality of non-orthogonal multiple access (NOMA). In the proposed scheme, a base station communicates with two destinations via a designated backscatter device. It is assumed that the relay node is fitted with two different interfaces and can simultaneously collect/decode and backscatter the received source signals. Such transmission mechanism benefits to design various applications in IoT as well as wireless systems with improved performance. To exhibit system performance metrics, the outage probability and the ergodic capacity of the recipient nodes are derived analytically. Furthermore, it is shown that employing AmBC NOMA together with CR for secondary communication can significantly improve overall network performance in terms of the achievable throughput in delay-limited and delay-tolerant modes and outage probability. Numerical results show that: <i>1) The proposed system can improve the spectrum efficiency by employing both CR and NOMA techniques; 2) Compared with the orthogonal multiple access (OMA)-aided AmBC systems, the considered CR AmBC system relying on NOMA can obtain better reliability in the whole range of SNR; 3) There are error floors for the outage probability in the high SNR regime due to required target rates; 4) There exists a trade-off between system performance of IoT devices and power allocation coefficients associated with NOMA; 5) We find energy efficiency factor as evident of further improvement in such system</i>.

Reconfigurable intelligent surfaces assisted wireless communication networks: ergodic capacity and symbol error rate

By enabling reconfigurable intelligent surfaces (RIS), we can deploy intelligent reflecting signals from the base station to destinations. Different from traditional relaying system, RIS relies on programmable metasurfaces and mirrors to improve system performance of destinations. We derive the formulas of main system performance metrics such as ergodic capacity and symbol error rate (SER). Based on types of modulation, we need to demonstrate other parameters which make influence to system performance. We show analytically that the number of reflecting elements along with the transmit power at the source can improve system performance. Moreover, we check the exactness of derived expressions by matching Monte-Carlo with analytical simulations. Finally, we find the best performance can be achieved at specific parameters and results are verified by explicit simulations.

Extended α-η-μ Fading Distribution: Statistical Properties and Applications

In this paper, the impact of the non-linearity of the propagation medium on the extended η-μ fading distribution is studied. In particular, the extended α-η-μ fading model in which the parameter α represents the non-linearity of the propagation environment is presented via providing the exact and asymptotic of the statistical properties, namely, the probability density function (PDF), cumulative distribution function (CDF), and generalized-moment generating function (G-MGF). To this effect, exact closed-form mathematically tractable expressions of the outage probability (OP), average symbol error probability (ASEP), amount of fading (AoF), channel quality estimation index (CQEI) and effective rate (ER) are obtained. The asymptotic behaviour at high average signal-to-noise (SNR) values is also analysed to gain further insights into the influence of the index α on the performance metrics of the wireless communication systems. Moreover, the average channel capacity (ACC) under different adaptive transmission techniques, such as, optimum rate and adaptation (ORA), capacity of the channel with inversion and fixed rate (CIFR), and truncated inversion and fixed rate (TIFR) are derived. The validation of the derived expressions is verified via comparing the numerical results with the Monte-Carlo simulations as well as some previous works for different scenarios.

Performance metrics for vehicular visible light communication systems

Vehicular Visible Light communication (VVLC) presents a new paradigm for providing vehicle connectivity, increasing road safety, and achieving autonomous driving. It can be chosen as an alternative solution to radio frequency-based inter-vehicle communication systems and/or as a complementary solution to ensure redundancy. Nevertheless, there are still significant challenges in incorporating visible light communication systems into vehicular networks. The main purpose of this paper is to provide an outline of the performance metrics of a VVLC system. Furthermore, the study is performed based on a vehicle-to-vehicle dynamic model close to reality, considering the effect of geometrical changes in the LOS path and the variation of the inter-vehicular distance. The analysis of the proposed system is discussed in terms of Signal to noise (SNR), Field of view (FOV), mobility, and average capacity.

Towards climate resilient municipal water supply in Bangkok: A collaborative risk informed analysis

Typical top-down approaches to climate change adaptation in the water sector rely on climate models to inform the adaptation design. In view of the inherent uncertainty associated with these models, this study uses a combined top-down and bottom-up approach called Collaborative Risk Informed Decision Analysis (CRIDA). Using the case of the Metropolitan Waterworks Authority, Bangkok, this study demonstrates the application of the approach, which includes (a) identifying critical thresholds that impact the system’s performance, (b) unearthing the system vulnerabilities through a stress test (scenario analysis), and (c) identifying feasible adaptation interventions. Through a stakeholder consultation process, it was found that streamflow, salinity, and turbidity are the key performance metrics of the water supply system. A series of stress tests to the system was conducted by adjusting input variables assuming a wide range of possible future climatic conditions. Frequency curves of the various input variables were developed to facilitate stakeholders’ planning for impending risks and for improving the overall robustness of the water supply system. Based on the stress test results and past studies of the study area, the raw water source of the Metropolitan Waterworks Authority is expected to be more saline in the future with more frequent and severe low flow conditions, for which a number of adaptation actions were formulated and proposed. It is suggested to develop adaptation pathways that can address a range of expected impacts of future climatic conditions on the Bangkok water supply system. The methodology presented is useful for study areas where a model of the system is unavailable, and data limitation is a challenge.

Many-Objective Adaptive Fuzzy With Sliding Mode Control for a Class of Switching Power Converters Using Global Optimization

Control of the power converters in renewable energy systems for stability and efficiency poses a technical challenge due to the intermittency of energy produced and inherent nonlinear dynamics. This paper presents a parametric optimization framework amid the synthesis of an adaptive fuzzy with sliding mode controller for a class of switching power converters suited for renewable energy systems. Four performance metrics essential to the practical needs are suggested. The potential design parameters of the controller are determined, and their influences on the performance metrics are studied and validated. A many-objective optimization problem is formulated accordingly, and a computational platform based on MATLAB/Simulink environment is established to solve the problem. Two multi-objective global search algorithms, i.e., particle swarm and bat optimization, are employed to obtain a set of Pareto optimal controllers, which noticeably enhance the performance metrics of the control system. An experimental platform with dSPACE controller board is utilized to further justify the simulation results. With those optimal controllers, the experimental results also demonstrate improvement of the performance.

A Survey on Mobile Charging Techniques in Wireless Rechargeable Sensor Networks

The recent breakthrough in wireless power transfer (WPT) technology has empowered wireless rechargeable sensor networks (WRSNs) by facilitating stable and continuous energy supply to sensors through mobile chargers (MCs). A plethora of studies have been carried out over the last decade in this regard. However, no comprehensive survey exists to compile the state-of-the-art literature and provide insight into future research directions. To fill this gap, we put forward a detailed survey on mobile charging techniques (MCTs) in WRSNs. In particular, we first describe the network model, various WPT techniques with empirical models, system design issues and performance metrics concerning the MCTs. Next, we introduce an exhaustive taxonomy of the MCTs based on various design attributes and then review the literature by categorizing it into: periodic and on-demand charging techniques. In addition, we compare the state-of-the-art MCTs in terms of objectives, constraints, solution approaches, charging options, design issues, performance metrics, evaluation methods, and limitations. Finally, we highlight some potential directions for future research.

QoS-Aware Multicast for Crowdsourced 360° Live Streaming in SDN Aided NG-EPON

The IEEE 802.3ca Task Force group has recently approved the standardization of the next-generation Ethernet passive optical network (NG-EPON) to satisfy future bandwidth demands. NG-EPON architecture classifies the optical network unit (ONU) transmission to allow simultaneous Wavelength-Agile (WA-PON) transmission, which increases the network capacity (50 Gb/s) and flexibility. The recently launched 5G services and related functional standards, new capabilities, and quality of service (QoS) imposed on the optical transport network. The Peer-to-peer (P2P) based live streaming application is the most popular multimedia application in access networks, i.e., Facebook Live, YouTube Live, Twitch, and other streaming and video conferencing services are increasing, especially in global epidemics which requires a higher QoS. Hence, media-based applications require adequate infrastructure resources to meet customer demands such as high bandwidth, low latency, high quality audiovisual, live streaming, and services. Therefore, this paper proposes an SDN enhanced P2P virtual reality (VR) live video streaming application NG-EPON multicast architecture based on 5G-enabled Tactile Internet (TI) and aims to improve the QoS, QoE and provide flexible services to the end-users. Finally, we proposed an SDN-based TI-dynamic wavelength and bandwidth allocation (SD-TI-DWBA) mechanism. Simulation results show that our proposed architecture can improve the system performance and QoS metrics regarding packet delay, jitter, system throughput, and packet loss.