Quality Estimator Research Articles

Reliable link quality estimation in low-power wireless networks and its impact on tree-routing

Radio link quality estimation is essential for protocols and mechanisms such as routing, mobility management and localization, particularly for low-power wireless networks such as wireless sensor networks. Commodity Link Quality Estimators (LQEs), e.g. PRR, RNP, ETX, four-bit and RSSI, can only provide a partial characterization of links as they ignore several link properties such as channel quality and stability. In this paper, we propose F-LQE (Fuzzy Link Quality Estimator, a holistic metric that estimates link quality on the basis of four link quality properties—packet delivery, asymmetry, stability, and channel quality—that are expressed and combined using Fuzzy Logic. We demonstrate through an extensive experimental analysis that F-LQE is more reliable than existing estimators (e.g., PRR, WMEWMA, ETX, RNP, and four-bit) as it provides a finer grain link classification. It is also more stable as it has lower coefficient of variation of link estimates. Importantly, we evaluate the impact of F-LQE on the performance of tree routing, specifically the CTP (Collection Tree Protocol). For this purpose, we adapted F-LQE to build a new routing metric for CTP, which we dubbed as F-LQE/RM. Extensive experimental results obtained with state-of-the-art widely used test-beds show that F-LQE/RM improves significantly CTP routing performance over four-bit (the default LQE of CTP) and ETX (another popular LQE). F-LQE/RM improves the end-to-end packet delivery by up to 16%, reduces the number of packet retransmissions by up to 32%, reduces the Hop count by up to 4%, and improves the topology stability by up to 47%.

Heuristic method for searches on large data-sets organised using network models

Searches on large data-sets have become an important issue in recent years. An alternative, which has achieved good results, is the use of methods relying on data mining techniques, such as cluster-based retrieval. This paper proposes a heuristic search that is based on an organisational model that reflects similarity relationships among data elements. The search is guided by using quality estimators of model nodes, which are obtained by the progressive evaluation of the given target function for the elements associated with each node. The results of the experiments confirm the effectiveness of the proposed algorithm. High-quality solutions are obtained evaluating a relatively small percentage of elements in the data-sets.

Improved signal quality indication for photoplethysmographic signals incorporating motion artifact detection.

Wearable monitoring systems have gained tremendous popularity in the health-care industry, opening new possibilities in diagnostic routines and medical treatments. Numerous hardware systems have been presented since, which allow for continuous acquisition of various biosignals like the ECG, PPG, EMG or EEG and which are suited for ambulatory settings. Unfortunately, these flexible systems are liable to motion artifacts and especially photoplethysmographic signals are seriously distorted when the patient is not at rest. A lot of work has been done to reduce artifacts and noise, ranging from simple filtering methods to very complex statistical approaches. With regard to the PPG, certain quality indices have been proposed to evaluate the signal conditions. As movements are the primary source of signal disturbances, the relation between the output of a signal quality estimator and acceleration data captured directly on the PPG sensor is focused in this work. It will be shown that typical motions can be detected on-line, thereby providing additional information which will significantly improve signal quality assessments.

Design optimality for models defined by a system of ordinary differential equations.

Many scientific processes, specially in pharmacokinetics (PK) and pharmacodynamics (PD) studies, are defined by a system of ordinary differential equations (ODE). If there are unknown parameters that need to be estimated, the optimal experimental design approach offers quality estimators for the different objectives of the practitioners. When computing optimal designs the standard procedure uses the linearization of the analytical expression of the ODE solution, which is not feasible when this analytical form does not exist. In this work some methods to solve this problem are described and discussed. Optimal designs for two well-known example models, Iodine and Michaelis-Menten, have been computed using the proposed methods. A thorough study has been done for a specific two-parameter PK model, the biokinetic model of ciprofloxacin and ofloxacin, computing the best designs for different optimality criteria and numbers of points. The designs have been compared according to their efficiency, and the goodness of the designs for the estimation of each parameter has been checked. Although the objectives of the paper are focused on the optimal design field, the methodology can be used as well for a sensitivity analysis of ordinary differential equation systems.

Temporal Adaptive Link Quality Prediction with Online Learning

Link quality estimation is a fundamental component of the low-power wireless network protocols and is essential for routing protocols in Wireless Sensor Networks (WSNs). However, accurate link quality estimation remains a challenging task due to the notoriously dynamic and unpredictable wireless environment. In this article we argue that, in addition to the estimation of current link quality, prediction of the future link quality is more important for the routing protocol to establish low-cost delivery paths. We propose to apply machine learning methods to predict the link quality in the near future to facilitate the utilization of intermediate links with frequent quality changes. Moreover, we show that, by using online learning methods, our adaptive link estimator (TALENT) adapts to network dynamics better than statically trained models without the need of a priori data collection for training the model before deployment. We implemented TALENT in TinyOS with Low-Power Listening (LPL) and conducted extensive experiments in three testbeds. Our experimental results show that the addition of TALENT increases the delivery efficiency 1.95 times on average compared with a 4B, state-of-the-art link quality estimator, as well as improves the end-to-end delivery rate when tested on three different wireless testbeds.

Full-Reference Quality Estimation for Images With Different Spatial Resolutions

Multimedia communication is becoming pervasive because of the progress in wireless communications and multimedia coding. Estimating the quality of the visual content accurately is crucial in providing satisfactory service. State of the art visual quality assessment approaches are effective when the input image and reference image have the same resolution. However, finding the quality of an image that has spatial resolution different than that of the reference image is still a challenging problem. To solve this problem, we develop a quality estimator (QE), which computes the quality of the input image without resampling the reference or the input images. In this paper, we begin by identifying the potential weaknesses of previous approaches used to estimate the quality of experience. Next, we design a QE to estimate the quality of a distorted image with a lower resolution compared with the reference image. We also propose a subjective test environment to explore the success of the proposed algorithm in comparison with other QEs. When the input and test images have different resolutions, the subjective tests demonstrate that in most cases the proposed method works better than other approaches. In addition, the proposed algorithm also performs well when the reference image and the test image have the same resolution.

A real-time video quality estimator for emerging wireless multimedia systems

Wireless Mesh Networks (WMNs) are increasingly deployed to enable thousands of users to share, create, and access live video streaming with different characteristics and content, such as video surveillance and football matches. In this context, there is a need for new mechanisms for assessing the quality level of videos because operators are seeking to control their delivery process and optimize their network resources, while increasing the user's satisfaction. However, the development of in-service and non-intrusive Quality of Experience assessment schemes for real-time Internet videos with different complexity and motion levels, Group of Picture lengths, and characteristics, remains a significant challenge. To address this issue, this article proposes a non-intrusive parametric real-time video quality estimator, called MultiQoE that correlates wireless networks' impairments, videos' characteristics, and users' perception into a predicted Mean Opinion Score. An instance of MultiQoE was implemented in WMNs and performance evaluation results demonstrate the efficiency and accuracy of MultiQoE in predicting the user's perception of live video streaming services when compared to subjective, objective, and well-known parametric solutions.

Practical Quality Assessment for Digitized Film Content

The European research project CineXPRES is focusing on improving the digitization, preservation, and restoration workflows for old film content. A central topic in this project is an attempt to define a practical quality assessment for digitized film content. The authors believe that there is no absolute measure of quality, but instead only measures dedicated to specific decision processes. To this end, three image quality estimators are defined, providing efficient tools in various situations that every archivist will have to face in the future: a multidimensional objective quality measure consisting of a collection of degradation estimators, a conditional subjective quality estimator taking the display into account, and a conditional objective quality estimator considering the ease of restoring content. This paper describes the computation of these estimators and reviews a few practical situations in which they provide answers to complex decision-making situations.

Determining Fuzzy Link Quality Membership Functions in Wireless Sensor Networks

Wireless Sensor Network routing protocols rely on the estimation of the quality of the links between nodes to determine a suitable path from the data source nodes to a data-collecting node. Several link estimators have been proposed, but most of these use only one link property. Fuzzy logic based link quality estimators have been recently proposed which consider a number of link quality metrics. In this work, we implemented the Fuzzy logic based link estimator in the WiseRoute routing protocol, which is a collection style protocol in MiXiM. We also present an experimental approach to determine a suitable fuzzy membership function based on varying the shape of the fuzzy set for a multipath wireless sensor network scenario and choosing an optimum shape that maximizes the Packet Delivery Ratio of the network. The computed fuzzy set membership functions were evaluated against an existing fuzzy link quality estimator under typical scenarios and it is shown the performance of the experimental optimal membership function was better in terms of packet reception ratio and end-to-end delay.

Efficient Modelling of Traffic and Quality of Scalable Video Coding (SVC) Encoded Streams

In this letter, a new model for generating SVC-like traffic and estimating its quality is introduced. Comprising two independent components - i.e., the traffic generator and the quality estimator - the model can significantly speed up the development of SVC applications in various use-cases by relying on approximated properties of streams instead of real traces. The model is verified based on a set of video streams and the performance of its components is assessed.

On the reliability of focal plane solutions using first motion readings

First motion fault plane solutions provide invaluable important information on the mechanism of seismogenic faults and the orientation of the local stress field. However, there are severe limitations and shortcomings regarding the reliability of the calculated solution and how accurately it reflects the real earthquake mechanism. In this study, we examine the dependence of the three mechanisms of ideal strike slip, normal, and thrust on different quality estimators, i.e., event location, velocity model, and reverse polarity stations. We intentionally perturb the original fault plane solutions by changing only one of the parameters that control the solution at a time and compare the perturbed solutions with the real one. Finally, we randomly perturb all the parameters for each earthquake in a large set of events. We then discuss the effect of the perturbations on the reliability of the solution.

Fuzzy Logic Based Multidimensional Link Quality Estimation for Multi-Hop Wireless Sensor Networks

In the applications of multi-hop wireless sensor networks, the effective evaluation of wireless link quality which can improve the network reliability is a crucial problem in the design of network protocols. The lossy and dynamic nature of the radio channel, however, makes link quality estimation a great challenge. First, we use data-driven modeling and statistical inference methods to model the burstiness of wireless link packet loss, which reflects the reliability of packet retransmission in the data link layer. Then, from a multidimensional view of characterizing the wireless link quality, we present the fuzzy logic based link quality indicator (FLI), which is a comprehensive reflection of single hop reliability of packet delivery, link volatility, and packet loss burst. Finally, we implement a wireless link quality estimator based on FLI in the collection tree protocol (CTP). Through the experimental comparison with the original link quality estimator in the CTP, the network performance with the new link quality estimator guarantees high end to end delivery reliability, while the average routing depth of the nodes and the dynamic changes of network topology are reduced.

A quality of experience handover architecture for heterogeneous mobile wireless multimedia networks

The convergence of emerging real-time multimedia services, the increasing coverage of high-speed wireless networks, and the evergrowing popularity of mobile devices are leading to an era of user-centric multimedia wireless services. In this scenario, heterogeneous wireless communications will coexist and ensure that the end user is always best connected. However, the quality of experience supported for highquality applications in multi-operator environments remains a significant challenge and is crucial for the success of wireless multimedia systems. This article proposes a quality of experience handover architecture for heterogeneous mobile wireless multimedia networks. The architecture extends the media independent handover/ IEEE 802.21 proposal with QoE-aware seamless mobility, video quality estimator, dynamic class of service mapping, and a set of content adaptation schemes. The proposed architecture always provides the best connection and considers the QoE needs of mobile clients and available wireless resources in IEEE 802.11e and IEEE 802.16e service classes. Simulation experiments were performed to show the impact and benefits of the proposed solution from the user's perception, by using both objective and subjective QoE metrics.

Correlation analysis of the variation of weld seam and tensile strength in laser welding of galvanized steel

Many advantages of laser welding technology such as high speed and non-contact welding make the use of the technology more attractive in the automotive industry. Many studies have been conducted to search the optimal welding condition experimentally that ensure the joining quality of laser welding that relies both on welding system configuration and welding parameter specification. Both non-destructive and destructive techniques, for example, ultrasonic inspection and tensile test are widely used in practice for estimating the joining quality. Non-destructive techniques are attractive as a rapid quality testing method despite relatively low accuracy. In this paper, we examine the relationship between the variation of weld seam and tensile shear strength in the laser welding of galvanized steel in a lap joint configuration in order to investigate the potential of the variation of weld seam as a joining quality estimator. From the experimental analysis, we identify a trend in between maximum tensile shear strength and the variation of weld seam that clearly supports the fact that laser welded parts having larger variation in the weld seam usually have lower tensile strength. The discovered relationship leads us to conclude that the variation of weld seam can be used as an indirect non-destructive testing method for estimating the tensile strength of the welded parts.

A QoE handover architecture for converged heterogeneous wireless networks

The convergence of real-time multimedia applications, the increasing coverage of heterogeneous wireless networks and the ever-growing popularity of mobile devices are leading to an era of mobile human-centric multimedia services. In this scenario, heterogeneous communications will co-exist and ensure that the end-user is always best connected. The rigorous networking demands of wireless multimedia systems, beyond quality-oriented control strategies, are necessary to guarantee the best user experience over time. Therefore, the Quality of Experience (QoE) support, especially for 2D or 3D videos in multi-operator environments, remains a significant challenge and is crucial for the success of multimedia systems. This paper proposes a QoE Handover Architecture for Converged Heterogeneous Wireless Networks, called QoEHand. QoEHand extends the Media Independent Handover (MIH)/IEEE 802.21 with QoE-awareness, seamless mobility and video adaptation by integrating a set of QoE-based decision-making modules into MIH, namely a video quality estimator, a dynamic class of service mapping and content adaptation schemes. The QoEHand video estimator, mapping and adaptation components operate by coordinating information about video characteristics, available wireless resources in IEEE 802.11e and IEEE 802.16e service classes, and QoE-aware human experience. The video quality estimator works without the need for any decoding, which saves time and minimises processing overheads. Simulations were carried out to show the benefits of QoEHand and its impact on user perception by using objective and subjective QoE metrics.

On a reference-free speech quality estimator for hearing aids

A reference-free speech quality measure is proposed and assessed for hearing aid applications. The proposed speech quality metric is validated with subjective ratings obtained from hearing impaired listeners under a number of noisy and reverberant conditions. In addition, a comparison is drawn between the proposed measure and a state-of-the-art electroacoustic measure that relies on a clean reference signal. The results showed that the reference-free measure had a lower correlation with the subjective ratings of hearing aid speech quality in comparison to the correlations achieved by the measure utilizing a reference signal. Nevertheless, advantages of the reference-free approach are discussed.

Adaptive illumination through spatial modulation of light intensity and image inversion

The paper introduces the concept of spatial modulation of light intensity in the context of vision-based quality control, with the aim to improve image quality, measurable by indices such as image contrast and Tenengrad, so as to enhance the level of confidence of the diagnosis performed by image processing. The proposed technique is based on the projection of spatially modulated light intensity distribution by a digital light projector that allows an arbitrary light distribution to be projected on the target. The projected spatial distribution of light is determined by implementing an algorithm based on image inversion: the image acquired by the camera under uniform illumination is inverted and it is then used to modulate the light spatial distribution for projection. The process is repeated iteratively with the purpose to enhance image quality until convergence. The technique proves particularly valuable to avoid saturation from reflecting surfaces, which are often found in industrial practice. The procedure is tested and validated both by a numerical model and by an experimental validation, referring to a significant problem for the washing machine manufacturing industry. The use of image quality estimators confirms the effectiveness of the method.

A routing protocol based on energy and link quality for Internet of Things applications.

The Internet of Things (IoT) is attracting considerable attention from the universities, industries, citizens and governments for applications, such as healthcare, environmental monitoring and smart buildings. IoT enables network connectivity between smart devices at all times, everywhere, and about everything. In this context, Wireless Sensor Networks (WSNs) play an important role in increasing the ubiquity of networks with smart devices that are low-cost and easy to deploy. However, sensor nodes are restricted in terms of energy, processing and memory. Additionally, low-power radios are very sensitive to noise, interference and multipath distortions. In this context, this article proposes a routing protocol based on Routing by Energy and Link quality (REL) for IoT applications. To increase reliability and energy-efficiency, REL selects routes on the basis of a proposed end-to-end link quality estimator mechanism, residual energy and hop count. Furthermore, REL proposes an event-driven mechanism to provide load balancing and avoid the premature energy depletion of nodes/networks. Performance evaluations were carried out using simulation and testbed experiments to show the impact and benefits of REL in small and large-scale networks. The results show that REL increases the network lifetime and services availability, as well as the quality of service of IoT applications. It also provides an even distribution of scarce network resources and reduces the packet loss rate, compared with the performance of well-known protocols.

A Routing Protocol Based on Energy and Link Quality for Internet of Things Applications

The Internet of Things (IoT) is attracting considerable attention from the universities, industries, citizens and governments for applications, such as healthcare,environmental monitoring and smart buildings. IoT enables network connectivity between smart devices at all times, everywhere, and about everything. In this context, Wireless Sensor Networks (WSNs) play an important role in increasing the ubiquity of networks with smart devices that are low-cost and easy to deploy. However, sensor nodes are restricted in terms of energy, processing and memory. Additionally, low-power radios are very sensitive to noise, interference and multipath distortions. In this context, this article proposes a routing protocol based on Routing by Energy and Link quality (REL) for IoT applications. To increase reliability and energy-efficiency, REL selects routes on the basis of a proposed end-to-end link quality estimator mechanism, residual energy and hop count. Furthermore, REL proposes an event-driven mechanism to provide load balancing and avoid the premature energy depletion of nodes/networks. Performance evaluations were carried out using simulation and testbed experiments to show the impact and benefits of REL in small and large-scale networks. The results show that REL increases the network lifetime and services availability, as well as the quality of service of IoT applications. It also provides an even distribution of scarce network resources and reduces the packet loss rate, compared with the performance of well-known protocols.

Towards No-Reference of Peak Signal to Noise Ratio

The aim of this work is to define a no-referenced perceptual image quality estimator applying the perceptual concepts of the Chromatic Induction Model The approach consists in comparing the received image, presumably degraded, against the perceptual versions (different distances) of this image degraded by means of a Model of Chromatic Induction, which uses some of the human visual system properties. Also we compare our model with an original estimator in image quality assessment, PSNR. Results are highly correlated with the ones obtained by PSNR for image (99.32% Lenna and 96.95% for image Baboon), but this proposal does not need an original image or a reference one in order to give an estimation of the quality of the degraded image.