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  • 1. Abate, F.
    et al.
    Carratu, M.
    Liguori, Consolatina
    University of Salerno .
    Pietrosanto, A.
    Smart meters and water leakage detection: A preliminary study2019In: I2MTC 2019  Proceedings, 2019, article id 8827020Conference paper (Refereed)
    Abstract [en]

    The paper deals with water leakage beyond the meter at household level. The automatic leakage detection is emerging as priority task for scientists and technicians. Each possible solution must include the use of smart meters for the continuous survey of domestic water consumption. Water smart meters aren't widespread yet, and the few either are prototypes or exhibit not adequate battery and communication performance. The authors, participants to the EMPIR 17IND13 Metrowamet project, propose an embedded system that can work with different water sensors, whose characteristics have been suitably designed for respecting stringent requirements of energy efficiency, computational burden and wireless transmission capability. 

  • 2. Abbas, Q.
    et al.
    Hassan, Syed Ali
    Pervaiz, H.
    Ni, Q.
    A Markovian Model for the Analysis of Age of Information in IoT Networks2021In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 10, no 7, p. 1596-1600, article id 9410556Article in journal (Refereed)
    Abstract [en]

    Age of Information (AoI) is a critical metric in status update systems as these systems require the fresh updates. This letter investigates the uplink of an Internet-of-Thing (IoT) network where L nodes transmit their information packets to a base station. The effects of the arrival rate of packets at the nodes, the number of nodes in the system, and queue length of each node have been studied by devising a discrete time Markov chain (MC) model. This model helps in predicting the values of AoI and probability of packet drops in such systems. The notion of first-in first-out is used for queuing, which transmits the oldest packet first, resulting in decreasing the overall AoI of the system. The results show that AoI increases with the increase in queue length, number of nodes and arrival rate and we quantify the aforementioned metrics using the MC model. The results found using the MC model are also validated using extensive simulations. © 2012 IEEE.

  • 3. Abbas, Q.
    et al.
    Zeb, S.
    Hassan, S. A.
    Age of Information in Backscatter Communication2021In: Internet Things, Springer , 2021, p. 67-80Conference paper (Refereed)
    Abstract [en]

    Age of Information (AoI) has been introduced to characterize the newness of data which is observed in real time. In other words, it is the measure of time elapsed since the generation of last received update about a process and is a vital metric in networks such as Internet of things (IoTs), especially when the application demands fresh updates. Most of the applications require fresh data e.g., applications related to environmental monitoring, smart agriculture, body area networks etc. On the other hand backscatter communication promises to resolve one of the most challenging issues of IoT devices, i.e., making them capable for communication without the batteries. The importance of AoI in backscatter communication is paramount to gauge performance of backscatter IoT networks. This chapter addresses the significance of AoI in backscatter communication and suggests some techniques to design a communication system with minimum AoI, maximum energy efficiency, and minimum outage. © 2021, Springer Nature Switzerland AG.

  • 4.
    Abdalla, Munir A
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Petersson, Sture
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    A CMOS APS for dental X-ray imaging using scintillating sensors2001In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 460, no 1, p. 197-203Article in journal (Refereed)
    Abstract [en]

    In this paper we present an integrating CMOS Active Pixel Sensor (APS) circuit to be used with scintillator type X-ray sensors for intra oral dental X-ray imaging systems. Different pixel architectures were constructed to explore their performance characteristics and to study the feasibility of the development of such systems using the CMOS technology. A prototype 64×80 pixel array has been implemented in a CMOS 0.8 μm double poly n-well process with a pixel pitch of 50 μm. A spectral sensitivity measurement for the different pixels topologies, as well as measured X-ray direct absorption in the different APSs are presented. A measurement of the output signal showed a good linearity over a wide dynamic range. This chip showed that the very low sensitivity of the CMOS APSs to direct X-ray exposure adds a great advantage to the various CMOS advantages over CCD-based imaging systems.

  • 5.
    Abdalla, Munir A
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Petersson, Sture
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    A new biasing method for CMOS preamplifier-shapers2000In: ICECS 2000: 7TH IEEE INTERNATIONAL CONFERENCE ON ELECTRONICS, CIRCUITS & SYSTEMS, VOLS I AND II, 2000, p. 15-18Conference paper (Refereed)
  • 6.
    Abdalla, Munir A
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Petersson, Sture
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    An integrating CMOS APS for X-ray imaging with an in-pixel preamplifier2001In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 466, no 1, p. 232-236Article in journal (Refereed)
    Abstract [en]

    We present in this paper an integrating CMOS Active Pixel Sensor (APS) circuit coated with scintillator type sensors for intra-oral dental X-ray imaging systems. The photosensing element in the pixel is formed by the p-diffusion on the n-well diode. The advantage of this photosensor is its very low direct absorption of X-rays compared to the other available photosensing elements in the CMOS pixel. The pixel features an integrating capacitor in the feedback loop of a preamplifier of a finite gain in order to increase the optical sensitivity. To verify the effectiveness of this in-pixel preamplification, a prototype 32 x 80 element CMOS active pixel array was implemented in a 0.8 mum CMOS double poly, n-well process with a pixel pitch of 50 mum. Measured results confirmed the improved optical sensitivity performance of the APS. Various measurements on device performance are presented.

  • 7.
    Abdalla, Munir
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Dubaric, Ervin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Petersson, Sture
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    A scintillator-coated phototransistor pixel sensor with dark current cancellation2001In: cecs2001: 8th IEEE international conference on electronics, circuits and systems, Vols. I-III, Conference Proceedings, 2001, p. 663-667Conference paper (Other academic)
  • 8.
    Abdalla, Suliman A
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Architecture and circuit design of photon counting readout for X-ray imaging sensors2007Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Hybrid pixel array detectors for X-ray imaging are based on different technologies for sensor and readout electronics. The readout electronics are based on standard CMOS technologies that are experiencing continuously rapid improvements by means of down-scaling the feature sizes, which in turn lead to higher transistor densities, lower power consumption, and faster circuits. For pixel-array imaging sensors the improvements in CMOS technology opens up new possibilities of integrating more functionality in the pixels for local processing of the sensor data. However, new issues related to the tight integration of both analog and digital processing circuits within the small area of a pixel must also be evaluated.

    The advantages of down-scaling the CMOS technology can be utilized to increase the spatial resolution by reducing the pixel sizes. Recent research indicates however that the bottleneck in reaching further spatial resolution in X-ray imaging sensors may not be limited by the circuit area occupied by the functions necessary in the pixels, but are instead related to problems associated with charge-sharing of charges generated by the sensor which are distributed over a neighbourhood of pixels and will limit the spatial resolution and lead to a distortion of the energy spectrum. In this thesis a mechanism to be implemented in the readout circuits is proposed in order to suppress the charge-sharing effects. The proposed architecture and its circuit implementation are evaluated with respect to circuit complexity (area) and power consumption. For a photon-counting pixel it is demonstrated that the complete pixel, with charge-sharing suppression mechanism, can be implemented using 300 transistors with an idle power consumption of 2.7μW in a 120nm CMOS technology operating with a 1.2V power supply.

    The improvements in CMOS technology can also be used for increasing the range of applications for X-ray imaging sensors. In this thesis, an architecture is proposed for multiple energy discrimination, called color X-ray imaging. The proposed solution is the result of balancing the circuit complexity and the image quality. The method is based on color sub-sampling with intensity biasing. For three-level energy discrimination, that corresponds to color imaging systems for visible light with R, G, and B color components, the increase in circuit complexity will be only 20% higher than that for the Bayer method but results in significantly better image quality.

    As the circuit complexity in the digital processing within each pixel is increased, the digitally induced noise may play an increasingly important role for the signal-to-noise ratio in the measurements. In this thesis an initial study is conducted regarding how the digital switching noise affects the analog amplifiers in the photon-counting pixel.

  • 9.
    Abdalla, Suliman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Circuit Implementation of Mechanism for Charge-Sharing Suppression for Photon-Counting Pixel Arrays2005In: 23rd NORCHIP Conference 2005, IEEE conference proceedings, 2005, p. 137-140, article id 1597008Conference paper (Refereed)
    Abstract [en]

    This work proposes an efficient circuit implementation of a mechanism for charge-sharing suppression in photon-counting pixel arrays based on current-mode circuits for the analog parts. The additional circuits needed for charge-sharing suppression in a four-pixel cluster, leads to an increase in power consumption of 36% and only a marginal increase in circuit area. The implemented pixel with window-discrimination, managing charge-sharing in a four-pixel cluster and with an event-counter of 13 bits, consists of 300 transistors and has a power consumption of 2.7 μW when idle. It is implemented in a 120nm CMOS process and the presented results are based on simulations.

  • 10.
    Abdalla, Suliman
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    O'Nils, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Thim [Lundgren], Jan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Architecture and Circuit Design for Color X-Ray Pixal Array Detector Read-Out Electronics2007In: 24th Norchip Conference, 2006, New York: IEEE conference proceedings, 2007, p. 271-276, article id 4126997Conference paper (Refereed)
    Abstract [en]

    This paper proposes an area- and power-efficient implementation of the read-out electronics for color X-ray pixel detectors for imaging. Introducing multiple levels of energy discrimination will increase the complexity of the read-out electronics in each pixel. The proposed architecture has full resolution for the intensity and reduced resolution for the energy spectrum (color), which leads to a good compromise of image quality and circuit complexity. We show that the increase in complexity, compared to single energy-range pixel, will lead to increase in circuit area of less than 20%.

  • 11.
    Abdul Waheed, Malik
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Thörnberg, Benny
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Cheng, Xin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Lawal, Najeem
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Imran, Muhammad
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Kjeldsberg, Per Gunnar
    NTNU.
    Generalized Architecture for a Real-time Computation of an Image Component Features on a FPGAManuscript (preprint) (Other academic)
    Abstract [en]

    This paper describes a generalized architecture for real-time component labeling and computation of image component features. Computing real-time image component features is one of the most important paradigms for modern machine vision systems. Embedded machine vision systems demand robust performance, power efficiency as well as minimum area utilization. The presented architecture can easily be extended with additional modules for parallel computation of arbitrary image component features. Hardware modules for component labeling and feature calculation run in parallel. This modularization makes the architecture suitable for design automation. Our architecture is capable of processing 390 video frames per second of size 640x480 pixels. Dynamic power consumption is 24.20mW at 86 frames per second on a Xilinx Spartran6 FPGA.

  • 12.
    Abedin, Sarder
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. Kyung Hee University, Yongin 17104, South Korea.
    Munir, M. S.
    Tran, N. H.
    Han, Z.
    Hong, C. S.
    Data Freshness and Energy-Efficient UAV Navigation Optimization: A Deep Reinforcement Learning Approach2021In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 22, no 9, p. 5994-6006Article in journal (Refereed)
    Abstract [en]

    In this paper, we design a navigation policy for multiple unmanned aerial vehicles (UAVs) where mobile base stations (BSs) are deployed to improve the data freshness and connectivity to the Internet of Things (IoT) devices. First, we formulate an energy-efficient trajectory optimization problem in which the objective is to maximize the energy efficiency by optimizing the UAV-BS trajectory policy. We also incorporate different contextual information such as energy and age of information (AoI) constraints to ensure the data freshness at the ground BS. Second, we propose an agile deep reinforcement learning with experience replay model to solve the formulated problem concerning the contextual constraints for the UAV-BS navigation. Moreover, the proposed approach is well-suited for solving the problem, since the state space of the problem is extremely large and finding the best trajectory policy with useful contextual features is too complex for the UAV-BSs. By applying the proposed trained model, an effective real-time trajectory policy for the UAV-BSs captures the observable network states over time. Finally, the simulation results illustrate the proposed approach is 3.6 % and 3.13 % more energy efficient than those of the greedy and baseline deep Q Network (DQN) approaches. 

  • 13. Aboelfotoh, M O
    et al.
    Fröjdh, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Petersson, Sture
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Schottky-barrier behavior of metals on n- and p-type 6H-SiC2003In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 67, no 7, p. 075312-Article in journal (Refereed)
  • 14.
    Aboelwafa, Mariam
    et al.
    American University of Cairo, Egypt.
    Seddik, Karim G.
    American University of Cairo, Egypt.
    Eldefrawy, Mohammed
    Halmstad University, Sweden.
    Gadallah, Yasser
    American University of Cairo, Egypt.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    A Machine Learning-Based Technique for False Data Injection Attacks Detection in Industrial IoT2020In: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 7, no 9, p. 8462-8471Article in journal (Refereed)
    Abstract [en]

    The accelerated move towards the adoption of the industrial Internet of Things (IIoT) paradigm has resulted in numerous shortcomings as far as security is concerned. One of the IIoT affecting critical security threats is what is termed as the ” False Data Injection” (FDI) attack. The FDI attacks aim to mislead the industrial platforms by falsifying their sensor measurements. FDI attacks have successfully overcome the classical threat detection approaches. In this study, we present a novel method of FDI attack detection using Autoencoders (AEs). We exploit the sensor data correlation in time and space, which in turn can help identify the falsified data. Moreover, the falsified data are cleaned using the denoising AEs. Performance evaluation proves the success of our technique in detecting FDI attacks. It also significantly outperforms a support vector machine (SVM) based approach used for the same purpose. The denoising AE data cleaning algorithm is also shown to be very effective in recovering clean data from corrupted (attacked) data.

  • 15.
    Adin, Veysi
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and Electrical Engineering (2023-).
    Zhang, Yuxuan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and Electrical Engineering (2023-).
    Ando, Bruno
    University of Catania, Catania, Italy.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and Electrical Engineering (2023-).
    Bader, Sebastian
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and Electrical Engineering (2023-).
    Tiny Machine Learning for Real-Time Postural Stability Analysis2023In: 2023 IEEE Sensors Applications Symposium (SAS), IEEE conference proceedings, 2023Conference paper (Refereed)
    Abstract [en]

    Postural sway is a critical measure for evaluating postural control, and its analysis plays a vital role in preventing falls among the elderly. Typically, physiotherapists assess an individual's postural control using tests such as the Berg Balance Scale, Tinetti Test, and time up-and-go test. Sensor-based analysis is available based on devices such as force plates or inertial measurement units. Recently, machine learning methods have demonstrated promising results in the sensor-based analysis of postural control. However, these models are often complex, slow, and energy-intensive. To address these limitations, this study explores the design space of lightweight machine learning models deployable to microcontrollers to assess postural stability. We developed an artificial neural network (ANN) model and compare its performance to that of random forests, gaussian naive bayes, and extra tree classifiers. The models are trained using a sway dataset with varying input sizes and signal-to-noise ratios. The dataset comprises two feature vectors extracted from raw accelerometer data. The developed models are deployed to an ARM Cortex M4-based microcontroller, and their performance is evaluated and compared. We show that the ANN model has 99.03% accuracy, higher noise immunity, and the model performs better with a window size of one second with 590.96 us inference time. 

  • 16.
    Adin, Veysi
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and Electrical Engineering (2023-).
    Zhang, Yuxuan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and Electrical Engineering (2023-).
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and Electrical Engineering (2023-).
    Bader, Sebastian
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and Electrical Engineering (2023-).
    Tiny Machine Learning for Damage Classification in Concrete Using Acoustic Emission Signals2023In: 2023 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), IEEE, 2023Conference paper (Refereed)
    Abstract [en]

    Acoustic emission (AE) is a widely used non-destructive test method in structural health monitoring applications to identify the damage type in the material. Usually, the analysis of the AE signal is done by using traditional parameter-based methods. Recently, machine learning methods showed promising results for the analysis of AE signals. However, these machine learning models are complex, slow, and consume significant amounts of energy. To address these limitations and to explore the trade-off between model complexity and the classification accuracy, this paper presents a lightweight artificial neural network model to classify damage types in concrete material using raw acoustic emission signals. The model consists of one hidden layer with four neurons and is trained on a public acoustic emission signal dataset. The created model is deployed to several microcontrollers and the performance of the model is evaluated and compared with a state-of-the-art machine learning model. The model achieves 98.4% accuracy on the test data with only 4019 parameters. In terms of evaluation metrics, the proposed tiny machine learning model outperforms previously proposed models 10 to 1000 times. The proposed model thus enables machine learning in real-time structural health monitoring applications. 

  • 17.
    Adolfsson, Jesper
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Automatisk maskinåterställning: Hur automatiserade hjälpmedel kan bidra till en bättre produktion2021Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A common problem with production equipment at Eberspächer is downtime where the root cause is difficult to identify. The use of sophisticated systems that isolate the source of the error can reduce the remediation time and therefore be of great benefit to productivity. The following report examines how to automate the restoration of a machine focused on measurement and quality control, to an original mode where operating personnel can resume production after a downtime. Initially, work began on a literature study from which information was obtained about the various automated parts of the measuring cell. Furthermore, the machine's PLC program was also studied to try to understand what the code in the various programmed blocks does. The programming of the automated recovery was done in accordance with Eberspächer's guidelines and specification. Based on collected information about the machine's function, it has been possible to create a program with the desired functionality. The conclusion that can be drawn from this work is that there are great advantages to automating functions that can be difficult and require a lot of the user. The automated reset is a good example of a feature where there are economic, ecological and ergonomic benefits of making a complicated action manageable.

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  • 18.
    Afram, Gabriel
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    A study on how to improve On-shelf availability: With deep learning2020Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    On-shelf availability is a measure of how available a product is for a shopper in a store. The products should be in the place where the shopper expects it and at the time the shopper wants to buy it. To ensure a high Onshelf availability store clerks must move around the store and look for products that must be replenished and products that are misplaced. However, this task is rather time consuming since there are usually hundreds of different products to keep track of in a store. This thesis therefore, aims to simplify this task for store clerks by creating an automatic system that can identify “out of stocks” and misplaced products. Different state of the art object detection algorithms and image classification methods were evaluated in order to solve this task. The object detection algorithms were used to find products and gaps on store shelves and were trained with a relatively small dataset. The bounding boxes obtained from the object detection algorithm was then forwarded to an image classification algorithm in order to predict the label of the product. The training data of the classification dataset consisted of a small dataset with 29 different detergent products. All the algorithms were evaluated on speed and F1-score while the object detection algorithms were also evaluated on an average precision with an intersection of union as 0.5 and 0.75. The results indicate that it is possible to use deep learning in order to improve on-shelf availability. However, the methods might only perform good on the small datasets used in this thesis. Furthermore, since no real test have been made in a real-life supermarket it is impossible to say for certain if it would indeed improve on-shelf availability.

  • 19.
    Ahmad, Awais
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System Science.
    Ahlin, Karin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System Science.
    Mozelius, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System Science.
    Technology-enhanced speech and language relearning for stroke patients: defining requirements for a software application development2020Conference paper (Refereed)
    Abstract [en]

    Speech and language relearning are challenging for stroke survivors as well as for medical caregiv-ers. After a stroke, a patient’s ability to read, write, speak, and listen is decreased to different degrees, which results in a compromised independent life and a decreased quality of life for the patient. Tech-nology enhances systems can play a vital role in this context. However, the available software are not specifically built for after the stroke patient’s needs. This paper is therefore aimed to gather require-ments for designing a tailor-made speech relearning software application for stroke survivors. A de-sign science approach was adopted, where different stakeholders such as medical caregivers and in-formation technology consultants were involved in the process. The well-informed and experienced participants in their fields highlighted some important requirements such as different types of inter-face for a patient than speech therapist with extra management functionality for speech therapists so that they can adjust the relearning exercises according to the patient’s needs. Software requirements vary from patient to patient where the intensity of speech and language impairments, general medical condition of the patient, age, prior experience, and knowledge about the information of the patient and social setup of the patient plays an important role. Since stroke is most common in adults and adults learn differently than children, adult learning theory might help understand the patients' needs. There-fore, adult learning principles were involved in the requirement analysis process. The established re-quirements will be used for the development of speech and language relearning software.

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  • 20.
    Ahmad, Awais
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System Science.
    Ahlin, Karin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System Science.
    Mozelius, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and System Science.
    The Technology-Enhanced Requirements for the Three-Fold Stroke Rehabilitation to Support Independent Living2020In: Information and Communication Technologies for Ageing Well and e-Health, Switzerland: Springer Nature, 2020Chapter in book (Refereed)
    Abstract [en]

    Stroke is a common and severe disease that can be found in all regions across the globe, and not onlyamong older adults. Result of a stroke can be death, or a variety of disabilities caused by impairments indifferent brain functions. This chapter discusses technology enhanced stroke rehabilitation from a threefoldview of cognitive, motoric and speech rehabilitation. The important research question was: Whatwould be the requirements for technology-enhanced stroke rehabilitation in the areas of cognitive, motoricand speech rehabilitation? The study was carried out with a requirement-focused Design Science approachcollecting data with semi-structured interviews. Informants were selected in a purposive sampling choosingprofessionals with valuable knowledge and skills in stroke rehabilitation. The findings in this study havegenerated useful general requirements for a future implementation and testing of technology enhancedstroke rehabilitation. Within each of the three rehabilitation categories cognitive, motoric and speech, thereseems to be potential for successful use of technology enhanced services. This development ofrehabilitation services must follow the fundamental principle for all forms of stroke rehabilitation: eachpatient needs a personalised treatment. However, in all three rehabilitation categories, there is a need todefine more specific requirements based on feedback from stroke patients testing the rehabilitationservices.

  • 21.
    Ahmad, Jawad
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Development and Characterization of Large Area Pressure Sensors and Sitting Posture Monitoring Systems2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    With the emergence of the Internet and rapid development of science and technology over the past few decades, many individuals worldwide now rely on the Internet to conduct daily activities ranging from education, business and creativity to communication and shopping. As we tend to spend more and more time on the Internet and engage less in physical activities, this persistent behaviour could result in some health-related issues within a relatively short period of time. This behaviour, known as sedentary lifestyle, may be related to a higher risk of cardiovascular disease, osteoporosis, obesity, anxiety, pressure ulcers and many other illnesses. As a consequence, there has been great interest in developing non-invasive and unobtrusive measurement techniques for a variety of health care-monitoring applications, such as for blood oxygen saturation, stress levels, electrocardiograms and glucose monitoring. In such systems, wearable and flexible electronics technologies may enable monitoring of vital signs, offering significant potential for early screening as well as long-term behaviour modelling.

    In this thesis, large area pressure sensors based on non-conventional materials are proposed and realised by screen printing technique for monitoring sitting postures. The developed pressure sensing system measures distributed pressure when an individual sits on a chair equipped with a pressure sensor array. This technology could provide grounding for the advancement of health-related monitoring systems for both able-bodied and disabled individuals and inform them of their sitting time and sitting posture, and this could be used to establish a sitting pattern. To accomplish this, pressure sensors have been designed using non-conventional flexible electronics. A blend of non-conductive and low-resistance ink is used as pressure-sensitive material to enable the realization of screen-printed sensors. To characterise the performance of the suggested pressure sensor, several tests, such as repeatability, drift and flexibility, are conducted. The sensor has also been exposed to different humidity and temperature conditions in a climate chamber to examine its functionalities.

    A graphical user interface was developed for real-time demonstration of data from distributed pressure points in the form of a pressure map to display the pressure values. Four sitting postures are identified: forward, backward, left, and right leaning. Furthermore, a stretchable pressure sensor is proposed that could follow slight stretching with regard to changes in the shape of the human skin. Machine learning algorithms have been employed to further enhance the sitting posture identification, and accuracy of 99.03% is attained. A standalone embedded system capable of illustrating real-time pressure data has been developed with the potential to be used in portable health monitoring systems. In summary, this work provides a promising framework for measuring pressure distribution and identifying irregular sitting postures that may help to reduce the potential risks of developing health-related issues associated with prolonged sitting time.

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  • 22.
    Ahmad, Jawad
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Screen Printed Large Area Sensors for Pressure Distribution Monitoring in Wheelchairs2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    A sedentary lifestyle can induce health related problems including pressure ulcers. Pro­longed sitting inadequacies constitute a risk for pressure ulcer to many individuals, in particular people with disabilities and re­duced mobility. The measurement of distributed pressure and detection of irregular sitting postures are essential in prevention of the risk of developing pres­sure ulcers.

    In this thesis, a screen-printed pressure sensor for a large area is presented, with the objective of measuring the distributed pressure of a seated per­son in a wheelchair. The conductors and interdigital patterns are printed with silver-based ink. A blend of a non-conductive and a low resis­tive ink is used for customized resistance for an optimal sensing range of the pressure sensor. The effect of moisture and temper­ature are realized in an environment chamber. For characterization, other key performance tests such as repeatability, drift and flexibility are carried out. The surface morphology is carried out for structural analysis of printed samples. The sensor data is acquired and processed using an 8-bit ATmega-2560 micro­controller and wirelessly transmitted to a PC for post-processing, storage and analysis. For real-time data presentation of dis­tributed pressure points, a GUI has been developed to display the values ob­tained from the large area sensor. The detection of four sit­ting pos­tures; forward leaning, backward leaning, left leaning and right leaning along with a normal sitting posture is attained. An analysis for stretchable printed tracks has been conducted to investigate the changes in electrical resistance using elon­ga­tion tests, surface morphology and EDS. The optimal curing time and tem­per­ature were investigated to manufacture stretchable conductive tracks.

    In summary, the contributions in this thesis provides an effective approach regarding pressure distribution measurement and recognizing irregular sitting postures for wheelchair users.

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    JawadAhmad_licentiatethesis159
  • 23.
    Ahmad, Jawad
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Sidén, Johan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Screen Printed Piezoresistive Sensors for Monitoring Pressure Distribution in Wheelchair2019In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 19, no 6, p. 2055-2063Article in journal (Refereed)
    Abstract [en]

    Prolonged sitting inadequacies cause pressure ulcer to many individuals, especially to disadvantaged with reduced mobility. The measurement of distributed pressure and detection of irregular sitting postures is essential for preventing the risk of developing pressure ulcer. In this paper, a pressure sensing system capable of recognizing sitting postures by means of measuring interface pressure through printed pressure sensors is presented. A thin and flexible large area sensor is screen-printed using silver flake and carbon particle inks and comprises 16 sensing elements. For the evaluation of practical usability, the sensor characterization is carried out by conducting stability, repeatability, drift and bending tests. The performance of the sensor is checked under varying environmental conditions. Sitting posture detection accuracy above 80 % is achieved using a classification algorithm for four different sitting postures. Pressure distribution is monitored at a scanning rate of 10 Hz. A low power and small form factor of read-out electronics enables a compact packaging inside the seat cushion. The presented sensor design targets smart wheelchairs, but it is extendable to much larger areas, for example to be used in beds. The proposed sensing system would be of a great assistance for caregivers and health professionals.

  • 24.
    Ahmad, Jawad
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Andersson, Henrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Sidén, Johan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Sitting Posture Recognition using Screen Printed Large Area Pressure Sensors2017In: Proceedings of IEEE Sensors, IEEE, 2017, p. 232-234Conference paper (Refereed)
    Abstract [en]

    In the biomedical sector, pressure sensors exhibit an important role towards monitoring and recognition of sitting posture for wheelchair users, which is helpful for pressure ulcer prevention and cure.  In this paper, a flexible and inexpensive screen printed large area pressure sensing system is presented. The large area sensor comprise three layers, is able to cancel-out false pressure detection, and achieves a sitting classification accuracy over 80 percent. The sensor matrix contains 16 sensors distributed over an area of 23.5 cm × 21.5 cm and the pressure points are monitored at a scanning rate of 77 Hz. The sensor system provides wireless communication and a Windows based GUI is developed that allows real-time presentation of pressure data by means of a pressure map. The presented sensor design targets smart wheelchairs but is suitable for any low cost and high throughput pressure distribution monitoring systems. 

  • 25.
    Ahmad, Naeem
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Modelling and optimization of sky surveillance visual sensor network2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    A Visual Sensor Network (VSN) is a distributed system of a largenumber of camera sensor nodes. The main components of a camera sensornode are image sensor, embedded processor, wireless transceiver and energysupply. The major difference between a VSN and an ordinary sensor networkis that a VSN generates two dimensional data in the form of an image, whichcan be exploited in many useful applications. Some of the potentialapplication examples of VSNs include environment monitoring, surveillance,structural monitoring, traffic monitoring, and industrial automation.However, the VSNs also raise new challenges. They generate large amount ofdata which require higher processing powers, large bandwidth requirementsand more energy resources but the main constraint is that the VSN nodes arelimited in these resources.This research focuses on the development of a VSN model to track thelarge birds such as Golden Eagle in the sky. The model explores a number ofcamera sensors along with optics such as lens of suitable focal length whichensures a minimum required resolution of a bird, flying at the highestaltitude. The combination of a camera sensor and a lens formulate amonitoring node. The camera node model is used to optimize the placementof the nodes for full coverage of a given area above a required lower altitude.The model also presents the solution to minimize the cost (number of sensornodes) to fully cover a given area between the two required extremes, higherand lower altitudes, in terms of camera sensor, lens focal length, camera nodeplacement and actual number of nodes for sky surveillance.The area covered by a VSN can be increased by increasing the highermonitoring altitude and/or decreasing the lower monitoring altitude.However, it also increases the cost of the VSN. The desirable objective is toincrease the covered area but decrease the cost. This objective is achieved byusing optimization techniques to design a heterogeneous VSN. The core ideais to divide a given monitoring range of altitudes into a number of sub-rangesof altitudes. The sub-ranges of monitoring altitudes are covered by individualsub VSNs, the VSN1 covers the lower sub-range of altitudes, the VSN2 coversthe next higher sub-range of altitudes and so on, such that a minimum cost isused to monitor a given area.To verify the concepts, developed to design the VSN model, and theoptimization techniques to decrease the VSN cost, the measurements areperformed with actual cameras and optics. The laptop machines are used withthe camera nodes as data storage and analysis platforms. The area coverage ismeasured at the desired lower altitude limits of homogeneous as well asheterogeneous VSNs and verified for 100% coverage. Similarly, the minimumresolution is measured at the desired higher altitude limits of homogeneous aswell as heterogeneous VSNs to ensure that the models are able to track thebird at these highest altitudes.

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    Lic Thesis 86
  • 26.
    Ahmad, Naeem
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Modelling, optimization and design of visual sensor networks for sky surveillance2013Doctoral thesis, comprehensive summary (Other academic)
  • 27.
    Ahmad, Naeem
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Imran, Muhammad
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Khursheed, Khursheed
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Lawal, Najeem
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    O'Nils, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Model, placement optimization and verification of a sky surveillance visual sensor network2013In: International Journal of Space-Based and Situated Computing (IJSSC), ISSN 2044-4893, E-ISSN 2044-4907, Vol. 3, no 3, p. 125-135Article in journal (Refereed)
    Abstract [en]

    A visual sensor network (VSN) is a distributed system of a large number of camera nodes, which generates two dimensional data. This paper presents a model of a VSN to track large birds, such as golden eagle, in the sky. The model optimises the placement of camera nodes in VSN. A camera node is modelled as a function of lens focal length and camera sensor. The VSN provides full coverage between two altitude limits. The model can be used to minimise the number of sensor nodes for any given camera sensor, by exploring the focal lengths that fulfils both the full coverage and minimum object size requirement. For the case of large bird surveillance, 100% coverage is achieved for relevant altitudes using 20 camera nodes per km² for the investigated camera sensors. A real VSN is designed and measurements of VSN parameters are performed. The results obtained verify the VSN model.

  • 28.
    Ahmad, Naeem
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Khursheed, Khursheed
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Imran, Muhammad
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Lawal, Najeem
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    O'Nils, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Cost Optimization of a Sky Surveillance Visual Sensor Network2012In: Proceedings of SPIE - The International Society for Optical Engineering, Belgium: SPIE - International Society for Optical Engineering, 2012, p. Art. no. 84370U-Conference paper (Refereed)
    Abstract [en]

    A Visual Sensor Network (VSN) is a network of spatially distributed cameras. The primary difference between VSN and other type of sensor network is the nature and volume of information. A VSN generally consists of cameras, communication, storage and central computer, where image data from multiple cameras is processed and fused. In this paper, we use optimization techniques to reduce the cost as derived by a model of a VSN to track large birds, such as Golden Eagle, in the sky. The core idea is to divide a given monitoring range of altitudes into a number of sub-ranges of altitudes. The sub-ranges of altitudes are monitored by individual VSNs, VSN1 monitors lower range, VSN2 monitors next higher and so on, such that a minimum cost is used to monitor a given area. The VSNs may use similar or different types of cameras but different optical components, thus, forming a heterogeneous network.  We have calculated the cost required to cover a given area by considering an altitudes range as single element and also by dividing it into sub-ranges. To cover a given area with given altitudes range, with a single VSN requires 694 camera nodes in comparison to dividing this range into sub-ranges of altitudes, which requires only 96 nodes, which is 86% reduction in the cost.

  • 29.
    Ahmad, Naeem
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Khursheed, Khursheed
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Imran, Muhammad
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Lawal, Najeem
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    O'Nils, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Modeling and Verification of a Heterogeneous Sky Surveillance Visual Sensor Network2013In: International Journal of Distributed Sensor Networks, ISSN 1550-1329, E-ISSN 1550-1477, p. Art. id. 490489-Article in journal (Refereed)
    Abstract [en]

    A visual sensor network (VSN) is a distributed system of a large number of camera nodes and has useful applications in many areas. The primary difference between a VSN and an ordinary scalar sensor network is the nature and volume of the information. In contrast to scalar sensor networks, a VSN generates two-dimensional data in the form of images. In this paper, we design a heterogeneous VSN to reduce the implementation cost required for the surveillance of a given area between two altitude limits. The VSN is designed by combining three sub-VSNs, which results in a heterogeneous VSN. Measurements are performed to verify full coverage and minimum achieved object image resolution at the lower and higher altitudes, respectively, for each sub-VSN. Verification of the sub-VSNs also verifies the full coverage of the heterogeneous VSN, between the given altitudes limits. Results show that the heterogeneous VSN is very effective to decrease the implementation cost required for the coverage of a given area. More than 70% decrease in cost is achieved by using a heterogeneous VSN to cover a given area, in comparison to homogeneous VSN. © 2013 Naeem Ahmad et al.

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    Ahmad_Modeling_and_verification
  • 30.
    Ahmad, Naeem
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Lawal, Najeem
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    O'Nils, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Imran, Muhammad
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Khursheed, Khursheed
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Model and placement optimization of a sky surveillance visual sensor network2011In: Proceedings - 2011 International Conference on Broadband and Wireless Computing, Communication and Applications, BWCCA 2011, IEEE Computer Society, 2011, p. 357-362Conference paper (Refereed)
    Abstract [en]

    Visual Sensor Networks (VSNs) are networks which generate two dimensional data. The major difference between VSN and ordinary sensor network is the large amount of data. In VSN, a large number of camera nodes form a distributed system which can be deployed in many potential applications. In this paper we present a model of the physical parameters of a visual sensor network to track large birds, such as Golden Eagle, in the sky. The developed model is used to optimize the placement of the camera nodes in the VSN. A camera node is modeled as a function of its field of view, which is derived by the combination of the lens focal length and camera sensor. From the field of view and resolution of the sensor, a model for full coverage between two altitude limits has been developed. We show that the model can be used to minimize the number of sensor nodes for any given camera sensor, by exploring the focal lengths that both give full coverage and meet the minimum object size requirement. For the case of large bird surveillance we achieve 100% coverage for relevant altitudes using 20 camera nodes per km2 for the investigated camera sensors.

  • 31.
    Ahmad, Nisar
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Design and Implementation of a High Frequency Flyback Converter2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The power supply designers choose flyback topology due to its promising features of design simplicity, cost effectiveness and multiple outputs handling capability. The designed product based on flyback topology should be smaller in size, cost effective and energy efficient. Similarly, designers focus on reducing the circuit losses while operating at high frequencies that affect the converter efficiency and performance. Based on the above circumstances, an energy efficient open loop high frequency flyback converter is designed and operated in MHz frequency region using step down multilayer PCB planar transformer. The maximum efficiency of 84.75% is observed and maximum output power level reached is 22.8W. To overcome the switching losses, quasi-resonant soft switching technique is adopted and a high voltage CoolMOS power transistor is used.

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  • 32.
    Ahmad, Shabir
    et al.
    Jeju National University, Jeju, South Korea.
    Hussain, Ishfaq
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Fayaz, Muhammad
    Jeju National University, Jeju, South Korea.
    Kim, Do-Hyeun
    Jeju National University, Jeju, South Korea.
    A Distributed Approach towards Improved Dissemination Protocol for Smooth Handover in MediaSense IoT Platform2018In: Processes, ISSN 2227-9717, Vol. 6, no 5, article id 46Article in journal (Refereed)
    Abstract [en]

    Recently, the Internet has been utilized by many applications to convey time-sensitive messages. The persistently expanding Internet coverage and its easy accessibility have offered to ascend to a problem which was once regarded as not essential to contemplate. Nowadays, the Internet has been utilized by many applications to convey time-sensitive messages. Wireless access points have widely been used but these access points have limitations regarding area coverage. So for covering a wider space, various access points need to be introduced. Therefore, when the user moves to some other place, the devices expected to switch between access points. Packet loss amid the handovers is a trivial issue. MediaSense is an Internet of Things distributed architecture enabling the development of the IoT application faster. It deals with this trivial handover issue by utilizing a protocol called Distributed Context eXchange Protocol. However, this protocol is centralized in nature and also suffers in a scenario when both sender and receiver address change simultaneously. This paper presents a mechanism to deal with this scenario and presents a distributed solution to deal with this issue within the MediaSense platform. The proposed protocol improves dissemination using retransmission mechanism to diminish packet loss. The proposed protocol has been delineated with a proof of concept chat application and the outcomes have indicated a significant improvement in terms of packet loss.

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  • 33.
    Ahmad, Waqas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Ghafoor, Mubeen
    COMSATS University Islamabad, Pakistan.
    Tariq, Syed Ali
    COMSATS University Islamabad, Pakistan.
    Hassan, Ali
    COMSATS University Islamabad, Pakistan.
    Sjöström, Mårten
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Olsson, Roger
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Computationally Efficient Light Field Image Compression Using a Multiview HEVC Framework2019In: IEEE Access, E-ISSN 2169-3536, Vol. 7, p. 143002-143014, article id 8853251Article in journal (Refereed)
    Abstract [en]

    The acquisition of the spatial and angular information of a scene using light eld (LF) technologies supplement a wide range of post-processing applications, such as scene reconstruction, refocusing, virtual view synthesis, and so forth. The additional angular information possessed by LF data increases the size of the overall data captured while offering the same spatial resolution. The main contributor to the size of captured data (i.e., angular information) contains a high correlation that is exploited by state-of-the-art video encoders by treating the LF as a pseudo video sequence (PVS). The interpretation of LF as a single PVS restricts the encoding scheme to only utilize a single-dimensional angular correlation present in the LF data. In this paper, we present an LF compression framework that efciently exploits the spatial and angular correlation using a multiview extension of high-efciency video coding (MV-HEVC). The input LF views are converted into multiple PVSs and are organized hierarchically. The rate-allocation scheme takes into account the assigned organization of frames and distributes quality/bits among them accordingly. Subsequently, the reference picture selection scheme prioritizes the reference frames based on the assigned quality. The proposed compression scheme is evaluated by following the common test conditions set by JPEG Pleno. The proposed scheme performs 0.75 dB better compared to state-of-the-art compression schemes and 2.5 dB better compared to the x265-based JPEG Pleno anchor scheme. Moreover, an optimized motionsearch scheme is proposed in the framework that reduces the computational complexity (in terms of the sum of absolute difference [SAD] computations) of motion estimation by up to 87% with a negligible loss in visual quality (approximately 0.05 dB).

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  • 34.
    Ahmad, Waqas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Olsson, Roger
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Sjöström, Mårten
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Towards a generic compression solution for densely and sparsely sampled light field data2018In: Proceedings of 25TH IEEE International Conference On Image Processing, 2018, p. 654-658, article id 8451051Conference paper (Refereed)
    Abstract [en]

    Light field (LF) acquisition technologies capture the spatial and angular information present in scenes. The angular information paves the way for various post-processing applications such as scene reconstruction, refocusing, and synthetic aperture. The light field is usually captured by a single plenoptic camera or by multiple traditional cameras. The former captures a dense LF, while the latter captures a sparse LF. This paper presents a generic compression scheme that efficiently compresses both densely and sparsely sampled LFs. A plenoptic image is converted into sub-aperture images, and each sub-aperture image is interpreted as a frame of a multiview sequence. In comparison, each view of the multi-camera system is treated as a frame of a multi-view sequence. The multi-view extension of high efficiency video coding (MVHEVC) is used to encode the pseudo multi-view sequence.This paper proposes an adaptive prediction and rate allocation scheme that efficiently compresses LF data irrespective of the acquisition technology used.

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  • 35.
    Ahmad, Waqas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Palmieri, Luca
    University of Padova, Italy.
    Koch, Reinhard
    Christian-Albrechts-University of Kiel, Germany.
    Sjöström, Mårten
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    The Plenoptic Dataset2018Data set
    Abstract [en]

    The dataset is captured using two different plenoptic cameras, namely Illum from Lytro (based on plenoptic 1.0 model) and R29 from Raytrix (based on plenoptic 2.0 model). The scenes selected for the dataset were captured under controlled conditions. The cameras were mounted onto a multi-camera rig that was mechanically controlled to move the cameras with millimeter precision. In this way, both cameras captured the scene from the same viewpoint.

  • 36.
    Ahmad, Waqas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Sjöström, Mårten
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Olsson, Roger
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Compression scheme for sparsely sampled light field data based on pseudo multi-view sequences2018In: OPTICS, PHOTONICS, AND DIGITAL TECHNOLOGIES FOR IMAGING APPLICATIONS V Proceedings of SPIE - The International Society for Optical Engineering, SPIE - International Society for Optical Engineering, 2018, Vol. 10679, article id 106790MConference paper (Refereed)
    Abstract [en]

    With the advent of light field acquisition technologies, the captured information of the scene is enriched by having both angular and spatial information. The captured information provides additional capabilities in the post processing stage, e.g. refocusing, 3D scene reconstruction, synthetic aperture etc. Light field capturing devices are classified in two categories. In the first category, a single plenoptic camera is used to capture a densely sampled light field, and in second category, multiple traditional cameras are used to capture a sparsely sampled light field. In both cases, the size of captured data increases with the additional angular information. The recent call for proposal related to compression of light field data by JPEG, also called “JPEG Pleno”, reflects the need of a new and efficient light field compression solution. In this paper, we propose a compression solution for sparsely sampled light field data. In a multi-camera system, each view depicts the scene from a single perspective. We propose to interpret each single view as a frame of pseudo video sequence. In this way, complete MxN views of multi-camera system are treated as M pseudo video sequences, where each pseudo video sequence contains N frames. The central pseudo video sequence is taken as base View and first frame in all the pseudo video sequences is taken as base Picture Order Count (POC). The frame contained in base view and base POC is labeled as base frame. The remaining frames are divided into three predictor levels. Frames placed in each successive level can take prediction from previously encoded frames. However, the frames assigned with last prediction level are not used for prediction of other frames. Moreover, the rate-allocation for each frame is performed by taking into account its predictor level, its frame distance and view wise decoding distance relative to the base frame. The multi-view extension of high efficiency video coding (MV-HEVC) is used to compress the pseudo multi-view sequences. The MV-HEVC compression standard enables the frames to take prediction in both direction (horizontal and vertical d), and MV-HEVC parameters are used to implement the proposed 2D prediction and rate allocation scheme. A subset of four light field images from Stanford dataset are compressed, using the proposed compression scheme on four bitrates in order to cover the low to high bit-rates scenarios. The comparison is made with state-of-art reference encoder HEVC and its real-time implementation X265. The 17x17 grid is converted into a single pseudo sequence of 289 frames by following the order explained in JPEG Pleno call for proposal and given as input to the both reference schemes. The rate distortion analysis shows that the proposed compression scheme outperforms both reference schemes in all tested bitrate scenarios for all test images. The average BD-PSNR gain is 1.36 dB over HEVC and 2.15 dB over X265.

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  • 37.
    Ahmad, Waqas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Vagharshakyan, Suren
    Tampere University of Technology, Finland.
    Sjöström, Mårten
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gotchev, Atanas
    Tampere University of Technology, Finland.
    Bregovic, Robert
    Tampere University of Technology, Finland.
    Olsson, Roger
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Shearlet Transform Based Prediction Scheme for Light Field Compression2018Conference paper (Refereed)
    Abstract [en]

    Light field acquisition technologies capture angular and spatial information ofthe scene. The spatial and angular information enables various post processingapplications, e.g. 3D scene reconstruction, refocusing, synthetic aperture etc at theexpense of an increased data size. In this paper, we present a novel prediction tool forcompression of light field data acquired with multiple camera system. The captured lightfield (LF) can be described using two plane parametrization as, L(u, v, s, t), where (u, v)represents each view image plane coordinates and (s, t) represents the coordinates of thecapturing plane. In the proposed scheme, the captured LF is uniformly decimated by afactor d in both directions (in s and t coordinates), resulting in a sparse set of views alsoreferred to as key views. The key views are converted into a pseudo video sequence andcompressed using high efficiency video coding (HEVC). The shearlet transform basedreconstruction approach, presented in [1], is used at the decoder side to predict thedecimated views with the help of the key views.Four LF images (Truck, Bunny from Stanford dataset, Set2 and Set9 from High DensityCamera Array dataset) are used in the experiments. Input LF views are converted into apseudo video sequence and compressed with HEVC to serve as anchor. Rate distortionanalysis shows the average PSNR gain of 0.98 dB over the anchor scheme. Moreover, inlow bit-rates, the compression efficiency of the proposed scheme is higher compared tothe anchor and on the other hand the performance of the anchor is better in high bit-rates.Different compression response of the proposed and anchor scheme is a consequence oftheir utilization of input information. In the high bit-rate scenario, high quality residualinformation enables the anchor to achieve efficient compression. On the contrary, theshearlet transform relies on key views to predict the decimated views withoutincorporating residual information. Hence, it has inherit reconstruction error. In the lowbit-rate scenario, the bit budget of the proposed compression scheme allows the encoderto achieve high quality for the key views. The HEVC anchor scheme distributes the samebit budget among all the input LF views that results in degradation of the overall visualquality. The sensitivity of human vision system toward compression artifacts in low-bitratecases favours the proposed compression scheme over the anchor scheme.

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  • 38.
    Ahmad, Waqas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Vagharshakyan, Suren
    Tampere Univ Technol, Korkeakoulunkatu 10, Tampere 33720, Finland..
    Sjöström, Mårten
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gotchev, Atanas
    Tampere Univ Technol, Korkeakoulunkatu 10, Tampere 33720, Finland..
    Bregovic, Robert
    Tampere Univ Technol, Korkeakoulunkatu 10, Tampere 33720, Finland..
    Olsson, Roger
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Shearlet Transform Based Prediction Scheme for Light Field Compression2018In: 2018 DATA COMPRESSION CONFERENCE (DCC 2018) / [ed] Bilgin, A Marcellin, MW SerraSagrista, J Storer, JA, IEEE, 2018, p. 396-396Conference paper (Refereed)
  • 39.
    Ahmad, Waqas
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Vagharshakyan, Suren
    Tampere University, Tampere, Finland.
    Sjöström, Mårten
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gotchev, Atanas
    Tampere University, Tampere, Finland.
    Bregovic, Robert
    Tampere University, Tampere, Finland.
    Olsson, Roger
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Shearlet Transform-Based Light Field Compression under Low Bitrates2020In: IEEE Transactions on Image Processing, ISSN 1057-7149, E-ISSN 1941-0042, Vol. 29, p. 4269-4280, article id 8974608Article in journal (Refereed)
    Abstract [en]

    Light field (LF) acquisition devices capture spatial and angular information of a scene. In contrast with traditional cameras, the additional angular information enables novel post-processing applications, such as 3D scene reconstruction, the ability to refocus at different depth planes, and synthetic aperture. In this paper, we present a novel compression scheme for LF data captured using multiple traditional cameras. The input LF views were divided into two groups: key views and decimated views. The key views were compressed using the multi-view extension of high-efficiency video coding (MV-HEVC) scheme, and decimated views were predicted using the shearlet-transform-based prediction (STBP) scheme. Additionally, the residual information of predicted views was also encoded and sent along with the coded stream of key views. The proposed scheme was evaluated over a benchmark multi-camera based LF datasets, demonstrating that incorporating the residual information into the compression scheme increased the overall peak signal to noise ratio (PSNR) by 2 dB. The proposed compression scheme performed significantly better at low bit rates compared to anchor schemes, which have a better level of compression efficiency in high bit-rate scenarios. The sensitivity of the human vision system towards compression artifacts, specifically at low bit rates, favors the proposed compression scheme over anchor schemes. The proposed compression scheme performed significantly better at low bit rates compared to anchor schemes, which have a better level of compression efficiency in high bit-rate scenarios. The sensitivity of the human vision system towards compression artifacts, specifically at low bit rates, favors the proposed compression scheme over anchor schemes. The proposed compression scheme performed significantly better at low bit rates compared to anchor schemes, which have a better level of compression efficiency in high bit-rate scenarios. The sensitivity of the human vision system towards compression artifacts, specifically at low bit rates, favors the proposed compression scheme over anchor schemes. 

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  • 40.
    Ahonen, Mikko
    et al.
    Institute of Environmental Health and Safety, Tallinn, Estonia.
    Koppel, Tarmo
    Tallinn University of Technology, Estonia.
    Voltage transients measurements and power line communication2016In: 2016 57th International Scientific Conference on Power and Electrical Engineering of Riga Technical University (RTUCON), IEEE, 2016, p. 1-4Conference paper (Refereed)
    Abstract [en]

    Power line communication (PLC) connects energy producers with energy consumers. In the European Union stricter guidelines are under development to limit disturbances in the 2-150 kHz frequency range, because devices utilising PLC do not work. This study measured voltage transients in 22 locations and identified sources for noise. Home environments and public buildings were measured. Measurements were conducted in the frequency range of 150 kHz-500 kHz (according to EN 55011 to EN 55022) and in the lower frequency range of 3 kHz to 95 kHz. Results indicate that voltage transients are generated mostly by switching mode power supplies, pumps, rectifiers, inverters and even low quality smart meters. Several of these devices exceeded PLC standard level, 122 dBμV. Additionally we demonstrate that basic power quality recordings do not provide enough information to mitigate PLC problems occurring within microseconds and frequency specific voltage transient measurements are needed.

  • 41.
    Ak, Ali
    et al.
    Nantes Université, École Centrale Nantes, CNRS, LS2N, UMR 6004, Nantes, France.
    Zerman, Emin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and Electrical Engineering (2023-).
    Quach, Maurice
    Université Paris-Saclay, CNRS, CentraleSupélec, Laboratoire des Signaux et Systèmes (UMR 8506), Gif-sur-Yvette, France.
    Chetouani, Aladine
    Laboratoire PRISME, Université d'Orléans, Orléans, France.
    Smolic, Aljosa
    Lucerne University of Applied Sciences and Arts (HSLU), Rotkreuz, Switzerland.
    Valenzise, Giuseppe
    Université Paris-Saclay, CNRS, CentraleSupélec, Laboratoire des Signaux et Systèmes (UMR 8506), Gif-sur-Yvette, France.
    Le Callet, Patrick
    Nantes Université, École Centrale Nantes, CNRS, LS2N, UMR 6004, Nantes, France.
    BASICS: Broad Quality Assessment of Static Point Clouds in a Compression Scenario2024In: IEEE transactions on multimedia, ISSN 1520-9210, E-ISSN 1941-0077Article in journal (Refereed)
    Abstract [en]

    Point clouds have become increasingly prevalent in representing 3D scenes within virtual environments, alongside 3D meshes. Their ease of capture has facilitated a wide array of applications on mobile devices, from smartphones to autonomous vehicles. Notably, point cloud compression has reached an advanced stage and has been standardized. However, the availability of quality assessment datasets, which are essential for developing improved objective quality metrics, remains limited. In this paper, we introduce BASICS, a large-scale quality assessment dataset tailored for static point clouds. The BASICS dataset comprises 75 unique point clouds, each compressed with four different algorithms including a learning-based method, resulting in the evaluation of nearly 1500 point clouds by 3500 unique participants. Furthermore, we conduct a comprehensive analysis of the gathered data, benchmark existing point cloud quality assessment metrics and identify their limitations. By publicly releasing the BASICS dataset, we lay the foundation for addressing these limitations and fostering the development of more precise quality metrics.

  • 42.
    Akbari-Saatlu, Mehdi
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Procek, Marcin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. Silesian University of Technology, 2 Krzywoustego St., 44-100 Gliwice, Poland.
    Mattsson, Claes
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Xiong, Wenjuan
    Guangdong Greater Bay Area Institute of Integrated Circuit and System; Chinese Academy of Sciences; University of Chinese Academy of Sciences.
    Xu, Buqing
    Guangdong Greater Bay Area Institute of Integrated Circuit and System; Chinese Academy of Sciences; University of Chinese Academy of Sciences.
    Li, You
    Guangdong Greater Bay Area Institute of Integrated Circuit and System; Chinese Academy of Sciences; University of Chinese Academy of Sciences.
    Radamson, Henry H.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. Guangdong Greater Bay Area Institute of Integrated Circuit and System; Chinese Academy of Sciences; University of Chinese Academy of Sciences.
    Silicon Nanowires for Gas Sensing: A Review2020In: Nanomaterials, E-ISSN 2079-4991, Vol. 10, no 11, article id 2215Article, review/survey (Refereed)
    Abstract [en]

    The unique electronic properties of semiconductor nanowires, in particular silicon nanowires (SiNWs), are attractive for the label-free, real-time, and sensitive detection of various gases. Therefore, over the past two decades, extensive efforts have been made to study the gas sensing function of NWs. This review article presents the recent developments related to the applications of SiNWs for gas sensing. The content begins with the two basic synthesis approaches (top-down and bottom-up) whereby the advantages and disadvantages of each approach have been discussed. Afterwards, the basic sensing mechanism of SiNWs for both resistor and field effect transistor designs have been briefly described whereby the sensitivity and selectivity to gases after different functionalization methods have been further presented. In the final words, the challenges and future opportunities of SiNWs for gas sensing have been discussed.

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  • 43. Akhtar, M. W.
    et al.
    Hassan, S. A.
    Jung, H.
    On the symbol error probability of stbc-noma with timing offsets and imperfect successive interference cancellation2021In: Electronics, E-ISSN 2079-9292, Vol. 10, no 12, article id 1386Article in journal (Refereed)
    Abstract [en]

    Due to the ability to handle a large number of users, low latency, and high data rates, NON-orthogonal multiple access (NOMA) is considered a promising access technology for next-generation communication systems. However, as the number of users increases, each user experiences a greater number of successive interference cancellations (SIC), causing the system’s performance to decline. With the increase in the number of users, the fraction of power allocated to each user becomes smaller. Cooperative communication in downlink NOMA is considered as a potential approach to enhance the reliability, capacity, and performance over wireless channels. Space-time block code (STBC)-aided cooperative NOMA (CNOMA) offers an opportunity to improve the weak users’ signal-to-interference-plus-noise (SINR) through strong user cooperation. In this paper, we study the symbol error probability (SEP) performance of the STBC-NOMA and derive the asymptotic expression for SEP when the network is impaired with imperfect SIC (ipSIC) and timing offsets. The simulation results show that the performance of STBC-NOMA was degraded significantly with an increase in the imperfection of SIC and timing errors and that traditional orthogonal access schemes, such as orthogonal frequency division multiple access (OFDMA) and time division multiple access (TDMA), should be used after a threshold SIC level. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

  • 44. Akhtar, M. W.
    et al.
    Hassan, S. A.
    Jung, H.
    Pervaiz, H.
    On the Performance of Alamouti-Coded Cooperative NOMA with Imperfect Channel State Information2021In: 2021 IEEE International Conference on Communications Workshops, ICC Workshops 2021 - Proceedings, Institute of Electrical and Electronics Engineers Inc. , 2021Conference paper (Refereed)
    Abstract [en]

    As the number of mobile devices grows exponentially, it is critical to design a robust access scheme that can handle a large number of devices with low latency. Non-orthogonal multiple access (NOMA) is an effective approach to meet such requirements that can provide higher spectral efficiency. As an extended version, cooperative NOMA has been introduced, where the users with higher channel gains forward signals for users with weak channel gains as cooperators. The conventional cooperative NOMA (CCN) technique can provide diversity gains, which can be used to improve reliability. However, in CCN, the overhead caused by successive interference cancellations (SIC) at each user may become significant, when there exist a massive number of users, which eventually degrades the performance of NOMA considering the power and computational resource limitations of mobile devices. As an alternative, the space-time block-coded NOMA (STBC-NOMA) has been proposed to achieve diversity gain with lower SIC overhead compared to CCN. To better evaluate it, in this paper, we investigate the impact of imperfect channel state information (ipCSI), which is more realistic in real-time processing. We dervie the closed-form expression of the outage probability of STBC-NOMA with ipCSI and compare its performance with CCN and conventional NOMA. © 2021 IEEE.

  • 45. Akhtar, M. W.
    et al.
    Hassan, S. A.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Jung, H.
    Qureshi, H. K.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Q2A-NOMA: A Q-Learning-based QoS-Aware NOMA System Design for Diverse Data Rate Requirements2022In: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, Vol. 18, no 11, p. 7549-7559Article in journal (Refereed)
    Abstract [en]

    Wireless use cases in industrial internet-of-thing (IIoT) networks often require guaranteed data rates ranging from a few kilobits per second to a few gigabits per second. Supporting such a requirement in a single radio access technique is difficult, especially when bandwidth is limited. Although non-orthogonal multiple access (NOMA) can improve the system capacity by simultaneously serving multiple devices, its performance suffers from strong user interference. In this paper, we propose a Q-learning-based algorithm for handling many-to-many matching problems such as bandwidth partitioning, device assignment to sub-bands, interference-aware access mode selection (orthogonal multiple access (OMA), or NOMA), and power allocation to each device. The learning technique maximizes system throughput and spectral efficiency (SE) while maintaining quality-of-service (QoS) for a maximum number of devices. The simulation results show that the proposed technique can significantly increase overall system throughput and SE while meeting heterogeneous QoS criteria. 

  • 46.
    Akhtar, Muhammad Waseem
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Abedin, Sarder
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Hassan, Syed Ali
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Exploiting NOMA for Radio Resource Efficient Traffic Steering Use-case in O-RAN2022In: 2022 IEEE Global Communications Conference, GLOBECOM 2022 - Proceedings, IEEE conference proceedings, 2022, p. 5771-5776Conference paper (Refereed)
    Abstract [en]

    In this work, we consider the design of a radio resource management (RRM) solution for traffic steering (TS) use-case in the open radio access network (O-RAN). The O-RAN TS deals with the quality-of-service (QoS)-aware steering of the traffic by connectivity management (e.g., device-to-cell association, radio spectrum, and power allocation) for emerging heterogeneous networks (HetNets) in 5G-and-beyond systems. However, TS in HetNets is a complex problem in terms of efficiently assigning/utilizing the radio resources while satisfying the diverse QoS requirements of especially the cell-edge users due to their poor signal-to-interference-plus-noise ratio (SINR). In this respect, we propose an intelligent non-orthogonal multiple access (NOMA)-based RRM technique for a small cell base station (SBS) within a macro gNB. A Q-learning-assisted algorithm is designed to allocate the transmit power and frequency sub-bands at the O-RAN control layer such that interference from macro gNB to SBS devices is minimized while ensuring the QoS of the maximum number of devices. The numerical results show that the proposed method enhances the overall spectral efficiency of the NOMA-based TS use case without adding to the system's complexity or cost compared to traditional HetNet topologies such as co-channel deployments and dedicated channel deployments. 

  • 47.
    Akhtar, Muhammad Waseem
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and Electrical Engineering (2023-).
    Saeed, Nasir
    United Arab Emirates Univ, Dept Elect & Commun Engn, Al Ain 15551, U Arab Emirates..
    UAVs-Enabled Maritime Communications: UAVs-Enabled Maritime Communications: Opportunities and Challenges2023In: IEEE SYSTEMS MAN AND CYBERNETICS MAGAZINE, ISSN 2380-1298, Vol. 9, no 3, p. 2-8Article in journal (Refereed)
    Abstract [en]

    The next generation of wireless communication systems will integrate terrestrial and nonterrestrial networks, targeting the coverage of the undercovered regions, especially those connected to marine activities. Unmanned aerial vehicle (UAV)-based connectivity solutions offer significant advances to support conventional terrestrial networks. However, the use of UAVs for maritime communication is still an unexplored area of research. Therefore, this article highlights different aspects of UAV-based maritime communication, including the basic architecture, various channel characteristics, and use cases. The article afterward discusses several open research problems, such as mobility management, trajectory optimization, interference management, and beam forming.

  • 48.
    Akram, Farhan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Gate driver solutions for high power density SMPS using Silicon Carbide MOSFETs2021Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Discrete silicon carbide (SiC) power devices have unique characteristics that outpace those of silicon (Si) counterparts. The improved physical features have provided better faster switching, greater current densities, lower on-resistance, and temperature performances. However, there is lack of suitable commercial gate drivers that are compatible for high-voltage, and high-speed devices. There has been a great research effort required for the advancement of gate drivers for high voltage SiC transistors. A drive circuit for a SiC MOSFET needs to be optimized in normal operation to give best efficiency and same drive circuit should secure the MOSFET under unsuitable conditions. To ensure the rapid switching of these advanced SiC MOSFETs, a gate driver capable of providing the high current capability is required. In this work, three different high-power-density, high-speed, and high-noise-immunity gate driver modules for 10 kV SiC MOSFET were built and optimized.  Double-pulse test was developed for the dynamic characterization of SiC MOSFETs and gate drivers. This setup provided clean measurements of DUT voltage and current under well-defined conditions and correlated to simulation results. Designed gate drivers have thoroughly investigated to test and compare it with our future design. The influential parameters such as dV/dt, dI/dt, and gate driving capability of gate driver were adjusted according to the requirements. The short circuit protection test was performed to check the reliability of driver modules in worst conditions. Furthermore, a DC-DC converter was designed and tested with the advanced gate drivers. The driver modules were tested in designed converter under different load conditions and influential parameters were successfully demonstrated. The driver modules effectively helped in reducing the EMI and switching losses. These designed gate drivers and prototype converter provide all the attractive features and can be widely implemented in industrial applications for energy efficient systems.

     

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  • 49.
    Akram, Shazad
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Alam, Farhan Muhammad
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Bertilsson, Kent
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Sidén, Johan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Capacitive and optical sensing for automatic detection and characterization of cleaning sponges in fiber optic microduct installations2019In: Proceedings - 2019 8th International Workshop on Advances in Sensors and Interfaces, IWASI 2019, IEEE, 2019, p. 274-278, article id 8791315Conference paper (Refereed)
    Abstract [en]

    Optical fiber duct installation requires blowing of cleaning sponges for dirt and moisture removal before blowing the fiber cables. The traditional method requires one operator that blows the sponge and one operator in the receiving end that manually evaluate the sponges until a dry sponge is received. The proposed system eliminates the need of a second operator by introducing a solution for automatic sponge detection and characterization of moisture in sponges at the receiving end. An optical sensor is used for detection and a capacitive sensor is developed to measure the sponge's wetness. Sensor data is automatically transmitted back to the operator at the feeding end via a mobile phone. The system is characterized to work with sponges ranging from saturated with wetness to what is deemed as dry. 

  • 50.
    Alain, Martin
    et al.
    Huawei Ireland Research Centre, Dublin, Ireland.
    Zerman, Emin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Computer and Electrical Engineering (2023-).
    Ozcinar, Cagri
    Samsung R&D UK, London, United Kingdom.
    Valenzise, Giuseppe
    CentraleSupelec, Laboratoire des Signaux et Systemes, Universite Paris-Saclay, CNRS, France.
    Introduction to Immersive Video Technologies2023In: Immersive Video Technologies / [ed] Giuseppe Valenzise, Martin Alain, Emin Zerman, Cagri Ozcinar, Cambridge, Massachusetts, USA: Academic Press, 2023, 1, p. 3-24Chapter in book (Other academic)
    Abstract [en]

    Immersive imaging technologies have become a topic of great interest in recent years due to the convergence of maturing research from different fields and broad aspects of signal and image processing, including but not limited to: computer vision, computer graphics, computational imaging, optics, and recent advances in deep learning. In particular, recent research and developments in these areas helped achieve better or faster content creation and image/video processing. This enables the design of complete practical systems covering capture to display for immersive imaging. In this chapter, we provide the theoretical background for the rest of the book and introduce key concepts commonly used for traditional imaging systems and immersive video technologies. We also describe the stages of the immersive imaging technologies from content capture to display and quality assessment for three immersive imaging technologies: omnidirectional video, light fields, and volumetric (also known as free-viewpoint) video.

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