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  • 101. Andrén, Linus
    et al.
    Håkansson, Lars
    Brandt, Anders
    Claesson, Ingvar
    Identification of Dynamic Properties of Boring Bar Vibrations in a Continuous Boring Operation2004In: Mechanical systems and signal processing, ISSN 0888-3270, E-ISSN 1096-1216, Vol. 18, no 4, p. 869-901Article in journal (Refereed)
    Abstract [en]

    Vibrations in internal turning operations are usually a cumbersome part of the manufacturing process. This article focuses on the boring bar vibrations. Boring bar vibrations in alloyed steel, stainless steel and cast iron have been measured in both the cutting speed direction and the cutting depth direction with the aid of accelerometers. The dynamic response of a boring bar seem to be a time varying process that exhibits non-linear behaviour. The process is influenced by non-stationary parameters that are not under the control of the operator or experimenter. The vibrations are clearly dominated by the first resonance frequency in one of the two directions of the boring bar. The problem with force modulation in rotary machinery, which appears as side band terms in the spectrum, is also addressed. Furthermore, the resonance frequencies of the boring bar are correlated to an Euler-Bernoulli beam model.

  • 102. Andrén, Linus
    et al.
    Håkansson, Lars
    Brandt, Anders
    Claesson, Ingvar
    Identification of Motion of Cutting Tool Vibration in a Continuous Boring Operation: Correlation to structural Properties2004In: Mechanical systems and signal processing, ISSN 0888-3270, E-ISSN 1096-1216, Vol. 18, no 4, p. 903-27Article in journal (Refereed)
    Abstract [en]

    The internal turning operation has a history of being a cumbersome metal working process as vibration in boring operations is usually inevitable. In this article, the deflection shapes and/or mode shapes as well as the resonance frequencies of a boring bar have been put under scrutiny. Three methods have been used in order to investigate dynamic properties of a clamped boring bar: a theoretical Euler-Bernoulli beam model, an experimental modal analysis and an operating deflection shape analysis. \\ The results indicate a correlation between the shapes of the deflection shapes and/or mode shapes produced by the three different analysis methods. On the other hand, the orientation of the forced deflection shapes and/or mode shapes and the resonance frequencies demonstrates differences between the three methods. During continuous cutting, it is demonstrated that the bending motion of the first two resonance frequencies is to a large extent in the cutting speed direction.

  • 103. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Active Control of Boring Bar Vibrations Using the Leaky Feedback Filtered X-LMS2003Conference paper (Refereed)
    Abstract [en]

    The boring operation is a cumbersome manufacturing process marred by noise and vibration related problems. The manufacturing industry is having trouble with these kinds of metal cutting operations. There exist several approaches to reduce the vibrations in cutting operations in general. Passive tuned dampers in boring bars have been commercially available for some time. An active solution is likely to be more robust to changes in the spectral content, where the passive counterpart have a small operable area, the active solution is able to adapt to these kinds of changes. Active vibration control in boring operations has been proven to be feasible. The algorithm used in the successful experiments was the feedback filtered X-LMS algorithm. This algorithm does however not guarantee a stable behavior, but incorporating a leakage factor will make the algorithm more robust. Power spectral density of boring bar vibration of real cutting experiments show that the leaky filtered X-LMS algorithm is a possible candidate to be a suitable control algorithm. Nyquist diagrams of the controller during operation show that the stability is increased significantly.

  • 104. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Active Control of Machine Tool Vibrations in External Turning Operations2003In: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, ISSN 0954-4054, E-ISSN 2041-2975, Vol. 217, no 6, p. 869-872Article in journal (Refereed)
    Abstract [en]

    Vibration and noise in metal cutting are ubiquitous problems in the workshop. The external turning operation is one kind of metal cutting that exhibits vibration related problems. Severe noise is also a problem growing in proportion due to regulations in preventing hearing loss. Active vibration control is a potential solution to such problems. With the piezo ceramic actuator technology of today, the size of the actuator can be kept small and still be able to produce a sufficient amount of force for the anti vibrations. Results from several continuous cutting experiments show a 40 dB reduction of the cutting tool vibration level. The design of the active technique enables this technology to be applicable to a general lathe provided the mounting arrangement is fairly similar.

  • 105. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Actuator placements and Variations in the Control Path estimates in the Active Control of Boring Bar Vibrations2004Conference paper (Refereed)
    Abstract [en]

    A classical example of chatter prone machining is the boring operation. Turning under conditions with high vibrations in the cutting tool deteriorates the surface finish and may cause tool breakage. Severe noise is also a consequence of the high vibration levels in the boring bar. Active control is one possible solution to the noise and vibration problem in boring operations. In boring operations the boring bar usually have vibration components in both the cutting speed and the cutting depth direction. The introduction of the control force in different angles in between the cutting speed and the cutting depth directions have been investigated. Furthermore, control path estimates produced when the active boring bar was not in contact with the workpiece and during continuous cutting operation are compared. Experimental results indicate that the control force should be introduced in the cutting speed direction. Although the vibrations are controlled in just the cutting speed direction the vibrations in the cutting depth direction are also reduced significantly.

  • 106. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Performance Evaluation of Active Vibration Control of Boring Operations Using Different Active Boring Bars2003Conference paper (Refereed)
    Abstract [en]

    Vibration and noise in boring operations are ubiquitous problems in the workshop. In boring operations, the boring bar is subjected to forces from both the cutting speed and the cutting depth direction. To solve the vibration problem using active techniques would normally require two actuators in order to enable the control of both directions. By mounting one actuator in between the cutting speed and the cutting depth direction it is possible to achieve an active control solution with one actuator. Using only one actuator not only simplifies the control algorithm and saves extra equipment but is also favourable in terms of modifications of the boring bar. The harsh environment in a lathe more or less requires that both sensors and actuators are embedded and sealed into the boring bar. Since the forces that are to be controlled are large, the space needed for the actuator is substantial. Thus using only one actuator will keep the modified boring bar stiffer than a two actuator design. Three boring bars with the actuator mounted at different angles between the cutting speed and the cutting depth directions have been tested. Results from cutting experiments show that the one actuator solution has good potentials to the vibration problem in boring operations.

  • 107. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Lagö, Thomas L
    Piezo Ceramic Actuators versus High Magnetostrictive Actuators in the Active control of Tool Vibration1999Conference paper (Refereed)
    Abstract [en]

    In the turning operation chatter or vibration is a frequent problem, which affects the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. In the active control system for the control of tool vibration a tool holder construction with integrated high magnetostrictive actuators was used. However, high magnetostrictive actuators generally have a non-linear behavior and it is a well known fact that non-linear properties in the forward path in an active control system is likely to degrade the robustness of the control system. A new generation embedded active tool holder shanks based on piezo ceramic actuators has been developed. Based on spectrum estimates, both coherence spectrum and frequency response function estimates has been calculated for both the old tool holder construction and the new generation active tool holder shank. From the results it follows that the phase delay is smaller and the linearity of the new generation active tool holder shank are superior compared to the old technology. The physical features and properties of the new generation active tool holders are superior to the old tool holder.

  • 108. Andrén, Linus
    et al.
    Johansson, Sven
    Winberg, Mathias
    Claesson, Ingvar
    Active Noise Control Experiments in a Fork-lift Truck Cabin2004Conference paper (Refereed)
    Abstract [en]

    High comfort for the driver in working vehicles is an important feature as well as a demand from the drivers. Low noise level is an essential factor for the manufacturer to maintain a high standard and comfort of vehicles. In many cases the noise inside the cabin can be related to the engine orders. Hydraulic pumps and fans are also related to the engine but not necessarily integers of the engine order. Passive absorbers are not suitable for the lowest frequencies and one approach is to use an active noise control system to solve the noise problem at low frequencies. In the present experiment loudspeakers were mounted inside the cabin of a fork lift-truck to produce the secondary noise field. To sense the residual noise, microphones were installed close to the driver's head. The aim is to create a zone of reduced noise around the head. Since a large portion of the noise inside the cabin can be related to the engine, an active control system based on a feedforward solution is possible. Experimental results from a feedforward solution of active noise control in a fork-lift truck cabin show that the noise level in the low frequency region can be reduced significantly.

  • 109. Angelin, Lars
    On the Properties of a Congestion Control Mechanism for Signaling Networks Based on a State Machine1996Report (Other academic)
    Abstract [en]

    Congestion control in signaling systems is a necessity to fulfil the requirements of a tele-communication network that aims satisfy the customers’ requirements on service quality. Heavy network load is an important source of customer dissatisfaction as congested net-works result in deteriorated service quality. Sessions of a signaling service with high real time demands which are subject to unacceptable delays may be obsolete or prematurely terminated by the customer; in either way, they are a burden to the signaling network. It would ease the load of the network and improve the performance of all sessions in progress, if such delayed sessions could be aborted as quickly as possible. By measuring the network delay on individual signals of a service session, it is possible to perform signaling network congestion control that considers the state in the entire signaling network. Under the assumption that a session comprises a sequence of signals between one originating node and an arbitrary number of destination nodes, it is possible to predict the total duration of a session. The prediction is calculated from previously completed signals using a state machine, which is defined per signaling link. The annihilation of sessions, for which the prediction exceeds a predefined time limit, is an embryo of a simple signaling network congestion control mechanism (CCM). This simple CCM increases the number of successfully completed services with several hundred percent under favorable circum-stances. The state machine approach is proven to perform well in all types of environ-ments. The robustness and stability of the proposed CCM is demonstrated in a wide range of environments. The fairness in the admission of signaling services into the network at very high loads are also shown to be good.

  • 110. Angelin, Lars
    et al.
    Arvidsson, Åke
    A Congestion Control Algorithm for Signalling Networks Based on a State Machine Controlled by Network Delays1995Conference paper (Refereed)
    Abstract [en]

    Congestion control in Signaling System number 7 faces new challenges as mobile com-munication systems and Intelligent Networks grow rapidly. New services change traffic patterns, add to signalling network load, and raise demands on shorter service completion times. To handle new demands, the congestion control mechanisms must foresee an over-load situation, and respond to it so that the network can maintain high throughput. With the introduction of a state machine and a memory function for each signaling link it is possible to predict the completion time of a service session and to detect an emerging congestion. If the predicted completion time of a service session is too long, the session is annihilated. This is the foundation of a congestion control mechanism that reacts fast on information supplied by the network. The congestion control mechanism enables the network to main-tain a high throughput during overload.

  • 111. Angelin, Lars
    et al.
    Arvidsson, Åke
    A Congestion Control Mechanism for Signaling Networks based on Network Delays1995Conference paper (Refereed)
    Abstract [en]

    Congestion control in Signaling System #7 faces new challenges as mo-bile communication systems and Intelligent Networks grow rapidly. New ser-vices change traffic patterns, add to signalling network load, and raise demands on shorter service completion times. To handle new demands, the congestion control mechanisms must foresee an overload situation, and respond to it so that the network can maintain high probability for successful service comple-tion. With the introduction of a state machine and a memory function for each signaling link it is possible to predict the completion time of a service session and to detect an emerging congestion. If the predicted completion time of a service session is too long, the session is annihilated. This is the foundation of a congestion control mechanism that reacts fast on information supplied by the congested part of the network. The congestion control mechanism increases the ratio of successfully completed service sessions during congestion by several hundred percent.

  • 112. Angelin, Lars
    et al.
    Arvidsson, Åke
    On the Robustness of a Congestion Control Algorithm for Signaling Networks Based on a State Machine1996Conference paper (Refereed)
    Abstract [en]

    Sessions of a signaling service with high real time demands which are subject to unaccept-able delays may be obsolete or prematurely terminated by the customer; in either way, they are a burden to the signaling network. It would ease the load of the network and im-prove the performance of all sessions in progress, if such delayed sessions could be abort-ed as quickly as possible. By measuring the network delay on individual signals of a service session, it is possible to perform signaling network congestion control that consid-ers the state in the entire signaling network. Under the assumption that a session comprises a sequence of signals between one originating node and an arbitrary number of destination nodes, it is possible to predict the total duration of a session. The prediction is calculated from previously completed signals using a state machine, which is defined per signaling link. The annihilation of sessions, for which the prediction exceeds a predefined time limit, is an embryo of a simple signaling network congestion control mechanism (CCM). This simple CCM increases the number of successfully completed services with a few hundred percent under favorable circumstances. The state machine approach has been proven to function well in all types of environments. The robustness and stability of the proposed CCM is demonstrated and the fairness in the admission of signaling services into the net-work at very high loads are also shown.

  • 113. Angelin, Lars
    et al.
    Pettersson, Stefan
    Arvidsson, Åke
    A Network Approach to Signalling Network Congestion Control1995Conference paper (Refereed)
    Abstract [en]

    Congestion control in Signaling System #7 faces new challenges as mobile communication systems and Intelligent Networks grow rapidly. New services change traffic patterns, add to signalling network load, and raise demands on shorter service completion times. To handle new demands, the congestion control mechanisms must foresee an overload situation, and respond to it so that the net-work can maintain high probability for successful service completion. By measur-ing the time consumption for the initial Message Signalling Units of a service session it is possible to predict the duration of the service session and to detect an emerging congestion. If the predicted duration of the service session is too long, the service session is annihilated. This is the foundation of a congestion control mechanism that reacts fast and on information supplied by the congested part of the network. The congestion control mechanism increases the ratio of successfully completed services during congestion by several hundred percent.

  • 114.
    Ansari, Yousuf Hameed
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Siddiqui, Sohaib Ahmed
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Quality Assessment for HEVC Encoded Videos: Study of Transmission and Encoding Errors2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There is a demand for video quality measurements in modern video applications specifically in wireless and mobile communication. In real time video streaming it is experienced that the quality of video becomes low due to different factors such as encoder and transmission errors. HEVC/H.265 is considered as one of the promising codecs for compression of ultra-high definition videos. In this research, full reference based video quality assessment is performed. The raw format reference videos have been taken from Texas database to make test videos data set. The videos are encoded using HM9 reference software in HEVC format. Encoding errors has been set during the encoding process by adjusting the QP values. To introduce packet loss in the video, the real-time environment has been created. Videos are sent from one system to another system over UDP protocol in NETCAT software. Packet loss is induced with different packet loss ratios into the video using NETEM software. After the compilation of video data set, to assess the video quality two kind of analysis has been performed on them. Subjective analysis has been carried on different human subjects. Objective analysis has been achieved by applying five quality matrices PSNR, SSIM, UIQI, VFI and VSNR. The comparison is conducted on the objective measurement scores with the subjective and in the end results deduce from classical correlation methods.

  • 115.
    Ansere, James Adu
    et al.
    Blekinge Institute of Technology, School of Engineering.
    Ehimiaghe, Odion
    Blekinge Institute of Technology, School of Engineering.
    APPLYING DISTRIBUTED ORTHOGONAL SPACE TIME BLOCK CODING IN COOPERATIVE COMMUNICATION NETWORKS2012Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    In this research, we investigate cooperative spectrum sensing using distributed orthogonal space time block coding (DOSTBC). Multiple antennas are introduced at the transmitter and the receiver to achieve higher cooperative diversity in the cooperative wireless (CW) networks. The received signals from the primary users (PUs) at the cooperative relays (CRs) are encoded and retransmitted to the cooperative controller (CC), where further decisions are made depending on the information sent from the CRs. The cooperative relaying protocol employed here in CRs is based on decoding forward (DF) technique. The proposed Alamouti scheme in orthogonal space time block code (OSTBC) has been found to enhance detection performance in CW networks. The analyses over independent Rayleigh fading channels are performed by the energy detector. In CW networks the secondary users (SUs) use the available frequency band as the PUs is absent. The SU discontinue using the licensed band and head off as soon as the PU is present. The SUs is more responsive and intelligent in detecting the spectrum holes. The principal aim of the CW network is to use the available holes without causing any interference to the PUs. The CRs are preferably placed close to the PU to detect transmitted signal, with decoding capability the information collected are decoded by CRs using Maximum Likelihood (ML) decoding technique. The CRs then re-encode the decoded data and retransmit it to the receiver. The energy detector accumulates information from various users, compares it using threshold value (T_f) predefined and the final decision made. The probabilities of detection and false alarm are observed using DOSTBC on PU and SU in cooperative communication via DF protocol. The system performance is investigated with single and multiple relays; with and without direct path between the PUs and SUs. Selection Combining (SC) and Maximum Ratio Combining (MRC) schemes are applied in energy detector and the outcomes are evaluated with and without direct link between PU and SU. The proposed cooperative spectrum sensing using DF protocol at CRs with Alamouti space time block code (STBC) is processed and results are validated by computer simulation.

  • 116.
    Anwar, Khurshid
    et al.
    Blekinge Institute of Technology, School of Computing.
    Khan, Asad
    Blekinge Institute of Technology, School of Computing.
    AC and QAR for Provisioning of QoS in MANETs2010Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Mobile Ad-hoc network (MANET) is a collection of mobile nodes which communicate over wireless channels without any centralized control or existing infrastructure. The freely movement of nodes allow them to join or leave the network independently. Due to node mobility, wireless channels and limited resources makes the provision of Quality of Services (QoS) in MANETs very challenging. With the emerging use of multimedia applications over MANETs which requires different types of QoS provision from the networks. The Admission Control (AC) and QoS-Aware routing (QAR) protocols have made a progress in provision of QoS up to some extents. In this thesis, various AC and QAR protocols are reviewed and their characteristics and limitations are identified. We also make a comparison between DSR and AODV routing protocols in different network scenarios.

  • 117.
    Anwar, Mahwish
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science.
    Connect2SmallPorts: An EU Project on Digitalizing Small Ports of the South Baltic Region. Poster ID: P20-206202020Other (Other (popular science, discussion, etc.))
    Abstract [en]

    Ports play pivotal role in the global supply chain network. To strengthen the ports’ business and to keep up with the overall economic development of the country, the port stakeholders have started to invest in the digital technologies. The ports as well as the individual municipalities in Europe are in contest with other ports within the region. One of the competing factors is that of the port’s technological development. Unlike large ports, the small ports within Europe, for example Port of Karlskrona, Port of Wismar or Port of Klaipeda, which also serve as crucial nodes within the trade flow for Sweden, Germany and Lithuania respectively, lack the knowledge and tools to leverage the potential of digital technologies. The digital disruption at ports is inevitable!

    With that being established the scope of the project - South Baltic Small Ports as Gateways towards Integrated Sustainable European Transport System and Blue Growth by Smart Connectivity Solutions – or Connect2SmallPorts project is to understand how to facilitate small and medium ports of the South Baltic region with the digital technologies - Blockchain and Internet of Things. During the project lifetime (2018 to 2021) the main goals are to perform the digital audit of small ports of the South Baltic region; to prepare an implementation strategy for Blockchain and Internet of Things specifically for the small ports in the South Baltic region and to conduct an evaluation of the proposed strategies. The project correspondingly aims to disseminate the knowledge and experiences through research publications, industrial conferences and international tradeshows.

  • 118.
    Anwar, Mahwish
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science.
    Connect2smallports Project: South Baltic Small Ports – Gateway to Integratedand Sustainable European Transport System: Project brief and updates on the project activities: Digital Audit. Blockchain Design Strategy. Call for Collaboration. Reports and scientific publications.2019Other (Other (popular science, discussion, etc.))
    Abstract [en]

    Ports play pivotal role in the global supply chain network. To strengthen the ports’ business and to keep up with the overall economic development of the country, the port stakeholders have started to invest in the digital technologies. The ports as well as the individual municipalities in Europe are in contest with other ports within the region. One of the competing factors is that of the port’s technological development. Unlike large ports, the small ports within Europe, for example Port of Karlskrona, Port of Wismar or Port of Klaipeda, which also serve as crucial nodes within the trade flow for Sweden, Germany and Lithuania respectively, lack the knowledge and tools to leverage the potential of digital technologies. The digital disruption at ports is inevitable!

    With that being established the scope of the project - South Baltic Small Ports as Gateways towards Integrated Sustainable European Transport System and Blue Growth by Smart Connectivity Solutions – or Connect2SmallPorts project is to understand how to facilitate small and medium ports of the South Baltic region with the digital technologies - Blockchain and Internet of Things. During the project lifetime (2018 to 2021) the main goals are to perform the digital audit of small ports of the South Baltic region; to prepare an implementation strategy for Blockchain and Internet of Things specifically for the small ports in the South Baltic region and to conduct an evaluation of the proposed strategies. The project correspondingly aims to disseminate the knowledge and experiences through research publications, industrial conferences and international tradeshows.

  • 119.
    Anwar, Mahwish
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science.
    Digitalization in Container Terminal Logistics: A Literature Review2019In: 27th Annual Conference of International Association of Maritime Economists (IAME), 2019, p. 1-25, article id 141Conference paper (Refereed)
    Abstract [en]

    Many terminals that are located in large ports, such as Port of Rotterdam, Port of Singapore, Port of Hamburg, etc. employ various emerging digital technologies to handle container and information. Some technologies deemed attractive by large ports are: Artificial Intelligence (AI), Cloud Computing, Blockchain and Internet of Things (IoT). The objective of this paper is to review the “state-of-the-art” of scientific literature on digital technologies that facilitate operations management for container terminal logistics. The studies are synthesized in form of a classification matrix and analysis performed. The primary studies consisted of 57 papers, out of the initial pool of over 2100 findings. Over 94% of the publications identified focused on AI; while 29% exploited IoT and Cloud Computing technologies combined. The research on Blockchain within the context of container terminal was nonexistent. Majority of the publications utilized numerical experiments and simulation for validation. A large amount of the scientific literature was dedicated to resource management and scheduling of intra-logistic equipment/vessels or berth or container storage in the yard. Results drawn from the literature survey indicate that various research gaps exist. A discussion and an analysis of review is presented, which could be of benefit for stakeholders of small-medium sized container terminals.

  • 120.
    Anwar, Mahwish
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science.
    Henesey, Lawrence
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science.
    Casalicchio, Emiliano
    Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science.
    The feasibility of Blockchain solutions in the maritime industry2019Conference paper (Other academic)
    Abstract [en]

    Purpose / Value

    The concept of Blockchain technology in supply chain management is well discussed, yet

    inadequately theorized in terms of its applicability, especially within the maritime industry,

    which forms a fundamental node of the entire supply chain network. More so, the assumptive

    grounds associated with the technology have not been openly articulated, leading to unclear

    ideas about its applicability.

    Design/methodology/approach

    The research is designed divided into two Stages. This paper (Stage one) enhanced

    literature review for data collection in order to gauge the properties of the Blockchain

    technology, and to understand and map those characteristics with the Bill of Lading

    process within maritime industry. In Stage two an online questionnaire is conducted to

    assess the feasibility of Blockchain technology for different maritime use-cases.

    Findings

    The research that was collected and analysed partly from deliverable in the

    Connect2SmallPort Project and from other literature suggests that Blockchain can be an

    enabler for improving maritime supply chain. The use-case presented in this paper highlights

    the practicality of the technology. It was identified that Blockchain possess characteristics

    suitable to mitigate the risks and issues pertaining to the paper-based Bill of Lading process.

    Research limitations

    The study would mature further after the execution of the Stage Two. By the end of both

    Stages, a framework for Blockchain adoption with a focus on the maritime industry would

    be proposed.

    Practical implications

    The proposed outcome indicated the practicality of technology, which could be beneficial

    for the port stakeholders that wish to use Blockchain in processing Bill of Lading or

    contracts.

    Social implications

    The study may influence the decision makers to consider the benefits of using the Blockchain

    technology, thereby, creating opportunities for the maritime industry to leverage the

    technology with government’s support.

  • 121. Apell, Maria
    et al.
    Erman, David
    Popescu, Adrian
    Testbed for Advanced Mobile Solutions2010Conference paper (Refereed)
    Abstract [en]

    This paper describes the implementation of an IMS testbed, based on open source technologies and operating systems. The testbed provides rich communication services, i.e., Instant Messaging, Network Address Book and Presence as well as VoIP and PSTN interconnectivity. Our validation tests indicate that the performance of the testbed is comparable to similar testbeds, but that operating system virtualization signi ficantly aff ects signalling delays.

  • 122.
    Appana, Dileep Kumar
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Kumar, Chinni Anil
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Nagappan, Nagappan Palaniappan
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Channel Estimation in GPRS based Communication System using Bayesian Demodulation.2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    With the increase use of portable devices such as Personal Digital Assistants (PDA), laptops, voice and data integrated cell phones and many more, there is a need of wireless communication method using air as the medium to transmit and receive information between terminals. Radio waves propagate from transmitting antenna and travel through free space undergoing reflections, diffractions and scattering. They are greatly affected by ground terrain, the atmosphere and the objects in their path like buildings, bridges, hills etc. Nowadays, the existence of a direct line of sight path between the transmitter and the receiver is unlikely. These multiple phenomena are responsible for most of the characteristic features like the quality of the received signal. In the above case propagation is mainly due to reflection and cattering from the buildings and by diffraction. So, in practice the transmitted signal arrives at the receiver via several paths with different time delays creating a multi path situation at the receiver, these multipath waves with randomly distributed amplitudes and phases combine to give a resultant signal that fluctuates in time and space. This phenomenon of random fluctuations in received signal level is termed as fading. The existing demodulation techniques like FM, AM will determine the signal from the received signal based on the mean distance method, which cannot provide the desired level of BER, which fails in proper estimation under high fading and high Doppler-Shift effect. SOLUTION: This project provides the implementation of an enhancement to the demodulation technique using Bayesian approach for the physical layer simulation of a General Packet Radio System (GPRS) considering variable Rician fading and variable Doppler-Shift effect for an AWGN channel. The system performance is evaluated based on Bit Error Rate (BER) and Signal to Noise Ratio (SNR) for the realized GPRS system. Matlab platform is used for the implementation, analysis of the proposed system with for functional verification in terms of BER and SNR. We have showed the comparative difference between the theoretical calculation of QPSK signal and to the values obtained by our program. The values show difference up to 0.4 db for a 1000 bit random vector. Moreover, we also compared with QAM demodulation technique in MATLAB code to show difference up to 1.4 db for a 1000 bit vector. These results signify better performance of the system as it has saved bandwidth.

  • 123.
    Appilla Chakravarthula, Rohan
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Veluru, Chaithanya Kumar Reddy
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Intelligent Beam Weight Computation for Massive Beamforming2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    LTE (Long Term Evolution) is likely the most complex wireless system ever developed. It incorporates features that could not have been economically implemented as recently as a decade ago. Today, with large-scale ICs, LTE can be easily accommodated in base stations and battery-powered handsets alike. LTE-Advanced is the upgraded version of LTE technology for providing more speed and greater reliability.

    In this report, the wireless communication between the user and base station is implemented by creating 4G LTE environment in MATLAB. Impact of Coherence time on beam weight computation varies for different delay profiles. Moreover, SNR of the transmitted signal varies significantly by the time gap between two successive uplink frames in TDD configuration. In this report, computationally efficient algorithm for reducing beam weight computations in system level LTE simulations is proposed.

    The wireless channel is modelled in both Rician and Rayleigh fading channel. Efficiency of beam forming algorithms is observed at different channel conditions like delay profile, fading channel, bandwidth, correlation, modulation technique.

    The MUSIC algorithm is implemented for detecting the movement of the users in Line of sight condition

  • 124.
    Appuni, Bala Satish
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Vemasani, Vamsi Krishna
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Performance Evaluation of Power Control Algorithms in Cellular Radio Communication Systems2004Independent thesis Advanced level (degree of Master (One Year))Student thesis
    Abstract [en]

    Radio resources in wireless communication systems, implementing different multiple access techniques, must be wisely managed. This perspective is pivotal since the variations in propagation channel are very fast and the system is highly complex due to random and unpredictable movement of mobile users continuously. This complexity in the cellular system periodically contributes to different interference levels, high or low, resulting in the degradation of the system capacity. Transmitter power control is an efficient technique to mitigate the effect of interference under fading conditions, combat the Near-Far problem and conserve the battery life. Thus, an effective implementation of different power control algorithms in cellular radio communication systems can offer a significant improvement in the Quality of Service (QoS) to all the users. Choice of an appropriate power control algorithm is of prime importance, as it should aim at increasing the overall efficiency of the system. In this thesis different distributed power control algorithms, each suited for implementation under different cellular technologies, were studied extensively. Specifically, six distributed power control algorithms are compared through simulations on the basis of performance metrics like Carrier to Interference Ratio (CIR) and Outage for the downlink case. The work involves in finding the link gain matrix by modeling the cellular system in MATLAB and simulating different power control algorithms. The results obtained from the simulation work are used to evaluate the efficiency of the Distributed Power Control (DPC), Fully Distributed Power Control (FDPC), Improved Fully Distributed Power Control (FDPC+) and Balanced Distributed Power Control (BDPC) algorithms on the basis of convergence speed and at the same time evaluating the limitations of the different algorithms. Also, with the results obtained on the basis of outage comparison between Fixed Step Power Control (FSPC) and Augmented Constant Improvement Power Control (ACIPC) algorithms, the quality of active link protection and cell removal procedures are demonstrated.

  • 125.
    Arguedas-Matarrita, Carlos
    et al.
    Universidad Estatal a Distancia, Escuela de Ciencias Exactas y Naturales. CRI.
    Beatriz Concari, Sonia
    Universidad Nacional de Rosario, ARG.
    García-Zubía, Javier
    Universidad de Deusto, ESP.
    Marchisio, Susana Teresa
    Universidad Nacional de Rosario, ARG.
    Hernández-Jayo, Unai
    Universidad de Deusto, ESP.
    Alves, Gustavo
    IPP, Felgueiras, PRT.
    Uriarte-Canivell, Iñigo
    Universidad de Deusto, ESP.
    Villalobos, Marco Conejo
    Universidad Estatal a Distancia, Escuela de Ciencias Exactas y Naturales. CRI.
    Gustavsson, Ingvar
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    Elizondo, Fernando Ureña
    Universidad Estatal a Distancia, Escuela de Ciencias Exactas y Naturales. CRI.
    A teacher training workshop to promote the use of the VISIR remote laboratory for electrical circuits teaching2017In: Proceedings of 2017 4th Experiment at International Conference: Online Experimentation, exp.at 2017, Institute of Electrical and Electronics Engineers Inc. , 2017, p. 1-6Conference paper (Refereed)
    Abstract [en]

    The learning of Physics involves building up and using lab experiments. In turn, teachers must be trained in experimenting and using several resources that enable them to design valuable teaching strategies and learning activities. Thanks to Information and Communication Technologies (ICT), virtual and remote labs can provide a framework where physical experiments can be developed. Altough remote labs have been in use for over a decade now in several countries and levels of education, its use at secondary schools in Latin America has not been reported yet. The Virtual Instruments System in Reality (VISIR) is one of these remote labs, suitable to practice in the area of electrical circuits. This paper aims at describing how this remote lab was used in a training workshop for secondary school level teachers of Physics in Costa Rica. © 2017 IEEE.

  • 126.
    Ariyaratne, Chamila Asanka
    Blekinge Institute of Technology, School of Engineering.
    Link Adaptation Improvements for Long Term Evolution (LTE)2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The Long Term Evolution (LTE) link adaptation is based on measured instantaneous Signal to Interference and Noise Ratio (SINR) which is used for selecting Modulation and Coding Scheme (MCS) for transmissions. In addition, depending on the scheduler, SINR may be used to determine which users are scheduled for a certain transmission time interval and on which frequency resources. The measured SINR can be inaccurate due to measurement errors, rounding errors due to quantization of the SINR values, and delay from time of measurement until the actual data transmissions. To compensate for SINR inaccuracies, the SINR can be adjusted by a certain offset before being used for link adaptation and scheduling. This offset value, referred to as the link adaptation margin in this thesis, can be a fixed value common to all the users in the system at all times or adaptively adjusted for each user based on some algorithm via a feedback loop, referred to as differentiated link adaptation. This thesis tries to improve the system performance for LTE downlink and uplink by using differentiated link adaptation based on packet error occurrences of each user as feedback. The performance of the differentiated link adaptation was compared to the best performance that is achievable using a fixed link adaptation margin. We investigated the influence of several parameters on the link adaptation error characteristics, such as settings for SINR estimation, scheduling algorithms, traffic patterns. It was shown that there are error clusters, but that these are short and difficult to react to on time. A performance gain was only possible in the downlink for FTP traffic with a proportional fair in time and frequency (PFTF) scheduler which was the scenario with the largest variations with regards to both scheduling and traffic model. It was seen that the gains of using differentiated link adaptation increased in the downlink as the transmissions got more random. For more stable situations, a fixed link adaptation margin performed better. The uplink performance was worse with differentiated link adaptation than with a fixed optimized link adaptation margin. This could be because the uplink SINR estimation was much better than in the downlink, with low estimation error variance, in which case frequent SINR adjustments could make the situation worse off.

  • 127. Arkoulis, Stamatios
    et al.
    Marias, Giannis
    Frangoudis, Pantelis
    Oberender, Jens
    Popescu, Alexandru
    Fiedler, Markus
    Meer, Hermann de
    Polyzos, George
    Misbehaviour Scenarios in Cognitive Radio Networks2010In: Future Internet, ISSN 1999-5903, E-ISSN 1999-5903, Vol. 2, no 3-4, p. 212-237Article, review/survey (Refereed)
    Abstract [en]

    Recent advances in the fields of Cognitive Radio and the proliferation of open spectrum access promise that spectrum-agile wireless communication will be widespread in the near future, and will bring significant flexibility and potential utility improvements for end users. With spectrum efficiency being a key objective, most relevant research focuses on smart coexistence mechanisms. However, wireless nodes may behave selfishly and should be considered as rational autonomous entities. Selfishness, pure malice or even faulty equipment can lead to behavior that does not conform to sharing protocols and etiquette. Thus, there is a need to secure spectrum sharing mechanisms against attacks in the various phases of the sharing process. Identifying these attacks and possible countermeasures is the focus of this work.

  • 128. Arlebrink, Ludvig
    et al.
    Linde, Fredrik
    Image Quality-Driven Level of Detail Selection on a Triangle Budget2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Background. Level of detail is an optimization technique used by several modern games. The level of detail systems uses simplified triangular meshes to determine the optimal combinations of 3D-models to use in order to meet a user-defined criterion for achieving fast performance. Prior work has also pre-computed level of detail settings to only apply the most optimal settings for any given view in a 3D scene.

    Objectives. The aim of this thesis is to determine the difference in image quality between a custom level of detail pre-preprocessing approach proposed in this paper, and the level of detail system built in the game engine Unity. This is investigated by implementing a framework in Unity for the proposed level of detail pre-preprocessing approach in this paper and designing representative test scenes to collect all data samples. Once the data is collected, the image quality produced by the proposed level of detail pre-preprocessing approach is compared to Unity's existing level of detail approach using perceptual-based metrics.

    Methods. The method used is an experiment. Unity's method was chosen because of the popularity of the engine, and it was decided to implement the proposed level of detail pre-preprocessing approach also in Unity to have the most fair comparison with Unity's implementation. The two approaches will only differ in how the level of detail is selected, the rest of the rendering pipeline will be exactly the same.

    Results. The pre-preprocessing time ranged between 13 to 30 hours. The results showed only a small difference in image quality between the two approaches, Unity's built-in system provides a better overall image quality in two out of three test scenes.

    Conclusions. Due to the pre-processing time and no overall improvement, it was concluded that the proposed level of detail pre-preprocessing approach is not feasible.

  • 129. Arlos, Patrik
    Application Level Measurement2011In: Network Performance Engineering: A Handbook on Convergent Multi-Service Networks and Next Generation Internet, Berlin / Heidelberg: Springer , 2011, p. 14-36Chapter in book (Other academic)
    Abstract [en]

    In some cases, application-level measurements can be the only way for an application to get an understanding about the performance offered by the underlying network(s). It can also be that an application-level measurement is the only practical solution to verify the availability of a particular service. Hence, as more and more applications perform measurements of various networks; be that fixed or mobile, it is crucial to understand the context in which the application level measurements operate their capabilities and limitations. To this end in this paper we discuss some of the fundamentals of computer network performance measurements and in particular the key aspects to consider when using application level measurements to estimate network performance properties.

  • 130.
    Arlos, Patrik
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    On the Quality of Computer Network Measurements2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Due to the complex diversity of contemporary Internet-services, computer network measurements have gained considerable interest during recent years. Since they supply network research, development and operations with data important for network traffic modelling, performance and trend analysis, etc. The quality of these measurements affect the results of these activities and thus the perception of the network and its services. This thesis contains a systematic investigation of computer network measurements and a comprehensive overview of factors influencing the quality of performance parameters obtained from computer network measurements. This is done using a novel network performance framework consisting of four modules: Generation, Measurement, Analysis and Visualization. These modules cover all major aspects controlling the quality of computer network measurements and thus the validity of all kinds of conclusions based on them. One major source of error is the timestamp accuracy obtained from measurement hardware and software. Therefore, a method is presented that estimates the timestamp accuracy obtained from measurement hardware and software. The method has been used to evaluate the timestamp accuracy of some commonly used hardware (Agilent J6800/J6830A and Endace DAG 3.5E) and software (Packet Capture Library). Furthermore, the influence of analysis on the quality of performance parameters is discussed. An example demonstrates how the quality of a performance metric (bitrate) is affected by different measurement tools and analysis methods. The thesis also contains performance evaluations of traffic generators, how accurately application-level measurements describe network behaviour, and of the quality of performance parameters obtained from PING and J-OWAMP. The major conclusion is that measurement systems and tools must be calibrated, verified and validated for the task of interest before using them for computer network measurements. A guideline is presented on how to obtain performance parameters at a desired quality level.

  • 131.
    Arlos, Patrik
    et al.
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    Fiedler, Markus
    Blekinge Institute of Technology, School of Engineering, Department of Telecommunication Systems.
    A Method to Estimate the Timestamp Accuracy of Measurement Hardware and Software Tools2007Conference paper (Refereed)
    Abstract [en]

    Due to the complex diversity of contemporary Internet applications, computer network measurements have gained considerable interest during the recent years. Since they supply network research, development and operations with data important for network traffic modelling, performance and trend analysis etc., the quality of these measurements affect the results of these activities and thus the perception of the network and its services. One major source of error is the timestamp accuracy obtained from measurement hardware and software. On this background, we present a method that can estimate the timestamp accuracy obtained from measurement hardware and software. The method is used to evaluate the timestamp accuracy of some commonly used measurement hardware and software. Results are presented for the Agilent J6800/J6830A measurement system, the Endace DAG 3.5E card, the Packet Capture Library (PCAP) either with PF_RING or Memory Mapping, and a RAW socket using either the kernel PDU timestamp (ioctl) or the CPU counter (TSC) to obtain timestamps.

  • 132. Arlos, Patrik
    et al.
    Fiedler, Markus
    Accuracy Evaluation of Ping and J-OWAMP2006Conference paper (Refereed)
    Abstract [en]

    Due to the complex diversity of contemporary Internet services, computer network measurements have gained considerable interest during the recent years. Computer network measurements supply network research, development and operations with data important for network traffic modelling, performance and trend analysis etc. Hence, the quality of these measurements affects the results of these activities and thus the perception of the network and its services. Active measurements are performed by injecting traffic into a network and observing the treatment that this traffic receives. Usually, active measurements are perfomed by writing special applications that act at sender and receiver. These applications are usually executed as user processes. This causes some concern since this can have serious implications on the obtained results, as they are affected by the scheduling mechanisms in the operating system. In this paper, we evaluate the accuracy of two active measurement tools, ping and J-OWAMP, by using high accuracy passive measurements. Our results show that ping is quite accurate, to 0.1~ms for Linux and 1~ms for Windows~XP, while J-OWAMP has a discrepancy of 25~ms plus serious time synchronization problems.

  • 133. Arlos, Patrik
    et al.
    Fiedler, Markus
    Influence of the Packet Size on the One-Way Delay in 3G Networks2010Conference paper (Refereed)
    Abstract [en]

    We currently observe a rising interest in mobile broadband, which users expect to perform in a similar way as its fixed counterpart. On the other hand, the capacity allocation process on mobile access links is far less transparent to the user; still, its properties need to be known in order to minimize the impact of the network on application performance. This paper investigates the impact of the packet size on the minimal one-way delay for the uplink in third-generation mobile networks. For interactive and real-time applications such as VoIP, one-way delays are of major importance for user perception; however, they are challenging to measure due to their sensitivity to clock synchronization. Therefore, the paper applies a robust and innovative method to assure the quality of these measurements. Results from measurements from several Swedish mobile operators show that applications can gain significantly in terms of one-way delay from choosing optimal packet sizes. We show that, in certain cases, an increased packet size can improve the one-way delay performance at best by several hundred milliseconds.

  • 134. Arlos, Patrik
    et al.
    Fiedler, Markus
    Influence of the Packet Size on the One-Way Delay on the Down-link in 3G Networks2010Conference paper (Refereed)
    Abstract [en]

    The number of mobile broadband users is increasing. Furthermore, these users have high expectations into the capabilities of mobile broadband, comparable to those in fixed networks. On the other hand, the capacity assignment process on mobile access links is far from transparent to the user, and its properties need to be known in order to minimize the impact of the network on application performance. This paper investigates the impact of the packet size on the characteristics of the one-way delay for the down-link in third-generation mobile networks. For interactive and real-time applications such as VoIP, one-way delays are of major importance for user perception; however, they are challenging to measure due to their sensitivity to clock synchronization. Therefore, the paper applies a robust and innovative method to assure the quality of these measurements. We focus on the down-link as this is still the link that carries the most traffic to the user, and the quality of it will have a significant impact on all IP-based services. Results from measurements from several Swedish mobile operators reveal the possibility to partly control one-way delay and its variability by choosing appropriate packet sizes. In particular, packet sizes leading to the use of WCDMA entail significant but hardly varying one-way delays. On the other hand, we also show that HDSPA networks can deliver large amounts of data at rather high speed, but the cost is a huge variability in the one-way delay.

  • 135. Arlos, Patrik
    et al.
    Fiedler, Markus
    Nilsson, Arne A.
    A Distributed Passive Measurement Infrastructure2005Conference paper (Refereed)
    Abstract [en]

    In this paper we describe a distributed passive measurement infrastructure. Its goals are to reduce the cost and configuration effort per measurement. The infrastructure is scalable with regards to link speeds and measurement locations. A prototype is currently deployed at our university and a demo is online at http://inga.its.bth.se/projects/dpmi. The infrastructure differentiates between measurements and the analysis of measurements, this way the actual measurement equipment can focus on the practical issues of packet measurements. By using a modular approach the infrastructure can handle many different capturing devices. The infrastructure can also deal with the security and privacy aspects that might arise during measurements.

  • 136. Arlos, Patrik
    et al.
    Kommalapati, Ravichandra
    Fiedler, Markus
    Evaluation of Protocol Treatment in 3G Networks2011Conference paper (Refereed)
    Abstract [en]

    In this work, we present a systematic study of how the traffic of different transport protocols (UDP, TCP and ICMP) is treated, in three operational Swedish 3G networks. This is done by studying the impact that protocol and packet size have on the one-way-delay (OWD) across the networks. We do this using a special method that allows us to calculate the exact OWD, without having to face the usual clock synchronization problems that are normally associated with OWD calculations. From our results we see that all three protocols are treated similarly by all three operators, when we consider packet sizes that are smaller than 250~bytes and larger than 1100~bytes. We also show that larger packet sizes are given preferential treatment, with both smaller median OWD as well as a smaller standard deviation. It is also clear that, ICMP is given a better performance compared to TCP and UDP.

  • 137.
    Armiński, Wojciech
    et al.
    Blekinge Institute of Technology, School of Engineering.
    Jüngst, Andrzej
    Blekinge Institute of Technology, School of Engineering.
    SEMI-AUTOMATED FORWARDER CRANE CONTROL2012Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The objective of this thesis is to develop and implement two control programs on an experimental hydraulic crane. The first program demonstrates a kinematic redundancy of the crane also called an extra degree of freedom. The second program is an experimental trajectory following solution that can aid crane operators. The trajectory is optimized to minimize hydraulic cylinders use. The thesis involves various issues concerning both low layer and high layer control. This includes a system identification, system nonlinearity compensation, dead zone compensation, gain scheduling, PI controllers tuning and optimization problems. The solutions like genetic algorithm and fuzzy logic are used. Both control programs are made in Mathworks Simulink and run in dSPACE system.

  • 138. Arolla, Srihari
    et al.
    Gurrala, Naga Venkata Sai Teja
    PHYSICAL LAYER SECURITY USING PSEUDO-RANDOM SEQUENCE KEY GENERATION2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Nowadays, network security plays a major role in the field of wireless communications. Wired networks propagate electrical signals or pulses through cables. Whereas wireless signals propagate through the air. If wireless networks are left open and exposed to the outside world, there are high chances of being misused by others. The intruders take advantage of this, to intercept the wireless signals. This is the reason why an extra level of security is required for wireless networks. The physical layer is one of the important layers of the Open System Interconnection (OSI) model which plays an important role in the network’s physical connections like wireless transmission, cabling, connections etc. The physical layer supports the bit-level transmission between various devices by connecting to the physical medium for synchronized communication.In this thesis, a method is studied for exchanging secret key [1] bits using a pseudo-random sequence generator based on Frequency Division Duplex (FDD) systems. The principle of this method is to generate a secret key in a manner that produces low correlation at the intruder. By uniquely relating the secret key bits to the channel in a private version of the universal codebook, a robust key exchange between the transmitter and the receiver is then performed.

  • 139.
    Arsalan, Muhammad
    Blekinge Institute of Technology, School of Engineering.
    Future Tuning Process For Embedded Control Systems2009Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    This master’s thesis concerns development of embedded control systems.Development process for embedded control systems involves several steps, such as control design, rapid prototyping, fixedpoint implementation and hardware-in-the-loop-simulations. Another step, which Volvo is not currently (September 2009) using within climate control is on-line tuning. One reason for not using this technique today is that the available tools for this task (ATI Vision, INCA from ETAS or CalDesk from dSPACE) do not handle parameter dependencies in a atisfactory way. With these constraints of today, it is not possible to use online tuning and controller development process is more laborious and time consuming.The main task of this thesis is to solve the problem with parameter dependencies and to make online tuning possible.

  • 140.
    Arslan, Muhammad
    et al.
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    , Usman
    Blekinge Institute of Technology, Faculty of Engineering, Department of Applied Signal Processing.
    PERFORMANCE EVALUATION OF VIDEO QUALITY ASSESSMENT METHODS BASED ON FRAME FREEZING2014Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    A Digital Video Communication System consists of a video encoder, a channel through which the video is transmitted and finally a video decoder. These three phases can cause different kinds of impairments or degradations in the quality of a video. One of the degradations that takes place due to an error prone channel is frame freezing and it affects the quality of a video. Frame freezing is a phenomenon in which a particular frame is repeated (displayed) for a certain period of time until the next correct frame is received hence producing a pause or a freeze in a video sequence. Frame freezing can be single or multiple depending on the channel characteristics. Research is being conducted in order to devise a metric which can help in quantifying a video sequence on the basis of its quality. Researchers design metrics and then using their mathematical models, they compare their results with subjective measurements. Subjective measurements help in telling the preciseness and correctness of the metric that whether the quality assessment metric is close enough to subjective test measurements. In this report, three metrics used for video quality assessment have been studied and compared mathematically as well as by careful experiments. The three metrics, chosen for this study, work on No Reference (NR) method for judging the quality of a video. Subjective tests have been performed keeping in view of the recommendations of ITU (International Telecommunication Union). After the study of these three metrics, their advantages and disadvantages over each other have been discussed and the metric that performs the best under certain conditions has been proposed. Finally, a conclusion has been made for the metric that performs the best and also for the metric that performs the worse or even does not perform at all under certain conditions.

  • 141.
    Arslan, Ömer
    et al.
    Blekinge Institute of Technology, School of Engineering.
    Anjorin, Olufemi Emmanuel
    Blekinge Institute of Technology, School of Engineering.
    Performance Evaluation of Packet Scheduling Algorithms for LTE Downlink2012Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    Long Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) is designed to revolutionize mobile broadband technology with key considerations of higher data rate, improved power efficiency, low latency and better quality of service. It promises high peak data rates of 100 Mbps downlink and 50 Mbps uplink transmissions and can operate in different bandwidths ranging from 1.4 MHz up to 20 MHz. Scheduler makes a decision on allocation of Resource Blocks (RB) to User Equipments (UE) through the frequency and time domains. Channel Quality Indicator (CQI) is used as a main parameter during the decision process. This master thesis focuses on performance of LTE downlink scheduling. Round Robin (RR), Best CQI and a proposed Empirical scheduling solution are investigated under different bandwidth and antenna configurations.

  • 142.
    Aruchamy, Logabharathi
    Blekinge Institute of Technology, School of Computing.
    Analysis of Radio Access Network Buffer Filling Based on Real Network Data2012Independent thesis Advanced level (degree of Master (Two Years))Student thesis
    Abstract [en]

    The 3G and 4G networks have drastically improved availability and quality in data transmission for bandwidth hungry services such as video streaming and location-based services. As 3G networks are very widely deployed, there exists increased capacity requirement and transport channel allocation to simultaneous users under a particular cell. Due to this reason, adequate resources are not available, which in turn degrades both service quality and user experienced quality. This research aims at understanding the characteristics of buffer filling during dedicated channel (DCH) transmission under fixed bit-rate assumptions on a per-user level taking different services into consideration. Furthermore, the resource utilisation in terms of empty buffer durations and user throughput achieved during dedicated channel transmission are also analysed for different data services existing in the mobile networks. The traces are collected from a real network and characteristics of the traffic are analysed prior to understanding its buffer filling in Radio Network Controller (RNC) during downlink data transmission. Furthermore, the buffer is modelled with some series of assumptions on channel bit-rates and simulations are performed taking single user scenario into consideration, for different services with the help of obtained traces as input to the buffer. This research is helpful in understanding the RNC buffer filling for different services, in turn yielding possible understanding on the existing transport channel switching scenario. With the help of analysing the buffer filling for different services and transport channel utilisation, we learn that most of the data services show low DCH utilisation of approximately around 20% and also found to have 80% of the total DCH session duration with empty buffer, causing sub-optimal radio resource utilization.

  • 143.
    Arvidsson, Mattias
    Blekinge Institute of Technology, School of Computing.
    Säkerhetsmedvetenhet: En kvantitativ studie beträffande mätning av säkerhetsmedvetenhet hos medarbetare2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Denna rapport syftar till att besvara tre frågeställningar; går det att mäta säkerhetsmedvetenhet, vilka variabler påverkar säkerhetsmedvetenheten samt är skillnaderna i variablerna signifikanta. Undersökningen har genomförts i en region och av yrkeskategorin brevbärare, inom företaget Posten Meddelande AB. För att besvara de tre frågeställningarna har en omfattande enkätundersökning genomförts på tio arbetsplatser, där ett dataunderlag på 164 svar inhämtats.  Underlaget har indexerats till ett index som är avsett att beskriva hur god säkerhetsmedvetenhet de svarande har. Säkerhetsmedvetenhetsindexet har sedan analyserats med olika sambandsanalyser för att se om de oberoende variablerna påverkar resultatet. Totalt har sju oberoende variabler analyserats, och av dessa har fem påverkat resultatet.  Till sist har dessa fem testats med medelvärdes- och variansanalyser för att se om skillnaderna i grupperna är signifikanta. Resultatet av det visar att skillnaderna är signifikanta och i princip alla med mer hög tillförlitlighet. Slutsatsen av dessa analyser är att äldre personer som jobbat länge inom Posten Meddelande och genomgått en säkerhetsutbildning har statistiskt säkerställt bättre säkerhetsmedvetenhet. Då ålder och erfarenhet är omöjligt att erhålla på kort sikt, anser författaren att den viktigaste framgångsfaktorn för att uppnå god säkerhetsmedvetenhet är att alla inom företaget bör genomgå en säkerhetsutbildning.

  • 144. Arvidsson, Åke
    High Level B-ISDN/ATM Traffic Management in Real Time1995In: Performance Modelling and Evaluation of ATM Networks / [ed] Kouvatsos, Demetres, London: Chapman & Hall , 1995, p. 177-207Chapter in book (Other academic)
    Abstract [en]

    We study real time traffic management in the perspective of a four-level model of traffic variations: cells, bursts, sessions, and links. Our interest is focused on the two latter levels: Using virtual channels (VCs) and virtual paths (VPs) as the managed entities on the two levels respectively, we put forward a simple and robust strategy for traffic management in real time: All nodes simultaneously monitor offered traffics and forward the result to a network management centre (NMC); The NMC computes a new set of optimal VPs and compares the result to the existing network; If a change appears profitable, the necessary information is sent back to the nodes and the new design is implemented. Applying our strategy to control general networks subject to traffics which in advance are known only as expectations, we develop simple methods for traffic observation, the optimal observation interval, a fast and efficient algorithm to compute VP networks, a test to determine whether to implement a new design in which costs related to lost traffic are compared to processing costs, and the optimal updating interval. Running our strategy in a simulator, we discover a considerable adaptivity, large savings in transmission capacity, and a performance far better than achieved by fixed redesign according to forecasts. Finally we discuss limits to the range of variations within which our strategy can be applied. The present work applies both to networks using SDH/SONET and/or networks based on ATM, i.e. both to present public switched telephony networks and broadband inte- grated services digital networks, and is a summary and extension of earlier works within this area [3{9].

  • 145. Arvidsson, Åke
    Management of Reconfigurable Virtual Path Networks1994In: The Fundamental Role of Teletraffic in the Evolution of Telecommunication Networks / [ed] Roberts, James; Labetoulle, Jaques, Amsterdam: Elsevier , 1994, p. 931-940Chapter in book (Other academic)
    Abstract [en]

    We study dynamically rearrangable end-to-end transport networks by means of SDH/SONET and/or ATM virtual paths. The concept and its advantages are brie y reviewed and we propose a new algorithm for designing such networks. Our algorithm provides integer solutions, handles non-linear equivalent bandwidths, finds its own paths, and allows for an arbitrary design optimisation criterion. It is found to perform equal to or better than an earlier, comparable though more restricted, algorithm. We also put forward a strategy for managing virtual paths in real time. It consists of a repeated cycle of on-line measurement of offered traffics followed by the design and implementation of a new virtual path network. Methods and parameters for traffic measurements and network updating frequency are studied and optimised. Applying the strategy to rearrangeable networks subject to variable traffics in a simulator, we discover considerable gains and a robustness in our parameter settings.

  • 146. Arvidsson, Åke
    On Dynamic Capacity Management in Voice/Frame Relaying Networks1992Conference paper (Refereed)
    Abstract [en]

    We consider call admission and capacity management in a dynamically reconfigurable network that carries a multitude of traffics. Our approach is a heuristic capacity as- signment algorithm designed to maximise an arbitrary profit function. The algorithm is based on the concept of equivalent circuits, i.e. a given relationship between transmis- sion capacities and call handling capabilities expressed as effective numbers of circuits. Such relationships are examined for the two traffics of our application, voice and frame relaying. Methods and results are independent of the transfer mode used.

  • 147. Arvidsson, Åke
    On the Usage of Virtual Paths, Virtual Channels, and Buffers in ATM Traffic Management1995Conference paper (Refereed)
    Abstract [en]

    Traffic in ATM networks can be described by numerous parameters. On a per session basis, one may use peak rate, average rate, sustainable rate, average burst duration, average silence duration, and others. In a longer time scale, parameters like the average and peakedness of connection request interarrival times, the average and variance of session holding times, and so on are proposed. Theoretically, users should provide the former parameters and network operators the latter. In reality, however, few users can be expected to provide all sorts of statistical information about their traffic in advance, and operators do not have enough experience to prepare traffic forecasts for new services and applications. Moreover, even if the information could be provided, the lack of simple yet valid traffic models for ATM networks means that it is far from clear how such information should be used. Realising that ATM networks, which are already being built, at least for the next few years will have to operate under these uncertain conditions, we propose a robust and forgiving network design and traffic management strategy. The idea is to use only little information about offered traffics and then dynamically control resource allocations, so as to provide acceptable quality of service combined with high utilisation. The network design is based on the idea of keeping congestion at the edges of the net- work, so that the operating areas of fast congestion control mechanisms are minimised. Traffic variations are characterised by a model of six layers, each of which is assigned a corresponding layer in a traffic management model. We define the functionalities of each level in the latter modell and review possible implementations. In particular, we report on an implementation of two of these layers and discuss in some detail how a third one could be added.

  • 148. Arvidsson, Åke
    Real Time Management of Virtual Paths1994Conference paper (Refereed)
    Abstract [en]

    We propose a simple and robust automatic strat- egy for managing SDH/SONET and/or ATM virtual paths in real time to handle slow traffic variations. It consists of on-line measurements of offered traffics followed by the design and possi- ble implementation of a new virtual path network in a repeated cycle. Methods and parameters for traffic measurements and network updating are studied and optimised to achieve maximal traffic carrying capability at minimal cost. Applying our strat- egy to networks subject to partially unknown, variable traffics we discover a considerable adaptivity, large savings in transmis- sion capacity, and a performance far better than achieved by deterministic management.

  • 149. Arvidsson, Åke
    Real Time Traffic Management by Dynamic Bandwidth Allocation1995Conference paper (Refereed)
    Abstract [en]

    We introduce a six layer model of traffic variations and a corresponding model of management actions. In particular, we traffic study real time traffic management on the traffic and session levels which correspond to variations on the hour and minute levels. Using virtual paths (VPs) and virtual channels (VCs) as the managed entities on the two levels respectively, we put forward a simple and robust strategy for traffic management in real time: For slow variations, i.e. on the traffic level, all nodes simultaneously monitor offered traffics and forward the result to a network management centre (NMC); The NMC computes a new set of optimal VPs compares the result to the existing network; If a change appears profitable, the necessary information is sent back to the nodes and the new design is implemented. For fast variations, i.e. on the session level, dynamic routing schemes similar to those of public switched telephone networks are employed. Applying our strategy to control general networks subject to traffics which in advance are known only as expectations, we develop simple methods for traffic observation, derive the optimal observation interval, brie y review algorithms to compute VP networks, develop a cost optimal test to determine whether to implement a new design or not, and derive the optimal updating interval. Running our strategy in a simulator, we discover a considerable adaptivity and a performance far better than obtained by alternative methods.

  • 150. Arvidsson, Åke
    Strategies for Dynamic Capacity Management1993Conference paper (Refereed)
    Abstract [en]

    We study networks based on virtual paths, i.e. rearrangable end-to-end transport network. Virtual paths networks are readily implemented in any network using the synchronous digital hierarchy and/or the asynchronous transfer mode. The concept and its advantages, for example cost savings, network operation simplification and enhanced network management capabilities, are discussed. Algorithms for virtual path designs are reviewed and a new algorithm is presented which is found to compare favourably with the algorithm providing the most similar features. Applying it to a real network, we turn to operational aspects of reconfigurable networks such as methods and parameters for traffic estimation and network updating. The validity of the results is demonstrated by means of simulations of a number of networks subject to variable traffics.

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