3,418 research outputs found
Final report on the evaluation of RRM/CRRM algorithms
Deliverable public del projecte EVERESTThis deliverable provides a definition and a complete evaluation of the RRM/CRRM algorithms selected in D11 and D15, and evolved and refined on an iterative process. The evaluation will be carried out by means of simulations using the simulators provided at D07, and D14.Preprin
Proactive model to determine information technologies supporting expansion of air cargo network
Shippers and recipients expect transportation companies to provide more than just the movement of a package between points; certain information must be available to them as well, to enable forecasts and plans within the supply chain.
The transportation companies also need the information flow that undergirds a transportation grid, to support ad-hoc routing and strategic structural re-alignment of business processes.
This research delineates the information needs for an expanding air cargo network, then develops a new model of the information technologies needed to support expansion into a new country. The captured information will be used by shippers, recipients, and the transportation provider to better guide business decisions. This model will provide a method for transportation companies to balance the tradeoffs between the operating efficiencies, capital expenditures, and customer expectations of their IT systems. The output of the model is a list of technologies – optimized by cost – which meet the specific needs of internal and external customers when expanding air cargo networks into a new country
Design and Assessment for Hybrid Courses: Insights and Overviews
Technology is influencing education, providing new
delivery and assessment models. A combination between online and traditional course, the hybrid (blended) course, may present a solution with many benefits as it provides a gradual transition towards technology enabled education. This research work provides a set of definitions for several course delivery approaches, and evaluates five years of data from a course that has been converted from traditional face-to-face delivery, to hybrid delivery. The collected experimental data proves that the revised course, in the hybrid delivery mode, is at least as good, if not better, than it previously was and it provides some benefits in terms of student retention
High Intensity Laser Power Beaming Architecture for Space and Terrestrial Missions
High Intensity Laser Power Beaming (HILPB) has been developed as a technique to achieve Wireless Power Transmission (WPT) for both space and terrestrial applications. In this paper, the system architecture and hardware results for a terrestrial application of HILPB are presented. These results demonstrate continuous conversion of high intensity optical energy at near-IR wavelengths directly to electrical energy at output power levels as high as 6.24 W from the single cell 0.8 cm2 aperture receiver. These results are scalable, and may be realized by implementing receiver arraying and utilizing higher power source lasers. This type of system would enable long range optical refueling of electric platforms, such as MUAV s, airships, robotic exploration missions and provide power to spacecraft platforms which may utilize it to drive electric means of propulsion
Quality of service optimization of multimedia traffic in mobile networks
Mobile communication systems have continued to evolve beyond the currently deployed Third
Generation (3G) systems with the main goal of providing higher capacity. Systems beyond 3G
are expected to cater for a wide variety of services such as speech, data, image transmission,
video, as well as multimedia services consisting of a combination of these. With the air interface
being the bottleneck in mobile networks, recent enhancing technologies such as the High Speed
Downlink Packet Access (HSDPA), incorporate major changes to the radio access segment of
3G Universal Mobile Telecommunications System (UMTS). HSDPA introduces new features
such as fast link adaptation mechanisms, fast packet scheduling, and physical layer retransmissions
in the base stations, necessitating buffering of data at the air interface which presents a
bottleneck to end-to-end communication. Hence, in order to provide end-to-end Quality of
Service (QoS) guarantees to multimedia services in wireless networks such as HSDPA, efficient
buffer management schemes are required at the air interface.
The main objective of this thesis is to propose and evaluate solutions that will address the
QoS optimization of multimedia traffic at the radio link interface of HSDPA systems. In the
thesis, a novel queuing system known as the Time-Space Priority (TSP) scheme is proposed for
multimedia traffic QoS control. TSP provides customized preferential treatment to the constituent
flows in the multimedia traffic to suit their diverse QoS requirements. With TSP queuing, the
real-time component of the multimedia traffic, being delay sensitive and loss tolerant, is given
transmission priority; while the non-real-time component, being loss sensitive and delay tolerant,
enjoys space priority. Hence, based on the TSP queuing paradigm, new buffer managementalgorithms are designed for joint QoS control of the diverse components in a multimedia session
of the same HSDPA user. In the thesis, a TSP based buffer management algorithm known as the
Enhanced Time Space Priority (E-TSP) is proposed for HSDPA. E-TSP incorporates flow
control mechanisms to mitigate congestion in the air interface buffer of a user with multimedia
session comprising real-time and non-real-time flows. Thus, E-TSP is designed to provide
efficient network and radio resource utilization to improve end-to-end multimedia traffic
performance. In order to allow real-time optimization of the QoS control between the real-time
and non-real-time flows of the HSDPA multimedia session, another TSP based buffer management
algorithm known as the Dynamic Time Space Priority (D-TSP) is proposed. D-TSP
incorporates dynamic priority switching between the real-time and non-real-time flows. D-TSP
is designed to allow optimum QoS trade-off between the flows whilst still guaranteeing the
stringent real-time component’s QoS requirements. The thesis presents results of extensive
performance studies undertaken via analytical modelling and dynamic network-level HSDPA
simulations demonstrating the effectiveness of the proposed TSP queuing system and the TSP
based buffer management schemes
Quality-Oriented Mobility Management for Multimedia Content Delivery to Mobile Users
The heterogeneous wireless networking environment determined by the latest developments in wireless access technologies promises a high level of communication resources for mobile
computational devices. Although the communication resources provided, especially referring to bandwidth, enable multimedia streaming to mobile users, maintaining a high user perceived quality is still a challenging task. The main factors which affect quality in multimedia streaming over wireless networks are mainly the error-prone nature of the wireless channels and the user mobility. These factors determine a high level of dynamics of wireless communication resources, namely variations in throughput and packet loss as well as network availability and delays in delivering the data packets. Under these conditions maintaining a high level of quality, as perceived by the user, requires a quality oriented mobility management scheme. Consequently we propose the Smooth Adaptive Soft-Handover Algorithm, a novel quality oriented handover management scheme which unlike other similar solutions, smoothly transfer the data traffic from one network to another using multiple simultaneous connections. To estimate the capacity of each connection the novel Quality of Multimedia Streaming (QMS) metric is proposed. The QMS metric aims at offering maximum flexibility and efficiency allowing the applications to fine tune the behavior of the handover algorithm. The current simulation-based performance evaluation clearly shows the better
performance of the proposed Smooth Adaptive Soft-Handover Algorithm as compared with other handover solutions. The evaluation was performed in various scenarios including
multiple mobile hosts performing handover simultaneously, wireless networks with variable overlapping areas, and various network congestion levels
IMPROVEMENT OF POWER QUALITY OF HYBRID GRID BY NON-LINEAR CONTROLLED DEVICE CONSIDERING TIME DELAYS AND CYBER-ATTACKS
Power Quality is defined as the ability of electrical grid to supply a clean and stable power supply. Steady-state disturbances such as harmonics, faults, voltage sags and swells, etc., deteriorate the power quality of the grid. To ensure constant voltage and frequency to consumers, power quality should be improved and maintained at a desired level. Although several methods are available to improve the power quality in traditional power grids, significant challenges exist in modern power grids, such as non-linearity, time delay and cyber-attacks issues, which need to be considered and solved. This dissertation proposes novel control methods to address the mentioned challenges and thus to improve the power quality of modern hybrid grids.In hybrid grids, the first issue is faults occurring at different points in the system. To overcome this issue, this dissertation proposes non-linear controlled methods like the Fuzzy Logic controlled Thyristor Switched Capacitor (TSC), Adaptive Neuro Fuzzy Inference System (ANFIS) controlled TSC, and Static Non-Linear controlled TSC. The next issue is the time delay introduced in the network due to its complexities and various computations required. This dissertation proposes two new methods such as the Fuzzy Logic Controller and Modified Predictor to minimize adverse effects of time delays on the power quality enhancement. The last and major issue is the cyber-security aspect of the hybrid grid. This research analyzes the effects of cyber-attacks on various components such as the Energy Storage System (ESS), the automatic voltage regulator (AVR) of the synchronous generator, the grid side converter (GSC) of the wind generator, and the voltage source converter (VSC) of Photovoltaic (PV) system, located in a hybrid power grid. Also, this dissertation proposes two new techniques such as a Non-Linear (NL) controller and a Proportional-Integral (PI) controller for mitigating the adverse effects of cyber-attacks on the mentioned devices, and a new detection and mitigation technique based on the voltage threshold for the Supercapacitor Energy System (SES). Simulation results obtained through the MATLAB/Simulink software show the effectiveness of the proposed new control methods for power quality improvement. Also, the proposed methods perform better than conventional methods
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