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Articles 61 - 90 of 95
Full-Text Articles in Electrical and Electronics
Novel Ac Side P&O Maximum Power Transfer Control For Grid Connected Photovoltaic Systems, Mohamed Moin Hanif, Malabika Basu, Kevin Gaughan
Novel Ac Side P&O Maximum Power Transfer Control For Grid Connected Photovoltaic Systems, Mohamed Moin Hanif, Malabika Basu, Kevin Gaughan
Conference papers
Grid connected Photovoltaic inverters can convert PV energy into electricity with very high efficiencies. Power from the PV panels fluctuates depending on various weather conditions. PV inverters usually include a maximum power point tracker (MPPT) to track this varying power, in order to transfer all the available power to the grid efficiently. Control of power transferred to the grid along with the MPPT plays a crucial role in determining the efficiency of a PV system. This paper discusses about the basic power transfer theory between sources (PV and Grid) and focuses on the need of a DC-DC boost circuit, along …
Interactive Music Archive Access System, Martin Gallagher, Mikel Gainza, Derry Fitzgerald, Dan Barry, Matt Cranitch, Eugene Coyle
Interactive Music Archive Access System, Martin Gallagher, Mikel Gainza, Derry Fitzgerald, Dan Barry, Matt Cranitch, Eugene Coyle
Conference papers
The goal of the Interactive Music Archive Access System (IMAAS) project was to develop an interactive music archive access system which was capable of allowing an end-user to easily extract rhythmic, melodic and harmonic musical metadata
descriptors from audio, and allow the user to interact with the archive contents in a manner not typically allowed in archive access systems. To this end, the IMAAS system incorporates a range of real-time interaction tools which allow the user to modify the retrieved audio in a number of ways including the ability to isolate individual instruments in stereo mixes, pitch and timescale modification, …
The Integrated Control Of The Rotor Side And Grid Side Converters In A Dfig To Reduce Both Power And Torque Pulsations During Network Voltage Unbalance Conditions., Joseph Kearney, Michael Conlon, Eugene Coyle
The Integrated Control Of The Rotor Side And Grid Side Converters In A Dfig To Reduce Both Power And Torque Pulsations During Network Voltage Unbalance Conditions., Joseph Kearney, Michael Conlon, Eugene Coyle
Conference papers
No abstract provided.
Optimisation Of Multicast Routing In Wireless Mesh Networks, Brian Keegan, Karol Kowalik, Mark Davis
Optimisation Of Multicast Routing In Wireless Mesh Networks, Brian Keegan, Karol Kowalik, Mark Davis
Conference papers
In recent years Wireless Mesh Networks have been deployed and grown in popularity in many metropolitan areas. The deployment of such networks has allowed clients to gain access to publicly available broadband networks. The implementation of wireless mesh networks requires that backhaul services (traditionally carried by wired networks) be maintained via wireless mesh points. Because of their structure, wireless mesh networks provide an excellent means for targeting a large group of end users or simply to relay data. This may be achieved by means of broadcasting or more specifically multicasting. The lack of standards and support for multicasting over wireless …
Investigation Of Across-Layer Modification To The Dsr Routing Protocol In Wireless Mesh Networks, Mustafa Ramadhan, Mark Davis
Investigation Of Across-Layer Modification To The Dsr Routing Protocol In Wireless Mesh Networks, Mustafa Ramadhan, Mark Davis
Conference papers
This work introduces a cross-layer modification to the DSR protocol that increases the global throughput in wireless mesh networks. In our modified DSR protocol we have introduced the Access Efficiency metric as an alternative to the hop-count metric in order to improve the route selection mechanism. The selected path in the route selection mechanism is identified by choosing the path with the highest minimum Access Efficiency value. We have employed the OPNET modeller as a simulator to examine two different patterns of traffic for a series of randomly generated network topologies. Each topology was simulated twice. One simulation used the …
An Investigation Of The Correlation Between Passive Monitoring And Activie Probing Techniques Used In Wlan Mesh Networks, Chenzhe Zhang, Mark Davis
An Investigation Of The Correlation Between Passive Monitoring And Activie Probing Techniques Used In Wlan Mesh Networks, Chenzhe Zhang, Mark Davis
Conference papers
In recent years, Wireless Mesh Networks (WMNs) have emerged as a promising solution to provide low cost networks that extend Internet access and other networking services. Mesh routers form the backbone connectivity through cooperative routing in an often unstable wireless medium. Therefore, the techniques used to monitor and manage the performance metrics to help optimize the link performance in WMNs. This paper presents an assessment of the correlation between passive monitoring and active probing techniques used for link performance measurement in WMNs. This paper presents an assessment of the correlation between passive monitoring and active probing techniques used for link …
Effects Of Lline Rate On Vvideo Qos Over Wireless Networks: An Experimental Approach, Stuart Wallace, Mark Davis
Effects Of Lline Rate On Vvideo Qos Over Wireless Networks: An Experimental Approach, Stuart Wallace, Mark Davis
Conference papers
Video streaming over Wireless Local Area Networks (WLANS) is becoming an increasingly popular service. However, end user OoS is highly influenced by many factors. These include the video codec used, the packetization scheme, error concealment and correction techniques, the complexity of the video, propagation losses, and the line rate. In this paper the effect of the line rate on the capacity of the network when streaming multimedia content is analyzed experimentally. It is shown that as the line rate decreases the bandwidth load of the video stream dramatically increases leading to poor QoS at the client side. As automatic line …
Control Of Double Fed Induction Generator Wind Turbine During Network Voltage Unbalance Conditions, Joseph Kearney, Michael Conlon
Control Of Double Fed Induction Generator Wind Turbine During Network Voltage Unbalance Conditions, Joseph Kearney, Michael Conlon
Conference papers
The behaviour of Double-Fed Induction Generators to supply network voltage unbalance is investigated. The paper describes a method to control the rotor-side converter in a DFIG when subjected to the effects of network voltage unbalance conditions. A parallel control scheme is implemented to control the positive and negative sequence components independently. A DFIG model is implemented in Matlab/Simulink and simulations show the reduction in power and torque oscillations and a reduction in the high unbalanced currents generated as a result of the applied voltage unbalance.
An Evaluation Of A Conservative Transmit Power Control Mechanism On An Indoor 802.11 Wireless Mesh Testbed, Karol Kowalik, Marek Bykowski, Brian Keegan, Mark Davis
An Evaluation Of A Conservative Transmit Power Control Mechanism On An Indoor 802.11 Wireless Mesh Testbed, Karol Kowalik, Marek Bykowski, Brian Keegan, Mark Davis
Conference papers
Power control techniques for IEEE 802.11 wireless networks have already gained considerable attention. Such techniques are particularly attractive because they can improve various aspects of wireless network operation such as interference mitigation, spatial reuse in dense wireless deployments, topology control, and link quality enhancement. In this paper we propose a novel delivery ration based Conservative Transmit Power Control (ConTPC) mechanism. Our implementation is conservative when it comes to deciding if the transmit power should be reduced for a given link. This is because we do not want poor quality wireless links to further reduce their quality and be overwhelmed by …
Practical Issues Of Power Control In Ieee 802.11 Wireless Devices, Karol Kowalik, Marek Bykowski, Brian Keegan, Mark Davis
Practical Issues Of Power Control In Ieee 802.11 Wireless Devices, Karol Kowalik, Marek Bykowski, Brian Keegan, Mark Davis
Conference papers
Power control techniques for IEEE 802.11 wireless networks have already gained much attention. Such techniques are particularly attractive because they can improve various aspects of wireless network operations such as interference mitigation, spatial reuse in dense wireless deployments, topology control, and link quality enhancement. However, until recently implementing such advanced power control using off-the-shelf wireless devices was not considered possible. For example, Abdesslem et al. [1] stated that “many novel power control solutions cannot be efficiently implemented over existing IEEE 802.11 cards”. However, in this paper we demonstrate that power control is now feasible and can be implemented in current …
Throughput Enhancement Through Combined Fragmentation And Rate Method In Ieee 802.11b Wlans, Marek Bykowski, Karol Kowalik, Brian Keegan, Mark Davis
Throughput Enhancement Through Combined Fragmentation And Rate Method In Ieee 802.11b Wlans, Marek Bykowski, Karol Kowalik, Brian Keegan, Mark Davis
Conference papers
IEEE 802.11 allows for fragmentation tuning and rate selection. Their combined usage is referred sometimes to link adaptation. However, the algorithms of link adaptation are beyond the 802.11 standards. In this paper we investigate the benefits arising from proper use of link adaptation. Particularly, we develop a mathematical model describing the fragmented transmission in 802.11b. We examine potential benefits of it over AWGN and fading channels. More significantly we combine fragmentation tuning with bit-rate selection to yield the highest achievable throughput performance for any given channel conditions. Finally, we propose an algorithm that performs the optimal link adaptation.
Teaching And Assessment Of Students Taking A First Year, Level 7 Subject: Analysis And Actions, Aidan O'Dwyer
Teaching And Assessment Of Students Taking A First Year, Level 7 Subject: Analysis And Actions, Aidan O'Dwyer
Conference papers
This contribution critically analyses the teaching and assessment strategies used on the core Electrical Systems subject in the first year of a three-year, Level 7, degree programme in Electrical Engineering at Dublin Institute of Technology. The author has the responsibility for development and instruction in the subject since 2004. In the 2004-5 and 2005-6 academic years, the didactic teaching approach and the assessment strategy ensured good educational outcomes. This was not the case in the 2006-7 academic year. The contribution will analyse the reasons for this, taking an evidence-based approach (i.e. analysing the assessment data in detail). Two conclusions that …
The Capability Of The Edca Mechanism To Support Voice Traffic In A Mixed Voice/Data Transmission Over 802.11e Wlans: An Experimental Investigation, Miroslaw Narbutt, Mark Davis
The Capability Of The Edca Mechanism To Support Voice Traffic In A Mixed Voice/Data Transmission Over 802.11e Wlans: An Experimental Investigation, Miroslaw Narbutt, Mark Davis
Conference papers
In this paper we experimentally evaluate the capability of the EDCA mechanism to support voice traffic in a mixed voice/data transmission over 802.11e WLANs. In particular we investigate how real-time voice transmission can be supported by tuning four EDCA parameters, namely AIFSN, CWmin, CWmax and TXOP and how this impacts on background data transmission. The experimental set-up involves fifteen VoIP terminals sending bi-directional traffic between wired and wireless subnets and another station injecting various types of heavy background load to the wireless subnet. End-to-end voice transmission quality is predicted from time-varying transmission impairments with the use of the latest Appendix …
Analysis Of A Variable Speed Double-Fed Induction Generator Wind Turbine During Network Voltage Unbalance Conditions., Joseph Kearney, Michael Conlon
Analysis Of A Variable Speed Double-Fed Induction Generator Wind Turbine During Network Voltage Unbalance Conditions., Joseph Kearney, Michael Conlon
Conference papers
The behaviour of Double-Fed Induction Generators to supply network voltage unbalance is investigated. The paper shows the effects that voltage unbalance can have on a DFIG, using Matlab/Simulink. The results from simulations show that voltage unbalance affects both the induction generator and the rotor converter, due to the high unbalanced currents generated. The ability to modify the control strategy of a DFIG to compensate for voltage unbalance is outlined and simulations show the improvements to the performance of the DFIG.
Video Frame Differentiation For Streamed Multimedia Over Heavilty Loaded Ieee 802.11e Wlan Using Txop, Nicola Cranley, Mark Davis
Video Frame Differentiation For Streamed Multimedia Over Heavilty Loaded Ieee 802.11e Wlan Using Txop, Nicola Cranley, Mark Davis
Conference papers
In this paper we perform an experimental investigation of using video frame differentiation in conjunction with the TXOP facility to enhance the transmission of parallel multimedia streaming sessions in IEEE 802.11e. The delay constraints associated with the audio and video streams that comprise a multimedia session pose the greatest challenge since real-time multimedia is particularly sensitive to delay as the packets require a strict bounded end-to-end delay. Video streaming applications are considered to be bursty. This burstiness is due to the frame rate of vide., the intrinsic hierarchical structure of the constituent video frame types. The TXOP facility is particularly …
Rare: Resource Aware Routing For Mesh, Karol Kowalik, Brian Keegan, Mark Davis
Rare: Resource Aware Routing For Mesh, Karol Kowalik, Brian Keegan, Mark Davis
Conference papers
An important element of any routing protocol used for Wireless Mesh Networks (WMNs) is the link cost function used to represent the radio link characteristic. The majority of the routing protocols for WMNs attempt to accurately characterise the radio link quality by constructing the link cost function from the measurements obtained using active probing techniques, which introduces overhead. In this paper we propose a new approach called Resource Aware Routing for mEsh (RARE) which instead employs passive monitoring to gather radio link information. This results in a smaller overhead than the other methods that require active network probing, and is …
Making Olsr Aware Of Resources, Karol Kowalik, Brian Keegan, Mark Davis
Making Olsr Aware Of Resources, Karol Kowalik, Brian Keegan, Mark Davis
Conference papers
An important element of any routing protocol used for Wireless Mesh Networks (WMNs) is the link cost function used to represent the radio link characteristic. The majority of the routing protocols for WMNs attempt to accurately characterise the radio link quality by constructing the link cost function from the measurements obtained using active probing techniques which introduces overhead. In this paper we present a modified version of the Optimized Link State Routing (OLSR) protocol which uses the link cost function values provided the Resource Aware Routing for mEsh (RARE) module which employs passive monitoring to gather radio link information. This …
Experimental Investigation On Voip Performance And The Resource Utilization In 802.11b Wlans, Miroslaw Narbutt, Mark Davis
Experimental Investigation On Voip Performance And The Resource Utilization In 802.11b Wlans, Miroslaw Narbutt, Mark Davis
Conference papers
In a shared medium network like the 802.11b WLAN, predicting the quality of VoIP calls from the resource usage of the wireless medium is highly desirable. Analyzing the bandwidth usage at the L2/MAC layer may be especially useful for potential QoS provisioning and call admission schemes. This paper experimentally investigates the relationship between resource utilization in WLANS and the quality of VoIP calls transmitted over wireless medium. Specifically we evaluate how the amount of free bandwidth influences transmission impairments (i.e. delay, loss and jitter) and thus call quality. Resource utilization (under the MAC bandwidth components framework) is calculated by a …
Experimental Analysis Of An 802.11b Wireless Mesh Network, Brian Keegan, Karol Kowalik, Mark Davis
Experimental Analysis Of An 802.11b Wireless Mesh Network, Brian Keegan, Karol Kowalik, Mark Davis
Conference papers
Wireless Mesh Networks (WMNs) are a type of radio-based network which require minimal configuration and infrastructure. They can be built using relatively low cost radio and computing platforms. In this paper we attempt to analyze the performance of a simple WNM using various packet sizes as well as a multi-hop WMN.
Experimental Investigation Of The Effects Of Background Traffic Loads On Streamed Video Over 802.11b Wlans, Tanmoy Debnath, Nicola Cranley, Mark Davis
Experimental Investigation Of The Effects Of Background Traffic Loads On Streamed Video Over 802.11b Wlans, Tanmoy Debnath, Nicola Cranley, Mark Davis
Conference papers
Video is a frame based media and video streaming is often described as “bursty” which has a large impact on the Quality of Service of the video streaming application over WLAN networks. In this paper the impact of background load on the performance of streaming MPEG-4 video with a video server located on the wired network streaming to wireless client is analysed. We experimentally investigate the performance for both uplink and downlink loads. The performance is measured in terms of the key parameters of bit rate, loss rate and mean delay since these are the primary factors that affect the …
Moving A Part-Time Engineering Course To A Student-Centred Paradigm, Kevin Kelly
Moving A Part-Time Engineering Course To A Student-Centred Paradigm, Kevin Kelly
Conference papers
This paper is a further reflection on two conference papers presented at the World Conference for Continuing Engineering Education (WCCEE) in Vienna in April 2006 and National University of Ireland (NUI) Galway Conference: The Challenge of Diversity: Teaching, Support and Student Learning , June 2006. Both conference papers dealt with different aspects of my experiences of the theoretical and pedagogical changes required in re-design and delivery of a part-time engineering programme for the continuing education development of electrical engineers in the workforce.
Gauging Voip Call Quality From 802.11 Wlan Resource Usage, Miroslaw Narbutt, Mark Davis
Gauging Voip Call Quality From 802.11 Wlan Resource Usage, Miroslaw Narbutt, Mark Davis
Conference papers
In this paper we experimentally study the relationship between resource utilization in the wireless LAN and the quality of VoIP calls transmitted over the wireless medium. Specifically we evaluate how its overall capacity is shared between three basic MAC bandwidth components (load, access and free) as the number of VoIP calls increases and how it influences transmission impairments (delay, loss and jitter) and thus call quality. Resource utilization (under the MAC bandwidth components framework) is calculated by a WLAN probe application that passively “sniffs” packets at the L2/MAC layer of the wireless medium and analyses their headers and temporal characteristics. …
Effect Of Free Bandwidth On Voip Performance In 802.11b Wlan Networks, Miroslaw Narbutt, Mark Davis
Effect Of Free Bandwidth On Voip Performance In 802.11b Wlan Networks, Miroslaw Narbutt, Mark Davis
Conference papers
In this paper we experimentally study the relationship between bandwidth utilization in the wireless LAN and the quality of VoIP calls transmitted over the wireless medium. Specifically we evaluate how the amount of free bandwidth decreases as the number of calls increases and how this influences transmission impairments (i.e. delay, loss and jitter) and thus degrades call quality. We show that the amount of free bandwidth is a good indicator for predicting VoIP call quality.
The Impact Of Tcp Sliding Window On The Performance Of Ieee 802.11 Wlans, Enrique Roques Gomez, Mark Davis
The Impact Of Tcp Sliding Window On The Performance Of Ieee 802.11 Wlans, Enrique Roques Gomez, Mark Davis
Conference papers
In this paper the TCP sliding window mechanism is experimentally investigated as one of the possible causes of the unfairness often observed as IEEE802.11 wireless LANs. We show how by appropriately sizing the sliding window it is possible to re-introduce fairness into the operation of the WLAN.
Study Of The Behaviour Of Video Streaming Over Ieee 802.11b Wlan Networks, Nicola Cranley, Mark Davis
Study Of The Behaviour Of Video Streaming Over Ieee 802.11b Wlan Networks, Nicola Cranley, Mark Davis
Conference papers
The performance of video streaming over WLAN networks is not only influenced by the state of the network but also by the encoding configuration parameters of the video stream, such as the video content being streamed, how the vide is encoded and how it is transmitted. In this paper, we analyse the unique delay characteristic of video streaming applications in a WLAN environment. We show that the “burstiness” of video is due to the frame-based nature of encoded video. We show how each video frame is transmitted as a burst of packets that is queued at the Access Point causing …
Experimental Comparison Of Wired Versus Wireless Video Streaming Over Ieee 802.11b Wlans, Tanmoy Debnath, Nicola Cranley, Mark Davis
Experimental Comparison Of Wired Versus Wireless Video Streaming Over Ieee 802.11b Wlans, Tanmoy Debnath, Nicola Cranley, Mark Davis
Conference papers
In this paper the performance of streaming MPEG-4 video with a video server located on the wired network streaming to wireless clients is compared with the performance of a video server located in the wireless network streaming to wireless video clients. We experimentally investigate the performance for a number of concurrent video streams with varying video frame sizes, frame rates and packetisation schemes. The performance is measured in terms of the key parameters of bit rate, loss rate and mean delay. We show how that there is a trade-off for these parameters for a wired and wireless located server. We …
Performance Evaluation Of Video Streaming With Background Traffic Over Ieee 802.11 Wlan Networks, Nicola Cranley, Mark Davis
Performance Evaluation Of Video Streaming With Background Traffic Over Ieee 802.11 Wlan Networks, Nicola Cranley, Mark Davis
Conference papers
There is an increasing demand for multimedia streaming applications over WLAN networks. MPEG-4 and H.264 are compression standards targeted at high-quality streamed multimedia services over wireless best-effort IP networks. However, the dynamic nature of wireless networks in terms of fluctuating bandwidth and time-varying delays makes it difficult to provide good quality streaming under such constraints. Multimedia streaming applications are a demanding and challenging service to deliver over wireless networks. There is a trade-off between the capacity of the wireless network and the quality of the multimedia streaming application. In this paper we investigate the effect the background traffic load has …
Performance Evaluation Of Resource Usage For Unicast Video Streaming Over Ieee 802.11 Wlan Networks, Nicola Cranley, Mark Davis
Performance Evaluation Of Resource Usage For Unicast Video Streaming Over Ieee 802.11 Wlan Networks, Nicola Cranley, Mark Davis
Conference papers
Multimedia streaming applications are a demanding and challenging service to deliver over wireless networks. Such services have a large impact on the resource requirements of the WLAN. However, there are many variables involved in video streaming, such as the video content being streamed, how the video is encoded and how it is sent. This makes the role of radio resource management and the provision of QoS guarantees extremely difficult. In this paper we investigate the network resource requirements for three scenarios: a single unicast video streaming session; multiple unicast video streaming sessions and finally multiple unicast streaming sessions in the …
An Assessment Of The Audio Codec Performance In Voice Over Wlan (Vowlan) Systems, Miroslaw Narbutt, Mark Davis
An Assessment Of The Audio Codec Performance In Voice Over Wlan (Vowlan) Systems, Miroslaw Narbutt, Mark Davis
Conference papers
In this paper we present results of experimental investigation into the performance of three audio codecs (ITU-T G.711, G.723.1 and G.729A) under varying load conditions on a Voice over WLAN system utilizing the IEEE 802.11b wireless LAN standard. The analysis is based upon a new technique for estimating user satisfaction of speech quality calculated from packet delay and packet loss/late measurements. We also demonstrate the importance of the de-jitter buffer playout scheme for insuring speech quality. From our results we conclude that the use of the G.711 audio codec in conjunction with the new adaptive playout scheme gives the highest …
Performance Analysis Of Network-Level Qos With Encoding Configuration For Unicast Video Streaming Over Ieee 802.11 Wlan Networks, Nicola Cranley, Mark Davis
Performance Analysis Of Network-Level Qos With Encoding Configuration For Unicast Video Streaming Over Ieee 802.11 Wlan Networks, Nicola Cranley, Mark Davis
Conference papers
Video streaming has a large impact on the resource requirements of the WLAN. However, there are many variables involved in video streaming, such as the video content being streamed, how the video is encoded and how it is sent. This makes the role of radio resource management extremely difficult. In this paper we investigate the effect that video encoding configurations has on the network resource requirements for unicast video streaming in a WLAN environment. We compare the network resource requirements of several content types encoded at various encoding configurations with varying I-frame frequencies, target encoding bit rates and hint track …