The Experts below are selected from a list of 786 Experts worldwide ranked by ideXlab platform
Nikolaos Pappas - One of the best experts on this subject based on the ideXlab platform.
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Wireless network-level partial relay cooperation: A stable throughput analysis
Journal of Communications and Networks, 2018Co-Authors: Nikolaos Pappas, Jeongho Jeon, Di Yuan, Apostolos Traganitis, Anthony EphremidesAbstract:In this work, we study the benefit of partial relay cooperation. We consider a two-node system consisting of one source and one relay node transmitting information to a common destination. The source and the relay have External Traffic and in addition, the relay is equipped with a flow controller to regulate the incoming Traffic from the source node. The cooperation is performed at the network level. A collision channel with erasures is considered. We provide an exact characterization of the stability region of the system and we also prove that the system with partial cooperation is always better or at least equal to the system without the flow controller.
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Network-Level Cooperation in Energy Harvesting Wireless Networks
2017Co-Authors: Nikolaos Pappas, Jeongho Jeonz, Anthony Ephremidesz, Marios Kountouris, Apostolos TraganitisyAbstract:We consider a two-hop communication network consisted of a source node, a relay and a destination node in which the source and the relay node have External Traffic arrivals. The relay forwards a fraction of the source node's Traffic to the destination and the cooperation is performed at the network level. In addition, both source and relay nodes have energy harvesting capabilities and an unlimited battery to store the harvested energy. We study the impact of the energy constraints on the stability region. Specifically, we provide inner and outer bounds on the stability region of the two-hop network with energy harvesting source and relay.
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Effect of Energy Harvesting on Stable Throughput in Cooperative Relay Systems
arXiv: Information Theory, 2015Co-Authors: Nikolaos Pappas, Marios Kountouris, Jeongho Jeon, Anthony Ephremides, Apostolos TraganitisAbstract:In this paper, the impact of energy constraints on a two-hop network with a source, a relay and a destination under random medium access is studied. A collision channel with erasures is considered, and the source and the relay nodes have energy harvesting capabilities and an unlimited battery to store the harvested energy. Additionally, the source and the relay node have External Traffic arrivals and the relay forwards a fraction of the source node's Traffic to the destination; the cooperation is performed at the network level. An inner and an outer bound of the stability region for a given transmission probability vector are obtained. Then, the closure of the inner and the outer bound is obtained separately and they turn out to be identical. This work is not only a step in connecting information theory and networking, by studying the maximum stable throughput region metric but also it taps the relatively unexplored and important domain of energy harvesting and assesses the effect of that on this important measure.
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GlobalSIP - Network-level cooperation in energy harvesting wireless networks
2013 IEEE Global Conference on Signal and Information Processing, 2013Co-Authors: Nikolaos Pappas, Jeongho Jeonz, Anthony Ephremidesz, Marios Kountouris, Apostolos TraganitisyAbstract:We consider a two-hop communication network consisted of a source node, a relay and a destination node in which the source and the relay node have External Traffic arrivals. The relay forwards a fraction of the source node's Traffic to the destination and the cooperation is performed at the network level. In addition, both source and relay nodes have energy harvesting capabilities and an unlimited battery to store the harvested energy. We study the impact of the energy constraints on the stability region. Specifically, we provide inner and outer bounds on the stability region of the two-hop network with energy harvesting source and relay.
Masoud Hamedi - One of the best experts on this subject based on the ideXlab platform.
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improving scats operation during congestion periods using internal External Traffic metering strategy
Promet-traffic & Transportation, 2016Co-Authors: Shahriar Afandizadeh Zargari, Nazli Dehghani, Hamid Mirzahossein, Masoud HamediAbstract:Traffic metering is one of the effective strategies of preventing gridlock at urban signalized intersections during oversaturated conditions. This strategy could be implemented by adjusting signal timing schemes of the connected intersections of congested network in dynamic setting. This paper demonstrates the benefits of internal/External Traffic metering strategy on a real case study in Tehran, the capital of Iran. For this purpose, the model outputs have been considered as input to set of SCATS scenarios for signal timing. In each test case the system is forced to use plans obtained from the model instead of using common built-in plans that had been used before, and the performance is measured using the VISSIM simulator to show differences. The results show significant improvement in network average travel time when using internal/External Traffic metering strategy. Additionally, the average queue lengths are maintained near the optimal level since the model utilizes upstream arterial capacity.
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Improving scats operation during congestion periods using internal/External Traffic metering strategy
PROMET - Traffic&Transportation, 2016Co-Authors: Shahriar Afandizadeh Zargari, Nazli Dehghani, Hamid Mirzahossein, Masoud HamediAbstract:Traffic metering is one of the effective strategies of preventing gridlock at urban signalized intersections during oversaturated conditions. This strategy could be implemented by adjusting signal timing schemes of the connected intersections of congested network in dynamic setting. This paper demonstrates the benefits of internal/External Traffic metering strategy on a real case study in Tehran, the capital of Iran. For this purpose, the model outputs have been considered as input to set of SCATS scenarios for signal timing. In each test case the system is forced to use plans obtained from the model instead of using common built-in plans that had been used before, and the performance is measured using the VISSIM simulator to show differences. The results show significant improvement in network average travel time when using internal/External Traffic metering strategy. Additionally, the average queue lengths are maintained near the optimal level since the model utilizes upstream arterial capacity.
Michael Anderson - One of the best experts on this subject based on the ideXlab platform.
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Spatial Economic Model for Forecasting the Percentage Splits of External Trips on Highways Approaching Small Communities
Transportation Research Record: Journal of the Transportation Research Board, 2005Co-Authors: Michael AndersonAbstract:The main difficulty in forecasting Traffic volumes in small urban communities is identifying the amount and destination of the External Traffic. Three methods exist for determining the percentage of External Traffic destined for the study community (External-internal trips) or through the study community (External-External trips): a comprehensive origin-destination study, a cordon line origin-destination study, and the use of regression equations. This paper examines the possibility of the use of an alternative technique, based on a spatial economic model, to determine the Traffic distribution. The project uses an economic model, which includes surrounding community factors, to determine the trip rates for three communities within Alabama and compares the results obtained from this model with the results given by a commonly accepted regression equation and a recently completed cordon line origin-destination study performed by using video surveillance. It is demonstrated that the economic model performs we...
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A Spatial Economic Model to Forecast External Trips in Small Communities
2004Co-Authors: Michael AndersonAbstract:A primary concern in forecasting Traffic volumes to support highway bypass infrastructure improvements, when proposed for a small community, is the quantification of External Traffic on approach roadways. Essentially, the question transportation professionals are trying to answer is how many vehicles are destined for town versus vehicles solely passing through the town. The current methods for calculating the External Traffic include conducting an origin-destination study or applying existing regression equations. This paper's objective is to examine the possibility of using spatial economic models to predict the External Traffic values. This paper applies two spatial economic models to predict the External Traffic for three small communities in Alabama, and compares the model results against a cordon-line origin-destination study. The paper identifies the model providing External Traffic volumes that best replicate the observed External Traffic in the case study cities and makes recommendations regarding the various models and their ability to forecast External Traffic.
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Evaluation of Models to Forecast External-External Trip Percentages
Journal of Urban Planning and Development-asce, 1999Co-Authors: Michael AndersonAbstract:The main difficulty in forecasting Traffic volumes along a rural bypass is identifying the External Traffic, both Traffic entering the town from outside and Traffic continuing through the town to an ultimate destination. Three methods exist for determining the percentage of External Traffic destined for town, External-internal, or through town, External-External: A comprehensive origin-destination study, cordon line origin-destination study, or a regression equation. The objective of this paper is to examine the possibility of using different techniques, based on spatial economic models to determine the Traffic percentages. This project will use three different models to determine the activity base for the city of Waverly, Iowa, and compare the models with the results given by the regression equation and a cordon line origin-destination study performed in the 1970s. This paper demonstrates that Huff's probability contour model performs well for the case study and recommends that this model be used in the ...
Xiaohui Zhang - One of the best experts on this subject based on the ideXlab platform.
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Analysis Method of External Traffic Demand in City Area
Journal of Transportation Systems Engineering and Information Technology, 2014Co-Authors: Shengwen Tu, Xiaohui ZhangAbstract:To overcome the disadvantages of the existing method, a “dual four-stage” method” is put forward to analyze External Traffic demand in city area considering the characteristics of External Traffic. The method is carried out by two steps, and in the first step the city area is regarded as an overall Traffic zone and the “four-stage” method of regional Traffic demand analysis is used to obtain the total generation volumes of internal-External (IE) & External-internal (EI) trips of city area as well as the Traffic volumes of both directions of all the arterial highways through the city in planning years. In the second step, the planning area of city is divided into several parts as internal Traffic zones, and the External Traffic zones are set near the junctions of highways and cordon line, then the “four-stage” method is applied for the second time to obtain the trip generation and distribution of IE & EI trips and (External-External) EE trips for internal Traffic zones and External Traffic zones in planning years. The application of the analysis on External Traffic demand for comprehensive transportation planning of Zhenjiang City shows that the proposed method combines the advantages of influence area method and Cordon Line method it overcomes disadvantages of the two methods, and the results are more consistent with the real situation.
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Analysis Method of External Traffic Demand in City Area
Journal of Transportation Systems Engineering and Information Technology, 2014Co-Authors: Shengwen Tu, Xiaohui ZhangAbstract:To overcome the disadvantages of the existing method, a “dual four-stage” method” is put forward to analyze External Traffic demand in city area considering the characteristics of External Traffic. The method is carried out by two steps, and in the first step the city area is regarded as an overall Traffic zone and the “four-stage” method of regional Traffic demand analysis is used to obtain the total generation volumes of internal-External (IE) & External-internal (EI) trips of city area as well as the Traffic volumes of both directions of all the arterial highways through the city in planning years. In the second step, the planning area of city is divided into several parts as internal Traffic zones, and the External Traffic zones are set near the junctions of highways and cordon line, then the “four-stage” method is applied for the second time to obtain the trip generation and distribution of IE & EI trips and (External-External) EE trips for internal Traffic zones and External Traffic zones in planning years. The application of the analysis on External Traffic demand for comprehensive transportation planning of Zhenjiang City shows that the proposed method combines the advantages of influence area method and Cordon Line method it overcomes disadvantages of the two methods, and the results are more consistent with the real situation.
Leyou Zhang - One of the best experts on this subject based on the ideXlab platform.
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Scalable Data Center Network Architecture With Distributed Placement of Optical Switches and Racks
Journal of Optical Communications and Networking, 2014Co-Authors: Jie Xiao, Xiaohong Jiang, Bin Wu, Hong Wen, Achille Pattavina, Leyou ZhangAbstract:Cloud services are fundamentally supported by data center networks (DCNs). With the fast growth of cloud services, the scale of DCNs is increasing rapidly, leading to great concern about system scalability due to multiple constraints. This paper proposes a scalable DCN architecture based on optical switching and transmission, with the distributed placement of optical switches and server racks at different nodes in a given optical network. This solves the scalability issue by relaxing power and cooling constraints and by reducing the number of (electronic) switches using high-capacity optical switches, as well as by simplifying DCN internal connections using wavelengths in the optical network. Moreover, the distributed optical switches provide service access interfaces to meet demand within areas, and thus reduce the transmission cost of the External Traffic. The major concern is the additional delay and cost for remote transmissions of the DCN internal Traffic. To this end, we study the component placement problem in DCNs under a given set of External demands and internal Traffic patterns. By leveraging among multiple conflicting factors such as scalability and internal overhead of the DCN as well as the transmission cost of External Traffic, we propose both an integer linear program and a heuristic to minimize the system cost of a DCN while satisfying all service demands in the network. This addresses both scalability and cost minimization issues from a network point of view.
