The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Rachid El-azouzi - One of the best experts on this subject based on the ideXlab platform.
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Flow-Level QoE of Video Streaming in Wireless Networks
IEEE Transactions on Mobile Computing, 2016Co-Authors: Salah Eddine Elayoubi, Eitan Altman, Rachid El-azouziAbstract:The Quality of Experience (QoE) of streaming service is often degraded by frequent play-back interruptions. To mitigate the interruptions, the media player prefetches streaming contents before starting playback, at a cost of initial delay. We study the QoE of streaming from the perspective of flow dynamics. Firstly, a framework is developed for QoE when streaming users join the network randomly and leave after downloading completion. We model the distribution of prefetching delay using partial differential equations (PDEs), and the probability generating function of playout buffer Starvations using ordinary differential equations (ODEs) for constant bit-rate (CBR) streaming. The explicit form Starvation probabilities and mean start-up delay are obtained by use of a matrix function approach. Secondly, we extend our framework to characterize the throughput variation caused by opportunistic scheduling at the base station, and the playback variation of variable bit-rate (VBR) streaming. Our study reveals that the flow dynamics is the fundamental reason of playback Starvation. The QoE of streaming service is dominated by the first moments such as the average throughput of opportunistic scheduling and the mean playback rate. While the variances of throughput and playback rate have very limited impact on Starvation behavior in practice.
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Flow Level QoE of Video Streaming in Wireless Networks
arXiv preprint arXiv: …, 2014Co-Authors: Yuedong Xu, Salah eddine E. Elayoubi, Eitan Altman, Rachid El-azouziAbstract:The Quality of Experience (QoE) of streaming service is often degraded by frequent playback interruptions. To mitigate the interruptions, the media player prefetches streaming contents before starting playback, at a cost of delay. We study the QoE of streaming from the perspective of flow dynamics. First, a framework is developed for QoE when streaming users join the network randomly and leave after downloading completion. We compute the distribution of prefetching delay using partial differential equations (PDEs), and the probability generating function of playout buffer Starvations using ordinary differential equations (ODEs) for CBR streaming. Second, we extend our framework to characterize the throughput variation caused by opportunistic scheduling at the base station, and the playback variation of VBR streaming. Our study reveals that the flow dynamics is the fundamental reason of playback Starvation. The QoE of streaming service is dominated by the first moments such as the average throughput of opportunistic scheduling and the mean playback rate. While the variances of throughput and playback rate have very limited impact on Starvation behavior.
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Impact of flow-level dynamics on QoE of video streaming in wireless networks
Proceedings - IEEE INFOCOM, 2013Co-Authors: Yuedong Xu, Salah eddine E. Elayoubi, Eitan Altman, Rachid El-azouziAbstract:The Quality of Experience (QoE) of streaming service is often degraded by frequent playback interruptions. To mitigate the interruptions, the media player prefetches streaming contents before starting playback, at a cost of delay. We study the QoE of streaming from the perspective of flow dynamics. First, a framework is developed for QoE when streaming users join the network randomly and leave after downloading completion. We compute the distribution of prefetching delay using partial differential equations (PDEs), and the probability generating function of playout buffer Starvations using ordinary differential equations (ODEs). Second, we extend our framework to characterize the throughput variation caused by opportunistic scheduling at the base station in the presence of fast fading. Our study reveals that the flow dynamics is the fundamental reason of playback Starvation. The QoE of streaming service is dominated by the average throughput of opportunistic scheduling, while the variance of throughput has very limited impact on Starvation behavior.
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Probabilistic Analysis of Buffer Starvation in Markovian Queues
2012Co-Authors: Eitan Altman, Rachid El-azouzi, Majed Haddad, Salah Eddine Elayoubi, Tania JimenezAbstract:Our purpose in this paper is to obtain the \emph{exact distribution} of the number of buffer Starvations within a sequence of $N$ consecutive packet arrivals. The buffer is modeled as an M/M/1 queue. When the buffer is empty, the service restarts after a certain amount of packets are \emph{prefetched}. With this goal, we propose two approaches, one of which is based on \emph{Ballot theorem}, and the other uses recursive equations. The Ballot theorem approach gives an explicit solution, but at the cost of the high complexity order in certain circumstances. The recursive approach, though not offering an explicit result, needs fewer computations. We further propose a fluid analysis of Starvation probability on the file level, given the distribution of file size and the traffic intensity. The Starvation probabilities of this paper have many potential applications. We apply them to optimize the quality of experience (QoE) of media streaming service, by exploiting the tradeoff between the start-up delay and the Starvation.
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Probabilistic Analysis of Buffer Starvation in
2011Co-Authors: Eitan Altman, Rachid El-azouzi, Majed Haddad, Salah Eddine Elayoubi, Tania JimenezAbstract:Our purpose in this paper is to obtain the exact dis- tribution of the number of buffer Starvations within a sequence of N consecutive packet arrivals. The buffer is modeled as an M/M/1 queue, plus the consideration of bursty arrivals characterized by an interrupted Poisson process. When the buffer is empty, the service restarts after a certain amount of packets are prefetched. With this goal, we propose two approaches, one of which is based on Ballot theorem, and the other uses recursive equations. The Ballot theorem approach gives an explicit solution, but at the cost of the high complexity order in certain circumstances. The recursive approach, though not offering an explicit result, needs fewer computations. We further propose a fluid analysi s of Starvation probability on the file level, given the distri bution of file size and the traffic intensity. The Starvation probabi lities of this paper have many potential applications. We apply them to optimize the quality of experience (QoE) of media streaming service, by exploiting the tradeoff between the start-up delay and the Starvation.
Eitan Altman - One of the best experts on this subject based on the ideXlab platform.
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Flow-Level QoE of Video Streaming in Wireless Networks
IEEE Transactions on Mobile Computing, 2016Co-Authors: Salah Eddine Elayoubi, Eitan Altman, Rachid El-azouziAbstract:The Quality of Experience (QoE) of streaming service is often degraded by frequent play-back interruptions. To mitigate the interruptions, the media player prefetches streaming contents before starting playback, at a cost of initial delay. We study the QoE of streaming from the perspective of flow dynamics. Firstly, a framework is developed for QoE when streaming users join the network randomly and leave after downloading completion. We model the distribution of prefetching delay using partial differential equations (PDEs), and the probability generating function of playout buffer Starvations using ordinary differential equations (ODEs) for constant bit-rate (CBR) streaming. The explicit form Starvation probabilities and mean start-up delay are obtained by use of a matrix function approach. Secondly, we extend our framework to characterize the throughput variation caused by opportunistic scheduling at the base station, and the playback variation of variable bit-rate (VBR) streaming. Our study reveals that the flow dynamics is the fundamental reason of playback Starvation. The QoE of streaming service is dominated by the first moments such as the average throughput of opportunistic scheduling and the mean playback rate. While the variances of throughput and playback rate have very limited impact on Starvation behavior in practice.
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analysis of buffer Starvation with application to objective qoe optimization of streaming services
IEEE Transactions on Multimedia, 2014Co-Authors: Eitan Altman, Rachid Elazouzi, Majed Haddad, Salah Eddine Elayoubi, Tania JimenezAbstract:Our purpose in this paper is to characterize buffer Starvations for streaming services. The buffer is modeled as a FIFO queue with exponential service time and Poisson arrivals. When the buffer is empty, the service restarts after a certain amount of packets are prefetched. With this goal, we propose two approaches to obtain exact distribution of the number of buffer Starvations, one of which is based on Ballot theorem, and the other uses recursive equations. The Ballot theorem approach gives an explicit result. We extend this approach to the scenario with a constant playback rate using Takacs Ballot theorem. The recursive approach, though not offering an explicit result, allows us to obtain the distribution of Starvations with non-independent and identically distributed (i.i.d.) arrival process in which an ON/OFF bursty arrival process is considered. We further compute the Starvation probability as a function of the amount of prefetched packets for a large number of files via a fluid analysis. Among many potential applications of Starvation analysis, we show how to apply it to optimize objective quality of experience (QoE) of media streaming, by exploiting the tradeoff between startup/rebuffering delay and Starvations.
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Flow Level QoE of Video Streaming in Wireless Networks
arXiv preprint arXiv: …, 2014Co-Authors: Yuedong Xu, Salah eddine E. Elayoubi, Eitan Altman, Rachid El-azouziAbstract:The Quality of Experience (QoE) of streaming service is often degraded by frequent playback interruptions. To mitigate the interruptions, the media player prefetches streaming contents before starting playback, at a cost of delay. We study the QoE of streaming from the perspective of flow dynamics. First, a framework is developed for QoE when streaming users join the network randomly and leave after downloading completion. We compute the distribution of prefetching delay using partial differential equations (PDEs), and the probability generating function of playout buffer Starvations using ordinary differential equations (ODEs) for CBR streaming. Second, we extend our framework to characterize the throughput variation caused by opportunistic scheduling at the base station, and the playback variation of VBR streaming. Our study reveals that the flow dynamics is the fundamental reason of playback Starvation. The QoE of streaming service is dominated by the first moments such as the average throughput of opportunistic scheduling and the mean playback rate. While the variances of throughput and playback rate have very limited impact on Starvation behavior.
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Impact of flow-level dynamics on QoE of video streaming in wireless networks
Proceedings - IEEE INFOCOM, 2013Co-Authors: Yuedong Xu, Salah eddine E. Elayoubi, Eitan Altman, Rachid El-azouziAbstract:The Quality of Experience (QoE) of streaming service is often degraded by frequent playback interruptions. To mitigate the interruptions, the media player prefetches streaming contents before starting playback, at a cost of delay. We study the QoE of streaming from the perspective of flow dynamics. First, a framework is developed for QoE when streaming users join the network randomly and leave after downloading completion. We compute the distribution of prefetching delay using partial differential equations (PDEs), and the probability generating function of playout buffer Starvations using ordinary differential equations (ODEs). Second, we extend our framework to characterize the throughput variation caused by opportunistic scheduling at the base station in the presence of fast fading. Our study reveals that the flow dynamics is the fundamental reason of playback Starvation. The QoE of streaming service is dominated by the average throughput of opportunistic scheduling, while the variance of throughput has very limited impact on Starvation behavior.
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Probabilistic Analysis of Buffer Starvation in Markovian Queues
2012Co-Authors: Eitan Altman, Rachid El-azouzi, Majed Haddad, Salah Eddine Elayoubi, Tania JimenezAbstract:Our purpose in this paper is to obtain the \emph{exact distribution} of the number of buffer Starvations within a sequence of $N$ consecutive packet arrivals. The buffer is modeled as an M/M/1 queue. When the buffer is empty, the service restarts after a certain amount of packets are \emph{prefetched}. With this goal, we propose two approaches, one of which is based on \emph{Ballot theorem}, and the other uses recursive equations. The Ballot theorem approach gives an explicit solution, but at the cost of the high complexity order in certain circumstances. The recursive approach, though not offering an explicit result, needs fewer computations. We further propose a fluid analysis of Starvation probability on the file level, given the distribution of file size and the traffic intensity. The Starvation probabilities of this paper have many potential applications. We apply them to optimize the quality of experience (QoE) of media streaming service, by exploiting the tradeoff between the start-up delay and the Starvation.
Mina Hoorfar - One of the best experts on this subject based on the ideXlab platform.
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Study of anode and cathode Starvation effects on the impedance characteristics of proton exchange membrane fuel cells
Journal of Electroanalytical Chemistry, 2016Co-Authors: Seyed Mohammad Rezaei Niya, Ryan K. Phillips, Mina HoorfarAbstract:Abstract The anode and cathode Starvations in proton exchange membrane fuel cells are studied using the electrochemical impedance spectroscopy. The impedances are measured while the anode and cathode feeding gasses are diluted using helium and nitrogen, respectively, and the Nyquist plots are compared against the normal operating conditions. It is shown that the cathode Starvation significantly inflates the mid-frequency (MF) arc; while similar anode Starvation does not affect the Nyquist plots of the measured impedances. These results are in agreement with the trends predicted from the process model presented.
Soung Chang Liew - One of the best experts on this subject based on the ideXlab platform.
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Temporal Starvation in CSMA Wireless Networks
IEEE Transactions on Mobile Computing, 2015Co-Authors: Caihong Kai, Soung Chang LiewAbstract:It is well known that links in CSMA wireless networks are prone to Starvation. Prior works focused almost exclusively on equilibrium Starvation. Links in CSMA wireless networks are also susceptible to temporal Starvation. Specifically, although some links have good equilibrium throughputs and do not suffer from equilibrium Starvation, they can still have zero or little throughputs for extended periods from time to time. For real-time applications such as VoIP and video streaming, it is desirable to understand and characterize temporal Starvation in CSMA wireless networks. To this end, we develop a “trap theory” to analyze temporal throughput fluctuations. The trap theory serves two functions. First, it allows us to derive new mathematical results that shed light on the transient behavior of CSMA networks. For example, we show that the duration of a trap, during which some links receive zero or little throughputs, is insensitive to the distributions of the transmission time (packet duration) and the backoff countdown time in the CSMA protocol given their respective means. This implies that the phenomenon of temporal Starvation is fundamental and cannot be solved by simply manipulating the probability distributions of the backoff countdown time and transmission time alone. Second, with the trap theory, we can develop analytical tools for computing the “degrees of Starvation” for CSMA networks to aid network design. For example, given a CSMA network, we can determine whether it suffers from Starvation, and if so, which links will starve. Furthermore, the likelihood and durations of temporal Starvation, if any, can also be computed. To further motivate the study of temporal Starvation, we show that the existing remedies designed to solve equilibrium Starvation may not work well as far as temporal Starvation is considered. We believe that the ability to identify and characterize temporal Starvation as established in this paper will serve as an important first step toward the design of effective remedies for it.
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ICC - Temporal Starvation in CSMA Wireless Networks
2011 IEEE International Conference on Communications (ICC), 2011Co-Authors: Caihong Kai, Soung Chang LiewAbstract:It is well known that links in CSMA wireless networks are prone to Starvation. Prior works focused almost exclusively on equilibrium Starvation. In this paper, we show that links in CSMA wireless networks are also susceptible to temporal Starvation. Specifically, although some links have good equilibrium throughputs and do not suffer from equilibrium Starvation, they can still have no throughput for extended periods from time to time. For real-time applications such as VoIP and video streaming, it is desirable to understand and characterize temporal Starvation in CSMA wireless networks. To this end, we develop a "trap theory" to analyze the temporal throughput fluctuations. Based on the trap theory, we can develop analytical tools for computing the "degrees of Starvation" for CSMA networks to aid network design. For example, given a CSMA wireless network, we can determine whether it suffers from Starvation, and if so, which links will starve. Furthermore, the likelihood and durations of temporal Starvation can also be computed. We believe that the ability to identify and characterize temporal Starvation as established in this paper will serve as an important first step toward the design of effective remedies for it.
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Temporal Starvation in CSMA Wireless Networks
arXiv: Networking and Internet Architecture, 2010Co-Authors: Caihong Kai, Soung Chang LiewAbstract:It is well known that links in CSMA wireless networks are prone to Starvation. Prior works focused almost exclusively on equilibrium Starvation. In this paper, we show that links in CSMA wireless networks are also susceptible to temporal Starvation. Specifically, although some links have good equilibrium throughputs and do not suffer from equilibrium Starvation, they can still have no throughput for extended periods from time to time. Given its impact on quality of service, it is important to understand and characterize temporal Starvation. To this end, we develop a "trap theory" to analyze temporal throughput fluctuation. The trap theory serves two functions. First, it allows us to derive new mathematical results that shed light on the transient behavior of CSMA networks. For example, we show that the duration of a trap, during which some links receive no throughput, is insensitive to the distributions of the backoff countdown and transmission time (packet duration) in the CSMA protocol. Second, we can develop analytical tools for computing the "degrees of Starvation" for CSMA networks to aid network design. For example, given a CSMA network, we can determine whether it suffers from Starvation, and if so, which links will starve. Furthermore, the likelihood and durations of temporal Starvation can also be computed. We believe that the ability to identify and characterize temporal Starvation as established in this paper will serve as an important first step toward the design of effective remedies for it.
Shuanglin Shen - One of the best experts on this subject based on the ideXlab platform.
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dynamic characteristics of local current densities and temperatures in proton exchange membrane fuel cells during reactant Starvations
International Journal of Hydrogen Energy, 2012Co-Authors: Guangsheng Zhang, Shuanglin ShenAbstract:Abstract Reactant Starvation during proton exchange membrane fuel cell (PEMFC) operation can cause serious irreversible damages. In order to study the detailed local characteristics of Starvations, simultaneous measurements of the dynamic variation of local current densities and temperatures in an experimental PEMFC with single serpentine flow field have been performed during both air and hydrogen Starvations. These studies have been performed under both current controlled and cell voltage controlled operations. It is found that under current controlled operations cell voltage can decrease very quickly during reactant Starvation. Besides, even though the average current is kept constant, local current densities as well as local temperatures can change dramatically. Furthermore, the variation characteristics of local current density and temperature strongly depend on the locations along the flow channel. Local current densities and temperatures near the channel inlet can become very high, especially during hydrogen Starvation, posing serious threats for the membrane and catalyst layers near the inlet. When operating in a constant voltage mode, no obvious damaging phenomena were observed except very low and unstable current densities and unstable temperatures near the channel outlet during hydrogen Starvation. It is demonstrated that measuring local temperatures can be effective in exploring local dynamic performance of PEMFC and the thermal failure mechanism of MEA during reactants Starvations.