The Experts below are selected from a list of 7761 Experts worldwide ranked by ideXlab platform
U Spagnolini - One of the best experts on this subject based on the ideXlab platform.
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medium access control protocols for wireless sensor networks with energy harvesting
IEEE Transactions on Communications, 2012Co-Authors: Fabio Iannello, Osvaldo Simeone, U SpagnoliniAbstract:The design of Medium Access Control (MAC) protocols for wireless sensor networks (WSNs) has been conventionally tackled by assuming battery-powered devices and by adopting the network lifetime as the main performance criterion. While WSNs operated by energy-harvesting (EH) devices are not limited by network lifetime, they pose new design challenges due to the uncertain amount of energy that can be harvested from the environment. Novel design criteria are thus required to capture the trade-offs between the potentially infinite network lifetime and the uncertain energy availability. This paper addresses the analysis and design of WSNs with EH devices by focusing on conventional MAC protocols, namely TDMA, framed-ALOHA (FA) and dynamic-FA (DFA), and by accounting for the performance trade-offs and design issues arising due to EH. A novel metric, referred to as delivery probability, is introduced to measure the capability of a MAC protocol to deliver the measurement of any sensor in the network to the Intended Destination (or fusion center, FC). The interplay between delivery efficiency and time efficiency (i.e., the data collection rate at the FC), is investigated analytically using Markov models. Numerical results validate the analysis and emphasize the critical importance of accounting for both delivery probability and time efficiency in the design of EH-WSNs.
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stable throughput of cognitive radios with and without relaying capability
IEEE Transactions on Communications, 2007Co-Authors: Osvaldo Simeone, Y Barness, U SpagnoliniAbstract:A scenario with two single-user links, one licensed to use the spectral resource (primary) and one unlicensed (secondary or cognitive), is considered. According to the cognitive radio principle, the activity of the secondary link is required not to interfere with the performance of the primary. Therefore, in this paper, it is assumed that the cognitive link accesses the channel only when sensed idle. Moreover, the analysis includes: (1) random packet arrivals; (2) sensing errors due to fading at the secondary link; (3) power allocation at the secondary transmitter based on long-term measurements. In this framework, the maximum stable throughput of the cognitive link (in packets/slot) is derived for a fixed throughput selected by the primary link. The model is modified so as to allow the secondary transmitter to act as a ldquotransparentrdquo relay for the primary link. In particular, packets that are not received correctly by the Intended Destination might be decoded successfully by the secondary transmitter. The latter can, then, queue and forward these packets to the Intended receiver. A stable throughput of the secondary link with relaying is derived under the same conditions as before. Results show that benefits of relaying strongly depend on the topology (i.e., average channel powers) of the network.
Paul A Dudchenko - One of the best experts on this subject based on the ideXlab platform.
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hippocampal place cells encode Intended Destination and not a discriminative stimulus in a conditional t maze task
Hippocampus, 2012Co-Authors: James A Ainge, Minija Tamosiunaite, Florentin Worgotter, Paul A DudchenkoAbstract:The firing of hippocampal place cells encodes instantane- ous location but can also reflect where the animal is heading (prospec- tive firing), or where it has just come from (retrospective firing). The current experiment sought to explicitly control the prospective firing of place cells with a visual discriminada in a T-maze. Rats were trained to associate a specific visual stimulus (e.g., a flashing light) with the occur- rence of reward in a specific location (e.g., the left arm of the T). A dif- ferent visual stimulus (e.g., a constant light) signaled the availability of reward in the opposite arm of the T. After this discrimination had been acquired, rats were implanted with electrodes in the CA1 layer of the hippocampus. Place cells were then identified and recorded as the ani- mals performed the discrimination task, and the presentation of the vis- ual stimulus was manipulated. A subset of CA1 place cells fired at dif- ferent rates on the central stem of the T depending on the animal's Intended Destination, but this conditional or prospective firing was inde- pendent of the visual discriminative stimulus. The firing rate of some place cells was, however, modulated by changes in the timing of presen- tation of the visual stimulus. Thus, place cells fired prospectively, but this firing did not appear to be controlled, directly, by a salient visual stimulus that controlled behavior. V C 2011 Wiley Periodicals, Inc.
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hippocampal ca1 place cells encode Intended Destination on a maze with multiple choice points
The Journal of Neuroscience, 2007Co-Authors: James A Ainge, Minija Tamosiunaite, Florentin Woergoetter, Paul A DudchenkoAbstract:The hippocampus encodes both spatial and nonspatial aspects of a rat's ongoing behavior at the single-cell level. In this study, we examined the encoding of Intended Destination by hippocampal (CA1) place cells during performance of a serial reversal task on a double Y-maze. On the maze, rats had to make two choices to access one of four possible goal locations, two of which contained reward. Reward locations were kept constant within blocks of 10 trials but changed between blocks, and the session of each day comprised three or more trial blocks. A disproportionate number of place fields were observed in the start box and beginning stem of the maze, relative to other locations on the maze. Forty-six percent of these place fields had different firing rates on journeys to different goal boxes. Another group of cells had place fields before the second choice point, and, of these, 44% differentiated between journeys to specific goal boxes. In a second experiment, we observed that rats with hippocampal damage made significantly more errors than control rats on the Y-maze when reward locations were reversed. Together, these results suggest that, at the start of the maze, the hippocampus encodes both current location and the Intended Destination of the rat, and this encoding is necessary for the flexible response to changes in reinforcement contingencies.
Minija Tamosiunaite - One of the best experts on this subject based on the ideXlab platform.
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hippocampal place cells encode Intended Destination and not a discriminative stimulus in a conditional t maze task
Hippocampus, 2012Co-Authors: James A Ainge, Minija Tamosiunaite, Florentin Worgotter, Paul A DudchenkoAbstract:The firing of hippocampal place cells encodes instantane- ous location but can also reflect where the animal is heading (prospec- tive firing), or where it has just come from (retrospective firing). The current experiment sought to explicitly control the prospective firing of place cells with a visual discriminada in a T-maze. Rats were trained to associate a specific visual stimulus (e.g., a flashing light) with the occur- rence of reward in a specific location (e.g., the left arm of the T). A dif- ferent visual stimulus (e.g., a constant light) signaled the availability of reward in the opposite arm of the T. After this discrimination had been acquired, rats were implanted with electrodes in the CA1 layer of the hippocampus. Place cells were then identified and recorded as the ani- mals performed the discrimination task, and the presentation of the vis- ual stimulus was manipulated. A subset of CA1 place cells fired at dif- ferent rates on the central stem of the T depending on the animal's Intended Destination, but this conditional or prospective firing was inde- pendent of the visual discriminative stimulus. The firing rate of some place cells was, however, modulated by changes in the timing of presen- tation of the visual stimulus. Thus, place cells fired prospectively, but this firing did not appear to be controlled, directly, by a salient visual stimulus that controlled behavior. V C 2011 Wiley Periodicals, Inc.
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hippocampal ca1 place cells encode Intended Destination on a maze with multiple choice points
The Journal of Neuroscience, 2007Co-Authors: James A Ainge, Minija Tamosiunaite, Florentin Woergoetter, Paul A DudchenkoAbstract:The hippocampus encodes both spatial and nonspatial aspects of a rat's ongoing behavior at the single-cell level. In this study, we examined the encoding of Intended Destination by hippocampal (CA1) place cells during performance of a serial reversal task on a double Y-maze. On the maze, rats had to make two choices to access one of four possible goal locations, two of which contained reward. Reward locations were kept constant within blocks of 10 trials but changed between blocks, and the session of each day comprised three or more trial blocks. A disproportionate number of place fields were observed in the start box and beginning stem of the maze, relative to other locations on the maze. Forty-six percent of these place fields had different firing rates on journeys to different goal boxes. Another group of cells had place fields before the second choice point, and, of these, 44% differentiated between journeys to specific goal boxes. In a second experiment, we observed that rats with hippocampal damage made significantly more errors than control rats on the Y-maze when reward locations were reversed. Together, these results suggest that, at the start of the maze, the hippocampus encodes both current location and the Intended Destination of the rat, and this encoding is necessary for the flexible response to changes in reinforcement contingencies.
Anthony Ephremides - One of the best experts on this subject based on the ideXlab platform.
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on the age of information in status update systems with packet management
IEEE Transactions on Information Theory, 2016Co-Authors: Maice Costa, Marian Codreanu, Anthony EphremidesAbstract:We consider a communication system in which status updates arrive at a source node, and should be transmitted through a network to the Intended Destination node. The status updates are samples of a random process under observation, transmitted as packets, which also contain the time stamp to identify when the sample was generated. The age of the information available to the Destination node is the time elapsed, since the last received update was generated. In this paper, we model the source-Destination link using the queuing theory, and we assume that the time it takes to successfully transmit a packet to the Destination is an exponentially distributed service time. We analyze the age of information in the case that the source node has the capability to manage the arriving samples, possibly discarding packets in order to avoid wasting network resources with the transmission of stale information. In addition to characterizing the average age, we propose a new metric, called peak age, which provides information about the maximum value of the age, achieved immediately before receiving an update.
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on the age of information in status update systems with packet management
arXiv: Information Theory, 2015Co-Authors: Maice Costa, Marian Codreanu, Anthony EphremidesAbstract:We consider a communication system in which status updates arrive at a source node, and should be transmitted through a network to the Intended Destination node. The status updates are samples of a random process under observation, transmitted as packets, which also contain the time stamp to identify when the sample was generated. The age of the information available to the Destination node is the time elapsed since the last received update was generated. In this paper, we model the source-Destination link using queuing theory, and we assume that the time it takes to successfully transmit a packet to the Destination is an exponentially distributed service time. We analyze the age of information in the case that the source node has the capability to manage the arriving samples, possibly discarding packets in order to avoid wasting network resources with the transmission of stale information. In addition to characterizing the average age, we propose a new metric, called peak age, which provides information about the maximum value of the age, achieved immediately before receiving an update.
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parallel tdma scheduling for multiple Destination wireless networks
IEEE Transactions on Wireless Communications, 2011Co-Authors: Gam D Nguyen, Sastry Kompella, Jeffrey E Wieselthier, Anthony EphremidesAbstract:We study transmission strategies in a multiple-source, multiple-Destination wireless network. Each source transmits packets that are Intended for a particular Destination. However, a transmitted packet can cause interference at other Destinations. Our primary performance measure is throughput, which we define to be the average number of packets that are successfully received per Intended Destination per time slot. The sources are first divided into groups, based on the Intended Destination of their packets. In our parallel method, each group operates according to its own local protocol (e.g., TDMA), concurrently with and independently of the other groups. Our results show the impact of transmission schedules, channel fading, receiver noise, and other-user interference on network performance. We then show that, for given channel statistics and topology configurations, the network performance can be significantly improved when the groups in the network coordinate their transmissions according to an optimal schedule. Further, in many cases, even the use of randomly generated parallel schedules can provide considerably higher performance than traditional TDMA.
Osvaldo Simeone - One of the best experts on this subject based on the ideXlab platform.
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medium access control protocols for wireless sensor networks with energy harvesting
IEEE Transactions on Communications, 2012Co-Authors: Fabio Iannello, Osvaldo Simeone, U SpagnoliniAbstract:The design of Medium Access Control (MAC) protocols for wireless sensor networks (WSNs) has been conventionally tackled by assuming battery-powered devices and by adopting the network lifetime as the main performance criterion. While WSNs operated by energy-harvesting (EH) devices are not limited by network lifetime, they pose new design challenges due to the uncertain amount of energy that can be harvested from the environment. Novel design criteria are thus required to capture the trade-offs between the potentially infinite network lifetime and the uncertain energy availability. This paper addresses the analysis and design of WSNs with EH devices by focusing on conventional MAC protocols, namely TDMA, framed-ALOHA (FA) and dynamic-FA (DFA), and by accounting for the performance trade-offs and design issues arising due to EH. A novel metric, referred to as delivery probability, is introduced to measure the capability of a MAC protocol to deliver the measurement of any sensor in the network to the Intended Destination (or fusion center, FC). The interplay between delivery efficiency and time efficiency (i.e., the data collection rate at the FC), is investigated analytically using Markov models. Numerical results validate the analysis and emphasize the critical importance of accounting for both delivery probability and time efficiency in the design of EH-WSNs.
-
stable throughput of cognitive radios with and without relaying capability
IEEE Transactions on Communications, 2007Co-Authors: Osvaldo Simeone, Y Barness, U SpagnoliniAbstract:A scenario with two single-user links, one licensed to use the spectral resource (primary) and one unlicensed (secondary or cognitive), is considered. According to the cognitive radio principle, the activity of the secondary link is required not to interfere with the performance of the primary. Therefore, in this paper, it is assumed that the cognitive link accesses the channel only when sensed idle. Moreover, the analysis includes: (1) random packet arrivals; (2) sensing errors due to fading at the secondary link; (3) power allocation at the secondary transmitter based on long-term measurements. In this framework, the maximum stable throughput of the cognitive link (in packets/slot) is derived for a fixed throughput selected by the primary link. The model is modified so as to allow the secondary transmitter to act as a ldquotransparentrdquo relay for the primary link. In particular, packets that are not received correctly by the Intended Destination might be decoded successfully by the secondary transmitter. The latter can, then, queue and forward these packets to the Intended receiver. A stable throughput of the secondary link with relaying is derived under the same conditions as before. Results show that benefits of relaying strongly depend on the topology (i.e., average channel powers) of the network.