The Experts below are selected from a list of 12138 Experts worldwide ranked by ideXlab platform
Roee Diamant - One of the best experts on this subject based on the ideXlab platform.
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leveraging the near far effect for improved Spatial Reuse scheduling in underwater acoustic networks
IEEE Transactions on Wireless Communications, 2017Co-Authors: Roee Diamant, Paolo Casari, Filippo Campagnaro, Michele ZorziAbstract:We present a Spatial Reuse resource allocation scheme for underwater acoustic networks that organizes communications so as to avoid destructive collisions. One prime source of collisions in underwater acoustic networks is the so called near–far effect, where a node located farther from the receiver is jammed by a closer node. While common practice considers such a situation a challenge, in this paper we consider it a resource, and use it to increase the network throughput of Spatial-Reuse time-division multiple access. Our algorithm serves two types of communications: 1) contention-free and 2) opportunistic. Our objective is to maximize the time slot allocation, while guaranteeing a minimum per-node packet transmission rate. The result is an increase in the number of contention-free packets received, and a decrease in the scheduling delay of opportunistic packets. Numerical results show that, at a slight cost in terms of fairness, our scheduling solutions achieve higher throughput and lower transmission delay than benchmark Spatial-Reuse scheduling protocols. These results are verified in a field experiment conducted in the Garda Lake, Italy, where we demonstrated our solution using off-the-shelf acoustic modems. To allow the reproducibility of our results, we publish the implementation of our proposed algorithm.
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robust Spatial Reuse scheduling in underwater acoustic communication networks
IEEE Journal of Oceanic Engineering, 2014Co-Authors: Roee Diamant, Ghasem Naddafzadeh Shirazi, Lutz LampeAbstract:Resource assignment in underwater acoustic communication (UWAC) networks has recently drawn much attention in the research community. Although in most applications the number of nodes in the UWAC network is relatively small, the long propagation delay of acoustic signals underwater motivates the application of Spatial Reuse in channel access protocols for throughput enhancement. In this paper, we address the problem of Spatial-Reuse scheduling in UWAC networks that support frequent transmission of broadcast packets and require robustness to inaccurate topology information. Taking the possibility of outdated network topology information into account is of great importance for UWAC applications due to time-varying topologies in the underwater environment. Our main contribution is the derivation of a broadcast scheduling algorithm that combines topology-transparent and topology-dependent Spatial-Reuse scheduling methodologies to achieve high throughput in static and dynamic topology scenarios. Simulation results demonstrate that our protocol provides a favorable tradeoff between network throughput and robustness to outdated topology information due to topology changes, and that it also achieves fairness in terms of per-node throughput.
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robust Spatial Reuse scheduling in underwater acoustic communication networks
Vehicular Technology Conference, 2011Co-Authors: Roee Diamant, Ghasem Naddafzadeh Shirazi, Lutz LampeAbstract:In this paper we address the problem of SpatialReuse scheduling for underwater acoustic communication (UWAC) networks that support high traffic broadcast communication and require robustness to inaccurate topology information. To this end, we derive a broadcast scheduling algorithm that combines topology-transparent and topology-dependent scheduling methodologies to achieve high-throughput in static and dynamic topology scenarios. While we focus on scheduling in UWAC networks, our approach can also be adopted for broadcast scheduling for radio ad-hoc network if robustness to topology uncertainties is desired. Simulation results for typical UWAC scenarios demonstrate that our protocol achieves high throughput and provides robustness to outdated topology information in dynamic topologies.
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Spatial Reuse time division multiple access for broadcast ad hoc underwater acoustic communication networks
IEEE Journal of Oceanic Engineering, 2011Co-Authors: Roee Diamant, Lutz LampeAbstract:Underwater acoustic communication (UWAC) is often the only viable solution to establish an ad hoc underwater communication network. The specific features of UWAC, arising from the physics of underwater acoustics, make the design of resource-efficient media access control (MAC) protocols important as well as challenging. In this paper, we tackle this task considering ad hoc UWAC networks that support high-traffic broadcast communication. To this end, we propose the application of the Spatial Reuse concept and the exploitation of direct sequence spread spectrum used at the UWAC physical layer to obtain a new hybrid Spatial Reuse time-division multiple-access (HSR-TDMA) protocol. By tracking the time-varying network topology, our protocol adaptively optimizes the set of active communication nodes and overcomes problems of UWAC networks such as the near-far problem, flickering, and formation of islands. Pertinent performance parameters, namely network availability, message reliability, and transmission rate, are analyzed for the proposed protocol. Evaluation of these analytical performance expressions demonstrates the significant advantages of HSR-TDMA over commonly used conventional TDMA for broadcast UWAC networks. We also report performance results for both the HSR-TDMA and the conventional TDMA protocol from a sea trial at the Haifa harbor, which corroborate the results obtained from the analysis.
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a hybrid Spatial Reuse mac protocol for ad hoc underwater acoustic communication networks
International Conference on Communications, 2010Co-Authors: Roee Diamant, Lutz LampeAbstract:The most widely used medium access control (MAC) scheme for underwater acoustic communication (UWAC) networks is conventional time-division multiple access (TDMA), in which only a single node transmits at each time. Since this TDMA is the bottleneck in high traffic networks, in this paper we present a new MAC protocol for UWAC ad-hoc networks that applies Spatial Reuse to improve network throughput. More specifically, in the proposed protocol selected additional nodes can transmit simultaneously to the active TDMA node, thus improving the efficiency of the MAC protocol. By tracking the time-varying network topology, our protocol adaptively optimizes the set of active nodes and overcomes problems of UWAC networks such as the near-far problem, flickering, and formation of islands. We report performance results for both the conventional TDMA protocol and the proposed protocol from a sea trial at the Haifa harbor. The results show that the new protocol greatly increases the availability of nodes to transmit messages, which leads to an improved overall network throughput in high traffic networks.
Lutz Lampe - One of the best experts on this subject based on the ideXlab platform.
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robust Spatial Reuse scheduling in underwater acoustic communication networks
IEEE Journal of Oceanic Engineering, 2014Co-Authors: Roee Diamant, Ghasem Naddafzadeh Shirazi, Lutz LampeAbstract:Resource assignment in underwater acoustic communication (UWAC) networks has recently drawn much attention in the research community. Although in most applications the number of nodes in the UWAC network is relatively small, the long propagation delay of acoustic signals underwater motivates the application of Spatial Reuse in channel access protocols for throughput enhancement. In this paper, we address the problem of Spatial-Reuse scheduling in UWAC networks that support frequent transmission of broadcast packets and require robustness to inaccurate topology information. Taking the possibility of outdated network topology information into account is of great importance for UWAC applications due to time-varying topologies in the underwater environment. Our main contribution is the derivation of a broadcast scheduling algorithm that combines topology-transparent and topology-dependent Spatial-Reuse scheduling methodologies to achieve high throughput in static and dynamic topology scenarios. Simulation results demonstrate that our protocol provides a favorable tradeoff between network throughput and robustness to outdated topology information due to topology changes, and that it also achieves fairness in terms of per-node throughput.
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robust Spatial Reuse scheduling in underwater acoustic communication networks
Vehicular Technology Conference, 2011Co-Authors: Roee Diamant, Ghasem Naddafzadeh Shirazi, Lutz LampeAbstract:In this paper we address the problem of SpatialReuse scheduling for underwater acoustic communication (UWAC) networks that support high traffic broadcast communication and require robustness to inaccurate topology information. To this end, we derive a broadcast scheduling algorithm that combines topology-transparent and topology-dependent scheduling methodologies to achieve high-throughput in static and dynamic topology scenarios. While we focus on scheduling in UWAC networks, our approach can also be adopted for broadcast scheduling for radio ad-hoc network if robustness to topology uncertainties is desired. Simulation results for typical UWAC scenarios demonstrate that our protocol achieves high throughput and provides robustness to outdated topology information in dynamic topologies.
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Spatial Reuse time division multiple access for broadcast ad hoc underwater acoustic communication networks
IEEE Journal of Oceanic Engineering, 2011Co-Authors: Roee Diamant, Lutz LampeAbstract:Underwater acoustic communication (UWAC) is often the only viable solution to establish an ad hoc underwater communication network. The specific features of UWAC, arising from the physics of underwater acoustics, make the design of resource-efficient media access control (MAC) protocols important as well as challenging. In this paper, we tackle this task considering ad hoc UWAC networks that support high-traffic broadcast communication. To this end, we propose the application of the Spatial Reuse concept and the exploitation of direct sequence spread spectrum used at the UWAC physical layer to obtain a new hybrid Spatial Reuse time-division multiple-access (HSR-TDMA) protocol. By tracking the time-varying network topology, our protocol adaptively optimizes the set of active communication nodes and overcomes problems of UWAC networks such as the near-far problem, flickering, and formation of islands. Pertinent performance parameters, namely network availability, message reliability, and transmission rate, are analyzed for the proposed protocol. Evaluation of these analytical performance expressions demonstrates the significant advantages of HSR-TDMA over commonly used conventional TDMA for broadcast UWAC networks. We also report performance results for both the HSR-TDMA and the conventional TDMA protocol from a sea trial at the Haifa harbor, which corroborate the results obtained from the analysis.
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a hybrid Spatial Reuse mac protocol for ad hoc underwater acoustic communication networks
International Conference on Communications, 2010Co-Authors: Roee Diamant, Lutz LampeAbstract:The most widely used medium access control (MAC) scheme for underwater acoustic communication (UWAC) networks is conventional time-division multiple access (TDMA), in which only a single node transmits at each time. Since this TDMA is the bottleneck in high traffic networks, in this paper we present a new MAC protocol for UWAC ad-hoc networks that applies Spatial Reuse to improve network throughput. More specifically, in the proposed protocol selected additional nodes can transmit simultaneously to the active TDMA node, thus improving the efficiency of the MAC protocol. By tracking the time-varying network topology, our protocol adaptively optimizes the set of active nodes and overcomes problems of UWAC networks such as the near-far problem, flickering, and formation of islands. We report performance results for both the conventional TDMA protocol and the proposed protocol from a sea trial at the Haifa harbor. The results show that the new protocol greatly increases the availability of nodes to transmit messages, which leads to an improved overall network throughput in high traffic networks.
W S Conner - One of the best experts on this subject based on the ideXlab platform.
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leveraging Spatial Reuse in 802 11 mesh networks with enhanced physical carrier sensing
International Conference on Communications, 2004Co-Authors: Jing Zhu, Xingang Guo, Liuyang Lily Yang, W S ConnerAbstract:Spatial Reuse in a wireless network can allow multiple communications to proceed simultaneously, hence proportionally improve the overall network throughput. To maximize Spatial Reuse, the MAC protocol must enable simultaneous transmitters to maintain the minimal separation distance to avoid interference. This paper demonstrates that physical carrier sensing enhanced with tunable sensing threshold is effective at avoiding interference in 802.11 mesh networks without requiring the use of virtual carrier sensing through RTS/CTS. We present analytical model that demonstrates how to derive the optimal sensing threshold given reception power, data rate and network topology. Simulation results are shown for large-scale 802.11b networks to demonstrate that physical carrier sensing with the optimally tuned threshold improves network throughput by maximizing the potential of Spatial Reuse. In the case of a regular chain topology of 90 nodes, with tuned physical carrier sensing, the end-to-end throughput approaches 90% of the theoretical upper bound that assumes a perfect MAC protocol. Hence, without modifying the 802.11 MAC protocol, our enhanced physical carrier sensing mechanism effectively maximizes the potential of improving network throughput with Spatial Reuse.
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Spatial Reuse in wireless ad hoc networks
Vehicular Technology Conference, 2003Co-Authors: Xingang Guo, Sumit Roy, W S ConnerAbstract:When investigating co-channel Spatial Reuse, typical studies on ad-hoc networks have adopted static, device-specific transmission/interference ranges regardless of the runtime environment. In this paper, we present an analytical framework to investigate co-channel Spatial Reuse in dense wireless ad-hoc networks based on RF propagation models for some common network topologies. We derive the minimum separation between simultaneous co-channel transmitters while maintaining desirable signal-noise-interference-ratio at receivers. Spatial Reuse is characterized by the ratio between co-channel transmitter (T-T) and transmit-receiver (T-R) distances. Our results show that increasing transmission power improves Spatial Reuse in ambient noise dominated environments. However, in co-channel interference limited scenarios, increasing transmission power has little effect on Spatial Reuse. On the other hand, more simultaneous transmissions can be physically possible by decreasing the average T-R separation, independent of transmission power. Our results confirm that the popular practice of using static transmission/interference ranges leads to an oversimplified model that is unable to accurately characterize the Spatial Reuse (and consequently aggregate network capacity) in ad-hoc networks.
Francesc Wilhelmi - One of the best experts on this subject based on the ideXlab platform.
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on the performance of the Spatial Reuse operation in ieee 802 11ax wlans
IEEE Conference on Standards for Communications and Networking, 2019Co-Authors: Francesc Wilhelmi, Sergio Barrachinamunoz, Boris BellaltaAbstract:The Spatial Reuse (SR) operation included in the IEEE 802.11ax-2020 (11ax) amendment aims at increasing the number of parallel transmissions in an Overlapping Basic Service Set (OBSS). However, many unknowns exist about the performance gains that can be achieved through SR. In this paper, we provide a brief introduction to the SR operation described in the IEEE 802.11ax (draft D4.0). Then, a simulation-based implementation is provided in order to explore the performance gains of the SR operation. Our results show the potential of using SR in different scenarios covering multiple network densities and traffic loads. In particular, we observe significant improvements on the channel utilization when applying SR with respect to the default configuration, thus allowing to increase the throughput and reduce the delay. Interestingly, the highest improvements provided by the SR operation are observed in the most pessimistic situations in terms of network density and traffic load.
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collaborative Spatial Reuse in wireless networks via selfish multi armed bandits
Ad Hoc Networks, 2019Co-Authors: Francesc Wilhelmi, Boris Bellalta, Cristina Cano, Gergely Neu, Anders Jonsson, Sergio BarrachinamunozAbstract:Abstract Next-generation wireless deployments are characterized by being dense and uncoordinated, which often leads to inefficient use of resources and poor performance. To solve this, we envision the utilization of completely decentralized mechanisms to enable Spatial Reuse (SR). In particular, we focus on dynamic channel selection and Transmission Power Control (TPC). We rely on Reinforcement Learning (RL), and more specifically on Multi-Armed Bandits (MABs), to allow networks to learn their best configuration. In this work, we study the exploration-exploitation trade-off by means of the e-greedy, EXP3, UCB and Thompson sampling action-selection, and compare their performance. In addition, we study the implications of selecting actions simultaneously in an adversarial setting (i.e., concurrently), and compare it with a sequential approach. Our results show that optimal proportional fairness can be achieved, even when no information about neighboring networks is available to the learners and Wireless Networks (WNs) operate selfishly. However, there is high temporal variability in the throughput experienced by the individual networks, especially for e-greedy and EXP3. These strategies, contrary to UCB and Thompson sampling, base their operation on the absolute experienced reward, rather than on its distribution. We identify the cause of this variability to be the adversarial setting of our setup in which the set of most played actions provide intermittent good/poor performance depending on the neighboring decisions. We also show that learning sequentially, even if using a selfish strategy, contributes to minimize this variability. The sequential approach is therefore shown to effectively deal with the challenges posed by the adversarial settings that are typically found in decentralized WNs.
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potential and pitfalls of multi armed bandits for decentralized Spatial Reuse in wlans
Journal of Network and Computer Applications, 2019Co-Authors: Francesc Wilhelmi, Sergio Barrachinamunoz, Boris Bellalta, Cristina Cano, Anders Jonsson, Gergely NeuAbstract:Abstract Spatial Reuse (SR) has recently gained attention to maximize the performance of IEEE 802.11 Wireless Local Area Networks (WLANs). Decentralized mechanisms are expected to be key in the development of SR solutions for next-generation WLANs, since many deployments are characterized by being uncoordinated by nature. However, the potential of decentralized mechanisms is limited by the significant lack of knowledge with respect to the overall wireless environment. To shed some light on this subject, we show the main considerations and possibilities of applying online learning to address the SR problem in uncoordinated WLANs. In particular, we provide a solution based on Multi-Armed Bandits (MABs) whereby independent WLANs dynamically adjust their frequency channel, transmit power and sensitivity threshold. To that purpose, we provide two different strategies, which refer to selfish and environment-aware learning. While the former stands for pure individual behavior, the second one considers the performance experienced by surrounding networks, thus taking into account the impact of individual actions on the environment. Through these two strategies we delve into practical issues of applying MABs in wireless networks, such as convergence guarantees or adversarial effects. Our simulation results illustrate the potential of the proposed solutions for enabling SR in future WLANs. We show that substantial improvements on network performance can be achieved regarding throughput and fairness.
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collaborative Spatial Reuse in wireless networks via selfish multi armed bandits
arXiv: Networking and Internet Architecture, 2017Co-Authors: Francesc Wilhelmi, Boris Bellalta, Cristina Cano, Gergely Neu, Anders Jonsson, Sergio BarrachinamunozAbstract:Next-generation wireless deployments are characterized by being dense and uncoordinated, which often leads to inefficient use of resources and poor performance. To solve this, we envision the utilization of completely decentralized mechanisms to enable Spatial Reuse (SR). In particular, we focus on dynamic channel selection and Transmission Power Control (TPC). We rely on Reinforcement Learning (RL), and more specifically on Multi-Armed Bandits (MABs), to allow networks to learn their best configuration. In this work, we study the exploration-exploitation trade-off by means of the $\varepsilon$-greedy, EXP3, UCB and Thompson sampling action-selection, and compare their performance. In addition, we study the implications of selecting actions simultaneously in an adversarial setting (i.e., concurrently), and compare it with a sequential approach. Our results show that optimal proportional fairness can be achieved, even when no information about neighboring networks is available to the learners and Wireless Networks (WNs) operate selfishly. However, there is high temporal variability in the throughput experienced by the individual networks, specially for $\varepsilon$-greedy and EXP3. These strategies, contrary to UCB and Thompson sampling, base their operation on the absolute experienced reward, rather than on its distribution. We identify the cause of this variability to be the adversarial setting of our setup in which the set of most played actions provide intermittent good/poor performance depending on the neighboring decisions. We also show that learning sequentially, even if using a selfish strategy, contributes to minimize this variability. The sequential approach is therefore shown to effectively deal with the challenges posed by the adversarial settings that are typically found in decentralized WNs.
Gustavo De Veciana - One of the best experts on this subject based on the ideXlab platform.
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Spatial Reuse and fairness of ad hoc networks with channel aware csma protocols
IEEE Transactions on Information Theory, 2014Co-Authors: Yuchul Kim, Francois Baccelli, Gustavo De VecianaAbstract:We investigate the benefits of channel-aware (opportunistic) scheduling of transmissions in ad hoc networks. The key challenge in optimizing the performance of such systems is finding a good compromise among three interdependent quantities: 1) the density of scheduled transmitters; 2) the quality of transmissions; and 3) the long term fairness among nodes. We propose two new channel-aware slotted CSMA protocols opportunistic CSMA and quantile-based CSMA (QT-CSMA) and develop new stochastic geometric models to quantify their performance in terms of Spatial Reuse and Spatial fairness. When properly optimized, these protocols offer substantial improvements in performance relative to CSMA—particularly, when the density of nodes is moderate to high. In addition, we show that a simple version of QT-CSMA can achieve robust performance gains without requiring careful parameter optimization. The quantitative results in this paper suggest that channel-aware scheduling in ad hoc networks can provide substantial benefits which might far outweigh the associated implementation overheads.
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Spatial Reuse and fairness of mobile ad-hoc networks with channel-aware CSMA protocols
2011Co-Authors: Yuchul Kim, Francois Baccelli, Gustavo De VecianaAbstract:We investigate the benefits of channel-aware (opportunistic) scheduling of transmissions in ad-hoc networks. The key challenge in optimizing the performance of such systems is finding a good compromise among three interdependent quantities, the density and channel quality of the scheduled transmitters, and the resulting interference at receivers. We propose two new channel-aware slotted CSMA protocols: opportunistic CSMA (O-CSMA) and quantile-based CSMA (QT-CSMA) and develop stochastic geometric models allowing us to quantify their performance in terms of Spatial Reuse and Spatial fairness. When properly optimized these protocols offer substantial improvements in terms of both of these metrics relative to CSMA - particularly when the density of nodes is moderate to high. Moreover, we show that a simple version of QT-CSMA can achieve robust performance gains without requiring careful parameter optimization. The paper supports the case that the benefits associated with channel-aware scheduling in ad hoc networks, as in centralized base station scenarios, might far outweigh the associated overhead, and this can be done robustly using a QT-CSMA like protocol.