| 1. |
- Capone, Antonio, et al.
(författare)
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A New Computational Approach for Maximum Link Activation in Wireless Networks under the SINR Model
- 2011
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Ingår i: IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS. - : Institute of Electrical and Electronics Engineers. - 1536-1276. ; 10:5, s. 1368-1372
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Tidskriftsartikel (refereegranskat)abstract
- A fundamental and computationally challenging optimization task in wireless networks is to maximize the number of simultaneous transmissions, subject to signal-to-noise-and-interference ratio (SINR) requirements at the receivers. The conventional approach guaranteeing global optimality is to solve an integer programming model with explicit SINR constraints. These constraints are however numerically very difficult. We develop a new integer programming algorithm based on a much more effective representation of the SINR constraints. Computational experiments demonstrate that the new approach performs significantly better in proving optimality.
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| 2. |
- Capone, Antonio, et al.
(författare)
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Joint routing and scheduling optimization in arbitrary ad hoc networks: Comparison of cooperative and hop-by-hop forwarding
- 2011
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Ingår i: Ad hoc networks. - : Elsevier Science B. V., Amsterdam. - 1570-8705 .- 1570-8713. ; 9:7, s. 1256-1269
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Tidskriftsartikel (refereegranskat)abstract
- Cooperation schemes form a key aspect of infrastructure-less wireless networks that allow nodes that cannot directly communicate to exchange information through the help of intermediate nodes. The most widely adopted approach is based on hop-by-hop forwarding at the network layer along a path to destination. Cooperative relaying brings cooperation to the physical layer in order to fully exploit wireless resources. The concept exploits channel diversity by using multiple radio units to transmit the same message. The underlying fundamentals of cooperative relaying have been quite well-studied from a transmission efficiency point of view, in particular with a single pair of source and destination. Results of its performance gain in a multi-hop networking context with multiple sources and destinations are, however, less available. In this paper, we provide an optimization approach to assess the performance gain of cooperative relaying vis-a-vis conventional multi-hop forwarding under arbitrary network topology. The approach joint optimizes packet routing and transmission scheduling, and generalizes classical optimization schemes for non-cooperative networks. We provide numerical results demonstrating that the gain of cooperative relaying in networking scenarios is in general rather small and decreases when network connectivity and the number of traffic flows increase, due to interference and resource reuse limitations. In addition to quantifying the performance gain, our approach leads to a new framework for optimizing routing and scheduling in cooperative networks under a generalized Spacial Time Division Multiple Access (STDMA) scheme.
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| 3. |
- Capone, Antonio, et al.
(författare)
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Minimizing end-to-end delay in multi-hop wireless networks with optimized transmission scheduling
- 2019
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Ingår i: Ad hoc networks. - : ELSEVIER SCIENCE BV. - 1570-8705 .- 1570-8713. ; 89, s. 236-248
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Tidskriftsartikel (refereegranskat)abstract
- The problem of transmission scheduling in single hop and multi-hop wireless networks has been extensively studied. The focus has been on optimizing the efficiency of transmission parallelization, through a minimum-length schedule that meets a given set of traffic demands using the smallest possible number of time slots. Each time slot is associated with a set of transmissions that are compatible with each other according to the considered interference model. The minimum-length approach maximizes the resource reuse, but it does not ensure minimum end-to-end packet delay for multiple source-destination pairs, due to its inherent assumption of frame periodicity. In the paper we study the problem of transmission scheduling and routing aiming at minimizing the end-to-end delay under the signal-to-interference-and-noise-ratio (SINR) model for multi-hop networks. Two schemes are investigated. The first scheme departs from the conventional scheduling approach, by addressing explicitly end-to-end delay and removing the restriction of frame periodicity. The second scheme extends the first one by featuring cooperative forwarding and forward interference cancellation. We study the properties of the two schemes, and propose novel mixed-integer programming models and solution algorithms. Extensive results are provided to gain insights on how the schemes perform in end-to-end delay. (C) 2019 Elsevier B.V. All rights reserved.
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| 4. |
- Capone, Antonio, et al.
(författare)
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On packet transmission scheduling for min-max delay and energy consumption in wireless mesh sensor networks
- 2016
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Ingår i: Electronic Notes in Discrete Mathematics. - : Elsevier BV. - 1571-0653. ; 52, s. 61-68
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Tidskriftsartikel (refereegranskat)abstract
- Optimization of channel utilization in wireless networks is typically based on transmission parallelization under signal-to-interference and noise constraint assuming minimum frame-length scheduling. In application scenarios like sensor networks this approach may not be suitable since it does not explicitly consider end-to-end packet delay nor energy consumption. In the paper we propose a mixed-integer programming formulation for scheduling optimization in wireless sensor networks characterized by periodic data gathering where minimization of the maximum packet delay and sensor node energy consumption are the main objectives. The model, which assumes cooperation in packet forwarding and interference cancellation, is compared to traditional single path forwarding.
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| 5. |
- Chiang, Michael F., et al.
(författare)
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International Classification of Retinopathy of Prematurity, Third Edition
- 2021
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Ingår i: Ophthalmology. - : Elsevier. - 0161-6420 .- 1549-4713. ; 128:10, s. 51-68
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The International Classification of Retinopathy of Prematurity is a consensus statement that creates a standard nomenclature for classification of retinopathy of prematurity (ROP). It was initially published in 1984, expanded in 1987, and revisited in 2005. This article presents a third revision, the International Classification of Retinopathy of Prematurity, Third Edition (ICROP3), which is now required because of challenges such as: (1) concerns about subjectivity in critical elements of disease classification; (2) innovations in ophthalmic imaging; (3) novel pharmacologic therapies (e.g., antievascular endothelial growth factor agents) with unique regression and reactivation features after treatment compared with ablative therapies; and (4) recognition that patterns of ROP in some regions of the world do not fit neatly into the current classification system.Design: Review of evidence-based literature, along with expert consensus opinion. Participants: International ROP expert committee assembled in March 2019 representing 17 countries and comprising 14 pediatric ophthalmologists and 20 retinal specialists, as well as 12 women and 22 men.Methods: The committee was initially divided into 3 subcommittees-acute phase, regression or reactivation, and imaging-each of which used iterative videoconferences and an online message board to identify key challenges and approaches. Subsequently, the entire committee used iterative videoconferences, 2 in-person multiday meetings, and an online message board to develop consensus on classification.Main Outcome Measures: Consensus statement.Results: The ICROP3 retains current definitions such as zone (location of disease), stage (appearance of disease at the avascular-vascular junction), and circumferential extent of disease. Major updates in the ICROP3 include refined classification metrics (e.g., posterior zone II, notch, subcategorization of stage 5, and recognition that a continuous spectrum of vascular abnormality exists from normal to plus disease). Updates also include the definition of aggressive ROP to replace aggressive-posterior ROP because of increasing recognition that aggressive disease may occur in larger preterm infants and beyond the posterior retina, particularly in regions of the world with limited resources. ROP regression and reactivation are described in detail, with additional description of long-term sequelae.Conclusions: These principles may improve the quality and standardization of ROP care worldwide and may provide a foundation to improve research and clinical care.
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| 6. |
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| 7. |
- Li, Yuan, et al.
(författare)
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On End-to-end Delay Minimization in Wireless Networks under the Physical Interference Model
- 2015
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Ingår i: 2015 IEEE CONFERENCE ON COMPUTER COMMUNICATIONS (INFOCOM). - : IEEE. - 9781479983810
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Konferensbidrag (refereegranskat)abstract
- The problem of scheduling transmission in single hop and multi-hop wireless networks with arbitrary topology under the physical interference model has been extensively studied. The focus has been on optimizing the efficiency of transmission parallelization through a minimum-frame-length schedule that meets a given set of traffic demands using the smallest number of time slots, each of which is associated with a set of compatible (according to the interference model) transmissions. This approach maximizes the resource reuse efficiency, but in general does not correspond to the best performance in terms of end-to-end packet delivery delay for multiple source-destination pairs, due to the inherent restriction of frame periodicity. In this paper, we study the problem of scheduling to minimize the end-to-end delay in wireless networks under the Signal to Interference plus Noise Ratio (SINR) constraints, and propose two schemes. The first scheme extends the minimum-frame-length approach with a phase of time slot ordering to account for the delay metric. The second scheme directly optimizes delay without the constraint of periodic framing. We propose novel mixed integer programming models for the two schemes and study their properties and complexity. Moreover, we present an efficient heuristic method that provides good quality solutions time-efficiently.
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| 8. |
- Pióro, Michał, et al.
(författare)
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Maximization of multicast periodic traffic throughput in multi-hop wireless networks with broadcast transmissions
- 2018
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Ingår i: Ad Hoc Networks. - : Elsevier BV. - 1570-8705. ; 77, s. 119-142
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Tidskriftsartikel (refereegranskat)abstract
- Although a number of different medium access control (MAC) schemes are adopted for wireless multi-hop networks, time division multiple access (TDMA) approaches based on a periodic frame of time slots are the most common when very high efficiency is needed in terms of use of radio and energy resources. Efficient resource usage is typically based on parallel compatible transmissions from multiple nodes that guarantee interference control at the receivers. Optimization of transmission scheduling in multi-hop packet delivery from sources to destinations for a set of traffic relations can be achieved by minimizing the frame length where all necessary transmissions are organized in compatible sets and assigned to the time slots of the frame. When properly designed, the resulting TDMA scheme guarantees the delivery of packets for each traffic relation at a rate of up to one packet per frame duration regardless of the number of the packet transmissions (hops) necessary from source to destination, and thus it is particularly suitable for periodic traffic. While similar traffic maximization problems have been studied quite extensively for the case of unicast traffic, its multicast generalization (where each packet should be delivered from the source node to possibly multiple destination nodes) has not been elaborated so far. In this paper we present such a (non-trivial) generalization, namely a mathematical programming model based on the extension of the compatible set concept where the signal-to-noise and interference (SINR) ratio is guaranteed above a threshold at multiple receivers. We first propose an algorithm for solving the problem that generates compatible sets and schedules the frame by splitting the (predefined) multicast routing trees into one-hop transmissions. The high computational efficiency of the algorithm is proven through numerical results on large networks. Next, we enrich the model by adding multicast tree optimization, illustrating its efficiency numerically as well. Finally, we present possible extensions that consider packets of different lengths (requiring multiple slots for transmission), multiple modulation and coding schemes (MCS) requiring different SINR thresholds at the receivers, and packet delay minimization.
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| 9. |
- Unger, Elisabeth
(författare)
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The Extremes of Neutrino Astronomy : From Fermi Bubbles with IceCube to Ice Studies with ARIANNA
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Fermi bubbles are extended regions of hard gamma-ray emission which were discovered with Fermi-LAT data to exist above and below the Galactic Center. In order to explain the origin of the gamma-rays, different theories are proposed. In particular, within hadronic models, highly-accelerated cosmic rays interact with interstellar matter and create the observed gamma-rays and in addition neutrinos. Data from the neutrino detector IceCube was analyzed using a maximum likelihood method. An upper limit on the possible neutrino flux from the Fermi bubbles at energies between 10 GeV and 200 GeV was determined.While this analysis is performed with the lowest energies IceCube can reach, the ARIANNA (Antarctic Ross Ice-shelf ANtenna Neutrino Array) experiment has the goal to detect the highest energy neutrinos by measuring radio wave radiation produced by their interaction products in the ice. With ARIANNA the propagation of radio waves in the firn (packed snow) of the Ross Ice Shelf was investigated. According to the classical approach the radio waves, produced in the firn, are supposed to bend down because of the changing density, and therefore changing refractive index, an effect which is called “shadowing”. Evidence that the waves can travel horizontally over a long distance will be presented. The horizontally propagating signals between two boreholes and to the ARIANNA stations were analyzed and characterized. Analyses were performed under two hypotheses to determine attenuation lengths for horizontal propagation signals. The results showed attenuation lengths between 310 m ± 83 m and 651 m ± 270 m, depending on the assumed hypothesis and performed analysis. In addition unexpected signals consistent with radio waves propagating along the firn surface, here called pre-pulses, were observed and characterized.
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