1,342 research outputs found
Scheduling in CDMA networks with end-to-end QoS guarantees - by Walid Emile Saad
No full textThesis (M.E.)--American University of Beirut, Dept. of Electrical and Computer Engineering, 2007.;"Advisor: Dr. Zaher Dawy, Assistant Professor, Electrical and Computer Engineering--Member of Committee: Dr. Ayman Kayssi, Professor, Electrical and ComputerBibliography : leaves 77-79.The major driver for deploying next generation CDMA-based cellular networks is t heir ability to efficiently deliver QoS demanding services, many of which involv e an end-to-end communication having an uplink user sending data to a downlink u ser. In thi
Downlink Interference Analysis of UAV-Based mmWave Fronthaul for Small Cell Networks
No full textIn this paper, an unmanned aerial vehicles (UAV)-based heterogeneous network is studied to solve the problem of transferring massive traffic of distributed small cells to the core network. First, a detailed three-dimensional (3D) model of the downlink channel is characterized by taking into account the real antenna pattern, UAVs' vibrations, random distribution of small cell base stations (SBSs), and the position of UAVs in 3D space. Then, a rigorous analysis of interference is performed for two types of interference: intra-cell interference and inter-cell interference. The interference analysis results are then used to derive an upper bound of outage probability on the considered system. Using numerical results show that the analytical and simulation results match one another. The results show that, in the presence of UAV's fluctuations, optimizing radiation pattern shape requires balancing an inherent tradeoff between increasing pattern gain to reduce the interference as well as to compensate large path loss at mmWave frequencies and decreasing it to alleviate the adverse effect of a UAV's vibrations.The work of Mohammad Taghi Dabiri and Mazen Hasna was supported by Qatar National Research Fund (QNRF) under Grant NPRP13S-0130-200200. The work of Walid Saad was supported by U.S. National Science Foundation under Grant CNS-1836802.Scopu
Distributed algorithms for optimized resource management of LTE in unlicensed spectrum and UAV-enabled wireless networks
No full textNext-generation wireless cellular networks are morphing into a massive Internet
of Things (IoT) environment that integrates a heterogeneous mix of wireless-enabled
devices such as unmanned aerial vehicles (UAVs) and connected vehicles.
This unprecedented transformation will not only drive an exponential growth in
wireless traffic, but it will also lead to the emergence of new wireless service
applications that substantially differ from conventional multimedia services. To
realize the fifth generation (5G) mobile networks vision, a new wireless radio
technology paradigm shift is required in order to meet the quality of service
requirements of these new emerging use cases. In this respect, one of the major
components of 5G is self-organized networks. In essence, future cellular networks
will have to rely on an autonomous and self-organized behavior in order to manage
the large scale of wireless-enabled devices. Such an autonomous capability can be
realized by integrating fundamental notions of artificial intelligence (AI) across
various network devices.
In this regard, the main objective of this thesis is to propose novel self-organizing
and AI-inspired algorithms for optimizing the available radio resources
in next-generation wireless cellular networks. First, heterogeneous networks that
encompass licensed and unlicensed spectrum are studied. In this context, a deep
reinforcement learning (RL) framework based on long short-term memory cells is
introduced. The proposed scheme aims at proactively allocating the licensed assisted
access LTE (LTE-LAA) radio resources over the unlicensed spectrum while
ensuring an efficient coexistence with WiFi. The proposed deep learning algorithm
is shown to reach a mixed-strategy Nash equilibrium, when it converges.
Simulation results using real data traces show that the proposed scheme can yield
up to 28% and 11% gains over a conventional reactive approach and a proportional
fair coexistence mechanism, respectively. In terms of priority fairness, results
show that an efficient utilization of the unlicensed spectrum is guaranteed when
both technologies, LTE-LAA and WiFi, are given equal weighted priorities for
transmission on the unlicensed spectrum. Furthermore, an optimization formulation
for LTE-LAA holistic traffic balancing across the licensed and the unlicensed
bands is proposed. A closed form solution for the aforementioned optimization
problem is derived. An attractive aspect of the derived solution is that it can be
applied online by each LTE-LAA small base station (SBS), adapting its transmission behavior in each of the bands, and without explicit communication with
WiFi nodes. Simulation results show that the proposed traffic balancing scheme
provides a better tradeoff between maximizing the total network throughput and
achieving fairness among all network
ows compared to alternative approaches
from the literature. Second, UAV-enabled wireless networks are investigated. In
particular, the problems of interference management for cellular-connected UAVs
and the use of UAVs for providing backhaul connectivity to SBSs are studied.
Speci cally, a deep RL framework based on echo state network cells is proposed
for optimizing the trajectories of multiple cellular-connected UAVs while minimizing
the interference level caused on the ground network. The proposed algorithm
is shown to reach a subgame perfect Nash equilibrium upon convergence. Moreover,
an upper and lower bound for the altitude of the UAVs is derived thus
reducing the computational complexity of the proposed algorithm. Simulation
results show that the proposed path planning scheme allows each UAV to achieve
a tradeoff between minimizing energy efficiency, wireless latency, and the interference
level caused on the ground network along its path. Moreover, in the context
of UAV-enabled wireless networks, a UAV-based on-demand aerial backhaul network
is proposed. For this framework, a network formation algorithm, which is
guaranteed to reach a pairwise stable network upon convergence, is presented.
Simulation results show that the proposed scheme achieves substantial performance
gains in terms of both rate and delay reaching, respectively, up to 3.8 and
4-fold increase compared to the formation of direct communication links with the
gateway node. Overall, the results of the different proposed schemes show that
these schemes yield significant improvements in the total network performance
as compared to current existing literature. In essence, the proposed algorithms
can also provide self-organizing solutions for several resource management problems
in the context of new emerging use cases in 5G networks, such as connected
autonomous vehicles and virtual reality headsets
Sum-Rate Analysis for High Altitude Platform (HAP) Drones with Tethered Balloon Relay
No full textHigh altitude platform (HAP) drones can provide broadband wireless connectivity to ground users in rural areas by establishing line-of-sight links and exploiting effective beamforming techniques. However, at high altitudes, acquiring the channel state information (CSI) for HAPs, which is a key requirement to perform beamforming, is challenging. In this paper, by exploiting an interference alignment (IA) technique, a novel method for achieving the maximum sum-rate in HAP-based communications without CSI is proposed. In particular, to realize IA, a multiple-antenna tethered balloon is used as a relay between multiple HAP drones and ground stations (GSs). Here, a multiple-input multiple-output X network system is considered. The capacity of the considered M × N X network with a tethered balloon relay is derived in closed-form. Simulation results corroborate the theoretical findings and show that the proposed approach yields the maximum sum-rate in multiple HAPs-GSs communications in absence of CSI. The results also show the existence of an optimal balloon's altitude for which the sum-rate is maximized
Life cycle assessment of seawater reverse osmosis plant powered by fossil fuels versus renewable energy
No full textThesis. M.S. American University of Beirut. Baha and Walid Bassatne Department of Chemical Engineering and Advanced Energy, 2019. ET:7188.Advisor : Dr. Mahmoud Al-Hindi, Associate Professor, Baha and Walid Bassatne Department of Chemical Engineering and Advanced Energy ; Committee members : Dr. Walid Saad, Associate Professor, Bahaa and Walid Bassatne Department of Chemical Engineering and Advanced Energy ; Dr. May Massoud, Associate Professor, Environmental Health.Includes bibliographical references (leaves 79-87)Coupling seawater reverse osmosis with renewable energy such as PV and wind is an active research area and understanding the environmental impact of these integrations using the Life Cycle Assessment (LCA) tool is a major concern for many communities. The aim of this study is to investigate the LCA of several renewable energy alternatives coupled with Seawater Reverse Osmosis (SWRO) for a small-medium town in remote areas and quantify the environmental impact reductions that can be achieved when powering this plant with electricity from biogas from Anaerobic Digestion (AD), PV and wind. To do so, a 4500 m3-day SWRO plant based in Lebanon was designed using WAVE software and each of biogas, PV and wind plants were designed using HOMER Pro. The LCA was performed using Simapro PhD version 9 and IMPACT2002+ impact assessment method was used. Results show that the most optimal integration is with wind energy because the highest environmental impact reductions were achieved in most categories. However, both biogas and PV did prove to have significant improvements compared to conventional fossil fuels
Fig. 7 in Genome-wide characterization and expression profiling of GASA gene family in Triticum turgidum ssp. durum (desf.) husn. (Durum wheat) unveils its involvement in environmental stress responses
No full textFig. 7. Expression pattern of durum wheat GASA genes. (A) Heatmap of the expression pattern of TdGASA genes in roots, stems, leaves, and seeds. (B) Heatmap showing the expression pattern of TdGASA genes T. durum plants subjected to 150 mM NaCl, 15% PEG-6000, 50 μM GA3 and 50 μM ABA. The data represent means of three independent experiments. Color code is presented above the heatmap. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)Published as part of Bouteraa, Mohamed Taieb, Romdhane, Walid Ben, Hsouna, Anis Ben, Amor, Fatma, Ebel, Chantal & Saad, Rania Ben, 2023, Genome-wide characterization and expression profiling of GASA gene family in Triticum turgidum ssp. durum (desf.) husn. (Durum wheat) unveils its involvement in environmental stress responses, pp. 1-13 in Phytochemistry (113544) 206 on page 8, DOI: 10.1016/j.phytochem.2022.113544, http://zenodo.org/record/823054
Fig. 5 in Genome-wide characterization and expression profiling of GASA gene family in Triticum turgidum ssp. durum (desf.) husn. (Durum wheat) unveils its involvement in environmental stress responses
No full textFig. 5. Analysis of 19 TdGASA genes structures. (A) An unrooted phylogenetic tree constructed based on TdGASA genes sequences. (B) Exon-intron structure analysis, blue boxes represent untranslated regions, yellow boxes and black lines were exon and intron positions, respectively. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)Published as part of Bouteraa, Mohamed Taieb, Romdhane, Walid Ben, Hsouna, Anis Ben, Amor, Fatma, Ebel, Chantal & Saad, Rania Ben, 2023, Genome-wide characterization and expression profiling of GASA gene family in Triticum turgidum ssp. durum (desf.) husn. (Durum wheat) unveils its involvement in environmental stress responses, pp. 1-13 in Phytochemistry (113544) 206 on page 7, DOI: 10.1016/j.phytochem.2022.113544, http://zenodo.org/record/823054
Fig. 6 in Genome-wide characterization and expression profiling of GASA gene family in Triticum turgidum ssp. durum (desf.) husn. (Durum wheat) unveils its involvement in environmental stress responses
No full textFig. 6. Predicted cis-acting elements in the TdGASA genes promoter regions. The 2-kb sequences upstream of the 19 TdGASA genes were analyzed with the PlantCARE (http://bioinformatics.psb.ugent.be/webtools/plantcare/html) and New PLACE (https://www.dna.affrc.go.jp/PLACE/?action=new place) databases. The cis-acting elements were classified into three major classes: hormone-related cis-elements, development-related cis-elements, and stress-related cis-elements.Published as part of Bouteraa, Mohamed Taieb, Romdhane, Walid Ben, Hsouna, Anis Ben, Amor, Fatma, Ebel, Chantal & Saad, Rania Ben, 2023, Genome-wide characterization and expression profiling of GASA gene family in Triticum turgidum ssp. durum (desf.) husn. (Durum wheat) unveils its involvement in environmental stress responses, pp. 1-13 in Phytochemistry (113544) 206 on page 8, DOI: 10.1016/j.phytochem.2022.113544, http://zenodo.org/record/823054
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