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1
Williams, Brian Geoffrey. "Hierarchical and cellular structures in cosmology." Thesis, University of Edinburgh, 1992. http://hdl.handle.net/1842/27678.
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Though great advances have been made in the field of cosmology by using numerical <i>n</i>-body techniques to investigate large-scale structure formation, these have been hampered by limited dynamic range. Thus there still remains considerable motivation for finding simple methods that link either the final structure or its statistical properties (such as mass and correlation functions) to the initial conditions. This thesis investigates two such approaches - linear theory and the Voronoi foam. <i>(i) Linear Theory</i> This is based on the principle of smoothing the non-linear density field in order to recover the underlying linear density field. Bound objects are then identified with regions where the density exceeds some critical value. Such a prescription allows the statistical properties of the bound objects to be described as a function of the power spectrum of the initial density field and the smoothing function. This thesis checks the accuracy of such models against the adhesion model, a fully non-linear description of gravitational clustering. In order to provide an accurate test of the linear theory predictions, the simulations are carried out in one dimension, where the adhesion model is <i>exact</i> and there is sufficient dynamic range to allow a thorough test of the linear theory predictions. It is found that despite some of the underlying assumptions of linear theory being incorrect in detail, the linear theory mass functions provide an excellent match to those calculated from the simulations. Linear theory correlation functions are also shown to be a good match to those from the simulations, but only in the case where dynamical evolution of the density field is unimportant (i.e. where large-scale power dominates over small-scale power). <i>(ii) Voronoi foam</i> This is a simple model where space is divided into cells, each containing a nucleus, with galaxies populating the boundaries between cells, which are equidistant between neighbouring nuclei. The geometric structure of the cells is entirely determined by the distribution of the nuclei. This forms a continuous network of walls, filaments and nodes, qualitatively similar to that observed.
2
Karlsson, Robert S. "Radio resource sharing in hierarchical cellular systems /." Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3200.
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Giang, Truong Minh Triet, and trietgiang@yahoo com. "Efficient Admission Control Schemes in Cellular IP Networks." RMIT University. Electrical and Computer Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20060829.113000.
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The thesis reviews current admission control schemes in cellular IP networks. It proposes an improved version of Threshold Access Sharing and a new scheme: weight-based scheme. Finally, an admission control scheme for hierarchical cellular network is introduced.
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Borchardt, Lars, Claudia Hoffmann, Martin Oschatz, Lars Mammitzsch, Uwe Petasch, Mathias Herrmann, and Stefan Kaskel. "Preparation and application of cellular and nanoporous carbides." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-138910.
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A tutorial review on cellular as well as nanoporous carbides covering their structure, synthesis and potential applications. Especially new carbide materials with a hierarchical pore structure are in focus. As a central theme silicon carbide based materials are picked out, but also titanium, tungsten and boron carbides, as well as carbide-derived carbons, are part of this review<br>Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich
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Borchardt, Lars, Claudia Hoffmann, Martin Oschatz, Lars Mammitzsch, Uwe Petasch, Mathias Herrmann, and Stefan Kaskel. "Preparation and application of cellular and nanoporous carbides." Royal Society of Chemistry, 2012. https://tud.qucosa.de/id/qucosa%3A27792.
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A tutorial review on cellular as well as nanoporous carbides covering their structure, synthesis and potential applications. Especially new carbide materials with a hierarchical pore structure are in focus. As a central theme silicon carbide based materials are picked out, but also titanium, tungsten and boron carbides, as well as carbide-derived carbons, are part of this review.<br>Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.
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Režnáková, Ema. "Příprava a charakterizace lehčených polymerních materiálů s hierarchickou celulární strukturou." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2020. http://www.nusl.cz/ntk/nusl-414127.
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The asymmetrical arrangement of cellular structure allows for an accurate functional adaptation at all levels of hierarchy, which derives excellent features for the development of new materials. The main objective of introducing a hierarchy into cellular structures is to improve the mechanical behaviour of the material while maintaining its elastic properties. A part of this work is devoted to the literature review related to the lightened cellular polymeric materials with hierarchical cellular structure. The rest is focused on the preparation of PLA based polymer structures using 3D printing, followed by a saturation in CO2 and a foaming in a silicon oil at elevated temperature. Samples were prepared from natural and white PLA filaments. Based on a series of experiments, optimal conditions for the saturation and foaming process were identified. Through 3D printing and foaming, a one-, two- and three-level hierarchy was introduced into the beam-shaped samples and the effect of the internal cell arrangement on the strain response of the material was examined by the means of a mechanical three-point bending test. Increasing the level of the hierarchy led to an increase in material resistance, which resulted in high values of strength and strain energy (toughness) based on the samples density. The best results were achieved by samples with “sandwich” structure with three levels of hierarchy and 30% filling. Despite the shorter plateau, there was a significant increase in strength and strain energy compared to gradient structures. At the same time, the contribution of the polymer structures prepared in this field of research was demonstrated by comparison with the theoretical model.
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Zabanoot, Zaid Ahmed Said. "Modelling and Analysis of Resource Management Schemes in Wireless Networks. Analytical Models and Performance Evaluation of Handoff Schemes and Resource Re-Allocation in Homogeneous and Heterogeneous Wireless Cellular Networks." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5383.
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Over recent years, wireless communication systems have been experiencing a dramatic and continuous growth in the number of subscribers, thus placing extra demands on system capacity. At the same time, keeping Quality of Service (QoS) at an acceptable level is a critical concern and a challenge to the wireless network designer. In this sense, performance analysis must be the first step in designing or improving a network. Thus, powerful mathematical tools for analysing most of the performance metrics in the network are required. A good modelling and analysis of the wireless cellular networks will lead to a high level of QoS. In this thesis, different analytical models of various handoff schemes and resource re-allocation in homogeneous and heterogeneous wireless cellular networks are developed and investigated. The sustained increase in users and the request for advanced services are some of the key motivations for considering the designing of Hierarchical Cellular Networks (HCN). In this type of system, calls can be blocked in a microcell flow over to an overlay macrocell. Microcells in the HCN can be replaced by WLANs as this can provide high bandwidth and its users have limited mobility features. Efficient sharing of resources between wireless cellular networks and WLANs will improve the capacity as well as QoS metrics. This thesis first presents an analytical model for priority handoff mechanisms, where new calls and handoff calls are captured by two different traffic arrival processes, respectively. Using this analytical model, the optimised number of channels assigned to II handover calls, with the aim of minimising the drop probability under given network scenarios, has been investigated. Also, an analytical model of a network containing two cells has been developed to measure the different performance parameters for each of the cells in the network, as well as altogether as one network system. Secondly, a new solution is proposed to manage the bandwidth and re-allocate it in a proper way to maintain the QoS for all types of calls. Thirdly, performance models for microcells and macrocells in hierarchical cellular networks have been developed by using a combination of different handoff schemes. Finally, the microcell in HCN is replaced by WLANs and a prioritised vertical handoff scheme in an integrated UMTS/WLAN network has been developed. Simulation experiments have been conducted to validate the accuracy of these analytical models. The models have then been used to investigate the performance of the networks under different scenarios.
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Ou, Xiaoxia. "Developing hierarchically structured catalysts on cellular foams for continuous flow catalysis." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/developing-hierarchically-structured-catalysts-on-cellular-foams-for-continuous-flow-catalysis(e3fb780b-5212-4428-894d-288d4b819c6c).html.
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The development of modern chemical and environmental industry requires novel reactor concepts to enable the transfer of catalysts developed in laboratories into the industrial context. The applications of structured reactors/catalysts such as cellular foams are one of the most promising technologies that can facilitate this crucial step. Open-cell foams with stochastically interconnected cells and high porosities (>60%) can promote the low pressure drop during operation and improve the transport phenomena, overtaking the conventional fixed beds for continuous flow catalysis. In this PhD project, silicon carbide (SiC) cellular foams were investigated to evaluate the potential for developing heterogeneous catalysis using foam-based catalysts in continuous flow regime, due to the good compatibility with framework catalyst coatings and features of the cellular structure. The work was carried out by (i) studying morphological and structural features of SiC foams using X-ray computed tomography technique in relation to their implications for applications in chemical engineering; (ii) developing a microwave-assisted method based on the microwave absorbing feature of SiC for fast yet selective synthesis of zeolite (ZSM- 5) coatings on SiC foams; (iii) developing Fe-ZSM-5/SiC structured catalysts using a chemical vapour deposition method and subsequently studying their application as the foam bed reactor in the catalytic wet peroxide oxidation (CWPO) reaction (using phenol as the model compound); and (iv) developing intra-framework Fe-ZSM-5 catalyst on SiC foams (ferrisilicate/SiC) to address the Fe leaching issue from the Fe-ZSM-5/SiC catalyst. Satisfactory results were obtained through the systematic study of the SiC foam based catalysts, showing the potential of using SiC foams to develop structured catalysts for continuous flow environmental catalysis.
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Genovese, Sara. "Emergence and regulation of cell hierarchy in a Drosophila model of neuro-developmental tumor." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0482.
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Dans les tumeurs hiérarchiques, les cellules souches du cancer (CSC), au sommet de la hiérarchie tumorale, peuvent s'auto-renouveler et se différencier en progéniteurs amplificateurs transitoires (TAP) avec un potentiel d'auto-renouvellement limité. Au cours du développement, les cellules souches neurales de Drosophile, appelées neuroblastes (NB), expriment en séquence deux protéines antagonistes se liant à l'ARN, Imp et Syncrip (Syp), qui respectivement favorise et réprime l'auto-renouvellement des NB. La perturbation de mécanismes de division asymétrique des NB peut générer leur amplification illimitée induisant de véritables tumeurs. À l’aide d’une analyse clonale et de modélisations mathématiques, nous avons démontré que les progéniteurs Imp+ dans les tumeurs agissent comme des cellules semblables aux CSC, capables de se renouveler indéfiniment et de se différencier en progéniteurs Syp+, qui, à l’instar des TAP, ont un potentiel d’auto-renouvellement limité et une forte tendance à entrer en quiescence. De plus, nous avons démontré que les tumeurs du NB suivent une organisation hiérarchique rigide dans laquelle la transition Imp-Syp est irréversible. Fait intéressant, en utilisant l’analyse transcriptomique, nous avons constaté que la transition Imp à Syp dans les NB de tumeurs induit une régulation négative des gènes glycolytiques et respiratoires, épuisant vraisemblablement la capacité de croissance et d’auto-renouvellement des progéniteurs Syp+. La conservation frappante de ces protéines de liaison à l'ARN ouvre la possibilité passionnante que des hiérarchies analogues puissent exister dans les cancers humain<br>In hierarchical tumors, cancer stem cells (CSCs), at the top of the tumor hierarchy, can self-renew and differentiate in transient-amplifying progenitors (TAPs), with a limited self-renewal potential. Understanding the molecular mechanisms that drive tumor hierarchy and heterogeneity is crucial to develop effective therapies to eliminate CSCs. During development, Drosophila asymmetrically-dividing neural stem cells, called neuroblasts (NBs), sequentially express two antagonistic RNA-binding proteins, Imp and Syncrip (Syp), that respectively promote and repress NB self-renewal. Genetic perturbation of NB asymmetric division cause NB amplification and malignant tumors. By using lineage tracing, clonal analysis and stochastic mathematical modeling of tumor growth, we demonstrated that Imp+ progenitors act as CSCs. They are able to self-renew endlessly and differentiate in Syp+ progenitors, that have a limited self-renewal potential and the high tendency to undergo quiescence. NB tumors follow a rigid hierarchical organization, where the Imp-to-Syp transition is irreversible. Hence, Syp+ progenitors cannot revert to an Imp+ malignant state. Transcriptomic analysis revealed that the Imp-to-Syp transition in tumors induces a downregulation of glycolytic and respiratory genes that exhausts the growth and self-renewing potential of Syp+ progenitors. The striking conservation of these RNA-binding proteins opens the exciting possibility that analogous Imp-Syp hierarchies may exist in human cancers
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Deschanels, Fabrice. "Pilotage d'une cellule flexible d'usinage." Besançon, 1989. http://www.theses.fr/1989BESA2013.
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On propose un modèle organisationnel de la cellule et du poste base sur la notion d'élément productif constitue par les matériels et logiciels spécifiques a une activité et décompose en un système de communication, de décision et d'application, ce dernier assurant la commande des éléments hiérarchiques inférieurs et la détection des dysfonctionnements
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HAJHOUJ, MOUAMD. "Programmation hors ligne : emulation des composants d'une cellule robotisee." Paris, ENSAM, 1988. http://www.theses.fr/1988ENAM0005.
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On traite du cas d'une cellule robotisee comportant plusieurs chaines cinematiques. Le module d'execution gene la synchronisation et la communication entr les differentes taches. Le passage au robot reel montre que l'emulation de la commande elimine les erreurs dues a l'utilisation d'algorithmes generaux
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Lo, Kuen-Rong, and 羅坤榮. "Channel Assignment Schemes for Hierarchical Cellular Systems." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/84177540136138851638.
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博士<br>國立交通大學<br>電子工程系<br>88<br>In this dissertation, channel assignment schemes of hierarchical
cellular systems with overlaying macrocells and overlaid microcells
are studied. First, a combined channel assignment (CCA)
mechanism is proposed. The objective of the proposed CCA mechanism
is to reduce the new-call blocking probability, decrease forced
termination probability, and increase the channel utilization for
the whole system. The proposed CCA mechanism combines overflow,
underflow, and reversible schemes to reduce both the new-call
blocking probability and forced termination probability. Also, it
adopts the buffering scheme and considers load balancing between
macrocell and microcell to obtain a high channel utilization.
Next, a novel scheme, a fuzzy channel allocation controller
(FCAC), is proposed for hierarchical cellular systems. The
objective of the proposed FCAC scheme is to increase the channel
utilization for the whole system and to guarantee the required QoS
of handoffs as well. The FCAC mainly contains a fuzzy channel
allocation processor (FCAP) which is designed to be in a two-layer
architecture: a fuzzy admission threshold estimator in the first
layer and a fuzzy channel allocator in the second layer. The FCAP
chooses the handoff failure probability, defined as
quality-of-service (QoS) index, and the resource availability as
input linguistic variables for the fuzzy admission threshold
estimator. The Sugeno''s position-gradient type reasoning method is
applied in the fuzzy admission threshold estimator to adaptively
adjust the admission threshold for the fuzzy channel allocator.
For achieving channel allocation with flexible admission and soft
rate control, a neural fuzzy channel allocation controller
(NFCAC) is designed for multimedia services in hierarchical
cellular system. The design concept of NFCAC is to support flexible
resource allocation and soft rate control so that the high blocking
rate in a hierarchical cellular system providing multi-channel
services can be reduced. The NFCAC mainly contains a neural fuzzy
channel allocation processor (NFCAP) which is designed to be in a
two-layer architecture that consists of a fuzzy channel selector
(FCS) in the first layer and a neural fuzzy call-admission and rate
controller (NFCRC) in the second layer. FCS is a fuzzy control
logic, and it can properly determine which channel in either
macrocell or microcell to be allocated. The NFCRC is a five-layer
neural fuzzy controller with the reinforcement learning
architecture to perform the flexible admission control and soft
rate management.
2. Hierarchical Cellular Systems
3. A Combined Channel Assignment Mechanism
4. A QoS-Guaranteed Fuzzy Channel Allocation Controller
5. A Neural Fuzzy Channel Allocation Controller for Multimedia Services
6. Conclusions
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Lin, Yung-Chun, and 林湧鈞. "Repacking on Demand for Hierarchical Cellular Networks." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/18481228547125557489.
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碩士<br>國立交通大學<br>資訊工程系<br>91<br>In mobile telecommunications operation, radio channels are scarce resources and should be carefully assigned.
One possibility is to deploy the hierarchical cellular network (HCN).
This thesis studies a HCN channel assignment scheme called repacking on demand (RoD).
RoD was originally proposed for wireless local loop networks.
We expend this work to accommodate mobile networks.
Moreover, for non-speed-sensitive and speed-sensitive cases, we propose different channel assignment and repacking procedures for RoD.
The simulation models are proposed to study the performance of HCN with RoD and some previously proposed schemes.
Our study quantitatively indicates that RoD may significantly outperform the previous proposed schemes on call incompletion and call handoffs.
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Ying-Yu, Chen. "Prioritized Handoff Dynamic Channel Allocation in Hierarchical Cellular Systems." 2000. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0021-2603200719110569.
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Li, Min-Tsang, and 李敏滄. "Soft Handoff Queueing Strategy in Hierarchical Cellular CDMA Network." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/50255207567756895012.
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碩士<br>國立臺灣科技大學<br>電機工程系<br>90<br>The key goals of the next generation wireless networks include high utilization of frequency spectrum, improvement of quality of service and provision of various multimedia services. Code division multiple access (CDMA) cellular communication systems utilize diversity technology to perform soft handoff. Compared to break-before-make hard handoff, make-before-break soft handoff can provide higher quality of service during handoff. On the other hand, mobile users can possess different mobility, e.g., move at vehicular or pedestrian speed. If the cell size is too small, fast-moving users may cause frequent handoffs, whereas if the cell size is too large, frequency reuse will decrease and thus reduce system capacity. In hierarchical cellular systems, a macrocell in the upper layer covers N microcells in the lower layer, where microcells are used to carry slow-moving users, whereas macrocells are for fast-moving users. Microcell layer has higher frequency reuse and thus can provide higher system capacity, whereas nacrocell layer can reduce the number of handoffs of fast-moving users. As forced termination of an ongoing call is less tolerable than blocking of a new call, handoff calls are usually given priority over new calls. Handoff queues are provided for handoff calls that can not obtain the required channel immediately, so that forced termination probability is reduced. In the thesis, we consider hierarchical cellular networks supporting soft handoff, where users with different mobility are assigned to different layers, and handoff queues are provided for handoff calls that can not obtain the required channel immediately. According to whether handoff queues are provided in microcells and/or macrocells, four different handoff queueing strategies are proposed and studied. We derive the mathematical model of the considered system with multi-dimensional Markov chain, and utilizes Gauss-Seidel iterative method to find the steady state probability distribution and thus the performance measures of interest: new call blocking probability, handoff failure probability, and forced termination probability. Analytical results show that providing handoff queues in both microcells and macrocells can achieve largest performance improvement.
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Chen, Ying-Yu, and 陳瀅羽. "Prioritized Handoff Dynamic Channel Allocation in Hierarchical Cellular Systems." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/5y56yt.
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碩士<br>國立臺灣師範大學<br>資訊教育研究所<br>89<br>We propose a channel assignment strategy, called Hierarchical cellular system - Prioritized Handoff Dynamic Channel Allocation strategy (HPHDCA), for use in hierarchical cellular networks, in which channel resources are shared by both tiers of cells. The HPHDCA is essentially a DCA scheme with additional operational features including prioritized-handoff, local-packing, reservation-sharing and overflow. In distributed operation environment, these features are achieved through looking up channel status maintained in an ACOR table. The ACOR table is developed to support enough information of channel usage patterns of interference cells sufficient for each cell to determine channel allocation by itself. By the mobility of nonuniform transition probability between cells and different dwell time distribution in microcells and macrocell-only areas, simulations show that the HPHDCA in macrocell/microcell overlay is able to yield favorable performance on handoff call blocking over new call blocking, at the cost of new call blocking probability. One additional feature is found that HPHDCA takes the conventional overflow technique completely into the reservation-sharing scheme, with no need to crank up a new overflow mechanism.
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Ho, Chia-hui, and 何家卉. "Multiuser Beamforming and Opportunistic Scheduling for Transparent Hierarchical Cellular Systems." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/xzn49r.
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碩士<br>國立中央大學<br>通訊工程學系<br>102<br>The idea of cognitive radio (CR) has embodied concretely in hierarchical cellular systems by deploying an underlying microcellular system to reuse the underutilized spectrum licensed by a macrocellular system. The fundamental challenges for successfully realizing such hierarchical systems are to manage the intercell interference between the macrocell and microcell and to pursue the goal of maximizing the spectrum recycling efficiency. Recently, the idea of interference alignment has been emerged to utilize the spatial dimension offered by multiple antennas to overcome the interference problem and achieve the maximum sum rate performance.
In this thesis, we jointly consider antenna beamforming, power allocation, and multiuser scheduling for the secondary system to utilize the uplink spectrum of the primary cell and to concurrently serve multiple secondary users in the uplink. IA is applied to manage the interference from the secondary users to the primary cellular system in a transparent hierarchical cognitive radio (HCR) system. By change of variables, we can remove the IA constraint by absorbing it into the sum rate formula, and the original beamforming problem becomes solvable and the optimal solution can be gotten by using an iterative water-filling approach.
The iterative water-filling algorithm transform the multiuser sum rate maximization into a series of single-user sum rate maximizations for each user by regarding all other users’ signals as additional noise at each step. The algorithm finds the single-user water-filling covariance matrix for each step. The sum rate objective is increasing with each water-filling step and the sum rate will converge to a limit.
Furthermore, the two-stage user scheduling that makes use of multiuser diversity is investigated to further improve the sum rate performance and the fairness among users via PF rule and orthogonality.
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Lu, Ssu-Han, and 呂思翰. "Smart Antenna Techniques for Interference Management in Hierarchical Cellular Systems." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/34864371791740949996.
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博士<br>國立交通大學<br>電信工程研究所<br>102<br>With the increasing demand for high data rates service, macro-cell and small cell coexist hierarchical cellular architecture become an extremely important issue which can improve signal quality of cell edge users and offer huge spectrum efficiency gain in current and future wireless communication systems.
In such hierarchical cellular systems, the spectrum efficiency can be further enhanced by managing the inter-cell interference (ICI) between macro-cells and small cells.
In this dissertation, we investigate smart multiple-input multiple-output (MIMO) antenna cooperation techniques for interference control in hierarchical cellular systems.
In the first part, we investigate the performance of hierarchical base station cooperation (HBSC) techniques in macro-cell and small cell coexist heterogeneous networks (HetNet) for the 3rd Generation Partnership Project (3GPP) Long-Term Evolution-Advanced (LTE-A) system.
HBSC techniques aim at reducing the co-channel interference between a macro-cell and a group of small cells by coordinating the transmissions of distributed antennas in the cell coverage area.
We find that joint intra- and inter-site cooperation will significantly reduce the inter-cell interference.
Compared to the case without joint intra-/inter-site coopearation, we demonstrate that HBSC techniques in the conventional pentagonal cell architecture can improve spectrum efficiency by $ 65\% $ at the cell edge.
When the narrow beam tri-sector cell architecture is considered, the spectrum efficiency can be further improved by $ 16.42\% $ at cell edge.
In the second part, we investigate different beamforming schemes and consider the channel feedback issue in the HBSC systems.
Base station cooperation techniques can enhance the system performance by reducing the ICI, but relying on the accurate channel state information (CSI) of the cooperative base stations in the feedback channels.
However, when the CSI is used for calculating the beamforming weights, the performance of a cooperative base station is very sensitive to the channel variations.
To overcome this issue, we present the design principles of a robust HBSC system by changing the role of the CSI in the feedback channel from calculating beamforming weights to user selection.
Because of different purposes and thus having a much margin to tolerate channel variations, the CSI of feedback channels can accurately select the pairs of the transmit antenna of a base stations and the receive antennas of users.
By applying a simple beamforming technique at the receiver, such as zero-forcing (ZF) algorithm, the ICI can be effectively reduced.
Based on the above idea, we design a HBSC systems, where the underlaying small cells coexist with a macro cell.
We also propose a dynamic small cell selection algorithm to obtain a group of appropriate small cells to cooperate with the corresponding macro cell.
Our results show that the proposed receive ZF beamforming techniques can improve the spectrum efficiency of the HBSC system at the cell edge by $ 34.6\% $ compared to the transmit ZF beamforming techniques when the standard deviation of channel errors is two times of the average value of the desired signal strength.
In the third part, we apply the receive beamforming technique in the hierarchical cognitive radio (HCR) systems which aim to serve the primary users in a macrocell and the secondary users in underlaying small cells by using the same spectrum.
The HCR system considered in this dissertation is defined as a few time-division-duplex (TDD) microcells on top of a frequency-division-duplex (FDD) macrocell, where the microcell is the secondary systems and the macrocell is the primary system.
The major challenge for HCR systems lies in controlling the inter-cell interference from the secondary users to the primary systems, and further enhancing capacity of the secondary users.
We first propose an effective user scheduling algorithm in the secondary system to mitigate the interference to the primary system.
Furthermore, we design an optimal receive beamforming scheme to maximize the uplink transmission rate of the underlaying secondary users in the HCR systems.
Our results show that the proposed integrated scheduling and beamforming technique can improve average spectrum efficiency by $ 82.5\% $ compare to the original primary system.
In summary, the main contribution of this dissertation is to investigate the interference management techniques for hierarchical cellular systems.
We investigate three kinds of MIMO antenna cooperation schemes to mitigate interference: (1) HBSC systems with joint intra- and inter-site cooperation; (2) HBSC systems with receive beamforming techniques; and (3) HCR systems with optimal beamforming and scheduling.
The proposed framework can help analyse the performance of hierarchical cellular systems and provide important insights into the design of base station cooperation techniques, antenna beamforming schemes, and scheduling algorithm to enhanced spectrum efficiency.
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Tsai, Chia-Sheng, and 蔡佳勝. "Radio Resource Allocation Strategies for Satellite and Hierarchical Cellular Systems." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/65344825687537801616.
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博士<br>國立成功大學<br>電機工程學系碩博士班<br>91<br>Future IMT-2000 (International Mobile Telecommunications after the year 2000) are expected to be integrated by terrestrial and satellite components to provide a seamless, wide rang of coverage areas, system capacity, and available service types for personal communications. In the space segment, low-earth orbit (LEO) satellite based systems are preferred with the consideration of some technical issues such as transmission delay, path loss, antenna aize, etc.. However, because of the short period for which the satellites are visible, users of LEO satellite systems face frequent handoff requirements between spot-beams (cells).
In the terrestrial part, cellular communication infrastructures envision to adopt hierarchical, multisized cells for covering non-homogeneous populated areas. Microcells have significantly higher capacity than large cells and are more cost-effective in reducing power consumption in densely populated districts. Meanwhile, large cell systems (macrocells) avoid the need for frequent cell boundary crossings (handovers) to serve high mobility mobile users.
In this thesis, based on the different features of the terrestrial and LEO satellite-based systems, we study some channel and power allocation strategies and show that these schemes can provide larger capacity and better performance for the cellular communication systems.
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HUANG, JUN-REN, and 黃俊仁. "A dynamic hierarchical structure for cellular mobile packet radio networks." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/05805902050524902353.
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Tsai, Chi-Hao, and 蔡祈豪. "The Effect of Channel Connection Pool Techniquewith CDMA Based Hierarchical Cellular Network." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/27462903226066542682.
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碩士<br>大同大學<br>資訊工程學系(所)<br>97<br>Nowadays, both wireless network technology and coverage are widely developing and more mature. 3G or upcoming 4G cell based wireless network is the infrastructure in order to provide more high speed network services. No doubt, a large number of multimedia applications and more voice calls will consume more bandwidth as well as channel resources. An efficient channel assignment scheme could increase resources utilization and decrease drop rate and blocking rate. Therefore, the hierarchical cellular network is proposed for solving this issue. According to the basic rule of channel assignment, the different types of wireless traffic will be assigned to specific cellular or base station. In out study and model, we defined two types of traffic, voice call and multimedia data call which will be carried or transported by macrocell and microcell separately. When network congestion occurs and macrocell has no channel available, voice call is able to be transferred by microcell in stead of macrocell. For multimedia data call, the character of non real-time data transfer is allowed a longer waiting time. Therefore, we created a “channel pool” to collect these calls in order to decrease the possibility of overall block rate and to increase the system utilization.
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Lue, Yan-Nan, and 劉彥男. "The Efficiency of Self-adaptive Subrating Channel Assignment for Hierarchical Cellular Network." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/16769052986355015472.
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碩士<br>大同大學<br>資訊工程學系(所)<br>99<br>Hierarchical Cellular Network architecture (HCN) is the most common architecture that widely used in the mobile telecommunications operation. Channel assignment is the key issue to improve System performance. Different kind of traffic types is applicable to recent proposed methods such as guard channel, overflow and subrating. But in real world, these traffics are intermixture. A fuzzy model for Self-adaptive Subrating Channel Assignment could trigger subrating ratio and overflow method. In the complex traffic environment, this channel assignment strategy can provide better performance on block, handoff failure, and system channel utilization.
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Lin, Yi-Liang, and 林奕良. "Cell Site Selection for CDMA Hierarchical Cellular System with Multi-Class Traffic." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/93189464063020437122.
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碩士<br>國立交通大學<br>電信工程系<br>90<br>CDMA is one of the most potential techniques in the third generation mobile communication system because of its resistance of interference and high frequency efficiency. Because the CDMA system can serve many users with various services requirements at the same time, radio resource management (RRM) becomes a very important issue. The goal of this thesis is to study cell site selection technique for hierarchical CDMA networks with multi class traffic.
Data services, such as WWW, E-mail and video, etc, will become primary services in the next generation mobile wireless communication system. Theses services require higher bandwidth and diverse QoS requirements. Thus, it is difficult to find a common traffic model that can approximate all kinds of data traffic. This thesis will compare two data traffic models, i.e. a modified on-off data traffic model and Pareto based data traffic model, and evaluate their impacts on the system performance of cellular network.
Secondly, hotspot micro cells often occur in a small area requesting high traffic load. Employing hotspot micro cells can increase system capacity and improve system performance. Because a micro cell and a macro cell use the same frequency band, the system may suffer interference with each other. In this thesis, we investigate different cell site selection algorithms for hierarchical cellular systems to ensure that the system can effectively improve system capacity without suffering severe interference with each other. For this purpose, we propose a new relative pilot based cell site selection algorithm. Through assigning a protection threshold, the relative pilot based cell site algorithm not only can ensure a micro cell to effectively relieve hotspot data traffic load, but avoid the micro cell from serving too much traffic beyond its capability. We will demonstrate that the proposed relative pilot based cell site selection algorithm outperforms most current site selection algorithms in hierarchical CDMA cellular system with multiple traffic classes.
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Lai, Wen-Pin, and 賴文彬. "Time Domain Coordination for Intercell Interference Reduction in LTE Hierarchical Cellular Systems." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/96239642963758103965.
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碩士<br>國立交通大學<br>電信工程研究所<br>101<br>In this thesis, we present an interference-aware slot allocation technique for improve the system performance of the low-power pico-cells and overlaying macro-cells. In the 3rd Generation Partnership Project (3GPP) Long-Term Evolution- Advanced (LTE-A), this kind of interference between pico-cells and its overlaying macro-cell is called the interference in heterogeneous network (HetNet), which will decrease the coverage area of pico-cells and overall system throughput. In the 3GPP LTE-A cellular system, enhanced inter-cell interference coordination (eICIC) technique adopts Almost
Blank Subframes (ABS) to control the inter-cell interference between pico-cells and macro-cells. However, because of the fixed ratio ABS design, the current eICIC techniques will degrade the macrocellular performance severely and the improvement of throughput of pico-cells is also limited in a dynamic traffic environment. Thus, we propose an interference-aware slot allocation technique to adjust the ratio of ABS dynamically based on the estimated interference between macro-cells and pico-cells. Furthermore, the proposed interference-aware slot allocation technique distributively designate the blank slots. Our results show that the proposed interference-aware slot allocation technique can improve the throughput for both macro-cells and pico-cells simultaneously. In the considered case, the throughput of pico-cells and macro-cell cell edge users are improved by at least 13% and 7% respectively, compared to the current fixed ratio ABS design approach.
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Jhan, Jhih-Dao, and 詹志道. "Analysis of Hierarchical Cellular CDMA Networks for Intelligent Transportation Systems with Multimedia Services." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/12891521271039030055.
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碩士<br>國立臺灣科技大學<br>電機工程系<br>93<br>We consider two-tier cellular CDMA networks for ITS (Intelligent Transpor- tation System), where mobile users can move in only one of two directions. Both narrowband voice service and broadband services are supported in the considered system. The broadband calls are assigned to the associated macrocell in order to reduce the times of handoff and the voice calls are assigned to the associated microcell. One guard channel scheme is implemented to prioritize handoff calls over new calls in the system. To avoid macrocell resource under-utilization, voice calls in microcells can be allowed to overflow to macorcells. To avoid excessive overflow from the microcells, another guard channel scheme is adopted to prioritize broadband calls over voice calls. Another way to avoid excessive overflow in macrocells is to allow overflowed voice calls to be taken back to microcells. For comparison purposes, we study three models: Model A (no overflow), Model B (overflow without takeback), and Model C (overflow and takeback).Two multi-dimensional Markov chains are used to describe microcells and macrocells, respectively, and the analytical results for the performance measures of interest are derived, e.g., new call blocking probability, handoff failure probability, forced termination probability, and utilization. Last but not least, simulation programs are written in C to collect simulation results for verifying the analytical results.
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Chou, Yu-Yun, and 周雨韻. "A Study of the Hierarchical Cellular-Based Management Worked by Power-Aware Technology." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/k548ey.
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碩士<br>朝陽科技大學<br>資訊管理系碩士班<br>93<br>In recent years, people are more inclined to depend on wireless network services so that they may obtain latest information at any time anywhere. Of wireless networks, to effectively allow several or more mobile devices to send data with one another has become an important research topic. Our research carries the topic discussion under Mobile Ad-Hoc Network. MANET is one type of non-fixed infrastructure mobile networks and consists of many Mobile Hosts in which these can be cellular phones. The power consumption rate and bandwidth of each mobile host device becomes an important issue. Besides, the reliability of the manager in the Hierarchical Cellular-Based Management is also our objective. This paper presents two fuzzy-based inference systems. Designing a Power-Aware Assignation Manager Inference System, an approach is proposed for selection of a network stable manager that takes into consideration speed, battery power and location. In stable time, the Power-Aware Multi-MA Inference System triggers the Mobile Agents to distribute workloading of manager.
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Yuan-Cheng, Chan. "A Hybrid Measurement-based Model for Hierarchical Location Area Design in Wireless Cellular Networks." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0009-1207200611535100.
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Chen, Yeu-An, and 陳禹安. "Joint Antenna Beamforming and Power Allocation for Hierarchical Non-Orthogonal Multiple Access Cellular System." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/sf3uce.
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碩士<br>國立中央大學<br>通訊工程學系<br>107<br>In this thesis, we investigate a hierarchical Non-orthogonal multiple access cellular system
simultaneously shares the macrocell uplink spectrum with the microcell secondary user who is
unlicensed. We also attempt the NOMA which is expected to improve the system capacity of
wireless communication systems.
We jointly design the allocated power and the beamforming weights for each downlink
microcell user to maximize the capacity of the hierarchical NOMA cellular system. We consider
two methods: (1) Using minimax decision theory to find the user rate. (2) Using the sum-MSE
decision theory to find the sum rate. When we seek out user rate through Zero-forcing precoding
to eliminate the interference from the other beam users and find the optimal power allocation.
This problem is non-convex so we convert the aforementioned ZF user rate maximization
problem into a convex semi-definite relaxation (SDR) techniques. Because this problem is a
joint design non convex problem, it is difficult to jointly find the optimal solutions of power
allocation and beamforming design. We divide the problem into two steps to alternatively find
the optimal solutions.
Second method is using sum-MSE to seek the maximization sum rate of the system, while
satisfying the constraints of the interference power to the primary user, the required SINR for
secondary users, and the SIC requirement for the user in the same beam. This problem is also the non-convex problem so we solved it by SDR approach. And then we proof that sum-MSE
method sum rate is equal to the initial designing sum rate problem.
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Chan, Yuan-Cheng, and 詹淵程. "A Hybrid Measurement-based Model for Hierarchical Location Area Design in Wireless Cellular Networks." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/27583323733810730720.
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碩士<br>元智大學<br>資訊工程學系<br>94<br>Location area design plays an important role to reduce the supererogatory traffic cost for location management which is due to rapidly increasing mobile users. This thesis proposes a hybrid measurement-based model to design the size of location area and group the cells into hierarchical location area architecture for minimizing signaling cost. By this proposed model, wireless cellular system would be assisted to improve traffic performance and traffic cost analysis of various network elements is included for optimizing location area design.
The most appropriate size of location area for service area would be found out by reducing overall traffic cost/signaling loading resulting from different behaviors, such as location update, paging, handoff, etc. The lower level of location area architecture called traffic-based location area is constructed by cell searching algorithm and traffic weighted calculation for optimization. Another level of location area architecture called user-based location area is determined by the user mobility and location update is decided by this level. Paging cost would be affected by paging area which is part of user-based location area.
For the service area with cells which have different radiuses and timing conditions, location area design using our proposed model could be improved by 10~20% from GSM model and 10~15% from other location area design based on cost of location management. In addition to increase the performance of location management, call service would be guaranteed.
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Huang, Pei-Ching, and 黃珮菁. "An H.263-based Hierarchical Coder and Packet Discard Policies for 3G Cellular Networks." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/69925105218985552575.
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Peng, Lin-Yi, and 彭令儀. "Fuzzy-based Cell Selection and Adaptive Repacking Strategy for Channel Assignment in Hierarchical Cellular Systems." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/56521897885795301368.
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碩士<br>國立臺灣師範大學<br>應用電子科技研究所<br>95<br>Since the traffic in mobile communication system increase rapidly, the radio channels are unable to meet the demand and must be assigned more accurately. It is possible to improve the channel allocation efficiency by upgrading the utility rate of spectrum. Further, the flexible application of hierarchical structure can be used to increase the coverage area and improve the utility rate of channels. In this thesis, Fuzzy Path Selector was developed to make path selection to meet the property of balanced-load cellular network. Fuzzy Cell Selector then was used to determine the cellular layer according to the velocity of MS and the resource state of cells to reduce the blocking rate. Third, Channel Assignment Evaluator was used to do adaptive repacking for reducing the dropping rate.
The simulation results of proposed strategy in this thesis improved the blocking rate of 13.48% and the handoff rate of 56.48％ compared to traditional threshold controlling mechanism. It can be a better choice for improving channel allocation efficiency.
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Griffin, Paula Jean. "Biological network models for inferring mechanism of action, characterizing cellular phenotypes, and predicting drug response." Thesis, 2016. https://hdl.handle.net/2144/14516.
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A primary challenge in the analysis of high-throughput biological data is the abundance of correlated variables. A small change to a gene's expression or a protein's binding availability can cause significant downstream effects. The existence of such chain reactions presents challenges in numerous areas of analysis. By leveraging knowledge of the network interactions that underlie this type of data, we can often enable better understanding of biological phenomena. This dissertation will examine network-based statistical approaches to the problems of mechanism-of-action inference, characterization of gene expression changes, and prediction of drug response.
First, we develop a method for multi-target perturbation detection in multi-omics biological data. We estimate a joint Gaussian graphical model across multiple data types using penalized regression, and filter for network effects. Next, we apply a set of likelihood ratio tests to identify the most likely site of the original perturbation. We also present a conditional testing procedure to allow for detection of secondary perturbations.
Second, we address the problem of characterization of cellular phenotypes via Bayesian regression in the Gene Ontology (GO). In our model, we use the structure of the GO to assign changes in gene expression to functional groups, and to model the covariance between these groups. In addition to describing changes in expression, we use these functional activity estimates to predict the expression of unobserved genes. We further determine when such predictions are likely to be inaccurate by identifying GO terms with poor agreement to gene-level estimates. In a case study, we identify GO terms relevant to changes in the growth rate of S. cerevisiae.
Lastly, we consider the prediction of drug sensitivity in cancer cell lines based on pathway-level activity estimates from ASSIGN, a Bayesian factor analysis model. We use penalized regression to predict response to various cancer treatments based on cancer subtype, pathway activity, and 2-way interactions thereof. We also present network representations of these interaction models and examine common patterns in their structure across treatments.
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Isik, Seckin Sinan. "Phosphoproteomic study on osmotic shock in Saccharomyces cerevisiae over sub-minute and half- hour timescales." Thèse, 2018. http://hdl.handle.net/1866/22274.
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