Dissertations / Theses on the topic 'Spatial Reuse'
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Grönkvist, Jimmi. "Assignment strategies for spatial reuse TDMA." Licentiate thesis, KTH, Signaler, sensorer och system, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1407.
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Oh, Inhee Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Spatial reuse in TDMA wireless networks." Publisher:University of New South Wales. Electrical Engineering & Telecommunications, 2008. http://handle.unsw.edu.au/1959.4/40910.
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In this thesis we investigate the performance of spatial reuse in wireless networks. More specifically, we investigate the performance of location-based spatial reuse built upon the identification of links in the network that form Collision-Free Sets (CFSs). We develop algorithms that efficiently find such CFSs. The main focus of this thesis is the application of our CFS-based algorithms to emerging WiMAX (Worldwide Interoperability for Microwave Access) networks. However, we will also apply our CFS-based algorithms to smaller scale networks, as well as to the issue of QoS routing. This thesis makes several contributions. We first show how CFSs can be found within polynomial time in small scale wireless networks. We then probe how CFSs can be used to enhance network efficiency when location is available. We also explore how CFS determination is affected by location error, determining what level of location error renders the use of CFSs ineffective. In this context, we discuss the density of access points required to ensure CFS-based spatial reuse remains effective. We then focus on the use of CFSs in emerging multihop WiMAX networks, showing in detail how enhanced spatial reuse is delivered. The spatial reuse gains are probed both in the presence of realistic channel conditions and realistic location errors. Within the context of the IEEE 802.16 standard we show how CFSs can enhance, by factors of two, the VoIP capacity of multihop WiMAX networks. We also discuss how our CFS algorithms can be applied to other ongoing efforts aimed at improving VoIP capacity in WiMAX networks. Finally, an application of our CFS algorithms in the context of QoS routing is studied. Specifically, we develop a two-hop QoS routing protocol that guarantees QoS specifications by securing higher bandwidth for the chosen routes.
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Grönkvist, Jimmi. "Interference-based scheduling in spatial reuse TDMA." Doctoral thesis, KTH, School of Electrical Engineering (EES), 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-441.
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Spatial reuse TDMA has been proposed as an access scheme for multi-hop radio networks where real-time service guarantees are important. The idea is to allow several radio terminals to use the same time slot when possible. A time slot can be shared when the radio units are geographically separated such that small interference is obtained. The transmission rights of the different users are described with a schedule.
In this thesis we will study various aspects of STDMA scheduling. A common thread in these various aspects is the use of an interference-based network model, as opposed to a traditional graph-based network model. While an interference-based network model is more complex than a graph-based model, it is also much more realistic in describing the wireless medium. An important contribution of this thesis is a comparison of network models where we show that the limited information of a graph model leads to significant loss of throughput as compared to an interference-based model, when performing STDMA scheduling.
The first part ot this thesis is a study of assignment strategies for centralized scheduling. Traditionally, transmission rights have been given to nodes or to links, i.e., transmitter/receiver pairs. We compare these two approaches and show that both have undesirable properties in certain cases. Furthermore, we propose a novel assignment strategy, achieving the advantages of both methods.
Next we investigate the effect of a limited frame length on STDMA schedules. We first show that the required frame length is larger for link assignment than for node assignment. Further, we propose a novel assignment strategy, the joint node and link assignment, that has as low frame length requirements as node assignment but with the capacity of link assignment.
In the last part of this thesis we describe a novel interfence-based distributed STDMA algorithm and investigate its properties, specifically its overhead requirement. In addition we show that this algorithm can generate as good schedules as a centralized algorithm can.
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Grönkvist, Jimmi. "Interference-based scheduling in spatial reuse TDMA /." Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-441.
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Mungara, Ratheesh Kumar. "System-level performance of interference-aware spatial frequency reuse." Doctoral thesis, Universitat Pompeu Fabra, 2016. http://hdl.handle.net/10803/400869.
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Spatial frequency reuse is a long-established approach for enhancing the capacity of wireless systems through increased spectral efficiency (bits per second per unit bandwidth). The future 5th generation of wireless systems is expected to incorporate various forms of frequency reuse. This includes multiple-input multiple-output (MIMO) communication enabling frequency reuse across antennas, device-to-device (D2D)-based densification allowing spectrum reuse across direct communication links, and full duplexing utilizing the same spectrum for communication in the transmit and receive directions.
This dissertation aims at determining the performance limits of emerging wireless systems underpinned by dense spatial frequency reuse and interference suppression, and to glean key system design insights. Stochastic geometry is the toolbox invoked to conduct the analysis, with network locations modeled as points of a Poisson process. A new framework is developed by introducing a Gaussian fit to the interference and variable degrees of spatial averaging, which enable more meaningful results and compact expressions compared to those of existing analyses.
Within this framework, we first consider MIMO spatial multiplexing and interference alignment (IA). The former scheme utilizes all available spatial dimensions for signaling and the latter minimizes interference at the expense of knowing the instantaneous fading states at both transmitters and receivers and of a reduction in spatial signaling dimensions. Despite the intense work on IA and spatial multiplexing, there is limited work aimed at understanding their engineering tradeoff in the context of practically relevant cellular settings such as propagation losses, fading dynamics due to user mobility and imperfect knowledge of the fading states. We have studied this problem in depth through both system- and link-level analyses. Even under perfect knowledge of the fading, IA is seen to be beneficial over spatial multiplexing only in very specific and relatively infrequent network situations, and IA loses all its advantages at vehicular speeds when the fading knowledge is imperfect.
Second, we focus on ITLinQ and FlashLinQ, the two principal channelization schemes proposed to date for controlling the interference in D2D networks. An analytical characterization of ITLinQ scheme is provided, opening the door to optimizing its controllable parameters. It is shown that both channelization schemes outperform the unchannelized baseline, with a slight edge for ITLinQ. On the most unfavorable network geometries, ITLinQ yields multiple-fold improvements in spectral efficiency with respect to an unchannelized network.
Finally, we introduce full-duplex transceivers in cellular networks and characterize the impact of increased interference on their performance. It is established through analysis and complemented by simulations on a Vodafone LTE field test network that additional user-to-user interference only has a minor impact while base-to-base interference would render full-duplex operation unfeasible in dense microcellular networks without any interference management.
In summary, MIMO spatial multiplexing and D2D-based densification are seen to play a vital role in improving wireless system capacity while IA and full duplexing are found to be ineffective.La reutilització de la freqüència espacial és l’aproximació més acceptada per tal de millorar la capacitat dels sistemes wireless mitjançant l'increment de l'eficiència espectral (bits per segon per unitat d'ample de banda). S'espera que la futura cinquena generació de sistemes wireless incorpori diverses formes de reutilització de freqüència. Això inclou la comunicació multi-input multi-output (MIMO) que permet la reutilització a través d'antenes, densificació dispositiu-a-dispositiu (D2D) que permet reutilitzar l'espectre a través d’enllaços de comunicació directa, així com un full-dúplex emprant el mateix espectre per a la comunicació en la transmissió i recepció de direccions. Aquest treball pretén determinar els límits de rendiment dels sistemes wireless emergents, basats en una densa reutilització de la freqüència espacial i en la supressió d'interferències, així com espigolar coneixement clau per al disseny de sistemes d'aquest tipus. La geometria estocàstica és l'eina que s'aplicarà a l'anàlisi que es durà a terme, modelitzant les localitzacions dins la xarxa com a punts d'un procés de Poisson. La introducció d'un ajust Gaussià a la interferència, conjuntament amb la consideració de nivells variables d'expectació espacial, han permès definir un nou marc matemàtic que fa possible unes expressions més compactes i uns resultats més significatius en comparació amb els anàlisis existents. Dins d'aquest marc, en primer lloc es prenen en consideració la multiplexació MIMO i l'aliniament d'interferència (IA, en les seves sigles en anglès). El primer esquema empra totes les dimensions espacials disponibles per a la senyalització i el segon minimitza la interferència a costa de conèixer els estats de esvaïment instantani dels transmissors i receptors, i d'una reducció en les dimensions de senyalització espacial. Malgrat l'intens treball en l'IA i la multiplexació espacial, s'ha prestat escassa atenció a tractar de comprendre el seu balanç d’enginyeria en el context d'xarxes cel.lulars de rellevància pràctica, com els de propagació de pèrdues, o les dinàmiques de esvaïment degudes a la mobilitat de l'usuari i al coneixement imperfecte dels estats de esvaïment. En aquest treball s'ha estudiat en profunditat aquest problema a través d'anàlisis tant a nivell dels enllaços com del sistema. Fins i tot en condicions de coneixement perfecte del esvaïment, l'IA resulta beneficiós sobre la multiplexació només en situacions de xarxa molt específiques i relativament infreqüents, mentre que perd tots els seus avantatges a velocitats vehiculars quan el coneixement del esvaïment és imperfecte. En segon lloc, el treball es centra en el ITLinQ i el FlashLinQ, els dos principals esquemes de canalització proposats fins al moment per controlar la interferència en xarxes D2D. S'ofereix una caracterització analítica de l'esquema ITLinQ, obrint així la porta a l'optimització dels seus paràmetres controlables. Es mostra que tots dos esquemes de canalització aconsegueixen millors resultats que l'esquema no canalitzat, amb un lleuger avantatge per al ITLinQ. Considerant la geometria de xarxa més desfavorable, el ITLinQ produeix millores múltiples en l'eficiència espectral en comparació amb la xarxa no canalitzada. Finalment, el treball introdueix els transreceptors full-dúplex en xarxes cel.lulars i caracteritza l'impacte de la interferència incrementada en el seu funcionament. A través d'anàlisis i de simulacions complementàries en una xarxa de test de Vodafone LTE, s'estableix que la interferència d'usuari a usuari té un impacte poc significatiu mentre que la interferència de base a base faria inviable l'operació full-dúplex en xarxes microcell.lulars sense gestió de les interferències. En resum, aquest tesis doctoral aporta evidència de que el multiplexat MIMO i la densificació basada en D2D juguen un paper vital en la millora de la capacitat dels sistemes wireless mentre que el IA i el full-dúplex resulten inefectius.
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Yan, Ziguang. "On exploiting spatial reuse in wireless ad hoc networks." School of Electrical, Computer and Telecommunications Engineering - Faculty of Informatics, 2008. http://ro.uow.edu.au/theses/111.
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Wireless ad hoc networks have been increasingly popular in recent years with the development of mobile devices. However, both theoretical and simulation works show that the capacity of wireless ad hoc networks is bounded due to its nature of distributed and multihop. Spatial reuse is a promising technology to increase the capacity of wireless ad hoc networks by allowing more transmissions to occur simultaneously. In this thesis, we enhance 802.11 performances by exploiting the benefits of spatial reuse in wireless ad hoc networks which is achieved by transmission power control (TPC) and directional antennas. We first propose spatial TPC based on basic TPC to fully exploit the benefits of spatial reuse achieved by transmission range control. Simulation results show that spatial TPC achieves higher throughput and lower power consumption compared to 802.11 and basic TPC. We also develop four schemes of directional MAC protocols with the intention of overcoming the new hidden node problem faced by directional antennas. By extensive simulations under different topologies and traffic patterns, we find the directional RTS/CTS (DD) scheme outperforms 802.11 as well as other three schemes by fully exploiting the benefits of spatial reuse achieved by directional antennas.
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Woods, Michael A. "Interference aware routing using spatial reuse in wireless sensor networks." Thesis, Monterey, California: Naval Postgraduate School, 2013. http://hdl.handle.net/10945/39039.
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Approved for public release; distribution is unlimited.A wireless sensor network (WSN) is comprised of sensor nodes designed to collect and transmit data efficiently. For this reason, WSNs are relied upon by the Department of Defense for deployment in remote and hostile areas. The performance of a WSN is degraded by the amount of interference experienced by nodes during simultaneous transmissions. Transmitting in the presence of interference can affect the lifetime of sensor nodes by requiring multiple re-transmissions of data. in this thesis, we propose a routing algorithm that uses spatial time-division multiple access (STDMA) to schedule simultaneous transmissions such that interference is mitigated and transmission time slots are reused appropriately. We integrate STDMA with a physical interference model that facilitates the calculation of interference metrics based on signal-to-interference ratio. Using the interference metrics as link costs, we implement Dijkstras algorithm to determine the least interference path from a sensor node to the gateway. Via simulations using MATLAB and QualNet, we show that this approach to interference mitigation helps network performance by decreasing end-to-end delay. We develop this algorithm as a proof-of-concept to show that, despite the computational complexity associated with interference based scheduling, STDMA can have a real impact on network design and performance.
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Roee, Diamant. "Spatial reuse scheduling and localization for underwater acoustic communication networks." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44893.
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Ocean exploration, through the development of ocean-observation systems, is a key step towards a fuller understanding of life on Earth. Underwater acoustic communication networks (UWANs) will help to fulfill the needs of these ocean-observation systems, whose applications include gathering of scientific data, early warning systems, ecosystem monitoring and military surveillance. The data derived from UWANs is typically interpreted with reference to the location of a data collecting node, e.g. when reporting an event occurrence, or the location of an object itself is of interest, e.g. when tracking a moving underwater vehicle or diver. In this dissertation, we develop methods for localization and efficient data exchange in UWANs.
In the first part of this work, we focus on underwater localization (UWL). Since global positioning system signals do not propagate through water, UWL is often based on fusing information from acceleration-based sensors and ranging information to anchor nodes with known locations. We consider practical challenges of UWL. The propagation speed varies with depth and location, anchor and unlocalized nodes are not time-synchronized, nodes are moving due to ocean currents, propagation delay measurements for ranging of non-line-of-sight communication links are mistakenly identified as line-of-sight, and unpredictable changes in the ocean current makes it hard to determine motion models for tracking. Taking these features of UWL into account, we propose localization and tracking schemes that exploit the spatially correlated ocean current, nodes' constant motion, and the periodicity of ocean waves.
In the second part of this thesis, we use location information to develop medium access control scheduling algorithms and channel coding schemes. We focus on adaptive scheduling in which each node transmits based on timely network information. Specifically, our scheduling algorithms utilize the long propagation delay in the channel and the sparsity of the network topology to improve throughput, reliability and robustness to topology changes.
To evaluate performance, we have developed a simulator combining existing numerical models of ocean current and of power attenuation in the ocean. We have also verified simulation results in four sea experiments of different channel bathymetry structures, using both industry and self-developed underwater acoustic modems.
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da, Silva Bruno Norberto. "Combining spatial hints with policy reuse in a reinforcement learning agent." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/27708.
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In this dissertation, we study the problem of knowledge reuse by a reinforcement learning agent. We are interested in how an agent can exploit policies that were learned in the past to learn a new task more efficiently in the present. Our approach is to elicit spatial hints from an expert suggesting the world states in which each existing policy should be more relevant to the new task. By using these hints with domain exploration, the agent is able to detect those portions of existing policies that are beneficial to the new task, therefore learning a new policy more efficiently. We call our approach Spatial Hints Policy Reuse (SHPR). Experiments demonstrate the effectiveness and robustness of our method. Our results encourage further study investigating how much more efficacy can be gained from the elicitation of very simple advice from humans.
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Chandramohan, Vijay. "Design and Performance Evaluation of a New Spatial Reuse FireWire Protocol." [Tampa, Fla.] : University of South Florida, 2003. http://purl.fcla.edu/fcla/etd/SFE0000128.
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Tayob, Ilhaam. "Seeking spatial justice : empowering the everyday through an architecture that integrates the spatial and social realms." Diss., University of Pretoria, 2016. http://hdl.handle.net/2263/60210.
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This dissertation explores Johannesburg's inner-city precinct of Joubert Park. It
intends to bridge the gap between the everyday community of the park and the
extraordinary heritage and memory of the site. Through a grassroots
investigation of 1he existing community, the project looks to empower the
everyday person and create a platform for their development, specifically
focusing on economy and education in the city. The project makes use of the
theories of spatial justice as a tool to analyse and understand the community's
relationship with the space they occupy and the social environment in which
they exist.
Architecturally, the project seeks to use this socio-spatial understanding as a
guideline of how to create a spatially just and empowering environment in the
inner city. Additionally, looking to establish a model for the development of the
existing inner-city fabric that begins to foster a relationship between building,
street edge, andl pedestrian. Exploring not just the physical upliftment of the
fabric, but the well-being and of the existing community and their needs, goals
and aspirations.Die verhandeling ondersoek die Johannesburg se middestad buurt van Joubertpark. Dit beoog om die gaping tussen die alledaagse gemeenskap van die Park en die buitengewone erfenis en geheue van die omgewing te oorbrug.Deur 'n voetsoolvlak ondersoek van die bestaande gemeenskap, is die projek se doel die bematigi111g van die alledaagse persoon en behels 'n platform vir die ontwikkeling daarvan,daar is n spesifike fokus op die ekonomie en onderwys in die stad. Die projek maak gebruik van die teoriee van ruimtelike geregtigheid as 'n 1instrument om te ontleed en te verstaan wat die gemeenskap se verhouding is met die ruimte wat hulle bewoon en die sosiale omgewing waarin hulle bestaan. Argitektonies, beoog die projek om hierdie sosio-ruimtelike begrip te gebruik as 'n riglyn om 'n ruimtelik net en bemagtigende omgewing te skep in die middestad. Daar word oak beoog om 'n model te vestig vir die ontwikkeling van die bestaande middestad konsepte om 'n verhouding te bevorder tussen die geboue, straat rand, en voetgangers. Ondersoek van nie net die fisiese opheffing van die struktuur nie, maar die welsyn van die bestaande gemeenskap en hul behoeftes, doelwitte en aspirasies.
Mini Dissertation (MArch (Prof))--University of Pretoria, 2016.
Architecture
MArch (Prof)
Unrestricted
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Sultan, A. (Akmal). "Understanding the impact of spatial reuse on autonomous sensing order channel selection." Master's thesis, University of Oulu, 2016. http://urn.fi/URN:NBN:fi:oulu-201612103244.
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In wireless communication systems, there is a need to design efficient schemes in order to overcome the problem of spectrum scarcity. One technology to address the problem of spectrum scarcity is cognitive radio (CR), in which a network entity is able to adapt intelligently to the environment through observation, exploration and learning.
When multiple autonomous cognitive radios are searching for spectrum opportunities, they face competition from each other in order to access the available free channel. This will result in reduced throughput which occurs due to collision between cognitive radios, when they try to transmit in the same channel.
The purpose of this thesis is to study a smart adaptation scheme for efficient channel access which enable autonomous cognitive radios to improve their overall bandwidth efficiency in a distributed cognitive radio network with the help of spatial reuse.
An adaptive persistent strategy with efficient collision detection has been studied in this work for autonomous channel sensing order selection which enable distributed CRs to avoid collision and allow them to improve their overall system efficiency by increasing the average number of successful transmissions, especially, when number of available channels are less than the number of CRs competing to access these free channels.
The performance of the studied strategy is compared with random selection of sensing orders. Simulation results are presented, which indicate that the studied strategy with spatial reuse achieves the highest number of successful transmissions in a given time slot as compared to other strategies. Simulation results are also compared for the case with no spatial reuse and the results indicate that it degrades the system efficiency by reducing the average number of successful transmissions in a given time slot.
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Jamil, Imad. "Improving spatial reuse in future dense high efficiency Wireless Local Area Networks." Thesis, Rennes, INSA, 2015. http://www.theses.fr/2015ISAR0033/document.
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Malgré leur réussite remarquable, les premières versions des normes de réseaux locaux sans fil IEEE 802.11, IEEE 802. 11 a/b/g WLAN, sont caractérisées par une efficacité spectrale faible qui est devenue insuffisante pour satisfaire la croissance explosive de la demande de capacité et de couverture. Grâce aux progrès considérables dans le domaine des communications sans fil et l'utilisation de la bande de fréquence autour de 5 gigahertz le standard IEEE 802.11n et plus récemment 1'IEEE 802.11ac ont amélioré les débits offerts par la couche physique. Cela été possible grâce principalement à l'introduction des techniques multi-antennaires (MIMO, pour Multiple-Input) et des techniques avancées de modulation et de codage. Aujourd'hui, deux décennies après sa première apparition, le Wi-Fi est présenté comme une technologie WLAN permettant des débits supérieurs à 1 gigabit par seconde. Cependant, dans la plupart des scénarios de déploiement du monde réel, il n'est pas possible d'atteindre la pleine capacité offerte par la couche physique. Avec la croissance rapide de la densité des déploiements des WLANs et l'énorme popularité des équipements Wi-Fi, la réutilisation spatiale doit être optimisée. D'autre part, des nouveaux cas d’utilisation sont prévus pour décharger les réseaux cellulaires et pour couvrir des grandes surfaces (stades, gares, etc.). Ces environnements de haute densité représentent un vrai défi pour les générations actuelles de Wi-Fi qui doivent offrir une meilleure qualité à moindre coût. C'est dans ce contexte que s’inscrit l'objectif de cette thèse qui porte sur l'amélioration de l'efficacité des protocoles de la couche MAC des réseaux WLAN de haute densité. Notamment, un des buts de cette thèse est de contribuer à la préparation de la prochaine génération du standard Wi-Fi : IEEE 802.11ax High Efficiency WLAN (HEW). Plutôt que de continuer à cibler l'augmentation des débits maximums théoriques, nous nous concentrons dans le contexte de HEW sur l'amélioration du débit réel des utilisateurs. Pour cela, on prend en compte tous les autres équipements associés à des WLANs voisins, qui essayent d'accéder au même canal de transmission d’une manière simultanée. Pour améliorer la performance du Wi-Fi dans ces environnements denses, nous proposons une adaptation dynamique du mécanisme de détection de signal. Comparé au contrôle de la puissance de transmission, le mécanisme proposé est plus incitatif parce que l'utilisateur concerné bénéficie directement de son application. Les résultats de nos simulations montrent des gains importants en termes de débit atteint dans les scénarios de haute densité. Ensuite, nous étudions l’impact de la nouvelle adaptation sur les mécanismes de sélection de débit actuellement utilisés. D'après les résultats obtenus, 1'adaptation proposée peut être appliquée sans avoir besoin de modifications substantielles des algorithmes de sélection de débit. Pour améliorer l'équité entre les différents utilisateurs, nous élaborons une nouvelle approche distribuée pour adapter conjointement le mécanisme de détection de signal et le contrôle de la puissance de transmission. Cette approche est évaluée ensuite dans différents scénarios de simulation de haute densité où elle prouve sa capacité à résoudre les problèmes d'équité en particulier en présence de nœuds d'anciennes générations dans le réseau, cela tout en améliorant le débit moyen d'un facteur 4 par rapport à la performance conventionnelle du standard. Enfin, nous concevons et mettons en œuvre une solution centralisée basée sur l'apprentissage à base de réseaux de neurones. Cette approche repose sur l'adaptation conjointe de puissance de transmission et du mécanisme de détection du signal. [...]Despite their remarkable success, the first widely spread versions of the Institute of Electrical and Electronics Engineers (IEEE) 802.11 Wireless Local Area Network (WLAN) standard, IEEE 802. 11 a/b/g, featured low spectral efficiencies that are becoming insufficient to satisfy the explosive growth in capacity and coverage demands. Thanks to the advances in the communication theory and the use of the 5 GHz frequency band, the IEEE 802.11n and recently the IEEE 802.1lac amendments improved the Physical Layer (PHY) data rates by introducing Multiple-Input Multiple Output (MIMO) techniques, higher Modulation and Coding Scheme (MCS), etc. Today, after almost two decades of its first appearance, Wi-Fi is presented as a gigabit wireless technology. However, the full potential of the latest PHY layer advances cannot be enabled in all real world deployment scenarios. With the rapidly increasing density of WLAN deployments and the huge popularity of Wi-Fi enabled devices, spatial reuse must be optimized. On another hand, the new challenging use case environments and the integration of mobile networks mainly for cellular offloading are limiting the opportunity of the current Wi-Fi generations to provide better quality at lower cost.In this thesis, we contribute to the current standardization efforts aiming to leverage the Wi-Fi efficiency in high density environments. At the time of writing this document, the IEEE 802.11ax Task Group (TG) is developing the specification for the High Efficiency WLAN (HEW) standard (next Wi-Fi evolution). Rather than continuing to target increased theoretical peak throughputs, we focus in the context of HEW on improving the throughput experienced by users in real life conditions where many other devices, belonging to neighboring overlapping networks, simultaneously contend to gain access. To enhance this performance, we propose a dynamic adaptation of the carrier sensing mechanism. Compare to controlling the transmission power, the proposed mechanism has more incentives because it benefits directly the concerned user. Extensive simulation results show impor1ant throughput gains in dense scenarios. Then, we study the impact of the new adaptation on the current rate control algorithms. We find that our adaptation mechanism operates efficiently without substantially modifying these algorithms that are widely used in today's operating WLANs. Furthermore, after analyzing the fairness performance of the proposed adaptation, we devise a new approach to jointly adapt the carrier sensing and the transmission power in order to preserve higher fairness degrees while improving the spatial reuse. This approach is evaluated in different dense deployment scenarios where it proves its capability to resolve the unfairness issues especially in the presence of legacy nodes in the network, while improving the achieved throughput by 4 times compared to the standard performance. Finally, we design and implement centralized learning-based solution that uses also an approach based on joint adaptation of transmission power and carrier sensing. This new solution takes benefit from the capability of artificial neural networks to model complex nonlinear functions to optimize the spatial reuse in dense WLANs while preserving fairness among contending nodes. The different contributions of this work have helped bring efficient solutions for future WiFi networks. We have presented these solutions to the IEEE 802.11ax TG where they were identified as important potential technical improvements for the next WLAN standard
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Wilhelmi, Roca Francesc. "Towards spatial reuse in future wireless local area networks: a sequential learning approach." Doctoral thesis, Universitat Pompeu Fabra, 2020. http://hdl.handle.net/10803/669970.
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The Spatial Reuse (SR) operation is gaining momentum in the latest IEEE 802.11 family of standards due to the overwhelming requirements posed by next-generation wireless networks. In particular, the rising traffic requirements and the number of concurrent devices compromise the efficiency of increasingly crowded Wireless Local Area Networks (WLANs) and throw into question their decentralized nature. The SR operation, initially introduced by the IEEE~802.11ax-2021 amendment and further studied in IEEE 802.11be-2024, aims to increase the number of concurrent transmissions in an Overlapping Basic Service Set (OBSS) using sensitivity adjustment and transmit power control, thus improving spectral efficiency. Our analysis of the SR operation shows outstanding potential in improving the number of concurrent transmissions in crowded deployments, which contributed to enabling low-latency next-generation applications. However, the potential gains of SR are currently limited by the rigidity of the mechanism introduced for the 11ax, and the lack of coordination among BSSs implementing it. The SR operation is evolving towards coordinated schemes where different BSSs cooperate. Nevertheless, coordination entails communication and synchronization overhead, which impact on the performance of WLANs remains unknown. Moreover, the coordinated approach is incompatible with devices using previous IEEE 802.11 versions, potentially leading to degrading the performance of legacy networks. For those reasons, in this thesis, we start assessing the viability of decentralized SR, and thoroughly examine the main impediments and shortcomings that may result from it. We aim to shed light on the future shape of WLANs concerning SR optimization and whether their decentralized nature should be kept, or it is preferable to evolve towards coordinated and centralized deployments. To address the SR problem in a decentralized manner, we focus on Artificial Intelligence (AI) and propose using a class of sequential learning-based methods, referred to as Multi-Armed Bandits (MABs). The MAB framework suits the SR problem because it addresses the uncertainty caused by the concurrent operation of multiple devices (i.e., multi-player setting) and the lack of information in decentralized deployments. MABs can potentially overcome the complexity of the spatial interactions that result from devices modifying their sensitivity and transmit power. In this regard, our results indicate significant performance gains (up to 100\% throughput improvement) in highly dense WLAN deployments. Nevertheless, the multi-agent setting raises several concerns that may compromise network devices' performance (definition of joint goals, time-horizon convergence, scalability aspects, or non-stationarity). Besides, our analysis of multi-agent SR encompasses an in-depth study of infrastructure aspects for next-generation AI-enabled networking.L'operació de reutilització espacial (SR) està guanyant impuls per a la darrera família d'estàndards IEEE 802.11 a causa dels aclaparadors requisits que presenten les xarxes sense fils de nova generació. En particular, la creixent necessitat de tràfic i el nombre de dispositius concurrents comprometen l'eficiència de les xarxes d'àrea local sense fils (WLANs) cada cop més concorregudes i posen en dubte la seva naturalesa descentralitzada. L'operació SR, inicialment introduïda per l'estàndard IEEE 802.11ax-2021 i estudiada posteriorment a IEEE 802.11be-2024, pretén augmentar el nombre de transmissions concurrents en un conjunt bàsic de serveis superposats (OBSS) mitjançant l'ajustament de la sensibilitat i el control de potència de transmissió, millorant així l'eficiència espectral. El nostre estudi sobre el funcionament de SR mostra un potencial destacat per millorar el nombre de transmissions simultànies en desplegaments multitudinaris, contribuint així al desenvolupament d'aplicacions de nova generació de baixa latència. Tot i això, els beneficis potencials de SR són actualment limitats per la rigidesa del mecanisme introduït per a l'11ax, i la manca de coordinació entre els BSS que ho implementen. L'operació SR evoluciona cap a esquemes coordinats on cooperen diferents BSS. En canvi, la coordinació comporta una sobrecàrrega de comunicació i sincronització, el qual té un impacte en el rendiment de les WLAN. D'altra banda, l'esquema coordinat és incompatible amb els dispositius que utilitzen versions anteriors IEEE 802.11, la qual cosa podria deteriorar el rendiment de les xarxes ja existents. Per aquests motius, en aquesta tesi s'avalua la viabilitat de mecanismes descentralitzats per a SR i s'analitzen minuciosament els principals impediments i mancances que se'n poden derivar. El nostre objectiu és donar llum a la futura forma de les WLAN pel que fa a l?optimització de SR i si s'ha de mantenir el seu caràcter descentralitzat, o bé és preferible evolucionar cap a desplegaments coordinats i centralitzats. Per abordar SR de forma descentralitzada, ens centrem en la Intel·ligència Artificial (AI) i ens proposem utilitzar una classe de mètodes seqüencials basats en l'aprenentatge, anomenats Multi-Armed Bandits (MAB). L'esquema MAB s'adapta al problema descentralitzat de SR perquè aborda la incertesa causada pel funcionament simultani de diversos dispositius (és a dir, un entorn multi-jugador) i la falta d'informació que se'n deriva. Els MAB poden fer front a la complexitat darrera les interaccions espacials entre dispositius que resulten de modificar la seva sensibilitat i potència de transmissió. En aquest sentit, els nostres resultats indiquen guanys importants de rendiment (fins al 100 \%) en desplegaments altament densos. Tot i això, l'aplicació d'aprenentatge automàtic amb múltiples agents planteja diversos problemes que poden comprometre el rendiment dels dispositius d'una xarxa (definició d'objectius conjunts, horitzó de convergència, aspectes d'escalabilitat o manca d'estacionarietat). A més, el nostre estudi d'aprenentatge multi-agent per a SR multi-agent inclou aspectes d'infraestructura per a xarxes de nova generació que integrin AI de manera intrínseca.
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Amdouni, Ichrak. "Wireless Self-adaptive Ad hoc and Sensor Networks : Energy Efficiency and Spatial Reuse." Paris 6, 2013. http://www.theses.fr/2013PA066003.
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La nécessité de maximiser la durée de vie du réseau sans fil dans les réseaux ad hoc et en particulier dans les réseaux de capteurs sans fil nécessite l'utilisation d'algorithmes d'efficacité énergétique. Motivée par le fait qu'un noeud consomme le moins d'énergie lorsqu’il est en veille, nous réalisons l'efficacité énergétique vi des algorithmes d'ordonnancement des activités des noeuds. Les noeuds reçoivent des slots temporels durant lesquels ils peuvent transmettre et ils peuvent éteindre leur radio quand ils ne sont ni en train de transmettre, ni en train de recevoir. Par rapport au TDMA classique, l’utilisation de la bande passante est optimisée: deux noeuds interférents ne partagent pas les mêmes slots. Dans notre travail sur l’ordonnancement, deux cas sont étudiés. Tout d'abord, lorsque les nœuds nécessitent le même temps d’accès au canal, nous utilisons le coloriage des nœuds. Deuxièmement, lorsque les nœuds requièrent des débits hétérogènes, nous utilisons une allocation de slots « traffic aware ». Contrairement à la majorité des travaux antérieurs, nous généralisons la définition du coloriage des noeuds et les problèmes d'attribution des slots. En effet, nous considérons que la distance maximale entre deux nœuds interférents est un paramètre de ces problèmes. Nous prouvons qu'ils sont NP-complets, ce qui rend inévitable l’utilisation des heuristiques dans la pratique. Une directive centrale de cette thèse est de concevoir des solutions auto-adaptatives. Cette adaptabilité concerne de nombreux aspects tels que la mission confiée par l'application, l'hétérogénéité des demandes de trafic de nœuds, la densité du réseau, de la régularité de la topologie du réseau, et la non fiabilité des liens sans filThe need to maximize network lifetime in wireless ad hoc networks and especially in wireless sensor networks requires the use of energy efficient algorithms and protocols. Motivated by the fact that a node consumes the least energy when its radio is in sleep state, we achieveenergy efficiency by scheduling nodes activity. Nodes are assigned time slots during which they can transmit and they can turn off their radio when they are neither transmitting nor receiving. Compared to classical TDMA-based medium access scheme, spatial bandwidth use is optimized: non interfering nodes are able to share the same time slots, collisions are avoided and overhearing and interferences are reduced. In our work about time slots assignment, two cases are studied. First, when nodes require equal channel access, we use node coloring. Second, when nodes have heterogeneous traffic demands, we designed the traffic aware time slot assignment algorithm TRASA. Unlike the majority of previous works, we generalize the definition of node coloring and slot allocation problems. Indeed, we set the maximum distance between two interfering nodes as a parameter of these problems. We prove that they are NP-complete, making heuristic approaches inevitable in practice. A central directive of this thesis is to design self-adaptive solutions. This adaptivity concerns many aspects such as the mission given by the application, the heterogeneity of nnode traffic demands, the network density, the regularity of network topology, and the failure of wirelesslinks
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Reed, Deborah A. "Spatial and temporal biogeochemical changes of groundwater associated with managed aquifer recharge in two different geographical areas /." Connect to this title, 2007. http://theses.library.uwa.edu.au/adt-WU2008.0074.
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Boyd, Steven Wesley. "A cross-layer approach to increase spatial reuse and throughput for ad hoc networks." Connect to this title online, 2006. http://etd.lib.clemson.edu/documents/1175016097/.
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AlSulaimani, Eman. "Reorientation: a journey through spatial sequence." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3468.
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Introduction | The building for this thesis project is one with a long history. Originally built as the First Baptist Church, it was converted over the years to fulfill a role completely different from its original intent; a student center! During this process and after a series of renovations, the Broad Street main grand entrance lost its place and the arrival into the building became much less choreographed. Essentially, over time one could say that this building had been flipped around, it has lost its original intent, grandeur and purpose. Hypothesis | I challenge the idea of flipping the building back to its original state to return its historical glory, significance and grand emotional experience. I hypothesize that a reorganization of spatial sequence (i.e. bringing the outside in and extending the inside out) can help flip this building around. Materials and Methods | I introduce an internal three sided staircase that mimics what exits exteriorly in an attempt to bring the outside in. This staircase becomes the center’s focal point as it rises to the third mezzanine level. The staircase is based on the “Golden Section” idea of proportional geometries which has been found inherent in the building. I extend the inside out by turning the “monumental” exterior grand steps into a place people can utilize. Results | Placing such a large structure by the building’s entry points had great impact on drawing people into the building and up the steps into the main lounge consequently re-choreographing the arrival experience. The design solution breathes new life into this building while still respecting and acknowledging all of its crucial and historic elements. Just as the altar was a main focal point when this building served as a church, the new transparent elevator shaft that is tucked in between the spiraling stairs becomes the center’s new focal point. The contemporary facade that was inserted asymmetrically on the west side of the building emphasizes the symmetry and contrasts the existing structure causing tension between the old and new but proving that they can coexist.
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Gossain, Hrishikesh. "Power Control and Spatial Reusability in Mobile Ad Hoc Networks." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1115308673.
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Reed, Deborah A. "Spatial and temporal biogeochemical changes of groundwater associated with managed aquifer recharge in two different geographical areas." University of Western Australia. School of Biomedical, Biomolecular and Chemical Sciences, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0074.
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[Truncated abstract] Managed Aquifer Recharge (MAR) is a technique that can be used to capture and store water in aquifers for later reuse. This method recycles water that would normally be lost or discarded to the environment. MAR has been observed to have the potential for improving the quality of recharged water through a combination of physical, chemical and biological processes. The aim of this study was to investigate the changes in groundwater microbial population structure during MAR and the major influences that drive these population changes. Biogeochemical MAR studies have the potential to assist in the improved prediction of the removal of contaminants such as nutrients, pathogens and trace organics from the recharged water. Biological clogging during recharge also has the potential to overwhelm an aquifers ability to process wastewater thus reducing the hydraulic conductivity of the aquifer. Therefore further research into the spatial and temporal biogeochemical processes that occur during MAR is required. The geochemical and microbial population dynamics of two contrasting MAR techniques were investigated at two different geographical locations (Perth, Western Australia and Adelaide, South Australia). These MAR sites contained aquifers of dissimilar properties that were recharged with wastewater that contrasted in water quality. The Perth MAR site received secondary treated effluent which continuously infiltrated the unsaturated zone into an unconfined aquifer aided by infiltration galleries. Reclaimed water was extracted from a well at distance from the infiltration gallery. ... Notably the background and recovered water was most dissimilar in microbial and chemical population structure to that described for the infiltration gallery and injection well. Microbial and chemical evidence suggested that the background and extraction well groundwater were unaffected by plume migration. These results suggested that extraction well groundwater was similar in quality to that of ambient groundwater. Significant geochemical and microbial changes of secondary treated effluent during infiltration and lateral movement through aquifer were implicated in addition to the forced hydraulic gradient created from extracting fives time the volume of infiltrating wastewater. This study demonstrated that microbial populations and the geochemical processes associated with MAR can be studied and compared. Multivariate statistical methodology greatly simplified a vast array of dynamic biogeochemical information that could be dissected for meaningful interpretation over distance and time. The study evaluated the major biogeochemical influences which resulted in microbial and geochemical changes where it was noted that microbial populations were more dynamic than geochemical variation over time. Additionally biogeochemical comparative analysis indicated that microbial populations could change in population structure before a shift in aquifer geochemistry was detected. It is anticipated that the results from this study will benefit further research into the biogeochemical processes involved in water quality changes (e.g. nutrient removal, pathogen decay and biodegradation of trace organics) as well as controlling biological clogging of MAR schemes.
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Phunchongharn, Phond. "Dynamic wireless access methods with applications to eHealth services." IEEE, 2009. http://hdl.handle.net/1993/9231.
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For opportunistic spectrum access and spectrum sharing in cognitive radio networks, one key problem is how to develop wireless access schemes for secondary users so that harmful interference to primary users can be avoided and quality-of-service
(QoS) of secondary users can be guaranteed. In this research, dynamic wireless access protocols for secondary users are designed and optimized for both infrastructure-based and ad-hoc wireless networks.
Under the infrastructure-based model, the secondary users are connected through a controller (i.e., an access point). In particular, the problem of wireless access for eHealth applications is considered. In a single service cell, an innovative wireless access scheme, called electromagnetic interference (EMI)-aware prioritized wireless access, is proposed to address the issues of EMI to the medical devices and QoS differentiation for different eHealth applications. Afterwards, the resource management problem for multiple service cells, specifically, in multiple spatial reuse time-division multiple access (STDMA) networks is addressed. The problem is formulated as a dual objective optimization problem that maximizes the spectrum utilization of secondary users and minimizes their power consumption subject to the EMI constraints for active and passive medical devices and minimum throughput guarantee for secondary users. Joint scheduling and power control algorithms based on greedy approaches are proposed to solve the problem with much less computational complexity.
In an ad-hoc wireless network, the robust transmission scheduling and power control problem for collision-free spectrum sharing between secondary and primary users in STDMA wireless networks is investigated. Traditionally, the problem only considers the average link gains; therefore, QoS violation can occur due to improper power allocation with respect to instantaneous channel gain realization. To overcome this problem, a robust power control problem is formulated. A column generation based algorithm is proposed to solve the problem by considering only the potential subset of variables when solving the problem. To increase the scalability, a novel distributed two-stage algorithm based on the distributed column generation method is then proposed to obtain the near-optimal solution of the robust transmission schedules for vertical spectrum sharing in an ad-hoc wireless network.
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Giang, Anh Tuan. "Capacity of vehicular Ad-hoc NETwork." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-00989836.
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In recent years, Inter Vehicle Communication (IVC) has become an intensive research area, as part of Intelligent Transportation Systems. It supposes that all, or a subset of the vehicles is equipped with radio devices, enabling communication between them. IEEE 802.11p (standardized for vehicular communication) shows a great deal of promise. By using ad hoc mode, this radio technology allows vehicles to extend their scopes of communication and thus forming a Multi-hop wireless Ad-hoc NETwork, also called Vehicular Ad-hoc NETwork (VANET). This thesis addresses a fundamental problem of VANET: the network capacity. Two simple theoretical models to estimate this capacity have been proposed: a packing model and a Markovian point process model. They offer simple and closed formulae on the maximum number of simultaneous transmitters, and on the distribution of the distance between them. An accurate upper bound on the maximum capacity had been derived. An analytical formula on distribution of the transmitters had been presented. This distribution allows us to optimize Clear Channel Assessment (CCA) parameters that leads to an optimization of the network capacity.In order to validate the approach of this thesis, results from the analytical models are compared to simulations performed with the network simulator NS-3. Simulation parameters was estimated from real experimentation. Impact of different traffic distributions (traffic of vehicles) on the network capacity is also studied. This thesis also focuses on extended perception map applications, which use information from local and distant sensors to offer driving assistance (autonomous driving, collision warning, etc.). Extended perception requires a high bandwidth that might not be available in practice in classical IEEE 802.11p ad hoc networks. Therefore, this thesis proposes an adaptive power control algorithm optimized for this particular application. It shows through an analytical model and a large set of simulations that the network capacity is then significantly increased.
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DE, LA CRUZ ELLEN IVONNE. "USE OF SPACE AND PATTERNS OF REFUSE DISPOSAL AT THE VILLAGE SITE OF MURCIELAGO, COSTA RICA (REFUSE PITS, SPATIAL ANALYSIS, ETHNOHISTORY)." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183946.
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Theoretical and methodological issues of disposal behavior are examined at the village site of Murcielago. Ethnoarchaeological, archaeological, and modern material culture studies of discard practices are discussed. The generalizations and conclusions contained therein are incorporated into a synthesis of the emerging body of disposal theory. The method used for the analysis of Murcielago, which is drawn from traditional geographic models of land use, is described. The model allows description of the conventions governing the regulation of space and the delineation of disposal patterns. Analysis of artifact distributions illuminated the organization of household activities and the definition of activity differences.
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Last, Jonathan Andrew. "Secondary refuse deposits and the spatial structure of settlement in the early and middle Neolithic of Central Europe." Thesis, University of Cambridge, 1995. https://www.repository.cam.ac.uk/handle/1810/273038.
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Fučíková, Jarmila. "Prázdné urbánní monumenty – aktivace zhlaví Pražského viaduktu v Brně urbanisticko-architektonická studie." Master's thesis, Vysoké učení technické v Brně. Fakulta architektury, 2019. http://www.nusl.cz/ntk/nusl-402121.
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First of all, the work should point out the possibilities of activating the non-functioning post-industrial area. The aim is to remove the “wedge” into the center and to bring missing urban activities to the site. For this purpose, I suggest the completion of a city blocks with a housing function, a square with a food market, a city park, and a connection to the surrounding of industrial buildings. The aim is to integrate the site into the city through the completion and rehabilitation of industrial houses. The great creative challenge is to preserve the genius loci of this post-industrial landscape.
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Witt, Jan [Verfasser], Wolf [Akademischer Betreuer] Arntz, and Karsten [Akademischer Betreuer] Reise. "Analysing brackish benthic communities of the Weser estuary: spatial distribution, variability and sensitivity of estuarine invertebrates / Jan Witt. Gutachter: Wolf Arntz ; Karsten Reise. Betreuer: Wolf Arntz." Bremen : Staats- und Universitätsbibliothek Bremen, 2004. http://d-nb.info/1072301792/34.
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Slouková, Hana. "Prázdné urbánní monumenty – aktivace zhlaví Pražského viaduktu v Brně urbanisticko-architektonická studie." Master's thesis, Vysoké učení technické v Brně. Fakulta architektury, 2019. http://www.nusl.cz/ntk/nusl-400735.
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The aim of the urban – architectural study is to connect the historic city centre with the so far problematic and neglected areas along to the viaduct via rehabilitation and conversion of industrial buildings and filling up the city structure with new volumes in order to integrate the area within the organism of the city. Creative efforts are supported by analysis of post-industrial cityscape generally and its problems. The focus will be on sustainable principles, connectivity, eco-friendly transport and creating quality public spaces.
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Lee, Wen-Shan, and 李文姍. "Performance Enhancement of IEEE 802.11 by Spatial reuse." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/38431659818428213151.
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碩士國立中山大學
資訊工程學系研究所
91
We question about multihop gets better performance than single hop in wireless networks. In this paper we design a new and simple multihop transmission model called PESR, performance enhancement of IEEE 802.11 by spatial reuse. We elect an intermediate node which between a source-destination pair for forwarding packets to become multihop instead of directly transmission from the source to the destination. By this way, we will have more links at the one time, the channel utilization should be grown and we will get better system performance. However, there is much overhead we have not considered. We will discuss the detail about overhead in coming sections. In fact, the results of simulation show that the performance is not present very well. And we wonder if the multihop in wireless networks is a pretty good idea.
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Kim, Yuchul. "Spatial spectrum reuse in wireless networks design and performance." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-05-3364.
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This dissertation considers the design, evaluation and optimization of algorithms/ techniques/ system parameters for distributed wireless networks specifically ad-hoc and cognitive wireless networks. In the first part of the dissertation, we consider ad-hoc networks using opportunistic carrier sense multiple access (CSMA) protocols. The key challenge in optimizing the performance of such systems is to find a good compromise among three interdependent quantities: the density and channel quality of the scheduled transmitters, and the resulting interference seen at receivers. We propose two new channel-aware slotted CSMA protocols and study the tradeoffs they achieve amongst these quantities. In particular, we show that when properly optimized these protocols offer substantial improvements relative to regular CSMA -- particularly when the density of nodes is moderate to high. Moreover, we show that a simple quantile based opportunistic CSMA protocol can achieve robust performance gains without requiring careful parameter optimization. In the second part of the dissertation, we study a cognitive wireless network where licensed (primary) users and unlicensed 'cognitive' (secondary) users coexist on shared spectrum. In this context, many system design parameters affect the joint performance, e.g., outage and capacity, seen by the two user types. We explore the performance dependencies between primary and secondary users from a spatial reuse perspective, in particular, in terms of the outage probability, node density and joint network capacity. From the design perspective the key system parameters determining the joint transmission capacity, and tradeoffs, are the detection radius (detection signal to interference and noise power ratio (SINR) threshold) and decoding SINR threshold. We show how the joint network capacity region can be optimized by varying these parameters. In the third part of the dissertation, we consider a cognitive network in a heterogeneous environment, including indoor and outdoor transmissions. We characterize the joint network capacity region under three different spectrum (white space) detection techniques which have different degrees of radio frequency (RF) - environment awareness. We show that cognitive devices relying only on the classical signal energy detection method perform poorly due to limitations on detecting primary transmitters in environments with indoor shadowing. This can be circumvented through direct use (e.g., database access) of location information on primary transmitters, or better yet, on that of primary receivers. We also show that if cognitive devices have positioning information, then the secondary network's capacity increases monotonically with increased indoor shadowing in the environment. This dissertation extends the recent efforts in using stochastic geometric models to capture large scale performance characteristics of wireless systems. It demonstrates the usefulness of these models towards understanding the impact of physical /medium access (MAC) layer parameters and how they might be optimized.text
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Guo, Da-Ren, and 郭達人. "Spatial Reuse in Multi-Radio, Multi-Hop Wireless Mesh Networks." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/21922725401066751706.
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碩士國立交通大學
資訊科學與工程研究所
94
Recently, wireless mesh networks (WMNs) have emerged as a key technology for next-generation wireless networking. Spatial reuse in a WMN can allow multiple communications to proceed simultaneously; thereby observably improve the overall network throughput. However, interferences between mesh nodes are a critical factor for maximizing the spatial reuse. In the thesis, we propose a novel scheduling mechanism without modifying the existing IEEE 802.11 MAC, called wireless Radio-Matching Protocol (RMP). It takes account of interferences in wireless environments to achieve maximum spatial reuse by using pre-specified radio transmissions. In contrast to existing random access approaches, RMP uses a decentralized controlled access approach to protect nodes from unintentional packet collisions. RMP adopts a chain topology of bidirectional transmissions, where nodes are equally spaced so that radios of non-neighboring nodes do not interference with each other. Simulation results indicate that the throughput of RMP is about 30% better than that of Ripple [14] and almost 200% better than that of the IEEE 802.11 DCF. Although RMP achieves higher throughput than Ripple, it still maintains the same delay time and transmission quality, as verified by our simulation results. RMP achieved a stable throughput and a low end-to-end transmission delay in both CBR and FTP traffic compared to the IEEE 802.11 DCF. In additions, RMP is simple, easy to implement, and it eliminates the back-off inefficiencies and the collision problem in IEEE 802.11 wireless environments.
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Alawieh, Basel. "Exploring spatial reuse effects on performance enhancements in wireless multihop networks." Thesis, 2008. http://spectrum.library.concordia.ca/975201/1/NR45647.pdf.
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Recent years have witnessed a remarkable interest in wireless multihop ad hoc networks that need little or no infrastructure support. Such networks have enabled the existence of various applications ranging from the monitoring of herds of animals to supporting communication in military battle-fields and civilian disaster recovery scenarios as well as providing an emergency warning system for vehicles on the road. Currently, the distributed coordination function (DCF) of the IEEE is the industry dominant MAC protocol for wireless multihop ad hoc environment due to its simple implementation and distributed nature. Nevertheless, the DCF access method does not make efficient use of the shared channel due to its inherent conservative approach in assessing the level of interference. Moreover, the implementation of DCF in multihop ad hoc networks suffers from the exposed and hidden terminal problems; both of these problems highly affect the spectrum spatial reuse and accordingly causes serious throughput deterioration. To date, various methods have been proposed to enhance the throughput of the DCF; namely, tuning the carrier sensing threshold, the transmission attempt probability through changing the binary exponential backoff, controlling the frame transmit power, adapting the physical transmission rate of data frame, and the use of directional antennas. In this thesis, we develop mathematical tools to study the effectiveness of the interplay among the various tunable parameters and propose suitable protocols for achieving better utilization of the wireless spectrum.
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Chou, Chien-Min, and 周建閔. "A Power Control MAC Protocol to Increase Spatial Reuse of WLANs." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/00736232504287758364.
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碩士淡江大學
資訊工程學系
92
Currently, wireless local area networks (WLAN) are applied to Internet accesses in numerous circumstances such as campuses, hotels, airports, etc. However, scarce resources (e.g., limited bandwidth and battery power) significantly restrict the applications of WLANs. Besides, the network with higher traffic loads and more stations is most likely incurs collisions, and further consumes bandwidth and energy. In this paper, a distributed protocol, Power-Efficient MAC Protocol (PEM), to avoid collisions and to save energy is proposed. PEM takes advantage of a power control technique which dynamically adjusts transmission power levels for different transmission pairs to reduce the interferences among transmission pairs. Based on the concept of Maximum Independent Set (MIS), a novel heuristic scheme with the aid of interference information is proposed in PEM to provide as many simultaneous transmission pairs as possible. To verify the performance of PEM, a lot of simulations are performed in the paper. The experimental results show that with the property of spatial reuse, PEM not only reduces power consumption, but also leads to higher network throughput in comparison with three different approaches, DCF, DCS, and DPSM.
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Shan-Tsyr, Pai, and 白珊慈. "A Knowledge Visualization Technology for Effective Knowledge Reuse: A Spatial Knowledge Perspective." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/36758235356697397522.
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碩士國立清華大學
工業工程與工程管理學系
93
Applications of information technologies have significantly improved efficiency of electronic document processing and management. The speed and amount of knowledge accumulation in the cyberspace have exceeded what common users can absorb. Therefore, in addition to data processing efficiency, the information technology should be used to overcome information overloading. In order to enhance the efficiency and accuracy for knowledge users to acquire knowledge, an appropriate knowledge representation scheme is required. Most of the traditional schemes for explicit knowledge representation are text-oriented and much time is required for readers to recognize the knowledge contents, especially for the spatial knowledge (e.g., the geographical information). This research develops a knowledge visualization methodology that computer systems can automatically convert the textual knowledge into visualized display. In the proposed methodology, the free-form documents are converted into formatted ones and the corresponding visualized display can be established based on the formatted contents. A data model supporting spatial knowledge representation is also proposed for spatial knowledge extraction and display. In addition to the proposed methodology, a web-based prototype system is developed to verify the feasibility and effectiveness of the proposed model. The goal of this research is to provide a knowledge visualization approach that can be widely applied in enterprise e-training and virtual simulation to enhance the effectiveness and efficiency of enterprise knowledge reuse.
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Lin, Yuan-Chieh, and 林元傑. "Clean-Air Spatial Reuse and Spectral Efficiency Analysis for Wireless Mesh Networks." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/49978731723154234667.
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碩士國立臺灣大學
資訊管理學研究所
95
The wireless mesh network is expected to provide large transmission capacity in order to serve as a complementary broadband wireless access technology. The interference plays an important role to the network capacity throughput of wireless mesh networks because when there are multiple concurrent wireless transmissions in a mesh network, the interference caused by the broadcast nature of wireless transmissions decreases the sustainable spectral efficiency (transmission speed) of each individual transmission. For a wireless mesh network, the network capacity throughput is determined by two factors: the individual transmission spectral efficiency and the number of concurrent transmissions. Therefore, the best way to increase the network capacity throughput is to increase both the individual transmission spectral efficiency as well as the number of concurrent transmissions. However, if we increase the individual transmission spectral efficiency, inevitably we have to reduce the number of concurrent transmission because we must keep interference low to make higher spectral efficiency feasible. Thus the choice between (1) increasing the transmission spectral efficiency and (2) increasing the number of concurrent transmissions is a trade-off and is critical to the network capacity throughput. In this paper, we explore the tradeoff between these two choices in a TDMA (time division multiple access) based distributed data access scheduler wireless mesh network with physical interference model and find the optimal design that achieves highest network capacity throughput.
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Lin, Yuan-Chieh. "Clean-Air Spatial Reuse and Spectral Efficiency Analysis for Wireless Mesh Networks." 2007. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-1807200715520300.
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鄭維中. "Interplay of Spatial Reuse and Transmission Reliability in CSMA/CA-based Wireless Networks." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/j8ubr6.
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碩士國立交通大學
電信工程研究所
103
In CSMS/CA-based, multi-hop, multi-rate wireless ad-hoc networks, we can balance the interplay of spatial reuse and transmission reliability by dynamicly tuning carrier-sensing threshold (Tcs) according to environmental situations in order to reach the maximum network capacity. Lower carrier-sensing thresholds generally lead to larger carrier-sensing ranges (dcs), which ensure higher transmission reliability. In this manner, we actually increase the transmission reliability by reducing packet collisions due to mitigated interference produced by concurrent transmissions. However, the total network capacity suffers because of too preservative channel access attempts. On the other hand, higher carrier-sensing thresholds usaually result in smaller carrier-sensing ranges, which encourage better spatial reuse yet transmission collisions will happen more frequently due to potentially increased interference. Therefore, it is important to make adequate adjustments of carrier-sensing thresholds according to environmental conditions in a CSMA/CA-based wireless network. In this thesis, we address the above issue by proposing an adaptive mechanism to dynamicly adjust carrier-sensing thresholds used by wireless nodes in a distributed manner within reasonable computation time. Simulation results show that our proposed algorithm outperforms other implemented carrier-sensing tuning approaches in terms of aggregate network capacity.
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Chang, Chia-Chen, and 張家甄. "The cultural and spatial study of reuse for restaurant facilities in historical buildings." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/46072059859961947730.
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碩士國立成功大學
建築學系碩博士班
93
The reuse of historical building has become a positive practice in recent years. To reuse these historical buildings as restaurants space is a newly and popular tactic since year 2000 because multitude usually take much time to stay in the space so that can shorten the distance between multitude and historical buildings, and increase operating profit. In Taiwan, the reuse of historical buildings as restaurants space doesn’t only provide them a new life but also create a new consumer style combining culture, dining and architecture that give customer a newborn consumer place and creative a new complex consumer vocabulary. This paper will discuss the relationship between the “customer” and historical buildings according to the requirement of customer in case of reusing them as a restaurant space. The issues include two parts, “human” and “culture”. The human issue focuses on the relation of multitude and dining space based on “function”, “Physical” and “psychology”, and the culture issue concerns the interaction of customer and society in view of “politics”, “history” and “consumer”. Also, this paper will discuss the design factor including “environment”, “esthetics” and “technology” from the relation of “designer” and “substance space” when the historical buildings and spots are reused as restaurant space. The environment issue argues how the dining space connects and interacts with the environment based on the viewpoint of “location” and “environment”. The esthetics debates the space modeling and ambiance construction in terms of “modeling”, “space present” and “light performance”. Finally, the technology discusses the construction method according to the “structure”, “building material” and “environment system”. This thesis quotes a concept of “degrees of intervention”, which is used for preserving the historical buildings, to expound several examples of historical buildings being reused in restaurants purpose. The first level of tactic of historical buildings is “Protection’’ and “Maintenance’’. The second level is “Maintenance’’ and “Stabilization’’. The third level is “Maintenance’’、“Removal’’ and “Restoration’’. The fourth level is “Destruction’’ and “Reconstruction’’. This paper uses the four degrees of intervention to discuss the consumer in the humane issue and the designer in the substance space, and illustrates several abroad cases to realize the actual state of historical buildings being reused in restaurants purpose.
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Kao, Su-Huei, and 高素慧. "Reuse The Taiwan Tobacco and Liquor spatial of Zhongshan distribution the use investigation." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/77050592435661507021.
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碩士中國文化大學
建築及都市設計學系碩士在職專班
102
Since 2001, the Council for Cultural Affairs has issued “2001 Pilot Implementation Guidelines for the Reuse of Unused Space” and President Ma,Ying-jeou has proposed a plan on youth policy. Both aim to enhance the reuse of idle premises by making use of unused space in older communities, improve the urban environment and strengthen local culture, while transforming the quality of the living environment and embracing the power of urban transformation. The Department of Urban Development, Taipei City Government, has become a key advocate for the urban renewal of public space, public issues and public life through its “Urban Regeneration Station (URS) Project.” The hope is that public-private sector cooperation will facilitate the reuse of idle premises and land, thereby improving relations with the community. In addition, it is hoped such projects will re-use empty urban plants and idle premises before the urban renewal areas are designated, enhancing quality of life in such areas by improving the poor urban environment and local landscape. This paper focuses on the former "Taiwan Tobacco and Liquor spatial of Zhongshan distribution " The main objective is to explore investments by civil society in the reuse of idle public premises and land. After collation and analysis of the relevant literature, a questionnaire was distributed to respondents and in-depth interviews conducted with representatives of industry, government officials and academics as a way of exploring the city’s unused public premises. A number of issues and countermeasures involving the reuse of unused premises and land were presented to deal with related problems and enhance the quality of the environment.
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Chang, Chinghsiang, and 張景翔. "A Relay Selection Scheme with Enhancing Spatial Channel Reuse in Cooperative Wireless Ad Hoc Networks." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/50215505588482739045.
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碩士國立交通大學
網路工程研究所
96
In the last few years, a new class of methods called cooperative communication has been proposed that enables single-antenna mobiles in a multi-user environment to share their antennas and generate a virtual multiple-antenna transmitter. A mobile station may not be able to support multiple transmit antennas due to some hardware limitations. Through cooperative communication, a single-antenna mobiles in a multi-user environment can utilize the virtual multiple-antenna transmitter to achieve the transmit diversity. In this thesis, we propose a relay selection scheme which considers neighbor traffic of the relay node in order to maximize the spatial channel reuse in the cooperative communication. Through the simulation with ns-2 simulator, we evaluated the performance of the proposed scheme. As presented by the simulation results, the more stable increase in the total network throughput and the reduction in delay even when affected by neighbor traffics show the outperformance by utilizing the proposed scheme.
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Wu, Chen-Yan, and 吳承諺. "A Transmission Scheduling Algorithm for Exploiting Spatial Reuse Opportunities with Smart Antenna Systems in WLANs." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/48709766972158932007.
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碩士淡江大學
資訊工程學系資訊網路與通訊碩士班
97
Exploiting smart antenna systems to improve both the network throughput and power efficiency is a promising issue for WLAN. This paper aims at developing a transmission scheduling scheme with smart antenna systems. The proposed schemes take into account the interference restriction and packet sizes for minimizing the average latency and maximizing the network throughput.
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YU, YEN-CHUN, and 余彥君. "The Forms of Spatial Planning and the Principle of Reuse on Chung Hsing New Village." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/53z9hw.
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碩士逢甲大學
建築碩士學位學程
106
The site of the Taiwan provincial government, Chung Hsing New Village in Nantou County, was formed as a result of the air-defense evacuation plan. Despite the lack of resources in that post-World War II period, Chung Hsing New Village was a lovely new town modeled on the Garden City of the West. In the present day, most of the population lacks and longs for such an enriched living environment and sound planning. However, due to the Taiwan government streamlining, 921 earthquake disaster and other unforeseeable occurrences, there was a substantial population outflow. Many of the original scenes and aspects no longer exist, and the houses have gone into disrepair. In this study, the future development of Chung Hsing New Village was taken as the starting point. In view of the overall planning of Chung Hsing New Village and the spatial design of the family dormitory during the period from the 45th-65th year of the "Republic Era", this paper reviews the history and related planning of Chung Hsing New Village with the literature review method. Through the field investigation method, the construction of the site is measured and plotted; lastly, the shape grammar is deduced to provide a composition of its space. The study divides the village into three blocks for analysis and deduction, highlighting and confirming its planning theory. In addition, we draw the family dormitory space based on the shape grammar, collect the dendrogram, analyze the characteristics of the dormitory space, discuss the possibility of its follow-up activation, and draw up a planning principle as a reference for subsequent reuse and planning.
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Chang, Han-Tien, and 張瀚天. "A Channel Access Scheme with Joint Clean-Air Spatial Reuse and Power Control in Wireless Mesh Networks." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/14494360341725700063.
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碩士臺灣大學
資訊管理學研究所
98
In general, there are two approaches to maximize network throughput capacity in a single-channel wireless mesh network: increasing the number of non-interfering transmissions at each time slot by exploiting spatial reuse, and increasing transmission rate of active transmitters. However, a tradeoff of the two ways encounters the wireless communication inference problem. Therefore, we want to investigate the tradeoff between spatial reuse and transmission power control on network throughput capacity in spatial TDMA-based wireless mesh network with single channel. In this paper, we propose a Clean-Air Spatial Reuse Policy to control clean air (interference free) zone and determine the set of concurrent access groups based on the policy. Then, we perform transmission power assignment to each transmitter to maximize the network throughput capacity. Experiment results of the network throughput capacity performance under different levels of the Clean-Air Spatial Reuse policy are presented.
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Chen, Yi-ling, and 陳怡伶. "Reuse of Industrial Heritages in the Japanese Colonial Period of Taiwan from the Perspective of Spatial Properties." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/53119159455229568733.
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碩士國立高雄大學
都市發展與建築研究所
99
With the structural changes in Taiwan's economic system, many state-owned enterprises and traditional industries began to go out of business and the shut down ,possess historical memory of the old plant and machinery to become a victim of changing times; in recent years, rising awareness of preservation of cultural assets, " Industrial Buildings Heritage " Also getting attention, Then derived from studies of many Industrial Buildings Heritage. This article discusses the construction of Japanese rule of Taiwan's sugar mills, breweries and mining buildings in the spatial attributes to do the analysis and research, and will be summarized for the plant buildings, warehouses, housing complex, office group, hall, pit , staff and transportation eight types of ancillary facilities; through after finishing the study concludes, The different nature of the plant to do the analysis on the spatial properties ,Use of the original property into the use of space based on the same time and make use of different types of defined. Analysis of field research methods to re-use of domestic cases of significant correspondence between the old and new space, while the study by Zumthor's "Atmosphere" Standards and International Charter, the criteria grouped into internal, external and around the three major factors for, and face down in a large industrial site IV proposed for re-use of Taiwan's design Enforcement Rules, in order to achieve minimal intervention, minimal damage, maximum efficiency, the best efficiency, thereby reducing the secondary site of the original value of the damage to the idle problem, this re-use of design guidelines for future government and academia will provide re-use of industrial sites and areas of design criteria.
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Ya-JyunLin and 林雅君. "The strategy of spatial transformation and the meaning of social phenomenon of reuse for old house: in the case of “Old House, New Life” movement in Tainan." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/78563399368130897698.
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碩士國立成功大學
建築學系碩博士班
100
For the past three years, the reuse for old house has become a new trend in Tainan due to the movement of “Old House, New Life”. The slogan of “Reborn Old House, Tremendous Vitality” has become the best reputation for the remodel of every old house. However, is the original intention of conservation of old house achieved? Besides the concept of adaptive reuse of historical buildings which has been promoted by government, the reuse of old house has also become popular in private buildings recently. The private sectors start the movement spontaneously without government’s funding which show their interests and love on old houses. However, the remodel of architectural space is not easy. Compare to experienced architects and/or designers, the remodel of old houses by ordinary people may be lack of comprehensive plan, professional knowledge of technology and concept. Besides, the value of remodel of old house may be also different for everyone, even the condition of reuse in every case shows disparities. Therefore, it’s difficult to identify, evaluate and analyze the differences between cases. While the reuse for old house has become common, it’s necessary for revisions and reflections on the concept now. In this thesis, ‘the strategy of spatial transformation and the meaning of social phenomenon of reuse for old house: in the case of “Old House, New Life” movement in Tainan’ is chosen as the subject of the study, and the research purposes are listed as follows: 1. To realize the recent situation of the reuse for old house in Taiwan and propose the issue of old house for further discussion; 2. To establish the concept of design operation of reuse for old house through reviewing the progress and history of reuse old buildings in Taiwan, and other literatures and theories; 3. To discuss how the history is designed in old houses through field-trip investigation of some actual cases and analysis of the design concepts and results in these cases; 4. Finally, to introspect the reuse for old house through the observation on recent social phenomena.
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Chen, Chia-Lin, and 陳嘉琳. "The study of the Spatial,structural and Aesthetic additions In the Adaptive Reuse of Historical Buildings -in case of public buildings built during the Japanese occupied period-." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/91114602971540493224.
Full textAbstract:
碩士國立成功大學
建築(工程)學系
86
Keywords: Adaptive Reuse, Historical Buildings, Architectural Additions This thesis is mainly divided into three parts in which the contents are summarized as followings: Part 1:The Basic Issues In Architectural Additions in the Adaptive Reuse of Historical Buildings In Taiwan Most historical buildings in Taiwan will have to face the necessary addition because of the functional need. However, many additions are in the questionable conditions because the spatial,structual and aesthetics issues were not taken into serious consideration. This part of study will review the basic issues in architectural addition in the adaptive reuse of historical buildings from case studies of foreign countries. Part 2:The Study of Tactics and Problems in the Real Cases of Architectural Additions in the Adaptive Reuse of Historical Buildings in Taiwan Various tactics will be applied in the architectural additions in the adaptive reuse because of different spatial need and different characteristics of historical buildings.Different problems exist in every tactic.Improper additions will not only affect the appearance of the historical buildings but also endanger the structure of the original buildings. This part of the study will use the samples collected in the field trip to analyze different tactics and their associated problems of the spatial,structuraland aesthetics issues in architectural additional in the adaptive reuse of historical buildings In Taiwan.Part 3:ConclusionThis part of the study is the summary of the above study and to generalize the fundamental principles of architecural additions in the adaptive reuse of historical buildings in Taiwan. Some future suggestions will also be proposed.
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Govender, Kamenthren. "An assessment of synthetic landfill leachate attenuation in soil and the spatial and temporal implications of the leachate on bacterial community diversity." Thesis, 2008. http://hdl.handle.net/10413/443.
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