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Artykuły w czasopismach na temat "Channel access methods"
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Cao, Zhan Mao, i Jian Chao Tang. "Routing Methods and Scheduling Patterns in MIMO WMN Virtual Model". Applied Mechanics and Materials 519-520 (luty 2014): 216–21. http://dx.doi.org/10.4028/www.scientific.net/amm.519-520.216.
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Multi-input multi-output wireless mesh networks (MIMO WMNs) act as backbone broadband networks for ubiquitous access. Topology model is a crucial factor in interference avoidance, simplifying channel allocation, and discussing optimal scheduling and routing. Cartesian product of graphs (CPG) is introduced for MIMO WMN as a virtual topology. By putting orthogonal channels into different channel layer meshes, some conclusions are explored on channel allocation, routing and scheduling. A path coherent realization is composed of combinatorial edges over multiple channels for all hops. Some important property propositions in CPG are also given, such as path hops with node address and path number counting. Practical mesh node addressing scheme and path number counting theorems are useful virtual topology properties.
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Dai, Yuan-Kao, Li-Hsing Yen i Jia-Wei Su. "Toward an Access Infrastructure for Mobile Cloud". International Journal of Grid and High Performance Computing 5, nr 3 (lipiec 2013): 6–19. http://dx.doi.org/10.4018/jghpc.2013070102.
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The provision of mobile cloud service calls for a wireless access infrastructure that offers high bandwidth to mobile users. Among all enabling technologies, wireless mesh networks (WMNs) have the advantage of low deployment cost and widely available user equipments. To provide more bandwidth, access points in WMNs are commonly equipped with multiple wireless interfaces (radios) that can operate on multiple non-overlapping channels in parallel. The objective of channel assignments in a multi-channel, multi-radio MWN is to reduce co-channel interference experienced by links so as to increase network capacity while maintaining network connectivity. Prior studies addressing this issue majorly considered effects of co-channel interference at the link layer. In this study, the authors consider co-channel interference at the physical layer. Furthermore, most existing methods are based on heuristic or game theory. This study applies simulated annealing technique to the channel allocation problem. The objective function for this approach is defined as the total signal-to-interference radio (SIR) experienced by each link. To maintain network connectivity, the proposed approach limits the set of assigned channels for each radio. Experimental results show that, compared with traditional heuristic-based and game-theoretic approaches, the proposed simulated annealing algorithm results in more operative links.
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Hong, Jingxiang, Jose Rodriguez-Pineiro i Xuefeng Yin. "FDD Channel Inference Methods With Experimental Performance Evaluation". IEEE Access 8 (2020): 10491–502. http://dx.doi.org/10.1109/access.2020.2965290.
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Boutalline, Mohammed, Belaid Bouikhalene i Said Safi. "Channel Identification and Equalization based on Kernel Methods for Downlink Multicarrier-CDMA Systems". Journal of Electronic Commerce in Organizations 13, nr 2 (kwiecień 2015): 14–29. http://dx.doi.org/10.4018/jeco.2015040102.
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In this paper the authors are focused on channel identification and equalization for Multi-Carrier Code Division Multiple Access (MC-CDMA) system. For this, they identify the impulse response of two practical selective frequency fading channels called Broadband Radio Access Network (BRAN A and BRAN B) normalized by the European Telecommunications Standards Institute (ETSI). To identify the channel parameters, they have the positive definite kernels to build on algorithm. The simulations show that the presented method confirms the good performance for different SNR values. In part of equalization, the authors use the Zero Forcing (ZF) and Minimum Mean Square Error (MMSE) equalizers.
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Khan, Zaheer, i Janne Lehtomäki. "Adaptive and Autonomous Channel Access Methods for Distributed Cognitive Radios". Wireless Personal Communications 81, nr 2 (7.11.2014): 861–80. http://dx.doi.org/10.1007/s11277-014-2161-9.
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Khan, Zaheer, Janne Lehtomaki, Simon Scott, Zhu Han, Marwan Krunz i Alan Marshall. "Distributed and Coordinated Spectrum Access Methods for Heterogeneous Channel Bonding". IEEE Transactions on Cognitive Communications and Networking 3, nr 3 (wrzesień 2017): 267–81. http://dx.doi.org/10.1109/tccn.2017.2709753.
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Farhan, Ikhlas Mahmoud, Dhafer R. Zaghar i Hadeel Nasrat Abdullah. "Enhancement of code division multiple access system performance using raptor codes". Indonesian Journal of Electrical Engineering and Computer Science 26, nr 3 (1.06.2022): 1460. http://dx.doi.org/10.11591/ijeecs.v26.i3.pp1460-1468.
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Some kinds of communication systems work in very low signal-to-noise (LSNR) environments. For these systems to function reliably, <span>specific techniques and methodologies have to be used to mitigate the degrading effects of the channel. The channel coding method is the key element in most LSNR communication systems, but emphasizing the code division multiple access (CDMA) is a new transmission technique in these channels. To enhance the CDMA scheme's system capacity and reach unprecedented ranges of LSNR values in wireless sensor network. This paper suggests combining CDMA with certain types of channel coding algorithms, such as the raptor codes. The raptor channel encoding technique has improved the CDMA system's performance when using binary phase-shift keying (BPSK) modulation in additive white gaussian noise (AWGN) channels. It has achieved a low bit error rate in range of 10-7 at Eb/No value of (-3) dB and about 10-6 at shannon's limit. The Raptor-coded CDMA scheme works well for channel signal to noise ration (SNR) values of greater than -9 dB, showing an improvement of about 7 dB compared with turbo/convolutional channel coding methods used with the CDMA system bit error rate (BER) and throughput. On the other hand, it has been shown that the convolutional encoder presents the weakest performance compared to both the turbo and raptor codes.</span>
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Gizzini, Abdul Karim, i Marwa Chafii. "Low Complex Methods for Robust Channel Estimation in Doubly Dispersive Environments". IEEE Access 10 (2022): 34321–39. http://dx.doi.org/10.1109/access.2022.3162928.
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Zidane, Mohammed, Said Safi, Mohamed Sabri i Ahmed Boumezzough. "Bit Error Rate Analysis of MC-CDMA Systems with Channel Identification Using Higher Order Cumulants". Indonesian Journal of Electrical Engineering and Computer Science 1, nr 1 (1.01.2016): 138. http://dx.doi.org/10.11591/ijeecs.v1.i1.pp138-152.
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The aim of this paper is to contribute to study the problems of the blind identification and equalization using Higher Order Cumulants (HOC) in downlink Multi-Carrier Code Division Multiple Access (MC-CDMA) systems. For this problem, two blind algorithms based on HOC for Broadband Radio Access Network (BRAN) channel are proposed. In the one hand, to assess the performance of these approaches to identify the parameters of non minimum phase channels, we have considered two theoretical channels, and one practical frequency selective fading channel called BRAN C, driven by non gaussian signal. In the other hand, we use the Minimum Mean Square Error (MMSE) equalizer technique after the channel identification to correct the channel distortion. Theoretical analysis and numerical simulation results, in noisy environment and for different signal to noise ratio (SNR), are presented to illustrate the performance of the proposed methods.
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Abbass, Waseem, Riaz Hussain, Jaroslav Frnda, Nasim Abbas, Muhammad Awais Javed i Shahzad A. Malik. "Resource Allocation in Spectrum Access System Using Multi-Objective Optimization Methods". Sensors 22, nr 4 (9.02.2022): 1318. http://dx.doi.org/10.3390/s22041318.
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The paradigm of dynamic shared access aims to provide flexible spectrum usage. Recently, Federal Communications Commission (FCC) has proposed a new dynamic spectrum management framework for the sharing of a 3.5 GHz (3550–3700 MHz) federal band, called a citizen broadband radio service (CBRS) band, which is governed by spectrum access system (SAS). It is the responsibility of SAS to manage the set of CBRS-SAS users. The set of users are classified in three tiers: incumbent access (IA) users, primary access license (PAL) users and the general authorized access (GAA) users. In this article, dynamic channel assignment algorithm for PAL and GAA users is designed with the goal of maximizing the transmission rate and minimizing the total cost of GAA users accessing PAL reserved channels. We proposed a new mathematical model based on multi-objective optimization for the selection of PAL operators and idle PAL reserved channels allocation to GAA users considering the diversity of PAL reserved channels’ attributes and the diversification of GAA users’ business needs. The proposed model is estimated and validated on various performance metrics through extensive simulations and compared with existing algorithms such as Hungarian algorithm, auction algorithm and Gale–Shapley algorithm. The proposed model results indicate that overall transmission rate, net cost and data-rate per unit cost remain the same in comparison to the classical Hungarian method and auction algorithm. However, the improved model solves the resource allocation problem approximately up to four times faster with better load management, which validates the efficiency of our model.
Rozprawy doktorskie na temat "Channel access methods"
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El, Joubari Oumaima. "Mobility and traffic models for VANETs". Electronic Thesis or Diss., université Paris-Saclay, 2022. http://www.theses.fr/2022UPASG018.
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La congestion routière devient de plus en plus un problème auquel il faut s'attaquer rapidement. Parmi les conséquences néfastes de la congestion figure les accidents de la route, l'empreinte environnementale, la vitesse commerciale des transports publics et les embouteillages. Il est donc nécessaire de développer un système de transport capable d'assurer la sécurité des usagers de la route et d'améliorer l'infrastructure de transport. Les systèmes de transport intelligents ont gagné d'importance comme une solution prometteuse pour réduire la congestion. Ces systèmes intègrent des technologies avancées pour fournir des services intelligents et robustes qui visent à prévenir les incidents routiers susceptibles de menacer la vie des passagers. L'une des exigences les plus rigoureuses de ces applications est la transmission fiable et sans risque des paquets de données. VANET est conçu spécifiquement pour fournir une infrastructure de communication sans fil pour que les véhicules et les équipements routiers puissent échanger des données de trafic. La caractéristique particulière de ce réseau est la forte mobilité des nœuds du réseau qui entraîne des changements fréquents dans la topologie et la densité. Ceci peut impacter les réseaux et par conséquent ne pas répondre aux exigences des applications de sécurité. Dans cette thèse, nous traitons spécifiquement les méthodes d'accès pour les VANETs qui sont basées sur la méthode TDMA. TDMA s'est avérée être la technique d'accès la plus appropriée pour ces réseaux car elle permet à un seul nœud d'accéder au canal à tout moment. Cependant, les protocoles classiques TDMA ne sont pas adaptés aux réseaux fortement dynamiques et leur utilisation dans un environnent véhiculaire peut engendrer des collisions d'accès et une utilisation inéquitable des ressources. Par conséquent, une bonne compréhension de la mobilité permettra de concevoir et d'évaluer des méthodes d'accès qui soient efficaces même dans un environnement mobile. Bien que l'on trouve des modèles de mobilité fidèles dans la littérature, ils ne parviennent pas à reproduire avec précision certains aspects de la mobilité des véhicules. Le comportement du trafic est influencé par plusieurs facteurs tels que l'architecture de la route, les limitations de vitesse, les règles de circulation et le comportement individuel des véhicules. Ceux-ci doivent être inclus dans un modèle de mobilité afin d'obtenir des résultats fidèles. Dans ce contexte, nous développons dans cette thèse des modèles stochastiques à base de chaînes de Markov basés sur des traces réelles de véhicules collectées par les RSUs en utilisant la communication V2X pour émuler le comportement des véhicules sur des routes urbaines et autoroutières. Les modèles proposés présentent le double avantage de modéliser et de prévoir le trafic. En utilisant une technique de résolution numérique, la densité du trafic, la longueur des files d'attente, le temps du trajet et le temps d'attente sont estimés. La densité de trafic estimée est ensuite exploitée pour développer une méthode d'accès basé sur TDMA appelée TA-TDMA qui a pour but principal de réduire les collisions d'accès et améliorer l'utilisation des ressources à travers la prédiction de mobilité et le clustering. Pour évaluer la performance de la méthode proposée, un outil de simulation de trafic basé sur les files d'attente a été développé à l'aide du logiciel SimEvents. Ce modèle de simulation permet de générer des mesures synthétiques importantes pour l'évaluation des performances des réseaux routiers. Le protocole TA-TDMA a ensuite été implémenté et comparé avec le protocole VeMAC, en considérant différents scénarios et environnements. La solution proposée a montré de meilleurs résultats par rapport au protocole VeMAC en termes d'efficacité et de robustesse face aux changements topologiquesThe ever-growing traffic congestion is becoming a serious issue that needs to be urgently addressed. The growing number of traffic accidents, the environmental footprint of transport, commercial speed of public transportation and traffic jams are few examples of the adverse consequences of congestion. This calls for an upgrade of the transport system in order to ensure road users safety and effectively enhance the transportation infrastructure. ITS have grown in importance as a promising solution to the congestion issue. These systems rely on the most advanced technologies to provide intelligent and robust safety services that seek to prevent road incident that may threaten the life of passengers. One of the most stringent requirements of these applications is an error-free and reliable transmission of data packets. VANET were designed specifically to provide a wireless communication infrastructure to allow vehicles and road equipment to exchange traffic data. The particular feature of this network is the highly dynamic mobility which results in frequent changes in the topology and density of the network. This has negative effects on the network performance which does not allow to cater safety applications requirements. In this thesis, we address specifically channel access methods for VANET that are based on TDMA method. TDMA has been proven the most suitable access technique for VANET as it allows a single node to access the channel at any time slot. However, conventional TDMA-based protocols might encounter difficulties in a dynamic networks such as access collision and unfair use of resources. Hence, a good understanding of mobility will allow the design and evaluation of channel access methods that are efficient and robust even in a mobile environment. Although faithful mobility models are found in the literature, they fail to accurately capture some aspects of vehicular mobility. The traffic behaviour is influenced by several factors such as road layout, speed limits, traffic rules and individual vehicle’s behaviour. Consequently, it is compulsory to include all these features in a mobility model for accurate results. In this context, we develop in this thesis stochastic Markov chain models based on real vehicle traces collected by RSUs using V2X communication to emulate vehicular behaviour in both urban and highway roads. The proposed models have the twofold benefit of modelling and predicting traffic. Using a direct numerical resolution technique, traffic density, waiting queue lengths, travel times and delays are predicted. The predicted traffic density is then exploited to design a Traffic-aware TDMA channel access method that aims to reduce access collisions and enhance resource utilization through mobility prediction and clustering. To evaluate the performance of the proposed method, a queue-based mobility simulation framework was developed using the SimEvents toolbox. The simulation framework allows the generation of synthetic measures relevant to the assessment of road network performance. The TA-TDMA MAC protocol was then implemented and compared with an existing MAC protocol called VeMAC, under different scenarios and environments. The proposed solution has shown better results than the VeMAC protocol in terms of efficiency and robustness against topological changes
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Joumessi, Demeffo Steve. "Dispositif communicant par optique sans fil pour les transmissions audio à l’intérieur du cockpit d’un avion". Thesis, Limoges, 2020. http://www.theses.fr/2020LIMO0065.
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Le travail de cette thèse s’inscrit dans le cadre du projet européen H2020 Clean Sky 2 intitulé ALC (« Aircraft Light Communication ») qui a pour objectif d’apporter une preuve de concept de l’intégration de la technologie optique sans fil dans le cockpit d’un avion en alternative des solutions radiofréquences et filaires qui présentent plusieurs limites telles que la sécurité et le confort. Les travaux menés concernent le développement d’un casque audio communiquant en infrarouge dans un réseau bidirectionnel constitué d’un point d’accès situé au plafond du cockpit et de quatre casques portés par les membres de l’équipage. Nous avons commencé par présenter les techniques de communication numérique applicables au contexte afin de motiver le choix pour les formats de modulations OOK (« on-off keying »), PPM (« pulse-position modulation ») et de la méthode d’accès au canal DCF (« distributed coordination function ») avec RTS/CTS (« request to send/clear to send »). Ensuite, nous avons décrit les émetteurs-récepteurs et modélisé le canal optique à partir du logiciel de simulation RaPSor, basé sur la méthode de lancer de rayon associé à une technique de Monte-Carlo, développé à XLIM/SYCOMOR. Cette modélisation réalisée à partir d’un modèle 3D du cockpit et des corps des membres de l’équipage, a permis de déterminer les angles à mi-puissance optimaux des sources situées sur le point d’accès et sur les casques en tenant compte de la robustesse face aux mouvements aléatoires que peuvent effectuer les membres d’équipage durant le vol. Les gains statiques issus de la modélisation du canal ont servi ensuite dans l’étude conjointe des performances des couches physiques et liaison de données. Cette étude a permis de mettre en lumière le compromis entre le niveau de puissance émis et la latence pour une qualité de service visée. Nous avons montré qu’il était possible de concevoir un réseau en optique sans fil dans un cockpit AIRBUS A350 compatible au standard IEEE802.11 avec : le format de modulation 4-PPM, la méthode d’accès au canal DCF avec RTS/CTS, un taux de perte de paquets de 10-4 et un délai de communication avec succès de 2,5 ms. Cela est possible à condition d’adapter la fenêtre de contention du standard IEEE802.11 en fonction de la probabilité de collision, de la taille des paquets et du débit binaire du réseau. Nous avons enfin conçu un banc de test modulaire en radio logicielle. Notre choix s’est porté sur l’environnement GNU Radio associé aux périphériques USRP (« universal software radio peripheral »). Des front-ends optiques ont été spécifiquement développés pour les USRP. Nous avons pu montrer expérimentalement l’influence des paramètres des sources sur le taux de perte des paquets. Le travail effectué dans cette thèse ouvre plusieurs perspectives sur le plan de la simulation et de l’expérimentationThe work developed in this thesis is part of the European project H2020 Clean Sky 2 entitled ALC (« Aircraft Light Communication ») which aims to provide a proof of concept of the integration of optical wireless technology in the aircraft cockpit, as an alternative to radio frequency and wired solutions, having several limitations like safety and comfort. The work carried out in this thesis concerns the development of a headset communicating in infrared in a bidirectional network made of an access point located at the cockpit ceiling and four helmets worn by the crewmembers. We started by presenting the digital communication techniques that can be used in the context to motivate the choice of the study of OOK (« on-off keying»), PPM (« pulse-position modulation») modulations and DCF («distributed coordination function») with RTS/CTS (« request to send/clear to send »). Then, the transceiver main characteristics have been identified and the optical channel was modeled using the RaPSor simulation software, developed at XLIM/SYCOMOR and based on raytracing method associated with a Monte-Carlo technique. This modelling, based on a 3D model of the cockpit and the bodies of the crewmembers, allowed determining the optimal half-power angles of the sources located on the access point and on the headsets, taking into account the robustness against the random movements of the crew members during the flight. The static gains from the channel modelling were then used in a joint study of the performance of the physical and data link layers. This study highlighted the trade-off between the emitted power level and latency for a targeted quality of service. We have shown that it is possible to design an optical wireless network in an AIRBUS A350 cockpit compliant with the IEEE802.11 standard with: 4-PPM modulation, DCF with RTS/CTS channel access method, a packet error rate of 10-4 and a successful communication delay of 2.5ms. This is possible if the contention window parameter defined in the IEEE802.11 standard specifications is adapted according to the network probability collision, packets size and the data rate. Finally, we designed a modular test bench based on software defined radio. We chose the GNU Radio environment associated with USRP (« universal software radio peripheral »). Specific optical front-ends have been developed for this aim. We have experimentally shown the influence of the source parameters on the packet error rate. The work carried out in this thesis opens several perspectives in terms of simulation and experimentation
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Brites, Alice Dantas. "Monitoramento dos efeitos ecológicos e socioeconômicos da comercialização de produtos florestais não madereiros". Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/90/90131/tde-24032011-215203/.
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A comercialização de produtos florestais não madeireiros (PFNMs) popularizou-se como atividade promotora do desenvolvimento socioeconômico de comunidades florestais com baixo impacto ambiental. Há evidências, contudo, de que a exploração possa produzir efeitos ecológicos e socioeconômicos negativos, sugerindo que é necessário monitorar tais iniciativas. A comercialização frequentemente ocorre em áreas remotas e em contextos de pobreza, como é o caso de muitas daquelas da Amazônia brasileira. Desta forma, é necessário que o monitoramento restrinja-se a avaliar os efeitos evidenciados como mais comuns em estudos anteriores. Este estudo revisa e sintetiza as evidências científicas dos efeitos da exploração de PFNMs sobre parâmetros ecológicos e socioeconômicos e, a partir daí, indica aqueles mais relevantes ao monitoramento. O estudo também levanta até que ponto o monitoramento é implementado no contexto da Amazônia brasileira e avalia quais os parâmetros importantes e viáveis de monitoramento neste caso específico. Para isso, foram realizadas revisões sistemáticas da literatura e a consulta a profissionais da área através do método Delphi. Os resultados indicam que efeitos ecológicos negativos são frequentes, principalmente quando se coletam folhas ou cascas. Alterações em órgãos ou processos fisiológicos e a taxa de sobrevivência dos espécimes explorados são parâmetros que devem ser monitorados, em particular quando se coletam frutos e partes vegetativas. Para todos os tipos de PFNMs, o tamanho e a estrutura populacional são parâmetros prioritários ao monitoramento. A riqueza de espécies da comunidade explorada merece atenção, principalmente quando se coletam frutos. Para os aspectos socioeconômicos, efeitos positivos foram mais frequentes que negativos. A contribuição da renda monetária obtida com o comércio na renda total, a regularidade de ingresso desta renda e o papel dos PFNMs como recursos de salvaguarda são parâmetros do capital financeiro prioritários ao monitoramento. Para o capital social, o empoderamento feminino, a coesão de grupo e o acesso aos benefícios gerados pela comercialização devem ser monitorados. Na Amazônia brasileira são poucas as iniciativas de implementação do monitoramento da comercialização de PFNMs. Embora este seja considerado importante, existem dificuldades que derivam principalmente da falta de apoio institucional, políticas de incentivo e de recursos financeiros. Os profissionais participantes do Delphi consideram que os parâmetros ecológicos mais importantes a monitorar neste contexto são o tamanho e a estrutura populacional do recurso explorado, o aumento da taxa de mortalidade, a quantidade total de recurso extraída e a técnica de coleta utilizada. Para os parâmetros econômicos, aspectos do mercado, como o preço pago ao coletor, a demanda e a qualidade do produto, bem como a renda monetária obtida pelos indivíduos são os parâmetros considerados mais importantes. Por fim, para os aspectos sociais, os efeitos na cultura, na qualidade de vida e na organização interna da comunidade foram priorizados. Os profissionais indicam que é viável estabelecer o monitoramento dos parâmetros levantados.Amazon, non-timber forest products, ecological effects, socioeconomic effects, monitoring.
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Devanarayana, Chamara Nilupul. "Predictive Channel Access in Cognitive Radio Networks Based on Variable order Markov models". 2011. http://hdl.handle.net/1993/4991.
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The concept of Cognitive radio enables the unlicensed users to share the spectrum with
licensed users, on the condition that the licensed users have preemptive priority. The use of the channel by unlicensed users should not result in more than acceptable interference level to the licensed users, if interference occurs. The sense and react strategy by unlicensed users sometimes does not lead to acceptable level of interference while maintaining an acceptable data transfer rate for the unlicensed users.
Proactive channel access has been proposed for the purpose of reducing the interference
to primary users and to reduce the idle channel search delay for the secondary users. There are many methods used in the literature to model the channel state fluctuations. Based on these models the future channel states are predicted. In this thesis we introduce a predictive channel usage scheme which is capable of reducing
the interference caused by the unlicensed users. Furthermore our scheme is capable
of increasing the data rates the unlicensed users experience through the reduction of the idle channel identification delay. In our scheme no assumptions are made about the distribution of licensed user channel usage. We learn the traffic characteristics of the channels using a learning scheme called Probabilistic Suffix Tree algorithm.
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LIN, TZU-YANG, i 林子揚. "Channel Access Method for IEEE80.11ac MAC Layer". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/vk3ngh.
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碩士國立臺北科技大學
電子工程系研究所
103
As the huge progress of modern technology and the prevalence of personal electronic devices, each person have more than one laptop or personal digital assistant devices. Therefore, the requirement of the wireless internet increases as well. IEEE802.11 Wireless Location Area Network (WLAN) resolves the problem of constructing wires, and also provides internet service while users are moving. In order to deal with the requirement of a large number of data transmissions, WLAN standard has been constantly updated and modified, the latest specification is IEEE802.11 ac. To increases throughput and transfer rate, IEEE modifies IEEE802.11n and defines IEEE802.11ac, known as Very High Throughput (VHT) which support some new features of MAC layer. This thesis will compare basic channel access method and QoS channel access method of IEEE802.11ac MAC layer with IEEE802.11e MAC layer. In addition, this thesis will also illustrate Wireless Mesh Network (WMN) channel access method which was not mentioned in the older IEEE802.11e MAC layer, and describe all the updated information.
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Wu, Li-Fu, i 吳立夫. "Dynamic Optimization for IEEE 802.11 DCF Access Method for Noisy Channels". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/33701349923425035989.
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碩士逢甲大學
資訊工程所
93
In wireless local area networks (WLANs), the medium access control (MAC) layer protocol is the main element that determines the efficiency of sharing the limited and unreliable communication bandwidth of the wireless channel. For IEEE 802.11 protocol, the standard of WLANs, the basic access method in its medium access control (MAC) layer protocol is the distributed coordination function (DCF), based on the mechanism of carrier sense multiple access with collision avoidance (CSMA/CA). According to the actual version of the standard, the backoff parameters of its collision avoidance mechanism are hard-wired in the physical layer, and are far from the optimal setting in some network configuration conditions especially in heavy load or error-phone WLANs environment. To begin with, this strategy incurs a high collision probability and channel utilization is degraded in bursty arrival or congested scenarios, and the size of Contention Window (CW) is set again to the minimum value without maintaining any knowledge of the current channel status after a successful transmission. Besides, when a frame is collided on wired network, the sender should slow down, but when one is lost on a wireless network, the sender should try harder. Extending the backoff time just makes matters worse because it brings bandwidth wastage. Although in the past there were adequate discussions on issues about DCF and the performance thereof, there were few papers on the relationship between backoff parameters and channel bit error rate (BER). In this paper, we attempt to identify the relationship between backoff parameters and channel BER and put forth a pragmatic problem-solving solution. The proposed distributed adaptive contention window mechanism not only dynamically expands and contracts the contention window size according to the current network contention level and channel BER, but also provably optimal in that it achieves optimal channel utilization for IEEE 802.11 DCF access method. In addition to theoretical analysis, simulations are conducted to evaluate the performance scheme. As it turns out, our design indeed provides a remarkable improvement in a heavy load and error-phone WLANs environment.
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Horner, Schwarz Kaylan. "Unequal Opportunities for Citizenship Learning? Diverse Student Experiences Completing Ontario’s Community Involvement Requirement". Thesis, 2010. http://hdl.handle.net/1807/25654.
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This thesis examined diverse students' experiences completing Ontario's community involvement requirement. An analysis of quantitative surveys and qualitative focus groups among 50 current and recently graduated secondary school students from widely contrasting socio-economic settings showed ways in which diverse participants perceived their community involvement activities, the support for community involvement in their schools, and their associated opportunities to develop capacity to make changes toward a more socially just world. Results indicated that low-income participants reported dissimilar experiences from high-income participants, in relation to the support for community involvement provided by school staffs, participants' direct or distant relationships with service recipients, and their sense of individual and collective agency to effect change. Thus, this study challenges the assumption that all students in Ontario have equal access to the citizenship education learning opportunities embedded in meaningful community involvement activities.
Książki na temat "Channel access methods"
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IEEE Computer Society. LAN/MAN Standards Committee. i American National Standards Institute, red. IEEE standards for local and metropolitan area networks: Supplement to token-passing bus access method and physical layer specifications : alternative use of BNC connectors and Manchester-encoded signaling methods for single-channel bus physical layer entities. New York, NY: Institute of Electrical and Electronics Engineers, Inc., 1997.
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Illusions of reality: A history of deception in social psychology. Albany: State University of New York Press, 1997.
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Knight, Andrew P. Innovations in unobtrusive methods. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198796978.003.0004.
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Andrew P. Knight explores developments in unobtrusive research methods using unconventional sources of data from computer-based systems and tools. These generate novel measures of behaviour based on the digital trace data that we all generate, online access to public and personal archives, wearable sensors, and the automatic coding of text, and audio and video recordings. Smartphones and wristbands are just two of the growing range of connected devices that are capable of capturing and sharing multimedia information in real-time. Devices such as these offer new ways in which researchers can gather data at low cost, avoiding reactance effects, allowing the study of how phenomena change over time, and expanding the scale of research, given the wide dissemination of the technology. Before adopting these methods, researchers need to consider whether they have the expertise, and the ethical issues raised by using information (which may be in the public domain) without informed consent.
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Schneider, Christopher J. Making the case. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198796978.003.0006.
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Christopher J. Schneider explains how he uses Qualitative Media Analysis (QMA) to exploit the unconventional data generated by social media in general, and by (public) Twitter feeds in particular. QMA is a method for analysing systematically the documents (tweets, videos) that are produced by social media platforms, which have changed the ways in which we communicate with each other, and also how we communicate with, and about, organizations. Through social media, therefore, researchers have ready access to a range of novel information that is not easily accessed by other means. The approach is illustrated by a study of police–public relationships in Canada; researchers can find it difficult to access police organizations directly. Twitter gives police organizations a ‘new visibility’ which opens them to greater scrutiny. However, police now conduct ‘image work’ through tweets. This research also explored how police respond to recorded instances of violence and untoward conduct posted on YouTube.
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Boadway, Robin. Cost-Benefit Analysis. Redaktorzy Matthew D. Adler i Marc Fleurbaey. Oxford University Press, 2016. http://dx.doi.org/10.1093/oxfordhb/9780199325818.013.2.
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This is an overview of the methods used to evaluate projects or policies when a normative approach is taken based on individual preferences. The evaluation of individual welfare change is first outlined and related to the concepts of willingness-to-pay and willingness-to-accept. The use of individual welfare measures in project evaluation is outlined. This is followed by approaches to aggregating individual welfare changes. The case for ignoring equity considerations based on the compensation criterion is critically discussed. The use of a social welfare function for cost-benefit analysis is presented, and it application to project evaluation outlined. Several extensions are considered, including the evaluation of non-marketed commodities, the treatment of uncertainty, and multi-period project evaluation. Throughout, the conceptual difficulties of measuring and aggregating welfare change are emphasized.
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Gullón, Pedro, i Gina S. Lovasi. Designing Healthier Built Environments. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780190843496.003.0008.
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The “built environment” is comprised of human-made structures and systems, and aspects include access to and attractiveness of walkable destinations (e.g., retail stores, parks) and community design features (e.g., street connectivity, sidewalk access). A variety of built environment characteristics can influence health outcomes and behaviors, including physical activity, obesity, type 2 diabetes, hypertension, and mental health, as well as sleep and use of tobacco and alcohol. This chapter discusses the large and complex accumulated research on the built environment as well as the methods used to study it, research challenges, policy implication, and how to bring together partnerships for policy change. This chapter also discusses the research conducted across populations (e.g., children, low-income individuals) and geographies (e.g., urban and rural geographies).
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Corse, Edward, i Marta García Cabrera, red. Propaganda and Neutrality. Bloomsbury Publishing Plc, 2023. http://dx.doi.org/10.5040/9781350325562.
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This is the first broad-ranging, comprehensive and comparative study of the concepts of propaganda and neutrality. Bringing together world-leading and early career historians, this open access book explores case studies from the time of the First World War to the end of the Cold War in countries such as Belgium, Greece, Spain, Portugal, Ireland, Switzerland, Vichy France, USA, Argentina, Turkey, Portuguese Macau, Brazil, South Africa, Laos, Yugoslavia, Egypt, India, Malta, and Sweden. The individual chapters analyse the methods and channels of propaganda utilised in neutral countries, including rumours, newspapers, cartoons, films, pamphlets and magazines as well as radio broadcasts, official reports, diplomatic movements, cultural campaigns and soft power. They look to understand how these methods and channels have been deployed and how effective they have been in changing or reinforcing opinions and outcomes. Finally the book highlights the interaction between the concepts of propaganda and neutrality. It considers whether neutrality is a form of propaganda in itself, whether it is possible to be truly neutral in any propaganda battle and how the different forms of neutrality, including projected strict neutrality, non-belligerency and non-alignment, have been utilised by neutrals and belligerents to achieve propaganda goals in the last 120 years.
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Dowd, Cate. Digital Journalism, Drones, and Automation. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190655860.001.0001.
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Advances in online technology and news systems, such as automated reasoning across digital resources and connectivity to cloud servers for storage and software, have changed digital journalism production and publishing methods. Integrated media systems used by editors are also conduits to search systems and social media, but the lure of big data and rise in fake news have fragmented some layers of journalism, alongside investments in analytics and a shift in the loci for verification. Data has generated new roles to exploit data insights and machine learning methods, but access to big data and data lakes is so significant it has spawned newsworthy partnerships between media moguls and social media entrepreneurs. However, digital journalism does not even have its own semantic systems that could protect the values of journalism, but relies on the affordances of other systems. Amidst indexing and classification systems for well-defined vocabulary and concepts in news, data leaks and metadata present challenges for journalism. By contrast data visualisations and real-time field reporting with short-form mobile media and civilian drones set new standards during the European asylum seeker crisis. Aerial filming with drones also adds to the ontological base of journalism. An ontology for journalism and intersecting ontologies can inform the design of new semantic learning systems. The Semantic CAT Method, which draws on participatory design and game design, also assists the conceptual design of synthetic players with emotion attributes, towards a meta-model for learning. The design of context-aware sensor systems to protect journalists in conflict zones is also discussed.
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Harper, Sarah. Demography: A Very Short Introduction. Oxford University Press, 2018. http://dx.doi.org/10.1093/actrade/9780198725732.001.0001.
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Demography—the study of people—addresses the size, distribution, composition, and density of populations, and considers the impact these factors have on individual lives and the changing structure of human populations. Each generation’s demographic composition influences a person’s life chances; the economic and political structures within which that life is lived; the person’s access to social and natural resources; and life expectancy. Demography: A Very Short Introduction considers how the global population has evolved over time and space and discusses the theorists, theories, and methods involved in studying population trends and movements. It also looks at the emergence of new demographic sub-disciplines and addresses some of the future population challenges.
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Hooley, Tristram, i Rachel Buchanan. Online Research. Bloomsbury Publishing Plc, 2024. http://dx.doi.org/10.5040/9781350319127.
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First published Open Access under a Creative Commons license as What is Online Research?, this title is now also available as part of the Bloomsbury Research Methods series. This book provides a concise and accessible introduction to online research, covering ethics, surveys, focus groups, ethnographies, experiments and the gathering and analysis of naturally occurring digital/big data. It also asks how researchers should use the digital environment to communicate their research and looks forward to the future of the field, asking what the next ten years hold. Online research is rarely well served by the direct translation of onsite methods onto the internet. Rather, researchers need to reflect, adapt and redesign research as they change the mode through which they conduct their research. Featuring an updated glossary, two new chapters and comprehensive updates throughout, this new edition provides new and experienced researchers with the foundation they need to conduct online research projects
Części książek na temat "Channel access methods"
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Kuhn, Nicolas, Olivier Mehani, Huyen-Chi Bui, Jérôme Lacan, José Radzik i Emmanuel Lochin. "Physical Channel Access (PCA): Time and Frequency Access Methods Simulation in NS-2". W Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 174–85. Cham: Springer International Publishing, 2013. http://dx.doi.org/10.1007/978-3-319-02762-3_16.
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Delan-Forino, Clémentine, i David Tollervey. "Mapping Exosome–Substrate Interactions In Vivo by UV Cross-Linking". W Methods in Molecular Biology, 105–26. New York, NY: Springer New York, 2019. http://dx.doi.org/10.1007/978-1-4939-9822-7_6.
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AbstractThe RNA exosome complex functions in both the accurate processing and rapid degradation of many classes of RNA in eukaryotes and Archaea. Functional and structural analyses indicate that RNA can either be threaded through the central channel of the exosome or more directly access the active sites of the ribonucleases Rrp44 and Rrp6, but in most cases, it remains unclear how many substrates follow each pathway in vivo. Here we describe the method for using an UV cross-linking technique termed CRAC to generate stringent, transcriptome-wide mapping of exosome–substrate interaction sites in vivo and at base-pair resolution.
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Vollmer, Rainer, Janeth Espirilla, Rosalva Villagaray, José Cárdenas, Mario Castro, Juan Carlos Sánchez, Norma Manrique-Carpintero, David Ellis i Noelle Lynette Anglin. "Correction to: Cryopreservation of Potato Shoot Tips for Long-Term Storage". W Methods in Molecular Biology, C1. New York, NY: Springer US, 2021. http://dx.doi.org/10.1007/978-1-0716-1609-3_21.
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Chapter 2 was previously published non-open access. It has now been changed to open access under a CC BY 4.0 license, and the copyright holder updated to ‘The Author(s)’. The book has been updated with this change.
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Cecconi, Daniela. "Correction to: Proteomics Data Analysis". W Methods in Molecular Biology, C1. New York, NY: Springer US, 2021. http://dx.doi.org/10.1007/978-1-0716-1641-3_19.
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In the original version of this book, chapter 16 was published non-open access. It has now been changed to open access under a CC BY 4.0 license, and the copyright holder has been updated to “The Author(s).” This book has been updated with these changes.
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Zieliński, Tomasz, Johnny Hay i Andrew J. Millar. "Correction to: Period Estimation and Rhythm Detection in Timeseries Data Using BioDare2, the Free, Online, Community Resource". W Methods in Molecular Biology, C1. New York, NY: Springer US, 2022. http://dx.doi.org/10.1007/978-1-0716-1912-4_19.
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The original version of the chapter “Period Estimation and Rhythm Detection in Timeseries Data Using BioDare2, the Free, Online, Community Resource” was previously published non-open access. This has now been changed to open access under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/), and the copyright holder updated to “The Author(s)”. For further details, see license information in the chapter. The chapter and the book have been updated with the change.
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Bouba, Goni Mahamadou, Jerôme Mbainaibeye, James Kouawa Tamgno i Claude Lishou. "LTE-Advanced Random Access Channel Congestion Detection Method for IoT". W Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 45–55. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-16042-5_5.
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Huang, Chung-Ming, Rung-Shiang Cheng i Yan-Jia Pan. "The Claim-Based Channel Access (CCA) Method for IEEE 802.11ah". W Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 516–26. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-69514-9_39.
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Mahajan, Shilpa, i Nisha Sharma. "A Hybrid Channel Access Method to Optimize Congested Switched Network". W Mobile Radio Communications and 5G Networks, 209–23. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-7130-5_16.
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Cao, Q., i M. K. Gurcan. "A Novel Radio Channel Control Method for Improved Multiple Access Schemes". W The Kluwer International Series in Engineering and Computer Science, 249–63. Boston, MA: Springer US, 1996. http://dx.doi.org/10.1007/978-1-4613-1353-3_16.
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Tocchetti, Andrea, Lorenzo Corti, Marco Brambilla i Diletta Di Marco. "Correction to: A Web-Based Co-Creation and User Engagement Method and Platform". W Lecture Notes in Computer Science, C2. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-74296-6_50.
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Chapter “A Web-Based Co-Creation and User Engagement Method and Platform” was previously published non-open access. It has now been changed to open access under a CC BY 4.0 license and the copyright holder updated to ‘The Author(s)’. The book has also been updated with this change.
Streszczenia konferencji na temat "Channel access methods"
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Lopez-Aguilera, Elena, Martin Heusse, Franck Rousseau, Andrzej Duda i Jordi Casademont. "Channel Access Unfairness of Wireless LAN Access Methods". W 2007 15th IEEE Workshop on Local and Metropolitan Area Networks. IEEE, 2007. http://dx.doi.org/10.1109/lanman.2007.4295987.
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Sun, Hui, Chengrui Bai, Lei Gao, Xianyu Wang, Sabir Ghauri i Rui Wang. "Analysis of Channel Selection Methods with Dynamic Spectrum Access Technology". W 2018 10th International Conference on Modelling, Identification and Control (ICMIC). IEEE, 2018. http://dx.doi.org/10.1109/icmic.2018.8529984.
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Khalifa, Abderrahman Ben, i Razvan Stanica. "Performance Evaluation of Channel Access Methods for Dedicated IoT Networks". W 2019 Wireless Days (WD). IEEE, 2019. http://dx.doi.org/10.1109/wd.2019.8734186.
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Loh, Frank, Simon Raffeck, Stefan Geibler i Tobias Hobfeld. "Generic Model to Quantify Energy Consumption for Different LoRaWAN Channel Access Methods". W 2022 18th International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob). IEEE, 2022. http://dx.doi.org/10.1109/wimob55322.2022.9941629.
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Sliwa, Joanna, Robert Matyszkiel i Jan Jach. "Efficient Methods of Radio Channel Access Using Dynamic Spectrum Access That Influences SOA Services Realization - Experimental Results". W 2015 IEEE 81st Vehicular Technology Conference (VTC Spring). IEEE, 2015. http://dx.doi.org/10.1109/vtcspring.2015.7145801.
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Zhdanovskiy, Vyacheslav, Vyacheslav Loginov, Andrey Lyakhov i Evgeny Khorov. "A Comparative Study on Multi-Channel Access Methods in 5G NR-U Networks". W 2020 IEEE International Black Sea Conference on Communications and Networking (BlackSeaCom). IEEE, 2020. http://dx.doi.org/10.1109/blackseacom48709.2020.9234992.
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Zidane, Karine, Jerome Lacan, Marie-Laure Boucheret, Charly Poulliat, Mathieu Gineste, Damien Roques, Caroline Bes i Arnaud Deramecourt. "Effect of Residual Channel Estimation Errors in Random Access Methods for Satellite Communications". W 2015 IEEE 81st Vehicular Technology Conference (VTC Spring). IEEE, 2015. http://dx.doi.org/10.1109/vtcspring.2015.7145797.
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Zidane, Karine, Jerome Lacan, Marie-Laure Boucheret i Charly Poulliat. "Improved channel estimation for interference cancellation in random access methods for satellite communications". W 2014 7th Advanced Satellite Multimedia Systems Conference and the 13th Signal Processing for Space Communications Workshop (ASMS/SPSC). IEEE, 2014. http://dx.doi.org/10.1109/asms-spsc.2014.6934526.
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Gorlov, Nikolai, Igor V. Bogachkov i Evgenia Kitova. "Predicting the Reliability of Physical Channel in Optical Access Networks by Non-destructive Methods". W 2019 International Multi-Conference on Engineering, Computer and Information Sciences (SIBIRCON). IEEE, 2019. http://dx.doi.org/10.1109/sibircon48586.2019.8958410.
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Eason, Cormac, Tara Dalton, Cian O’Mathu´na, Mark Davies i Orla Slattery. "Direct Comparison Between a Variety of Microchannels: Part 1 — Channel Manufacture and Measurement". W ASME 2004 2nd International Conference on Microchannels and Minichannels. ASMEDC, 2004. http://dx.doi.org/10.1115/icmm2004-2329.
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This paper is the first part of a two part study into the pressure-flow characteristics of a range of microchannels measured over a range of typical Reynolds numbers. Here the manufacture of the channels and their resulting quality is addressed. The target application is silicon cooling. Wet Etching, Deep Reactive Ion Etching (DRIE) and Precision Sawing have been used to create microchannels in silicon and thermoset plastic. Anodic bonding has been used to bond covers onto the DRIE and Wet Etched channels. Wet etching a (100) silicon wafer using a KOH solution produced trapezoidal channels of width 577 μm and height 413μm. DRIE using the Bosch process produced rectangular channels in (100) silicon of width 304μm and height 332μm. Mechanical sawing using a Disco Dicing Saw produced near rectangular channels in both silicon and plastic. The silicon channels were 52μm wide and 423μm deep, and the plastic channels were 203μm wide by 344 or 382μm deep. Channel dimensions were measured using a scanning electron microscope. Silicon was the main material chosen, since it is possible to cut cooling channels directly into one side of a silicon device, while the electronic parts are deposited on the other, giving effective cooling with minimal thermal resistance. The plastics chosen are commonly used to encapsulate electronic packages and will also be in close proximity to the heat producing regions of the device it protects. Embossed channels on a plastic encapsulant also potentially offer a low cost mass producible means of cooling electronic devices with a low overall thermal resistance. A glass cover was anodically bonded over the silicon channels to prevent channel to channel leakage and provide optical access. The plastic channels were also covered by a glass slide, bonded in position using SU8 Photoresist spun on the glass. This paper demonstrates the feasibility of producing relatively large microchannels in two materials by three methods. Part two of this paper will describe the modular flow test system and analyze the flow friction through the channels.
Raporty organizacyjne na temat "Channel access methods"
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Howard, Jo. Practical Guides for Participatory Methods: Mapping and Power Analysis. Institute of Development Studies, styczeń 2023. http://dx.doi.org/10.19088/ids.2023.002.
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This method enables participants to create a visual map of the key resources and assets in their community, organisation, workplace etc, that are important for their wellbeing and thriving. It is designed to encourage marginalised groups to visually represent and reflect on these resources and the power relations that shape who accesses and controls resources. They map and rank the actors who have more/less power, control and access, and discuss the reasons behind these differences. Finally, a discussion of possible strategies and actions for change can be facilitated.
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Hayashi, Ryotaro, David Raitzer, Xylee Javier i Milan Thomas. Assessment of Changes in Secondary School Learning Outcomes in Post-COVID-19 Bhutan. Asian Development Bank, sierpień 2023. http://dx.doi.org/10.22617/brf23329-2.
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Bhutan’s schools maintained their relatively strong performance during the pandemic as access to remote learning, the opening of boarding facilities, and moves to prioritize education for secondary school pupils prevented performance gaps widening. This brief shows how Bhutan tried to minimize the impact of school closures on students, provided social safety nets to vulnerable households, and offered a mix of remote learning methods including television and internet. Analyzing exam grades for the Dzongkha national language, English, and science, it shows how the compensatory actions and steps to ensure continuity for secondary school pupils resulted in little decline in their results.
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Anderson, Paul, Yakuta Baghat, Brad Bartelme, Nicole Stolic i Melissa Vaccarino. Cuyahoga Valley National Park headwater stream inventory: Final report. National Park Service, 2024. http://dx.doi.org/10.36967/2302348.
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EnviroScience, Inc. (EnviroScience) was contracted by the National Park Service (NPS) to design and implement a study plan to inventory the headwater stream resources within the Cuyahoga Valley National Park (CUVA). The parameters and expectations of the study are described in a Statement of Work (SOW) developed by NPS staff (NPS, 2021) to collect and analyze data to guide decision-making in the development of management plans to protect these resources within CUVA. The headwater stream inventory was comprised of three components to evaluate the resources as follows: 1. habitat and biological assessments to classify the streams in the context of the Ohio EPA Primary Headwater (PHW) stream classification system (Ohio EPA, 2020) and the beneficial aquatic life uses promulgated in Chapter 3745-1 of the Ohio Administrative Code (OAC), where applicable; 2. fluvial geomorphological assessments to determine stream channel types and to evaluate the potential and degree of streambank erosion associated with the assessment sites; and 3. development and testing of a visitor use impact assessment (VUIA) protocol for potential park-wide application to manage and protect stream resources in the context of public access. A total of 125 headwater stream sites were assessed to complete the inventory. The SOW identified eighty-three (83) of the sites designated as Primary sites by NPS. These sites were selected to document the condition of headwater streams with watershed areas of approximately 1.0 mi2. These sites were assessed using desktop methods and field reconnaissance. The final list of sites was modified as appropriate for approval by NPS. Forty-two (42) additional sites were proposed for assessment as Secondary sites following the assessment of Primary sites according to the SOW and study plan. These sites were selected to either provide additional data within Primary site watersheds or to expand coverage of the inventory within the park to target specific tributaries of interest. All inventoried sites were selected to meet the definition of Primary Headwater (PHW) streams as that term is defined in Ohio EPA headwater stream protocols. The identified locations were used to characterize the biological communities within the streams and to identify factors affecting the ecological integrity and water quality of the headwater streams within CUVA.
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Dudley, J. P., i S. V. Samsonov. Système de traitement automatisé du gouvernement canadien pour la détection des variations et l'analyse des déformations du sol à partir des données de radar à synthèse d'ouverture de RADARSAT-2 et de la mission de la Constellation RADARSAT : description et guide de l'utilisateur. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/329134.
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Remote sensing using Synthetic Aperture Radar (SAR) offers powerful methods for monitoring ground deformation from both natural and anthropogenic sources. Advanced analysis techniques such as Differential Interferometric Synthetic Aperture Radar (DInSAR), change detection, and Speckle Offset Tracking (SPO) provide sensitive measures of ground movement. With both the RADARSAT-2 and RADARSAT Constellation Mission (RCM) SAR satellites, Canada has access to a significant catalogue of SAR data. To make use of this data, the Canada Centre for Mapping and Earth Observation (CCMEO) has developed an automated system for generating standard and advanced deformation products from SAR data using both DInSAR and SPO methods. This document provides a user guide for this automated processing system.
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Zanoni, Wladimir, i Ailin He. Citizenship and the Economic Assimilation of Canadian Immigrants. Inter-American Development Bank, marzec 2021. http://dx.doi.org/10.18235/0003117.
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In this paper, we examine whether acquiring citizenship improves the economic assimilation of Canadian migrants. We took advantage of a natural experiment made possible through changes in the Canadian Citizenship Act of 2014, which extended the physical presence requirement for citizenship from three to four years. Using quasi-experimental methods, we found that delaying citizenship eligibility by one year adversely affected Canadian residents' wages. Access to better jobs explains a citizenship premium of 11 percent in higher wages among naturalized migrants. Our estimates are robust to model specifications, differing sampling windows to form the treatment and comparison groups, and whether the estimator is a non-parametric rather than a parametric one. We discuss how our findings are relevant to the optimal design of naturalization policies regarding efficiency and equity.
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Ruisi-Besares, Pia, Matthias Sirch, Alyx Belisle, James Duncan, Josephine Robertson, Jennifer Pontius, Danielle Cook i Elissa Schuett. Technical Report on Assembling Indicators to Monitor Climate-Driven Change in Northeastern Forests. Forest Ecosystem Monitoring Cooperative, wrzesień 2021. http://dx.doi.org/10.18125/99o4tq.
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Forest ecosystems are experiencing the impacts of climate change in many forms, however, comprehensive monitoring efforts are not always available to identify changing baselines. In order to improve our understanding of the impacts of climate change on ecosystem processes, the FEMC developed the Forest Impacts of Climate Change: Monitoring Indicators tool (Version 1.0). The Forest Impacts of Climate Change: Monitoring Indicators tool was developed for use by researchers and professionals to be able to easily access protocols used to monitor high priority indicators of the impacts of climate change in New England and New York. The monitoring protocols provide information for landowners and managers to implement their own monitoring programs that will be comparable to other studies being conducted across the region. By centralizing information about this network of monitoring sites, more data will become available to the community to help discern how forest ecosystems are changing. This report describes the methods and implementation used to build this tool. To develop the Forest Impacts of Climate Change: Monitoring Indicators tool, FEMC formed a committee of partners to select indicators and provide guidance about the literature review and eventual tool. The committee identified four ecological categories as important for monitoring climate change in the Northeast: Wildlife, Forest Systems, Trees, and Aquatic Systems. FEMC identified who is currently conducting monitoring efforts, what monitoring protocols are available for replication, gaps in monitoring data, and how we can make data and monitoring information easily available so that land managers can have the most up-to -date information possible. The developed tool compiles over 350 studies across 24 different indicators of the impacts of climate change. Through a filterable webtool users can find these studies, as well as 168 replicable protocols to direct implementation. The tool helps to identify gaps in monitoring efforts and provides a platform for users to contribute to regionally cohesive datasets. Monitoring of indicators across systems is critical for tracking and understanding climate change impacts. The Forest Impacts of Climate Change: Monitoring Indicators tool, developed for use by researchers, professionals, and land managers across the region, lets users find methods and protocols for monitoring climate change impacts and see where these monitoring efforts are already being conducted in our region. In addition, you can quickly visualize where there are gaps in our monitoring. As contributors in the Cooperative region share more information about their own monitoring efforts, this will become available to the community through this tool, increasing our ability to track and identify change in our forested ecosystems.
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Shaheen, Susan, Elliot Shaheen, Adam Cohen, Jacquelyn Broader i Richard Davis. Managing the Curb: Understanding the Impacts of On-Demand Mobility on Public Transit, Micromobility, and Pedestrians. Mineta Transportation Institute, lipiec 2022. http://dx.doi.org/10.31979/mti.2022.1904.
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In recent years, innovative mobility and shifts in travel and consumption behavior are changing how people access and use the curb. Shared mobility—the shared use of a vehicle, bicycle, scooter, or other mode—coupled with outdoor dining, curbside pick-up, and robotic delivery are creating new needs related to the planning, management, and enforcement of curb access. This study examines curb planning and management from several angles, such as safety, social equity, and multimodal connections. This research employs a multi-method approach to identify the changing needs for curb space management and how to meet these needs through new planning and implementation policies and strategies. As part of this study, the authors conducted 23 interviews. Respondents were chosen to represent public, private, and non-profit sector perspectives. Additionally, the authors employed a survey of 1,033 curb users and 241 taxi, transportation network company (TNC), and public transportation drivers. The study finds that changes in mode choice and curbside use can result in a variety of impacts on access, social equity, congestion, device management, pick-up and drop-off, and goods delivery, to name a few. The curb also has the potential to be disrupted by emerging modes, such as robotic delivery vehicles (also known as personal delivery devices) and automated vehicles. As these emerging developments continue to impact the curb, it is becoming increasingly important for policymakers to have an appropriate framework for planning and managing curb space in urban areas.
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Wright, Louise, i Louise Crocker. PR-670-183826-R03 Extended Evaluation of LSM-Magnetostrictive Pipe Models. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), maj 2021. http://dx.doi.org/10.55274/r0012097.
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Integrity assessment of pipelines is vital to ensure that oil and gas pipes have adequate strength to prevent leaks and ruptures. Regular inspections are conducted to confirm safe operation conditions of pipelines. The industry's principal method for assessing pipelines is in-line inspection (ILI), involving the passing of a device along the inside of a pipe to assess the condition of the pipeline. ILI devices can be fitted with a number of sensors allowing various measurement parameters to be obtained simultaneously. Not all pipelines are suited to ILI for reasons such as small diameter, obstructions within the pipe, or insufficient access to deploy or retrieve the ILI tools. These pipelines are sometimes referred to as 'difficult to inspect'. Alternative methods for examining pipeline condition are required with a range of technologies collectively known as Large Standoff Magnetometry (LSM) offering a promising solution for detection of pipe defects from a distance, reducing the need for excavation. LSM utilizes coupling between defects and changes in the magnetic properties of the pipeline material as a method for evaluation of pipe walls to identify the location of areas that require repair or further monitoring. Trials of existing commercial instruments by the pipeline industry have shown sufficient promise to investigate these technologies further. However, the vendors have supplied limited information on the underpinning physics of both the materials being tested and the instrument technology, meaning that further study is required in order to build confidence in the technique. The purpose of the project is to establish the ability of LSM to detect corrosion in API 5L pipe grades B to X70. The aim of the modelling work has been to use quantitative physics-based modelling techniques to predict the performance of LSM as a defect detection technique in situations that cannot easily be recreated in a laboratory environment, after validating the modelling approach by comparing measurements made in the laboratory to model results.
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Finch, Graeme, i Stuart Harmon. PR-670-183826-R01 Assessment of Science Behind LSM for Pipeline Integrity. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), wrzesień 2020. http://dx.doi.org/10.55274/r0011803.
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Integrity assessment of pipelines is vital to ensure that oil and gas pipes have adequate strength to prevent leaks and ruptures. Regular inspections are conducted to confirm safe operation conditions of pipelines. The industry's principle method for assessing pipelines is in-line inspection (ILI), involving the passing of a device along the inside of a pipe to assess the condition of the pipeline. ILI devices can be fitted with a number of sensors allowing various measurement parameters to be obtained simultaneously. Not all pipelines are suited to ILI for reasons such as small diameter, obstructions within the pipe, or insufficient access to deploy or retrieve the ILI tools. These pipelines are sometimes referred to as 'difficult to inspect'. Alternative methods for examining pipeline condition are required, with a range of technologies collectively known as Large Standoff Magnetometry (LSM) offering a promising solution for detection of pipe defects from a distance, reducing the need for excavation. LSM utilises the coupling between defects and changes in the magnetic properties of the pipeline material as a method for evaluation of pipe walls to identify the location of areas that require repair or further monitoring. Trials of existing commercial instruments by the pipeline industry have shown sufficient promise to investigate the technologies further. However, vendors have supplied limited information on the underpinning physics of both the materials being tested and the instrument technology. The purpose of the project is to establish the ability of LSM to detect corrosion in API 5L pipe grades B to X70. The aim of Work Package 02 is to review the physics of the agreed pipeline defects and fluxgate type magnetic sensors. The properties of pipeline-specific soft magnetic materials are investigated to understand corrosion, how this alters the material properties and how this can affect the associated magnetic fields surrounding the material. The physics of fluxgate magnetometers and gradiometers are also reviewed to assess the ability of LSM to detect these two features.
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Lehmann, Johannes, i Nina Dwerlkotte. Carbon Farming and Its Impact on Agricultural Technology. SAE International, listopad 2023. http://dx.doi.org/10.4271/epr2023026.
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<div class="section abstract"><div class="htmlview paragraph">The agricultural sector is responsible for a large share of anthropogenic greenhouse gases. At the same time, methods such as targeted land use change can reduce emissions from landscape elements and sequester carbon from the atmosphere in the soil. This process, also known as carbon farming, has not been uniformly defined, and faces challenges regarding establishing new requirments for agricultural vehicles and technology, creating profitable business models (that preclude “greenwashing”), and developing governmental frameworks and industry acceptance.</div><div class="htmlview paragraph"><b>Carbon Farming and Its Impact on Agricultural Technology</b> discusses the large development gap for carbon farming methods, especially with regard to agricultural technology. In addition to the new hardware requirements arising from land use change, there is also a need for the further development of software. The establishment of suitable interfaces and solutions that are interoperable with existing technologies is also crucial at this point. This report clearly shows that more funding for research and development is needed today so that appropriate standards can be set and carbon farming can contribute to climate protection in the future.</div><div class="htmlview paragraph"><a href="https://www.sae.org/publications/edge-research-reports" target="_blank">Click here to access the full SAE EDGE</a><sup>TM</sup><a href="https://www.sae.org/publications/edge-research-reports" target="_blank"> Research Report portfolio.</a></div></div>