147,317 research outputs found
Toward Authentication Mechanisms for Wi-Fi Mesh Networks
No full text>Magister Scientiae - MScWi-Fi authentication mechanisms include central authentication, dynamic and distributed authentication and some encryption methods. Most of the existing authentication methods were designed for single-hop networks, as opposed to multihop Wi-Fi mesh networks. This research endeavors to characterize and compare existing Wi-Fi authentication mechanisms to find the best secure connection mechanism associated with Wi-Fi mesh network fragmentation and distributed authentication. The methodology is experimental and empirical, based on actual network testing. This thesis characterizes five different types of Wrt54gl firmware, three types of Wi-Fi routing protocols, and besides the eight Wi-Fi mesh network authentication protocols related to this research, it also characterizes and compares 14 existing authentication protocols. Most existing authentication protocols are not applicable to Wi-Fi mesh networks since they are based on Layer 2 of the OSI model and are not designed for Wi-Fi mesh networks. We propose using TincVPN which provides distributed authentication, fragmentation, and can provide secure connections for backbone Wi-Fi mesh networks
Toward Authentication Mechanisms for Wi-Fi Mesh Networks
No full text>Magister Scientiae - MScWi-Fi authentication mechanisms include central authentication, dynamic and distributed authentication and some encryption methods. Most of the existing authentication methods were designed for single-hop networks, as opposed to multihop Wi-Fi mesh networks. This research endeavors to characterize and compare existing Wi-Fi authentication mechanisms to find the best secure connection mechanism associated with Wi-Fi mesh network fragmentation and distributed authentication. The methodology is experimental and empirical, based on actual network testing. This thesis characterizes five different types of Wrt54gl firmware, three types of Wi-Fi routing protocols, and besides the eight Wi-Fi mesh network authentication protocols related to this research, it also characterizes and compares 14 existing authentication protocols. Most existing authentication protocols are not applicable to Wi-Fi mesh networks since they are based on Layer 2 of the OSI model and are not designed for Wi-Fi mesh networks. We propose using TincVPN which provides distributed authentication, fragmentation, and can provide secure connections for backbone Wi-Fi mesh networks
Win Farm Safety Prize (Echo Hill WI - Reflector Tape)
No full textNewspaper Article - 'Win Safety Prize' (Echo Hill WI - Reflector Tape, March 12, 1960)AWI CollectionM- URDA. Y, MARCH 12, 1960
WIN SAFETY PRIZE — Mrs. W. B. H. Squair of Legal,
seated right, is a member of Echo Hill Women's Institute, a group
which Thursday received news that it had won the $ 500 second
prize in the annual Carol Lane safety awards. Mrs. Squair,
constituency convener for the WI in her area when the safety
project was undertaken, is in Edmonton this week and attended
a WI conference at the Corona Hotel Wednesday and Thursday.
She is pictured with Mrs. Harold Lefsrud of Viking, standing,
provincial health convener, and Mrs. G. D. Spargo of Alcomdale,
present constituency convener for mid- Pembina. To win the
safety prize, the 17 members of Echo Hill WI bought S180 worth
of red reflector tape and themeselves applied it to five farm
machines on each of 73 farms in a 40- square miles area. The
project was designed to prevent accidents involving farm machines
being moved on the roads from field to field. Left- over reflector
tape was sold to farmers in neighboring areas, who became
interested in the safety measure after hearing of the WI project.
Mrs. Lloyd McMillan is president of the branch, and the safety
project was her idea, Mrs. Squair says. Money for the project
had been raised at chicken suppers, bazaars, card parties and
sales of home baking. — Photo by Goertz Studios
Awareness and use of Wi-Fi infrastructure in student’s community: a case study Pondicherry University on campus students
No full textThe new technology that is making an inroad to the teaching and research domain can be a boon to the teaching learning community. Wi-Fi for instance has a tremendous contribution in the way students connect and access information. This paper looks into the level of Wi-Fi awareness and the problems faced by the student community in the campus and their level of competence. The study involved a questionnaire survey of students residing in the campus. The parameter for the research was ICT literacy, Wi-Fi awareness, connectivity problem, usage, gadget preference. The outcome of the finding suggest that although the calls for radical transformation in educational approaches may be legitimate it would be misleading to ground the arguments for such change solely in students’ opinion and that the infrastructure indeed shows a great deal of benefit to the student in the way they connect online.The finding also identified the problems in WiFi hotspots and coverage
Comparative Survey Of Studies Of Coexisting Wi-Fi And LTE Networks
No full textThe recent global increase in mobile data traffic has service providers examining new ways to meet this traffic demand. While the licensed spectrum is the main way of providing data services, the available spectrum in the licensed band is limited and expensive. The Unlicensed band, on the other hand, has a vast amount of available spectrum (> 400 MHz), together in the 2.4 and 5 GHz bands. Based on the link performance, medium access control, and advanced scheduling algorithms, LTE is an efficient way of leveraging the unlicensed spectrum by service providers. Depending on the regulation requirements, LTE in the unlicensed band can be deployed as LTE-U (unlicensed) or as LAA (licensed assisted access). However, deploying LTE in the Unlicensed band interferes with the existing technologies that use the same frequency band like Wi-Fi. It is unclear to what extent this interference impacts both legacy technologies and LTE-U/LAA. This thesis surveys the research that has been done until now in this field and compares the evaluations of the performance of LTE and Wi-Fi and the issues that arise when they coexist
Wi-Fi RTT Ranging Performance Characterization and Positioning System Design
No full textThe aim of this research is to implement a precise Wi-Fi indoor positioning system (IPS) or localization system based upon the IEEE 802.11mc Fine-Timing Measurement (FTM) scheme also known as the Wi-Fi Round Trip Time (RTT) ranging technique, where ranging refers to a sub-process of positioning that determines the distance between a transmitter and receiver. Our system and its algorithms were implemented using a COTS (Commercial-Off-The-Shelf) smartphone and Wi-Fi access points. Experiments were conducted in several real-life indoor environments. This paper presents the detailed Wi-Fi RTT ranging performance of these devices in different system configurations and characterizes the systematic biases and noise model to improve the ranging accuracy. A novel three-step-positioning method is proposed to overcome the issues of no or multiple intersect points in trilateration due to ranging errors to improve positioning accuracy. This consists of first, systematic bias determination and removal; second, Clustering-based Trilateration (CbT) supported by Weighted Concentric Circle Generation (WCCG), namely CbT & WCCG; third, positioning result and trajectory optimization using a Kalman filter. As a result, the evaluation experiments gave a position accuracy of ±1.2 m in 2D static positioning and ±1.3 m for dynamic motion tracking. Also, our CbT & WCCG method demonstrate good tolerance against ranging errors. Moreover, the computational cost and positioning accuracy of CbT & WCCG methods are compared with Least Square (LS) and Recursive Least Square (RLS) methods and the accuracy standard deviation of our algorithm is the closest to the Cramer–Rao bound (CRB)
Pushing the envelope of Wi-Fi networks using distributed multi-user MIMO
No full textThis dissertation presents a distributed multi-user MIMO Wi-Fi architecture referred to as D-MIMO that boosts network throughput performance compared to state-of-the-art Wi-Fi access points with co-located antennas. D-MIMO, at a high level, is a technique by which a set of wireless access points are synchronized and grouped together to jointly serve multiple users simultaneously. The cooperation between the access points reduces intra-network interference and hence improves spatial reuse of channels. We study D-MIMO Wi-Fi networks in four broad sections: (i) by prescribing lightweight and effective solutions to the problems of channel access and multi-user MIMO user selection in D-MIMO Wi-Fi, (ii) through experimental evaluations of the proposed solutions on a D-MIMO Wi-Fi network implemented in an indoor testbed using software defined radio platforms, (iii) by constructing a deep reinforcement learning framework to address dynamic resource management in D-MIMO Wi-Fi networks, and (iv) by investigating the benefits that the D-MIMO architecture brings to dense Wi-Fi networks operating in mmWave (60 GHz) bands. These components form the original contributions of this dissertation to knowledge.
Designing a D-MIMO Wi-Fi network invites us to revisit fundamental Wi-Fi concepts such as carrier sensing multiple access that governs medium/channel access among Wi-Fi access points. We propose a medium access protocol for D-MIMO that assimilates channel sensing observations from different access points to resolve channel contention among D-MIMO groups. We also propose a novel way of using channel reciprocity and the network topology to select downlink multi-user (MU) MIMO recipients without requesting any form of channel state information feedback from the users during the selection phase. The proposed solutions are lightweight, do not require modifications at the user equipment, and hence will work with legacy 802.11ac devices. We compare the performance of the D-MIMO configuration to that of baseline dense Wi-Fi deployments (access points with co-located antennas), operating in 5 GHz bands, through extensive network simulations. We observe an improvement of 3.5x in median and 191% in mean user throughput, as well as a reduction of 61% in channel access delay with D-MIMO.
Next, we present an implementation of a distributed MIMO Wi-Fi group---using software defined radio platforms---in an indoor experimental testbed. The implemented setup consists of four two-antenna Wi-Fi access points (synchronized in time and phase using a GPS-disciplined clock reference system) and twenty two-antenna users, and is compliant with the 802.11ac very high throughput framework. We use this setup to serve as a proof-of-concept of the proposed lightweight MU-MIMO user selection algorithm. Through extensive experimental evaluations, we demonstrate that the proposed algorithm outperforms a simple random user selection strategy by achieving an improvement of up to 60% in median and 43% in mean group throughput performance. Furthermore, the proposed user selection algorithm performs close to optimality---the difference in performance between the proposed user selection algorithm and optimal user selection is a mere 13%.
As the third installment of this dissertation, we address two dynamic resource management problems germane to D-MIMO Wi-Fi networks: (i) channel assignment of D-MIMO groups, and (ii) deciding how to cluster access points to form D-MIMO groups, in order to maximize user throughput performance. These problems are known to be NP-Hard for which only heuristic solutions exist in literature and we explore the potential of harnessing principles from deep reinforcement learning (DRL) to address these challenges. We construct a DRL framework through which a learning agent interacts with a D-MIMO Wi-Fi network, learns about the network environment, and successfully converges to policies that effectively address the aforementioned challenges. Through extensive simulations and on-line training based on D-MIMO Wi-Fi networks, we demonstrate the efficacy of DRL agents in achieving an improvement of 20% in user throughput performance compared to heuristic solutions, particularly when network conditions are dynamic. This work also showcases the effectiveness of DRL agents in meeting multiple network objectives simultaneously, for instance, maximizing throughput of users as well as fairness of throughput distribution among them.
In the final part of this dissertation, we consider dense Wi-Fi networks operating in mmWave (60 GHz) bands and use the D-MIMO architecture to improve user throughput performance in these networks compared to baseline arrangements. Rigorous network simulation results reveal an enhancement of 395% in average user throughput and a reduction of 75% in channel access delay with D-MIMO compared to baseline. We observe an interesting behavior wherein a user achieves very high modulation and coding scheme indices more number of times with the baseline configuration compared to D-MIMO, especially when the user is located close to an access point (AP). This behavior can be ascribed to two causes: i) a higher probability of line-of-sight of the short distance AP-user link (that favors baseline), and ii) a ramification of the use of zero-forcing precoding to cancel inter-user interference in D-MIMO. This observation motivates the design of future networks as amalgams of both baseline and D-MIMO arrangements.Ph.D.Includes bibliographical reference
Selección cognitiva del punto de acceso en redes WI-FI bajo restricciones de coexistencia
No full textEste trabajo enfrenta el problema del bajo rendimiento de un terminal Wi-Fi debido al método de selección del punto de acceso basado en el nivel de RSSI, con la introducción de la técnica de Spectrum Sensing en el proceso de Scanning en modo tal de crear una nueva métrica de asociación que no sólo considera el valor de RSSI sino también otros parámetros como la ocupación del canal y la interferencia debida a entidades Wi-Fi y no Wi-Fi que potencialmente operan en el mismo canal y al mismo tiempo. El estudio se realiza en lenguaje de programación OMNeT++ basado en C++, en conjunto con el paquete de simulación INET para OMNeT++, siguiendo las normativas del estándar para radio cognitiva IEEE 1900.6 y el estándar para redes Wi-Fi IEEE 802.11
Modular cosmology, thermal inflation, baryogenesis and a prediction for particle accelerators
No full textModular cosmology is plagued by overproduction of unwanted relics, gravitinos and especially moduli, at relatively low energy scales. Thermal inflation provides a compelling solution to this moduli problem, but invalidates most baryogenesis scenarios. We propose a simple model in which the MSSM plus neutrino mass term (LHu)(2) is supplemented by a minimal flaton sector to drive the thermal inflation, and make two crucial assumptions: the flaton vacuum expectation value generates the mu-term of the MSSM and m(L)(2) + m(Hu)(2) < 0. The second assumption is particularly interesting in that it violates a well known constraint, implying that there exists a nearby deep non-MSSM vacuum, and provides a clear signature of our model which can be tested at future particle accelerators. We show that our model leads to thermal inflation followed by Affleck-Dine leptogenensis along the LHu flat direction. A key feature of our leptogenesis scenario is that the HuHd flat direction is also induced to temporarily acquire a large value, playing a crucial role in the leptogenesis, as well as dynamically shielding the field configuration from the deep non-MSSM minimum, ensuring that the fields relax into our MSSM vacuum
Strömbaserade Klass D Effektförstärkare för 2.4GHz Wi-Fi
No full textModern wireless communication techniques employed in the Wi-Fi® protocol, such as orthogonal frequency-division multiplexing exhibit analogue signals with high peak-to-average power ratio. Therefore, power amplifiers for Wi-Fi suffer from low efficiency when operating in back-off mode, away from their maximum efficiency at peak power. In recent years, digital power amplifiers have been developed to replace their analogue equivalent, taking advantage of easier scaling and circumventing transition frequency issues. Since the digital power amplifier technology for Wi-Fi application is recent, it has not yet replaced robust analogue amplifiers in industrial context. This work proposes to investigate the feasibility and complexity to replace an analogue amplifier with its digital counterpart, with at least the same specification. Among several possible architectures, the reverse class D is chosen for its apparent simplicity. It achieves low power loss into transistors parasitics by operating in square-current mode instead of voltage mode, hence displaying a current-based RF-DAC behaviour. After elaborating the core design with simple efficiency enhancement techniques specific to reverse class D, the layout of the circuitry has been designed. Post-layout simulations have shown the reverse class D digital amplifier designed in CMOS 22nm achieves the required specification of 18dBm average output power with -28dB error vector magnitude in the 2.4GHz range. This basic architecture achieves 19% average drain efficiency, a small improvement over its analogue equivalent currently in use.Moderna trådlösa kommunikationstekniker som används i Wi-Fi®-protokollet, till exempel ortogonal frekvensdelningsmultiplexering, uppvisar analoga signaler med hög variation i amplitud. Därför har effektförstärkare för Wi-Fi låg verkningsgrad eftersom de arbetar i back-off-läge, långt ifrån sin maximala verkningsgrad vid hög uteffekt. Under de senaste åren har digitala effektförstärkare utvecklats för att byta ut deras analoga motsvarigheter. Eftersom digitala effektförstärkare för Wi-Fi är nya, har de ännu inte ersatt robusta analoga förstärkare i industriella sammanhang. I detta arbete föreslås en undersökning av genomförbarheten och komplexiteten i att ersätta en analog förstärkare med dess digitala motsvarighet, med åtminstone samma specifikation. Bland flera möjliga arkitekturer har den strömbaserade klass D valts på grund av sin enkelhet. Den uppnår låg effektförlust i transistorparasiter genom att arbeta i strömsläge istället för i spänningsläge, och fungerar som en strömbaserade RF-DAC. Efter att ha utarbetat kärnkonstruktionen med enkla tekniker för effektivitetsförbättring som är specifika för strömbaserade klass D har kretsens layout utformats. Simuleringar efter layouten har visat att den digitala förstärkaren i strömbaserade klass D som konstruerats i CMOS 22nm uppnår den nödvändiga specifikationen på 18 dBm genomsnittlig uteffekt med -28 dB felvektorstorlek vid 2,4 GHz. Denna arkitektur uppnår en genomsnittlig verkningsgrad på 19%, vilket är en liten förbättring jämfört med den analoga motsvarighet som för nuvarande används
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