In a passive radio-frequency identification (RFID) system the reader communicates with the tags using the EPC Global UHF Class 1 Generation 2 (EPC Gen-2) protocol with dynamic framed slotted ALOHA. Due to the unique challenges presented by a low-power, random link, the channel efficiency of even the most modern passive RFID system is less than 40%. Hence, a variety of methods have been proposed to estimate the number of tags in the environment and set the optimal frame size. Some of the algorithms in the literature even claim system efficiency beyond 90%. However, these algorithms require fundamental changes to the underlying protocol framework which makes them ineligible to be used with the current hardware running on the EPC Gen-2 platform and this infrastructure change of the existing industry will cost billions of dollars. Though numerous types of tag estimation algorithms have been proposed in the literature, none had their performance analyzed thoroughly when incorporated with the industry standard EPC Gen-2. In this study, we focus on some of the algorithms which can be utilized on today’s current hardware with minimal modifications. EPC Gen-2 already provides a dynamic platform in adjusting frame sizes based on subsequent knowledge of collision slots in a given frame. We choose some of the popular probabilistic tag estimation algorithms in the literature such as Dynamic Frame Slotted ALOHA (DFSA) – I, and DFSA – II, and rule based algorithms such as two conditional tag estimation (2CTE) method and incorporate them with EPC Gen-2 using different strategies to see if they can significantly improve channel efficiency and dynamicity. The results from each algorithm are also evaluated and compared with the performance of pure EPC Gen-2. It is important to note that while integrating these algorithms with EPC Gen-2 to modify the frame size, the protocol is not altered in any substantial way. We also kept the maximum system efficiency for any MAC layer protocol using DFSA as the upper bound to have an impartial comparison between the algorithms. Finally, we present a novel and comprehensive analysis of the probabilistic tag estimation algorithms (DFSA-I & DFSA-II) in terms of their statistically significant correlations between channel efficiency, algorithm estimation accuracy and algorithm utilization rate as the existing literature only look at channel efficiency with no auxiliary analysis. In this study, we use a scalable and flexible simulation framework and created a light-weight, verifiable Gen-2 simulation tool to measure these performance parameters as it is very difficult, if not impossible, to calculate system performance analytically. This framework can easily be used to test and compare more algorithms in the literature with Gen-2 and other DFSA based approaches.

Abstract The current Internet infrastructure must be architected to handle future media-rich, and content rich applications. The success of applications such as video-on-demand, multicast and content distribution depends on Quality of Service and bandwidth guarantees. Over the years, the Internet has encompassed many changes in traffic profiles and applications, in bandwidths and utilization, but the future Internet infrastructure necessitates a very different architecture supporting Quality of Service (QoS). A satellite, distinguished by features such as global coverage, bandwidth flexibility, broadcast, multicast, and reliability, is an excellent candidate to provide broadband integrated Internet access. The aim of this thesis is to explore suitability of satellite technologies for broadband Internet services with significant emphasis on the question of defining, assessing, and developing QoS models for satellite ATM and IP broadband networks with and without onboard processing. For the satellite Internet, Transmission Control Protocol (TCP) performance is degraded due to long propagation delays, link errors, and bandwidth asymmetry. In this thesis, for satellite ATM, fundamental questions such as buffer requirements, TCP/ATM efficiency, fairness, and multiple access are addressed through extensive simulations in a quantitative way. Buffer designs for TCP over satellite ATM Unspecified Bit Rate (UBR) service are performed. A buffer size equal to half the round trip delay-bandwidth product of the TCP connections provides high efficiency for TCP over satellite UBR. An extensive TCP analysis via simulation study for various TCP mechanisms and end system policies show that for satellite environment end system policies are more important than switch drop policies in terms of efficiency and fairness for World Wide Web traffic. A bandwidth allocation scheme is proposed and analytical model for supporting voice and video service over a broadband satellite network is developed. The study results demonstrate that non-contiguous allocation can afford higher gain in uplink utilizations. In this thesis, for the first time, Integrated Services and Differentiated Services based QoS architectures for broadband satellite IP networks are proposed and analyzed. In multimedia applications where User Datagram Protocol (UDP) is used along with TCP, a fair excess bandwidth allocation is not possible because TCP is congestion sensitive whereas UDP is congestion insensitive. An extensive simulation model is developed to study the effect of precedence levels for reserved rate utilization and fairness with different buffer management policies. The simulation results indicate that three levels of precedence are required for better utilization. Multiprotocol Label Switching (MPLS) over Satellite network has been proposed and a simulation model developed to study the throughput performance impacts for TCP and UDP. The traffic engineering of MPLS facilitates efficient and reliable network design to optimize the utilization of network resources and enhance the network QoS. A novel Code Division Multiple Access based Spread ALOHA single code multiple access scheme for broadband satellite return channel is proposed as an alternative to Multifrequency-Time Division Multiple Access based Digital Video Broadcasting-Return Channel via Satellite protocol. It is shown through Monte Carlo simulations that throughput for Spread ALOHA One Long Code equivalent to packet length, is better than Spread ALOHA One Code in which spreading sequence repeats every symbol. The reduction of throughput due to multi-user interference for different number of users is shown. Further research on QoS architectures, performance models for TCP enhancements, interworking functions, interoperability, and standardization efforts is included.

Jag har beskrivit och diskuterat de möjligheter och utmaningar som fjärrundervisning har inneburit för mig och mina sångstudenter under Coronapandemin. Mitt syfte var att fånga studenternas uppfattningar om huruvida traditionellt platsbunden, gehörstraderad sångundervisning var utbytbar mot nätbaserad synkron undervisning. Jag ville veta hur och om undervisningsformen har påverkat studenternas motivation – lust att lära. Undersökningen bygger på studenternas egna reflektioner efter två fjärrbaserade kurser i folksång på plattformarna Zoom och Aloha. Resultatet visar att variation och musikaliskt fokus, flexibelt lärande, enskild handledning och feedback bidrog både till lust att lära och motiverade till självstudier. / Högskolepedagogisk kurs 2 på KMH.

No / This paper is not a survey related to generic wireless sensor networks (WSNs), which have been largely treated in a number of survey papers addressing more focused issues; rather, it specifically addresses architectural aspects related to WSNs in some way connected with a satellite link, a topic that presents challenging interworking aspects. The main objective is to provide an overview of the potential role of a satellite segment in future WSNs. In this perspective, requirements of the most meaningful WSN applications have been drawn and matched to characteristics of various satellite/space systems in order to identify suitable integrated configurations. Copyright (c) 2012 John Wiley & Sons, Ltd.

Le but de cette thèse est d'étudier la mise en œuvre de services de type Internet of Thing (IoT) ou Machine to Machine (M2M) par satellite. Ce type de système pose une double problématique: d'une part au niveau couche physique : les contraintes liées au terminal (limité en puissance, énergie, taille d'antenne), au canal (potentiellement avec masquage et multitrajet) et au segment spatial impliquent la mise en œuvre de différentes techniques (entrelacement, suppression d'interférents, ...) permettant d'assurer le bilan de liaison adéquat pour le service. D'autre part, le besoin d'offrir un accès à la ressource à un grand nombre de terminaux demandant un débit faible implique l'utilisation de techniques d'accès à contention optimisées, ainsi que la prise en compte au niveau accès des problématiques d'économie d'énergie. Cette couche accès doit également être en mesure de s'interfacer avec des architectures réseaux plus vastes. On peut citer par exemple les architectures Internet afin de supporter des services IP pour l'IoT, avec des notions de services intermittents, telles qu'on les retrouve dans les réseaux DTN, ou bien les architectures 4G/5G pour la mise en œuvre de services mobiles. Cette thèse va investiguer deux approches systèmes innovantes ainsi que différentes techniques aussi bien couche physique que couche accès (potentiellement couplée) permettant leur mise en œuvre. Le premier scénario système consiste à l'utilisation d'un terminal satellite relais très bas débit (contrairement au cas classique traité dans la littérature reposant sur des terminaux broadband), s'interfaçant avec des capteurs en technologie accès terrestres. Des techniques innovantes de gestion des ressources et d'économie d'énergie au travers d'une couche accès dédiée (non DVB) pourraient permettre de supporter le nombre très important de terminaux dans ce type de système. Le second scénario repose sur une communication directe avec des capteurs/objets via une constellation satellite. Cette approche pose le problème de l'efficacité de la forme d'onde pour des services extrêmement sporadique et de la fiabilisation de la communication. Il existe de nombreux travaux coté DLR sur ce type de forme d'onde avec notamment la définition de S-MIM. Néanmoins, cette solution semble complexe et de nombreuses optimisations pourraient être apportées. Coté accès, E-SSA (communication asynchrone à spectre étalé avec SIC) défini par l'ESA est également une piste de travail intéressante même si sa mise en œuvre au niveau système et sa complexité doivent être consolidées. / The aim of this thesis is to study the implementation of Internet-based services of Thing (IoT) and Machine to Machine (M2M) through a satellite link. This type of system have to deal with two issues: first the physical layer level: terminal related constraints (limited in power, energy, and antenna size), channel (potentially with masking and multipath) and the space segment involve the implementation of different techniques (interleaving, interference cancellation,) to ensure proper link budget allowing the communication. On the other hand , the need to provide access to the resource to a large number of terminals requiring low throughput involves the use of optimized contention access techniques , as well as taking into account the level of access issues energy saving. The access layer should also be able to interface with larger networks architectures. Internet architectures for example include supporting IP services for Iota, with sporadic services, such as the ones found in the DTN networks, or 4G architectures / 5G for the implementation of mobile services. This thesis will investigate two innovative approaches and different techniques as well as physical layer access layer (potentially coupled) to their implementation. The first scenario involves the use of a very low throughput satellite relay terminal (unlike in the conventional case found in the literature based on broadband terminals), interfacing with terrestrial access technology sensors. Innovative resource management and energy saving techniques through a dedicated access layer (not DVB) could absorb the large number of terminals in this type of architecture. The second scenario is based on direct communication with sensors / objects via satellite constellation. This approach raises the question of the efficiency of the waveform for extremely sporadic services and the reliability of communication. DLR works on this type of waveform including the definition of S -MIM. However, this solution seems to be complex and many optimizations can be made. From the access layer point of view, E -SSA (asynchronous spread spectrum communication with SIC) defined by the ESA is also interesting even if its implementation to the system and its complexity level should be consolidated.

No description available.

No description available.

In the context of an increasing production of industrial toxic substances (TIC; Toxic Industrial Compound), the risk of accidental release of hazardous substances is growing in spite of the gradual implementation of safer technological processes and safety improvement measures. To mitigate the consequences of chemical accidents or to prepare preventive protective measures before the accident, it is necessary to know or at least estimate the course of accidents. In particular, it applies to the range of traumatic events and fatal accidents. One of the tools that can express the impact of accidents is modelling programs. This diploma thesis presents a comparison of outputs from two special types of software ? a foreign program the ALOHA and the TerEx developed in the Czech Republic. The purpose of the thesis was to indicate theoretical aspects related to gaseous toxic substances diffusion in the ground atmospheric layer and to describe modelling of their ill effects range. To achieve this objective, scientific literature and consultation with experts were used. The practical section of the thesis aimed at determining to what extent the results of both programs differ when initial conditions were identical. To achieve this goal, the intercomparison of outputs (e.g. hurtful concentration range) of the two programs that provided results for the same input data sets (type and quantity of hazardous substances, environmental temperature, wind speed, degree of cloud cover, weather stability class, type of ground surface) was used. After the assessment of the comparison it is possible to generalize the results stating that the software ALOHA compared to the TerEx is more conservative, which means that the ALOHA software provides longer anticipated ranges of danger. Therefore, it depends on the user (the person responsible ? crisis manager, intervention commander, mayor of the village), which approach they select or recommend ? to prepare a greater or a smaller area for a possible accident (to ensure public awareness, to implement technical measures to mitigate the impact of that accident, to assess the amount of financial resources, etc.). As a subsequent step it would be appropriate to verify the theoretical results experimentally, by field testing, which would be conducted under the same meteorological conditions under which the modelling was made by the mentioned programs. This would thus confirm the legitimacy of the special software use for the purpose of estimating the range of negative effects of chemical accidents.

<p>  </p> <p>Many viewers—especially those from the continental United States—have praised Disney for such recent actions as casting Pacific Islanders in the animated feature film <em>Moana</em> (2016) and assembling a group of cultural advisors (named the Oceanic Story Trust) to guide the filmmakers’ creative decisions. However, my project contends that Disney continues to play a significant role in the maintenance of settler colonialism in Hawai‘i, despite these seemingly progressive attempts at challenging Hollywood’s whitewashing. In this project, I argue that Disney creates and replicates the structures of settler colonialism in Hawai‘i through a mechanism that I term <em>imagineered imperial tourism</em>. In my formulation, imagineered imperial tourism involves commodifying historical narratives of colonization to serve the Disney brand by “innocently” repackaging them for the purpose of settler tourist consumption. To signal a Disney-specific branding and reproduction of settler colonial tropes and ideologies, I use the term “imagineered”—a play on Disney’s trademarked term <em>Imagineering</em>, which names the work of the creative team tasked with engineering the company’s most innovative devices, built environments, and technologies.</p> <p>Through a sustained study of Disney’s relevant productions—from the feature films <em>Lilo & Stitch</em> (2002) and <em>Moana</em> to its built environments at the Walt Disney World Resort in Orlando, FL, and Aulani, A Disney Resort & Spa in Ko Olina, Hawai‘i—I suggest that over time, Disney has normalized a version of Native Hawaiian people and history in US popular culture that reproduces common settler colonial discourses which have structured popular perceptions of Hawai‘i. The company’s almost century-long history of media production has cemented these discourses into a set of public pedagogies that have been reproduced across generations. Disney’s Pacific Island-themed productions and attractions are rife with tropes of native primitivism and imperialist nostalgia. They also reveal the primacy of the discursive framework of hegemonic multiculturalism vis-à-vis the commodified “spirit of aloha,” a sentiment which is superficially rooted in Native Hawaiian epistemologies and branded as a key selling point by the tourism industry. Furthermore, Disney has actively colonized Hawaiian lands since 2007, capitalizing on the Islands’ exploitative tourist industry while also obscuring longstanding battles over land ownership and denying Native Hawaiians sovereignty over their stolen lands. Ultimately, I suggest that Disney’s ostensibly “innocent” repackaging contributes to the violent erasure of Native Hawaiian history in popular culture. </p>

This thesis presents an evaluation of the performance, in terms of throughput and latency, of two Media Access Control (MAC) mechanisms in Underwater Acoustic Networks (UANs), using a model designed in the COTS simulation tool OPNET 10.5. The carrier sense multiple access with collision avoidance is the predominant approach for implementing the MAC mechanism in UANs. However, the underwater acoustic environment is characterized by extreme propagation delays and limited bandwidth, which suggests that an Aloha-like scheme may merit consideration. The performance of these two schemes was compared with respect to two topologies: tree and grid. The results showed that an Aloha-like scheme that does not segment messages outperforms the contention-based scheme under all load conditions, in terms of both throughput and latency, for the two topologies. This thesis is the first to establish that Aloha-like MAC mechanisms can be more than a limited alternative for lightly loaded networks; more specifically, they can be the preferred choice for an environment with large propagation delays. / Lieutenant Commander, Portuguese Navy