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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Προσομοίωση φυσικού καναλιού κατερχόμενης ζεύξης (PDSCH) τεχνολογίας LTE

Μπουργάνη, Ευαγγελία 25 January 2012 (has links)
Τα Long Term Evolution (LTE) δίκτυα αποτελούν το πιο πρόσφατο πρότυπο στην τεχνολογία της ιεραρχίας των κινητών δικτύων (GSM/EDGE και UMTS/HSPA τεχνολογίες δικτύων). Οι απαιτήσεις για γρήγορη κινητή, ευρυζωνική πρόσβαση αυξάνει εκθετικά τις τελευταίες δεκαετίες και αναμένεται μεγαλύτερη ακόμα ανάπτυξη στο μέλλον, το οποίο απαιτεί απεριόριστες δυνατότητες σε υπηρεσίες και εφαρμογές διαδικτύου και ανάπτυξη σε συσκευές χειρός και κινητούς εξοπλισμούς. Για να επιτευχθούν αυτές οι απαιτήσεις για μεγάλους ρυθμούς δεδομένων στα κινητά δίκτυα, η International Telecommunication Union (ITU) όρισε τα αρχικά επίπεδα για την εξέλιξη των 4ης γενιάς δικτύων. Στα πλαίσια της διπλωματικής αυτής εργασίας στόχος είναι η υλοποίηση του φυσικού κατερχόμενου καναλιού Physical Downlink Shared Channel (PDSCH) του Long Term Evolution (LTE), ενός φυσικού καναλιού μεταφοράς δεδομένων (κάνει τη μετάδοση του DL-SCH καναλιού μεταφοράς). Στο πρώτο κεφάλαιο γίνεται μια αναδρομή στην εξέλιξη των δικτύων μέχρι να φτάσουμε στην σημερινή εποχή και το LTE. Στο δεύτερο κεφάλαιο περιγράφεται η αρχιτεκτονική που ακολουθεί το LTE. Στο τρίτο κεφάλαιο γίνεται αναφορά στις βασικές αρχές που διέπουν το OFDMA, της τεχνικής διαμόρφωσης που χρησιμοποιείται στην κατερχόμενη μετάδοση. Στο τέταρτο κεφάλαιο περιγράφονται οι MIMO τεχνολογίες, ενώ στο πέμπτο περιγράφεται αναλυτικά το συγκεκριμένο κανάλι και τέλος στο έκτο κεφάλαιο παρατίθενται τα αποτελέσματα και τα συμπεράσματα. / LTE Networks is the latest standard in mobile networks technologies hierarchy (GSM/EDGE and UMTS/HSPA). The requirements for fast mobile, broadband access increases exponentially during the last decades and even larger and even more significant development is expected in the future, which (future) is guided from the unlimited features in services and internet applications and from the development of mobile equipment and portable devices).To fulfill these demands for the large data rates in mobile networks , International Telecommunication Union (ITU) defined those primal levels for 4th Generation Networks evolution. The purpose of this thesis is the implementation of LTE’s Physical Downlink Shared Channel (PDSCH), a physical channel for data transfer . In the first chapter a recursion is made through the development of networks and up to current technologies and LTE. In chapter two LTE architectures are described. In chapter three, basic OFDMA principles are described , which is the modulation method used in downlink transmission. In chapter four MIMO technologies are described while in the fifth chapter the particular channel is described in depth. Finally in chapter six are laid down the results and conclusions.
2

Space-time-frequency methods for interference-limited communication systems

Nieman, Karl Frazier 20 January 2015 (has links)
Traditionally, noise in communication systems has been modeled as an additive, white Gaussian noise process with independent, identically distributed samples. Although this model accurately reflects thermal noise present in communication system electronics, it fails to capture the statistics of interference and other sources of noise, e.g. in unlicensed communication bands. Modern communication system designers must take into account interference and non-Gaussian noise to maximize efficiencies and capacities of current and future communication networks. In this work, I develop new multi-dimensional signal processing methods to improve performance of communication systems in three applications areas: (i) underwater acoustic, (ii) powerline, and (iii) multi-antenna cellular. In underwater acoustic communications, I address impairments caused by strong, time-varying and Doppler-spread reverberations (self-interference) using adaptive space-time signal processing methods. I apply these methods to array receivers with a large number of elements. In powerline communications, I address impairments caused by non-Gaussian noise arising from devices sharing the powerline. I develop and apply a cyclic adaptive modulation and coding scheme and a factor-graph-based impulsive noise mitigation method to improve signal quality and boost link throughput and robustness. In cellular communications, I develop a low-latency, high-throughput space-time-frequency processing framework used for large scale (up to 128 antenna) MIMO. This framework is used in the world's first 100-antenna MIMO system and processes up to 492 Gbps raw baseband samples in the uplink and downlink directions. My methods prove that multi-dimensional processing methods can be applied to increase communication system performance without sacrificing real-time requirements. / text
3

實體通路與虛擬通路下動態能力及智慧資本關係之個案研究 / The relation between dynamic capabilities and intellectual capital under physical channels and virtual channels: a case study

何怡陵, He, Yi Ling Unknown Date (has links)
由於網際網路的蓬勃發展,電子商務的興起為消費者帶來新的消費模式。為了拓展客群,企業開始選擇同時發展其實體通路及虛擬通路。隨著知識時代的來臨,若要兼採實體及虛擬通路之優點,企業必須整合並辨識出重要智慧資本,發展出不同的企業動態能力以因應快速變動的商業環境及不同的顧客群。 本研究採用個案研究法,以台灣知名化工原料公司為研究對象,探討企業在實體通路及虛擬通路下,所應發展之重要動態能力、需蓄積之重要智慧資本及相關管理議題。得出結論如下: 一、 個案公司實體通路之重要動態能力共有9項,且支持重要動態能力之智慧資本共有16項。 二、 個案公司設有相對應之管理制度來蓄積實體通路下之重要智慧資本。 三、 個案公司虛擬通路之重要動態能力共有11項,且支持重要動態能力之智慧資本共有30項。 四、 個案公司設有相對應之管理制度來蓄積虛擬通路下之重要智慧資本。 五、 個案公司實體通路及虛擬通路所重視之動態能力及支持動態能力之智慧資本有其相同與相異之處。 / With the rapid developing Internet environment in recent years, the rise of E-commerce has brought a new consumption model to the consumers. In order to expand the customer base, companies begin to develop their physical channels and virtual channels simultaneously. With the advent of knowledge-based era, in order to take the advantage of both physical and virtual channels, companies have to integrate and identify the important intellectual capitals, and develop different dynamic capabilities to cope with the dramatically-changing business environment and different customer base. This research adopts the case study method and selects a renowned raw materials company in the chemical industry in Taiwan as study subject. The purpose of this research is to study the importance of dynamic capabilities of the company, the importance of intellectual capitals and relevant management system under physical and virtual channels. The conclusions are as follows: 1. Under the case company’s physical channel, there are 9 important dynamic capabilities, and 16 intellectual capitals that support important dynamic capabilities. 2. The case company has a corresponding management system to accumulate important intellectual capitals under physical channels. 3. Under the case company’s virtual channel, there are 11 important dynamic capabilities, and 30 intellectual capitals that support important dynamic capabilities. 4. The case company has a corresponding management system to accumulate important intellectual capitals under virtual channels. 5. There are similarities and differences in important dynamic capabilities and intellectual capitals that can support dynamic capabilities between physical and virtual channels.
4

A Physical Channel Model And Analysis Of Nanoscale Neuro-spike Communication

Balevi, Eren 01 August 2010 (has links) (PDF)
Nanoscale communication is appealing domain in nanotechnology. There are many existing nanoscale communication methods. In addition to these, novel techniques can be derived depending on the naturally existing phenomena such as molecular communication. It uses molecules as an information carrier such as molecular motors, pheromones and neurotransmitters for neuro-spike communication. Among them, neuro-spike communication is a vastly unexplored area. The ultimate goal of this thesis is to accurately investigate it by obtaining a realistic physical channel model. This model can be exploited in different disciplines. Furthermore, the model can help designing novel artificial nanoscale communication paradigms. The modeled channel is analyzed regarding the error probability of detecting spikes depending on channel parameters. Moreover, channel delay is characterized and information theoretical analysis of packet release mechanism in the channel is performed. The modeled channel is extended to multi-input single output terminal. In this case, input neurons can simultaneously send information through the same synapse leading to interference. However, there is an interference repressing technique in these synapses called automatic gain control. It decreases the interference level observed on weaker signal. The first aim for this case is to define the interference channel at synapse having automatic gain control. The second aim is to analyze the achievable rate region of this channel. The analysis shows that gain control mechanism prevents the decrease in achievable rate region because of the weaker signal. Moreover, power, firing rate and number of stronger inputs do not affect the achievable rate region.
5

Den fysiska butikens värde i en förändrad detaljhandel : En kvalitativ studie av den svenska möbel- och heminredningsbranschen / The value of the physical store in a changing retail : A qualitative study of the Swedish furniture and home decoration industry

Nilsson, Terese, Nizic, Michaela, Wikingsson, Mathilda January 2017 (has links)
Digitaliseringens framfart har skapat en förändring i kundbeteende. Försäljning via e-handel har ökat alltmer vilket har setts som ett hot mot den fysiska butikens tillvaro. Andra antyder att digitalisering bör betraktas som en möjlighet för fysisk handel och komplement till en växande e-handel. Omnikanal är strategin där alla säljkanaler ses som en säljkanal för att ge en enhetlig varumärkesupplevelse. ”Fygital” strategi syftar till bryggan mellan den fysiska och digitala världen för att skapa upplevelserika butiksatmosfärer. Trots att e-handeln ligger i framkant med att möta och tillgodose konsumenters förändrade behov och förväntningar sker fortfarande största andelen inköp i svensk detaljhandel i fysisk butik. Likväl ställer digitaliseringens etablering nya krav på det fysiska butiksformatet. Syftet ämnar ur ett företagsperspektiv inom svenska möbel- och heminredningsbranschen skapa förståelse för hur upprätthållandet av den fysiska butiken kan vara värdeskapande åt varumärken, genom integrering mellan fysiska och digitala kanaler. Studien innehar en abduktiv forskningsansats, framförd med en hermeneutisk kunskapssyn och bygger på förståelse och tolkning. De teoretiska utgångspunkterna har formulerats i Värdediamanten vilken är en abstrakt redogörelse för hur kanalerna tillsammans kan vara värdeskapande och skapa större varumärkesupplevelser. Det empiriska materialet bottnar i kvalitativa, semistrukturerarde intervjuer med företagsrepresentanter från Rum21, Svenssons i Lammhult, Fröjd af Sverige och Royal Design. Studiens resultat visar att det finns en framtid för den fysiska kanalen i möbel- och heminredningbranschen eftersom sortimentet som tillhandahålls inbegriper sensoriska behov. Butiksformatet har ett stort marknadsföringsvärde men är i förändring. Mycket talar för mindre ytor med större fokus på service och butiksatmosfär. Digitala medel kan vara fördelaktiga även för fysisk kanal genom att visa upp sortiment, förenkla köpprocessen och öka tillgänglighet för interaktion mellan konsument och varumärken. Slutsatsen är att handelsföretag med fördel kan arbeta med en fygital kanal, hur det kan enhetliggöra, erbjuda större upplevelser och således vara värdeskapande för varumärken. / The digitalization has influenced a change in consumer behavior. The e-commerce has increased and the digitalization has been seen as a threat to the existence of physical stores. Others have thought it should be considered an opportunity for physical stores and use it as a complement to e-commerce. Within retail, omnichannel is a strategy for creating a unified message for consumers across all channels. ”Phygital” strategy is the mixture of the physical and digital world within the physical shopping environment to create memorable experiences. Although e-commerce is at the forefront in meeting consumers’ changing needs and expectations, most of the purchases in Swedish retail are still made in-store. Nevertheless, the establishment of digitalization requires other demands on the physical store. The study aims to create a comprehension from a business perspective within the Swedish furniture and home decoration industry, of how the physical store can create brand value through the integration of physical and digital channels. The study has an abductive approach conducted within the hermeneutical perception of knowledge and is based on understanding and interpreting. Based on theory, an abstract figure called ”The Diamond of Value” have been formulated, which describes how the physical and digital channels can contribute to greater brand experiences together and thus create value. The empirical material were collected through qualitative, semi-structured interviews with representatives from the Swedish brands Rum21, Svenssons i Lammhult, Fröjd af Sverige and Royal Design. The study shows that there is a future for the physical channel within the furniture and home decoration industry, as the range of products provided includes sensory needs. The physical store has a marketing value but the format is changing with smaller retail spaces with greater focus on service and physical environment. Digital resources can be beneficial even for physical channels by displaying assortment, simplifying the customer’s buying process and increasing accessibility for consumer and brand interaction. The conclusion is that retail companies can benefit from a phygital channel, it can unify, offer greater experiences and therefore create greater value for brands.

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