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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.
341

Call admission control in cloud radio access networks

Sigwele, Tshiamo, Pillai, Prashant, Hu, Yim Fun January 2014 (has links)
No / Over the past decade, wireless communications has experienced tremendous growth, and this growth is likely to multiply in the near future. The proliferation of mobile users and an ever increasing demand for multimedia services has resulted in greater capacity requirements. Radio frequency spectrum is scarce and cannot meet this ever increasing demand and the required Quality of Service (QoS) will no longer be achieved if efficient Radio Resource Management (RRM) solutions are not found. Conventional Radio Access Networks (RAN) have standalone Base Stations (BS) with capacity preconfigured for peak loads. These RANs have high call blocking and dropping rates since BSs resources cannot be shared. Cloud based RANs (C-RAN) have been proposed as a cost and energy efficient way of meeting high capacity demand of future wireless access networks by consolidating BSs to the cloud. Instead of relying on rejection of new call requests due to limited BS resources, C-RAN takes benefit of the cloud elasticity, which allows dynamic provisioning of cloud BS resources. This paper presents a novel C-RAN Call Admission Control (C-RAN CAC) to ensure Grade of Service (GoS) by improving blocking probability and improvement of call waiting times. Call blocking probability, call average waiting time and system utilization are used to evaluate the performance of the proposed CAC algorithm.
342

MIMO Antenna System for Modern 5G Handheld Devices with Healthcare and High Rate Delivery

Kiani, S.H., Altaf, A., Anjum, M.R., Afridi, S., Arain, Z.A., Anwar, S., Khan, S., Alibakhshikenari, M., Lalbakhsh, A., Khan, M.A., Abd-Alhameed, Raed, Limiti, E. 02 November 2021 (has links)
Yes / In this work, a new prototype of the eight-element MIMO antenna system for 5G communications, internet of things, and networks has been proposed. This system is based on an H-shaped monopole antenna system that offers 200 MHz bandwidth ranges between 3.4-3.6GHz, and the isolation between any two elements is well below -12dB without using any decoupling structure. The proposed system is designed on a commercially available 0.8mm-thick FR4 substrate. One side of the chassis is used to place the radiating elements, while the copper from the other side is being removed to avoid short-circuiting with other components and devices. This also enables space for other systems, sub-systems, and components. A prototype is fabricated and excellent agreement is observed between the experimental and the computed results. It was found that ECC is 0.2 for any two radiating elements which is consistent with the desirable standards, and channel capacity is 38 bps/Hz which is 2.9 times higher than 4x4 MIMO configuration. In addition, single hand mode and dual hand mode analysis are conducted to understand the operation of the system under such operations and to identify losses and/or changes in the key performance parameters. Based on the results, the proposed antenna system will find its applications in modern 5G handheld devices and internet of things with healthcare and high rate delivery. Besides that, its design simplicity will make it applicable for mass production to be used in industrial demands.
343

Novel localised quality of service routing algorithms. Performance evaluation of some new localised quality of service routing algorithms based on bandwidth and delay as the metrics for candidate path selection.

Alghamdi, Turki A. January 2010 (has links)
The growing demand on the variety of internet applications requires management of large scale networks by efficient Quality of Service (QoS) routing, which considerably contributes to the QoS architecture. The biggest contemporary drawback in the maintenance and distribution of the global state is the increase in communication overheads. Unbalancing in the network, due to the frequent use of the links assigned to the shortest path retaining most of the network loads is regarded as a major problem for best effort service. Localised QoS routing, where the source nodes use statistics collected locally, is already described in contemporary sources as more advantageous. Scalability, however, is still one of the main concerns of existing localised QoS routing algorithms. The main aim of this thesis is to present and validate new localised algorithms in order to develop the scalability of QoS routing. Existing localised routing, Credit Based Routing (CBR) and Proportional Sticky Routing (PSR), use the blocking probability as a factor in selecting the routing paths and work with either credit or flow proportion respectively, which makes impossible having up-to-date information. Therefore our proposed Highest Minimum Bandwidth (HMB) and Highest Average Bottleneck Bandwidth History (HABBH) algorithms utilise bandwidth as the direct QoS criterion to select routing paths. We introduce an Integrated Delay Based Routing and Admission Control mechanism. Using this technique Minimum Total Delay (MTD), Low Fraction Failure (LFF) and Low Path Failure (LPF) were compared against the global QoS routing scheme, Dijkstra, and localised High Path Credit (HPC) scheme and showed superior performance. The simulation with the non-uniformly distributed traffic reduced blocking probability of the proposed algorithms. Therefore, we advocate the algorithms presented in the thesis, as a scalable approach to control large networks. We strongly suggest that bandwidth and mean delay are feasible QoS constraints to select optimal paths by locally collected information. We have demonstrated that a few good candidate paths can be selected to balance the load in the network and minimise communication overhead by applying the disjoint paths method, recalculation of candidate paths set and dynamic paths selection method. Thus, localised QoS routing can be used as a load balancing tool in order to improve the network resource utilization. A delay and bandwidth combination is one of the future prospects of our work, and the positive results presented in the thesis suggest that further development of a distributed approach in candidate paths selection may enhance the proposed localised algorithms. / Umm AlQura University in Mecca
344

Broadening of Bragg Reflection of Polymer Stabilized Cholesteric Liquid Crystals with Small Cell Gap Induced by Low DC Voltage

Chen, Dengcheng 22 November 2021 (has links)
No description available.
345

An Evaluation of Ethernet as Data Transport System in Avionics

Doverfelt, Rickard January 2020 (has links)
ÅF Digital Solutions AB are looking to replace their current legacy system for audio transmissions within aircrafts with a new system based on Ethernet. They also want the system to be as closely matching the current Audio Integration System as possible as well as preferably using commercial off the shelf components. The issue evaluated in this thesis is whether it is feasible to port the legacy protocol over to an Ethernet based solution with as few modifications as possible, what performance requirements are present on the Ethernet solution as well as what remaining capacity is available in the network. Furthermore is ÅF Digital Solutions AB interested in what avionics related Ethernet based protocols and standards are already present on the market.The work is conducted in two tracks - one track of experimental measurements and statistical analysis of the latency present in the proposed solutions and one track with a survey regarding the integration of the present Audio Integration System protocol into the propesed Ethernet based solutions. The study finds two standards present on the market: Avionics Full-Duplex Ethernet (AFDX) and Time-Triggered Ethernet (TTEthernet). Two prototype implementations are built, one implementing AFDX and one custom built upon Ethernet and UDP. The latency of these are measured and found to be largely similar at ideal conditions. Ethernet is found to be more flexible, whilst AFDX allow for interoperation with other manufacturers and TTEthernet facilitates strict timing requirements at the cost of specialised hardware. The bandwidth utilisation of AFDX at ideal conditions is found to be 0.980% per stream and for the Ethernet solution 0.979% per stream.It is proposed that ÅF Digital Solutions AB pursue a custom Ethernet based solution unless they require interoperability on the same network with other manufacturers as a custom solution with full control over the network allows the largest flexibility in regards to timings and load. If interoperability is required is AFDX proposed instead as it is a standardised protocol and without the, for ÅF Digital Solutions AB, unnecessary overhead of TTEthernet. / Åf Digital Solutions AB vill undersöka möjligheterna att byta sitt nuvarande legacysystem för kommunikation inom flygplan till ett Ethernet-baserat system. Detta på ett sätt som håller implementationen så nära deras nuvarande Audio Integration System som möjligt. Problemet som undersöks är huruvida det är rimligt att flytta legacyprotokollet till Ethernet med så lite modifikationer som möjligt. Utöver detta vill ÅF Digital Solutions AB veta prestandakraven som blir på en Ethernet-lösning samt hur mycket resterande kapacitet som eventuellt finns kvar för framtida användning. Vidare vill de veta vilka standarder som redan finns på marknaden.Arbetet genomförs genom två spår - ett med experimentella mätningar och statistisk analys och en med ett case-study av integrationen av Audio Integration System och Ethernet. Undersökningen finner två standarder på marknaden relaterat till avionik; Avionics Full-Duplex Ethernet (AFDX) samt Time-Triggered Ethernet (TTEthernet).Två prototyper byggs, en baserad på AFDX och en baserad på UDP och Ethernet. Latencyn för dessa två mäts och finns vara snarlika vid deras respektive ideala scenarion. Ethernet finns vara mer flexibelt, AFDX merinteroperabel och TTEthernet mer lämplig vid strikta tidskrav. Bandbreddsutnyttjandet för AFDX finns vara 0.980% vid ideala förhållanden och 0.979% för Ethernetvid ideala förhållanden.Det rekommenderas att ÅF Digital Solutions använder sig av en egenutformad Ethernetbaserad lösning om de inte har krav på interoperabilitet ty det ger mer flexibilietet gällande tidskrav, protokoll och dataflödet.
346

Effects of electric field, surface alignment and guest materials in cholesteric liquid crystals

Zola, Rafael S. 22 March 2012 (has links)
No description available.
347

RF CMOS Tunable Gilbert Mixer with Wide Tuning Frequency and Controllable Bandwidth: Design Sythesis and Verification

Hu, Xin 31 May 2017 (has links)
No description available.
348

Dynamic Bandwidth and Laser Scaling for CPU-GPU Heterogenous Network-on-Chip Architectures

Van Winkle, Scott E. 20 September 2017 (has links)
No description available.
349

Adaptive Resizing of Deadline-Driven Requests for Provisioning Traffic in Elastic Optical Networks

Morell, Jared Anthony 20 August 2013 (has links)
No description available.
350

HIGH SPEED ATOMIC FORCE MICROSCOPY

Jeong, Younkoo 27 August 2009 (has links)
No description available.

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