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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

Performance issues in cellular wireless mesh networks

Zhang, Dong 14 September 2010
This thesis proposes a potential solution for future ubiquitous broadband wireless access networks, called a cellular wireless mesh network (CMESH), and investigates a number of its performance issues. A CMESH is organized in multi-radio, multi-channel, multi-rate and multi-hop radio cells. It can operate on abundant high radio frequencies, such as 5-50 GHz, and thus may satisfy the bandwidth requirements of future ubiquitous wireless applications.<p> Each CMESH cell has a single Internet-connected gateway and serves up to hundreds of mesh nodes within its coverage area. This thesis studies performance issues in a CMESH, focusing on cell capacity, expressed in terms of the max-min throughput. In addition to introducing the concept of a CMESH, this thesis makes the following contributions.<p> The first contribution is a new method for analyzing theoretical cell capacity. This new method is based on a new concept called Channel Transport Capacity (CTC), and derives new analytic expressions for capacity bounds for carrier-sense-based CMESH cells.<p> The second contribution is a new algorithm called the Maximum Channel Collision Time (MCCT) algorithm and an expression for the nominal capacity of CMESH cells. This thesis proves that the nominal cell capacity is achievable and is the exact cell capacity for small cells within the abstract models.<p> Finally, based on the MCCT algorithm, this thesis proposes a series of greedy algorithms for channel assignment and routing in CMESH cells. Simulation results show that these greedy algorithms can significantly improve the capacity of CMESH cells, compared with algorithms proposed by other researchers.
2

Performance issues in cellular wireless mesh networks

Zhang, Dong 14 September 2010 (has links)
This thesis proposes a potential solution for future ubiquitous broadband wireless access networks, called a cellular wireless mesh network (CMESH), and investigates a number of its performance issues. A CMESH is organized in multi-radio, multi-channel, multi-rate and multi-hop radio cells. It can operate on abundant high radio frequencies, such as 5-50 GHz, and thus may satisfy the bandwidth requirements of future ubiquitous wireless applications.<p> Each CMESH cell has a single Internet-connected gateway and serves up to hundreds of mesh nodes within its coverage area. This thesis studies performance issues in a CMESH, focusing on cell capacity, expressed in terms of the max-min throughput. In addition to introducing the concept of a CMESH, this thesis makes the following contributions.<p> The first contribution is a new method for analyzing theoretical cell capacity. This new method is based on a new concept called Channel Transport Capacity (CTC), and derives new analytic expressions for capacity bounds for carrier-sense-based CMESH cells.<p> The second contribution is a new algorithm called the Maximum Channel Collision Time (MCCT) algorithm and an expression for the nominal capacity of CMESH cells. This thesis proves that the nominal cell capacity is achievable and is the exact cell capacity for small cells within the abstract models.<p> Finally, based on the MCCT algorithm, this thesis proposes a series of greedy algorithms for channel assignment and routing in CMESH cells. Simulation results show that these greedy algorithms can significantly improve the capacity of CMESH cells, compared with algorithms proposed by other researchers.
3

Battery field data-oriented investigation of cell capacity spread and its impacts

Bilal, Muhammad January 2022 (has links)
In this research thesis, a new data-centric approach is used to determine the individual cell capacities in Li-ion batteries used in electric vehicles (EVs). This approach could also be extended to batteries for static energy storage applications. The method is based on real-world data collected from pouched-shaped cells having Nickel Manganese Cobalt (NMC) based chemistry of different capacities, used in electric buses. An algorithm has been developed which takes as input the charging and discharging current data of the battery, and voltages of the individual cell either from sensors installed on the terminals of a cell or from a battery simulator software. As an output, the algorithm tries for finding the best two resting states on the time axis of the current profile and net charging or discharging of the battery in between those times. A reasonable amount of net charge is required for capacity calculation, for this reason, the recommended SOC difference between those two resting states should be at least ±10% or more. Several experiments were also performed to firm up the results. For the experiments, 100 pouch-shaped NMC-based cells of 40 Ah capacity each were used. These 100 cells were connected in series as 1P100s and it is one module of the xP100s larger battery pack of an electric trolley bus. The algorithm has three levels: at the first level, it uses only simulator data of current and cell voltages to determine the total capacities of individual cells from partial charging or discharging. In the second level, it takes real current data and simulator voltages from the individual cells to determine the same total capacities of individual cells. The third level uses real current charging and discharging data and only minimum, average, and maximum cell voltages to find an indicator of the skewed capacities of cells. Further, the second and third level is compared with the first. For more accuracy and exact calculations of the individual cell capacity, special tests and data collection procedures are proposed as well. Irrespective of the type of data available, a non-destructive diagnostic of the battery is carried out. Abnormal cells are detected with cell number and its location inside the pack in the case where individual cell data are available. In the case where only maximum and minimum cell voltages are available, the cell will be determined which limits the capacity of all the cells connected in series with it. For better diagnostics of the battery new data collection techniques are proposed, given that the owner of the vehicle allows the transfer of data from BMS.
4

WCDMA Cell Load Control in a High-speed Train Scenario : Development of Proactive Load Control Strategies / Belastningsreglering av WCDMA celler i ett tågscenario : Utvecklings av strategier för proaktiv belastningsreglering

Joshi, Raoul, Sundström, Per January 2012 (has links)
Load control design is one of the major cornerstones of radio resource management in today's UMTS networks. A WCDMA cell's ability to utilize available spectrum efficiently, maintain system stability and deliver minimum quality of service (QoS) requirements to in-cell users builds on the algorithms employed to manage the load. Admission control (AC) and congestion control (CC) are the two foremost techniques used for regulating the load, and differing environments will place varying requirements on the AC and CC schemes to optimize the QoS for the entire radio network. This thesis studies a real-life situation where cells are put under strenuous conditions, investigates the degrading effects a high-speed train has on the cell's ability to maintain acceptable levels of QoS, and proposes methods for mitigating these effects. The scenario is studied with regard to voice traffic where the limiting radio resource is downlink power. CC schemes that take levels of fairness into account between on-board train users and outdoor users are proposed and evaluated through simulation. Methods to anticipatorily adapt radio resource management (RRM) in a cell to prepare for a train is proposed and evaluated through simulation. A method to detect a high-speed train in a cell, and the users on it, is outlined and motivated but not simulated. Simulation results are promising but not conclusive. The suggested CC schemes show a surprising tendency towards an increase in congestion avoidance performance. Proactive RRM shows a significant increase in QoS for on-board users. No negative effects to users in the macro environment is noticed, with regard to the studied metrics.
5

Efekt bezlepkové diety na zbytkovou kapacitu β-buněk, imunitní funkci a střevní mikrobiom dětí s nově manifestovaným diabetem 1. typu / The effect of gluten-free diet on β-cell residual capacity, immune function and gut microbiome in children with newly diagnosed type 1. diabetes

Neuman, Vít January 2021 (has links)
The effect of gluten-free diet on β-cell residual capacity, immune function and gut microbiome in children with newly diagnosed type 1. diabetes Abstract The pathophysiology of the onset and progression of type 1 diabetes (T1D) is not fully understood. Gluten has a proinflammatory effect on the immune system and is therefore considered as one of the factors affecting the onset and progression of T1D. The aim of the thesis is to allow a complex insight into the role of the GFD on the residual β-cell capacity, T1D control, gut microbiome, gut permeability, subtypes of immune cells and the effect of gut microbiome transfer into germ-free non-obese diabetic (NOD) mice on the incidence of diabetes. On the group of 45 children with T1D (26 intervention group, 19 control group) we proved the association of the GFD with slower decrease of β-cell residual capacity (the difference in the trend of C-peptide decrease 409 pmol/l/year; p = 0,04) and lower HbA1c (by 7,8 mmol/mol; p=0,02). We also described the changes in the gut bacteria that were differentially abundant after the administration of the GFD and the changes in abundance of the regulatory and effector immune cells. We showed there was no change in the gut permeability with respect to the study group. We also proved that the transfer of human gut microbiota...

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