Radio resource scheduling in homogeneous coordinated multi-point joint transmission of future mobile networks

A thesis submitted to the University of Bedfordshire, in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD)The demand of mobile users with high data-rate services continues to increase. To satisfy the needs of such mobile users, operators must continue to enhance their existing networks. The radio interface is a well-known bottleneck because the radio spectrum is limited and therefore expensive. Efficient use of the radio spectrum is, therefore, very important. To utilise the spectrum efficiently, any of the channels can be used simultaneously in any of the cells as long as interference generated by the base stations using the same channels is below an acceptable level. In cellular networks based on Orthogonal Frequency Division Multiple Access (OFDMA), inter-cell interference reduces the performance of the link throughput to users close to the cell edge. To improve the performance of cell-edge users, a technique called Coordinated Multi-Point (CoMP) transmission is being researched for use in the next generation of cellular networks. For a network to benefit from CoMP, its utilisation of resources should be scheduled efficiently. The thesis focuses on the resource scheduling algorithm development for CoMP joint transmission scheme in OFDMA-based cellular networks. In addition to the algorithm, the thesis provides an analytical framework for the performance evaluation of the CoMP technique. From the system level simulation results, it has been shown that the proposed resource scheduling based on a joint maximum throughput provides higher spectral efficiency compared with a joint proportional fairness scheduling algorithm under different traffic loads in the network and under different criteria of making cell-edge decision. A hybrid model combining the analytical and simulation approaches has been developed to evaluate the average system throughput. It has been found that the results of the hybrid model are in line with the simulation based results. The benefit of the model is that the throughput of any possible call state in the system can be evaluated. Two empirical path loss models in an indoor-to-outdoor environment of a residential area have been developed based on the measurement data at carrier frequencies 900 MHz and 2 GHz. The models can be used as analytical expressions to estimate the level of interference by a femtocell to a macrocell user in link-level simulations

Indoor-to-outdoor empirical path loss modelling for femtocell networks at 0.9, 2, 2.5 and 3.5 GHz using singular value decomposition

Two empirical indoor-to-outdoor path loss models to facilitate femtocell network deployment are derived from continuous wave power measurements. A large set of indoor-outdoor transmitter locations in two residential streets in an urban setting and operating at 900 MHz, 2 GHz, 2.5 GHz and 3.5 GHz have been used to derive the model parameters by using singular value decomposition (SVD). The path loss models have been compared and validated against existing models as well as independent measurement data and good comparison is shown. The root mean square error of the residual path loss data obtained from the measurement data, which directly relates to the channel shadowing characteristics, is compared and validated with known results and has led to new model parameters being proposed. The expressions derived from the modelling can be used in system-level simulators, as well as for shadowing interference analysis of two-tier heterogeneous networks operating in indoor-outdoor scenarios at or close to the operating frequencies considered. In this study, the models extend the operating frequency range compared to related models and introduce SVD as a convenient means of deriving parameters from measured path loss data

Effect of electric load and dual atmosphere on the properties of an alkali containing diopside-based glass sealant for solid oxide cells

© 2019 Elsevier B.V. All rights reserved.A new alkali-containing diopside based glass-ceramic sealant for solid oxide cells was synthesized, characterized and tested. The composition was designed to match the coefficient of thermal expansion (CTE) of Crofer22APU interconnect. The sealant has a glass transition temperature of 600°C, a crystallization peak temperature of 850°C and a maximum shrinkage temperature of 700°C, thus suggesting effective densification prior to crystallization. The CTE of the glass-ceramic is 11.5 10-6 K-1, a value which is compatible with the CTE for Crofer22APU stainless steel. Crofer22APU/glass-ceramic/Crofer22APU joined samples were tested in simulated real-life operating conditions at 800°C in dual atmosphere under an applied voltage, monitoring the electrical resistivity. The effect of two different applied voltages (0.7V and 1.3V) was evaluated. A voltage of 1.3V led to a rapid decrease in the electrical resistivity during the test;such a drop was due to the formation of Cr2O3 “bridges” that connected the two Crofer22APU plates separated by the sealant. There was no decrease in the resistivity when a voltage of 0.7V was applied. Instead,resistivity value remained stable at around 105 Ω cm for the 100h test duration. The degradation mechanisms, due to both the alkali content and the applied voltage, are investigated and discussed.Peer reviewe

Gestational Age Specific Postnatal Growth Curves for Singleton Babies in Tertiary Hospital of Western Nepal

Introduction: Measurement of birth weight (BW), crown heel length (CHL), head circumference (HC) and chest circumference used to assess the intrauterine growth of a baby vary with altitude, race, gender, socio economic status, maternal size, and maternal diseases. The study aimed to construct centile charts for BW, CHL and HC for new born at different gestational ages in western Nepal. Methods:  This was a descriptive cross sectional study done over a period of 15 months in a tertiary care hospital of western Nepal. BW, length, HC and CC were measured within 12-24 hours of birth. Gestational age was estimated from first day of last menstrual period, maternal ultrasonology and New Ballard’s scoring system. Microsoft 2007 Excel and SPSS-16 was used for data analysis. Cole’s Lambda Mu Sigma method was used for constructing centile curves. Results: Out of 2000 babies analysed, 1910 samples were used to construct smoothed intrauterine growth curve of BW, CHL, and HC from 33-42 weeks of gestation. 57.35% (1147) were male, mean gestational age was 38.13 ±2.44 weeks, where 21.5% were preterm and 1.7% post term. The means of BW, CHL, HC and CC were 2744.78 gm, 47.80 cm, 33.18 cm, and 30.20 cm with standard deviations of 528.29, 3.124, 1.78, and 2.35 respectively. These data vary as compared to the Kathmandu data, in case of birth weight for 10th and 90th centiles, and at 90th centile in case of length. Conclusions: This necessitates the update in the existing growth charts and develop in different geographical regions of a country

Device-independent randomness certification using multiple copies of entangled states

We demonstrate to what extent many copies of maximally entangled two-qubit states enable for generating a greater amount of certified randomness than that can be certified from a single copy. Although it appears that greater the dimension of the system implies a higher amount of randomness, the non-triviality lies in the device-independent simultaneous certification of generated randomness from many copies of entangled states. This is because, most of the two-outcome Bell inequalities (viz., Clauser-Horne-Shimony-Holt, Elegant, or Chain Bell inequality) are optimized for a single copy of two-qubit entangled state. Thus, such Bell inequalities can certify neither many copies of entangled states nor a higher amount of randomness. In this work, we suitably invoke a family of n-settings Bell inequalities which is optimized for ⌊n/2⌋ copies of maximally entangled two-qubit states, thereby, possess the ability to certify more randomness from many copies of two-qubit entangled state. © 2022 Elsevier B.V

Hybrid model for throughput evaluation of OFDMA networks

Data throughput is an important metric used in the performance evaluation of the next generation cellular networks such as Long-Term Evolution (LTE) and LTE-Advanced. To evaluate the performance of these networks, Monte Carlo simulation schemes are usually used. Such simulations do not provide the throughput of intermediate call state, instead it gives the overall performance of the network. We propose a hybrid model consisting of both analysis and simulation. The benefit of the model is that the throughput of any possible call state in the system can be evaluated. Here, the probability of possible call distribution is first obtained by analysis, which is used as input to the event-driven based simulator to calculate the throughput of a call state. We compare the throughput obtained from our hybrid model with that obtained from event-driven based simulation. Numerical results are presented and show good agreement between both the proposed hybrid model and the simulation. The maximum difference of relative throughput between our hybrid model and the simulation is found in the interval of(0.04%;1.06%) over a range of call arrival rates, meanholding times and number of resource blocks in the system

Dynamic user equipment-based hysteresis-adjusting algorithm in LTE femtocell networks

In long-term evolution (LTE) femtocell networks, hysteresis is one of the main parameters which affects the performance of handover with a number of unnecessary handovers, including ping-pong, early, late and incorrect handovers. In this study, the authors propose a hybrid algorithm that aims to obtain the optimised unique hysteresis for an individual mobile user moving at various speeds during the inbound handover process. This algorithm is proposed for two-tier scenarios with macro and femto. The centralised function in this study evaluates the overall handover performance indicator. Then, the handover aggregate performance indicator (HAPI) is used to determine an optimal configuration. Based on the received reference signal-to-interference-plus-noise ratio, the distributed function residing on the user equipment (UE) is able to obtain an optimal unique hysteresis for the individual UE. Theoretical analysis with three indication boundaries is provided to evaluate the proposed algorithm. A system-level simulation is presented, and the proposed algorithm outperformed the existing approaches in terms of handover failure, call-drop and redundancy handover ratios and also achieved better overall system performance

Relationship of Oxygen Saturation with Neonatal and Maternal factors in Vaginal and Cesarean Deliveries

Introduction: Hypoxemia is the major cause of neonatal morbidity and mortality. The study aims to determine the influence of birth weight, Apgar score, gestation age, body mass index and hemoglobin of mother on levels of SpO2 in healthy newborns born vaginally and through cesarean section. 
 Methods: A hospital Based, observational study conducted in Department of Pediatrics, Universal College of Medical Sciences-Teaching Hospital, Bhairahawa, Lumbini, Nepal; on 49 vaginal and 49 cesarean deliveries with Apgar Score ≥ 6. SpO2 was estimated by pulse oximeter post-ductally between 1 to 30 minutes of birth. The observed SpO2 values were correlated with neonatal and maternal factors. 
 Results: Vaginal and Cesarean deliveries SpO2 were comparable for birth weight, gestational age, Apgar score of neonates, body mass index and hemoglobin of the mother. Birth weight in vaginally delivered babies and Apgar score in cesarean births showed significant change in SpO2 (P<0.05). At all points of time the SpO2 values were higher in neonates, born by cesarean than those born out of spontaneous vaginal deliveries (P<0.001). 
 Conclusions: SpO2 levels in neonates born through cesarean section were higher in comparison to thoseborn by vaginal route. Birth weight and Apgar score had correlation with SpO2 in vaginal and cesarean births, respectively. Keywords: Apgar score; birth weight; newborn; pulse oximeter; SpO2