SDN-BASED MECHANISMS FOR PROVISIONING QUALITY OF SERVICE TO SELECTED NETWORK FLOWS

Despite the huge success and adoption of computer networks in the recent decades, traditional network architecture falls short of some requirements by many applications. One particular shortcoming is the lack of convenient methods for providing quality of service (QoS) guarantee to various network applications. In this dissertation, we explore new Software-Defined Networking (SDN) mechanisms to provision QoS to targeted network flows. Our study contributes to providing QoS support to applications in three aspects. First, we explore using alternative routing paths for selected flows that have QoS requirements. Instead of using the default shortest path used by the current network routing protocols, we investigate using the SDN controller to install forwarding rules in switches that can achieve higher bandwidth. Second, we develop new mechanisms for guaranteeing the latency requirement by those applications depending on timely delivery of sensor data and control signals. The new mechanism pre-allocates higher priority queues in routers/switches and reserves these queues for control/sensor traffic. Third, we explore how to make the applications take advantage of the opportunity provided by SDN. In particular, we study new transmission mechanisms for big data transfer in the cloud computing environment. Instead of using a single TCP path to transfer data, we investigate how to let the application set up multiple TCP paths for the same application to achieve higher throughput. We evaluate these new mechanisms with experiments and compare them with existing approaches

Digital signal processing techniques for peak-to-average power ratio mitigation in MIMO–OFDM systems

The focus of this thesis is to mitigate the very large peak-to-average transmit power ratios (PAPRs) inherent to conventional orthogonal frequency division multiplexing (OFDM) systems, particularly in the context of transmission over multi-input multi-output (MIMO) wireless broadband channels. This problem is important as a large PAPR generally needs an expensive radio frequency (RF) power amplifier at the transmitter due to the requirement for linear operation over a wide amplitude range and such a cost would be compounded when multiple transmit antennas are used. Advanced signal processing techniques which can reduce PAPR whilst retain the integrity of digital transmission therefore have considerable potential for application in emergent MIMO–OFDM wireless systems and form the technical contributions of this study. [Continues.

Purification and Characterization of O2-insensitive Pyruvate Decarboxylase from Sulfolobus species

Pyruvate decarboxylase (PDC) is a key enzyme in a two-step pathway for the production of ethanol. It catalyzes the non-oxidative decarboxylation of pyruvate to acetaldehyde in many mesophilic organisms. No conventional PDC has been found in hyperthermophiles, a group of microorganisms growing optimally at 80°C and above; however, bifunctional PDC/pyruvate ferredoxin oxidoreductase (POR) activities have been found to be present in several hyperthermophilic bacteria and archaea, but most of them are oxygen-sensitive and CoA-dependent. It was reported that the CoA is not required for a recombinant PDC/POR from Sulfolobus tokodaii (Topt = 80ºC) and it is oxygen insensitive, but it’s not known why it has a much lower activity compared to other PDCs/PORs. Since PORs from hyperthermophilic crenarchaea Sulfolobus solfataricus (Topt = 80ºC) and Sulfolobus acidocaldarius (Topt = 80°C) are not oxygen-sensitive, it was hypothesized that they might be the most thermostable O2-insensitive PDCs. PDCs/PORs enzymes from S. solfataricus (Ss) and S. acidocaldarius (Sa) were purified using a fast performance liquid chromatography system (FPLC) anaerobically. POR activity was measured by monitoring the pyruvate-dependent reduction of benzyl viologen at 578 nm. PDC activity was measured by monitoring the pyruvate-dependent production of acetaldehyde. The acetaldehyde production was determined by using 2,4-dinitrophenylhydrazine (DNPH) derivatization method followed by high performance liquid chromatography (HPLC). Both enzymes from S. solfataricus and S. acidocaldarius were purified and SDS-PAGE showed that each heterodimeric enzyme had two subunits with a molecular mass of 373 kDa and 652 kDa respectively. S. solfataricus PDC and POR activities present in its cell-free extract (CFE) were determined to be 0.0027±0.0003 U/mg and 0.18±0.01 U/mg, respectively. Similarly, S. acidocaldarius PDC and POR activities present in its CFE were determined to be 0.0011±0.0004 U/mg and 0.10±0.01 U/mg, respectively. The enzyme from S. solfataricus was purified approximately 42-fold with a recovery of 25%, while the enzyme from S. acidocaldarius was purified approximately 70-fold with a recovery of 19%. Optimal pH for both S. solfataricus and S. acidocaldarius PORs were determined to be at pH 8.6, while optimal pH for their PDCs were 7.8. PDC/POR enzyme from S. solfataricus showed maximum activity at 80 ºC for PDC activity and at 90 ºC for POR activity; however, the optimum temperatures of PDC/POR from S. acidocaldarius were at 90 ºC for PDC activity and at 80 ºC for POR activity. PDCs/PORs enzymes from S. solfataricus and S. acidocaldarius were CoA dependent for both PDCs and PORs activities, a common feature of other PDCs/PORs except the one from S. tokodaii. Thermostability of the purified enzymes from S. solfataricus and S. acidocaldarius were determined by measuring the time required for losing 50% activity (t1/2) at 80 °C, which were approximately 2.9 h and 1.1 h respectively. It was determined that PDCs/PORs from S. solfataricus, and S. acidocaldarius were not oxygen sensitive. These thermostable and oxygen-stable PDCs may have great potential in applications in developing a more efficient system for bioethanol fermentation at high temperatures

Peak-to-average power ratio mitigation in quasi-orthogonal space time block coded MIMO-OFDM systems using selective mapping.

A study of a peak-to-average power ratio (PAPR) reduction scheme for quasi-orthogonal spacetime block coded multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems based on selective mapping (SLM) is presented. The reduction technique is based upon combining the PAPRs of the transmission blocks from four antennas and exploits the associated antenna diversity gain to mitigate errors in the transmission of the side information (SI) necessary for SLM. Simulation studies are presented which show the cumulative complementary distribution functions (CCDFs) with and without the combining scheme and bit error rates of the overall system. Comparisons are made with single antenna and conventional OFDM schemes

The role of lifestyle habits in the prevalence of overweight and obesity among students

The key objective of the present study is to explore the prevalence of being overweight and/or being obese using the body mass index (BMI). We investigated the relationship between lifestyle habits (sleeping patterns, dietary habits, physical activities, and screen times) and obesity. We used a cross-sectional study involving male students of medical and non-medical at the College of Medicine and College of Management and Economics at Saudi Arabia’s Qassim University. To gather data, a tailor-made, self-administered questionnaire was the tools of choice. The first part of the form collected a data pertaining to the height and weight of respondents. This measured BMI. Participants then categorized as underweight (BMI < 18.5), normal weight (BMI = 18.5–24.9), overweight (BMI = 25–29.9), and obese (BMI >30.0). The second part of the study involved questions about the participants’ lifestyle habits. To assess the significance of the questions, aChi-squared test was applied. We found that prevalence of being overweight and obese among medical students was (24.4%) and (19%) respectively. for non-medical students the prevalence of being overweight and obesity was (25.6%) and (16.5%) respectively. regarding dietary habits more than half of the students (54.2%) who had three meals or more have a positive relation with obesity. A positive relation was noticed between lack of physical activity and high BMI. Positive relation was found between high BMI and screen time. Regarding sleep hours more than half of the students spend 6-8 hours in sleeping per day

The Effect of Vitamin D3 Supplementation on Markers of Glycaemia, Lipidaemia and Oxidative Stress in Saudi Men with Poorly-Controlled Type-2 Diabetes Mellitus

The pathogenesis of diabetes mellitus type 2 (T2DM) has been associated with vitamin D deficiency which plays a role in impaired insulin action in humans. The purpose of this research is to investigate the effect of vitamin D3 supplementation on biomarkers of glycaemia, lipidaemia and oxidative stress in Saudi men aged >18 years with poorly controlled T2DM. A double-blind, randomised, placebo-controlled, parallel trial was used to investigate 128 Saudi men with poorly-controlled T2DM randomised to receive: 1) a placebo supplement, 2) 50μg/day vitamin D3 or 3) 100μg/day vitamin D3 as capsules matched in shape and size over a 16-week period. Fasting glucose, HbA1c, fasting insulin, lipid profile, serum 25(OH)D, and total antioxidant status were measured, and advanced glycation end products (AGEs) in skin were also measured using an AGE-reader. Vitamin D supplementation of either 100μg or 50μg per day were found to give a significant improvement in the HbA1c (p<0.001) and a reduction in glucose levels (p<0.001) after 16-weeks’ intervention as compared to the placebo group in both supplementation groups. Significant reductions in total cholesterol (p<0.001) and improvements in HDL levels (p<0.001) after 16-weeks’ intervention were seen compared to the placebo group in both treatment groups. Triglycerides were significantly reduced after 16-weeks’ intervention (p<0.001) only with the higher dose of vitamin D3 (100μg/day) without any change in the 50μg/day vitamin D3 group. Vitamin D supplementation failed to demonstrate any improvement in insulin resistance, insulin secretion or oxidative stress such as total antioxidant levels or AGEs as compared to the placebo group after 16-weeks’ intervention. Vitamin D status seems to have a significant role in controlling the development and treatment of diabetes. It is likely that optimised levels of serum vitamin D may be variable between those at high risk