Investigation of efficient resource allocation schemes for WiMAX networks

This thesis was submitted for the degree of Master of Philosophy and was awarded by Brunel University on 9 July 2008.WiMax (Worldwide Interoperability for Microwave Access) is a promising wireless technology with the aim of providing the last mile wireless broadband access designed for both fixed and mobile consumers as an alternative solution to the wired DSL and cable access schemes. The purpose of this research project is to investigate efficient resource allocation algorithms for WiMax. To achieve this goal, we investigate efficient PHY layer Partial Usage of SubCarriers (PUSC) allocation as well as MAC layer piggyback bandwidth request mechanisms. At the PHY layer we proposed improvements on the Uplink and Downlink PUSC subcarrier allocation scheme. For the Uplink PUSC we suggested a method by allocating different frequencies to neighbouring cells in combination with the Integer Frequency Reuse (IFR) and Fractional Frequency Reuse (FFR) in order to reduce interferences and collisions. The simulation results exhibit that collision rates can be reduced to zero for both IFR and FFR patterns with the proposed improvement by assuming that perfect power control is used in the system. In addition, there is no collision at cell edges. The results also show that FFR patterns achieve lower inter-cell interference and higher capacities as compared to the IFR patterns. For the Downlink PUSC we introduced an offset scheme with the purpose of increasing the number of users in the system. At the MAC layer we propose an improvement on the piggyback bandwidth request mechanism by increasing the size of the piggyback bandwidth request in order to reduce the number of bandwidth requests and hence improve the resource utilisation. The simulation results demonstrate that our improved scheme achieves higher throughput, less delay and packet loss rates as compared to the standardised piggyback bandwidth request mechanism

Flow-Aware Elephant Flow Detection for Software-Defined Networks

Software-defined networking (SDN) separates the network control plane from the packet forwarding plane, which provides comprehensive network-state visibility for better network management and resilience. Traffic classification, particularly for elephant flow detection, can lead to improved flow control and resource provisioning in SDN networks. Existing elephant flow detection techniques use pre-set thresholds that cannot scale with the changes in the traffic concept and distribution. This paper proposes a flow-aware elephant flow detection applied to SDN. The proposed technique employs two classifiers, each respectively on SDN switches and controller, to achieve accurate elephant flow detection efficiently. Moreover, this technique allows sharing the elephant flow classification tasks between the controller and switches. Hence, most mice flows can be filtered in the switches, thus avoiding the need to send large numbers of classification requests and signaling messages to the controller. Experimental findings reveal that the proposed technique outperforms contemporary methods in terms of the running time, accuracy, F-measure, and recall

Analysing the role of corporate social responsibility in determining firm value

Business entities are basically established to maximize wealth in order to create additional value for their owners. The concept of corporate social responsibility presupposes that corporate bodies should not only be concerned with shareholders wealth maximization but should equally care for the need of other noninvesting stakeholders. Hence, to ensured long-term value for corporate firms, attention should be tailored at satisfying the needs of both investing and non-investing stakeholders. Stakeholder’s welfare in overall enhanced corporate valuation. This paper highlight the takeholder’s theory as the underpinning theory of the study

Assessing the Relevance of Practical Activities in the Teaching and Learning of Integrated Science in Juniour Secondary Schools in Gombe Metropolis of Gombe State

The study was carried out to find out the level of application of practical activities in learning science concepts in integrated science in the secondary schools in Gombe metropolis, also it sought to find out the problems that militate against the successful application of practical activities in learning science concepts. The study was guided by five research questions and one hypothesis. The study adopted a quasi experimental research design and consists of the control and experimental group in determining the effect of practical activities on students’ academic achievement, the control group received no treatment while the experimental group was taught for a period of two weeks employing practical activities.  Also a questionnaire was designed for the teachers, to get their opinion about practical activities in learning science concepts as test was administered to the students to determine the difference in the academic achievement of students taught employing practical activities and those taught with the conventional method. The SPSS was used for the statistical analysis of Pearson Product moment correlation coefficient and the study made the following findings, practical activities in learning science concepts increases students achievement in science, spurs their motivation for learning and makes learning more meaningful as theories are concretized. The study also suggested training and retraining of integrated science teachers to enable the mastery of methodologies recommended for the teaching of integrated science and application of practical activities in the learning of science concepts

Research Trends and Geographical Contribution in the Field of Perinatal Mental Health: A Bibliometric Analysis from 1900 to 2020

ObjectiveThe object of this research is to identify growth and geographical distribution of research in the field of perinatal mental health and key research areas.Materials and methodsWe performed a bibliometric analysis on research documents on perinatal mental health from 1900 to 2020. Web of Science was used to download bibliometric data. Search strategy used generic index terms with specific free text searches using "AND" as Boolean function. For example, psycho AND perinatal. Microsoft Excel was used to identify research growth, geographical and research institutes contribution to research in the field. Citation analysis was done using VOSviewer.ResultsA total of 11,081 articles were extracted. The most cited research was by Cox et al., which introduced Edinburgh Postnatal Depression Scale. There was exponential increase in the research documents from 1990 to 2020. However, most of the research was contributed by the global north. Among emerging countries, India, South Africa, and Brazil did not contribute in the perinatal research. Postnatal depression and its risk factors were most studied themes. Paternal perinatal mental health and impact on mental health of children were understudied themes.ConclusionPerinatal mental health research outpaced growth in biomedical research in the past 30 years. The work of leading researcher in the field was initially inspired by his experience in Uganda encountering postnatal depression. However, even after half a century, there is still less contribution from developing countries. This analysis highlights research and possibly access to services inequities in developing countries

An Investigation of the Reliability of Senior Secondary School Certificate Examination (SSSCE) Results in Gombe Metropolis, Gombe State, Nigeria

This paper tests the reliability of the results obtained by students who sat for National Examination council Examination (NECO). Using the result obtained by the students in the same school in WAEC. The paper finds the correlation coefficients of percentage achievement in Mathematics and English – language in WAEC and NECO. The correlation coefficient was found for two consecutive years 2012 and 2013. It was observed that the correlation coefficients between the two examination bodies in 2012 are o.61 in Mathematics and 0.77 in English – language. In 2013, the correlation coefficient between WAEC and NECO are 0.87 in Mathematics and 0.24 in English – language. Except for that of English – language in 2013, the other correlation coefficients are positive and close to perfect. This shows that there is a strong relationship between the achievements. Keywords: West Africa Examination Council (WAEC), National Examination Council (NECO), Correlation Coefficient, Relationship, Percentage achievement, Candidate, Credit

Investigating Role of Vegetation in Protection of Houses during Floods

Flood flows have the potential to cause substantial damage to infrastructure, mankind, livestock and agricultural land which all stacks up to greatly affect the financial condition of the region. During 2010 Pakistan floods, more than two million houses were damaged partly or totally [1]. To minimize these types of destructions, inland vegetation can be considered a natural barrier to dissipate the energy of flood flow and limits widespread inundation. This study involves volume of fluid (VOF) modelling approach to figure out the role of vegetation of finite width in energy reduction of flood flow, in front of houses, against: vegetation of varying Aspect Ratio (A/R width-length ratio) and distance between vegetation & houses (Lr). Channel domain was built in ANSYS workbench toolkit and meshing was done in meshing building toolkit. For the postprocessing and simulation, FLUENT was used. Various contour plots & profiles of cross stream-wise velocities and water level measurements are presented in this paper. The simulation results of cross stream-wise velocities and water level measurements were identical with experimental data. At vegetation upstream and downstream, velocity reduction observed in higher A/R (2.40) compared to vegetation of A/R-1. Whereas, outside the vegetation and near the walls of channel domain flow velocities were high. The water level was raised on the upstream side of the vegetation due to resistance offered by vegetation. On the upstream side of vegetation, the rise in backwater depth increased by increasing A/R. Contrarily, on the downstream side of vegetation, an undular hydraulic jump was observed in between vegetation and a house. By increasing A/R, the energy loss increases under constant vegetation conditions (G/d = 0.24, Fro = 0.70; G = spacing of each cylinder in cross-stream direction and d= diameter of cylinder and Fro = initial Froude number) and increase in house distance from 1W to 2W, the energy reduction increased from 2.40% to 3.15% which was further increased to 5.04% for another 5W increase in house distance, where W is the vegetation width. Simulation results also shown that with increasing Froude no from 0.60 to 0.70 water level depth has also an incremental pattern which ultimately results in increase in energy dissipation along the varying building distance (1W, 2W & 5W).  Thus, to minimize the structural damage, a structure must be located at a safe distance away from the vegetation where flow becomes sub-critical

Localization performance evaluation of extended kalman filter in wireless sensors network

This paper evaluates the positioning and tracking performance of Extended Kalman Filter (EKF) in wireless sensors network. The EKF is a linear approximation of statistical Kalman Filter (KF) and has the capability to work efficiently in non-linear systems. The EKF is based on an iterative process of estimating current state information from the previously estimated state. Its working is based on the linearization of observation model around the mean of current state information. The EKF has small computation complexity and requires low memory compared to other Bayesian algorithms which makes it very suitable for low powered mobile devices. This paper evaluates the localization and tracking performance of EKF for (i) Position (P) model, (ii) Position-Velocity (PV) model and (iii) Position-Velocity-Acceleration (PVA) model. The EKF processes distance measurements from cricket sensors that are acquired through time difference of arrival between ultrasound and Radio Frequency (RF) signals. Further, localization performance under varying number of beacons/sensors is also evaluated in this paper. © 2014 Published by Elsevier B.V.Peer ReviewedPostprint (published version