Electrical & Computer Engineering

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Research from the Department of Electrical & Computer Engineering. The department website may be found at https://www.ndsu.edu/ece/

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An Active Power Supply Filter with Ultra Wide Bandwidth
(North Dakota State University, 2016) Booth, Brian
An active transformerless common mode ﬁlter is designed for use with switching mode power supplies with a switching frequency greater than 1MHz. The ﬁlter utilizes an ampliﬁer in a voltage sensing current adjusting architecture to cancel out common mode noise generated by the switching power supply. The ﬁlter is analyzed using a transfer function, simulation, and measurements. Several possible feedback conﬁgurations are examined and beneﬁts of diﬀerent conﬁgurations are explained. The active ﬁlter is shown to have superior performance to only passive components at frequencies up to 20MHz. Spectral domain, time domain, and S21 measurements are given to show the ﬁlter’s eﬀectiveness.
Adaptive Beamforming for Antennas on General Wedge- and Cylindrical-Shaped Surfaces
(North Dakota State University, 2014) Irfanullah, Irfanullah
Adaptive beamforming antennas capable of accommodating the growing number of wireless subscribers throughout the world has become an essential part of modern wireless systems. In this work, the beamforming of a conformal antenna on a changing conformal surface is studied by relating the varying position of each antenna element in the array to the weighting coefficients (i.e, array weights) required to give a desired antenna beam formation. In particular, the beamforming of a 1 x 4 array on a changing wedge- and cylindrical-shaped surface is studied using the projection method on a wavefront of a transmitted wave in a particular direction. To validate the theory, a 1 x 4 prototype antenna with individual voltage-controlled phase shifters and attenuators is used to implement the computed weights of each individual antenna element for measurements in an anechoic chamber. Overall agreement between theory, simulations and measurements is shown throughout the work. Furthermore, the effects of mutual coupling and changing conformal surfaces on the behavior of the beamforming pattern and array weights is investigated and summarized.
Analyses, Mitigation and Applications of Secure Hash Algorithms
(North Dakota State University, 2020) Al-Odat, Zeyad Abdel-Hameed
Cryptographic hash functions are one of the widely used cryptographic primitives with a purpose to ensure the integrity of the system or data. Hash functions are also utilized in conjunction with digital signatures to provide authentication and non-repudiation services. Secure Hash Algorithms are developed over time by the National Institute of Standards and Technology (NIST) for security, optimal performance, and robustness. The most known hash standards are SHA-1, SHA-2, and SHA-3. The secure hash algorithms are considered weak if security requirements have been broken. The main security attacks that threaten the secure hash standards are collision and length extension attacks. The collision attack works by finding two different messages that lead to the same hash. The length extension attack extends the message payload to produce an eligible hash digest. Both attacks already broke some hash standards that follow the Merkle-Damgrard construction. This dissertation proposes methodologies to improve and strengthen weak hash standards against collision and length extension attacks. We propose collision-detection approaches that help to detect the collision attack before it takes place. Besides, a proper replacement, which is supported by a proper construction, is proposed. The collision detection methodology helps to protect weak primitives from any possible collision attack using two approaches. The first approach employs a near-collision detection mechanism that was proposed by Marc Stevens. The second approach is our proposal. Moreover, this dissertation proposes a model that protects the secure hash functions from collision and length extension attacks. The model employs the sponge structure to construct a hash function. The resulting function is strong against collision and length extension attacks. Furthermore, to keep the general structure of the Merkle-Damgrard functions, we propose a model that replaces the SHA-1 and SHA-2 hash standards using the Merkle-Damgrard construction. This model employs the compression function of the SHA-1, the function manipulators of the SHA-2, and the $10*1$ padding method. In the case of big data over the cloud, this dissertation presents several schemes to ensure data security and authenticity. The schemes include secure storage, anonymous privacy-preserving, and auditing of the big data over the cloud.
Analysis and Characterization of Cloud Based Data Center Architectures for Performance, Robustness, Energy Efficiency, and Thermal Uniformity
(North Dakota State University, 2014) Bilal, Kashif
Cloud computing is anticipated to revolutionize the Information and Communication Technology (ICT) sector and has been a mainstream of research over the last decade. Today, the contemporary society relies more than ever on the Internet and cloud computing. However, the advent and enormous adoption of cloud computing paradigm in various domains of human life also brings numerous challenges to cloud providers and research community. Data Centers (DCs) constitute the structural and operational foundations of cloud computing platforms. The legacy DC architectures are inadequate to accommodate the enormous adoption and increasing resource demands of cloud computing. The scalability, high cross-section bandwidth, Quality of Service (QoS) guarantees, privacy, and Service Level Agreement (SLA) assurance are some of the major challenges faced by today’s cloud DC architectures. Similarly, reliability and robustness are among the mandatory features of cloud paradigm to handle the workload perturbations, hardware failures, and intentional attacks. The concerns about the environmental impacts, energy demands, and electricity costs of cloud DCs are intensifying. Energy efficiency is one of mandatory features of today’s DCs. Considering the paramount importance of characterization and performance analysis of the cloud based DCs, we analyze the robustness and performance of the state-of-the-art DC architectures and highlight the advantages and drawbacks of such DC architecture. Moreover, we highlight the potentials and techniques that can be used to achieve energy efficiency and propose an energy efficient DC scheduling strategy based on a real DC workload analysis. Thermal uniformity within the DC also brings energy savings. Therefore, we propose thermal-aware scheduling policies to deliver the thermal uniformity within the DC to ensure the hardware reliability, elimination of hot spots, and reduction in power consumed by cooling infrastructure. One of the salient contributions of our work is to deliver the handy and adaptable experimentation tools and simulators for the research community. We develop two discrete event simulators for the DC research community: (a) for the detailed DC network analysis under various configurations, network loads, and traffic patterns, and (b) a cloud scheduler to analyze and compare various scheduling strategies and their thermal impact.
An Analysis and Improvement of Brushless DC Motor Control System
(North Dakota State University, 2013) Sumon, Md Yiasin
Trapezoidal Back-EMF (Brushless DC) motors are gaining increasing importance in automotive industries, HVAC applications, home appliances etc. Traditionally, Brushless DC motors are commutated electronically using position sensors. In these systems, mechanical or electromagnetic sensors are used. In sensorless control, rotor back EMF detection is the most popular technique for speed and position control. Detection of back EMF by novel speed independent commutation function is a very well researched topic that has overcome most of the problems of traditional back EMF detection scheme. In this thesis, a thorough study and speed control scheme for Brushless DC motors using position sensor is presented along with simulation and experimental results. An improved sensorless scheme based on speed independent commutation and state observer based back EMF sensing is analyzed. Both methods use hysteresis control for the current loop and a PI controller for the speed loop to reduce steady state speed error.
The Analysis of Noise Voltage Coupling Between Right-Handed and Meta-Materials Transmission Lines on Printed Circuit Boards
(North Dakota State University, 2013) Nariyal, Sanjay
An important consideration of RF circuitry in terms of Electromagnetic Compatibility is the correct modeling of the coupling between printed transmission lines. This is very important because the coupled noise voltages that are generated between two lines may cause adverse eects on sensitive components placed in the close vicinity. To study this problem of coupling in terms of noise voltages, rst the analytical expressions for computing the near-end and far-end voltages between the conventional Right-Handed (RH) and Composite Right-/Left-Handed Transmission Lines (CRLH-TLs) and then RH and Complementary Split Ring Resonators (CSRR-TLs) were derived. The obtained expressions were then successfully validated with the simulation and measurements results. These expressions will give us an insight on how to reduce the induced noise voltages on the CRLH- and CSRR-TLs by varying the capacitance and inductance values that support left-handed propagation. In particular, it will be shown that the noise voltages coupled to the CRLH-TL are approximately 10 dB lower than the voltages coupled to the CSRR-TL. This could prove to be a useful alternative to conventional sheilding.
Analysis of Power Line Communication Channel Model using Communication Techniques
(North Dakota State University, 2013) Singh, Varinder Pal
With the advent of technology, human dependency on power (electricity) and communication has grown beyond leaps and bounds. Many efforts have been made to continuously improve and increase the efficiency in both areas. Power Line Communication (PLC) is a technology where power lines or transmission lines are being used for communication purposes along with transmitting electrical energy. Because the power grid is already in place, the PLC has the obvious advantage of reducing communication infrastructure cost. However, the power grid is designed optimally for power delivery (not the data). The power transmission line generally appears as a harsh environment for the low-power high-frequency communication signals. In order to evaluate the performance of PLC, this paper simulates a practical multipath power line communication channel model and provides the Bit Error Rate (BER) vs signal-to-noise ratio (SNR) curves for orthogonal frequency division multiplexing.
Analysis of Secrecy in Multi-User Wireless Network
(North Dakota State University, 2018) Ghosh, Anirban
We consider an Ergodic Fading Broadcast Channel with one Legitimate receiver and one Eavesdropper (BCoLoE) having arbitrary fading statistics, where the instantaneous Channel State Information (CSI) are known only at the receivers (CSIR). The secrecy capacity of this channel is characterized within 11 bits irrespective of fading statistics and Signal-to-Noise Ratios (SNRs). This is achieved by deriving a new upper bound to the secrecy capacity of the channel and two new lower bounds. The upper bound is derived by approximating Complementary Cumulative Distribution Functions (CCDFs) of the two links by corresponding staircase functions. The smaller lower bound, although looser, has a form which can be analytically compared with the upper bound and facilitates the approximate secrecy capacity characterization. It is proved that, the so called Binary Expansion Signaling with Reverse Stripping (BES-RS) scheme can achieve a secrecy rate larger than both these lower bounds with the help of numerical computation for several BCoLoEs with practical fading statistics. We further characterize the secrecy capacity of a class of 2-user binary fading interference channel (BFIC) and 2-user layered fading interference channel (LFIC), under the same assumptions as for the wiretap channel. The secrecy capacity region for a very weak BFIC turns out to be quadrangular while for LFIC it is polygonal. We explicitly characterize the corner points in both the cases. The converse in either case is proved by dividing the set of upper bounds into two carefully chosen regions depending on the values of ω - the weighting factor of the weighted sum bounds. In case of LFIC each of the regions are also shown to be piece-wise linear. The achievability on the other hand is proved by using capacity optimal code for a layered erasure wiretap channel at both the transmitters and treating interference as erasure while decoding the signals at the receivers. In addition, the achievability of the layered case also involves proper assignment of the layers to the two transmitters based on some constraints. We also prove the secrecy capacity of strong BFIC and LFIC as zero.
Automating the design of deep learning models using neural architecture search for medical image classification
(North Dakota State University, 2024) Balamurugan, Ridhanya
Designing Deep Learning (DL) models for medical image classification tasks poses significant challenges, demanding substantial expertise owing to the intricate nature and critical importance of the undertaking. Creating a DL model tailored for such purposes entails iterative processes of designing, implementing, and fine-tuning algorithms to achieve optimal performance. To mitigate these difficulties, Neural Architecture Search (NAS) has risen as a key field to generate the most effective DL models automatically. However, much of the previous studies involving NAS focus on automating the design of DL models for well-established datasets such as CIFAR-10 and ImageNet. This technique should also be extended to medical image datasets where detecting crucial features accurately in medical images is essential to detect specific illnesses correctly. Therefore, in this study, we investigate NAS to autonomously design best performing DL models for skin lesion detection, thereby demonstrating its usefulness for additional medical image classification endeavours.
An Autonomous Reconfigurable Antenna
(North Dakota State University, 2019) Hinsz, Lee
Today’s wireless communications involve more antenna capabilities while occupying the same amount of space. Antennas are able to operate at multiple frequencies [1]-[2], change polarizations [6], have selectable radiation patterns [1] and are becoming smaller. Likewise, antennas are serving multiple applications. However, many reconfigurable antennas use a separate power source to operate or use software defined radios. In certain instances this can be a limiting factor. To address this limit a novel autonomously reconfigurable antenna is presented in this thesis which allows for simple use at multiple frequencies [21]. This design uses power harvesting circuitry in combination with a reconfigurable antenna to demonstrate the ability to transmit at different frequencies, without the use of a separate power source. Furthermore this thesis presents a prototype for an autonomous reconfigurable antenna that operates at 1.25 GHz and 1.6 GHz.
Bit Optimized Reconfigurable Network (BORN): A New Pathway Towards Implementing a Fully Integrated Band-Switchable CMOS Power Amplifier
(North Dakota State University, 2020) Hamidi Perchehkolaei, Seyyed Babak
The ultimate goal of the modern wireless communication industry is the full integration of digital, analog, and radio frequency (RF) functions. The most successful solution for such demands has been complementary metal oxide semiconductor (CMOS) technology, thanks to its cost-effective material and great versatility. Power amplifier (PA), the biggest bottleneck to integrate in a single-chip transceiver in wireless communications, significantly influences overall system performance. Recent advanced wireless communication systems demand a power amplifier that can simultaneously support different communication standards. A fully integrated single-chip tunable CMOS power amplifier is the best solution in terms of the cost and level of integration with other functional blocks of an RF transceiver. This work, for the first time, proposes a fully integrated band-switchable RF power amplifier by using a novel approach towards switching the matching networks. In this approach, which is called Bit Optimized Reconfigurable Network (BORN), two matching networks which can be controlled by digital bits will provide three operating frequency bands for the power amplifier. In order to implementing the proposed BORN PA, a robust high-power RF switch is presented by using resistive body floating technique and 6-terminal triple-well NMOS. The proposed BORN PA delivers measured saturated output power (Psat) of 21.25/22.25/ 23.0dBm at 960MHz/1317MHz/1750MHz, respectively. Moreover, the proposed BORN PA provides respective 3-dB bandwidth of 400MHz/425MHz/550MHz, output 1-dB compression point (P1dB) of 19.5dBm/20.0dBm/21.0dBm, and power-added efficiency (PAE) of 9/11/13% at three targeted frequency bands, respectively. The promising results show that the proposed BORN PA can be a practical solution for RF multiband applications in terms of the cost and level of integration with other functional blocks of an RF transceiver.
Calculating Cardiovascular Lumped-Parameter Model Values by Injecting Small Volume Perturbations in an Isovolumic Heart
(North Dakota State University, 2011) Wandler, Jeff
Diagnosing cardiac patient problems contains many uncertainties, and to fully diagnose the patient's condition usually requires a lengthy drug regimen to see what works and what does not. Compounding this problem is that even after the correct drug regimen has been discovered, the underlying cause for the problem may remain a mystery. Thus, the uncertainty and the length of time required to provide an accurate and adequate solution makes it very difficult to provide quality care to the patient. Templeton and others have shown that lumped cardiac muscle parameters can be extracted from an isolated heart by injecting small volumes at high frequencies relative to the heart rate and measuring the pressure response to this volume change. Using the Hill muscle model of two springs and a dash pot to portray the different elements of the cardiac muscle, the pressure and volume relationship makes it possible to calculate these muscle parameters using frequency response analysis techniques. The hypothesis to be tested is "Is it possible to develop a method to test cardiac muscle for stiffness, resistance, and contractile force from measuring ventricular pressure and injected flow?" To test this hypothesis, an isovolumic heart model is developed and allowed to develop pressure, along with a small volume injected to create a pressure response. Analysis of the pressure and flow waveforms produces a measured value of the cardiac model parameter values to compare to the model values. Results from injecting small volume changes into a mathematical heart model show that it is possible to extract the muscle model parameters of non-linear resistance, inertia of the fluid and muscle, and stiffness of the muscle while filling and contracting. The injected frequency and volume were varied to find usable conditions, both with regard to the calculations and the practical limits. Analyzing the error between the measured and model values for a large number of different combinations of model parameters shows an average error of less than 1%.
The Capacity Region of the Gaussian Z-Interference Channel with Gaussian Input and Weak Interference
(North Dakota State University, 2016) Sarkar, Avik
We consider a wireless communication scenario with two transmit-receive pairs where each of the transmitters has a message for its corresponding receiver and only one of the receivers face interference from the undesired transmitter. In our research, we focused on devising optimal ways to manage this undesired interference and characterize the best communication rates for both transmit-receive pairs. Currently, this problem of interference is dealt with by restricting the two communications in di erent frequency or time bands. We explore the possibility of achieving better rates by allowing them to operate in the same band. Such channels were identi ed about 4 decades ago, but the maximum rate of communication when the transmitters have a power constraint is still unknown. In this work, we characterize the best rates for this channel under a reasonable practical constraint of using Gaussian signals at both the transmitters.
Capacity Region of Two Interfering Mimo Multiple Access Channels With Strong Interference
(North Dakota State University, 2015) Modi, Noopur
We consider a communication network, where two mutually interfering 2-user MIMO Multiple Access Channels (MAC) operate simultaneously via the same time-frequency space, and characterize the capacity region of this network when the channel matrices satisfy a strong interference condition. This interfering MAC (IMAC) with aforementioned channel matrices is called strongly ordered IMAC in this work. We characterize the capacity region first using the genie aided approach to find out several constraints that must be satisfied by any achievable rate tuple. Then we show that independent Gaussian coding at each transmitter and joint decoding of the messages at the receivers can achieve all the rate pairs that satisfy all the aforementioned constraints. In an IMAC, there are two types of tradeoffs between rates of communication; it is between the rates of users from different MACs and among rates of users belonging to the same MAC. Result shows two tradeoffs are homogeneous.
The Capillary-Centric Model of Coupling-As-Thermodynamics
(North Dakota State University, 2015) Taylor, Andrew James David
Models of ventricular-arterial coupling (VAC) have historically described the heart as a function of its energetic interaction with the arterial system. However, these models either represent the dynamic, adaptive cardiovascular system (CVS) in isolation or sacrifice cardiac mechanics to use simplified, time-averaged values across the cardiac cycle. In this thesis a facsimile CVS is constructed that characterizes ventricular-arterial interactions with intact cardiac mechanics as a function of whole-body thermo-fluid homeostatic regulation. Simulation results indicate proportional-integral (PI) control of heart rate and arterial resistance is conditionally sufficient to maintain body temperature during square-wave exercise, but further elements may be required to mimic genuine physiological responses. These simulations of the primitive model lay the framework of capillary-centric VAC through the perspective of coupling-as-thermodynamics.
Carbon Microfiber Material for Electromagnetic (Shielding) Applications
(North Dakota State University, 2015) Rafiq, Muhammad Nadeem
Electromagnetic shielding is becoming more and more important with the abundance of wireless devices. Therefore a need has arisen for more versatile, flexible and low-cost solutions for shielding. For these requirements, carbon microfiber material has been proposed for electromagnetic shielding applications. For this purpose its shielding effectiveness has been measured and modeled in a simulation environment. A parametric simulation was conducted for the material property ’conductivity’ and the results were compared to measured ones. These simulation results were also verified by the analytical solution for the shielding effectiveness and the agreement between the simulated values and analytical results demonstrated that the carbon microfiber material, though having less conductivity than the traditional metallic shields is a good candidate for electromagnetic shielding applications. Carbon microfiber not only provides comparable shielding effectiveness to a metallic shield but it can be advantageous because of its light weight, corrosion resistance and flexibility. Also, its porous nature can help with cooling of enclosed electronic circuits.
Cardiac Output Improvement in Mechanical Circulatory Support Devices
(North Dakota State University, 2017) Qureshi, Muhammad Bilal
Mechanical circulatory support devices (MCSDs) have gained widespread clinical acceptance as an effective heart failure (HF) therapy. The concept of harnessing the kinetic energy (KE) available in the forward aortic flow (AOF) is proposed as a novel control strategy to further increase the cardiac output (CO) provided by MCSDs. A complete mathematical development of the proposed theory and its application to an example MCSDs (two-segment extra-aortic cuff) are presented. To achieve improved device performance and physiologic benefit, the example MCSD timing is regulated to maximize the forward AOF KE and minimize retrograde flow. The proof-of-concept was tested to provide support with and without KE control in a computational HF model over a wide range of HF test conditions. The simulation predicted increased stroke volume (SV) by 20% (9 mL), CO by 23% (0.50 L/min), left ventricle ejection fraction (LVEF) by 23%, and diastolic coronary artery flow (CAF) by 55% (3 mL) in severe HF at a heart rate (HR) of 60 beats per minute (BPM) during counterpulsation (CP) support with KE control. This research also explains how selection of inflation and deflation timing points for extra-aortic two-segmented cuff counterpulsation device (CPD) can affect the hemodynamic of the cardiovascular system (CVS). A comprehensive analysis of compliance profile timings generated through exhaustive search technique and the one selected through steepest descent method is carried out to predict and compare the difference in SV via computer simulation models. The influence of control modes (timing and duration) of deflation and inflation for extra-aortic two-segmented CPD on hemodynamic factors compared to no-assist HF were investigated. Simulation results (P < 0.05) predicted that the two-segmented CPD with late deflation and early inflation mode would be a suitable mode with 80% augmentation in peak diastolic aortic pressure (AOP), reduction in peak systolic pressure up to 15%, increases in CO by 60% and mean CAF by 80%. The proposed KE control concept may improve performance of other MCSDs to further enhance their potential clinical benefits, which warrants further investigation. The next step is to investigate various assist technologies and determine where this concept is best applied.
Characterization of a Structure Consisting of Magnetostatic Responsive Microscopic Particles and Its Applications In Antennas
(North Dakota State University, 2015) Iftikhar, Adnan
Wireless communication systems often require that a single antenna work at different frequencies. Thus the recon gurable antennas are useful in frequency agile environments to receive a signal over multiple bands. Research on antenna recon gurability using mechanical systems and radio frequency (RF) switches have been implemented in the past years. One problem for these voltage- controlled switches is that they require direct current (DC) bias control lines for operation. The incorporation of DC biasing circuitry also limits designers to explore the recon gurable capacity of many antennas. The DC bias control lines can possibly degrade the antenna performance. Moreover, because of the additional control signals, many existing multiband systems cannot use recon gurable antennas. In this research, magnetostatic responsive particles are used in micro-sized cavities to manufacture novel magnetic switches that are activated in a magnetic eld. Furthermore, the characterization, modeling in simulation software, and lumped element model extraction of these micro electromechanical systems (MEMS) based on magnetic switches is presented. A re ned method of quantifying the micro sized magnetic particles in a cavity and the response of the proposed micro level magnetic switches in the RF eld is also explained in detail. Then, a microstrip patch antenna loaded with Electromagnetic Band Gaps (EBGs) that cannot be recon gured using existing RF switching devices was recon gured using the proposed magnetic switches and is presented in this research for the rst time. A comparison between PIN diodes and the proposed magnetic switches on a microstrip patch is also included in this research to show the efficiency of the proposed structure. Overall, the proposed magnetic switches showed good results when used in antenna systems to achieve recon gurability and do not effect the radiation characteristics of the recon gured antenna.
Characterization of Inflationary and Deflationary Auscultatory Blood Pressure Measurements
(North Dakota State University, 2022) Alvarez, Enrique
This document is a paper-based dissertation. The dissertation is a collection of articles written by the author in the pursuit to develop a novel method to measure blood pressure (BP). The introduction chapter describes how the documents are interrelated. This work starts with the description of the development and design of a non-invasive medical device capable of measuring arterial BP with a combination of inflationary and deflationary procedures. In addition to the device, we conducted a human-based study to characterize the properties of the BP signal in the inflationary and deflationary curves. With the signals acquired, we focused on the uncertainty occurring when taking two consecutive BP measurements. The prototype was composed of 1) a modified off-the-shelf oscillometric BP system, 2) a contact microphone with an amplifier, and 3) a high-sensitivity pulse oximeter, and its control electronics. The device captured the cuff pressure signal, arterial skin-surface acoustics, and photoplethysmography (PPG). The captured signals were processed and analyzed. We focused our analysis on the characterization of the uncertainty of two consecutive BP measurements by studying the biosignals captured with the custom-made apparatus. Accurate non-invasive BP measurements are vital in preventing and treating many cardiovascular diseases. The “gold standard” for non-invasive procedures is the auscultatory method, which is based on detecting Korotkoff sounds while deflating an arm cuff. Using this method as a “gold standard” requires highly-trained technicians and has an intrinsic uncertainty in its BP predictions. In this document, we analyze and characterize the origins of BP uncertainty. By analyzing the captured bio signals we postulate an uncertainty model for two consecutive BP measurements. Our research group developed a computer-based simulation of auscultatory BP measurement uncertainty, and these modeled results were compared to a humansubject experiment with a group of 20 diverse-conditioned individuals. Uncertainties were categorized and quantified. The total computer-simulated uncertainty ranged between -8.4 mmHg to 8.4 mmHg in systolic BP and -8.4 mmHg to 8.3 mmHg in diastolic BP at a 95% confidence interval. The limits in the human-based study ranged from -8.3 mmHg to 8.3 mmHg in systolic BP and -16.7 mmHg to 4.2 mmHg in diastolic BP.
Cloud Based Recommendation Services for Healthcare
(North Dakota State University, 2016) Abbas, Assad
With the inception of portable computing devices, enormous growth in the healthcare data over the Internet has been observed. Consequently, the Web based systems come across several challenges, such as storage, availability, reliability, and scalability. By employing the cloud computing to offer healthcare services helps in overcoming the aforementioned challenges. Besides the healthcare organizations, cloud computing services are also equally beneficial for general public in devising patient-centric or user-centric methodologies that involve users in managing health related activities. This dissertation proposes methodologies to: (a) make risk assessment about diseases and to identify health experts through social media using cloud based services, (b) recommend personalized health insurance plans, and (c) secure the personal health data in the cloud. The proposed disease risk assessment approach compares the profiles of enquiring users with the existing disease specific patient profiles and calculates the risk assessment score for that disease. The health expert consultation service permits users to consult with the health specialists that use Twitter by analyzing the tweets. The methodology employs Hyperlink-Induced Topic Search (HITS) based approach to distinguish between the doctors and non-doctors on the basis of tweets. For personalized health insurance plans identification, a recommendation framework to evaluate different health insurance plans from the cost and coverage perspectives is proposed. Multi-attribute Utility Theory (MAUT) is used to permit users evaluate health insurance plans using several criteria, for example premium, copay, deductibles, maximum out-of-pocket limit, and various other attributes. Moreover, a standardized representation of health insurance plans to overcome the heterogeneity issues is also presented. Furthermore, the dissertation presents a methodology to implement patient-centric access control over the patients’ health information shared in the cloud environment. This methodology ensures data confidentiality through the El-Gamal encryption and proxy re-encryption approaches. Moreover, the scheme permits the owners of health data to selectively grant access to users over the portions of health records based on the access level specified in the Access Control List (ACL) for different groups of users. Experimental results demonstrate the efficacy of the methodologies presented in the dissertation to offer patient/user-centric services and to overcome the scalability issues.

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