Browsing by Author "Akkaya, Ali."

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    An end-to-end QoS architecture for all-IP 4G mobile networks
    (Thesis (M.S.)-Bogazici University. Institute for Graduate Studies in Science and Engineering, 2008., 2008.) Akkaya, Ali.; Tuğcu, Tuna.
    Fourth Generation (4G) Networks can be defined as the convergence of wired and wireless network technologies and formation of all-IP based integrated system with premium quality and high security. As an integrated system, providing end-to-end Quality of Service (QoS) similar to legacy networks has been a challenging issue in such a network. In this thesis, an all-IP next generation wireless network architecture that supports end-to-end QoS is presented. A new packet based Medium Access Control (MAC) layer, which runs on top of Frequency Hopping Orthogonal Frequency Division Multiple Access (FH-OFDMA) based physical layer is designed and implemented. The proposed MAC layer is based on one of the promising proposals to IEEE 802.20 by Qualcomm. Multi Protocol Label Switching (MPLS) and DiffServ support of MPLS is utilized at the backbone of the architecture to provide end-to-end QoS. By integrating Internet Protocol (IP) Layer QoS parameters to proposed packet-based air interface, end-to-end QoS including the air interface is provided. Two new nodes, Wireless Access Router (WAR) and Mobile Node (MN), which implement the new MAC layer, are introduced. WAR is integrated to the backbone via standard Label Edge Router (LER) of MPLS architecture. The architecture is implemented with OPNET Modeler simulation tool to analyze the QoS perception of MNs within the architecture.|Keywords: All IP networks, Mobile networks, Wireless networks, QoS, OFDM
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    Analysis of reception process for an absorbing receiver in molecular communication via diffusion
    (Thesis (Ph.D.) - Bogazici University. Institute for Graduate Studies in Science and Engineering, 2015., 2015.) Akkaya, Ali.; Tuğcu, Tuna.
    Nanotechnology is currently being applied to vast number of elds to overcome the challenges faced with existing technologies that cannot e ciently scale down to nano level. However, considering the limited processing and memory resources of nano-machines, performing complex tasks requires new communication mechanisms. Communication is one of the important issues to be addressed in nano-scale environment. Inspired by the nature, molecular communication via di usion is a candidate to address this issue. Although the reception process of the messenger molecules has a signi cant impact on the performance of molecular communication via di usion, the factors that e ect the received signal for an absorbing receiver have not been investigated in the literature. In this thesis, we rst introduce methods for e cient simulation of molecular communication via di usion to enable further analysis. We propose two novel simulation architectures; a dual-zone simulation model to decrease execution time while preserving simulation accuracy and an HLA based architecture for distributed simulation of molecular communication via di usion. Then, we analyse di erent dimensions of reception process for an absorbing receiver to derive closed form formulations. The results presented enable optimizations that will have a direct e ect on production costs of receptors and the receivers. Finally, we propose a new approach for demodulation of information for an absorbing receiver and analyse energy consumption and data rate for the proposed model.
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    The effects of serious games on students’ conceptual knowledge of object-oriented programming and computational thinking skills
    (Thesis (M.A.) - Bogazici University. Institute for Graduate Studies in the Social Sciences, 2018., 2018.) Akkaya, Ali.; Akpınar, Yavuz.
    The aim of this study is to investigate the effects of a serious game, Curious Robots: Operation Asgard (Meraklı Robotlar: Operasyon Asgard), on undergraduate students’ learning performance on conceptual knowledge of object-oriented programming (OOP) of and computational thinking (CT) skills in Turkish. The study was conducted with a pre-test and post-test quasi-experimental design model. Data were collected from 30 freshman students without programming experience and 31 sophomore students with procedural programming experience. Each student took a creative problem-solving test and a pre-test before playing the game. After playing the developed game, students took a post-test and an attitude scale for serious game assisted programming learning. Analyses showed that the game helped students to develop conceptual knowledge of OOP and improve their CT skills. Analysis also showed that there were no significant two-way or direct interactions among students’ creative problem-solving skills, attitudes towards digital game-based learning of programming on the achievement scores of students. This study makes a significant contribution to the literature by providing empirical data about the effects of serious games on novice programmers’ conceptual knowledge of OOP and CT skills. It is thought that in the lights of the findings of the study, serious game designers and instructors would have the opportunity to design effective games that help novice programmers to overcome their learning difficulties and improve their learning.