Now showing items 1-20 of 25

  • Analysis of structures formed with shunt capacitor seperated by transmission lines 

    Authors:Cakmak, Gokhan
    Publisher and Date:(Kadir Has University, 2018)
    Bobin ve kondansatorlerden olusan merdiven devreler hakkinda literaturde bircok calisma bulunmaktadir. Fakat genellikle agir ve buyuk olduklari icin uretilebilecek deger araliklarinin sinirli olmasi ve mikrodalga frekanslardaki uretim gucluklerinden dolayi tasarlanan devrelerde bobin olmasi istenmez dagitilmis elemanlar (iletim hatlari) ile yaklasik olarak gerceklenmeye calisilirlar. Toplu elemanlarin dagitilmis elemanlara cevrilmesinde Richards donusumu kullanilir. Paralel bagli kondansatorlerin ...

  • Analysis of visible light communation sytems and adaptive equalization effects 

    Authors:Mamus, Atilla
    Publisher and Date:(Kadir Has University, 2015)
    Communication by means of visible light is a newly developing technology that has been brought up as an alternative to the current electromagnetic based communication systems. The recently conducted studies led to the use of LED Technology for illumination purposes and for this technology to have an edge over devices that consume excessive energy as presently being used by us. LED technology is predicted to become an important part of illumination systems especially in consideration of the low ...

  • Artificial neural network based sparse channel estimation for OFDM systems 

    Authors:Tahir, Abdur Rehman Bin
    Publisher and Date:(Kadir Has University, 2017)
    In order to increase the communication quality in frequency selective fading channel environment, orthogonal frequency division multiplexing (OFDM) systems are used to combat inter-symbol-interference (ISI). In this thesis, a channel estimation scheme for the OFDM system in the presence of sparse multipath channel is studied. The channel estimation is done by using the artificial neural networks (ANNs) with Resilient Backpropagation training algorithm. This technique uses the learning capability ...

  • Bayesian learning for cellular neural networks 

    Authors:Ozer, Metin
    Publisher and Date:(Kadir Has University, 2013)
    Cellular Neural Networks have been an active research eld since their introduction in the late 80s. Several training algorithms are proposed since then. All have their advantages and disadvantages. Most of them uses deterministic methods to acquire the network parameters. in this thesis a new training method is proposed for Cellular Neural Networks and Discrete-Time Cellular Neural Networks are used for implemented applications. This new method is a probabilistic method. Maximum A Posteriori ...

  • Coexistence of cognitive radio based networks in tv white space 

    Authors:Karatalay, Onur
    Publisher and Date:(Kadir Has University, 2016)
    Due to increasing data rates in enhancing wireless communications RF spectrum which is one of the most crucial natural sources has become more valuable. in order to utilize the limited spectrum e_ciently and solve the scarcity problem regulatory agencies granted unlicensed networks or secondary users (SUs) access to licensed bands for wireless communication with the condition that they should not cause harmful interference to primary users (SUs). Cognitive radio (CR) technology enables devices to ...

  • Computation of two-variable mixed element network functions 

    Authors:Tabassum, Nauman
    Publisher and Date:(Kadir Has University, 2017)
    in this dissertation the algorithm known as “Standard Decomposition Technique (SDT)” is used together with Belevitch’s canonic representation of scattering polynomial for two-port networks operate on high frequency to find the analytical solutions for “Fundamental equation set (FES)”. This FES is extracted by using Belevitch canonic polynomials “ ??(?? ??) ?(?? ??) and ??(?? ??)” used for the description of mixed lumped and distributed lossless two-port cascaded networks in two variables of degree ...

  • Detection of interdependent multiband systems for cognitive radios and ultra-wideband systems 

    Authors:Yılmaz, Burak
    Publisher and Date:(Kadir Has University, 2012)
    As a result of advances in the wireless technology new systems have been proposed and hence more frequency bands are occupied in the spectrum. Therefore the number ofavailable frequency bands for future wireless communication systems is decreasing and alternative communication technologies have appeared in recent years. These are cognitive radio and ultra wideband systems which use the spectrum more efficiently. -- Abstract'dan.

  • Femtocell design for data communications in mobile networks 

    Authors:Cogalan, Tezcan
    Publisher and Date:(Kadir Has University, 2013)
    in this thesis game theoretic utility-based adaptive power control algorithm for uplink of femtocell networks is performed for mitigation of interference in two different ways. The first one is allocation of femtocell interference threshold in randomly activated femtocell base stations in a known macrocell coverage area and the second one is adaptation of the power of the femtocell users for mitigating total interference from femtocell users at the macrocell base station. Accordingly we consider ...

  • Load flow based electrical system design and short circuit analysis 

    Authors:Rana, Subhan
    Publisher and Date:(Kadir Has University, 2019)
    Load flow and short circuit behaviour of electrical energy systems are investigated. The system to be investigated, is designed based on a 230kVA power grid analytical model. Load flow analysis is crucial for the design of electrial power systems where tests related to load flow are indispensible. This work includes modelling of several electrical power components (transformer, power grid, bus bar, circuit breakers, etc. ) to highlight the methods in the study of the system behaviour. Faults ...

  • Log analysis with anomaly detection 

    Authors:Şahin, Uygar
    Publisher and Date:(Kadir Has University, 2019)
    Detection of anomalies in the data is an important data analysis job for server logs as they will reveal many benefits. Different types of methods can be used for anomaly detection: supervised, semi-supervised, and supervised anomaly detection. Similarly different algorithms exist for each category. In this work, four anomaly detection algorithms are utilized and their performance metrics are compared for public Hadoop Distributed File System (HDFS) data. Among the others, the support vector ...

  • Low energy fixed clustering algorithm for wireless sensor networks 

    Authors:Cengiz, Korhan
    Publisher and Date:(Kadir Has University, 2016)
    Wireless sensor networks (WSNs) have become an important part of our lives as they can be used in vast application areas from disaster relief to health care. As a consequence the life span and the energy consumption of a WSN has become a challenging research area. According to the existing studies instead of using direct transmission or multi-hop routing clustering can significantly reduce the energy consumption of sensor nodes and can prolong the lifetime of a WSN. in this thesis low energy fixed ...

  • Modelling of visible light channels and performance analysis for optical ofdm systems 

    Authors:Alsan, Hüseyin Fuat
    Publisher and Date:(Kadir Has University, 2016)
    This work is concerned with a challenging problem of modeling and simulation of visible light communications (VLC) channels for optical wireless communication (OWC) systems. A proper channel model for VLC is absent in the current literature. For this reason two different indoor channel model with different material types and different receiver-transmitter locations have been obtained and implemented for asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) technique. ...

  • New channel estimation techniques for cooperative underwater acoustic OFDM systems 

    Authors:Mustafa, Erdoğan
    Publisher and Date:
    Cooperative underwater acoustic communication systems come into prominence in recent years. Since underwater channels are sparse and additive noise entering the system is colored Gaussian noise it is very difficult to estimate the underwater channels and theoretically makes it interesting. in the first part of the thesis the transmission from source to the target recipient is realized by means of a relay system. Orthogonal frequency division multiplexing (OFDM)-based channel estimation problem is ...

  • Performance of ieee 802.11af systems under realistic channel conditions 

    Authors:Macit, Mustafa Can
    Publisher and Date:(Kadir Has University, 2016)
    As the analog TV broadcasting channels have become less frequently used in the last decade there has been a great interest in these frequency bands for the deployment of regional local and personal area networks. Among them the local area network standard iEEE 802.11af denes PHY and MAC layer implementation of such networks in these unused frequency bands also named television white space (TVWS). According to the standard the systems may use contiguous or non-contiguous channels during their ...

  • Performance of orbital angular momentum based communication systems under varied atmospheric turbulence 

    Authors:Ashfaq Sheikh, Abdul Ahad
    Publisher and Date:(Kadir Has University, 2016)
    Orbital Angular Momentum is gaining a lot of attention in the past years as it is providing the means to break free from the ever increasing shortage of options when it comes to Data Rates and Effective Frequency Utilization. OAM promises to break the shackles and provide a solution where a beam which can be transformed into multiple beams within itself and become independent streams of data (pertaining to the principle of orthogonality) to be transferred when properly utilized. in this thesis the ...

  • Power control and multihop communication approaches for the coexistence of ieee 802.11af and iEEE 802.22 networks in tv white space 

    Authors:Ulgen, Oguz
    Publisher and Date:(Kadir Has University, 2017)
    Communication networks have been among the most important research fields of scientists in the recent years. Researches have been conducted in various different topics and contents as technology has evolved. As some new technologies become available some technologies become out of date. One of the outdated technologies in recent years is the analog TV broadcasting. With the shift from analog TV broadcasting to digital TV broadcasting the frequency bands of old analog TV broadcasting has become ...

  • Practical implementation of combinational cooperative detection method 

    Authors:Çatak, Evren
    Publisher and Date:(Kadir Has University, 2012)
    in conventional cooperative detection a fusion center decides on the presence or theabsence of the primary user by gathering all the information from the secondaryusers (SUs) and conveys this decision to all users. This approach does not take intoaccount the locations of the SUs where a user far from the primary user (PU) mayalso have to keep silent. An alternative method referred to as the combinationalcooperative detection method in this study was recently proposed to solve thisproblem. This ...

  • Primary user detection in Ultrawide-band based wireless sensor networks 

    Authors:Sabucu, Yağmur
    Publisher and Date:(Kadir Has University, 2013)
    in this thesis ultra-wideband (UWB) based wireless sensor networks (WSNs) are considered for the detection of a primary user. Different from earlier works (i) both uplink and downlink information of the primary user are assessed for the primary user detection and (ii) iEEE 802.15.4a standard is considered for the implementation of each secondary user. Specifically the worked focused on the comparison of the two iEEE 802.15.4a based signalling namely binary pulse position modulation (BPPM) and ...

  • Quality of service constrained scheduling for massive m2m communications in future cellular networks 

    Authors:Mohemine, Muhammad Abdul
    Publisher and Date:(Kadir Has University, 2018)
    Radio resource allocation for massive M2M communications is one of the key problems in next generation cellular networks. Satisfying strict and very diverse quality-of-service requirements increases the hardness of this problem. in this thesis flexible scheduling problem for massive M2M communications is solved considering the physical layer architecture of 5G cellular networks. First envisioned physical layer architectures and waveforms proposed for 5G are investigated and a physical layer ...

  • Real frequency design of narrowband impedance equalizer with complex terminations 

    Authors:Yeşilyurt, Gökmen
    Publisher and Date:(Kadir Has University, 2018)
    in this thesis the real frequency design of L Pi and T type networks with complex terminations has been analyzed. The main purpose of the proposed approach is to compare the existing methods against the proposed method on impedance matching design in narrowband with complex termination. There are two types of models the serial model for T type network design and the parallel model for Pi and L type networks design. The generator and load termination impedances are given as measured values. Thus ...