Now showing items 1-20 of 109

  • A broadband microwave amplifier design by means of immittance based data modelling tool 

    In this paper a practical broadband microwave amplifier design algorithm is introduced utilizing the immittance data-modelling tool. In the course of design first the optimum input and output terminations for the active device are produced employing the real frequency technique. Then these terminations are modelled utilizing the new immittance-modelling tool to synthesize the front-end and back-end matching networks. An example is included to exhibit the implementation of the proposed design ...

  • A New Technique for OFDM: OFDM-Index Modulation 

    Authors:Basar, Ertugrul; Aygölü, Ümit; Panayirci, Erdal
    Publisher and Date:(IEEE, 2013)
    In this study a novel scheme called orthogonal frequency division multiplexing with index modulation (OFDMIM) is proposed for frequency selective channels. In this scheme the information is conveyed not only by only M -ary signal constellations as in classical OFDM but also by the indices of the active subcarriers which are determined according to the information bits. Different transceiver structures have been investigated for the proposed scheme and it has been shown via computer simulations ...

  • A Novel Indoor Channel Model for TVWS Communications based on Measurements 

    Authors:Hashir, Syed Muhammad; Erküçük, Serhat; Baykaş, Tunçer
    Publisher and Date:(IEEE, 2018)
    In this paper we present an indoor measurement campaign for TV white space bands inside a university building. The measurement results are compared with different indoor propagation models in the literature. We observed large estimation errors for the total path loss value from all existing models. Consequently we are proposing a new indoor propagation model for TVWS frequencies which concatenates the effects of frequency dependent path loss with penetration losses due to walls and windows. ...

  • A numerical method for frequency determination in the astable cellular neural networks with opposite-sign templates 

    Authors:Özmen, Atilla; Tander, Baran
    Publisher and Date:(IEEE, 2006)
    In this study a numerical method is proposed to determine the oscillation frequencies in the astable cellular neural networks with opposite-sign templates [1]. This method depends on the training of a multilayer perceptron that uses various template coefficients and the correspondant frequency values as inputs and outputs. First of all a frequency surface is obtained from templates and then training samples are picked from this surface in order to apply to multilayer perceptron. The effects of the ...

  • A Simple Iterative Equalizer for Space Time Coded Multiple Antenna Systems 

    Authors:Güçlüoǧlu, Tansal
    Publisher and Date:(IEEE, 2009)
    In this paperg a simple low complexity iterative receiver for spacetime coded zSTCg transmission is proposed and the pen formance over frequencyyselective fast and quasistatic fading channels is investigatedF Simulation results show that the pery formance of the proposed structure improves with each iteraytionF Considering the practically prohibitive complexity of opytimal equalizersg the proposed iterative receiver can be more desirable in wireless systems with large number of antennasg big ...

  • Achievable Performance of Bayesian Compressive Sensing Based Spectrum Sensing 

    Authors:Başaran, Mehmet; Erküçük, Serhat; Cirpan, Hakan Ali
    Publisher and Date:(IEEE, 2014)
    In wideband spectrum sensing compressive sensing approaches have been used at the receiver side to decrease the sampling rate if the wideband signal can be represented as sparse in a given domain. While most studies consider the reconstruction of primary user's signal accurately it is indeed more important to analyze the presence or absence of the signal correctly. Furthermore these studies do not consider the achievable lower bounds of reconstruction error and how well the selected method performs ...

  • Alternative Transducer Power Gain Expression in Broadband Matching Network Designs 

    Authors:Şengül, Metin Y.
    Publisher and Date:(IEEE, 2016)
    In this paper a reflection coefficient based transducer power gain expression has been derived which is an alternative to the impedance based expression exists in the literature. A broadband double matching problem is solved by using the derived gain expression and the obtained performance has been compared with the performance obtained via the existing expression.

  • An efficient joint data detection and channel estimation technique for uplink MC-CDMA systems based on SAGE algorithm 

    This paper is concerned with joint channel estimation and data detection for uplink multicarrier code-division multiple-access (MC-CDMA) systems in the presence of frequency fading channel. The detection and estimation algorithm implemented at the receiver is based on a version of the expectation maximization (EM) technique called the spece-alternating-generalized-expectation-maximization (SAGE) algorithm which is very suitable for the the multicarrier signal formats. Application of the SAGE ...

  • An Efficient SAGE-based Data Detection Algorithm for OFDM Systems in the Presence of Very Fast Fading Channels 

    Authors:Dong, Zhicheng; Fan, Pingzhi; Panayirci, Erdal
    Publisher and Date:(IEEE, 2013)
    In this paper an iterative and computationally efficient data detection algorithm is proposed based on the space alternating generalized expectation maximization (SAGE) technique for orthogonal division multiplexing (OFDM) systems under fast fading channels. The proposed detector includes the original detector presented in [1] as one of its special cases. With a proper choice of its parameters simulations show that the new detector has negligible performance loss than original one in [1] with ...

  • Analysis of Extended Busy Tone Performance for Coexistence between WRAN and WLAN TVWS Networks 

    Authors:Karatalay, Onur; Erküçük, Serhat; Baykaş, Tunçer
    Publisher and Date:(IEEE, 2015)
    TV White Spaces indicate spectrum bands which were reserved for licensed terrestrial TV broadcasting and opened to unlicensed use under regulatory conditions. One important regulation which is common in all regulatory domains is no harmful interference is created to licensed devices. On the other hand interference between unlicensed devices is not regulated. As a result system designers developed new methods to improve coexistence between TVWS networks. Extended busy tone one of such methods is ...

  • Anomaly Detection in Walking Trajectory 

    Authors:Öğrenci, Arif Selçuk
    Publisher and Date:(IEEE, 2018)
    Analysis of the walking trajectory and the detection of anomalies in this trajectory, provide important benefits in the fields of health and security. In this work, two methods to detect anomalies in trajectories, are compared. Firstly, an unsupervised method is used where the conformance among trajectories are taken into consideration. Trajectories that deviate from others are qualified as anomalies. Secondly, the points in the trajectories are considered as a time series. Artifical neural networks ...

  • Bayesian compressive sensing for ultra-wideband channel models 

    Authors:Ozgor, Mehmet; Erküçük, Serhat; Cirpan, Hakan Ali
    Publisher and Date:(IEEE, 2012)
    Considering the sparse structure of ultra-wideband (UWB) channels compressive sensing (CS) is suitable for UWB channel estimation. Among various implementations of CS the inclusion of Bayesian framework has shown potential to improve signal recovery as statistical information related to signal parameters is considered. In this paper we study the channel estimation performance of Bayesian CS (BCS) for various UWB channel models and noise conditions. Specifically we investigate the effects of (i) ...

  • Beacons for Indoor Positioning 

    This work aims to develop a system for the tracking and control of elderly or handicapped people in an indoor environment. We have developed both a special box using an Arduino board and a mobile application on Android to determine the location of the target based on the Bluetooth Low Energy signals transmitted by special Beacons which are placed in the area of interest. Both systems are used to determine the position of the person and to monitor any event that would cause an alert. Those events ...

  • Broadband Single Matching with Lumped Elements 

    Authors:Şengül, Metin Y.
    Publisher and Date:(IEEE, 2015)
    While designing broadband single matching networks for microwave communication systems via commercially available software tools it is necessary for these tools to select the proper matching network topology and element values. But how to make these selections is an unknown problem. But the proposed approach in this paper presents a practical method to generate single matching networks with good initial element values. After completing the design the performance of the designed single matching ...

  • Busy Tone Based Power Control for Coordination of IFFY 802.11af and 802.22 System 

    Authors:Ülgen, Oğuz; Erküçük, Serhat; Karatalay, Onur; Baykas, Tuncer
    Publisher and Date:(IEEE, 2017)
    In this paper, a new power control algorithm based on busy tone approach has been proposed for the coordination of IEEE 802.22 and IEEE 802.11af systems in TV white space. Different from the earlier studies, in addition to both 802.11af access point and clients listening to the busy tone, they also adjust their communication power according to the location information and use hopping for communication, if needed Acccordingly, interference caused to 802.22 systems has been reduced while the 802.11af ...

  • Busy Tone Implementation for Coexistence of IEEE 802.22 and 802.11 af Systems 

    Authors:Karatalay, Onur; Erküçük, Serhat; Baykaş, Tunçer
    Publisher and Date:(IEEE, 2015)
    In this paper a new algorithm based on busy tone approach has been proposed for the coexistence of IEEE 802.22 and IEEE 802.11af systems in TV white space. Different from the earlier study in addition to 802.11af access points listening to the busy tone signal their clients also listen to the busy tone and let the access points know once they hear it. Accordingly interference caused to 802.22 systems has been reduced. This study quantifies the improved system performance in terms of interfering ...

  • Cascaded Lossless Commensurate Line Synthesis 

    Authors:Şengül, Metin Y.
    Publisher and Date:(IEEE, 2009)
    In this paper a synthesis algorithm for cascaded lossless commensurate lines is summarized. The algorithm is based on transfer matrix factorization. Firstly the characteristic impedance of the extracted element is calculated and then after extracting the element the reflection factor of the remaining network is calculated. This process is repeated until the termination resistance is reached. An example is included to illustrate the implementation of the algorithm.

  • Channel estimation for MIMO-OFDM systems in fixed broadband wireless applications 

    Authors:Karakaya, Bahattin; Cirpan, Hakan Ali; Panayirci, Erdal
    Publisher and Date:(IEEE, 2007)
    Systems employing multiple transmit and receive antennas known as multiple input multiple output (MIMO) systems can be used with OFDM to improve the resistance to channel impairments. Thus the technologies of OFDM and MIMO are equipped in fixed wireless applications with attractive features including high data rates and robust performance. However since different signals are transmitted from different antennas simultaneously the received signal is the superposition of these signals which implies ...

  • Channel Estimation for SM Systems over Time-Varying Rayleigh Fading Channels 

    Authors:Acar, Yusuf; Dogan, Hakan; Panayirci, Erdal
    Publisher and Date:(IEEE, 2014)
    This paper is concerned with the challenging and timely problem of channel estimation for spatial modulated systems in the presence of time varying channels. Recently estimation of channel state information for SM systems is investigated by the recursive least square (RLS) algorithm for slow fading channels. However it is clear that the RLS based receiver will have a performance degradation for fast fading channels. Therefore we developed iterative channel estimation based on detected symbols and ...

  • Channel Estimation for Spatial Modulation Orthogonal Frequency Division Multiplexing Systems 

    Authors:Acar, Yusuf; Doğan, Hakan; Panayırcı, Erdal
    Publisher and Date:(IEEE, 2015)
    A combination of spatial modulation and orthogonal frequency division multiplexing (SM-OFDM) has been recently proposed for multicarrier systems while assuming the perfect channel state information (P-CSI) available at the receiver. But in practical scenarios the estimation of CSI is crucial in order to detect the transmitted data coherently. In this work(1) a new frame structure and pilot symbol aided channel estimation (PSA-CE) technique with a piecewise linear interpolation is proposed for the ...