Now showing items 1-20 of 79

  • 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 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 ...

  • 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 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 ...

  • 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; Dogan, Hakan; Panayirci, 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 ...

  • Comparison of Compressed Sensing Based Algorithms for Sparse Signal Reconstruction 

    Compressed sensing theory shows that any signal which is defined as sparse in a given domain can be reconstructed using fewer linear projections instead of using all Nyquist-rate samples. In this paper we investigate basis pursuit matching pursuit orthogonal matching pursuit and compressive sampling matching pursuit algorithms which are basic compressed sensing based algorithms and present performance curves in terms of mean squared error for various parameters including signal-tonoise ratio ...

  • Connected navigation of non-communicating mobile agents 

    Authors:Kerestecioǧlu, Feza; Cezayirli, Ahmet
    Publisher and Date:(IEEE, 2012)
    This article discusses the connectivity of autonomous mobile robots that do not have communication capabilities. We show that if the group members follow the proposed Local Steering Strategy which utilizes information only about the relative positions of neighbor robots they can sustain their connectivity even in the case of bounded position measurement errors and the occultation of robots by other robots in the group. To reduce the computational burden in the implementation of the proposed ...

  • Data Detection Based Iterative Channel Estimation for Coded SM-OFDM Systems 

    Authors:Acar, Yusuf; Leblebici, M. Merih; Dogan, Hakan; Panayirci, Erdal
    Publisher and Date:(IEEE, 2016)
    The combination of spatial modulation (SM) and orthogonal frequency division multiplexing (OFDM) as SM-OFDM is a recently proposed efficient modulation scheme with exploiting the index of transmit antenna to convey information bits for multiple-input multiple-output (MIMO) wireless communication systems due to its low complexity feature. The pioneering works assume that the perfect channel state information (P-CSI) or pilot symbols aided channel estimation (PSA-CE) is available at the receiver. ...

  • Data-Aided Autoregressive Sparse Channel Tracking for OFDM Systems 

    In order to meet future communication system requirements channel estimation over fast fading and frequency selective channels is crucial. In this paper Space Alternated Generalized Expectation Maximization Maximum a Posteriori (SAGE-MAP) based channel estimation algorithm is proposed for Orthogonal Frequency Division Multiplexing (OFDM) systems for Autoregressive (AR) modeled time-varying sparse channels. Also an initialization algorithm has been developed from the widely used sparse approximation ...

  • Detection of jointly active primary systems 

    Authors:Yılmaz, Burak Alptug; Erküçük, Serhat
    Publisher and Date:(IEEE, 2012)
    Recent studies in cognitive radios consider the detection of multiple bands for a better utilization of the spectrum. If the cognitive radio (CR) is an ultra wideband (UWB) or a wideband system then the CR should ensure all the coexisting primary systems in these bands are detected before the CR can start data transmission. In this work we study the primary system detection performance of a wideband CR assuming that there are multiple coexisting primary systems and that these primary systems may ...