Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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Now showing 1 - 10 of 12
  • Conference Object
    Citation - WoS: 2
    Citation - Scopus: 3
    Performance of Semi-Orthogonal User Selection for Multiuser Miso Systems
    (Institute of Electrical and Electronics Engineers Inc., 2008) Le Ruyet, Didier; Khanfir, Hajer; Özbek, Berna
    In MISO multiuser downlink wireless communication systems with precoding at the transmission, the capacity depends on the channel state information at the transmitter. Since the feedback data rate increases with the number of users in the cell it is important to perform a selection of the users at the receiver. In this paper, we evaluate the performance of different user selection algorithms at the receiver side through the noisy uplink channel. We evaluate the effect of the noisy channel on the classical norm criterion and on a criterion based on the orthogonality between the user channels. Without cooperation between the users, we only allow users that are semi-orthogonal to feedback their channel information as analog and quantized information to the base station through the noisy uplink channel. We propose an algorithm to reduce the noise effect on the analog feedback for semi-orthogonal user selection algorithm. We show that the semi-orthogonal criterion with quantized feedback gives better performance compared to the norm criterion for perfect and noisy uplink channels.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 2
    A Case Study on Logging Visual Activities: Chess Game
    (Springer Verlag, 2006) Ozan, Şükrü; Gümüştekin, Şevket
    Automatically recognizing and analyzing visual activities in complex environments is a challenging and open-ended problem. In this study this task is performed in a chess game scenario where the rules, actions and the environment are well defined. The purpose here is to detect and observe a FIDE (Fédération International des Ėchecs) compatible chess board, generating a log file of the moves made by human players. A series of basic image processing operations have been applied to perform the desired task. The first step of automatically detecting a chess board is followed by locating the positions of the pieces. After the initial setup is established every move made by a player is automatically detected and verified. Intel® Open Source Computer Vision Library (OpenCV) is used in the current software implementation.
  • Conference Object
    Citation - WoS: 4
    Citation - Scopus: 4
    A distributed behavioral model for landmine detection robots
    (International Association of Engineers, 2007) Bayram, Çağdaş; Sevil, Hakkı Erhan; Özdemir, Serhan
    This paper presents a distributed navigation, detection and swarming model for a group of minimalist identical robotic agents. Decision making process of agents is weight based in contrast to widely used precedence based rules. The group is indirectly controlled by an alpha agent that has more sophisticated systems. Computer simulations of the proposed behavioral model generated promising results.
  • Conference Object
    Citation - WoS: 2
    Citation - Scopus: 2
    A novel square-spiral strip antenna
    (Institute of Electrical and Electronics Engineers Inc., 2007) Saynak, Uğur; Kuştepeli, Alp
    A square-spiral strip antenna is designed considering the procedure used to obtain log-periodic antennas. Simulation results of the new design are compared with those of the well known and widely used Archimedean spiral antenna in terms of the frequency dependency. The effect of dielectric substrate used to support the antennas is also investigated.
  • Conference Object
    Computational Sciences Learning Project for Pre-University Students
    (Springer Verlag, 2007) İnceoğlu, Mustafa Murat; Aslan, Burak Galip
    It is quite useful for high school students to study on computational sciences, especially for those who are planning to have a higher education in engineering. This paper proposes a pilot study on 9th and 10 th grade students for teaching them the basic aspects of computer sciences. This study focuses on a schedule consisting two consecutive courses - first one theoric and the second one is applied - for student volunteers from science high schools.
  • Conference Object
    Citation - WoS: 1
    Citation - Scopus: 1
    Satellite Networks for Key Management
    (Institute of Electrical and Electronics Engineers Inc., 2007) Koltuksuz, Ahmet
    The cryptographic key management center is the place where all the cryptographical protocols and related keys are in action. Traditionally the key management centers operate on the ground. However; with the satellites, it is possible to conceive a space based key management center. This paper underlines the pros and cons of having a satellite networks key management center.
  • Conference Object
    Citation - WoS: 7
    Citation - Scopus: 11
    Noise Robust Speaker Verification Using Mel-Frequency Discrete Wavelet Coefficients and Parallel Model Compensation
    (Institute of Electrical and Electronics Engineers Inc., 2005) Tüfekçi, Zekeriya; Gürbüz, Sabri
    Interfering noise severely degrades the performance of a speaker verification system. The Parallel Model Combination (PMC) technique is one of the most efficient techniques for dealing with such noise. Another method is to use features local in the frequency domain. Recently, Mel-Frequency Discrete Wavelet Coefficients (MFDWCs) [1, 2] were proposed as speech features local in frequency domain. In this paper, we discuss using PMC along with MFDWCs features to take advantage of both noise compensation and local features (MFDWCs) to decrease the effect of noise on speaker verification performance. We evaluate the performance of MFDWCs using the NIST 1998 speaker recognition and NOISEX-92 databases for various noise types and noise levels. We also compare the performance of these versus MFCCs and both using PMC for dealing with additive noise. The experimental results show significant performance improvements for MFDWCs versus MFCCs after compensating the Gaussian Mixture Models (GMMs) using the PMC technique. The MFDWCs gave 5.24 and 3.23 points performance improvement on average over MFCCs for -6 dB and 0 dB SNR values, respectively. These correspond to 26.44% and 23.73% relative reductions in equal error rate (EER), respectively.
  • Conference Object
    Citation - WoS: 6
    Citation - Scopus: 8
    A Cluster-Based Dynamic Load Balancing Middleware Protocol for Grids
    (Springer Verlag, 2005) Erciyeş, Kayhan; Payli, Reşat Ümit
    We describe a hierarchical dynamic load balancing protocol for Grids. The Grid consists of clusters and each cluster is represented by a coordinator. Each coordinator first attempts to balance the load in its cluster and if this fails, communicates with the other coordinators to perform transfer or reception of load. This process is repetaed periodically. We show the implementation and analyze the performance and scalability of the proposed protocol.
  • Conference Object
    Citation - WoS: 6
    Citation - Scopus: 11
    Dynamically Adaptive Partition-Based Data Distribution Management
    (Institute of Electrical and Electronics Engineers Inc., 2005) Kumova, Bora İsmail
    Performance and scalability of distributed simulations depends primarily on the effectiveness of the employed data distribution management (DDM) algorithm, which aims at reducing the overall computational and messaging effort on the shared data to a necessary minimum. Existing DDM approaches, which are variations and combinations of two basic techniques, namely region-based and grid-based techniques, perform purely in the presence of load differences. We introduce the partition-based technique that allows for variable-size partitioning shared data. Based on this technique, a novel DDM algorithm is introduced that is dynamically adaptive to cluster formations in the shared data as well as in the physical location of the simulation objects. Since the re-distribution is sensitive to inter-relationships between shared data and simulation objects, a balanced constellation has the additional advantage to be of minimal messaging effort. Furthermore, dynamic system scalability is facilitated, as bottlenecks are avoided.
  • Conference Object
    Citation - WoS: 4
    Citation - Scopus: 4
    Merging Clustering Algorithms in Mobile Ad Hoc Networks
    (Springer Verlag, 2005) Dağdeviren, Orhan; Erciyeş, Kayhan; Çokuslu, Deniz
    Clustering is a widely used approach to ease implementation of various problems such as routing and resource management in mobile ad hoc networks (MANET)s. We first look at minimum spanning tree(MST) based algorithms and then propose a new algorithm for clustering in MANETs. The algorithm we propose merges clusters to form higher level clusters by increasing their levels. We show the operation of the algorithm and analyze its time and message complexities.