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ERCAN, Ali Özer

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Ali Özer

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Now showing 1 - 10 of 30
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    Conference paperPublicationMetadata only
    Recovery of temporal synchronization error through online 3D tracking with two cameras
    (ACM, 2014) Topçu, O.; Ercan, Ali Özer; Alatan, A. A.; Electrical & Electronics Engineering; ERCAN, Ali Özer
    Multiple object tracking within a network of cameras with overlapping fields of views has gained interest. The acquisition of images in an asynchronous manner hinders the practical implementation of such systems. Most of the previous work reported tests over short intervals, leaving the performance degradation due to asynchronous image acquisition unknown. In this work, we propose an online method to recover the synchronization error while tracking objects. The recovered error is fed back to trackers so as to restore their performance. The time synchronization error is measured by the mismatch in the epipolar constraint between the two cameras. We show that successful recovery of the synchronization error is possible when its product with the object motion speeds are within some limits.
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    ArticlePublicationOpen Access
    Design and implementation of dual band microstrip patch antenna for WLAN energy harvesting system
    (2018-07) Amjad, Osama; Munir, Syeda Wajiha; Imeci, S. T.; Ercan, Ali Özer; Electrical & Electronics Engineering; ERCAN, Ali Özer; Amjad, Osama; Munir, Syeda Wajiha
    Since the demand for self-sustained wireless systems is increasing, there is a trend towards RF energy harvesting. It is a key solution to energize the low power systems such as the Internet of Things (IoT) devices without replacing the batteries periodically. This paper presents the design and analysis of RF energy harvesting system that consists of dual-band microstrip patch antenna operating at 2.4 GHz and 5.8 GHz, an impedance matching network, 4-stage voltage doubler and a storing circuit. The antenna is designed using ADS Agilent and sonnet suites software that provides a directivity of 5.5 dBi and 6.3 dBi at 2.4 GHz and 5.8 GHz respectively. The measured results of the fabricated antenna are well agreement with the simulated results. Simulated results show that for an input received power of 10 mW, the proposed system can provide 4.5 mW power at the output of 4-stage voltage rectifier with an overall efficiency of 45%.
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    Dağıtık bir openflow kontrol birimi mimarisi
    (IEEE, 2012) Yazıcı, Volkan; Sunay, Mehmet Oğuz; Ercan, Ali Özer; Electrical & Electronics Engineering; Computer Science; ERCAN, Ali Özer; SUNAY, Mehmet Oğuz; YAZICI, Volkan
    Considering the modern internet traffic rates, the network architecture is of particular importance as the running services itself. On the other hand, due to the increasing complexity and black-box structure of the available networking hardware (switches, routers, etc.), the necessary network innovation imposed by the running services becomes infeasible in practice. The software-defined networking notion introduced to solve this problem and one of its emerging and powerful implementations, the OpenFlow protocol, advocate the idea of providing the control and data paths in separate planes. A network operating system running on this control plane, is anticipated to provide necessary measures for scalability and reliability in order to stand against the gigantic traffic pumped by the network. In this paper, we propose a distributed OpenFlow network operating system built with necessary scalability and reliability qualifications without requiring any changes to the existing OpenFlow protocol and networking equipment.
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    Successive refinement of models for model-based testing to increase system test effectiveness
    (IEEE, 2016) Sahin Gebizli, C.; Sözer, Hasan; Ercan, Ali Özer; Electrical & Electronics Engineering; Computer Science; SÖZER, Hasan; ERCAN, Ali Özer
    Model-based testing is used for automatically generating test cases based on models of the system under test. The effectiveness of tests depends on the contents of these models. Therefore, we introduce a novel three-step model refinement approach. We represent test models in the form of Markov chains. First, we update state transition probabilities in these models based on usage profile. Second, we perform an update based on fault likelihood that is estimated with static code analysis. Our third update is based on error likelihood that is estimated with dynamic analysis. We generate and execute test cases after each refinement. We applied our approach for model-based testing of a Smart TV system and new faults were revealed after each refinement.
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    Effect of camera-IMU displacement calibration error on tracking performance
    (IEEE, 2015) Maxudov, Nekruzjon; Ercan, Ali Özer; Erdem, Tanju; Electrical & Electronics Engineering; Computer Science; ERCAN, Ali Özer; ERDEM, Arif Tanju; Maxudov, Nekruzjon
    Due to their complementary properties, inertial measurement units (IMU) and cameras are used in ego-motion tracking applications. For this, the relative rotation and displacement between the camera and IMU reference frames has to be known. There are established methods for the accurate estimation of the relative orientation, however, accurate estimation of the displacement is still a challenging problem. When this is not possible, one might resort to the alternative approach of fusing camera and gyroscope data only, as this does not require the displacement information. To be able to asses such alternatives, this paper presents a systematic methodology based on realistic simulations to analyze the effect of the camera - IMU displacement calibration error on tracking performance, and discusses in detailed simulations the dependency of tracker performance metrics on the camera - IMU displacement's magnitude and calibration error.
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    IEEE 802.11ac aǧların çok kullanıcılı ÇGÇÇ özelliǧi üzerine incelemeler
    (IEEE, 2016) Çakmak, Kıvanç; Sunay, Mehmet Oğuz; Ercan, Ali Özer; Electrical & Electronics Engineering; Computer Science; SUNAY, Mehmet Oğuz; ERCAN, Ali Özer; Çakmak, Kıvanç
    This paper studies the multi-user MIMO feature of IEEE 802.11ac networks that serve, along with IEEE 802.11ac nodes, also legacy IEEE 802.11n nodes. For this purpose, we develop a simulator that models the IEEE 802.11ac and IEEE 802.11n networks. Then, using a setup, we first study the tradeoff between the amount of overhead used in channel sounding and the corresponding rate of information, concluding that in this setting, channel sounding with all clients lead to better throughput. Secondly, we observe the negative impact of IEEE 802.11n nodes on the IEEE 802.11ac traffic due to the deafness problem, and analyze the performance of the usage of RTS/CTS handshake and cts2self mechanisms to mitigate this effect. We show that the regular RTS/CTS handshake mitigates the deafness problem to a certain degree. However, the cts2self mechanism achieves a better performance since no airtime is wasted to collisions with the RTS frames.
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    Object tracking in the presence of occlusions using multiple cameras: a sensor network approach
    ( Association for Computing Machinery, 2013) Ercan, Ali Özer; El Gamal, A.; Guibas, L. J.; Electrical & Electronics Engineering; ERCAN, Ali Özer
    This article describes a sensor network approach to tracking a single object in the presence of static and moving occluders using a network of cameras. To conserve communication bandwidth and energy, we combine a task-driven approach with camera subset selection. In the task-driven approach, each camera first performs simple local processing to detect the horizontal position of the object in the image. This information is then sent to a cluster head to track the object. We assume the locations of the static occluders to be known, but only prior statistics on the positions of the moving occluders are available. A noisy perspective camera measurement model is introduced, where occlusions are captured through occlusion indicator functions. An auxiliary particle filter that incorporates the occluder information is used to track the object. The camera subset selection algorithm uses the minimum mean square error of the best linear estimate of the object position as a metric, and tracking is performed using only the selected subset of cameras.Using simulations and preselected subsets of cameras, we investigate (i) the dependency of the tracker performance on the accuracy of the moving occluder priors, (ii) the trade-off between the number of cameras and the occluder prior accuracy required to achieve a prescribed tracker performance, and (iii) the importance of having occluder priors to the tracker performance as the number of occluders increases. We find that computing moving occluder priors may not be worthwhile, unless it can be obtained cheaply and to high accuracy. We also investigate the effect of dynamically selecting the subset of camera nodes used in tracking on the tracking performance. We show through simulations that a greedy selection algorithm performs close to the brute-force method and outperforms other heuristics, and the performance achieved by greedily selecting a small fraction of the cameras is close to that of using all the cameras.
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    ArticlePublicationOpen Access
    Multivariate sensor data analysis for oil refineries and multi-mode identification of system behavior in real-time
    (IEEE, 2018) Khodabakhsh, Athar; Arı, İsmail; Bakır, M.; Ercan, Ali Özer; Electrical & Electronics Engineering; Computer Science; ARI, Ismail; ERCAN, Ali Özer; Khodabakhsh, Athar
    Large-scale oil refineries are equipped with mission-critical heavy machinery (boilers, engines, turbines, and so on) and are continuously monitored by thousands of sensors for process efficiency, environmental safety, and predictive maintenance purposes. However, sensors themselves are also prone to errors and failure. The quality of data received from these sensors should be verified before being used in system modeling. There is a need for reliable methods and systems that can provide data validation and reconciliation in real-time with high accuracy. In this paper, we develop a novel method for real-time data validation, gross error detection and classification over multivariate sensor data streams. The validated and high-quality data obtained from these processes is used for pattern analysis and modeling of industrial plants. We obtain sensor data from the power and petrochemical plants of an oil refinery and analyze them using various time-series modeling and data mining techniques that we integrate into a complex event processing engine. Next, we study the computational performance implications of the proposed methods and uncover regimes where they are sustainable over fast streams of sensor data. Finally, we detect shifts among steady-states of data, which represent systems' multiple operating modes and identify the time when a model reconstruction is required using DBSCAN clustering algorithm.
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    Optimization and analysis of WLAN RF energy harvesting system architecture
    (IEEE, 2016) Munir, Syeda Wajiha; Amjad, Osama; Zeydan, E.; Ercan, Ali Özer; Electrical & Electronics Engineering; ERCAN, Ali Özer; Munir, Syeda Wajiha; Amjad, Osama
    This paper presents the design, analysis and optimization of RF energy harvesting system for WLAN source operating at 2.4 GHz and 5.8 GHz. The system architecture comprises of RF WLAN source, wireless channel, an efficient dual band microstrip patch antenna, an impedance matching network, 4-stage voltage rectifier and a storing circuit. Matching network ensures the maximum power transfer from source to load. HSMS-2850 Schottky diodes are used in rectifier design, which provide low forward voltage and low substrate leakage. The proposed system design is used to analyze the effect of distance on RF power obtained at receiving side. The size of storage capacitor is chosen carefully such that it can store sufficient amount of charge and takes reasonable charging time. Moreover, the circuit parameters are varied to optimize the designed circuit that provides the maximum efficiency of 45% and 22% at 2.4 GHz and 5.8 GHz respectively, at a distance of 1 meter from source. Simulated results show that for received RF power of 5 dBm the system can provide 1.3 mW power across 10 kΩ load, which can be enough to energize the low power devices. The voltage supplied by the harvesting system can be increased further by increasing the number of stages in voltage rectifier according to the application but at the cost of parasitic loss.
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    Energy sensing strategy optimization for opportunistic spectrum access
    (IEEE, 2012-06) Ercan, Ali Özer; Sunay, Mehmet Oğuz; Electrical & Electronics Engineering; Computer Science; ERCAN, Ali Özer; SUNAY, Mehmet Oğuz
    This paper introduces a correlator-based energy sensing strategy for opportunistic spectrum access in a slow, flat-fading channel. The correlator provides weighted energy accumulation in time. We assume that the noise variance is known and the primary user (PU) traffic follows a two state Markov chain with known idle and busy rates. Using Chebyshev bounds on missed detection and false alarm probabilities, we find that the optimal weighting function is an increasing function of time and its shape is dependent on the PU traffic characteristics and SNR. We show that the traditional flat-integration based energy collection method is suboptimal both in the error probability and channel utilization sense.