Yazar "Alaca, Ozgur" seçeneğine göre listele

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    Adaptive Envelope Detector-Based Phase Fault Detection Method for Power System Grid Distortions
    (Institute of Electrical and Electronics Engineers Inc., 2023) Alaca, Ozgur; Ekti, Ali Riza; Wilson, Aaron; Piersall, Elizabeth; Snyder, Isabelle; Yarkan, Serhan; Stenvig, Nils M
    In this study, a phase fault detection algorithm is developed by employing the envelope detector method. The proposed method diagnoses faults among phases and defines fault areas in the incoming signal. The designed algorithm consists of three steps: analytical signal conversion, complex magnitude, and fault detection. Initially, an analytical signal is obtained from the incoming power signal to determine the instantaneous amplitude and phase of the signal. A complex magnitude operation is applied to analytical signals to display changes in amplitude. On the basis of the threshold values specified by the user, the last step identifies the distortion signal in terms of the type of error and size. The proposed method is tested with realistically simulated substation power signal data and real power system data from the Grid Event Signature Library. The obtained results revealed that the proposed method detects distortions accurately.
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    Analysis and Compensation of Tx and Rx IQ Imbalances in Uplink IM-OFDMA Systems
    (Institute of Electrical and Electronics Engineers Inc., 2023) Alaca, Ozgur; Althunibat, Saud; Yarkan, Serhan; Miller, Scott L.; Qaraqe, Khalid A.
    Index modulation-based orthogonal division multiple access (IM-OFDMA) has recently been proposed as a potential technique for future wireless communication systems due to its su perior spectral efficiency and error performance over conventional multiple access schemes. However, its performance is still under investigation by researchers in light of a variety of scenarios and assumptions. Following this direction, in this Article, the individual and joint effects of the transmitter (Tx) and receiver (Rx) in-phase and quadrature imbalances (IQI) on the bit-error-rate (BER) per formance of the uplink IM-OFDMA scheme are investigated by considering whether each user’s RF front-end is identical or not. Moreover, to reduce the detrimental effect of IQI, a preamble-based estimation and compensation method is proposed for IM-OFDMA. Closed-form expressions for the average BER of IM-OFDMA are obtained by considering the physical effect of the Tx and Rx IQI. Also, using Monte Carlo simulations, the derived expressions are verified under different system configurations. Analytical and sim ulation results reveal that Tx and Rx IQI cause an error floor in the BER performance of IM-OFDMA schemes. However, the proposed estimation and compensation method not only reduces the impact of IQI but also leads to a better BER performance compared to the case of no IQI, which mainly refers to the frequency diversity caused by the IQI.
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    CNN-Based Signal Detector for IM-OFDMA
    (Institute of Electrical and Electronics Engineers Inc., 2022) Alaca, Ozgur; Althunibat, Saud; Yarkan, Serhan; Miller, Scott L.; Qaraqe, Khalid A.
    The recently proposed index modulation-based up-link orthogonal frequency division multiple access (IM-OFDMA) scheme has outperformed the conventional schemes in terms of spectral efficiency and error performance. However, the induced computational complexity at the receiver forms a bottleneck in real-time implementation due to the joint detection of all users. In this paper, based on deep learning principles, a convolutional neural network (CNN)-based signal detector is proposed for data detection in IM-OFDMA systems instead of the optimum Maximum Likelihood (ML) detector. A CNN-based detector is constructed with the created dataset of the IM-OFDMA transmission by offline training. Then, the convolutional neural network (CNN)-based detector is directly applied to the IM-OFMDA communication scheme to detect the transmitted signal by treating the received signal and channel state information (CSI) as inputs. The proposed CNN-based detector is able to reduce the order of the computational complexity from O(n2n) to O(n2) as compared to the ML detector with a slight impact on the error performance.
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    Detection of Grid-Signal Distortions Using the Spectral Correlation Function
    (Institute of Electrical and Electronics Engineers Inc., 2023) Alaca, Ozgur; Ekti, Ali Riza; Wilson, Aaron; Holliman, John; Piersall, Elizabeth; Yarkan, Serhan; Stenvig, Nils
    This study proposes a novel method for signal detection and feature extraction based on the spectral correlation function, enabling improved characterization of grid-signal dis tortions. Our approach differs from existing treatments of signal distortion in its analysis of the varied spectral content of signals observed in real-world scenarios. The method we propose has state-of-the-art discriminative power that provides meaningful and understandable characterizations of various grid events and anomalies. To validate the approach, we use real world data from the Grid Event Signature Library, which is maintained jointly by Oak Ridge National Laboratory and Lawrence Livermore National Laboratory.
  • Küçük Resim Yok
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    A low-cost, high-precision signal generation algorithm and prototype implementation for software-defined radios
    (Institute of Electrical and Electronics Engineers Inc., 2017) Alaca, Ozgur; Boyaci, Ali; Yarkan, Serhan
    Next generation wireless communications systems are built on highly-adaptive components in order to meet the ever-increasing requirements and to keep up with the dynamically changing environmental conditions. Software-defined radio (SDR) is considered among vital components of next generation wireless communications due to its capabilities such as spectrum monitoring and sensing along with application-specific waveform generation as well as fast switching between several standards. Therefore, it is expected from SDR that it fulfills fundamental communications operations and functionalities of high-precision with the lowest computational complexity. In this study, a low-computational complexity and high-precision signal generation algorithm operating on digital signal processor (DSP) is proposed for SDR and implemented. Its performance results are compared with those of several algorithms. Results are discussed along with future directions. © 2016 The Chamber of Turkish Electrical Engineers.
  • Küçük Resim Yok
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    A Low-cost, High-precision Signal Generation Algorithm and Prototype Implementation for Software-Defined Radios
    (IEEE, 2016) Alaca, Ozgur; Boyaci, Ali; Yarkan, Serhan
    Next generation wireless communications systems are built on highly-adaptive components in order to meet the ever-increasing requirements and to keep up with the dynamically changing environmental conditions. Software-defined radio (SDR) is considered among vital components of next generation wireless communications due to its capabilities such as spectrum monitoring and sensing along with application-specific waveform generation as well as fast switching between several standards. Therefore, it is expected from SDR that it fulfills fundamental communications operations and functionalities of high-precision with the lowest computational complexity. In this study, a low-computational complexity and high-precision signal generation algorithm operating on digital signal processor (DSP) is proposed for SDR and implemented. Its performance results are compared with those of several algorithms. Results are discussed along with future directions.
  • Küçük Resim Yok
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    Microstrip Dual-Bandpass Filter Design
    (IEEE, 2017) Eren, Bora; Akyuz, Burhan; Dikkafa, Mustafa; Alaca, Ozgur; Imeci, Taha; Gungor, Oguzhan Salih
    Dual-bandpass microstrip filter design is suggested for small-scale device. Design of dual-bandpass microstrip filter has been created with concentric square structure by using microstrip resonator. Both of resonators have been used to get dual-bandpass frequencies and fed with only one source. Proposed design has been created and simulated on Sonnet software and also prototype has been builted and tested. According to result of simulation, value of S11 is -29.79 dB and value of S12 is 0.04797 dB about 4.6 GHz, as for about 12.65 GHz, value of S11 is -22.67 dB and value of S12 is -0.09642 dB.
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    Performance Analysis of Uplink IM-OFDMA Systems in the Presence of CFO and Rx-IQI
    (IEEE Computer Society, 2023) Alaca, Ozgur; Althunibat, Saud; Yarkan, Serhan; Miller, Scott L.; Qaraqe, Khalid A.
    Index modulation-based orthogonal frequency divi sion multiple access (IM-OFDMA) has been recently proposed as a promising candidate for future wireless communication systems due to its superior spectral efficiency and error performance compared to conventional multiple access schemes. Therefore, it has been under investigation by researchers analyzing its performance considering different scenarios and assumptions. Following this direction, this paper presents the error perfor mance of the uplink IM-OFDMA in the presence of carrier fre quency offset (CFO) and receiver (Rx) in-phase and quadrature imbalance (IQI). In particular, the individual and joint effects of the CFO and Rx-IQI on the bit-error-rate (BER) performance of the uplink IM-OFDMA scheme are investigated, and then the IM-OFDMA is compared with the conventional OFDMA scheme by considering the detrimental effect of CFO and Rx IQI. Accordingly, this paper shows that IM-OFDMA achieves better BER performance results than the OFDMA scheme in the presence of CFO and Rx-IQI. However, the obtained results also reveal that the IM-OFDMA scheme is very sensitive to RF impairments even though it performs better than conventional OFDMA.
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    Physical Layer Authentication for Uplink IM-OFDMA System
    (Institute of Electrical and Electronics Engineers Inc., 2023) Alaca, Ozgur; Althunibat, Saud; Yarkan, Serhan; Miller, Scott L.; Qaraqe, Khalid A.
    This study investigates the physical layer authentica tion (PLA) for the index modulation-based orthogonal frequency division multiple access (IM-OFDMA) systems by considering users’ in-phase and quadrature imbalances (IQI). Specifically, the PLA scheme is created for the uplink IM-OFDMA systems exploiting the IQI, forming at each user’s RF front-end as an identity. In a malicious user’s presence, the uplink IM-OFDMA scheme is examined, and the mathematical model for the proposed authentication scheme is established. Through the Monte Carlo simulation method, the performance of the proposed scheme is presented by employing two well-known performance metrics: authentication false rate and detection of malicious/authenticated users rate. The results for the proposed PLA scheme are demon strated under the different parameters of IM-OFDMA and IQI. The first-time implementation of a PLA scheme for the uplink IM-OFDMA system has shown promising results.
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    Secrecy Analysis of Uplink IM-OFDMA Systems in the Presence of IQ Imbalance
    (Institute of Electrical and Electronics Engineers Inc., 2023) Alaca, Ozgur; Althunibat, Saud; Yarkan, Serhan; Miller, Scott L.; Qaraqe, Khalid A.
    This paper introduces the secrecy analysis of the index modulation-based orthogonal frequency division multiple access (IM-OFDMA) schemes by considering the in-phase and quadrature imbalance (IQI) presence at the users’ RF front ends. In particular, by assuming the existence of an eavesdropper, the secrecy performance of the considered uplink multiple-access sys tem is investigated through the strictly positive secrecy capacity and secrecy outage probability, and closed-form expressions are derived for both quantities. Moreover, the secrecy performance is conducted regarding IQI compensation based on a preamble based estimation method. Further, analysis of the impact of the different parameters of IM-OFDMA, IQI, and estimation method is included via analytical and simulation-based results. The results reveal that IM-OFDMA is more reliable in secrecy performance than OFDMA, regardless of whether IQI is present. Also, IQI compensation can lead to a better secrecy performance compared to the case of no IQI.
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    Secure Uplink IM-OFDMA With Artificial IQ Imbalance
    (Institute of Electrical and Electronics Engineers Inc., 2023) Alaca, Ozgur; Althunibat, Saud; Yarkan, Serhan; Miller, Scott L.; Qaraqe, Khalid A.
    This study proposes a novel secure uplink index modulation-based orthogonal frequency division multiple access (IM-OFDMA) systems using artificial in-phase and quadrature imbalance (A-IQI). The fact of the distinct A-IQI induced at the users’ end and the unpredictable allocation of users based on confidential data brings a different perspective on physical layer security. Accordingly, in this study, the non-identical effect of A-IQI is exploited to provide a physical-layer security scheme for the IM-OFDMA systems. Specifically, the estimation method is created with preamble data in order to achieve each user’s unique A-IQI information from a legitimate receiver. The A-IQI will help to secure the transmitted data against a potential eavesdropper, and hence, improving data confidentiality. The proposed scheme’s performance is analytically evaluated by deriving closed-form expressions of the average bit error rate (BER) at both the base station and the eavesdropper. The image rejection ratios of A-IQI and practical IQI are provided for IM-OFDMA to indicate the region of intentionally generated A-IQI. Under the different system model specifications of IM-OFDMA, the analytical results are provided with simulation results obtained using the Monte Carlo simulation method. Further, the proposed secure scheme is compared with the state of-the-art artificial noise method. Results reveal a significant improvement in the BER at the base station, accompanied by severe degradation in the BER at the eavesdropper.