Yazar "Miller, Scott L." seçeneğine göre listele

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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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    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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    Physical Layer Security of Dual-Hop Hybrid FSO-mmWave Systems
    (Institute of Electrical and Electronics Engineers Inc., 2023) Althunibat, Saud; Tokgöz, Sezer C.; Yarkan, Serhan; Miller, Scott L.; Qaraqe, Khalid
    Hybrid free-space optical (FSO) and millimeter wave (mmWave) systems have been proposed as an efficient solution to improve spectral efficiency and maintain link reliability. The comparable supported data rate and the complementary characteristics in different weather conditions of both links, i.e., FSO and mmWave) have attracted research efforts towards analyzing the different performance aspects of hybrid FSO-mmWave systems. Following this direction, in this article, the physical-layer security analysis of the dual-hop hybrid FSO-mmWave systems is addressed. In the considered system, both FSO and mmWave links are simultaneously used to carry data at each hop, while an eavesdropper is assumed to present to wiretap either one or both links. The analysis includes building a mathematical framework to derive different secrecy metrics, such as the average secrecy capacity, secrecy outage probability and effective secrecy throughput metrics, in mathematical expressions. Obtained analytical results are verified using Monte Carlo simulations where exact matching are achieved. Moreover, the presented results include investigation of the impact of the different operational parameters on the overall secrecy performance.
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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.