Researcher: Başar, Ertuğrul
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Başar, Ertuğrul
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Publication Metadata only Ris-aided angular-based hybrid beamforming design in mmwave massive mimo systems(IEEE, 2022) Koc, Asil; Tho Le-Ngoc; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Yıldırım, İbrahim; Başar, Ertuğrul; Graduate School of Sciences and Engineering; College of EngineeringThis paper proposes a reconfigurable intelligent surface (RIS)-aided and angular-based hybrid beamforming (AB-HBF) technique for the millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) systems. The proposed RIS-AB-HBF architecture consists of three stages: (i) RF beam-former, (ii) baseband (BB) precoder/combiner, and (iii) RIS phase shift design. First, in order to reduce the number of RF chains and the channel estimation overhead, RF beamformers are designed based on the 3D geometry-based mmWave channel model using slow time-varying angular parameters of the channel. Second, a BB precoder/combiner is designed by exploiting the reduced-size effective channel seen from the BB stages. Then, the phase shifts of the RIS are adjusted to maximize the achievable rate of the system via the nature-inspired particle swarm optimization (PSO) algorithm. Illustrative simulation results demonstrate that the use of RISs in the AB-HBF systems has the potential to provide more promising advantages in terms of reliability and flexibility in system design.Publication Metadata only Machine learning-based PHY-authentication without prior attacker information for wireless multiple access channels(Springer, 2024) Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Altun, Ufuk; Başar, Ertuğrul; Graduate School of Sciences and Engineering; College of EngineeringPhysical layer (PHY) authentication methods provide spatial security by exploiting the unique channel between two users. In recent years, many studies focused on substituting traditional threshold-based detection mechanisms with machine/deep learning classifiers to solve the threshold selection problem and obtain better detection accuracy. However, these studies assume that receivers have access to spoofer's channel information at the training of the classifier, which is unrealistic for real-time scenarios. In this study, we propose a PHY-authentication architecture for wireless multiple access channels (W-MACs) that removes this assumption and works without any prior information about the spoofer. The proposed method is designed for multi-user systems and is suitable for any classifier model or communication protocol. The feasibility and the performance of the proposed method are investigated via computer simulations and compared with a benchmark model. The results proved the feasibility of the proposed method as it can detect spoofers successfully without requiring spoofers' channel information.Publication Metadata only Joint pulse index and spatial modulation(Institute of Electrical and Electronics Engineers, 2024) Aldirmaz-Colak, Sultan; Aydin, Erdogan; Gundem, Sumeyra; Celik, Yasin; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; College of EngineeringAccording to the planned key performance indicator (KPI) standards, 6G technology should achieve higher throughput than 5G. More efficiency in transceiver schemes is required to meet this demand. In this study, we take advantage of spatial modulation (SM) and pulse index modulation (PIM) techniques to increase spectral efficiency. The proposed PIM-SM scheme utilizes well-localized and orthogonal Hermite-Gaussian pulses along with spatial indexing. Thanks to the orthogonality between pulses in the set, multiple pulses are transmitted together. The design, simulation, and analytical bit error rate performance derivations of PIM-SM are discussed in this letter to verify the viability and compatibility of pulse-based data transfer utilizing the spatial domain. The performance is compared with generalized code index modulation-spatial modulation (GCIM-SM), code index modulation-quadrature spatial modulation (CIM-QSM), and classical spatial modulation (SM) schemes.Publication Metadata only Index modulation: from waveform design to reconfigurable intelligent surfaces(Springer Science and Business Media Deutschland Gmbh, 2024) Wen, Miaowen; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Doğukan, Ali Tuğberk; Başar, Ertuğrul; Graduate School of Sciences and Engineering; College of EngineeringWhile the first 5G-Advanced standard is being developed step by step with certain advancements, wireless researchers have already begun exploring radical communication paradigms toward 6G wireless networks of 2030 and beyond. Within this context, index modulation (IM) technologies might provide spectrum- and energy-efficient solutions by utilizing the promising concept of indexing transmit entities. © 2024, The Author(s), under exclusive license to Springer Nature Switzerland AG.Publication Open Access Intelligent surfaces empowered wireless network: recent advances and the road to 6G(Institute of Electrical and Electronics Engineers Inc, 2024) Wu, Qingqing; Zheng, Beixiong; You, Changsheng; Zhu, Lipeng; Shen, Kaiming; Shao, Xiaodan; Mei, Weidong; Di, Boya; Zhang, Hongliang; Song, Lingyang; Di Renzo, Marco; Luo, Zhi-Quan; Zhang, Rui; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; College of EngineeringIntelligent surfaces (ISs) have emerged as a key technology to empower a wide range of appealing applications for wireless networks, due to their low cost, high energy efficiency, flexibility of deployment, and capability of constructing favorable wireless channels/radio environments. Moreover, the recent advent of several new IS architectures further expanded their electromagnetic functionalities from passive reflection to active amplification, simultaneous reflection, and refraction, as well as holographic beamforming. However, the research on ISs is still in rapid progress and there have been recent technological advances in ISs and their emerging applications that are worthy of a timely review. Thus, in this article, we provide a comprehensive survey on the recent development and advances of ISs-aided wireless networks. Specifically, we start with an overview on the anticipated use cases of ISs in future wireless networks such as 6G, followed by a summary of the recent standardization activities related to ISs. Then, the main design issues of the commonly adopted reflection-based IS and their state-of-the-art solutions are presented in detail, including reflection optimization, deployment, signal modulation, wireless sensing, and integrated sensing and communications. Finally, recent progress and new challenges in advanced IS architectures are discussed to inspire future research.Publication Metadata only On the performance of OFDM-IM systems in the presence of CFO effects(Elsevier Inc., 2024) Besseghier, Mokhtar; Ghouali, Samir; Djebbar, Ahmed Bouzidi; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; ; College of Engineering;This study presents a comprehensive analysis of the performance degradation effects of carrier frequency offset (CFO) on orthogonal frequency division multiplexing with index modulation (OFDM-IM) systems operating over frequency-selective multipath fading channels. CFO is an impairing factor that degrades the signal-to-noise ratio (SNR) through signal attenuation and inter-carrier interference (ICI). We derive a closed-form expression to quantify the SNR degradation under CFO for OFDM-IM systems. Additionally, we formulate a very tight upper bound for the bit error rate (BER), accounting for index modulation errors, CFO distortion, and multipath fading. The presented analytical formulations capture the unique characteristics of OFDM-IM systems and facilitate precise performance evaluation. The findings yield valuable insights into mitigating CFO-induced BER degradation through appropriate system parameter selection and CFO compensation techniques. Moreover, this investigation makes significant contributions towards designing reliable OFDM-IM communication links resilient to the combined effects of index modulation, frequency offsets, and dispersive channel conditions.Publication Metadata only Pairwise sequency index modulation with OTSM for green and robust single-carrier communications(IEEE-Institute of Electrical and Electronics Engineers, 2024) Doosti-Aref, Abed; Masouros, Christos; Arslan, Huseyin; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; College of EngineeringIn this letter, inspired by the fundamental thoughts of sequency index modulation (SeIM) and orthogonal time sequency multiplexing (OTSM), a novel technique is introduced for green and robust single-carrier communications in wireless networks. More specifically, pairwise SeIM (PSeIM) is proposed as a novel indexing scheme making SeIM robust to error propagation and significantly reduces the peak power of SeIM-based systems with a lower complexity of detection. Analytical results are presented for the bit error rate (BER), peak-to-average power ratio (PAPR), and spectral efficiency to reveal the trade-off and advantages in PSeIM-OTSM. Simulation and analytical results verify that for 4-QAM uncoded data, PSeIM-OTSM outperforms OTSM by 50% in terms of both PAPR and complexity of detection along with 125.32% energy efficiency improvement to achieve a BER of 10-8 in high mobility doubly spread channels.Publication Metadata only A novel reconfigurable intelligent surface-supported code index modulation-based receive spatial modulation system(IEEE-Institute of Electrical and Electronics Engineers, 2024) Ozden, Burak Ahmet; Cogen, Fatih; Aydin, Erdogan; Ilhan, Haci; Wen, Miaowen; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; College of EngineeringToday's wireless communication networks have many requirements such as high data rate, high reliability, low latency, low error data transmission, and high energy efficiency. High-performance index modulation (IM) techniques and reconfigurable intelligent surface (RIS) technology, which has recently attracted the attention of researchers, are strong candidates to meet these requirements. This paper introduces a novel RIS-supported code IM-based receive spatial modulation (RIS-CIM-RSM) system. The proposed RIS-CIM-RSM system uses quadrature amplitude modulation (QAM) symbols, receive antenna indices, and spreading code indices for wireless data transmission. In the proposed system, an RIS applies a phase rotation that maximizes signal-to-noise ratio (SNR) to the signals coming to the reflecting elements and directs them to the selected receive antenna. Performance analyses of the proposed RIS-CIM-RSM system such as data rate, throughput, and energy saving are obtained. The results obtained show that the proposed RIS-CIM-RSM system is superior to the counterpart RIS-based IM systems in the literature in terms of data rate, throughput, energy saving, and error performance.Publication Metadata only Coordinate interleaved OFDM with repeated in-phase/quadrature index modulation(IEEE-Inst Electrical Electronics Engineers Inc, 2024) ; Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Tuğtekin, Ömer Furkan; Doğukan, Ali Tuğberk; Arslan, Emre; Başar, Ertuğrul; ; Graduate School of Sciences and Engineering; College of Engineering; Communications Research and Innovation Laboratory (CoreLab)Orthogonal frequency division multiplexing with index modulation (OFDM-IM), which transmits information bits through ordinary constellation symbols and indices of active subcarriers, is a promising multicarrier transmission scheme and has attracted the attention of researchers due to numerous benefits such as flexibility and simplicity. Nonetheless, OFDM-IM cannot satisfy the needs of future wireless communication services such as superior reliability, high data rates, and low complexity. In this article, we propose a novel OFDM-IM scheme named coordinate interleaved OFDM with repeated in-phase/quadrature IM (CI-OFDM-RIQIM), which provides superior error performance and enhanced spectral efficiency due to its diversity order of two and clever subcarrier activation pattern (SAP) detection mechanism, respectively. In addition, CI-OFDM-RIQIM is further extended to coordinate interleaved OFDM with in-phase/quadrature IM (CI-OFDM-IQIM) by doubling information bits transmitted by IM. Furthermore, log-likelihood ratio (LLR) based low-complexity detectors are designed for both proposed schemes. Theoretical analyses are performed and an upper bound on the bit error probability is derived. Comprehensive computer simulations under perfect and imperfect channel state information (CSI), are conducted to compare the proposed and reference schemes. It is shown that CI-OFDM-RIQIM and CI-OFDM-IQIM show superior results and can be considered promising candidates for next-generation wireless communication systems.Publication Metadata only Noise modulation(IEEE-Institute of Electrical and Electronics Engineers, 2024) Department of Electrical and Electronics Engineering; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; College of EngineeringInstead of treating the noise as a detrimental effect, can we use it as an information carrier? In this letter, we provide the conceptual and mathematical foundations of wireless communication utilizing noise and random signals in general. Mainly, the concept of noise modulation (NoiseMod) is introduced to cover information transmission by both thermal noise and externally generated noise signals. The performance of underlying NoiseMod schemes is evaluated under both additive white Gaussian and fading channels and alternative NoiseMod designs exploiting non-coherent detection and time diversity are proposed. Extensive numerical and computer simulation results are presented to validate our designs and theoretical derivations.