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Publication Metadata only A unified framework for multi-hop wireless relaying with hardware impairments(IEEE-Inst Electrical Electronics Engineers Inc, 2024) Soleimani-Nasab, Ehsan; Department of Electrical and Electronics Engineering; Ergen, Sinem Çöleri; Department of Electrical and Electronics Engineering; ; College of Engineering;Relaying increases the coverage area and reliability of wireless communications systems by mitigating the fading effect on the received signal. Most technical contributions in the context of these systems assume ideal hardware (ID) by neglecting the non-idealities of the transceivers, which include phase noise, in-phase/quadrature mismatch and high power amplifier nonlinearities. These non-idealities create distortion on the received signal by causing variations in the phase and attenuating the amplitude. The resulting deterioration of the performance of wireless communication systems is further magnified as the frequency of transmission increases. In this paper, we investigate the aggregate impact of hardware impairments (HI) on the general multi-hop relay system using amplify-and-forward (AF) and decode-and-forward (DF) relaying techniques over a general bf H-fading model. bf H-fading model includes free space optics, radio frequency, millimeter wave, Terahertz, and underwater fading models. Closed-form expressions of outage probability, bit error probability and ergodic capacity are derived in terms of bf H-functions. Following an asymptotic analysis at high signal-to-noise ratio (SNR), practical optimization problems have been formulated with the objective of finding the optimal level of HI subject to the limitation on the total HI level. The analytical solution has been derived for the Nakagami-m fading channel which is a special case of bf H-fading for AF and DF relaying techniques. The overall instantaneous signal-to-noise-plus-distortion ratio has been demonstrated to reach a ceiling at high SNRs which has a reciprocal proportion to the HI level of all hops' transceivers on the contrary to the ID.Publication Metadata only Cluster index modulation for reconfigurable intelligent surface-assisted mmwave massive MIMO(IEEE-Inst Electrical Electronics Engineers Inc, 2024) Koç, Asil; Le-Ngoc, Tho; Department of Electrical and Electronics Engineering; Raeisi, Mahmoud; Yıldırım, İbrahim; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; ; Graduate School of Sciences and Engineering; College of Engineering; Communications Research and Innovation Laboratory (CoreLab)In this paper, we propose a transmission mechanism for a reconfigurable intelligent surface (RIS)-assisted millimeter wave (mmWave) system based on cluster index modulation (CIM), named best-gain optimized cluster selection CIM (BGCS-CIM). The proposed BGCS-CIM scheme considers effective cluster power gain and spatial diversity gain obtained by the additional paths within the indexed cluster to construct an efficient codebook. We also integrate the proposed scheme into a practical system model to create a virtual path between transmitter and receiver where the direct link has been blocked. Thanks to the designed whitening filter, a closed-form expression for the upper bound on the average bit error rate (ABER) is derived and used to validate the simulation results. It has been shown that the proposed BGCS-CIM scheme outperforms the existing benchmarks thanks to its higher effective cluster gain, spatial diversity of indexed clusters, and lower inter-cluster interference.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; Tuğtekin, Ömer Furkan; Doğukan, Ali Tuğberk; Arslan, Emre; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; ; 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 Frequency-domain detection for molecular communication with cross-reactive receptors(IEEE-Inst Electrical Electronics Engineers Inc, 2024) ; Department of Electrical and Electronics Engineering; Civaş, Meltem; Akan, Özgür Barış; Department of Electrical and Electronics Engineering; ; Graduate School of Sciences and Engineering; College of Engineering;Molecular Communications (MC) is a bio-inspired communication paradigm using molecules as information carriers, necessitating novel transceivers and modulation/detection techniques. In realizing practical MC receivers (MC-Rxs), biosensor field-effect transistor (bioFET)-based architectures are promising, having surface receptors that undergo reversible reactions with ligands. These interactions are converted into electrical signals via field effect, enabling the decoding of transmitted information. A significant challenge in these receivers is the limited specificity of receptors to target ligands, which leads to molecular cross-talk from similar interfering ligands co-existing in the MC channel. Decoding transmitted symbols under such interference is challenging in the time domain, especially when MC-Rx lacks prior knowledge of interferer statistics or operates near saturation. To address this, we introduce a frequency-domain detection (FDD) technique for bioFET-based MC-Rxs, which exploits the distinct binding reaction rates of different ligand types, reflected in the power spectrum of binding noise. Compared to conventional time-domain detection (TDD) technique, this method offers improved detection performance under stochastic molecular interference. We analyze the bit error probability (BEP) of FDD, confirming its superior performance in various interference scenarios. Moreover, the theoretical performance limits of FDD are validated through a particle-based spatial stochastic simulator, simulating binding reactions on MC-Rx within microfluidic channels. © 1972-2012 IEEE.Publication Metadata only From concept to implementation: streamlining sensor and actuator selection for collaborative design and engineering of interactive systems(IEEE-Inst Electrical Electronics Engineers Inc, 2024) Yıldırım, İhsan Ozan; Keskin, Ege; Department of Electrical and Electronics Engineering;Department of Media and Visual Arts; Kocaman, Yağmur; Kuşcu, Murat; Özcan, Oğuzhan; Research Center for Creative Industries (KUAR) / KU Arçelik Yaratıcı Endüstriler Uygulama ve Araştırma Merkezi (KUAR); Graduate School of Social Sciences and Humanities; College of Engineering; College of Social Sciences and Humanities;Selecting appropriate sensors and actuators is a pivotal aspect of design and engineering, particularly in projects involving interactive systems. This article introduces the design thinking-based iterative sensor and actuator selection flow, a structured decision-making approach aimed at streamlining this essential, yet often complex task. Created to accommodate individuals with diverse levels of technical expertise, our approach is uniquely suited for interdisciplinary teams of designers and engineers. Through the application of the flow to four real-world case studies, we highlight its broad applicability and demonstrate its efficacy in expediting project timelines and enhancing resource utilization. Our work lays a foundation for a more streamlined and user-centered process in selecting sensors and actuators, significantly benefiting the practice of interactive system design. This contribution serves as a seminal foundation for future research, offering significant contributions to both academic inquiry and practical applications across various industries. While the focus of the flow is on streamlining the selection process rather than on in-depth technical considerations, which are beyond the scope of this study, it provides a comprehensive guide for efficient and informed decision-making in the realm of interactive system design.Publication Metadata only HyperE2VID: improving event-based video reconstruction via hypernetworks(IEEE-Inst Electrical Electronics Engineers Inc, 2024) Ercan, Burak; Eker, Onur; Sağlam, Canberk; Erdem, Erkut; Department of Computer Engineering; Erdem, Aykut; Department of Computer Engineering; Koç Üniversitesi İş Bankası Enfeksiyon Hastalıkları Uygulama ve Araştırma Merkezi (EHAM) / Koç University İşbank Center for Infectious Diseases (KU-IS CID); College of Engineering;Event-based cameras are becoming increasingly popular for their ability to capture high-speed motion with low latency and high dynamic range. However, generating videos from events remains challenging due to the highly sparse and varying nature of event data. To address this, in this study, we propose HyperE2VID, a dynamic neural network architecture for event-based video reconstruction. Our approach uses hypernetworks to generate per-pixel adaptive filters guided by a context fusion module that combines information from event voxel grids and previously reconstructed intensity images. We also employ a curriculum learning strategy to train the network more robustly. Our comprehensive experimental evaluations across various benchmark datasets reveal that HyperE2VID not only surpasses current state-of-the-art methods in terms of reconstruction quality but also achieves this with fewer parameters, reduced computational requirements, and accelerated inference times.Publication Metadata only Index modulation-based information harvesting for far-field RF power transfer(IEEE-Inst Electrical Electronics Engineers Inc, 2024) İlter, Mehmet C.; Wichman, Risto; Hamalainen, Jyri; Department of Electrical and Electronics Engineering; Pıhtılı, Mehmet Ertuğ; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; ; Graduate School of Sciences and Engineering; College of Engineering; Communications Research and Innovation Laboratory (CoreLab)As wireless information transmission (WIT) progresses into its sixth generation (6G), a challenge arises in sustaining terminal operations with limited batteries for Internet-of-Things (IoT) platforms. To address this, wireless power transfer (WPT) emerges as a solution, empowering battery-less infrastructures and enabling nodes to harvest energy for sustainable operations. Thus, the eclectic integration of WPT with WIT mechanisms becomes crucial to mitigate the need for battery replacements while providing secure and reliable communication. A novel protocol that amalgamates WIT and WPT called Information Harvesting (IH) has recently been proposed to effectively handle challenges in wireless information and power transfer (WIPT) by employing index modulation (IM) techniques for data communication atop the existing far-field WPT mechanism. This paper presents a unified framework for IM-based IH mechanisms and evaluates their energy harvesting capability, bit error rate (BER), and ergodic secrecy rate (ESR) performance for diverse IM schemes. The findings indicate the significant potential of the IM-based IH mechanism in facilitating reliable data communication within existing far-field WPT systems while underscoring promising refinements in green and secure communication paradigms for next-generation IoT wireless networks. AuthorsPublication Metadata only Indoor measurements for RIS-aided communication: practical phase shift optimization, coverage enhancement, and physical layer security(IEEE-Inst Electrical Electronics Engineers Inc, 2024) Hökelek, İbrahim; Görçin, Ali; Department of Electrical and Electronics Engineering; Kayraklık, Sefa; Yıldırım, İbrahim; Gevez, Yarkın; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; ; Graduate School of Sciences and Engineering; College of Engineering; Communications Research and Innovation Laboratory (CoreLab)Practical experiments are a crucial step to demonstrate the viability of reconfigurable intelligent surface (RIS)-empowered communication, which is one of the emerging technologies for next-generation networks. In this paper, we present practical measurements to demonstrate the RIS capabilities for enhancing signal coverage and providing physical layer security (PLS) in an indoor environment. First, extensive measurements are performed in a single-user deployment using iterative, grouping, and codebook-based phase shift optimization methods. The iterative method achieves approximately 10 dB performance improvement in the received signal power through careful adjustments of RIS phase configurations when the receiver is placed at different locations. The grouping method reduces the training time to find a suitable RIS configuration by sacrificing only a few dBs in the received signal power. Another set of experiments is conducted for a multi-user deployment to exhibit PLS, where the RIS is partitioned into two regions serving the intended and unintended users. The results demonstrate that the codebook method can effectively boost the secrecy capacity on the move without utilizing feedback other than the users' positions during the phase shift optimization process, while the iterative method requires a continuous feedback channel for the received signal powers.Publication Metadata only 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; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; 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 Joint delay-Doppler index modulation for orthogonal time frequency space modulation(IEEE-Inst Electrical Electronics Engineers Inc, 2024) ; Department of Electrical and Electronics Engineering; Tek, Yusuf İslam; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; ; Graduate School of Sciences and Engineering; College of Engineering;Orthogonal time frequency space (OTFS) is a promising waveform with outstanding performance in doubly-selective channels. Spreading information symbols across the entire delay-Doppler plane enables OTFS to exploit full diversity. Nevertheless, there is a need for enhanced reliability in OTFS systems to satisfy the rigorous requirements of forthcoming communication systems. To tackle this concern, we propose a scheme called joint delay-Doppler index modulation OTFS (JDDIM-OTFS). This scheme activates delay or Doppler resource elements in a subframe, and in order to obtain higher spectral efficiency, we use different constellations for each active resource block. Furthermore, we utilize a low-complex detector with the help of a greedy approach. Moreover, a theoretical upper bound is derived for the bit error rate (BER). Simulation results validate that JDDIM-OTFS outmatches classical OTFS and other benchmark schemes in terms of BER under perfect and imperfect channel conditions.