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https://hdl.handle.net/20.500.12511/4107

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Joint adaptive ofdm and reinforcement learning design for autonomous vehicles: leveraging age of updates
(2025) Delamou, Mamady; Naeem, Ahmed; Arslan, Hüseyin; Amhoud, El Mehdi
Millimeter wave (mmWave)-based orthogonal frequency-division multiplexing (OFDM) stands out as a suitable alternative for high-resolution sensing and high-speed data transmission. To meet communication and sensing requirements, many works propose a static configuration where the wave's hyperparameters such as the number of symbols in a frame and the number of frames in a communication slot are already predefined. However, two facts oblige us to redefine the problem, 1) the environment is often dynamic and uncertain, and 2) mmWave is severely impacted by wireless environments. A striking example where this challenge is very prominent is autonomous vehicle (AV). Such a system leverages integrated sensing and communication (ISAC) using mmWave to manage data transmission and the dynamism of the environment. In this work, we consider an autonomous vehicle network where an AV utilizes its queue state information (QSI) and channel state information (CSI) in conjunction with reinforcement learning techniques to manage communication and sensing. This enables the AV to achieve two primary objectives: establishing a stable communication link with other AVs and accurately estimating the velocities of surrounding objects with high resolution. The communication performance is therefore evaluated based on the queue state, the effective data rate, and the discarded packets rate. In contrast, the effectiveness of the sensing is assessed using the velocity resolution. In addition, we exploit adaptive OFDM techniques for dynamic modulation, and we suggest a reward function that leverages the age of updates to handle the communication buffer and improve sensing. The system is validated using advantage actor-critic (A2C) and proximal policy optimization (PPO). Furthermore, we compare our solution with the existing design and demonstrate its superior performance by computer simulations.
AutoCOR: autonomous condylar offset ratio calculator for post-operative total knee arthroplasty radiographs
(2025) Çakmak, Gülsade Rabia; Hamamcı, İbrahim Ethem; Yılmaz, Mehmet Kürşat; Alhajj, Reda; Azboy, İbrahim; Özdemir, Mehmet Kemal
Background: This study aims to automate the measurement process of posterior condylar offset ratio (PCOR) and anterior condylar offset ratio (ACOR) to improve the Total Knee Arthroplasty (TKA) evaluation. Accurate calculation of PCOR and ACOR, performed manually by orthopedic surgeons, is crucial for assessing postoperative range of motion and implant positioning. Manual measurements, however, are time-consuming, prone to human error, and subject to variability. Automating this process could improve precision in clinical practice. Methods: We developed AutoCOR, a software system that autonomously calculates PCOR and ACOR by utilizing built-in function, employing k-means clustering, from the OpenCV library for image segmentation. The software detects key anatomical landmarks on true postoperative lateral radiographs. The definitions of PCOR and ACOR are PCO (posterior condylar offset) divided by femoral diameter, and ACOR is defined as ACO (anterior condylar offset) divided by femoral diameter, respectively. We tested the algorithm on 50 postoperative lateral radiographs of 32 patients from the Istanbul Kosuyolu Medipol Hospital, which included data from. The assessment process included calculating the mean, standard deviation and plotting the Bland-Altman plots, comparing AutoCOR's results against ground truth values. Results: The mean PCOR was 0.984 (SD 0.235) for AutoCOR and 0.972 (SD 0.164) for ground truth values, showing a strong correlation (Pearson r = 0.845, p < 0.0001). The mean ACOR was 0.107 (SD 0.092) for AutoCOR and 0.107 (SD 0.070) for ground truth values, with moderate correlation (Spearman's rs = 0.519, p = 0.0001). Conclusion: AutoCOR provides accurate measurements and shows potential to reduce variability in TKA evaluation, improving precision in clinical practice.
Design of dc to 40 ghz gaas-based mmic attenuators by utilizing full-chip numerical analyses
(2024) Bayrak, Mehmet Emin; Tekin, Harun; Savcı, Hüseyin Şerif
In this study, a numerical analysis-based design methodology of monolithic microwave integrated circuit (MMIC) attenuators on a GaAs-based microwave integrated passive device (IPD) technology is presented. The designs have 0 dB, 3 dB, 4 dB, 6 dB, 10 dB, 12 dB, 20 dB, and 30 dB attenuation from DC to 40 GHz. The attenuators are designed for a maximum RF power of 26 dBm and a maximum die area of 0.25 mm2. The circuits are physically compact but electrically large. The finite element method and Method of Moments (MoM)based analyses are used. The MoM-based solutions show close correlations with the measurements. The measured return losses are better than 20 dB, and insertion loss variation is less than 0.5 dB across the entire band. This paper explains the detailed design steps and numerical electromagnetic setup to achieve first-pass success.
Post-earthquake network restoration statistical seismic road closure prediction and efficient mdru routing
(2025) Duranay, Ahmet Enes; Kodheli, Xhelja; Abdelhady, Amr; Çelik, Abdulkadir; Eltawil, Ahmed; Arslan, Hüseyin
Post-earthquake scenarios have brought connectivity challenges to the forefront of research in recent years. Particularly, the randomness and large-scale of road and telecom network infrastructure damage within the aftermath hinders communications coverage restoration during the most critical hours when lives are at stake. This paper proposes a seismic-based post-earthquake city and cellular network model to statistically predict the status of road closures and base station failures based on fundamental earthquake measurements. The presented model considers a generic Manhattan grid-based city model, with buildings featuring random heights. In addition, it quantifies the probability of building collapse and the consequent probability of road closure which accounts for the random debris nature. Moreover, the model accounts for the dependencies between the debris width, height, and the relative location with respect to the earthquake epicenter. Furthermore, a routing algorithm for movable and deployable resource units (MDRUs) that exploits the derived statistical model is proposed to ensure that MDRUs are efficiently deployed and connectivity is restored swiftly. The proposed routing algorithm is extensively tested over a large set of simulation scenarios depicting different earthquake magnitudes and was shown to provide up to 31% traveling time reduction compared to a blind distance-based approach. Finally, the conducted simulations showed the effectiveness of the proposed MDRUs deployment approach in restoring the communications coverage from a signal-to-interference plus noise ratio perspective in the majority of the considered locations.
A novel ofdm-fmcw waveform for low-complexity joint sensing and communication
(2025) Bouziane, Amir; Eddine Zegrar, Salah; Arslan, Hüseyin
With the advent of 6th Generation (6G) wireless networks, integrating Orthogonal Frequency Division Multiplexing (OFDM) and Frequency Modulated Continuous Wave (FMCW) waveforms presents a promising solution for simultaneous communication and sensing. While OFDM offers high communication performance, it requires complex transceivers for sensing applications. Conversely, FMCW is easily implemented for sensing but provides low data rates for communication. This letter derives the mathematical relationship between OFDM and FMCW, showing how FMCW can be generated from the diagonal elements of the OFDM modulator (i.e.ifnextchar.gobble, the Discrete Fourier Transform (DFT) matrix). We propose a novel approach that leverages the DFT matrix to seamlessly integrate these two waveforms, minimizing interference and enabling high data rate communication alongside low-complexity sensing receiver design. Extensive simulations demonstrate the effectiveness of our technique in achieving simultaneous sensing and communication.
Waveform management approach with machine learning for 6g systems
(2024) Demir, Yusuf İslam; Yazar, Ahmet; Arslan, Hüseyin
5th Generation (5G) systems are designed with a more flexible structure compared to previous generations with an increasing variety of applications and services. Thus, new flexibility dimensions are observed in 5G technologies. Furthermore, emergence of these flexibility dimensions is triggered a need for advanced management paradigms for 5G and beyond. It is expected that application richness, flexibility dimensions, and the related management paradigms will show an increase with 6th Generation (6G) systems. It is possible that different flexibilities related to the waveform design can be introduced in 6G while a uniform method is used in 5G and previous generations. One of these flexibilities can be the ability to make selection through a waveform set for a new capability to meet different application and user requirements with the waveform selection. In this paper, waveform selection approaches are proposed based on machine learning (ML) with single-stage and multi-stage networks for the waveform management in the same coverage area under the assumption that multiple waveforms can be used in 6G. Hence, the problem of deciding on the best waveform for a coverage area considering different requirements and environmental conditions is studied. To provide environmental awareness, a new synthetic dataset is formed with an example simulation setup. Moreover, a feature control algorithm is proposed to limit side effects of the waveform selection approaches.
Design of balansens: functional evaluation in ankle preparation phase
(2024) Ersoy, Tuğçe; Hocaoğlu, Elif; Kaya, Pınar; Ünal, Ramazan
In this study, we present the design and development evaluation of BalanSENS toward the realization of the Integrated Balance Rehabilitation (I-BaR) framework. BalanSENS is designed to encourage active participation by integrating multi-sensory information with the co-improvement of sensory and motor functions. Moreover, it can offer individual rehabilitation design with the integration of three phases. The first phase provides foot-ankle muscle activation and movement sensation development. In the second phase, sensory weighting skills and upper extremities independence can be improved by using multi-sensory input. In the last/stepping phase, walking parameters are aimed to be improved with modulated distance. The parallel manipulator is designed through simulations to determine actuation properties and analyze the load-bearing capacity and feasibility of the materials. Drawing from simulation outcomes, an operational 3 DoF platform is constructed to demonstrate their design suitability for the I-BaR framework. Furthermore, design evaluations demonstrated promising results in quantifying force and real-time data monitoring during the passive ankle preparation phase.
Design of balansens: functional evaluation in ankle preparation phase
(2024) Ersoy, Tuğçe; Hocaoğlu, Elif; Kaya, Pınar; Ünal, Ramazan
In this study, we present the design and development evaluation of BalanSENS toward the realization of the Integrated Balance Rehabilitation (I-BaR) framework. BalanSENS is designed to encourage active participation by integrating multi-sensory information with the co-improvement of sensory and motor functions. Moreover, it can offer individual rehabilitation design with the integration of three phases. The first phase provides foot-ankle muscle activation and movement sensation development. In the second phase, sensory weighting skills and upper extremities independence can be improved by using multi-sensory input. In the last/stepping phase, walking parameters are aimed to be improved with modulated distance. The parallel manipulator is designed through simulations to determine actuation properties and analyze the load-bearing capacity and feasibility of the materials. Drawing from simulation outcomes, an operational 3 DoF platform is constructed to demonstrate their design suitability for the I-BaR framework. Furthermore, design evaluations demonstrated promising results in quantifying force and real-time data monitoring during the passive ankle preparation phase.
Robust tracking-based phy-authentication in mmwave mimo systems
(2024) Afeef, Liza; Furqan, Haji Muhammad; Arslan, Hüseyin
Physical Layer Authentication (PLA) is a topic of considerable interest in ensuring strong security for upcoming wireless networks. However, existing PLA methods face challenges in maintaining performance in dynamic environments. To overcome this, we propose a novel tracking-based PLA approach, utilizing properties of the beamspace multiple-input multiple-output (MIMO) channel in narrowband millimeter-wave (mmWave) networks. Specifically, In particular, the proposed technique involves extracting a distance signature vector from the positions of the principal components within the beamspace MIMO channel representation. These components are then sorted in descending order based on their indices. To address mobility concerns in dynamic settings, a tracking filter is introduced. This filter allows the authentication system to continuously track and update the stored signature, enhancing overall authentication performance. Additionally, the proposed technique is extended to ultra-wideband signaling. In this extension, the richness of the derived signature is further improved by exploiting the beam squint effect, contributing to a more robust authentication process. Simulation results demonstrate that our approach overcomes the limitations of previous methods, resulting in improved authentication performance measured by detection and false alarm rates.
Interference burden in wireless communications: a comprehensive survey from phy layer perspective
(2025) Tusha, Armed; Arslan, Hüseyin
Interference represents one of the most common barriers for the wireless communications society to bring the fully connected world to life, where everybody and everything is connected at any time, aiming to support a wide range of services and applications with increasing demand in terms of data rate with a higher degree of reliability and security, while keeping an affordable overall system capacity, complexity, and latency. Essentially, interference clearly explains the primitive nature of the wireless communications systems, where there is always an unwanted physical signal that disrupts the communication link, occurring from the physical layer (PHY) architecture of transmission signal, its interaction with the wireless channel and transceiver architecture in particular. Therefore, in past wireless technologies, waveform design along with wireless channel impairments and handset architecture define the main sources of interference, leading to inter-symbol interference (ISI), inter-carrier interference (ICI) and co-channel interference (CCI) types. In this line, recent advances in wireless technologies have revealed unprecedented interference types including inter-numerology interference (INI), inter-antenna interference (IAI), inter-waveform interference (IWI), cross-link interference (CLI) and inter-Doppler interference (IDI), while additional unique interference types are expected in near future. Consequently, a broader view of the interference has become a crucial need in order to avoid and relax its impact towards beyond 5G radio access technologies. Despite the extensive research in the literature performed by academia and industry, to the best of the authors' knowledge, there is no work that provides a comprehensive taxonomy framework of interference sources and types, and a review of management techniques from the perspective of the PHY layer. This work aims to fill this gap in the literature. With this notation, in this survey, we propose an intuitive, generic, and expandable framework that categorizes the interference sources and their corresponding management solutions. In particular, we split the interference sources into two main groups by taking into account the user of interest such as self-user-interference (SUI) and other-user-interference (OUI), which we further classify considering the user's intention about the presence of interference named intentional SUI (I-SUI), unintentional SUI (U-SUI), intentional OUI (I-OUI), and unintentional OUI (U-OUI). In line with this, we offer a classification of the interference management techniques regarding the source of interference. Lastly, the survey presents open research perspectives for beyond 5G wireless systems and concluding remarks.
Visibility region exploitation for phy authentication in xl-mimo systems
(2025) Demirci, Senanur; Afeef, Liza; Arslan, Hüseyin
Wireless networks are open to identity spoofing attacks because of their broadcast nature, emphasizing the need for strong security. Physical layer authentication (PLA) is a crucial strategy for securing wireless networks against such threats. Extra-large multiple-input multiple-output (XL-MIMO) technology, with its unique visibility region (VR) concept due to the near-field effect, offers a promising way to enhance network performance. This letter proposes a PLA approach using VR to create unique and robust signatures from the power and beamspace domain of XL-MIMO. Simulation results confirm the effectiveness of the proposed method in detecting attacks with high accuracy and low false alarm rates.
Machine learning-driven integration of terrestrial and non-terrestrial networks for enhanced 6G connectivity
(2024) Aygül, Mehmet Ali; Türkmen, Halise; Çırpan, Hakan Ali; Arslan, Hüseyin
Non-terrestrial networks (NTN)s are essential for achieving the persistent connectivity goal of sixth-generation networks, especially in areas lacking terrestrial infrastructure. However, integrating NTNs with terrestrial networks presents several challenges. The dynamic and complex nature of NTN communication scenarios makes traditional model-based approaches for resource allocation and parameter optimization computationally intensive and often impractical. Machine learning (ML)-based solutions are critical here because they can efficiently identify patterns in dynamic, multi-dimensional data, offering enhanced performance with reduced complexity. ML algorithms are categorized based on learning style—supervised, unsupervised, and reinforcement learning—and architecture, including centralized, decentralized, and distributed ML. Each approach has advantages and limitations in different contexts, making it crucial to select the most suitable ML strategy for each specific scenario in the integration of terrestrial and non-terrestrial networks (TNTN)s. This paper reviews the integration architectures of TNTNs as outlined in the 3rd Generation Partnership Project, examines ML-based existing work, and discusses suitable ML learning styles and architectures for various TNTN scenarios. Subsequently, it delves into the capabilities and challenges of different ML approaches through a case study in a specific scenario.
Service-based resource scheduling optimization for multi-user otfs-based systems
(2024) Jaradat, Ahmad M.; Alayedi, Mohanad; Arslan, Hüseyin
In this letter, we investigate a flexible resource allocation (RA) in the delay and Doppler domains to accommodate services with varying requirements. We demonstrate that our problem is NP-hard and propose an optimization method based on linear programming (LP) and Lagrangian dual (LD). The adoption of flexibility in the delay and Doppler domains for capacity enhancement and addressing the needs of mission-critical services has considerable advantages, according to the obtained numerical results. They show that the new scheduling method outperforms conventional time-frequency (TF) domains in terms of bit rate and latency per user, making it valuable for fifth generation (5G) applications and beyond.
High-accuracy indoor ranging using microwave ofdm signals
(2024) Yazgan, Mehmet; Arslan, Hüseyin; Vakalis, Stavros
High-accuracy wireless ranging and positioning becomes necessary in many applications, and while many waveforms promise high accuracy, their performance in cluttered environments is not optimal. This article confers about the potential of high-accuracy wireless ranging using orthogonal frequency-division multiplexing (OFDM) signals. The excellent correlation properties of OFDM signals for high-accuracy ranging in real-life environments are discussed and the Cramer-Rao lower bound (CRLB) is derived for OFDM ranging independent of the transmitted information. Simulation results and experimental measurements at a carrier frequency of 1.4 GHz with 200 MHz of bandwidth are included. Range estimation is demonstrated with a standard deviation of 1.6 mm in a realistic laboratory environment with no anechoic walls.
Power-efficient time-domain scheduling for isac beamforming
(2024) Memişoğlu, Ebubekir; Janjua, Muhammad Bilal; Arslan, Hüseyin
Power efficiency is a critical metric for a sustainable 6G network. The emergence of integrated sensing and communication (ISAC) services leads to significant power consumption due to additional signal transmission for sensing. An ISAC beamforming is an efficient transmission method for reducing power consumption in mmWave multi-input multi-output (MIMO) systems while meeting the requirements of communication users (CUs) and sensing users (SUs). This approach is only feasible when both users are within the coverage of the same beam. Otherwise, separate beams are required which results in high power consumption. In this letter, we propose a novel time-domain scheduling method for ISAC beamforming to achieve high-power efficiency. The performance gains compared to conventional scheduling method are demonstrated for the different number of users, periodicity values, and user distribution ratios.
Fractional delay and fractional doppler estimation and mitigation framework in otfs systems
(2025) Zegrar, Salah Eddine; Sümer, Ahmet Sacid; Arslan, Hüseyin
Orthogonal time-frequency space (OTFS) modulation is fast becoming a popular modulation scheme for high-mobility wireless communication due to its ability to render time-varying channels invariant and sparse. However, due to the limited time duration and frequency bandwidth of the transmitted OTFS signal, the occurrence of fractional delay and Doppler shifts becomes inevitable, causing both inter-delay interference (IDeI) and inter-Doppler interference (IDI). In this paper, an impulse-based channel estimation method is used, which takes advantage of the fact that the pilot impulse is a pulse tone (pulsone). A pulsone maintains its shape despite time delay and Doppler shift operations, as well as being self-dual between time and frequency domains. Exploiting these two features, a low-complexity algorithm is proposed to estimate the fractional delay and fractional Doppler channel. We derive the Cramer-Rao lower bound (CRLB) of the estimated fractional channel and show that the developed estimator is efficient. Then, we provide the computational complexity analysis of the proposed algorithm. After that, we show and stress that the proposed channel estimation scheme is better in terms of the channel normalized mean squared error (NMSE) and the bit-error rate (BER). Lastly, the simulation results are confirmed via real experimental results.
Performance analysis of otsm under hardware impairments and imperfect csi
(2024) Doosti Aref, Abed; Masouros, Christos; Zhu, Xu; Başar, Ertuğrul; Çöleri, Sinem; Arslan, Hüseyin
Orthogonal time sequency multiplexing (OTSM) has been recently proposed as a single-carrier waveform offering similar bit error rate to orthogonal time frequency space (OTFS) and outperforms orthogonal frequency division multiplexing (OFDM) in doubly-spread channels (DSCs); however, with a much lower complexity making it a potential candidate for 6G wireless networks. In this paper, the performance of OTSM is explored by considering the joint effects of multiple hardware impairments (HWIs) such as in-phase and quadrature imbalance (IQI), direct current offset (DCO), phase noise, power amplifier non-linearity, carrier frequency offset, and synchronization timing offset for the first time in the area. First, the discrete-time baseband signal model is obtained in vector form under all mentioned HWIs. Second, the system input-output relations are derived in time, delay-time, and delay-sequency (DS) domains in which the parameters of all mentioned HWIs are incorporated. Third, analytical expressions are derived for the pairwise and average bit error probability under imperfect channel state information (CSI) as a function of the parameters of all mentioned HWIs. Analytical results demonstrate that under all mentioned HWIs, noise stays additive white Gaussian, effective channel matrix is sparse, DCO appears as a DC signal at the receiver interfering with only the zero sequency, and IQI redounds to self-conjugated sequency interference in the DS domain. Simulation results reveal the fact that by considering the joint effects of all mentioned HWIs and imperfect CSI not only OTSM outperforms OFDM by 29% in terms of energy of bit per noise but it performs same as OTFS in high mobility DSCs.
Novel ocdm transceiver design for doubly-dispersive channels
(2024) Haif, Hamza; Zegrar, Salah Eddine; Arslan, Hüseyin
Orthogonal chirp division multiplexing (OCDM) is a new multi-carrier scheme that has been emerging as a new candidate for 6G waveform taking advantage of the unique features of the chirp spread spectrum that makes it immune to intersymbol interference raised due to delay spread. However, a thorough analysis of OCDM under doubly-dispersive channels has not been conducted yet to verify its robustness against Doppler spread as well. In this paper, we investigate the input-output relationship of an OCDM system under doubly-selective channel, where we demonstrate that the circular convolution property of OCDM partially holds even under Doppler spread. Building on previous results, we show the difficulties and problems associated with estimating and equalizing the channel at the receiver side in conventional OCDM systems, especially in case of having fractional delay and Doppler shifts. Then, we propose a new OCDM transceiver by adding fast Fourier transform (FFT) and windowing blocks to ensure channel tap separability and reduce the effect of fractional Doppler shift, respectively. Accordingly, a new channel estimation scheme is developed for the proposed OCDM system. The numerical and simulation results validate the advantages of the proposed OCDM system performance under doubly-dispersive channels over the conventional where the proposed leverages a bit-error-rate (BER) gain in perfect channel state information (CSI) of 2 dB and 3 dB for minimum mean squared error (MMSE) and message passing (MP) equalizers, respectively, and show that it holds great promise as an emerging radio access technology for 6G wireless systems.
How to leverage double-structured sparsity of ris channels to boost physical-layer authentication
(2024) Bendaimi, Amira; Abdallah, Asmaa; Çelik, Abdulkadir; Eltawil, Ahmed M.; Arslan, Hüseyin
Reconfigurable Intelligent Surfaces (RIS)-assisted systems are promising technology in next-generation wireless networks, but are susceptible to spoofing attacks due to their broadcast nature. This letter reveals the unique characteristics of RIS-aided multiple-input multiple-output (MIMO) systems, that improve channel entropy compared to conventional MIMO. By capitalizing on the additional paths introduced by the cascaded channel and the distinctive double-structured sparsity inherent in its virtual representation, we develop a novel channel-based physical layer authentication (PLA) approach. In particular, we construct a robust signature for authentication purposes by extracting the intrinsic RIS features of the virtual angle of arrivals and departures indices. Furthermore, the distribution of the digital signature is analyzed to derive analytical expressions for the false alarm and detection probabilities of the proposed scheme. Simulation results show that the proposed approach surpasses the limitations of previous works, with 14.89% and 72% authentication performance improvements in detection and false alarm rates, respectively.
A circular shape arc slot ultra-wideband antenna for biomedical applications
(2024) Awan, Dawar; Bashir, Shahid; Bari, Inam; Bashir, Muhammad Adil; Ali, Haider; Ibrahim, Imran Mohd; Kiani, Saad Hassan; Savcı, Hüseyin Şerif; Zakaria, Zahriladha
In modern communication systems, ultra-wideband (UWB) technology has garnered substantial attention due to its superior attributes compared to traditional narrowband communication systems. Over the past decade, UWB technology has also found applications in microwave-based imaging systems. This study introduces a simple planar coplanar waveguide-fed circular shape arc slot antenna designed specifically for biomedicine and microwave medical imaging applications. The proposed design is implemented on a 1.6-mm-thick FR4 substrate with a relative permittivity of 4.4 and a loss tangent of 0.0009. The antenna has physical dimensions of 26 mm × 29 mm and achieves an impressive bandwidth of 16.6 GHz, spanning 2.4 to 19 GHz. It exhibits a peak gain of 2.5 dBi and consistent omnidirectional radiation characteristics. Thorough temporal analysis validates the antenna’s performance within acceptable limits, which is further affirmed through practical fabrication and testing, demonstrating strong agreement with simulation results.

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