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Öğe Conceptual biomechatronic distractor design to minimize surgical intervention in distraction osteogenesis(2024) Hocaoğlu, Elif; Hocaoğlu, EmreThis study presents a conceptual design for a fully implantable biomechatronic system aimed at minimizing intervention in the treatment of skeletal deformities and deficiencies. Current treatment methods often require a series of operations, prolonged hospital stays, and frequent, burdensome follow-up visits post-discharge. The proposed system aims to reduce the number and duration of surgeries, significantly enhancing the patient’s quality of life during the treatment process. Moreover, the necessity for frequent manual adjustments is reduced, which can alleviate the workload for healthcare providers and potentially decrease the likelihood of human error.Öğe Quantitative analysis of ankle spasticity through electromyography signal(2024) Gürlük, Ayşe; Bilal, Hafiz Muhammad; Hocaoğlu, ElifThis study presents a more accurate evaluation method for assessing ankle spasticity compared to conventional goniometric techniques by utilizing measurements obtained from Inertial Measurement Units (IMU) and surface electromyography (sEMG) devices. Integrating IMU and EMG sensors provides substantial benefits for accurately determining the range of motion (ROM) associated with spasticity during targeted movements. In this study, the proposed method provides precise measurement and an objective evaluation of onset time detection of antagonistic muscle co-contraction, and accordingly the ROM of the actuated joint. Moreover, the implementation of cost-effective wearable sensors enables the monitoring of muscle spasticity in clinical environments and can be particularly valuable in regions with limited access to experienced therapists, providing a more efficient approach to tracking spasticity levels.Öğe Rain rate and rain attenuation analysis over millimeter wave in microwave 5G/6G link systems(2024) Tashan, Waheeb; Yaşar, Halimcan; Shayea, Ibraheem; El Saleh, Ayman A.Future mobile communication systems require high data rate, efficient capacity and more secure communication system. However, 5G/6G millimeter waves (mm-Waves) are introduced as the promising solution method for the network operators. In contrast, rainfall may severely affect negatively on signal quality since the wave length of 5G/6G frequency spectrum almost near to raindrops sizes. Thereby, deteriorating system performance. This study comprehensively surveys rain rate (RR) and rain attenuation (RA) using mm-Waves in microwave 5G/6G link systems. Moreover, most of the studies are implemented in tropical and equatorial regions due to heavy rain which increases the rain attenuation. Furthermore, different models with various operating frequencies were applied to investigate the measured/or predicted dataset. Therefore, these models were compared to investigate their effectiveness. However, several models may not working perfectly for all regions. Thus, while implementing 5G/6G radio frequency (RF) links, using real measurements gives more reliable results than using models in terms of the RR and RA.Öğe Comparison of ofdm and lfm waveform schemes for ranging: a correlation perspective(2024) Yazgan, Mehmet; Arslan, Hüseyin; Vakalis, StavrosOrthogonal frequency division multiplexing (OFDM) waveforms have been employed in communications systems for years and are the key waveform candidates for beyond-fifth-generation (5G) communication networks. In this paper, we compare OFDM waveforms to linear frequency- modulated (LFM) waveforms which are widely exploited in modern radar systems. We discuss the utility of OFDM waveforms for joint communications and sensing but also provide a comparison between the two in terms of their correlation properties. OFDM waveforms exhibit improved cross-correlation properties compared to LFM waveforms which can yield excellent resistance to interference between multiple radar transmitters without any cooperation. We express the theory behind our work and include simulations supporting our claims.Öğe A novel physical layer secret key generation method for wireless sensor networks(2024) Aygül, Mehmet Ali; Çırpan, Hakan Ali; Arslan, HüseyinWireless sensor networks are indispensable across various applications, from environmental surveillance to indus-trial automation, owing to their ability to collect and transmit data autonomously. However, due to the broadcast nature of wireless systems, these systems are vulnerable to eavesdropping attacks. Recently, channel-based secret key generation methods have been widely used in the literature. In these methods, Alice and Bob generate random signals and share these signals with each other. Then, using the secret key paired multiplication with the channel between them, a secret key is shared between legitimate users, while illegitimate nodes cannot access the key. However, these methods consider only two users. This paper proposes a novel method for multiple users. Extensive simulation proves the effectiveness of the proposed method. However, when the number of users increases, the performance of the proposed method decreases.Öğe Menzil profili kullanılarak havadan-yere otomatik hedef tanıma ve hedef yönelim açısı kestirme(2024) Kökçü, Murat; Karabayır, Osman; Alagöz, Yusuf; Güntürk, Bahadır KürşatAktif elektronik tarama yapan radar sistemleri açısından yer yüzeyindeki hedeflerin otomatik olarak tanımlanması büyük önem arz etmektedir. Hedef tanıma aşamasında kestirilen bilgiler ve kestirim doğruluğu gerçekleştirilen operasyonun seyrine doğrudan etki etmektedir. Bu çalışmada, X frekans band bir radar sisteminin yerde konuşlu farklı hedeflerden toplayacağı yüksek çözünürlüklü menzil profilleri ile söz konusu hedeflerin sınıflarını ve yatay yönelim açılarını belirleme performansı incelenmiştir. Derin öğrenme ve şablon eşleme teknikleri kullanılarak yapılan çalışmada, yeryüzü hedeflerinin %85’ten fazlası doğru sınıflandırılabilmiştir. Hedeflerin simetrik yapısı, yönelimlerinin de simetrik dağılmasına neden olmuştur.Öğe 3gpp 5g numeroloji gruplamalarının çok boyutlu performans analizi(2024) Demir, Yusuf İslam; Yazar, Ahmet; Arslan, Hüseyin5. Nesil (5G) kablosuz iletişim sistemleriyle kullanılmaya başlanan çoklu numeroloji yapıları, uygulama çeşitliliğine cevap verebilme açısından önemli bir esneklik kabiliyeti getirmiştir. Bununla beraber çoklu numeroloji yapılarının kullanımı yeni bir durum olan numerolojiler arası girişim (INI) problemini ortaya çıkarmıştır. Literatürde INI konusu farklı kaynaklarda analiz edilmiş ve çoklu numeroloji yapılarına yönelik farklı tasarımlar geliştirilmiştir. Bu çalışmada ise 3GPP 5G numeroloji yapılarının gruplamalarına yönelik çok boyutlu bir performans analizi gerçekleştirilerek çoklu numeroloji yapılarının kullanımı sırasında dikkat edilmesi gereken bazı önemli hususlar ortaya konmuştur. Farklı spektrum frekans aralıkları için analizler sunularak spektral verimlilik değişimine göre sinyal-girişim oranının (SIR) numeroloji gruplamaları için nasıl değişebildiği gösterilmiştir. Uygun numeroloji gruplaması seçimlerinin performans üzerinde olan etkisi verilerek, literatürdeki kullanıcı-numeroloji ilişkilendirmesi çalışmalarının zayıf yönlerine değinilmiştir.Öğe Investigation of ofdm signals for microwave ranging(2024) Yazgan, Mehmet; Arslan, Hüseyin; Vakalis, StavrosWireless ranging and positioning plays a pivotal role across numerous applications, encompassing wireless networks, robotics, navigation, and distributed wireless systems. A common limitation encountered in many ranging algorithms relates to the requirement for waveforms with sufficiently wide bandwidth to attain precise ranging accuracy. In this study, we investigate the applicability of orthogonal frequency-division multiplexing (OFDM) signals for microwave-ranging without necessitating any modifications. OFDM, being a joint communications and sensing waveform, offers the advantage of repurposing existing communication signals for ranging purposes without additional spectrum utilization. We discuss the theoretical underpinnings of our investigation and present simulated and experimental ranging measurements employing OFDM signals, complemented by range estimation and error analyses.Öğe Performance comparison of handover mechanisms for leo networks in s and ka-bands(2024) Kodheli, Xhelja; Solaija, Muhammad Sohaib J.; Arslan, HüseyinLow-Earth orbit (LEO) non-terrestrial networks (NTNs) have become increasingly popular due to their ability to provide high-bandwidth communication in otherwise unserved regions. However, this comes at the cost of high satellite mobility, necessitating efficient handover (HO) strategies. Till now the focus has been on the S-band, however Ka-band is expected to be deployed for high-bandwidth applications necessitating HO studies for higher frequency bands. To address this, we evaluate the performance of the conventional received power-based HO, as well as alternatives such as elevation angle and distance-based triggers for Ka-band LEO networks, and compare them with S-band frequencies. Moreover, a dynamic threshold approach is also evaluated in terms of the number of HOs, unnecessary handovers (UHOs), radio link failures (RLFs), and distributions of downlink carrier-to-noise-plus-interference ratio (CNIR) and mean time-of-stay of a user in a cell. The obtained results indicate the efficacy of power-based mechanisms for the S-band while showing that the alternative methods provide a much better balance at the Ka-band in terms of the overhead and the overall communication link quality.Öğe Joint imaging and communication using sparse antenna arrays(2024) Abusanad, Nusaibah A.; Ayasrah, Mus'ab; Arslan, HüseyinThis paper expands sensing capabilities by providing a Joint Imaging and Communication (JIC) system, leveraging millimeter-wave (mm-Wave) technology and sparse antenna array. To address the challenges associated with the high cost and power consumption of dense antenna arrays, we use a sparse antenna array (SAA) to avoid such a problem at the expense of image resolution. The enhancement of acquired image resolution is achieved through the incorporation of multiple low-resolution image components corresponding to distinct transmission-reception combinations. In order to achieve a high level of fairness between communication and imaging performance we formulate a non-convex optimization problem, and then propose an algorithm for finding an approximate solution in a fully digital beamforming case. Numerical results on achievable capacity and image resolution are presented to validate the proposed approach and provide insights into system performance.Öğe Deep multi-task learning-based simultaneous channel tap and coefficient estimation(2024) Aygül, Mehmet Ali; Çırpan, Hakan Ali; Arslan, HüseyinWireless communication systems depend on accurate channel estimation to ensure efficient and reliable data transmission. The channel estimation process consists of two essential steps: channel tap and coefficient estimation. Physical layer features such as time arrival, and signal strengths are well used for the tap estimation. However, prior knowledge is required to use these methods. Recently, machine learning-based methods have been proposed. In particular, deep learning (DL)-based methods are promising because they can learn from raw data without much preprocessing, scale well with extensive and diverse datasets, and capture complex relationships. However, these methods overlook the relationship between the channel taps and coefficients. In this paper, we propose a DL-based multi-task learning method to estimate channel taps and coefficients simultaneously. Simulation results reveal that the performance of the proposed tap estimation method is superior to the traditional DL-based tap estimation. Furthermore, the proposed method removes the need to train two models to estimate channel taps and coefficients.Öğe Centralized and decentralized ml-enabled integrated terrestrial and non-terrestrial networks(2024) Aygül, Mehmet Ali; Türkmen, Halise; Sağlam, Mehmet İzzet; Çırpan, Hakan Ali; Arslan, HüseyinNon-terrestrial networks (NTNs) are a critical enabler of the persistent connectivity vision of sixth-generation networks, as they can service areas where terrestrial infrastructure falls short. However, the integration of these networks with the terrestrial network is laden with obstacles. The dynamic nature of NTN communication scenarios and numerous variables render conventional model-based solutions computationally costly and impractical for resource allocation and parameter optimization. Machine learning (ML)-based solutions can perform a pivotal role due to their inherent ability to uncover the hidden patterns in time-varying, multi-dimensional data with superior performance and less complexity. Centralized ML (CML) and decentralized ML (DML), named so based on the distribution of the data and computational load, are two classes of ML that are being studied as solutions for the various complications of terrestrial and non-terrestrial networks (TNTN) integration. Both have their benefits and drawbacks under different circumstances, and it is integral to choose the appropriate ML approach for each TNTN integration issue. To this end, this paper goes over the TNTN integration architectures as given in the 3GPP standard releases, proposing possible scenarios. Then, the capabilities and challenges of CML and DML are explored from the vantage point of these scenarios.Öğe Enablers for efficient wi-fi sensing(2024) Aygül, Mehmet Ali; Türkmen, Halise; Özbakış, Başak; Çırpan, Hakan Ali; Arslan, HüseyinWireless fidelity (Wi-Fi) technology gained popularity due to its ability to provide reliable connectivity, enabling high-speed communication and information sharing. However, in recent years, the focus has shifted from mere communications to sensing and awareness of the environment that can be attained using the same communication signals. Along with this line, there are wide varieties of promising sensing applications, such as crowd counting, person tracking, and sick person detection. However, different sensing applications require different performance and quality of service metrics, so it is difficult to enable all of these applications simultaneously. In this paper, we highlight the importance of the usage of flexible and adaptable Wi-Fi sensing parameters for different applications, environments, and scenarios. Afterward, we introduce our perspective for efficient Wi-Fi sensing through a framework. The first aspect of this framework is about flexible and adaptable transmission design. The second one is about identifying sensing applications according to frame design. In the last aspect of the framework, multi-access point coordination is highlighted in different scenarios of Wi-Fi sensing.Öğe Satellite(2023) Kota, Sastri; Giambene, Giovanni; Abdelsadek, Mohammed; Alouini, Mohamed Slim; Amay, Marc; Babu, Sarath; Bas, Joan; Cassara, Pietro; Chaudhari, Sachin; Dalai, Debabrata; Darwish, Tasneem; De Cola, Tomaso; Delamotte, Thomas; Dutta, Ashutosh; Dwivedi, Ayush; Enright, Michael; Giordani, Marco; Gotta, Alberto; Hammad, Eman; Khattab, Tamer; Knopp, Andreas; Karabulut Kurt, Güneş; Madoery, Pablo G.; Manoj B.S.; Me Biomo, Jean Daniel Medjo; Pillai, Prashant; Rawat, Pramud; Saxena, Paresh; Scanlan, Pat; Sharma, Avinash; Solaija, Muhammad Sohaib Jamal; Sperber, Ray; Sun, Zhili; Tarchi, Daniele; Varshney, Neeraj; Verma, Seema; Watts, Simon; Yanıkömeroğlu, Halim; Zhao, Kanglian; Zhao, LiangThe fifth generation (5G) wireless communication systems development has brought about a paradigm shift using advanced technologies; including softwarization, virtualization, massive MIMO, and ultradensification, in addition to introducing new frequency bands. However, as societal needs for any form of information grow, it is necessary to satisfy the UN's Sustainable Development Goals (SDGs). Migrations to 6G and beyond systems are envisioned to provide augmented capacity, so massive IoT, with better performance relying on optimization made possible by artificial intelligence, it is absolutely necessary. Non-Terrestrial Networks (NTNs), including satellite systems, High-Altitude Platforms (HAPs), and Unmanned Aerial Vehicles (UAVs), provide the best solutions to connect the unconnected, unserved, and underserved in remote and rural areas. Over the past few decades, Geo Synchronous Orbits (GSO) satellite systems have been deployed to support broadband services, backhauling, Disaster Recovery and Continuity of Operations (DR-COOP), and emergency services. Recently, novel non-GSO satellite systems are attracting significant interest. Within the next few years, several thousands of Low Earth Orbit (LEO) satellites and mega-LEO constellations will provide global internet services, offering user throughput comparable to terrestrial mobile or fixed access networks. This report represents the 2023 Edition of the INGR Satellite Working Group Report, following the previous three editions [1]-[3]. This edition of the INGR Satellite Working Group Report addresses NTN and 6G more in detail, adding further contributions on optical wireless communications, artificial intelligence techniques, seamless handover, security, and recent standardization efforts given the prospected unification of terrestrial and NTN components of 6G.Öğe Physical layer security using chaotic antenna arrays in point-to-point wireless communications(2024) Ranstrom, Thomas; Arslan, Hüseyin; Mumcu, GökhanChaotic antenna array (CAA)s are phased antenna arrays in which individual elements are randomized in their array position, shape, and feed line length. These randomizations generate spatially dependent large scale phase errors (with respect to antenna elements of a uniform array) that enables distinct physical layer security solutions not available to other wireless systems. Herein, a preliminary study on one such novel method, developed to combat eavesdropping is presented. In the proposed method, the CAA equipped transmitter intentionally distorts its signals based on its own array factor (AF) which includes the phase errors. This distortion significantly hampers demodulation at an eavesdropper, while a legitimate receiver that is aware of the phase errors can compensate for the added distortion.Öğe Non-cooperative high-efficiency multi-user ranging using OFDM signals(2024) Yazgan, Mehmet; Arslan, Hüseyin; Vakalis, StavrosJoint radar and communication (JRC) is attracting increasing interest due to the finite nature of the electromagnetic spectrum and the importance of spatial positioning in modern communications networks. Focusing on the challenge of utilizing the same spectrum for both communication and sensing among multiple users, we discuss the exceptional properties of waveform orthogonal frequency-division multiplexing (OFDM) for joint communications and sensing. OFDM's excellent correlation properties make it particularly suitable for this purpose. We delve into the theory of performing ranging with OFDM signals, including their cross-correlation with other signals in the same spectral bands, and clarify how multiple users can operate in an environment without being multiplexed in the frequency or time domain. Simulations are presented alongside experimental measurements from a two-user OFDM radar system operating at center frequencies of 1.5 GHz and 1.55 GHz, demonstrating simultaneous operation and the efficient use of spectral resources.Öğe CSI-based sensing with NOMA of multiple sensing users for ISAC(2023) Demir, Ayşe Betül; Memişo?lu, Ebubekir; Arslan, HüseyinAs wireless technology continues to evolve, the integration of sensing and communication layers is becoming increasingly necessary. However, this integration presents significant technical and commercial challenges. The main challenges are the issues of coexistence, scheduling, and interference which arise due to the increase in the number of signals transmitted over networks. Transmitting signals orthogonally may not be spectrally efficient, hence the need for non-orthogonal multiple access (NOMA) technology is increasing in the future wireless technology. This paper proposes the use of integrated sensing and communication (ISAC) with iterative channel estimation (ICE) to overlap sensing and communication signals, for multiple sensing users (SUs). To assess the effectiveness of this approach, we compared the bit error rate (BER), mean square error (MSE), and spectral efficiency of sending both sensing users (SUs) and communication users (CUs) using non-orthogonal and orthogonal techniques.Öğe An X-band class-B push-pull power amplifier on a 0.25 ?m SiGe-C process(Institute of Electrical and Electronics Engineers Inc., 2023) Çağdaş, Engin; Aniktar, Hüseyin; Savcı, Hüseyin Şerif; Palamutçuoğulları, OsmanThis paper presents design of an X-band power amplifier (PA) with Class-B push-pull configuration in 0.25-?m SiGe-C Heterojunction Bipolar Transistor (HBT) BiCMOS process. The PA consists of input balun, driver stage, interstage transformer, output stage and the output transformer. The cascoded structure is chosen to obtain adequate power gain. The simulations show an output power of 21.5 dBm with associated power added efficiency (PAE) of 41% at the operating frequency of 10 GHz. The simulated small signal gain is 21.5 dB with ±1 dB gain flatness from 8 to 12 GHz.Öğe Dual band (28/38 GHz) antenna design for 5G mmWave communication networks(Institute of Electrical and Electronics Engineers Inc., 2023) Sethi, Waleed Tariq; Kiani, Saad HassanThe goal of the 5G millimeter-wave (mmWave) technology is to outperform the earlier wireless technology generations in terms of data throughput, latency, and connection reliability. It has the potential to revolutionize the way information is communicated and accessed. Keeping in mind the potential benefits of mmWave technology, this study presents a planar dual-band antenna design for the prospective fifth-generation (5G) frequency spectrum. The simplicity of the proposed antenna design is achieved by utilizing a rectangular patch antenna with an optimized placement of semi-circular notches and vertical rectangular slits on the patch and the ground plane. An offset microstrip feeding technique is used to excite the antenna. Observations from the simulated and measurements suggest that the proposed antenna offers a dual-band response for the 28 and 38 GHz frequency bands. In addition, a wide impedance bandwidth of 8.9% (26.5-29 GHz) and 21% (34-42 GHz) is achieved in the operating bands. Furthermore, the peak realized gain achieved for both the central bands is approximately 6.29 dBi and 6.73 dBi, respectively.Öğe Network-independent and user-controlled RIS: An experimental perspective(IEEE Computer Society, 2023) Arslan, Emre; Kılınç, Fatih; Başar, Ertuğrul; Arslan, HüseyinThe march towards 6G is accelerating and future wireless network architectures require enhanced performance along with significant coverage especially, to combat impairments on account of the wireless channel. Reconfigurable intelligent surface (RIS) technology is a promising solution, that has recently been considered as a research topic in standards, to help manipulate the channel in favor of users' needs. Generally, in experimental RIS systems, the RIS is either connected to the transmitter (Tx) or receiver (Rx) through a physical backhaul link and it is controlled by the network and requires significant computation at the RIS for codebook (CB) designs. In this paper, we propose a practical user-controlled RIS system that is isolated from the network to enhance communication performance and provide coverage to the user based on its location and preference. Furthermore, a low-complexity algorithm is proposed to aid in CB selection for the user, which is performed through the wireless cloud to enable a passive and energy efficient RIS. Extensive experimental test-bed measurements demonstrate the enhanced performance of the proposed system while both results match and validate each other.
