Yazar "Akkaş, Mustafa Alper" seçeneğine göre listele

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    6G'de Nesnelerin İnterneti Teknolojisinin Medikal Alandaki Gelişmeleri
    (2024) Sak, Semih; Akkaş, Mustafa Alper
    Günümüzde internet ortamında metne dayalı veri çok hızlı bir şekilde artış göstermektedir ve bu büyük veri içinden istenilen bilgiyi barındıran doğru içeriklere ulaşabilmek önemli bir ihtiyaçtır. İçeriklere ait anahtar sözcüklerin bilinmesi bu ihtiyacı karşılamada olumlu bir etki sağlayabilmektedir. Bu çalışmada, doğal dil işleme ve derin öğrenme modelleri ile Türkçe metinleri temsil eden anahtar sözcüklerin belirlenmesi amaçlanmıştır. Veri kümesi olarak Türkçe Etiketli Metin Derlemi ve Metin Özetleme-Anahtar Kelime Çıkarma Veri Kümesi birlikte kullanılmıştır. Derin öğrenme modeli olarak çalışmada iki farklı model ortaya konmuştur. İlk olarak Uzun Ömürlü Kısa Dönem Belleği ( LSTM) katmanlı bir Diziden Diziye (Seq2Seq) model tasarlanmıştır. Diğer model ise BERT (Transformatörler ile İki Yönlü Kodlayıcı Temsilleri) ile oluşturulmuş Seq2Seq bir modeldir. LSTM katmanlı Seq2seq modelin başarı değerlendirmesinde ROUGE-1 ölçütünde 0,38 F-1 değerine ulaşılmıştır. BERT tabanlı Seq2Seq modelde ROUGE-1 ölçütünde 0,399 F-1 değeri elde edilmiştir. Sonuç olarak dönüştürücü mimarisini temel alan BERT tabanlı Seq2Seq modelin, LSTM tabanlı Seq2seq modele görece daha başarılı olduğu gözlemlenmiştir.
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    Characterization of terahertz band transmittance from sea-level to drone altitudes
    (Institute of Electrical and Electronics Engineers Inc., 2021) Saeed, Akhtar; Saleem, Ammar; Gürbüz, Özgür; Akkaş, Mustafa Alper
    Terahertz (THz) communications has been recognized as a candidate technology for the next generation networks as the THz band offers large bandwidth and data rates, catering for the problem of spectrum scarcity. However, THz band propagation is highly affected by atmospheric absorption due to water vapor molecules, in addition to the high spread loss. Modeling of the absorption loss is essential for a realistic closed form THz path loss model, which can be employed in link level analysis and formulations. For this purpose, in this paper, we characterize the THz transmittance i.e., absorption gain using the data obtained from Line-by-Line Radiative Transfer Model (LBLRTM) tool, considering the available frequency channels selected via water-filling, altitudes from sea-level to drone altitudes and various transmission ranges. We analyze the modeling of transmittance as a function of: (1) Frequency, (2) Distance and (3) Altitude, using different statistical models including, Polynomial, Exponential and Gaussian models. Numerical results depict that modeling transmittance as a function of distance and altitude are feasible approaches using the exponential and the polynomial models, respectively. This work can be extended to characterize the transmittance for all frequencies over the entire THz band, and also for higher altitudes and longer ranges. © 2021 IEEE.
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    Detailed analysis of water vapor with all isotopologues, air gas mixtures and air molecules at terahertz range
    (Springer, 2020) Akkaş, Mustafa Alper
    The scarcity of radio spectrum led regulators to consider new frequency bands including Terahertz frequencies between 0.275 and 1 THz, which is previously reserved only for passive services such as satellite telemetry and radio astronomy. One of the major advantages of Terahertz bands is the available bandwidth. For example, future generation cellular networks would be able support extreme throughputs via Terahertz backhaul links. But the medium that the electromagnetic waves propagate need to be analyzed by this way theoretical results will turn to practical and commercially attractive results. This work will give the channel characteristics of detailed analyzes of CO2, H2O, O-2, USA model (high latitude, winter)-USA model (tropics) between 0.275 and 10 THz range. The developed model in this paper evaluates the total absorption loss, path loss, SNR and capacity properties. The water vapor-H2O (which is the biggest enemy of high frequencies) with all isotopes is analyzed in this paper. This paper also presents the theoretical estimations of absorption properties of CO2, H2O, O-2, USA model (high latitude, winter)-USA model (tropics) at the THz frequency band from 0.275 to 10 THz.
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    Enhancing performance of M2M random access in 3GPP LTE networks
    (Ieee, 2017) Balcı, Abdullah; Sokullu, Radosveta; Akkaş, Mustafa Alper
    The proliferation of smart devices that can autonomously connect and exchange information over the internet has given rise to a new dynamic area of research, Machine-to-Machine (M2M) communications. M2M refers to networks, which connect devices together and enable them to make smart decisions based on the generated and/or transferred data. The most viable option of implementing M2M communications is over cellular networks. These networks are designed for Human-to-Human (H2H) communication, which is characterized by smaller number of connection requests and longer connection times as compared to the thousands of M2M that will try to connect simultaneously to transmit only a minimum amount of data. When such enormous number of devices is introduced, the existing network will be exposed to high collision rate and extreme connection delays. In LTE, the uplink resources for random access (RA) procedure will be insufficient, and the number of successfully connected devices will bottom out. 3GPP has proposed some solutions to overcome the congestion during the random access procedure. Access Class Barring (ACB) is the most efficient method which increases the access success rate, but it has a disadvantage in terms of access delay. In this paper, we propose to control the ACB parameters adaptively in order to maximize the use of RA resources. Different from other existing methods, our method is based on predicting the number of accessing devices at the beginning of each RA slot and then adjusting the ACB parameters accordingly. Our results show that, the proposed scheme improves delay up to nearly 70% and converges to optimal throughput.
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    An evaluation of internet of nano-things simulators
    (Institute of Electrical and Electronics Engineers Inc., 2021) Şahin, Emre; Dağdeviren, Orhan; Akkaş, Mustafa Alper
    Nowadays, distributed systems consisting of a large number of simple devices are used to perform complex operations rather than advanced devices alone. Particularly, networked systems of nanoscale devices are called Internet of Nano-Things (IoNT). This new field has emerged with new problems to be solved where simulation of nanonetworks is one of these problems. In this study, Electromagnetic (EM) communication-based nanonetwork simulators used in IoNT applications are examined in detail to determine the advantages and their drawbacks. Different than the related studies, our contribution is a detailed and up-to-date roadmap for simulator selection for researchers working in different layers of nanonetwork applications such as channel modeling, antenna design, modulation methods, medium access control (MAC) protocols, and routing algorithms. © 2021 IEEE
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    Investigation of environmental effects in terahertz band vehicular communication
    (Institute of Electrical and Electronics Engineers Inc., 2022) Körpe, Enis; Akkaş, Mustafa Alper; Sokullu, Radosveta
    Terahertz (THz) waves are electromagnetic waves that vary in the range of 0.1-10 THz in the electromagnetic spectrum. It is a band gap that is underexplored and open to new research topics. Filling the gap between radio and optical frequency ranges, THz technology is a promising technology for next-generation wireless networks. It causes less damage to tissues than X-rays. When it comes to vehicular communication, the technologies used for vehicular communication today have begun to be insufficient in the rapidly increasing data traffic. New technologies are needed to support less latency, higher reliability, and more users. THz technology is considered to be a candidate technology that can meet these specifications. In this paper, the effects of environmental factors such as reflection, scattering and absorption on the transmission in different specific THz vehicular communication scenarios are investigated. The opportunities and drawbacks brought by the THz band for vehicular communication are also introduced. © 2022 IEEE.
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    An IoT-based greenhouse monitoring system with Micaz motes
    (Elsevier Science Bv, 2017) Akkaş, Mustafa Alper; Sokullu, Radosveta
    The wireless sensor network (WSN) is one of the most significant technologies in the 21st century and they are very suitable for distributed data collecting and monitoring in tough environments such as greenhouses. The other most significant technologies in the 21(st) century is the Internet of Things (IoT) which has rapidly developed covering hundreds of applications in the civil, health, military and agriculture areas. In modern greenhouses, several measurement points are required to trace down the local climate parameters in different parts of a large scale greenhouse in order to ensure proper operation of the greenhouse automation system. Cabling would make the measurement system expensive, vulnerable and also difficult to relocate once installed. This paper presents a WSN prototype consisting of MicaZ nodes which are used to measure greenhouses temperature, light, pressure and humidity. Measurement data have been shared with the help of IoT. With this system farmers can control their greenhouse from their mobile phones or computers which have internet connection. (c) 2017 The Authors. Published by Elsevier B.V.
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    LNG ortamında çalışan telsiz duyarga ağları için gigahertz kanal modellenmesi
    (2017) Akkaş, Mustafa Alper
    LNG (Sıvılaştırılmış Doğal Gaz) doğal gazın -162 ºC'de soğutulması ile oluşturulan temiz, renksiz ve zehirsiz bir sıvıdır. Bu soğutma işlemi sayesinde doğal gazın hacmi 600 kat daha küçültülerek, LNG'nin depolanmasını ve taşınmasını kolaylaştırmaktadır. LNG' nin özgül ağırlığı basınç, sıcaklık ve karışıma göre değişir ve ortalama 1,0 kg/litre su ile mukayese edildiğinde, 0,46 kg/litre'ye eşittir. LNG'nin özgül ağırlığının düşük olması elektromanyetik dalgaların yayılımı ve TDA (Telsiz Duyarga Ağları)'nın haberleşebilmesi için bir avantajdır. Ayrıca bu çalışmada TDA'lar için LNG yol kaybı, yansıma etkisi ve BHO (Bit Hata Oranı)'a ya göre LNG ortamı analiz edilip, modellenmiştir. Yayılım karakteristikleri teorik yaklaşım ile incelenmiştir. Teorik analizler ve simülasyon sonuçları 10 GHz - 13 GHz bant aralığında, 10 metre civarı bir kablosuz haberleşme olacağını ispatlamaktadır.
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    Nano iletişim teknolojilerinin biyomedikale katkısı
    (2018) Akkaş, Mustafa Alper
    Nano teknoloji biyomedikal alanında birçok yeni çözümler vaat etmektedir. Nano ölçek de, bir nano makinede en temel fonksiyonları yerine getirebilen bir birimdir. Nano makinalar arası iletişim, dağıtılmış şekilde nano makinelerin daha karmaşık fonksiyonlarını yerine getirmesine izin verir. Bio-Nano nesnelerin interneti ise, geliştirmek için yeni zorlukların beklediği, verilerin güvenli bir şekilde değiştirilip, işlenip ve biyokimyasal alan içerisinde iletişim kurabileceği aynı zamanda internet ara yüzüne verilerin ulaştırılabileceği bir paradigma-kayması konseptidir. Bu makalede ileri teknoloji ürünleri olan Moleküler Haberleşme ve Bio-Nano Nesnelerin İnterneti, nano makineler arasındaki nano haberleşme temel alınarak anlatılmaktadır.
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    Nano sensörlerin farklı gaz ortamlarında geçiş pencerelerinin hesaplanması
    (2018) Akkaş, Mustafa Alper
    Nano ve Terahertz terimlerini her geçen gün daha çok duymaktayız. Nano teknolojisi adından da anlaşılacağı gibi nano boyutta materyal yapımı ve tasarlanmasını inceler. Nano teknolojisi birçok sektörde devrim niteliğinde değişiklikler meydana getirmiştir. Bunlardan bir tanesi ise nano boyutta sensörlerin tasarlanıp kullanılmasıdır. Nano sensörlerin tasarlanması ve kullanılabilmesinde bazı noktalara dikkat edilmesi gerekmektedir. Nano ölçekli makineler boyutları itibariyle nano boyutlu antenlere ihtiyaç duyar, bu nedenledir ki nano boyutlu antenler Terahertz frekanslarında çalışır. Terahertz frekansları ortamı oluşturan atomların titreşimlerinden etkilenir. Terahertz frekansları titreşimlerin olduğu bölgelerden geçmekte zorlanır bunun için elektromanyetik dalgaların rahat geçebileceği geçiş pencereleri bulunmalıdır. Bu yüzden bu çalışmada farklı gazların geçiş pencerelerinin nasıl bulunduğunu anlatılacaktır.
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    Nano-sensor modelling for intra-body nano-networks
    (Springer, 2021) Akkaş, Mustafa Alper
    In this work, the author has evaluated the propagation of electromagnetic waves inside the human tissue such as blood, skin and fat for single-path and multi-path layers according to nano sensor transmit power calculations. In particular, the propagation characteristics of the Intra-Body Nano-Network communication channel are calculated using a theoretical approach. The analysis in this paper provides an evaluation related to the path loss, bit error rate, signal to noise ratio and the channel capacity. The model is evaluated for each single-path effect and multi-path effect. The effects of human tissue for each blood, skin and fat for single-path effect and multi-path are included in the analysis. The model frequency range is chosen from 0.01 to 1.5 THz frequencies, which are ideal for designing nano sensors antennae and using THz range for communication. This paper will also guide other researchers who are working on the electromagnetic radiation performance of Intra-Body Nano-Network and Nano sensors designed at the THz range.
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    Nanonetwork-based search and rescue operations in debris areas
    (Elsevier, 2023) Şahin, Emre; Akkaş, Mustafa Alper; Dagdeviren, Orhan
    Earthquake is one of the most destructive natural disasters. It is vital to carry out search and rescue (SAR) operations in the debris area after such a major disaster. Although there are various technologies to rescue living things in the debris area, reaching narrow gaps in the rubble is a very difficult process. Nanonetworks operating on terahertz (THz) communication channels are composed of thousands of nanodevices that can pass through even ultrasmall gaps. In this paper, we propose an application that utilizes nanodevices for SAR operations in debris areas. To the best of our knowledge, our paper is the first study to provide a detailed and specialized analysis of this application. We work on channel models by extensively analyzing transmittance, propagation loss, absorption loss, path loss, signal-to-noise ratio (SNR), and capacity. Besides, we investigate a physical layer (PHY) model by considering the effects of using directional or omnidirectional antennas to ensure optimal throughput and energy consumption. Moreover, we present an exhaustive performance analysis of the modulation technique with respect to various nanodevice counts and densities.
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    NUMERICAL ANALYSIS OF THE ALVEOLAR SPACES AND HUMAN TISSUES FOR NANOSCALE BODY-CENTRIC WIRELESS NETWORKS
    (2019) Akkaş, Mustafa Alper
    This paper investigates the propagation of Terahertz (THz) electromagnetic waves inside thehuman body and discusses a model of the system performance of Nanoscale Body-Centric WirelessNetworks inside the alveolar spaces and human tissues. THz band wireless communication enables newapplications especially in nanoscale wireless communication. The model developed in this papercalculates the total absorption loss, path loss and capacity properties of EM waves propagating throughthe Alveolar Spaces and Human Tissues in nanoscale environment for THz band wirelesscommunication. Based on the modeling of noise level and path losses, the channel capacity is calculated.The results show that Wireless Nanosensor Networks (WNSNs) can communicate through the humanbody. According to the numerical analysis of the model several transmission windows which are ?1 =[0.01 THz – 0.5 THz], ?2 = [0.58 THz – 0.74 THz] and ?3 = [0.77 THz – 0.96 THz] have been foundfor Nanoscale Body-Centric Wireless Networks. The longest and lowest transmission window which is inthe range of 0.01 THz – 0.5 THz values have been analyzed for blood, plasma, RCBs and water to designuniversal nanonode for Nanoscale Body-Centric Wireless Networks at gases in lungs and blood.
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    Path loss analysis for terahertz band single-lane vehicular communication
    (Institute of Electrical and Electronics Engineers Inc., 2023) Körpe, Enis; Akkaş, Mustafa Alper; Sokullu, Radosveta
    The Terahertz (THz) band lies between the millimeter wave and the far infrared band (0.1-10 THz) and has an important potential for 5G and 6G communication systems. It is a band gap open to future research as it has not been sufficiently explored. The THz band promises an ultra-high data rate and capacity. Considering vehicular communications, the rapidly increasing data traffic is excessive for current vehicular communication technologies to handle. New technologies and approaches are thus needed to deliver higher capacity and data rates with lower latency. Therefore, it is acknowledged that THz technology is a promising technology that can meet these requirements. In this study, the propagation of the THz signal in single-lane vehicular communication was examined. Respective path loss analyses were performed using the High-Resolution Transmission Molecular Absorption Database (HITRAN). The obtained results were compared with the measurement results in the existing studies. The effect of reflections on the path loss results of the system was also investigated. © 2023 IEEE.
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    Study of absorption-defined transmission windows in the terahertz band
    (Elsevier Science Bv, 2018) Akkaş, Mustafa Alper
    Communications over the terahertz (THz) frequency band will feature a number of attractive properties, including miniature transceivers, terabit-per-second link capacities and high energy efficiency. Meanwhile, a number of specific research challenges have to be addressed to convert the theoretical estimations into commercially attractive and practical solutions. This paper presents the theoretical estimations of absorption properties of the THz frequency band from 0.3 THz to 3 THz which is chartered to explore by IEEE 802.15 THz Interest Group. The frequency band is called "no man's land" because the range is too high for RF (radio frequency) but it is also too low being considered of light. (C) 2018 Elsevier B.V. All rights reserved.
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    Terahertz band channel properties according to transmit power estimation
    (Springer, 2020) Akkaş, Mustafa Alper
    Over the last decade, short-range communications in the THz (Terahertz) band have been extensively studied as a technology-enabler for dense and ultra-dense wireless networks. The increasing demand for high data rates for wireless communication systems will inevitably lead to the extension of operation frequencies with larger bandwidths. THz range enables bandwidths on the order or hundreds of GHz. Thus, THz Band communication will alleviate the capacity limitations and spectrum scarcity of current wireless systems, and enable new classical networks and novel nanoscale networks applications. The main aim of this paper is to provide design guidelines for close proximity links with transmission capacity beyond 100 Gbit/s. We present the path loss, absorption loss, signal to noise ratio (SNR) and capacity of propagating electromagnetic waves at THz Band in different air medium types. The channel capacity and SNR properties are calculated according to transmit power estimation. In this paper, five air medium types are investigated which are average latitude-summer, high latitude-summer, average latitude-winter, high latitude-winter and tropics.
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    TeraHertz channel model for search and rescue nanonetwork applications in debris areas
    (Institute of Electrical and Electronics Engineers Inc., 2021) Şahin, Emre; Dağdeviren, Orhan; Akkaş, Mustafa Alper
    Disasters such as earthquakes cause thousands of deaths every year. Since it is not possible to predict such disasters, research has generally focused on search and rescue operations in the debris area after these disasters. Due to the structures of the debris areas, where there are very tiny gaps between the wracks, the use of large-scale advanced devices is very limited in these operations. On the other hand, nanodevices that can easily pass through these gaps and scatter into the debris area can be used to gather information from under the wreckage. The computing complexities and transmission ranges of nanodevices differ according to their size and the amount of energy they have. In this study, TeraHertz (THz) channel models in debris areas of different densities were investigated for different types of nanodevices. Our contribution is a detailed analysis of channel properties using 0.1-0.35 THz for debris areas in terms of transmittance, absorption loss and path loss. Moreover, a novel research topic is suggested for nanonetwork applications generally associated with biomedical and agricultural studies. © 2021 IEEE.
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    Terahertz communications at various atmospheric altitudes
    (Elsevier, 2020) Saeed, Akhtar; Gürbüz, Özgür; Akkaş, Mustafa Alper
    Terahertz communications offers a massive potential for the prospective beyond 5G wireless systems, as the band offers huge bandwidth and data rates as compared to the existing sub 6 GHz bands, which are almost saturated. In this paper, we investigate the feasibility of wireless communications over the Terahertz-band (0.75–10 THz) at various atmospheric altitudes, considering different transmission distances and directions by realistically calculating the absorption loss, which is the major limiting factor affecting the propagation of THz waves through the earth’s atmosphere. Four practical altitudes are considered, corresponding to Drone-to-Drone (D2D), Jet plane-to-Jet plane (J2J), Unmanned Aerial Vehicle (UAV)-to-UAV, and near-space Satellite-to-Satellite (S2S) communications. Following comparison and validation with two real-world experimental results from the literature measured at the sea-level, Line by Line Radiative Transfer Models (LBLRTM) is used to obtain realistic THz-band transmittance values against each altitude case and setting. Subsequently, absorption loss and total path loss values are computed and mean total path loss sensitivity is further observed against a range of transmission directions via zenith angle variations from vertically-up to vertically-down communication. Numerical results show that as the altitude increases, the concentration of the water vapor molecules decreases, enabling the communication over the THz-band (0.75–10 THz) to be more feasible as compared to the sea-level communication. Moreover, the total usable bandwidth results over the THz-band (0.75–10 THz) exhibit that the upper bounds of 8.218 THz, 9.142 THz and 9.25 THz are usable up to the transmission distance of 2 km against the total antenna gains of 80 dBi for J2J, U2U and S2S communication cases, respectively.
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    Terahertz Teknolojisi Uygulamaları ve Terahertz Dalgalarının Kablosuz Haberleşme için Elektromanyetik Modellemesi
    (2018) Akkaş, Mustafa Alper
    Bu araştırmada 0.1 ile 10 THz aralığında mikrodalga ve kızılötesi arasında uzanan, elektromanyetik spektrumda çıplak gözle görülemeyen Terahertz (THz) frekanslarının farklı ortamlarda nasıl davrandığı incelenmiştir. Makalenin birinci ve ikinci bölümünde, yüksek hızda kablosuz iletişim için, artan talebi karşılamaya yönelik önemli bir teknoloji olarak öngörülmekte olan Terahertz teknolojisi ve uygulamaları hakkında bilgi verilmiştir. Bu araştırma aynı zamanda hava ve doğal gaz ortamları için hesaplanmış kanal modellenmesi sonucu ortaya çıkan yol kaybı ve emilim kaybı hesaplamalarını göstermektedir. Teorik analiz ve benzetim sonuçları, hava ve doğalgazın THz Bant kısa menzilli kablosuz iletişim kurabileceğini göstermiş ve bu alanda birçok önemli yönlerini vurgulamıştır. Son olarak hava ve doğal gaz ortamı için en ideal performansı sağlayan geçiş pencereleri elde edilmiş ve bu bu geçiş pencereleri makaledeki grafiklerde gösterilmiştir.
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    Terahertz wireless data communication
    (Springer, 2019) Akkaş, Mustafa Alper
    In recent years Terahertz (THz) Band communications have gained even greater interest and higher expectations to meet an ever increasing demand for the speed of wireless communications. This paper provides the characteristics of electromagnetic waves propagating in the THz Band, which is one of the key technology to satisfy the increasing demand for Terahertz Wireless Data Communication (ThWDC). The performance of future terabit super channels implemented using bipolar phase-shift-keying which gives the best BER (Bit Error Rate) with today's technology is investigated through the simulations for ThWDC. The objective of this paper is to describe the important issues related to the transmission in of ThWDC in air environment and to determine the best transmission windows in the THz range. In particular, ThWDC channel is modeled considering effects like capacity, channel performance and BER is investigated through simulation. The simulation results and the theoretical analysis show that data communication is possible from 0.01 to 0.5 THz frequency range and the best transmission window in this range have been found omega(1) = [0.01-0.05 THz], omega(2) = [0.06-0.16 THz] and omega(3) = [0.2-0.3 THz] in this paper.