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Öğe 5. Nesil ve Ötesi Teknolojiler için Çok Girişli Çok Çıkışlı Sistemler ile Spektral Verimliliğin Gerçekleştirilmesi(2018) Dikmen, Osman; Kulaç, SelmanGünümüzde, kablosuz iletişim sistemleri hem verimlilik hem de maliyet açısından büyük bir ilerleme göstermiştir. Çok Girişli Çok Çıkışlı (ÇGÇÇ) sistem 5. Nesil ve ötesi teknolojiler için gelişmiş bir sistemdir. ÇGÇÇ, 2X2, 3X3, 4X4 vb. gibi farklı binlerce antenlerle aynı anda çok yüksek veriyle iletişimin sağlanabileceği konudur. Kablosuz sistemin verimini, kapasitesini ve kapsamını iyileştirmek için kullanılan ÇGÇÇ ile 10 kata kadar spektral verimlilikte artış gözlenebilmektedir. Bu çalışmada, 5. Nesil ve ötesi teknolojilerde Çok Girişli Çok Çıkışlı sistemlerle spektral verimliliğin bit/s/Hz/Hücre bakımından literatürde elde edilen simülasyon çalışmaları hakkında bilgiler verilerek çeşitli değerlendirmeler yapılmıştır.Öğe Araç Fren Test Cihazının Döner Elemanlı Rulmanın Arıza Teşhisi için Çoğunluk Kuralına Dayalı Titreşimsel Sinyal Analizi Yöntemi(Duzce University, 2024) Kulaç, SelmanFarklı ağırlıktaki araçlar, yasal düzenlemeler gereği düzenli aralıklarla araç muayene istasyonlarında araç fren testlerine tabi tutulmaktadır. Araç fren test cihazlarının güvenliği ve etkinliği, araç muayene istasyonlarında güvenilir denetimler için önemlidir. Zamanla bu araç fren test cihazlarında mekanik arızalar oluşmaktadır. Araç fren test cihazlarında kullanılan döner elemanlı rulmanın arızalanması ise en sık karşılaşılan arızalardandır. Bu çalışmada bir araç fren test cihazında kullanılan döner elemanlı rulmanların gerçekçi titreşim ölçüm verileri kullanılarak elde edilen sinyallere dayalı olarak, medyan filtreli sinyallerin toplam enerji, ortalama, varyans, çapraz korelasyon ve korelasyon katsayısı değerleri hesaplanmıştır. Bu çalışma ile zaman içerisindeki kullanımlarla tüm yöntemlerle elde edilen değerlerin yükselerek belirlenen eşikleri aştığı doğrulanmıştır. Bu eşiklerin çoğunluk kuralına dayalı olarak önerilen birleşik aşımı, bir araç fren test cihazında kullanılan döner elemanlı rulmanın mekanik bir arızaya çok yakın olduğunu ifade etmektedir.Öğe Determination of Effective Mode Selection for Ensuring Spectrum Efficiency with Massive MIMO in IoT Systems(Mdpi, 2019) Dikmen, Osman; Kulaç, SelmanWireless Sensor Networks (WSNs) based on Internet of Things (IoT) applications are increasing day by day. These applications include healthcare, infrastructure monitoring, smart homes, wearable devices and smart cars. However, considering the fact that many different application areas will emerge in next generation wireless communication systems, efficient use of frequency spectrum is important. Because the whole frequency spectrum is now very crowded, it is important to ensure maximum spectrum efficiency for effective WSNs based on IoT. This study sought to determine which mode more effectively achieves spectrum efficiency for the performance of effective IoT systems under given conditions with respect to the length of the pilot sequence, Time Division Duplexing (TDD) or Frequency Division Duplexing (FDD). The results were obtained by Monte Carlo simulations. To the best of our knowledge, a study of effective mode selection analysis for spectrum efficiency in IoT based systems has not been available in the literature yet. The results of this study are useful for determining the appropriate design conditions for WSNs based on IoT.Öğe Determining Threshold Distance Providing Less Interference for Wireless Medical Implant Communication Systems in Coexisting Environments under Shadow Fading Conditions(2017) Kulaç, SelmanImportant interference problems will be able to be encountered especially close areas to the hospitals where wireless implantable medical systems’ communication traffic occurs heavily in near future. It is possible that these interferences could cause wireless implant devices to malfunction and harmful effects on patients. In this study, it is proposed to determine threshold distance in order to get less interference for wireless implantable medical systems under shadow fading conditions where MICS band and MetAids band users coexist intensely simultaneously. In this method, threshold power according to the [1] is pulled down by adding extra distance margin in order to minimize the interference effects to the MICS systems using confidence interval calculations. Because received signal strength just below the monitoring threshold power according to the [1] brings about much more interferences for the MICS systems even if listen-before-talk technique is applied.Öğe Effective cooperative DTV detection using the Goertzel algorithm(Tubitak Scientific & Technical Research Council Turkey, 2015) Kulaç, Selman; Sazlı, Murat HüsnüIn digital TV (DTV) detection, to monitor the DTV spectrum, only pilot tone frequency values can be observed in order to achieve calculation and energy savings. These savings can be achieved using the Goertzel algorithm. However, more than one receiver sensor is needed in order to increase the detection quality. In this technique, the Goertzel algorithm is used for energy-efficient pilot tone detection and a new effective cooperative structure is proposed. There is no extra fusion center and more than one DTV band can be monitored with this OR rule-based cooperative structure. With this new cooperative structure, reaching the desired levels of ROC curves for probability of detection and probability of false alarm with the total energy efficiency is also demonstrated with detailed simulations for all DTV multipath profiles.Öğe ENERJİ VERİMLİ İŞBİRLİKÇİ DTV SPEKTRUM ALGILAMA(Gazi Univ, Fac Engineering Architecture, 2013) Kulaç, Selman; Sazlı, Murat HüsnüGelişmekte olan bilişsel radyoda spektrum algılama kalitesinin iyi olması önem arz etmektedir. Etkin spektrum algılama yöntemlerinden birisi de pilot ton algılama yöntemidir. DTV (Sayısal TV) pilot enerji algılamada, 6 MHz’lik DTV kanalı için enerji toplamı yerine, sadece pilot sinyali frekans bölgesindeki genlik değerleri ile enerji toplamı hesaplanarak ciddi anlamda hesaplama tasarrufu sağlanması ile de enerji tasarrufu sağlanabilmektedir. Fakat bir alıcıda, 6 MHz’lik bir DTV kanalına odaklanmak yerine sadece bir pilot sinyali ile ilgilenilmesi ile direkt pilot sinyalinin derin sönümlemeye uğraması durumunda algılamanın yapılamaması olasılığı da vardır. Bu çalışmada, yenilikçi bir yaklaşımla, işbirlikçi yapı ile Goertzel algoritmasından yararlanarak ve sadece pilot sinyali dar bandında enerji algılama yapılması durumunda, tüm işbirlikçi alıcılara gelen pilot sinyalinin derin sönümlemeye uğrama olasılığının çok düşük olduğu ve spektrum algılama kalitesi yanında toplamda enerji verimliliğinin de arttığı yapılan detaylı benzetimlerle gösterilmiştir.Öğe Enerji Verimli İşbirlikçi Dtv Spektrum Algılama(2013) Kulaç, Selman; Sazlı, Murat HüsnüGelişmekte olan bilişsel radyoda spektrum algılama kalitesinin iyi olması önem arz etmektedir. Etkin spektrum algılama yöntemlerinden birisi de pilot ton algılama yöntemidir. DTV (Sayısal TV) pilot enerji algılamada, 6 MHzlik DTV kanalı için enerji toplamı yerine, sadece pilot sinyali frekans bölgesindeki genlik değerleri ile enerji toplamı hesaplanarak ciddi anlamda hesaplama tasarrufu sağlanması ile de enerji tasarrufu sağlanabilmektedir. Fakat bir alıcıda, 6 MHzlik bir DTV kanalına odaklanmak yerine sadece bir pilot sinyali ile ilgilenilmesi ile direkt pilot sinyalinin derin sönümlemeye uğraması durumunda algılamanın yapılamaması olasılığı da vardır. Bu çalışmada, yenilikçi bir yaklaşımla, işbirlikçi yapı ile Goertzel algoritmasından yararlanarak ve sadece pilot sinyali dar bandında enerji algılama yapılması durumunda, tüm işbirlikçi alıcılara gelen pilot sinyalinin derin sönümlemeye uğrama olasılığının çok düşük olduğu ve spektrum algılama kalitesi yanında toplamda enerji verimliliğinin de arttığı yapılan detaylı benzetimlerle gösterilmiştir.Öğe Evaluation of Reconfigurable Multiple and Compact Micro-Strip Antennas for MIMO Systems(2018) Aslan, Batuhan; Dikmen, Osman; Kulaç, Selman; Elbir, Ahmet M.In wireless communication systems, theimprovement of data rate and quality is a priority as a result ofusers' requests. During the improvement of these prioritysituations, there will also be a number of losses in the signals. It isknown that the techniques used in large systems to solve suchproblems are not efficient in small systems like modem. Therefore,when using a smaller system such as a modem, the recommendedtechniques will have to be different. Multimode antenna designswill be an important alternative for next generation wirelesscommunication systems especially for MIMO systems due to thephysical advantages of small antenna structures. In this study,MIMO channel structure is shown and performance analysis andtheories of compact micro-strip and reconfigurable multipleantenna designs used for the development of MIMOcommunication systems are mentioned.Öğe Exponentially-Weighted Based Dynamic Pilot Power Allocation in Massive MIMO Systems(Int Information & Engineering Technology Assoc, 2022) Pakyürek, Muhammet; Dikmen, Osman; Kulaç, SelmanIn this paper, we propose a distinctive pilot power allocation algorithm to maximize the sum rate in a multi-cell multi-user massive multiple-input multiple-output (MIMO) system. The algorithm optimizes pilot powers by polarizing the corresponding SINR values. In order to polarize SINRs, the difference between average SINR per cell and individual SINR is calculated for each user of the whole cells. The exponential form of the difference is used in the calculations of the weights for power allocation. New power values are obtained in proportion to these weights. Therefore, the power budget is utilized more efficiently thanks to these optimized power values. The efficiency of the algorithm is measured using the cumulative average SINR of the simulation system. Furthermore, equal pilot power allocation (EPPA) and water-filling pilot power allocation (WF-PPA) schemes are also implemented to compare the performances under the same simulation environments. A vast number of simulations results prove that our proposed heuristic approach is more efficient than EPPA and WF-PPA methods.Öğe External Relaying Based Security Solutions for Wireless Implantable Medical Devices : A Review(Ieee, 2018) Kulaç, Selman; Sazlı, Murat Hüsnü; İlk, H. GökhanThe use of wireless applications is increasing in health care services. One of these areas is communicating with wireless Implantable Medical Devices (IMD). For existing or already implanted IMDs, wireless communication security and privacy is very important when it is against active and passive adversaries. In this study, current proposed solutions with external relaying devices that protect the wireless communication data of IMDs are explained. The advantages and disadvantages of these solutions are emphasized comparatively.Öğe External relaying based security solutions for wireless implantable medical devices: A review(Institute of Electrical and Electronics Engineers Inc., 2018) Kulaç, Selman; Sazlı, Murat Hüsnü; İlk, H. GökhanThe use of wireless applications is increasing in health care services. One of these areas is communicating with wireless Implantable Medical Devices (IMD). For existing or already implanted IMDs, wireless communication security and privacy is very important when it is against active and passive adversaries. In this study, current proposed solutions with external relaying devices that protect the wireless communication data of IMDs are explained. The advantages and disadvantages of these solutions are emphasized comparatively. © 2018 IFIP.Öğe ID Identification by Using Face Detection and Recognition Systems(Ieee, 2014) Holat, Recep; Kulaç, SelmanIn recent years, significant achievements have been achieved in the field of face recognition. Face recognition are special pattern recognition which are used in banking for identity approving and the entrance of controlled areas, the places where the security control impending to airports, to control machines,to follow-up of persons. In this study, face recognition applications on the Yale face databases have been performed by using PCA (Principal Component Analysis), LDA (Linear Discriminant Analysis), LBP (Local Binary Patterns). Database consist of right-light, center-light, left-right, no glasses, glasses, normal, wink, sleepy, surprised, happy, sad images. In the face recognition pre-processing steps, HE (Histogram Equalization), HE+ Median Filter, HE+Gaussian filter, He+Laplace Filter was used. It is provided to select the appropriate method from the system depending on state of image. Thus the system recognition rate increases of up to 6% was observed. Application was developed by using Microsoft Visual Studio 2010 C #. EMGU CV library for image processing algorithms and SQL Server 2008 Express for database processing were usedÖğe Joint Placement and Device Association of UAV Base Stations in IoT Networks(Mdpi, 2019) Ahmed, Ashfaq; Awais, Muhammad; Akram, Tallha; Kulaç, Selman; Alhussein, Musaed; Aurangzeb, KhursheedDrone base stations (DBSs) have received significant research interest in recent years. They provide a flexible and cost-effective solution to improve the coverage, connectivity, quality of service (QoS), and energy efficiency of large-area Internet of Things (IoT) networks. However, as DBSs are costly and power-limited devices, they require an efficient scheme for their deployment in practical networks. This work proposes a realistic mathematical model for the joint optimization problem of DBS placement and IoT users' assignment in a massive IoT network scenario. The optimization goal is to maximize the connectivity of IoT users by utilizing the minimum number of DBS, while satisfying practical network constraints. Such an optimization problem is NP-hard, and the optimal solution has a complexity exponential to the number of DBSs and IoT users in the network. Furthermore, this work also proposes a linearization scheme and a low-complexity heuristic to solve the problem in polynomial time. The simulations are performed for a number of network scenarios, and demonstrate that the proposed heuristic is numerically accurate and performs close to the optimal solution.Öğe Medikal İmplant Haberleşme Sistemleri için Bandgenişliği Verimli Örtüşmeli FSK Kodlamalı Güvenli Komut iletimi(2018) Kulaç, SelmanGünümüzde kablosuz iletişim çoğu sağlık sisteminde yer almaktadır. Implante edilebilenmedikal sistemler de kablosuz iletişim yeteneğine sahiptirler. Fakat bu sistemlerde kablosuziletişimin güvenli olması hem hasta hakları hem de hasta sağlığı açısından çok önemlidir. Bunedenle kablosuz implante edilebilen medikal sistemlerinin iletimlerinin güvenli olması, aktifve pasif saldırganlara karşı korunması gerekir. Bu çalışmada, özel bir örtüşmeli ve kodlamalıfrekans kaydırmalı anahtarlama tekniği geliştirilmiş ve bu teknikle komut iletimindekarmaşıklığı düşük güvenlik sağlanmıştır. Önerilen yöntem karmaşıklığı düşük ve güvenlikyanında band genişliği verimliliği de sağladığından kablosuz implante edilebilen medikalsistemler için uygun durmaktadır.Öğe A New Externally Worn Proxy-Based Protector for Non-Secure Wireless Implantable Medical Devices: Security Jacket(Ieee-Inst Electrical Electronics Engineers Inc, 2019) Kulaç, SelmanWireless transmission systems of implantable medical devices (IMDs) should be secure against eavesdroppers and adversaries because of patient rights and health. This paper focuses on full-duplex secure communication of wireless IMD systems, proposing a new protector that is compatible with existing unsecure systems. This new protector is an externally worn jacket and therefore called a security jacket. Because some advanced sensors are placed on the jacket to provide physical layer security. Randomly multi-jamming with a great number of sensors is applied when IMD transmission occurs with the jamming extraction and maximum ratio combining (MRC) reception simultaneously. When reception by IMD is performed, a randomized spoofing-based transmit beamforming technique is applied. This protector also supports higher power efficiency and longer battery life.Öğe A New Method in Pilot Reuse Factor Selection in Spectrum Efficient Massive MIMO Systems(Kaunas Univ Technology, 2019) Dikmen, Osman; Kulaç, SelmanSpectrum efficiency studies of Massive MIMO systems have continued and still have not been fully explored in the literature. Therefore, the spectrum efficiency definition of a particular user in a cell in a Massive MIMO network is expressed in this paper. In addition, the uplink spectrum efficiency expressions for the Rayleigh fading are included. The Monte Carlo simulations are performed to verify these expressions. Due to the expectation of reaching to a thousand antennas together with the millimetre wave structure in the next years, in this study, it is contributed to the literature by explaining how to select the pilot reuse factor. The realization of this contribution is based on Zero Forcing (ZF) and Maximum Ratio Combining (MRC) schemes. The results of this study are useful for optimal design conditions, such as the number of antennas on the base station and pilot reuse factor selection for the next generation networks in order to obtain spectrum efficiency in Massive MIMO systems.Öğe A novel pilot power allocation method based on energy efficiency maximization in massive MIMO systems for future generation wireless technologies(Wiley, 2023) Dikmen, Osman; Pakyürek, Muhammet; Kulaç, SelmanIn this paper, we propose a novel pilot power allocation method that focuses on the maximization of the energy efficiency. The core algorithm of this method, which is a dynamic approach that takes into account signal-to-interference-plus-noise ratio (SINR), is called pilot power allocation polarizing SINRs (PS-PPA). The aim is to maximize the energy efficiency of the system along with the proposed pilot power allocation method using this algorithm in a multi-cell multi-user massive multiple-input multiple-output (MIMO) system. The algorithm determines difference between average SINR per cell and SINRs of users individually, during the scan of the whole cells sequentially. Therefore, it always updates the allocation for the latest SINR of users in power updates to improve the energy efficiency of the system. In power updates, PS-PPA calculates weights using an exponential function of the SINR difference. This weighting function is defined for each real number, so it can always result in a specific number. In addition, the weighting function is performed in the [ rho min,rho max$$ {\rho}_{min},{\rho}_{max} $$] range where the power values are predefined. The energy efficiency of the system is measured in a number of simulations by calculating the average SINR per cell. Furthermore, all these performance results are obtained for equal pilot power allocation (EPPA) and water-filling pilot power allocation (WF-PPA) schemes. As a result of simulation results, proposed pilot power allocation method has proven to be more superior than EPPA and WF-PPA methods.Öğe Reliable Listen-Before-Talk Mechanism for Medical Implant Communication Systems(Ieee, 2016) Kulaç, Selman; Arslan, HüseyinHealth care applications of wireless communication have been finding places dramatically. One of these applications is communication of implantable medical devices (IMD)s. It is expected that the number of IMDs will increase greatly in the near future. As a result, significant congestion will be experienced in medical implant communication service (MICS) band, leading to interference problems. In this study, we propose reliable listen-before-talk (LBT) mechanism at low signal-to-noise ratios (SNR) s for medical implant communication systems in order to mitigate the interference effects. In our method, we have just brought out power difference between mean peak and mean lowest power spectral values and it provides reliable and simple monitoring of MICS channels' occupation fastly. Our proposed method has superior performance when threshold power level is considered according to the federal communication commission (FCC) Part 95 regulatory standard.Öğe Secure Transmission of Commands Using Multicarrier Structure for Wireless Implantable Medical Devices(Ieee, 2016) Kulaç, Selman; Yılmaz, Mustafa Harun; Arslan, HüseyinWireless communication has growing interests in health care domain, especially in implantable medical devices (IMD). Because of the open nature of the wireless signals, providing a secure communication between IMD and physician device becomes a significant concern. In this study, we propose a security mechanism against eavesdroppers to protect the data sent by a physician. The importance of keeping these data in safe stems from the fact that the data consists of commands and remote control information which are vital for the patients. In the proposed method, secure transmission of command data by embedding and hiding data in multicarrier structure and less complex reception for IMD with customized frequency dehopping technique is employed. As indicated in performance evaluations, even with super computers, an eavesdropper can not decode the protected data in tremendous amount of time (years).Öğe Security Belt for Wireless Implantable Medical Devices(Springer, 2017) Kulaç, SelmanIn this study, a new protective design compatible with existing non-secure systems was proposed, since it is focused on the secure communication of wireless IMD systems in all transmissions. This new protector is an external wearable device and appears to be a belt fitted around for the patients IMD implanted. However, in order to provide effective full duplex transmissions and physical layer security, some sophisticated transceiver antennas have been placed on the belt. In this approach, beam-focused multi-antennas in optimal positions on the belt are randomly switched when transmissions to the IMD are performed and multi-jammer switching with MRC combining or majority-rule based receiving techniques are applied when transmissions from the IMD are carried out. This approach can also reduce the power consumption of the IMDs and contribute to the prolongation of the IMD's battery life.
