Adnan Kavak
Kocaeli Universty, Computer Engineering, Faculty Member
Emerging 5G and beyond networks have been proposed to provide communication of anywhere, anytime, and any type for massive machine type objects and Internet of Things (IoT) that can be broadly called as Internet of Everything (IoE). With... more
Emerging 5G and beyond networks have been proposed to provide communication of anywhere, anytime, and any type for massive machine type objects and Internet of Things (IoT) that can be broadly called as Internet of Everything (IoE). With such next generation networks, creating, processing, storing, and sharing of large amount of data will take place at everywhere in every time. The problem is how to manage this life cycle of data, its critical timing and data traffic accurately and efficiently. This paper discusses issues and challenges with Cloud gateways with a focus on Cloud Based IoE Globe architecture for next generation networks, thorough which a large amount of data is assumed to be carried in the network. Cloud gateway that forms the middleware layer in IoE architecture is one of the most effective solutions for the issues identified in this paper. Cloud Gateway Engines are the cornerstone of its architecture. This paper also proposes an architecture for connectivity engines in IoE, which is called as Topologically Connected Gateway Engine (TCGE) architecture. Requirements and functionalities of proposed TCGE architecture are discussed.
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Cooperative diversity is one of the most promising techniques for next-generation wireless networks for accomplishing high signal quality even in the degrading fading environment. Various cooperative techniques can be employed to achieve... more
Cooperative diversity is one of the most promising techniques for next-generation wireless networks for accomplishing high signal quality even in the degrading fading environment. Various cooperative techniques can be employed to achieve desired performance according to given scenarios. This study evaluates the performance of two different cooperative relay networks, i.e., a cooperative network and multi dual-hop network, in which non-regenerative relaying protocol is assumed to work at relay nodes. A moment generation function (MGF) based performance analysis is carried out for both cases of a relay network. The analytical and simulation results with regard to the varying number of relay nodes are presented. The results show that cooperative network is robust to multi dual-hop cooperative network.
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Özet-Hızla gelişen teknoloji hayatımıza büyük kolaylıklar getirmektedir. Bunlardan bir tanesi de akıllı telefonlardır. Akıllı telefonlar her geçen gün hayatımıza daha fazla dahil olmaktadır ve akıllı telefonlara olan ihtiyaç artmaktadır.... more
Özet-Hızla gelişen teknoloji hayatımıza büyük kolaylıklar getirmektedir. Bunlardan bir tanesi de akıllı telefonlardır. Akıllı telefonlar her geçen gün hayatımıza daha fazla dahil olmaktadır ve akıllı telefonlara olan ihtiyaç artmaktadır. Yapılan çalışmada akıllı telefonlar ve Beacon teknolojisi kullanılarak belirli mesafeler içerisindeki eşyaların yerinin tespit edilmesini sağlayacak bir uygulama geliştirilmiştir. Geliştirilen uygulama ile insanların hayatlarını kolaylaştıracak ve aynı zamanda zaman kaybını azaltacak teknolojik bir çözüm sunulmuştur. Uygulamanın etkinliği hem kapalı hem de açık ortamlarda test edilmiştir ve her iki ortamda da doğru sonuçlar ürettiği gözlemlenmiştir. Anahtar Kelimeler-Bluetooth 4.0, Beacon, Android, Konum Tespiti Abstract-Rapid developments in technology bring significant benefits to our life. One of them is smartphones. Smartphones are involved to our life more than before and need of them increases day by day. In this paper, an application that wil...
In wireless communications, smart antenna systems employing an antenna array at the base station along with advanced space-time signal processing capabilities can increase capacity, extend range and mitigate interference. We study the... more
In wireless communications, smart antenna systems employing an antenna array at the base station along with advanced space-time signal processing capabilities can increase capacity, extend range and mitigate interference. We study the transmit diversity configuration at the mobile, which may possibly be used to alleviate the fast fading effect on the received signal vector at the smart antenna base station.
Research Interests: Smart Antenna, Signal Processing, Antenna arrays, Fading, Space Time, and 12 moreUrban Environment, Real Time, Space-Time Adaptive Processing (STAP), Interference, Capacity, Smart Antennas, Antenna Array, Time Division Multiplexing, Wireless Communication, Base station, Fading channels, and Downlink
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Cdma2000 is a third generation wireless communications technology that provides seamless evolution from voice to high speed data and video through 3Glx, IxEV-DO, and IxEV-DV path. Integrating both voice and data services, IxEV-DV supports... more
Cdma2000 is a third generation wireless communications technology that provides seamless evolution from voice to high speed data and video through 3Glx, IxEV-DO, and IxEV-DV path. Integrating both voice and data services, IxEV-DV supports packet data rates up to 3 Mbps. However, simultaneous operation of 3Glx and IxEV-DV calls may degrade system capacity significantly as compared to operation of 3Glx calls alone. This paper presents analytical methodology in calculating interference for mixed 3Glx and IxEV-DV calls made in the forward link. Monte Carlo simulations are performed to obtain capacity of the system. Results show that 3Glx system capacity is lowered by 2/3 and 1/3 at 0.1% and at 0.5% outage levels, respectively, when 3Glx and IxEV-DV calls are simultaneously made.
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This paper presents the results from analysis of the forward link capacity for the third generation CDMA wireless system employing adaptive antenna arrays (AAA) at the base station. The capacity performance for mixed traffic scenarios of... more
This paper presents the results from analysis of the forward link capacity for the third generation CDMA wireless system employing adaptive antenna arrays (AAA) at the base station. The capacity performance for mixed traffic scenarios of the forward link is studied in a multi-cell CDMA network including the array topology, multipath angle spread, and mean DOA beamforming technique. The effect of fast fading, log-normal shadowing, multiple access interference, and thermal noise is considered. The simulation results show that with the AAA, system capacity can be increased several fold compared to non-adaptive antenna base stations
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Smart antennas are considered to be promising technology for increasing the performance of wireless communication systems. A smart antenna consists of several antenna elements, whose signals are processed adaptively in order to exploit... more
Smart antennas are considered to be promising technology for increasing the performance of wireless communication systems. A smart antenna consists of several antenna elements, whose signals are processed adaptively in order to exploit the spatial domain of the mobile radio channel (1). Usually, the signals received at the different antenna elements are multiplied with complex weights w, and then summed up; the weights are chosen adaptively. Not the antenna itself, but the whole antenna system including the signal processing is called "adaptive" (2). Only the antenna is not smart, the antenna system which contains also antenna elements is called smart.
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Radio resource management (RRM) in a heterogeneous network (HetNet) has gained significant attention in order to manage the radio resources efficiently. In this paper, an adaptive radio resource management (ARRM) strategy is presented to... more
Radio resource management (RRM) in a heterogeneous network (HetNet) has gained significant attention in order to manage the radio resources efficiently. In this paper, an adaptive radio resource management (ARRM) strategy is presented to implement the fractional frequency reuse with three sectors and three layers (FFR-3SL) model more efficiently in a conventional long term evolution advanced (LTE-A) HetNet system. In the FFR-3SL model, the entire macro-cell coverage area is split into three sectors and three layers; while the total available bandwidth is fractioned into seven subbands. The radio resources (subbands) are assigned to femto-cells and macro-cells according to the user equipment (UE) demand in high-density areas. In order to examine the model, four different cases of user location distribution (ULD) such as central layer focused (CLF), middle layer focused (MLF), outer layer focused (OLF), and uniform distribution are considered. A Monte Carlo simulation is applied to assess and analyze the overall system performance in terms of throughput and efficiency. The simulation results show that the CLF achieves higher throughput and better efficiency under the given parameters when the ARRM strategy applied properly.
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PURPOSE: A device for demodulating an M-binary of a digital communication system is provided to demodulate a set of orthogonal modulation signals received with a binary data type in serial, thereby applicable to a base station system of a... more
PURPOSE: A device for demodulating an M-binary of a digital communication system is provided to demodulate a set of orthogonal modulation signals received with a binary data type in serial, thereby applicable to a base station system of a wireless network. CONSTITUTION: An M-bit Walsh code is simultaneously inputted to an input 00 processor(610), an input 01 processor(620), an input 10 processor(630), and an input 11 processor(640) performing functions of a matching filter. Each input processor(610,620,630,640) carries out a matching filter operation between a portion of an incoming signal and binary pairs(00,01,10,11). Outputs of the processors(610,620,630,640) and matching filters are inputted to an input decision processor(650). The input decision processor(650) supplies information on which input processor is matched with the incoming signal to a controller(660). The controller(660) loads the first row of a preset code mask table of the matched input processor, and adds a value ...
Ucuncu nesil (Third Generation, 3G) haberlesme sistemleri tum dunyada yaygin olarak kullanilmaktadir ve hizla gelismektedir. Isin sekillendirme yetenegine sahip akilli anten algoritmasi ucuncu nesil haberlesme sistemleri icin ortaya... more
Ucuncu nesil (Third Generation, 3G) haberlesme sistemleri tum dunyada yaygin olarak kullanilmaktadir ve hizla gelismektedir. Isin sekillendirme yetenegine sahip akilli anten algoritmasi ucuncu nesil haberlesme sistemleri icin ortaya atilmistir. Bu calismada, uzay kod korelatoru (Space Code Correlator, SCC) olarak isimlendirilen yeni bir akilli anten algoritmasi tasarimi ve gerceklestirimini oneren bir calisma sunulmaktadir. Onerilen algoritma onceden belirlenmis dogrultu vektorleri ve istenilir kullanici kodu ile kod korelasyonu ve depolanmis dogrultu vektorleri ile genisletilmis sinyalin uzaysal korelasyonu temeline dayanmaktadir. Tasarimdaki amac, yakinsama problemini ortadan kaldirarak sabit gerceklestirme zamanina sahip, yeterli sinyal girisim gurultu orani (SINR) performansini saglayan isin sekillendirme agirlik vektorlerinin bulunmasidir. Bu calismada, SCC algoritmasi coklu yol yayilim kosullarinda, farkli Texas Instruments (TI) TMS320C67x kayan nokta dijital sinyal islemciler...
Research Interests: Smart Antenna, Software Defined Radio, Communication System, Design Methodology, Least Mean Square, and 11 moreDirection of Arrival Estimation, Digital Signal Processor, Spatial Correlation, Floating Point, Adaptive Beamforming, Design and Implementation, Texas Instruments, Code Division Multiple Access, Adaptive Algorithm, Adaptive arrays, and Multipath Propagation
mobile receivers is limited primarily by co–channel interference (CCI). Adaptive Antenna Arrays (AAAs) that employ antenna arrays along with advanced signal processing at the base station (BS) have been proposed to mitigate this... more
mobile receivers is limited primarily by co–channel interference (CCI). Adaptive Antenna Arrays (AAAs) that employ antenna arrays along with advanced signal processing at the base station (BS) have been proposed to mitigate this limitation. We present FL capacity analysis for mixed voice and data user traffic scenarios in third generation (3G) CDMA cellular network, where each BS is equipped with either three–sector uniform linear array (ULA) or non–sectorized uniform circular array (UCA). We demonstrate that the FL capacity of the system is considerably affected by the antenna array topology. We find that the optimum element spacing resulting in the largest FL system capacity is 0,5O for both ULA and UCA topologies. Also, it is found that the UCA provides larger FL capacity when compared to the ULA under the same array parameters, i.e., element spacing and number of elements per cell.
This paper presents malicious relay node detection in a cooperative network using unsupervised learning based on the received signal samples over the source to destination (S-D) link at the destination node. We consider the situations in... more
This paper presents malicious relay node detection in a cooperative network using unsupervised learning based on the received signal samples over the source to destination (S-D) link at the destination node. We consider the situations in which possible maliciousness of the relay is the regenerative, injection or garbling type attacks over the source signal according to attack modeling in the communication. The proposed approach here for such an attack detection problem is to apply unsupervised machine learning using one-class classifier (OCC) algorithms. Among the algorithms compared, One-Class Support Vector Machines (OSVM) with kernel radial basis function (RBF) has the largest accuracy performance in detecting malicious node attacks with certain types and also detect trustable relay by using specific features of the symbol constellation of the received signal. Results show that we can achieve detection accuracy about 99% with SVM-RBF and k-NN learning algorithms for garbling type relay attacks. The results also encourage that OCC algorithms considered in this study with different feature selections could be effective in detecting other types of relay attacks.
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Orthogonal variable spreading factor (OVSF) codes are widely used to provide variable data rates for supporting different bandwidth requirements in wideband code division multiple access (WCDMA) systems. Many works in the literature have... more
Orthogonal variable spreading factor (OVSF) codes are widely used to provide variable data rates for supporting different bandwidth requirements in wideband code division multiple access (WCDMA) systems. Many works in the literature have intensively investigated code placement and replacement schemes in OVSF code trees to reduce the code blocking probability and increase the code spectral efficiency. This paper describes a
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The emergence of optical wireless networks (OWNs) is a potential solution to the quest for the increasing bandwidth demand. Existing bandwidth assignment strategies are not suitable for OWNs, considering factors such as differences... more
The emergence of optical wireless networks (OWNs) is a potential solution to the quest for the increasing bandwidth demand. Existing bandwidth assignment strategies are not suitable for OWNs, considering factors such as differences between the physical properties of radio networks and OWNs. In order to eliminate collision, minimize delay and enhance system utilization and fairness, we propose the non-contention bandwidth assignment protocol called adaptive polling medium access control (APMAC) protocol for OWNs. The APMAC protocol involves association, data transmission and dissociation phases. Moreover, the APMAC protocol exploits features of the IEEE 802.15.7 visible light communication (VLC) standard. While assigning bandwidth to the visible light nodes (VLNs), the visible light access point (VLAP) establishes a polling table that contains the identity, buffer size and round-trip time of each VLN that issued bandwidth request. The contents of the polling table enable the computat...
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Location information along with sensed data is important for most of the applications in wireless sensor networks (WSNs). This paper presents a modified sectoral sweeper based localization estimation (SSLE) method which is improved... more
Location information along with sensed data is important for most of the applications in wireless sensor networks (WSNs). This paper presents a modified sectoral sweeper based localization estimation (SSLE) method which is improved version of our previously studied SSLE method and it's modeling in OPNET. This technique requires simplified message formats. Only a central node which needs to have smart antenna processing capability estimates locations of sensor nodes. The modified SSLE is modeled using OPNET modeler with log-normal shadowing effects. The present OPNET wireless module uses standard log-distance model without any shadowing effects. We add log-normal shadowing effects by providing a user with ability to choose variance of shadowing effects from 0 dB to 5 dB according to the wireless environment. The detailed implementation methodology in OPNET is presented in terms of node and process models. The performance of modified SSLE is evaluated through different network and channel parameters in terms of localization error and average throughput. The simulation results show that the modified SSLE method can achieve with 9.5% average localization error under log normal shadowing channel conditions.
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We propose an improved fast algorithm for spatial signature estimation in array antenna systems. We provide an analysis for a fast estimation algorithm, which is not fully exploited in the previous work of Kim and Xu (see Proc. of IEEE... more
We propose an improved fast algorithm for spatial signature estimation in array antenna systems. We provide an analysis for a fast estimation algorithm, which is not fully exploited in the previous work of Kim and Xu (see Proc. of IEEE Vehicular Technology Conference, 1997). Based on the analysis, we derive an improved algorithm which yields more accurate estimates with tolerable increment of computational complexity. The improvement is accomplished by compensation of noise power. Two different estimation methods for the noise power are presented. We investigate the performance of the proposed method via computer simulation
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Joint detection with the minimum-mean square error (MMSE) criterion has been explored in previous works. Yang, Liu, Xu and Kim (see Asilomar Conference on Signals, Systems and Computers, Asilomar, CA, 1999) discussed joint detection with... more
Joint detection with the minimum-mean square error (MMSE) criterion has been explored in previous works. Yang, Liu, Xu and Kim (see Asilomar Conference on Signals, Systems and Computers, Asilomar, CA, 1999) discussed joint detection with cyclic reduction, which has been proved to be faster than the popular Cholesky decomposition based algorithm under many scenarios. In this paper, a faster version
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Abstract In time-division-duplex (TDD) mode wireless communications, downlink beamforming performance of a smart antenna system at the base station can be degraded due to variation of spatial signature vectors of an antenna array... more
Abstract In time-division-duplex (TDD) mode wireless communications, downlink beamforming performance of a smart antenna system at the base station can be degraded due to variation of spatial signature vectors of an antenna array especially in fast fading ...
Research Interests: Smart Antenna, Neural Networks, Antenna arrays, Neuronal Network, Performance Improvement, and 15 moreDegradation, Predictive models, LINEAR PREDICTIVE CODING, Vectors, Smart Antennas, DR-AR Model, Antenna Array, Time Division Multiplexing, Change Propagation, Wireless Communication, Base station, Neural Network Model, Downlink, Time Division Duplex, and Neural nets
Fatih (Fırsatları Arttırma ve Teknolojiyi İyileştirme Hareketi) projesinde öngörülen yapıda tabletler eğitim verilerini bulut sunuculardan almaktadırlar. Eğitsel verinin artması, internet bağlantı hızının düşmesi, sınırlı bant genişliği... more
Fatih (Fırsatları Arttırma ve Teknolojiyi İyileştirme Hareketi) projesinde öngörülen yapıda tabletler eğitim verilerini bulut sunuculardan almaktadırlar. Eğitsel verinin artması, internet bağlantı hızının düşmesi, sınırlı bant genişliği gibi kısıtlamalar veriye ulaşım süresinin ve maliyetinin artışına neden olmaktadır. Tabletler ile bulut sunucu arasındaki trafiği azaltmak için okul düzeyinde vekil sunucu kullanımı uygun bir yöntemdir. Burada vekil sunucu ile bulut sunucu arasındaki senkronizasyon işlemi için en uygun zamanın belirlenmesi kritiktir. Bu çalışmada, uygun zaman bulmak için geliştirdiğimiz iki farklı yöntem karşılaştırılmıştır. Bu yöntemlerden ilki CPU ve bellek kullanımını gibi sistem kaynaklarını temel alırken diğeri RTT (Round-trip Time) değerini temel alarak ağ yoğunluğu tahmin etmeye çalışmaktadır.
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ABSTRACT Localization methods enable estimating locations accurately and provide location information pertaining to mobile devices, people, cars, data and equipment. Accurate location detection is a vital process for most of... more
ABSTRACT Localization methods enable estimating locations accurately and provide location information pertaining to mobile devices, people, cars, data and equipment. Accurate location detection is a vital process for most of location-based applications such as emergency rescue, in-building guidance, security services, and product tracking in hospitals. This paper addresses localization of student/teacher tablets and school level proxy servers for educational data synchronization. For this purpose, locations of proxy servers and tablets are detected using Android Location API. After localization, if tablets are outside of school, they access cloud server directly to take educational data and if tablets are at school access data via proxy server. Experimental results show that proposed technique increases the efficiency in data transfers between the end users and cloud services.
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Tablets receive educational data from cloud servers in envisaged structure of Fatih (Movement of Enhancing Opportunities and Improving Technology) project. Constraints such as increasing educational data size, droping in internet... more
Tablets receive educational data from cloud servers in envisaged structure of Fatih (Movement of Enhancing Opportunities and Improving Technology) project. Constraints such as increasing educational data size, droping in internet connection speed and limited bandwidth cause increasing time and cost for data transfers. Employing school level proxy server in Fatih project ecosystem is promising approach to overcome these problems. It is critical to estimate idle time for synchronization between cloud and proxy server. In this study, two different idle time estimation approaches are compared. While former one is based on local system resources such as CPU and memory usage, latter one is based on measuring and clustering RTT values.
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This paper presents measurement and modeling results of the statistical characteristics of narrowband vector channel (spatial signature) variations at different wireless scenarios in a suburban environment. The measurements were performed... more
This paper presents measurement and modeling results of the statistical characteristics of narrowband vector channel (spatial signature) variations at different wireless scenarios in a suburban environment. The measurements were performed using a real-time smart antenna system with a uniform circular array at the base station and a mobile transmitter with a vertically polarized dipole antenna. Measurements were taken at five different mobile locations that had line-of-sight (LOS), line-of-sight with a local scatterer (LOSWLS), and non-line-of-sight (NOLOS) scenarios. Using this data we characterize the variation of spatial signature correlations in terms of probability distribution and cumulative distribution functions. An empirical model that best fits to the measured complementary cumulative distribution function is obtained for each scenario
Research Interests: Computer Science, Smart Antenna, Statistical Analysis, Probability, Antenna arrays, and 12 moreReal Time Systems, Real Time, Radio Transmitters, UHF, Empirical Model, Complementary Cumulative Distribution Function, Base station, Cumulative distribution function, Antenna measurements, Probability Distribution, Probability Distribution Function, and Uniform circular array
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This paper demonstrates implementation of some CDMA system compatible antenna array algorithms namely LMS and space code correlator (SCC) on an FPGA. A comparative study of FPGA and DSP implementation issues such as architecture... more
This paper demonstrates implementation of some CDMA system compatible antenna array algorithms namely LMS and space code correlator (SCC) on an FPGA. A comparative study of FPGA and DSP implementation issues such as architecture complexity and weight vector computation time is also given. The implementations of the algorithms are performed on Xilinx Virtex II Pro FPGA and Texas Instruments (TI)