Erküçük, Serhat

Erküçük, Serhat

Name Variants

Erküçük, Serhat
S.,Erküçük
S. Erküçük
Serhat, Erküçük
Erkucuk, Serhat
S.,Erkucuk
S. Erkucuk
Serhat, Erkucuk
Erküçük, S.
Erküçük,S.

Job Title

Prof. Dr.

Email Address

Serkucuk@khas.edu.tr

Main Affiliation

Electrical-Electronics Engineering

Status

Former Staff

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Scholarly Output

68

Articles

20

Citation Count

0

Supervised Theses

9 Scholarly Output Search Results

Now showing 1 - 10 of 20

Citation - WoS: 3
Citation - Scopus: 3
Bayesian Compressive Sensing for Ultra-Wideband Channel Estimation: Algorithm and Performance Analysis
(Springer, 2015) Özgör, Mehmet; Erküçük, Serhat; Erküçük, Serhat; Çırpan, Hakan Ali; Electrical-Electronics Engineering
Due to the sparse structure of ultra-wideband (UWB) channels compressive sensing (CS) is suitable for UWB channel estimation. Among various implementations of CS the inclusion of Bayesian framework has shown potential to improve signal recovery as statistical information related to signal parameters is considered. In this paper we study the channel estimation performance of Bayesian CS (BCS) for various UWB channel models and noise conditions. Specifically we investigate the effects of (i) sparse structure of standardized IEEE 802.15.4a channel models (ii) signal-to-noise ratio (SNR) regions and (iii) number of measurements on the BCS channel estimation performance and compare them to the results of -norm minimization based estimation which is widely used for sparse channel estimation. We also provide a lower bound on mean-square error (MSE) for the biased BCS estimator and compare it with the MSE performance of implemented BCS estimator. Moreover we study the computation efficiencies of BCS and -norm minimization in terms of computation time by making use of the big- notation. The study shows that BCS exhibits superior performance at higher SNR regions for adequate number of measurements and sparser channel models (e.g. CM-1 and CM-2). Based on the results of this study the BCS method or the -norm minimization method can be preferred over the other one for different system implementation conditions.
Citation - WoS: 7
Citation - Scopus: 9
Detection of Interdependent Primary Systems Using Wideband Cognitive Radios
(Elsevier GMBH Urban & Fischer Verlag, 2013) Yılmaz, Burak; Erküçük, Serhat; Erküçük, Serhat; Electrical-Electronics Engineering
Cognitive radios (CRs) may be sharing multiple frequency bands with primary systems if the CR is a wideband or an ultra wideband (UWB) system. In that case the CR should ensure all the coexisting primary systems in these bands are detected before it can start data transmission. In this work we study the primary system detection performance of a wideband CR assuming that there are multiple coexisting primary systems and that these primary systems may be jointly active. Accordingly we consider the implementation of energy detection scheme in multiple bands followed by two detection methods: (i) a maximum-a-posteriori (MAP) based detection (i.e. joint detection) that takes into account the statistics of simultaneously operating systems in independent bands and (ii) a Neyman-Pearson (NP) test based detection that optimizes the threshold values independently in each band (i.e. independent detection). For a simpler implementation of the independent detection we show that the threshold values obtained from joint detection can be used in order to achieve the optimum NP test based independent detection results. In addition to quantifying the gain of joint detection over independent detection in terms of probabilities of false alarm and detection for practical scenarios we also present the operation capability of CRs in terms of the fractions of time the CR can access the channel without interfering with the primary systems. The results are important for the practical implementation of multiband detection when the primary systems are known to be interdependent. (C) 2013 Elsevier GmbH. All rights reserved.
Citation - WoS: 5
Citation - Scopus: 6
Code Shift Keying Impulse Modulation for Uwb Communications
(IEEE-INST Electrical Electronics Engineers Inc, 2008) Erküçük, Serhat; Erküçük, Serhat; Kim, Dong In; Kwak, Kyung Sup; Electrical-Electronics Engineering
In this paper the system performance of M-ary code shift keying (MCSK) impulse modulation is studied in detail and compared to M-ary pulse position modulation (MPPM) under single- and multi-user scenarios. For that bounds on the semi-analytic symbol-error rate (SER) expressions are derived and simulation studies are conducted. When practical implementations of MCSK and MPPM are considered it is shown that MCSK can provide about 2 dB performance gain over MPPM as it reduces the effects of multipath delays on the decision variables by randomizing locations of the transmit pulse.
Citation - WoS: 4
Citation - Scopus: 4
Evaluation of Noise Distributions for Additive and Multiplicative Smart Meter Data Obfuscation
(IEEE-Inst Electrical Electronics Engineers Inc, 2022) Erküçük, Serhat; Erkucuk, Serhat; Anpalagan, Alagan; Venkatesh, Bala; Electrical-Electronics Engineering
In this paper, we compare and analyze light-weight approaches for instantaneous smart meter (SM) data obfuscation from a group of consumers. In the literature, the common approach is to use additive Gaussian noise based SM data obfuscation. In order to investigate the effects of different approaches, we consider Gaussian, Rayleigh, generalized Gaussian and chi-square distributions to achieve either additive or multiplicative data obfuscation. For each type of obfuscation approach, we calculate the required parameters to achieve obfuscation such that 50% of the obfuscated data fall outside an interval equalling twice the mean of the instantaneous SM measurements. We also calculate the minimum number of SMs required to estimate the mean of the actual SM measurements, such that the estimate varies within only 0.5% of the actual mean with a 99.5% probability. Simulation results are used to verify the calculations, and it is shown that multiplicative Rayleigh and generalized Gaussian noise require the least number of SMs, which is 90% less than the traditional approach of additive Gaussian noise-based SM data obfuscation.
Citation - WoS: 22
Citation - Scopus: 29
Sparse Code Multiple Access-Based Edge Computing for Iot Systems
(IEEE-Inst Electrical Electronics Engineers Inc, 2019) Alnoman, Ali; Erküçük, Serhat; Erküçük, Serhat; Anpalagan, Alagan; Electrical-Electronics Engineering
In this paper, a sparse code multiple access (SCMA)-based edge computing scheme is proposed for Internet-of- Things (IoT) systems. The aim of implementing SCMA, which is a nonorthogonal multiple access resource allocation technique, is to improve network connectivity and maximize data rate provision. The proposed edge-IoT system is investigated under different SCMA configurations to explore the various performance aspects such as connectivity, throughput, task completion time, and complexity. First, the problem is formulated as a data rate maximization problem for SCMA-based heterogeneous networks under power constraints. Then, the problem is subdivided into a power allocation problem, which is solved using the water filling approach, and a codebook allocation problem that is solved using a heuristic algorithm. The results show that the SCMA scheme can significantly improve the IoT performance compared to the conventional orthogonal frequencydivision multiple access resource allocation scheme in terms of connectivity, throughput, and task completion time provided that SCMA configurations are suitable with IoT processing capabilities to avoid undesired detection latency.
Citation - WoS: 22
Citation - Scopus: 30
Energy Efcient Downlink Resource Allocation in Cellular Iot Supported H-Crans
(Institute of Electrical and Electronics Engineers Inc., 2021) Ferdouse, Lilatul; Erküçük, Serhat; Woungang, Isaac W.; Anpalagan, Alagan S.; Erküçük, Serhat; Electrical-Electronics Engineering
The cloud computing supported heterogeneous cloud radio access network (H-CRAN) is one of the promising solutions to support cellular IoT devices with the legacy cellular systems. However, the dense deployment of small cells with fractional frequency reuse in orthogonal frequency division multiple access (OFDMA) based H-CRANs increases intra- and inter-cell interference, turning the resource allocation into a more challenging problem. In general, the macro cell users are considered as the legacy users, whereas the cellular IoT devices and small cell users share the macro cell users resource blocks in an underlaid approach. In this paper, we investigate an underlaid approach of resource allocation for small and macro cell users to improve the energy efficiency (EE) in H-CRANs. The solution approaches are derived with the Dinkelbach, Lagrange and Alternating Direction Method of Multipliers (ADMM) methods by considering maximum power, resource block allocation, fronthaul capacity and quality of service (QoS) constraints of macro cell users. A two-step energy efficient underlaid cellular IoT (UCIoT) supported H-CRAN method is proposed and evaluated with overlaid cellular IoT (OC-IoT) supported H-CRAN and underlaid H-CRAN without cellular IoT devices. The proposed method is evaluated in terms of energy efficiency and the Jain's fairness index, considering the effect of number of cellular IoT density in each small cell of the H-CRAN. The simulation results demonstrate the effectiveness of the proposed approach compared to earlier approaches.
Citation - WoS: 5
Citation - Scopus: 8
Joint Detection of Primary Systems Using Uwb Impulse Radios
(IEEE-INST Electrical Electronics Engineers Inc, 2011) Erküçük, Serhat; Erküçük, Serhat; Lampe, Lutz; Schober, Robert; Electrical-Electronics Engineering
Regulation in Europe and Japan requires the implementation of detect-and-avoid (DAA) techniques in some bands for the coexistence of licensed primary systems and secondary ultra wideband (UWB) systems. In a typical coexistence scenario a primary system may have potentially interdependent uplink-downlink communication channels (e. g. simultaneous uplink-downlink communications in a frequency division duplex system) overlapping with the frequency band of a UWB system. If such interdependencies of primary systems' activities are known the UWB system's ability to detect primary systems can be improved. In this study we are interested in determining the possible gains in the detection performance when taking interdependencies into account for practically implementable detection methods. Contrary to selecting the detection thresholds individually for each band as in a conventional detection approach the bands are jointly processed. To this end maximum a posteriori (MAP) decision variables are generated at the receiver and bias terms are introduced to achieve a desired trade-off between the probabilities of detection and false alarm. In addition to finding the optimal detection results based on the Neyman-Pearson (NP) test a suboptimal but practically implementable approach is also considered and the gain compared to conventional independent detection is quantified for various practical scenarios. The results obtained from this study can be used for improving the primary system detection performance of UWB systems as well as for cognitive radios that perform spectrum sensing in multiple bands.
Citation - WoS: 3
Citation - Scopus: 4
Busy Tone Based Coexistence Algorithm for Wran and Wlan Systems in Tv White Space
(Inst Engineering Technology-IET, 2018) Karatalay, Onur; Baykaş, Tunçer; Erküçük, Serhat; Erküçük, Serhat; Baykaş, Tunçer; Electrical-Electronics Engineering
TV White Space (TVWS) refers to frequency band reserved only for licensed terrestrial TV broadcasting and is opened to unlicensed use under regulatory conditions. While regulations protect licensed systems from interference interference among unlicensed systems is left mainly to manufacturers. Consequently there is a need to develop new coexistence approaches between TVWS networks. Busy tone broadcasting is a coexistence method which can be used by TVWS networks to announce the selected frequency band is occupied. In this paper a busy tone based coexistence algorithm is proposed for IEEE 802.11af and IEEE 802.22 networks and analyzed by considering different client distributions experiencing log-normal shadowing where the exact interfering packet rate and successful packet transmission rate expressions are obtained and validated by simulations for different scenarios. The results show that with the proposed coexistence approach a WLAN can reliably detect the busy tone signal to change its frequency band and can reduce interference to WRAN. Even if there is no available frequency band for the WLAN the WRAN still maintains its enhanced successful packet transmission performance. The deployment of the proposed algorithm is important for successful coexistence between cognitive wireless networks where interference is not regulated such as in TVWS bands.
Citation - WoS: 14
Citation - Scopus: 16
Bayesian Compressive Sensing for Primary User Detection
(Inst Engineering Technology-IET, 2016) Başaran, Mehmet; Erküçük, Serhat; Erküçük, Serhat; Cirpan, Hakan Ali; Electrical-Electronics Engineering
In compressive sensing (CS)-based spectrum sensing literature most studies consider accurate reconstruction of the primary user signal rather than detection of the signal. Furthermore possible absence of the signal is not taken into account while evaluating the spectrum sensing performance. In this study Bayesian CS is studied in detail for primary user detection. In addition to assessing the signal reconstruction performance and comparing it with the conventional basis pursuit approach and the corresponding lower bounds signal detection performance is also considered both analytically and through simulation studies. In the absence of a primary user signal the trade-off between probabilities of detection and false alarm is studied as it is equally important to determine the performance of a CS approach when there is no active primary user. To reduce the computation time and yet achieve a similar detection performance finally the effect of number of iterations is studied for various systems parameters including signal-to-noise-ratio compression ratio mean value of accumulated energy and threshold values. The presented framework in this study is important in the overall implementation of CS-based approaches for primary user detection in practical realisations such as LTE downlink OFDMA as it considers both signal reconstruction and detection.
Citation - WoS: 47
Citation - Scopus: 51
Joint Communication and Computing Resource Allocation in 5g Cloud Radio Access Networks
(IEEE-Inst Electrical Electronics Engineers Inc, 2019) Ferdouse, Lilatul; Erküçük, Serhat; Anpalagan, Alagan; Erküçük, Serhat; Electrical-Electronics Engineering
Cloud-radio access network (C-RAN) is regarded as a promising solution to manage heterogeneity and scalability of future wireless networks. The centralized cooperative resource allocation and interference cancellation methods in C-RAN significantly reduce the interference levels to provide high data rates. However, the centralized solution is not scalable due to the dense deployment of small cells with fractional frequency reuse, causing severe inter-tier and inter-cell interference turning the resource allocation and user association into a more challenging problem. In this paper, we investigate joint communication and computing resource allocation along with user association, and baseband unit (BBU) and remote radio head (RRH) mapping in C-RANs. We initially establish a queueing model in C-RAN, followed by formulation of two optimization problems for communication [e.g., resource blocks (RBs) and power] and computing [e.g., virtual machines (VMs)] resources allocation with the aim to minimize mean response time. User association along with the RB allocation, interference, and queueing stability constraints are considered in the communication resource optimization problem. The computing resource optimization problem considers BBU-RRH mapping and VM allocation for small cells, constrained to BBU server capacity and queueing stability. To solve the communication and computing resource optimization problem, we propose a joint resource allocation solution that considers a double-sided auction based distributed resource allocation (DS-ADRA) method, where small cell base stations and users jointly participate using the concept of auction theory. The proposed method is evaluated via simulations by considering the effect of bandwidth utilization percentage, signal-to-interference ratio threshold value and the number of users. The results show that the proposed method can be successfully implemented for 5G C-RANs.