Elektrik - Elektronik Mühendisliği Bölümü Koleksiyonu

Permanent URI for this collectionhttps://gcris.khas.edu.tr/handle/20.500.12469/47

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Browsing Elektrik - Elektronik Mühendisliği Bölümü Koleksiyonu by Author "Anpalagan, Alagan"

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    Article
    Citation Count: 11
    Energy Efficient SCMA Supported Downlink Cloud-RANs for 5G Networks
    (IEEE, 2020) Erküçük, Serhat; Erküçük, Serhat; Anpalagan, Alagan; Woungang, Isaac
    Cloud-radio access networks (C-RANs) are regarded as a promising solution to provide low cost services among users through the centralized coordination of baseband units for 5G wireless networks. The coordinated multi-point access, visualization and cloud computing technologies enable C-RANs to provide higher capacity and wider coverage, as well as manage the interference and mobility in a centralized coordinated way. However, C-RANs face many challenges due to massive connectivity and spectrum scarcity. If not properly handled, these challenges may degrade the overall performance. Recently, the non-orthogonal multiple access (NOMA) scheme has been suggested as an attractive solution to support multi-user resource sharing in order to improve the spectrum and energy efficiency in 5G wireless networks. In this paper, among various NOMA schemes, we consider and implement the sparse code multiple access (SCMA) scheme to jointly optimize the codebook (CB) and power allocation in the downlink of C-RANs, where the utilization of SCMA in C-RANs to improve the energy efficiency has not been investigated in detail in the literature. To solve this NP-hard joint optimization problem, we decompose the original problem into two sub-problems: codebook allocation and power allocation. Using the conflict graph, we propose the throughput aware SCMA CB selection (TASCBS) method, which generates a stable codebook allocation solution within a finite number of steps. For the power allocation solution, we propose the iterative level-based power allocation (ILPA) method, which incorporates different power allocation approaches (e.g., weighted and NOMA successive interference cancellation (SIC)) into different levels to satisfy the maximum power requirement. Simulation results show that the sum data rate and energy efficiency performances of SCMA supported C-RANs depend on the selected power allocation approach. In terms of energy efficiency, the performance significantly improves with the number of users when the NOMA-SIC aware geometric water-filling based power allocation method is used.
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    Article
    Citation Count: 38
    Joint Communication and Computing Resource Allocation in 5G Cloud Radio Access Networks
    (IEEE-Inst Electrical Electronics Engineers Inc, 2019) Erküçük, Serhat; Anpalagan, Alagan; Erküçük, Serhat
    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.
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    Article
    Citation Count: 18
    Joint Wavelet-Based Spectrum Sensing and FBMC Modulation for Cognitive mmWave Small Cell Networks
    (Inst Engineering Technology-IET, 2016) Erküçük, Serhat; Anpalagan, Alagan; Raahemifar, Kaamran; Erküçük, Serhat; Habib, Salman
    Millimetre-wave (mmWave) 5G communications is an emerging technology to enhance the capacity of existing systems by thousand-fold improvement. Heterogeneous networks employing densely distributed small cells can optimise the available coverage and throughput of 5G systems. Efficiently utilising the spectrum bands by small cells is one of the approaches that will considerably increase the available data rate and capacity of the heterogeneous networks. This challenging task can be achieved by spectrum sensing capability of cognitive radios and new modulation techniques for data transmission. In this study a wavelet-based filter bank is proposed for spectrum sensing and modulation in 5G heterogeneous networks. The proposed technique can mitigate the spectral leakage and interference by adapting the subcarriers according to cognitive information provided by wavelet packet based spectrum sensing (WPSS) and lowering sidelobes using wavelet-based filter bank multicarrier modulation. The performance improvement of WPSS compared with Fourier-based spectrum sensing is verified in terms of power spectral density comparison and probabilities of detection and false alarm. Meanwhile the bit error rate performance demonstrates the superiority of the proposed wavelet-based system compared with its Fourier-based counterpart over the 60 GHz mmWave channel.
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    Article
    Citation Count: 18
    Sparse Code Multiple Access-Based Edge Computing for IoT Systems
    (IEEE-Inst Electrical Electronics Engineers Inc, 2019) Erküçük, Serhat; Erküçük, Serhat; Anpalagan, Alagan
    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.
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    Article
    Citation Count: 14
    Wavelet-based cognitive SCMA system for mmWave 5G communication networks
    (Inst Engineering Technology-IET, 2017) Erküçük, Serhat; Anpalagan, Alagan; Raahemifar, Kaamran; Erküçük, Serhat
    Fifth generation (5G) communication networks can achieve high spectral efficiency using sparse code multiple access (SCMA) scheme when large number of users are trying to transmit their data simultaneously. The sparsity of SCMA codewords offers the possibility of applying a low-complexity message passing algorithm as an alternative to maximum likelihood detector. However the requirement of densely deployed 5G users is to opportunistically explore new frequencies via cognitive features to overcome spectrum scarcity challenges. In this study spectrum sensing enables cognitive radio capabilities for the SCMA system applied in millimetre wave (mmWave) 5G communications. Proposed cognitive SCMA system can sense the spectrum holes and adapt the transmission in order to utilise the available subcarriers. Besides wavelet packet transform based techniques are used instead of conventional Fourier-based spectrum sensing (FSS) and orthogonal frequency-division multiple access (OFDMA). Wavelet packet spectrum sensing offers more accurate estimation of frequency and power compared with FSS. On the other hand wavelet packet multiple access is more flexible and robust against interference compared with OFDMA. The simulation results verify that the proposed method can significantly improve the performance of SCMA system in terms of probabilities of false alarm and detection and symbol error rate.