Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği

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Author: search.filters.author.Özbek, BernaScopus Q: search.filters.scopusQuartile.Q1

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  • Correction
    Corrections To “massive Mimo-Noma Based Mec in Task Offloading for Delay Minimization”
    (IEEE, 2023) Yılmaz, Saadet Simay; Özbek, Berna
    [No abstract available]
  • Article
    Citation - WoS: 15
    Citation - Scopus: 17
    Massive Mimo-Noma Based Mec in Task Offloading for Delay Minimization
    (IEEE, 2023) Yilmaz, Saadet Simay; Özbek, Berna
    Mobile edge computing (MEC) has been considered a promising technology to reduce task offloading and computing delay by enabling mobile devices to offload their computation-intensive tasks. Non-orthogonal multiple access (NOMA) is regarded as a promising method of increasing spectrum efficiency, while Massive multiple-input multiple-output (MIMO) can support a larger number of users for simultaneous offloading. These two technologies can effectively facilitate offloading and further improve the performance of MEC systems. In this work, we propose a NOMA and Massive MIMO assisted MEC system for delay-sensitive applications. Our objective is to minimize the overall computing and transmission delay under users' transmit power and MEC computing capability. Through the pairing scheme for Massive MIMO-NOMA, the users with the higher channel gain can offload all their data, while the users with the lower channel gain can offload a portion of their data to the MEC. Performance results are provided regarding to the sum data rate and overall system delay compared with the orthogonal multiple access (OMA)-MIMO based and Massive MIMO (M-MIMO) based MEC systems.
  • Article
    Citation - WoS: 10
    Citation - Scopus: 13
    User Selection and Codebook Design for Noma-Based High Altitude Platform Station (haps) Communications
    (IEEE, 2022) Cumalı, İrem; Özbek, Berna; Karabulut Kurt, Güneş; Yanıkömeroğlu, Halim
    High altitude platform station (HAPS) communications have made a tremendous impact on recent research into sixth-generation (6G) and beyond wireless networks. The large coverage area and significant computational capability of HAPS systems enable many areas of utilization in 6G and beyond applications, including Internet of Things (IoT) services, augmented reality, and connected autonomous vehicles. In addition, non-orthogonal multiple access (NOMA) is a cutting-edge technology that can be utilized to enhance spectral efficiency in HAPS systems. In this paper, we exploit NOMA-based HAPS communications and multiple antennas to meet the connectivity, reliability, and high-data-rate requirements of 6G and beyond applications. We propose a user selection and correlation-based user pairing algorithm for a NOMA-based multi-user HAPS system. Moreover, we investigate the codebook design for HAPS communication and adapt the polar-cap codebook (PCC) to the HAPS channel which shows Rician fading propagation characteristics dominated by the line-of-sight (LOS) component. Performance evaluations show that the proposed user selection algorithm is perfectly suited to the HAPS channel and that the PCC provides a remarkable spectral efficiency.
  • Article
    Citation - WoS: 8
    Citation - Scopus: 11
    Delay Minimization for Massive Mimo Based Cooperative Mobile Edge Computing System With Secure Offloading
    (IEEE, 2022) Mümtaz, Rao; Yılmaz, Simay; Özbek, Berna
    Mobile edge computing (MEC) has been envisioned as a promising technology for enhancing the computational capacities of mobile devices by enabling task offloading. In this paper, we present a novel framework for a cooperative MEC system by employing Massive Multiple-Input Multiple-Output (MIMO) and non-orthogonal multiple access (NOMA) technologies, including security aspects. Specifically, in the proposed cooperative MEC system, there is no strong direct transmission link between the cell-edge user and the MEC server; consequently, the user sends their tasks to the MEC server through the helpers at the cell-centers. In the proposed framework, we minimize the overall delay, including secure offloading under the constraints of computing capability and transmit power. The proposed algorithm minimizes the overall delay in downlink and uplink transmission while satisfying security constraints to solve the formulated problem. The simulation results show that Massive MIMO based NOMA improves the performance of the secure MEC system by employing more than one helper.
  • Article
    Citation - WoS: 7
    Citation - Scopus: 8
    The Resilience of Massive Mimo Pnc To Jamming Attacks in Vehicular Networks
    (Institute of Electrical and Electronics Engineers Inc., 2021) Okyere, Bismark; Musavian, Leila; Özbek, Berna; Busari, Sherif A.; Gonzalez, Jonathan
    In this article, we investigate the resilience of Massive MIMO Physical Layer Network Coding (PNC) to jamming attack in both sub-6 GHz and millimeter-Wave (mmWave) systems in vehicular networks. Massive MIMO generally is resilient to jamming attacks, and we investigate the impact that PNC has on this resilience, if combined with Massive MIMO. The combination of Massive MIMO and PNC has shown a significant improvement in the bit error rate (BER) in our previous investigation. The corresponding framework is analysed against a barraging attack from a jammer, where the jamming channel is not known to the base station (BS), and the jammer can use any number of transmit antennas. Over Rayleigh channel, our simulation results reveal that Massive MIMO PNC performs better in the lower signal-to-noise ratio (SNR) regions to jamming attacks and this is achieved at twice the spectral efficiency. A similar performance is observed over mmWave channel.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 5
    Design and Implementation of Spatial Correlation-Based Clustering for Multiuser Miso-Noma Systems
    (Institute of Electrical and Electronics Engineers Inc., 2021) Göztepe, Caner; Özbek, Berna; Karabulut Kurt, Güneş
    In this letter, we propose a novel user clustering algorithm for downlink multiuser multiple-input single-output (MISO) non-orthogonal multiple access (NOMA) systems along with its implementation in a real-time testing environment. The proposed method selects the clusters by considering users' spatial channel properties against the generated orthogonal directions. This is then followed by power allocation and zero-forcing precoding steps to mitigate the interference between the selected clusters. Performance comparisons are provided in terms of both real-time tests and simulations. It is demonstrated that a notable improvement in capacity and reliability can be obtained through the proposed approach in multiuser MISO-NOMA systems with reduced complexity.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 8
    Coverage Analysis of Physical Layer Network Coding in Massive Mimo Systems
    (Institute of Electrical and Electronics Engineers Inc., 2021) İlgüy, Mert; Özbek, Berna; Mumtaz, Rao; Busari, Sherif A.; Gonzalez, Jonathan
    Wireless networks are prone to interference due to their broadcast nature. In the design of most of the traditional networks, this broadcast nature is perceived as a performance-degrading factor. However, Physical Layer Network Coding (PNC) exploits this broadcast nature by enabling simultaneous transmissions from different sources and thereby enhances the performance of the wireless networks with respect to improvement in spectral efficiency, coverage, latency and security of the system. For fifth generation (5G) networks and beyond, massive multiple input multiple output (MIMO) is considered as a key physical layer technology. Thus, its combination with PNC can significantly enhance the performance of the network, facilitating capacity-coverage improvement, among other benefits. While the bit error rate performance of multiuser massive MIMO-PNC systems through linear detection has been investigated extensively, their coverage probability for a given target signal-to-noise ratio has not been explored yet. In this paper, we derive a closed form expression for coverage probability in PNC based multiuser massive MIMO systems employing zero-forcing equalization. Both theoretical and simulation results are provided for different number of users and antennas in the multiuser massive MIMO-PNC communications systems.
  • Article
    Citation - WoS: 10
    Citation - Scopus: 13
    User Selection for Noma Based Mimo With Physical Layer Network Coding in Internet of Things Applications
    (Institute of Electrical and Electronics Engineers Inc., 2022) Yılmaz, Saadet Simay; Özbek, Berna; İlgüy, Mert; Okyere, Bismark; Musavian, Leila; Gonzalez, Jonathan
    Non-orthogonal multiple access (NOMA) based multiple-input multiple-output (MIMO), which has the potential to provide both massive connectivity and high spectrum efficiency, is considered as one of the efficient techniques for sixth generation (6G) wireless systems. In massive Internet of Things (IoT) networks, user-set selection is crucial for enhancing the overall performance of NOMA based systems when compared with orthogonal multiple access (OMA) techniques. In this paper, we propose a user-set selection algorithm for IoT uplink transmission to improve the sum data rate of the NOMA based MIMO systems. In order to exchange data between the selected IoT pairs, we propose to employ wireless physical layer network coding (PNC) to further improve the spectral efficiency and reduce the delay to fulfill the requirements of future IoT applications. Performance evaluations are provided based on both sum data rate and bit error rate for the proposed NOMA based MIMO with PNC in the considered massive IoT scenarios. IEEE
  • Article
    Citation - WoS: 28
    Citation - Scopus: 28
    Multi-Helper Noma for Cooperative Mobile Edge Computing
    (Institute of Electrical and Electronics Engineers, 2022) Yılmaz, Saadet Simay; Özbek, Berna
    The next-generation wireless networks are expected to support a number of computation-intensive and delay-sensitive applications such as virtual reality (VR), autonomous driving, telesurgery and unmanned aerial vehicles (UAVs). Since many devices are computation and power limited, mobile edge computing (MEC) has been deemed as a promising way to enhance computation service. In this paper, we propose a novel cooperative MEC that exploits the combination of non-orthogonal multiple access (NOMA) and multiple helpers. In the proposed system featuring a user, multiple helpers and a base station (BS), the user can simultaneously offload its computation-intensive tasks to the helpers using NOMA when there is no strong direct transmission link between the user and the BS. Then, the helpers can compute and offload these tasks through NOMA. Thus, in the proposed scheme, the computation and offloading modes at the helpers are determined with respect to the optimized task offloading decision factor. The simulation results show that the proposed NOMA-based cooperative MEC significantly increases the total offloading data under the latency constraints compared to the benchmark schemes featuring one helper with strong direct transmission link. IEEE
  • Article
    Citation - Scopus: 3
    A Novel Joint Index Modulation and Physical Layer Network Coding Mechanism for Beyond 5g
    (Institute of Electrical and Electronics Engineers Inc., 2021) Okyere, Bismark; Musavian, Leila; Özbek, Berna; Busari, Sherif A.; Gonzalez, Jonathan
    In beyond 5G communications, besides energy efficiency (EE) and spectral efficiency (SE), latency and reliability are among the main metrics that extreme ultra-reliable low-latency communications (URLLC) applications must fulfill. Although new techniques are sought after to meet the crunching requirements of URLLC, combining existing phys-ical-layer techniques have become a compelling, attractive, and cost saving approach to achieving the same goal. In this article, we describe a novel mechanism combining physical layer network coding (PNC) and index modulation (IM) to achieve a balance between SE and EE for URLLC applications beyond 5G. PNC has the potential to increase SE because it leverages on interference from many transmissions occurring at the same time. Although fewer resources are required for IM the capacity gain is the same as if all transmission resources are used, and as a result, both EE and SE can increase simultaneously. Our simulation results show the feasibility of combining these two key physical-lay-er techniques, affirming the complementary role this approach will play in meeting the performance KPIs of URLLC beyond 5G. © 2017 IEEE.