Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Conference Object Adaptive Limited Feedback Scheme for Stream Selection Based Interference Alignment in Heterogeneous Networks(IEEE, 2016) Beyazıt, Esra Aycan; Özbek, Berna; Le Ruyet,D.This paper presents a stream selection based interference alignment approach with imperfect channel state information for heterogeneous networks. The proposed algorithm performs the selection of a stream sequence among a predetermined set of sequences. Those selected sequences are the ones that mostly contribute to the sum rate when performing the exhaustive search. These stream sequences form a regular structure where the first stream is associated to a pico user. The effect of imperfect channel state information on the proposed algorithm is analyzed and a bit allocation scheme is proposed by deriving an upper bound on the rate loss due to quantization. © 2016 IEEE.Conference Object Carrier Frequency Offset Based Shared Randomness for Secure Transmission in M-Psk Noma(IEEE, 2023) Göztepe, Caner; Karabulut Kurt, Güneş; Özbek, BernaPower domain non-orthogonal multiple access (NOMA) enhances spectral efficiency by superposing multiple users in the same time-frequency resource block at the expense of exposing the users' data. However, current approaches to improve the secrecy levels of users are limited to rate reduction. This paper proposes a secure NOMA system based on the shared randomness extracted from the reciprocal carrier frequency offsets (CFOs) between the transmitter-receiver pairs for M-ary phase-shift keying. As multiple users will have physically separated oscillators, it will result in independent CFOs among users. This randomness is used to introduce a constellation rotation in the transmitted symbols. We show that under ideal CFO estimates, the proposed approach achieves perfect secrecy among all NOMA users without introducing any rate reduction. We also demonstrate the practical applicability of the proposed approach by using a software-defined radio-based test bed. © 2023 IEEE.Correction Corrections To “massive Mimo-Noma Based Mec in Task Offloading for Delay Minimization”(IEEE, 2023) Yılmaz, Saadet Simay; Özbek, Berna[No abstract available]Conference Object A Framework for Physical Layer Network Coding With Multiple Antennas for Bpsk(IEEE, 2023) İlgüy, Mert; Özbek, BernaPhysical layer network coding (PNC) is combined with multiple antennas to increase the spectral efficiency of wireless communication systems. In this work, we present a PNC framework including both uplink and downlink for binary phase shift keying (BPSK). In the uplink, we propose a scheme for detecting network-coded symbol (NCS) with reduced complexity. For the downlink, we propose a transmission scheme of NCS through maximum ratio transmission (MRT) by defining the precoding vector as an average of users' channels. The bit-error-rate (BER) performances and the comparison results with the conventional scheme in both downlink and uplink are provided for the proposed low-complexity PNC framework.Conference Object Testbed Sdr Implementation Approach for Millimetre Wave Iot Applications(IEEE, 2022) Glazkov, Roman; Özbek, Berna; Pyattaev, Alexander; Musavian, Leila; Koucheryavy, YevgeniMillimetre wave (mmWave) communication is a promising technology which can fulfil the growing demands for spectrum for future wireless networks. One of the key areas for the development of the mmWave networks is the Internet of Things (IoT) communications within fifth generation (5G) and beyond 5G networks. For significant analysis and development of the compliant IoT systems through testbed implementation, current mmWave spectrum transceivers are too expensive when substantial number of the nodes is required by the IoT applications. Considering all the above, it is suggested to use Software Defined Radio (SDR) transceivers with a lower frequency band and with an increased distance between the nodes. The idea is to scale observation time and distance to emulate mmWave radio without actual mmWave hardware. Using scaling factors for the certain system parameters to keep the signal characteristics in accordance with the mmWave band makes it possible. This approach allows to develop mmWave IoT testbeds with significant improvement in the system scalability and cost-effectiveness without the need to transmit and receive the signal in the mmWave band. In this paper, the concept of SDR-based Hardware-in-the-loop (HIL) system combined with the observation time and distance scaling approach is proposed. As an example, a testbed with a simple Wireless Physical Network Coding scheme is implemented and demonstrated. © 2022 IEEE.Conference Object Citation - WoS: 2Citation - Scopus: 2Physical Layer Network Coding Enabled Noma With Multiple Antennas(IEEE, 2022) İlgüy, Mert; Özbek, Berna; Okyere, Bismark; Musavian, Leila; Pereira, AathurIn this work, a combination of non-orthogonal multiple access (NOMA) with multiple antennas and physical layer network coding (PNC) scheme is proposed to increase the overall data rate. In the proposed scheme, we employ higher-order modulations for the users with relatively high signal-to-noise ratio (SNR) in the PNC-NOMA pair to increase the data rate. Meanwhile, lower-order modulations are chosen for the users with relatively lower SNR values in the PNC-NOMA pair. We showed the results in terms of bit error rate (BER) for different number of antennas and users in the proposed PNC-NOMA scheme. © 2022 IEEE.Conference Object Citation - Scopus: 1Interference Mitigation for Device-To Based Cellular Communications(IEEE, 2022) Acar, Süleyman Onur; Özbek, BernaDevice-to-device (D2D) communication underlaying cellular networks can improve the performance of cellular systems and it provides an effective way to meet growing mobile traffic and capacity demand. When user equipments are located in close proximity, they can communicate through direct links. In this case, D2D links can increase both energy and spectrum efficiency by reusing uplink (UL) cellular resources while satisfying the users' quality-of-service requirements. However, integrating D2D links into the cellular infrastructure causes an interference since D2D communication can increase co-channel interference and degrade cellular users' transmission link quality. In this paper, the interference mitigation techniques including power control, multiple antenna and resource allocation based on graph coloring are proposed for D2D communications underlaying cellular systems to increase the data rate of both the cellular users and D2D pairs. Compared to the prior works, in the proposed algorithm, D2D and cellular users have same priority for resource allocation. Finally, the proposed algorithm improves the overall system capacity significantly.Article Citation - WoS: 15Citation - Scopus: 17Massive Mimo-Noma Based Mec in Task Offloading for Delay Minimization(IEEE, 2023) Yilmaz, Saadet Simay; Özbek, BernaMobile 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: 10Citation - Scopus: 13User Selection and Codebook Design for Noma-Based High Altitude Platform Station (haps) Communications(IEEE, 2022) Cumalı, İrem; Özbek, Berna; Karabulut Kurt, Güneş; Yanıkömeroğlu, HalimHigh 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: 8Citation - Scopus: 11Delay Minimization for Massive Mimo Based Cooperative Mobile Edge Computing System With Secure Offloading(IEEE, 2022) Mümtaz, Rao; Yılmaz, Simay; Özbek, BernaMobile 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.