Browsing by Author "Namdar, Mustafa"

Now showing 1 - 9 of 9

BER performance analysis for downlink NOMA systems over cascaded Nakagami-m fading channels
(Springer Int Publ Ag, 2023-11-24) Koçak, Fatih; Namdar, Mustafa; Başgümüş, Arif; BAŞGÜMÜŞ, ARİF; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik ve Elektronik Mühendisliği Bölümü.; 0000-0002-0611-3220; E-9497-2015
In this study, the downlink non-orthogonal multiple access (NOMA) system in which successive interference cancellation (SIC) errors exist is discussed. The new closed-form expressions for the bit error rate (BER) performance analysis over cascaded Nakagami-m fading channels are analytically derived for near and far users. In addition, new mathematical equations are obtained for the asymptotic BER as well as the diversity order to analyze the system performance. The theoretical results precisely match the simulations in all cases, validating the effectiveness of the theoretical analysis. The results demonstrate that the system performance decreases as the degree of N cascading increases. As for a fixed degree of cascading, BER performance increases as the m parameter increases. Moreover, for the power allocation coefficient alpha influences the SIC operation performed on the near user, it also substantially affects the BER performance. Monte Carlo simulations using 10(6) iterations are presented to validate the derived analytical results.
Ber performance analysis for noma systems with otfs modulation
(Ieee, 2023-01-01) Umakoğlu, İnci; Namdar, Mustafa; Özyurt, Serdar; Kulaç, Selman; Başgümüş, Arif; BAŞGÜMÜŞ, ARİF; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik ve Elektronik Mühendisliği Bölümü.; 0000-0002-0611-3220; 0000-0002-7737-1569; JFJ-2682-2023; KWU-5570-2024; E-9497-2015; I-1158-2016
This study examines the non-orthogonal multiple access (NOMA) system that is modulated with orthogonal time-frequency-space (OTFS), which is a potential waveform candidate that is frequently used in sixth-generation (6G) wireless communication networks and is shown to improve performance in high mobility scenarios. In the proposed OTFS modulated NOMA system, bit error rate performance for near and far users is presented with the help of the message passing detection algorithm.
Ergodic capacity estimation with artificial neural networks in noma-based cognitive radio systems
(Springer Heidelberg, 2023-09-21) Namdar, Mustafa; Güney, Abdulkadir; Bardak, Fatma Kebire; Basgümüş, Arif; BAŞGÜMÜŞ, ARİF; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik ve Elektronik Mühendisliği Bölümü.; E-9497-2015
The aim of this study is to predict the total ergodic capacity of near users in a cognitive radio (CR)-based non-orthogonal multiple access (NOMA) system model using the proposed artificial neural network (ANN) architecture. The input dataset used in this study was collected from the CR-NOMA system model and consists of the path loss coefficient, power allocation coefficient, signal-to-noise ratio, the distance between the source-relay-destination, and the ratio of the power of the secondary user to that of the primary user. Using a supervised learning method, the output data are trained and input into the ANN to estimate the ergodic capacity of nearby users using test data. The trained system model demonstrates an accuracy of 96.43% for training data, 96.34% for validation data, and 95.66% for test data when estimating the total ergodic capacity.
Irs-aided communication systems in the presence of multiple eavesdroppers
(Ieee, 2023-01-01) Namdar, Mustafa; Alakoca, Hakan; Ata, Serdar Özgür; Durak-Ata, Lütfiye; Basgümüş, Arif; BAŞGÜMÜŞ, ARİF; 0000-0002-0611-3220; 0000-0002-4368-2967; E-9497-2015; IWV-3354-2023; I-1158-2016; AAC-4912-2020
In this study, the performance analysis of secrecy capacity and secrecy outage probability in the presence of multiple eavesdroppers that cooperate (colluding) and do not cooperate (non-colluding) with each other, respectively, is studied for the intelligent reflective surfaces (IRS) assisted communication system model in urban wireless networks. In both approaches, realistic security problems and solutions regarding the system model related to physical layer security for legitimate users, designed with the help of the IRS, are evaluated.
Metasurface manipulation attacks: Potential security threats of ris-aided 6g communications
(IEEE-inst Electrical Electronics Engineers Inc, 2023-01-01) Alakoca, Hakan; Namdar, Mustafa; Aldırmaz-Çolak, Sultan; Başaran, Mehmet; Başgümüş, Arif; Durak-Ata, Lütfiye; Yanıkomeroğlu, Halim; BAŞGÜMÜŞ, ARİF; Bursa Uludağ Üniversitesi; E-9497-2015
The physical layer security (PLS) of reconfigurable intelligent surfaces (RIS) is critical for providing secure and reliable communications in sixth generation (6G) wireless systems. This article contributes to a debate on many aspects of unique vulnerabilities that can arise in the PLS of RIS with malicious attacks on signal processing (SP) in 6G networks. We address and categorize future security threats in RIS-aided networks considering PLS aspects. Metasurface manipulation attacks (MSMA) are based on manipulating metasurface behavior for malicious purposes. In this study, we present the potential hostile activities of MSMA considering the impact of electromagnetic and time-frequency deterioration. In addition, we evaluate various interference-based MSMA and eavesdropping booster-based MSMA (EaB-MSMA), which are novel potential PLS attacks that involve manipulating phase shifting activity with SP on malicious RIS. We also compare performance degradation in the presence of hostile interference-based MSMA through the manipulation of maliciously configured RIS. Additionally, in the EaB-MSMA case, the loss of secrecy capacity is shown to be considerably greater in passive eavesdropping scenarios.
NOMA tabanlı bilişsel radyo sistemlerinde sinir ağı yöntemleri ile ergodik kapasite tahmini ve başarım analizi
(Bursa Uludağ Üniversitesi, 2023-01-24) Namdar, Mustafa; Güney, Abdulkadir; Bardak, Fatma Kebire; Başgümüş, Arif; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik Elektronik Mühendisliği Bölümü.; 0000-0002-0611-3220
Bu çalışmada, bilişsel radyo (BR) tabanlı dikgen olmayan çoklu erişim tekniği (NOMA) kullanılarak, yakın kullanıcıya ait toplam ergodik kapasite değerinin, önerilen ileri beslemeli geri yayılımlı yapay sinir ağı (YSA) ve doğrusal olmayan dışsal girdili otoregresif ağ (Nonlinear Autoregressive Network with Exogenous Inputs, NARX) modeli ile farklı eğitim algoritmaları yoluyla yüksek doğruluk oranında ve hızlı eğitim sürelerinde tahmin edilmesi amaçlanmıştır. Sinir ağında kullanılan veri seti, üstel sönümleme kanalı karakteristiği ile modellenen BR-NOMA sistem modelinden elde edilmiştir. Denetimli öğrenme yöntemi kullanılarak tasarlanan YSA’ya girdi ve çıktı verileri öğretilerek yakın kullanıcıya ait ergodik kapasite tahmini yapılmıştır. YSA ve NARX sinir ağları başarımı değerlendirilirken eğitim süresi, iterasyon sayısı, ağın doygunluğa ulaşmaması durumları göz önünde bulundurulmuştur. Yakın kullanıcıya ait gerçek ergodik kapasite değeri ile ileri beslemeli geri yayılımlı YSA ve NARX ağlarının tahmin etmiş olduğu değerler karşılaştırılmıştır. Önerilen sinir ağlarının Levenberg-Marquardt, Bayesian ve Scaled-Conjugate eğitim algoritmaları altındaki performans analizi, hatanın minimuma ulaştığı epok değer grafiği, hata histogram analizi ve eğitim durum analizi açılarından incelenmiştir.
Optimum transmission distance for relay-assisted free-space optical communication systems
(Elsevier, 2016-04-16) Başgümüş, Arif; Hiçdurmaz, Bahadır; Temurtaş, Hasan; Namdar, Mustafa; Altuncu, Ahmet; Yılmaz, Güneş; Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik-Elektronik Mühendisliği Bölümü.; 7004543197
In this paper, optimum transmission distances are obtained for different relay nodes in the serial and parallel decode-and-forward relaying schemes by using differential evolution algorithm in free-space optical communication systems. The transmission distances are investigated by optimizing the place of the relay nodes at a target outage probability of 10(-6). In this study, the numerical results reveal that the optimum transmission distances are increased for both the whole power margins and different number of relay nodes with the help of the proposed optimization technique.
Performance comparison of the differential evolution and particle swarm optimization algorithms in free-space optical communications systems
(Univ Suceava, 2015) Başgümüş, Arif; Namdar, Mustafa; Altuncu, Ahmet; Yılmaz, Günes; Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik-Elektronik Mühendisliği Bölümü.; 0000-0001-8972-1952; AAH-4182-2021; 7004543197
In this comparative study we evaluate the performance of Differential Evolution (DE) and Particle Swarm Optimization (PSO) algorithms in free space optical communications systems. In particular we obtain the optimal transmission distances for different relay nodes in the parallel decode-and-forward relaying schemes by optimizing the relay placements. We analyze that the cost functions are suitably minimized. Then we investigate the execution time and the stability of the DE and PSO algorithms for decode-and-forward relay-assisted free space optical links. The simulation results demonstrate that the PSO algorithm outperforms DE algorithm in terms of the minimization of the cost function. Furthermore the results indicate that we get the similar performance for the execution-time and optimization results in the DE and PSO algorithms.
UAV-assisted cooperative NOMA system with the nth Best Relay Selection
(Univ Suceava, 2023-08-01) Umakoğlu, İnci; Namdar, Mustafa; Başgümüş, Arif; BAŞGÜMÜŞ, ARİF; Bursa Uludağ Üniversitesi/Mühendislik Fakültesi/Elektrik-Elektronik Mühendisliği Bölümü.; 0000-0002-0611-3220; E-9497-2015
We propose a downlink non-orthogonal multiple access (NOMA) architecture with a source, N one-way unmanned aerial vehicle (UAV) relays, and K destination users where the amplify-and-forward protocol is considered with the partial relay selection strategy. Then, we derive closed-form expressions for the bit error probability (BEP) of the NOMA users over the Rayleigh fading channel. This research investigated the selection of the nth best available UAV relay while presenting the bit error rate (BER) performance of a NOMA system. In addition, we analyze the diversity order and develop an asymptotic closed-form expression of the BEP in the high signal-to-noise ratio regime. To verify the accuracy of the analytical study of BER, numerical results are also provided taking into account the number of UAV relays, path loss exponent, power allocation coefficient, and channel gains. Finally, we validate that the simulation results precisely match our proposed theoretical analysis.