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Article Quality of Service Assessment: a Case Study on Performance Benchmarking of Cellular Network Operators in Turkey(2015) Kadıoğlu, Rana; Dalveren, Yaser; Kara, AliAbstract: This paper presents findings on performance benchmarking of cellular network operators in Turkey. Bench- marking is based on measurements of standard key performance indicators (KPIs) in one of the metropolitan cities of Turkey, Ankara. Performance benchmarking is formulated by incorporating customer perception by conducting surveys on how important KPIs are from the user s point of view. KPIs are measured, with standard test equipment, by drive test method on specified routes. According to the performance benchmarking results, the GSM and UMTS network operators achieving the best performance were determined in Ankara. Speech qualities of network operators, as the most popular service, were also evaluated by several statistical methods including pdf/cdf analysis and chi-square and Fisher s exact tests. The network operator providing the highest speech quality in Ankara was determined with the methods applied. Overall, the results and approaches on benchmarking of cellular networks in Turkey are reported for the first time in this paper. The approaches proposed in this paper could be adapted to wide-scale benchmarking of services in cellular networks.Article Citation - WoS: 5Citation - Scopus: 10Quality of Service Assessment: a Case Study on Performance Benchmarking of Cellular Network Operators in Turkey(Tubitak Scientific & Technological Research Council Turkey, 2015) Kadioglu, Rana; Dalveren, Yaser; Dalveren, Yaser; Kara, Ali; Kara, Ali; Dalveren, Yaser; Kara, Ali; Department of Electrical & Electronics Engineering; Department of Electrical & Electronics EngineeringThis paper presents findings on performance benchmarking of cellular network operators in Turkey. Benchmarking is based on measurements of standard key performance indicators (KPIs) in one of the metropolitan cities of Turkey, Ankara. Performance benchmarking is formulated by incorporating customer perception by conducting surveys on how important KPIs are from the user's point of view. KPIs are measured, with standard test equipment, by drive test method on specified routes. According to the performance benchmarking results, the GSM and UMTS network operators achieving the best performance were determined in Ankara. Speech qualities of network operators, as the most popular service, were also evaluated by several statistical methods including pdf/cdf analysis and chi-square and Fisher's exact tests. The network operator providing the highest speech quality in Ankara was determined with the methods applied. Overall, the results and approaches on benchmarking of cellular networks in Turkey are reported for the first time in this paper. The approaches proposed in this paper could be adapted to wide-scale benchmarking of services in cellular networks.Article Citation - WoS: 8Citation - Scopus: 15Distributed denial-of-service attack mitigation in network functions virtualization-based 5G networks using management and orchestration(Wiley, 2021) Koksal, Sarp; Dalveren, Yaser; Maiga, Bamoye; Kara, AliThe fifth generation (5G) technology is expected to allow connectivity to billions of devices, known as Internet of Things (IoT). However, IoT devices will inevitably be the main target of various cyberattack types. The most common one is known as distributed denial-of-service (DDoS) attack. In order to mitigate such attacks, network functions virtualization (NFV) has a great potential to provide the benefit of elasticity and low-cost solutions for protecting 5G networks. In this context, this study proposes a new mechanism developed to mitigate DDoS attacks in 5G NFV networks. The proposed mechanism utilizes intrusion prevention system's (IPS) virtual machines (VMs) to intercept the queries. Based on the volume of DDoS traffic, IPS's VMs are dynamically deployed by means of management and orchestration (MANO) in order to balance the load. To evaluate the effectiveness of the mechanism, experiments are conducted in a real 5G NFV environment built by using 5G NFV environment tools. To our best knowledge, this is the first time that NFV-based mechanism is experimentally tested in a real 5G NFV environment for mitigating DDoS attacks in 5G networks. The experimental results verify that the proposed mechanism can mitigate DDoS attacks effectively.Article Citation - WoS: 6Citation - Scopus: 7An Enhanced Course in Digital Communications(Tempus Publications, 2014) Kara, Ali; Cagiltay, Nergiz Ercil; Dalveren, Yaser; Department of Electrical & Electronics Engineering; Software EngineeringToday technological improvements provide several alternatives and opportunities for improving traditional educational systems. However, integrating these technologies in an appropriate and successful way into the curriculum of traditional systems is a challenge. This work presents the enhancements added to an undergraduate course on Digital Communications which is an introductory course offered to senior undergraduates or first year graduate students. The Digital Communications course covers some essential stages in a typical digital communication system, namely, signal formatting such as analog to digital conversion, baseband modulation and bandpass modulation by concentrating on demodulation and detection at the receiver end. The enhancements include computer simulations, web-based simulation tools and remote laboratory experiments along with several out of class activities. The enhancements have improved the course significantly by supporting constructivist and blended learning methods. The improvement to the course was demonstrated over two years, from the student progress assessed from the collated results of the student evaluation forms and a questionnaire on the course learning outcomes, and a comparison of their performance in the written exams. The results show that there is a significant improvement both in the progress and satisfaction of the students on the enhanced course curriculum. This study shows how different technologies have been successfully integrated to the curriculum of Digital Communications course in a higher education organization and concludes its success factors.Article Citation - WoS: 5Citation - Scopus: 8Optimal Operation Mode Selection for Energy-Efficient Light-Weight Multi-Hop Time Synchronization in Linear Wireless Sensor Networks(Springer, 2020) Al Imran, Md Abdullah; Dalveren, Yaser; Tavli, Bulent; Kara, AliWe explored the joint effect of synchronization window and offset/drift mode selection on the time synchronization of linear wireless sensor networks (LWSNs). Recent advances in the field along with the availability of capable hardware led to adoption of LWSNs in diverse areas like monitoring of roads, pipelines, and tunnels. The linear topology applications are susceptible to single point of failure; therefore, energy efficient operation of LWSNs is even more important than the traditional WSNs. To address the challenge, we investigate the time synchronization mode selection for the optimum operation of a multi-hop and low-overhead LWSN. We investigate two modes of synchronization: synchronization by using only offset and synchronization by using offset in addition to the clock drift. Furthermore, we investigate the effects of synchronization window size. Our experimental results reveal that computation of offset alone for smaller window sizes and resynchronization periods is sufficient in achieving acceptable degree of synchronization.Article Citation - WoS: 18Citation - Scopus: 19Performance Analysis of Modular Rf Front End for Rf Fingerprinting of Bluetooth Devices(Springer, 2020) Uzundurukan, Emre; Ali, Aysha M.; Dalveren, Yaser; Kara, AliRadio frequency fingerprinting (RFF) could provide an efficient solution to address the security issues in wireless networks. The data acquisition system constitutes an important part of RFF. In this context, this paper presents an implementation of a modular RF front end system to be used in data acquisition for RFF. Modularity of the system provides flexible implementation options to suit diverse frequency bands with different applications. Moreover, the system is able to collect data by means of any digitizer, and enable to record the data at lower frequencies. Therefore, proposed RF front end system becomes a low-cost alternative to existing devices used in data acquisition. In its implementation, Bluetooth (BT) signals were used. Initially, transients of BT signals were detected by utilizing a large number of BT devices (smartphones). From the detected transients, distinctive signal features were extracted. Then, support vector machine (SVM) and neural networks (NN) classifiers were implemented to the extracted features for evaluating the feasibility of proposed system in RFF. As a result, 96.9% and 96.5% classification accuracies on BT devices have been demonstrated for SVM and NN classifiers respectively.
