Browsing by Author "Ulgen, Oguz"

Now showing 1 - 6 of 6

Citation - Scopus: 1
Busy Tone Based Power Control For Coordination Of Ieee 802.11af And 802.22 System [ıeee 802.11af ve 802.22 Sistemlerinin Uyumlu Çalışmaları için Meşgul Ton Tabanlı Güç Kontrolü]
(Institute of Electrical and Electronics Engineers Inc., 2017) Ulgen, Oguz; Baykaş, Tunçer; Erküçük, Serhat; Erküçük, Serhat; Karatalay, Onur; Baykaş, Tunçer
In this paper a new power control algorithm based on busy tone approach has been proposed for the coordination of IEEE 802.22 and IEEE 802.11af systems in TV white space. Different from the earlier studies in addition to both 802.11af access point and clients listening to the busy tone they also adjust their communication power according to the location information and use hopping for communication if needed. Acccordingly interference caused to 802.22 systems has been reduced while the 802.11af systems are still able to communicate. This study quantifies the 802.11af and 802.22 system performances in terms of interfering packet rate and succesful packet transmission rate for different scenarios considering the communication parameters and channel models adapted for the standards. © 2017 IEEE.
Citation - WoS: 0
Citation - Scopus: 0
A Comparative Analysis of Diversity Combining Techniques for Repetitive Transmissions in Time Spreading Scma Systems
(John Wiley & Sons Ltd, 2024) Ulgen, Oguz; Şadi, Yalçın; Tufekci, Tolga Kagan; Erküçük, Serhat; Sadi, Yalcin; Baykaş, Tunçer; Erkucuk, Serhat; Anpalagan, Alagan; Baykas, Tuncer
Sparse Code Multiple Access (SCMA) is a recently introduced wireless communication network technology. There are various techniques in SCMA systems to increase the system's efficiency, and one of these techniques is time spreading. By adding repetitive transmission and time spreading into SCMA, it is shown in previous works that the Bit-Error-Rate (BER) results are improved convincingly. However, in the previous works, other diversity combining techniques have not been considered. This paper introduces a new approach to further improve the performance of repetitive transmission in SCMA systems with time spreading by adding imperialist competitive algorithm in diversity combining. Alongside, four different combining techniques; equal gain combining, maximal ratio combining, selection combining, and genetic algorithm are considered to bring comparative analysis to show the significance of the new technique. Results show that the proposed method offers up to 2.3 dB gain in terms of BER, under certain conditions.
Citation - WoS: 1
Citation - Scopus: 2
A New Approach for Coexistence of Ieee 802.11af and Ieee 802.22 Systems
(Institute of Electrical and Electronics Engineers Inc., 2018) Ulgen, Oguz; Baykaş, Tunçer; Baykaş, Tunçer; Erküçük, Serhat; Erküçük, Serhat
In this paper various algorithms are proposed to help IEEE 802.11af and IEEE 802.22 wireless systems to coexist in TV white space by considering multiple techniques. By using busy tone power control and multihop communication techniques improvements have been made compared to prior approaches. With this approach while IEEE 802.22 systems are protected from intra-network interference IEEE 802.11af systems are still able to continue transmitting packets. Considering the communication parameters and channel models compliant for the standards IEEE 802.11af and IEEE 802.22 system performances are investigated in terms of interfering packet rate and successful packet transmission rate for different scenarios and the improved results are presented. © 2018 IEEE.
Citation - WoS: 0
Citation - Scopus: 0
Performance of Scma Systems in Fast-Fading Channels
(Ieee, 2022) Erküçük, Serhat; Baykaş, Tunçer; Erkucuk, Serhat; Baykas, Tuncer
In order to satisfy the need for high data rate and high number of users, new generation communication techniques are developed. One of the techniques that may be used in future generation communication networks is Sparse Code Multiple Access (SCMA). With this new technique, the aim is to allocate users frequency resources in a non-orthogonal way by using code books. For this new technique, which is has a potential to be used in 5G and beyond communication networks, most researches have focused on flat fading channels and related results have been provided. In this work, different from earlier studies, fast fading channels have been considered for channels varying at different rates, and bit-error performance results have been provided with computer simulations.
Power Control and Multihop Communication Approaches for the Coexistence of Ieee 802.11af and Ieee 802.22 Networks in Tv White Space
(Kadir Has Üniversitesi, 2017) Ulgen, Oguz; Erküçük, Serhat; Erküçük, Serhat
Communication networks have been among the most important research fields of scientists in the recent years. Researches have been conducted in various different topics and contents as technology has evolved. As some new technologies become available some technologies become out of date. One of the outdated technologies in recent years is the analog TV broadcasting. With the shift from analog TV broadcasting to digital TV broadcasting the frequency bands of old analog TV broadcasting has become available for the implementation of new technologies. This spectrum is called TV White Space (TVWS). Due to wide coverage and good signal transmission properties in TVWS researchers and engineers have focused on developing standards for this valuable spectrum. Within the same period of time another new technology based on cognitive radios has been investigated and implemented. Among the standards and technologies developed for TV White Space one focus area has been to allow the access of unlicensed (secondary) users to the spectrum. Even though solutions for protecting the licensed (primary) users has been successful researches for protecting the secondary users in coexistence have not given conclusive results. Several of these researches are on the coexistence of iEEE 802.22 wireless regional area network and iEEE 802.11af wireless local area network. However due to the nature of two heterogeneous networks not communicating with each other there is a need for further coexistence mechanisms. in this thesis different from the earlier works busy tone based power control and multihop communication algorithms are implemented for different coexistence scenarios of iEEE 802.22 and iEEE 802.11af. interfering packet rate results and successful packet transmission rate results obtained via computer simulations and improved results are presented. in addition interfering packet rate results and successful packet transmission rate results are presented under realistic channel models ii and log-normal shadowing. The presented results are important to improve the results of existing busy tone based approaches.
Citation - WoS: 0
Citation - Scopus: 0
Sparse Code Multiple Access With Time Spreading and Repetitive Transmissions
(Wiley, 2025) Ulgen, Oguz; Tufekci, Tolga Kagan; Sadi, Yalcin; Erkucuk, Serhat; Anpalagan, Alagan; Baykas, Tuncer
For the next-generation communication systems, to improve spectral efficiency and increase the data rate, new multiple access techniques have been investigated. Orthogonal multiple access techniques are widely used in traditional communication systems while nonorthogonal multiple access (NOMA), proposed in 5G, has been a promising technology for satisfying the demand for future wireless communication networks. Sparse code multiple access (SCMA) is a code-domain NOMA method that provides diversity gain with signal constellation coding. However, to increase the performance of SCMA, there are only limited works provided in the literature in terms of codebook design and receiver design. In this paper, a new multiple-access model is proposed by applying various diversity techniques for downlink SCMA. The performance of the proposed model is evaluated with both computer simulations and theoretical analysis. Results show that the proposed model provides a 1.6 dB gain in terms of the bit error rate (BER) under the Rayleigh fading channel.