WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Conference Object Citation - WoS: 2Citation - Scopus: 2Gezgin Rölelerin Dfbçe Tabanlı Hücresel Ağ Performansına Etkisi(Institute of Electrical and Electronics Engineers Inc., 2014) Baştürk, İlhan; Özbek, BernaOFDMA-based mobile relay enhanced cellular networks which have lower infrastructure cost and larger coverage areas are important technologies for the next generation communication systems since they allow to communicate at higher data rates. However, it is required to develop efficient radio resource management algorithms in order to reveal these advantages. Thus, in this study, relay selection and resource allocation algorithms are proposed for the mobile relay enhanced cellular networks. It is revealed that the number of satisfied users and the data rate of the cell-edge users that are far from the base station and have lower channel gains are increased by using mobile relays with the proposed algorithms.Article User-Relay Assisted Cellular Networks With Multiple Antennas(Taylor & Francis, 2019) Baştürk, İlhan; Özbek, BernaUser-relay assisted OFDMA-based cellular networks have gained great importance recently since these networks are indicated as one of the powerful technologies that will contribute the 5G standard. These networks can be used with novel three-phase frame structure unlike classical two-phase frame structure and can be enhanced with multiple antennas to utilise the advantages of them. The main advantage of the three-phase frame structure is taking care of the limitations of the current transceiver design in practical systems and not allowing users to be relay and user simultaneously. Diversity and capacity gains are also the advantages of extending the network with multiple antennas. In this paper, we will use the novel three-phase frame structure for downlink MISO-OFDMA cellular networks and develop resource management algorithms as relay selection and resource allocation to observe the benefits of this system.Conference Object Citation - Scopus: 1Interference Management for Multiuser Multiantenna Ofdma Underlaying Device-To Communications(IEEE, 2017) Özbek, Berna; Pischella, Mylene; Le Ruyet, DidierUnderlaying device-to-device (D2D) transmission in cellular wireless systems is one of the promising transmission techniques for fifth generation (5G) and beyond 5G applications. Nevertheless, the interference between the D2D pairs, the interference from cellular users to D2D receivers and the interference that affects the cellular communications should be mitigated to increase the overall system performance. In this paper, we propose interference management techniques for D2D underlaying communications in multiuser multiantenna orthogonal frequency division multiple access (OFDMA) systems. Our goal is to increase the data rate of both the cellular users and D2D pairs by performing interference management in frequency, power and spatial dimensions. The performance evaluations illustrate the effectiveness of the proposed algorithm in terms of average data rate and average transmitted power for both cellular users and D2D pairs.Conference Object Citation - WoS: 11Citation - Scopus: 17Resource Allocation for Underlaying Device-To Communications Using Maximal Independent Sets and Knapsack Algorithm(IEEE, 2018) Köse, Alper; Özbek, BernaIn this paper, we address the resource allocation problem of device-to-device (D2D) communications underlaying orthogonal frequency division multiple access (OFDMA) based cellular systems by exploiting the efficiency that comes from an ensemble of graph theory and Knapsack problem. It is possible to construct the conflict graph of the D2D pairs by finding the maximal independent sets. Then, we use those independent sets as inputs to Knapsack problem iteratively in order to find D2D groups which allocate the subchannels. In Knapsack problem, we consider a maximum interference level that the base station is exposed at each subchannel. We illustrate that the proposed resource allocation method significantly outperforms graph coloring in terms of average data rate for the high number of underlaying D2D pairs in cellular systems.Article Citation - WoS: 9Citation - Scopus: 10Radio Resource Management for User-Relay Assisted Ofdma-Based Wireless Networks(Urban und Fischer Verlag GmbH und Co. KG, 2016) Baştürk, İlhan; Özbek, BernaOrthogonal frequency division multiple access (OFDMA) based relay assisted networks are important for current and next-generation wireless networks since they have great potential to provide high data rate to users at anywhere, anytime. Towards that end, fixed relay assisted OFDMA networks are commonly utilized by the operators. However, they require supplementary costly infrastructure. User-relay assisted OFDMA-based networks are promising candidates to fulfill the demanding coverage and capacity requirements of future wireless networks in a cost efficient way. Thus, they have become popular as a complementary solution to fixed relay networks. Generic frame structure that divides the resource allocation frame into two subframes is mostly used in the literature for fixed and user-relay assisted networks in which it is assumed that a user can act as a destination and a relay simultaneously. However, it may be difficult to apply this assumption to practical systems because of the limitations of the current transceiver design. Thus, we propose a novel frame structure for user-relay assisted OFDMA-based wireless networks in order to cope with these drawbacks. The efficient radio resource management algorithms including relay selection and resource allocation are developed in order to exploit the opportunities of the proposed frame structure.Article Citation - WoS: 4Citation - Scopus: 7Adaptive Reduced Feedback Links for Distributed Power Allocation in Multicell Miso-Ofdma Networks(IEEE Computer Society, 2014) Özbek, Berna; Le Ruyet, Didier; Pischella, MyleneFor multi-antenna Orthogonal Frequency-Division Multiple Access (OFDMA) based multicell networks, the channel state information (CSI) of all users is required to share among base stations in order to perform distributed power allocation. However, the amount of feedback increases with the number of users, base stations, subcarriers and antennas. Therefore, it is important to perform a selection at the user side to reduce the feedback load and the complexity of resource allocation. In this letter, we propose adaptive reduced feedback links by choosing the users based on their approximate signal to interference noise ratio (SINR) and their locations in the cell to satisfy users' rate constraints. We illustrate the performance results of reduced feedback links by employing distributed resource allocation with link adaptation.