Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/11
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Article Citation - WoS: 10Citation - Scopus: 10Observer-Based Adaptive Output Feedback Tracking Control of Dynamically Positioned Surface Vessels(Springer Verlag, 2017) Bıdıklı, Barış; Tatlıcıoğlu, Enver; Zergeroğlu, ErkanIn this work, we propose an observer-based adaptive output feedback tracking controller for dynamically positioned surface vessels. Specifically, to remove the velocity measurement dependency of the control formulation a nonlinear, model-free observer formulation have been proposed. The proposed observer does not make use of the system dynamics and together with the proposed controller structure ensure that the tracking error signal and the velocity estimation error asymptotically converges to zero. Stability of the closed-loop system is ensured by Lyapunov-based arguments. Simulation studies are also presented to illustrate the effectiveness of the proposed method.Article Reduced Feedback Link Design for Devicerelaying Enhanced Multiple-Input Singleoutput Orthogonal Frequency-Division Multiple Access Wireless Systems(Institution of Engineering and Technology, 2016) Özbek, BernaDevice-relaying enhanced multiple-input single-output (MISO) orthogonal frequency-division multiple access (OFDMA) systems are one of the promising and cost-effective methods to satisfy data rate requirements of future wireless networks. To implement device relaying in MISO-OFDMA systems efficiently, the channel state information belonging to all links is required at the base station. However, the feedback load increases with the number of users, device-relay candidates, antennas and subcarriers. A novel scheduling and a joint feedback link design and relay selection algorithm in device-relaying enhanced downlink MISO-OFDMA systems are proposed, while reducing the feedback load significantly without sacrificing the system performance.Article Citation - WoS: 6Citation - Scopus: 9Adaptive Limited Feedback Links for Cooperative Multi-Antenna Multicell Networks(Springer Verlag, 2014) Özbek, Berna; Ruyet, Didier LeThe overall performance of cooperative networks is quite sensitive to channel state information (CSI) of serving and interfering base stations (BSs) and affected strongly by quality of limited feedback links. In this paper, we propose two adaptive limited feedback strategies for intercell interference cancelation in multi-antenna multicell networks. The first proposed strategy is developed to improve average multicell capacity assuming a fixed rate feedback link. This algorithm is based on adaptation of the number of bits to quantize CSI of serving and interfering BSs according to transmitter power and location of the user in its own cell. The second proposed strategy is designed in a way to increase average capacity of cell-edge users assuming an adaptive rate feedback link. This algorithm is based on the idea of allocating more bits to quantize CSI of users at cell-edge regions while allocating less bits for users near the serving BS. We illustrate performance of the proposed feedback links for downlink cooperative multi-antenna multicell networks in wireless channels.Conference Object Citation - Scopus: 2Sum Capacity Maximization in Distributed Multicell Miso-Ofdma Systems With Reduced Feedback Links(Institute of Electrical and Electronics Engineers Inc., 2014) Özbek, Berna; Le Ruyet, Didier; Pischella, MyleneIn this paper, we examine distributed and fair resource allocation for weighted sum multicell capacity maximization in multi-input single-output (MISO)-Orthogonal Frequency-Division Multiple Access (OFDMA) multicell systems with reduced feedback links. We apply zero forcing (ZF) precoding to reduce interference between the users in the same cell and then propose iterative distributed power allocation algorithm for the users with high signal-to-interference-plus-noise ratio (SINR) to reduce the interference between BSs. In order to perform distributed RA for MISO-OFDMA multicell systems, the channel state information (CSI) of all required links are fed back to all base stations. However, the feedback load increases with the number of users, base stations, subcarriers and antennas. Therefore, we propose a user selection algorithm at the receiver side to reduce the feedback load while providing CSI of the users with high SINR at the BSs. The performance results of the proposed algorithms are illustrated for multicell MISO-OFDMA systems in wireless channels. © 2014 IEEE.Conference Object Citation - WoS: 5Citation - Scopus: 5On Precoding Mimo-Fbmc With Imperfect Channel State Information at the Transmitter(Institute of Electrical and Electronics Engineers Inc., 2014) Le Ruyet, Didier; Zakaria, Rostom; Özbek, BernaThis paper studies the impact of imperfect channel state information (CSI) due to limited feedback link on the performance of multi-user MIMO system using filter bank based multicarrier (FBMC) modulation. The system is composed of a transmitter performing Zero Forcing (ZF) precoding and single antenna receivers applying decoding techniques. Simulation-based results show that except when the number of users is less than the number of transmit antennas, the BER performance and capacity of FBMC and OFDM modulation are the same. These results are theoretically justified due to the distribution of the interfering terms. As in OFDM, depending on the number of interferers, for a given BER performance target, the required number of feedback bits per channel vector can be rather high. FBMC becomes attractive not only because it relaxes the synchronization with respect to OFDM, but also because it achieves the same performance results as OFDM for multiuser MIMO precoding even in the case of imperfect CSI at the transmitter. © 2014 IEEE.