Browsing by Author "Le Ruyet, Didier"

Now showing 1 - 20 of 36

Citation - Scopus: 2
Adaptive Bit Partitioning Strategy for Cell-Edge Users in Multi-Antenna Multicell Networks
(Institute of Electrical and Electronics Engineers Inc., 2011) Özbek, Berna; Le Ruyet, Didier
In this paper, we improve the performance of cell-edge users by applying adaptive bit partitioning for intercell interference cancelation in cooperative downlink multicell systems. The strategy for partitioning quantization bits between serving and interfering base stations affects the performance of the cooperative networks which is quite sensitive to the quality of the channel state information. The existing transmission strategies are based on the maximization of average cell rate which results in a reduced rate for the users in the cell-edge regions. We propose an adaptive bit partitioning strategy to improve the rate of cell-edge users at the same average feedback link rate. We show the performance of the cell-edge users is significantly increased while keeping the same average cell rate. © 2011 IEEE.
Citation - Scopus: 5
Adaptive Limited Feedback for Intercell Interference Cancelation in Cooperative Downlink Multicell Networks
(Institute of Electrical and Electronics Engineers Inc., 2010) Özbek, Berna; Le Ruyet, Didier
In this paper, we evaluate intercell interference cancelation techniques in cooperative downlink multicell systems. We compare two classical beamforming strategies for the design of the beamforming vectors: maximum ratio combining precoding and partial zero-forcing. Since full channel state information at the transmission is unfeasible, we consider a limited feedback link and compare different strategies for bit partitioning of the feedback information for serving and interferer base stations. We propose a simple adaptive bit partitioning strategy to select an optimum transmission scheme at the base station. We show that the adaptive bit portioning algorithm is improved the sum capacity performance of the multicell networks significantly.
Citation - WoS: 4
Citation - Scopus: 7
Adaptive Reduced Feedback Links for Distributed Power Allocation in Multicell Miso-Ofdma Networks
(IEEE Computer Society, 2014-04) Özbek, Berna; Le Ruyet, Didier; Pischella, Mylene
For 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.
Citation - WoS: 6
Citation - Scopus: 11
Adaptive Resource Allocation for Multicast Ofdm Systems With Multiple Transmit Antennas
(Institute of Electrical and Electronics Engineers Inc., 2006) Özbek, Berna; Le Ruyet, Didier; Khiari, Hajer
We evaluate the impact of multiple transmit antennas on the performance of multicast OFDM systems by proposing a suboptimal low complexity algorithm. Associated with a powerful erasure code, it is possible to increase the data rate of multicast OFDM systems by selecting for each subcarrier to the users with a good channel condition. We show that the resource allocation which includes the precoding vector selection, subcarrier allocation and bit loading is a difficult optimization problem. We propose a suboptimal algorithm to solve this problem by avoiding the optimization to reduce complexity. When the users are not symmetrically distributed around the base station, we add a fair scheduler to guarantee that each user receives the same amount of data. We present simulation results where we compare the proposed multicast systems with the classical multicast OFDM systems. When the users are symmetrically distributed around the base station, the gain is rather small, whereas when the users are non-symmetrically distributed, the proposed algorithm outperforms OFDM systems with subcarrier allocation.
Citation - WoS: 2
Citation - Scopus: 2
Adaptive Resource Allocation for Sdma-Ofdma Systems With Genetic Algorithm
(Institute of Electrical and Electronics Engineers Inc., 2009) Özbek, Berna; Le Ruyet, Didier
In this paper, we propose an adaptive resource allocation algorithm to maximize the sum data rate for spatial division multiplexing access (SDMA) orthogonal division multiple access (OFDMA) systems using genetic algorithm. We perform Zero forcing (ZF) beamforming at the transmitter constructing single and multiple beams for OFDMA systems with multiple transmit antennas. In order to reduce the complexity and convergence time of genetic algorithm (GA), we present an initial condition obtained by allocating the user to the subcarrier with maximum precoding gain. The proposed algorithm reduces the complexity without sacrificing the performance. We obtain the simulation results and compare them with the classical static and adaptive allocation methods. We show that the GA with the proposed initial condition increases the sum data rate compared to classical GA and reduces the convergence time significantly for SDMA-OFDMA systems.
Citation - WoS: 20
Citation - Scopus: 28
Breadth First Algorithms for App Detectors Over Mimo Channels
(Institute of Electrical and Electronics Engineers Inc., 2004) Le Ruyet, Didier; Bertozzi, Tanya; Özbek, Berna
For iterative decoding of multiple antenna systems concatenated with an outer error correcting code, it is important to use an a posteriori probability detector for the MIMO detection to achieve near capacity performance. To avoid full APP detection, we propose a reduced complexity detector based on breadth first algorithms. Although these algorithms are sub-optimal, we show that they can provide a good list of candidates for the APP calculation. Furthermore, by exploiting the a priori information delivered from the outer decoder, it is possible to decrease the MIMO detector complexity at each iteration. Using simulation results, we will compare the performance of the proposed detectors with the list sphere detector.
Citation - WoS: 2
Citation - Scopus: 2
Deep Learning Based Adaptive Bit Allocation for Heterogeneous Interference Channels
(Elsevier, 2021) Aycan, Esra; Özbek, Berna; Le Ruyet, Didier
This paper proposes an adaptive bit allocation scheme by using a fully connected (FC) deep neural network (DNN) considering imperfect channel state information (CSI) for heterogeneous networks. Achieving an accurate CSI has a crucial role on the system performance of the heterogeneous networks. Different quantization techniques have been employed to reduce the feedback overhead. However, the system performance cannot increase linearly with the number of bits increasing exponentially. Since optimizing the total number of bits is too complex for the entire network, an initial step is performed to distribute the bits to each cell in the conventional method. Then, the distributed bits are further allocated to each channel optimally. In order to enable direct allocation for the entire network, a FC-DNN based method is presented in this study. The optimized number of bits can be directly obtained for a different number of bits and scenarios by the proposed approach. The simulations are performed by using various scenarios with different allocation schemes. The performance results show that the DNN based method achieves a closer performance to the conventional approach. (C) 2021 Elsevier B.V. All rights reserved.
Citation - WoS: 7
Citation - Scopus: 8
Dynamic Shared Spectrum Allocation for Underlaying Device-To Communications
(Institute of Electrical and Electronics Engineers Inc., 2017-10) Özbek, Berna; Pischella, Mylene; Le Ruyet, Didier
This article provides an overview on spectrum sharing in D2D underlaying communications for 5G and beyond 5G applications. Various spectrum sharing algorithms are summarized within a framework of underlaying D2D communications in cellular networks to increase spectrum efficiency. Dynamic spectrum sharing algorithms in the frequency, power, and spatial dimensions are proposed for underlaying D2D communications with both single antenna and multiple antennas at the base station. Performance evaluations show the effectiveness of the proposed algorithms in terms of average data rate per D2D pair.
Citation - WoS: 13
Citation - Scopus: 22
Energy Efficient Resource Allocation for Underlaying Multi-D2d Enabled Multiple-Antennas Communications
(Institute of Electrical and Electronics Engineers Inc., 2020-06) Özbek, Berna; Pischella, M.; Le Ruyet, Didier
Energy efficiency has a significant importance to optimize the wireless communications systems by providing high data rates. In order to develop energy efficient systems, one of the promising methods is to use multiple device-to-device (D2D) underlaying multiple antenna cellular systems. The interference from cellular users to D2D pairs, the interference between D2D pairs and the interference at the base station (BS) caused by D2D pairs occur in these communications systems. In this article, we propose energy efficient resource allocation algorithms for underlaying multi-D2D enabled multiple-antennas communications by employing different multiple antenna processing techniques at the BS. A joint method based on Dinkelbach algorithm and Message Passing Algorithm (MPA) and an approach based on deep learning with multi-layer artificial neural network are proposed to maximize the global energy efficiency (GEE) while satisfying the data rate requirements of both cellular users and D2D pairs. In MPA, the factor graph of the D2D pairs is constructed by taking into account the interference among the D2D pairs and the interference level at the BS to avoid any interruption in the cellular transmission. By relying on the training based on the proposed joint algorithm, a deep neural network approach is presented for off-line implementation. The performance results of the proposed energy efficient resource allocation algorithms show the superiority of multi-D2D communications over conventional single-D2D communications. © 1967-2012 IEEE.
Erratum To: on Stream Selection for Interference Alignment in Heterogeneous Networks
(Springer Verlag, 2016) Aycan, Esra; Özbek, Berna; Le Ruyet, Didier
Citation - Scopus: 17
Feedback Strategies for Wireless Communication
(Springer, 2014) Özbek, Berna; Le Ruyet, Didier
This book explores the different strategies regarding limited feedback information. The book analyzes the impact of quantization and the delay of CSI on the performance. The author shows the effect of the reduced feedback information and gives an overview about the feedback strategies in the standards. This volume presents theoretical analysis as well as practical algorithms for the required feedback information at the base stations to perform adaptive resource algorithms efficiently and mitigate interference coming from other cells. © 2014 Springer Science+Business Media New York. All rights are reserved.
Citation - Scopus: 2
Genetik Algoritma ile Çok Kullanıcı Dfbç Sistemleri için Toplam Veri Hızı Enbüyüklemeli Uyarlanır Alttaşıyıcı ve Bit Yerleşimi
(Institute of Electrical and Electronics Engineers Inc., 2008) Özbek, Berna; Le Ruyet, Didier
In this work, we perform the adaptive subcarrier and bit allocation to maximize the sum data rate for multiuser OFDM systems using genetic algorithm. Since the convergence time of the genetic algorithm could be slow, we propose to use a different initial condition to accelerate it without increasing the complexity of genetic algorithm and sacrificing the performance of the system. We obtain the simulation results and compare them with the classical methods. We show that the genetic algorithm with proposed initial condition gives better performances than the classical ones for sum data rate maximized allocation.
Citation - WoS: 2
Citation - Scopus: 3
Heterojen ağlarda iyileştirilmiş veri katarı seçimi ile girişim hizalama
(IEEE, 2015) Le Ruyet, Didier; Aycan, Esra; Özbek, Berna
In this article, interference that occurs in heterogeneous networks is studied and a new stream selection approach with an interference alignment solution is presented. In the proposed algorithm, stream selection starts with the streams that belongs to the pico cell users and continues to select the strongest streams that increase the total sum rate. The power of each stream with the precoding and the postcoding vectors are calculated by performing singular value decomposition (SVD). Virtual channels that belong to the selected stream are calculated by using precoding and postcoding vectors. After the selection procedure, the interferences between the selected stream and the remaining streams are mitigated by orthogonally projecting the channel matrices of the remaining streams to the virtual channels of the selected stream.
Heterojen Ağlarda Veri Katarı Seçimi Tabanlı Girişim Hizalama için Uyarlamalı Sınırlı Geri Besleme Yöntemi
(Institute of Electrical and Electronics Engineers Inc., 2016) Aycan, Esra; Özbek, Berna; Le Ruyet, Didier
Bu bildiride, sınırlı geri beslemeli heterojen ağlar için veri katarı seçimi tabanlı bir girişim hizalama yöntemi sunulmuştur. Sunulan veri katarı seçimi yöntemi, veri katarlarını ilk olarak piko kullanıcılarından seçmeye başlar, daha sonra veri hızını artıran en güçlü veri katarı ile seçim işlemi devam eder ve tüm kullanıcıların en az bir veri katarının olması sağlanır. Seçim işleminden sonra, seçilen veri katarı ile diğerleri arasında oluşan girişimler ortogonal projeksiyonlarla önlenir. Sınırlı geri beslemeli kanalda toplam kapasite, uyarlanır bit paylaşımıyla iyileştirilmektedir.
Citation - WoS: 5
Citation - Scopus: 3
Hierarchical Successive Stream Selection for Heterogeneous Network Interference
(Institute of Electrical and Electronics Engineers Inc., 2014) Aycan, Esra; Özbek, Berna; Le Ruyet, Didier
This paper presents a hierarchical stream selection approach to deal with the interference in a heterogeneous network where different cell types are coexisting with each other to increase the sum capacity. Due to the variety of the transmit powers between the macro and small cells, interference levels are different. The proposed solution hierarchically selects the strongest streams of each cell with a contribution to the sum rate, while constructing the streams via singular value decomposition (SVD). In order to reduce the interference, the channel matrices of the remaining streams are projected orthogonally to the virtual transmit channel and virtual receive channel of the selected stream. The performance evaluations are obtained by considering different locations of small cells with respect to the macro cell. It is shown that the proposed method can dynamically select more streams in heterogeneous networks and achieve higher data rates compared to the existing algorithms. © 2014 IEEE.
Citation - Scopus: 3
Improved Successive Stream Selection With Quantized Channel in Heterogeneous Networks
(Institute of Electrical and Electronics Engineers Inc., 2015) Aycan, Esra; Özbek, Berna; Le Ruyet, Didier
This paper focuses on different distortion metrics in order to analyze the influence of the imperfect channel state information (CSI) on the improved successive stream selection algorithm that manages the interference in a heterogeneous network. The presented approach initially selects the streams from the user of the pico cell, continuing with the strongest streams among the remaining streams that increase the sum rate and satisfy the constraint that at least one stream is selected from each user. In order to reduce the interference, the channel matrices of the remaining streams are projected orthogonally to the virtual transmit and receive channels of the selected stream. The impact of the quantization distortion on the precoding and postcoding design is examined. The performance of two distortion metrics which are the Chordal distance and the Euclidean distance are compared for different number of quantization bits. The performance evaluations are obtained by considering different locations of small cells with respect to the macro cell.
Citation - Scopus: 1
Interference Management for Multiuser Multiantenna Ofdma Underlaying Device-To Communications
(IEEE, 2017) Özbek, Berna; Pischella, Mylene; Le Ruyet, Didier
Underlaying 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.
Citation - WoS: 1
Citation - Scopus: 1
Interference-Based Clustering for Mimo D2d Underlay Communications
(IEEE, 2018) Pischella, Mylene; Özbek, Berna; Le Ruyet, Didier
Clustering of Device-to-Device (D2D) pairs with cellular transmissions is particularly challenging to manage interference in future fifth generation networks. D2D pairs should coexist with cellular users in underlay scenario, taking advantage of frequency and spatial dimensions. We consider a Multiple Input Multiple Output (MIMO) channel where all users (whether cellular or devices) are equipped with N > 1 antennas, and the Base Station (BS) has M >= N antennas. Interference between D2D pairs, between D2D transmitters and the BS and between cellular users and D2D receivers is then managed by determining clusters of D2D pairs and cellular users with very low relative interference levels. Clusters are obtained after graph-coloring on a pairwise interference-leakage based matrix. Then, several Resource Blocks (RB) allocation algorithms are proposed, with various fairness levels. A final orthogonalization step using Minimum Mean Square Error (MMSE) may be added at the BS in order to further reduce interference. Simulation results show very large D2D data rates improvements, while cellular data rates degradation due to interference can be controlled.
Citation - WoS: 2
Citation - Scopus: 3
Low Complexity Zf Receiver for Orthogonal Sfbc-Ofdm in Broadband Wireless Channels
(Institution of Engineering and Technology, 2006-04) Özbek, Berna; Le Ruyet, Didier
Orthogonal space-frequency block coded (SFBC) orthogonal frequency division multiplexing (OFDM) systems are analysed in broadband wireless channels where adjacent subcarriers do not have the same channel coefficients and the matched filter receiver causes an error floor in bit error rate performance. To avoid this, a low complexity zero forcing (ZF) receiver for the orthogonal schemes with two and three transmit and one receive antennas are proposed.
Citation - Scopus: 2
Message-Passing Algorithm for Sum-Rate Maximization in Multi-Antenna Underlay D2d Communications
(IEEE, 2018) Özbek, Berna; Pischella, Mylene; Le Ruyet, Didier
In this paper, we propose a resource allocation of device-to-device (D2D) communications underlaying multiantenna cellular systems by employing message-passing algorithm. It is possible to construct the factor graph of the D2D pairs by considering the interference power at the base station and among the D2D pairs. The goal is to avoid interfering the cellular transmission while increasing the sum data rate of D2D pairs. We show that the proposed resource allocation based on message passing algorithm allow us to almost reach the performance of the exhaustive search and outperforms the random allocation. Since the associated factor graph is not fully connected, the complexity of the algorithm is significantly reduced compared to the exhaustive search. © 2018 IEEE.