Electrical - Electronic Engineering / Elektrik - Elektronik Mühendisliği

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Now showing 1 - 7 of 7
  • Article
    Secrecy performance of full-duplex space-air integrated networks in the presence of active/passive eavesdropper, and friendly jammer
    (Wiley, 2024) Buyuksar, Ayse Betul; Erdoğan, Eylem; Altunbas, Ibrahim
    In this paper, a full-duplex (FD) space-air ground integrated network (SAGIN) system with passive and active eavesdroppers (PE/AE) and a friendly jammer (FJ) is investigated. The shadowing side information (SSI)-based unmanned aerial vehicle relay node (URN) selection strategy is considered to improve signal-to-interference plus noise power ratio (SINR) at the ground destination unit. To quantify the secrecy performance of the considered scenario, outage probability (OP), interception probability (IP), and transmission secrecy outage probability (TSOP) are investigated in the presence of FJ and PE/AE. The results have shown that aerial AE is an important threat since it can severely degrade the OP of the main transmission link. Furthermore, the FJ can decrease the IP of the eavesdropper by causing interference with the cost of power consumption of URNs. Simulations are performed to verify the theoretical findings.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 7
    Signal Reconstruction in Diffusion-Based Molecular Communication
    (Wiley, 2019) Atakan, Barış; Güleç, Fatih
    Molecular communication (MC) is an important nanoscale communication paradigm, which is employed for the interconnection of the nanomachines (NMs) to form nanonetworks. A transmitter NM (TN) sends the information symbols by emitting molecules into the transmission medium and a receiver NM (RN) receives the information symbols by sensing the molecule concentration. In this paper, a model of how an RN measures and reconstructs the molecular signal is proposed. The signal around the RN is assumed to be a Gaussian random process instead of the less realistic deterministic approach. After the reconstructed signal is derived as a doubly stochastic poisson process, the distortion between the signal around the RN and the reconstructed signal is derived as a new performance parameter in MC systems. The derived distortion, which is a function of system parameters such as RN radius, sampling period, and the diffusion coefficient of the channel, is shown to be valid by employing random walk simulations. Then, it is shown that the original signal can be satisfactorily reconstructed with a sufficiently low level of distortion. Finally, optimum RN design parameters, namely, RN radius, sampling period, and sampling frequency, are derived by minimizing the signal distortion. The simulation results reveal that there is a trade-off among the RN design parameters which can be jointly set for a desired signal distortion.
  • Other
    Erratum To: on Stream Selection for Interference Alignment in Heterogeneous Networks
    (Springer Verlag, 2016) Aycan, Esra; Özbek, Berna; Le Ruyet, Didier
  • Article
    Citation - Scopus: 1
    On Stream Selection for Interference Alignment With Limited Feedback in Heterogeneous Networks
    (John Wiley and Sons Inc., 2016) Aycan, Esra; Özbek, Berna; Le Ruyet, Didier
    This paper presents a stream selection based interference alignment approach with imperfect channel state information for heterogeneous networks. The proposed solution constructs stream sequences by selecting only the strongest stream of each user where the first stream of the constructed stream sequences is associated to a pico user. While selecting the streams, the channel matrices of the unselected streams are projected orthogonally to the virtual transmit and receive channels of the selected stream in order to align the interference in the null space of these virtual channels. In addition, the influence of imperfect channel state information on the proposed algorithm is analysed. A bit allocation scheme is given by deriving an upper bound on the rate loss because of quantisation. The simulation results are carried out by considering various scenarios with different locations of pico cells at the cell edge regions of the macro cell. The performance results show that the proposed algorithm with the imperfect channel state information achieves higher performance than the existing algorithms.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 5
    On stream selection for interference alignment in heterogeneous networks
    (Springer Verlag, 2016) Aycan, Esra; Özbek, Berna; Le Ruyet, Didier
    This paper proposes a stream selection algorithm to deal with the interference and increase the sum capacity in the context of heterogeneous networks where cells of different types coexist. Due to the different transmit powers between the macro and small cells, interference levels are also different. Since the small cells are densely deployed, fully connected interference network between small cells is considered in this paper. The proposed algorithm performs the selection of a stream sequence among a predetermined set of sequences. Those selected sequences are the ones that mostly contribute to the sum rate when performing the exhaustive search. As a consequence, since the search space is reduced, the complexity is significantly decreased. These stream sequences form a regular structure where the first stream is associated to a pico user. Another distinguishing property of the proposed approach is that the stream sequences include at least one stream for each user. When selecting the streams, the channel matrices of the unselected streams are projected orthogonally to the virtual transmit and virtual receive channels of the selected stream in order to align the interference in the null space of these virtual channels. The performance evaluations are carried out by considering different scenarios with different numbers and locations of pico cells. It is shown that the proposed method can significantly reduce the computational complexity while achieving a very close performance to the exhaustive search.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 9
    Adaptive Limited Feedback Links for Cooperative Multi-Antenna Multicell Networks
    (Springer Verlag, 2014) Özbek, Berna; Ruyet, Didier Le
    The 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.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 3
    Reduced Feedback Load Using User Selection Algorithms for the Multiuser Multi-Input Single-Output Systems
    (John Wiley and Sons Inc., 2013) Khanfir, Hajer; Le Ruyet, Didier; Özbek, Berna
    Locate full-text(opens in a new window)|Full Text(opens in a new window)|View at Publisher| Export | Download | Add to List | More... Transactions on emerging telecommunications technologies Volume 24, Issue 7-8, November-December 2013, Pages 809-819 Reduced feedback load using user selection algorithms for the multiuser multi-input single-output systems (Article) Khanfir, H.a , Le Ruyet, D.a, Özbek, B.b a Electronics and Communications Laboratory, CNAM, 292 Rue Saint Martin, 75141, Paris, France b Electrical and Electronics Engineering Department, Izmir Institute of Technology, Urla, 35430, Izmir, Turkey View references (27) Abstract For wireless multiuser multi-input single-output communication systems with adaptive scheduling and precoding, the users have to feed back their channel state information. However, the amount of feedback data increases with the number of users and the number of transmit antennas. In this paper, we propose a criterion based on the orthogonality between the users' channels to reduce this uplink load. Without cooperation between the users, we only allow users that are semi-orthogonal to feed back their quantized channel information to the base station. We propose a lower bound on the sum rate for the proposed criterion. We show that the performance is almost independent of the number of quantized channel quality information and only channel direction information is important at the transmitter. Then, we consider a noisy feedback channel and propose an algorithm to reduce the noise effect on the analogue feedback