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Start date: 2010End date: 2019Type: search.filters.itemtype.Conference PaperHas files: NoAuthor: search.filters.author.Soysal, AlkanAuthor: search.filters.author.Aygün, Bengi

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    A fast power allocation algorithm for MIMO relay channels, MIMO aktarma kanallarinda güç tahsisi i̇çin hizli bir algoritma
    (2011) Aygün, Bengi; Soysal, Alkan; Aygün, Bengi, Bahçeşehir Üniversitesi, Istanbul, Turkey; Soysal, Alkan, Bahçeşehir Üniversitesi, Istanbul, Turkey
    By assuming full-duplex mode, we consider a MIMO relay channel where the receivers have perfect channel state information (CSI) and the transmitters have partial CSI. Lower bound achieving transmit covariance matrices are derived using an iterative algorithm. Lower bound to the capacity is analyzed for three cases depending on the channel covariance matrix. In the first case, lower bound on the capacity is equal to the capacity of the link from source to relay. In the second case, lower bound on the capacity is equal to the multi access channel capacity from source and relay to the destination. In the last case, lower bound on the capacity depends on both multi access channel and source to relay channel. In that case, under a certain practical channel assumption, we propose a fast power allocation algorithm. © 2011 IEEE. © 2011 Elsevier B.V., All rights reserved.
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    Achieving the lower bound of fading MIMO relay channels with covariance feedback at the transmitters
    (2011) Aygün, Bengi; Soysal, Alkan; Aygün, Bengi, Department of Electrical and Electronic Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey; Soysal, Alkan, Department of Electrical and Electronic Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey
    In this paper, we consider a full-duplex mode MIMO relay channel for decode and forward strategy where the receivers have perfect channel state information (CSI) and the transmitters have only covariance feedback at the transmitters. We derive a lower bound to the ergodic capacity for this scenario and propose an iterative algorithm that finds lower bound achieving transmit covariance matrices of the source and relay nodes. The solution of the optimization problem in the lower bound expression is given for three cases depending on channel covariance matrices. For one of these cases, it seems that an efficient and fast algorithm achieving the lower bound is not possible. However, under a certain practical channel assumption, we propose a power allocation algorithm that gives a solution much faster than classical convex optimization methods. Moreover, we show that this fast algorithm results in a data rate which is very close to the lower bound to the capacity. © 2011 IEEE. © 2011 Elsevier B.V., All rights reserved.
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    Fading MIMO relay channels with covariance feedback
    (2012) Aygün, Bengi; Soysal, Alkan; Aygün, Bengi, Department of Electrical and Electronic Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey; Soysal, Alkan, Department of Electrical and Electronic Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey
    In this paper, the source and relay transmit covariance matrices are jointly optimized for a fading multiple antenna relay channel when the transmitters only have partial channel state information (CSI) in the form of covariance feedback. For full-duplex transmission, we evaluate lower and upper bounds on the ergodic channel capacity. These bounds require a joint optimization over the source and relay transmit covariance matrices. The methods utilized in the previous literature fail to find fast and efficient algorithms for the system model considered in this paper. Therefore, we utilize matrix differential calculus in order to solve the joint optimization problem. In this method, there is no need to specify the eigenvectors of the transmit covariance matrices first. Through simulations, we observe that lower and upper bounds are close to each other. © 2012 IEEE. © 2012 Elsevier B.V., All rights reserved.
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    Fading MIMO relay channels with channel estimation error
    (Institute of Electrical and Electronics Engineers Inc., 2013) Aygün, Bengi; Soysal, Alkan; Aygün, Bengi, Department of Electrical and Electronic Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey; Soysal, Alkan, Department of Electrical and Electronic Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey
    In this paper, we consider a full-duplex, decode-and-forward, fading MIMO relay channel where the transmitters have partial channel state information (CSI) and the receivers have noisy channel estimates. Under block fading assumption, we divide the transmission block into two parts: training phase and data transmission phase. The destination and relay receivers estimate the instantaneous channel realizations during the training phase by using linear minimum mean square error (MMSE) estimation, extract the covariance information of the channel, and feed it back to the source and relay transmitters. We obtain a lower bound expression to the relay channel capacity in terms of a max-min optimization problem over channel estimation and data transmission parameters. By applying matrix differential calculus, we jointly optimize this achievable rate over source and relay transmit covariance matrices, training phase length, training phase powers and training sequences. © 2013 IEEE. © 2016 Elsevier B.V., All rights reserved.
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    Short paper: Performance analysis of MIMO-based decode-and-forward relaying VANETs
    (2013) Aygün, Bengi; Soysal, Alkan; Wyglinski, Alexander M.; Aygün, Bengi, Wireless Innovation Laboratory, School of Engineering, Worcester, United States; Soysal, Alkan, Department of Electrical and Electronic Engineering, Bahçeşehir Üniversitesi, Istanbul, Turkey; Wyglinski, Alexander M., Wireless Innovation Laboratory, School of Engineering, Worcester, United States
    In this paper, we present a novel transceiver architecture for vehicular ad hoc networks (VANETs) employing a combination of decode-and-forward (DF) cooperative communications and multiple-input multiple-output (MIMO) transmission. To assess the performance of the proposed architecture, we have developed a geometric model that is applicable to high mobility environments, where each channel element consists of a sum of complex harmonic exponentials. To assist with the performance assessment, we derived the lower bound on the ergodic channel capacity for the DF scenario. We perform iterative algorithms and provide the transmit covariance matrices which present the certain lower bound for given power constraints. Simulation results show that allocated power over the spatial dimension converge to their optimum value and consequently the exact lower bound is obtained instead of getting sub-optimal achievable rates. © 2013 IEEE. © 2014 Elsevier B.V., All rights reserved.