Browsing by Author "Panayirci, Erdal"
Now showing items 1-20 of 57
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A low-complexity KL expansion-based channel estimator for OFDM systems
This paper first proposes a computationally efficient pilot-aided linear minimum mean square error (MMSE) batch channel estimation algorithm for OFDM systems in unknown wireless fading channels. The proposed approach employs a convenient representation of the discrete multipath fading channel based on the Karhunen-Loeve (KL) orthogonal expansion and finds MMSE estimates of the uncorrelated KL series expansion coefficients. Based on such an expansion no matrix inversion is required in the proposed ...
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A Monte Carlo implementation of the SAGE algorithm for joint soft-multiuser decoding channel parameter estimation and code acquisition
Authors:Kocian, Alexander; Panayirci, Erdal; Poor, H. Vincent; Ruggieri, Marina
Publisher and Date:(2010)This paper presents an iterative scheme for joint timing acquisition multi-channel parameter estimation and multiuser soft-data decoding. As an example an asynchronous convolutionally coded direct-sequence code-division multiple-access system is considered. The proposed receiver is derived within the space-alternating generalized expectation-maximization framework implying that convergence in likelihood is guaranteed under appropriate conditions in contrast to many other iterative receiver ...
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A Reliable Successive Relaying Protocol
Authors:Başar, Ertuğrul; Aygölü, Ümit; Panayırcı, Erdal; Poor, H. Vincent
Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2014)Successive relaying has recently emerged as an effective technique for cooperative networks and provides significant improvements in bandwidth efficiency over traditional relaying techniques ;however to achieve full-diversity the available successive relaying protocols generally assume noise-free sourcerelay and interference-free inter-relay channels. In this paper a novel successive relaying protocol is proposed for N-relay wireless networks by removing these optimistic assumptions. The proposed ...
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An Improved Adaptive Subspace Tracking Algorithm Based on Approximated Power Iteration
Authors:Wu, Qiang; Zheng, Jian-Sheng; Dong, Zhicheng; Panayirci, Erdal; Wu, Zhi-Qiang; Ren, Qingnuobu
Publisher and Date:(IEEE-INST Electrical Electronics Engineers Inc, 2018)A subspace tracking technique has drawn a lot of attentions due to its wide applications. The main objective of this approach is to estimate signal or noise subspace basis for the sample covariance matrix. In this paper we focus on providing a fast stable and adaptive subspace tracking algorithm that is implemented with low computational complexity. An alternative realization of the fast approximate power iteration (FAPI) method termed modified FAPI (MFAPI) is also presented. Rather than solving ...
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Analysis of visible light communation sytems and adaptive equalization effects
Communication by means of visible light is a newly developing technology that has been brought up as an alternative to the current electromagnetic based communication systems. The recently conducted studies led to the use of LED Technology for illumination purposes and for this technology to have an edge over devices that consume excessive energy as presently being used by us. LED technology is predicted to become an important part of illumination systems especially in consideration of the low ...
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Channel estimation for visible light communications using neural networks
Authors:Yeşilkaya, Anıl; Karatalay, Onur; Öǧrenci, Arif Selçuk; Panayirci, Erdal
Publisher and Date:(Institute of Electrical and Electronics Engineers Inc., 2016)Visible light communications (VLC) is an emerging field in technology and research. Estimating the channel taps is a major requirement for designing reliable communication systems. Due to the nonlinear characteristics of the VLC channel those parameters cannot be derived easily. They can be calculated by means of software simulation. In this work a novel methodology is proposed for the prediction of channel parameters using neural networks. Measurements conducted in a controlled experimental setup ...
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Channel estimation in underwater cooperative OFDM system with amplify-and-forward relaying
Authors:Şenol, Habib; Panayirci, Erdal; Erdoğan, Mustafa; Uysal, Murat
Publisher and Date:(IEEE, 2012)This paper is concerned with a challenging problem of channel estimation for amplify-and-forward cooperative relay based orthogonal frequency division multiplexing (OFDM) systems in the presence of sparse underwater acoustic channels and of the correlative non-Gaussian noise. We exploit the sparse structure of the channel impulse response to improve the performance of the channel estimation algorithm due to the reduced number of taps to be estimated. The resulting novel algorithm initially estimates ...
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Effect of power and rate adaptation on the spectral efficiency of MQAM/OFDM system under very fast fading channels
Authors:Dong, Zhicheng; Fan, Pingzhi; Panayirci, Erdal; Mathiopoulos, P. Takis
Publisher and Date:(Springer International Publishing Ag, 2012)In this article the effect of power and rate adaptation on the spectral efficiency of orthogonal frequency division multiplexing (OFDM) systems using M-ary quadrature amplitude modulation (MQAM) is investigated in the presence of frequency selective and very rapidly time-varying fading channels under power and instantaneous bit error rate (BER) constraints. Lower bounds on the maximum spectral efficiency of adaptive OFDM/MQAM systems with perfect and imperfect channel state information (CSI) are ...
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EM-MAP based initialization of PIC receiver for downlink MC-CDMA systems
The quality of multiple access interference (MAI) which can be improved by using channel estimation and data estimation of all active users effects considerably the performance of PIC detector. Therefore data and channel estimation performance is obtained in the initial stage has a significant relationship with the performance of PIC. So obviously it is necessary to make excellent joint data and channel estimation for initialization of PIC detector. In this work to initiate PIC module efficiently ...
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Femtocell design for data communications in mobile networks
in this thesis game theoretic utility-based adaptive power control algorithm for uplink of femtocell networks is performed for mitigation of interference in two different ways. The first one is allocation of femtocell interference threshold in randomly activated femtocell base stations in a known macrocell coverage area and the second one is adaptation of the power of the femtocell users for mitigating total interference from femtocell users at the macrocell base station. Accordingly we consider ...
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Frequency selective fading channel estimation in OFDM systems using KL expansion
This paper proposes a computationally efficient linear minimum mean square error (MMSE) channel estimation algorithm based on KL series expansion for OFDM systems. Based on such expansion no matrix inversion is required in the proposed MMSE estimator. Moreover truncation in the linear expansion of channel is achieved by exploiting the optimal truncation property of the KL expansion resulting in a smaller computational load on the estimation algorithm. The performance of the proposed approach is ...
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Guest editorial: special issue on high mobility wireless communications
Authors:Fan, Pingzhi; Panayirci, Erdal; Li, Ping; Wang, Chengxiang; Tarokh,Vahid
Publisher and Date:(2012)
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Interpolation Based Pilot-Aided Channel Estimation for STBC Spatial Modulation and Performance Analysis Under Imperfect CSI
Authors:Acar, Yusuf; Dogan, Hakan; Basar, Ertugrul; Panayirci, Erdal
Publisher and Date:(Inst Engineering Technology-IET, 2016)A combination of space-time block coding and spatial modulation (STBC-SM) has been recently proposed for multiple input-multiple output systems to obtain both spatial diversity gain and more capacity simultaneously while assuming the perfect channel state information (P-CSI) was available at the receiver. However in practical scenarios the CSI is unknown to the receiver and should be estimated in order to detect the transmitted data in a reliable way. Therefore channel estimation (CE) is a major ...
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Iterative channel estimation for spatial modulation systems over fast fading channels [Hızlı sönümlemeli kanallarda uzaysal modülasyon sistemleri için iteratif kanal kestirimi]
Authors:Acar, Yusuf; Doğati, Hakan; Panayirci, Erdal
Publisher and Date:(IEEE Computer Society, 2014)Spatial Modulation (SM) based on the use of antenna indices to transmit information in addition to the conventional signal constellations has been recently proposed to solve practical problems encountered in MIMO systems. In the literature estimation of CSI for SM systems is simply investigated by RLS for slow fading channels. However iterative receivers that offer significant performance gains over a non-iterative when the total number of pilot is not sufficient and the channel is fast fading ...
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Iterative channel estimation techniques for uplink MC-CDMA systems
In this work maximum likelihood (ML) channel estimation for uplink multicarrier code-division multiple-access (MC-CDMA) systems is considered in the presence of frequency fading channel. The expectation-maximization (EM)- and a space-alternating generalized expectation-maximization (SAGE) algorithm are introduced to avoid matrix inversion for the ML channel estimation problem. We compare the both algorithms in terms of the number of used iteration and show that the proposed algorithms converge the ...
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Iterative joint data detection and channel estimation for uplink MC-CDMA systems in the presence of frequency selective channels
Authors:Panayirci, Erdal; Dogan, Hakan; Cirpan, Hakan Ali; Kocian, Alexander; Fleury, Bernard Henri
Publisher and Date:(2010)This paper is concerned with joint multiuser detection and multichannel estimation (JDE) for uplink multicarrier code-division multiple-access (MC-CDMA) systems in the presence of frequency selective channels. The detection and estimation implemented at the receiver are based on a version of the expectation maximization (EM) algorithm and the space-alternating generalized expectation-maximization (SAGE) which are very suitable for multicarrier signal formats. The EM-JDE receiver updates the data ...
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Iterative receiver for DS-CDMA systems in the presence of time-varying channels
In this paper we present an efficient iterative receiver structure of tractable complexity for joint multiuser detection and multichannel estimation (JDE) ofdirect-sequence code-division multiple-access systems operating in the presence of timevarying flat fading channel. The tilne-varying channel is assumed to be modeled according to a piece-wise constant channel. An optimality criterion is defined and analytical expressions for the corresponding optimized weight coefficients are given. Monte-Carlo ...
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Joint phase noise estimation and source detection [Ortak faz gürültüsü kestirimi ve kaynak sezimlemesi]
Rapidly time-varying and random disturbing effects on the phase of a signal waveform are known as phase noise. In this paper we consider the problem of joint detection of continuous-valued information source output and estimation of a phase noise by using expectation maximization (EM) algorithm. In order to estimate phase noise initial phase noise values are determined by cubic interpolation that utilizes pilot symbols. Computer simulations are performed for the proposed algorithm and the average ...
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Low-complexity joint data detection and channel equalisation for highly mobile orthogonal frequency division multiplexing systems
This study is concerned with the challenging and timely problem of channel equalisation and data detection for orthogonal frequency division multiplexing (OFDM) systems in the presence of frequency-selective and very rapidly time-varying channels. The algorithm is based on the space alternating generalised expectation-maximisation (SAGE) technique which is particularly well suited to multicarrier signal formats and can be easily extended to multi-input multi-output-OFDM systems. In fast fading ...
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Modelling of visible light channels and performance analysis for optical ofdm systems
This work is concerned with a challenging problem of modeling and simulation of visible light communications (VLC) channels for optical wireless communication (OWC) systems. A proper channel model for VLC is absent in the current literature. For this reason two different indoor channel model with different material types and different receiver-transmitter locations have been obtained and implemented for asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) technique. ...