Browsing by Author "Cirpan, Hakan Ali"
Now showing items 1-20 of 43
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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 low-complexity time-domain MMSE channel estimator for space-time/frequency block-coded OFDM systems
Authors:Şenol, Habib; Cirpan, Hakan Ali; Panayirci, Erdal
Publisher and Date:(Hindawi Publishing Corporation, 2006)Focusing on transmit diversity orthogonal frequency-division multiplexing (OFDM) transmission through frequency-selective channels this paper pursues a channel estimation approach in time domain for both space-frequency OFDM (SF-OFDM) and space-time OFDM (ST-OFDM) systems based on AR channel modelling. The paper proposes a computationally efficient pilot-aided linear minimum mean-square-error (MMSE) time-domain channel estimation algorithm for OFDM systems with transmitter diversity in unknown ...
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Achievable Performance of Bayesian Compressive Sensing Based Spectrum Sensing
In wideband spectrum sensing compressive sensing approaches have been used at the receiver side to decrease the sampling rate if the wideband signal can be represented as sparse in a given domain. While most studies consider the reconstruction of primary user's signal accurately it is indeed more important to analyze the presence or absence of the signal correctly. Furthermore these studies do not consider the achievable lower bounds of reconstruction error and how well the selected method performs ...
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Advanced signal processing algorithms for wireless communications
Traditional wireless technologies are not well suited to meet the extremely demanding requirements of providing the very high data rates with the ubiquity mobility and portability characteristic of cellular systems. Some fundamental barriers related to the nature of the radio channel as well as the limited bandwidth availability at the frequencies of interest stand in the way. Unique sets of efficient advanced signal processing algorithms and techniques is the one of the primary enablers that will ...
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An efficient joint channel estimation and decoding algorithm for turbo-coded space-time orthogonal frequency division multiplexing receivers
Authors:Dogan, Hakan; Cirpan, Hakan Ali; Panayirci, Erdal
Publisher and Date:(Inst Engineering Technology-IET, 2008)The challenging problem in the design of digital receivers of today's and future high-speed high data-rate wireless communication systems is to implement the optimal decoding and channel estimation processes jointly in a computationally feasible way. Without realising such a critical function perfectly at receiver the whole system will not work properly within the desired performance limits. Unfortunately direct implementation of such optimal algorithms is not possible mainly due to their ...
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An efficient joint data detection and channel estimation technique for uplink MC-CDMA systems based on SAGE algorithm
Authors:Panayirci, Erdal; Dogan, Hakan; Cirpan, Hakan Ali; Fleury, Bernard Henri
Publisher and Date:(IEEE, 2007)This paper is concerned with joint channel estimation and data detection for uplink multicarrier code-division multiple-access (MC-CDMA) systems in the presence of frequency fading channel. The detection and estimation algorithm implemented at the receiver is based on a version of the expectation maximization (EM) technique called the spece-alternating-generalized-expectation-maximization (SAGE) algorithm which is very suitable for the the multicarrier signal formats. Application of the SAGE ...
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Bayesian Compressive Sensing For Primary User Detection
Authors:Başaran, Mehmet; Erküçük, Serhat; Cirpan, Hakan Ali
Publisher and Date:(Inst Engineering Technology-IET, 2016)In compressive sensing (CS)-based spectrum sensing literature most studies consider accurate reconstruction of the primary user signal rather than detection of the signal. Furthermore possible absence of the signal is not taken into account while evaluating the spectrum sensing performance. In this study Bayesian CS is studied in detail for primary user detection. In addition to assessing the signal reconstruction performance and comparing it with the conventional basis pursuit approach and the ...
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Bayesian compressive sensing for ultra-wideband channel models
Considering the sparse structure of ultra-wideband (UWB) channels compressive sensing (CS) is suitable for UWB channel estimation. Among various implementations of CS the inclusion of Bayesian framework has shown potential to improve signal recovery as statistical information related to signal parameters is considered. In this paper we study the channel estimation performance of Bayesian CS (BCS) for various UWB channel models and noise conditions. Specifically we investigate the effects of (i) ...
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Blind-phase noise estimation in OFDM systems by sequential Monte Carlo method
Authors:Panayirci, Erdal; Cirpan, Hakan Ali; Moeneclaey, Marc; Noels, Nele
Publisher and Date:(John Wiley and Sons Ltd, 2006)One of the main drawbacks of orthogonal frequency division multiplexing (OFDM) systems is the phase noise (PN) caused by the oscillator instabilities. Unfortunately due to the PN the most valuable feature namely orthogonality between the carriers is destroyed resulting in a significant degradation in the performance of OFDM systems. In this paper based on a sequential Monte Carlo method (particle filtering) a computationally efficient algorithm is presented for estimating the residual phase noise ...
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Channel estimation for MIMO-OFDM systems in fixed broadband wireless applications
Systems employing multiple transmit and receive antennas known as multiple input multiple output (MIMO) systems can be used with OFDM to improve the resistance to channel impairments. Thus the technologies of OFDM and MIMO are equipped in fixed wireless applications with attractive features including high data rates and robust performance. However since different signals are transmitted from different antennas simultaneously the received signal is the superposition of these signals which implies ...
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Compressive sensing for ultra-wideband channel estimation: on the sparsity assumption of ultra-wideband channels
Authors:Başaran, Mehmet; Erküçük, Serhat; Cirpan, Hakan Ali
Publisher and Date:(Wiley-Blackwell, 2014)Due to the sparse structure of ultra-wideband (UWB) multipath channels there has been a considerable amount of interest in applying the compressive sensing (CS) theory to UWB channel estimation. The main consideration of the related studies is to propose different implementations of the CS theory for the estimation of UWB channels which are assumed to be sparse. In this study we investigate the suitability of standardized UWB channel models to be used with the CS theory. In other words we question ...
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Data-Aided Autoregressive Sparse Channel Tracking for OFDM Systems
Authors:Buyuksar, Ayse Betul; Şenol, Habib; Erküçük, Serhat; Cirpan, Hakan Ali
Publisher and Date:(IEEE, 2016)In order to meet future communication system requirements channel estimation over fast fading and frequency selective channels is crucial. In this paper Space Alternated Generalized Expectation Maximization Maximum a Posteriori (SAGE-MAP) based channel estimation algorithm is proposed for Orthogonal Frequency Division Multiplexing (OFDM) systems for Autoregressive (AR) modeled time-varying sparse channels. Also an initialization algorithm has been developed from the widely used sparse approximation ...
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Effect of Inter-Block-Interference-Free Region on Compressed Sensing Based Channel Estimation in TDS-OFDM Systems
Authors:Başaran, Mehmet; Erküçük, Serhat; Şenol, Habib; Cirpan, Hakan Ali
Publisher and Date:(IEEE, 2016)Time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) is the basis technology for digital television standard (DTV) employed in some countries thanks to its high spectral efficiency when compared to traditional cyclic prefix OFDM. Moreover it does not require pilot usage in frequency domain channel estimation. Instead of data usage as cyclic prefix pseudo-noise (PN) sequences are transmitted in guard intervals. Due to interference from the previous OFDM data symbol the ...
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EM based Stochastic maximum likelihood approach for localization of near-field sources in 3-D
Authors:Kabaoǧlu, Nihat; Cirpan, Hakan Ali; Paker, Selçuk
Publisher and Date:(Walter De Gruyter Gmbh, 2004)The goal of this paper is to estimate the locations of unknown sources in 3-D space from the data collected by a 2-D rectangular array. Various studies employing different estimation methods under near-field and far-field assumptions were presented in the past. In most of the previous studies location estimations of sources at the same plane with the antenna array were carried out by using algorithms having constraints for various situations indeed. In this study location estimations of sources ...
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EM-based joint data detection and channel estimation for uplink MC-CDMA systems over frequency selective channels
Authors:Dogan, Hakan; Panayirci, Erdal; Cirpan, Hakan Ali; Fleury, Bernard Henri
Publisher and Date:(IEEE, 2007)This paper is concerned with joint channel estimation and data detection for uplink multicarrier code-division multiple-access (MC-CDMA) systems in the presence of frequency fading channel. The detection and estimation algorithm implemented at the receiver is based on a version of the expectation maximization (EM) technique which is very suitable for the multicarrier signal formats. Application of the EM-based algorithm to the problem of iterative data detection and channel estimation leads to a ...
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EM-Based MAP channel estimation and data detection for downlink MCC-CDMA systems
In this work we propose a joint MAP channel estimation and data detection technique based on the Expectation Maximization (EM) method with paralel interference cancelation(PIC) for downlink multi-carrier (MC) code division multiple access (CDMA) systems in the presence of frequency selective channels. The EM algorithm derived estimates the complex channel parameters of each subcarriers iteratively and generates the soft information representing the data a posterior probabilities. The soft information ...
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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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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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Iterative channel estimation and decoding of turbo coded SFBC-OFDM systems
We consider the design of turbo receiver structures for space-frequency block coded orthogonal frequency division multiplexing (SFBC-OFDM) systems in the presence of unknown frequency and time selective fading channels. The Turbo receiver structures for SFBC-OFDM systems under consideration consists of an iterative MAP Expectation/Maximization (EM) channel estimation algorithm soft MMSE-SFBC decoder and a soft MAP outer-channel-code decoder. MAP-EM employs iterative channel estimation and it ...
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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 ...