Browsing by Author "Dogan, Hakan"

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Citation Count: 0
Channel Estimation for SM Systems over Time-Varying Rayleigh Fading Channels
(IEEE, 2014) Acar, Yusuf; Dogan, Hakan; Panayırcı, Erdal
This paper is concerned with the challenging and timely problem of channel estimation for spatial modulated systems in the presence of time varying channels. Recently estimation of channel state information for SM systems is investigated by the recursive least square (RLS) algorithm for slow fading channels. However it is clear that the RLS based receiver will have a performance degradation for fast fading channels. Therefore we developed iterative channel estimation based on detected symbols and curve fitting to track the channel variations for SM systems. Simulation results have demonstrated that the proposed iterative channel estimation offer substantial performance gains over the RLS channel estimation. In particular a savings of about 4dB is obtained at BER = 10(-7) as compared with RLS based receiver at 150km/h for 2 x 4 single carrier SM systems.
Citation Count: 3
Data Detection Based Iterative Channel Estimation for Coded SM-OFDM Systems
(IEEE, 2016) Acar, Yusuf; Leblebici, M. Merih; Dogan, Hakan; Panayırcı, Erdal
The combination of spatial modulation (SM) and orthogonal frequency division multiplexing (OFDM) as SM-OFDM is a recently proposed efficient modulation scheme with exploiting the index of transmit antenna to convey information bits for multiple-input multiple-output (MIMO) wireless communication systems due to its low complexity feature. The pioneering works assume that the perfect channel state information (P-CSI) or pilot symbols aided channel estimation (PSA-CE) is available at the receiver. The open question is whether the accuracy of pilot based channel estimation is satisfactory to accomplish high data rate transmission in SM-OFDM systems. This paper explores the iterative channel estimation (ICE) problem for the coded SM-OFDM systems. We showed that the quality of the channel estimation can be further enhanced by the detection of symbols at the receiver. Through comparative simulations we show that the proposed ICE method has notable bit error rate (BER) performance compared with the PSA-CE method for the binary phase shift keying (BPSK) modulation over the typical urban (TU) channel model.
Citation Count: 0
EM-MAP based initializaition of PIC receiver for downlink MC-CDMA systems
(IEEE, 2007) Dogan, Hakan; Cirpan, Hakan A.; Panayarct, Erdal
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 a joint MAP channel estimation and data detection technique based on the Expectation Maximization (EM) method has been proposed. Moreover, the MAP-EM approach considers the channel variations as random processes and applies the Karhunen-Loeve (KL) orthogonal series expansion. The performance of the proposed approach are studied in terms of bit-error rate (BER). Throughout the simulations, extensive comparisons with previous works in literature are performed, showing that the new scheme can offer superior performance.
Citation Count: 9
Interpolation Based Pilot-Aided Channel Estimation for STBC Spatial Modulation and Performance Analysis Under Imperfect CSI
(Inst Engineering Technology-IET, 2016) Panayırcı, Erdal; Dogan, Hakan; Basar, Ertugrul; Panayırcı, Erdal
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 challenge in designing the STBC-SM systems. In this study the problem of CE is investigated and a new pilot-aided channel estimation (PA-CE) technique coupled with an interpolation is proposed for the STBC-SM systems operating in the presence of rapidly time-varying mobile channels. Several interpolation schemes such as the linear nearest neighbour piecewise cubic Hermite and the low-pass interpolations are applied and their performances are compared to determine the best suitable interpolation technique to be employed in STBC-SM systems. Bit error rate (BER) performance of the proposed CE technique is then investigated in time-varying channels with different modulation. Moreover the pairwise error probability of the STBC-SM scheme is derived and its average bit error probability is evaluated analytically in the presence of CE errors.
Citation Count: 9
Iterative joint data detection and channel estimation for uplink MC-CDMA systems in the presence of frequency selective channels
(2010) Panayırcı, Erdal; Dogan, Hakan; Cirpan, Hakan Ali; Kocian, Alexander; Fleury, Bernard Henri
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 bit sequences in parallel while the SAGE-JDE receiver reestimates them successively. The channel parameters are updated in parallel in both schemes. Application of the EM-based algorithm to the problem of iterative data detection and channel estimation leads to a receiver structure that also incorporates a partial interference cancelation. Computer simulations show that the proposed algorithms have excellent BER end estimation performance. Crown Copyright © 2009.
Citation Count: 26
Low-complexity joint data detection and channel equalisation for highly mobile orthogonal frequency division multiplexing systems
(2010) Panayırcı, Erdal; Panayırcı, Erdal; Poor, H. Vincent
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 channels the orthogonality between subcarriers is destroyed by the time variation of a fading channel over an OFDM symbol duration which causes severe inter-carrier interference (ICI) and in conventional frequency-domain approaches results in an irreducible error floor. The proposed joint data detection and equalisation algorithm updates the data sequences in series leading to a receiver structure that also incorporates ICI cancellation enabling the system to operate at high vehicle speeds. A computational complexity investigation as well as detailed computer simulations indicate that this algorithm has significant performance and complexity advantages over existing suboptimal detection and equalisation algorithms proposed earlier in the literature. © 2010 The Institution of Engineering and Technology.
Citation Count: 24
Low-Complexity MAP-Based Successive Data Detection for Coded OFDM Systems Over Highly Mobile Wireless Channels
(IEEE-INST Electrical Electronics Engineers Inc, 2011) Panayırcı, Erdal; Dogan, Hakan; Poor, H. Vincent
This paper is concerned with the challenging and timely problem of data detection for coded orthogonal frequency-division multiplexing (OFDM) systems in the presence of frequency-selective and very rapidly time varying channels. New low-complexity maximum a posteriori probability (MAP) data detection algorithms are proposed based on sequential detection with optimal ordering (SDOO) and sequential detection with successive cancellation (SDSC). The received signal vector is optimally decomposed into reduced dimensional subobservations by exploiting the banded structure of the frequency-domain channel matrix whose bandwidth is a parameter to be adjusted according to the speed of the mobile terminal. The data symbols are then detected by the proposed algorithms in a computationally efficient way by means of the Markov chain Monte Carlo (MCMC) technique with Gibbs sampling. The impact of the imperfect channel state information (CSI) on the bit error rate (BER) performance of these algorithms is investigated analytically and by computer simulations. A detailed computational complexity investigation and simulation results indicate that particularly the algorithm based on SDSC has significant performance and complexity advantages and is very robust against channel estimation errors compared with existing suboptimal detection and equalization algorithms proposed earlier in the literature.
Citation Count: 19
On Channel Estimation in DC Biased Optical OFDM Systems Over VLC Channels
(IEEE Computer Society, 2016) Panayırcı, Erdal; Dogan, Hakan; Panayırcı, Erdal
Visible Light Communication(VLC) has been considered as a potential access option for 5G wireless systems to solve performance limitation due to bandwidth shortage at radio frequency (RF) band. In (VLC) system illumination infrastructure has dual usage at the same time namely illumination and wireless data transmission. DC Biased optical (DCO)-OFDM has been proposed for VLC systems to provide optically power efficient solution and easy implementation. Wireless communication systems generally require estimating and tracking the fading channel in order to detect transmitted data coherently. In this work comb type pilot arrangement with interpolation and block type pilot arrangement are proposed for the DCOOFDM systems over visible light channels. Simulation results have verified that the proposed block type pilot arrangement based channel estimation has clear BER performance advantages compared with comb type pilot arrangement based channel estimation. © 2016 IEEE.
Citation Count: 6
Pilot assisted channel estimation for asymmetrically clipped optical OFDM over visible light channels
(Institute of Electrical and Electronics Engineers Inc., 2017) Panayırcı, Erdal; Şayli, Osman; Panayırcı, Erdal
The Visible Light Communication(VLC) has drawn significant attention recently for wireless communication in addressing the performance limitations of wireless systems due to the scarcity of bandwidth. In VLC system the visible lights is used not only for illuminating rooms but also for an optical data transmission. Asymmetrically clipped optical orthogonal frequency-division multiplexing (ACO-OFDM) has been proposed for VLC systems to provide optically power efficient solution in the optical domain. The estimation of wireless channel is crucial in order to detect the transmitted data coherently. In this work different interpolation based channel estimations for comb-type pilot distribution are proposed over visible light channels. Computer simulation results have confirmed that the proposed spline and low pass interpolation based channel estimation techniques have a clear BER performance advantages compared with linear and pchip interpolation based channel estimations for higher order modulations. © 2016 IEEE.
Citation Count: 3
Spline Interpolation Based Channel Estimation for ACO-OFDM over Visible Light Channels
(IEEE, 2016) Sayli, Osman; Dogan, Hakan; Panayırcı, Erdal
Visible light communication has been considered one of promising candidate technology to solve performance limitation due to bandwidth shortage at radio frequency (RF) band. In VLC system, the visible light is used not only for illuminating rooms but also for an optical data transmission. ACO-OFDM is a power efficient modification of OFDM to use in VLC systems. Wireless communication systems generally require estimating and tracking the fading channel in order to detect transmitted data coherently. In this work, spline interpolation based channel estimations for comb type pilot distribution is proposed over visible light channels. Computer simulation results have confirmed that the proposed channel estimation technique has a clear BER performance advantages compared with linear interpolation based channel estimation for higher order modulations.