Elektrik - Elektronik Mühendisliği Bölümü Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12469/47

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Now showing 1 - 6 of 6

Citation - WoS: 1
Citation - Scopus: 3
The Effect of Primary User Bandwidth on Bayesian Compressive Sensing Based Spectrum Sensing
(IEEE Computer Society, 2016) Başaran, Mehmet; Erküçük, Serhat; Cirpan, Hakan Ali
The application of compressive sensing (CS) theory has found great interest in wideband spectrum sensing. Although most studies have considered perfect reconstruction of the primary user signal it is actually more important to assess the presence or absence of the signal. Among CS based methods Bayesian CS (BCS) takes into consideration the prior information of signal coefficients to be estimated which improves signal reconstruction performance. On the other hand the sparsity level of the signal to be estimated has a direct impact on signal reconstruction and detection performances. Considering all of the above the effect of sparsity level on BCS based spectrum sensing is studied in this paper. More specifically a BCS based spectrum sensing scheme is considered and its mean-square error (MSE) performance is compared with the Bayesian Cramer-Rao bound for various user bandwidths. BCS MSE is also compared with the deterministic lower MSE (DL-MSE) which is a tight lower bound of the conventional basis pursuit approach. Furthermore complementary receiver operating characteristic (ROC) curves are obtained to examine the trade-off between probabilities of false alarm and detection depending on the user signal bandwidth.
Citation - Scopus: 1
Why Do Students Prefer Search Engines Over Academic Databases
(IEEE Computer Society, 2013) Öğrenci, Arif Selçuk
Students' preference of search engines in online information retrieval has been a problem for several reasons. This work tries to share our experience about the reasons why they do not utilize academic databases. Past experiences seeking convenience and the availability of automatic translation in search engines seem to be the main reasons. Several suggestions are offered that aim to increase the level of competency of students in utilizing academic databases. Furthermore students should also be informed adequately about the potential threats in using search engines as their only online information source. © 2013 IEEE.
Citation - Scopus: 2
Iterative Channel Estimation For Spatial Modulation Systems Over Fast Fading Channels [hızlı Sönümlemeli Kanallarda Uzaysal Modülasyon Sistemleri için İteratif Kanal Kestirimi]
(IEEE Computer Society, 2014) Acar, Yusuf; Doğati, Hakan; Panayırcı, Erdal
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 have not been investigated for SM based systems. In this paper it shown that the RLS based receiver has a performance degradation for fast fading channels and a new iterative channel estimation techniques is proposed with the necessary signal model to enhance receiver performance for fast fading channels. Computer simulation results indicate that proposed iterative receiver has a significant performance advantage over the RLS based receiver for time-varying Rayleigh channels. © 2014 IEEE.
Citation - WoS: 22
Citation - Scopus: 26
On Channel Estimation in Dc Biased Optical Ofdm Systems Over Vlc Channels
(IEEE Computer Society, 2016) Sayli, Osman; 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 - WoS: 2
Citation - Scopus: 2
Noncoherent Ultra Wideband Wireless Sensor Networks for Primary User Detection
(IEEE Computer Society, 2016) Sabucu, Yağmur; Erküçük, Serhat
As a result of increasing demand for new technologies unlicensed usage of available spectrum has become very essential to provide an efficient usage of spectrum. For that reason sensor networks may be a reliable option to decide on the absence/presence of licensed users and to communicate without causing much interference as a secondary user network. These networks consist of two communication links for primary user detection. One link is between the primary user and the sensors and the other link is between the sensors and the fusion center. In this study we consider an IEEE 802.15.4a based ultra wideband (UWB) network with a noncoherent receiver structure for the first link. For the second link binary pulse position modulation is implemented to convey primary user information to the fusion center. Numerical expressions for probabilities of false alarm and detection for the overall system are obtained and validated by simulations where the performance of the system improves with number of sensors and the reliability of the first link. The results obtained from this study can be used for improving the primary user detection performance of UWB based wireless sensor networks in noncoherent operation mode. © 2016 IEEE.
Citation - WoS: 1
Citation - Scopus: 1
Sparse Channel Estimation for Ofdm-Based Underwater Cooperative Systems With Amplify-And Relaying
(IEEE Computer Society, 2014) Şenol, Habib; Panayırcı, Erdal; Uysal, Murat
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 the overall sparse channel taps from the source to the destination as well as their locations using the matching pursuit (MP) approach. The correlated non-Gaussian effective noise is modeled as a Gaussian mixture. Based on the Gaussian mixture model an efficient and low complexity algorithm is developed based on the combinations of the MP and the space-alternating generalized expectation-maximization (SAGE) technique to improve the estimates of the channel taps and their location as well as the noise distribution parameters in an iterative way. The proposed SAGE algorithm is designed in such a way that by choosing the admissible hidden data properly on which the SAGE algorithm relies a subset of parameters is updated for analytical tractability and the remaining parameters for faster convergence Computer simulations show that underwater acoustic (UWA) channel is estimated very effectively and the proposed algorithm has excellent symbol error rate and channel estimation performance. © 2014 IEEE.

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