Yazar "Ertug, Ozgur" seçeneğine göre listele

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    CAPACITY IMPROVEMENT OF IEEE802.11N MIMO-OFDM WLANS USING JOINT TRANSMIT/RECEIVE ANTENNA SELECTION OVER SPATIALLY MULTIPLEXING CORRELATED CHANNELS
    (IEEE, 2014) Savaşçıhabeş, Asuman; Ertug, Ozgur
    In this paper, we study and compare performance of joint transmit/receive antenna selection in MIMO-OFDM WLANs using dual polarized stacked circular microstrip antennas (SMP-SCP-ULA).At receiver side we use a flexible two-step selection algorithm (TSSA) and variable per-tone selection algorithm at transmitter side. The support of high data-rate MIMO spatial multiplexing communication in OFDM WLAN systems conforming to IEEE802.11n standard requires the use of compact antennas. Using antenna selection in conjunction with higher order modal SMP-SCP-ULA provides an additional performance improvement in terms of modal correlation and ergodic spectral efficiency.
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    M-CSK moduled flip-OFDM communication systems in visible light communications
    (Gazi Univ, Fac Engineering Architecture, 2023) Tekin, Meral; Savaşçıhabeş, Asuman; Ertug, Ozgur
    In this paper, it is proposed to use M-level color shift keying (M-CSK) modulation without vibration problem in Flip-OFDM waveform, which is an efficient unipolar version of OFDM for optical wireless communication systems. The performance of the proposed scheme is compared with the M-QAM modulated Flip-OFDM and M-CSK-modulated VLC OFDM methods based on the criteria of bit-error-rate (BER) and peak average power ratio (PAPR). The BER performance has also been analyzed, firstly by using uncoded proposed scheme then two channel coding techniques i.e.Reed-Solomon (RS) channel encoder and Convolutional Codes (CC) by using two channels i.e. AWGN and optical LOS channel. The entire channel coding techniques is carried out using QAM modulation. The simulation results show that, the proposed M-CSK Flip-OFDM method achieves good performance at high SNR values for both AWGN channel and optical LOS channel and also with applying RS and CC, the BER performance is also improved.
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    M-CSK-Flip OFDM for Visible Light Communication Systems
    (IEEE, 2021) Tekin, Meral; Savaşçıhabeş, Asuman; Ertug, Ozgur
    In last few years, research in visible light communications (VLC) based on the idea of using leds for both illumination and data communications in optical communication systems has been increasing. In this study, we propose M-ary CSK-Flip-OFDM system for optical wireless communication systems. The performance of the proposed scheme is compared with both the Flip-OFDM and classical OFDM systems in terms of bit error rate (BER) performance criteria. From the simulation results, it has been revealed that the results obtained with the proposed method provide better power efficiency than CSK-OFDM and QAM-Flip-OFDM performances.
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    On the Comparative Performance Analysis of Turbo-Coded Non-Ideal Single-Carrier and Multi-Carrier Waveforms over Wideb and Vogler-Hoffmeyer HF Channels
    (Spolecnost Pro Radioelektronicke Inzenyrstvi, 2014) Genc, Fatih; Resat, M. Anil; Savaşçıhabeş, Asuman; Ertug, Ozgur
    The purpose of this paper is to compare the turbo-coded Orthogonal Frequency Division Multiplexing (OFDM) and turbo-coded Single Carrier Frequency Do-main Equalization (SC-FDE) systems under the effects of Carrier Frequency Offset (CFO), Symbol Timing Offset (STO) and phase noise in wide-band Vogler-Hoffmeyer HF channel model. In mobile communication systems multipath propagation occurs. Therefore channel estimation and equalization is additionally necessary. Furthermore a non-ideal local oscillator generally is misaligned with the operating frequency at the receiver This causes carrier frequency offset. Hence in coded SC-FDE and coded OFDM systems; a very efficient, low complex frequency domain channel estimation and equalization is implemented in this paper Also Cyclic Prefix (CP) based synchronization synchronizes the clock and carrier frequency offset. The simulations show that non-ideal turbo-coded OFDM has better performance with greater diversity than non-ideal turbo-coded SC-FDE system in HF channel.
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    On the design and performance analysis of low-correlation compact space-multimode diversity stacked microstrip antenna arrays for MIMO-OFDM WLANs over statistically-clustered indoor radio channels
    (Czech Technical University, 2015) Savaşçıhabeş, Asuman; Ertug, Ozgur; Yazgan, Erdem
    The support of high spectral efficiency MIMO spatial-multiplexing communication in OFDM-based WLAN systems conforming to IEEE 802.11n standard requires the design and use of compact antennas and arrays with low correlation ports. For this purpose, compact space-multimode diversity provisioning stacked circular multimode microstrip patch antenna arrays (SCP-ULA) are proposed in this paper and their performance in terms of spatial and modal correlations, ergodic spectral efficiencies as well as compactness with respect to antenna arrays formed of vertically-oriented center-fed dipole elements (DP-ULA) and dominantmode operating circular microstrip patch antennas (CPULA) are presented. The lower spatial and modal correlations and the consequent higher spectral efficiency of SCP-ULA with ML detection over statistically-clustered Kronecker-based spatially-correlated NLOS Ricean fading channels with respect to DP-ULA and CPULA at significantly lower antenna and array sizes represents SCP-ULA as a promising solution for deployment in terminals, modems and access points of next-generation high-speed 802.11n MIMO-OFDM WLAN systems.