OFDM ORTHOGONAL FREQUENCY-DIVISION MULTIPLEXING


Orthogonal frequency-division multiplexing (OFDM) is a method of digital signal modulation in which a single data stream is split across several separate narrowband channels at different frequencies to reduce interference and crosstalk

Channel estimation techniques based on pilot arrangement in OFDM systems
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The channel estimation techniques for OFDM systems based on pilot arrangement are investigated. The channel estimation based on comb type pilot arrangement is studied through different algorithms for both estimating channel at pilot frequencies and interpolating

Transmit power adaptation for multiuser OFDM systems
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In this paper, we develop a transmit power adaptation method that maximizes the total data rate of multiuser orthogonal frequency division multiplexing ( OFDM ) systems in a downlink transmission. We generally formulate the data rate maximization problem by allowing that a

Comparison of asymmetrically clipped optical OFDM and DC-biased optical OFDM in AWGN
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We present theoretical and simulation results for the performance of asymmetrically-clipped optical OFDM (ACOOFDM) and DC-biased optical OFDM (DCO- OFDM ) in AWGN for intensity-modulated direct-detection systems. Constellations from 4 QAM to 1024 QAM are

Analysis and design of OFDM /OQAM systems based on filterbank theory
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A discrete-time analysis of the orthogonal frequency division multiplex/offset QAM ( OFDM /OQAM) multicarrier modulation technique, leading to a modulated transmultiplexer, is presented. The conditions of discrete orthogonality are established with respect to the

A robust timing and frequency synchronization for OFDM systems
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A robust symbol-timing and carrier-frequency synchronization scheme applicable to orthogonal frequency-division-multiplexing systems is presented. The proposed method is based on a training symbol specifically designed to have a steep rolloff timing metric. The

On the effect of Wiener phase noise in OFDM systems
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Multicarrier modulation exhibits a significant sen-sitivity to the phase noise of the oscillator used for frequency down-conversion at the portable receiver. For this reason, it is important to evaluate the impact of the phase noise on the system performance. In this letter we

Intercarrier interference in MIMO OFDM
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In this paper, we examine multicarrier transmission over time-varying channels. We first develop a model for such a transmission scheme and focus particularly on multiple-input multiple output (MIMO) orthogonal frequency division multiplexing ( OFDM ). Using this

Channel estimation for wireless OFDM systems
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Orthogonal frequency division multiplexing ( OFDM ) is a special case of multi-carrier transmission and it can accommodate high data rate requirement of multimedia based wireless systems. Since channel estimation is an integral part of OFDM systems, it is critical

ICI mitigation for pilot-aided OFDM mobile systems
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Orthogonal frequency-division multiplexing ( OFDM ) is robust against frequency selective fading due to the increase of the symbol duration. However, for mobile applications channel time-variations in one OFDM symbol introduce intercarrier-interference (ICI) which degrades

Space-time-frequency coded OFDM over frequency-selective fading channels
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(STF) coding for multiantenna orthogonal frequency-division multiplexing ( OFDM ) transmissions over frequency-selective Rayleigh fading channels. Incorporating subchannel grouping and choosing appropriate system parameters, we first convert our system into a set

On the comparison between OFDM and single carrier modulation with a DFE using a frequency-domain feedforward filter
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Most comparisons between single carrier and multi-carrier modulations assume frequency- domain linear equalization of the channel. In this paper we propose a new frequency- domain decision feedback equalizer (FD-DFE) for single carrier modulation, which makes

Pilot-assisted time-varying channel estimation for OFDM systems
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In this paper, we deal with channel estimation for orthogonal frequency-division multiplexing ( OFDM ) systems. The channels are assumed to be time-varying (TV) and approximated by a basis expansion model (BEM). Due to the time-variation, the resulting channel matrix in the

Phase estimation for coherent optical OFDM
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Phase estimation is one of the enabling functionalities in coherent optical orthogonal frequency-division-multiplexing (CO- OFDM ) receivers. In this letter, we compare pilot-aided and data-aided phase estimation methods for a CO- OFDM transmission experiment at 8

Subspace-based blind and semi-blind channel estimation for OFDM systems
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This paper proposes a new blind channel estimation method for orthogonal frequency division multiplexing ( OFDM ) systems. The algorithm makes use of the redundancy introduced by the cyclic prefix to identify the channel based on a subspace approach. Thus

Simple equalization of time-varying channels for OFDM
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(MMSE) equalizer for orthogonal frequency-division multiplexing ( OFDM ) systems over time- varying multipath channels. The equalization algorithm exploits the band structure of the frequency-domain channel matrix by means of a band LDL H factorization. The complexity of

Performance analysis and design optimization of LDPC-coded MIMO OFDM systems
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We consider the performance analysis and de-sign optimization of low-density parity check (LDPC) coded multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing ( OFDM ) systems for high data rate wireless transmission. The tools of density

Joint symbol timing and channel estimation for OFDM based WLANs
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The orthogonal frequency-division multiplexing ac-cess technique has recently been attracting considerable interest especially for wireless local area networks (WLANs). In this letter, we consider the joint estimation of the symbol timing, the channel length and the

Modulation formats and waveforms for 5G networks: Who will be the heir of OFDM : An overview of alternative modulation schemes for improved spectral
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OFDM and OFDMA are the modulation technique and the multiple access strategy adopted in LTE fourthgenereation (4G) cellular network standards, respectively . OFDM and OFDMA succeeded code division multiple access (CDMA), employed in thirdgeneration

Design of wide-bandwidth envelope-tracking power amplifiers for OFDM applications
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An efficiency-enhanced power-amplifier system design is presented based on wide- bandwidth envelope tracking (WBET) with application to orthogonal frequency-division multiplexing wireless local area network systems. Envelope elimination and restoration

Peak-to-average power ratio in MIMO- OFDM systems using selective mapping
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This letter evaluates the peak-to-average power ratio (PAR) performance in a space-time block coded (STBC) multi-input multi-output orthogonal frequency-division multiplexing (MIMO- OFDM ) system using the selective mapping (SLM) approach. The investigated SLM


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