Showing 1-25 of 53,981 resultsfor "Index Terms":Orthogonal frequency division multiplexing (OFDM)
"Index Terms":Orthogonal frequency division multiplexing (OFDM)
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A novel minimum output variance estimator for carrier frequency offset in OFDM systems
Tsinghua Science and Technology
Cited by: Papers (2)
In orthogonal frequency-division multiplexing (OFDM) systems, the carrier frequency offset (CFO) destroys the orthogonality among subcarriers which degrades system performance. Various CFO estimation methods have been developed to compensate for the CFO at the receiver. This paper describes a novel minimum output variance method for OFDM systems with CFO in additive white Gaussian nois...Show More
Particle-based iterative blind receiver for orthogonal frequency-division multiplexing with frequency offset
Orthogonal frequency-division multiplexing (OFDM) systems are sensitive to carrier frequency offset (CFO) which introduces intercarrier interference and significantly degrades system performance. This paper describes an iterative blind receiver consisting of a sequential Monte Carlo detector, a CFO estimator, and a compensator to reduce intercarrier interference. The framework is of low comp...Show More
Carrier Frequency Offset Estimation for OFDM Systems Over Mobile Radio Channels
In this paper, a new technique is proposed for blind estimation of carrier frequency offset (CFO) in wireless orthogonal frequency-division multiplexing (OFDM) systems with constant-modulus constellations. The proposed scheme is based on the assumption that the channel slowly changes in the time domain with respect to the OFDM symbol duration. As a consequence, the channel effect on a ...Show More
In this letter, we analyze the transmitter design for coherent optical orthogonal frequency-division multiplexing (CO-OFDM) employing predistortion. Digital clipping and digital predistortion processes are introduced to the radio frequency OFDM transmitter to compensate the nonlinearity effect introduced by the optical in-phase/quadrature modulator. We first provide a detailed description of signa...Show More
An Experimental Proof of Concept for OFDM-based ISAC System Utilizing Stepped-Carrier and TDM MIMO scheme
2024 IEEE 25th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC)
Year: 2024 | Conference Paper |
The problem with orthogonal frequency-division multiplexing (OFDM)-based integrated sensing and communication (ISAC) system is that the bandwidth required for high range resolution cannot be obtained. This problem can be overcome by using a stepped-carrier method, where the carrier frequency of each OFDM signal increases linearly to achieve wide overall RF bandwidth. In this article, f...Show More
Pulsed-OFDM Modulation for Ultrawideband Communications
In this paper, we describe a novel approach for reducing the power consumption and complexity of a multiband orthogonal frequency-division multiplexing (MB-OFDM) ultrawideband (UWB) system by applying ideas from pulsed UWB systems. The approach is quite general and applicable to many other systems. Unlike the MB-OFDM system, the enhancement that we propose uses pulses with duty cycles ...Show More
Blind symbol-timing and frequency-offset estimation in OFDM systems with real data symbols
In this letter, the problem of blind symbol-timing and frequency-offset estimation in orthogonal frequency-division multiplexing (OFDM) systems with real data symbols is considered. Maximum-likelihood (ML) estimators for the parameters of interest have been derived by modeling the OFDM signal as a proper complex Gaussian random process. However, when data symbols belong to a real const...Show More
Maximum-Likelihood-Based Performance Enhancement of Clipped and Filtered OFDM Systems With Clipping Noise Cancellation
Clipping and filtering (CAF) technique is known as a simple and effective approach that reduces the peak-to-average power ratio (PAPR) of orthogonal frequency-division multiplexing (OFDM) signals at the cost of increasing in-band distortion. Clipping noise cancelation (CNC) can compensate for the performance degradation due to the in-band distortion caused by CAF, especially when the number ...Show More
Comments on "Semi-Blind Channel Estimation and Equalization for MIMO Space - Time Coded OFDM
For original paper see ibid., vol.53, no.2, p.363-374, Feb. 2006. A semiblind channel estimation scheme of the multiple-input-multiple-output space-time coded orthogonal frequency-division multiplexing system was proposed in the aforementioned paper for either real or complex with symmetric signals. We point out that this scheme cannot work correctly for complex signal scenario.Show More
Transmission of Wavelength-Division-Multiplexed Channels With Coherent Optical OFDM
IEEE Photonics Technology Letters
Cited by: Papers (6)
Transmission performance for wavelength-division-multiplexed (WDM) systems with coherent optical orthogonal frequency-division multiplexing is simulated including the fiber nonlinearity effect. The simulation shows that the system Q of the WDM channels at 10 Gb/s is over 13.0 dB for a transmission up to 4800 km of standard single-mode fiber without dispersion compensationShow More
A New Blind Joint Timing and Frequency Offset Estimator for OFDM Systems Over Multipath Fading Channels
A blind joint timing and frequency synchronization algorithm is derived for orthogonal frequency-division multiplexing (OFDM) signals transmitting over multipath fading channels. The proposed estimator requires neither the knowledge of the signal-to-noise ratio (SNR) nor the power delay profile of the fading channels, except that the maximum delay spread L should be known and should be short...Show More
A closed-form blind CFO estimator based on frequency analysis for OFDM systems
This letter proposes a blind carrier frequency offset (CFO) estimator for orthogonal frequency-division multiplexing (OFDM) systems based on the frequency analysis of the received signal, and derives a closed-form CFO estimate. Since only one OFDM symbol is utilized instead of multi-symbol averaging, the proposed method is effective even when the CFO is time varying. Finally, analysis ...Show More
A Novel Two-Step Channel-Prediction Technique for Supporting Adaptive Transmission in OFDM/FDD System
This paper introduces a novel channel-prediction technique for an orthogonal frequency-division multiplexing (OFDM)/frequency-division duplex (FDD) system to support an adaptive-modulation and coding (AMC) scheme over a rapidly time-varying multipath fading channel. Most channel-prediction techniques assume that there is no channel variation in the predefined time duration, e.g. the slot. As...Show More
Precoded Multiuser OFDM Transceiver in Timing Asynchronous Environment
The performance of a multiuser orthogonal frequency-division multiplexing (OFDM) transceiver, called the precoded multiuser OFDM (PMU-OFDM), with time asynchronous access is investigated in this paper. It is shown that multiaccess interference (MAI) due to time asynchronism is asymptotically zero as the number of parallel input symbols N becomes large in the PMU-OFDM system...Show More
LDPC-Coded OFDM Transmission Over Graded-Index Plastic Optical Fiber Links
IEEE Photonics Technology Letters
Cited by: Papers (13)
The possibility of 10-Gb/s transmission over graded-index plastic optical fiber (GI-POF) using the orthogonal frequency-division multiplexing (OFDM) and iteratively decodable codes is demonstrated by simulations. Several classes of low-density parity-check (LDPC) codes suitable for use in LDPC-coded OFDM transmission over GI-POF are presented as well. Several power efficient OFDM...Show More
ML-based symbol timing and frequency offset estimation for OFDM systems with noncircular transmissions
This paper deals with the problem of joint symbol timing and carrier-frequency offset (CFO) estimation in orthogonal frequency-division multiplexing (OFDM) systems with noncircular (NC) transmissions. Maximum-likelihood (ML) estimators of symbol timing and CFO have been derived under the assumption of nondispersive channel and by modeling the OFDM signal vector as a circular complex Ga...Show More
A novel non-data-aided symbol timing recovery technique for OFDM systems
A new highly efficient non-data-aided technique to recover symbol timing of orthogonal frequency-division multiplexing systems is proposed. The algorithm in the proposed work exploits the interference that results due to the loss of orthogonality between subcarriers, where the second-order statistics of the resulting interference is proportional to the offset from the optimum sampling point. The p...Show More
An Efficient Frequency Offset Estimation Method With a Large Range for Wireless OFDM Systems
An efficient frequency offset estimation method is proposed for wireless orthogonal frequency-division multiplexing (OFDM) systems. In the proposed method, the received samples of the training symbol are processed by a novel envelop equalized processing method, and the estimation of the frequency offset in the OFDM systems turns out to be the frequency estimation of a complex tone. A n...Show More
An EM-Based Semiblind Joint Channel and Frequency Offset Estimator for OFDM Systems Over Frequency-Selective Fading Channels
We propose an estimator that will jointly estimate the channel and the carrier frequency offset (CFO) for orthogonal frequency-division multiplexing (OFDM) systems based on the maximum-likelihood criterion. The proposed estimator uses only one received OFDM symbol to perform estimation and does not require the knowledge of power delay profile, except that the number of delay paths shou...Show More
Noniterative Joint Frequency Offset and Channel Estimation for MIMO OFDM Systems Using Cascaded Orthogonal Pilots
In this paper, we reconsider the issues of frequency offset and channel estimation in multiple-input-multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) systems. We first design “cascaded orthogonal” pilot symbols and adopt the properties of Fourier transform and Hadamard product to deliver a closed-form estimate of frequency offset; meanwhile, another closed-form estimate...Show More
We show the first experiment of bit and power loading for coherent optical orthogonal frequency-division-multiplexing (CO-OFDM) systems. The data rate of CO-OFDM systems can be dynamically adjusted according to the channel condition. The system performance can be further improved through optimal power loading into each modulation band.Show More
QAM Symbol Error Rate in OFDM Systems Over Frequency-Selective Fast Ricean-Fading Channels
For digital data transmission using an orthogonal frequency-division multiplexing (OFDM) over fading channels, the interchannel- interference (ICI) term caused by the Doppler spread is correlated with the desired signal term. Nonetheless, many researchers have assumed the ICI term to be uncorrelated with the desired signal term. In this paper, we present the symbol-error-rate (SER) performan...Show More
Transmission performance of adaptively modulated optical OFDM signals in multimode fiber links
A novel optical signal modulation concept of adaptively modulated optical orthogonal frequency-division multiplexing (AMOOFDM) is proposed and numerical simulations of the transmission performance of AMOOFDM signals are undertaken in unamplified multimode fiber (MMF)-based links using directly modulated distributed feedback lasers (DMLs). It is shown that 28 Gb/s intensity modulation and direct-de...Show More
Space-Frequency Conjugate Two-Path Transmission for Precoded OFDM Systems
This brief presents space-frequency (SF) conjugate two-path transmission orthogonal frequency division multiplexing (OFDM) systems with precoders to combat inter-carrier interference in mobile fading channels. Initially, an SF architecture is developed to form an SF-OFDM system. Second, a conjugate cancellation two-path transmission scheme is integrated with the SF-OFDM system to...Show More
Interference Cancellation Between OFDM Radars Using Pre-Assigned Pilot Signal and Strong Target Elimination
2024 21st European Radar Conference (EuRAD)
Year: 2024 | Conference Paper |
This paper proposes a simple approach to cancel mutual interference between orthogonal frequency-division multiplexing (OFDM) radars, which is implemented by inserting pre-assigned pilot signals into OFDM radar waveforms. This enables a victim radar to estimate the modulated data as well as the time and frequency offsets of the interfering signal from an aggressor radar. This allows al...Show More
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