CFO Estimation Research Articles

Deep Learning-Based CFO Estimation for Multi-User Massive MIMO With One-Bit ADCs

Deep Learning-Based CFO Estimation for Multi-User Massive MIMO With One-Bit ADCs

Innovative Joint CFO and Channel Estimation for RIS-Aided OFDM Systems

Innovative Joint CFO and Channel Estimation for RIS-Aided OFDM Systems

Low-complexity Precoding-aided CFO Estimation for ICA-based MIMO OFDM Systems in URLLC

Low-complexity Precoding-aided CFO Estimation for ICA-based MIMO OFDM Systems in URLLC

Performance analysis of a hybrid OFDM-MIMO multiresonator system: synchronization, CFO estimation, and return loss evaluation

Performance analysis of a hybrid OFDM-MIMO multiresonator system: synchronization, CFO estimation, and return loss evaluation

Joint Estimation and Compensation of CFO, IQ Imbalance and Channel Parameters for Zero Padded OTSM Systems

Joint Estimation and Compensation of CFO, IQ Imbalance and Channel Parameters for Zero Padded OTSM Systems

Blind Joint CFO and STO Estimation for FBMC/OQAM Systems

Blind Joint CFO and STO Estimation for FBMC/OQAM Systems

Joint STO and DFO Estimation for SEFDM in Low-Earth-Orbit Satellite Communications

In this article, a joint symbol timing offset (STO) and Doppler frequency offset (DFO) estimation algorithm is proposed for spectrally efficient frequency division multiplexing (SEFDM) system in the downlink of low-earth-orbit (LEO) satellite communications. Considering the nonorthogonality of SEFDM, the proposed algorithm is derived by maximizing likelihood function. To reduce computation complexity of STO estimator, all unnecessary terms in likelihood function are ignored. Further, the proposed CFO estimator is simplified by replacing the inverse trigonometric function with polynomial approximation. According to relevant standards issued by the International Telecommunications Union and the 3rd Generation Partnership Project, simulation parameters are set to evaluate the estimation performance. Simulation results show that the proposed algorithm is robust to different packing factors of SEFDM, and outperforms traditional estimation methods.

Modified Bi-SVD and Modified Gradient Algorithms for Noise Subspace Estimation with Full Rank Update for Blind CFO Estimator in OFDM Systems

This paper proposes a modified Gradient algorithm and a modified Bi-SVD algorithm for the estimation of noise subspace and their utility in blind CFO estimation. The proposed modified Bi-SVD and modified Gradient algorithms have the dual advantageous features of not only the improved of noise subspace estimation but also the reduced computational complexities. The results obtained through the modified Gradient and modified Bi-SVD algorithms show excellent agreement with the results of the direct SVD technique requiring relatively more computational complexity. Another important contribution of this paper is the adoption of full-rank updated inverse autocorrelation matrix Rinv into the proposed noise subspace estimation algorithms. The improved noise estimation algorithms have been eventually used to aid the MUSIC algorithm to facilitate improved estimation of CFO required in OFDM systems. This paper substantiates the envisaged improved estimation accuracy of CFO through simulation results derived through proposed algorithms relative to conventional SVD.

Semi-blind estimation of CFO and channels for STBC-OFDM system

Semi-blind estimation of CFO and channels for STBC-OFDM system

Semi-blind estimation of CFO and channels for STBC-OFDM system

Semi-blind estimation of CFO and channels for STBC-OFDM system

CFO Estimation Based on Auto-Correlation With Flexible Intervals for OFDM Systems With 1-bit ADCs

For orthogonal frequency division multiplexing (OFDM) systems, the carrier frequency offset (CFO) estimation is required for the frequency synchronization before the data reception. When 1-bit ADCs are employed in OFDM systems, the available information is limited to the sign of the received signal, and the acquisition of the CFO is not easy problem. To overcome this limitation, we utilize the extended preamble and construct the bank of the CFO estimators based on auto-correlation (AC) taking the samples from the preamble with flexible intervals, which produces the candidates for CFO estimate. We propose the CFO estimation algorithms using the normalized squared errors (NSEs) as the concept to check the quality of the candidates of CFO estimate. The simulation results show that the proposed algorithm works well in the multipath fading channel, and is superior to the conventional CFO estimation method based on AC with fixed interval.

Develop of CFO in High Mobility Environments for OFDM-DMWT Based Mobile Wireless Applications

An “Orthogonal Frequency division Multiplexing (OFDM)” systems are sensitive to “service Frequency Offset (CFO)” mistakes. OFDM- “Discrete Multi-wavelet remodel (DMWT)” based totally cellular wireless with a sender, a provider Frequency Offset errors turns into similarly tough for cellular applications in view that power postpone outline of the channel may trade quick because of the sporadic start and dying of the channel paths. We discover analytical expressions for channel estimation mistakes inside the existence of CFO mistakes and excessive mobility. We display that the sensitivity of the channel estimator be capable of still be exploited to increase CFO in high mobility environments. A comparative have a look at amongst extraordinary techniques of service frequency offset estimation in OFDM systems is offered. We keep in mind strategies in frequency area are considered, namely; training image approach and Pilot tone technique. Mean square blunders (MSE) is the evaluation criteria used within the look at. Simulation consequences display that the CFO estimation strategies the schooling image technique outperforms the pilot tone approach with the aid of about 2dB. The contrast results are considered at MSE of 10-4 and normalized CFO of 0.2. Keywords— CFO, ICI, BER, SNR, OFDM, DMWT, MSE, Frequency domain. DOI : 10.7176/NCS/10-04 Publication date :July 31 st 2019

Message Passing-Based Joint CFO and Channel Estimation in mmWave Systems With One-Bit ADCs

Channel estimation at millimeter wave (mmWave) carrier frequencies is challenging when large antenna arrays are used. Prior work has leveraged the sparse nature of mmWave channels via compressed sensing-based algorithms for channel estimation. Most of these algorithms, though, assume perfect synchronization and are vulnerable to phase errors that arise due to carrier frequency offset and phase noise. Recently, sparsity-aware, non-coherent beamforming algorithms that are robust to phase errors were proposed for narrowband phased array systems with full resolution analog-to-digital converters. Such energy-based algorithms, however, are not robust to heavy quantization at the receiver. In this paper, we develop a joint carrier frequency offset and wideband channel estimation algorithm that is scalable across different hardware architectures. Our method exploits the sparse nature of mmWave channels in the angle-delay domain, in addition to the compressibility of the phase error vector. We formulate the joint estimation as a quantized sparse bilinear optimization problem and then use message passing for recovery. We also give an efficient implementation of a generalized bilinear message passing algorithm for the joint estimation in one-bit receivers. Simulation results show that our method is able to estimate the frequency offset and the channel compressibility, even in the presence of phase noise.

CFO sensitivity and efficient joint estimation for the short filter multicarrier system FBMC-PAM

Sensitivity to carrier frequency offset, due to oscillator inaccuracy and terminal mobility, is a key issue that modern multicarrier systems have to face. In that respect, FBMC-PAM holds a specific position due to its short prototype filter: the overlapping factor is K=2 and the width of the main lobe of its frequency response is 3 times the sub-carrier spacing, while OFDM and FBMC-OQAM schemes have frequency response whose main lobe width is 2 times the sub-carrier spacing. As a consequence, it is shown in the present paper that FBMC-PAM outperforms other multicarrier techniques in terms of CFO sensitivity. In order to best exploit this property in burst transmission, an efficient and accurate approach for joint symbol timing and CFO estimation is proposed, based on a specific preamble. A theoretical in-depth analysis of the scheme is provided as well as performance validation in multipath channel through simulations.

Angle-Domain Approach for Parameter Estimation in High-Mobility OFDM With Fully/Partly Calibrated Massive ULA

In this paper, we consider a downlink orthogonal frequency division multiplexing (OFDM) system from a base station to a high-speed train (HST) equipped with fully/partly calibrated massive uniform linear antenna-array (ULA) in wireless environments with abundant scatterers. Multiple Doppler frequency offsets (DFOs) stemming from intensive propagation paths together with transceiver oscillator frequency offset (OFO) result in a fast time-varying frequency-selective channel. We develop an angle domain carrier frequency offset (CFO, general designation for DFO and OFO) estimation approach. A high-resolution beamforming network is designed to separate different DFOs into a set of parallel branches in angle domain such that each branch is mainly affected by a single dominant DFO. Then, a joint estimation algorithm for both maximum DFO and OFO is developed for fully calibrated ULA. Next, its estimation mean square error (MSE) performance is analyzed under inter-subarray mismatches. To mitigate the detrimental effects of inter-subarray mismatches, we introduce a calibration-oriented beamforming parameter (COBP) and develop the corresponding modified joint estimation algorithm for partly calibrated ULA. Moreover, the Cramer-Rao lower bound of CFO estimation is derived. Both theoretical and numerical results are provided to corroborate the proposed method.

Adaptive Joint Semi-blind Estimation of CFO and Channel for OFDM Systems

The large number of subcarriers, used in OFDM systems, increases the sensivity to frequency offset which results from a Doppler shift, due to mobile movement, as well as from a mismatch between the carrier frequencies at the transmitter and receiver. The problem of channel estimation in a practical OFDM receiver that suffers from CFO has been addressed in this paper. We first derived the modified MUSIC based blind CFO estimator. Next, we propose new joint training-based and joint semi-blind CFO and channel estimation for OFDM systems. Whereas the training-based estimator only assumes knowledge of pilot tones, the semi-blind estimator assumes knowledge of the virtual subcarriers (VSCs). For both estimators we derive a maximum likelihood (ML) algorithm for block processing and LMS algorithm for adaptive processing. It is demonstrated that the CFO estimators are able to perform well with a very small number of OFDM blocks. The performance of our estimators was investigated by simulations.

Pilot Extraction for CFO Estimation using Comb-Type Pilot Arrangement

Frequency synchronization is vital issue in execution of OFDM system. In this paper we proposed a technique to estimate and compensate CFO in frequency domain. Estimation is based on Comb-type pilot sequence, which can measure phase rotation of received signal pass through fading channel. Performance of proposed scheme is evaluated on basis of MSE and BER. CFO estimation can be computed by pilot, phase information obtained at receiver side. It is estimated at receiver by fine CFO estimation.

Synchronization approach for dynamic hexagonal time–frequency lattice MCM system

In this paper, effects of time offset and carrier frequency offset on dynamic hexagonal lattice multi-carrier modulation (HMCM) system are first analyzed. Then the synchronization acquisition approach for dynamic lattice HMCM system over non-stationary doubly dispersive (NSDD) channel, including preamble structure (using two CAZAC sequences), time and frequency synchronization algorithms, is proposed. The closed-form Cramér–Rao lower bound of the proposed CFO estimation scheme is given after a detailed theoretical analysis. Simulation results show that the proposed preamble structure, time and frequency synchronization algorithms for dynamic lattice HMCM system can obtain robust performance over NSDD channel. Meanwhile, the performance of the proposed time offset and frequency offset estimation schemes outperform that of traditional schemes and degrade with the increasing of mobile terminalʼs velocity.

Preamble Design for Joint estimation of Channel, CFO and Receiver I/Q-Imbalance in OFDM Systems

Preamble Design for Joint estimation of Channel, CFO and Receiver I/Q-Imbalance in OFDM Systems

Blind Symbol Timing and CFO Estimation for OFDM/OQAM Systems

The paper deals with the problem of blind synchronization for OFDM/OQAM systems. Specifically, by exploiting the approximate conjugate-symmetry property of the beginning of a burst of OFDM/OQAM symbols, due to the presence of the time offset, a new procedure for blind symbol timing and CFO estimation is proposed. The performance of the derived blind estimators is analyzed by computer simulations; the results show that the proposed methods may provide acceptable performance for reasonable values of the signal-to-noise ratio.