Dynamic Feedback Carrier Frequency Offset Estimator for OFDM Systems
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This paper presents an efficient feedback synchronization technique for joint estimation of integer and fractional carrier frequency offsets in orthogonal frequency division multiplexing (OFDM) systems. The proposed technique has high accuracy, broad estimation range, and works effectively over frequency-selective radio channels. A dynamic self-noise reduction technique is introduced to enhance the estimation accuracy over a wide range of signal-to-noise ratios by changing the synchronizer S-curve.Keywords:
Synchronizer
Carrier frequency offset
Pilot signal
Synchronization is one of the most crucial techniques in OFDM. This paper proposes a carrier frequency offset estimation algorithm for interleaved multi-user OFDM. It analyzes interleaved uplink OFDM signal structure, utilizes its cyclic characteristic to form specified data matrixes, and implements the carrier frequency offset estimation. This estimation algorithm doesn't need any training sequences or pilot signal, therefore improves band efficiency and lower computational complexity. The simulation shows that this algorithm has good performance when SNR is above zero.
Carrier frequency offset
Pilot signal
SIGNAL (programming language)
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Synchronization is one of the most crucial techniques in OFDM. This paper proposes a carrier frequency offset estimation algorithm for interleaved multi-user OFDM. We introduce interleaved uplink OFDM signal structure, utilize its cyclic characteristic to form specified data matrixes, and implement the carrier frequency offset estimation based on ESPRIT. This estimation algorithm doesn't need any training sequences or pilot signal, therefore improves band efficiency and lower computational complexity. It shows that this algorithm has good performance when SNR is above zero.
Carrier frequency offset
Pilot signal
SIGNAL (programming language)
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OFDM is a practical and efficient modulation technology. Frequency synchronization for OFDM is very important because the carrier frequency offset (CFO) will damage the performance. Based on the correlation between the front half-symbol and the back half-symbol, a cost function is deduced which varies with the carrier frequency offset as a sine function, and then a new carrier frequency offset estimation algorithm is presented. The papers will all be in a 2-column format and the final publication will be A4 size
Carrier frequency offset
Sine
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In this paper, we propose a new pilot tone placement scheme and a novel pilot sequence design to estimate the carrier frequency offset (CFO) in OFDM systems. Unlike the conventional approach in which isolated pilot tones are used, we cluster two pilot tones together as a group and these tone groups are equally spaced along the subcarrier axis. The pilot sequence of each group is carefully designed, in which the pilot symbol on the left side in each cluster is made antipodal to the one on the right. The performance in terms of the signal-to-interference ratio (SIR) can be significantly improved by the proposed scheme. Theoretical analysis and simulation results show that the clustered pilot tones can give a substantially lower variance of CFO estimate than that of the isolated pilot tones. For a given CFO, it demonstrates that the variance of the estimate can be reduced by 3 - 14 dB. The bit error rate (BER) is reduced by about 1 dB both in AWGN and multipath fading channels in the simulated cases
Pilot signal
Carrier frequency offset
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In this paper, the impact on carrier capture of high dynamic and low SNR signal in satellite communication caused by the rate of change of the carrier frequency offset is analyzed. Firstly, the existing large carrier frequency offset estimate technology is described. Secondly, the rate of change of the carrier frequency offset impact on the carrier frequency offset is analyzed. Finally, the Doppler shift characteristics of Low SNR high dynamic signal and performance impact on the capture carrier are simulated by MATLAB. The results showed that the rate of change of Doppler shift will seriously affect the number of non-coherent accumulation times of the carrier frequency offset estimate.
Carrier frequency offset
Carrier recovery
Doppler frequency
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A new pilot tone placing and pilot sequence design is proposed to compensate the carrier frequency offset (CFO) in OFDM systems. Unlike the conventional approach where isolated pilot tones are used, in this paper every two pilot tones are clustered as a group and these groups are equally spaced. The pilot sequence is carefully designed, of which the left hand sided pilot symbol in each cluster is antipodal with the right hand sided one. The performance in terms of the pilot channel interference ratio (CIR) can be significantly improved by the proposed pilot scheme. Theoretical analysis shows that the clustered pilot tones can give a substantially lower CFO variance than that of the isolated pilot tones. Simulation results are presented to verify our newly proposed theory.
Pilot signal
Carrier frequency offset
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OFDM is one of technology that can be utilized in a variety of telecommunication systems that being widely developed today, for application in LAN, WLAN, 3G, 4G, or 5G. One of the problem faced by the OFDM technology that its sensitivity to Carrier Frequency Offset (CFO) and the lack of synchronization in the OFDM signal. This research aims to design the synchronization that estimates Carrier Frequency Offset (CFO) to obtain synchronization of OFDM signal, where the error of the estimated Carrier Frequency Offset can be obtained, minimized and better than previous studies. The CFO estimation method in this research is using the training symbol on the OFDM symbol and utilize the statistical characteristics of the timing metric. This researchs result shows the Mean Square Error (MSE) of estimated Carrier Frequency Offset to Carrier Frequency Offset input, with range MSE 9.43 x 10-3 at 0 dB SNR input and MSE 1.687 x 10-5 at 30 dB SNR input. If Signal to Noise Ratio is greater, then the value of the mean square error (MSE) will be smaller. The position of the timing metric for timing estimation also affects to CFO estimation. CFO estimation accuracy will be maximized when using maximum timing metric.
Carrier frequency offset
Carrier-to-noise ratio
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A new coarse carrier frequency synchronization algorithm is proposed that can estimate a coarse carrier frequency offset using only two symbols in the frequency domain for orthogonal frequency division multiplexing (OFDM) systems. The problem of conventional carrier frequency synchronization algorithms is that they require many symbols to compensate for a carrier frequency offset when the offset is close to +0.5 or -0.5, where the frequency is normalized to the subcarrier space. In contrast, the proposed algorithm estimates a coarse carrier frequency offset of around +0.5 or -0.5, thereby reducing the remaining carrier frequency offset to within -0.25/spl sim/+0.25. As a result, the proposed algorithm can significantly reduce the time required to synchronize a carrier frequency.
Carrier frequency offset
Frequency deviation
Carrier recovery
Frequency-division multiplexing
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This paper discusses the effect of carrier frequency offset on the performance of OFDM communications systems. The sensitivity of OFDM systems to frequency offset compared with single carrier systems is a major disadvantage. In general, Frequency offset is defined as the difference between the nominal frequency and actual output frequency. In OFDM, the uncertainty in carrier frequency, which is due to a difference in the frequencies of the local oscillators in the transmitter and receiver, gives rise to a shift in the frequency domain. This shift is also referred to as frequency offset. The frequency offset disturbs the orthogonality of the sub-carriers and eventually gives rise to lower SNR and ISI which affects the overall performance of the OFDM system. The demodulation of a OFDM signal with an frequency offset in the carrier frequency can cause large bit error rate and it may to make contemptible the performance of a symbol synchronizer. It is therefore important to estimate the frequency offset and minimize/eliminate its impact. In this paper we will study the effects of CFO upon signal to noise ratio (SNR) for an OFDM system, and also estimate the amount of frequency offset. In the first part of paper we discusses Conjugate ICI Cancellation scheme. method for estimating of frequency offset. In second part we will discuss another method i.e Extended Kalman Filtering (EKF) for estimating CFO and then Simulation results illustrate comparison of performance of these two methods for BPSK modulation scheme for different values of frequency offset.
Carrier frequency offset
Symbol rate
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Frequency offset estimation is an important module in the synchronisation of underwater acoustic (UWA) orthogonal frequency division multiplexing (OFDM) systems. Different ways are used for carrier frequency offset (CFO) estimation such as maximum likelihood based on a cyclic prefix. In this paper, the Zadoff-Chu (ZC) sequences are used for OFDM synchronisation in underwater communications. The normalised carrier frequency offset can be estimated using the ZC cross-correlation between the primary synchronisation signal and the corresponding local signal, which causes large complexity. The ZC sequences have a time centre symmetric property, and thus the autocorrelation of the received primary synchronisation signal can be used for frequency offset estimation. In this paper, we propose a modified algorithm with low complexity for frequency offset estimation. Simulation results demonstrate that the proposed algorithm can estimate the frequency offset accurately with simple implementation in comparison with the traditional methods.
Cyclic prefix
Carrier frequency offset
Pilot signal
UTC offset
SIGNAL (programming language)
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