Integer Frequency Offset Estimation Research Articles

A Neural Network based Integer Frequency Offset Estimation and PSS Detection in 5G NR Systems

A Neural Network based Integer Frequency Offset Estimation and PSS Detection in 5G NR Systems

The impact of PSS autocorrelation on cell search based on robust maximum likelihood scheme in LTE system

Robust Maximum Likelihood scheme for primary synchronization signal (PSS) detection and integer frequency offset (IFO) in Long Term Evolution (LTE) system has the best performance of cell search [5]. This scheme provides good synchronization performance based on correlation properties of Zadoff-Chu (ZC) sequences and reduced-rank representation of channel frequency response in multi-path propagation fading environment. The three ZC sequences used for PSS in LTE system cannot be said to have sufficient correlation properties in considering impact of symbol timing error. In this paper, we evaluate impact of the autocorrelation of PSS on PSS detection and IFO estimation and raise an issue of using other ZC sequence with better correlation properties. The simulation results show that PSS detection and IFO estimation performances are improved by using proposed ZC sequence.

Timing and Integer Frequency Offset Estimation for DLMT System over Time-Varying Rayleigh Fading Channel

In this paper, we study the timing and integer carrier frequency offset (ICFO) estimation problem for dynamic lattice multicarrier transmission (DLMT) system over time-varying Rayleigh fading channel. Firstly, a novel preamble structure based on two constant amplitude zero auto-correlation (CAZAC) sequences is designed for DLMT system. Then, by using the designed dual-CAZAC preamble, a discrete cross ambiguity function (DCAF) based timing and ICFO estimation algorithm is proposed. Simulation results show that the proposed DCAF based timing and ICFO estimation algorithm can mitigate the impact of time-varying multipath Rayleigh fading channel and outperforms traditional estimators on the correct estimation probability performance.

Efficient Integer Frequency Offset Estimation Architecture for Enhanced OFDM Synchronization

In orthogonal frequency-division multiplexing (OFDM) systems, integer frequency offset (IFO) causes a circular shift of the subcarrier indices in the frequency domain. The IFO can be mitigated through strict RF front-end design, which tends to be expensive, or by strictly limiting mobility and channel agility, which constrains operating scenarios. The IFO is, therefore, often estimated and removed at baseband, allowing implementations to benefit from the relaxed RF front-end specifications and to be tolerant to both Doppler shift and multistandard channel selection. This paper proposes a novel architecture for the IFO estimation which achieves reduced power consumption and lower computational cost than contemporary methods, while achieving excellent estimation performance, close to theoretically achievable bounds. A pilot subsampling technique enables fourfold resource sharing to reduce the computational cost, while multiplierless computation yields further power reduction. Performance exceeds that of the conventional techniques, while being much more efficient. When implemented on field-programmable gate array for IEEE 802.16-2009, the dynamic power reductions of 78% are achieved. The architecture and method is applicable to other OFDM standards including IEEE 802.11 and IEEE 802.22.

A Low-Complexity Integer Frequency Offset Estimation Scheme Using Combined Training Symbols for OFDM Systems

In orthogonal frequency division multiplexing (OFDM) systems, an integer part of a frequency offset (IFO) that causesambiguity in data demodulation is estimated generally by comparing correlations between the received and local signalsfor IFO candidates. In this paper, we propose an IFO estimation scheme that provides a tradeoff between the estimationperformance and the computational complexity including a conventional scheme as a special case. In the proposedscheme, template signals are formed by combining frequency-shifted training symbols, allowing the receiver to reducethe number of IFO candidates in the estimation process. Numerical results illustrate the tradeoff of the proposed scheme:The proposed scheme exhibits a tradeoff between the correct estimation probability and the computational complexitytaking the number of the training symbols used to construct the template signal as a parameter.

Integer Frequency Offset Estimation for OFDM Systems With Residual Timing Offset Over Frequency Selective Fading Channels

Accurate integer frequency offset (IFO) estimation is crucial for orthogonal frequency-division multiplexing (OFDM) systems, particularly in the presence of frequency-selective fading and residual timing offset (RTO). For existing algorithms, however, it is still a challenge to obtain a good tradeoff among the estimation performance, complexity, and spectrum overhead. In this paper, we propose a novel cross ambiguity function (CAF)-based IFO estimator using only one training sequence. By designing the training sequence, which has only a single sharp peak on its ambiguity function surface, a highly accurate and full acquisition range estimation of the IFO can be obtained in the presence of frequency-selective fading and RTO. Moreover, the adoption of the CAF expression in terms of time-domain signals ensures that the complexity of the proposed algorithm is relatively low. Simulation results verify its superior accuracy in frequency-selective fading channels and in the presence of RTO.

Frequency synchronization for TD-LTE-A downlink receiver

A high accuracy frequency synchronization method is proposed for the 3rd generation partnership project (3GPP) long term evolution advanced (LTE-A) downlink receiver in time division duplexing (TDD) mode. In general, cyclic prefix (CP) correlation based fractional frequency offset (FFO) estimation method and primary synchronization signal (PSS) differential correlation based integer frequency offset (IFO) estimation method are applied for LTE-A frequency synchronization. However, the polarity of CP based FFO estimation result may get reversed when system FFO is closer to the edge of frequency estimation range on account of noise interference; PSS based IFO estimation has performance degradation in low signal noise ratio (SNR). We propose polarity detection aided CP based FFO estimation and frequency domain enhanced differential correlation based IFO estimation to obtain higher accuracy of frequency synchronization. Computer simulation shows that the proposed method greatly outperforms the conventional methods, especially in low SNR scenario.

Pilot Subset Partitioning Based Integer Frequency Offset Estimation for OFDM Systems With Cyclic Delay Diversity

Cyclic delay diversity (CDD) is a simple transmit diversity technique for coded OFDM systems with multiple transmit antennas. However, high frequency selectivity caused by CDD degrades the performance of post- FFT estimation, i.e., integer frequency offset (IFO). This paper suggests a simple way of improving the performance of the IFO estimator based on the pilot subset partitioning which is designed to reduce the effect of frequency selective fading by adopting the CDD. By partitioning uncorrelated pilot subcarriers into subsets to satisfy high correlation, and performing frequency estimation for each pilot subset, a robust IFO estimation scheme is derived. The simulation results show that the proposed method can provide benefit to the overall system performance .

Low-cost integer frequency offset estimation for OFDM-based DRM receiver

In this paper, we propose an improved and low-cost integer frequency offset (IFO) estimation method by partitioning pilot symbols effectively in an orthogonal frequency division multiplexing based digital radio mondiale (DRM) system. To this end, the time reference cell (TRC) symbol for frequency estimation is grouped into a number of pilot clusters, so that the TRC subcarriers in each cluster are closely spaced to show approximately frequency-nonselective characteristics. The performance of the proposed IFO estimator is compared with that of the conventional estimator, and shows that the proposed technique can effectively achieve lower estimation errors in frequency offset estimation as well as can be implemented with reduced computational complexity.

Bayesian integer frequency offset estimator for MIMO-OFDM systems

Carrier frequency offset (CFO) in MIMO-OFDM systems can be decoupled into two parts: fraction frequency offset (FFO) and integer frequency offset (IFO). The problem of IFO estimation is addressed and a new IFO estimator based on the Bayesian philosophy is proposed. Also, it is shown that the Bayesian IFO estimator is optimal among all the IFO estimators. Furthermore, the Bayesian estimator can take advantage of oversampling so that better performance can be obtained. Finally, numerical results show the optimality of the Bayesian estimator and validate the theoretical analysis.

An efficient technique for the integer frequency offset estimation in OFDM systems

This communication proposes a novel null subcarrier based algorithm for the integer frequency offset (IFO) estimation in orthogonal frequency division multiplexing (OFDM) systems. Bandwidth overhead of the proposed algorithm is less than 5% of the bandwidth of first OFDM symbol in a frame. The IFO is estimated by computing the energy of subcarriers at the DFT output just once and by finding the shift in null subcarrier indices using a simple statistical approach. The proposed method is computationally very efficient as compared to the methods which use exhaustive search procedures. It also achieves advantages over a few recently published methods in terms of the number of real additions (RAs) and bandwidth overhead required for IFO estimation. Computer simulation studies show that the estimator is able to achieve an IFO estimation range equal to the OFDM bandwidth.

Pilot-Aided Frequency Offset Estimation for Digital Video Broadcasting Systems

This letter introduces a simple way of estimating the integer frequency offset (IFO) of OFDM-based digital video broadcasting (DVB) systems. By modifying the conventional maximum likelihood (ML) estimator to include the multi-stage estimation strategy, the IFO estimator is derived. Simulations indicate that the proposed IFO estimator works robustly when compared to ML estimator.

OFDM Carrier Frequency Offset Estimation Methods With Improved Performance

Orthogonal frequency division multiplexing (OFDM) systems are highly sensitive to carrier frequency offset and symbol timing error. This paper deals with estimation method of integer frequency offset (IFO) without the aid of pilot symbols. The proposed IFO estimator exploits two consecutive identical OFDM data symbols with only change of phase. In order to improve the accuracy of the IFO estimator, receive diversity is adopted. To demonstrate the efficiency of the proposed IFO estimators, comparisons are made with other existing estimators in terms of error performance, estimation range, and complexity.

Further Results on the Maximum-Likelihood IFO Estimation for OFDM Systems

Zhang has proposed the maximum-likelihood (ML) integer frequency offset (IFO) estimator for orthogonal frequency-division multiplexing (OFDM) systems. However, his solution to multi-path channels is quite limited. We further investigate the problem and propose an improved IFO estimator to solve the problem in multi-path channels.