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In this paper, a blind symbol timing offset (STO) estimation method is proposed for offset quadrature phase‐shift keying (OQPSK) modulated signals, which also works for other linearly modulated signals (LMS) such as binary‐PSK, QPSK, π/4‐QPSK, and minimum‐shift keying. There are various methods available for blind STO estimation of LMS; however, none work in the case of OQPSK modulated signals. The popular cyclic correlation method fails to estimate STO for OQPSK signals, as the offset present between the in‐phase (I) and quadrature (Q) components causes the cyclic peak to disappear at the symbol rate frequency. In the proposed method, a set of close and approximate offsets is used to compensate the offset between the I and Q components of the received OQPSK signal. The STO in the time domain is represented as a phase in the cyclic frequency domain. The STO is therefore calculated by obtaining the phase of the cyclic peak at the symbol rate frequency. The method is validated through extensive theoretical study, simulation, and testbed implementation. The proposed estimation method exhibits robust performance in the presence of unknown carrier phase offset and frequency offset. 相似文献
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Serafin Salido F. Javier Lopez-Martinez Eduardo Martos-Naya J. Tomas Entrambasaguas 《Wireless Personal Communications》2014,78(2):1129-1141
In orthogonal frequency division multiplexing (OFDM) systems, since the cyclic prefix (CP) is designed to be longer than the channel impulse response, there exists a certain range within the CP where symbol timing synchronization can be accomplished avoiding adjacent inter symbol interference. However, the appearance of a linear phase term across subcarriers in the frequency-domain due to symbol timing offset (STO) is known to affect the performance of channel interpolation. In this paper, we analyze the performance degradation due to the interaction between STO and channel interpolation in OFDM systems affected by multipath Rayleigh fading. Particularly, simple closed-form expressions for the bit error rate (BER) are obtained for different quadrature amplitude modulation constellations. Results show that there exists an irreducible BER floor due to STO and channel interpolation, which depends on the STO, the subcarrier index, the pilot spacing and the correlation between pilot subcarriers. 相似文献
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In this paper a novel technique for timing and carrier frequency offset (CFO) estimation for orthogonal frequency division multiplexing (OFDM) systems is presented. This technique is a modification of extended cyclic prefix for correlation sequence (ECPCS) based technique, called as selective extended cyclic prefix for correlation sequence (SECPCS) based technique. In cyclic prefix (CP) based technique, magnitude of timing metric near the exact starting point of CP is quite similar which causes problem in timing estimation. SECPCS is utilized in order to increase the difference between magnitudes of timing metric at the exact starting point of time of CP and its adjacent timing instants. In SECPCS technique, first of all correlation length of CP is extended using available CP samples and then those sequences which enlarge the difference in the magnitude of timing metric is selected. In the proposed technique the difference between magnitude of timing metric at exact starting point and its adjacent timing instants is significantly large compared to the previous techniques. The performance of different techniques is evaluated in terms of mean square error (MSE) in estimation of timing and CFO estimate. Further signal-to-interference-plus-noise ratio (SINR) loss of different techniques in different channel conditions is also estimated. From the simulation results it is observed that under different channel conditions, performance of the proposed SECPCS based technique is significantly better than previous techniques. 相似文献
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针对广义频分复用( GFDM)系统对符号定时同步要求较高的问题,提出了一种新的基于前缀码的同步算法。在接收端,在获取粗略定时信息的基础上,利用前缀码前后两部分的相位差实现载波频偏估计,并对接收序列的频率偏移进行纠正,然后通过纠正后序列与已知发射前缀的互相关函数实现精确的符号定时估计。由于该前缀码具有共轭对称的特性,使其避免了“平顶效应”的出现。结合5G中低时延高可靠场景,在频率选择性信道中对其进行仿真,并通过均方误差对其性能进行了评估。理论分析及仿真结果表明,该算法相对于原算法具有更好的定时同步性能和更低的复杂度,提升了GFDM系统的整体性能。 相似文献
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Thinh Hung Pham Ian V. McLoughlin Suhaib A. Fahmy 《Circuits, Systems, and Signal Processing》2014,33(8):2475-2493
Orthogonal frequency division multiplexing (OFDM) is a popular modulation technique that can combat impulsive noise, is robust to multipath fading, is spectrally efficient, and can allow flexible allocation of spectrum. It has become a key standard in cognitive radio systems as well as an enabling technology for mobile data access systems. An OFDM receiver’s performance is heavily impacted by the accuracy of its symbol timing offset (STO) and carrier frequency offset (CFO) estimation. This paper proposes a novel OFDM synchronization method that combines robust performance with computational efficiency. FPGA prototyping is used to explore the trade-off between the number of computations to be performed and computation word length with respect to both synchronization performance and power consumption. Through simulation, the proposed method is shown to provide accurate fractional CFO estimation as well as STO estimation in a range of channels. In particular, it can yield excellent synchronization performance in the face of a CFO that is larger than many state-of-the-art synchronization implementations can handle. The system implementation demonstrates efficient resource usage and reduced power consumption compared with existing methods, and this is explored as a fine-grained trade-off between performance and power consumption. The result is a robust method suitable for use in low-power radios, enabling less precise analog front ends to be used. 相似文献
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In this paper, we study carrier frequency offset (CFO) and symbol timing offset (STO) estimation in the uplink of multiuser offset QAM filter bank multicarrier (FBMC) communication systems. A low-complexity frequency-domain CFO estimator using periodical training sequence is proposed. Also a good estimate of STO is obtained by maximizing the energy of subcarriers subject to training sequence at the output of analysis filter bank. Furthermore we derive the theoretical MSE for the proposed CFO estimator. Computer simulations show that the derived MSE matches the simulated MSE closely. Compared with state-of-the-art time domain estimator, the proposed estimator achieves better performance with a lower computational complexity. 相似文献
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Eu-Suk Shim Sang-Tae Kim Hyoung-Kyu Song Young-Hwan You 《Broadcasting, IEEE Transactions on》2007,53(2):567-573
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. 相似文献
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In order to obtain unknown symbol rate of incoming signal at a receiver, in this paper, cyclostationary features of linear digitally modulated signals are exploited by proposed periodic variation method. A low complexity but highly accurate symbol rate estimation technique is obtained. The proposed method is based on a superposed epoch analysis over autocorrelations obtained blindly in different sampling frequencies. The obtained autocorrelations are analyzed in the frequency domain, and it is seen that there are large oscillations when the autocorrelation is obtained around the symbol rate. Then, a superposed epoch analysis is developed in order to estimate symbol rate based of the periodic variations on the frequency responses of autocorrelations. The proposed algorithm is quite accurate in the noisy environment because the noise is having no frequency component after taking Fourier transform of autocorrelations in all sampling rates, and this feature is also valid for the offset frequency that the purposed estimation is not affected by offset frequency. Thus, a successful blind symbol rate estimation algorithm is obtained, and it performs much better error performance than those using the well‐known cyclic correlation based symbol rate estimations, as it is proven by the obtained performances presented in the paper. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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本文提出了一种新的适合于OFDM系统的符号定时估计算法。该算法利用经过特殊处理的前后两段信息序列的内在相关性进行准确的符号定时估计。理论分析和仿真表明,该算法能在大频偏低信噪比的条件下完成定时捕获的任务,并且无需专门的训练符号,从而大大提高了系统传输的效率。 相似文献
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《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2008,16(12):1620-1630
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A novel timing estimation method for OFDM systems 总被引:7,自引:0,他引:7
Byungjoon Park Hyunsoo Cheon Changeon Kang Daesik Hong 《Communications Letters, IEEE》2003,7(5):239-241
We present a novel timing offset estimation method for orthogonal frequency division multiplexing systems. The estimator proposed here is designed to avoid the ambiguity which occurs in Schmidl's (1997) timing offset estimation method. The performance of the proposed scheme is presented in terms of mean and mean-square error (MSE) obtained by simulations. The simulation results show that the proposed estimator has a significantly smaller MSE than the other estimators. 相似文献
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Tellambura C. Johnson I.R. Guo Y.J. Barton S.K. 《Communications, IEEE Transactions on》1999,47(8):1137-1139
Frequency-offset correction is considered for a HIPERLAN (HIgh-PErformance Radio LAN) system over the indoor radio channel. Since the multipath channel response is not known a priori, a viable frequency-offset estimator should not depend on such knowledge. Such an estimator, using a single sample per symbol, is derived for HIPERLAN. The estimator is shown to approach the Cramer-Rao bound for frequency-offset estimation over a multipath channel. A HIPERLAN system simulation example shows that the performance with an offset of 150 kHz is within 0.5 dB of that of a system with zero frequency offset 相似文献
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为了提高船舶自动识别系统(AIS)的容量,提出了基于正交频分复用技术(OFDM)的新型AIS系统设计方案.新系统设计主要包括系统参数设计、系统帧结构设计.新系统链路容量和信道传输速率均较传统AIS系统提高了6倍,实现了频域资源的有效利用.该系统对符号定时偏差和载波频率偏差特别敏感,因此对接收信号的同步处理必不可少,在设计的新系统基础之上提出了一种新的盲估计算法,利用包含在循环前缀内的冗余信息,在多径信道信息未知的情况下,直接通过对接收信号做相关构造一个归一化的相关特性函数,通过此函数可得到符号时延位置和多径信道长度,进而得到载波频率偏差.仿真结果表明在多径信道下该算法也具有较好的性能. 相似文献