共查询到20条相似文献,搜索用时 62 毫秒
1.
2.
本文提出了一种正交频分复用(OFDM)系统的频率同步方案。该方案包含一个细同步算法和一个粗同步算法。细同步算法是对MOOSE算法的改进,使其频率捕获范围扩大一倍;粗同步算法通过对特殊的长训练序列进行频域相关运算,来估计大范围的频率偏移,它与改进的细同步算法合,能够纠正达到半个系统带宽的频偏。仿真表明这是一种准确而可靠的频率同步方案。 相似文献
3.
4.
一种有效的OFDM载波频率偏移的盲估计 总被引:2,自引:2,他引:0
导出了具有循环前缀(CP)和虚子载波的正交频分复用(OFDM)通信系统信号的薮学模型。提出了基于PM—ESPRIT算法的0FDM系统载波频率偏移(CFO)偏移不变性的估计算法。经过粗略估计,该算法可以同时获得频率偏移和包含信道信息的矩阵,它们均有利于接收信号的偏移补偿和解调。仿真结果说明了该方法是有效的。 相似文献
5.
载波频率偏移是正交频分复用(OFDM)系统性能的重要影响因素。本文概述了OFDM的发展史,建立了OFDM系统模型,分析了载波频率偏移对OFDM的影响,在此基础上在计算机上模拟了当OFDM系统的子信道数N不同时载波频率偏移对OFDM的影响,最后简单论证了一种降低载波频率偏移影响的方法--linear。 相似文献
6.
提出了一种正交频分复用(OFDM)系统的频率同步方案。该方案包含一个细同步算法和一个粗同步算法。细同步算法是对MOOSE算法的改进,使其频率捕获范围扩大一倍;粗同步算法通过对特殊的长训练序列进行频域相关运算,来估计大范围的频率偏移,它与改进的细同步算法相结合,能够纠正达到半个系统带宽的频偏。仿真表明这是一种准确而可靠的频率同步方案。 相似文献
7.
8.
9.
10.
11.
A. B. Kokhanov 《Radioelectronics and Communications Systems》2013,56(2):82-88
This paper considers a phase recovery method for the coherent carrier frequency of the signal Revised by a digital receiver using a unit of digital recovery of the coherent carrier phase. The use of digital phase filter makes it possible to do without the application of traditional phase-locked loop frequency control. The paper also presents a technique for deriving a transfer function of the specified digital filter and considers the issue of its robustness in relation to self-excitation. In addition, the paper presents a functional diagram of this filter. 相似文献
12.
13.
14.
研究了多径信道下OFDM系统的一种新的载波频率跟踪算法,这种算法以判决反馈和接收端的时域信号重构为基础。推导了估计结果的精确解,比较了使用原估计结果和新的估计结果进行频偏补偿时系统跟踪性能的不同。通过对算法的仔细分析,发现除了通常的加性噪声外,信道估计误差、子载波数目和子载波的调制方式也影响频偏的估计结果和跟踪范围,而且子载波的数目和调制方式是决定性的因素。这种频率跟踪方法的优点是即使在很低的信噪比下仍然能获得高的跟踪精度,且实现相对简单。 相似文献
15.
This paper introduces a new carrier frequency recovery approach. It can be applied before modulation classification and/or demodulation of the M-ary PSK signals. It relies on the entropy of the instantaneous phase probability density function, and uses the fact that it reaches minimum when the receiver is fine-tuned to the unknown carrier frequency. This estimator is applicable to algorithms requiring high accuracy without any a priori knowledge concerning modulation scheme, signal contents (bit-stream), or its timing parameters. Simulation results have proved the robustness of the algorithm: for low carrier to noise ratios (CNR), corresponding variances are proportional and close to Cramer-Rao lower bounds (CRLB). For CNR greater than 20 dB, they are constant and limited by the resolution of the algorithm. 相似文献
16.
A time-frequency decision-feedback loop for carrier frequency offset tracking in OFDM systems 总被引:1,自引:0,他引:1
Linling Kuang Zuyao Ni Jianhua Lu Junli Zheng 《Wireless Communications, IEEE Transactions on》2005,4(2):367-373
Acquisition and tracking are two crucial stages necessary to the carrier frequency synchronization in orthogonal frequency division multiplexing (OFDM) systems. In this letter, by employing the rotation property of OFDM data subcarriers, a simple time-frequency decision-feedback loop without the use of pilot subcarriers is proposed for the fine carrier frequency offset (CFO) tracking. Specifically, with proper loop parameters, a residual CFO less than 10% of the subcarrier spacing may be well tracked for quarternary phase-shift keying (QPSK) modulation in the presence of noise, while for systems using QPSK, 16-QAM, and 64-QAM modulation schemes, the bit-error rate (BER) performance very close to that of an offset-free system may be achieved in both additive white Gaussian noise (AWGN) and frequency selective fading channels. Moreover, a hardware implementation in a practical OFDM system is fulfilled which verifies the effectiveness of the proposed scheme. 相似文献
17.
Two recent carrier recovery loops for high-order quadrature amplitude modulation (QAM) and optimisation of their parameters for minimum frequency acquisition times are analysed. All variations on the parameters were analysed and optimised to obtain optimal loop bandwidths and damping factors, for given signal-to-noise ratios. Simulation results show that after optimisation, the average acquisition time for 64-QAM is kept below 1000 symbols over the entire range of initial frequency offsets from 0 to 1/8 the symbol rate. This number increases to 3200 symbols for 256-QAM. 相似文献
18.
GMSK信号的多普勒频移快捕和跟踪 总被引:3,自引:0,他引:3
GMSK信号具有良好的频谱和功率特性,特别适用于功率受限和信道存在非线性、衰落以及多普勒频移的数字卫星移动突发通信系统。本文提出了一种GMSK信号的多普勒频移快捕和跟踪方法。该方法根据突发通信时帧结构的特点,采用独特码和FFT并行处理信号能量检测、帧同步检测和多普勒频移快捕,并采用判决反馈PLL环跟踪多普勒频移的变化。仿真结果表明,多普勒频移在-Rb/2~Rb/2范围内变化时,与理论值相比,采用该方法的准相干解调器误比特率Pb 性能恶化仅为0.3dB。在信息速率Rb=9.6kbps时,多普勒频移速率可达4000Hz/s。 相似文献
19.
This work is aimed at researching and analyzing the performance of carrier recovery (CR) with two transmit antennas on a multicarrier digital TV system operating in time‐selective fading channel. It is shown in the paper that CR can correct the performance degradation caused by Doppler effect when the terminal is receiving high resolution digital TV signals in a fast moving environment. To have the ability to cover a large frequency range, the CR system should do a frequency sweep first. Then the coarse and fine frequency offset estimation is introduced. Both the theoretical and simulated results give valuable insight that the CR is able to perform well with a certain amount of channel fading. The phase and noise effect on the CR performance is also studied. The CR system and the working procedure concerning CR and timing recovery are also researched to give a full solution on synchronization. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
20.
A novel symbol-timing recovery scheme is presented that is insensitive to carrier-phase error and is not susceptible to hangup at large values of timing error as is the case for the conventional two-point non-data aided (2p-NDA) scheme. The new scheme is applicable for symbol-timing recovery for M-ary PSK modulation formats.<> 相似文献