共查询到18条相似文献,搜索用时 562 毫秒
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适用于QAM信号的载波同步与均衡实现 总被引:3,自引:1,他引:2
载波同步和均衡是正交幅度调制(QAM)解调器中的2个重要组成部分。提出了一种适用于QAM信号的载波同步与自适应均衡的联合结构,载波同步采用通用环,均衡器采用基于CMA和LMS算法的DFE结构。使用CMA算法进行初步收敛,载波同步后,均衡器转到LMS算法,保证了良好的稳态跟踪性能。通过对算法的简化,减少了硬件资源。该方案载波捕获范围超过40 kHz,完全满足侦察接收机的需要。 相似文献
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对多频带正交频分复用超宽带系统同步技术进行研究,提出一种基于时域扩展技术(TDS)的盲载波频偏(CFO)跟踪算法。利用数据符号与其时域扩展符号的特殊映射关系,在时域和频域分别推导出残余载波频偏的盲估计公式,并构建相应的时频跟踪环路。仿真结果表明,该盲算法具有比导频辅助法更优的跟踪性能。10dB信噪比下,基于TDS进行时频跟踪的残余CFO均方根误差均达到2×10?4,系统误比特率可达10?6数量级。 相似文献
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对OFDM系统中一种基于接收时域信号重构的载波频率盲估计算法进行了进一步的研究,分析了在这种方法中影响估计精度的4个方面的因素。为了减少载波频率估计的剩余误差,通过在频率补偿时增加反馈因子,提出了一种基于判决反馈的载波频率同步环路结构。通过调整同步环路的环路增益,可以获得更好的频率跟踪性能。如果信噪比达到9dB,即使存在较大的频率漂移,剩余频偏也被限制在子载波间隔的1%以内。 相似文献
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为了提高多径衰落信道下的盲解调性能,提出了一种结构简单的MPSK信号盲解调算法。首先利用超指数迭代分数间隔盲均衡器实现联合定时同步与均衡,然后对均衡器输出信号进行非线性变换实现载波频偏的估计,最后利用二阶数字判决锁相环跟踪相位变化纠正剩余频偏和相偏。仿真结果表明,在多径衰落信道条件下,与现有算法相比,基于超指数迭代分数间隔盲均衡器的盲解调算法实现简单,误码率低,而且具有收敛速度快、性能稳定等优点。 相似文献
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针对MIMO SC-FDMA系统载波频率偏移敏感问题,本文提出一种基于OSIC的载波同步算法。该算法对载波频偏(CFO)的信号进行排序、零化、迭代均衡实现干扰消除。理论分析和仿真实验表明该算法实现了载波频偏干扰消除的目的,并且提高了系统性能。 相似文献
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均衡嚣是通信信号解调的必要部分,对系统性能有较大的影响.针对高阶QAM信号,提出了一种新的判决反馈自适应均衡算法,该均衡器的系数为实数,便于算法的实现.当使用训练序列时,该算法不仅可以消除传输系统的符号间干扰,还可以纠正小的载波频偏.与文献[4]中的均衡算法相比,提出的算法具有低的稳态误差.当应用于可等效为加性高斯噪声信道的视距传输时,该算法可以进行盲均衡处理来纠正较小的载波频偏,且收敛速度很快.理论分析和仿真结果证明了该算法的有效性. 相似文献
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本文通过对传统的常模算法进行改进和推广,提出了一种新的常模算法.该算法结合了常模算法优势,利用判决符号的指数幂构成的加权项调整代价函数的模值.在均衡器系数迭代的过程中,可以通过选择权系数,调整MSE的估计值,达到提高算法的稳态性能的目的.理论分析和仿真结果表明,对于高阶的QAM信号来说,在相同的条件下,与常规常模算法相比,提出的算法具有更快的收敛速度和更低的稳态残差;当载波频偏较大时,与多模算法相比,提出的算法仅仅均衡信号的能量,不影响其相位,因此,更适合后端的载波同步处理,得到更好的系统性能. 相似文献
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主要研究在第3代合作伙伴计划的长期演进(3GPP-LTE)下行链路低信噪比情况下,当手机终端晶振和基站之间存在较大的载波频率偏差(CFO)时,如何实现手机终端和基站的初始主同步,并提出了一种整数频偏(IFO)补偿后检测主同步信道(P-SCH)序列的具有鲁棒性的初始主同步算法。仿真结果表明提出的算法在低信噪比场景下能够达到较高的P-SCH序列检测正确率和较低的载波频偏估计均方误差(MSE)。 相似文献
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Khaled Ramadan Moawad I. Dessouky Fathi E. Abd El‐Samie Ahmed S. Fiky 《International Journal of Communication Systems》2020,33(3)
In wireless communication systems, equalization is one of the most important schemes to improve the system performance. This paper consists of two main parts. The first part presents a blind carrier frequency offset (CFO) estimation scheme based on discrete cosine transform (DCT). The second part presents a joint low‐complexity equalization, and CFO compensation in orthogonal frequency division multiplexing (OFDM) systems. Moreover, in the second part, we present a joint low‐complexity regularized zero‐forcing (JLRZF) equalizer based on the proposed CFO estimation scheme. Simulation results show that the proposed configuration has the ability to perform blind CFO estimation and enhance the system performance in the presence of estimation errors. 相似文献
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A.B. Djebbar K. Abed-Meraim A. Djebbari 《AEUE-International Journal of Electronics and Communications》2009,63(3):220-225
It is well known that multipath channel and carrier frequency offset (CFO) destroy the orthogonality between subcarriers in the downlink of MC-CDMA and degrade the system performance. In this paper, a new low complexity algorithm is proposed to iteratively estimate the CFO and the channel equalizer using only the guard interval (GI) redundancy, or excess codes (EC) or both GI and EC without additional pilots. Simulations illustrate and compare the performance efficiency of these schemes in different scenarios. 相似文献
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残留频偏会导致星座点发生旋转,而且这种旋转与时间有关,时间越长,旋转越大。若残留频偏长时间得不到校正,将会使星座点旋转到其他象限从而出现判决错误,使系统的性能急剧恶化。针对这个问题,提出了一种基于星座点特征的残留频偏跟踪算法。该算法要求在信道估计之后完成,并假定一个OFDM帧内的信道频率响应保持不变。该算法包括三个步骤,首先将每个OFDM符号的星座点划分为四个子集,然后对每个子集的均值求相位角获得相位误差,最后经环路滤波器输出一个校正量补偿时域频偏。由于残留频偏估计值的提取充分利用了所有数据子载波信息,并对每个子集进行了求均值处理,所以有效的改善了环路的输入信噪比。它适用于子载波为QPSK或QAM调制的OFDM系统,不同的子载波调制方式跟踪范围不同,最大跟踪范围为±0.05个子载波间隔。仿真表明:新算法性能要优于基于循环前缀的算法,与基于导频的跟踪算法性能相当。 相似文献
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In this paper, we propose a novel carrier frequency offset (CFO) tracking algorithm for orthogonal frequency division multiplexing (OFDM) systems by exploiting scattered pilot carriers and virtual carriers embedded in the existing OFDM standards. Assuming that the channel remains constant during two consecutive OFDM blocks and perfect timing, a CFO tracking algorithm is proposed using the limited number of pilot carriers in each OFDM block. Identifiability of this pilot based algorithm is fully discussed under the noise free environment, and a constellation rotation strategy is proposed to eliminate the c-ambiguity for arbitrary constellations. A weighted algorithm is then proposed by considering both scattered pilots and virtual carriers. We find that, the pilots increase the performance accuracy of the algorithm, while the virtual carriers reduce the chance of CFO outlier. Therefore, the proposed tracking algorithm is able to achieve full range CFO estimation, can be used before channel estimation, and could provide improved performance compared to existing algorithms. The asymptotic mean square error (MSE) of the proposed algorithm is derived and simulation results agree with the theoretical analysis. 相似文献
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An adaptive equalization method is proposed for use with differentially coherent detection of M-ary differential phase-shift keying (DPSK) signals in the presence of unknown carrier frequency offset. A decision-feedback or a linear equalizer is employed, followed by the differentially coherent detector. The equalizer coefficients are adjusted to minimize the post-detection mean squared error. The error, which is a quadratic function of the equalizer vector, is used to design an adaptive algorithm of stochastic gradient type. The approach differs from those proposed previously, which linearize the post-detection error to enable the use of least mean squares (LMS) or recursive least squares (RLS) adaptive equalizers. The proposed quadratic-error (Q) algorithm has complexity comparable to that of LMS, and equal convergence speed. Simulation results demonstrate performance improvement over methods based on linearized-error (L) algorithm. The main advantages of the technique proposed are its simplicity of implementation and robustness to carrier frequency offset, which is maintained for varying modulation level. 相似文献