共查询到20条相似文献,搜索用时 140 毫秒
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针对较低信噪比下的深衰落稀疏多径信道,提出了一种基于信道缩短的自适应稀疏均衡改进算法。该算法采用前置分数间隔信道缩短均衡器与后置自适应稀疏均衡器级联的均衡器结构,其中,首先利用短训练序列设计基于最小均方误差准则的前置均衡器,前置均衡器与稀疏多径信道级联后得到能量集中于较短时间区域且分布稀疏的等效信道,使得原始信道的深衰落畸变得到部分有效补偿;然后采用能实现稀疏信号重构的随机梯度追踪算法调整后置自适应均衡器的抽头系数,后置均衡器用于消除等效信道的剩余符号间干扰。仿真结果表明,与传统的单级分数间隔自适应均衡器相比,该算法具有收敛速度快和运算复杂度低的优点。 相似文献
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针对判决反馈均衡器在低信噪比时存在误差传递、高信噪比时均衡效果好的特点,对窄带短波单音串行数据通信,在提出时变信道系数VCC-DDEA和判决反馈VCC-DDEA(DFE-VCC-DDEA)信道均衡算法的基础上,研究了利用实时信噪比估计指导信道均衡方式动态切换的DS-VCC-DDEA算法。该算法摒弃了传统DDEA算法中信道系数在一帧数据范围内恒定的假设,结合判决反馈均衡器的优点,可获取到信道均衡整体性能的提高。仿真结果验证了DS-VCC-DDEA相对DDEA、VCC-DDEA和DFE-VCC-DDEA算法的优越性。 相似文献
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在迭代均衡中,通过计算后验概率密度求解输入信息可以被视为一个广义线性回归问题。为解决此问题,采用了一种名为广义矢量消息传递的新算法。该算法与之前的广义消息传递算法相比,可以适用于包含任意分布的输出。使用该算法的检测器中,包含一个内部软均衡器和软分块交织器,原理与软均衡器和软译码器的消息传递类似,其按照迭代算法逐块交换外信息,从而改善均衡器的性能。通过对该算法的性能分析,提出增加半自适应的阻尼系数来保证内部软均衡器和交织器的独立性。对改进后的算法进行性能分析,结果表明其计算复杂度和低信噪比条件下性能均优于逐符号的迭代均衡以及广义消息传递算法的迭代均衡。 相似文献
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与传统时分发送训练序列的信道估计算法相比,隐含训练序列信道估计算法将训练序列与信息序列直接相加后通过天线发送,从而节约了信道带宽.然而,在天线发送总功率一定时,训练序列的功率越大,信息序列的功率便越小,从而导致信道均衡器的信噪比减小.本文研究了基于MIMO系统的隐含训练序列信道估计算法,分析了信道均衡器信噪比与训练序列功率的关系,并根据均衡器信噪比最大原则推导出训练序列与信息序列的最佳功率分配.分析和仿真结果表明:在训练序列的最佳功率点上,信道均衡器的信噪比最高;随着接收天线信噪比的增加,训练序列的最佳功率增大. 相似文献
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In multicarrier systems with a cyclic prefix, interblock interference can be limited by shortening the channel impulse response using time-domain equalizers. In this paper, we present two blind channel-shortening algorithms that exploit the second-order statistics of the channel outputs. The equalizer parameter vector is chosen from a space that forces the length constraint on the effective channel impulse response. The first algorithm is less sensitive to channel-order estimation errors, whereas the second one is simpler to implement. Furthermore, we show that the two algorithms are equivalent for noiseless channels. Simulation examples are provided to demonstrate their superior performance over some existing algorithms. 相似文献
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Vanbleu K. Ysebaert G. Cuypers G. Moonen M. 《Signal Processing, IEEE Transactions on》2006,54(2):483-498
The classical discrete multitone receiver as used in, e.g., digital subscriber line (DSL) modems, combines a channel shortening time-domain equalizer (TEQ) with one-tap frequency-domain equalizers (FEQs). In a previous paper, the authors proposed a nonlinear bit rate maximizing (BM) TEQ design criterion and they have shown that the resulting BM-TEQ and the closely related BM per-group equalizers (PGEQs) approach the performance of the so-called per-tone equalizer (PTEQ). The PTEQ is an attractive alternative that provides a separate complex-valued equalizer for each active tone. In this paper, the authors show that the BM-TEQ and BM-PGEQ, despite their nonlinear cost criterion, can be designed adaptively, based on a recursive Levenberg-Marquardt algorithm. This adaptive BM-TEQ/BM-PGEQ makes use of the same second-order statistics as the earlier presented recursive least-squares (RLS)-based adaptive PTEQ. A complete range of adaptive BM equalizers then opens up: the RLS-based adaptive PTEQ design is computationally efficient but involves a large number of equalizer taps; the adaptive BM-TEQ has a minimal number of equalizer taps at the expense of a larger design complexity; the adaptive BM-PGEQ has a similar design complexity as the BM-TEQ and an intermediate number of equalizer taps between the BM-TEQ and the PTEQ. These adaptive equalizers allow us to track variations of transmission channel and noise, which are typical of a DSL environment. 相似文献
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为能够检测出快变信道中低信噪比下的电视空白信号,同时考虑到噪声对信号的影响,在对信号进行互相关前对接收信号进行平均以提高检测器的检测性能。结果表明,基于数据平滑的感知算法比时域互相关感知算法的检测性能提高了约8dB,比时域自相关感知算法提高了约13dB。 相似文献
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针对低压电力线信道噪声强、衰减大的问题,基于OFDM技术的电力线通信系统采用时域扩充结构,提高导频数据的可靠性.确定了在OFDM时域扩充结构中应用LMMSE准则时最大多径时延的最优取值.在此基础上提出一种更适合时域扩充系统的信道估计优化算法,通过利用OFDM符号内所有导频参与信道估计从而在低信噪比条件下获得更低的误码率.仿真结果表明提出的改进算法与传统LMMSE算法相比具有更好的信道估计性能,在信噪比低于0dB时改进算法的性能优势更加明显. 相似文献
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基于JUMMSE准则的前向分数间隔判决反馈均衡器 总被引:1,自引:1,他引:0
研究了前向分数间隔判决反馈均衡器的原理与结构,并推导了基于联合无偏差MMSE(JUMMSE)准则设计的最优解。文中讨论了均衡器长度对误符号率(SER)性能的影响。仿真结果表明,在较高的信噪比、选择恰当的均衡器长度时,这种均衡器对于高频信道的均衡效果是显著的。 相似文献
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Channel shortening equalizers are used in acoustics to reduce reverberation, in error control decoding to reduce complexity,
and in communication receivers to reduce inter-symbol interference. The cascade of a channel and channel shortening equalizer
ideally produces an overall impulse response that has most of its energy compacted into fewer adjacent samples. Once designed,
channel shortening equalizers filter the received signal on a per-sample basis and need to be adapted or re-designed if the
channel impulse response changes significantly. In this paper, we evaluate sparse filters as channel shortening equalizers.
Unlike conventional dense filters, sparse filters have a small number of non-contiguous non-zero coefficients. Our contributions
include (1) proposing optimal and sub-optimal low complexity algorithms for sparse shortening filter design, and (2) evaluating
impulse response energy compaction vs. design and implementation stage computational complexity tradeoffs for the proposed
algorithms. We apply the proposed equalizer design procedures to (1) asymmetric digital subscriber line channels and (2) underwater
acoustic communication channels. Our simulation results utilize measured channel impulse responses and show that sparse filters
are able to achieve the same channel energy compaction with half as many coefficients as dense filters. 相似文献
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Optimum space-time processors with dispersive interference: unifiedanalysis and required filter span
Ariyavisitakul S.L. Winters J.H. Inkyu Lee 《Communications, IEEE Transactions on》1999,47(7):1073-1083
We consider optimum space-time equalizers with unknown dispersive interference, consisting of a linear equalizer that both spatially and temporally whitens the interference and noise, followed by a decision-feedback equalizer or maximum-likelihood sequence estimator. We first present a unified analysis of the optimum space-time equalizer, and then show that, for typical fading channels with a given signal-to-noise ratio (SNR), near-optimum performance can be achieved with a finite-length equalizer. Expressions are given for the required filter span as a function of the dispersion length, number of cochannel interferers, number of antennas, and SNR, which are useful in the design of practical near-optimum space-time equalizers 相似文献
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利用DFE非线性均衡器,通过数学处理对其进行线性化拆分,拆分后的两个线性均衡器分别置于信道的接收和发送端,使其能用于强多径干扰的信号传输环境(如存在强多径干扰的隧道中的高速信号传输).该方法降低了实现的复杂度,同时保持了高抗干扰性,且这种相互对称的均衡器结构有利于系统双向传输的实现.计算机仿真结果验证了该方法的有效性. 相似文献