共查询到20条相似文献,搜索用时 15 毫秒
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利用毫米波MIMO系统的稀疏特性,信道估计可以转化为稀疏信号重构的问题。解决毫米波MIMO稀疏信道估计问题时,传统的OMP方法需要信号的稀疏度作为先验信息,实际系统难以满足此需要。文中引入StOMP算法,根据信号已知的稀疏先验信息确定阈值,并结合动态的阈值调整,提出一种新的StOMP-D算法,实现了稀疏度自适应的毫米波MIMO信道估计。仿真结果表明,所提的方法与传统的LS方法比较,信道估计性能显著提高,并且与稀疏度已知的OMP方法性能十分接近,在稀疏度未知时有明显的优势。 相似文献
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基于信道统计特性的中继选择算法 总被引:2,自引:0,他引:2
该文提出了一种在非再生协作网络中,基于信道统计特性的最优中继选择方法。首先在等功率条件下,根据信道统计特性,定义一个等效信道增益的参数,该参数反映了中继节点在协作过程中两个阶段的信道特性。然后提出一种基于该参数的降序排列的中继选择方法。该方法在不同的信噪比范围内,选择不同的节点集合,使得系统的吞吐率中断概率最小。分析表明该选择方法的分集增益阶数能达到N+1,N为中继节点数目。仿真结果表明这种中继选择算法的中断概率性能优于其他算法。该方法进一步与功率分配相结合,构成了一种低复杂度的次优的中继选择方法。仿真结果表明这种次优算法能够取得和穷举算法相似的性能。 相似文献
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In reliable orthogonal frequency division multiplexing systems, channel estimator (CE) plays a crucial role. A pilot‐aided orthogonal frequency division multiplexing CE often employs denoising thresholds to identify significant and noisy channel impulse response taps. When the knowledge of channel statistics (KCS) is completely unavailable, the existing suboptimal thresholds require consistent estimation of one or more KCS parameters. In this paper, the effect of noise variance parameter estimation on CE's mean square error (MSE) performance is characterized analytically by computing threshold's tap‐detection probability. To mitigate MSE degradation due to KCS estimation, an eigen‐select threshold, which does not require any KCS estimation, is proposed. It utilizes eigen values of the auto‐covariance matrix formed by estimated channel impulse response. The proposed threshold is compared with existing state‐of‐art alternatives, for CE's MSE performance and system's BER performance, in correlated Rayleigh fading channel environments. Results reveal that, with the proposed threshold, performance plots converge to optimal solution more closely than the others. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Maria Jose Canet Vicenç Almenar Santiago J. Flores Javier Valls 《Journal of Signal Processing Systems》2012,68(3):287-301
In this paper, a new time synchronization algorithm for OFDM systems with repetitive preamble is proposed. This algorithm makes use of coarse and fine time estimation; the fine time estimation is performed using a cross-correlation similar to previous proposals in the literature, whereas the coarse time estimation is made using a new metric and an iterative search of the last sample of the repetitive preamble. A complete analysis of the new metric is included, as well as a wide performance comparison, for multipath channel and carrier frequency offset, with the main time synchronization algorithms found in the literature. Finally, the complexity of the VLSI implementation of this proposal is discussed. 相似文献
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This letter proposes a non‐coherent blind time‐of‐arrival (TOA) estimation scheme for impulse radio ultra‐wideband systems. The TOA estimation is performed in two consecutive phases: the Rayleigh‐quotient theorem‐based coarse‐signal acquisition (CSA) and the iterative‐threshold‐test‐based fine time estimation (FTE). The proposed scheme serves in a blind manner without demanding any a priori knowledge of the channel and the noise. Analysis and simulations demonstrate that the proposed scheme significantly increases the signal detection probability in CSA and ameliorates the TOA estimation accuracy in FTE. 相似文献
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Tongliang Fan Yucang Wen Shengbo Huang Xinli Ma 《Circuits, Systems, and Signal Processing》2014,33(4):1277-1288
It is well known that channel impairment caused by multipath reflections can deeply degrade the transmission efficiency in wireless communication systems. The conventional DFT-based channel estimation methods improve the performance by neglecting nonsignificant channel taps. However, in multipath channels with non-sample-spaced time delays, this will cause power leakage and result in an error floor. In order to overcome this problem, based on the property of Channel impulse response, we describe a utility of channel estimation technology for OFDM systems using discriminant analysis. Usually, significant channel taps are detected on the basis of a predetermined threshold, so the optimal threshold value becomes a crucial factor. But it is difficult to decide channel taps that are approximately equal to the threshold value. To solve this disadvantage, the proposed algorithm improves performance by using Mahalanobis distance discriminant analysis for channel taps. This approach can mitigate the aliasing effect in the DFT-based channel estimator and reduce the leakage power efficiently when there is non-sample-spaced path delay. Simulation results show that the proposed channel estimators can eliminate the error floor substantially and its performance is better than the LS and conventional DFT estimators. 相似文献
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Diversity combining with imperfect channel estimation 总被引:1,自引:0,他引:1
The optimal diversity-combining technique is investigated for a multipath Rayleigh fading channel with imperfect channel state information at the receiver. Applying minimum mean-square error channel estimation, the channel state can be decomposed into the channel estimator spanned by channel observation, and the estimation error orthogonal to channel observation. The optimal combining weight is obtained from the first principle of maximum a posteriori detection, taking into consideration the imperfect channel estimation. The bit-error performance using the optimal diversity combining is derived and compared with that of the suboptimal application of maximal ratio combining. Numerical results are presented for specific channel models and estimation methods to illustrate the combined effect of channel estimation and detection on bit-error rate performance. 相似文献
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信道估计误差对MIMO系统信道容量的影响研究 总被引:1,自引:0,他引:1
为了分析信道估计误差对信道容量的影响,结合MIMO系统接收端信道估计误差的特点,重新构建了MIMO信道的统计模型。利用Wishart分布的性质,推导了当MIMO信道矩阵满秩时,仅接收端已知信道CSI情况下系统信道容量的下限。仿真结果表明,MIMO系统信道容量对信道估计误差比较敏感。 相似文献
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This paper deals with the estimation of the time of arrival (TOA) of ultra‐wideband signals under IEEE 802.15.4a channel models. The proposed approach is based on a randomness test and consists of determining whether an autoregressive (AR) process modeling an energy frame is random or not by using a distance to measure the randomness. The proposed method uses a threshold that is derived analytically according to a preset false alarm probability. To highlight the effectiveness of the developed approach, simulation setups as well as real data experiments are conducted to assess the performance of the new TOA estimation algorithm. Thereby, the proposed method is compared with the cell averaging constant false alarm rate technique, the threshold comparison algorithm, and the technique based on maximum energy selection with search back. The obtained results are promising, considering both simulations and collected real‐life data. 相似文献
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《AEUE-International Journal of Electronics and Communications》2014,68(4):277-281
A novel efficient time domain threshold based sparse channel estimation technique is proposed for orthogonal frequency division multiplexing (OFDM) systems. The proposed method aims to realize effective channel estimation without prior knowledge of channel statistics and noise standard deviation within a comparatively wide range of sparsity. Firstly, classical least squares (LS) method is used to get an initial channel impulse response (CIR) estimate. Then, an effective threshold, estimated from the noise coefficients of the initial estimated CIR, is proposed. Finally, the obtained threshold is used to select the most significant taps. Theoretical analysis and simulation results show that the proposed method achieves better performance in both BER (bit error rate) and NMSE (normalized mean square error) than the compared methods has good spectral efficiency and moderate computational complexity. 相似文献
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针对OFDM(正交频分复用)符号粗同步定时点会随路径能量变动的缺点,利用信道估计得出的信道脉冲响应,提出一种基于能量收集的精同步算法,不需设定判决门限,得到的最终定时点能有效避免ISI(符号间干扰)和ICI(信道间干扰)的引入.多径信道中的仿真验证了该算法的良好性能. 相似文献
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阈值后处理是针对TD-SCDMA系统中B Steiner信道估计器受加性噪声影响而提出的一种去噪方法,该方法误滤除信息径,保留噪声径.本文提出一种基于阈值处理的多用户信道估计方法,它基于某一下行用户会收到所有其它下行用户的训练序列这一特性,设定一个值,与各用户幅度加权值比较,去掉信噪比很小的用户对应的信道估计窗,将其余用户的信道估计窗进行平均,然后将平均后的结果再进行阈值后处理,抑制由噪声贡献的信道响应.仿真结果表明,提出的方法与直接进行阈值后处理法在同一误码率下,所需平均信噪比(SNR)降低1~4dB;在SNR低于5dB时,与复杂度高的加权合并法具有相同的误码率. 相似文献
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精确的信道估计是提高多输入多输出正交频分复用(MIMO-OFDM,Multiple Input Multiple Output-Orthogonal Frequency Division Multiplexing)系统性能的关键,针对现有的信道估计算法的不足,提出了一种基于DFT的最小二乘(LS,Least Square)信道估计算法,利用噪声方差设定一个门限进行阈值,进一步消除噪声干扰,充分利用了时变无线信道中时域和频域的相关性,改善了信道估计的性能。为验证其有效性进行了仿真。仿真结果表明,在慢时变信道环境下,改进方法可以进一步提高信道估计的精度,同时保持了较低的复杂度。 相似文献
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Jie Jin Meihao Chen Xiaoxiao Jiang Baoli Ai Enkai Wu 《International Journal of Communication Systems》2019,32(8)
With wireless communications in high‐mobility environment becoming popular, this poses a big challenge for communication systems based on the comb‐pilot OFDM, such as IEEE 802.11p, since it has not the enough pilots to estimate the time‐ and frequency‐selective channel accurately. In this paper, several comb‐pilot schemes and three comb‐pilot design rules are proposed to meet the Nyquist criterion for sampling the vehicle‐to‐vehicle (V2V) channel and the requirements of second‐order statistic of V2V channel. Based on the proposed pilot schemes, an iterative channel estimation method from the CE‐BEM model is proposed, together with three ICI cancellation methods. After thorough simulation, the effectiveness of the comb‐pilot design rules, the proposed channel estimation method, and intercarrier interference (ICI) cancellation methods is verified. Compared with other channel estimation methods, the proposed method performs better. The simulation results also reveal that the channel order L+1 has a great impact on the performance of the comb‐pilot OFDM system. 相似文献