共查询到20条相似文献,搜索用时 250 毫秒
1.
2.
传统叠加导频算法应用在正交频分复用系统中存在信道估计精度差的缺点。针对比特交织编码调制(BICM)联合正交频分复用(OFDM)的系统(BICM—OFDM),提出一种利用叠加导频的迭代信道估计算法。该算法充分利用了均衡器的反馈信息,分两步进行。首先,导频信号叠加在发送信号上,接收端采用一阶统计量进行初始信道估计;然后利用均衡器的硬判决反馈信息,在信道估计与均衡之间进行信息交换,通过迭代的方式提高信道估计精度。在短波宽带信道下的仿真结果表明,与传统叠加导频算法相比,新算法经过二次迭代可有效提高信道估计精度和系统误码率性能。 相似文献
3.
一种新的导频符号辅助下的信道衰落估计方法 总被引:1,自引:0,他引:1
本文提出一种新的导频符号辅助下的信道衰落估计方法。它同时利用导频符号和数据符号进行信道衰落估计和补偿,而不同于传统的信道衰落估计只利用导频符号的信息。此方法具有实现简单,延时小的优点。针对16PSK和16QAM调制方式作了仿真,结果显示导频符号辅助下的16QAM的性能优于16PSK,采用信道衰落估计与相干检测结合的16PSK性能又好于采用差分检测的16PSK的性能。 相似文献
4.
5.
6.
针对IEEE802.16d帧结构提出一种结合前导训练序列和导频的信道估计算法。算法通过前导完成初始精确的信道估计,再使用判决反馈方式提高导频估计准确度,并根据前后符号导频估计结果得到反映信道变化的时变因子,利用它来调整前导估计和导频估计比例,联合完成信道估计。仿真结果表明,与传统的信道估计方法相比,此算法能够更有效的对抗频率选择性衰落和更大的多普勒频移,改善系统的性能。 相似文献
7.
针对正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)系统在高速移动场景下时/频域选择性衰落(双选衰落)和非平稳特性给信道估计带来的技术挑战,本文采用导频与数据叠加的帧结构,提出一种基于基扩展模型(Basis Expansion Model,BEM)的迭代扩展卡尔曼滤波(iterative Extend-Kalman Filter,iEKF)信道估计方法.基于BEM信道模型且采用EKF信道估计方法可以联合估计出信道冲激响应(Channel Impulse Response,CIR)与时变的时域自相关系数,有效消除子载波间干扰(Inter Carrier Interference,ICI).同时,为了进一步消除叠加导频位置处的数据符号干扰,我们提出将叠加位置处的数据和导频先解耦、后重构再进行迭代EKF的信道估计方法.仿真分析表明,相较传统叠加导频的信道估计方法和导频符号辅助调制(Pilot Symbol Assisted Modulation,PSAM)估计方法,本文提出的信道估计方法在高速场景特别是低信噪比的条件下,具有更高的估计精度,更强的鲁棒性及更大的吞吐量. 相似文献
8.
9.
10.
提出了一种基于编码的OFDM系统的导频符号迭代辅助信道估计。利用信道解码器中的APP符号来形成虚拟的导频。与原有的信道估计算法相比,此种算法不仅在一般的信道条件下具有良好的性能,而且更加适合快变信道条件下的OFDM系统。仿真结果表明:提出的OFDM信道估计算法不仅可以给出精度较高的信道信息,而且近似达到EM信道估计的性能。 相似文献
11.
12.
A novel pilot-aided joint channel estimation and data detection method for MIMO communication systems is proposed. Unlike, conventional methods where pilots are time-multiplexed with data symbols, a pilot-embedding method where low-level pilots are transmitted concurrently with the data is used to obtain an initial estimate of the channel such that a turbo decoding process can be started. The soft information obtained from the turbo decoder is subsequently used to improve channel estimates. 相似文献
13.
针对现有的联合信道估计及OFDM信号检测算法性能不高的问题,该文提出一种基于整体最小二乘的联合信道估计及OFDM信号检测算法。该算法首先通过导频估计初始的信道信息,在此基础上不断地采用整体最小二乘进行OFDM信号检测及信道估计,有效缓解迭代模型误差的影响,加快了算法迭代的收敛速度,提高了信道估计的精度,从而降低了OFDM系统的误码率。该文推导的信道估计克拉美罗界及仿真结果均表明所提出的算法在时变信道环境下优于现有的联合信道估计及OFDM信号检测算法。 相似文献
14.
Applying multiple input multiple output (MIMO) technique to OFDM-based wireless local area networks (WLANs) promises impressive high capacity and spectral efficiency compared with conventional systems. However, similar to SISO-OFDM, MIMO-OFDM suffers significant performance degradation due to the presence of phase noise. Many methods have been developed to mitigate phase noise for a single antenna system with perfect channel estimation, whereas none has been proposed for correlated MIMO-OFDM scenarios. Therefore, in this letter, by using the phase noise correlation function, a new phase noise mitigation scheme is proposed for the general M/sub T//spl times/M/sub R/ MIMO WLANs system with channel estimation errors. Numerical results show that, compared with conventional approaches, the proposed scheme achieves significant performance gain with high spectral efficiency, requiring few pilots, and is robust to spatial correlation and channel estimation errors, which makes it very attractive for practical applications. 相似文献
15.
16.
17.
18.
A frequency-domain channel expanding technique (FD-CET) is proposed for channel estimation in an iterative receiver of a low-density
parity-check coded orthogonal frequency division multiplexing system. The FD-CET can expand a subset of the frequency-domain
channel gains to all of them in a short-point FFT/IFFT format. This technique is applied to estimate the channel gains utilizing
the pilots and information from the decoder in an iterative manner. It is a novel low complexity channel estimation method.
Numerical results demonstrate that the proposed channel estimator approaches a maximum-likelihood performance within only
a few iterations under multi-path channels. 相似文献
19.
Conventional time-varying (TV) channel estimation (CE) methods for OFDM systems need optimal evenly spaced pilots to track channel time variations in one symbol period and the inter-carrier interference (ICI) on pilots caused by Doppler spread are regarded as noise. For practical OFDMA systems, the required evenly spaced pilots are unsatisfied and the ICI on pilots increase estimation errors. In this letter, a TV CE method for practical OFDMA systems is proposed. The time variations of the frequency domain transmission function in one symbol period are approximated by a linear model in time-frequency blocks for each user. Time domain transformations are avoided and evenly spaced pilots are not required. Furthermore, the ICI on pilots are mitigated by correlative coding. Simulation results demonstrate the Symbol-Error-Rate (SER) and Mean-Square- Error (MSE) performances of the proposed OFDMA CE method over TV channels. 相似文献
20.
对于FDD模式的大规模MIMO-OFDM系统,本文研究了将结构化压缩感知理论用于该系统的稀疏信道估计。考虑在该系统中将每个发送天线上的导频重叠放置,即每个发送天线可以在相同的时频资源块上发送导频符号,那么此时的系统稀疏信道估计问题可以建模为结构化压缩感知重建问题。为了优化导频位置和导频符号来改进稀疏信道估计的质量,提出了一种最小化完全块间相关值的导频优化准则以及基于此准则的导频搜索算法,完全块间相关值是结构化压缩感知框架下衡量恢复矩阵子块间相关程度的量值。仿真结果表明,与其他导频相比,使用此优化方法获得的导频可以使信道估计误差明显减小,其性能增益大约为2~5 dB。另外,仿真结果还表明,在相同的导频数量前提下,使用优化导频获得的性能增益会随着发送天线数量的增加而变得更加明显。 相似文献