共查询到19条相似文献,搜索用时 265 毫秒
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OFDM/OQAM系统中联合迭代信道估计和信号检测 总被引:3,自引:2,他引:1
与基于复数域空间正交条件的传统正交频分复用系统(OFDM with Cyclic Prefix, CP-OFDM)有所不同,基于交错正交调制的正交频分复用系统(OFDM/Offset QAM, OFDM/OQAM)满足实数域空间严格正交条件。因此在多径衰落信道条件下,CP-OFDM系统中的信道估计方法会导致OFDM/OQAM系统严重的字符间干扰和载波间干扰。该文结合OFDM/OQAM系统结构特点,提出了一种基于迭代信道估计和信号检测算法。该算法通过信道估计器和接收到的信号互相交换信息,消除导频序列中的字符间干扰和载波间干扰,提高信道估计和信号检测的准确度。仿真分析结果表明,经过一定次数迭代处理后,OFDM/OQAM迭代信道估计性能趋近于理想信道估计性能。 相似文献
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针对同时同频全双工无线通信系统,考虑远端到近端的无线信道为多径瑞利衰落信道,近端发射天线到接收天线的自干扰信道为加性白高斯噪声信道,分析了同时同频全双工传输场景中,自干扰射频抵消幅度及载波相位误差对OFDM误码率的影响。结果表明,在相同信干比和信噪比条件下,幅度和载波相位估计误差的绝对值越小,误码率越低;针对载波频率2.3 GHz, OFDM子载波个数4096,子载波间隔15 kHz的同时同频全双工传输方式,在信干比为-70 dB,误码率为10-2时,若期望信噪比损失小于0.8 dB,则需要射频干扰抵消的载波相位估计误差的绝对值小于610-6,幅度估计相对误差的绝对值小于310-5;若期望获得40 dB的射频自干扰抑制效果,则射频干扰抵消的载波相位估计误差的绝对值小于0.5,幅度估计相对误差绝对值小于1%。 相似文献
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基于神经网络均衡器的小波包多载波扩频系统 总被引:1,自引:0,他引:1
在多径衰落信道下,本文提出了一种基于神经网络均衡器的小波包多载波扩频系统(Neural Network Equalizers Wavelet Packet Spread Spectrum,NNE-WPSS).本文利朋基于最小均方算法(Least Mean Square algorithm,LMS)的复径向基函数神经网络均衡器(Complex Radial Basis Function Network Equalizers,CRBF)来抑制由多径衰落信道引起的码间干扰(Inter-Symbol Interference,ISI)并且利用最大似然算法对解调后的码元进行检测.在多径衰落信道和白高斯噪声情况下,本文分析了基于神经网络均衡器的新型小波包多载波扩频系统的传输性能.仿真结果表明,本文所提出的基于神经网络均衡器的新型小波包多载波扩频系统的性能要优于传统的基于正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)多载波扩频系统;本文提出的复径向基函数神经网络均衡器(CRBF)的性能也优于迫零均衡器(Zero-Forcing Equalizer,ZFE). 相似文献
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针对高速移动环境下多普勒频偏造成信道的快衰落和正交频分复用(OFDM)系统中子载波间干扰(ICI)的问题,提出了一种适合快衰落环境的OFDM系统子载波间干扰抑制算法。此算法用线性变化模型来近似一个OFDM符号周期内的信道冲激响应,并以此为基础采用迭代MMSE均衡方法抑制载波间干扰。分析和仿真结果表明,此方法能有效地保证载波间的正交性,从而改善了OFDM系统的误码率(BER)性能。 相似文献
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研究了OFDM中当CP长度小于信道冲激响应长度时,OFDM通信系统的子载波间的正交性遭到破坏,接收信号存在ISI和ICI,频域单抽头均衡器不再适用。针对频率选择性衰落信道下的OFDM系统中的ISI干扰问题,本文研究了一种基于递归最小二乘的OFDM系统自适应均衡算法,仿真结果表明了该算法的有效性。 相似文献
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当正交频分复用(OFDM)通信系统的循环保护前缀(CP)长度小于信道冲激响应长度时,常采用时域均衡方法消除符号间干扰(ISI)和子载波间干扰(ICI)。但时域均衡器结构复杂,且收敛速度较慢。为此,利用OFDM系统的零子载波信息,设计了一种频域均衡器。该均衡器具有稀疏矩阵结构,因此计算量小。理论分析和计算机仿真表明:它能有效消除由于循环前缀不足引起的符号间干扰和子载波间干扰,从而较好地恢复传输信号。 相似文献
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针对电力线通信(PLC)正交频分复用(OFDM)系统存在频率掩码和频谱资源利用率低等问题,提出将正交频分复用/偏移正交幅度调制(OFDM/OQAM)技术应用到PLC系统中。该技术通过选用频率选择性较好的滤波器来抑制带外干扰,且不需要循环前缀,但是OFDM/OQAM系统在PLC频域复数信道下会产生严重的自干扰,传统的均衡算法并不能有效地消除OFDM/OQAM系统的固有干扰。针对这种情况提出了一种基于信道相位预处理的均衡算法。该算法的思想是让接收信号乘以一个信道相位调整因子,使等效信道的虚部尽量小,以此来减小接收信号中的干扰分量。仿真结果表明,与传统的均衡算法相比,所提算法在误比特率为1.0×10-6时可以获得0.5dB的性能提升。 相似文献
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A loss of subchannel orthogonality due to time-variant multipath channels in orthogonal frequency division multiplexing (OFDM) systems leads to interchannel interference (ICI) which increases the error floor in proportion to the Doppler frequency. A simple frequency-domain equalization technique which can compensate for the effect of ICI in a multipath fading channel is proposed. In this technique, the equalization of the received OFDM signal is achieved by using the assumption that the channel impulse response (CIR) varies in a linear fashion during a block period and by compensating for the ICI terms that significantly affect the bit-error rate (BER) performance 相似文献
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该文针对在密集多径室内环境中超宽带(UWB)信道的延迟扩展时间长,脉冲超宽带(IR-UWB)系统在高速数据传输时码间干扰(ISI)严重致使误码率(BER)增加以至于系统无法工作的问题,基于ISI的成因,提出了一种分数间隔判决反馈居中均衡(FS-DFME)均衡接收机,该均衡接收机能够联合实现匹配滤波和信道均衡,从而能够有效地收集多径信号能量和抑制ISI影响。研究结果表明均衡接收机的观察窗口长度是影响ISI消除效果的重要参数;与线性均衡(LE)和分数间隔判决反馈非居中均衡(FS-DFNME)均衡接收机相比,FS-DFME均衡接收机能够更加有效地消除ISI,提高系统的BER性能。 相似文献
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The use of orthogonal frequency division multiplexing (OFDM) in frequency‐selective fading environments has been well explored. However, OFDM is more prone to time‐selective fading compared with single‐carrier systems. Rapid time variations destroy the subcarrier orthogonality and introduce inter‐carrier interference (ICI). Besides this, obtaining reliable channel estimates for receiver equalization is a non‐trivial task in rapidly fading systems. Our work addresses the problem of channel estimation and ICI suppression by viewing the system as a state‐space model. The Kalman filter is employed to estimate the channel; this is followed by a time‐domain ICI mitigation filter that maximizes the signal‐to‐interference plus noise ratio (SINR) at the receiver. This method is seen to provide good estimation performance apart from significant SINR gain with low training overhead. Suitable bounds on the performance of the system are described; bit error rate (BER) performance over a time‐invariant Rayleigh fading channel serves as the lower bound, whereas BER performance over a doubly selective system with ICI as the dominant impairment provides the upper bound. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Orthogonal frequency division multiplexing (OFDM) has been adopted for several wireless network standards due to its robustness against multipath fading. Main drawback of OFDM is its high peak‐to‐average power ratio (PAPR) that causes a signal degradation in a peak‐limiting (e.g., clipping) channel leading to a higher bit error rate (BER). At the receiver end, the effect of peak limitation can be removed to some extent to improve the system performance. In this paper, a joint iterative channel estimation/equalization and clipping noise reduction technique based on minimum mean square error (MMSE) criterion is presented. The equalization weight that minimizes the mean square error (MSE) between the signal after channel equalization and feedback signal after clipping noise reduction is derived assuming imperfect channel state information (CSI). The MSE performance of the proposed technique is theoretically evaluated. It is shown that the BER performance of OFDM with proposed technique can be significantly improved in a peak‐limited and doubly‐selective (i.e., time‐ and frequency‐selective) fading channel. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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《Broadcasting, IEEE Transactions on》2009,55(1):132-139