共查询到19条相似文献,搜索用时 109 毫秒
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在CDMA系统中,为了对抗多径衰落,使用Rake接收机对接收信号进行处理。在发射端,通过扰码对信号进行加扰处理。Rake接收机对接收的信号进行解扰,相干积分处理,根据功率时堑函数PDP值来计算多径的相位信息。在信噪比比较差的情况下,搜索出来的多径可能是噪声径,这对Rake接收机解调的性能有一定的影响。介绍一种根据扰码自相关特性,来判断搜索出多径是否为噪声径的方法,提高Rake接收机的性能。 相似文献
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Rake接收机在3G系统中已被广泛使用,实际应用证明它能够有效对抗移动无线信道中的多径衰落。传统Rake接收机有其时域一维处理的局限性,为获得更好的系统性能,本文在分析空时信道模型的基础上提出一种新的空时2D-Rake接收机算法,它将波束形成技术与Rake相结合。这种波束形成算法能够在干扰方向上完全陷零,其权重仅与阵列天线的导向矢量有关,与接收信号无关。最后简要分析了所提出的2D-Rake接收机的性能。仿真结果表明,这种空时2D-Rake接收机与传统Rake接收机相比,具有较好的性能,而且该算法对噪声具有鲁棒性。 相似文献
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对多径IR-UWB信号的Rake接收技术原理和结构进行了详细分析。在此基础上仿真了不同Rake接收机的性能,包括部分Rake和选择性Rake,以及具有不同叉指的Rake接收机的性能。仿真结果表明在具有相同叉指条件下,选择性Rake接收机比部分Rake接收机的性能高出3dB。而在相同接收原理下,叉指越多,接收机的性能越好。而2路选择性Rake接收机和5路部分Rake接收机在较低信噪比的情况下,性能并无很大差别。 相似文献
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室内环境中超宽带(UWB)信号经过密集多径传播会产生严重的时间弥散,采用Rake接收是提高UWB接收机性能的重要手段.在IEEE802.15.3a工作组推荐的信道模型基础上,采用脉冲位置调制(PPM)方式对超宽带信号在不同信道情况下不同Rake接收机的性能进行了系统的研究,可以在选择Rake接收机时,为综合考虑系统复杂度和性能改善的优化问题提供有价值的参考. 相似文献
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由于移动环境的复杂性,无线信号在发送传输和接收过程中有很明显的衰落现象。通过分集接收技术在移动通信特别是第三代移动通信中的应用,介绍了传统Rake接收机和WCDMA中采用的典型Rake接收机的工作原理和结构框图。多径信号的每路信号都可能含有可以利用的信息,所以接收机可以通过接收多路信号来改善信噪比。Rake接收机算法就是通过多个相关接收器接收多径信号中各路信号,并把他们合并在一起,以此为原理基础的。 相似文献
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针对Rake接收结构由于快衰落导致多普勒散布,导致系统性能下降的问题,在时频Rake、时空Rake接收机设计基础上,提出一种联合时空频3D-Rake接收结构。利用自适应天线在空间形成定向波束和利用联合时频处理技术,将频域多普勒频率分集的分析方法应用到时空二维处理中,实现基于天线阵列的时空频三维信号处理。通过接收合并具有不同时延、多普勒频移和来自不同方向的信号,实现最大信噪比准则下的最优接收,提高系统分集增益,和时频Rake、时空Rake相比,其系统性能得到进一步提高,数值仿真表明,联合时空频3D-Rake比时空Rake平均信干噪比提高了3dB。 相似文献
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本文首先介绍了DS-SS系统的基本原理,为了克服多重路径衰落DS-SS系统中采用了Rake接收机,本文进一步介绍了Rake接收机的设计原理,最后通过MATLAB仿真了Rake接收机的信道估算结果和其性能. 相似文献
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Differential space–time modulation (DSTM) schemes were recently proposed to fully exploit the transmit and receive antenna diversities without the need for channel state information. DSTM is attractive in fast flat fading channels since accurate channel estimation is difficult to achieve. In this paper, we propose a new modulation scheme to improve the performance of DS‐CDMA systems in fast time‐dispersive fading channels. This scheme is referred to as the differential space–time modulation for DS‐CDMA (DST‐CDMA) systems. The new modulation and demodulation schemes are especially studied for the fast fading down‐link transmission in DS‐CDMA systems employing multiple transmit antennas and one receive antenna. We present three demodulation schemes, referred to as the differential space–time Rake (DSTR) receiver, differential space–time deterministic (DSTD) receiver, and differential space–time deterministic de‐prefix (DSTDD) receiver, respectively. The DSTD receiver exploits the known information of the spreading sequences and their delayed paths deterministically besides the Rake‐type combination; consequently, it can outperform the DSTR receiver, which employs the Rake‐type combination only, especially for moderate‐to‐high SNR. The DSTDD receiver avoids the effect of intersymbol interference and hence can offer better performance than the DSTD receiver. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
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DS/CDMA系统上行链路的2D-Rake及PPIC接收方案 总被引:8,自引:7,他引:1
针对DS/CDMA系统的上行链路提出了2D-Rake加上强干扰并行对消(PPIC)的接收结构。该结构利用智能天线技术在空域对DOW不同于期望信号的干扰信号进行抑制,同时对期望信号的相关多径分量进行收集,利用Rake接收机对期望信号的不相关时延分量进行时间上的分集,然后再对多径合成结果进行PPIC处理,以对天线阵主瓣内的干扰信号进行进一步的抑制,该方法不仅最大程度地增强了期望信号地能量,同时对所有干扰信号进行了比较完全的抑制。仿真实验表明了该接收结构的有效性。 相似文献
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联合均衡块迭代软判决反馈干扰抵消接收机 总被引:1,自引:0,他引:1
CDMA扩频通信系统在低扩频比时,路径间干扰(IPI, inter-path interference)变得非常严重。本文将块迭代干扰抵消同MMSE均衡器相结合,提出了一种适用于CDMA扩频通信系统低扩频比情况下的联合均衡块迭代软判决反馈干扰抵消(MMSE-BIIC)接收机结构。理论分析与计算机仿真表明,本文提出的MMSE-BIIC接收机同传统的Rake接收机、线性MMSE均衡器以及多级干扰抵消接收机相比在性能上有较大改善。 相似文献
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Jiang Bofeng Zhang Jianguo Yin Qinye 《电子科学学刊(英文版)》2001,18(2):127-134
2-D RAKE receiver is an efficient way to realize the space-time processing for CDMA systems with aperiodic spreading codes. The Direction Of Arrival (DOA) and the relative time delay of every user's multipath must be known to realize the 2-D RAKE receiver. In the third generation CDMA mobile communication system, auxiliary pilot channel is used in the uplink channels. The different user's Vector Channel Impulse Response (VCIR) can be estimated from the pilot channel easily. The VCIR contains spatial and temporal information. In this paper, by utilizing the known pulse shape function, a parameter matrix method used to estimate the Spatial Signature Vector (SSV) and the relative time delay is proposed in frequency domain. The DOA can be estimated from the SSV. By reconstructing the SSV and utilizing approximate Capon space filter, the performance of the 2-D RAKE receiver with uniform circular array can be improved with a little additional computation work. 相似文献
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Rake接收技术是CDMA蜂窝移动通信系统中的关键技术之一。分集的基本思想是将接收到的多径信号分离成不相关的多路信号,把这些多径信号的能量按一定的规则合并,使接收到的有用信号能量最大化,进而提高接收信号信噪比达到抗衰落的目的。文中以异步DS-CDMA系统为例,论述了分集技术并对Rake接收机的误码率进行了分析与仿真。 相似文献
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Amira I. Zaki Said E. El-Khamy Ehab F. Badran 《Wireless Personal Communications》2013,71(4):2877-2894
In this research, a novel smart UWB system is introduced. The proposed system is based on using an adaptive maximum ratio combining (MRC) Rake receiver. The proposed adaptive Rake receiver uses Genetic algorithm (GA) to adaptively select the delays of the fingers of the Rake receiver depending on the channel impulse response. It adaptively selects the delays that will allow the Rake receiver to capture most of the energy in the multipath components with minimum complexity. This adaptive Rake receiver is referred to as a GA Rake. The adaptive GA Rake is applied to a single-input single-output and space time coding (STC) multi-input single-output UWB systems. The performance of those systems using a GA Rake is compared to their performance when using a conventional MRC-Rake receiver and showed a great enhancement in performance with less receiver complexity. Also, in this paper, the smart UWB system using STC is modified by using the time reversal (TR) pre-coding technique. The modified system is referred to as a TR smart UWB system. This modification leads to more enhancements in performance and more reduction in receiver complexity over the smart UWB system. Moreover, this paper also shows the ability a TR smart UWB system in combating interference from other UWB systems. 相似文献