共查询到18条相似文献,搜索用时 966 毫秒
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为提高符号间干扰(ISI)信道条件下信号接收的可靠性,该文研究单载波通信系统的多天线空间分集接收问题,提出一种迭代频域合成均衡算法。该算法推导先验信息条件下合成均衡器的频域传输函数,并借助快速傅里叶变换(FFT)实现合成均衡器系数和均衡滤波的高效计算。仿真结果表明,相比时域算法,该算法能够在不损失性能的前提下,大幅降低运算复杂度。与单载波频域均衡(SC-FDE)算法相比,该算法不需要在数据传输的结构中插入循环前缀(CP),提高频谱利用率,能够直接应用于现有单载波通信系统。 相似文献
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基于多天线接收的空间分集技术与均衡技术相结合的空间分集均衡算法可以克服衰落带来的不利影响,有效提高通信系统接收端的性能。文中将多天线支路间的合并权值和均衡器的权值统一合并于盲均衡算法中的系数估计,形成一种新的空间分集盲均衡算法,该算法具有较小的实现复杂度和很好的均衡效果。通过仿真实验表明,在误符号率相同的条件下,本文提出的分集均衡算法比单路信号盲均衡算法所需信噪比低1 dB-2 dB。同时分析了多天线接收的支路信号间存在的相位差以及延迟对算法的性能影响。 相似文献
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摘 要:信道失真和多径衰落特性会造成符号间串扰,从而导致系统性能下降。以QAM信号为对象,研究提高信号盲自适应均衡性能的算法,该算法利用联合MCMA DD的误差函数并结合分集合并技术运用到非线性结构的判决反馈均衡器中形成一种混合盲算法来均衡QAM信号。混合算法中同时利用两误差函数对系数进行更新以提高QAM信号的均衡适应能力,利用空间分集减少衰落的影响和利用非线性结构适应频响起伏大的信道。从仿真结果看,与其他算法相比该混合算法加快了收敛速度、减小了稳态误差并且纠正了相位旋转,有效性得到验证。 相似文献
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时域自适应均衡技术的分析与应用 总被引:1,自引:0,他引:1
概述了频率选择性衰落信道的传输特性,论述了采用均衡技术的必要性。通过对各种均衡器结构和自适应均衡算法在抵抗符号间干扰能力、收敛速度以及运算复杂度等方面的分析与比较,选择了判决反馈作为均衡器结构、最小均方自适应算法作为自适应准则的均衡器方案。仿真及试验结果证实了设计的时域自适应均衡器不仅具有较强的抵抗符号间干扰能力,而且能够获得隐分集增益,在频率选择性衰落信道中具有良好的应用效果。 相似文献
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基于冗余预编码的STBC-SC-FDE系统的频率域盲信道估计 总被引:1,自引:0,他引:1
针对频率选择性衰落信道下空时分组编码单载波频域均衡(STBC-SC-FDE)系统的信道盲估计问题,设计了一种基于冗余预编码的频率域盲子空间信道估计算法,并讨论了算法的可辨识性条件以及去模糊度方法。该算法仅利用冗余预编码STBC-SC-FDE系统的频率域接收信号的二阶统计量即可获得系统的时域信道响应。仿真结果表明,算法稳定、可靠,具有良好的估计精度和均衡性能。 相似文献
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为了提高多径衰落信道下的盲解调性能,提出了一种结构简单的MPSK信号盲解调算法。首先利用超指数迭代分数间隔盲均衡器实现联合定时同步与均衡,然后对均衡器输出信号进行非线性变换实现载波频偏的估计,最后利用二阶数字判决锁相环跟踪相位变化纠正剩余频偏和相偏。仿真结果表明,在多径衰落信道条件下,与现有算法相比,基于超指数迭代分数间隔盲均衡器的盲解调算法实现简单,误码率低,而且具有收敛速度快、性能稳定等优点。 相似文献
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A new method called joint Matched Filter (MF) combining and turbo equalization is proposed for wireless communications over
Inter-Symbol Interference (ISI) channels with diversity reception. This method takes diversity combining and equalization
as integrity and need just one turbo equalizer for all diversity branches. Computer simulations prove that our method can
take advantage of turbo equalization and diversity reception to combat fading of wireless channels. 相似文献
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Blind equalization for short burst wireless communications 总被引:4,自引:0,他引:4
In this paper, we propose a dual mode blind equalizer based on the constant modulus algorithm (CMA). The blind equalizer is devised for short burst transmission formats used in many current wireless TDMA systems as well as future wireless packet data systems. Blind equalization is useful for such short burst formats, since the overhead associated with training can be significant when only a small number of bits are transmitted at a time. The proposed equalizer overcomes the common problems associated with classic blind algorithms, i.e., slow convergence and ill-convergence, which are detrimental to applying blind equalization to short burst formats. Thus, it can eliminate the overhead associated with training sequences. Also, the blind equalizer is extended to a two branch diversity combining blind equalizer. A new initialization for fractionally spaced CMA equalizers is introduced. This greatly improves the symbol timing recovery performance of fractionally spaced CMA equalizers with or without diversity, when applied to short bursts. Through simulations with quasi-static or time-varying frequency selective wireless channels, the performance of the proposed equalizer is compared to selection diversity and conventional equalizers with training sequences. The results indicate that its performance is far superior to that of selection diversity alone and comparable to the performance of equalizers with short training sequences. Thus, training overhead can be removed with no performance degradation for fast time-varying channels, and with slight performance degradation for static channels 相似文献
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For unknown mobile radio channels with severe intersymbol interference (ISI), a maximum likelihood sequence estimator, such as a decision feedback equalizer (DFE) having both feedforward and feedback filters, needs to handle both precursors and postcursors. Consequently, such an equalizer is too complex to be practical. This paper presents a new reduced-state, soft decision feedback Viterbi equalizer (RSSDFVE) with a channel estimator and predictor. The RSSDFVE uses maximum likelihood sequence estimation (MLSE) to handle the precursors and truncates the overall postcursors with the soft decision of the MLSE to reduce the implementation complexity. A multiray fading channel model with a Doppler frequency shift is used in the simulation. For fast convergence, a channel estimator with fast start-up is proposed. The channel estimator obtains the sampled channel impulse response (CIR) from the training sequence and updates the RSSDFVE during the bursts in order to track changes of the fading channel. Simulation results show the RSSDFVE has nearly the same performance as the MLSE for time-invariant multipath fading channels and better performance than the DFE for time-variant multipath fading channels with less implementation complexity than the MLSE. The fast start-up (FS) channel estimator gives faster convergence than a Kalman channel estimator. The proposed RSSDFVE retains the MLSE structure to obtain good performance and only uses soft decisions to subtract the postcursor interference. It provides the best tradeoff between complexity and performance of any Viterbi equalizers 相似文献
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《IEEE transactions on information theory / Professional Technical Group on Information Theory》2008,54(11):4908-4924
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Diversity reception is incorporated into the structure of approximate maximum likelihood differential phase detection (MLDPD) for M-ary DPSK. The bit error rate (BER) performance improvements obtained with MLDPD are evaluated by computer simulation for 4DPSK in frequency selective Rician fading channels 相似文献
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粒子滤波是一种基于贝叶斯估计的算法,在信道盲辨识和盲均衡问题上具有快收敛、抗深衰信道等优势。Turbo盲均衡在低信噪比条件下有较好的误码性能。为了在深衰信道下使通信具有良好的误码性能,对粒子滤波盲均衡算法进行改进,改进算法的重要性采样函数利用了粒子的先验信息,得到一种软输入软输出的粒子滤波盲均衡算法。依据Turbo盲均衡的框架结构实现了一种基于粒子滤波的Turbo盲均衡算法,该算法利用信道编码带来的编码增益,提高了均衡和信道辨识的性能。仿真结果表明相比粒子滤波盲均衡算法本文提出算法的误码率性能提高1dB左右,误帧率性能则提高了3dB以上,经分析可知在信道系数估计较为准确的条件下,系统数据帧几乎没有误码。 相似文献
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Sakai T. Kobayashi K. Kubota S. Morikura M. Kato S. 《Selected Areas in Communications, IEEE Journal on》1995,13(2):285-290
Diversity combining methods for mobile satellite communication systems employing convolutional encoding and soft-decision Viterbi decoding are evaluated. Computer simulation clarifies that the pre-Viterbi-decoding maximal ratio combining method has better performance than other methods in Rician fading channels. The simulation results agree with the Pe (bit error probability) performance derived from the numerical analysis for slow fading using the approximate Pe performance of Viterbi decoding in AWGN (additive white Gaussian noise) channels and the probability density function of Rician fading. Applying this diversity method to the multi-beam mobile satellite communication systems, a satellite beam diversity reception scheme is proposed. A computer simulation result shows that the proposed scheme decreases the packet error rate of the control signals to less than 1/100 around the satellite beam boundary 相似文献
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Postdetection diversity is attractive for narrowband digital FM signal reception because the cophasing function, which may be difficult to realize in a fast Rayleigh fading environment, is not required. The combining scheme evaluated here is to weight each frequency demodulator (FD) output in proportion to the νth power of the received signal envelope of that branch. Maximum diversity improvement can be obtained with ν=2 (this combiner is referred to as a postdetection maximal ratio chamber (MRC)). Experimental results are presented on postdetection diversity reception in the Gaussian minimum shift keying (GMSK) signal transmission system. Diversity combining and FD-decision algorithms (decision feedback equalizer (DFE) and maximum-likelihood sequence estimator (MLSE)) are performed by software on a computer using the data of the sampled FD output and received signal envelope obtained from a laboratory transmission system. It is shown that the MRC can attain about a 1-dB larger diversity gain than the selection combiner (SC) when two-branch diversity is used. The degradations of two-branch diversity improvement caused by the differences between demodulator sensitivities and between received signal envelope detector gains are evaluated 相似文献