共查询到18条相似文献,搜索用时 78 毫秒
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与最大似然检测算法相比,解相关算法具有线性运算复杂度和不需要估计信道特征的优点。传统的逆矩阵滤波器在移动环境下不易实现,而滑动窗口算法对系统的定量有较严格的要求。基于信息码元之间的相关性随着时间间隔的加大而逐渐减小这个事实,本文提出了多用户异步DS/CDMA系统一种新的解相关算法--延迟截断解相关算法,要判决当前时刻的信息码元,只需在延迟德行一定数量的码元之后截断,对截断后的码元按照传统的方法判决 相似文献
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提出了一种新颖的变步长符号算法用于DS/CDMA系统的多用户检测。这种算法对盲平均符号算法的步长又一次采用二次最小均方误差算法,克服了盲平均符号算法受步长影响的缺点,并利用符号算法计算复杂度低的特点,加快了算法的收敛速度。仿真表明,这种算法能够自动迅速地适应环境的变化并且不受初始步长和学习率的影响,在性能上优于与其类似的自适应接收机。 相似文献
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本文在直接序列/码分多址(DS/CDMA)系统盲检测自适应梯度算法(BAG)的基础上,提出了一种多用户检测盲自适应梯度算法的改进算法(IBAG).BAG算法包括自适应梯度算法(TBAG)和时变自适应梯度算法(TIBAG),TBAG算法的跟踪特性较好,但起始收敛特性不好;TIBAG算法的收敛特性较好,但跟踪特性较差,几乎不具备跟踪能力.本改进算法结合了这两种自适应梯度算法的优点,在不增加算法复杂度的前提下,使其收敛性和跟踪特性较BAG算法有所提高. 相似文献
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综合了近年来发展起来的线性类解相关多址干扰消除技术,对各种线性类解多址干扰技术的性能进行了分析,对其实现进行了一定程度的探讨,并得出了实际系统的误码率表达式。分析表明,该类算法能够较好地克服边缘效应,具有很好的应用前景。 相似文献
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异步多相DS/CDMA系统模型分析 总被引:4,自引:0,他引:4
文章在文献「1」的基础上了以直接序列扩频为基础的正交多相位编码载波多相扩频CDMA系统模型,就扩频序列的相关性与多址干扰的关系进行了定量分析,修正了扩邓列的非周期相关函数的定义,给出了多址干扰与扩频序列的广义奇相关函数的数学关系式。文章还对文献「1」中的错误进行了分析。 相似文献
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This paper analyzes the application of macrodiversity in Code DivisionMultiple Access (CDMA) asynchronous systems with decorrelatingdetection in the reverse link. It is shown that decorrelatingdetectors allow predetection combining and, utilizing this property,several combining strategies are studied. We obtain the set ofcombining factors which minimize the bit error probability, andbased on these results, we propose the Simplified Minimum ErrorCriterion (SMEC), which has little impact on the overallcomplexity of the system and outperforms theMaximal Signal to Interference plus Noise Ratio Combiner(MSINRC). Using this technique, it is possible to perform a distributeddetection in the area influenced by the mobile, allowing thecoexistence of heterogeneous cells and the effective useof microcells. 相似文献
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This paper addresses the use of decorrelating detectors for a dual rate DS/CDMA system that serves both low bit rate and high bit rate users. We assume that in an interval of duration T
0, a low rate user transmits one bit while a high rate user transmits M bits. Applying a standard decorrelator to the interval of duration T
0 yields an M bit processing delay for high rate users and a computational complexity that grows with M. In this paper, we propose a decorrelator that generates bit decisions for each high rate user in every subinterval of duration T0/M. To decode a low rate user, a soft decoding rule applies maximal ratio combining on M separate decorrelated outputs of each low rate user. The soft decoding dual rate decorrelator eliminates the bit processing delay for high rate users and also reduces the computational complexity of a standard decorrelator. Further, it is shown that the asymptotic efficiency of the standard decorrelator is greater than or equal to the proposed decorrelator. By evaluation, it is observed that when the signature sequences have good correlation properties, the proposed soft decoding decorrelator is found to perform nearly as well as the standard decorrelator. However, when the signature sequences have high cross-correlation, then the proposed decorrelator suffers in terms of bit error rate while retaining the near-far resistance property. 相似文献
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This paper addresses the problem of channel estimation andequalization in asynchronous uplink DS/CDMA. We propose a completereceiver structure which contains a multichannel estimator suitablefor time-varying channels, a MMSE equalizer and a propagation delayestimator. The multichannel estimator is a stochastic gradientalgorithm which does not require any knowledge about the propagationdelays. It estimates a matrix which contains a linear combination ofthe impulse response of each channel and the propagation delays. Thisestimate is used to derive a MMSE equalizer. In the despreading stageknowledge on the integer part (chip period multiple) of thepropagation delays is needed. Two reduced complexity schemes forpropagation delay estimation are presented. The channel estimatorconvergence is studied in stationary conditions while the overallalgorithm performance is demonstrated by using simulations intime-varying channel conditions. 相似文献
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Effect of Signature Sequence on the Performance of an Asynchronous Multiple-Chip-Rate DS/CDMA System
Dugin Lyu 《Wireless Personal Communications》2003,24(4):449-462
The effects of signature sequence on the performance of an asynchronousmultiple-chip-rate (MCR)-DS/CDMA system are considered.The equations for the multiple access interference (MAI)and the variance of the MAI are developed.The bit error rate is derived by using the Gaussianapproximation.The deterministic signature sequences such as maximal-lengthsequences and Gold sequences are compared with random signature sequencesin terms of the variance of the MAI and bit error rate.We find that the performance of signature sequences in an asynchronousMCR-DS/CDMA system depends not onlyon the crosscorrelation properties of sequences but also on the carrierfrequencyseparation between the interfering and desired users. 相似文献
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本文首先给出了多径异步多用户DS/CDMA系统的一种数学模型,得出了恒参信道下最大似然检测(MLSE)算法的一种新的表示形式。然后作者具体分析了以RAKE接收机作为衰落信道的匹配滤波器时,最大似然检测器的算法设计问题。分析指出,在多径环境下MLSE算法的复杂度和计算量与多径时延的分布有关,如果用户时延扩散在一个信息码元之内,算法复杂度和恒参信道下相同,而其实现可以用状态数可变的Viterbi算法来实现。最后,本文用传统判决方法得出的初始判决信息缩减Viterbi算法的搜索空间,在保证一定性能的前提下,算法的计算复杂度大大降低。 相似文献