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该文提出了用于MC DS-CDMA系统中的两种SDCMA(最陡下降常模算法)盲检测方法,一种是SDCMA盲均衡算法,在此基础上,提出了另一种联合均衡和多用户检测的SDCMA盲算法。同时还将这两种算法与基于子空间的MMSE(最小均方误差)盲检测算法进行比较。仿真结果表明,这两种SDCMA算法的BER(误比特率)性能均优于子空间法,而且联合均衡和多用户检测的SDCMA盲算法利用同时对均衡权值向量和多用户检测器向量进行自适应更新,能较大程度地改善系统性能,是这3种盲算法中性能最佳的一个。 相似文献
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基于最小平均峰度(Least MeanKurtosis,LMK)准则],该文提出了一种适用于同步直扩码分多址(DS/CDMA)系统多径慢衰落信道中的线性盲自适应多用户检测算法。这种算法基于高阶统计量(High Order Statistics,HOS)特性,算法复杂度相对较低。文中分析了算法在多径信道中无噪声情况下的收敛特性,指出在这种情况下,算法具有全局最小点,此时算法满足解相关条件。仿真结果表明,文中给出的检测器具有较强的多址干扰抑制性能。 相似文献
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将相关矩阵多次幂技术与MOE(最小输出能量)盲自适应空时多用户检测相结合提出了一种新的空时多用户检测算法。并且,从噪声方差、采样数目和u次幂的角度,对这种改进的MOE盲空时多用户检测接收机的性能进行了分析。理论证明和仿真结果表明,这种新的检测技术在噪声方差非常小、采样数目趋于无穷以及u→∞的情况下,它的性能收敛于MMSE盲自适应空时多用户检测。 相似文献
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本文提出了一种加性高斯白噪声(AWGN)信道下,同步直扩码分多址(DS/CDMA)系统的基于LMK(最小平均峰度,Least Mean Kurtosis)准则的线性盲自适应多用户检测器.这种检测器的算法是一种具有较低计算量的基于高阶统计量的算法.分析证明了这种检测器的算法的收敛性和可以实现多用户信号的盲解相关.并对基于该准则的线性盲自适应检测器和基于LMS(最小均方,Least Mean Square)准则的检测器的收敛性能进行了仿真比较. 相似文献
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To reduce the complexity of space-time multiuser detection, it has been proposed recently to exploit the spatial dimension by forming groups of users and apply the detection individually to each group. In this work we propose a new space-time receiver structure based on the group-optimal MMSE linear detector along with a new grouping algorithm that respects practical hardware limitations. Furthermore, an extension of the proposed structure which allows non-mutually exclusive grouping is presented. The simulation results show that the proposed reduced-complexity receiver structure provides a bit error rate (BER) performance close to the full linear MMSE multiuser detector. 相似文献
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The technique of linear multiuser detection in DS-CDMA systems is studied in this paper. The purpose is to find a receiver structure with good performance and moderate complexity, so that the receiver can efficiently suppress multiple-access interference(MAI) and multipath interference and has good near-far resistant ability, which may improve the system's capability while reducing the requirement for power control. The main work of the dissertation can be summarized as follows: the performance of MMSE multiuser detector in synchronous/asynchronous DS-CDMA systems over different channels is analyzed in chapter 2 of the dissertation. Using matrix method, we analyze the relation between performance measurement and spreading code correlation matrix, Signal-Interference-Ratio(SIR) and near-far factor, and prove that the performance of MMSE detector is better than that of the decorrelating detector. For fading channel, we analyze the performance of MMSE detector in DS-SS system firstly. Results show that the detector can efficiently suppress multipath interference. Extending to synchronous/asynchronous DS-CDMA systems over fading channels, we propose a simple linear detector structure that accomplishes despreading, detection and combining. Thus, the receiver is easy for implementation. Based on the proposed notion of combined spreading codes, we prove that the synchronous/asynchronous CDMA system is equivalent to the synchronous CDMA system over AWGN channel with double users. Therefore, the MMSE detector can efficiently suppress MAI and multipath interference in steady state, and has good near-far resistant ability. In chapter 3, we study the adaptive algorithm based on MMSE criterion. Firstly, the approach to the blind algorithm based on subspace is analyzed. We improve the algorithm in the part of channel estimation, which decreases the computational complexity while guaranteeing the performance. Meanwhile, we point out that CMOE-RLS algorithm is essentially an algorithm based on subspace approach. Also, it is shown from simulation that PASTd subspace tracking algorithm is not applicable for multiuser detection. Secondly, we propose an adaptive algorithm based on pilot channel, called PCA/PCRA. The algorithm does not require channel estimation, and has a rapid convergence rate. The steady state performance can be achieved by increasing the transmitting power in pilot channel. Computational complexity is only O(N2). Therefore, PCA/PCRA is suitable for the engineering application. The cost is that a pilot channel is needed for each user in the system. In chapter 4, constant algorithms for multiuser detection are studied. Firstly, we analyze the capture performance of CMA, and point out there exist many local stationary points. Initializations to guarantee CMA converges to the desired point are discussed. Results show that the convergence of CMA is decided by constant, step-size, spreading code correlation matrix and near-far factor. Secondly, we propose the constrained constant algorithm (C-CMA) for multiuser detection. It is shown that when the constant is greater than the triple power of the desired user, C-CMA globally converges to the desired point. Simulations illustrate that C-CMA has a rapid convergence rate and the steady state performance is good. However, great step-size can also reult in dispersion for the algorithm. Since C-CMA is a variable step-size CMOE-LMS algorithm, we propose a variable step-size constraint algorithm (VSCA). VSCA has the advantages of both CMOE-LMS and C-CMA such as robust, rapid convergence rate and good steady state performance. Thus, VSCA is suitable for engineering application. But the improper selection of step-size coefficients may degrade performance seriously. The computational complexity of the above constant algorithms is only O(N). In Section 5, the cyclostationarity of spreading signals is analyzed in the first part. We prove that spreading signals are ergodic cyclostationary signals with a cyclic period that is equal to the period of spreading code. Methods for processing cyclostationary signals are then given. It is shown that this method can mitigate the interference from a stationary noise for channel estimation. But the computational complexity for cyclostationary correlation is high, which prevents its application in implementation. In the second part, we discuss the application of oversampling technique in spreading communication systems. Although the oversampling can improve the performance of the linear multiuser detector, the improvement is trivial. On the contrary, oversampling increases the computational complexity of the weight vector greatly, which prevents its application in implementation. Additionally, we prove that FSE plus despreading or despreading pus FSE is equivalent to the linear detector with different lengths of delay line. However, the two kinds of structure have lower computational complexity. 相似文献
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Blind adaptive multiuser detection 总被引:26,自引:0,他引:26
Honig M. Madhow U. Verdu S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》1995,41(4):944-960
The decorrelating detector and the linear minimum mean-square error (MMSE) detector are known to be effective strategies to counter the presence of multiuser interference in code-division multiple-access channels; in particular, those multiuser detectors provide optimum near-far resistance. When training data sequences are available, the MMSE multiuser detector can be implemented adaptively without knowledge of signature waveforms or received amplitudes. This paper introduces an adaptive multiuser detector which converges (for any initialization) to the MMSE detector without requiring training sequences. This blind multiuser detector requires no more knowledge than does the conventional single-user receiver: the desired user's signature waveform and its timing. The proposed blind multiuser detector is made robust with respect to imprecise knowledge of the received signature waveform of the user of interest 相似文献
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This paper introduces a new multiuser detection algorithm based on a gradient guided search that can achieve near-optimum performance while its implementation complexity is linear in the number of users. The new algorithm attempts to perform jointly optimum multiuser detection by updating one user's bit decision each iteration in the best possible way. When a decorrelating multiuser detector is employed to initialize the proposed algorithm, in all cases tested the gradient guided search converges to a solution with performance very close to optimum. Further, tests indicate that the proposed algorithm provides excellent performance for cases where other suboptimum algorithms perform poorly. Although we focus only on synchronous multiuser detection, the algorithm is equally applicable to asynchronous multiuser detection problems 相似文献
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Based on the minimum mean squared error (MMSE) between the data stream and the linear combiner output, a new multiuser detection
(MUD) algorithm that combines space–time (ST) processing and antenna array on direct-sequence CDMA signals is proposed. The
proposed ST-MUD algorithm is proved to be equivalent to two existing MMSE-based ST-MUD algorithms, and the theoretical BER
performances for all the three algorithms are the same. The most attractive feature of the new ST-MUD algorithm is based on
the fact that the new method does not require explicit estimation of channel and signaling information. This avoids any channel
estimation error, and the method is thus more robust and more accurate than the other two ST-MUD algorithms in practical implementation.
Adaptation of the proposed ST-MUD algorithm is implemented by using training sequences. Performance of this new multiuser
detector is compared with that of two existing MMSE multiuser detectors and the conventional single-user space–time rake receiver
through simulations. The proposed ST-MUD algorithm provides a performance better than existing algorithms and is especially
suitable for practical CDMA systems. 相似文献
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Deng Ke Yin Qinye Zhang Hong 《电子科学学刊(英文版)》2006,23(1):14-19
Focusing on the space-time coded multiuser mobile communication systems in the frequencyselective fading environment, this paper proposes a Vertical Bell labs LAyered Space-Time (V-BLAST) coded Multicarrier Code-Division Multiple-Access (MC-CDMA) scheme and its blind channel identification algorithm. This algorithm employs an ESPRIT-like method and the singular value decomposition, and the channels between every transmit antenna of every user and every receive antenna of the base station are blindly estimated with a closed-form solution. Based on it, an equivalent Minimum Mean-Squared Error (MMSE) time-domain multiuser detector is derived. Moreover, the proposed scheme exploits the precoding in the transmitter in order to eliminate the constraint of more receive antennas than transmit ones, required by most conventional V-BLAST codec schemes. Computer simulation results demonstrate the validity of this proposed scheme. 相似文献
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在现有盲自适应多用户检测技术基础上,本文提出一种更具有实际应用价值的基于干扰空间线性MMSE盲自适应多用户检测器及其相应的基于干扰自相关矩阵C1跟踪算法。数学分析和仿真结果表明:与现有盲自适应多用户检测器相比,该检测器具有更低的实现复杂度、更快的跟踪速度和更强的健壮性。 相似文献
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A covariance shaping framework for linear multiuser detection 总被引:1,自引:0,他引:1
Eldar Y.C. Shamai S. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2005,51(7):2426-2446
A new class of linear multiuser receivers, referred to as the covariance shaping multiuser (CSMU) receiver, is proposed, for suppression of interference in multiuser wireless communication systems. This class of receivers is based on the recently proposed covariance shaping least-squares estimator, and is designed to minimize the total variance of the weighted error between the receiver output and the observed signal, subject to the constraint that the covariance of the noise component in the receiver output is proportional to a given covariance matrix, so that we control the dynamic range and spectral shape of the output noise. Some of the well-known linear multiuser receivers are shown to be special cases of the CSMU receiver. This allows us to interpret these receivers as the receivers that minimize the total error variance in the observations, among all linear receivers with the same output noise covariance, and to analyze their performance in a unified way. We derive exact and approximate expressions for the probability of bit error, as well as the asymptotic signal-to-interference+noise ratio in the large system limit. We also characterize the spectral efficiency versus energy-per-information bit of the CSMU receiver in the wideband regime. Finally, we consider a special case of the CSMU receiver, equivalent to a mismatched minimum mean-squared error (MMSE) receiver, in which the channel signal-to-noise ratio (SNR) is not known precisely. Using our general performance analysis results, we characterize the performance of the mismatched MMSE receiver. We then treat the case in which the SNR is known to lie in a given uncertainty range, and develop a robust mismatched MMSE receiver whose performance is very close to that of the MMSE receiver over the entire uncertainty range. 相似文献
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Adaptive power control and MMSE interference suppression 总被引:8,自引:0,他引:8
Power control algorithms assume that the receiver structure is fixed and iteratively update the transmit powers of the users
to provide acceptable quality of service while minimizing the total transmitter power. Multiuser detection, on the other hand,
optimizes the receiver structure with the assumption that the users have fixed transmitter powers. In this study, we combine
the two approaches and propose an iterative and distributed power control algorithm which iteratively updates the transmitter
powers and receiver filter coefficients of the users. We show that the algorithm converges to a minimum power solution for
the powers, and an MMSE multiuser detector for the filter coefficients.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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多用户检测技术在实际应用中,难以解决的问题是在减少计算复杂度的同时又提高系统性能。本文针对空时CDMA系统设计了一种多用户检测算法,即附带噪声梯度的最速下降算法。此算法利用变步长迭代的思想实现多用户检测,避免了最小均方误差(MMSE)多用户检测庞大而复杂的求逆运算和固定步长收敛速度较慢的问题。计算机仿真结果表明,在空时CDMA系统中使用本文算法,收敛速度大大增加,同时在保持系统性能的前提下能够容纳较多的用户。 相似文献