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In [1], an evolution strategy (ES) multiuser detector was proposed and exhibits good performance. This letter analyzes the search behavior of the ES detector and points out it can be greatly enhanced via a simple technique. A heuristic multiuser detection algorithm is presented, which employs the neighborhood structure characteristics of the optimum multiuser detection (OMD) problem and produces local optima efficiently. A well-chosen perturbation strategy is applied to improve the solution quality in the following step. Simulations results show the meta-heuristic algorithm proposed can find the (near) optimum solution rapidly with lower computational complexity and has better bit error rate (BER) performance. 相似文献
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Shaowei Wang Qiuping Zhu Lishan Kang 《Communications Letters, IEEE》2006,10(6):423-425
This letter introduces a new multiuser detection algorithm based on (1+/spl lambda/) evolution strategy for asynchronous DS-CDMA systems. By setting the offspring population size and the mutation probability appropriately, the new algorithm can approach the minimum probability of error with great computation efficiency. Simulation results show that the proposed algorithm converges very rapidly and provides good BER performance for cases where other suboptimum algorithms perform poorly. The average computation time is polynomial complexity in the number of users. 相似文献
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In this paper novel algorithms are introduced for solving NP hard discrete quadratic optimization problems commonly referred to as unconstrained binary quadratic programming. The proposed methods are based on hypergraph representation and recursive reduction of the dimension of the search space. In this way, efficient and fast search can be carried out and high quality suboptimal solutions can be obtained in real-time. The new algorithms can directly be applied to the quadratic problems of present day communication technologies, such as multiuser detection and scheduling providing fast optimization and increasing the performance. In the case of multiuser detection, the achieved bit error rate can approximate the Bayesian optimum and in the case of scheduling better Weighted Tardiness can be achieved by running the proposed algorithms. The methods are also tested on large scale quadratic problems selected from ORLIB and the solutions are compared to the ones obtained by traditional algorithms, such as Devour digest tidy-up, Hopfield neural network, local search, Taboo search and semi definite relaxing. As the corresponding performance analysis reveals the proposed methods can perform better than the traditional ones with similar complexity. 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
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The powerful iterative algorithm of Turbo code is employed in the proposed iterative multiuser receiver for the downlink of a forward error correction (FEC) coded direct-sequence code-division multiple access (DS-CDMA) environment. The receiver iterates between the 2 coding dimensions, namely the spreading codes and the FEC codes. The optimum iterative multiuser receiver uses the optimum decentralised single-user detector to generate the single-user extrinsic information for the single-user decoders. This paper suggests a near-optimum detector using a folded trellis preselection stage for the multiuser signal detection, in order to reduce the dominating complexity of the optimum decentralised detector. Simulation results show that performance is close to optimum. The effect of the single-user decoders' extrinsic information on the signal detection stage is also investigated and it is found that extrinsic information improves performance. 相似文献
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DS-CDMA通信系统中基于独立分量分析的盲多用户检测 总被引:3,自引:0,他引:3
本文研究了直接序列扩频码分多址(DS-CDMA)通信系统的多用户检测问题,提出了基于独立分量分析(ICA)方法的盲多用户检测算法,实现多用户信号的盲检测。该方法不需知道用户的扩频码就可完成多用户信号的盲检测。仿真结果验证了本文提出的方法的优良性能。 相似文献
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基于低复杂度算法的QPSK多用户检测 总被引:1,自引:0,他引:1
提出了一种低复杂度的QPSK准最优多用户检测算法。该算法保证在多项式复杂度下收敛到全局最优解附近。实验和仿真结果表明:该算法性能十分逼近最优多用户检测器,为解决CDMA系统的多用户检测问题提供了一条新的途径。 相似文献
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Jibing Wang Xiaodong Wang 《Selected Areas in Communications, IEEE Journal on》2006,24(1):113-120
In this paper, we study the design of linear dispersion (LD) codes for uplink multiuser channels with multiple antennas at the base station and each mobile unit. In the considered scheme, each user employs LD codes to transmit the data, i.e., the transmitted codeword is a linear combination over space and time of certain dispersion matrices with the transmitted symbols. The linear space-time spreading can also be utilized to separate multiple users at the base station. We propose a simulation-based optimization method together with gradient estimation to systematically design the multiuser linear space-time coding under either optimal or suboptimal receivers. We perform the gradient estimation through the score function method. The proposed method can also be applied to design codes under different fading statistics. Simulation results show that under the optimal maximum-likelihood (ML) receiver, the codes obtained by the new algorithm provides roughly the same performance as the low-dimensional spread modulation, as well as the interference-resistant modulation. Moreover, the new codes perform significantly better with suboptimal multiuser receiver structures. 相似文献
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H. H. El Morra A. Zerguine A. U. Sheikh 《Wireless Communications and Mobile Computing》2009,9(10):1331-1342
In this work, we present a new multiuser detection (MUD) structure which results from incorporating the tabu search (TS) heuristic algorithm with the local search (LS) heuristic algorithm. The new proposed structure brings much improvement when compared to both the conventional (matched filter) detector and the decorrelating detector. Moreover, the new TS‐LS‐detector proposed here approximates well the performance of the optimal MUD detector but with a very low computational complexity. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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The prohibitive - exponential in the number of users - computational complexity of the maximum-likelihood multiuser detector for direct-sequence code-division multiple-access communications has fueled an extensive research effort for the development of low-complexity multiuser detection alternatives. We show that we can efficiently and effectively approach the error rate performance of the optimum multiuser detector as follows. We utilize a multiuser zero-forcing or minimum mean-square error (MMSE) linear filter as a preprocessor and we establish that the output magnitudes, when properly scaled, provide a reliability measure for each user bit decision. Then, we prepare an ordered, reliability-based error search sequence of length linear in the number of users; it returns the most likely user bit vector among all visited options. Numerical and simulation studies for moderately loaded systems that permit exact implementation of the optimum detector indicate that the error rate performance of the optimum and the proposed detector are nearly indistinguishable over the whole predetection. signal-to-noise ratio range of practical interest. Similar studies for higher user loads (that prohibit comparisons with the optimum detector) demonstrate error rate performance gains of orders of magnitude in comparison with straight decorrelating or MMSE multiuser detection. 相似文献
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S. Nayeb Nazar W.-P. Zhu M.O. Ahmad M.N.S. Swamy 《Circuits, Systems, and Signal Processing》2004,23(5):409-432
In this paper, the problem of multiuser detection for synchronous code division
multiple access systems in both additive white Gaussian noise and multipath channels is
addressed. A new multiuser detection receiver that uses an adaptive blind array along with
an adaptive parallel interference canceler is proposed. The replacement of a conventional
antenna array with a two-dimensional RAKE receiver is also considered for frequency
selective Rayleigh fading channels. By using a constrained optimization criterion along
with the gradient-projection algorithm, a blind algorithm for the adaptation of the array response
vector is proposed. The new algorithm is superior to a few typical blind algorithms
in the literature in terms of both performance and computational complexity. The proposed
receiver has the ability to cancel very strong multiple access interference coming from the
same direction as the desired signal. Simulation results are presented to show the excellent
performance of the proposed combination scheme in comparison to that of using either a
multiuser detection or adaptive antenna arrays in a severe near-far situation. 相似文献
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L. K.K. Y.M. L. R.S. 《AEUE-International Journal of Electronics and Communications》2006,60(7):513-520
In a code-division multiple-access (CDMA) system, multiuser detection (MUD) can exploit the information of signals from other interfering users to increase the system capacity. However, the optimum MUD for CDMA systems requires the solution of an NP-hard combinatorial optimization problem. It is well known that the computational complexity of the optimum multiuser detector is exponential with the number of active users in the system. In this paper, we apply a hybrid algorithm to develop a suboptimal MUD strategy. The result of symmetric successive overrelaxation (SSOR) preconditioned conjugate-gradient method is first used to initialize the reduced-complexity recursive (RCR) multiuser detector. Then, RCR algorithm is applied to detect the received data bit by optimizing an objective function in relation with the linear system of decorrelating detector. Simulation results for the synchronous case show that the performance of our proposed SSOR-RCR multiuser detector is promising and outperform the decorrelator and linear minimum mean squared error multiuser detector with lower computational complexity. 相似文献
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In this paper, we present an efficient evolutionary algorithm for the multi-user detection (MUD) problem in direct sequence-code division multiple access (DS-CDMA) communication systems. The optimum detector for MUD is the maximum likelihood (ML) detector, but its complexity is very high and involves an exhaustive search to reach the best fitness of transmitted and received data. Thus, there has been considerable interest in suboptimal multiuser detectors with less complexity and reasonable performance. The proposed algorithm is a combination of adaptive LMS Algorithm and modified genetic algorithm (GA). Indeed the LMS algorithm provides a good initial response for GA, and GA will be applied for this response to reach the best answer. The proposed GA reduces the dimension of the search space and provides a suitable framework for future extension to other optimization algorithms. Our algorithm is compared to ML detector, Matched Filter (MF) detector, conventional detector with GA; and Adaptive LMS detector which have been used for MUD in DS-CDMA. Simulation results show that the performance of this algorithm is close to the optimal detector with very low complexity, and it works better in comparison to other algorithms. 相似文献
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Tjeng Thiang Tjhung Xiaoming Xue Yongmei Dai Kar Ngai Wong Ping He 《Vehicular Technology, IEEE Transactions on》2002,51(4):788-793
An adaptive asynchronous code-division multiple-access (CDMA) multiuser detector is proposed that uses a recently derived extended Kalman filter based algorithm (see Lim, T.J. and Rasmussen, L.K., IEEE Trans. Commun., vol.45, p.213-20, 1997) to perform joint data detection and parameter tracking in frequency-selective Rayleigh fading channels. A receiver structure based on this adaptive multiuser detector is presented and its performance in terms of parameter tracking and bit error rate (BER) is investigated. The receiver is a form of an adaptive RAKE that exploits multipaths to achieve performance gain 相似文献
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Two simple structures employing multilayer perceptrons are proposed for demodulation of spread-spectrum signals in both synchronous and asynchronous Gaussian channels. The optimum receiver is used to benchmark the performance of the proposed receiver; in particular, it is proved to be instrumental in identifying the decision regions for the neural networks. The neutral networks are trained for the demodulation of signals via backpropagation-type algorithms. A modified backpropagation-type algorithm is introduced for single-user and multiuser detection with near-optimum performance that could have applications in other classification and pattern recognition problems. A comparative performance analysis of the three receivers, optimum, conventional, and the one employing neural networks, is carried out via Monte Carlo simulations. An importance sampling technique is employed to reduce the number of simulations necessary to evaluate the performance of these receivers in a multiuser environment. In examples given, the receiver significantly outperforms the conventional receiver 相似文献
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基于遗传算法的最小误码率线性多用户检测 总被引:1,自引:1,他引:0
本文提出了一种多用户检测算法,算法基于最小误码率准则,应用内核密度估计方法来估计误码率函数,并采用基于实数编码的遗传算法来搜索误码率函数全局最小点。该算法解决了由于误码率函数存在局部最小点而难以用普通的梯度算法来求解全局最优点的问题。算法对初值的选取无特殊要求,可随机选取。仿真结果表明,梯度算法求解最小误码率检测器由于可能收敛到次优的局部极小点,故检测器不能达到最小误码率性能;而本文基于遗传算法的多用户检测由于能很好的避免收敛到次优的局部极小点,因而得到的检测器性能逼近最小误码率。 相似文献