共查询到19条相似文献，搜索用时 125 毫秒
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姚洁 《宁德师专学报(自然科学版)》2009,21(2):168-174
在CDMA（Code Divisin Muhiple Access,码分多址）通信系统中,由于多个用户的随机接人,所使用的扩频码集一般并非严格正交,码片之间的非零互相关系数将引起各用户间的干扰,这种干扰称为多址干扰．为了能够有效的抑制CDMA移动通信系统中的多址干扰,抗“远近效应”,就引进了多用户检测（MUD）．多用户检测技术在传统检测的基础上,能有效地消除MAI的影响,从而改善系统性能,增大系统容量．对系统中的多用户检测技术和与之密切相关的MMSE检测技术进行了研究． 相似文献
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近年来,第三代移动通信系统将多用户检测这项关键技术作为CDMA系统中克服多址干扰的一种有效方法,同时解决了远近效应问题,显著提高了系统性能和容量。本文对CDMA系统中基于子空间的盲多用户检测算法进行了详细的阐述。 相似文献
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基于奇异值分解提出了一种改进的kalman滤波盲自适应多用户检测算法．理论分析和数值仿真表明，在异步CDMA系统中，与现有的基于RLS算法盲自适应多用户检测方法相比，该方法具有收敛速度快、跟踪性能好、数值稳定性高的优点． 相似文献
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为了进一步提高光纤通信系统的容量和传输速率，光CDMA技术成为研究热点。寻找一种具有好的传输特性的正交编码成为解决问题的关键。文章提出了一种正交设计的二维时空编码设计方案，该编码方案具有强的自相关性和弱的互相关性。针对多用户干扰和接受机噪声两种情况，对它在光CDMA网络传输时的特性进行了仿真实验，结果表明该时空编码具有较好的接受效果。 相似文献
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针对CDMA系统中抗干扰技术，本文提出一种结合多用户检测和扇区分区的算法，对接收信号在时域和空间上进行联合处理，能大大抑制干扰，提高系统容量。 相似文献
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为了进一步提高光纤通信系统的容量和传输速率,光CDMA技术成为研究热点。寻找一种具有好的传输特性的正交编码成为解决问题的关键。文章提出了一种正交设计的二维时空编码设计方案,该编码方案具有强的自相关性和弱的互相关性。针对多用户干扰和接受机噪声两种情况,对它在光CDMA网络传输时的特性进行了仿真实验,结果表明该时空编码具有较好的接受效果。 相似文献
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将独立分量分析，即ICA应用于DS-CDMA系统的多用户检测中，提出了基于ICA后处理的最小均方误差MMSE多用户检测方法。该方法用MMSE检测的输出来初始化独立分量分析的迭代．既利用了信源的独立性，又充分利用了已知扩频码的信息，从而提高了多用户检测器的性能。仿真结果表明：此方法在高信噪比的情况下，误码性能得到了较大改善。 相似文献
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在超宽带（UWB）通信系统里，当用户数增加和脉冲重复频率下降时，多址干扰会严重影响系统容量和性能．文章提出了UWB-MA系统多用户检测算法．仿真结果表明，多用户检测接收机性能优于传统单用户检测接收机． 相似文献
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This paper presents the architectures, algorithms, and implementation considerations of the digital phase locked loop (DPLL) used for burst-mode packet DS-CDMA receivers. As we know, carrier offset is a rather challenging problem in CDMA system. According to different applications, different DPLL forms should be adopted to correct different maximum carrier offset in CDMA systems. One classical DPLL and two novel DPLL forms are discussed in the paper. The acquisition range of carrier offset can be widened by using the two novel DPLL forms without any performance degradation such as longer acquisition time or larger variance of the phase error. The maximum acquisition range is 1/(4T), where T is the symbol period. The design can be implemented by FPGA directly. 相似文献
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INTRODUCTIONDS CDMAtechniquesplayanimportantroleincurrentHFCnetworksandwirelesscommuni cationsystems (Chungetal.,1993;Gaudenzietal.,1996 ;Viterbi,1997) .CrucialtotheDS CDMAsystemispropercodeandcarriersyn chronization .Literatureoncodesynchronizationisabun… 相似文献
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This paper presents the architectures, algorithms, and implementation considerations of the digital phase locked loop (DPLL)
used for burst-mode packet DS-CDMA receivers. As we know, carrier offset is a rather challenging problem in CDMA system. According
to different applications, different DPLL forms should be adopted to correct different maximum carrier offset in CDMA systems.
One classical DPLL and two novel DPLL forms are discussed in the paper. The acquisition range of carrier offset can be widened
by using the two novel DPLL forms without any performance degradation such as longer acquisition time or larger variance of
the phase error. The maximum acquisition range is 1/(4T), whereT is the symbol period. The design can be implemented by FPGA directly.
Project (No. 60002003) supported by the National Natural Science Foundation of China 相似文献
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This paper presents an improved error function of dithered signed-error constant modulus algorithm （IDSE-CMA） for blind multiuser interference suppression in DS/CDMA systems. It uses a different error function to replace the former one in sign operation of the DSE-CMA and compares their performance in multiple access interference （MAI） suppression ability. Simulations indicate that the new algorithm has better performance than the similar CMA in terms of convergence speed and steady-state performance： 相似文献
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随着第三代移动通信(3G)技术的发展,如何开设3G实验项目是本课程面临的一大问题。3G设备相对十分昂贵,又存在WCDMA、CDMA2000、TD-SCDMA 3种不同的标准,全面开设实验存在不少困难。利用已购买的大型仪器完成对CDMA2000信号的实时捕获及分析,给出了实验步骤、指标测试与相关分析。 相似文献
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An important feature of the traffic in mobile networks is burstiness. Drawbacks of conventional power control algorithms for time division duplex （TDD）-code division multiple access （CDMA） systems are analyzed. A joint power control algorithm based on service factor is presented to address the TDD-CDMA mobile services in the burst mode according to the Markov modulated Bernoulli process. The joint power control equation is derived. A function model is developed to verify the new algorithm and evaluate its performance. Simulation results show that the new power control algorithm can estimate interference strength more precisely, speed up convergence of power control, and enhance power efficiency and system capacity. It is shown that the proposed algorithm is more robust against link gain changes, and outperforms the reference algorithms. 相似文献
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INTRODUCTION The technology of smart or adaptive antennawhich can increase capacity and range, and reducesmultipath propagation of mobile radio communi-cation system, has aroused great interest in recentyears (Haardt and Spencer, 2003; Bellofiore, 2002;Godara, 1997). Beamforming is a key technologyin smart antenna systems (SAS) and many differentadaptive beamforming algorithms have been pro-posed. Code division multiple access (CDMA)system will be applied in most mobile communi-… 相似文献
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The paper presents a modified least squares despread respread multitarget constant modulus algorithm(LS-DRMTCMA). The cost function of the original algorithm was modified by the minimum bit error rate(MBER)criterion.The novel algorithm tries to optimize weight vectors by directly minimizing bit error rate(BER)of code division multiple access(CDMA)mobile communication system. In order to achieve adaptive update of weight vectors,a stochastic gradient adaptive algorithm was developed by a kernel density estimator of possibility density function based on samples. Simulation results showed that the modified algorithm remarkably improves the BER performance,capacity and near-far effect resistance of a given CDMA communication system. 相似文献