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空时分组码MC-CDMA系统多用户检测 总被引:4,自引:2,他引:2
本文研究了在频率选择性瑞利衰落信道中工作于时分双工(TDD)模式的多载波码分多址(MC-CDMA)系统上行链路,在用户终端处使用两个发射天线,采用基于空时分组码的发射分集。考虑对应于子载波的衰落系数是信道冲激响应的离散傅里叶变换,给出了基于空时分组码的MC-CDMA系统上行链路信号模型。采用适用于同步CDMA系统的低代价Steiner估计器来进行基于空时分组码的MC-CDMA系统的信道估计,每个用户终端的两个发射天线各分配一个midamble。研究了基于空时分组码的MC-CDMA系统的解相关多用户检测、最小均方误差(MMSE)多用户检测,进行联合的多用户检测和空时码解码。仿真结果验证了上述模型及算法的有效性。 相似文献
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空时分组码是无线通信系统中的一种抗信道衰落和提高系统容量的编码方法,能够同时获得分集增益和编码增益。由此将MIMO通信和MIMO脉冲雷达中应用较多的空时分组码引入FMCW车载毫米波雷达信号处理中,通过对发射信号和接收信号的编码解耦,形成更大天线孔径的虚拟阵列,提高了系统角度分辨率。相比于基于时间分集的虚拟阵列算法,基于空时分组码的虚拟阵列算法能够在单天线功率受限的场景下,获得多根天线同时工作带来的功率增益。同时,针对空时分组码中目标运动带来的相位误差问题,根据FMCW车载毫米波雷达低复杂度的系统需求,设计了一种适用于相干目标的运动相位校准算法。仿真结果表明,基于空时分组码的FMCW车载毫米波雷达信号处理算法相比于已有算法能够获得更好的系统性能。 相似文献
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针对MIMO系统,提出了一种改进的基于子空间的盲MMSE空时多用户检测算法。该算法结合MIMO系统的空间分集技术与Alamouti空时分组码方案,预估计MIMO信道信息并对信号子空间进行预处理,使用正交性能和稳态性能较好的NOOja算法跟踪信号子空间,在自适应过程中对特征值矩阵进行优化,去除迭代带来的噪声,解决了跟踪过程中信号特征值矩阵的近似估计会带来检测器性能恶化的问题。仿真结果表明这种算法,能有效地抑制多址干扰,抗远近效应能力强,尤其在低信噪比、远近效应明显的恶劣环境下,有稳定良好的性能表现。 相似文献
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恒模算法(CMA)是一种广泛应用于阵列处理、均衡和多用户检测中的盲算法。现对恒模算法及其在盲多用户检测技术中的应用进行了分析,并指出其研究方向。 相似文献
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在高速数据传输的频率选择性信道的直接序列扩频系统中,基于恒模算法(CMA)的二级盲接收机能够在只知道期望用户的扩频码以及定时信息的情况下进行自适应联合均衡和多用户检测,具有较好的实时处理性能。但是其第一级检测器的自适应求取采用的是递归最小二乘(RLS)算法,该算法在收敛稳定性等方面具有一系列缺陷,从而对整个算法的性能造成了损害。本文将戴彧虹 袁亚湘自适应步长迭代算法作为第一级检测器的自适应处理方式,并给出了新的方案的完整实现流程。理论和仿真结果显示,经过改进后的二级CMA盲自适应接收机比起原先的算法有着更低的误码率和更高的稳态输出信干比(SINR),在总体性能上有了很大提高。 相似文献
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The presence of non-Gaussian impulsive noise in wireless system can degrade the performance of existing equalizers and signal detectors. In this paper, the problem of blind source separation and equalization for MIMO systems in heavy-tailed impulsive noise is studied. A generalized multiuser constant modulus cost function by employing the fractional lower-order statistic of the equalizer input signal is proposed. The associated adaptive blind equalization algorithm based on a stochastic gradient descent method is defined as fractional lower-order multi-user constant modulus algorithm (FLOS MU CMA). Computer simulations are presented to illustrate the performance of the new algorithm. 相似文献
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In digital communication systems, the constant modulus algorithm (CMA) for blind multiuser detector has some disadvantage
such as slow convergence speed and weight phase rotation. In this paper, we put forward a novel receiver, which combines CMA
blind adaptive multiuser detection and particle swarm optimization (PSO) technique in frequency domain for multi-carrier direct
sequence code division multiple access (MC DS-CDMA) systems. By this approach we present an adaptive multistage structure
based on PSO technique. In this structure, the weights are obtained by PSO technique between the received signal and its estimate
through a CMA. The resulting weights contain reliability information for the hard decisions made in the previous stage. The
simulation results show that BER performance of the PSO-based CMA blind multiuser detector is superior to that of steepest
decreasing constant modulus algorithm (SDCMA), linearly constrained constant modulus algorithm (LCCMA), CMA based multiuser
detection and is worthy due to its significant detection performance to achieve desirable improvement in convergence speed
and tractability. 相似文献
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XuChangqing WangHongyang SongWentao 《电子科学学刊(英文版)》2004,21(6):490-494
As the Projection Approximation Subspace Tracking with deflation(PASTd) algorithm is sensitive to impulsive noise, an improved subspace tracking algorithm is proposed and applied to blind adaptive multi-user detection. Simulation results show that the improved PASTd algorithm not only remains the properties of the conventional PASTd algorithm, but also has good Bit Error Rate(BER) performance in impulsive noise environment, thus it can effectively improve the system performance. 相似文献
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随着数字移动通信技术的飞速发展,以码分多址(CDMA)为核心的第三代移动通信(3G)技术已经走入人们的日常生活。CDMA系统具有容量大、软容量、抗多径衰落强等优点,但多址干扰(MAI)的存在却严重的影响了系统的性能和容量,因此如何消除和抑制这种干扰就成了CDMA技术研究的热门话题之一,第三代移动通信系统已经将多用户检测技术(MUD)作为克服多址干扰的有效方法之一。文中主要研究了直接序列扩频码分多址(DS-CDMA)系统中的盲多用户检测算法,深入的研究了基于卡尔曼滤波的盲多用户检测算法,通过在卡尔曼滤波算法上引入子空间提高了原有卡尔曼滤波算法的效率。 相似文献
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Blind equalization is a technique for adaptive equalization of a communication channel without the aid of the usual training
sequence. Although the Constant Modulus Algorithm (CMA) is one of the most popular adaptive blind equalization algorithms,
it suffers from slow convergence rate. A novel enhanced blind equalization technique based on a supervised CMA (S-CMA) is
proposed in this paper. The technique is employed to initialize the coefficients of a linear transversal equalizer (LTE) filter
in order to provide a fast startup for blind training. It also presents a computational study and simulation results of this
newly proposed algorithm compared to other CMA techniques such as conventional CMA, Normalized CMA (N-CMA) and Modified CMA
(M-CMA). The simulation results have demonstrated that the proposed algorithm has considerably better performance than others. 相似文献
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A subspace-based linear conjugate constant modulus algorithm (CMA) for blind adaptive multiuser detection in BPSK-Modulated MC-CDMA systems is proposed. First, a linear conjugate CMA algorithm is presented which jointly elaborates the received signal and its complex conjugate to utilize the information contained in the pseudo-autocorrelation of the observable, thus is capable of achieving much better performance. Second, to further improve the performance, the subspace method is applied to the linear conjugate CMA algorithm to obtain a subspace-based linear conjugate CMA algorithm, which mitigates the influence of the noise subspace. Finally, an improved projection approximation subspace tracking with deflation algorithm is proposed for adaptive signal subspace estimation to reduce the computational complexity. The proposed algorithm provides an improved robustness against the signature waveform mismatch, good tracking capability in dynamic environment and better output signal-to-interference-plus-noise-ratio and bit error rate performance. The superiority of the proposed algorithm is demonstrated through computer simulations. 相似文献
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研究了空时编码多载波码分多址系统(STBC MC—CDMA)盲信道估计技术。根据信道位于信号子空间的特点,提出基于信号子空间投影线性约束恒模算法(SP—LCCMA)的盲信道估计,避免了噪声子空间信道估计的缺点,将估计信道应用于STBC MC—CDMA系统多用户检测。仿真结果表明,提出算法的收敛速度和信干噪比(SINR)性能优于一般恒模算法。 相似文献