共查询到19条相似文献,搜索用时 109 毫秒
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多天线是天线技术的发展趋势,TD-LTE引入了8发2收的天线配置.基于小间距多天线阵列,利用TDD系统信道互易性,波束赋形技术可以根据上行导频获得信道信息,形成对基带(中频)信号的最佳组合或者分配,补偿无线传播过程中由空间损耗、多径效应等因素引入的信号衰落与失真,同时降低同信道用户间的干扰.EBB(Eigen-based Beamforming)算法是波束赋形主要算法之一,该算法中在整个波束空间中,找到使接收信号功率最大的赋形权矢量.通过仿真,对EBB算法在各种应用场景下的性能进行了分析,结果表明八天线EBB波束赋形算法可以正确实现波束合成,在低速或上行信道信息估计误差较小情况下能够明显提高系统性能. 相似文献
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多用户波束优化设计在智能天线系统中的应用 总被引:10,自引:0,他引:10
本文讨论了智能天线系统中的下行波束形成问题。智能天线可以通过阵列天线技术在同一信道中利用多个波束同时给多个用户发送不同的信号,以提高通信容量和质量。本文提出了蜂窝小区移动通信体制下波束形成的约束模型,并基于该模型利用Chebyshev线阵实现多波束优化设计。理论分析及仿真结果表明,与目前其它方法相比,该方法具有空间分辨力高、计算量小、稳健性好等优点,有较强的实用性。 相似文献
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《电子科技文摘》2006,(7)
0617287分布式目标下行波束形成〔刊,中〕/徐卫//中国电子科学研究院学报.—2006,1(1).—98-101(G)研究了智能天线在下行链路的应用,利用上行链路接收数据,建立分布式目标信道模型,估计移动用户的发射角、扩展角度和发射功率以及下行信道相关矩阵,确定下行链路的波束形成方法,即对频分复用(FDD)系统进行上行相关矩阵变换,构建下行信道协方差矩阵,利用最大合并比准则获得下行链路权值。计算机仿真证实了这种方法的有效性。参50617288基于数字波束合成的空间信号分离研究〔刊,中〕/贾朝文//中国电子科学研究院学报.—2006,1(1).—86-88,65(G… 相似文献
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徐卫 《中国电子科学研究院学报》2006,1(1):98-101
研究了智能天线在下行链路的应用。利用上行链路接收数据,建立分布式目标信道模型。估计移动用户的发射角、扩展角度和发射功率以及下行信道相关矩阵,确定下行链路的波束形成方法。即对频分复用(FDD)系统进行上行相关矩阵变换,构建下行信道协方差矩阵,利用最大合并比准则获得下行链路权值。计算机仿真证实了这种方法的有效性。 相似文献
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讨论了TD-SCDMA系统的下行信号模型,并根据TD-SCDMA系统上行信道估计可以直接用于下行波束赋形的特点,研究了特征值分解方法下的下行波束成形算法的性能并仿真比较了其与基于最大径准则等下行波束形成算法在不同环境下的性能。 相似文献
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时空信道可以用矢量信道冲激响应(VCIR)来描述,正确估计VCIR是智能天线系统实现的关键技术。该文分析了WCDMA的物理信道帧格式,提出了利用上行信道中的辅助导频信号实现VCIR估计的方法,借助已有的角度与相对时延联合估计方法,可以得到实现下行选择性发送及二维相干RAKE接收机的一组信道参数(DOA、相对时延及复衰落)。利用这样一种间接的方法,可以解决用户数远大于阵元数及频率选择性衰落信道中存在大量相干源时的DOA估计问题。计算机仿真实验表明,时空信道的估计精度完全可以满足信道参数估计的要求。 相似文献
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研究了在频分双工智能天线系统中基站与移动台之间上下行信道的协方差矩阵,根据不随频率变化的上下行信道特性,得到下行的协方差矩阵,以使期望用户接收的信干噪比最大为准则确定下行波束形成的权矢量,不需要估计用户的DOA和平均信号强度的信息。计算机仿真进一步显示了算法的性能。 相似文献
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智能天线教学实验系统的实现 总被引:2,自引:0,他引:2
智能天线是移动通信系统中广泛采用的一种新技术.本文主要介绍在移动通信实验箱中增加智能天线实验功能时对智能天线阵列类型、下行波束赋形、上行波束成形和天线校准等关键算法的选择以及智能天线教学实验系统的整体实现方案.由于实验系统可对信道环境等实验条件做适当简化,因而可以通过合理设计,在不影响实验效果的前提下,降低实验系统的复杂度和成本. 相似文献
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Downlink channel covariance matrix (DCCM) estimation and itsapplications in wireless DS-CDMA systems
The downlink channel covariance matrix (DCCM) is of vital importance in determining downlink beamforming weights for base station (BS) antenna array systems. For the frequency-division-duplex (FDD) mode, DCCM is difficult to obtain due to a lack of direct measurement of downlink channel responses. In this paper, a novel technique is proposed for estimating DCCM using uplink channel responses only, which does not need direction-of-arrival (DOA) estimation and its association. The downlink beamforming scheme is then proposed for wireless DS-CDMA systems, using the obtained DCCM information together with the so-called virtual uplink beamforming and power control technique. Computer simulations show that using the BS antenna array together with this new beamforming technique can provide larger system capacity than traditional DOA-based approaches, which just direct the main beam toward the desired user 相似文献
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A smart antenna concept was studied in the context of a GSM1800 downlink. In practice, it is not possible to estimate the actual downlink channel when using frequency division duplexing (FDD). Therefore, the current approach is based on uplink direction-of-arrival (DoA) estimation. The downlink beam is then directed to the DoA obtained from the uplink. The purpose was to study the dependence of downlink performance on the angular and delay distribution of the desired signal. The downlink beamforming was studied in this work using simulations with 2D channel models for different test environments. The probability of error in DoA estimation of the desired mobile station was evaluated in conjunction with DoA averaging. In addition, downlink BER performance was examined in a noise-limited situation and compared to the results of the corresponding uplink and a conventional 2-branch GSM receiver. With a 1*8-element antenna configuration, downlink performance degradation compared to the corresponding uplink case was approximately 1.3 dB, 2.4 dB, and 0 dB in typical Urban, Suburban, and Rural environments. The losses were greater in environments with very large angular spread. It was also found that increasing accuracy in uplink DoA estimation does not necessarily correspond to improved downlink performance. 相似文献
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Downlink beamforming is a promising technique for direct-sequence code-division multiple-access (DS-CDMA) systems with multimedia services to effectively reduce strong interference induced by high data rate users. A new downlink beamforming technique is proposed that converts the downlink beamforming problem into a virtual uplink one and takes into account the data rate information of all users. Since the main complexity of this method is due to the existence of multidelay paths, two simplified algorithms are suggested using an equivalent one-path channel vector to replace multipath channel vectors. Computer simulation results are given to evaluate the downlink capacity of DS-CDMA systems using a base station antenna array and the new algorithms proposed 相似文献
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Adapting a downlink array from uplink measurements 总被引:3,自引:0,他引:3
In a frequency division duplex system, a transmitter adaptive antenna array can potentially improve the performance of a wireless downlink, but because the uplink and downlink channels have different wavelengths, and, therefore, different responses, direct downlink adaptation based on channel estimates of the uplink is generally not feasible. Instead, there has been some interest in adaptations that require only the second-order statistics of the uplink and downlink to be similar. These algorithms derive adaptive weights from the covariance of the received signal to apply to a downlink transmitter array. We make two contributions to this area. First, we introduce an array configuration employing M+1 elements with log-periodic spacing that comprises two overlapping subarrays, each with M elements, that are scaled versions of each other, with the scale factor equal to the ratio of the uplink wavelength to the downlink wavelength. This array has identical beampatterns at the two wavelengths, thus helping to fulfill the requirement that the uplink and downlink second-order statistics be the same. Second, we demonstrate that obtaining a good estimate of the uplink covariance matrix is not essential for the successful operation of the adaptive scheme. Even when the mobile is at rest and the uplink information comprises only a single snapshot from the receiver array, an adaptive scheme can improve the SNR 相似文献
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The outage occurring from beamformer-based smart antennas is analysed for an antenna array deployed in an urban macro-cell environment. Spatio-temporal channel data obtained from a small, urban cell and from within the UTRA frequency allocation has enabled beamforming performance to be determined from the measured uplink and downlink frequency bands. The analysis shows a sub-optimum uplink beamformer performance is observed for 8% of occasions and a 25% downlink beamforming outage for an eight-element uniformly spaced linear array 相似文献
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Yanrong Zhao Wenjing Zhao Gongpu Wang Bo Ai Hervin Hidayat Putra Bagus Juliyanto 《中国通信》2020,(3):90-100
Channel estimation is a well-known challenge for wireless orthogonal frequency division multiplexing(OFDM)communication systems with massive antennas on high speed rails(HSRs).This paper investigates this problem and design two practicable uplink and downlink channel estimators for orthogonal frequency division multiplexing(OFDM)communication systems with massive antenna arrays at base station on HSRs.Specifically,we first use pilots to estimate the initial angle of arrival(AoA)and channel gain information of each uplink path through discrete Fourier transform(DFT),and then refine the estimates via the angle rotation technique and suggested pilot design.Based on the uplink angel estimation,we design a new downlink channel estimator for frequency division duplexing(FDD)systems.Additionally,we derive the Cramér-Rao lower bounds(CRLBs)of the AoA and channel gain estimates.Finally,numerical results are provided to corroborate our proposed studies. 相似文献
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Wei-Chiang Wu 《电子科技学刊:英文版》2020,18(3):266-275
This paper addresses the problem of channel estimation in a multiuser multi-cell wireless communications system in which the base station (BS) is equipped with a very large number of antennas (also referred to as “massive multiple-input multiple-output (MIMO)”). We consider a time-division duplexing (TDD) scheme, in which reciprocity between the uplink and downlink channels can be assumed. Channel estimation is essential for downlink beamforming in massive MIMO, nevertheless, the pilot contamination effect hinders accurate channel estimation, which leads to overall performance degradation. Benefitted from the asymptotic orthogonality between signal and interference subspaces for non-overlapping angle-of arrivals (AOAs) in the large-scale antenna system, we propose a multiple signals classification (MUSIC) based channel estimation algorithm during the uplink transmission. Analytical and numerical results verify complete pilot decontamination and the effectiveness of the proposed channel estimation algorithm in the multiuser multi-cell massive MIMO system. 相似文献