TD-SCDMA系统下行联合波束功控技术

TD-SCDMA系统最重要技术特征是智能天线技术。本文基于时延和角度扩散空间信道模型,提出了一种下行基站联合优化波束和发射功率的智能天线技术。     

智能天线系统中动态信道分配算法性能研究

在讨论了智能天线技术对动态信道分配算法性能影响的基础上,通过对智能天线系统下的动态信道分配算法进行仿真研究,与没有利用智能天线技术时的动态信道分配算法比较,两种情况在接收端误比特率的分析,说明采用智能天线技术时,能够在很大程度上改善系统在接收端的误比特率指标。     

TD-SCDMA上行链路智能天线的效益

ＴＤ－ＳＣＤＭＡ系统最重要技术特征是智能天线技术。本文提出了智能天线下的方向性的信道模型。在此基础上研究了智能天线的算法。由此分析了ＴＤ－ＳＣＤＭＡ上行链路智能天线的效益。     

微小区环境下角度扩散特性的仿真结果

智能天线及其他空间滤波技术的研究与应用为无线信道的研究提出了新的课题－需要对无线信道的时空联合扩散特性进行全面地分析和研究.本文利用射线跟踪技术对典型微小区下信道的时域扩散和角度扩散特性进行了大量仿真.作者按照时域扩散的研究方法,利用角度扩散的一阶矩和二阶中心矩来说明问题.通过典型环境下的仿真,得到了存在直达信号和无直达信号两种接收条件下的角度扩散结果.     

智能天线及其在TD-LTE中的应用

智能天线在基站进行各天线间的相干发送,实现信号的定向发送,可以提高信号的强度和覆盖,从而提升系统的整体性能。对于TDD系统,由于上下行信道共享同一发送频率,在相干时间内,可以认为上下行链路的信道互易,即信道经历相同的衰落。TDD 系统可以利用上下行信道的互易性,采用智能天线技术对 LTE-A 的整体性能进行增强。本文介绍智能天线技术在TD-LTE系统中的应用及其性能。     

TD-LTE系统中的单双极化智能阵列天线性能分析

研究了TD-LTE系统中双极化技术对智能阵列天线性能的影响,理论分析了下行波束赋型算法中赋型增益与信道矩阵SVD分解后的奇异值的关系,并基于相关阵信道模型利用数值计算统计出单、双极化智能阵列天线的信道特征参数。然后,通过蒙特卡洛数值仿真方法对TD-LTE系统在单、双极化智能阵列天线配置下的误块率性能进行评估。理论分析和仿真结果都表明,双极化智能阵列天线在误块率性能损失较小情况下显著减小了阵列尺寸,具有实际应用价值。     

无线系统中的智能天线

本文介绍了智能天线在未来移动通信系统中的重要作用.分别介绍了多波束天线和自适应天线阵,阐明了智能天线的定义、组成.着重介绍了在自适应天线阵通信系统中的时空信号模型、空间信道模型和时空通信理论,比较了智能天线中的智能算法.最后,结合智能天线技术的应用进展,探讨了实现智能天线的难点和发展前景.     

TD-SCDMA系统所采用的技术(一)

１智能天线１．１智能天线的基本概念近年来，智能天线技术已成为移动通信中最具吸引力的技术之一。在移动通信环境条件下，复杂的地形和建筑物结构对电波传播存在一定影响，大量用户信号间的相互作用，会产生时延扩散、瑞利衰落、多径和共信道干扰，影响通信质量，智能天线可以有效地解决这些问题。智能天线采用空分多址（SDMA）技术,利用信号在传输方向上的差别，将同频率或同时隙、同码道的信号区分开来，最大限度地利用有限的信道资源。无线基站中的智能天线由天线阵和基于基带数字信号处理技术组成，通过调节各阵元信号的加权幅度和…     

智能天线及其加权向量

智能天线利用天线阵,以相同信道的不同用户之间的空间特征差异来实现信道倍增,并实现用户信号的分离。文章以智能天线的基本理论为基础,首先讨论了如何确定加权向量W,以达到提取期望信号、抑制干扰信号和滤除噪声的目的,然后描述了智能天线阵列的波束形成以及调整的过程,接着介绍了常用的智能天线算法准则,最后回顾了智能天线的发展历程。     

TD-LTE基站智能天线性能分析

多天线技术是移动通信技术发展的重要趋势,是实现移动通信系统高容量、高频谱效率的重要手段.LTE系统引入了多向多天线技术,并定义了多种多天线的工作模式,其中基于非码本预编码的智能天线是TD-LTE的核心技术,可以充分利用TDD的上下行信道互易性,显著提升系统的吞吐量和频谱效率.本文从理论上给出了2天线及8天线在TD-LTE系统性能上的差异,并且分析了8天线智能天线技术在实际应用中可能面临的挑战,从广播信道的无功率加权、下行链路质量估计补偿、SRS协调发送、多用户配对算法优化、接收机性能增强等角度对智能天线的产品实现进行优化,可提升性能10％～30％.     

Decoupled estimation of DOA and angular spread for a spatiallydistributed source

In mobile communications, local scattering in the vicinity of the mobile results in angular spreading as seen from a base station antenna array. In this paper, we consider the problem of estimating the parameters [direction-of-arrival (DOA) and angular spread] of a spatially distributed source, using a uniform linear array (ULA). A two-step procedure enabling decoupling the estimation of DOA from that of the angular spread is proposed. This method combines a covariance matching algorithm with the use of the extended invariance principle (EXIP). More exactly, the first step makes use of an unstructured model for the part of the covariance matrix that depends on the angular spread. Then, the solution is refined by invoking EXIP. Instead of a 2-D search, the proposed scheme requires two successive 1-D searches. Additionally, the DOA estimate is robust to mismodeling the spatial distribution of the scatterers. A statistical analysis is carried out, and a formula for the asymptotic variance of the estimates is derived. Numerical examples illustrate the performance of the method     

考虑高斯误差和Doppler扩展的最大比合并性能分析

在高斯误差和Doppler扩展条件下,研究信道估计时公共导频信道相关长度对天线阵的合并性能影响.假设信道估计通过相关WCDMA公共导频信道的N个符号来获得,文章首先推导了相干BPSK解调时平均BER性能的闭解表达式,然后利用该平均BER表达式对导频信道最优相关长度进行了分析,给出了最优相关长度的计算方法,并证明了最优相关长度N只与最大Doppler扩展f_d和符号周期有关,与阵列参数以及天线接收的信噪比无关.     

A Cramér Rao bounds based analysis of 3D antenna array geometries made from ULA branches

In the context of passive sources localization using antenna array, the estimation accuracy of elevation, and azimuth are related not only to the kind of estimator which is used, but also to the geometry of the considered antenna array. Although there are several available results on the linear array, and also for planar arrays, other geometries existing in the literature, such as 3D arrays, have been less studied. In this paper, we study the impact of the geometry of a family of 3D models of antenna array on the estimation performance of elevation, and azimuth. The Cramér-Rao Bound (CRB), which is widely spread in signal processing to characterize the estimation performance will be used here as a useful tool to find the optimal configuration. In particular, we give closed-form expressions of CRB for a 3D antenna array under both conditional, and unconditional observation models. Thanks to these explicit expressions, the impact of the third dimension to the estimation performance is analyzed. Particularly, we give criterions to design an isotropic 3D array depending on the considered observation model. Several 3D particular geometry antennas made from uniform linear array (ULA) are analyzed, and compared with 2D antenna arrays. The isotropy condition of such arrays is analyzed. The presented framework can be used for further studies of other types of arrays.     

BER performance of linear STBC from orthogonal designs over MIMO correlated Nakagami-m fading channels

This paper presents the evaluation of the average bit error rate (BER) performance of linear space-time block codes (STBC) from orthogonal designs over correlated identically distributed Nakagami-m fading channels. Starting from the moment-generating function (MGF) of the multipath component signals at the antenna array elements, analytical expressions of the BER performance for both integral and nonintegral Nakagami-m fading parameters are derived. Closed-form expressions of the spatial cross-correlation function for mobile nonfrequency selective Nakagami-m fading multiple-input-multiple-output (MIMO) channels are obtained, which are valid for small angle-of-arrival (AOA) spread. In this expressions, various parameters of interest, such as the mean AOA of the signal, AOA spread, and array configurations, are all taken into account. The effects of antenna array configuration and the operating environment (mean AOA, AOA spread, Nakagami fading parameter) on the BER performance of the system are illustrated by several numerical examples.     

Angle-of-arrival statistics for low resolution antennas

In a scattering environment, the propagation paths to a receiving antenna arrive from a certain angular spread of directions. For a low-resolution antenna, an apparent direction of arrival may be defined as the azimuth direction of maximum power. A small array is used as the antenna and the spatial derivative of the phase along the array axis is taken as a measure of the sine of the apparent angle of arrival. The sine of the angle is shown to be Student's t-distributed and from this result the PDF and power spectrum of the angle-of-arrival is determined. The distributions are compared with experimental results for indoor as well as for outdoor measurements     

One-user/one-group soft-decision aided layered detection for multiuser MIMO 2D spread multi-carrier DS-CDMA systems

We consider the uplink of a multiuser, multiple input multiple output (MIMO), frequency-time-domain spread, multi-carrier (MC), direct sequence code division multiple access (DS-CDMA) system. In this two-domain (2D) spread system, users are arranged in groups. Each user is assigned a unique time-domain (T-domain) signature code and also shares a frequency-domain (F-domain) signature code with users in the same group. Moreover, each user employs his/her individual T-domain signature code and the shared F-domain signature code to spread multiple symbols, and then sends the spreading signals in parallel from multiple transmit antennas to the antenna array at the base station. However, the multiple access interference (MAI) effect, which results from the non-orthogonality of signature codes and is the main performance limitation, still exists in such an MC DS-CDMA system. To mitigate the MAI effect and improve the performance, we propose user-based and group-based layered detection schemes. Specifically, to enable a trade-off between the performance and the computational complexity, the schemes only use one user's/group's soft decisions for user-based/group-based layered detection. The results of simulations demonstrate that the proposed schemes outperform existing approaches, and their computational complexity is modest.     

The Jakes fading model for antenna arrays incorporating azimuth spread

A new method for simulating the multiplicative fading of the narrow-band, flat wireless channel for antenna array receivers is presented. The new approach produces a set of fading waveforms, one waveform associated with each receiver element, in which the waveforms are appropriately correlated to take into account the spread, or dispersion, in the azimuth (arrival angle) of the received signal. The new method is an extension of the Jakes (1974) method of simulating fading in which the appropriate correlation of the set of waveforms is accomplished by directly considering the azimuth of scatterers in a particular distribution about the mobile transmitter. The models used for this cluster of scatterers are a ring and a disk of scatterers. Further modifications of the disk model permit the generation of fading waveforms which are correlated in a manner which reflect actual field measurements of azimuth dispersion. Analytical correlation of these models is reviewed for purposes of verification with the waveforms generated by the method.     

Interference analysis and capacity for forward link 3G CDMA network with adaptive antennas

In code division multiple access (CDMA) systems, the capacity of forward link (FL) communication to mobile receivers is limited primarily by co‐channel interference (CCI). Adaptive antenna arrays (AAAs) that use antenna arrays along with advanced signal processing at the base station (BS) have been proposed to mitigate this limitation. For a 3G CDMA cellular network, where each BS equipped with an AAA serves mixture of voice and data users within its coverage, we study FL capacity and investigate the effects of different factors (array topology, multipath angle spread, data rate, and beamforming algorithm) on this capacity under Rayleigh fading channel. By modeling the instantaneous signal‐to‐interference power ratio received at the mobile, we derive the system outage equation that considers blocking of either desired voice or data user. Simulation results show that for the same element spacing and number of antenna elements per cell, the uniform circular array (UCA) topology results in larger capacity than the sectorized uniform linear array (ULA) topology does, and that a larger angle spread or data user rate reduces FL capacity. Copyright © 2007 John Wiley & Sons, Ltd.     

Effects of polarization, antenna directivity, and room size ondelay spread in LOS indoor radio channel

This paper presents results of experiment and computer simulation based on a three-dimensional (3-D) ray-tracing method for various directional polarized antennas, where the effects of polarization, antenna directivity, and room size on delay spread (measured at 94 GHz) are investigated in the line-of-sight (LOS) indoor channel. These results indicate that the delay spread can be reduced significantly by the directional circularly polarized antenna. It is also found that the delay spread increases almost proportionally with the square root of the room floor area