一种有效的多径信号DOA估计算法

本文讨论了移动通信环境中的信号多径DOA估计问题,文中首先对典型算法作了简要回顾,然后给出了阵接收多径信号模型,给出了基于时间平均的多径DOA估计算法原理,指出了其存在的问题,并提出了一种有效的解决方法.最后给出的计算机仿真实验结果验证了提出方法的有效性.     

WCDMA上行信道SIR估计算法研究

在WCDMA系统中的功控命令,是根据上行DPCCH信道的SIR生成的.常用的估计SIR算法有Morphics的SIR估计方法.但是,当信道中的噪声出现瞬时变化时,Morphics的SIR估计方法会产生较多功控命令,导致用户的发射功率不停波动,不利于用户发射功率的稳定.首先阐述了Morphics的SIR估计方法,然后针对WCDMA系统的要求,对Morphcis算法中的噪声干扰估计进行IIR滤波,以得到平稳的SIR估计值.     

基于循环平稳性的约束自适应多径时延估计

在有多径信号、多通道非平稳干扰信号以及平稳背景噪声的情况下,不考虑多径信号传输的时延估计方法不能准确地估计时延,甚至估计性能会恶化.为此,本文提出了基于循环平稳性的约束自适应多径时延估计算法,并对算法的收敛性能进行了分析.该算法可以有效地抑制干扰和噪声的影响,在低信噪比的情况下直接地、准确地进行自适应多径时延估计,特别对噪声是空间相关的情形也适用,克服了传统算法不能直接估计非整数倍采样间隔的时延和多径时延的缺点.计算机仿真试验验证了新方法的有效性.     

多径条件下的时差估计研究

研究了多径条件下的时差估计问题。在多径条件下,运用谱相干校正法（SPECCOA）和多径多信号环境下的时差估计去模糊（DATEMM）算法相结合的方法进行信号到达时差（TDOA）的参数估计,该方法能够从估计出的多个峰值中提取出真实TDOA值,消除多径带来的估计模糊,得到正确的估计值。最后的计算机仿真结果验证了文中的结论。     

多通道干扰下的多径时延估计

在考虑多通道非平稳信号干扰及背景噪声的情况下,本文提出的基于循环相关的参数型时间延时估计方法,可准确地进行多径传输情况下的时间延时估计,有效地抑制干扰和噪声的影响.在估计性能方面,该方法优于基于相关的方法.在运算量和适应性能方面,该方法优于基于高阶累积量的方法.文章最后采用计算机模拟验证了文中的结论.     

未知波形信号的多径时延估计新方法

该文提出了一种从单个阵元接收数据中估计未知波形信号多径回波时延的新方法。该方法通过建立单阵元接收数据的频域信号模型,分析得出了利用该模型估计多径时延与利用阵列估计来波方向问题的相似性。进而,估计来波方向的ESPRIT算法被改造用于估计多径时延。文中还对通过信号模型估值存在的模糊问题进行了分析,并提出了解决办法。仿真实验结果证明了新方法的有效性。     

一种新的非瑞利信道的多普勒估计算法

针对多径信道中非瑞利环境,提出了基于信道冲激响应相位信息进行多普勒估计的方法.提出了局部最大径的找径方法和径的轨迹跟踪方法,分析了估计误差并提出减小误差的误差修正因子配置方法,使得算法估计更准确、估计精度不受信噪比影响.     

ISI信道下的突发通信信噪比估计

信噪比(SNR)是通信系统的重要参数,SNR估计是信号处理的重要环节,而无线通信中常见的多径效应会给SNR估计带来恶劣影响.丈中首先介绍了突发通信中借助训练序列进行SNR估计的主要方法,分析了ISI信道对估计产生的不利影响.根据信道函数的特性,文中提出了基于相关峰捕获和DFE均衡器处理的两种SNR估计法.随后文中讨论分析了这两种算法的估计性能.仿真表明,这两种算法都能对ISI信道的SNR进行可靠的估计.     

基于随机集模型的MIMO-OFDM信道估计算法

在多径分量数确定的前提下,MIMO-OFDM系统采用传统的基于导频辅助和盲信道估计算法能获得较好性能。实际无线环境中,多径分量数目与幅度都是时变的,则传统信道估计方法不再适用。该文采用随机集理论建模MIMO-OFDM系统信道多径分量数的变化和MIMO信道。基于此模型提出了集中粒子空间重采样方法(CRS),在保留大概率粒子抽样样本的同时主动抛弃小概率抽样样本,以获得更为准确的真实样本逼近。并提出了基于集中重采样Rao-Blackwellised粒子滤波的信道估计方法(RBPFC)。仿真结果表明:所提出的RBPFC方法信道估计性能最好,基本Rao-Blackwellised粒子滤波方法次之但优于基本粒子滤波算法,卡尔曼滤波的信道估计方法性能最差。     

基于循环互相关的LFM多径时延和衰减因子估计

针对复线性调频信号在多径条件下的参数估计问题进行了研究。本文提出的基于信号循环互相关的多径时延和衰减因子估计方法，可有效地进行多径条件下复线性调频信号多径时延和衰减因子估计，有效地抑制平稳噪声或干扰的影响，同时也避开了相关交叉项的影响。文章最后采用计算机仿真实验验证了文中的结论。     

TD-SCDMA中的二阶快速收敛功率控制

基于信号干扰比(SIR)测量的归一化功率控制在无线蜂窝系统中有着广泛的应用。论文提出TD-SCDMA系统中的基于SIR测量的二阶快速收敛分布式功率控制算法,使用当前功率和前次功率共同参与运算控制移动台发射功率。仿真结果表明,论文提出的二阶快速收敛DPC算法在相同的传播环境下比DPC和SOPC具有更快的收敛速度。     

WCDMA系统功率控制策略中的内环SIR测量

功率控制是使CDMA系统容量最大化的关键技术之一.在IMT-2000指定的宽带码分多址接入(WCDMA)系统中,实现高精度的快速闭环功率控制的基础是内环SIR的精确测量.由此,基于3GPP协议,本文提出了一种新的易实现模块化的内环SIR测量的方法,在原理和性能上与Shunsuke所提SIR的测量方法进行了比较,通过仿真证明了新方法测量性能的优越性,并给出了基于业务质量的快速闭环功率控制的性能.     

SIR Estimation in Hexagonal Cellular Networks with Best Server Policy

The evaluation of the Signal to Interference Ratio (SIR) in cellular networks is of primary importance for network dimensioning. For static studies, which evaluate cell capacity and coverage, as well as for dynamic studies, which consider arrivals and departures of mobile stations (MS), the SIR is always an important input. Contrary to most of the analytical works evaluating SIR, we assume in this paper that the MS is attached to the best server, i.e., to the base station (BS) from which it receives the highest power. This is a more realistic policy compared to the classical one that considers MSs to be attached to the nearest BS. The exact formulation of the SIR is however in this case uneasy to handle and numerical methods remain heavy. In this paper, we thus propose an approximate analytical study on the average SIR and SIR distribution in lognormally shadowed networks based on truncated lognormal distributions that provides very close results with respect to Monte Carlo simulations.     

Outer-loop control of target SIR for fast transmit power control inturbo-coded W-CDMA mobile radio

A technique for obtaining outer-loop control of the target SIR for closed-loop fast transmit power control (TPC) is presented for turbo-coded wideband DS-CDMA (W-CDMA) mobile radio systems. The frame error rate (FER) of an intermediate decoding output in the turbo-decoder. i.e. before the final iteration stage is reached, is measured to control the target SIR. The bit error rate (BER) after the final decoding iteration can be maintained accurately at the prescribed BER value, e.g. BER=10^-6, without losing the tracking ability in the presence of slowly changing propagation channel conditions. Computer simulation results supporting this ability are reported     

Transmitter Power Control with Adaptive Safety Margins Based on Duration Outage

Transmitter power control in cellular networks is principally used to maintaina stable voice quality and to improve bandwidth utilization. There are twomain types of quality based power control algorithms that have been extensivelystudiedin the literature and implemented in practice. One is the Signal toInterferenceRatio (SIR) based algorithms, and the other is the Bit Error Rate(BER) basedalgorithms. Several practical issues however, were left open in the algorithms that havebeen proposed in the literature. The most critical issue in the SIR-basedalgorithms is how to determine the SIR target parameter; and the most critical one in theBER-basedalgorithms is how to derive good BER estimators in light of the rareoccurrences of erroneous bits. Another issue that is shared by both algorithm types is thefunctional relation between the BER and the SIR. This relationship is required as one mayserve as a control valve and the other as a control objective. Determining the SIR target control parameter (in SIR or BER based algorithms) involves more than just a static transformation between the BER and the SIR.Sincethe actual SIR values is a stochastic process in nature, its variation andtimecorrelation must be accounted for. This paper addresses the problems described above by evaluating a durationoutage probability of the underlying time process of the SIR values. Weshow that this probability can reasonably be approximated by a simple expressionthat relates between the duration outage probability and the SIR targetcontrolparameter. The distributed algorithm that is implied by this method is adurationoutage based power control that uses an estimator for the most likelyevent (incontrast to BER-based algorithms).     

Local Coverage Probability Estimation in Single Frequency Networks

In OFDM based Single Frequency Networks (SFNs) such as Digital AudioBroadcasting (DAB) and Digital Video Broadcasting (DVB), the mobilereceiver is provided by the same signal from several synchronoustransmitters at the same carrier frequency.This transmitter diversity structure makes SFNs very efficientin fading channels with an excellent spectrum saving, and very goodpower utilization over the service area.However, depending on the position of the mobile within the servicearea, these signals arrive with different delays causing possibleechoes at the receiver.These echoes contribute to both the useful and the interferingparts of the signal.As the average received power in radio channels is a stochasticprocess, such contribution creates correlation between the differentcomponents of the Signal-to-Interference Ratio (SIR).In broadcasting practice, correlation was not taken into accountwhen estimating the distribution of the SIR and the local coverageprobability.This paper considers the effect of correlation on the estimation ofthe SIR and the coverage probability in OFDM based SFNs.Analyses are provided to show that in some situations the estimationerror can be considerable when neglecting this correlation.To obtain a better estimation, the correlation coefficient between thetotal useful and total interfering parts of the received signal isfirst evaluated and then used as a correction factor in estimating themean and standard deviation of the SIR.The obtained results show that such method can significantly reducethe estimation error of local coverage probability without increasingthe computation complexity.     

提高W-CDMA通信系统容量的技术

文章主要讨论了提高W-CDMA通信系统容量采取的技术,包括:小区间异步操作和3步快速小区搜索、引导符号辅助相干信道估计、基于信干功率比的快速发射功率控制、位置分集、前向链路的发射分集,以及干扰抵消和自适应天线阵列分集接收和发射。     

Subspace based estimation of the signal to interference ratio for TDMA cellular systems

The Signal‐to‐Interference Ratio (SIR) has been highlighted in the literature to be a most efficient criterion for several methods aiming at reducing the effects of cochannel interference, e.g., diversity reception, dynamic channel allocation and power control. In this paper we address the problem of how to obtain fast and accurate measurements of this parameter in a practical context. We develop a general SIR estimation technique for narrow‐band cellular systems that is based on a signal subspace approach using the sample covariance matrix of the received signal. Simulation results using the frame structure in the GSM system show that the SIR can be estimated to within an error of 0.3 dB after only 200 ms, or within an error of 0.1 dB after only 0.6 seconds.     

TD-SCDMA中基于连续型模糊控制的外环功率控制算法

该文提出一种基于连续型模糊控制的外环功率控制算法,它对误块率的变化量进行模糊化处理,通过模糊控制规则和解模糊化处理得到输出值,作为内环功率控制的信干比目标值调整步长。该算法能精确给出最佳调整步长,在很大程度上避免了已有的外环功率控制方法的过调现象。并能随着网络及无线环境的变化,使实际系统的平均误块率快速收敛于满足服务质量所需的误块率目标值。实验结果验证了该算法的优良特性。     

基于正交解扩的信干比估计方法

研究了TDD-CDMA(时分双工-码分多址)系统中的SIR(信干比)估计问题。现有的SIR估计方法准确度依赖于信道条件和观测时间,而TDD-CDMA系统复用时隙短,车速条件下信道变化剧烈的特点使得估计准确度降低。针对这种情况,提出了一种基于正交解扩的SIR估计方法。通过COSSAP仿真对比结果表明,该方法在瑞利衰落信道和AWGN(加性高斯白噪声)信道条件不同调制方式下,从低SIR到高SIR的很大范围内都有比较好的性能。