共查询到20条相似文献,搜索用时 15 毫秒
1.
Baccarelli E. Cusani R. Galli S. 《Selected Areas in Communications, IEEE Journal on》1998,16(9):1630-1639
The paper presents a novel fast-adaptive nonlinear receiver which exploits soft statistics for tracking the random fluctuations experienced by time division multiple access (TDMA) mobile radio links impaired by frequency-selective time-variant multipath phenomena. The detection task is accomplished by an Abend-Fritchman-like symbol-by-symbol maximum likelihood (SbS-ML) detector which delivers both hard decisions and soft statistics in form of a posteriori probabilities (APPs) of the states of the intersymbol interference (ISI) channel. In the proposed adaptive receiver, these APPs are employed in place of the conventional hard-detected data to feed an ad hoc developed nonlinear recursive Kalman-type channel estimator. Extensive computer simulations show that the exploitation of soft statistics enhances the tracking capability of the channel estimator so that the proposed receiver generally outperforms the usual ones based on adaptive maximum likelihood sequence estimators (MLSEs) for signal-to-noise ratio (SNR) values over 12-13 dB. Furthermore, the experienced performance gap with respect to more complex per-survivor processing (PSP)-based multi-estimator detectors appears generally small on slowly and moderately fast time-varying channels characterized by values of the product Doppler bandwidth × signaling period BDTS below 5×10-3 相似文献
2.
3.
Cassioli D. Win M.Z. Molisch A.F. 《Selected Areas in Communications, IEEE Journal on》2002,20(6):1247-1257
We establish a statistical model for the ultra-wide bandwidth (UWB) indoor channel based on an extensive measurement campaign in a typical modern office building with 2-ns delay resolution. The approach is based on the investigation of the statistical properties of the multipath profiles measured in different rooms over a finely spaced measurement grid. The analysis leads to the formulation of a stochastic tapped-delay-line (STDL) model of the UWB indoor channel. The averaged power delay profile can be well-modeled by a single exponential decay with a statistically distributed decay constant. The small-scale statistics of path energy gains follow Gamma distributions whose parameters m are truncated Gaussian variables with mean values and standard deviations decreasing with delay. The total received energy experiences a lognormal shadowing around the mean energy given by the path-loss power law. We also find that the correlation between multipath components is negligible. Finally, we propose an implementation of the STDL model and give a comparison between the experimental data and the simulation results. 相似文献
4.
We develop a statistical geometric propagation model for a macrocell mobile environment that provides the statistics of angle-of-arrival (AOA) of the multipath components, which are required to test adaptive array algorithms for cellular applications. This channel model assumes that each multipath component of the propagating signal undergoes only one bounce traveling from the transmitter to the receiver and that scattering objects are located uniformly within a circle around the mobile. This geometrically based single bounce macrocell (GBSBM) channel model provides three important parameters that characterize a channel: the power of the multipath components, the time-of-arrival (TOA) of the components, and the AOA of the components. Using the GBSBM model, we analyze the effect of directional antennas at the base station on the fading envelopes. The level crossing rate of the fading envelope is reduced and the envelope correlation increases significantly if a directional antenna is employed at the base station 相似文献
5.
A statistical model, based on experimental data, is presented to characterize the multipath propagation medium in typical manufacturing environments. The statistical behavior of the medium is described by a time-varying impulse response which includes the distribution of the parameters of the channel such as the gain, the interarrival time, and the number of paths. The resolvable components in a number of experimentally measured pulse responses of indoor factory radio channels were used to estimate the channel statistics. The interarrival times of the signals were modeled by the Weibull distribution. A model for the distribution of signals was presented using the modified beta distribution. The path gain coefficients were represented using the Rayleigh, Rician, or log-normal distributions. The model for the factory channel is flexible enough to fit the data for other indoor sites by changing the parameters of the factory channel appropriately relative to the size, topography, and other structural features of the site 相似文献
6.
Jie Zhou Hao Jiang Hisakazu Kikuchi 《International Journal of Communication Systems》2016,29(3):459-477
To test an adaptive array algorithm in cellular communications, we developed a geometry‐based statistical channel model for radio propagation environments, which provides the statistics of the angle of arrival and time of arrival of the multipath components. This channel model assumes that each multipath component of the propagating signal undergoes only one bounce traveling from the transmitter to the receiver and that scattering objects are located according to Gaussian and exponential spatial distributions, and a new scatterer distribution is proposed as a trade‐off between the outdoor and the indoor propagation environments. Using the channel model, we analyze the effects of directional antennas at the base station on the Doppler spectrum of a mobile station due to its motion and the performance of its MIMO systems. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
7.
Spencer Q.H. Jeffs B.D. Jensen M.A. Swindlehurst A.L. 《Selected Areas in Communications, IEEE Journal on》2000,18(3):347-360
Most previously proposed statistical models for the indoor multipath channel include only time of arrival characteristics. However, in order to use statistical models in simulating or analyzing the performance of systems employing spatial diversity combining, information about angle of arrival statistics is also required. Ideally, it would be desirable to characterize the full spare-time nature of the channel. In this paper, a system is described that was used to collect simultaneous time and angle of arrival data at 7 GHz. Data processing methods are outlined, and results obtained from data taken in two different buildings are presented. Based on the results, a model is proposed that employs the clustered “double Poisson” time-of-arrival model proposed by Saleh and Valenzuela (1987). The observed angular distribution is also clustered with uniformly distributed clusters and arrivals within clusters that have a Laplacian distribution 相似文献
8.
The impact of local oscillator intensity noise and the threshold level on the performance of the {2×2} and the {3×3} phase-diversity amplitude-shift keying (ASK) receiver has been investigated for the first time for non-Gaussian statistics. Exact equations are derived for the bit-error-rate (BER), taking into account the non-Gaussian statistics and the statistical dependency of the relative intensity noise (RIN) in the receiver branches. The results differ substantially from the case in which a priori Gaussian statistics were assumed. The sensitivity penalty of the receivers is calculated with respect to the performance of an ideal heterodyne ASK receiver for a BER of 10-9. It is shown that for a minimum sensitivity penalty the threshold level should be chosen in relation to the local oscillator power and the intensity noise level 相似文献
9.
针对基于长期演进(LTE)信号的无源雷达存在同频基站干扰的问题,该文提出一种基于2阶统计量的盲源分离算法,该算法是在卷积混合模型下,通过多通道最小均方(LMS)算法实现分离信号之间的相关性最小。由于各发射基站信号之间统计不相关,当分离信号之间的相关性达到最小时,完成观测信号的分离。在此基础上,改进了传统无源雷达信号处理的流程,增加了分离同频干扰基站直达波和多径杂波的步骤,实现了对同频干扰基站杂波的抑制。通过仿真分析,验证了算法的有效性,为基于LTE信号的无源雷达数据处理提供了参考。
相似文献10.
11.
Cognitive radio combined with multiple-input multiple-output (MIMO) communications provides high data rate, efficiency and high reliability. One of the most important challenges in MIMO communication is combating MIMO multipath channel. MIMO blind equalizers and channel estimators combat MIMO multipath channels without the use of training or pilot sequences. First, the multipath channel is converted into instantaneous mixture channel (IMC), using second-order statistics of the data. Then using higher-order statistics, these mixtures are separated. However, proper selection of IMC is a major challenge. In this paper, a novel blind algorithm for choosing the best IMC is proposed. The proposed algorithm is based on the cumulant value of the received signal. 相似文献
12.
In this paper we present a geometric multipath propagation model for a microcell mobile environment. The proposed model provides
the statistics for the direction-of-arrival (DOA) of multipath components. These statistics are required to test adaptive
array algorithms for cellular applications. The proposed model assumes that (1) a line-of-sight (LOS) path exists between
the transmitter and the receiver, (2) the scatterers lie within a circle of radius R around the mobile station, and (3) the base station lies within this circle. The distances between the scatterers and the
mobile station are subject statistically to a hyperbolic distribution. The model also provides the multipath power delay profiles
(PDP), which are used to evaluate the bit error rate (BER) and the signal to interference ratio (SIR) for the direct-sequence
code division multiple access (DS-CDMA). We derive and simulate the joint probability density functions (pdfs) of the power—DOA
and the power—Doppler shift. Further we determine expressions for the BER performance and for the SIR of a DS-CDMA system
over the proposed channel model. A simplified expression based on the improved Gaussian approximation (SEIGA) is used to evaluate
the BER and the SIR in a wideband multipath channel. Although the proposed model is applicable for downlink as well, in this
paper we will analyze the uplink environment only. 相似文献
13.
A statistical model of urban multipath propagation 总被引:11,自引:0,他引:11
《Vehicular Technology, IEEE Transactions on》1972,21(1):1-9
An urban multipath propagation experiment, involving the simultaneous transmission from a fixed site of 100-ns pulses at 488, 1280, and 2920 MHz and their reception at a mobile van, is described. A statistical analysis of the data in the resulting multipath responses is given and used as a basis for a statistical model of urban multipath propagation. 相似文献
14.
为研究城市战场环境下战术自组织网络(tactical mobile ad hoc network,TacMAN)通信节点间的信道特性,针对城区场景超短波频段展开信道测量与建模。测量结果表明,TacMAN通信场景下,多径信号存在明显的非平稳性和生灭现象。针对信道非平稳性,首先设计了一种多径识别与跟踪算法,有效地估计出多径信号的存在概率。其次,使用基于马尔科夫链的改进型抽头延迟线(tapped delay line,TDL)模型对实测数据的非平稳过程进行建模。最后基于赤池信息准则(akaike information criterion,AIC)给出了小尺度衰落的统计模型,分析表明双高斯混合分布(bimodal Gaussian mixture distribution,BGMD)和Ricean分布分别是描述模型首径与最强径幅度分布的最佳模型。论文建立的非平稳信道模型可以较好地描述TacMAN场景下信道特性,为提高相关军事通信场景下通信系统的性能提供参考。 相似文献
15.
This letter presents a mathematical model for the statistics of wideband code-division multiple-access signals which experience multipath fading. The statistics are obtained from numerically generated signals, and are then modeled with an offset noncentral chi distribution with three degrees of freedom. The mathematical model is tested against the numerically generated data by the use of a chi-square goodness-of-fit test. 相似文献
16.
F. Perez‐Fontn S. Martínez B. Sanmartín C. Enjamio P. Mario F. Machado 《International Journal of Satellite Communications and Networking》2005,23(2):111-128
In this paper, a technique to derive the transition probabilities for a Markov chain model for the land mobile satellite (LMS) channel in built‐up areas is presented. This technique contributes to improving empirically derived parameters in that it can account for elevation and street orientation effects as well as building density. Physical‐statistical or ‘virtual city’ techniques are used to relate observed edification statistics to signal attenuation statistics. This methodology can also be applied to generating correlated time‐series for simultaneous links to a constellation of satellites from the same mobile terminal. The proposed approach also allows the generation of enhanced time‐series which take into account diffuse multipath and diffraction effects. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
17.
F. P. Fontan A. Mayo D. Marote R. Prieto‐Cerdeira P. Mariño F. Machado N. Riera 《International Journal of Satellite Communications and Networking》2008,26(4):291-316
The land mobile satellite (LMS) propagation channel is frequently described using statistical models. These models usually make different assumptions regarding the behavior of the direct signal, the diffuse multipath component and the shadowing effects. This paper analyzes the theoretical formulation and implementation of time‐series synthesizers based on three typical statistical models: Loo, Corazza–Vatalaro and Suzuki, describing their similarities and differences. The discussion is not limited to the amplitude of the complex envelope but also to the phase variations and Doppler spectra. Finally, guidelines are also provided for comparing model parameters supplied by different authors. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
18.
Image fiber-optic two-dimensional (2-D) parallel data links based upon optical space-code division multiple access (CDMA) is implemented and experimentally demonstrated for the first time to the authors' knowledge. In the experiment, each input 4×4 bit-plane is optically encoded by an 8×8 2-D optical orthogonal signature pattern. The encoded bit-planes are spatially multiplexed, and it is transmitted through a 16 m-long image fiber having 3×104 pixels. Each receiver can properly recover the intended input bit-plane in the optical decoding process. This result will encourage the application of optical space-CDMA to future high-throughput 2-D parallel data links 相似文献
19.
针对短距离无线通信应用中低功耗的要求,提出了一种基于多径传播模型的双向动态功耗调节算法。通过实时预测环境链路损耗,保存在随负荷传送的功耗控制字节中,动态调节链路终端发射功率,实现在短距离复杂时变电磁环境下基于传播信道的无线链路的能耗管理。针对2.4 GHz短距离无线收发方案进行实验与性能分析,结果表明该算法能有效地延长电池供电时间。 相似文献
20.
UWB室内视距环境多径传播模型 总被引:2,自引:0,他引:2
提出了一种全新超宽带(UWB,ultra-widebandwidth)室内视距(LOS,line-of-sight)环境的多径传播模型(简称多径模型)。该模型以南加州大学UltRa实验室的UWB室内LOS环境实测数据为基础,信道冲激响应具有两个确定的簇,每个簇内具有随机到达的多径射线。模型有效地利用特定环境的几何参数数据,在预测室内LOS环境的小尺度多径传播特性(平均附加时延、RMS时延扩展、最强多径数量)上较传统的统计模型更加简化和准确,与传统的确定模型相比,明显地降低了模型建立的复杂度。 相似文献