Correlation Bandwidth and Delay Spread Multipath Propagation Statistics for 910-MHz Urban Mobile Radio Channels

Distributions of delay spread and correlation bandwidth at 0.9 and 0.5 correlation for Gaussian wide-sense stationary uncorrelated scattering (GWSSUS) channels associated with 100 small-scale areas at different locations within a 2 × 2.5 km region of New York City are presented. For delay spread the maximum value observed was3frac{1}{2};mus and l0 percent of the areas exceeded2frac{1}{2}mus; for correlation bandwidth at 0.9 correlation the minimum was 20 kHz and 10 percent of the areas were less than 30 kHz; for correlation bandwidth at 0.5 correlation the minimum was 55 kHz and 10 percent of the areas were less than 130 kHz. The region is representative of the heavily built-up areas of many large cities in the United States.     

910 MHz urban mobile radio propagation: Multipath characteristics in New York city

Small scale statistics of multipath propagation in a heavily built-up urban mobile radio environment are presented. The statistics cover vehicle travel distances on the order of 30 m along streets. Measuring equipment time delay resolution is about 0.1 µs. In some locations, paths with significant amplitudes are observed with excess delays of 9 to 10 µs. The delay spreads (√second central moment of power delay profile) in this environment are on the order of 2 µs. Often the signal at fixed delays has a Rayleigh-distributed amplitude but large departures from the Rayleigh distribution also occur. From the measurements it appears reasonable to model the urban mobile radio channel as a Gaussian quasi-wide-sense stationary uncorrelated scattering channel within a bandwidth of 10 MHz and for intervals along the street of up to 30 m.     

无线多径特性及其对陆地移动通信系统规划设计的影响

本文对无线多径传播特及其对陆地移动通信系统规划设计的影响、抗多径衰落措施等进行了论述.     

Propagation Properties of Radio Wave in Multipath Scattering Mobile Channel

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Propagation characteristics on microcellular urban mobile radiochannels at 910 MHz

The results of measurements made to determine propagation characteristics on urban mobile radio channels with low base-station antennas and line of sight between the base and mobile units are reported. Results show that multipath propagation conditions would be significantly less severe if small-celled systems were implemented. Root-mean-square delay spread averages computed by considering all multipath signal components with powers greater than 25 dB below the peak were reduced by a factor of approximately four in comparison to those typical in conventional systems. In addition, microcellular-type channels have Rician, rather than Rayleigh, envelope fading characteristics and correspondingly different frequency correlation statistics. The area bounded by the correlation envelope is introduced as a measure of channel quality, and these areas are shown to be larger for Rician channels than for Rayleigh channels     

Effects of Multipath Propagation on Digital Radio

This paper summarizes experimental work at Bell Laboratories in the field of multipath propagation as it affects digital radio. Field and laboratory measurements are presented on commercial-quality high-speed digital radio systems working in the 4, 6, and 11 GHz common carrier bands. Circuits and equipment used in these systems are all state of the art, but no attempt has been made to describe them in any detail. Modulation types are offset-4 PSK, conventional 8 PSK, and 16 QAM. Outages(BER > 10^{-3})vastly exceeding accepted objectives are measured on unprotected radio hops. A very effective method for reducing outages has been the use of a space diversity combiner followed by an amplitude slope equalizer. Results from single, as well as dual-polarized digital radio relay systems, are presented. The paper also describes the laboratory measurement of an equipment "signature" as a means to compare different digital radio designs in their sensitivity to multipath fading.     

A Multipath Fading Simulator for Mobile Radio

A simple device to simulate the Rayleigh distributed fast fading encountered in mobile radio is described and evaluated. The Rayleigh envelope statistics are obtained by adding two independent Gaussian noise source in quadrature. The theoretical spectrum of the received signal is approximated by shaping the spectrum of the noise sources with filters. A design is given whose performance is shown to agree very closely with theory.     

海面环境700MHZ频段传输特性测试与模型校正

在海面环境下通过船-岸测量方式对700 MHz频段的无线传输特性进行测量.基于实测数据分析,引入海面双径传输损耗模型对ITU-R P.1546-5标准传输模型进行校正,该校正模型可实现700 MHz频段无线传输损耗预测.在仿真中,分别利用自由空间模型、ITU-R P.1546-5模型和ITU-R P.1546-5校正模型对700 MHz频段的海面无线传输损耗进行预测,通过与实测数据对比分析,证明ITU-R P.1546-5校正模型预测结果准确性更高,能够为海面无线通信系统的设计提供重要依据.     

多径衰落移动无线系统中的同频道干扰预测

同频道干扰是微蜂窝结构移动通信网所要考虑的一个核心问题，要想成功地对任何一种频率再用无线系统进行规划设计，就必须很好地了解并分析研究同频道干扰对系统性能的影响。本文对具有Ｎａｋａｇａｍｉ衰落和对数正态衰落的同频道干扰特性进行了理论分析，并提出了对微蜂窝多径衰落移动无线电系统中的同频道干扰及其影响进行预测的近似方法。     

Multipath Time Delay Jitter Measured at 850 MHz in the Portable Radio Environment

Time delay jitter in digital personal communications systems, caused by moving the antenna by a few wavelengths, was studied at two office buildings and two residences at a frequency of 850 MHz. A wide-band pseudonoice code technique was used. The results indicate that peak-to-peak time delay, variations on the order of 375 ns may be encountered. The worst case jitter was not necessarily found when there was a large time delay spread. It was also found that the excess mean delay and the root mean-square (rms) time delay spread of the delay distribution profiles were approximately the same.     

随机射线方法研究无线电波多径传播特性

把无线电波的物理传播环境建模为随机网格信道,使用最大熵原理得到发生k次反射随机射线在二维传播空间的概率分布.使用随机桥过程产生基本随机变量,以自由布朗桥过程和自由Langevin桥过程为例研究其统计特性,发现基本随机变量服从Rayleigh分布或者x分布随机变量之和的分布.由基本随机变量得到描述无线信道特征参量(包括多径分量的到达时延,幅度增益绝对值和相位等)的表达式.对一个障碍物完全随机分布的二维传播环境的信道特性使用随机射线方法进行仿真分析,得到无线信道的一些特征参量的统计规律,结果与经典的信道特性一致,验证了随机射线方法的有效性.     

900 MHz Land Mobile Radio Improved Using Circular Polarization

Land mobile systems currently use vertically polarized antennas while trying to solve the problem of small sector signal variations, which are greater for vertical polarization than for either horizontal or circular polarization; This difference in small sector variations is shown from results of tests at 430 MHz. The variations at 900 MHz should be more rapid and have amplitudes at least as great as those shown for 450 MHz. At 900 MHz antennas can be made small for mobile service and the improvements noted here may spur developments in circularly polarized antennas.     

城市微区多径色散传播信道的数学模型分析

城市微蜂窝移动无线电信道的传播特性相当复杂，因此如何建立这种信道的传播模型无论对理论分析还是对网络工程应用来说都是非常重要的，本文在分析讨论多径色散信道基本特征的基础上，对反映城市微蜂窝移动无线电信道传播特性的一些重要特征函数的数学模型进行了较为系统的分析和研究，并对一些重要模型进行了计算机仿真。     

Multipath Delay Characteristics on Line-of-Sight Microwave Radio System

Multipath properties on microwave line-of-sight links for the purpose of applying to microwave systems design are discussed. The theoretical analyses of the fading mechanism and the relation between multipath delay and radio duct parameters are carried out using the ray-optical method. Multipath delay have been measured with the frequency-sweep method and the three-frequency method on several paths in Japan since 1954. These paths are distributed in length from 20 km to 80 km, and include horizontal and slant paths. Through these theoretical and experimental analyses, a number of wave components in multipath propagation, the probability density function of multipath delay, the maximum delay and the relation between multipath delay and radio duct parameters are examined. The estimation method for path-length difference statistics, needed for evaluation of propagation distortion, is quantitatively given.     

Analysis of Scattering in Mobile Radio Channels Based on Clustered Multipath Estimates

This paper presents the results of angle and delay measurements in physically nonstationary radio channels obtained in an outdoor urban environment. The multidimensional estimation data are obtained using a recently developed 3-D high-resolution channel sounder. The estimation results are compared with results obtained from a 3-D deterministic propagation prediction tool. For a better analysis, a hierarchical clustering method is presented that can separate and group the multidimensional estimation data into clusters. Measurements performed at a fixed position as well as along a trajectory are used to characterize the angular dispersion in both azimuth and elevation. The angular dispersion in terms of the rms cluster angular spread in both elevation and azimuth of the different clusters is analyzed over space and time and related to its physical scattering sources. Compared to the measurements, a large number of multipath clusters are missing in the predictions. Furthermore, it is observed from the measurements that different objects cause different angular spread values in azimuth and elevation. The results can be very helpful for the identification, improvement and calibration of deterministic propagation prediction models.     

The Combined Effects of Noise and Multipath Propagation in Multilevel PSK Radio Links

A general analysis of the behavior of multilevel PSK radio links is carried out under multipath propagation conditions. A method is proposed to evaluate system unavailability due to the combined effects of noise and faded channel distortion. The "outage domain," having fixed the transmission channel, is calculated in the space of the variables which characterize any anomalous propagation condition. In particular, with reference to a "twopath model" (a "direct ray" and an "echo"), variations of carrier and symbol synchronisms due to the echo are taken into account and their importance is emphasized in realizing the numerical results. These are shown to be in very good agreement with the experimental ones which have appeared in the literature. An analytical realization of the results obtained is developed and leads to a simple asymptotic formula explaining outage probability as a function of some parameters of the echo statistics, the transmission channel adopted, and the number of modulation levels. Rapid evaluation of this formula allows us to plot outage probability as a function of spectral efficiency, measured in bits/s/Hz.     

陆地移动通信多径传播的实时模拟技术研究

根据移动无线信道多径传播的特点，提出一种径衰落信道实时模拟技术，利用该技术，已制成实时多径衰落信道模拟器，它可作为移动通信系统的测试仪器在室内对通信设备进行信道传输测试。