Cumulative slant path rain attenuation associated with COMSTAR beacon at 28.56 GHz for Wallops Island, Virginia

Yearly, monthly, and time of day fade statistics are presented and characterized. A 19.04 GHz yearly fade distribution, corresponding to a second COMSTAR beacon frequency, is predicted using the concept of effective path length, disdrometer, and rain rate results. The yearly attenuation and rain rate distributions follow with good approximation log normal variations for most fade and rain rate levels. Attenuations were exceeded for the longest and shortest periods of times for all fades in August and February, respectively. The eight hour time period showing the maximum and minimum number of minutes over the year for which fades exceeded 12 db were approximately between 1600 to 2400, and 0400 to 1200 hours, respectively. In employing the predictive method for obtaining the 19.04 GHz fade distribution, it is demonstrated theoretically that the ratio of attenuations at two frequencies is minimally dependent of raindrop size distribution providing these frequencies are not widely separated

Propagation effects by roadside trees measured at UHF and L-band for mobile satellite systems

Propagation field tests were performed in Central Maryland and involved a helicopter and mobile van as the source and receiving platforms, respectively. Tests were implemented at both UHF (870 MHz) and L-band (1.5 GHz) during a period in which the trees were in full blossom and contained maximum moisture. Cumulative fade distributions were determined from the data for various fixed elevation angles, side of the road driving, and road types for both worst and best case path geometries and for overall average road conditions

A description of results from the handbook on signal fade degradation for the land mobile satellite service

During the period 1983 to 1988 a series of experiments were undertaken by the Electrical Engineering Research Laboratory of the University of Texas and the Applied Physics Laboratory of the Johns Hopkins University in which propagation impairment effects were investigated for the Land Mobile Satellite Service (LMSS). The results of these efforts have appeared in a number of publications, technical reports, and conference proceedings. The rationale for the development of a 'handbook' was to locate the salient and useful results in one single document for use by communications engineers, designers of planned LMSS communications systems, and modelers of propagation effects. Where applicable, the authors have also drawn from the results of other related investigations. A description of sample results contained in this handbook which should be available in the latter part of 1990 is given

Propagation effects for land mobile satellite systems: Overview of experimental and modeling results

Models developed and experiments performed to characterize the propagation environment associated with land mobile communication using satellites are discussed. Experiments were carried out with transmitters on stratospheric balloons, remotely piloted aircraft, helicopters, and geostationary satellites. This text is comprised of compiled experimental results for the expressed use of communications engineers, designers of planned Land Mobile Satellite Systems (LMSS), and modelers of propagation effects. The results presented here are mostly derived from systematic studies of propagation effects for LMSS geometries in the United States associated with rural and suburban regions. Where applicable, the authors also draw liberally from the results of other related investigations in Canada, Europe, and Australia. Frequencies near 1500 MHz are emphasized to coincide with frequency bands allocated for LMSS by the International Telecommunication Union, although earlier experimental work at 870 MHz is also included

Results of 1987 MSS helicopter propagation experiment at UHF and L band in Central Maryland

This effort emphasizes several important results pertaining to a mobile satellite system propagation experiment performed in Central Maryland during June 1987. Fade distributions due to multipath and roadside trees at L Band (1.5 GHz) during a period in which the deciduous trees were in full bloom are examined. The multipath statistics for roadside trees are compared with previous multipath measurements made in canyon terrain in North Central Colorado. Also examined is the repeatability of previous UHF measurements made in Central Maryland and the attenuation effects of foliage on trees at UHF. Fade duration for the multipath mode for fade levels of 5 dB and 10 dB is also presented

An overview of results derived from mobile-satellite propagation experiments

During the period 1983-1988, a series of Land Mobile Satellite Service (LMSS) propagation experiments were performed. These experiments were implemented with transmitters on stratospheric balloons, remotely piloted aircraft, helicopters, and geostationary satellites. The earlier experiments were performed at UHF (870 mega-Hz) and the latter at both L band (1.5 giga-Hz) and UHF. The general objective of the above tests was to assess the impairment to propagation caused by trees and terrain for predominantly suburban and rural regions where cellular communication services are impractical. This paper presents an overview of the results derived from the above experiments

Altimeter height measurement errors introduced by the presence of variable cloud and rain attenuation

It has recently been recognized that spatially inhomogeneous clouds and rain can substantially affect the height precision obtainable from a spaceborne radar altimeter system. Through computer simulation, it has been found that typical levels of cloud and rain intensities and associated spatial variabilities may degrade altimeter precision at 13.5 GHz and, in particular, cause severe degradation at 35 GHz. This degradation in precision is a result of radar signature distortion caused by variable attenuation over the beam limited altimeter footprint. Because attenuation effects increase with frequency, imprecision caused by them will significantly impact on the frequency selection of future altimeters. In this paper the degradation of altimeter precision introduced by idealized cloud and rain configurations as well as for a realistic rain configuration as measured with a ground based radar is examined

Prediction of attenuation of the 28 GHz COMSTAR beacon signal using radar and measured rain drop spectra

Disdrometer measurements and radar reflectivity measurements were injected into a computer program to estimate the path attenuation of the signal. Predicted attenuations when compared with the directly measured ones showed generally good correlation on a case by case basis and very good agreement statistically. The utility of using radar in conjunction with disdrometer measurements for predicting fade events and long term fade distributions associated with earth-satellite telecommunications is demonstrated

The Australian experiment with ETS-V

Land-mobile satellite propagation measurements were implemented at L Band (1.5 GHz) in South-Eastern Australia during an 11 day period in October 1988. Transmissions (CW) from both the Japanese ETS-5 and INMARSAT Pacific geostationary satellites were accessed. Previous measurements in this series were performed at both L Band (1.5 GHz) and UHF (870 MHz) in Central Maryland, North-Central Colorado, and the southern United States. The objectives of the Australian campaign were to expand the data base acquired in the U.S. to another continent, to validate a U.S. derived empirical model for estimating the fade distribution, to establish the effects of directive antennas, to assess the isolation between co- and cross-polarized transmissions, to derive estimates of fade as well as non-fade durations, and to evaluate diversity reception. All these objectives were met

Multi-year slant path rain fade statistics at 28.56 and 19.04 GHz for Wallops Island, Virginia

Multiyear rain fade statistics at 28.56 GHz and 19.04 GHz were compiled for the region of Wallops Island, Virginia covering the time periods, 1 April 1977 through 31 March 1978, and 1 September 1978 through 31 August 1979. The 28.56 GHz attenuations were derived by monitoring the beacon signals from the COMSTAR geosynchronous satellite, D sub 2 during the first year, and satellite, D sub 3, during the second year. Although 19.04 GHz beacons exist aboard these satellites, statistics at this frequency were predicted using the 28 GHz fade data, the measured rain rate distribution, and effective path length concepts. The prediction method used was tested against radar derived fade distributions and excellent comparisons were noted. For example, the rms deviations between the predicted and test distributions were less than or equal to 0.2dB or 4% at 19.04 GHz. The average ratio between the 28.56 GHz and 19.04 GHz fades were also derived for equal percentages of time resulting in a factor of 2.1 with a .05 standard deviation