Project IEEE 802.16 Broadband Wireless Access Working Group Title Power-Law Parameters of Rain Specific Attenuation
01 Jan 1999-
TL;DR: In this paper, the power-law form of rain specific attenuation is expressed as α R k ⋅, where k and α are the powerlaw parameters, and R is the rain rate in mm/h.
Abstract: A fundamental quantity in the calculation of rain attenuation statistics is the specific attenuation (attenuation per unit distance). The power-law form of rain specific attenuation is very convenient and is commonly used. It is expressed as α R k ⋅ , where k and α are the power-law parameters, and R is the rain rate in mm/h. Limited number of power-law parameters were available in the technical literature for certain raindrop size distributions. Some of these parameters had reservations for rain-rate ranges. New power-law parameters for four different (gamma, lognormal, Laws and Parsons, and Marshall and Palmer) raindrop size distributions are made. For a rain temperature of 0 C, k and α with polarization dependence are presented here for rain rates from 0 to 150 mm/h over the frequency range of 100 5 − GHz.
Citations
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TL;DR: In this paper, the root mean squared error (RMSE) expression for path-averaged and point rainfall estimation was derived for microwave radio links forming cellular communication networks, and the dependence of the optimal coefficients of a conventional wet antenna attenuation model on spatial rainfall variability and link length has been shown.
Abstract: . Commercial microwave radio links forming cellular communication networks are known to be a valuable instrument for measuring near-surface rainfall. However, operational communication links are more uncertain relatively to the dedicated installations since their geometry and frequencies are optimized for high communication performance rather than observing rainfall. Quantification of the uncertainties for measurements that are non-optimal in the first place is essential to assure usability of the data. In this work we address modeling of instrumental impairments, i.e. signal variability due to antenna wetting, baseline attenuation uncertainty and digital quantization, as well as environmental ones, i.e. variability of drop size distribution along a link affecting accuracy of path-averaged rainfall measurement and spatial variability of rainfall in the link's neighborhood affecting the accuracy of rainfall estimation out of the link path. Expressions for root mean squared error (RMSE) for estimates of path-averaged and point rainfall have been derived. To verify the RMSE expressions quantitatively, path-averaged measurements from 21 operational communication links in 12 different locations have been compared to records of five nearby rain gauges over three rainstorm events. The experiments show that the prediction accuracy is above 90% for temporal accumulation less than 30 min and lowers for longer accumulation intervals. Spatial variability in the vicinity of the link, baseline attenuation uncertainty and, possibly, suboptimality of wet antenna attenuation model are the major sources of link-gauge discrepancies. In addition, the dependence of the optimal coefficients of a conventional wet antenna attenuation model on spatial rainfall variability and, accordingly, link length has been shown. The expressions for RMSE of the path-averaged rainfall estimates can be useful for integration of measurements from multiple heterogeneous links into data assimilation algorithms.
73 citations
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TL;DR: The proposed SS-WDM scheme can improve the FSO communication system performance compared to WDM-FSO scheme, and its adaptive and scalable network architecture support high bandwidth and wide coverage area over the heavy rain weather, without power penalty.
Abstract: In the paper, the spectrum sliced wavelength division multiplexed (SS-WDM) is proposed for Free Space Optic (FSO) communication in the heavy rain weather of Changsha, China. The study seeks to investigate the possibility of communication links up to 3 km with 1.56 Gb/s data rate on the wavelength of 1550 nm. A WDM-Demux is used to operate as slicing system. The SS-WDM-FSO system has been realized and investigated for 4 channels with data rate up to 1.56 Gb/s using a continue wave (CW) laser source with and without SS technique. The simulation results show that, using the SS-WDM technique, a data rate of 1.56 Gb/s is achieved over a transmission distance of 2.5 km with the bit error ratio of nearly 9.816×10 –11 and the power of 0 dBm. Meanwhile transmitting over FSO channel using WDM without spectrum slicing, the sampled data rate is achieved over a transmission distance of 2.5 km with the BER of 10 −3 on power supply of 10 dBm. In addition, the proposed SS-WDM scheme can improve the FSO communication system performance compared to WDM-FSO scheme. Also, its adaptive and scalable network architecture support high bandwidth and wide coverage area over the heavy rain weather, without power penalty.
36 citations
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TL;DR: In this paper, specific attenuation and specific differential attenuation of 5-cm-wavelength radiation (C band) is compared with measurements at 10-cm wavelength (S band), which are much less affected by attenuation.
Abstract: Presented are quantitative estimates of specific attenuation and specific differential attenuation of 5-cm-wavelength radiation (C band) obtained by comparison with measurements at 10-cm wavelength (S band), which are much less affected by attenuation. The data originated from two almost-collocated radars in central Oklahoma. To avoid biases in estimates, the slopes with respect to range of differences in reflectivities and differential reflectivities are assumed to represent the specific attenuations. Observations on a day with no reports of hail on the ground and on a day with large hail are contrasted. A simple one-dimensional model of melting hail is used to qualify these observations. Examples of volumetric fields of the polarimetric variables obtained at the two wavelengths are presented to illustrate that much can be learned about size, orientation, and phase of hydrometeors over volumes that play a role in precipitation formation.
30 citations
Cites background or methods from "Project IEEE 802.16 Broadband Wirel..."
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TL;DR: New parameters for specific rain attenuation prediction model that represents tropical weather condition are proposed, derived from data measured in Malaysia and using methods recommended by ITU-R.
Abstract: As the demand for higher and unlimited bandwidth for communication channel is increased, Free Space Optics (FSO) is a good alternative solution. As it is protocol transparent, easy to install, cost effective and have capabilities like fiber optics, its demand rises very fast. Weather condition, however is the limiting factor for FSO link. In the temperate region the major blockage for FSO link feasibility is fog. In the tropical region high rainfall rate is expected to be the major drawback of FSO link availability. Rain attenuation is the most significant to influence FSO link availability in tropical region. As for now the available k and α values are developed using data from temperate regions. Therefore, the objective of this paper is to propose new parameters for specific rain attenuation prediction model that represents tropical weather condition. The proposed values are derived from data measured in Malaysia and using methods recommended by ITU-R.
26 citations
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TL;DR: In this paper, different rain attenuation prediction models proposed by different authors on terrestrial paths are studied and compared on a monthly basis, as well with the measured upper and lower attenuation bounds for a 6.73-km line-of-sight link operating at 19.5 GHz in Durban.
Abstract: [1] The different rain attenuation prediction models proposed by different authors on terrestrial paths are studied in this paper. Subsequently, for paths not exceeding 22 km, the rain attenuation exceeded for 0.01% of the time for these four geographical locations is estimated for South Africa using the ITU-R Model, the Crane Global model, and the Moupfouma model, at different frequencies. Finally, the predicted attenuation values are compared on a monthly basis, as well with the measured upper and lower attenuation bounds for a 6.73-km line-of-sight link operating at 19.5 GHz in Durban.
18 citations
References
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01 Jan 1978
TL;DR: This IEEE Classic Reissue presents a unified introduction to the fundamental theories and applications of wave propagation and scattering in random media and is expressly designed for engineers and scientists who have an interest in optical, microwave, or acoustic wave propagate and scattering.
Abstract: A volume in the IEEE/OUP Series on Electromagnetic Wave Theory Donald G. Dudley, Series Editor This IEEE Classic Reissue presents a unified introduction to the fundamental theories and applications of wave propagation and scattering in random media. Now for the first time, the two volumes of Wave Propagation and Scattering in Random Media previously published by Academic Press in 1978 are combined into one comprehensive volume. This book presents a clear picture of how waves interact with the atmosphere, terrain, ocean, turbulence, aerosols, rain, snow, biological tissues, composite material, and other media. The theories presented will enable you to solve a variety of problems relating to clutter, interference, imaging, object detection, and communication theory for various media. This book is expressly designed for engineers and scientists who have an interest in optical, microwave, or acoustic wave propagation and scattering. Topics covered include:
5,782 citations
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3,290 citations
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TL;DR: In this paper, a three-parameter gamma distribution was used for dual-measurement techniques to determine rainfall rate, and the relationship between pairs of integral rainfall parameters using a three parameter gamma drop size distribution was investigated.
Abstract: Empirical analyses are shown to imply variation in the shape or analytical form of the raindrop size distribution consistent with that observed experimentally and predicted theoretically. These natural variations in distribution shape are demonstrated by deriving relationships between pairs of integral rainfall parameters using a three parameter gamma drop size distribution and comparing the expressions with empirical. There comparisons produce values for the size distribution parameters which display a systematic dependence of one of the parameters on another between different rainfall types as well as from moment to moment within a given rainfall type. The implications of this finding are explored in terms of the use of a three-parameter gamma distribution in dual-measurement techniques to determine rainfall rate.
1,134 citations
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TL;DR: The applicability of such results to conditions of natural rainfall has been thrown in doubt as discussed by the authors, and the results have been found to be affected by the drop-size and velocity of the artificial rains applied.
Abstract: Curiosity concerning the drop-size composition of natural rain has arisen from attempts to measure erodibility and infiltration-capacity by sprinkling small areas of land with artificial rain. The results have been found to be affected by the drop-size and velocity of the artificial rains applied, and the applicability of such results to conditions of natural rainfall has been thrown in doubt.
891 citations
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TL;DR: In this paper, the empirical relation A = aR^{b} between the specific attenuation A and the rain rate R is used in the calculation of rain attenuation statistics.
Abstract: Because of its simplicity, the empirical relation A = aR^{b} between the specific attenuation A and the rainrate R is often used in the calculation of rain attenuation statistics. Values for the frequency-dependent parameters a and b are available, however, for only a limited number of frequencies. Some of these values, furthermore, were obtained experimentally, and may contain errors due to limitations in the experimental techniques employed. The aR^{b} relation is shown to be an approximation to a more general relation, except in the low-frequency and optical limits. Because the approximation is a good one, however, a comprehensive and self-consistent set of values for a and b is presented in both tabular and graphical form for the frequency range f = 1-1000 GHz. These values were computed by applying logarithmic regression to Mie scattering calculations. The dropsize distributions of Laws and Parsons, Marshall and Palmer, and Joss et al., were employed to provide calculations applicable to "widespread" and "convective" rain. Empirical equations for some of the curves of a(f) and b(f) are presented for use in systems studies requiring calculations at many frequencies. Some comparison is also made with experimental results, and suggestions are given regarding application of the various calculations.
633 citations
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