Distribution Of Rain Attenuation Research Articles

A Small Power Margin and Bandwidth Expansion Allow Data Transmission during Rainfall despite Large Attenuation: Application to GeoSurf Satellite Constellations at mm–Waves

The traditional approach of considering the probability distribution of rain attenuation leads to provide very large power margin (overdesign) in data channels. We have extended a method which, with a small power margin, bandwidth expansion and variable symbol rate, avoids overdesign and can transfer the same data volume as if the link were in clear–sky conditions. It is characterized only by the link mean efficiency, suitably defined. It is useful only if: (a) data must be up– and downloaded when it is raining; (b) real–time communication is not required. We have applied it to the links of GeoSurf satellite constellations (in which, at any latitude of ground stations, propagation paths are at the local zenith) by simulating rain attenuation time series at 80 GHz (mm–wave)–the new frontier of satellite frequencies–with the Synthetic Storm Technique, from rain–rate time series recorded on–site, at sites located in different climatic regions. The power margin to be implemented at 80 GHz ranges from 2.0 dB to 7.4 dB–well within the current technology–regardless the instantaneous rain attenuation. The clear–sky bandwidth is expanded 1.75 to 2.80 times, a factor not large per se, but it may challenge current technology if the clear–sky bandwidth is already large.

Estimating Annual Temperate Rain Attenuation Distributions at 20/40 GHz With a High-Resolution Numerical Weather Prediction Model

Earth-space communications are to make use of higher frequencies, at and above 20 GHz, to offer new services and increased data rates. A consequence is a strong attenuation of the carrier waves by the troposphere, particularly during rain events. The statistical characterization of the rain attenuation on high-frequency channels is thus paramount to their link budget. Traditionally this knowledge is obtained via long-term ground measurements of spaceborne beacon signals. Here, simulated results based on numerical weather prediction models are considered as an alternative. A comparison is given based on two years of beacon data at 20 and 40 GHz in Toulouse (France). Four parametrizations of the weather research forecasting model's microphysics are tested: the best performances are achieved with the NSSL-2 moment scheme.

Global Formulation of the Synthetic Storm Technique Oriented to Satellite Link–Budget Design

We have updated the global Synthetic Storm Technique (referred to as the global SST) by reformulating it according to a larger database of rain rate time series collected in several sites in different climatic regions. For each site, the average annual probability distribution of rain attenuation obtained with the global SST, PSST,gloA, in a slant path, was compared with that given by the full SST, PSSTA, which we have considered as experimental data. The test was performed for frequency ranging from 10 to 100 GHz, for elevation angle θ ranging from 20° to 60° and for annual probabilities 10% to 0.01%. The global SST tends to underestimate the attenuation by approximately 10% for elevation angle θ≤30° and about 20% for 30°<θ<60° in the probability range 10% to 0.1%, and approximately 15% in the probability range 0.1% to 0.01%. For any probability, the error is zero for θ=90° because at the zenith, the global SST coincides with the full SST.

Millimetre-Wave Propagation Channel Based on NYUSIM Channel Model With Consideration of Rain Fade in Tropical Climates

The impact of atmospheric attenuation on wireless communication links is much more severe and complicated in tropical regions. That is due to the extreme temperatures, intense humidity, foliage and higher precipitation rain rates with large raindrop sizes. This paper investigates the propagation of the mm-waves at the 38 GHz link based on real measurement data collected from outdoor microcellular systems in Malaysia. The rainfall rate and received signal level have been measured simultaneously in 1-minute time intervals for one year over a 300 m path length. The rain attenuation distributions at different percentages of exceedance time have been compared with the modified distance factor of the ITU-R P.530-17 model. The average link availability calculated with the measured rain rates has been analysed. Additionally, the key propagation channel parameters such as the path loss, path loss exponent, Rician K-factor, root mean square, delay spread and received power have been investigated considering the rain attenuation. These propagation channel parameters have been analysed using MATLAB software and explained with the help of the latest NYUSIM channel model software package (Version 2.0). The analysis results have been classified considering rain attenuation, antenna setup, link distances, antenna height and antenna gain. The outcomes revealed that the rain fade predicted by applying the modified distance factor provides high consistency with the measured fade in Malaysia and several available measurements from different locations. The large-scale path loss model in the NYUSIM simulation result was around 126.23 dB by considering the rain attenuation effects on the 300m path length. This work shows that the NYUSIM channel model offers more accurate rendering results of path loss for omnidirectional and directional antenna transmissions without rain fade. This study proves that the ability to provide good coverage and ultra-reliable communication for outdoor and outdoor-to-indoor applications during rain in tropical regions must be sufficiently addressed.

The Effects of Rain on Terrestrial Links at K, Ka and E-Bands in South Korea: Based on Supervised Learning

At the rise of the fourth industrial revolution, artificial intelligence (AI), along with key enabling technologies such as millimeter waves (mm-waves) can be used to launch the fifth-generation (5G) and beyond communication links. However, the quality of radio links at higher frequency bands is limited by atmospheric elements. Among others, rainfall is the major propagation impairment at millimetric wave bands, which needs to be considered during the link budget planning. In this study, we investigated the rain attenuation results obtained from experimental data, existing models, and proposed supervised artificial neural network (SANN) at $K$ , $Ka$ , and $E$ -bands, respectively, for terrestrial links in South Korea. The measurement campaigns were between Incheon, National Radio Research Agency (RRA) tower station, to the EMS Dongyoksang tower station operating at 75 GHz over a 100-m path length, and between Incheon, RRA tower station to Khumdang, Korea Telecom (KT) tower station, operating at 18 and 38 GHz over a 3.2-km path length. The three-year rainfall and received signal level data measurements over these paths were used to determine rain attenuation distributions at different percentages of exceedance time distribution. Additionally, three existing attenuation models, ITU-R 530.17, Lin, and Revised Silva Mello (RSM) models were compared with measured rain attenuation. Our results indicate that these models did not correspond with measured results. Therefore, in this research, we proposed a supervised learning-based attenuation prediction method, which provides better performance than existing models. Furthermore, we validated our proposed model with measured received-signal level and rainfall data at the above-mentioned operating frequencies.

Optimized rain drop size distribution model for microwave propagation for equatorial Africa

In radio propagation, modelling of rainfall rate, rain attenuation and drop size distribution is highly location-dependent and thus requires availability of reliable data from various locations. Models and mathematical predictions obtained based on data from one location often prove inadequate when applied to another location with either slightly or radically different rainfall pattern. In this paper, the focus is to develop a new rainfall drop size distribution model for equatorial Africa using disdrometer data obtained in Butare, Rwanda (2°35’53.88”S and 29° 44’ 31.5” E). Rainfall data was classified into annual, monthly and rainfall regimes which are drizzle, widespread, shower and thunderstorm, based on their rainfall rates. The maximum likelihood estimation technique was applied to construct estimates of input Drop Size Distribution (DSD) fit parameters of the developed statistical distribution for rainfall DSD in Butare. The newly obtained distribution was compared to the existing rainfall DSD models, namely, Lognormal, Gamma, Marshall-Palmer and Weibull distributions, and found to be an improvement over the existing ones. The Mie Scattering technique is employed to derive the scattering parameters. Thereafter, the derived scattering parameters with DSD models are used for the estimation of rainfall attenuation for the Central African region.

Rain attenuation distribution for satellite microwave links application in Tanzania

<table width="741" border="1" cellspacing="0" cellpadding="0"><tbody><tr><td valign="top" width="484"><p>Rain rate and Rain Attenuation predictions are important in radio system operating at Ku and Ka bands as they affect telecommunication systems performance. To adequately estimate rain-induced attenuation and fading, the International Telecommunication Union (ITU) recommends use of rainfall data collected using 1-minute integration time. For Tanzania, no rainfall data with 1-minute integration time is available either through measurements or conversion from rainfall data with longer integration time. In this paper the rain attenuation is predicted for seven locations in the coastal area of Tanzania. The 1- minute rainfall rate is determined by Chebil’s model using long-term measurements from Tanzania Metrological Agency (TMA) collected for a period of forty years, results obtained are used to estimate rain attenuations. By using the International Telecommunication Union-Recommendation (ITU-R) model, rain attenuation is predicted at horizontal polarization at Ku and Ka band. The results show that Unguja has the highest average annual rainfall accumulation with rain attenuation as high as ~53.22dB for Ka band and ~15.14dB for Ku band making the difference of about 38.08 between the two frequency bands. On the other hand, Kibaha which has the lowest average annual rainfall accumulation along the coast has rain attenuation of ~47.27dB for Ka and ~13.41dB for Ku bands, making the difference of 33.86dB between the frequency bands. Results obtained from this study can be useful in designing earth-satellite microwave links in the coastal area of Tanzania.</p></td></tr></tbody></table>

Statistical Analysis of Rain at Millimeter Waves in Tropical Area

The high frequencies of millimeter wave (mm-wave) bands have been recognized for the fifth generation (5G) and beyond wireless communication networks. However, the radio propagation channel at high frequencies can be largely influenced by rain attenuation, especially in tropical regions with high rainfall intensity. In this paper, we present the results of rainfall intensity and rain attenuation in tropical regions based on one-year measurement campaign. The measurements were conducted from September 2018 until September 2019 at 21.8 GHz (K-band) and 73.5 GHz (E-band) in Malaysia. The rainfall intensity was collected using three rain gauges installed along a 1.8 km link. The rain attenuation is computed from the difference between the measured minimum received signal level (RSL) during clear sky and rain conditions. The measured rain rate and rain attenuation distributions are then analysed and benchmarked with several previous measurements and well-known prediction models such as the ITU-R P. 530-17. The rainfall rate results showed that the best agreement between the measured rainfall rate in Malaysia and the ITU-R PN.837-1 prediction value for Zone P is up to 0.01% of time (99.99% of time agrees well and only disagrees for 0.01% of time). For the E-band, the maximum measured rain attenuation exceeding 0.03% of the year is around 40.1 and 20 dB for 1.8 and 0.3 km links, respectively, at the maximum rain rate of 108 mm/h. For the K-band, the maximum rain attenuation exceeding 0.01% of the year is around 31 dB for the 1.8 km link. Finally, the rain rates exceeding 108 and 180 mm/h at 73.5 and 21.8 GHz, respectively, along the 1.8 km path caused an outage on our measurement setup. The rain rate of 193 mm/h and above caused an outage for the 0.3 km E-band link. The experimental data as well as the presented data analysis can be utilized for efficient planning and deployments of mm-wave wireless communication systems in tropical regions.

Development of software for Ku-Band signal availability due to rain attenuation

<span>Ku-Band signal is often used for satellite communication mainly for direct to home (DTH) broadcasting. One of the major issues using this band is that the signal will be affected by raindrops. Raindrops absorb and scatter signal that operates at a frequency of more than 10 GHz. However, studies have been done to predict and measure the rainfall rate and rain attenuation. The rain attenuation in Ku-Band range and the rain rate were measured at satellite receiving dish, pointed towards the orbital slot 91.5 E over a one-year period in 2013. The cumulative distribution of rain rate obtained as well as a cumulative distribution of rain attenuation obtained are presented and compared with the rain prediction models. The aim is to get the best model to be used for the purpose of software development. It was found out that the DAH prediction model is fairly equitable when compared to direct satellite dish receiving measurements in Malaysia. The model provided a suitable baseline in developing a user interface software for weather prediction.</span>

Rain Rate Distributions for Microwave Link Design Based on Long Term Measurement in Malaysia

Attenuation due to rain is an important constraint in microwave radio link design especially at frequencies above 10 GHz. It restricts the path length of radio communication systems and limits the use of higher frequencies for line-of-sight microwave links and satellite communications. In order to predict the attenuation due to rain accurately rainfall intensity is required with 1-minute integration time. Rainfall is a meteorological phenomenon with complex structure due to its variability in space, duration and occurrence frequency, particularly in tropical and equatorial regions. Since, the statistical distribution of rain attenuation is obtained from the rain rate distribution for the region considered, it should be noted that the accuracy of the rain rate measurement affects the accuracy of the attenuation estimation. This paper presents rain intensity with 1-minute integration time measured for 6 years in Malaysia, it’s distribution, comparison with other prediction models and impact on high frequency microwave links.

Probability distributions of rain attenuation obtainable with linear combining techniques in space‐to‐Earth links using time diversity

SummaryThe purpose of this paper is to show how the complementary probability distribution of rain attenuation is drastically changed in the lower rain attenuation range by applying linear combining techniques, namely, equal‐gain combining and the maximal‐ratio combining, discussed in the historical paper by Brennan in 1959. These combing techniques can also be applied to the Automatic Repeat Request techniques. Defined the instantaneous processing gain and the equivalent attenuation in the 3 cases, we show examples of time series of the various parameters, based on the experimental rain attenuation time series recorded with the ITALSAT 18.7 GHz beacon, in a 37.8° slant path in Spino d'Adda (Italy). Then, we report long‐term complementary probability distribution functions of the instantaneous gain and equivalent attenuation, by simulating rain attenuation time series at 19.7 and 39.4 GHz, path elevation angle 35.5°, with the Synthetic Storm Technique, using on‐site measured rain rate time series of 10 years, by simulating the ALPHASAT link at Spino d'Adda. Similar results are also found at different frequencies and elevation angles in Tampa (Advanced Communications Technology Satellite, ACTS result test), the Isle of Guam, and Prague. The main conclusions are as follows: (1) As expected, the instantaneous time diversity gain can be large when the delay time is large and rain attenuation is large; (2) scintillation affects time diversity links as the direct links; (3) equal‐gain and maximal‐ratio combining can add up to 3 dB to the selection diversity gain when the time diversity gain is very small; and (4) equal‐gain and maximal‐ratio combining reduce the fraction of time of rain attenuation in an average year to a value less than the probability of exceeding 3 dB in the link without diversity.

Seasonal Variations of Site Diversity Along Earth-Space Paths in Nigeria

Site diversity (SD) is an effective technique for mitigating rain attenuation in satellite communications, especially in regions where rainfall rates are high. Nigeria is characterised by the tropical climate, this implies that rainfall rates are generally high. This paper presents a study of the seasonal variation of site diversity technique in Nigeria at Ka-band frequency of 20 GHz. Rainfall data obtained from the Nigerian Meteorological Agency (NIMET) over a period of five years (2010 to 2014) were analysed to derive the one-minute rainfall rate distribution for four selected earth stations (University of Uyo, Uyo (UNIUYO); Akwa Ibom International Airport, Uyo (AKIA); Margaret Ekpo International Airport, Calabar (MEIA); and Port Harcourt International Airport, Port Harcourt (PHIA)) within the South-South Nigeria. The link parameters of Nigerian Communication Sattelite-1R (NigComSat-1R) were incorporated into the ITU-R model for rain attenuation to estimate the rain attenuation distribution through a seasonal cumulative distribution and percentage of outage time between 0.01 to 100%. Site diversity was implemented, taking University of Uyo as the reference site. The results obtained show that SD technique is most effective between the months of March and May and least effective between September and December.

Statistical Evaluation of Measured Rain Attenuation in Tropical Climate and Comparison with Prediction Models

Substantial modifications have been made to the expressions for calculating distance factor and extrapolation techniques in the latest ITU-R P.530-14. However, its performance has not been rigorously evaluated in the tropical and equatorial climates. In this article, the new ITU-R method and three prediction models are validated using measurement data from tropical Malaysian climate. The data were collected on six geographically spread terrestrial microwave DIGI MINI-LINKs operating at 15 GHz. When tested against measurements, the Da Silva Mello model yields a significant improvement for the prediction of rain attenuation distributions. The prediction errors observed in the ITU-R model suggest the need for more data campaign in the afore-mentioned climates.

Rain Attenuation Prediction Model for Satellite Communications in Tropical Regions

This paper proposes a model for predicting rain attenuation in the tropical region. Slant path rain attenuation measurements were carried out in Singapore by analyzing the beacon signals from two satellites, namely WINDS and GE23, operating at frequencies of 18.9 and 12.75 GHz, respectively. Rainfall rates at the location of the beacon receivers were recorded. The cumulative distributions of the rainfall rate and the corresponding rain attenuation are presented and analyzed. It is found that the cumulative distribution of the measured rainfall rate is close to that predicted by the ITU-R model. Measurement data from a total of nine countries are compared with four existing rain attenuation prediction models, namely the Yamada, DAH, Karasawa, and Ramachandran models. Results show that although three of these models have relatively good prediction capability for the tropical region, they could be improved. Therefore, in this paper, a slant path rain attenuation model suitable for the tropical region is proposed. This is done by using the complementary cumulative distributions of rain attenuation for satellite links measured in Singapore and five other tropical countries. The proposed model is found to outperform exisitng models.

Development of rain attenuation model for Southeast Asia equatorial climate

Statistical distribution of rain attenuation is essential for development of microwave and millimeter-wave communication links. Therefore rain-related statistics are very important for a commercialisation system designer. This study proposes modifications to the International Telecommunication Union (ITU-R P.618-10) model and an appropriate rain attenuation prediction model for tropical countries. The model was developed based on data obtained from tropical and equatorial regions. The proposed model uses rainfall rate and rain attenuation at 0.01% of the time, R 0.01 and A 0.01 , elevation angle θ and altitude of site h s , respectively, as input parameters. The proposed model showed remarkable agreement with existing rain attenuation measured data in terms of prediction errors for mean square, standard deviation and root-mean square. The proposed rain attenuation model was used for validation by comparing the model with measured data collected from Nigeria, Kenya and Papua New Guinea, whereby the proposed model gave a percentage error below 12%.

국내 지역별 연평균 및 최악월 강우율 분포 특성

In this paper, models for the average-year rain rate distribution and the correlation between the worst-month and the average-year rain rate distribution in domestic environment were proposed, using the rainfall measurement data with 1-minute integration time of Korea Meteorological Administration. Comparison of the proposed model with the existing ITU-R model showed that the average rain rate of the proposed model for the exceed time rate of 0.01 % is about 28 % higher than that of the ITU-R recommendation. In addition, the correlation model between the worst-month and the average-year rain rate distribution was quite different from the ITU-R model. It is recommended that the domestic rain rate distribution model should be used for calculation of the statistical characteristics of rain attenuation(exceeded-time-rate distribution of rain attenuation) which is essential for the design of wireless communication systems in domestic environment.

Unified method for the prediction of rain attenuation in satellite and terrestrial links

In this paper, a semi-empirical method for the prediction of rain attenuation in slant paths and terrestrial links is proposed. The method uses the same simplified model of equivalent rain cell that is the basis for the ITU-R rain attenuation prediction methods but, additionally, the concept of an effective rain rate is introduced. This allows the use of the full rainfall rate distribution for the prediction of the rain attenuation distribution and the unification of the slant path and terrestrial links prediction algorithms. The numerical coefficients in the method’s expressions were derived by multiple non-linear regressions using the experimental data currently available in the ITU-R data banks. Test results indicate that the proposed method provides significant improvement over the current ITU-R methods.

Analysis of rain attenuation prediction models at Ku-band in Thailand

The performance of the existing rain attenuation models in tropical zones is still a debated issue due to the lack of measurements reported from these areas of the world to develop and validate prediction models. A three-year (2003–2005) campaign of rainfall rate and rain attenuation measurements was conducted on a satellite beacon link located in a tropical region of Thailand. The cumulative distributions of rain attenuation derived from the measured data are presented and compared with those obtained with existing prediction models.

Terrestrial rain attenuation time series synthesizers for tropical regions

The aim of this paper is to present and validate rain attenuation time series synthesizers relying on the Maseng-Bakken principle for terrestrial links in tropical areas. Data obtained in experimental measurements at four links operating at 15 GHz in São Paulo, Brazil, are used to parameterize the synthesizers. Two models are tested with respect to long-term statistics including cumulative distributions of rain attenuation, fade durations and fade slope.

Errata corrige to the paper ‘An optimum design of deep‐space downlinks affected by tropospheric attenuation’

In 1, some input data required to calculate the long-term rain attenuation probability distributions for two sites (namely, Canberra and New Norcia) were mistaken. They were the long-term rain rate probability distribution and the precipitation height, both given by the ITU-R. For Canberra, the correct precipitation height (given by the ITU-R) is 3.688 km, instead of 2.870, for New Norcia is 3.116 km instead of 4.980 km. Therefore Figures 7 and 8 of 1 are wrong and must be replaced by the new Figures 7 and 8 reported below. Also the comparison reported in Table II is wrong for these sites, so that Table II must be replaced by the new Table II below. As the correct Table II now shows, the only change is that at New Norcia the 1-hop downlink is feasible for the annual case, but remains unfeasible for the worst-month case. Design chart for Canberra at 32 GHz. The ordinate gives the symbol rate or the probability of exceeding the tropospheric attenuation in abscissa. The solid slant straight line labelled Pt gives the spacecraft power (x-axis), as a function of symbol rate (y-axis). The solid slant line labelled A2h gives the power margin (or tropospheric attenuation) allowed in the 2nd hop (x-axis), as a function of symbol rate (y-axis). The vertical line reports the constant attenuation allowed in the 1-hop downlink. The curves labelled 32 GHz (red) and 20 GHz (blue) report the probability distributions of rain attenuation (solid curves) and total attenuation (solid curves with asterisks) at 20 GHz (elevation angle according to Table I) and 32 GHz (elevation angle 20°), in an average year. The dashed curves (WM) refer to the worst month at the same frequencies (20–32 GHz), according to the global model of the ITU-R. Design chart for New Norcia at 32 GHz. Same as Figure 7.