Rain Attenuation Statistics Research Articles

A study on the rain attenuation statistics using the different Ku-band satellite signals measured at multiple locations

A study on the rain attenuation statistics using the different Ku-band satellite signals measured at multiple locations

Twelve years of rain attenuation statistics of Earth–space propagation experiment at Ka band in Toulouse

SummarySince 2009, ONERA has been running Ka band propagation experiments in Toulouse (France, latitude 43.57°N, longitude 1.47°E). A rain gauge was also deployed on site to collect rainfall rate measurements concurrently to beacon data. Since April 2011, the beacon receiver has been recording the 20.2 GHz (vertical polarisation) Astra 3B beacon signal along a slant path of 35.1° of elevation angle. All years of the experiment had excellent data availability, hence giving 12 years of data at Ka band. First, the propagation experiment and the data processing methodology are described. Second, a statistical analysis of rain attenuation and rainfall rate is conducted. Comparisons are then performed with the prediction methods of Recommendations ITU‐R P.837‐7 (rainfall rate), P.618‐13 (rain attenuation) and P.678‐3 (variability of propagation phenomena).

Prediction of Q-Band Rain Attenuation Statistics Using Frequency Scaling Models for Temperate Location, Vigo, Spain

The prediction of yearly rain attenuation statistics at Q-band is made from Ka-band measurement for a temperate location, Vigo, Spain, using different frequency scaling models. The validity of the different frequency scaling models is tested for the present location by graphical comparison between measurement and prediction and also in terms of mean, standard deviation, and root mean square errors (RMSE). The Battesti model performs better compared to other existing frequency scaling models, RMSE is only 4.16% and 5.52% for the periods July 2016 to June 2017 and July 2017 to June 2018 respectively. The proposed new power law model increases the accuracy of the prediction for which the RMSE error is 1.09% and 2.17% less compared to the Battesti model for the periods July 2016 to June 2017 and July 2017 to June 2018, respectively. In predicting monthly statistics, the proposed model performs better compared to the Battesti model for all the months except December, January, and February. While predicting monthly statistics, for the proposed model, the maximum and minimum prediction errors are 18.50% and 0.39%, respectively. For the prediction of diurnal statistics, the proposed model performs better compared to the Battesti model with a very small prediction error, less than 4% for both days. The present study can be useful in the design and planning of satellite communication links in present or similar climatic regions for estimating rain attenuation at Q band or above, for which the experimental setup's cost is very high and requires a large receiver margin.

Prediction of 3 Years of Annual Rain Attenuation Statistics at Ka‐Band in French Guiana Using the Numerical Weather Prediction Model WRF

AbstractThis paper highlights the interest of using an Atmospheric Numerical Simulator (ANS) relying on a high resolution weather forecast model coupled with an ElectroMagnetic Module to compute Ka‐band rain attenuation statistics in an equatorial region. An optimization of the parametrization of the Weather Research and Forecasting meteorological model (WRF) is carried out using measurements collected from a propagation experiment carried out by Centre National d’Études Spatiales and Office National d’Études et de Recherches Aérospatiales near Kourou in French Guiana. Both simulated and experimental annual Complementary Cumulative Distribution Functions of rain attenuation are presented and compared. An additional comparison to the rain attenuation prediction method of Rec. ITU‐R P.618‐13 is presented to evaluate the potentialities of the WRF‐EMM ANS to produce synthetic propagation statistics in equatorial regions.

A Long‐Term Experimental Investigation on the Impact of Rainfall on Short 6G D‐Band Links

AbstractResults from a long‐term propagation campaign are presented, whose main goal is to investigate the impact of rainfall on short terrestrial links operating at frequencies in the D‐band, to be possibly exploited for backhaul links in future 6G mobile networks. To this aim, data are collected at two sites with different climatic conditions (Milan, Italy; Athens, Greece) for 24 and 20 months, respectively, using two links (path length of 325 and 100 m, respectively), operating at 156 GHz carrier frequency. At the same sites, disdrometers are also installed to concurrently collect information on precipitation, not only in terms of rain rate but also of its microphysical properties. The received power data are carefully pre‐processed to exclude outliers and further elaborated to derive the rain attenuation. The data are afterward used to evaluate the accuracy of different prediction models, both on an event basis and on a statistical basis. Results indicate that the information delivered by the Drop Size Distribution allows a more accurate estimation of the rain attenuation and that the model currently adopted by the ITU‐R to predict rain attenuation statistics on terrestrial links (recommendation ITU‐R P.530‐18) yields a significant overestimation for such short links, due to the unrealistic value of its path reduction factor. On the contrary, the statistical prediction model proposed by Lin turns out to offer a very satisfactory prediction accuracy.

Model to Scale Rain Attenuation Time Series With Link Elevation Angle for LEO Satellite Based Systems

AbstractA model to scale time series of rain attenuation along an Earth‐to‐satellite path with variable elevation angle is proposed. Starting from the time series at the lowest elevation the algorithm scales up each sample to the elevation of interest while maintaining the space and time correlation of the rain process and by correctly reproducing the local long‐term rain attenuation statistics. Because of these peculiarities, the model represents a key element for the development of attenuation time series synthesizers for LEO satellite‐based applications, where the time decorrelation of the rain event during the quick spacecraft passage over the ground station (roughly 10 min) is quite limited. Moreover, the comparison with the simple geometric scaling (i.e., the cosecant law) carried out among the attenuation Complementary Cumulative Distribution Functions shows a definite improvement in the prediction accuracy, even more so when the elevation angle falls below 20°.

Comparative Study of Worst Month Rain Rate and Attenuation Statistics for Satellite Links in Nigeria

AbstractThis study aims to characterize the dynamic trend of the worst case scenario of rain rate and attenuation for satellite links applications in Nigeria. Rain rate data for four locations (Akure, Jos, Ikeja, and Port Harcourt) were obtained from the Tropospheric Data Acquisition Network at the Centre for Atmospheric Research, NASRDA at an integration time of 5 min from January 2013 to December 2014. The statistics of time series of worst month rain induced attenuation were computed using the method of Synthetic Storm Technique. The International Telecommunication Union model was found to overestimate the Q‐factor in Akure, Port Harcourt, and Ikeja by 34%, 115%, and 50%, respectively while a 25% underestimation was observed in Jos. The results obtained in this study will be useful for location based link design in tropical Nigeria to reduce the uncertainty of specification of design for communication links.

Preliminary Investigation of the Potentialities of a Mesoscale Meteorological Model to Reproduce Experimental Statistics of Rain Attenuation on Earth-Space Links

Current spatial resolutions achieved by mesoscale weather forecast models allow them to be used to generate the state of the lowest layers of the atmosphere over areas as small as a few square kilometers which corresponds to the typical size of the tropospheric area crossed by Earth-space links. Furthermore, they allow the evolution of the troposphere to be predicted with a time stamp of five minutes instead of every hour with large-scale weather forecast models which makes them attractive for radio propagation predictions for satellite communication applications. This paper aims at studying the capability of the Weather Research and Forecast (WRF) model coupled with an electromagnetic physical model to reproduce rain attenuation statistics for Earth-space paths at Ka-band. To this purpose, one year of propagation measurements collected at 20 GHz in different places at midlatitudes in Toulouse and Salon de Provence (France), Spino d’Adda (Italy), Aveiro (Portugal), and Madrid (Spain), at high latitudes in Svalbard (Norway) and at low latitudes in Kourou are used to make comparisons between simulations and measurements. Comparisons between the simulated and the experimental annual statistics considered in this paper provide encouraging results, with a similar accuracy as Recommendation ITU-R P.618–13 for midlatitude European locations and with better accuracy for a high latitude area in Svalbard and for an equatorial location in French Guiana.

Performance evaluation of metric measures for converting 30-min GPM rain data to 1-min for microwave applications in Tropical region of Nigeria: A multivariate approach

The quest for a one-minute rain rate is high because it is an important input for generating high accuracy of rain-induced attenuation and will in turn earn good use by radio engineers in designing good and high-quality terrestrial and satellite links. This study utilizes eleven (11) years (2008–2018) rain rate data obtained from a satellite-based program, the Global Precipitation Measurement (GPM) over five different locations in the South West, Nigeria, and 2 years (2017 and 2018) gauge measured rain rate data in one of the locations Akure, Nigeria for validation. The GPM platform was an improved satellite-based program over the Tropical Rainfall Measuring Mission (TRMM) for measuring tropical rainfall with spatial and temporal resolution. Hence, a good application of measured GPM rain rate data can be a good tool for estimating rain-induced attenuation if an adequate conversion is made for a one-minute integration regime as recommended by the \\International Telecommunication Union (ITU). The 30 min GPM rain rate data was converted to one-minute integration time based on a multivariate approach. The coefficient of determination of GPM rain rate data closely matches with the gauge and was found to be 0.9194. Analyses were also performed on seasonal bases for rain rate and rain-induced attenuation ranging from frequencies 10 GHz, to 30 GHz, to assess the seasonal trend between the two sources of data. The seasonal analyses were scaled as pre-monsoon, intensive, cessation, and dry months. A seasonal comparison shows that the GPM data presented the highest rain rate and rain attenuation during the intense rainy regime. Attenuations are considerably high at 0.01, 0.005, and 0.001 percentages of time. Overall, a deduction was made that the GPM rain rate measurements offered reliability in the estimation of rain-induced attenuation analyses in the tropical region of Nigeria due to the spatial–temporal coverage when compared with the rain gauge coverage which is sparse and costly to implement. This research has presented a reliable 30 min to one-minute integration time conversion model suitable for tropical locations, as well as information on seasonal rain attenuation statistics which would be utilized for effective satellite communication systems by the radio engineers.

Low-Cost Ka-Band Satellite Receiver Data Preprocessing for Tropospheric Propagation Studies.

Satellite tropospheric propagation studies strongly rely on beacon receiver measurements. We were interested in performing a measurement campaign to characterize rain attenuation statistics. In this article, we outline some of the characteristics and drawbacks one faces when trying to perform a radio wave satellite beacon propagation experiment at the Ka-band with low-cost measurement equipment. We used an affordable beacon receiver consisting of a commercial low-noise block down-converter, an outdoor dual-reflector antenna, and a software-defined radio unit. To measure rain attenuation events, we needed to work out where the reference signal level was at all times. However, as we did not have a radiometer to remove the impact of gases and clouds, since it is a very expensive device, we used a procedure that involved the subtraction of a stable and reliable reference level (template) from the raw received beacon level. This template was extracted from observations during non-rainy periods. The procedure implemented for extracting the template was based on the same data processing methodology used by other authors in this field. Here, we describe through specific examples the main characteristics of the templates extracted on non-rainy days, as well as the impact of some meteorological parameters and unavoidable, but small antenna pointing errors.

Characteristics of rain fade slopes on microwave communication in Mowe, Nigeria

In this paper, the rain fade characteristics at Ka-band (30 GHz) in Mowe (Lat 6.80° N, Lon 3.40° E) Nigeria have been presented. The analysis includes both the first- and second-order statistics of rain rate and rain attenuation, and fade duration and fade slope, respectively. Both parameters are useful for planning the point-to-point microwave link for various communication feeder networks. The estimated fade duration and the fade slope were compared with the ITU-R P.837-5 model. The results of this study would be valuable for improving rain fade mitigation techniques in Nigeria.

Characterization of rain specific attenuation and frequency scaling technique for satellite communication systems in a tropical location

Increased demand for satellite system applications and congestion of the lower frequency bands has mandated the foray into higher frequency spectrum which is more susceptible to rain-induced attenuation. This research explores the characterization of rain specific attenuation and frequency scaling technique for satellite communication system in Akure (7.17°N, 5.18°E, 358 m), Nigeria. Two-year archived rain-attenuation data on Ku-Band satellite link over the earth-space path of Akure was used for the study. Concurrent measurement of rainfall parameters and Eutelsat W4/W7 satellite radio beacons was carried out at the Department of Physics, Federal University of Technology Akure, between January 2017 and December 2018 using Tektronix Y400 NetTek spectrum analyzer. Estimated and measured rain attenuation statistics were compared, and exact determination of the power law coefficients which support the computation of explicit attenuation from measured rain rate was carried out. Recommended frequency scaling technique was also employed to investigate the magnitude of rain-induced attenuation at higher frequency bands. Results show that, at 0.01 percentage exceedance window, combined estimated and measured rain attenuation have respective magnitudes of about 13.09 dB and 21.43 dB. Also, estimated and scaled attenuation at 16 GHz, 20 GHz, 30 GHz and 40 GHz are about 21.97 dB, 31.78 dB, 56.64 dB, 77.23 dB and 28.36 dB, 33.95 dB, 42.17 dB, 46.07 dB respectively.

Rain fade margin of terrestrial line-of-sight (LOS) links for 5G networks in Peninsular Malaysia

AbstractAdvanced telecommunication systems are moving toward a high data transfer rate and wider bandwidth. The 5G communication network has recently been implemented for such aims. However, 5G networks operating with high operating frequency (typically above 20 GHz) could lead to impairments because of the atmospheric phenomena mainly precipitation and especially heavy rain. To address this, an optimum rain fade margin for the 5G network in Peninsular Malaysia is proposed using 77 sites of the rain-gauge network, which convert 1-h rain data to 1-min rain data by means of the international telecommunication union recommendation (ITU-R) P.837-7 model. Long-term rain attenuation statistics are obtained from ITU-R P.530-17 and the synthetic storm technique. The predicted rain attenuation is also presented in monthly statistics and in rain attenuation contour maps. The analysis showed that at 99.99% of link availability, the optimum rain fade margin operating at 26 GHz link should be in the range of 6.50 to 10 dB and 7 to 11 dB at 28 GHz link for a 5G network. Such information is useful for network operators and system engineers for the operation of 5G terrestrial microwave links in heavy rain regions.

Analysis of rain fade characteristics from experimental satellite measurements at Ka/Q bands for a temperate location Vigo, Spain

Rain is one of the most dominant factors for satellite communication systems link performance at frequencies above 10 GHz, increasing rapidly at higher frequencies. The prediction of time dynamics of the rain attenuation is required to improve the efficiency of various fade mitigation techniques (FMTs) to reduce signal fading. Fade duration and fade slope statistics are used to describe the dynamic behavior of attenuation experienced by radio communication links. The present study is based on experimental measurements from a Ka band (KaSAT) and Q band (AlphaSAT) beacon receiver at the frequencies 19. 7 GHz and 39. 4 GHz respectively. In this paper, annual and monthly variation of rain attenuation statistics for a temperate location Vigo, Spain is presented. Monthly variation of rain attenuation statistics is much larger than the yearly variation for the present location. This paper also analyzes the fade duration and fade slope statistics for both the bands. The conditional probability density function (PDF) of fade slope shows general symmetry between positive and negative slope values for both Ka and Q bands. All the measured statistics (1st order and 2nd order) are compared with the existing ITU-R and COST-205 models. Predictions of rain attenuation by both the models are close to the measured data. For fade duration statistics, as attenuation threshold increases, performance of both ITU-R and COST-205 models improves for Ka band. For Q band, COST model performs better compared to ITU-R model. Measured probability density function of fade slope fits with the ITU-R model more closely for Q band compared to Ka band.

Second order experimental statistics of rain attenuation at Ka band in a tropical location

Abstract Some second order rain attenuation statistics such as fade duration and fade slope are investigated on the basis of experimental measurements of received signals using the GSAT-14 satellite beacon signal at 20.2 GHz for three years (2014–2016) over the tropical location Ahmedabad (23.02 0E, 72.510N), India with an Elevation angle of 630. Existing models of fade duration are compared with experimental data in this study and exponent of power law model of fade duration at Ka band is further explored. A new model for fade duration for Ka band for tropical locations is proposed where the constant of exponent of attenuation in the power law is found to be 0.143 instead of 0.055 used in ITU-R. Other relevant parameters for implementation of fade mitigation technique to prevent the link outage like cumulative distribution of signal fade rate, maximum and minimum fade rise and fade fall are also studied. Fade slope asymmetry over tropical region is also investigated. Keeping in view of exploiting the commercial launch of Ka band in Indian region there is an urgent need for validation of the existing models of fade slope (specially looking into fade symmetry) and fade duration. It will help the SATCOM (Satellite Communication) link designer to improve closed loop fade mitigation technique to minimize the possible link failure/link outage over the tropical region.

A Time Diversity Model for EHF Satellite Communication Systems

A simple yet effective time diversity model, referred to as Time Diversity Stratiform Convective EXCELL (TD-SCEX), is presented. The model, conceived to support the design of EHF Earth-space communication systems implementing Fade Mitigation Techniques, takes advantage of the Stratiform Convective EXponential CELL (SC EXCELL) model to predict the joint rain attenuation statistics and, hence, the time diversity gain, starting from the geometrical and electrical characteristics of the link, as well as from the joint rain rate statistics. The model performance is evaluated against the data collected in Milan, Madrid, and Spino d'Adda at Ka-, Q-, and V-bands in the framework of different long-term propagation campaigns. Results indicate that TD-SCEX is a useful tool to predict the effectiveness of time diversity in improving the performance of EHF Earth-space communication systems.

Characterization of Rain Attenuation Statistics for 5G Communication System in the Equatorial Region

Characterization of Rain Attenuation Statistics for 5G Communication System in the Equatorial Region

Fade slope analysis for Ku‐band earth‐space communication links in Malaysia

Heavy precipitation severely degrades the performance of satellite communication systems operating at frequencies higher than 10 GHz. For the implementation of effective countermeasures, rain attenuation statistics are needed, second order statistics in particular. Here, the characteristics of rain fade slope are extensively investigated, exploiting one year of Ku-band attenuation measurements collected in Malaysia .

Rain attenuation statistics for mobile satellite communications estimated from radar measurements in Malaysia

Mobile satellite communications will play a significant role in the next 5th generation mobile services. The use of high-frequency bands will be the enabler of this advancement. However, at high frequencies, excess rain attenuation causes severe signal losses and presents a major threat for the system availability, especially in the tropical region. To that end, this study presents the rain attenuation impact on mobile satellite communications estimated using long-term radar measurements in Malaysia, by exploiting the horizontal structure of rain from the radar database and simulating inner-city and highway mobile terminals scenarios. Additionally, a scaling factor was presented to scale available fixed satellite terminals measurements to mobile terminals operating at the same locality under similar conditions. In comparison to the available link measurements, the radar database was reliable enough to provide highly accurate estimates. In all simulation scenarios, the mobile terminal will depart the rainy area soon enough and experience lower attenuation statistics in comparison with the fixed terminal. The provided results will help determine the overall future system performance, especially in tropical regions.

Rain attenuation statistics over 5G millimetre wave links in Malaysia

<p>Millimetre wave band is a solid contender to be utilized for the future 5G wireless systems deployment. Rain-induced attenuation is a major disadvantage at these frequencies. This paper presents statistics of rain-induced attenuation and rainfall data for two years of horizontally polarized links propagating at 38 GHz and 26 GHz over a terrestrial path link of 301 meters. From the analysed datasets, a rain rate around 116 mm/h exceeded at 0.01% of the time of an average year, while the links recorded 16 and 9.5 dB at the same percentage of time for 38 and 26 GHz respectively. The study aims to identify the prediction model that deliver most reasonable predictions for 5G links operating in Malaysian tropical climate. ITU-R P.530-17, Mello’s, and Ghiani’s models were all examined. Using ITU-R model, relative error margins of around 3.8%, 30% and 49.7% alongside 22.3, 9.5, 33% were obtained in 0.1%, 0.01% and 0.001% of the time for 26 and 38 GHz respectively. Curiously, ITU-R model demonstrates better predictions to measured rain attenuation with lower error probability. This study highlights the need for new prediction models for short path-length 5G links and helps to improve the design of terrestrial links operating at millimetre wave frequencies in tropical regions.</p>