Estimation Of Rain Attenuation Research Articles

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.

Estimating losses at 40-GHz downlink using non-meteorological techniques in heavy rain areas

The advancement of satellite communication has arisen tremendously where higher capacity communications systems are needed. Most satellite engineers are shifting to Ka, Q, and V-band upcoming since the low frequencies such as below 10 GHz are already congested. Actual measurement data at millimetre-wave frequencies in tropical regions are minimal. The prediction of rain attenuation at frequencies above 10 GHz is required to determine a reliable fade margin. In this paper, a statistical frequency scaling technique has been developed as an alternative way of estimating rain attenuation. The technique was derived based on the correlation between the attenuation ratio of a higher and lower frequency against the attenuation at a lower frequency. The attenuations from the proposed model were compared to the proposed frequency scaling by International Telecommunication Union-R (ITU-R) as well as the conventional ITU-R rain prediction model. To deliver a reliable model, validation methods have been done using a set of data with different years and locations in tropical regions. A dependent prediction technique with the lowest root mean square error (RMSE) value and error was produced. This technique is beneficial in applying suitable mitigation techniques to moderate rain fade in tropical regions.

Estimation of satellite link’s fade margin using non-meteorological technique and worst month analysis

<span lang="EN-US">Satellite technology is shifting to higher frequencies such as Q or V-band to cater to greater bandwidth and higher data rates applications such as videoconferencing, internet of things (IoT) and telemedicine. The main challenge in deploying high-frequency bands in heavy precipitation areas is severe rain attenuation. In this paper, a frequency scaling technique was developed to estimate the fade margin at a higher frequency. The worst month analysis was also conducted since the analysis is also important in determining dependable fade margin. The result was evaluated and analyzed using root mean square error (RMSE) and percentage error. The proposed model offers the smallest RMSE and lowest percentage error when compared to all existing prediction models. A dependable fade margin acquired from high-accuracy rain attenuation estimation is very important. This is to apply the best mitigation technique in overcoming rain attenuation in the satellite-Earth link so that, the best system performance can be delivered.</span>

Millimeter Wave Attenuation Due to Wind and Heavy Rain in a Tropical Region.

Millimeter wave fixed wireless systems in future backhaul and access network applications can be affected by weather conditions. The losses caused by rain attenuation and antenna misalignment due to wind-induced vibrations have greater impacts on the link budget reduction at E-band frequencies and higher. The current International Telecommunications Union Radiocommunication Sector (ITU-R) recommendation has been widely used to estimate rain attenuation, and the recent Asia Pacific Telecommunity (APT) report provides the model to estimate the wind-induced attenuation. This article provides the first experimental study of the combined rain and wind effects in a tropical location using both models at a frequency in the E band (74.625 GHz) and a short distance of 150 m. In addition to using wind speeds for attenuation estimation, the setup also provides direct antenna inclination angle measurements using the accelerometer data. This solves the limitation of relying on the wind speed since the wind-induced loss is dependent on the inclination direction. The results show that the current ITU-R model can be used to estimate the attenuation of a short fixed wireless link under heavy rain, and the addition of wind attenuation via the APT model can estimate the worst-case link budget during high wind speeds.

Effective Path Length for Estimating Rain Attenuation Over an Earth‐Space Path Using Features of Stratiform and Convective Precipitation at a Tropical Location

AbstractThe effective path length (LE) for the rain attenuation estimation over the Earth‐space path depends on rain cell size, rain rate, and rain height which in turn are determined by the types of rain. The present study examines the variation of LE based on the experimental measurements of Ku‐band attenuation and rain rate at a tropical location Kolkata (22°34′N, 88°22′E) in comparison with the ITU‐R. The study also utilizes measurements from a 24‐GHz micro rain Doppler radar to differentiate the precipitation types as stratiform and convective rain on the basis of the presence and absence of a melting layer. Power‐law models of LE in terms of rain rate are proposed for convective and stratiform types of rain. The investigation reveals the physical phenomena behind the variability of LE at low and high rain rates which are associated with stratiform and convective rain respectively. The proposed models provide a significantly better agreement with the experimental data compared to the ITU‐R model and also account for distinguishing features of two types of rain, thus giving a physical basis of the proposed model which is not reflected in the ITU‐R formulations.

Evaluation of 1-Minute Integration Time Rain Rate Statistics in Ecuador for Radio Propagation Applications

In this letter, rain rate measurements performed in Ecuador are used to evaluate the performance of prediction models for estimating complementary cumulative distributions (CCDs) of rainfall rate at 1-minute integration time, which are required, for example, for rain attenuation estimation in wireless communication systems operating at frequencies above 10 GHz. Additionally, the aforementioned measurements are utilized in order to analyze the interannual variability of the rain rate, useful for the assessment of the reliability of the CCDs in terms of communication system availability. It was observed that overall the Recommendation ITU-R P.837-7 Annex 1 exhibited the best performance in estimating equivalent 1-minute integration time rain rate statistics. Furthermore, it was found that the lowest level of inter-annual variability of the rainfall rate was observed in the western zone adjacent to the Andes Cordillera of Ecuador.

Effect of Vertical Downdraft on Rain Attenuation Modeling Over an Earth-Space Path

The impact of vertical downdraft on rain attenuation estimation from rain rate measurements has been studied. The rain rate (<i>R</i>) and specific attenuation (&#x03B3;) are derived from rain drop size distributions (DSD) by considering the widely accepted Gunn&#x2013;Kinzer (G-K) relationship between drop size and drop fall velocity that is valid for stagnant air. In the real atmosphere, drops are carried with the vertical wind draft, and the actual fall velocity of the raindrops deviates from the G&#x2013;K formulation. The ITU-R estimated rain attenuation values, based on DSDs, which are mostly valid for temperate regions, can deviate from actual rain attenuation measurements in tropical regions, especially at higher rain rates when downdraft is prominent. The present study uses disdrometer measurements of DSD, optical rain gauge measurements of rain rates, and Ku-band rain attenuation data over an earth-space path at a tropical location Kolkata (22&#x00B0;34&#x2032; N, 88&#x00B0;29&#x2032; E) to show that vertical downdrafts impact the rain attenuation estimation from rain rate measurements. At the present location, an overall representative vertical downdraft of 2 m&#x002F;s needs to be considered to match the experimental attenuation measurements with the estimated values using the modified &#x03B3;&#x2013;<i>R</i> relationship in the ITU-R model.

Comparison of Bright Band Radar from GPM and MRR Observation in West Sumatera

The Bright band (BB) observation can be used as an indication of the melting layer height. Measurement of BB from Normal Scan (NS) on Global Precipitation Measurement (GPM) had been compared with Micro Rain Radar (MRR), which is installed in Kototabang, West Sumatera (0.23° S; 100.32°E; 865 m above sea level). The GPM data were collected from December 2014 to June 2018 and compared with MRR observation from January 2012 to August 2016. The BB values from these instruments were compared with those recommended by the International Telecommunication Union Recommendation (ITU-R) P.839. The BB from GPM and MRR showed slightly diurnal and seasonal variations. BB observations from GPM and MRR show good agreement with slight diurnal and seasonal variations differences. BB observations are more similar when the intensity of solar radiation is lower, i.e., at night (18.00-24.00 LT) until early morning (00.00-06.00 LT). Furthermore, MRR showed a slight bimodal pattern in the seasonal variation, while GPM did not. Thus, the seasonal variation in the observation of both instruments is different. The most significant difference from the seasonal variation was observed in the summer season (June-August (JJA)). The mean BB of the two instruments is lower than the Freezing Height Level (FHL) value calculated from the ITU-R model. However, many BB from the two instruments (&gt;36 %) have a BB altitude higher than FHL. Thus, the constant assumption of FHL in West Sumatera for the rain attenuation estimation of microwaves may not be appropriate.

Telemetering of Rainfall Measurement Results Using 433 MHz Wireless Transmission

The line of sight (LOS) microwave communication system, especially those operating at frequencies above 10 GHz, is very susceptible to rain attenuation, particularly in tropical countries such as Indonesia. Therefore, it is essential to calculate rain attenuation estimation values as a basis for consideration in designing a line of sight microwave communication system to get stable communication. In this study, telemetering was designed to measure the rainfall intensity from a rain gauge device through a 433 MHz wireless transceiver. Measurement of rainfall intensity values via an Arduino-controlled rain gauge was transmitted directly to the monitoring room, which then processed to be displayed in graphical form in real time and can also be stored as data loggers. The rainfall telemetering device users can measure rainfall remotely and without having to wait for the rain like the rainfall manual measurement.

A Survey of Rain Attenuation Prediction Models for Terrestrial Links-Current Research Challenges and State-of-the-Art.

Millimeter-wave (30–300 GHz) frequency is a promising candidate for 5G and beyond wireless networks, but atmospheric elements limit radio links at this frequency band. Rainfall is the significant atmospheric element that causes attenuation in the propagated wave, which needs to estimate for the proper operation of fade mitigation technique (FMT). Many models have been proposed in the literature to estimate rain attenuation. Various models have a distinct set of input parameters along with separate estimation mechanisms. This survey has garnered multiple techniques that can generate input dataset for the rain attenuation models. This study extensively investigates the existing terrestrial rain attenuation models. There is no survey of terrestrial rain mitigation models to the best of our knowledge. In this article, the requirements of this survey are first discussed, with various dataset developing techniques. The terrestrial links models are classified, and subsequently, qualitative and quantitative analyses among these terrestrial rain attenuation models are tabulated. Also, a set of error performance evaluation techniques is introduced. Moreover, there is a discussion of open research problems and challenges, especially the exigency for developing a rain attenuation model for the short-ranged link in the E-band for 5G and beyond networks.

Effects of reduction factor on rain attenuation predictions over millimeter-wave links for 5G applications

Millimeter-wave will be the strong contender for the terrestrial link using for 5G networks. So it is imperative to examine these frequency bands to ensure the uninterrupted services when 5G network is connected in tropical regions. A critical challenge of link-budgeting in mm-wave 5G networks is the precise estimation of rain attenuation for short-path links. The difficulties are further intensified in the tropical areas where the rainfall rate is very high. Different models are proposed to predict rain attenuation, however recent measurements show huge discrepancies with predictions for shorter links at mm-wave. The path reduction factor is the main parameter in the prediction model for predicting total attenuation from specific rain attenuation. This study investigates four path reduction factor models for the prediction of rain attenuation. A comparison was made between these models based on rain attenuation data measured at 26 GHz at 300 m and 1.3 km links in Malaysia. All models are found to predict rain attenuation at a 1.3 km link with minimum errors, while tremendous discrepancies are observed for 300 m link. Hence it is highly recommended to further investigate the reduction factor model for shorter links less than 1 km

Spatial variations of rain intensity over a short length propagation for 5G links based on a rain gauge network

Millimeter-wave (mm-wave) frequency range is among operating bands designated for terrestrial 5G networks. A critical challenge of link-budgeting in mm-wave 5G networks is the precise estimation of rain attenuation for short-path links. The difficulties are further amplified in tropical and subtropical regions where the rainfall rate has a higher intensity. Different models have been proposed to predict rain attenuation. The distance factor is an important parameter in predicting total attenuation from specific rain attenuation. This study investigates the distance factor based on rain gauge networks and measured rain attenuation at 26 GHz for a 300 m link in Malaysia. Considerable discrepancies between available models were observed especially when applied for shorter path links. Also, significant variability of rain intensity is observed from the rain gauge network. This study recommends further investigation of the distance factor for a shorter link. Hence, a measurement campaign incorporating rain gauge networks was established to examine spatial variations of rain intensity over a less than 1 km link. The motivation is to develop a suitable distance factor model for 5G mm-wave propagation.

A methodology for precise estimation of rain attenuation on terrestrial millimetre wave links from raindrop size distribution measurements

Attenuation by atmospheric rain is the most significant impairment in millimetre wave frequencies (mmWave). Modern instruments could provide detailed measurements of rain, such as raindrop size distributions (DSDs). The analysis of DSDs could estimate their effects on past or co-located links measurements. This study presents propagation analysis in the mmWave bands using measurements of two terrestrial links working at 26 and 38 GHz carried out in Johor, Malaysia. Statistics obtained have been analysed in detail to extract any excess attenuation. The DSDs provided by a disdrometer have been used to estimate rain attenuation. The derived results show that the estimation can provide reasonable accuracy after extracting the wet antenna effects and having the advantage of the availability of measurements from various types of equipment.

Validation of New ITU-R Rain Attenuation Prediction Model over Malaysia Equatorial Region

Attenuation due to rainfall is one of the most fundamental constraints on the performance of satellite links above 10 GHz. This work presents the results of rain attenuation measurement using radar data collected from MMD and DIDM, Malaysia. The results were compared with newly improved ITU-R P530-16 and four other selected tropical rain attenuation prediction models. The statistical analysis showed that ITU-R P 530-16 has significantly addressed the problem of rain attenuation underestimation prediction as presented by the older version of the recommendation. Although point accuracy is far-fetched in reality, more improvement is needed on the model so as to address its insufficiency in tropical and equatorial rain attenuation estimation.

Comparison of rain attenuation estimation in high frequency in Indonesia region for LAPAN communication satellite

Rain attenuation is one of the factors taken into consideration in the telecommunication system using frequencies above 10 GHz. As a tropical country, Indonesia has an annual average weather of high rainfall, causing the atmospheric conditions to contain a lot of water vapor. At frequencies above 10 GHz, the rain greatly affects the attenuation of the signal transmitted from/to telecommunication satellites. The objective of the research is to know the rain attenuation value estimation that used in link budget communication design to compensate the appropriate margin in LAPAN communication satellite. The study compared the rain attenuation estimation using ITU-R, Global Crane, and DAH modelling. The highest estimated rainfall value is found in Pare-pare using the Global Crane method. The result of the calculation with ITU-R model is the closest method for rain attenuation prediction in LAPAN communication satellite. The study recommends that the method to be used in the design of high frequency communication satellite operating in Indonesia is the ITU-R modelling.

Estimation of rain attenuation at microwave bands in Nigeria.

Estimation of rain attenuation at microwave bands in Nigeria.

Rain attenuation of millimetre wave above 10 GHz for terrestrial links in tropical regions

AbstractMillimeter waves (mm‐waves) within frequency bands of 10 to 86 GHz will be used for both microwave and access link fifth‐generation (5G) systems. Thus, it is very important to investigate these bands to ensure reliability when 5G is applied in tropical regions like Malaysia in the coming few years. One of the major obstacles facing the propagation of mm‐waves in tropical regions is the rain attenuation. Rainfall results in the absorption, scattering, and diffraction of radio waves. This contributes to increased transmission losses and a reduction in the received signal levels. The effect is more severe in tropical regions that are characterized by intense heavy rainfall and large raindrop sizes. This paper provides a general overview on rain attenuation of mm‐wave bands. It highlights the nature of rain in tropical regions and its effects on the propagation of mm‐waves. It also reports the latest measurement studies focused on rain attenuation in mm‐wave frequency bands and the prediction methods used to estimate rain attenuation in mm‐waves. It contributes to the understanding of channel behavior and the characterization of mm‐wave bands during rainfall in tropical regions, especially in Malaysia. This study further strives to determine research gaps in this field as well as the future work and various propagation measurement systems that can be used to conduct real measurements and to develop prediction models for rain attenuation in mm‐waves for 5G systems. Furthermore, this paper analyzes the rain rate and rain attenuation on the basis of real measurement data conducted in Universiti Teknologi Malaysia at Skudai Campus, Malaysia. The analyzed results indicated that the rain attenuation at 38 GHz is critical and it can result in 18.4 dB/km as specific rain attenuation at 0.01% percentage of the time.

Rain attenuation statistics at Ka‐band estimated from weather radar observations in Belgium

SummaryThis paper presents rain attenuation statistics for satellite‐ground transmission links at Ka‐band based on 10‐year reflectivity observations from a C‐band weather radar. The ground receiving station and the radar are both located in Belgium. Only precipitation under the freezing level is considered, and the attenuation produced by hail is removed by applying a reflectivity threshold. The radar‐derived attenuations are analyzed to investigate the influence of elevation and azimuthal angles on the attenuation statistics. It is shown that the azimuthal dependence is extremely low. In contrast, the exceedance probability for a given attenuation threshold strongly increases with decreasing elevation angles, as foreseen by ITU‐R recommendations. The radar‐derived attenuations are used to estimate rain attenuation complementary cumulative distribution functions computed according to ITU‐R recommendations for a low Earth orbit satellite. The sensitivity to the hail reflectivity threshold is very limited. In contrast, our results show that reliable attenuation statistics cannot be obtained without taking carefully into account the height of the freezing level. Monthly averages of the freezing levels allow producing satisfactory results, but it is recommended to incorporate freezing level heights with high temporal and spatial resolutions.

Statistical Modelling of 1-min Rain Rate Derived from 1-h Integration Time in Malaysia

Statistical analysis of 1 min rain rate used in estimation of rain attenuation is presented. In rainy condition, the electromagnetic signal tend to experience serious degradation in satellite communication system that operate above 10 GHz. Prediction of 1-min rain rate requires conversion method from longer integration time is important due to its limited 1 min availability in most places. A linear model was proposed in this paper and compared with few existing model in Malaysia. The proposed model achieved good result for Malaysia data which is at par with established models such as Segal, Burguẽno, and Chebil and Rahman.

Modelling of rain decay parameter for attenuation estimation at a tropical location

Owing to the wide rain variability of the tropical region, the Simple Attenuation Model (SAM) estimated rain attenuation values are often found to exhibit substantial deviation from the actual measurements over the location, Kolkata (22°34′N, 88°22′E). This is due to the variability in rain cell sizes resulting from the diverse rain characteristics of the region. Thus, an attempt has been made to model the rain decay parameter in SAM on the basis of the tropical rain characteristics. A model of rain decay parameter in terms of rain rate is proposed which accounts for different types of rain at the present location. The incorporation of the model of decay parameter provides a better estimation of rain attenuation than the existing SAM and ITU-R model.