Rain Attenuation Research Articles

Rain Fade Analysis on High Frequency Signal: A Review

A reliable transmission of high-frequency signal of more than 10 GHz is crucial for various communication systems, especially in the era of advanced technologies and wireless communications. Rain-induced signal fades pose a significant challenge to signal integrity, making accurate rain rate measurement methods essential for system optimization. This review critically examines the existing techniques for measuring rain rate and the applicability in analysing high-frequency signal fades. Several case studies and practical examples are presented to illustrate the significance of accurate rain rate measurements in predicting and mitigating signal degradation. Researchers are working to enhance existing models to better fit local environmental variables based on all the case studies. Having an accurate estimation of the level of rain attenuation in the signal is one of the components to ensuring the quality of service of a communication signal. Signal availability can be ensured with suitable rain attenuation modelling, assuming that all other communication elements are functioning as planned.

Durable Superhydrophobic Coatings with Attapulgite for Inhibiting 5G Radome Rain Attenuation.

5G radomes are easily wetted and stained by rainfall, which greatly reduces the quality of signal transmission. Superhydrophobic coatings are expected to solve this problem because of their unique wettability, but it is still challenging to develop robust superhydrophobic coatings via simple methods. Here, we report the design of robust superhydrophobic coatings containing oxalic acid-modified attapulgite (MDP) for inhibiting rain attenuation of 5G radomes. First, a homogeneous suspension was prepared by nonsolvent-induced phase separation of a silicone-modified polyester adhesive (SMPA) solution containing fluorinated MDP (F-MDP) nanorods. Superhydrophobic coatings can be easily prepared by spraying the suspension. The effects of phase separation and the SMPA/F-MDP ratio on the surface morphology, superhydrophobicity, and stability of the coatings were systematically investigated. The micro-/nanostructure and low surface energy endow the coatings with excellent static and dynamic superhydrophobicity. Compared with previous studies, the coatings exhibit excellent mechanical stability, flexibility, chemical stability, and pressure resistance due to the combined effects of adhesion by SMPA, self-similar micro-/nanostructures, reinforcement by the MDP nanorods, etc. Consequently, the coatings show good performance in preventing rain attenuation of 5G radomes, an emerging application of Superhydrophobic coatings. We believe that the coatings have great application potential in various fields, including 5G communication.

Inter-beam handover schemes for LEO satellites in 5G satellite–terrestrial integrated networks

Unlike terrestrial handover schemes, the handover schemes in 5G satellite–terrestrial integrated network (STIN) face several challenges, such as large propagation delay, complex channel environment, and fast satellite movement. Therefore, the handover schemes designed in the 5G terrestrial network is not suitable for the 5G STIN. In view of this, this paper considers the inter-beam handover problem for the 5G STIN with a low earth orbit satellite and a ground user. We establish the satellite channel model, which includes path loss, rain attenuation, and multi-beam antenna gain. To model the mobile feature of the user, we consider a two-dimensional random walk model. Then, we propose A5 event-based conditional handover (CHO) scheme, time factor-based CHO scheme, and load factor-based CHO scheme to achieve efficient inter-beam handover. Considering that there may be multiple beams that meet the triggering condition in each handover scheme, we also propose three kinds of beam selection schemes, namely random beam selection scheme, maximum power-based beam selection scheme, and minimum distance-based beam selection scheme. To evaluate the performance of the proposed handover schemes, key performance indicators, such as handover frequency, ping-pong handover rate, unnecessary handover rate, handover failure rate, and average transmission rate are analyzed. Simulation results verify the superiority of the proposed handover schemes by comparing them with the benchmark scheme.

Investigating high altitude platform stations communication in Tanzania under heavy rain conditions

AbstractHigh altitude platform station (HAPS) is one of the promising solutions to many of the developing and less developed countries. To a great extent, HAPS is relatively cost‐effective and can be easily moved on demand while observing the required quality of service. For tropical countries, rain attenuation is the main factor that affects HAPS performance. This study investigated HAPS performance in Tanzania under heavy rain conditions. Rain rate, rain attenuation, and carrier‐to‐noise ratio were used to quantify the system's performance. In this study, the rain rate exceeds by 0.01% of an average, was obtained using the Chebil model. Based on Tanzania Meteorological Agency data, the registered a high amount of rainfall for the five selected regions: Dar es Salaam, Kagera, Tanga, Unguja, and Pemba. By using ITU‐R model, rain attenuation for the downlink was predicted, assuming horizontal polarisation, for 31.0–31.3 GHz. Finally, the HAPS link budget was analysed with a platform altitude of 22 km at frequency of 31.0–31.3 GHz for different elevation angles. Results showed that the performance of the system was promising in the given rainfall scenarios.

Resource Dimensioning of Broadband Satellite Return Networks Affected by Spatially-Correlated Rain Fade

Resource Dimensioning of Broadband Satellite Return Networks Affected by Spatially-Correlated Rain Fade

COMPUTATION OF RAIN-INDUCED ATTENUATION AT CENTIMETRIC WAVE BAND FOR SLANT PATH COMMUNICATION IN NORTH CENTRAL NIGERIA

In this paper, five globally recognised rain attenuation models for slant path communication are considered in order to compute the amount of attenuation and obtain the optimal rain attenuation models for North Central region of Nigeria. The models are Bryant, Garcia-Lopez, ITU-R P.618-9, Simple Attenuation and Svjatogor. These models were evaluated at Ku and Ka-bands and at three elevation angles of 55o, 42.5o and 23o. 5-minute integration time rainfall data obtained from the Tropospheric Data Acquisition Network (TRODAN), Anyigba, Nigeria was converted to 1-minute integration time using Lavergnat and Gole rain rate model. Predictions were made for circularly polarised signals at different percentages of time of the year. The cumulative distribution of rain attenuation computed showed that attenuation values generally ranged between 9 and 19 dB at time percentage exceedance of 0.01% for the Ku-band, while it ranged between 21 and 41 dB at 0.01% for the Ka-band. Also, computations by the Garcia-Lopez and Bryant models were in agreement with the ITU-R P.618-9 model, while the Simple Attenuation and Svjatogor models underestimated the computed rain attenuation values at every percentage of time in all the stations considered

A Study on Rainfall Rate, Temperature and Rain Attenuation of Ka-Band Satellite signal

This research paper is studied rainfall, temperature and rain attenuation of Ka-Band satellite signal by using rainfall and temperature data in 2023. Department of Electronics and Telecommunications Engineering, Faculty of Engineering is where the station is housed. Therefore, this paper aims to investigate the relationship between rainfall values, temperature and rain attenuation in Vientiane Capital using advanced technologies to facilitate and monitor the data in real time. A rain gauge Tipping Bucket 0.1mm/Tip is used to detect the amount of rain, and a DHT22 sensor is used to monitor the temperature. The research procedure entails analyzing temperature and rainfall, designing and setting up measurement sites, setting up a central monitoring station and using the Internet of Things to collect temperature and rainfall data. The analysis showed that the high precipitation amount of the actual rainfall and actual daily data contains two maximum values from August 15, 2023 at 85.3mm/hr with 26°C and September 7, 2023 at 110mm/hr with 25.1°C. ITU-R model is used to analyze the rain attenuation by applying the abovementioned rainfall values. As a result, the rain attenuation of Ka-Band Satellite Signal is 85.3mm/hr the rain attenuation is 11.63 dB and 110mm/hr the rain attenuation is 10.58 dB, respectively, which showed the interlinkage between rainfall amount and temperature while it is raining. The temperature change will not affect the rain attenuation as much as the increase of rainfall amount.

AI based short-term prediction of Q-band rain attenuation

AI based short-term prediction of Q-band rain attenuation

Dependence of rain attenuation on rain rate and drop size distribution for Ka-band satellite communication over India

The Raindrop size distribution (DSD) is the most effective parameter to calculate rain-induced attenuation, which can be severe at Ka-band and higher frequencies. The authors have investigated the impact of rain rate and DSD on rain-induced specific attenuation over a tropical location Kolkata, India. DSD data from disdrometer has been used to calculate the specific rain attenuation with the help of Mie scattering theorem. Low to medium drop diameters (up to 3 mm) are the largest contributors to the various classes of rain rate and attenuation. Double peaks of drop sizes are significant for medium rain rate. The contribution of smaller drop diameters decrease, whereas the contribution of higher drop diameters increase with increasing rain attenuation. At lower rain attenuation, (up to 1.5 dB), complementary cumulative distribution function (CCDF) shows higher value for stratiform rain, with respect to convective rain. The higher attenuation occurrences are mostly observed during 12–18 Indian standard time (IST), i.e., in the afternoon. The results will be helpful for Ka-band (GSAT-14) and higher frequency satellite communication channel modeling over India.

Improving millimetre-wave path loss estimation using automated hyperparameter-tuned stacking ensemble regression machine learning

Path loss prediction is a crucial aspect of designing and operating wireless communication systems, especially in the millimetre-waves (mmWaves) frequency bands. However, these bands are associated with climate-related challenges: rain attenuation, and free space path loss. To address these challenges, an advanced stacking ensemble-regression machine learning (SEML) model with automated hyperparameter tuning (AHT) was proposed. The AHT-SEML model leverages multiple base regressors integrated with a meta-regressor. The model's performance was optimised using the AHT tuning technique. The AHT-SEML model's efficiency was tested using simulated path loss data from a Composite 3D Raytracing-Image-Method propagation model across four sub-Saharan cities, at mmWaves frequencies. The AHT-SEML model's performance was compared to three empirical path loss models, namely Close-In (CI), Floating Intercept (FI), and Alpha-Beta-Gamma (ABG), using evaluation metrics such as Mean Absolute Error (MAE) and Root Mean Squared Error (RMSE). AHT-SEML outperformed other models in the four cities across all frequencies and scenarios with the highest Index of Agreement and lowest Bayesian information criterion. Model confidence set (MCS) analysis with CI benchmark indicates that all the models except AHT-SEML performed below the critical t-value of 2.3530 at 95% confidence level with a degree of freedom of 3, implying no significant differences in their MAEs compared to the CI. However, AHT-SEML's t-statistic values exceed this critical t-value, indicating statistically significant differences and better performance than the CI benchmark models. Similarly, F-statistics of 29.45 and 26.54 correspond to p-values of 1.91×10−14 and 2.50×10−13 for MAE and RMSE, respectively, corroborating significant differences in the AHT-SEML's performance.

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.

Site Diversity Mitigation Technique for Satellite Services for Ku and Ka-band in Tropical Region

The demand for satellite communication has increased which led to spectral congestion. Recently, the satellite services use Ku and Ka-band as additional spectrum for satellite communication services. Ku and Ka-band are categorized as high frequency range which is around 12 to 14 GHz and 20 to 30 GHz respectively. However, the higher frequency will affect the quality of services and lead to signal impairment. This is mainly caused by the atmosphere effect which is oxygen, liquid water, and precipitation. But among the list, rain causes most signal fading due to the scattering and depolarization. The aim of this research is to study the site diversity as mitigation techniques operating at Ku and Ka-band for enhancing the gain of the signal and calculating diversity gain. There are modelling of diversity gain that has been proposed by previous researchers namely Hodge, Panagopolous, ITU-R, X.Yeo and Semire models which were validated in different climate regions respectively. By using all previous modelling of diversity gain, it will also compare with the measured local diversity gain. Suitable modelling that can be used in this tropical region has been proposed by improving the mathematical model that will be suitable in the tropical regions. This is important for encouraging the finding of new theories for the future broadcasting systems to decrease the power loss during the rain fade.

Fade Duration Analysis on a Ka-Band Link Operating in the Tropical Region

Communication systems are rapidly shifting towards higher frequencies due to congestion experienced at lower frequencies and the growing demand for higher data transmission rates within the network. However, it has been observed that as frequency increases, the susceptibility of the system to weather-related factors, particularly adverse weather conditions like rain, becomes more pronounced. This has raised significant concerns regarding the dependability of satellite communication links. This research investigates the dynamic characteristics of signal degradation caused by atmospheric effects, specifically focusing on the impact of rain fade. The study involves an analysis of fading duration using a year's worth of data extracted from Measat-5, operating at a beacon frequency of 20.199 GHz and positioned at an elevation angle of 68.8°. Such data is useful when developing a fade mitigation technique (FMT) that mitigates the disruptive effects caused by heavy rainfall, ultimately leading to an enhancement in both signal quality and overall signal availability.

Evaluation of Rain Attenuation Models for 5G Frequencies: Regions in Turkey

Rain attenuation in 5G satellite communications needs to be considered in planning the communication settings due to the fact that it causes significant attenuation especially above 10 GHz and in low elevation angle Earth-space connection paths. Even though various rain attenuation models have been developed by using measured meteorological data, it is important to know especially which model provides better results for 5G frequencies since direct satellite communication over 5G channels is planned to be used in the near feature. Hence, in this study, prominent rain attenuation models such as the Simple Attenuation Model, Garcia-Lopez model, and ITU-R P.618-14 model were examined. Using these models, rain attenuations occurring at elevation angles of 30°, 60°, and 85° were identified in three different cities in Turkey. Average annual precipitation data from the General Directorate of Meteorology of Turkey for the years 1930-2023 were utilized. The studies on various rain models using different parameters revealed that the attenuation in the 470-780 MHz frequency band is 2.849x10-4 dB, whereas there is a 12.63 dB attenuation in the range of 40.5-43.5 GHz. It was observed that the attenuation increases further with frequencies above 43.5 GHz. Therefore, it is evident that rain attenuation is a crucial parameter in satellite communication systems, particularly in 5G and beyond. This study has revealed that ITU-R P.618-14 model is the best suitable one for high elevation angles and at high frequencies (above 40GHz). As for lower elevation angles Garcia model is more appropriate.

Attapulgite-Based Stable Superhydrophobic Coatings for Preventing Rain Attenuation of 5G Radomes.

Superhydrophobic coatings hold immense promise for various applications. However, their practical use is currently hindered by issues such as poor stability, high costs, and complex preparation processes. Here, we present the preparation of cost-effective and stable superhydrophobic coatings through fluorination of natural attapulgite (F-ATP) nanorods and subsequent solvent-induced phase separation of a silicone-modified polyester adhesive (SMPA) with the F-ATP nanorods dispersed in it. Phase separation of the F-ATP/SMPA system forms a uniform suspension of microaggregates, which can be easily utilized for preparing superhydrophobic coatings via spray coating. The coatings have a low-surface-energy hierarchical micro/nanostructure due to phase separation of SMPA and adhesion of F-ATP to it. Moreover, the effects of the solvent composition (i.e., phase separation degree of SMPA) and the SMPA/F-ATP mass ratio on the morphology, superhydrophobicity, and stability of the coatings were investigated. After systematic optimization, the coatings exhibit excellent static and dynamic superhydrophobicity as well as high mechanical, chemical, thermal, and UV aging stability. Finally, the coatings were applied to the 5G radome surface and showed good rain attenuation prevention performance. Thus, we are confident that the superhydrophobic coatings have great application potential due to their advantages of outstanding performance, straightforward preparation procedures, cost-effectiveness, etc.

Rain Attenuation Prediction at Different Time Percentages for Ku, K, and Ka Bands Satellite Communication Systems over Nigeria

This paper evaluates the influence of rainfall on propagated signal at different time exceedance percentages of an average year, over the climate zones of the country. Specifically, it demonstrates critical and non critical signal fade or signal outage time exceedance (0.001% to 1%) for Ku, K, and Ka-band systems in an average year. The study was carried out using meteorological data made available by the Nigerian Meteorological Agency (NiMet) over a period of 10 years (2009–2018). The four climate zones in the country were represented by five (5) locations; Maidugiri (warm desert climate), Sokoto (tropical dry climate), Port Harcourt (tropical monsoon climate), Abuja and Enugu (tropical savanna climate). The parameters were simulated into the International Telecommunications Union Recommended (ITU-R) models for rain attenuation over the tropics and results presented using MatLab and Origin Lab. Results of Ku band propagations showed that only locations in the tropical savanna and tropical monsoon climates experienced total signal outage for time percentage exceedance equal to or below 0.01% for both horizontal and vertical polarizations. At K band propagations, the five locations showed to have experienced signal outage at time exceedance equal to and below 0.01%, almost same was recorded for the Ka-band propagation. It was also observed that horizontal and vertical polarization of signal had slightly different rain attenuation values for the studied bands at the five locations, with horizontal polarization having higher values than vertical polarization.

Duration of Rainfall Fades in GeoSurf Satellite Constellations

We have studied the stochastic processes A and B concerning fade durations due to rain, by simulating attenuation time series A(t) (dB) in the zenith paths of GeoSurf satellite constellations, at sites located in different climatic regions, with the Synthetic Storm Technique. Process B gives the statistics of outages (occurrences) and process A gives the statistics of outage duration (fraction of time), for the same rain attenuation threshold A(t)>S. The two processes are not independent; therefore, we have studied the relationship between their probabilities and defined a uniformity index 0<U(S)≤1. U(S) is useful for comparing real cases–fade durations fragmented in many different intervals, with changing S and site—and the limiting case of all fades lasting the same time. As S increases, U(S) increases, approaching 1 at very large thresholds. These results should guide the designers of satellite constellations to consider the impact of A(t) on diverse communications services. Process B (occurrences) impacts mainly on non–real-time services, such as data delivery, more disturbed by the number of outages rather than by their duration. Process A (fraction of time) impacts mainly on real–time services such as television, video conference etc., more disturbed by the duration of the outage.

Evaluation of rainfall rates and rain-induced signal attenuation for satellite communication in the South-South Region of Nigeria

Rain fade causes signal attenuation which can relatively results in signal quality performance degradation, increased pathloss and coverage area reduction in satellite communication networks, most especially in the tropics and at higher operational frequencies above 10GHz. Analysis of rain attenuation provides useful insight for satellite communication engineers for efficient network planning and design within the region of study. Hence this paper presents threeyear analysis of signal-induced attenuation in the South-South States of Nigeria for the cities of Port-Harcourt, Uyo, Calabar and Eket, whose terrain characteristics could be generalized to represent urban, sub-urban and rural terrains in Nigeria. The International Telecommunications Union Radio-wave propagation (ITU-R P618-13) model was used to estimate the long-term rain attenuation at 10GHz, 20GHz and 30GHz for satellite communication applications. Results obtained at 10GHz, 20GHz and 30GHz operational frequencies show that at high frequency, rain fade can cause signal attenuation levels in the south-south region of Nigeria. In all, Calabar recorded the highest rain rate and corresponding highest attenuation level of 96.13dB at 30GHz compared to 50.29dB at 20GHz for the period under review.

A Backscatter Model Combing Wind and Rain Effect at Low Incidence Angles

As the Wind blows over the ocean surface, the generated waves are the primary factor affecting the microwave backscatter of the remote sensing radar. In addition, there are also some influencing factors, such as rainfall, which is the best-known atmospheric phenomenon. This paper proposes a wind and rain backscatter model whose angle of incidence is from 1 to 6 deg. The model is developed by considering the influence of ocean surface wind, atmospheric rain attenuation, rain volume backscatter and interactions between raindrops and ocean surface. The wind-induced component of the model adopted a quasi-specular theoretical model for the isotropic rough surface of Gaussian statistics. Rain attenuation is expressed as a coefficient of the model, and rain volume backscatter is expressed as a function of the rain volume backscattering coefficient, the thickness of precipitation layer and the incidence angle. Interactions between raindrops and ocean surface are complicated and deduced from the collocated dataset from the Precipitation Radar onboard the Tropical Rainfall Measuring Mission satellite and the European Centre for Medium-Range Weather Forecasts. Based on the collocated dataset, the result shows the proposed model can estimate reasonably accurate estimates surface backscatter within wind speeds range from 8 to 18 m s−1.

The Path Reduction Factor for the Prediction of Rain Attenuation Affecting Short EHF Terrestrial Links

The Path Reduction Factor for the Prediction of Rain Attenuation Affecting Short EHF Terrestrial Links