In this paper, real measurements were conducted to investigate the impact of rain on the propagation of millimeter waves at 26 GHz. The measurements were accomplished using a microwave fifth generation radio link system with 1.3 km path length implemented at Universiti Teknologi Malaysia Johor Bahru, Malaysia. The implemented system consisted of Ericsson CN500 mini E-link, radio unit, rain gauge, and data logger. The measurements were attained and logged daily for a continuous year, with 1-min time intervals. Next, the MATLAB software was used to process and analyze the annual rain rate and rain attenuation, including for the worst month. From the analyzed results, it was found that at 0.01% percentage of time, the rain rate was 120 mm/hr; while the specific rain attenuation was 26.2 dB/km and the total rain attenuation over 1.3 km was 34 dB. In addition, the statistics acquired from the measurements for the worst month were lower than what was predicted by the international telecommunication union (ITU) model; around 51% and 34% for the rain rate and rain attenuation, respectively. The average percentage of error calculated between the measurements and predicted results for the rain rate and rain attenuation were 143% and 159%, respectively. Thus, it can be concluded that the statistics for the worst month in Malaysia is lower than what was predicted by the ITU model.

Real Measurement Study for Rain Rate and Rain Attenuation Conducted Over 26 GHz Microwave 5G Link System in Malaysia

The attenuation induced by rain is prominent in the satellite communication at Ku and Ka bands. The paper studied the empirical determination of the power law coefficients which support the calculation of specific attenuation from the knowledge of rain rate at Ku and Ka band for Koreasat 6 and COMS1 in South Korea that are based on the three years of measurement. Rain rate data was measured through OTT Parsivel which shows the rain rate of about 50 mm/hr and attenuation of 10.7, 11.6, and 11.3 dB for 12.25, 19.8, and 20.73 GHz, respectively, for 0.01% of the time for the combined values of rain rate and rain attenuation statistics. Comparing with the measured data illustrates the suitability for estimation of signal attenuation in Ku and Ka band whose validation is done through the comparison with prominent rain attenuation models, namely, ITU-R P.618-12 and ITU-R P. 838-3 with the use of empirically determined coefficient sets. The result indicates the significance of the ITU-R recommended regression coefficients of rain specific attenuation. Furthermore, the overview of predicted year-wise rain attenuation estimation for Ka band in the same link as well as different link is studied which is obtained from the ITU-R P. 618-12 frequency scaling method.

/pdf/characterization-of-rain-specific-attenuation-and-frequency-3klgvzs481.pdf

Characterization of Rain Specific Attenuation and Frequency Scaling Method for Satellite Communication in South Korea

Millimeter 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 

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

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.

/pdf/statistical-analysis-of-rain-at-millimeter-waves-in-tropical-fulgltu2mz.pdf

Statistical Analysis of Rain at Millimeter Waves in Tropical Area

In the Earth-space link communication system design, rain attenuation must be considered, especially with a frequency above 10 GHz. Therefore, a reliable rain attenuation prediction model is necessary for the design of these systems. Recently, two anomalous behaviors have been reported in existing rain attenuation prediction models. First, predicted rain attenuation results from many models vary nonmonotonically with elevation angles. Second, the rain attenuation predicted by the ITU-R model varies nonmonotonically with a percentage of time or rain rate in low latitudes (between 36° S and 36° N) and low elevation angles (below 25°). To tackle these problems and improve the prediction accuracy, a new rain attenuation model is developed based on the exponential rain cell profile, and a concept of rain rate adjustment factor is proposed. Evaluating performance by utilizing the Recommendation ITU-R P.311-15, the new model provides better prediction results than other existing models. Moreover, the anomalous behaviors are also improved in this model.

A New Rain Attenuation Prediction Model for the Earth-Space Links

This paper is a brief review of Rain AttenuationModelling and Mitigation in the Tropics. The fast depleting availability of the lower frequency bands like the Ku-band as a result of congestion by commercial satellite operations coupled with severe rain attenuations experienced at higher frequency bands (Ka and Q/V), particularly in the tropical regions which was caused by higher rainfall rates and bigger raindrop size, amongst others; it was pertinent that deliberate effforts be geared towards research along this direction. This became even more critical owing to a dearth database along the slant path in the tropical regions for use in rain propagation studies at microwave frequencies, especially at millimeter wave bands (where most signal depolarization and fading takes place). The results presented in this work are valuable for design and planning of the satellite link, particularly in the tropical regions.DAH, ITU-R and SAM model simulations along the slant-path were investigated using local rainfall data at 0.01% of the time, while making use of TRMM data from NigComSat-1 satellite to obtain the measured data for Lagos. Terrestrial attenuation data for 0.01% of the time for UTM were obtained from the UTM wireless communication center (WCC). The attenuation data were thereafter transformed to slant path using transformation technique proposed for Ku band byA. Y. Abdulrahman. Theattenuation exceeded for other percentages of the average year was obtained using statistical interpolation extrapolation method.It was observed that the proposed model predicts creditably well for the ka down link frequency band, by producing the best performance when compared with SAM, DAH and ITU-R models. DOI: http://dx.doi.org/10.11591/ijece.v2i6.1222

/pdf/rain-attenuation-modelling-and-mitigation-in-the-tropics-4gg7byeltm.pdf

Rain Attenuation Modelling and Mitigation in The Tropics: Brief Review

Most satellite communication takes place above the 10 GHz frequency bands, a direct consequence of over-congestion of lower frequency bands. A dearth of database along the slant path in the tropical regions for use in rain propagation studies at microwave frequencies, made further studies at millimeter wave band quite attractive. Rain height data were sourced from the Tropical Rainfall Measuring Mission (TRMM) 3B43 V6 and NigComSat-1 satellite for 37 stations in Nigeria as reported in the literature. Terrestrial attenuation measurement data at 0.01% of time, sourced from the Universiti Teknologi Malaysia’s Wireless Communication Centre (WCC) were transformed to slant path attenuation values using a transformation technique. Attenuation exceeded for other percentages of time were obtained using statistical methods. The ITU-R model is modified to suit the results. Further analysis at 12 GHz suggested that the proposed modified ITU-R model show good performance when compared with other models of interest.

/pdf/modified-itu-r-rain-attenuation-prediction-model-for-a-16abasdynx.pdf

Modified ITU-R Rain Attenuation Prediction Model for a Tropical Station

An improved method for predicting slant path attenuation in tropical climates is presented in this paper. The proposed approach is based on rain intensity data R0.01 (mm/h) from 37 tropical and equatorial stations; and is validated by using the measurement data from a few localities in tropical climates. The new method seems to accurately predict the slant path attenuation in tropical localities, and the comparative tests seem to show significant
improvement in terms of the RMS of the relative error
variable compared to the RMS obtained with the SAM,
Crane, and ITU-R prediction models.

An Improved Slant Path Attenuation Prediction Method in Tropical Climates

Lagos, Nigeria (6.358N, 3.28E), is a coastal station in the rain forest area of southwestern Nigeria with an altitude of 38m. Since most communication now takes place above the X band because of congestion of lower bands, it was necessary to look into ways of maximizing X-band usage. There are inadequate data for use in rain propagation studies at microwave frequencies, and even less so at millimeter wave bands where most of the signal depolarization and fading has been discovered to exist. The proposed model is a modification of the International Telecommunication Union‐Radio Communication Sector (ITU-R) model combined with locally obtained regression coefficients for estimating specific attenuation as proposed by G. Olalere Ajayi. The Dissanayake, Allnutt, and Haidara (DAH), Simple Attenuation Model (SAM), and ITU-R attenuation prediction models were investigated along with the proposed model. The ITU-R model was observed to produce the best results at 40GHz, with percentage error values of 0.61%, 0.55%, and 0.49% at 0.1%, 0.01%, and 0.001% of the time, respectively. In comparison, the proposed prediction model showed good performance at 20-GHz down-link frequency, with percentage error values of 3.6%, 3.3%, and 2.9% at 0.1%, 0.01%, and 0.001% of the time, respectively. The obtained results also showed good agreement with other similar works in the open literature. The results presented in this work are valuable for the design and planning of a satellite link in the tropical regions.

https://journals.ametsoc.org/doi/pdf/10.1175/JTECH-D-13-00024.1

Rain Attenuation Prediction Model for Lagos at Millimeter Wave Bands

Good knowledge of the formation and recognition of the bright band is necessary to determine the location of the melting layer. This is partly because the melting layer is one of the major hydrometeors (others include as rain, hail, and cloud) responsible for signal degradations along the slant-path, in the tropical regions of the world. These may result in signal fading, amongst others, which may lead to errors in slant-path attenuation predictions. This paper involves the comparative analysis of radar data sourced from both ground 3D RAPIC bistatic radar and space-borne precipitation radar above the Malaysian air space. For this research work, the terrestrial meteorological radar data were sourced from the Meteorological Department of Malaysia, while the satellite radar data were obtained from the near-real-time TRMM Multi-Satellite Precipitation Analysis (TMPA-RT) version 7 products. Frozen hydrometeors are observed to exhibit peculiar characteristics in terms of increased radar reflectivity as they fall from the sky, transiting from solid to liquid, and manifesting in the popular bright band signature. The melting layer is the region where melting occur, just below the 0℃ isotherm height. It is a major factor responsible for the problems being encountered in characterization and modelling of microwave signal propagation along the earth-space link.

/pdf/comparative-analysis-of-bright-band-data-from-trmm-and-4kv3u21fbm.pdf

Abayomi Isiaka Yussuff

Papers

Rain Attenuation Modelling and Mitigation in The Tropics: Brief Review

Modified ITU-R Rain Attenuation Prediction Model for a Tropical Station

An Improved Slant Path Attenuation Prediction Method in Tropical Climates

Rain Attenuation Prediction Model for Lagos at Millimeter Wave Bands

Comparative analysis of bright band data from TRMM and ground radar data in Malaysia