Rain Attenuation Study over an 18 GHz Terrestrial Microwave Link in South Korea

Abstract

Absorption of microwave radio frequency signal by atmospheric rain and losses is prevalent at frequencies above 5 GHz. The functioning frequencies of 18 GHz are taken for the point-to-point microwave link system. This paper presents studies on rain attenuation at 18 GHz, which specifies minimum performance parameters for terrestrial fixed service digital radio communication equipment. It presents a 3.2 km experimental link at 18 GHz between Khumdang (Korea Telecom, KT station) and Icheon (National Radio Research Agency, RRA station). The received signal data for rain attenuation and the rain rate were collected at 10-second intervals over three year’s periods from 2013 to 2015. During the observation period, rain rates of about 50 mm/hr and attenuation values of 33.38 dB and 21.88 dB occurred for 0.01% of the time for horizontal and vertical polarization. This paper highlights the discussion and comparison of ITU-R P.530-16, Moupfouma, Silva Mello, and Abdulrahman models and proposed an attenuation prediction approach where it presents the relationship between theoretical specific rain attenuation as specified by ITU-R P.838-3, γ%p, and effective specific rain attenuation, γeff. Additionally, it studies 1-minute rain rates derived from higher time integration of 5-minute, 10-minute, 20-minute, 30-minute, and 60-minute instances which are obtained from experimental 1-minute rainfall amounts that are maintained by the Korea Meteorological Administration (KMA). The effectiveness of the proposed approach is further analyzed for 38 and 75 GHz links which shows better prediction capability. Particularly, in an 18 GHz link under horizontal polarization, ITU-R P. 530-16 shows the relative error margin of 71%, 60%, and 38% where as 64%, 49%, and 42% were obtained under vertical polarization for 0.1%, 0.01%, and 0.001% of the time, respectively. The limitation of research lies on the experimental system that is set up in only one location; however, the preliminary results indicate the application of a suitable 1-minute rain attenuation model for a specific site. The method provides useful information for microwave engineers and researchers in making decisions over the choice of the most suitable rain attenuation prediction for terrestrial links operating in the South Korea region, particularly for lower frequency ranges.

A Comprehensive Survey on Millimeter Wave Communications for Fifth-Generation Wireless Networks: Feasibility and Challenges

“…Hence, mmWave signals are increasingly risked to blockage by raindrops than sub-6 GHz signals with longer wavelengths. The rain-induced attenuation A(dB) [31], [107], that corresponds to a rainfall rate that surpassed 0.01% of the time is of the form (5) where γ R denotes the specific attenuation expressed in dB/km, d eff is the effective propagation path length or effective hop length expressed in kilometers. Notably, (6) where the regression constants k and α, determined as functions of frequency, f [GHz] and the polarization type, can be derived from ITU references [31].…”

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

“…The rainfall data were collated by OTT Parsivel at a 10-s time interval according to [17]. Meanwhile, RSL measurements at a 10-s integration time for the above links were conducted as described in [18]. The corresponding rain attenuation from RSL is obtained by determining the differences between the RSL measured during rainy and non-rainy conditions, as expressed in equation (1).…”

Statistical Analysis of Rain at Millimeter Waves in Tropical Area

“…For regions with four seasons, the rain attenuation was examined using different frequencies at K and Ka-bands in [60]- [69]. In [66] and [67], the rain attenuation was assessed for a 3.2 km experimental link at 18 GHz in South Korea, while the characteristics of seasonal rain attenuation were analyzed in South Africa based on measurements recorded for one year at 19.5 GHz along 6.73 km terrestrial link in [62] and [63]. The rain attenuation and its yearly variations was performed during a four-year period along 5.5 km link at 26 GHz in Prague, Czech Republic [65].…”

“…The rain attenuation at 18 GHz band was analyzed in South Korea and Brazil. Based on three years rainfall rate measurements at South Korea, the rain rate values are 50 and 100 mm/h at the time percentage of 0.01% and 0.001%, respectively [66], [67]. The corresponding rain attenuation values for 50 mm/h along 3.2 km link are 33.38 and 21.88 dB for horizontal and vertical polarizations, respectively.…”