International Journal of Electrical and Computer Engineering (IJECE) Vol.2, No.6, December 2012, pp. 748~757 ISSN: 2088-8708  748 Journal homepage: http://iaesjournal.com/online/index.php/IJECE Rain Attenuation Modelling and Mitigation in The Tropics: Brief Review Yussuff Abayomi I.O. *,** , Nor Hisham Haji Khamis ** *Department of Electronic and Computer Engineering, Faculty of Engineering, Lagos State University, Nigeria. **Department of Radio and Communications Engineering, Universiti Teknologi Malaysia, Malaysia. Article Info ABSTRACT Article history: Received Jul 17, 2012 Revised Nov 12, 2012 Accepted Nov 27, 2012 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 Keyword: FMT, Millimeter-wave bands, Rain attenuation, Rain rate, Tropics. Copyright ©2012 Institute of Advanced Engineering and Science. All rights reserved. Corresponding Author: Yussuff Abayomi I. O., Department of Radio and Communications Engineering, Universiti Teknologi Malaysia, Malaysia. Email: ayussuff@yahoo.com 1. INTRODUCTION The weak point of satellite communication is the inability to guarantee communication during rainfall or when the line of sight (LOS) is obstructed [1]. The restrained use of millimeter bands for commercial operations in tropical countries is due to severe rain attenuation.Attenuation experienced in tropical areas is caused by considerably higher rainfall rates and bigger size of raindrops compared to other parts of the world [2]. Since the Ku frequency band (14/12GHz) has shown serious signs of depletion, research activity are now directed towards the full utilization of the Ka band (30/20 GHz), while the V band (50/40 GHz) is being considered for applications in the near future [3]. Rain fading channel is a function of frequency, elevationangle, polarization angle, rain intensity, raindrop size distribution and rain temperature. For temperate regions, the rain attenuation increases inversely with elevation angle due to large rain cell size while for tropical regions, attenuation is directly proportional to elevation angle for the same rain rate. This necessitates the need for modeling the propagation factors for tropical regions [4].