Rain attenuation prediction for satellite communications link At Ku and Ka bands over Bangladesh

Abstract

The growing demand of microwave communications system has overcrowded frequency band below 10 GHz. The system designers and RF engineers are forced to shift at higher band frequencies because of large bandwidth, smaller equipment and less interference. But, signal power degradation due to attenuation, depolarization and scintillation are the prominent impairments in these bands, coping up with which is a challenge in satellite communications system. Attenuation is mainly due to rain and is more at Ku and Ka band frequencies. This leads to higher BER and also frequent loss of lock in the receiver and required to be predicted in an efficient manner. For reliable communication link in any specific region, the attenuation is required to be predicted a-priori. It is essential to have reliability 99.99% for standard satellite or microwave communications link. We attempted to obtain annual rainfall rate variation, attenuation due to average annual rainfall rate and comparison of attenuation with ITU and major eight different parts of Bangladesh. The selected areas are central, mid western, north western, north eastern, northern, south eastern, south western and southern zone. We have collected daily rainfall data from those eight major zones from 1948-2011 years over the Bangladesh. Daily rainfall data is accumulated to get annual rainfall data in millimeter. Annual rainfall data is converted to yearly rain intensity and this annual rain intensity is used to obtain rain attenuation prediction purposes for any specific region. Finally, obtained specific attenuation in eight different zones is compared with ITU-R rain attenuation based on rain intensity. The work provides in depth knowledge of the attenuation variation characteristics in the aforesaid band and presents major working components for specific rain attenuation prediction in key parts of Bangladesh. Bangladesh Government is going to launch first commercial satellite in geo-stationary orbit. This rain attenuation profile will be helpful to design Ku and Ka band transponder and calculate link budget for advance communication satellite.