Site diversity is an effective technique to mitigate rain attenuation, especially in regions where rainfall rates are high. The South-South region of Nigeria is characterized by the tropical rain forest climate, exhibiting high rainfall rates almost all year round. This paper investigates the performance of site diversity technique in the South-South Nigeria at Ka-band frequency of 20 GHz. Rainfall data obtained from the Nigerian Meteorological Agency (NIMET) over a period of five years (2010 to 2014) were analysed to derive the one-minute rainfall rate distribution for four selected earth stations (University of Uyo, Uyo; Akwa Ibom International Airport, Uyo; Margaret Ekpo International Airport, Calabar; and Port Harcourt International Airport, Port Harcourt) within the South-South Nigeria. The link parameters of NigComSat-1R were used with the ITU-R model for rain attenuation to estimate the rain attenuation distribution through an annual cumulative distribution and percentage of outage time between 0.01 to 100 %. Site diversity (SD) was implemented, taking University of Uyo as the reference site. The results obtained shows that the SD gain between the University of Uyo and Port Harcourt International Airport is higher than the SD gain recorded between University of Uyo and Margaret Ekpo International Airport. This is consistent with the fact that longer distances between the earth stations yield higher SD gain
