Rain attenuation is one of the main problems in wireless communications above 10 GHz in tropical areas, including radio access networks that involve multiple links with coordinated multipoint (CoMP) transmission. To evaluate the impact of rain attenuation on millimeter-wave transmission, spatial characterization of rainfall rate is carried out using weather radar data in the form of CAPPI. Radar data processing is able to produce an autocorrelation function of rainfall in the area covered by the rain event. This information can be used in spatial generation of rain attenuation in simulations to evaluate performance of mm-wave CoMP transmission. Results of processing tropical rain radar data show that by focusing on an area in the same order of the area occupied by a rain event, small details including multiple peaks of rain rate can be observed within a single rain event. With a smaller area of observation covering the middle part of the rain event area, the spatial correlation of rainfall rate decreases more steeply with the distance compared to the case of a wider area. Furthermore, observation focused on a 3 km × 3 km area is more appropriate for evaluating the impact of tropical rain in a mm-wave radio access network where the maximum length of access links is typically 200-500 m.