Localization of Rain and Its Effect on Propagation in Tokyo Tech Millimeter-wave Model Network

Millimeter wave band is still under exploited compared to the microwave band and it can be a potential frequency band for resolving the spectrum congestion. Therefore, millimeter-wave networks are undergoing intensive development to meet the necessity for high speed wireless data transmission. However, millimeter-wave band is largely affected by attenuation due to rain. While calculating link budget for wireless systems using this frequency band, behavior of rain, attenuation due to rain and amount of degradation must be accurately understood. In the Ookayama Campus of Tokyo Tech, 25GHz and 38GHz band small-scale model network has been operated for testing the broadband (Gigabit) wireless systems. Data about Rain rate, Bit Error Rate (BER) and Rx level are being collected since March 2008. Based on the data, we performed conventional statistical analysis such as measuring rain attenuation constant, cumulative rain rate distribution, relation between availability and path distance. Comparison between rain attenuation of 25GHz and 38 GHz band network has been done. These measurements will be used for link design and also for enhancing the link reliability. Based upon the study up to now, the unique effects due to highly localized/microscopic behaviors of the strong rain have become clear. The cell size of the strong rain frequently becomes smaller than 1km, the size of the campus. In this paper, evaluation of localized behaviors of rain and its effect on wave propagation is focused upon.