An experimental analysis of impact of rainfall on microwave links

Rain attenuation on Microwave (MW) links in tropical countries like India is a serious concern for mobile backhaul planning engineers due to restriction of frequency usage. In India 6/7/8 GHz frequency spectrum can be used only for MW links of hop lengths greater than 15km, else 15/18/23 GHz to be used. Performance of 15/18/23 GHz MW links of hop lengths 10-15km is severely affected by rain attenuation as compared to shorter hop lengths of 5-8km. Rain attenuation may cause MW Link outages. Over the years, many types of rain attenuation prediction models have been developed. But very few experimental studies were conducted on Point to Point terrestrial microwave links operating above 10 GHz in a tropical climate like India. In this article we present results of the trials conducted on a live 155Mbps capacity, 15 GHz MW link to analyze the impact of rainfall intensity. The test case MW link was deployed along the west coast of India by one of the Cellular operators. Comparison of ITU and Crane rain attenuation estimation methods, differences in their estimation figures, their suitability for tropical climate, different aspects to be considered for performance improvement and mitigating the impact of rain attenuation on a 15/18/23 GHz microwave path, are also discussed.