Rain Attenuation Prediction Model

By Prima Setiyanto Widodo

The rain attenuation for wireless communication links can be calculated using following models:

ITU – R (formerly CCIR Model)
SAM (Simple Attenuation Model)
Global Crane Model
Model DAH (Dissanayake, Allnutt, Haidara Model)

To confirm which model is the prefered model to be used in Indonesia, field measurements should also be carried out.

Measurements of rain attenuation in Indonesia have been done for satellite communication links in Padang, Cibinong, Surabaya and Bandung. It has been found out, after due analysis, that the DAH Model for rain attenuation prediction is valid for Indonesia, besides the ITU Model. The DAH Model has become an ITU Recommendation since 2001 (Recommendation No. ITU-R P.618-7).

Based on calculations using the Rainfall Rate Prediction Model for Indonesia, the rainfall rate can be found for several locations in Indonesia. The values of the rainfall rate are then used for calculating the Rain Attenuation using the DAH Model. Thus can be calculated the “link availability” predictions for Ku-band systems in Indonesia.

The calculations by the author of this article show that the use of the Ku-band for satellite communications systems is feasible with a link availability of 99.7%. As a practical experience, based on field test results for 512 kbps data rate using a 1.8 m diameter antenna, 4 watts RF power and distance between transmitter and receiver of 180 km, demonstrated a link availability of 99.9%, confirming our previous calculations.