Developing a frequency diversity models for rain fade mitigation in Malaysia

Abstract

Microwave communication systems in tropical region like Malaysia, operating at higher frequency ranges, are degraded in its performance severely during rains. Hence, the rain fade must be taken in consideration for the microwave link design to track the service outage and quality. This research aims to develop and propose frequency diversity prediction models for rain fade mitigation from 5 - 40 GHz. The rain attenuation are predicted based on ITU-R rain attenuation prediction method using measured rain rate in Malaysia. The predicted data are analysed to develop and propose a prediction for the frequency diversity gain and improvement factor. The estimated gains are not uniform along the frequency range of 5 - 40 GHz, hence gain model is proposed for different frequency separation (5, 10, 15, 20 GHz) at 0.001 to 1% outages. A general model is also proposed for any path length at 0.01% outage only. An alternative approach named as frequency diversity improvement is also proposed. However this model is limited to 1 Km path length only. Proposed gain models are validated by comparing the measured rain attenuation data at 15, 23, 26, 38 GHz frequencies in UTM, Skudai. The difference varies from -2 to 2 dB. The effects of the frequency separation, the outage percentage and the path length on the gain models are discussed. The effect of fade margin on the improvement factor is also investigated. This analysis will help the designer to understand how these models can identify the best diversity frequency to use under rain fade