What is Rain Fade?

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- everything RF

May 1, 2021

Rain Fade is a phenomenon that negatively affects the propagation of radio frequency in the atmosphere. There are various types of fading and rain fade is one of the most prominent of them. It mostly affects radio signals that have frequencies higher than 11 GHz. 

Rain fade occurs when a signal encounters rain, snow, ice or storm in its path of propagation, which means it can affect signals if there is precipitation at t. It can affect both point-to-point terrestrial and satellite communication causing path loss, distortion, signal absorption, the introduction of noise, etc.

How to Tackle Rain Fade

As these are natural obstacles, they cannot be removed but there are ways by which we can combat rain fade. One way to compensate for rain fade is to use brute force i.e. increase the transmission power to make up for the absorption. This is called the Uplink Power Control (UPC) method. UPC methods have improved and can detect when rain fade is affecting the signal and boost the power of transmission automatically. This is a straight forward method but requires using higher power which can be an issue if there is limited power available at the transmitter.

Another approach is to introduce site diversity which is primarily effective in satellite communication. The satellite can be connected to more than one ground stations and the satellite can stop communication, temporarily, with the ground stations which are experiencing rain fade.

There is another, more sophisticated, method to tackle rain fading namely Adaptive Coding and Manipulation (ACM). Increasing the modulation of a link makes it more susceptible to external disturbances and interference. Using this method, the modulation of a signal can be lowered temporarily when affected by rain fade which will make the signal more resilient to interference.

These natural phenomena are an integral part of wireless communication and with the introduction of new technologies that use higher frequency radio signals, they become even more susceptible to noise and interference. As our reliance on wireless communication keeps growing, there is a need to tackle the sources of disturbance and interference for better accuracy and efficiency.

Click here to learn about the impact of rain on RF Signal Propagation.

Click here to learn about RF fading.