NRF24L01 Distance Measuring

Hi, I want to measure distance between the tx and rx by using NRF24L01. The transmitter sends a signal at fixed power and the receiver gets the signal with lower power. I will make an assumption relatively losing power due to distance. How can i know what is the received power at rx ?

I don't think there is any means to measure distance from signal strength - it can be affected by many different things. You may get crude indications by reading the value in the RPD register.