The Friis Transmission formula is a basic equation used to calculate the received power of a basic receiver at a fixed distance from a transmitting system.
This formula is considered a basic calculation due to the limited number of variables, which include transmit and receive antenna gain, transmitter output power, transmission frequency, and distance between the transmit and receive antennas. However, it can be useful for general information purposed when considering different antennas to be used in a system.