# Friis Transmission Equation $P_\gamma=P_tG_tG_\gamma\left(\frac{\lambda}{4\pi d_0}\right)^2\left(\frac{d_0}{d}\right)^nL$ $G_t\rightarrow$ [antenna gain](antenna%20gain.md) $d_0 \rightarrow$ measurement distance constant. $L\rightarrow$ distance independent losses $\left(\frac{\lambda}{4\pi d_0}\right)^2$ or rewritten: $\frac{P_\gamma}{P_t}=\frac{\alpha}{d^n}$ where $\alpha = G_tG_\gamma\left(\frac{\lambda}{4\pi d_0}\right)^2d_0^nL$ and $\alpha \ll 1$ [^1] ## Other formulations $P_r=\frac{P_tG_tG_rc^2}{16\pi^2d^2f^2} \ [Watt]$ ### Remarks The loss is a function of the carrier frequency - higher frequency means faster attenuation with distance. Usually frequency is given (fixed). Whole thing is a function of distance.  # References [^1]: [UNSW Lecture 1 on Wireless Fading Channel Modeling and Estimation](../../03%20-%20University/Thesis/src/UNSW%20Lecture%201%20on%20Wireless%20Fading%20Channel%20Modeling%20and%20Estimation.mp4)