A smartphone wireless path is between the smartphone and a second terminal. In the case of mobile communications, this second terminal is a base station. In the case of Wi-Fi communications, the second terminal is an access point. Finally, in the case of Bluetooth communications, the second terminal is a device such as a speaker on an in-car entertainment system. Communication over such a path is via the propagation of radio waves. In an ideal world, the path would be free of obstruction, i.e., have a line-of-sight (LOS) between transmitter and receiver and attenuate the transmitted signal by a fixed amount across the transmitted signal spectrum, resulting in a predictable and undistorted signal level at the receiver input. Such attenuation is referred to as free space loss. In the real smartphone world, however, paths are often not LOS. Rather, they may be non-line of sight (NLOS), there may be multiple paths, and the intervening topography and atmospheric conditions may result in a received signal that deviates significantly from ideal. In this chapter a study is presented of propagation between (a) the smartphone and the mobile base station and (b) the smartphone and the Wi-Fi access point/Bluetooth terminal.