Detecting a Stochastic Signal in Noise

In the detection models considered thus far we have assumed that the receiver either had complete knowledge of the transmittable waveforms or knew them except for parameters such as phase, amplitude, and/or doppler rf carrier shift. However, in communication systems which, for example, employ the reflecting characteristics of the ionospheric layers of the earth’s atmosphere, the transmitted signals become distorted to such an extent that their received version can be described only statistically, in which cases they have the appearance of a narrowband stochastic process. Such systems are called scatter or multipath communication systems and are often used for conveying information beyond the horizon.