Propagation models are mathematical frameworks used to predict how signals, such as radio waves, travel through different environments. These models take into account various factors, including terrain, obstacles, and frequency, to estimate signal strength and coverage. They are essential for designing communication systems, such as cellular networks and satellite communications. There are several types of propagation models, including free-space, empirical, and theoretical models. Each type serves different purposes and is chosen based on the specific conditions of the environment. By using these models, engineers can optimize network performance and ensure reliable communication.