Semi-Markov Model for Low-Elevation Satellite–Earth Radio Propagation Channel

This paper presents a semi-Markov model for the low-elevation satellite–Earth propagation channel. The model describes long-term variations of the received signal by a chain of four distinct states representing line of sight, shadowing, blockage, and those periods of time when the receiver is unable to carry out the acquisition and tracking of the satellite. Short-term variations within line-of-sight, shadowing, and blockage states are modeled by Nakagami–Rice, Loo, and Rayleigh distributions. The time or distance spent in each state is given by a log-normal distribution. Parameters for both short-term and duration distributions together with state and transition probabilities were obtained from a measurement campaign carried out using GPS L1 signals from satellites with elevation angles lower than 10∘in urban, suburban, rural, lightly wooded, and heavily wooded environments.