ABSTRACT
The land mobile satellite (LMS) link traverses three distinct layers: the ionosphere, the troposphere, and the local environment in the vicinity of the terminal. Normally, the modeling of the LMS channel is based on the supposition that there are three main components making up the channel: the direct, the specular, and the diffuse scattered contributions. LMS is a very harsh channel where outages can be unsurmountable given the limited fade margins available. Channel models, as in the case of the LMS channel, can be classified as empirical, statistical, or analytical. The LMS channel has been mainly described using statistical models in which parameters are derived from experimental data. In the case of satellite navigation systems, based on direct sequence spreading techniques, the echoes that count and may cause distance estimation errors are those within the duration of one transmitted chip of the ranging code.
