Overview

Propagation and interference characteristics are very important for providing quality and reliability of MSC propagation channels. The Quality of Service (QoS) can be expressed in terms of the Bit Error Rate (BER) performance, which depends on the Carrier-to-Noise C/N ₀ density ratio; meanwhile, the service reliability is manifested in the relation of service availability. The intervening medium between MES within the network and satellites is termed a transmission channel. The fixed satellite services have two constant channels between a minimum of two FES using the same spacecraft, while in the GMSC network there are two types of channels to be considered: the variable channel between the MES and satellite or service link and the constant channel between the LES (Gateway) and the satellite or feeder link. These two channels have many different characteristics, which need to be taken into account during the system design examination. The more critical are the variable channels used by MES, since transmitter power, receiver gain and satellite visibility are sometimes quite restricted in comparison to the constant link. In this case the propagation path profile between all kind of MES and satellites varies continuously whenever the mobiles (ships, land vehicles or airplanes) are in motion. These variations are most significant and frequent in the case of maritime and aeronautical environments.

The common satellite channel environment affects radiowave propagation in changeless ways. The different parameters influenced are mainly path attenuation, polarization and noise. The factors to be considered are gaseous absorption in the atmosphere,...