Downlink DS CDMA performance over a mobile satellite channel

Code division multiple access (CDMA) has been proposed for personal communications networks for both terrestrial and satellite links. We analyze the performance of the downlink (i.e., the base-to-mobile link) of a low earth orbiting (LEO) mobile satellite channel. An important characteristic of this fading channel is that the desired signal and the multiple access interference from all spot beams of the corresponding satellite fade simultaneously. In this respect, the satellite downlink is also different from its terrestrial counterpart. A two-state fading channel model is considered. In the nonshadowed state, the signal envelope is characterized by Rician statistics and in the shadowed state by the Rayleigh statistics. We analyze the probability of error performance when coherent detection, diversity, spectrum sharing by two service providers, and forward error correction are employed.