Satellite Diversity Gain Over The LEOS Channel, Based CDMA Systems

There is a trend for mobile satellite system architectures aimed at the deployment of multi-satellite constellations in Non-Geostationary Earth Orbits (NGEOs). This allows the user terminals to be small size, low cost and having low power demand. In present and next generation satellite systems, CDMA has been proposed as the multiple access technique for a number of mobile satellite communication systems. To enhance the coverage and quality of service, Low Earth Orbiting (LEO) constellations are usually selected. In this paper, we analyze the performance of the downlink of a LEO satellite channel. The provision of such a service requires that the user have sufficient link quality for the duration of service. To have sufficient link quality, the user must have an adequate power to overcome the path loss and other physical impairments to provide acceptable communication and improve the performance of the system. This paper addresses satellite diversity with the effect of both power control error and voice activity factor for downlink mobile satellite systems. Both Rician and Rayleigh channel statistics are modeled. Results of simulation show that satellite diversity has a significant effect on the system performance. Moreover, the quantitative results indicate that to combat system capacity reduction due to shadowing and the multiple access interference (MAI), perfect power control system, voice activity factor and suitable coding techniques must be employed in the system.