The effect of dual satellite diversity on the total capacity of multiple band-shared CDMA LEOS systems

It has been proposed to use path diversity for improved performance of CDMA systems over a low-earth orbiting satellite channel. The authors are interested in determining the feasibility of having multiple service providers share the same spectrum in a mobile communication scenario. To accomplish this, they compare the total capacity when n systems are operational to that when only a single system uses the frequency band; in either case, a single system employs two satellites to achieve path diversity. This comparison is made for the downlink under one of two possible constraints, either a maximum power flux density limit per system or an aggregate power flux density limitation. In previous work the authors showed that, when each system has one satellite in view and each employs orthogonal spreading, that multiple systems can achieve larger capacity than a single system in some situations, depending upon shadowing conditions and system design parameters. That this is possible at all is due to constraints on the power spectral density (PSD) either from each satellite, or from the aggregate of all satellites. The results of the present paper, for the case when two satellites are in view in each system, show no fundamental or qualitative change in the conclusions; however the actual crossover conditions for when an increase in capacity is possible do change