CDMA satellite capacity dynamics and efficiency with imperfect power control for simultaneous QoS classes and diversity

Abstract

We focus on a non-GEO scenario and investigate the effect of actual power control performance on the return capacity dynamics of a DS-CDMA system. We consider mobile users at different speeds and transmission rates yielding several classes of services. We compute analytically the ideal maximum return capacity of the system which is shown not to be fixed but limited by a hyperplane in the space of the considered quality of service (QoS), so that different resource assignment criteria can be applied. At maximum ideal capacity, for the different percentages of users that can be served, it is shown that the more restraining the QoS, the more resources that must be assigned. We then explore the appropriate efficiency of the system, i.e. the actual used resources as a function of the distribution of QoS. We finally look into the inter-beam effect by applying different degrees of diversity gains and we show the trade-off between improving the capacity efficiency which is poor due to power control error and the net capacity achieved by the overall system.