Two-state CDMA reception for satellite UMTS

In the third generation communication system, due to the average increase of the radio link bandwidth requirements and the power constraints at the mobile S-UMTS terminal, the system capacity will meet its physical limitations even in a moderated deployment scenario. In the 3GPP standard, due to the complexity constraints at the user equipment, the DTX implementation on the uplink channel is heavily limited. The transmission scheme presented in this paper is an extension of the traditional informative symbol set with a zero energy symbol. The silence symbols are integrated with the informative ones and delivered to the radio link layer for transmission. The paper presents a theoretical formulation of the optimum two-state receiver. Comparisons with the traditional single-states receiver are obtained with a theoretical approach and through computer simulations. In the latter case a real Globalstar-like S-UMTS environment show the better performances of the proposed scheme for fast varying sources.