CDMA/PRMA analytical model for voice users in satellite-UMTS systems

The third generation UMTS (Universal Mobile Telecommunication System) provides worldwide multimedia wireless services in a host of environments encompassing indoor picocells to satellite megacells. The UMTS and satellite-UMTS consists of two modes, a frequency division duplex (FDD) mode and a time division duplex (TDD) mode. The agreement recommends the use of wideband code division multiple access (WCDMA) for FDD mode and time division-code division multiple access (TD-CDMA) for TDD mode. A modified CDMA/PRMA (code division multiple access/packet reservation multiple access) protocol for LEO (low earth orbit) satellite system that we proposed previously is presented and an analytical model for CDMA/PRMA in LEO satellites is worked out. The proposed protocol is a modified CDMA/PRMA that adapts to the TD-CDMA mode for LEO satellite used in UMTS. An analytical computation is presented in order to determine the main parameters that influence the protocol and to choose the best of them. The goal is to have a statistical multiplexing that uses resources (slots defined both in time and code domain) as efficiently as possible. Analytical results are then validated by simulations, which give an additional proof of the efficiency of our protocol.