Space-time coded transmit diversity in multi-satellite UMTS

The paper analyzes and compares the performance of some space-time codes applied to the forward link of a WCDMA multi-satellite UMTS environment. Space-time trellis codes (STTrC) have been considered as a first comparison with already implemented transmit diversity schemes, such as maximal ratio combining (MRC), space-time block codes (STBC) and selection transmit diversity (STD). Furthermore, in order to improve their performance, convolutional codes (CC) have been added as outer encoders to MRC, STBC and STD, while for STTrC, a CC plus iterative decoding has been considered in order to perform space-time turbo coded modulation (STTuCM). All these schemes have been implemented in a multi-satellite environment. An intra- and inter-cell interference model is presented in order to evaluate the performance of these schemes for a loaded system. The effect of a feedback delay and errors in channel state identification have been introduced in order to have a real behavior of closed-loop schemes.