Capacity of Generalized UTRA FDD Closed-Loop Transmit Diversity Modes

JYRI HÄMÄLÄINEN, RISTO WICHMAN, ALEXIS DOUWHUSZKO, GRACIELA CORRAL-BRIONES

Wireless Personal Communications

Springer Netherlands

Año: 2009 p. 1 - 17

0929-6212

  Transmit diversity techniques have received a lot of attention recently, and open-loop and closed-loop downlink transmit diversity modes for two transmit antennae have been included into universal terrestrial radio access (UTRA) frequency division duplex (FDD) specification. Closed-loop modes provide larger system capacity than open-loop modes, but they need additional side information of the downlink channel in the trans-mitter. In FDD systems this requires a separate feedback channel. Quantization of channel state information (CSI) in closed-loop transmit diversity schemes decreases the performance when compared to a closed-loop system where the transmitter has access to complete CSI. Inthis paper, we analyze the effect of quantization of CSI and deduce approximate capacity formulae for closed-loop transmit diversity schemes that are generalizations of the closed-loopschemes included in UTRA FDD specification. Moreover, we calculate approximation error and show by simulations that our approximation is tight for flat Rayleigh fading environments with and without fast transmit power control.