Impacts of higher order modulation on HS-DSCH system performance

To support high peak rates the possibility to use higher-order modulation is included in the WCDMA high-speed downlink shared channel (HS-DSCH). In an initial roll-out, higher-order modulation may not be available in all terminals and it is therefore interesting to understand to what extent enhancements offered by HS-OSCH depends on higher-order modulation. We study the impacts of higher-order modulation on HS-DSCH system performance. Our results indicate that performance gains when introducing HS-DSCH are significant, even if higher-order modulation is not available. When time dispersion is small, higher-order modulation may improve system throughput. To take advantage of higher-order modulation in environments with significant time dispersion advanced receivers structures should be considered. Furthermore, higher order modulation is found to be more sensitive to errors in the channel quality estimates.