9 High-Speed Downlink Packet Access The introduction of High-Speed Downlink Packet Access , (HSDPA), implies a major extension of the WCDMA radio interface, enhancing the WCDMA downlink packet-data performance and capabilities in terms of higher peak data rate, reduced latency and increased capacity. This is achieved through the intro- duction of several of the techniques described in Part II, including higher-order modulation , rate control , channel-dependent scheduling , and hybrid ARQ with soft combining . The HSDPA specifications are found in [100] and the references therein.