HSPA+
Supplemental Downlink
Mobile data traffic is growing significantly and is largely downlink centric. Supplemental Downlink is a feature analyzed by the Qualcomm R&D HSPA+ program to use unpaired spectrum bands to offer additional downlink capacity.
Supplemental Downlink boosts capacity where DL data-hungry apps, such as video on-demand, are a factor and can be implemented in different unpaired bands around the globe. The Qualcomm R&D HSPA+ program analyzed the European-Band at 1.4GHz which proved to be feasible from a technical perspective.
Qualcomm was the first company to demonstrate supplemental downlink for HSPA (at MWC 2011).