As per my knowledge, Dual connectivity is implemented for down link data streams.In DC mode, Data stream coming from the core network is splitted at the PDCP layer. One stream of IP packets follow the LTE protocol stack while the other one follows the Wi-FI AP path. At the receiver side, these PDCP packets coming from both the ends are combined and delivered to upper layer.
As far as I know, this concept is yet not considered for uplink data streams.
