Methods are provided to perform multiple-connectivity operation in the heterogeneous network. In one novel aspect, multiple-connectivity is configured with one microwave macro cell and multiple small cells. UE establishes control plane connectivity with the microwave macro cell, where the S1-MME interface is terminated. Multiple small-cell base stations provide traffic data together to the UE and are connected with Xn interfaces. One small-cell base station in the set of the configured small base stations is an UP anchor small-cell base station, where S1-U interface is terminated. Other small base stations are UP assistance small base station. In one embodiment, the set of small base stations and the UP anchor small base stations can be changed based on the measurement report/results of the different cells as well as the cell loading status. The anchor base station can be changed either by the UE or through network configuration.