Dual Connectivity in LTE HetNets with Split Control- and User-Plane

Recently, a new network architecture with split control-plane and user-plane has been proposed and gained a lot of momentum in the standardisation of Long Term Evolution (LTE) Release 12. In this new network architecture, the controlplane, which transmit system information and handles user connectivity, and the user-plane, which manages user data, are split and no longer transmitted necessarily by the same network node. This dual connectivity confers a large flexibility to the system, and allows for a more energy efficient operation and enhanced mobility management. In this paper, we present a detailed description of our dual connectivity framework based on the latest LTE-Advanced MIMO enhancements, in which macrocellassisted small cells use different channel state informationreference signals (CSI-RS) to differentiate among each other and allow UEs to take adequate measurements for cell (re)selection. Taking into account the limited number of available CSI-RSs, we study the assignment problem of CSI-RSs to MA small cells and its feasibility, analyse CSI-RS collision and confusion issues and present simulation results to demonstrate the flexibility of the proposed network architecture.