User-centric scheduled ultra-dense radio access networks

Massive densification of the radio access network is considered a key technology enabler to significantly increase the capacity of future radio communication systems, beyond today's capabilities. Densification, however, come at a price of an increased complexity of radio resource management (RRM), network control and an increased signalling load, all to the extent that today's 4G RRM mechanisms will no longer be adequate. This article presents a new user-centric cell-less network paradigm for ultra-dense networks where users are served by radio access resources provided by multiple access nodes. For the efficient allocation of resources to users, we propose novel network-scheduling concepts that allow for flexible and efficient usage of the network resources in ultra-dense networks. Furthermore, we elaborate on a hierarchical structure of access and mobility network resource controllers, and on the value of such a structure in various ultra-dense network scenarios. To support these new radio resource management concepts, we investigate their feasibility by means of simulations and we propose a radio access network architecture based on a control-plane with hierarchical organization.