Best-fit cell attachment for decoupling DL/UL to promote traffic offloading in HetNets

Heterogeneous Networks (HetNets), in which small cells are ultra-densely deployed within a macro cell, is widely regarded as a key solution to mobile traffic offloading. However, this kind of traffic offloading is confronted by two challenges. Firstly, the number of users in any small cell is really limited due to the larger power gap between macros and small cells in HetNets. In return, this phenomenon may degrade traffic offloading performance. Secondly, spectrum efficiency may be deteriorated since uplink channel states are not involved in the conventional cell attachment strategies. To address these challenges, we propose a best-fit cell attachment where downlink and uplink are decoupled and attached to cells independently. Specifically, in this paper, we conceive best-fit strategies for downlink and uplink cell attachment, for taking into account of both channel quality and cell load. And then, their implementation issues in different scenarios are discussed in detail. System-level simulation results demonstrated that our proposal can effectively offload traffic from macros to small cells, and improve data rates for cell-edge users significantly.