ARCHoN: Adaptive range control of hotzone cells in heterogeneous cellular networks

Heterogeneous networks (HetNets) are typified by cellular deployments with multiple types of cells of different sizes and overlapping coverage areas using a common frequency band. Especially, hotzone cells overlaid on a macrocell to cover hotspot areas are expected to prevail in HetNets, thus cost-effectively enhancing cellular capacity via spatial reuse of spectrum resource and offloading macrocells. In order to fully achieve such benefits, users need to be properly distributed/assigned to the overlaid hotzone cells such that the radio resources therein are fully utilized. To this end, we propose a new architecture called Adaptive Range Control of Hotzone Cells for Heterogeneous Networks (ARCHoN) that jointly controls the radio resource allocations and ranges of OFDMA-based hotzone cells. The use of cell ranges for distributing users in ARCHoN is advantageous in that it can be implemented within a conventional cell-selection framework without modifying user devices or an air interface. In ARCHoN, each cell allocates users radio (frequency, time and power) resources in a non-cooperative manner, deriving a sequence of allocations monotonically decreasing the entire load. For range control, two algorithms are proposed: per-cell and universal, which have a tradeoff between performance and computational complexity. The solution yielded by the combination of these radio resource and range control algorithms is analytically proven to converge to a unique fixed point. Our in-depth evaluation has shown ARCHoN to significantly improve the service quality of users; in an example simulation scenario, ARCHoN is shown to improve the signal-to-interference and noise ratios (SINRs) of users, on average, by up to 3.5 dB in downlink and 18.8 dB in uplink, over the case of the conventional handover framework.