Optimized ABS in LTE-Advanced Heterogeneous Networks with Adaptive Macro Cell Transmission

Interference coordination in heterogeneous cellular networks is a major bottleneck. In LTE-A (release 10), enhanced inter cell interference coordination (eICIC) scheme is proposed as an effective solution. It notably involves the approach of almost blank subframes (ABS) consisting of muting the macro cell during a set of predefined subframes. This offers the opportunity to the overlay small cells to schedule their most interfered users during these blanked periods. Nevertheless, this muting has the disadvantage of decreasing the performance of the macro cell. In order to fully optimize the resource allocation and maximize the total throughput of the entire system, we require solving a global NP hard non convex optimization problem. In this paper, we propose an improved eICIC technique with adaptive macro cell transmission during ABS periods. In fact, the original global optimization problem is decomposed into disjoint tractable sub-problems by means of macro cell users grouping. The sub-problems are then optimally solved through a solution combining joint spatial beamforming and fair user scheduling algorithm. Compared to the conventional ABS, simulation results show that the proposed scheme considerably reduces the impact of ABS on the macro cell throughput without reducing the gains achieved at the small cell.