Hybrid Protected Subframes Resource Allocation and Throughput Estimation in LTE-A HetNet

Hierarchical macro cell/small cells overlaying networks is regarded as a key role to the success of the next generation wireless systems. To increase the spectrum efficiency through cell splitting, Cell Range Expansion (CRE) in small cells is an effective way to help offloading macro user equipment (UE), but pose many challenges on managing the interference between the small cells and macro cells. To protect offloaded UEs from severe macro cell interference, a specific protected sub frames is introduced in 3GPP Release 10 enhanced Inter-Cell Interference Coordination (eICIC), known as Almost Blank Sub frames (ABS). However, with a large CRE zone that induces more victim UEs, more ABS are required, which decrease the throughput of macro UE. An alternative to ABS is the Reduce Power Sub frames (RPS), where reduced transmission power from macro cell is applied to mitigate the interference to small UEs. In this paper, a Hybrid Protected Sub frames (HPS) resource allocation scheme is designed, which jointly considers ABS and RPS. We propose a two-stage configuration method which is based on the Proportional Fair (PF) metrics to determine the best allocation of HPS pattern. Comparing to previous work, simulation results show that the proposed scheme efficiently improves the small UE throughput, and maintain the macro UE throughput as the protected sub frames is increased.