On interference management based on subframe blanking in Heterogeneous LTE networks

A Heterogeneous network (HetNet) of LTE is expected to have macros, picos with biased association, and, femtos in closed access mode. An user equipment (UE) which associates to a pico eNodeB due to biasing experiences severe interference from macro eNodeB. Similarly, a UE associated to the macro eNodeB in the proximity of closed access femto can go into outage due to heavy interference from the femto, thus creating coverage holes in the network. Such UEs experiencing severe interference are referred to as victim UEs and the nodes that cause the interference are referred to as aggressors. Inter-cell interference coordination (ICIC) techniques are considered in LTE-A to overcome these problems. One of the solutions considered is by blanking some subframes at the aggressor for protecting victim UEs from interference caused by these nodes. In this paper, a scheme based on almost blank subframes (ABS) defined in LTE-A to handle the interference in a HetNet scenario is proposed. This is done by blanking certain subframes of a node, which has potential to create severe interference to the UEs associated to other nodes. The proposed scheme determines the number and location of subframes that are to be blanked at each aggressor node. It is observed that, the victim UE performance can be significantly improved with careful selection of ABS pattern at macro and femto eNodeBs within the cell.