Adaptive Clustering Method for Femtocells Based on Soft Frequency Reuse

Abstract

Femtocell base station (FBS) is one solution to improve performance of indoor and outdoor user equipments (UEs) with low cost and low complexity. To gain the benefit of deployment of FBS, we consider a frequency assignment method to mitigate cross-tier interference between macrocell and femtocell. Previous studies proposed the channel assignment schemes where macrocell base stations (MBSs) and FBSs orthogonally use subbands. However, they have low efficiency in terms of frequency reuse and high complexity due to exchanging information of FBSs via network. Therefore, we consider the FBS with soft frequency reuse (SFR) scheme to improve the efficiency of frequency reuse. For performance improvement of macrocell UEs (MUEs), we propose a method to cluster FBSs with same SFR pattern. Since the proposed clustering scheme utilizes self-organization network (SON) technique without any information exchange of FBSs, it can improve the performance of MUEs with low complexity. By simulations, we confirm that FBSs with proposed clustering method mitigate cross-tier interference in downlink and increase the throughputs of MUEs.