A Cluster-Aware Soft Frequency Reuse scheme for inter-cell interference mitigation in LTE based femtocell networks

Due to the requirement for extensive coverage, Long Term Evolution (LTE) has developed small cellular base stations called femtocells that can dramatically improve voice and data coverage for the indoor subscribers. However, limited spectrum availability in the cellular networks causes severe interference issues in the neighboring femtocell users transmitting in the same radio band. In densely deployed environments, interference problems in co-channel femtocell networks causes significant degradation in performance. In this paper, we propose a Cluster-Aware Soft Frequency Reuse (CASFR) scheme, that assigns distinct set of Physical Resource Blocks (PRB)s to each interfering femtocells. The scheme first uses periodic messages from the femto-user (FUE) to identify the interfering femtocells. It then divides each femtocell area into cell-center and cell-edge. Finally, it uses the CASFR algorithm to assign un-interfering sets of PRBs to the cell-center and cell-edge users of all the interfering femtocells. We also proposed a PRB Swapping and Exchange (PSE) algorithm for the uplink to further reduce any interference that may remain after performing CASFR. The simulation results show 14% decrease in the Inter Cell Interference (ICI) levels in the femto users, thereby increasing their average throughput by 25%.