Mitigating cross-tier cross-boundary interference in fractional frequency reuse scheme for multi-tier networks

Fractional frequency reuse scheme is an interference mitigation scheme suitable for multi-tier networks. However, critical examination of existing fractional frequency reuse schemes based on the orthogonal frequency division multiple access technique for a multi-tier network consisting of Macro-cells and Femto-cells reveals a cross-tier, cross-boundary interference for the Femto-cell users located at the boundary region of the cell centre and edge region. In this paper, we addressed this interference issue by introducing a modified resource allocation scheme that adds a buffer zone between the centre and edge region. In addition, the hybrid spectrum usage concept was incorporated into the proposed design to determine the extent of the buffer zone. System level simulation results showed our technique significantly improved signal to interference plus noise ratio (SINR) and throughput performance for the Femto-users located at the boundary region when compared to the traditionally existing scheme.