Improved fractional frequency reuse in OFDMA based multi-cell networks

Abstract

In this thesis, we consider an inter-cell interference problem in OFDMA (Orthogonal Frequency Division Multiple Access) based multi-cell networks. In OFDMA systems, there exists inter-cell interference (ICI) when the same sub-channel is used by different users in neighboring cells. To solve the inter-cell interference problem, there have been proposed various ICI mitigation methods, such as frequency reuse factor (FRF) 3, soft frequency reuse (SFR), partial frequency reuse (PFR), and adaptive fractional frequency reuse (AFFR). However, they experience performance degradation in frequency-selective fading channels. We propose a novel ICI mitigation scheme, called IFFR (Improved Fractional Frequency Reuse), for the downlink in OFDMA based multi-cell networks. IFFR adopts a water-filling algorithm and adaptively allocates transmission power to sub-channels according to their various channel conditions. As a result, IFFR can improve the cell throughput. We evaluate the proposed algorithm through extensive MATLAB simulations.