Downlink performance of cellular networks is mainly limited by Inter-cell Interference (ICI). A promising concept for ICI mitigation is Fractional Frequency Reuse (FFR), which effectively allows to trade off overall performance against enhanced cell-edge performance. In this work, a novel FFR scheme is proposed. It assigns a given user to a frequency sub band depending on the achievable capacity density (bit/s/m). An optimization problem is formulated, which aims at maximizing average per-user throughput while maintaining a minimum performance at cell-edge. Simulations are carried out for omnidirectional and sectorized cellular scenarios, using both Two-dimensional (2-D) and Three dimensional (3-D) antenna radiation patterns. The simulation results show that the proposed scheme outperforms conventional reuse-1- and reuse-3 schemes in terms of average and cell-edge performance.