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This paper considers the problem of subcarrier allocation in the downlink of multi-cell OFDMA networks. Firstly, a novel fractional frequency reuse architecture is proposed, where all available subcarriers are partitioned into two groups to which subcarriers are dynamically allocated. The first group is used in the center of each cell whereas the other which is partitioned into three sectors orthogonally is used for the edge of the cell. All subcarriers are owned by both of the groups but in every scheduling slot each subcarrier is allocated to only one of them. For each subcarrier is used in both of the groups, this architecture improves the spectrum utilization efficiency dramatically. Next, to mitigate the inter-cell interference in our proposed architecture, a new inter-cell interference coordination (ICIC) scheme based on adaptive sub-band avoidance on the inter-cell level is proposed, where for each cell a certain ratio of the subcarriers are avoided in the subcarriers group used for the center region. The avoiding ratio is dynamically generated on the basic of the reports of interference levels from the neighboring cells. Simulation results illustrate the effectiveness of our proposed architecture and scheme.