Dynamic hard Fractional Frequency Reuse for mobile WiMAX

Fractional frequency reuse (FFR) is gaining much attention in WiMAX standardization bodies to mitigate the inter-cell interference and reduce the throughput outage at the cell edges. A hard FFR pattern based on a time division of the available total bandwidth between inner and outer cell users is recommended in the IEEE 802.16e standard. The DL subframe is configured so that users close to the base station operate on the zone with all subchannels available, while for the edge users, each cell operates on the zone with a fraction of all subchannels available. In this paper, we propose a hard FFR scheme that dynamically adjusts the size of each zone according to the system load. Our approach is based on either a partial or a full coordination between the base stations. The effectiveness of our scheme is particularly proved when a non-uniform distribution of the users in the cell is considered.