CoSFR: coordinated soft frequency reuse for OFDMA-based multi-cell networks with non-uniform user distribution

Inter-cell interference coordination (ICIC) technology has been extensively studied to improve service quality of users near cell boundaries. Most ICIC schemes available make an assumption that users in the same cell are distributed uniformly. This is reasonable but incomplete. Mobility may result in users distributed non-uniformly, so this paper proposes a novel semi-static ICIC scheme, coordinated soft frequency reuse (CoSFR), for multi-cell networks with non-uniform user distribution. A finer cell partition structure with a tunable parameter r is proposed. With this structure, dedicated user classification rules and opportunistic scheduling strategies are designed for different cells. Assisted by a simple but efficient coordination scheme, a cell with overloaded cell-edge traffic, named aggressor cell, calls adjacent neighboring cells for help. Some reuse opportunities can be created after coordination and the aggressor cell can expand its cell-edge band to alleviate the overloaded state. No additional entity is required for being compatible with the flat network structure of LTE/LTE-Advanced. In addition, CoSFR can deal with the scenario that more than one cell suffering overloaded cell-edge traffic and it can also be applied to irregular cells with minimal modifications. Simulation results show that more than 97.4 % users are satisfied with their data rate. Average cell-edge user throughput is raised substantially and the outage probability declines significantly.