Optimal subchannel, rate and power allocation for OFDM-based two-tier Femtocell networks

The problem of subchannel, rate and power allocation in OFDM-based two-tier Femtocell networks, which comprises a conventional macrocell and multiple Femtocells, is addressed. Our objective was maximizing the multiple Femtocell users weighted rate sum by jointly adjusting their subchannel, rate and power allocation under the constraints of cross-tier interference (CTI) between macrocell and multiple Femtocells and the cochannel interference (CCI) between multiple Femtocells. We formulated this optimization problem and solved it using the Lagrangian dual method and interpreted it from the angle of economics. Simulation results show that our system has better performance than the usually employed system, in which the Femtocells can only use the subchannels unoccupied by macrocell. Meanwhile, the utilization of spectrum can be improved significantly.