An improved adaptive user classification algorithm for FFR scheme

In general, users are classified as cell-center and cell-edge users based on the SINR threshold in multi-cell orthogonal frequency division multiple access (OFDMA) systems, as frequency spectrum is divided into internal frequency band and external frequency band in fractional frequency reuse (FFR) scheme. Considering the SINR threshold for user classification is always predefined based on experience, an adaptive user classification algorithm is proposed for FFR scheme in this paper. The proposed approach can achieve the optimal SINR threshold adaptively through maximizing the proportion of the harmonic sum of individual user´s SINR to the ratio of the number of cell-center users to the number of cell-edge users minus the ratio of the corresponding subcarriers. Not only the user´s SINR can be improved but also the variability of the user distribution is considered in the presented approach. Simulation results show that FFR scheme with the optimal threshold performs better than that with the traditional predetermined threshold.