Downlink Femtocell Interference Mitigation and Achievable Data Rate Maximization: Using FBS Association and Transmit Power-Control Schemes

How to associate a femto user (FU) to an appropriate femto base station (FBS) to avoid interference and maximize the achievable data rate (ADR) of FUs has attracted a lot of attention in femtocell networks. The evidence provided in this paper proves it to be an NP-complete problem. To maximize the ADR of the FUs, the methods for assigning FUs to neighboring FBSs are examined to determine the required transmit power level (TPL) adjustments for the FBSs to mitigate the downlink (DL) interference among the FBSs and the macro base station (MBS). Traditionally, the linear programming (LP) approach is adopted to obtain the optimal solution for this problem. However, the LP approach requires substantially more time to obtain the solution. To lessen this drawback, we propose an easy but smarter scheme, i.e., the smart FBS selection algorithm (SFSA), to distribute FUs to the noninterfered FBSs and to obtain the maximal ADR for each FU. If the SFSA fails to solve this problem, a DL power-control algorithm (DPCA) is employed to find a solution that causes the least amount of interference. The simulation results show that the SFSA and DPCA require only a minor amount of computation time to obtain a feasible solution. The results show that the maximal data rates of the FUs obtained using the SFSA and DPCA are comparable to that of the LP approach.